A TEXTBOOK OF 
 
 ORGANIC CHEMISTRY* 
 
 The English Translation 
 from the German of 
 A. BERNTHSEN, Ph.D. 
 
 EDITED AND REVISED tO DATE BY 
 J. J. SUDBOROUGH, Ph.D., D.Sc., F.I.C. 
 
 Professor of Organic Chemistry in the Indian Institute 
 of Science, Bangalore 
 
 NEW YORK 
 
 D. VAN NOSTRAND COMPANY 
 EIGHT WARREN STREET 
 
PREFACE 
 
 The present edition is on much the same lines as the former, 
 but contains the following new chapters: XL VIII. Fermen- 
 tation and Enzyme Action ; XLIX. Catalytic Action of Finely- 
 divided Metals and Metallic Oxides; L. Unsaturation; LI. Ali- 
 phatic Diazo- and Triazo-compounds. 
 
 The Chapters on Alkaloids, Terpenes and Camphors, and 
 Proteins have been rewritten. 
 
 The earlier Chapters give an outline of General Systematic 
 Organic Chemistry, and the later ones deal in somewhat more 
 detail with some of the problems which have attracted a 
 considerable amount of attention within recent years. 
 
 Numerous references to original papers are given in the 
 text, and the following works are recommended for special 
 study : 
 
 Meyer and Jacobson. Handbuch der organischen Chemie. 
 
 Lassar-Cohn. Arbeitsmethoden. 
 
 Th. Weyl. Die Methoden der organischen Chemie. 
 
 Werner. Lehrbuch der Stereochemie. 
 
 Landolt. Das optische Drehungsvermogen. 
 
 0. Aschan. Chemie der alicydischen Verbindungen, 
 
 E. Fischer. Aminosduren und Polypeptide, 1906. 
 
 Do. Purin Gruppe, 1907. 
 
 Do. Kohlenhydrate und Fermente, 1909. 
 
 Cain. The Diazo-compounds. 
 
 Smiles. Relations between Chemical Constitution and Physical 
 Properties. 
 
 iii 
 
IV PREFACE 
 
 Stewart. Stereo-chemistry. 
 
 Do. Eecent Advances in Organic Chemistry. 
 Sidgwick. Organic Chemistry of Nitrogen. 
 Harden. Alcoholic Fermentation. 
 E. F. Armstrong. Simple Carbohydrates and Glucosides. 
 Bayliss. Enzyme Action. 
 Schryver. Proteins. 
 
 Valuable Summaries of certain fields of Organic Work, such 
 as Combustion, Diazo-compounds, Grignard's Reagents, Cam- 
 phor, Tautomerism, Stereo-chemistry of Nitrogen, &c., will be 
 found in the Reports of the British Association since 1900, 
 and also in Ahren's Sammlung chemischer und chem.-technischer 
 Vortmge from 1897 onwards. 
 
 J. J. SUDBOROUGH. 
 
 BANGALORE, March, 1912. 
 
ABBEEVIATIONS 
 
 A. = Liebig's Annalen der Chemie. 
 
 Abs. = Journal of the Chemical Society. Abstracts. 
 Am. = American Chemical Journal. 
 Annales Annales de Chemie et de Physique. 
 Arch. f. Phys. = Archivfur Physiologic. 
 
 B. = Berichte der deutschen Chemischen Cfesellschaft. 
 
 B. A. Rep. = British Association Report. 
 
 Bull. Soc. Chirn. = Bulletin de la Socitte Chimique a Paris. 
 
 C. C. = Chemisches Central-Uatt. 
 
 C. R. = Comptes rendus de I' Academic des Sciences. 
 
 J. A. C. S. = Journal of the American Chemical Society. 
 
 J. C. S. = Journal of the Chemical Society. Transactions. 
 
 J. Ind. = Journal of the Society of Chemical Industry. 
 
 J. pr. = Journal fur praktische Chemie. 
 
 M. = Monatshefte fiir Chemie (Wien). 
 
 P. = Proceedings of the Chemical Society. 
 
 Phil. Mag. = Philosophical Magazine. 
 
 Rec. = Recueil des Travaux Chimiques des Pays Bas. 
 
 S. J. = Sudborough and James's Practical Organic Chemistry. 
 
 Walker, Phys. Chem. = James Walker's Introduction to Physical Chemistry. 
 
 Zeit. phys. = Zeitschrift fiir physikalische Chemie. 
 
 n = normal. 
 
 0-ether = Oxygen ether. 
 
 N-ether = Nitrogen ether. 
 
 B.-pt. = Boiling-point. 
 
 M.-pt. = Melting-point. 
 
 d = dextro. 
 
 I = Isevo. 
 
 r = racemic. 
 
 = symmetrical. 
 
 i = inactive. 
 R = alkyl radical. 
 Me = Methyl, CH 3 . 
 Et = Ethyl, C 2 H 6 . 
 Ph = Phenyl, C 6 H 6 . 
 o = ortho. 
 m = meta. 
 p = para. 
 
TABLE OF CONTENTS 
 
 INTRODUCTION 
 
 Page 
 
 Qualitative Analysis ...-..-. 2 
 
 Quantitative Analysis - 4 
 
 Calculation of the Empirical Formula - .... 7 
 
 Determination of Molecular Weight - - 7 
 
 Polymerism and Isomerism - 12 
 
 Chemical Theories - - - 13 
 
 Explanation of Isomerism; Determination of the Constitution of 
 
 Organic Compounds 16 
 
 Rational Formulae - - 19 
 
 The Nature of the Carbon Atom 19 
 
 Homology ........ ... - 20 
 
 Radicals - - 22 
 
 Classification of Hydrocarbons 
 
 Physical Properties of Organic Compounds - - - - 21 
 
 CLASS I. ALIPHATIC OR OPEN -CHAIN 
 COMPOUNDS 
 
 i. HYDROCARBONS - - . 30 
 
 A. Saturated Hydrocarbons, C n H2n +2 30 
 
 B. Olefines, CnH^ - 42 
 c. Acetylene Series, C n H 2n -2 ... 49 
 D. Hydrocarbons, C n H 2n -6 * " ^3 
 
 ii. HALOID SUBSTITUTION PRODUCTS OF THE HYDROCARBONS - 54 
 
 A. Halogen Derivatives of the Paraffins - - - 54 
 
 B. Halide Derivatives of Unsaturated Hydrocarbons - - 64 
 
 vii 
 
vili CONTENTS 
 
 Page 
 
 in. MONOHYDRIC ALCOHOLS OK ALKYL HYDROXIDES 65 
 
 A. Monohydric Saturated Alcohols, C n H 2n+1 OH - - 66 
 
 B. Monohydric Unsaturated Alcohols, C n H 2 n_iOH - - 81 
 
 C. Monohydric Unsaturated Alcohols, C n H 2n _3OH - - 82 
 
 iv. DERIVATIVES OF THE ALCOHOLS 83 
 
 A. Ethers Proper or Alkyl Oxides 83 
 
 B. Thio-alcohols and Thio-ethers 87 
 
 c. Esters of the Alcohols with Inorganic Acids, and their 
 
 Isomers 91 
 
 Esters of Nitric Acid 93 
 
 Derivatives of Nitrous Acid 94 
 
 Esters of Sulphuric Acid 98 
 
 Derivatives of Sulphurous Acid 99 
 
 Alkyl Derivatives of Hydrocyanic Acid - - - 101 
 
 D. Amines or Nitrogen Bases of the Alkyl Radicals - - 104 
 
 Hydroxylamines, Hydrazines - - - - - 111 
 
 E. Alkyl Derivatives of Phosphorus, Arsenic, &c. - - 113 
 
 F. Organo -metallic Compounds 118 
 
 v. ALDEHYDES AND KETONES - - 121 
 
 A. Aldehydes 122 
 
 B. Ketones 131 
 
 Aldoximes and Ketoximes - - - = - - 137 
 
 vi. MONOBASIC FATTY ACIDS 139 
 
 A. Saturated Acids, C n H 2n O 2 '- - - - 139 
 
 B. Unsaturated Acids, C n H 2n -zO-2 - - 161 
 
 C. Propiolic Acid Series, C n H 2n - 4 O2 - - 166 
 
 D. Halogen Substitution Products of the Monobasic Acids - 167 
 
 vii. ACID DERIVATIVES - - - .-**,- . - 171 
 
 A. Esters of the Fatty Acids ,;. -r V r ! - - - 172 
 
 B. Acid Chlorides, Bromides, &c. - /. ' ,?* , -- ' * " 178 
 
 C. Acid Anhydrides - ; w j ;. . - - 180 
 
 D. Thio-acids and Thio-anhydrides - .. * - - 181 
 
 E. Acid Amides and Hydrazides - - - 182 
 
 F. Amido- and Imido-chlorides - 185 
 
 G. Thiamides and Imido-thio-ethers - - 186 
 H. Amidines and Amidoximes - . -c - ; - - - 187 
 
CONTENTS IX 
 
 Page 
 
 VIII. POLYHTDRIC ALCOHOLS- . ; "iJ .'* r ' ^'i-.-'n^' S .*;;.!/.. ,': 188 
 
 A. Dihydric Alcohols or Glycols '.-' i ; "v^.,/.^.-..! . jgg 
 
 B. Trihydric Alcohols *' '' ''. - ''"''"" - :< ' '' - 19 ? 
 c. Tetra-, Penta-, and Hexahydric Alcohols - - 201 
 
 ix. HYDROXY MONOBASIC ACIDS AND COMPOUNDS RELATED TO 
 
 THEM ... - '''--''''-' v^- r.>' : -$ >. . 205 
 
 A. Monohydroxy Fatty Acids - - '' '"'-'-**"' - 205 
 
 B. Polyhydric Monobasic Acids 218 
 
 c. Hydroxy-aldehydes - - ->~n --4MO- - 220 
 
 D. Dialdehydes ' i j " : ^ /ij s;- )L> , ' ^ - ' - - 221 
 
 E. Diketones - - ...... - - - 221 
 
 p. Aldehydic Monobasic Acids 222 
 
 G. Monobasic Ketonic Acids 222 
 
 x. DIBASIC ACIDS - ' - 231 
 
 A. Saturated Dibasic Acids, or Oxalic Series - - 231 
 
 B. Unsaturated Dibasic Acids 241 
 
 C. Hydroxy Dibasic Acids 247 
 
 D. Dihydroxy Dibasic Acids .... - 249 
 
 Stereo-isomerism of the Tartaric Acids - - - 250 
 
 E. Polyhydroxy Dibasic Acids .... - 259 
 p. Dibasic Ketonic Acids ..-.-.- 260 
 
 xi. POLYBASIO ACIDS 261 
 
 A. Saturated and Unsaturated Polybasic Acids - - - 261 
 
 B. Hydroxy Polybasic Acids 262 
 
 xii. CYANOGEN COMPOUNDS - - - - - - 263 
 
 A. Cyanogen and Hydrocyanic Acid 266 
 
 B. Halogen Compounds of Cyanogen 272 
 
 C. Cyanic and Cyanuric Acids - - 273 
 
 D. Thiocyanic Acid and its Derivatives .... 275 
 
 E. Cyanamide and its Derivatives - - 277 
 
 xin. CARBONIC ACID DERIVATIVES 279 
 
 A. Esters - 279 
 
 B. Chlorides - 280 
 
X CONTENTS 
 
 Page 
 
 C. Amides, Ureides, Purine Group - - - - - 261 
 
 D. Sulphur Derivatives of Carbonic Acid - - - 295 
 K. Amidines of Carbonic Acid - . . . 297 
 
 xiv. CARBOHYDRATES - 298 
 
 A. Monosaccharoses 300 
 
 B. Di- and Trisaccharoses - - 314 
 
 C. Polysaccharoses - 317 
 
 CLASS II. CHEMISTRY OF THE CYCLIC 
 COMPOUNDS 
 
 xv. INTRODUCTION ... 321 
 
 CARBOCYCLIC COMPOUNDS 
 
 XVI. POLYMETHYLENE DERIVATIVES 322 
 
 xvii. BENZENE DERIVATIVES Introduction 327 
 
 Characteristic Properties of Benzene Derivatives - 328 
 
 Isomeric Relations 329 
 
 Constitution of Benzene 332 
 
 Determination of Positions of Substituents - 337 
 
 Occurrence of Benzene Derivatives 340 
 
 Formation of Benzene Derivatives, &c. ... 341 
 
 xvni. BENZENE HYDROCARBONS 344 
 
 A. Homologues of Benzene, C n H2n-6 344 
 
 B. Unsaturated Benzene Hydrocarbons .... 353 
 
 xix. HALOGEN DERIVATIVES - . '- . " . . - 354 
 
 A. Additive Compounds - - .... 354 
 
 B. Substituted Derivatives --./-- - - - 354 
 
 XX. NlTRO- SUBSTITUTION PRODUCTS OF THE AROMATIC HYDRO- 
 CARBONS - -- '*'/.-''-' ' - - - 359 
 
 Nitroso-derivatives ,- - 1 : : ; - - - - 365 
 
 xxi. AMINO-DERIVATIVES OR ARYLAMINES - 366 
 
 A. Primary Monamines . v ' .. i . . . 367 
 
 B. Secondary Monamines 375 
 
 c. Tertiary Monamines 377 
 
CONTENDS XI 
 
 Page 
 
 Do The Quaternary Bases - - '- ' '='* ; '; - '' * '> ' - - 379 
 
 E. Diamines, Triamines, &c. - f '- ; - -'- ' lT3&fi'iiO - - 380 
 
 Acyl Derivatives of Arylamines ----- 381 
 
 Primary Amines with the Amino-group in the Side Chain 383 
 
 XXII. DlAZO- AND AZO-COMPOUNDS ; HYDEAZINES - "' "' ' ' ''-~ 384 
 
 A. Diazo-compounds - - - ; : ..- .,..*. " 384 
 
 B. Diazo-amino-compounds -- : .- - - 392 
 
 C. Azo-compounds and Compounds intermediate between 
 
 Nitro- and Amino-compounds ._'..'!'. - - 394 
 
 D. Hydrazines - - - - -.. ' ' - - - 397 
 
 E. Azo-dyes - * - - 399 
 
 F. Phosphorus Compounds, &c.; Organo-metallic Derivatives 402 
 
 xxiii. AROMATIC SULPHONIO ACIDS- '-''""' '"' '' '"' ^^' > . } . 403 
 
 xxiv. PHENOLS -,-- - - 407 
 
 A. Monohydric Phenols - - 410 
 
 B. Dihydric Phenols - .- -- - - - - 417 
 
 c. Trihydric Phenols - - 419 
 
 xxv. AROMATIC ALCOHOLS, ALDEHYDES, AND KETONES - - - 421 
 
 A. Aromatic Alcohols . - 421 
 
 B. Aromatic Aldehydes - - 423 
 
 C. Aromatic Ketones - .".... 427 
 
 D. Hydroxy or Phenolic Alcohols, Aldehydes, and Ketones 429 
 
 E. Quinones 430 
 
 F. Quinone Chlorimides, Quinone Aniles, and Anilino- 
 
 quinones 433 
 
 G. Pseudo-phenols. Methylene-quinones - 434 
 
 xxvi. AROMATIC ACIDS 435 
 
 A. Monobasic Aromatic Acids 442 
 
 1. Monobasic Saturated Acids 444 
 
 2. Monobasic Unsaturated Acids - - - - 454 
 
 3. Saturated Phenolic Acids 456 
 
 4. Alcohol- and Keto-acids 461 
 
 5. Unsaturated Monobasic Phenolic Acids - - - 463 
 
 B. Dibasic Acids ...-.--- 464 
 c. Polybasic Acids - 470 
 
v PREFACE 
 
 Stewart. Stereo-chemistry. 
 
 Do. Recent Advances in Organic Chemistry. 
 Sidgwick. Organic Chemistry of Nitrogen. 
 Harden. Alcoholic Fermentation. 
 E. F. Armstrong. Simple Carbohydrates and Glucosides. 
 Bayliss. Enzyme Action. 
 Schryver. Proteins. 
 
 Valuable Summaries of certain fields of Organic Work, such 
 as Combustion, Diazo-compounds, Grignard's Eeagents, Cam- 
 phor, Tautomerism, Stereo-chemistry of Nitrogen, &c., will be 
 found in the Reports of the British Association since 1900, 
 and also in Ahren's Sammlung chemischer und chem.-technischer 
 Vortmge from 1897 onwards. 
 
 J. J, SUDBOROUGH. 
 
 BANGALOKE, March, 1912. 
 
ABBEEVIATIONS 
 
 A. = Liebig's Annalen der Chemie. 
 
 Abs. = Journal of the Chemical Society. Abstracts. 
 Am. = American Chemical Journal. 
 Annales = Annales de Chemie et de Physique. 
 Arch. f. Phys. = Archiv filr Physiologic. 
 
 B. = Berichte der deutschen Chemischen Cfesellschaft. 
 
 B. A. Rep. = British Association Report. 
 
 Bull. Soc. China. = Bulletin de la Socie'te' Chimique a Paris. 
 
 C. C. = Chemisches Central-Uatt. 
 
 C. R. = Comptes rendus de VAcaddmie des Sciences. 
 
 J. A. C. S. = Journal of the American Chemical Society. 
 
 J. C. S. = Journal of the Chemical Society. Transactions. 
 
 J. Ind. = Journal of the Society of Chemical Industry. 
 
 J. pr. = Journal filr pralctische Chemie. 
 
 M. = Monatshefte fur Chemie (Wien). 
 
 P. = Proceedings of the Chemical Society. 
 
 Phil. Mag. = Philosophical Magazine. 
 
 Rec. = Recueil des Travaux Chimiques des Pays Bas. 
 
 S. J. = Sudborough and James's Practical Organic Chemistry. 
 
 Walker, Phys. Chem. = James Walker's Introduction to Physical Chemistry. 
 
 Zeit. phys. = Zeitschrift fur physikalische Chemie. 
 
 n = normal. 
 
 0-ether = Oxygen ether. 
 
 N-ether = Nitrogen ether. 
 
 B.-pt. = Boiling-point. 
 
 M.-pt. = Melting-point. 
 
 d dextro. 
 
 I = Isevo. 
 
 r = racemic. 
 
 = symmetrical. 
 
 i inactive. 
 R = alkyl radical. 
 Me = Methyl, CH 3 . 
 Et = Ethyl, C 2 H 6 . 
 Ph = Phenyl, C 6 H 6 . 
 o = ortho. 
 m, = meta. 
 p = para. 
 
TABLE OF CONTENTS 
 
 INTRODUCTION 
 
 Page 
 
 Qualitative Analysis - , .. ; ..^r 2 
 
 Quantitative Analysis : , - 4 
 
 Calculation of the Empirical Formula ir .-...i -,..r- /,,*A 7 
 
 Determination of Molecular Weight - - 7 
 
 Polymerism and Isomerism ' - <-.if* r, "'O^rfTf " * 12 
 
 Chemical Theories - . ,. ?/ ,,j .;,,.- , ; . i ,.'..,. ^ ,.. ; - 13 
 Explanation of Isomerism; Determination of the Constitution of 
 
 Organic Compounds 16 
 
 Rational Formulae 19 
 
 The Nature of the Carbon Atom 19 
 
 Homology 20 
 
 Radicals 22 
 
 Classification of Hydrocarbons 23 
 
 Physical Properties of Organic Compounds - - - - -21 
 
 CLASS I. ALIPHATIC OR OPEN -CHAIN 
 COMPOUNDS 
 
 i. HYDROCARBONS - - 30 
 
 A. Saturated Hydrocarbons, CnH^+a 30 
 
 B. Olefines, C n H2n - 42 
 c. Acetylene Series, C n H 2 n-2 - 49 
 D. Hydrocarbons, C n H 2n _ 6 - 53 
 
 ii. HALOID SUBSTITUTION PRODUCTS OF THE HYDROCARBONS - 54 
 
 A. Halogen Derivatives of the Paraffins - - 54 
 
 B. Halide Derivatives of Unsaturated Hydrocarbons - - 64 
 
 vii 
 
Vlll CONTENTS 
 
 Page 
 in. MONOHYDEIC ALCOHOLS OK ALKYL HYDROXIDES 65 
 
 A. Monohydric Saturated Alcohols, C n H 2n +iOH - - 66 
 
 B. Monohydric Unsaturated Alcohols, C n H 2n _iOH - - 81 
 0. Monohydric Unsaturated Alcohols, CnH^.sOH - - 82 
 
 iv. DERIVATIVES OF THE ALCOHOLS ...... 83 
 
 A. Ethers Proper or Alkyl Oxides ..... 83 
 
 B. Thio-alcohols and Thio-ethers ..... 87 
 c. Esters of the Alcohols with Inorganic Acids, and their 
 
 Isomers ......... 91 
 
 Esters of Nitric Acid ....... 93 
 
 Derivatives of Nitrous Acid ..... 94 
 
 Esters of Sulphuric Acid ...... 98 
 
 Derivatives of Sulphurous Acid ..... 99 
 
 Alkyl Derivatives of Hydrocyanic Acid - - - 101 
 
 D. Amines or Nitrogen Bases of the Alkyl Kadicals - - 104 
 
 Hydroxylamines, Hydrazines ..... Ill 
 
 E. Alkyl Derivatives of Phosphorus, Arsenic, &c. - - 113 
 
 F. Organo-metallic Compounds ...... 118 
 
 v. ALDEHYDES AND KETONES - - ..... 121 
 
 A. Aldehydes ......... 122 
 
 B. Ketones ......... 131 
 
 Aldoximes and Ketoximes - - - - - - 137 
 
 vi. MONOBASIC FATTY ACIDS ....... 139 
 
 A. Saturated Acids, C n H 2 nO 2 - - - 139 
 
 B. Unsaturated Acids, C n H 2n _ 2 O 2 . - 161 
 
 C. Propiolic Acid Series, C n H 2n _ 4 O2 - A, *I 1 *.: - 166 
 
 D. Halogen Substitution Products of the Monobasic Acids - 167 
 
 vn. ACID DERIVATIVES ..... . -171 
 
 A. Esters of the Fatty Acids - fr/JI-i -' - - 172 
 
 B. Acid Chlorides, Bromides, &c. -.'>.;'* & * '-, - - 178 
 
 C. Acid Anhydrides ..... .; ' * . - - 180 
 
 D. Thio-acids and Thio-anhydrjdes - .-.- - 181 
 
 E. Acid Amides and Hydrazides - - - - - 182 
 
 F. Amido- and Imido-chlorides - 185 
 
 G. Thiamides and Imido-thio-ethris - 186 
 H. Amidines and Amidoximes - _-- - 187 
 
CONTENTS IX 
 
 Page 
 
 viii. POLYHYDRIC ALCOHOLS- ^ -.qh^'i " . .-?v;r>jtfir. .;..., , iss 
 
 A. Dihydric Alcohols or Glycols r -. : . 188 
 
 B. Trihydric Alcohols - - -V - ' ' - ;s - 197 
 c. Tetra-, Penta-, and Hexahydric Alcohols - - 201 
 
 ix. HYDROXY MONOBASIC ACIDS AND COMPOUNDS RELATED TO 
 
 THEM - - - - - -' : ''' ; "'-*" '"'^ r i^ r<"4 ' . . 205 
 
 A. Monohydroxy Fatty Acids - - -'-*'-.' . 205 
 
 B. Polyhydric Monobasic Acids - - - - - - 218 
 
 c. Hydroxy-aldehydes - ; ' -~' : '* ' ^ v ->1 ; -.*i'. - - 220 
 
 D. Dialdehydes ' 1 ! ' : '. s - : J: ' . . . - - 221 
 
 E. Diketones - - - - *.. * r^rnj.^ivy 221 
 
 F. Aldehydic Monobasic Acids 222 
 
 G. Monobasic Ketonic Acids - ' ' *r' a * t $ ... 222 
 
 x. DIBASIC ACIDS - - - - - - - . - - 231 
 
 A. Saturated Dibasic Acids, or Oxalic Series - - 231 
 
 B. Unsaturated Dibasic Acids 241 
 
 C. Hydroxy Dibasic Acids 247 
 
 D. Dihydroxy Dibasic Acids .... . 249 
 
 Stereo-isomerism of the Tartaric Acids - - - 250 
 
 E. Polyhydroxy Dibasic Acids .... - 259 
 
 F. Dibasic Ketonic Acids 260 
 
 xi. POLYBASIG ACIDS 261 
 
 A. Saturated and Unsaturated Polybasic Acids - - - 261 
 
 B. Hydroxy Polybasic Acids 262 
 
 xn. CYANOGEN COMPOUNDS -....--- 263 
 
 A. Cyanogen and Hydrocyanic Acid 266 
 
 B. Halogen Compounds of Cyanogen - ... 272 
 
 C. Cyanic and Cyanuric Acids ... - 273 
 
 D. Thiocyanic Acid and its Derivatives .... 275 
 
 E. Cyanamide and its Derivatives ... . 277 
 
 xin. CARBONIC ACID DERIVATIVES 279 
 
 A. Esters - 279 
 
 B. Chlorides 280 
 
X CONTENDS 
 
 Page 
 
 c. Amides, Ureides, Purine Group - - - - - 261 
 
 D. Sulphur Derivatives of Carbonic Acid - 295 
 
 E. Amidines of Carbonic Acid - - - - - 297 
 
 xiv. CARBOHYDRATES - 298 
 
 A. Monosaccharoses 300 
 
 B. Di- and Trisaccharoses - - - - - - 314 
 
 c. Polysaccharoses 317 
 
 CLASS II. CHEMISTRY OF THE CYCLIC 
 COMPOUNDS 
 
 xv. INTRODUCTION ... 321 
 
 CAEBOCYCLIC COMPOUNDS 
 
 XVI. POLYMETHTLENE DERIVATIVES .... - 322 
 
 xvii. BENZENE DERIVATIVES Introduction ..... 327 
 
 Characteristic Properties of Benzene Derivatives - 328 
 
 Isomeric Relations 329 
 
 Constitution of Benzene .... . 332 
 
 Determination of Positions of Substituents - 337 
 
 Occurrence of Benzene Derivatives 340 
 
 Formation of Benzene Derivatives, &c. - - - 341 
 
 xviii. BENZENE HYDROCARBONS 344 
 
 A. Homologues of Benzene, C n il2n-6 344 
 
 B. Unsaturated Benzene Hydrocarbons .... 353 
 
 xix. HALOGEN DERIVATIVES ... .... 354 
 
 A. Additive Compounds 354 
 
 B. Substituted Derivatives -'..-- - . - 354 
 
 XX. NlTRO- SUBSTITUTION PRODUCTS OF THE AROMATIC HYDRO- 
 CARBONS ... . . ,./ ... . . 359 
 
 Nitroso-derivatives - - - - - - - 365 
 
 xxi. AMINO-DERIVATIVES OR ARYLAMINES - 366 
 
 A. Primary Monamines * <.- . 367 
 
 B. Secondary Monamines - - -. - - - -375 
 c. Tertiary Monamines - - - r . -V - - 377 
 
CONTENDS XI 
 
 Page 
 
 Do The Quaternary Bases - : "' ':- ' ' '-^:^~i >.;-.'? - - 379 
 
 E. Diamines, Triamines, &c. - :; '. - ; ^ - j ;-... ;i<': . . 350 
 
 Acyl Derivatives of Arylamines - - - - - 381 
 
 Primary Amines with the Amino-group in the Side Chain 383 
 
 XXII. DlAZO- AND AZO-COMPOUNDS ; HTDEAZINES - ' ' ; "- L 384 
 
 A. Diazo-compounds - - ,, ,._,..._...- -,. - 384 
 
 B. Diazo-amino-compounds ^ . 7 r - - - 392 
 c. Azo-compounds and Compounds intermediate between 
 
 Nitro- and Amino-compounds - . - ', - - - 394 
 
 D. Hydrazines - - - - -_ - ' ''<.', - - 397 
 
 E. Azo-dyes - - - ... *^ - - 399 
 
 F. Phosphorus Compounds, &c.; Organo -metallic Derivatives 402 
 
 xxm. AROMATIC SULPHONIO ACIDS- '''"" '"' ''' " ;"- : ''* ''' 403 
 
 xxiv. PHENOLS ..-.... . 407 
 
 A. Monohydric Phenols - . Jl * *'*' . . 410 
 
 B. Dihydric Phenols - - - :' - - - - 417 
 c. Trihydric Phenols - - 419 
 
 xxv. AROMATIC ALCOHOLS, ALDEHYDES, AND KETONES - - - 421 
 
 A. Aromatic Alcohols 421 
 
 B. Aromatic Aldehydes 423 
 
 c. Aromatic Ketones - - :""''* - 427 
 
 D. Hydroxy or Phenolic Alcohols, Aldehydes, and Ketones 429 
 
 E. Quinones 430 
 
 P. Quinone Chlorimides, Quinone Aniles, and Anilino- 
 
 quinones 433 
 
 G. Pseudo-phenols. Methylene-quinones - 434 
 
 xxvi. AROMATIC ACIDS 435 
 
 A. Monobasic Aromatic Acids 442 
 
 1. Monobasic Saturated Acids 444 
 
 2. Monobasic Unsaturated Acida - - - - 454 
 
 3. Saturated Phenolic Acids - 456 
 
 4. Alcohol- and Keto-acids - - - - 461 
 
 5. Unsaturated Monobasic Phenolic Acids - - - 463 
 
 B. Dibasic Acids ...---.. 464 
 c. Polybasic Acids - 470 
 
xii CONTENTS 
 
 Page 
 xxvu. COMPOUNDS CONTAINING TWO OR MORE BENZENE NUCLEI; 
 
 DIPHENYL GROUP - 470 
 
 XXVIII. DlPHENYL-METHANE GROUP 474 
 
 XXIX. DlBENZYL GROUP 477 
 
 xxx. TRIPHENYL-METHANE GROUP 480 
 
 Triphenyl-methane Dyes 482 
 
 1. Amino- and Diamino-triphenyl-methane Group 483 
 
 2. Rosaniline Group 484 
 
 3. Aurine Group 490 
 
 4. Eosin Group - 491 
 
 xxxi. COMPOUNDS WITH CONDENSED BENZENE NUCLEI- - 494 
 
 Naphthalene Group 494 
 
 xxxn. ANTHRACENE AND PHENANTHRENE GROUPS- - 504 
 
 A. Anthracene 504 
 
 B. Phenanthrene 510 
 
 C. Complex Hydrocarbons 512 
 
 HETEROCYCLIC COMPOUNDS 
 
 xxxm. INTRODUCTION - - " - - - - - 513 
 
 xxxiv. FURANE GROUP ... - 515 
 
 xxxv. COMPOUNDS FORMED BY THE CONDENSATION OF A BENZENE 
 NUCLEUS WITH A FURANE, THIOPHENE, OR PYRROLE 
 
 RING- - ;-, r- v 'Oi>M';:K. * " 52 
 
 Indole Group - 521 
 
 Indigo and Related Compounds - - 525 
 
 xxxvi. PYRAZOLE GROUP - - / '-. - ': -... 528 
 
 A. Pyrazole Group - .;;-.;" J - 528 
 
 B. Thiazole Group - 529 
 
 XXXVII. SlX-MEMBERED HETEROCYCLIC RlNGS - 530 
 
 A. Pyrones ----- 531 
 
 B. Pyridine - - - - -. ., r. " ; - 533 
 
CONTENTS Xiii 
 
 Page 
 
 XXXVIII. QUINOLINE AND AOBIDINE GROUPS - *41 
 
 A. Quinoline Group 541 
 
 1. Chromone Group - 541 
 
 2. Quinoline and its Derivatives - 542 
 
 3. Iso-quinoline - - T^ , ,;; . . 547 
 
 B. The Acridine Group - - ^ i * '> X . 547 
 
 XXXIX. SlX-MKMBEEED HETEROCYCLIO COMPOUNDS WITH POUK CAB- 
 BON ATOMS IN RING - - 549 
 The Diasines - - . . . . 550 
 Phenoxazines and Phenthiazines - ' '" ' - 1 " - 554 
 
 XL, ALKALOIDS ..... . 554 
 
 A, Alkaloids related to Pyridine - "V 557 
 
 B. Bases derived from Quinoline - 558 
 c. Bases derived from Iso-quinoline - - - 560 
 
 D. The Morphine Group - - 564 
 
 E. Strychnine Bases 565 
 
 F. Solanine Bases - .... 565 
 
 XLL TERPENES AND CAMPHORS- ...... 567 
 
 A. Open Chain Olefinic Terpenes and Camphors 568 
 
 BO Monocyclic Terpenes and Camphors 572 
 o. Complex Cyclic Terpenes and Camphors - .581 
 
 D. Compounds related to Terpenes - - - 589 
 
 XLII. RESINS; GLUCOSIDES 591 
 
 A. Resins ...... 591 
 
 B. Glucosides- .... * =592 
 
 XLIII. ALBUMINS; PHYSIOLOGICAL CHEMISTRY - 593 
 
 xxiv. REDUCTION 601 
 
 A. Nascent Hydrogen ....... 601 
 
 B. Other Chemical Methods - - - - - -609 
 
 C. Catalytic Reduction 610 
 
 D. Electrolytic Reduction - * - - 614 
 
XIV CONTENTS 
 
 Page 
 
 XLV. OXIDATION ... * . * 616 
 
 A. Permanganate - 618 
 
 B. Chromic Acid Derivatives - 620 
 c. Nitric Acid - >>- 621 
 D. Sulphuric Acid - ...... 622 
 
 B. Peroxides ...... 622 
 
 r. Oxygen and Ozone 623 
 
 G. Other Oxidizing Agents 625 
 
 H. Electrolytic Oxidation - - 626 
 
 XLVI. STEREOCHEMISTRY OF SULPHUR, SELENION, TIN, AND NITRO- 
 GEN COMPOUNDS- - - - 627 
 
 A. Sulphur Compounds - 628 
 
 B. Selenion Compounds - 628 
 o. Tin Compounds - - 629 
 
 D. Silicon Compounds .... . 629 
 
 E. Nitrogen Compounds ...... 631 
 
 p. Phosphorus Compounds - - - - 634 
 
 G. Cobalt Compounds 634 
 
 H. Carbon Compounds, with Semicyclic Double Linkings 63$ 
 
 XLVH. RELATIONSHIPS BETWEEN PHYSICAL PROPERTIES AND 
 
 CHEMICAL CONSTITUTION - . 635 
 
 A. Boiling-point -'-"''.. 635 
 
 B. Melting-point ---..-.. 638 
 
 0. Molecular Volume - ' ' " J - "'"- 4 - - 639 
 
 D. Molecular Refraction - 641 
 
 E. Molecular Magnetic Rotation - " - - 644 
 p. Absorption Spectra - - - .-'."-. . 647 
 G. Anomalous Electric Absorption - . - . . 655 
 H. Optical Activity -656 
 
 Asymmetric Synthesis - - - .... 660 
 
 The Walden Inversion - - 661 
 
 1. Electrical Conductivity " - -"--. -663 
 
 XLVIIL FEBMENTATION AND ENZYME ACTION a: C- >*:. - - 666 
 
 A. Alcoholic Fermentation - - . i .V ; . . 666 
 
 B. Enzyme Action . 671 
 
CONTENTS XV 
 
 Page 
 XLIX. CATALYTIC ACTION OP FINELY -DIVIDED METALS AND 
 
 METALLIC OXIDES - - 674 
 
 Oxidations 674 
 
 Dehydration ... - 674 
 
 Esterification - > - - 677 
 
 Formation of Amines, Thiols, Ketones .... 677 
 
 L. UNSATURATION 678 
 
 A. Types of Unsaturation 678 
 
 B. Properties of Unsaturated Acids as affected by the 
 
 position of the Double Bond 679 
 
 c. Compounds with Conjugate Double Bonds - - - 681 
 
 D. Compounds of Di- and Trivalent Carbon - - - 683 
 
 Carbon Monoxide - - -' - - - 683 
 
 Carbylamines - - - - - - - 684 
 
 Metallic Cyanides - - - - - - 684 
 
 Keactions of Metallic Cyanides. Formation of 
 
 Nitriles and Carbylamines - - 685 
 
 FulminicAcid ....... 687 
 
 Tervalent Carbon : Triphenyl-methyl - - - 690 
 
 E. Ketens - 691 
 
 P. Unsaturation and Physical Properties - 693 
 
 LL ALIPHATIC DIAZO- AND TRIAZO-COMPOUNDS - 694 
 
 A. Diazo-compounds ....... 694 
 
 B. Triazo-compounds 695 
 
 INDEX ...... . * . 697 
 
ORGANIC CHEMISTRY 
 
 INTRODUCTION 
 
 Organic Chemistry is the Chemistry of the Carbon Com- 
 pounds. Formerly those compounds which occur in the 
 animal and vegetable worlds were classed under Organic, and 
 those which occur in the mineral world under Inorganic 
 Chemistry, the first to adopt this arrangement having been 
 Ltmfoy in his Cours de Chimie (1675). After the recognition 
 of the fact that all organic substances contain carbon, it was 
 thought that the difference between organic and inorganic 
 compounds could be explained by saying that the latter were 
 capable of preparation in the laboratory, but the former only 
 in the organism, under the influence of a particular force, the 
 life force vis vitalis (Berzelius). But this assumption was 
 rendered untenable when Wohler in 1828 synthetically pre- 
 pared urea, CON 2 H 4 , a typical secretion of the animal 
 organism, from cyanic acid and ammonia, two compounds 
 which were at that time held to be inorganic; and when, 
 shortly afterwards, the synthesis of acetic acid, by the use of 
 carbon, sulphur, chlorine, water, and zinc, was effected. 
 
 Since then so many syntheses of this kind have been achieved 
 as to prove beyond doubt that the same chemical forces act 
 both in the organic and inorganic worlds. 
 
 The separation of the two branches, Organic and Inorganic 
 Chemistry, from each other is, however, still retained for con- 
 venience sake, although the original reasons for this separation, 
 which at the time was more or less a matter of necessity, have 
 since been found to be erroneous. In consequence of the great 
 capacity of combining with one another which carbon atoms 
 possess, the number of organic compounds is extraordinarily 
 large, and in order to be in a position to study them, it is 
 necessary to have a knowledge of the other elements, including 
 
 (B480) 1 A 
 
this htetal?.: -This 'garbojx compounds, many of the most im- 
 portant bf which ntain k only carbon and hydrogen, or carbon, 
 hydrogen, and oxygen, also stand in a closer relationship to 
 each other than do the compounds of the other elements. 
 Partly upon grounds of convenience, carbon itself and some 
 of its principal compounds, such as carbonic acid, which is 
 so widely distributed in the mineral kingdom, are treated of 
 under Inorganic Chemistry. 
 
 The expressions "organic" and "organized" substances 
 should not be confused; organized substances, e.g. leaves, 
 nerves and muscles, and also the life-processes which go on 
 in the interior of the organism, are treated of under Physiology 
 and Physiological Chemistry. 
 
 Constituents of the Carbon Compounds 
 
 Many organic substances are composed of carbon and hydro- 
 gen only, and are then termed hydrocarbons, for instance, 
 ethylene, benzene, petroleum, naphthalene, and oil of turpen- 
 tine; a vast number consist of carbon, hydrogen, and oxygen, 
 for instance, wood spirit, alcohol, glycerine, aldehyde, oil of 
 bitter almonds, formic acid, acetic acid, stearic acid, tartaric 
 acid, benzoic acid, carbolic acid, tannic acid, and alizarin; 
 many compounds contain carbon, hydrogen, and nitrogen, 
 for instance, prussic acid, aniline, and coniine; as examples 
 of compounds containing carbon, hydrogen, nitrogen, and 
 oxygen, may be taken urea, uric acid, indigo, morphine, and 
 quinine. In addition to these, sulphur, chlorine, bromine, 
 iodine, phosphorus, and, generally speaking, the larger number 
 of the more important elements, are also frequent constituents 
 of the carbon compounds. 
 
 Qualitative Analysis of Organic Compounds 
 
 The presence of Carbon in a compound is often proved by 
 the "carbonization" of the latter, e.g. starch, sugar, &c., when 
 heated in a glass tube, or when warmed with concentrated 
 sulphuric acid. Carbon compounds which readily volatilize, 
 e.g. alcohol, chloroform, acetic acid, do not give these tests, 
 but many of them deposit carbon when their vapours are led 
 through a red-hot tube. The best proof of the presence of 
 carbon is obtained by completely oxidizing the organic com- 
 pound by either heating it with copper oxide (see below), or 
 
QUALITATIVE ANALYSIS 3 
 
 by leading its vapour over the glowing oxide. The carbon 
 present is thus converted into carbon dioxide, and the Hydro- 
 gen into water. 
 
 Nitrogen in organic compounds is recognized 
 
 (a) Frequently by a smell resembling that of burnt hair, 
 upon heating; 
 
 (b) Frequently by the presence of red fumes, or by explosion, 
 upon heating (nitro- and diazo-compounds); 
 
 (c) In many cases by the liberation of ammonia upon heating 
 with soda-lime (Wohler)-, 
 
 (d) In all cases by heating with potassium (and in most 
 cases with sodium), and testing the metallic cyanide formed 
 (see Cyanogen Compounds) by dissolving the fused mass 
 in water, adding a few drops of ferrous sulphate solution, 
 boiling, and acidifying with hydrochloric acid (formation of 
 Prussian Blue) ; or by converting the cyanide into thiocyanate, 
 and proving the presence of the latter by means of the blood- 
 red coloration with ferric chloride. [See tests for hydrocyanic 
 acid (Lassaigne).] If sulphur be likewise present, iron filings 
 must be added. 
 
 Testing for the Halogens. Direct precipitation by nitrate 
 of silver is usually not practicable; thus, no chlorine can bo 
 detected in chloroform even upon boiling it with AgN0 3 . 
 The halogens are therefore tested for: 
 
 (a) By heating the substance on a platinum wire with cupric 
 oxide in the Bunsen flame, or by causing the vapour of the 
 compound to pass over glowing copper gauze; in this way 
 chlorine gives first a blue and then a green flame coloration, 
 and iodine a green (Beilsteiri) ; 
 
 (b) By heating the substance strongly with pure lime, and 
 testing the solution of the naloid calcium salt produced with 
 silver nitrate; 
 
 (c) By heating in a sealed tube with fuming nitric acid and 
 nitrate of silver, when the haloid silver salt is produced 
 (Carius). 
 
 Testing for Sulphur: 
 
 (a) In many cases, upon boiling with an alkaline solution 
 of lead oxide, brown sulphide of lead is formed (e.g. white of 
 
 e gg); 
 
 (b) By heating with sodium, and testing the resulting sodium 
 sulphide with water upon a silver coin (black stain); or by 
 means of sodium nitroprusside solution (purple-violet colora- 
 tion) (Schonri); 
 
4 INTRODUCTION 
 
 (c) By complete oxidation in the dry way, by fusing with 
 potassium carbonate and nitre, or by heating with mercuric 
 oxide and sodium carbonate; or in the wet way, by fuming 
 nitric acid (Carius), and testing the sulphuric acid produced, 
 by barium chloride solution. 
 
 In like manner Phosphorus is converted by complete oxida- 
 tion into phosphoric acid; or, upon heating with powdered 
 magnesia, and moistening the resulting mass with water, 
 the presence of phosphuretted hydrogen can be recognized 
 (Schonn). 
 
 All the other Elements are tested for, after complete oxida- 
 tion of the compound (preferably by Carius' method), in the 
 usual way. 
 
 Another method (B. 1904, 37, 2155) is to heat a small 
 amount of the substance with sodium peroxide and twenty- 
 five times its weight of naphthalene or cinnamic acid in an 
 iron tube, and then test for haloids, sulphates, phosphates, &c. 
 
 Quantitative Organic or Elementary Analysis 
 
 Estimation of Carbon and Hydrogen (Combustion). The 
 substance is oxidized by heating it to redness with cupric 
 oxide (Liebig), or with other substances which readily give up 
 oxygen, such as lead chromate, platinum and oxygen (Denn- 
 stedt)* &c., in a tube of difficultly fusible glass, which is 
 open either at one or at both ends. 
 
 The carbon dioxide, thus produced by the oxidation of the 
 carbon, is absorbed by a concentrated solution of caustic pot- 
 ash contained in specially shaped bulbs,* and the water, pro- 
 duced by the oxidation of the hydrogen, in a U-shaped calcic 
 chloride tube, both tubes being weighed before and after the 
 combustion. If the substance (0'2 to 0*3 grm.) is solid, it 
 is either mixed with fine, dry copper oxide (Liebig, Jlunsen), or 
 placed in a porcelain or platinum boat and burnt in a stream 
 of air or oxygen (open tube). Liquids are weighed out in 
 small tubes or thin sealed glass bulbs. When nitrogen is 
 present, a coil of tightly -rolled copper-wire gauze is placed 
 in the front part of the combustion tube and heated to red- 
 ness, in order to reduce any oxides of nitrogen which may 
 be formed in the subsequent combustion. In the presence of 
 sulphur or of the halogens, lead chromate, which has been 
 
 * For details see Sudborough and James' Practical Organic Chemistry, 
 Chap. V, B. 
 
QUANTITATIVE ANALYSIS 6 
 
 fused and then powdered, is used instead of copper oxide, so 
 as to convert any Cl, S0 2 , &c., into PbCl 2 , PbS0 4 , &c., and thus 
 prevent them from passing into the potash solution. When 
 only halogens, without sulphur, are present, the combustion is 
 carried out with copper oxide, a copper, or still better a silver 
 spiral, which is kept cool, being placed in the fore-part of the 
 tube to retain the halogens. 
 
 In the presence of alkalis or alkaline earths (which would 
 retain carbon dioxide), lead chromate mixed with -^ of its 
 weight of potassic bichromate is used; the chromic acid then 
 expels all the carbonic acid. 
 
 Explosive compounds must be burnt in a vacuum. From 
 the weights of carbon dioxide and water found, the percentages 
 of C and H are readily calculated: 
 
 C = AC0 2 ; H = i Hs(X 
 
 Estimation of Nitrogen. This estimation is either relative 
 or absolute. In the former case the proportion between the 
 nitrogen and the carbon dioxide evolved is determined (LieUg, 
 Bunsen); in the latter the nitrogen is either estimated as such 
 volumetrically, or as ammonia. 
 
 The conversion into Ammonia is effected by heating the 
 substance strongly with soda-lime (Will, Farrentrapp), or by 
 creating it with strong sulphuric acid and permanganate of 
 potash (Kjeldahlj Z. Anal. Ch. 22, 366; also B. 19, Kef. 852; 
 24, 3241; 27, 1633). The ammonia is then either titrated 
 directly by absorption in standard acid, or transformed into 
 ammonium platinichloride, (NH 4 ) 2 PtCl 6 , which is weighed, 
 or else ignited, and the weight of the residual metallic pla- 
 tinum noted. 
 
 In the Gasometric Estimation of Nitrogen the substance is 
 mixed with copper oxide, a copper spiral being also used in 
 the front part of the tube, and the combustion is carried out 
 in the usual way, but in a stream of carbon dioxide; the C0 2 
 is either generated from magnesite in the tube itself, or led 
 through it. The nitrogen is collected over mercury and 
 aqueous caustic potash (Dumas), or directly over potash 
 (ZulkowsJcy, Schwarz, Scliiff, &c.), in some special form of 
 nitrometer. 
 
 Its percentage is obtained by reducing the volume to the 
 volume at normal temperature and pressure, determining the 
 -weight of this volume of nitrogen from the fact that 1 c.c. of 
 
6 INTRODUCTION 
 
 dry nitrogen at and 760 mm. weighs 1*2489 mg., and ex- 
 pressing the result in percentage. 
 
 The Gasometric method may be used for all classes of 
 nitrogen compounds, but the Soda-lime method cannot be used 
 for nitro compounds, certain bases, and various other groups 
 of compounds, as the nitrogen of these is not completely 
 transformed into ammonia upon heating with soda-lime. 
 
 For the simultaneous determination of carbon, hydrogen, 
 and nitrogen the combustion must be carried on in a stream 
 of pure oxygen, the mixture of gases escaping from the potash 
 bulbs being collected over a solution of chromous chloride, 
 which absorbs the oxygen, but not the nitrogen (A. 1886, 
 233, 375). 
 
 Estimation of Sulphur and Phosphorus. The Sulphur is 
 estimated as sulphuric acid, being converted into this 
 
 (a) In the wet way, by heating the substance with fuming 
 nitric acid at 150-300 in a sealed tube (Carius), or in a com- 
 bustion-tube in a mixed stream of nitric oxide and oxygen 
 (Claessori), or nitric acid vapour (Klasori). 
 
 (b) In the dry way (and this method is only available in 
 the case of the less volatile compounds) by fusing the sub- 
 stance with potassic hydroxide and nitre, or with soda and 
 chlorate or chromate of potash, also by heating with soda and 
 mercuric oxide, or with lime in a stream of oxygen. 
 
 Phosphorus is estimated by analogous methods. 
 Estimation of the Halogens. Here also the organic sub- 
 stance is completely decomposed 
 
 (a) After Carius, as above, in a sealed tube, with fuming 
 nitric acid and solid silver nitrate, by which means the halogen 
 is converted into its silver salt; 
 
 (b) By heating the compound strongly with pure lime in a 
 hard glass tube, or in two crucibles, one of which is inverted 
 in the other, or with sodic carbonate and nitre in a tube. The 
 chloride formed is precipitated with silver nitrate in the usual 
 way; 
 
 (c) By the action of nascent hydrogen (sodium and alcohol), 
 the halogen in the organic substance can frequently be con- 
 verted into its hydrogen compound (Stepanow). 
 
 Dennstedt, B. 1897, 30, 1590, 2861, has described methods 
 for estimating C, H, Cl, and S in one operation. 
 
 Metallic and acidic radicals, contained in organic salts, can 
 often be estimated directly by the usual methods. 
 
 Oxygen is almost invariably determined by difference j direct 
 
DETERMINATION OF MOLECULAR WEIGHT 7 
 
 methods of estimation have been proposed by Baumhauer, Laden- 
 burg, Stromeyer, and others. 
 
 The carbon estimation is usually too low (0"05 O'l), owing 
 to leakage and incomplete absorption, that of hydrogen too 
 high (0-1 0'2), owing to the difficulty of completely drying 
 the cupric oxide. Nitrogen estimations are also usually too 
 high, owing to the difficulty of completely freeing the carbon 
 dioxide from air. 
 
 The Calculation of the Empirical Formula 
 
 The same principle applies here as in the case of inorganic 
 compounds, i.e. the percentage numbers found are divided by 
 the atomic weights of the respective elements, the relative pro- 
 portions of the quotients obtained being expressed in whole 
 numbers. For instance, acetic acid being found to contain 
 40-11 p.c. carbon, 6 '80 p.c. hydrogen, and, consequently, 53*09 
 p.c. oxygen, the quotients are to each other as 3-34 : 6 -80 : 3 -32 
 = 1:2:1. The simplest analysis-formula of acetic acid would 
 therefore be CH 2 0. Sometimes figures are obtained which 
 correspond with equal nearness to different formulae, between 
 which it is therefore impossible, without further data, to 
 choose. 
 
 For instance, a sample of naphthalene yields on analysis 
 93-70 p.c. carbon and 6 '30 p.c. hydrogen; the quotient pro- 
 portion here is 7 -81 to 6'30 = 1-239:1, which corresponds 
 equally well with the numbers 5:4 or 11:9. The formula 
 C 5 H 4 requires 93'75 p.c. carbon and 6-25 p.c. hydrogen, and 
 the formula C n H 9 , 93-62 p.c. carbon and 6*38 p.c. hydrogen, 
 the deviations from the actual numbers found being in both 
 cases within the limits of experimental error. Therefore other 
 considerations must be taken into account here, in order to 
 decide between the two formulae. 
 
 The formula derived from the results of analyses is termed 
 the Empirical Formula, and expresses the simplest numerical 
 relationship between the atoms of the elements present. The 
 actual molecular formula may be a multiple of this, and has to 
 be determined according to special principles. 
 
 Determination of Molecular Weight 
 
 1. BY CHEMICAL METHODS. 
 
 Our chemical formulae (e.g. CH 2 0) express not merely a 
 
8 INTRODUCTION 
 
 percentage relation, but at the same time the smallest quantity 
 of the compound which is capable of existing as such, i.e. a 
 molecule of it. This molecule is ideally no longer divisible ' * 
 mechanical means, but only by chemical, and then into its J 
 stituent atoms. If the formula CH 2 were the correct on/f( 
 acetic acid, then the amount of oxygen (or carbon) contained ii 
 a molecule would be indivisible, and that of hydrogen divrsibl 
 only by 2. Since, however, it has been observed that ; on< 
 fourth of the total hydrogen in acetic acid is replaceable, e.l 
 by a metal, with the formation of a salt, it is obvious that ' ' 
 quantity of hydrogen in the molecule must be divisible 
 and so the formula must contain at least 4 atoms of hydro^ 
 and must therefore be C 2 H 4 2 , or some multiple of it. 1 
 is, in fact, the case. Acetate of silver contains 64 '67 p.c. sil 1 
 and therefore 35*33 p.c. of the acetate radical; or, to 1 aton 
 silver =108 parts by weight, there are 59 parts by weigh] 
 the acid radical. This 59, together with 1 atom of hydro! 
 = 1, makes the molecular weight of acetic acid 60, = 2 x 
 = 2 x CH 2 0, = C 2 H 4 2 . 
 
 This is a determination of molecular weight by chemi 
 means. Such determinations are carried out in the easel 
 acids generally by means of their silver salts; these are iisi 
 normal salts, are easy to purify, are almost always 
 from water of crystallization, and are readily analysed, 
 is, however, absolutely necessary to know whether the 
 is mono- or polybasic. In the case of a di-, tri-, &c., basic 
 the above calculation must be made with reference to 2, 
 &c., atoms of silver, whereas acetic acid being monobasic! 
 contains only one replaceable atom of hydrogen, which \ 
 therefore exchanged for one atom of silver. Consequent^, 
 its formula cannot be a multiple of C 2 H 4 2 . 
 
 In the determination of the molecular weights of Bases, theii 
 platinichlorides are similarly made use of, these being almost 
 always constituted on the type of ammonium platinichloride : 
 (NH 3 ) 2 H 2 PtCl 6 : i.e. they contain two molecules of a mono- 
 acid base such as ammonia combined with one atom of 
 platinum. 
 
 To determine the molecular weights of Neutral Compounds, 
 derivatives must be prepared and examined for the proportion 
 of the total hydrogen which is replaceable, e.g., by chlorine. 
 For example, by the action of chlorine upon naphthalene, 
 there is first formed the substance monochloronaphthalene, 
 which contains 73'8 per cent 0, 4 -3 per cent H, and 21-9 per 
 
DETERMINATION OF MOLECULAR WEIGHT 9 
 
 cent Cl, these numbers giving the formula C 10 H r Cl. In the 
 same way benzene yields the compound C 6 HcCl. In both 
 these cases the halogen ajts by replacing hyarogen, and at 
 least one atom of the latte in the molecule must be replaced, 
 since fractions of an atom are necessarily out of the question. 
 If, then, the compound oltained has the formula C 10 H 7 C1, it 
 follows that |^th of the H present has been replaced by Cl, 
 and there must consequently be 8, 8 X 2, or 8 X 3, &c., atoms 
 of hydrogen in the compound, and likewise 10 atoms, or some 
 multiple of 10, of carbon. But a multiple of 8 or 10 may be 
 rejected, since no compounds have been observed which would 
 indicate the replacement of T Vth of the total hydrogen. This 
 leads to the formula C 10 H 3 for naphthalene, the other possible 
 formula got by analysis viz. C n H 9 (see p. 7), being now 
 untenable. In a similar way the formula of benzene is found 
 to be C 6 H 6 . 
 
 2. BY PHYSICAL METHODS. 
 
 (a) By Estimating the Fapour Density. 
 
 According to the law of Avogadro (1811) and Ampere (1814), 
 all gases under similar conditions, i.e. in the perfectly gaseous 
 state and under the same temperature and pressure, contain in 
 equal volumes equal numbers of molecules. It follows from 
 this that the weights of equal volumes of different gases are 
 proportional to the weights of equal numbers of their con- 
 stituent molecules, in other words, the molecular weight is 
 proportional to the specific gravity of the gas. Thus, if M x be 
 the molecular weight of any given substance required, M 
 that of oxygen, S the vapour density or specific gravity of the 
 former as compared with oxygen taken as 16*, 
 
 M X :M = S:16. 
 
 And since M = 32, M x = S X 2. To determine, therefore, 
 the molecular weight of a gas or vapour, one has only to find 
 its density, and to multiply this by 2. 
 
 To take an example, the specific gravity of acetic acid 
 vapour being found to be 30, then M = 60, and the mole- 
 cular formula is C 2 H 4 2 = 60. 
 
 * Oxygen is taken as standard (0 = 16) for vapour density, since it is now 
 customary to take it as standard in atomie-weight determinations. For all 
 practical purposes, one may take the density compared with hydrogen as 
 unity. 
 
16 INTRODUCTION 
 
 It is essential to the application of this method that the 
 temperature of the vapour shall be so high above the boiling- 
 point of the substance that the latter is in the perfectly gaseous 
 state, remaining at the same time undecomposed. 
 
 The only common method employed in the chemical labora- 
 tory for vapour-density determinations is that due to Victor 
 and Carl Meyer. In this process the small tube containing 
 the substance is dropped into a vertical glass tube, the lower 
 and wider part of which is cylindrically shaped and sealed. 
 This is kept warm at a constant temperature, being surrounded 
 by a long glass mantle in which a suitable liquid boils, the 
 upper part of the mantle itself serving for the condensation of 
 the vapour. The displaced air alone escapes, and is collected 
 over water and measured. No determination, therefore, of 
 the temperature of the vapour of the substance in question is 
 required. Only about Ol grm. substance is required. In all 
 cases the vapour density is the weight of the vapour, divided 
 by the weight of an equal volume of hydrogen (see note, p. 9), 
 which can readily be calculated in the usual manner. 
 
 If, instead of having the apparatus filled with air, hydrogen 
 is employed, the greater molecular velocity of the latter 
 allows of the conversion of substances into vapour at 30-40 
 below their ordinary boiling temperatures (V. Meyer and De- 
 muth, B. 1890, 23, 311). 
 
 Until a few years ago, the determination of molecular weights 
 by physical means was restricted to the different modifications 
 of the method which has just been described, and consequently 
 it could only be carried out with substances which were either 
 already gaseous, or which could be rendered so without decom- 
 position. 
 
 The recent important researches of van't Hoff, Eaoult, Ar- 
 rhenius, Ostwald, and others, upon the nature of solution in 
 particular, the proof that the laws of Boyle, Gay-Lussac, and 
 Avogadro are applicable to solutions as well as to gases now 
 permit, however, of the ready determination of the molecular 
 weights of substances in solution, and therefore of compounds 
 which could not be volatilized without decomposition. This is accom- 
 plished as follows : 
 
 (b) By Measuring the Depression of the Freezing Tempera- 
 ture of Solutions, or Cryoscopic Method. 
 
 This method is based upon the following data : Each solvont 
 has a perfectly definite freezing-point (e.g. water 0, benzene, 
 
DETERMINATION OF MOLECULAR WEIGHT 11 
 
 5'0, and glacial acetic acid, 16-75), but the introduction of a 
 solute into such a solvent lowers the freezing-point, and within 
 certain limits the lowering is directly proportional to the con- 
 centration of the solute. Raoult has shown that gram mole- 
 cules of different substances dissolved in equal weights of the 
 same solvent lower the freezing-point of the solvent to. the 
 same extent, or " equimolecular solutions have the same 
 freezing-point ". The molecular lowering of the freezing-point 
 is the lowering which would be produced when ,the gram 
 molecule (M) of the substance was dissolved in 100 grams of 
 solvent, and is usually denoted by C. This varies for different 
 solvents, and may be determined experimentally by using 
 substances of known molecular weight, e.g., p grams of a sub- 
 stance of molecular weight M dissolved in 100 grams of 
 solvent caused a depression of A in the freezing-point of 
 the solvent. 
 
 'A = depression for p grams in 100 grams of solvent 
 
 
 M 100 
 . C = M|- 
 
 The value C may also be calculated theoretically from van't 
 
 2T 2 
 
 Hoffs equation C = , where T =. absolute freezing- 
 
 100 L 
 
 point of the solvent, and L is the latent heat of fusion of the 
 solvent. 
 
 Having determined the value C (for water C = 18-5, for 
 glacial acetic acid 39, and for benzene 50), we may use the 
 same equation 
 
 C = M- or M = 9? 
 p A 
 
 for calculating M when A = lowering of the freezing-point 
 produced by dissolving p grams of a substance of unknown 
 molecular weight M in 100 grams of solvent. 
 
 It is obvious that this method cannot be employed with 
 satisfactory results for determining the molecular weights of 
 electrolytes in ionizing media. It has also been found that 
 certain hydroxylic substances give abnormal values in benzene 
 solution, owing to the fact that benzene tends to cause the 
 association of molecules of such compounds. 
 
 Ebulliscopic Method. Molecular weights may also be 
 determined by the raising of the boiling-point of a suitable 
 
12 INTRODUCTION 
 
 solvent produced by the introduction of known weights of 
 the substance into a given weight (or volume) of the solvent. 
 The principles involved are exactly the same as those dis- 
 cussed above in the cryoscopic method, but the forms of 
 apparatus are different. (J. C. S. 1898, 73, 502.) 
 
 Descriptions of apparatus employed in these physical 
 methods are given in Sudborough and James' Practical Or- 
 ganic Chemistry, Chap. VIII. 
 
 (c) By Measurement of the Osmotic Pressure. 
 According to van't Hoff (Z. phys. Chem. I. 481), equimole- 
 
 cular solutions exert the same osmotic pressure, or are isotonic, 
 equality of temperature being assumed. From this it follows, 
 by reasoning analogous to that in section (&), that the mole 
 cular weight of a compound can be ascertained by measuring 
 the osmotic pressure of its solution. The method is rarely 
 used in chemical laboratories. (Ladenburg, B. 1889, 22, 1225; 
 M. Planck, Z. phys. Chem., 1890, 6, 187.) 
 
 (d) By Measurement of the Lowering of the Vapour Pressure. 
 
 According to Eaoult, the same generalizations hold for the 
 lowering of the vapour pressure of a solvent by the introduc- 
 tion of a solute, as for the lowering of the freezing-points or 
 the raising of the boiling-point. Three methods of applying 
 the principle for the determination of molecular weights have 
 been described. This law can be deduced theoretically from the 
 preceding one (c), and it also stands in theoretical continuity 
 with that of (b). (See Will & Bredig, B. 1889, 22, 1084; 
 Barger, J. C. S. 1904, 85, 206; Perman, ibid. 1905, 87, 194; 
 Blacbnan, ibid. 1474.) 
 
 (e) By Measuring the Decrease in Solubility. 
 (Nernst, B. 23, Eef. 619. See also Ostwald-Luther.) 
 
 Polymerism and Isomerism 
 
 The determination of molecular weight is of the first im- 
 portance, because different substances very frequently have the 
 same percentage composition and therefore the same empirical 
 formula, and yet are totally distinct from one another. This 
 difference is often due to differences in the complexities of the 
 molecules. Thus formic aldehyde, CH 0; acetic acid, C 2 H 4 2 ; 
 lactic acid, C 3 H 6 3 ; and grape-sugar, C 6 H 12 G , have all the 
 same percentage composition; as have also ethylene, C 2 H 4 ; 
 
THEORY OF VALENCY 13 
 
 propylene, C 3 H 6 ; and butylene, C 4 H 8 . Compounds standing 
 in such relation to each other are termed polymers. Very 
 frequently, however, substances which are totally distinct 
 from each other possess both the same percentage composition 
 and the same molecular weight; that is to say, these com- 
 pounds are made up not only of the same elements, but also 
 of an equal number of atoms of these elements; such sub- 
 stances are termed isomers or metamers. (See Ethers.) 
 Thus, for instance, common alcohol and methyl ether, the 
 latter of which is obtained by heating methyl alcohol with sul- 
 phuric acid, have one and the same molecular formula, C 2 H 6 0. 
 The striking phenomenon of isomerism is most readily ex- 
 plicable on the assumption that for the molecule of each com- 
 pound there is a definite arrangement of the atoms, and that 
 this arrangement or grouping is different in the molecules of 
 the two isomerides. This difference in grouping may be con- 
 sidered as being due to a difference in the linking powers of 
 the atoms, as is indicated by the dissimilar chemical behaviour 
 of isomers, and explained by the theory of valency. 
 
 Chemical Theories; the Theory of Valency 
 
 After the fall of the Electro - Chemical theory, unitary 
 formulae in contradistinction to the earlier dualistic formulae 
 were much used; thus alcohol had the formula C 4 H 6 2 
 (using the old equivalent weights). The necessity for com- 
 paring substances of complicated composition with simpler 
 ones, taken as " Types ", had already repeatedly led to the 
 propounding of new theories for representing the constitution 
 of organic compounds, e.g. the older Type theory (Dumas), and 
 the Nucleus theory (Laurent). 
 
 These obtained a firmer basis through Gerhardfs Theory of 
 Types, which received support more especially from the dis- 
 covery of ethylamine and other ammonia bases (Wurtz, 1849, 
 and Hofmann, 1849, 1850), the proper interpretation of the 
 formulae of the ethers (Williamson, 1850), and the discovery 
 of the acid anhydrides (GerharcU, 1851). All compounds, 
 inorganic as well as organic, were in this way compared with 
 simpler inorganic substances taken as " Types", of which 
 Gerhardt named four, viz. 
 
 \ H\ H1 SUr 
 
 I ClI H/ || N 
 
14 INTRODUCTION" 
 
 The first two of these really belong to the same type. Thus 
 the following formulae were arrived at: 
 
 : g} 5) 
 
 Potassium chloride Ethyl chloride Acetyl chloride 
 
 )0 1)0 N H }0 
 
 Potassium hydroxide Nitric acid Alcohol Acetic acid 
 
 Potassium oxide Nitric anhydride Ether Acetic anhydride 
 
 C 2 H 6 ) C 2 H 3 0) 
 
 H ^N H VN 
 
 H J H J 
 
 Ethylamine Acetamide 
 
 &c. &c. Organic compounds could thus, like inorganic, be 
 referred to inorganic types by assuming in them the presence 
 of Radicals (e.g. ethyl, C 2 H 5 ; acetyl, C 2 H 3 0, &c.), i.e. of groups 
 of atoms which play a part analogous to that of an atom of 
 an element, and which can be transferred by double decom- 
 position from one compound to another. Thus ethyl chloride, 
 C 2 H 5 C1; alcohol, C 2 H 0; ethylamine, C 2 H 7 N; ether, C 4 H 10 0; 
 &c., were represented as containing the same radical C 2 H 5 , 
 ethyl, and the close relationship existing between these com- 
 pounds now found expression in the type formulae. 
 
 Sulphuric acid, H 2 S0 4 , was derived from the double water- 
 type, thus 
 
 and chloroform, CHC1 3 , and glycerin, C 3 H 8 3 , from the triple 
 hydrochloric acid and water types 
 
 the assumption being made that the radicals (C 2 H 5 )', (S0 2 )", 
 (CH)"', and (C 3 H 5 )"' could replace a number of hydrogen atoms 
 corresponding with the number of accents (') marked upon them, 
 %,e. that they were monatomic, diatomic, &c. To the above 
 
THEORY OF VALENCY 16 
 
 three types KekuU afterwards added a fourth, of especial im- 
 portance as regards the carbon compounds, viz. 
 
 It was then found that many compounds could be referred 
 equally well to one or another of these types, methylamine, 
 for instance, either to CH 4 or to NHg, thus 
 
 CH,} 
 or H IN. 
 
 The assumption, already mentioned, of the atomic groups 
 (radicals) which in these types replaced hydrogen, led further 
 to more exact investigations of the chemical value, i.e. the 
 replaceable value, of those groups as compared with that of 
 hydrogen. In this way chemists Learnt to distinguish between 
 mono-, di-, tri-, &c., valent groups, and, generally speaking, to 
 pay more attention to equivalent proportions. 
 
 As the outcome of his researches upon organo-metallic com- 
 pounds, Frankland formulated in 1852 (A. 85, 368) the law 
 that the elements nitrogen, phosphorus, arsenic, and antimony 
 tend to form compounds which contain three or five equivalents 
 of other elements. 
 
 KekuU then, in 1857-58 (A. 104, 129; 106, 129), proceeded 
 to show that a more profound idea (the " Type idea ") lay at 
 the root of the types themselves, viz., that there are mono-, 
 di-, tri-, and tetra valent, &c., elements, which possess a corre- 
 sponding replacing or combining value as regards hydrogen; 
 and that hydrogen is therefore monovalent, oxygen divalent, 
 nitrogen trivalent, carbon tetravalent, and so on. 
 
 With the introduction of the CH 4 type by Kekuli, and the 
 establishment of the tetravalent nature of the carbon atom 
 accompanying this, were connected the endeavours of Kolbe 
 to derive the constitution of organic compounds from carbonic 
 acid (according to Kolbe C 2 4 , C = 6, = 8), by the ex- 
 change of oxygen for organic radicals (A. 113, 293); see also, 
 for further details, Kopp's " Entwickelung der Chemie in der 
 neueren Zeit" (Oldenbourg, Munich, 1873), and E. V. Meyer's 
 
16 INTRODUCTION 
 
 " History of Chemistry " (Macmillan, 1891), Schorlemmer's "Rise 
 and Development of Organic Chemistry " (Macmillan). 
 
 The question of the valency of elements, a point which it Is 
 often difficult to decide in inorganic chemistry, is infinitely 
 easier of determination in the case of the carbon compounds, 
 because the carbon atom is tetravalent towards hydrogen as 
 well as towards chlorine and oxygen. Since the atom of 
 hydrogen, as the unit of valency, is monovalent, and, further, 
 since the divalence of the oxygen atom cannot reasonably be 
 doubted, the valency of the three " organic " elements hydrogen, 
 oxygen, and carbon may be considered as resting upon a sure 
 basis, as may also the conclusions drawn therefrom, and this 
 all the more since the most important carbon compounds are 
 made up of those three elements. 
 
 Within the past few years the divalency of the oxygen 
 atom in many organic compounds has been brought into ques- 
 tion. The readiness with which many oxy-derivatives form 
 definite compounds with mineral acids and with metallic salts 
 would appear to indicate that in many cases the oxygen atom 
 can even be tetravalent (see Oxonium Salts). In certain com- 
 pounds it has also been suggested that the carbon atom may 
 be trivalent (see Triphenylmethyl). 
 
 Explanation of Isomerism; Determination of the 
 Constitution of Organic Compounds 
 
 The phenomenon known as isomerism is elucidated to a 
 great extent by the theory of valency. If two substances 
 have the same molecular formula, i.e. both contain the same 
 elements and the same number of atoms of the respective 
 elements in their molecules, then the obvious conclusion to 
 be drawn is that in the two molecules the atoms are differently 
 arranged. The methods adopted in determining the manner 
 in which the atoms are linked together, or, as it is called, the 
 determination of the chemical constitution of the compound, 
 is usually based on the following points: (a) The respective 
 valencies of the atoms constituting the molecule. A compound 
 
 C 9 EL must have the structural formula H-)CC^-H, or, as 
 
 H/ X H 
 
 it is often more shortly written, CH 3 CH 3 , if each atom of 
 carbon is to be represented as tetravalent, and each hydrogen 
 atom as monovalent. Similarly the compound CH 4 must be 
 
DETERMINATION OF CONSTITUTION 17 
 
 TT TT 
 
 represented as TTX^XO _ H' or ^ 3 ' ^"^ ^ ^ e car ^ on atom 
 j^ tetravalent, the oxygen atom divalent, and the hydrogen 
 atoms monovalent. (b) A study of the more important methods 
 of formation and of the chemical reactions in which the com- 
 pound in question can take part. To select as an example 
 ethyl alcohol, C 2 H 6 0. We can start from ethane, CH 3 CH 3 , 
 and by the action of chlorine replace one of the hydrogen 
 atoms by a chlorine atom, and thus obtain the compound 
 CH 3 .CH 2 C1. When this is boiled with dilute alkalis (KOH), 
 it gives potassic chloride and ethyl alcohol, C 2 H 5 C1 + KOH = 
 C 2 H 6 -f KC1. From this it is obvious that the monovalent 
 chlorine atom becomes replaced by an atom of oxygen and 
 an atom of hydrogen. This can be readily understood if 
 we assume that these two atoms enter in the form of the 
 monovalent hydroxyl group, O H, and the constitutional 
 
 Hv /H 
 
 formula for ethyl alcohol would then be H-^C C^-H 
 
 W X) H 
 
 CH 3 CH 2 OH. This formula is further supported by a study 
 of most of the chemical reactions in which ethyl alcohol can 
 take part. It can react with metallic sodium, yielding a com- 
 pound, sodic ethoxide, C 2 H 5 NaO; however much sodium is 
 employed, only one of the six hydrogen atoms present in the 
 alcohol molecule can be replaced by sodium, and this atom is 
 presumably the one differently situated from the remaining 
 five, namely, the one attached to oxygen. The presence of 
 the hydroxyl, H, group is further confirmed by the 
 action of hydric chloride or of phosphorus trichloride on the 
 alcohol, when an atom of chlorine takes the place of the OH 
 group. 
 
 or 
 
 and 3CH 3 .CH 2 .OH + PC1 3 = 3CH 3 .CH 2 C1 + P(OH) 3 . 
 
 Isomeric with ethyl alcohol is the substance known as 
 dimethyl ether. Although it has the same molecular formula, 
 it differs altogether from ethyl alcohol in its chemical and 
 physical properties. The only other possible method of link- 
 
 ing up the atoms 2C, 6H, and 0, is H^C O C^H, in 
 
 which the two carbon atoms are not directly united to one 
 another, and in which the six hydrogen atoms are all similarly 
 
 (B480) B 
 
18 INTRODUCTION 
 
 situated. The chemical reactions of dimethyl ether are in per- 
 fect harmony with this constitutional formula. It does not 
 react with metallic sodium, and hence presumably does not 
 contain an OH group. When acted upon by hydriodic acid, 
 under suitable conditions, the molecule is ruptured, as repre 
 sented by the following equation: 
 
 CH a .O.CH 3 -f HI = CH 3 I + CH 3 .OH. 
 
 Similarly, whenever the oxygen atom is removed a rupture 
 of the molecule occurs, and the two carbon atoms in the mole- 
 cule become separated. 
 
 The constitutional formula for acetic acid is written 
 
 H \ O 
 
 H-pC C^Q TT- This formula corresponds perfectly with 
 
 the chemical behaviour of acetic acid and explains the fol- 
 lowing facts: (a) that one of the hydrogen atoms of the acid 
 possesses properties different from those of the three others, 
 the first-named being easily replaceable by metallic radicals; 
 (b) that the two oxygen atoms behave differently, not being 
 equally readily exchangeable for other radicals; (c) that dif- 
 ferent functions appertain to the two carbon atoms, so that 
 one of them being already joined to two atoms of oxygen 
 easily gives rise to carbonic acid, while the other connected 
 as it is with three atoms of hydrogen readily passes into 
 methane or methyl compounds. 
 
 On account of the innumerable cases of isomerism which 
 have been observed, simple molecular formulae alone are in 
 most cases insufficient for the discrimination of organic com- 
 pounds; it generally requires the constitutional formulae to 
 give a clear idea of their behaviour and of their relations to 
 other substances. Careful study has made it possible within 
 the last few decades to find out the mode in which the atoms 
 are combined in the molecules of most organic compounds, and 
 from this to deduce new methods for their preparation. The 
 constitutional formulas thus arrived at are sometimes very 
 simple, sometimes, however, very complicated, as, for instance, 
 in the cases of citric acid and grape-sugar (which see). 
 
NATURE OF CARBON ATOM 19 
 
 Rational Formulae 
 
 Great latitude is permissible as regards the mode of writin* 
 constitutional formulae, according to the particular points 
 which it is desired to emphasize. A formula on paper is not 
 as a rule intended to represent the symmetrical or spatial 
 arrangement of the atoms in a compound. 
 
 A shortened constitutional formula, which indicates more 
 chemical relations than an empirical one does, is called a 
 rational formula; e.g. C 2 H 5 OH, alcohol; (CH 3 ) O, methyl ether. 
 
 For acetic acid, instead of the constitutional formula already 
 given on page 18, the following rational formulas may be 
 used: 
 
 CH 3 -C<OH, CH 3 -CO.OH, CH 3 -C0 2 H, CH 3 .C0 2 H, 
 (CH 3 .CO)OH, C S H 3 O.OH, H^A); and so on. 
 
 The Nature of the Carbon Atom 
 
 The theoretical views and the knowledge thereby gained of 
 the nature of the carbon atom may be expressed somewhat as 
 follows : 
 
 1. The carbon atom is tetravalent. 
 
 2. Its four valencies are all equal; a mono-substituted deri- 
 ative of methane exists in only one form, that is, isomerism is 
 ot met with. 
 
 3. The atoms or atomic groups which are held bound by 
 hese four valencies cannot readily exchange places with each 
 ther (the Le Bel-van 't Ho/ law, 1874). Proof: there are in 
 early every case two physically different tetra-substitution 
 roducts, C, a, b, c, d of methane (see Stereochemistry). 
 
 4. Several carbon atoms can be connected together by either 
 ne, two, or three valencies (see p. 23): CC, C:C, C:C. 
 
 5. Similarly, three or more carbon atoms may be united, 
 rming in this way the so-called "carbon chains" (see p. 32), 
 
 nus 
 
 The number of the atoms so linked together may be very 
 irge, in some cases probably several hundreds. 
 6. These carbon atoms form either open or ring-shaped 
 
 losed chains. 
 
20 INTRODUCTION 
 
 Open chains are those which have separate constituent atoms 
 at either end, as in (5). In closed chains or rings, on the con- 
 trary, the first and last constituent atoms are linked together 
 (although there may at the same time be subsidiary branches 
 from them), thus 
 
 A /x /V 
 
 A i, ^ A A. 
 
 \- 
 
 c-c-c. 
 
 7. The atoms of other elements, with the exception, of 
 course, of monovalent ones, may likewise take part in the 
 formation of such chains, both open and closed; for example: 
 
 C Cv C Cv sC (X 
 
 c <y c c/ \c-cx 
 
 The above figures (the hexagon, &c.), which are made use 
 of to represent such chains or rings, are merely meant to be 
 pictorial (schematised) and not geometrical; the question of the 
 spatial arrangement of atoms in compounds will be dealt with 
 later. 
 
 Homology 
 
 In the study of carbon compounds it is customary to grou 
 together all the compounds with similar chemical structur 
 and similar chemical properties, and to arrange the member 
 of such a group, or homologous series as it is termed, accordin 
 to the order of their molecular complexity, i.e. according t 
 the number of carbon atoms contained in the molecule. 
 
 For example: 
 
 Paraffins. Fatty acids. 
 
 methane ...... CH 2 O 2 formic 
 
 ethane ...... C 2 H 4 O 2 acetic 
 
 propane ...... C 3 H 6 O 2 propionic 
 
 o butane ...... C 4 H 8 2 butyric 
 
 &c. 
 
 It is found that in any such homologous series a number c 
 generalizations can be drawn. Some of the more important c 
 these are : 
 
 1. For each homologous series we can write a general f& 
 
HOMOLOGOUS SERIES 21 
 
 mula which will represent the composition of all the members 
 of the series; for example, the general formula for the paraffins 
 is C n H 3n+2 , and for the saturated fatty acids Cyi.^^ 
 
 2. If any particular member in a series is selected, it is 
 found to differ in composition from the member immediately 
 preceding, and also from the one immediately succeeding, it by 
 a definite amount, namely, CH 2 . Or, expressed in other words, 
 any member of the series may be regarded as derived from 
 the member immediately preceding it by the introduction of 
 a methyl group, CH 3 , for an atom of hydrogen. It follows, 
 therefore, that all the members of the paraffin series may be 
 regarded as derived from GEL by the addition of a given 
 number of CH 2 groups, and the general formula is for this 
 series CH 4 -f- CH 2 , or more simply 0^3^+ a- 
 
 3. The chemical properties of the different members of the 
 series vary but slightly, so that a description of the chemical 
 properties of any one member may be taken, as a rule, to 
 apply to the other members. 
 
 4. In studying the physical properties, well-marked grada- 
 tions are observed as the number of carbon atoms increases. 
 In the case of liquids, the boiling-point is found to rise as the 
 complexity of the molecule increases. In certain series, e.g. 
 the paraffins, the first few members are gases, then follow 
 liquids with gradually increasing boiling-points, and ultimately 
 solids with extremely high boiling-points. Other physical 
 data, such as melting-point, specific gravity, solubility, &c., 
 are affected in very much the same manner. 
 
 In the paraffin series the grouping together of the carbon 
 atoms must be conditioned by themselves, since hydrogen, as 
 a monovalent element, cannot be the cause of it. In all^the 
 higher hydrocarbons the carbon atoms are therefore combined 
 together in the form of a chain, as shown in the following 
 graphical representations : 
 
 C C 
 
 C, C, C'C-C'C, or C'C; and so on. 
 
 C C C 
 
 in C 2 H 6 in C 3 H 8 in C 4 H 10 
 
 Various cases can occur in the mode of combination of the 
 carbon atoms (Isomers). (See Hydrocarbons of the Methane 
 Series.) 
 
 Law Q f Even Numbers of Atoms. The u^ ber of hydrogen 
 
22 INTRODUCTION 
 
 atoms in the above hydrocarbons is always divisible by two. 
 Should they therefore be partially replaced by other elements, 
 the sum of these latter, if their valencies are expressed by odd 
 numbers, e.g. Cl, N, and P, and of the remaining hydrogen 
 atoms taken together must, as a necessary consequence of the 
 law of equivalent proportions, remain an even number. 
 
 Radicals 
 
 According to LieUg, radicals were groups of atoms capable 
 of a separate existence, which played the parts of elements, 
 and, like these latter, could combine among themselves and be 
 exchanged from one compound to -another. 
 
 Later on, the postulate that such radicals must also be 
 capable of existing in the free state was allowed to lapse, and 
 they were frequently defined shortly as "the residues left un- 
 attacked by certain decompositions ". 
 
 Now, however, it is usual to designate as radicals only those 
 atomic groups which are found repeating themselves in a 
 comparatively large number of compounds derived from one 
 another, and which play in these compounds the part of a 
 simple element, e.g. CH 3 , methyl; C 2 H 3 0, acetyl; by this defi- 
 nition the question of their existence or non-existence in the 
 free state does not arise. The radical methyl, for example, 
 is not known in the free state, since, when its formation 
 might be expected, ethane (dimethyl), CH 3 CH 3 , is obtained 
 instead (see p. 37). Such radicals may be mono-, di-, or tri- 
 valent, &c., according to the number of monovalent atoms 
 which they are capable either of replacing or of combining 
 with, so as to form a saturated compound; for instance, 
 (CoH 4 )", ethylene, is divalent; (CgHg)'", glyceryl, trivalent; 
 (CH)'", methine or methenyl, likewise trivalent, &c. The 
 monovalent residues, C n H 2n+1 (methyl, ethyl, &c.), which 
 form the radicals of the monovalent alcohols, CJEt^OH, are 
 frequently termed alJcyls, or alphyls, while the divalent residues, 
 CaHay are known as alkylenes. 
 
 At the present time it is also customary to speak of single 
 atoms as radicals; e.g. we have the chloride or iodide radical, 
 and further, the hydric radical which is characteristic of 
 acids. 
 
CLASSIFICATION 23 
 
 Classification of the Hydrocarbons, &c. 
 
 The hydrocarbons which have already been described are 
 termed "saturated" compounds, since they cannot take up 
 more hydrogen. But besides these there are hydrocarbons, 
 &c., poorer in hydrogen, or " unsaturated ", such as C 2 H 4 , 
 ethylene, and C 2 H 2 , acetylene, corresponding with which there 
 are numerous homologous series. 
 
 The constitution of these is explained, as will be seen later, 
 by the assumption of a double or triple bond between neigh- 
 bouring carbon atoms, for instance 
 
 C 2 H 4 is written CH 2 :CH^ 
 C a H 2 is written CH'CH. 
 
 From these different hydrocarbons, as starting-points, the most 
 various substitution products, such as alcohols, aldehydes, 
 ke tones, acids, amines, &c., are derived by exchange of the 
 hydrogen for halogen, oxygen, nitrogen, &c. 
 
 To another class of hydrocarbons belongs that most impor- 
 tant compound benzene, C 6 EL which contains eight atoms of 
 hydrogen less than hexane, C 6 H 14 . With regard to its con- 
 stitution, the theory of the existence of a closed chain of six 
 carbon atoms has been advanced. (See Benzene Derivatives.) 
 From benzene are derived an immense number of the most 
 different homologous and analogous hydrocarbons and substi- 
 tution products, alcohols, aldehydes, acids, and so on. Thus 
 benzene, like methane, is the mother substance of numerous 
 organic compounds. 
 
 What has just been said with regard to benzene also holds 
 good for various other compounds, which are characterized from 
 a chemical point of view by containing a closed (ring) chain. 
 These are : 
 
 (a) Trimethylene, C 3 H 6 ; Tetramethylene, C 4 H 8 ; and Penta- 
 methylene, C 5 H 10 . 
 
 (b) Pyridine, C 5 H 5 N, a strongly basic nitrogenous compound, 
 but one which at the same time resembles benzene closely in 
 many respects. 
 
 (c) Furane, C 4 H 4 0; Pyrrol, C 4 H 5 N; Thiophene, C 4 H 4 S; 
 Pyrazole, C 3 H 4 N 2 ; Thiazole, C 3 H 3 NS; &c. 
 
 Some of these fatter compounds are extremely like benzene, 
 others like pyridine ; several of them are as yet only known in 
 the form of derivatives. Like benzene, they are all mother- 
 substances of in many cases long series of compounds. 
 
24 INTRODUCTION 
 
 Organic chemistry is therefore divided into the following 
 sections : 
 
 1. Chemistry of the Methane Derivatives or Fatty Com- 
 pounds, or Aliphatic Compounds (from dAoi^, fat), so called 
 because the fats and many of their derivatives belong to this 
 group. This section comprises all carbon compounds with 
 open chains. A few compounds, which are really closed-chain 
 or ring compounds, will be mentioned in this section on account 
 of their close relationship to certain open- chain compounds; 
 
 as an example, we may take succinic anhydride 
 
 CH 2 .CO\ 
 
 GH 2 
 
 which is formed by the elimination of water from succinic 
 acid, OH-CO.CH 2 .CH 2 .CO.OH. 
 
 2. Cyclic or closed-cnain compounds. This section is usu- 
 ally divided into two sub-sections. 
 
 (a) Chemistry of the carbocydic compounds, which comprises 
 the study of all compounds built up of a ring of carbon 
 
 /~1TT 
 
 atoms. As examples we have 2 ^>CH 2 , Trimethylene ; 
 
 CH 2 ' 
 
 Tetramethylene carboxylic acid; 
 
 Benzene ; &c - 
 
 (b) Chemistry of the heterocyclic compounds, comprising the 
 study of all ring compounds which contain other atoms, in 
 addition to carbon atoms, as part of the ring, e.g. 
 
 CH.CH, CH.CH, OTT 
 
 8 E 
 
 Furane Thiophene Pyridine 
 
 Physical Properties of Organic Compounds 
 
 The physical properties of organic compounds are often of 
 the greatest importance for their characterization, and physical 
 data are frequently made use of in determining the purity of 
 a chemical compound. 
 
 Solubility. The carbon compounds vary enormously as 
 regards their solubility in various solvents. As a rule, a 
 given solvent dissolves those substances which are chemically 
 closely allied to it. As example of this, we have the fact that 
 water tends to dissolve hydroxylic compounds, especially if 
 
SPECIFIC GRAVITY 25 
 
 there are several hydroxy groups in the molecule, e.g. 
 mannitol, glucose, and pyrogallol. 
 
 Benzene tends to dissolve most hydrocarbons, and ether 
 dissolves the majority of simple organic compounds, with the 
 exception of salts of acids. 
 
 The usual method of determining the solubility of the given 
 sjubstance is to prepare a saturated solution of the substance at 
 the temperature required. This is accomplished by one of two 
 methods : (a) Shaking the finely-divided solute for some time 
 in contact with the solvent at the given temperature, care being 
 "taken that there is always some undissolved solute left over. 
 (b) If the solute is more soluble in hot than in the cold solvent, 
 a concentrated hot solution is prepared, and is then allowed 
 to cool down to the temperature required, care being taken 
 to stir the solution so that the excess of solute crystallizes 
 out and a supersaturated solution is not obtained. A known 
 weight or volume of the clear saturated solution is taken, and 
 the solvent removed by evaporation, and the residual solute 
 weighed. The result is usually expressed in the form 100 
 grams of solvent dissolve x grams of solute at f . 
 
 Specific Gravity and Specific Volume. The specific gravity 
 of a liquid is an important criterion for the purity of the sub- 
 stance. This is usually determined in a specific-gravity bottle, 
 Sprengel tube, or Pyknometer. The pyknometer is filled with 
 pure water at a given temperature (usually 4 or 15) and 
 carefully weighed. It is then dried, filled with the liquid 
 at a fixed temperature, and again weighed. The ratio 
 
 w ' 1( ^ U1 is the specific gravity. It is usual in giving the 
 
 specific gravity to denote the temperature at which the deter- 
 mination was made, as this varies with the temperature, and 
 
 also the temperature of the water, e.g. d-^- denotes the 
 
 specific gravity of the liquid at 20 compared with that of 
 water at 4. The reciprocal of the specific gravity is known 
 as the specific volume, and the product of this and the mole- 
 cular weight as the molecular volume. 
 
 Melting-Point. Each fusible compound has a fixed definite 
 melting-point, and this constant is often made use of in deter- 
 mining the purity of a solid, as the introduction of even small 
 amounts of impurities lowers the melting-point considerably. 
 When appreciable amounts of impurities are present, the 
 
26 INTRODUCTION 
 
 melting-point is not sharp, but ranges over a number of 
 degrees. The melting-point is best defined as the temperature 
 at which the liquid and solid phases of the compound are in 
 equilibrium. The most direct and most accurate method of 
 determining the melting-point is to place a thermometer in 
 the molten substance and allow it to partially solidify, and 
 note the temperature at which the mercury remains constant 
 when the mixed solid and liquid is stirred by the thermometer. 
 As this method involves the use of a relatively large amount 
 of the substance, the determination is usually made by intro- 
 ducing a very small amount of the finely-divided substance 
 into a narrow capillary tube closed at one end. This tube is 
 then attached to a thermometer, the substance being at the 
 same level as the middle of the bulb of the thermometer, and 
 the two are carefully heated in a bath of sulphuric acid. Just 
 before the melting-point is reached the flame is removed occa- 
 sionally, so that the temperature rises very slowly, and the 
 melting-point can be read accurately to within -5 or -25 of 
 a degree. As a rule, a short thermometer is used, so that the 
 whole thread of mercury is in the bath, otherwise a correction 
 has to be made for the length of the mercury thread which is 
 not immersed in the hot bath. 
 
 Boiling - Point. The purity of a volatile substance can 
 usually be determined by means of the boiling-point, i.e. the 
 temperature at which the vapour pressure of the substance is 
 equal to the atmospheric pressure. It is usually determined by 
 placing the bulb of the thermometer in the vapour, and if a 
 short thermometer is employed, and the whole of the mercury 
 thread is surrounded by the vapour, no correction is required. 
 In each case the barometric pressure should be stated, and also 
 whether the thread of mercury was completely immersed in 
 the vapour. 
 
 Many substances which decompose when heated under 
 atmospheric pressure, may be distilled without undergoing 
 decomposition under reduced pressure. This is accomplished 
 by attaching the flask, condenser, and receiver to a mercury 
 or water pump and exhausting. When the pressure is suffi- 
 ciently reduced the substance is distilled, care being taken 
 that the pressure under which the distillation occurs is mea- 
 sured by means of a manometer. As a rule, considerable 
 difficulty in avoiding bumping is encountered in distillations 
 under diminished pressure; this is most readily got over by 
 placing a piece of porous material (unglazed pot) in the liquid, 
 
STEAM DISTILLATION 27 
 
 or by slowly aspirating bubbles of air through the boiling 
 liquid. (Compare Auschutz and fieilter, Brochure. Bonn, 
 1895). 
 
 Fractional Distillation. Two miscible liquids with widely 
 differing boiling-points, e.g. alcohol, 78, and aniline, 185, can 
 be separated by the process of fractional distillation, as the 
 lower boiling liquid distils over first. In all cases an inter- 
 mediate fraction consisting of a mixture of the substances is 
 obtained, but, as a rule, the greater the difference between the 
 boiling-points of the two substances the smaller is this fraction. 
 In many cases where the boiling-points are not very far re 
 moved, e.g. benzene, 80, and toluene, 111, the two compounds 
 cannot be separated by a single fractionation; it is thus cus 
 tomary to collect fractions every 5 and to subject each oi 
 these fractions to further distillation, using the same flask for 
 distillation, and again collecting every 5. It is then found 
 that there is a large fraction boiling at 80-85 and consisting 
 of nearly pure benzene, and a large fraction, 110-111, consist- 
 ing of pure toluene, and a number of small fractions boiling at 
 85-90, 90-95, &c., and consisting of mixtures of benzene and 
 toluene. The process is often quickened by using some form 
 of fractionating column. This consists of a long tube with 
 bulbs blown on, and serves to lengthen the neck of the flask. 
 The Linneman tube contains small wire -gauze cups in the 
 constricted parts, and in these drops of the higher boiling 
 liquid collect, and thus all the vapour has to pass through 
 or be washed by these drops. The same purpose is served in 
 the Glynsky tube by placing a glass ball in each constriction. 
 (See S. Young, "Fractional Distillation". London, 1903.) 
 
 It is not always possible to separate liquids by fractional 
 distillation, for example, when the boiling-points are very 
 close, or when the two substances form a mixture of definite 
 boiling-point. When dilute nitric acid is distilled, water first 
 passes over, and then a mixture of water and nitric acid, until 
 the residue in the flask is 68 per cent nitric acid, and then it 
 boils constantly at 126, since the vapour and the liquid in the 
 flask have the same composition. 
 
 Mixtures of constant boiling-point are always characterized 
 by the fact that they have a vapour pressure either higher or 
 lower than that of either of the constituents, or than that of 
 any other mixture of the same compounds. 
 
 Steam Distillation. This is the process frequently resorted 
 to in the separation of a compound readily volatile in steam 
 
28 INTRODUCTION 
 
 from other substances, e.g. tars or inorganic salts, which are 
 not volatile. It consists in blowing steam through the mixture, 
 and condensing the steam and volatile compound by means of 
 a Liebig condenser. Very often the volatile compound is prac- 
 tically insoluble in water, and separates as an oil or solid in 
 the distillate. The rapidity with which a given substance 
 distils with steam depends on the vapour pressure of the sub- 
 stance at the given temperature, and also on its molecular 
 weight or vapour density compared with that of water. Thus 
 a mixture of nitro-benzene and water, which may be regarded 
 as non-miscible liquids, boils at 99; i.e. the vapour pressure of 
 the mixture at 99 is 760 mm. The vapour pressure of water at 
 99 is 733 mm., and therefore the partial pressure of the nitro- 
 
 733 
 benzene is 27 mm. In a given volume of the mixed vapours j 
 
 27 . 
 
 will consist of steam and -- of nitro-benzene, and the relative 
 760 
 
 weights of these volumes will be the volumes x relative den- 
 sities, i.e. 9 * 733 : 61 * 27 i.e. 4 : 1; or, in other words, Uh 
 760 760 
 
 by weight of the total distillate will consist of nitro-benzene. 
 
 Other methods very frequently used in the purification of 
 solid compounds are crystallization and fractional crystalliza- 
 tion. The method employed is essentially the same as that 
 made use of in purifying inorganic compounds, except that 
 organic solvents, e.g. alcohol, chloroform, benzene, carbon disul- 
 phide, and low -boiling petroleums, are largely used. Often 
 a mixture of two solvents is more serviceable than a single 
 one, e.g. substances are often crystallized by solution in warm 
 alcohol and addition of water, or solution in benzene and addi- 
 tion of petroleum, until a slight turbidity ensues. The fact 
 that a substance crystallizes from a given solvent in well- 
 defined crystals does not necessarily indicate that the substance 
 is a single chemical individual, as numerous examples of mixed 
 crystals with definite melting-points are known, and these 
 are not resolved when repeatedly crystallized from the same 
 solvent. 
 
 Extraction with Ether, Benzene, &c, Partition Coefficient, 
 An organic compound can often be separated from other 
 substances, especially inorganic salts, by shaking out with 
 ether, separating the ethereal layer by means of a separating 
 funnel, drying the solution with granular calcium chloride or 
 some other suitable drying agent, and removing the ether by 
 
EXTRACTION WITH ETHER, ETC. 29 
 
 distillation. The method gives very good results when the 
 compound to be extracted is much more soluble in ether than 
 in water, and when the substances from which it is to be 
 separated are insoluble in ether. When there is no marked 
 difference in the solubilities of the given compound in ether 
 and in water, the extraction must be repeated a number of 
 times, in some cases even twenty, since for each compound 
 
 . cone, of ethereal solution . 
 
 the ratl cone, of aqueous solution ls a constant ' and ls usuall y 
 termed the partition coefficient or coefficient of distribution of the 
 particular substance between the two solvents. In extractions 
 with ether it must be borne in mind that ether dissolves to an 
 appreciable extent in water, and also water in ether.. Other 
 liquids, such as benzene, carbon-disulphide, chloroform, &c., 
 may be used in place of ether. 
 
 When the amount of solvent to be used is limited, it is 
 more economical to extract two or three times with small 
 amounts of solvent rather than only once with the whole 
 amount. As an illustration. 11 grams of a substance and 
 1 litre each of the non-miscible liquids, water and benzene. 
 The solubility of the substance in benzene is ten times its 
 solubility in water, and it has the same molecular weight in 
 both solvents. 
 
 Case /. Extracting at once with the litre of benzene, 
 
 cone, of benzene solution 10 , , 
 
 - j - i -. = -=-, i.e. iVth of the whole, or 
 cone, of water solution 1 ' 
 
 1 gram, remains in the water. 
 
 Case //.Extract twice with 500 c.c. of benzene. After 
 first extraction, suppose x grams passes into the benzene, then 
 cone, of aqueous solution is 11 x, and of the benzene 2x t 
 
 = -y-, or x = 9 (approx.), and 2 grams are left 
 
 .. - 
 
 I I " ' 
 
 in the water. 
 
 After extraction with second quantity of benzene, y grams 
 
 go into the benzene. Then ^ _ = y, or y 1'7 
 
 (approx.), and only 0'3 gram remains in the aqueous solu- 
 tion. Whereas, after the single extraction with a litre of 
 benzene 1 gram was left. 
 
 For applications of this method in determining the relative 
 strengths of acids and amines, compare Farmer and Warth 
 (J. C. S. 1904, 1713). 
 
CLASS L ALIPHATIC OE OPEN-CHAIN 
 COMPOUNDS 
 
 I. HYDEOCAEBONS 
 
 A. Saturated Hydrocarbons, cyi^ 
 
 This constitutes the simplest homologous series of carbon 
 compounds, and all the saturated open-chain compounds may 
 be regarded as derived from these. 
 
 The following list includes the more important normal 
 hydrocarbons : 
 
 Formula. 
 
 Name. 
 
 Melting- 
 point. 
 
 Boiling- 
 point. 
 
 Specific gravity. 
 
 CH 4 
 
 C 2 H 6 
 
 Methane 
 Ethane 
 
 186 
 -172 
 
 164 
 
 -84 
 
 0-415 at b.-p. 
 0-446 at 
 
 cX 
 
 Propane 
 
 
 -37 
 
 0-536 at 
 
 C 4 H 10 
 
 Butane 
 
 
 +1 
 
 0-600 at 
 
 ^6-^-12 
 
 Pentane 
 
 
 37 
 
 0-627 at 14 
 
 C 6 H 14 
 
 Hexane 
 
 
 69 
 
 0-658 at 20 
 
 C 7 H 16 
 
 Heptane 
 
 
 98 
 
 0-683 at 20 
 
 CoHjo 
 
 Octane 
 
 
 125 
 
 0-702 at 20 
 
 n TT 
 
 O 9 1 20 
 
 Nonane 
 
 -51 
 
 150 
 
 0-718 at 20 
 
 n TT 
 
 V - J '10 X - L 22 
 
 Decane 
 
 31 
 
 173 
 
 0-730 at 20 
 
 C n H24 
 
 TJndecane 
 
 -26 
 
 195 
 
 0-774 at m.-p. 
 
 ^12^-26 
 
 Dodecane 
 
 -12 
 
 214 
 
 0-773 at ni.-p. 
 
 C 14 H 30 
 
 Tetradecane 
 
 +4 
 
 252 
 
 0-775 at m.-p. 
 
 ^16^-34 
 
 Hexadecane 
 
 18 
 
 287 
 
 0-775 at m.-p. 
 
 C 2 oH 42 
 
 Eicosane 
 
 37 
 
 205* 
 
 0-778 at m.-p. 
 
 ^21-^-44 
 
 Heneicosane 
 
 40 
 
 215* 
 
 0-778 at rn.-p. 
 
 ^23^48 
 
 Tricosane 
 
 48 
 
 234* 
 
 0779 at m.-p. 
 
 C 31 H 64 
 
 Hentriacontane 
 
 68 
 
 302* 
 
 0-781 at m.-p. 
 
 ^36-^-72 
 
 Pentatriacontane 
 
 75 
 
 331* 
 
 0-782 at m.-p. ! 
 
 r< TT 
 
 v ^60 rL 122 
 
 Hexacontane 
 
 101 
 
 
 
 * Under 16 mm. pressure. 
 
 The first members of the series, including those with about 
 four atoms of carbon, are gases, which gradually become more 
 easily condensable as the number of carbon atoms in the mole- 
 cule increases. The members which follow are liquid at the 
 
SATURATED HYDROCARBONS 31 
 
 ordinary temperature, their boiling-point rising with increasing 
 number of carbon atoms. An increase of CH 2 in the mole- 
 cular formula does not necessarily denote a definite increase 
 in the boiling-point. The difference in boiling-point between 
 hexane and heptane is 29, and between undecane and dode- 
 cane only 19: thus with compounds of high molecular weight 
 an increase of CH 2 does not produce so marked an effect on 
 the boiling-point as with simpler compounds. The higher 
 homologues, from about C 16 H 34 (melting-point 18) on, are 
 solid at the ordinary temperature, and their melting-point 
 gradually rises up to about 100. The highest members can be 
 distilled under diminished pressure only. The methane homo- 
 logues are almost or quite insoluble in water; alcohol dissolves 
 the gaseous members to a slight extent, the liquid members 
 easily, and the solid with gradually increasing difficulty. Their 
 specific gravities at the melting-point increase with increasing 
 number of carbon atoms from 0'4: up to 0*78, which is the 
 maximum limit. This value is already almost reached by the 
 hydrocarbon C n H 24 , so that for the higher members of the 
 series the following law holds good: "the molecular volumes 
 are proportional to the molecular weights " (Krafft). 
 
 They are incapable of combining further with hydrogen or 
 halogens (see p. 23), and absorb neither bromine nor sulphuric 
 acid. They are therefore termed the Saturated Hydro- 
 carbons. Even fuming nitric acid has little or no action 
 upon the lower members of the series; thus, methane is not 
 attacked by a mixture of fuming nitric and sulphuric acids, 
 even at 150. They are also very indifferent towards chromic 
 acid and permanganate of potash in the cold,* when oxidation 
 does take place, they are mostly converted directly into car- 
 bonic acid. The name of " The Paraffins " (from parum affinis), 
 which was originally applied only to the solid hydrocarbons 
 from lignite, has therefore been extended to the whole homo- 
 logous series. 
 
 By the action of the halogens (01, Br), substitution takes 
 place, the substituted hydrogen combining with an amount of 
 halogen equal to that which has entered the hydrocarbon (see 
 Substitution products of the Hydrocarbons) : 
 CH 3 H + C1C1 = CH,C1 + HC1. 
 
 As the number of carbon atoms increases, the percentage 
 composition of these hydrocarbons approaches a definite limit, 
 
 * With the exception of compounds containing the grouping R'R"R"'CH. 
 
32 
 
 I. HYDROCARBONS 
 
 viz. that of the hydrocarbons, C n H 2n , or CH 2 , as is shown by 
 the following table : 
 
 Per 
 
 cent. 
 
 CH 4 
 
 C 2 H 6 
 
 C 3 H 8 
 
 C 6 H U 
 
 C]cHs4 
 
 C^HIS 
 
 C^H^ 
 
 CssHre 
 
 Limit 
 Value, 
 
 CnHfc, 
 
 c 
 
 H 
 
 i 
 
 75-00 
 25-00 
 
 80-00 
 20-00 
 
 81-82 
 18-18 
 
 83-72 
 16-28 
 
 84-60 
 15-40 
 
 85-16 
 14-84 
 
 85-21 
 14-79 
 
 85-36 
 14-64 
 
 85-71 
 14-29 
 
 It is therefore impossible to distinguish by elementary 
 analysis between two of the neighbouring higher homologues, 
 e.g. C 22 and C 24 , C 24 and C 30 ; the only reliable data here are 
 the methods of formation from compounds in which the 
 number of carbon atoms in the molecule is already known, 
 and the melting-points. 
 
 homers. Only one representative each of the formula! 
 CH 4 , C 2 H 6 , and C 3 H 8 is known, but of C 4 H 10 there are two, 
 of C 5 H 12 three, and of C 6 H 14 already five isomers, and most of 
 the higher hydrocarbons are known in various isomeric forms. 
 From this the conclusion is drawn that in these different 
 isomers the carbon atoms are differently combined, in the one 
 case in a straight line without branching, like the links of a 
 chain; in the other, with the formation of a branching chain. 
 (This is of course not to be taken as meaning that they ar 
 grouped together in space in straight lines.) Thus: 
 
 or 
 
 The first of these hydrocarbons, with a non-branching chain, 
 are termed the normal hydrocarbons; the last, the iso-hydro- 
 carbons. 
 
 The principles by which such constitutional formulae are 
 arrived at will be explained under Butane and Pentane. 
 
 Only those homologues are comparable whose constitutions 
 are similar, as in the case of the normal hydrocarbons. 
 
 Occurrence. The hydrocarbons of the paraffin series occur 
 naturally in great variety. Thus, methane is exhaled from 
 the earth's crust, as "fire-damp" and as marsh-gas. The next 
 higher homologues are found dissolved in petroleum, which 
 also contains the higher hydrocarbons in large amount. Solid 
 hydrocarbons occur as ozokerite or earth-wax. By the frac- 
 tional distillation of petroleum a large number of these com- 
 
MODES OF FORMATION 33 
 
 pounds have been isolated. Heptane and hexadecane are also 
 found in the vegetable kingdom. 
 
 Modes of formation. A. Various members of this series are 
 obtained by the distillation of lignite (Boghead, Cannel coal), 
 wood, bituminous shale, and, in very much smaller quantity, 
 from pit coal. Paraffins are also obtained by dissolving car- 
 bide of iron in acids, and by heating wood, lignite, and coal, 
 but riot graphite, with hydriodic acid. 
 
 B. From substances containing an equal number of carbon 
 atoms in the molecule. 
 
 1. From the halogen alkyls,* C n H 2n+1 X, and, generally 
 speaking, from the substitution products of the hydrocarbons 
 by exchange of the halogen for hydrogen (inverse substitu- 
 tion). This is effected by the action of reducing agents, that 
 is, agents which give rise to nascent hydrogen. Some of the 
 commoner reducing agents " employed for such purposes are 
 sodium amalgam and water, zinc and a dilute acid, zinc and 
 water at 160, the copper-zinc couple in presence of water 
 and alcohol (Gladstone-Tribe), aluminium- or magnesium-amal- 
 gam and alcohol, and one of the most vigorous reducing agents, 
 concentrated hydriodic acid at high temperatures, especially 
 in contact with red phosphorus, which serves to continually 
 renew the hydrogen iodide. (See chapter on Reduction.) 
 
 2. From monohydric alcohols, CnR,^ OH, polyhydric alco- 
 hols, C n H 2n (OH) 2 , CJHs^OH)* &c., also from aldehydes, 
 C n H ta+1 'CHO, ketones, C n H ta+1 .COC ll H an . tl , and other com- 
 pounds containing oxygen, by heating with hydriodic acid 
 and red phosphorus at relatively high temperatures. In all 
 these reactions the oxygen is ultimately removed as water. 
 
 3. From hydrocarbons poorer in hydrogen, i.e. unsaturated 
 hydrocarbons (see these), by the addition of hydrogen; e.g. 
 ethane from ethylene or acetylene and hydrogen, either in 
 presence of platinum black or finely-divided nickel or by heat- 
 ing the mixture of gases to 400-500. Also by heating with 
 hydriodic acid (Kraffl\ or by addition of halogen or halogen 
 hydride, and exchange of the halogen for hydrogen, according 
 to 1. Thus: 
 
 = C 2 H 6 , f C 2 H 4 + HBr = C 3 H 6 Br, 
 
 C;HI O + 2HI = C 6 H 12 + I 2 ; \C 2 H 6 Br + 2H = C 3 H fl + HBr. 
 
 * The monovalent residues, C n Ha n .M, methyl, ethyl, &c., which are at the 
 same time the radicals of the monohydric alcohols, CnHjn + iOH, are fre- 
 quently termed alkyl groups, 
 
 (B480) C 
 
34 L HYDROCARBONS 
 
 4. By decomposing the organo-zinc compounds (zinc-alkyls) 
 with water (Fmnkland) 
 
 Zn(C 2 H 6 ) 2 + 2H 2 = Zn(OH) 2 + 2C 2 H fi . 
 
 Or more readily by decomposing Grignard's organo-magnesium 
 compounds with water. Thus ethyl iodide and magnesium, in 
 presence of dry ether, yield ethyl magnesium iodide, C 2 H 6 
 MgI, and this with water evolves ethane: 
 
 C 2 H 6 .Mg.I-t-H.OH = C 2 H 6 -f OH-Mg.L 
 
 C. From acids containing more carbon, with separation of 
 carbon dioxide. Thus, by heating acetate of calcium with 
 soda-lime, methane and carbonic acid are formed: 
 
 (CH 3 COO) 2 Ca + Ca(OH) 2 = 2CH 4 + 2CaCO s . 
 
 In the case of the acids of higher molecular weight, this 
 separation of carbonic acid is conveniently effected by heating 
 with sodic ethoxide. 
 
 D. By the combination of two radicals containing a smaller 
 number of carbon atoms. 
 
 1. By the action of sodium upon the alkyl iodides in ethereal 
 solution (Wurtz)\ or by heating with zinc in a sealed tube 
 (Frankland): 
 
 2 CH 3 I -f 2 Na = C 2 H G + 2 Nal. 
 
 By this method also two different radicals can be combined, 
 e.g. C 2 H 5 I + C 4 H 9 I give C 2 H 5 + C 4 H 9 = C 6 H 14 , ethyl-butyl 
 (Wur&s "Mixed Radicals"). 
 
 2. By the electrolysis of solutions of the potassic salts of 
 fatty acids (Kolbe, 1848). The anions, for example, CH 3 .COO, 
 when discharged at the anode, break up into CH 3 and C0 2 , 
 and two of the CH 3 groups immediately combine to form a 
 molecule, CH 3 CH 3 , viz. ethane. The hydrogen is here evolved 
 at the cathode, and the hydrocarbon at the anode; the carbon 
 dioxide is to a large extent retained in the solution. 
 
 Methane, CH 4 (Folta, 1778). Occurrence. As an exhalation 
 from the earth's crust, more especially at Baku in the neigh- 
 bourhood of the Caspian Sea (the "Iloly Fire" of Baku)j from 
 the large gas wells at Pittsburg, in North America, and in 
 numerous other places; in the exhalations from mud volcanoes, 
 for instance at Bulganak in the Crimea, where the gas is almost 
 pure methane (Bunsen); and as pit gas or "fire-damp" in mines, 
 where, when mixed with air, it is apt to cause explosions. 
 
 As marsh-gas, together with carbon dioxide and nitrogen, 
 
METHANE 35 
 
 by the decomposition of organic substances under water; 
 further, by the fermentation of cellulose, e.g. by river mud, 
 by means of Schizomycetes (fission-fungi). 
 
 It is also found in rock-salt (the Knistersalz of Wieliczka), 
 and in the human intestinal gases (up to 57 per cent CH 4 
 after eating pulse). 
 
 The illuminating gas obtained by the destructive distillation 
 of coal contains about 40 per cent methane. 
 
 Modes of preparation. 1. Methane is formed synthetically by 
 the direct union of carbon and hydrogen. Pure sugar carbon 
 freed from all traces of hydrogen by treatment with chlorine 
 is heated in a current of dry hydrogen in a porcelain tube, and 
 the issuing gas is found to contain one per cent of methane 
 (Bonezud Jerdan, J. C. S., 1897, 41; 1901, 1042; Pring, 1910, 
 489; Pring and Fairlie, 1911, 1796, 1912, 91); and is also 
 formed by the decomposition of ethane, ethylene, and acety- 
 lene at moderate temperatures (Bone and Coward, 1908, 1197). 
 
 2. When carbon monoxide and hydrogen are passed over 
 reduced nickel at 200-250. The nickel acts as a catalytic 
 agent, and apparently undergoes no change. Carbon dioxide 
 may be substituted for the monoxide. (Sabatier and Sender ens.) 
 The reactions are: 
 
 CO + 3H 2 = CH 4 + H 2 and C0 2 + 4H 2 = CH 4 + 2H 2 
 
 3. By leading sulphuretted hydrogen and carbon bisulphide 
 vapour over red-hot copper (Saihelot); CS 2 -f 2H 2 S -f 8Cu 
 = CH 4 -f 4Cu 2 S. Steam may be substituted for the sul- 
 phuretted hydrogen. 
 
 4. It is usually prepared by heating anhydrous sodic acetate 
 with baryta, or, less advantageously, with soda-lime (cf. p. 34), 
 ethylene, C 2 H 4 , and hydrogen (up to 8 per cent) being formed 
 at the same time. 
 
 5. Pure methane is obtained from magnesium methyl iodide 
 
 and water, CH^-Mg-I + H-OH = CH 4 + OH-Mg-I; also 
 (see B, 1) by the reduction of methyl iodide, CH 3 I, e.g. in 
 alcoholic solution by means of zinc in the presence of pre- 
 
 ni-rv!4ri4-<->s3 f.f\-r\-r\r\m /V./-k ffl n J0ir\m a^ / 7 T /n/7n> " r~!rrnpT_7.Tnp. liOlTnlft i t"*" 
 
 cipitated copper (the Gladstone-Tribe "Copper-zinc Couple"), 
 also by the inverse substitution of chloroform, CHCl^ or carbon 
 tetrachloride, CC1 4 . 
 
 Properties. -It is a gas with a dersity = 8 (H = 1), and 
 is condensed under a pressure of ^0 atmospheres at 0. It 
 boils at 164, and solidifies at 186. Absorption coefficient 
 in cold water about 0'05, in cold alcohol 0'5. It burns with a 
 
36 I. HYDROCARBONS 
 
 pale and only faintly luminous flame, yielding carbon dioxide 
 and water, and when mixed with air or oxygen in certain pro- 
 portions forms an explosive mixture. It is decomposed by the 
 electric spark into its elements, and a similar decomposition 
 occurs when the gas is led through a red-hot tube; but there 
 are formed at the same time C 2 H 6 , C 2 H 4 , C 2 H 2 , and, in smaller 
 quantity, C 6 H 6 , benzene, C 10 H 8 , naphthalene, and other pro- 
 ducts. The first three hydrocarbons just mentioned, ethane, 
 &c., behave similarly. 
 
 Combustion of Hydrocarbons. When methane and hydro- 
 carbons generally are burnt or exploded with excess of air or 
 oxygen, the final products are carbon dioxide and water vapour, 
 and the reaction is generally represented, e.g., by the equation 
 CH 4 -f 2 2 = C0 2 -f 2 H 2 0. This undoubtedly represents 
 the final products which are formed, and also their relative 
 amounts, but does not give an idea of the mechanism of com- 
 bustion. Numerous investigators have conducted experiments 
 on combustion, especially on combustion in the presence of 
 limited amounts of oxygen. The conclusion was first drawn 
 that with a defective supply of oxygen the hydrogen is oxi- 
 dized in preference to the carbon. Somewhat later, Kersten 
 (1861) suggested the preferential burning of the carbon, since 
 when ethylene is exploded with its own volume of oxygen, 
 carbon monoxide and hydrogen are the chief products. (Cf. 
 Smitkdls, J. C. S. 1892, 61, 220.) 
 
 The recent work of Bone and others on the slow combustion 
 of methane, ethane, ethylene, and acetylene (J. C. S. 1902, 535; 
 1903, 1074; 1904, 693, 1637; Proc. 1905, 220; B. A. Eeport, 
 1910, 469), shows that by passing a mixture of methane and 
 oxygen in a continuous stream through a tube filled with 
 porous material (pot or magnesia), at a fixed temperature 
 between 350 and 500, appreciable amounts of formaldehyde 
 are obtained. Gaseous products are also obtained, but these 
 are probably due to secondary reactions, e.g. either the further 
 oxidation of the aldehyde to carbon monoxide, carbon dioxide, 
 and steam, or the thermal decomposition of the aldehyde into 
 carbon monoxide and hydrogen. Thus : 
 
 ^^*CO + H a + H 2 
 
 CH 4 > CH 2 (OH) a OH, :0+H a O < C^^Thermal decomposition 
 
 .Oxidation * 
 
 CO, 4- H 2 + H 2 
 
 Thermal decomposition. 
 
ETHANE 37 
 
 By the expression thermal decomposition is meant that at the 
 temperature mentioned the aldehyde is unstable, and imme- 
 diately decomposes into the simpler products, CO and H 2 . 
 
 Ethane behaves similarly, and the reactions can be repre- 
 sented by the following scheme : 
 
 CH 3 .CH 3 CH 3 .CH(OH) 2 -* CH 3 .CH:0 + ELO 
 
 o a o, 
 
 OH.CH 2 .C0 2 H 
 
 i 
 CH 2 :0-hCO + H 2 0. 
 
 Secondary reactions are the thermal decompositions of the 
 formaldehyde into CO and H 2 ,. and of the acetaldehyde into 
 CH 4 and CO. In reality some 80 per cent of the ethane can 
 be collected as formaldehyde. With ethylene the reactions 
 are probably 
 
 CH 2 :CH 2 OH.CHrCH-OH 2CH 2 :O H-CO 2 H , 
 O 2 00 
 
 OH-CO-OH, 
 
 and the thermal decomposition products of the formaldehyde, 
 formic acid, and carbonic acid, viz. H 2 , CO, C0 2 , H 2 0. 
 
 It is thus obvious that at the temperatures mentioned (350- 
 500) combustion consists primarily in the addition of oxygen 
 and the production of hydroxylic compounds, which then yield 
 aldehydes. It is highly probable that reactions of a similar 
 nature occur during explosive combination ana detonation at 
 high temperatures (B. A. Report, 1910, 492). 
 
 Ethane, C 2 H 6 , occurs in crude petroleum and constitutes 
 the gas of the Delamater gas well in Pittsburg, and is there 
 utilized for technical purposes. 
 
 Preparation. By the electrolysis of acetic acid (Kolbe, 1848), 
 and therefore formerly called " methyl " since it was supposed 
 to be CH 3 ; subsequent molecular-weight determinations proved 
 it to have the double formula C 2 H 6 . It is also obtained from, 
 ethyl iodide, alcohol, and zinc dust, or from zinc ethyl (Frank- 
 land), hence the name "ethyl hydride". "Ethyl hydride" and 
 " methyl ", which were formerly supposed by FranHand and 
 Kolbe to be different substances, were proved to be identical by 
 Schorlemmer in 1863 by their conversion into C 2 H 5 C1, which 
 may be prepared from both in exactly the same way. 
 
 It is a gas which can be condensed under a pressure of 
 46 atmospheres at 4, and is somewhat more soluble than 
 
88 L HYDROCARBONS 
 
 methane in water and alcohol. It burns with a faintly- 
 luminous flame. 
 
 Propane, C 3 Hg, and the two butanes, C 4 H 10 , are also gaseous 
 at the ordinary temperature, and are present to a certain ex- 
 tent in crude petroleum. 
 
 Theoretically propane can exist in only one form, represented 
 by the constitutional formula CH 3 CH 2 CH 3 , as this is the 
 only manner in which three carbon and eight hydrogen atoms 
 can be grouped up if we assume that the carbon atoms are 
 tetravalent and the hydrogen atoms monovalent. 
 
 ISOMERISM, NOMENCLATURE, CONSTITUTION 
 
 To determine whether the next homologue, C 4 H 10 , can 
 theoretically exist in more than one modification, we can start 
 
 a /3 a 
 
 with propane, CH 3 CH 2 'CH 3 , and replace one of the eight hy- 
 drogen atoms by "a methyl group. It is obvious that we can 
 obtain two distinct compounds according to whether we re- 
 place one of the six terminal hydrogens (a) or one of the central 
 hydrogens (/?). The two compounds would have the respective 
 formulae 
 
 CH 3 .CH 2 .CH 2 .CH 3 and 
 
 and are known as normal butane and iso-butane (or trimethyl 
 methane). 
 
 Two compounds having the formula C 4 H 10 are actually 
 known, and their constitutional formulae derived from their 
 methods of formation agree with the two formulae CH 3 CH 2 
 CH 2 -CH 3 and (CH 3 ) 2 : CH CH 3 , as the ^compound may be 
 obtained by the action of zinc on ethyl iodide, CH 3 CH 2 T, 
 and the ^so-compound by the reduction of tertiary butyl iodide, 
 (CH 3 ) 2 :CI.CH 3 . 
 
 All the succeeding hydrocarbons can, according to theory, 
 exist in various isomeric modifications. The number of modi- 
 fications possible can be derived in exactly the same manner 
 as already described for the butanes. 
 
 As an example, take the hydrocarbons C 5 H 12 , the pentanes. 
 
 a /3 B a 
 
 Starting with n-butane, CH 3 CH 2 'CH 2 -CH 3 , and replacing 
 one H atom by a CH 3 group, we can get either 
 
 (1) CH 3 .CH a .CH 2 .CH 2 .CH 3 or (2) 
 
NOMENCLATURE 3$ 
 
 according as we replace an H atom in the a or ft position. 
 Starting from iso-butane, 
 
 We can similarly get 
 :'' (3) >CH.CH 2 .CH s or (4) 
 
 but formulae (2) and (3) are identical, and the three isomerides 
 possible are therefore CH 3 .CH 2 -CH 2 .CH 2 .CHo, (CHA>:CH. 
 CH 2 .CH 3 and (CH 3 ) 2 :C:(CH 3 ) 2 . Of hydrocarbons with six 
 carbon atoms, five isomers are possible, and they are all known. 
 Of the nine possible heptanes, C^H 16 , the existence of five has 
 already been proved. 
 
 The number of theoretically possible isomers increases very 
 rapidly with the number of carbon atoms, so that, according to 
 Cayley, 802 isomeric hydrocarbons of the formula C 13 H 28 are 
 possible. 
 
 Of these isomers only one can be normal, i.e. can have a 
 single chain of carbon atoms, in which each of the two terminal 
 carbon atoms is combined with three atoms of hydrogen, and 
 all the middle ones with two, according to the formula, CEL 
 (CH 2 ) n .CH 3 . 
 
 A convenient Nomenclature for the more complicated paraffins 
 is arrived at by making methane the starting-point for all of 
 them, that carbon atom from which the branching chain ema- 
 nates being considered as originally belonging to CH 4 , in which 
 the hydrogen atoms are supposed to be wholly or partially re- 
 placed by hydrocarbon radicals, thus: 
 
 = 
 
 dimethyl-ethyl-methane. 
 
 The names of the well-known lower hydrocarbon radicals 
 (alkyls) are also frequently used as a basis; for instance, the 
 group (CH 3 ) 2 CH is termed isopropyl (see Isopropyl Alcohol), 
 hence the compounds: 
 
 : di-isopropyl. 
 
 The boiling-points of the normal hydrocarbons are alway* 
 
40 I. HfJJiiOC ARSONS 
 
 higher than those of the isomers; indeed the boiling-point 
 becomes lowered continuously the more the carbon atom chain 
 is branched, i.e. the more methyl groups are gathered together 
 in the molecule. 
 
 The Constitution of the higher paraffins can in most cases only 
 be arrived at with certainty from their synthetical formation 
 (e.g. normal butane and hexane), or from their chemical rela- 
 tion to oxygenated derivatives whose constitution is already 
 known, especially to the ketones and acids. (See Ketones.) 
 
 If, for instance, by the action of PC1 5 upon acetone, for 
 which the constitution CH 3 COCH 3 is proved, the substance 
 CH 3 CClg CH 3 (acetone chloride) be formed, and this be then 
 treated with zinc methyl, the resulting hydrocarbon, a pentane, 
 will have the constitution (CH 3 ) 4 C: 
 
 = ZnCl 2 + (CH 3 ) 2 :C:(CH 3 ),. 
 
 As a second example, we have w-hexane, which can be ob- 
 tained by the action of metals upon w-propyl iodide, as repre- 
 sented by the equation : 
 
 2CH 3 .CH 2 .CH 2 I + Zn = ZnI 2 
 
 The system of nomenclature suggested by the International 
 Congress at Geneva is as follows: The normal paraffins re- 
 tain their present names. Thus hexane means the compound 
 CH 3 (CH 2 ) 4 CH 3 . In the case of those with branching chains 
 the longest normal chain gives the name, the branches being 
 regarded as substituents, and the position of substitution being 
 indicated by the successive numbering of the atoms of the 
 carbon chain (the carbon atom which is nearest to the point 
 of ramification is numbered 1; should there be more than one 
 branching say, a longer and a shorter then No. 1 begins 
 with the end carbon atom which stands nearest to the shorter 
 branching). Trimethyl-methane is therefore called 2-methyl- 
 propane; dimethyl-ethyl-methane, 2-methyl-butane ; and tetra- 
 methyl-methane, 2 : 2-dimethyl-propane. 
 
 The following paraffins have been obtained from crude 
 petroleum: n- and eso-pentane, 7i-hexane and an isomer, and 
 n-heptane, all these being present in the so-called " gasoline ", 
 which is obtained by the distillation of petroleum, and is used 
 for carburetting coal-gas; further, normal Heptane, n-Octane,* 
 n-Nonane, and 7i-Decane, besides an isomer of each, and in 
 
 * The petroleum ether and ligroin of commerce consist principally of the 
 hydrocarbons C 6 H 14 , C7H 1G , and C 8 H 18 . 
 
PETROLEUM 41 
 
 addition to these (as also from the distillation of cannel and 
 Boghead coal), a large number of the higher hydrocarbons. 
 In all probability these products are not chemical individuals, 
 but mixtures of homologues and isomers standing very near to 
 each other, as is shown by a comparison with the artificially- 
 prepared normal hydrocarbons. 
 
 P. Krafft has prepared those normal hydrocarbons from 
 C n H 24 to C 35 H 72 , which are mentioned in the table on p. 30, 
 from the acids C^, C 14 , C 16 , and C 18 of the acetic acid series 
 (see these), for which the normal constitution, i.e. non-branching 
 carbon chain, has been demonstrated; and also from the ketones, 
 C n H 2u O, which are obtained by subjecting the barium salts of 
 these acids to dry distillation, either alone or together with 
 acetate or heptoate of calcium; and which, as a consequence of 
 their mode of formation, yield normal hydrocarbons. (See 
 Ketones.) Krafft has further isolated the normal hydro- 
 carbons C ]r H 36 to C 23 H 48 , also C 24 H 50 , C 26 H 54 , and C^EU, by 
 subjecting the paraffin obtained from lignite to fractional dis- 
 tillation in vacua. 
 
 These are, from about C 16 H 34 (m.-pt. 18) on, solid at the 
 ordinary temperature. When distilled under atmospheric 
 pressure, or heated with AlBr 3 + HI, the higher hydrocarbons 
 partially decompose into lower ones of the formulae CJSan+a an d 
 C n H to ; this process is known as "cracking". But they may 
 be distilled in a vacuum, whereby their boiling-points are 
 reduced by 100 or more. (See table.) 
 
 Petroleum, Mineral Oils. These are probably produced by 
 the decomposition of animal or vegetable organisms* (Engler, 
 C. C. 1906, II, 1017), and are found between Pittsburg and 
 Lake Erie in America; between Lake Erie and Lake Huron 
 in Canada; in Hanover, Holstein, and Elsass in Germany; in 
 Boryslaw in Galicia; in the Crimea; in the Caucasus; in 
 Borneo, &c. The American oil consists mainly of paraffin 
 hydrocarbons, whereas the Eussian oil contains large quantities 
 of hydrocarbons of the general formula CJl,^. These latter 
 have been shown to be closed- chain compounds, they are 
 known as naphthenes, and are isomeric with the olefines. 
 
 The American and Russian oils are worked up on a large 
 scale for the preparation of commercial products. The crude 
 petroleum is a thick, oily liquid of dark colour and sp. gr. 0'8 
 to 0-92. It is usually washed with alkalis and sulphuric acid, 
 
 * This view is supported by the fact that many paraffin oils have a slight 
 optical activity. 
 
42 I. HYDROCARBONS 
 
 and then subjected to fractional distillation. The fraction 
 50-60 is termed petroleum ether or petrol, the fraction 70-90 
 is termed benzoline or benzine, ligroin is the fraction 90-120. 
 Burning oil is the fraction 150-300, and from the higher frac- 
 tions are obtained lubricating oils, vaseline, and paraffin-wax. 
 
 Paraffin- Wax, obtained by Eeichenbach in 1830 from wood 
 tar, is got by the distillation of lignite or peat. It also is a 
 mixture of many hydrocarbons, about 40 per cent of it con- 
 sisting of the compounds C 22 H 46 , C 24 H 50 , CggH^, and C 28 H 58 . 
 
 Liquid Paraffin (Reichenbach's " Eupion ") and the butter-like 
 Vaseline are high -boiling distillation products of lignite or 
 petroleum, and the same applies to many lubricating oils. 
 
 Ozokerite, green, brown, and red, and of the consistency of 
 wax, melting-point 60-80, is a natural paraffin found at 
 Boryslaw in Galicia, at Tscheleken near Baku (also called 
 Neftgil), on the Caspian Sea, and forms the ceresine of com- 
 merce when bleached. 
 
 Asphalt, or Earth Pitch, found in India, Trinidad, Java, 
 and Cuba, is a transformation product of the higher-boiling 
 mineral-oils, produced by the action of the oxygen of the air 
 just as paraffin absorbs oxygen and becomes brown upon pro- 
 longed heating in the air. It is used for cements and salves, 
 and in asphalting, photo-lithography, &c. 
 
 B. defines OP Hydrocarbons of the Ethylene 
 Series (Alkylenes): CJI^ 
 
 There are two series of hydrocarbons of the general formula 
 CnHan, the members of which differ from the corresponding 
 paraffins by containing two atoms of hydrogen less in the 
 molecule. The one series is that of the Olefines, of which 
 ethylene, C<>H 4 , is the first member; the other is that which 
 contains Trimethylene, Tetramethylene, Hexamethylene, &c. 
 (Cf. Polymethylenes.) 
 
 The properties exhibited by these two series are so different 
 that different constitutions must be accorded to them. The 
 olefmes form additive compounds with exceptional facility, 
 being thus converted into the paraffins or their derivatives; 
 from this the conclusion is drawn that, like the latter, they 
 contain an open carbon chain. 
 
 The names given to the hydrocarbons are similar to those 
 for the paraffins, except that the termination ane is replaced by 
 ene, or often by yUne. 
 
OLEFINES 
 SUMMAKY 
 
 43 
 
 
 
 Melting-point. 
 
 Boiling-point. 
 
 Ethylene 
 
 CUL 
 
 169 
 
 .10*? 
 
 Propylene 
 
 CH 
 
 
 48 
 
 Butylene (3>: 
 
 fa 
 G.HJ 8 
 
 
 -5 
 
 4-1 
 
 Amylene (5) ... 
 
 17 
 C,H in * 
 
 
 -6 
 _|_39 
 
 
 OK 
 
 
 68 
 
 Heptylene . 
 
 
 
 QK 
 
 Octylene 
 
 E 
 
 
 124 
 
 Nonylene 
 
 CalLo 
 
 
 153 
 
 Decylene.. .. 
 
 r H 
 
 
 172 
 
 TJndecylene . . . . 
 
 CJI 
 
 
 195 
 
 Dodecylene 
 
 
 31 
 
 {96t 
 
 Tridecylene . . . 
 
 3 2 I 2 2 j 
 
 
 233 
 
 Tetradecylen e 
 
 
 12 
 
 {127 
 
 Pentadecylene .. . 
 
 FT 
 
 
 247 
 
 Hexadecylene (Cetene).. 
 Octadecylene . . . 
 
 CicHga 
 C 18 H,, 
 
 +4 
 18 
 
 / 274 
 \{155 
 (179 
 
 Eicosylene 
 
 P 18 rf 3n 
 
 
 
 Cerotene 
 
 tiX 
 
 58 
 
 
 Melene . . 
 
 
 62 
 
 
 
 
 
 
 The general formula C n H 2n for this series indicates that each 
 member differs from the corresponding member of the paraffins 
 by two hydrogen atoms. 
 
 In their physical properties they resemble the methane 
 homologues very closely. C 2 H 4 , C 3 H 6 , and C^Hg are gases, 
 C 5 H 10 a volatile liquid, the higher members liquids with rising 
 boiling-point and diminishing mobility, while the highest are 
 solid and similar to paraffins. The boiling-points of members 
 of both series containing the same number of carbon atoms, 
 and whose constitutions are comparable, lie very close together, 
 but the melting-points of the olefines are somewhat the lower 
 of the two; e.g. C ]6 H, 4 , m.-pt. 21, b.-pt. {157, and C 16 H 32 , 
 m.-pt. 4, b.-pt. {155. 
 
 * The melting- and boiling-points given from C 5 Hi on, are those of the 
 normal hydrocarbons, 
 t { signifies boiling-point under 15 mm. pressure. 
 
44 I. HYDROCARBONS 
 
 Most of the olefines are readily soluble in alcohol and ether, 
 but insoluble in water, only the lower members dissolving 
 slightly in the latter. The specific gravities of the normal 
 olefines, determined at the melting-points, rise from about O63 
 upwards, and approach with increasing carbon to a definite 
 limit, viz. about 0'79. 
 
 In their chemical relations, the olefines differ materially from 
 the paraffins. Most of their special chemical characteristics 
 are undoubtedly due to the presence of a double or olefine 
 bond in the molecule, e.g. ethylene, CH 2 :CH 2 . (Cf. Con- 
 stitution of Olefines.) 
 
 (a) They combine readily with nascent hydrogen, with 
 chlorine, bromine, iodine, and their hydracids, fuming sul- 
 phuric acid, hypochlorous acid, nitrous acid, and, generally 
 speaking, with two monad atoms or monovalent groups, 
 whereby members of the methane series or their derivatives 
 ensue; hence their name of " Unsaturated Hydrocarbons". 
 
 - as- 
 
 = C 2 H 6 (S0 4 H). 
 
 In the formation of these additive compounds the double 
 bond present in the molecule becomes converted into a single 
 bond, and the two monovalent groups (e.g. Br, H,.OH, &c.) add 
 themselves on to the two carbon atoms between which the 
 double bond previously functionated, e.g. CH 2 :CH 2 + Br 2 
 gives CH 2 Br'CH 2 Br. Thus by the addition of bromine to an 
 olefine the two bromine atoms must always be attached to two 
 adjacent carbon atoms. (Cf. Polymethylene Hydrocarbons.) 
 
 Combination with hydrogen is sometimes effected, e.g. in 
 the case of ethylene, by the aid of platinum black at the 
 ordinary temperature, by means of finely-divided nickel at 
 a higher temperature, or by heating the olefines or their 
 dichlor-, &c., additive products with fuming hydriodic acid 
 and phosphorus. (Cf. Modes of Formation of the Saturated 
 Hydrocarbons.) 
 
 Ethylene chloride, C 2 H 4 C1 2 , obtained by the combination 
 of ethylene with chlorine, was formerly called the oil of the 
 Dutch chemists, hence the name of "Olefines" for the whole 
 class of hydrocarbons C n H 2n (Guthrie). 
 
 Chlorine adds itself on more easily than iodine, but hydro- 
 chloric acid less readily than hydriodic, bromine and hydro- 
 
MODES OF FORMATION 45 
 
 bromic acid standing midway. When a halogen hydride is 
 
 used, the halogen attaches itself to that carbon atom to which 
 
 the smaller number of hydrogen atoms are already united, *e.g. 
 
 CH 3 .CH:CH 2 + HI = CH 3 .CHI.CH 3 . 
 
 Particular olefines, e.g. isobutylene, also combine slowly with 
 water to alcohols under the influence of dilute acids. 
 
 Ethylene combines with fuming sulphuric acid at the ordinary 
 temperature, and with the concentrated acid at 160-170. 
 
 Amylene forms with nitrogen tetroxide, N 2 4 , amylene 
 nitrosate (A. 248, 161); nitrogen trioxide and nitrosyl chloride 
 also unite directly with the olefines. 
 
 (b) They readily polymerize, especially in presence of sul- 
 phuric acid or zinc chloride. "Thus amylene, C 5 H 10 , in presence 
 of sulphuric acid yields the polymers C 10 H 20 , C, H 30 , and C 20 H 40 ; 
 and tertiary butyl alcohol, warmed with acid of a definite 
 strength, di-isobutylene. 
 
 (c) Unlike the paraffins, they are readily oxidized by KMn0 4 
 or Cr0 3 , but not by cold HN0 3 . 
 
 In this reaction, two hydroxyl groups are added to the 
 molecule of the olefine if a dilute (1 per cent) solution of 'per- 
 manganate is used, and a dihydric alcohol (a glycol) is formed. 
 CH 2 :CH 2 T* OH.CH 2 .CH 2 .OH. 
 
 But if stronger solutions are used, or if chromic anhydride is 
 employed, the molecule of the olefine is ruptured at the point 
 where the double bond exists and a mixture of simpler acids 
 or ketones is obtained. The readiness with which unsaturated 
 compounds discharge the colour of acidified permanganate is 
 frequently made use of as a qualitative test for such compounds. 
 
 The "official name" (p. 40) of the olefines is formed by 
 replacing the last syllable " ane " of the paraffins by " ene ". 
 The position of the double bond is denoted by the number of 
 the carbon atom from which it proceeds. In a branching 
 chain the numbering is the same as in the case of the corre- 
 sponding saturated hydrocarbons; in a normal chain it begins 
 at the end carbon atom which is nearest to the double bond. 
 
 Example: * 2 8 * 
 
 is 4-methyl-2-pentene. 
 
 Modes of formation. (a) Together with paraffins by the 
 destructive distillation of many substances, such as wood, 
 
 *Cf. Michael, J. pr. 1888, [ii] 37, 524; 1903, 68, 487; B. 1906, 39, 2138, 
 
46 I. HYDROCARBONS 
 
 lignite, and coal, and also by the distillation of the higher 
 paraffins (process of "cracking", p. 41); illuminating gas con- 
 sequently contains the olefines C 2 H 4 , C 8 H 6 , C 4 H 8 , &c. 
 
 (b) By abstraction of water from the alcohols, CnH^^OH, 
 by heating them with sulphuric acid, phosphorus pentoxide, 
 zinc chloride, anhydrous formic acid, syrupy phosphoric acid, 
 &c. When sulphuric acid is used, an alkyl-sulphuric acid, e.g. 
 ethyl hydrogen sulphate, C 2 H 5 S0 2 OH, is first formed, and 
 this decomposes upon further warming into alkylene and sul- 
 phuric acid. This method is especially applicable in the case 
 of the lower homologues. Many alcohols yield olefines when 
 heated alone, or with finely divided solids (Chap. XLIX). 
 
 The palmitic esters of the higher alcohols, when distilled 
 under somewhat diminished pressure, yield palmitic acid and 
 an olefine. 
 
 (c) By heating the halogen compounds C n H 2n+1 X with alco- 
 holic potash, or by passing their vapour over red-hot lime or 
 hot oxide of lead, &c. ; sometimes by simple distillation : 
 
 C 6 H n I + KOH = C 6 H 10 + KI + H 2 0. 
 
 The iodine and bromine compounds are particularly suited 
 for this. The reaction may be regarded as the elimination of a 
 molecule of halogen hydracid from the molecule of the com- 
 pound, the halogen coming from the one carbon atom and the 
 hydrogen from an adjacent. (Cf. also Nef, A. 1901, 318, 3.) 
 
 (d) Sometimes from the haloid compounds CnH^X, by ab- 
 straction of the halogen,* e.g. ethylene from ethylene bromide 
 by treatment with zinc, magnesium, or zinc dust and alcohol: 
 
 C 2 H 4 Br 2 + Zn = C 2 H 4 + ZnBr 2 . 
 
 (e) By the electrolysis of potassic salts of dibasic acids 01 
 the succinic acid series; thus succinic acid itself yields ethy- 
 lene: 
 
 C 2 H 4 (COOH) 2 = C 2 H 4 + 2C0 2 + H 2 . 
 
 The complex anion CO CH 2 CH 2 CO 0, when discharged 
 decomposes into ethylene and carbon dioxide. 
 
 Constitution of the Olefines. For ethylene the following for 
 mulae may be given: 
 
 CH 3 CH 2 - CH 2 
 
 * Only when the halogen atoms are attached to adjacent carbon at*#is. 
 
]] METHYLENE U 47 
 
 . ^_^v ft t*W 1^0^ 
 
 In the formulae I and II, two free carbon bonds or valencies 
 are assumed in the ethylene molecule. Formula III follows 
 from the assumption that the bonds which are not used up in 
 attaching the hydrogen atoms to carbon are used in uniting 
 the carbon atoms themselves. 
 
 Now the ethylene bromide which is formed by the addition 
 of bromine to ethylene has, for reasons which will be given 
 under that compound, the constitution CH 2 BrCH 2 Br, and 
 likewise the compound obtained by the addition of C10H 
 (i.e. Cl and OH), viz. glycol chlorhydrin, the constitution 
 CH 2 C1CH 2 OH; consequently formula I, according to which 
 these substances would have the constitutions CH 3 CHBr 2 
 and CH 8 .CHC1(OH), is excluded. 
 
 Formula III is more probable than formula II: 
 
 (a) Since methylene, CH 2 :, appears to be incapable of 
 existence; all attempts to isolate it have yielded ethylene, 
 C 2 H 4 (see below), so that free valencies attached to the carbon 
 atom probably cannot exist. 
 
 (b) Because the free affinities to be assumed according to II 
 are never found singly (which should in that case be possible), 
 but invariably in pairs only, and indeed only on neighbouring 
 carbon atoms. This is proved from the constitution of the 
 compounds obtained by the addition, for instance, of Br 2 . 
 Unsaturated compounds containing only one carbon atom, 
 and unsaturated hydrocarbons containing an odd number of 
 hydrogen atoms, are unknown. 
 
 It is therefore to be concluded that in ethylene and its 
 homologues a double carbon bond, corresponding with formula 
 III, exists. 
 
 By this term " double bond " is not, however, to be under- 
 stood a closer or more intimate combination. The defines, on 
 the contrary, are more readily oxidized than the paraffins, 
 being thereby attacked at the point of the double bond. 
 Other properties, especially physical ones, also give indications 
 that a double bond between two carbon atoms is looser, and 
 therefore more easily broken, than a single one. (Cf. Bruhl, 
 A. 211, 162.) 
 
 1. Methylene (Methene), CH 2 , does not exist. Numerous 
 attempts to prepare it, e.g. by the withdrawal of hydrogen and 
 chlorine from methyl chloride, or of iodine from methylene 
 jodide, have invariably yielded ethylene, thus: 
 
 2CH 3 C1 -2HC1 = C 2 H 4 . 
 
 / \~\ ^"Nl 
 
 .* - z- 
 
48 I. HYDROCARBONS 
 
 Here the two resulting CH 2 -residues have united together, in 
 the same way as the two methyl-groups coalesced to ethane 
 (p. 34). 
 
 2. Ethylene (Ethene), olefiant gas, CH 2 :CH 2 . 
 
 This compound was discovered in 1795 by four Dutch 
 chemists. Its formula was established by Dalton. 
 
 Illuminating gas generally contains 4 to 5 per cent of ethy- 
 lene. For formation from elements see Pring and Fairlie, 
 J. C. S. 1911, 99, 1806. It is usually prepared by heating 
 alcohol with excess of concentrated sulphuric acid, with addi- 
 tion of sand, a mixture of equal portions of the two liquids 
 being subsequently dropped into the evolution flask; sulphur 
 dioxide, &c., are produced at the same time by secondary re- 
 actions. A better method is to heat alcohol with syrupy 
 phosphoric acid at 200 (Newtli). Small quantities can be 
 conveniently prepared from ethylene bromide and zinc or 
 magnesium. It is further formed by heating ethylidene 
 chloride, CH 3 -CHC1 2 , with sodium. 
 
 It may be liquefied at under a pressure of 44 atmos., 
 is very slightly soluble in water and alcohol; burns with a 
 luminous flame, and forms an explosive mixture with oxygen. 
 When rapidly mixed with two volumes of chlorine and set fire 
 to, it burns with a dark-red flame, with formation of hydro- 
 chloric acid and deposition of much soot. It is converted at 
 a red heat into methane, CH 4 , ethane, C 2 H 6 , acetylene, C 2 H 2 , 
 &c., with separation of carbon. (See p. 36.) It combine! 
 with hydrogen in presence of spongy platinum to ethane, 
 C 2 H 6 . " 
 
 3. Propylene (Propene), C 3 H 6 , CH 2 :CH-CH 3 . Only one 
 olefine, C 3 H 6 , is theoretically possible and only one is known, 
 viz. methylethylene. It can be prepared from isopropyl iodide 
 and caustic potash, or by heating glycerol with zinc dust. It 
 is isomeric with trimethylene (see Polymethylenes). 
 
 4. Butylene, C 4 H 8 . Three butylenes are possible according 
 to theory, and three are known. All of them are gaseous, 
 their boiling-points lying between 6 and +3. Butylene 
 and pseudo-butylene are derived from normal butane, and iso- 
 butylene from isobutane, since they severally combine with H 2 
 to form these hydrocarbons. The first, a-butylene, is prepared 
 from normal; the second, /3-butylene, from secondary; and the 
 third, y-butylene, from tertiary butyl iodide, by the action of 
 caustic potash upon these; the last can also be obtained from 
 isobutyl alcohol and sulphuric acid. The isomerism of the two 
 
V 'a 
 
 ACETYLENE HYDROCARBONS 49 
 
 butylenes derived from normal butane is explained by the 
 assumption of a double bond at different points, thus: 
 
 CH 2 : CH . CH 2 CH 3 CH 3 CH : CH CH 3 
 
 a-butylene (l-butene) /3-butylene (2-butene). 
 
 Isobutylene has the formula (CH 3 ) 2 C : CH 2 (methylpropene). The 
 behaviour of these isomers upon oxidation is in accordance 
 with the above formulae, the oxidation always taking place at 
 the point of the double bond. 
 
 The butylenes are isomeric with tetra-methylene (cydo- 
 butane, see Polymethylenes). 
 
 5. Amylene, C 5 H 10 . A large number of isomeric amylenes 
 are known, among them being Amylene (b.-pt. 35), which is 
 obtained, together with an isomer, Iso-amylene, by heating 
 ordinary amyl alcohol with chloride of zinc. For it the con- 
 stitutional formula (CH 3 ) 2 C : CH CH 3 ( = trimethylethylene) is 
 assumed. This is known in the pure form under the name of 
 "pental". 
 
 The higher defines of normal constitution, with 12, 14, 16, 
 and 18 atoms of carbon, have been prepared by Kraft accord- 
 ing to method b. 
 
 Cerotene and Melene (m.-pt. 62) are obtained by the distil- 
 lation of Chinese wax and bees'- wax respectively. They are like 
 paraffin in appearance, and are only sparingly soluble in alcohol. 
 
 C. Hydrocarbons, C n H 2n _ 2 : Acetylene Series 
 
 The hydrocarbons of this series again differ from those of 
 the preceding by containing two atoms of hydrogen less. In 
 physical properties they closely resemble both the latter and 
 those of the methane series; thus the lowest members up to 
 C,H 6 are gaseous, the middle ones liquid, and the highest 
 solid, and in their melting- and boiling-points they do not 
 differ to any extent from those of the other series with an 
 equal number of carbon atoms. The specific gravities of the 
 normal hydrocarbons C 12 , C 14 , C 16 , and C 18 , at the melting- 
 point, gradually approach with increasing carbon to a definite 
 limit (0-80), and are somewhat higher than those of the corre- 
 sponding members of the ethylene series throughout. ^ 
 
 Constitution. Upon grounds similar to those which have 
 already been explained under ethylene, the constitutional for- 
 mula for acetylene, C 2 H 2 , is assumed to be CH-CH, according 
 to which the carbon atoms are joined together by a triple bond. 
 
 ( B 480 ) P 
 
50 I. HYDROCARBONS 
 
 For a compound C 3 H 4 , the two following constitutional for- 
 mulae are possible : 
 
 CH : C CH 3 (allylene) and CH 2 : C : CH 2 (allene). 
 
 As a matter of fact, two hydrocarbons C 3 H 4 do exist, only one 
 of which, allylene, yields metallic compounds. It is therefore 
 to be considered the true homologue of acetylene, containing a 
 triple bond, according to the first of the two above formulae, 
 while to allene the second formula, with the two double bonds, 
 is to be ascribed. The constitution of the tetrabromopropanes, 
 which are formed from these by the addition of bromine, agrees 
 with this conception. 
 
 In their chemical relations the acetylenes stand nearer to 
 the olefines than to the paraffins, in so far that they are un- 
 saturated and therefore capable of forming additive products. 
 
 1. A molecule of an acetylene can combine either (a) with 
 two atoms of hydrogen or halogen, or with one molecule of 
 halogen hydride, to olefines or their substitution products, 
 thus : 
 
 CH:CH + 2H = CH 2 :CH 2 
 
 CHiCH + HBr = CH 2 :CHBr (vinyl bromide) 
 
 CH:CH + Br 2 = CHBnCHBr; ' 
 
 or (b) with four atoms of hydrogen or halogen, or two mole- 
 cules of halogen hydride, to paraffins or paraffin substitution 
 products, thus: 
 
 CH 3 .C:CH + 4H = CH 3 .CH 2 .CH 3 
 
 (in presence of platinum black) 
 CH : CH + 2 Br, = CHBr 2 CHBr 2 
 CH 3 -C:CH + 2"HI = CH 3 .CI 2 .CH 3 . 
 
 Like many of the olefines, various members of this series 
 combine with water under the influence of dilute acids, thus 
 allylene, C 3 H 4 , gives acetone, C 3 H 6 0; and acetylene, C 2 H 2 , 
 gives crotonic aldehyde, with intermediate formation of acetic 
 aldehyde. The combination with water may be accomplished 
 (a) by the action of sulphuric acid when, as in the case of the 
 olefines, alkyl hydrogen sulphates are formed as intermediate 
 products; (b) by means of mercuric chloride solution; or (c) by 
 directly heating the hydrocarbon with water at 300 in sealed 
 tubes. HgCl 2 and other mercury salts also induce such hy- 
 dration : 
 
 CH:CH-fH 2 O = CH 3 .CHO 
 CH 3 -C:CH + OH 2 = CH 3 .CO-CH 3 . 
 
FORMATION OF ACETYLENE HYDROCARBONS 51 
 
 2. Many of the acetylene hydrocarbons are readily poly- 
 merized; thus, acetylene is transformed into benzene when 
 led through a red-hot glass tube. This is an important syn- 
 thesis of benzene: 
 
 3C 2 H 2 = CJH,. 
 
 At the same time the compounds C 8 H 8 , 10 H 8 , &c., are 
 formed. Similarly allylene, C 3 H 4 , gives mesitylene, C 9 Hi 2 , 
 in contact with sulphuric acid and a little water. (See Ben- 
 zene Derivatives.) 
 
 3. Acetylene and some of its homologues react even at the 
 ordinary temperature, in a manner which is peculiar to them, 
 with an ammoniacal solution of cuprous or argentic oxide, to 
 form reddish - brown or yellow-white precipitates, e.g. CCu: 
 CCu; CAgiCAg; CH 3 C:CAg, &c., which are explosive, and 
 which are decomposed by acids, such as HC1, with regeneration 
 of the hydrocarbon. 
 
 The hydrogen of acetylene can be replaced by potassium or 
 sodium; thus, when the hydrocarbon is heated with sodium, 
 the compounds C 2 HNa and C 2 Na 2 are obtained. These are 
 decomposed by water or acids with evolution of acetylene. 
 
 All the hydrocarbons CJE^^ do not, however, give such 
 metallic compounds, but only the true homologues of acetylene 
 containing the grouping C : CH. 
 
 Hydrocarbons such as allene, CH 2 :C:CH 2 , which do not 
 contain a triple bond, and even acetylene compounds such as 
 CH 3 C C CH 3 , where no hydrogen atoms are attached to the 
 C atoms between which the triple bond is supposed to exist, 
 do not yield these metallic derivatives. 
 
 In the case of the higher homologues, isomerism may be 
 due either to the difference in position of the triple carbon 
 bond in the molecule, or to the presence and different positions 
 of the two double bonds. The constitution of a compound 
 is fixed by the formation or otherwise of metallic derivatives, 
 and by its behaviour upon oxidation. (See Oxidation of the 
 Butylenes, p. 49.) 
 
 The official name of the acetylene homologues proper, with 
 a triple carbon-linking, ends in "ine"; that of the isomeric 
 hydrocarbons, with two double bonds, in "diene". 
 
 Formation. 1. They are obtained, together with the hydro- 
 carbons already described, by the distillation of wood, lignite, 
 coal, &c.; thus illuminating gas contains acetylene, allylene, 
 and crotonylene. 
 
52 I. HYDROCARBONS 
 
 2. By treating the haloid, preferably the bromine, com- 
 pounds C n H 2n X 2 and CyB^^X with alcoholic potash or sodium 
 ethoxide (C 2 H 5 ONa): 
 
 H \ / Br 
 
 H^C-Cr-H 2HBr = HC:CH. 
 
 Br/ \H 
 
 With alcoholic potash, even when excess is used, the re- 
 action tends to stop at the first stage, and a brominated olefine 
 is formed, e.g. vinyl bromide (p. 65) from ethylene dibromide; 
 with sodic ethoxide, the elimination of hydric bromide pro- 
 ceeds more readily. 
 
 Further, from the unsaturated alcohols, CJE^^'OH, by the 
 separation of the elements of water from them. 
 
 3. By the electrolysis of potassium salts of the acids of the 
 fumaric acid series (KekuU). 
 
 4. Certain acetylene hydrocarbons, R-CiC-CH 3 , when 
 heated with sodium, pass into the sodium compounds of their 
 isomers, R-CH 2 C:CH; on the other hand, when the latter 
 are warmed with alcoholic potash, the opposite reaction takes 
 place (Faworsky, B. 20, Ref. 781; 25, Ref. 81; 25, 2244). 
 
 Acetylene (Bibine), C 2 H 2 , was first obtained impure by 
 E. Davy from calcium carbide in 1839, and pure by Berthelot 
 in 1849. Illuminating gas contains 0'06 per cent. It is syn- 
 thesised from its elements, when an electric arc is caused to 
 pass between two carbon poles in an atmosphere of hydrogen 
 (Berthelot), but other hydrocarbons are formed at the same 
 time (Bone and Jerdan, J. C. S. 1901, 1042; cf. also Button 
 and Pring, 1906, 1591). It may be obtained from ethylene 
 bromide and sodium ethoxide solution ; also by the incomplete 
 combustion of many carbon compounds, for instance, when the 
 gas in a Bunsen lamp burns at the base; and from ethane, 
 ethylene, and methane at a red heat, or by the action of the 
 induction spark. (See pp. 36 and 48.) The simplest method 
 of preparation is by the action of water on calcium carbide, 
 the water being allowed to drop gradually on to the carbide : 
 
 C 2 H 2 . 
 
 It becomes liquid at 1 under a pressure of 48 atmospheres, 
 burns with a luminous and very sooty flame, and has a peculiar 
 disagreeable smell. Its flame has a high illuminating power- 
 when burnt in specially-constructed burners, and is now largely 
 made use of as an illuminating agent. It dissolves in its own 
 
DIPROPARGYL 53 
 
 volume of water, and in six times its volume of alcohol; is 
 poisonous, combining with the hsemoglobin of the blood, 
 It is decomposed into its elements with detonation by ex- 
 plosive fulminate of silver, and also by the electric spark, 
 It combines with hydrogen to ethane, when heated with the 
 latter in presence of platinum black, or to ethylene, upon treat 
 ing its copper compound with zinc and ammonia. A mixture 
 of acetylene and oxygen explodes violently when a light is 
 applied to it. Chromic acid oxidizes acetylene to acetic acid, 
 and permanganate of potash to oxalic acid. It combines with 
 nitrogen under the influence of the induction spark to hydro- 
 cyanic acid (see this), and detonates upon being mixed with 
 chlorine, but additive products, e.g. C 2 H 2 C1 2 , can, however, be 
 prepared. As little as ^J<y milligramme of it can be detected 
 by the formation of the dark-red copper compound C 2 Cu 2 . 
 This latter explodes when struck, or when heated to a little 
 over 100. 
 
 Allylene (Propine), C 3 H 4 , or CH 3 C:CH, can be prepared 
 from propylene bromide, CH 3 CHBr CH 2 Br. It resembles 
 acetylene. 
 
 Allene (Propadiene), C 3 H 4 , or CH 2 :C:CH 2 , is obtained by 
 the electrolysis of itaconic acid. It is gaseous, and does not 
 yield metallic compounds. 
 
 Diallyl (Hexa-l : 5 -diene), CH 2 : CH . CH 2 . CH 2 CH : CH 2 , is 
 obtained from allyl iodide, CH 2 :CHCH 2 I, and sodium. ^ 
 
 Isomeric with these hydrocarbons are certain hydro-deriva- 
 tives of aromatic hydrocarbons, e.g. tetrahydrobenzene, C 8 H 14 ; 
 decahydronaphthalene, C 10 H 18 . (See Aromatic Compounds.) 
 
 D. Hydrocarbons C n H, 
 
 2n- 
 
 Di-acetylene (Butadiine), C 4 H 2 , or CH-C-C-CH. This is 
 prepared by heating the ammonic salt of diacetylene-dicar- 
 boxylic acid (see this) with ammoniacal copper solution, 
 whereby it is transformed into the cuprous compound of di- 
 acetylene, and then warming this with potassium cyanide. It 
 is a gas of a peculiar odour, which yields a violet-red copper 
 compound and a yellow silver one, the latter exploding upon 
 
 bromide, and the subsequent elimination of four molecules of 
 hydric bromide from each molecule of the tetra-bromide; b.-pt. 
 
64 II. HALOID SUBSTITUTION PRODUCTS 
 
 85. It gives copper and silver compounds, and takes up eight 
 atoms of bromine, &c. It possesses an especial interest, as it 
 is isomeric with benzene. Another isomeride is 2 : 4:-Hexadiine, 
 CH 3 . C i C C : C CH 3 . (B. 20, R. 564.) 
 
 II. HALOID SUBSTITUTION PRODUCTS OF THE 
 HYDROCARBONS 
 
 A. Halogen Derivatives of the Paraffins 
 
 These are to be regarded as paraffin hydrocarbons in which 
 one or more hydrogen atoms have become replaced by one or 
 more halogen atoms. 
 
 General Properties. Only a few of these compounds, e.g. 
 CH 3 C1, C 2 H 5 C1, and CH 3 Br, are gaseous at the ordinary tem- 
 perature, most of them being liquid, and those with a very 
 large number of carbon atoms in the molecule solid, e.g. cetyl 
 iodide, C 16 H 33 I. The introduction of a halogen atom in any 
 hydrocarbon in place of an atom of hydrogen always tends to 
 raise the boiling-point; the introduction of iodine has the 
 most marked effect, and chlorine the least (cf. Table, p. 56). 
 Such, also, as contain a large number of halogen atoms, e.g. 
 CI 4 , C 2 C1 6 , are solid. Under comparable conditions, the boiling- 
 points of the iodides lie, for each atom of halogen, about 50 
 (40-60), and those of the bromides about 22 (20-24), 
 above those of the chlorides. 
 
 The lowest members of the series have, in the liquid form, 
 at first a higher specific gravity than water, e.g. CH 3 I, sp. gr. 
 2*2, C 2 H 5 Br, sp. gr. 1'47. With an increasing number of 
 carbon atoms, however, they become more like the paraffins, 
 the influence of the halogen diminishes, and they are lighter 
 than water. 
 
 The halogen substitution products of the hydrocarbons are 
 very sparingly soluble in water, but readily in, and therefore 
 miscible to any extent with, alcohol or ether; they also dissolve 
 in glacial acetic acid. They often possess a sweet ethereal 
 odour, but this becomes less marked with diminishing vola- 
 tility. Most of them are combustible; thus methyl and ethyl 
 chloride burn with a green-bordered flame, while ethyl iodide 
 and chloroform can only be set fire to with difficulty. Many 
 
MODES OF FORMATION 55 
 
 members of the series containing one or two atoms of carbon 
 produce insensibility and unconsciousness when inhaled, e.g. 
 CHClg, C 2 H 3 C1 3 , C 2 H 5 Br, and C 2 HC1 5 . The liquid iodine 
 derivatives are readily decomposed, and on exposure to light 
 turn deep-brown in colour, owing to the liberation of free 
 iodine, e.g. ethyl iodide liberates iodine and gives C 4 H 10 . 
 
 In all these compounds the halogen is more firmly bound 
 than in inorganic salts, so that, for instance, when silver 
 nitrate is added to an aqueous solution of a chlorine com- 
 pound, e.g. chloroform, it causes no precipitation of AgCl. 
 Nevertheless, the halogen is in most cases readily exchangeable 
 for other elements or groups, a circumstance of the utmost 
 importance for many organic reactions. This is especially 
 true for the iodine and .bromine compounds, which react more 
 readily than the chlorides, and, on account of their lesser 
 volatility, are easier to work with; thus C 2 ILBr reacts with 
 AgN0 3 at the boiling temperature, and C 2 H 5 I in the cold 
 even. 
 
 In all these halogen compounds the halogen can be again 
 replaced by hydrogen by inverse substitution, e.g. by sodium 
 amalgam, by zinc dust and hydrochloric or acetic acid, or by 
 heating with hydriodic acid. (See p. 33.) 
 
 Of fluorine compounds, only a few are known as yet; CH 3 F 
 and C 2 H 5 F are gases. 
 
 Nomenclature. The best system of nomenclature is to regard 
 them as derived from the corresponding hydrocarbons, e.g. 
 CHClg trichloro-methane, CH 3 I mono-iodo-methane, and if 
 necessary to indicate the carbon atoms to which the halogen 
 radicals are attached, e.g. CH 2 C1CH 2 C1 1 : 2-dichloro-ethane, 
 CH 3 .CHBr 2 l:l-dibromo-ethane, CH 2 Br.CH 2 .CH 2 Br l:3-di- 
 bromo-propane, CH 3 . CH(CH 3 ) . CHBr . CH 2 CH 2 Br 2-methyl- 
 3 : 5-dibromo-pentane. 
 
 The following are some of the most important methods em- 
 ployed for the preparation of these halogen derivatives : - 
 
 1. By Substitution. Chlorination and Bromination. Chlorine 
 and bromine act for the most part as direct substituents (see 
 p. 31) With the gaseous hydrocarbons their action even in 
 the cold is an extremely energetic one (e.g. chlorine mixed 
 with methane easily causes an explosion, so that dilution with 
 C0 2 is necessary); the higher members require to be heated. 
 
56 
 
 II. HALOID SUBSTITUTION PRODUCTS 
 
 HALOGEN SUBSTITUTION PKODUCTS 
 
 Saturated Compounds 
 
 (a) Mono-substituted Derivatives. 
 
 Chloride. 
 
 B.-p. 
 -237 
 
 + 12-2 
 46-5 
 365 
 
 78 
 
 Sp. gr. 
 0-952 
 0-918 
 0-912 
 0-882 
 0-907 
 
 Bromide. 
 
 Iodide. 
 
 Siy] 
 
 Ethyl 
 
 w-Propyl 
 
 iso-Propyl 
 
 Prim. n-Butyl 
 
 (b) Di-substituted Derivatives. 
 
 Chloride. 
 B.-p. Sp. gr. 
 
 Methylene... 42 1-337 
 
 Ethylene 84 T260 
 
 Ethylidene... 58* M89 
 
 (c) Tri-substituted Derivatives. 
 
 Chloroform. 
 
 CHX 3 b.-p. 61 
 
 B.-p. 
 
 +4-5 
 
 38-4 
 
 71 
 
 60 
 
 101 
 
 Sp. gr. 
 
 1-732 
 
 1-468 
 1-383 
 1-340 
 1-305 
 
 B.-p. 
 +45 
 
 72-3 
 
 102-5 
 
 89 
 
 130 
 
 Sp.gr 
 2-293 
 1-944 
 1-786 
 1-744 
 1-643 
 
 Bromide. 
 B.-p. Sp. gr. 
 
 97 2-498 
 131 2-189 
 110 2-080 
 
 Iodide. 
 
 B.-p. Sp. gr. 
 180 3-292 
 solid; m.-p. 81-82 r 
 178 2-84 
 
 Bromoform. lodoform. 
 
 b.-p. 151 melts at H9 C 
 
 sublimes 
 (d} Tetra-substituted Derivative. 
 
 Chloride. Bromide. 
 
 CX 4 76 solid; m.-p. 92; b.-p. 189 
 
 Carbon tetra- 
 
 Unsaturated Compounds 
 
 Chloride. 
 
 Vinyl, CH 2 :CHX -18 
 
 Allyl, CH 2 :CH.CH 2 X 46 
 
 Bromide. Iodide. 
 +23 56 
 
 70 101 
 
 Trichlorethylene boils at 88, tetrachlorethylene at 121. 
 Monochlor- and monobrom-acetylene are gaseous. 
 
 Compounds of the type CCl 3 Br, CCl 2 Br 2 , CC1 2 I 2 , &c., arc 
 also known. 
 
 The first halogen atom enters most easily into the com- 
 pound, the substitution becoming more difficult as the number 
 of those atoms present increases. In the case of the higher 
 hydrocarbons there usually result two isomeric mono-substi- 
 tution products. The action of the halogens is further facili- 
 tated by sunlight, and by the presence of iodine, this latter 
 acting as a carrier of chlorine by the alternate formation of 
 IC1 3 and IC1, thus: IC1 3 = IC1 + 2 Cl. Antimony penta- 
 
FORMATION OF HALOGEN DERIVATIVES 57 
 
 chloride and ferric chloride act in the same way (and also for 
 brominating and iodating, B. 18, 2017; A. 231, 195); iron 
 wire is especially useful in brominating (B. 24, 4249). When 
 complete chlorination is required, the substance in question is 
 repeatedly saturated with chlorine in presence of iodine, and 
 heated in a tube to a high temperature. 
 
 From methane are formed the whole series of substitution 
 products up to CC1 4 . 
 
 Ethane first yields ethyl chloride, C 2 H 5 C1, then ethylidene 
 chloride, C 2 H 4 C1 2 , and so on up to C 2 C1 6 . 
 
 From propane is first produced normal propyl chloride, 
 3 H 7 C1, and finally C 3 C1 8 . The latter decomposes, upon 
 vigorous chlorination, first into C 2 C1 6 and CC1 4 , and the 
 perchloro-ethane subsequently into two molecules CC1 4 . On 
 chlorinating butane and the higher hydrocarbons strongly, an 
 analogous splitting up of the molecule is effected. Strong 
 chlorination or bromination readily gives rise at the same time 
 to hexachloro- or hexabromo-benzene. 
 
 Iodine seldom acts as a direct substituent, since by this 
 reaction hydrogen iodide would be formed, which would then 
 reduce the iodine compound back to the hydrocarbon. (See 
 p. 33.) To induce the action, therefore, the HI formed must be 
 removed by HI0 3 or HgO. The iodine substitution products of 
 the hydrocarbons are usually prepared indirectly (according to 
 2 or 3). 
 
 2. From Unsaturated Hydrocarbons. These combine readily 
 with halogen or halogen hydride. (See p. 44.) 
 
 Ethylene gives with hydrochloric, hydrobromic, and hydri- 
 odic acids, ethyl chloride, &c., i.e. mono-substitution products 
 of ethane; with chlorine, &c., it gives di-substitution products. 
 
 The compound C 2 H 4 C1 2 , obtained by the action of chlorine, 
 is called ethylene chloride, has the constitutional formula 
 CH 2 C1.CH 2 C1, and is isomeric with the ethylidene chloride 
 CH 3 .CHC1 2 , obtained by the chlorination of C 2 H 5 C1. (For an 
 explanation of this isomerism, see p. 62.) 
 
 Propylene combines with hydriodic acid to isopropyl iodide, 
 C 3 H 7 I, which is reconverted into propylene by elimination of 
 HI. But the same propylene results from a compound isomeric 
 with isopropyl iodide, viz. normal propyl iodide (and also, of 
 course, from the above-mentioned normal propyl chloride), by 
 the elimination of hydrogen iodide (or chloride), so that by this 
 reaction normal propyl iodide can be transformed into iso- 
 propyl iodide. (See p. 60.) From the three butylenes there 
 
58 II. HALOID SUBSTITUTION PRODUCTS 
 
 are formed two butyl iodides, viz. secondary and tertiary, 
 which, as well as the two other existing butyl iodides, yield 
 these butylenes again with alcoholic potash; in this way the 
 two last-mentioned butyl iodides are convertible into their 
 isomers, the two first (see p. 61). 
 
 A study of the constitution of the compounds formed, shows 
 that in these additive reactions the halogen invariably attaches 
 itself to that carbon atom with which are combined the least number 
 of hydrogen atoms, e.g. 
 
 CH 3 CH : CH 2 -f HI = CH 3 CHI CH 3 (not CH 3 CH 2 CH 2 I) ; 
 
 from C 3 H 7 X onwards, therefore, we obtain only " secondary " 
 and " tertiary " * compounds. 
 
 3. From Compounds containing oxygen. 
 
 (a) From the alcohols C^H^OH. In these the OH is 
 readily exchangeable for chlorine, bromine, or iodine by the 
 action of halogen hydride, thus: 
 
 C 2 H 6 OH + HBr ^ C 2 H 6 Br + H 2 0. 
 
 In such exchange the halogen takes the place of the hy- 
 droxyl, so that the constitution of the haloid product corre- 
 sponds with that of the alcohol used. 
 
 These reactions are reversible or balanced, and a state of 
 equilibrium is reached; according to the law of mass action, 
 it is therefore necessary either to use a large excess of halogen 
 hydride (e.g. to saturate with the gas or to heat in a sealed 
 tube), or to remove the water formed, by sulphuric acid, zinc 
 chloride, &c. 
 
 Methyl and ethyl chlorides are easily prepared by distilling 
 the corresponding alcohol with common salt and sulphuric 
 acid, or by leading hydrochloric -acid gas into the warmed 
 alcohol containing half its weight of zinc chloride in solution 
 (Groves). 
 
 The chlorides of phosphorus are also applicable for the sub- 
 stitution of OH by Cl, since they react in the same way with 
 alcohols as with water, thus : 
 
 POL + 3 HOH = P(OH) 3 4- 3 HC1 
 PC1 3 4- 3C 2 H 6 OH = P(OH) 3 4- 3C 2 H 6 C1. 
 
 * The names "primary", "secondary", and "tertiary" compounds are 
 founded upon those of the alcohols primary, secondary, and tertiary ir 
 question, from which they can be prepared according to method 3, a. 
 
MONO-SUBSTITUTION PRODUCTS 59 
 
 Phosphorus pentachloride is most frequently used for this 
 purpose, 
 
 PC1 6 H- C 2 H 6 OH = C 2 H 6 C1 + HC1 + POC1 3 . 
 
 Phosphorus oxychloride itself is also sometimes employed. 
 Of especial importance here is the application of the halogen 
 compounds of phosphorus in the production of bromine and 
 iodine compounds. The former need not be prepared before 
 band, the end being achieved by gradually bringing phosphorus 
 and iodine or bromine together in presence of the alcohol: 
 3CH 3 OH + P + 31 = 3CH 3 I 
 
 This is the method usually employed for the preparation of 
 methyl and ethyl iodides. 
 
 (b) The halogen -derivatives may also be prepared from 
 polyhydric alcohols, e.g. trichlorhydrin, C 3 H 6 C1 3 , from gly- 
 serol, C 3 H 5 (OH) 3 , and PC1 5 ; isopropyl iodide, C 3 H 7 I, or allyl 
 iodide, C 3 H 5 I, from glycerol and PI 3 according to the con- 
 ditions of the experiment (see p. 60); hexyl iodide, C 6 H 13 I, 
 f rom mannitol, C 6 H 8 (OH) 6 and HI, the latter acting here as 
 
 t reducing agent also. 
 
 (c) From aldehydes and ketones (see these), dichloro-sub- 
 stitution products are formed by the action of PC1 5 , e.g. ethyli- 
 lene chloride, CH 3 .CHC1 2 , from aldehyde, CH 3 .CH:0; ace- 
 tone chloride, CH 3 CC1 2 CH 3 , from acetone CH 3 -CO-CH 3 . 
 
 4. Chlorine and bromine compounds are frequently formed 
 Tom the corresponding iodine or bromine ones by direct ex- 
 change, e.g. isopropyl bromide from the iodide, or methylene 
 >romide from methylene iodide ; (also by treatment with mer- 
 curic chloride, stannic chloride, or fuming hydrochloric acid). 
 Conversely the chlorides and bromides may be transformed 
 nto the iodides by heating with sodium iodide in alcoholic 
 jr acetone solution (B. 18, 519), dry calcium iodide (B. 16, 
 392), or with fuming hydriodic acid. 
 
 MONO-SUBSTITUTION PKODUCTS 
 
 The methyl and ethyl compounds are usually obtained from 
 fche corresponding alcohols by one or other of the following 
 methods: (a) Grove's method (p. 58); (b) action of concen- 
 trated sulphuric acid and sodium halide; (c) phosphorus and 
 halogen. 
 
 Methyl chloride is often obtained by heating trimethy- 
 lamine hydrochloride at 360. (For physical properties, see 
 
60 II. HALOID SUBSTITUTION PRODUCTS 
 
 Table.) Methyl chloride is used for the production of artificiE 
 cold, for extracting perfumes from flowers, and for methylal 
 ing dyes in the colour industry. It burns with a greer 
 bordered flame. 
 
 Ethyl Fluoride, C 2 H 5 F. A gas of ethereal odour, whic 
 liquefies at 48; it burns with a blue flame, and does no 
 attack glass. 
 
 Each Propyl halide, C 3 H 7 X, exists in two isomeric form* 
 the normal propyl and the isopropyl compounds, the forme 
 boiling at a somewhat higher temperature than the latter. T 
 the normal compounds the constitutional formula CH 3 'CH 2 
 CH 2 X is ascribed, and to the iso-compounds the formul 
 CH 3 CHX'CH 3 , since they are derivable respectively fror 
 normal propyl alcohol and from isopropyl alcohol or acetone 
 the constitutions of which can readily be determined. 
 
 According to theory only these two cases are possible, sine 
 propane, CH 3 CH 2 'CH 3 , contains but two types of hydroge 
 atoms, viz.: (1) six combined with the end carbon atoms, an< 
 (2) two combined with the middle ones. For the transform* 
 tion of the normal into the iso-compounds, see p. 57. 
 
 Isopropyl iodide, 2-iodopropane, is prepared from glycero 
 phosphorus, iodine, and water (see p. 59); allyl iodide (p. 65 
 is formed as intermediate product, and at the same time som 
 propylene (p. 48): 
 
 C 3 H 6 (OH) 3 + SHI - 3H 2 = C 3 H 6 I 3 = C 3 H 6 I + I 2 . 
 C 3 H 6 I + HI = C 3 H 6 + I 2 . C 3 H 6 I -f 2 HI = C 3 H 7 I + I 2 . 
 
 Each Butyl-haloid compound, C 4 H 9 X, is known in for 
 isomeric forms, which differ from one another in boiling-poir 
 (up to 30). 
 
 Four isomers are theoretically possible; thus from norm? 
 butane, CH 3 -CH 2 .CH 2 .CH 3 , are derived: 
 
 (a) CH 3 .CH 2 .CH 2 .CH 2 I and (b) CH 3 .CH 2 .CHI.CH 3 
 
 Normal butyl iodide (I-iodobutane) Secondary butyl iodide (2-iodobutane 
 
 according to whether a " terminal " or " central " hydroge 
 atom is replaced; similarly from trimethylmethane, CH(CH 3 ) 
 are derived: 
 
 (c) 3>CH.CH 2 I and (d) ]|j>CI.CH 3 
 
 Is'obutyl iodide Tertiary butyl iodide 
 
 (Z-methyl-B-iodopropane) (Z-methyl-Z-iodopropane). 
 
 The constitutions of these four compounds follow fror 
 
Y 
 
 DI-SUBSTITUTION PRODUCTS 61 
 
 hose of the four corresponding butyl alcohols (p. 67), from 
 hich they can be prepared by the action of halogen hydride. 
 For transformations, see p. 58. Isobutyl bromide changes 
 nto the tertiary compound when heated at 230-240, prob- 
 bly owing to the intermediate formation of butylene. 
 
 The Isobutyl compounds are the easiest to prepare (from 
 sobutyl alcohol). The Tertiary readily react with H 2 to 
 orm the alcohol and halogen hydride, this taking place even 
 n the cold in the case of the iodide. 
 
 These mono-halogen derivatives are one of the most impor- 
 ant groups of reagents employed by the organic chemist, on 
 ccount of the readiness with which the halogen atoms may 
 >e replaced by other radicals. 
 
 ome of the more characteristic reactions are: 
 I. Eeplacement of halogen by hydrogen. Inverse substi- 
 , 1C ution (see p. 33). 
 , e 2. Eeplacsment of halogen by OH (hydroxyl) (p. 71), 
 
 C 2 H 5 I + H 2 = C 2 H 6 OH + HI, 
 
 generally by the aid of aqueous alkali, moist silver oxide, or 
 ead oxide and water. 
 
 3. Alkalis in alcoholic solution, or alcoholic solutions of 
 odium methoxide (CH 3 ONa) or sodium ethoxide (C 2 H 5 ONa), 
 is a rule, eliminate halogen hydracids, and yield olefines, 
 3H 2 ICH 3 HI = CH 2 :CH 2 . For the reaction it is neces- 
 ary that the halogen derivative contain at least two carbon 
 atoms, and that a hydrogen atom should be attached to a car- 
 )on atom adjacent to the one to which the halogen is united. 
 
 4. The halogen may be replaced by the amino group .NH 2 
 by the aid of ammonia under pressure, by the nitro group 
 
 or nitrite radical .0N:0 (p. 94), and by the nitrile 
 
 radical .C|N (p. 100). 
 For their use as synthetical reagents, see pp. 121, 228, 237. 
 
 DI-SUBSTITUTION PRODUCTS 
 
 Methylene chloride, CH 2 C1 2 , Methylene bromide, CH 2 Br 2 , 
 ind Methylene iodide, CH 2 I 2 , are colourless liquids which 
 ire obtained either from the tri-haloid substitution products 
 Dy inverse substitution, or from the mono-substitution pro- 
 lucts by the introduction of more halogen. (See table, 
 
 56.) 
 
62 II. HALOID SUBSTITUTION PRODUCTS 
 
 The compounds C 2 H 4 X 2 are known in two isomeric forms, 
 to which are assigned the constitutional formulae: 
 
 CH 2 X-CH 2 X (ethylene) and CH 3 -CHX 2 (ethylidene). 
 
 The former result from the addition of halogen to ethylene, or 
 from the action of halogen hydride or phosphorus haloids upon 
 glycol, C 2 H 4 (OH) 2 (see this), e.g. ethylene bromide, by passing 
 ethylene into bromine and water at the ordinary temperature. 
 
 The ethylene compounds yield acetylene with alcoholic 
 potash, or better, alcoholic solution of sodium ethoxide, and 
 are transformed into glycol by exchanging their halogen atoms 
 for hydroxyl under the influence of potassium carbonate solu- 
 tion. Glycol, CH 2 (OH).CH 2 .OH, with hydrochloric acid 
 yields glycol mono-chlorhydrin, CH 2 C1 CH 2 OH, and this on 
 oxidation yields mono-chloracetic acid, CH 2 C1-COOH. In 
 this acid it can be shown that the chlorine and hydroxyl 
 radicals are attached to distinct carbon atoms; hence in 
 glycol the two hydroxyl groups, and in ethylene dibromide 
 the two bromine atoms, are almost certainly united to distinct 
 and not to the same carbon atoms. 
 
 The Ethylidene compounds are obtained from aldehyde 
 (para-aldehyde) by exchange of the oxygen for halogen by 
 means of phosphorus chloride, &c. 
 
 Ethylidene chloride, also called ethidene chloride, or 1:1- 
 dichloroethane, is, however, most conveniently prepared with 
 phosgene, COC1 2 , thus: 
 
 CH 3 .C<J + COC1 2 = C 
 
 It is also formed by the further chlorination of CgHgCl, and is 
 a by-product in the manufacture of chloral. Its boiling-point 
 (57) is lower than that of ethylene chloride (84). It is an 
 anaesthetic. 
 
 Propylene chlorides, C 3 H 6 C1 2 , bromides and iodides, are 
 likewise known. One group is formed by the addition of 
 halogen to propylene, and thus has an unsymmetrical con- 
 stitution, e.g. propylene chloride, 1:2- dichloropropane, 
 CH 3 CHC1 CHgCl. Isomeric .with this group are the sym- 
 metrically-constituted Trimethylene derivatives, of which tri- 
 methylene-bromide, 1 : 3-dibrorno-propane, CH 2 Br CH 2 CH 2 Br, 
 results from the addition of hydrobromic acid^to allyl bromide ; 
 
 = CH 2 Br.CH 2 .CH 2 Br. 
 
CHLOROFORM, ETC. 63 
 
 TRI-SUBSTITUTION PRODUCTS 
 
 Chloroform, CHC1 3 (Liebig and Soubeiran, 1831; formula 
 established by Dumas, 1835). 
 
 Fwmation. 1. From methane and methyl chloride (see 
 p. 57). 2. By heating alcohol, or even better, acetone, with 
 bleaching -powder and water. When alcohol is used, the 
 bleaching-powder probably first oxidizes it to aldehyde, then 
 chlorinates to chloral, and ultimately hydrolyses (see below) 
 to chloroform. 3. Together with alkali formate by warming 
 chloral or chloral hydrate with aqueous alkali: 
 
 CCl 3 .CHO + NaOH = CHC1 3 + HC0 2 Na. 
 
 This last method of formation is the best for the preparation 
 of pure chloroform. 
 
 It is a colourless liquid of a peculiar ethereal odour and 
 sweetish taste, is sparingly soluble in water, and solidifies 
 below -70. B.-pt. 61-2. Sp. gr. 1-527. It dissolves fats, 
 resins, caoutchouc, iodine, &c., and is also a most valuable 
 anaesthetic (Simpson, Edinburgh, 1848). 
 
 The carbylamine reaction (see Iso-nitriles) furnishes a deli- 
 cate test for the presence of chloroform. 
 
 Bromoform, CHBr 3 , is sometimes present in commercial 
 bromine. 
 
 lodoform, CHI 3 (Serullas, 1822; formula established by 
 Dumas), is prepared by warming alcohol with iodine and 
 ulkali or alkaline carbonate: 
 C 2 H 5 OH + 4 1 2 + 6 KOH = CHI 3 + HCO 2 K + 5 KI + 5 H 2 O. 
 
 It can also be prepared in the same way from acetone, 
 aldehyde, lactic acid, and, generally, from compounds which 
 "contain the group CH 3 CH(OH) - C, or GHg-GQ-G (Ueben). 
 
 An electrolytic method consists in passing an electric current 
 through a solution containing potassium iodide, sodium car- 
 bonate, and alcohol, the temperature being kept at 65. Some 
 85 per cent of the potassium iodide is thus converted into 
 iodoform. 
 
 It crystallizes in yellow hexagonal plates, melts at 119, has 
 a peculiar odour, is volatile with steam, and is an^ important 
 antiseptic. It contains only 0'25 per cent H, which at first 
 caused the presence of the latter to be overlooked. 
 
 Methyl chloroform, CH 3 -CC1 3 . This compound, the tri- 
 chloride of acetic acid, also acts as an anaesthetic. 
 
64 II. HALOID SUBSTITUTION PRODUCTS 
 
 Glyceryl chloride, Trichlorhydrin, l:2:3-trichloropropane, 
 CHgCl-CHCl-CHjCl, is obtained from glycerol and PC1 5 
 (p. 59). B.-pt. 158. The corresponding bromine compound 
 is also known, but not the iodine one, C 3 H 5 I 3 , which decom- 
 poses in the nascent state (i.e. when glycerine, phosphorus, 
 and iodine react together) into allyl iodide, C 3 H 5 I, and I 2 . 
 
 HIGHER SUBSTITUTION PRODUCTS 
 
 Carbon tetrachloride, CC1 4 . Can be prepared from chloro- 
 form or carbon disulphide and chlorine. It is a colourless 
 liquid, boils at 77, and is used as a solvent for fats, &c. 
 
 Perchloro-ethane, C 2 CI 6 . Ehombic plates of camphor-like 
 odour. Melts and sublimes at 185. 
 
 The chemical properties of these polyhalogen derivatives 
 are somewhat similar to those of the monohalogen derivatives. 
 They may be reduced, transformed into the corresponding 
 alcohols, or the halogen atoms replaced by NH 2 radicals, &c. 
 The action of alkalis on the polyhalogen derivatives, in which 
 the halogen atoms are attached to the same carbon atom, 
 
 OTT 
 
 is interesting, e.g. CH 2 C1 2 gives not CH 2 <^QTT, but CH 2 :0 
 
 formaldehyde and H 2 0; CHC1 3 gives not CH(OH) 3 , but this 
 compound water, viz. 0:CHOH, formic acid. Similarly, 
 C01 4 gives not C(OH) 4 , but C0 2 + 2H 2 0, and CH 3 .CHBr 2 
 gives CH 3 .CH(OH) 2 - H 2 0, i.e. CH 3 .CHO. 
 
 Many of these reactions require high temperatures; the 
 substances must be heated with the alkali in sealed tubes 
 under pressure. It is characteristic of carbon derivatives 
 that compounds which contain two or more hydroxyl radicals 
 attached to the same carbon atom are unstable, and, as a rule, 
 immediately eliminate water yielding an aldehyde, acid, &c. 
 Ammonia and chloroform at a red heat yield HCN and HC1. 
 
 B. Haloid Derivatives of the Unsaturated 
 Hydrocarbons 
 
 These compounds are obtained either by partially withdraw- 
 ing halogen or halogen hydride from the halogen derivatives 
 of the saturated hydrocarbons, or by incompletely saturating 
 the hydrocarbons poorer in hydrogen with halogen or halogen 
 hydride, e.g. : 
 
 C 2 H 4 Br 2 - HBr = C 2 H 3 Br. C 2 H 2 -f HBr = C ? H 3 Br. 
 
III. MONOHYDRIC ALCOHOLS 65 
 
 The allyl compounds, C 3 H 5 X, are obtained from ailyl alcohol 
 and halogen hydride or phosphorus haloids. 
 
 These unsaturated products are very similar to the corre- 
 sponding saturated ones, but they are, of course, capable of 
 combining further with halogen or halogen hydride, and they 
 exist in stereo-isomeric modifications. (See Fumaric Acid.) 
 
 In the unsaturated compounds the halogen atoms are, as a 
 rule, not so readily replaced by other radicals, e.g. OH, NH 2 , 
 as in the saturated halogen derivatives. 
 
 The following may be mentioned : 
 
 Vinyl bromide, bromo-ethylene, CH 2 :CHBr; is usually pre- 
 pared from ethylene di-bromide and alkali. 
 
 Allyl -chloride, -bromide, and -iodide, 3-iodo-l-propene, 
 CH 2 :CH.CH 2 X. 
 
 These are of importance on account of their relation to the 
 allyl compounds found in nature, e.g. oil of mustard and oil of 
 garlic. The iodide is prepared from glycerol, phosphorus, and 
 iodine, and from it, by means of HgCl 2 , the chloride. 
 
 Isomeric with these are the propylene compounds, e.g. 
 a-chloro-propylene (I-chloro-l-propene), CHC1:CHCH 3 . 
 
 III. MONOHYDRIC ALCOHOLS, OR ALKYL 
 HYDROXIDES 
 
 Alcohols may be regarded as paraffins in the molecules of 
 which one or more hydrogen atoms have been replaced by one 
 or more monovalent hydroxyl groups, H. The H group 
 is thus characteristic of alcohols. For the proof of the presence 
 of the OH group, see p. 17. They are usually divided into 
 groups, according to the number of such radicals contained in 
 the molecule: d%dnc,e.g.C 2 H 4 (OH) 2 ; trihydric, e.g. C 3 H 5 (OH) 3 ; 
 hemhydric, e.g. C 6 H 8 (OH) , &c. 
 
 The monohydric alcohols are either saturated or unsaturated, 
 according to the hydrocarbons from which they are derived. 
 The unsaturated closely resemble the saturated, except that 
 they are capable of forming additive compounds. 
 
 (B480) 
 
66 III. MONOHYDRIC ALCOHOLS 
 
 A. Monohydrie Saturated Alcohols, C n H to+1 OH 
 
 (See Table, p. 67.) 
 
 The lowest members of this series are colourless mobile 
 liquids, the middle ones are more oily, and the highest from 
 dodecyl alcohol, C 12 H 25 OH, onwards are solid at the ordi- 
 nary temperature, and like paraffin in appearance. Gaseous 
 alcohols are unknown; and it is thus obvious that the intro- 
 duction of OH for H raises the boiling-point of a substance. 
 Compare 
 
 B.-p. B.-p. 
 
 CH 4 -164 CH 3 OH 66 
 
 CH, -93 C 9 H 5 OH 78 
 
 C! 2 H 6 (OH) 78 C;H 4 (OH) 2 197 
 
 With compounds of analogous constitution the boiling- 
 point rises with tolerable regularity; in the case of the lower 
 members by about 19, and higher up in the series by a 
 smaller number. 
 
 The lowest members are miscible with water, but this 
 solubility rapidly diminishes as the molecular weight in- 
 creases; thus butyl alcohol requires 12 parts, and amyl alco- 
 hol 40 parts of water for solution, while the higher members 
 are no longer soluble in water. The former can be separated 
 or "salted out" from their aqueous solution by the addition 
 of salts, e.g. K 2 C0 3 and Ca01 2 . 
 
 The specific gravity is always < 1. The highest members 
 (over C 16 ) can be distilled undecomposed only in a vacuum; 
 at the ordinary pressure they break up into olefine and water. 
 The lowest members possess a spirituous odour, those with 
 more than five C atoms an odour of fusel, and both have a 
 burning taste, while the highest members are like paraffin in 
 appearance and without either taste or smell. 
 
 CONSTITUTION AND ISOMERS; CLASSIFICATION OF THE 
 ALCOHOLS 
 
 Propyl alcohol, C 3 H 7 OH, and the higher members exist in 
 different isomeric modifications; thus there are two propyl, 
 four butyl, and eight amyl alcohols, &c. 
 
 The number of isomeric forms theoretically possible can be 
 determined by taking the formulae for the corresponding satu- 
 rated hydrocarbons, and seeing in how many different positions 
 
MONOHYDRIC SATURATED ALCOHOLS 
 
 67 
 
 tqoooooqooccco6qooooo 
 
 ;-> : i ! : : : I 
 
 I 
 
 Si 
 
 O O b O 00 00 00 
 
 ooooooooooo 
 
 ss 
 
 
 sssssss 
 
 * O5 O 
 
 O 00 i i 
 
 00 1^ 00 
 
 66 6 
 
 oo !> 
 
 66 
 
 w M9 
 
 
 oo 
 
 W"W M 
 oo 
 
 ?'?'?'? 
 
 ^ - CC W 
 
 O C3 C fl 
 
 ^H^-ftft 
 
 i 
 
 22 
 
 PL(Pk 
 
 1 1 i i i W i !JH II 
 
 !1K 
 
 a ;-p 
 
 
68 III. MONOHYDRIC ALCOHOLS 
 
 the OH group can be introduced, e.g. CH 3 CH 2 CH 3 , propane, 
 can obviously give 
 
 CH 3 .CH 2 .CH 2 .OH and CH 3 .CH(OH).CH,, 
 
 two distinct propyl alcohols. 
 Butane exists in two forms : 
 
 CH 3 CH 2 CH 2 CH 3 or normal and (CH 3 ) 3 CH or iso. 
 
 From the n we can get 
 
 CH 3 .CH 2 .CH 2 .CH 2 .OH and CH 3 .CH 2 .CH(OH)-CH 3 ; 
 
 from the iso 
 
 (CH 3 ) 2 CH CH 2 OH and (CH 3 ) 3 C OH; 
 
 but no more. 
 
 Of these isomerides, some only are oxidizable to acids, 
 C n H 2n O 2 , containing an equal number of carbon atoms, an 
 aldehyde, C n H 2n O, being formed as intermediate product. 
 Such alcohols are termed primary alcohols (primary propyl, 
 butyl, and isobutyl alcohols, &c.). 
 
 Another class of alcohols is not oxidizable to acids with 
 an equal number of atoms of carbon, but to ketones, C n H 2n O, 
 by the removal of 2 atoms of hydrogen, e.g. isopropyl alcohol 
 yields acetone, C 3 H 6 0. These are termed secondary (secon- 
 dary butyl alcohol). Upon further oxidation the ketones do 
 indeed yield acids, which, however, contain not an equal but 
 always a smaller number of carbon atoms, the carbon chain 
 having thus been broken up. 
 
 Lastly, the third class of alcohols, the tertiary, yield upon 
 oxidation neither aldehydes, ketones, nor acids with an equal 
 number of carbon atoms, but only ketones or acids containing 
 fewer atoms of carbon. 
 
 Constitution of the Alcohols. In the molecule of a mono- 
 hydric alcohol one of the hydrogen atoms plays a part different 
 from that of the others; thus it is replaceable by metals (K 
 and Na), and by acid radicals, and, together with the oxygen 
 atom, combines with the hydrogen of a halogen hydride to 
 form water, while the other hydrogen atoms of the alcohol 
 remain unchanged. This hydrogen atom, which has already 
 been formulated under the Theory of Types apart from the 
 others, is called the "typical" or "extra-radical" hydrogen 
 atom. It is not joined directly to the carbon atom, but 
 through the oxygen one, a conclusion which is confirmed by 
 
CONSTITUTION OF MONOHYDRIO ALCOHOLS 69 
 
 the formation of alcohols by the action of alkalis (KOH) on 
 monohalogen derivatives of the paraffins. (See p. 71.) This 
 point has been previously discussed (p. 17) for ethyl alcohol. 
 
 The alcohols therefore contain a hydroxyl group, OH, and 
 their general constitutional formula is (C n H 2n+1 ) OH. 
 
 According to theory, this hydroxyl can either replace an 
 atom of hydrogen in a methyl group, in which case an alcohol 
 containing the group CH 2 OH (one carbon atom being joined 
 to the other by a single bond) results, e.g. CHg'CHg'OH. 
 Or it can replace the hydrogen of a CH 2 : group in a hydro- 
 carbon, so that the resulting compound contains the group 
 :CH'OH, the carbon being here joined to two other carbon 
 atoms. Or, lastly, it is possible that in a hydrocarbon with 
 a branching carbon chain, the hydrogen of a methine group 
 CH* may be replaced by hydroxyl, when the resulting alcohol 
 would contain the group :COH, in which one carbon atom is 
 joined to three others. 
 
 TT 
 
 Now, it is easy to see that the group m G^\r\ 2 ii can ) by 
 
 further oxidation, be transformed into *G\Q.jj- The latter, 
 
 which is termed carboxyl, is contained in the acids CJI^O^ 
 or Cn.jHgn^COOH, which are formed by the oxidation of the 
 primary alcohols. Consequently it is the primary alcohols 
 which contain the group CH 2 OH. 
 
 The group :CH-OH can likewise be changed into :C:0 
 
 (i.e. C<Cojj H 2 0\ which is the characteristic group of 
 
 the ketones, by oxidation. A further introduction of or 
 OH, whereby acids containing the group CO'OH would 
 ensue, is not possible in this case without a rupture of the 
 carbon chain, since the carbon atom is tetravalent. Since 
 then it is the secondary alcohols which upon oxidation yield 
 ketones, and not acids with an equal number of carbon atoms, 
 the group :CH-OH is characteristic of these. 
 
 Finally, the group jC-OH already contains the maximum 
 of oxygen which can be combined with a carbon atom already 
 linked to 3 other atoms of carbon. A compound, therefore, in 
 which this atomic group is present, cannot yield, when oxi- 
 dized, an aldehyde, acid, or ketone with an equal number of 
 carbon atoms in the molecule, but the result of such oxidation 
 must be the breaking of the carbon chain, and the formation 
 of acids or ketones containing a smaller number of carbon 
 
70 III. MONOHYDRIC ALCOHOLS 
 
 atoms in the molecule. This being the behaviour of tertiary 
 alcohols, the group iC-OH is peculiar to them. 
 
 The existence of the three classes of alcohols finds in this 
 \vay a thoroughly satisfactory explanation from theory. 
 
 The secondary and tertiary alcohols were predicted by Kolbe 
 in 1859 from theoretical considerations (A. 113. 301: 132, 
 102). 
 
 Among the isomeric alcohols the primary possess the highest, 
 and the tertiary the lowest boiling-points (cf. p. 67). Similar 
 generalizations appear to hold good for other physical pro- 
 perties, e.g. specific gravity, specific refractive indices, and 
 capillarity constants. The tertiary have the highest melting- 
 points. 
 
 Determination of Constitution. The determination of the con- 
 stitution of any special alcohol is based largely on its method 
 of formation and on its products of oxidation. E.g. Isopropyl 
 alcohol may be obtained by the reduction of acetone (CH 3 ) 2 
 C:O, and must therefore have the constitutional formula 
 (CH 3 ) 2 .CH.OH, and not CH 3 .CH 2 -CH 2 .OH. This is con- 
 firmed by the fact that on oxidation it yields the ketone 
 acetone, and must necessarily be a secondary alcohol with 
 the grouping :CH-OH. 
 
 Similarly isobutyl alcohol must be represented as (CH 3 ) 2 - 
 CHCH 2 'OH, since on oxidation it yields zso-butyric acid, 
 the constitution of which is known to be (CH^-CH-CO-OH. 
 
 Occurrence. Different alcohols are found in nature combined 
 with organic acids as esters in ethereal oils and waxes; e.g. 
 methyl, ethyl, butyl, hexyl, and octyl alcohols, and also those 
 with 16, 27, and 30 carbon atoms; ethyl alcohol also occurs in 
 the free state. 
 
 /. General Methods of Formation. 1. By " saponification " or 
 "hydrolysis" of their esters, i.e. by boiling these. with alkalis or 
 mineral acids, or by the action of superheated steam, thus: 
 
 C 6 H 5 .CO-OC 2 H 6 -f KOH = C C H 5 .(X).OK + C 2 H 6 OH. 
 Ethyl benzoate Potassium benzoate. 
 
 Some esters, e.g. ethyl hydrogen sulphate, decompose when 
 simply warmed with water: 
 
 /SO 2 VOH"+H-OH = C 2 H f) .OH + SO 2 (OH) 2 . 
 
 Most of these processes of hydrolysing require some little 
 time, and the ester is boiled with the alkali (KOH solution) 
 in a flask fitted with a reflux condenser. 
 
METHODS OF FORMATION 71 
 
 2. From the halogen compounds C n H 2n+1 X, and therefore 
 indirectly from the paraffins and olefines (pp. 55 and 57). In 
 the latter case secondary or tertiary alcohols, from C 3 on, are 
 obtained since the halogen of the haloid compounds becomes 
 attached to that carbon atom to which the smaller number of 
 hydrogen atoms are united. 
 
 (a) By warming these, especially the iodides, with excess of 
 water to 100; sometimes by simply allowing the mixture to 
 stand (tertiary iodides) : 
 
 C 2 H 6 };+HX)H = C 2 H 5 .OH-f HI. 
 
 When but little water is used, a state of equilibrium is 
 reached as the reaction is reversible. These halogen com- 
 pounds may also be termed the esters of the halogen hydracids, 
 so that, strictly speaking, the mode of formation 2 a is in- 
 cluded in 1. 
 
 (b) Frequently by digesting with moist silver oxide (which 
 acts here like the unknown hydroxide, AgOH), or by boiling 
 with lead oxide and water: 
 
 OH = C 2 H 6 .OH 
 
 (c) Upon warming with silver or potassium acetate, the 
 acetate of the alcohol in question is formed, and this is then 
 hydrolysed : 
 
 C 2 H 5 I + CH, COO Ag = CH 3 - COOC 2 H 6 + Agl 
 CH 3 .COOC 2 H 5 + HOK = C 2 H 6 -OH + CH^COOK. 
 
 3. By the fermentation of the carbohydrates (e.g. grape-sugar), 
 the alcohols with 2, 3, 4, 5, and, under certain conditions, even 
 6 atoms of carbon are produced. (Yeast fermentation.) 
 
 4. On treating the primary amines (see these) with nitrous 
 acid: 
 
 5. From polyhydric alcohols by replacing several of the 
 hydroxyl groups by halogen atoms, and then reducing the 
 halogen derivative: 
 
 C 3 H 6 (OH) 3 + 2HC1 = C 3 H 6 C1 2 (OH) + 2H 2 O. 
 
 Glycerol Dichlor-hydrin. 
 
 C 3 H 6 (OH)C1 2 + 4H = C 3 H r .OH + 2HC1. 
 Isopropyl alcohol. 
 
 Secondary alkyl iodides are often obtained by the action 
 
72 III. MONOHYDRIC ALCOHOLS 
 
 of HI and P on polyhydric alcohols, and these on hydrolysis 
 yield secondary alcohols, e.g.: 
 
 C 3 H 6 (OH) 3 C 3 H r I C 3 H 7 .OH. 
 
 Glycerol s-Propyl iodide s-Propyl alcohol. 
 
 C 4 H 6 (OH) 4 C 4 H 9 I C 4 H 9 .OH. 
 
 Erythritol s-Butyl iodide s-Butyl alcohol. 
 
 II. Special Metlwds of Formation. 1. Primary alcohols are 
 obtained from aldehydes by reduction with sodium amalgam 
 and very dilute sulphuric acid (Wurtz); or with acetic acid 
 and zinc dust, when the alkyl acetates are formed : 
 CH 3 .CH:0+2H = CH 3 .CH 2 .OH. 
 
 This reaction is somewhat similar to the reduction of an 
 olefine to a paraffin. In both cases a double bond is converted 
 into a single bond, and an atom of hydrogen is added on to 
 each atom between which the double bond originally existed. 
 
 Similarly from acid anhydrides (or esters, but not the free 
 acids) and nascent hydrogen, or by the reduction of the acid 
 chlorides, when an ester of the alcohol is formed by the action 
 of the unreduced chloride on the alcohol. 
 
 2. Secondary alcohols are formed by the action of nascent 
 hydrogen (sodium amalgam) on the ke tones, CJS.^0: 
 
 CH 3 .CO.CH 3 + 2H = CH 3 .CH(OB>CH 3 . 
 
 Pinacones are obtained here as by-products. (See Ketones.) 
 
 3. Secondary alcohols are also formed by the action of 
 aldehydes on dry ethereal solutions of magnesium alkyl 
 halides (p. 120), and treating the product which results with 
 water or dilute acid: 
 
 CH 3 CH : + CH 3 . Mg I = CH 3 . CH(OMgl) . CH 3 
 
 CH 3 CH(OMgl) . CH 3 + H OH = CH 3 CH(OH) - CH 3 + 1 Mg OH. 
 
 4. Tertiary alcohols are formed by the action of (a) ketones, 
 (b) acid chlorides, or (c) esters of organic acids, on magnesium 
 alkyl haloids (Grignard, Ann. Chem. Phys. 1901, 24, 433), and 
 decomposing the products with water : 
 
 (a) o + C 2 H 6 .Mg.Br = 
 
 (6) CH 3 - CO Cl -f 2 CH 3 Mg I = (CH 3 ) 3 C - O - Mgl + MglCl. 
 (c) CH 3 .C 
 
BEHAVIOUR OF THE ALCOHOLS 73 
 
 A somewhat similar reaction is that between acid chlorides 
 and zinc alkyl compounds an older and less effective method 
 due to Butleroff. 
 
 5. Secondary or tertiary alcohols sometimes ensue by the 
 direct combination of an olefine with water, e.g. tertiary butyl 
 alcohol, (CH 3 ) 3 COH, from isobutylene. This often gives a 
 simple method for converting a primary into a secondary or 
 tertiary alcohol. 
 
 The Nomenclature of the alcohols, especially of the secondary 
 and tertiary, is based upon a comparison of them with methyl 
 alcohol, also called carbinol. They are looked upon as carbinol, 
 CH 3 -OH, in which the three hydrogen atoms are wholly or 
 partially replaced by alkyl radicals, thus: 
 
 Tertiary butyl' alcohol, (CH,) 3 C-OH = triraethyl carbinol: 
 Secondary butyl alcohol, CH 3 .CH 2 .CH(OH).CH 3 , 
 
 = CH(OH)(CH 3 )(C 2 H 6 ), = methyl-ethyl carbinol 
 
 The systematic name of the alcohols terminates in "ol", 
 As examples: 
 
 CH 3 CH 2 CH 2 CH 2 OH Butanol . 
 
 CH(CH 3 ) CH(OH) CH 3 2 : 3-Dimethylpentan-4-ol. 
 
 Behaviour. 1. The typical hydrogen atom (p. 68) is replace- 
 able by metals, e.g. readily by K or Na, less readily by Ca, Mg, 
 or Al, with formation of alcoholates, EtONa, Mg(OEt) 2 , &c. : 
 
 2 C 2 H 6 OH + 2 Na = 2 C 2 H 6 ONa + H 2 . 
 
 These react with water, giving rise to a state of equilibrium 
 as represented in the equation 
 
 Et-ONa + H-OH ^ Et-OH + Na-OH. 
 
 Briihl (B. 1904, 37, 2066) has described a method for pre- 
 paring the compound CH 3 ONa free from water and alcohol. 
 
 Primary and secondary, but not tertiary, alcohols combine 
 with baryta and lime to alcoholates at 130. Crystalline com- 
 pounds are formed with calcium chloride, so that this salt 
 cannot be used for drying the alcohols; these compounds are 
 decomposed by water. 
 
 2. They enter into the composition of many compounds, as 
 " alcohol of crystallization ". (See pp. 75 and 79.) 
 
 3. They react with acids both mineral and organic in some- 
 
74 III. MONOHYDRIC ALCOHOLS 
 
 what the same manner as metallic hydroxides do, yielding 
 '-alkyl salts or esters and water (cf. Esterification) : 
 
 CH 3 .COOH = CH 3 .COOK + H 2 O, 
 
 Acetic acid. 
 
 OOH ^ CH 3 .COOC 2 H 5 + H 2 0. 
 
 The methyl and ethyl esters derived from certain substituted 
 benzole acids, e.g. paranitrobenzoic acid, N0 2 C 6 H 4 C0 2 H, are 
 solids with definite melting-points, and are sometimes used in 
 identifying small amounts of these alcohols. 
 
 4. Dehydrating agents convert them into defines. 
 
 5. With halogen hydracids or phosphorus halides, they 
 yield monohalide derivatives of the hydrocarbons (p. 58). 
 
 6. For the behaviour of primary, secondary, and tertiary 
 alcohols upon oxidation, see p. 68 et seq. 
 
 Methyl alcohol is oxidized to carbon dioxide as the primary 
 product (formic acid) is itself readily oxidized. 
 
 7. The primary, secondary, and tertiary alcohols can also be 
 distinguished from one another by the behaviour of the nitro 
 compounds, which are formed by the action of silver nitrite 
 on the iodides (cf. Meyer and Jacobson, I, p. 221). 
 
 8. Halogens do not substitute but oxidize. 
 
 9. Many alcohols when heated with excess of soda lime 
 yield the sodium salts of the corresponding acids. 
 
 Methyl alcohol, Methanol, Wood Spirit, CH 3 OH, was' dis- 
 covered in wood-tar by Boyle in 1661, and its difference from 
 ordinary alcohol recognized in 1812 by Phillips Taylor. Its 
 -composition was established in 1834 by Dumas and Peligot. 
 It occurs as methyl salicylate in Gaultheria pivcumbens (oil of 
 winter green, Canada), as butyric ester in the unripe seeds of 
 Heradeum giganteum, and as ester of benzoylecgonin in cocain. 
 
 Formation. 1. By chlorinating methane, CH 4 , and hydro- 
 lysing the resulting methyl chloride (Berthelot}. Methyl iodide 
 may be hydrolysed in a similar manner. 
 
 2. By the destructive distillation of wood (beech wood) at 
 about 350. 
 
 By this distillation there are obtained (a) Gases (CH 4 , C 2 H 6 , 
 C 2 H 4 , C 2 H 2 , C 3 H 6 , C 4 H 8 , CO, C0 2 , H 2 ). (b) An aqueous dis- 
 tillate of " pyroligneous acid", containing methyl alcohol (1-2 
 per cent), acetic acid (10 per cent), acetone (0-1-0-5 per cent), 
 methyl acetate, allyl alcohol, &c. (c) Wood-tar, containing para- 
 ffins, naphthalene, phenol, guaiacols, &c. (d) Wood charcoal. 
 
 3. Also by the dry distillation of vinasse. 
 
ETHYL ALCOHOL 75 
 
 It is prepared commercially from the crude pyroligneous- 
 acid by repeated distillation after neutralization with lime, 
 and is purified by formation of the CaCl 2 compound, which 
 is a solid, and stable at 100; or, better, by transformation into 
 the oxalic or benzoic ester, both of which are easy to purify 
 and hydrolyse. 
 
 Properties. It is a colourless liquid, boils at 66, and has a 
 specific gravity about O8. The alcohol of commerce usually 
 contains acetone. It burns with a non-luminous flame, dis- 
 solves fats, oils, &c., and acts as an intoxicant like ethyl 
 alcohol. It also enters into the composition of compounds as 
 "alcohol of crystallization", e.g. BaO + 2CH 4 0; MgCL + 
 6CH 4 0; CaCl 2 + 4 CH 4 O (six-sided plates). It is readily 
 oxidized to formic aldehyde and formic acid, being also con- 
 verted into the latter when heated with soda-lime. Potassium 
 methoxide, CH 3 OK, is a white crystalline powder, and forms 
 a definite crystalline compound CH 3 OK -f CH 3 OH. 
 
 The anhydrous alcohol dissolves a small amount of dehy- 
 drated cupric sulphate to a blue -green solution. Distilled 
 over heated zinc dust, it decomposes almost quantitatively 
 into CO + 2 H 2 . 
 
 Uses. For tar colours (also as CH 3 I and CH 3 C1); as 
 methyl ether in the manufacture of ice; for polishes and var- 
 nishes; as Wiggersheim's preservative liquid; for methylating 
 spirits of wine, &c. 
 
 Ethyl alcohol, Ethanol, Spirits of Wine, C 2 H 5 OH. Liquids 
 containing spirits of wine have been known from very early 
 times, and their concentration either by distillation or by 
 dehydration with carbonate of potash is also an old art. We 
 read of it as " alcohol " in the sixteenth century. Lavoisier 
 arrived at the qualitative, and de Saussure in 1808 the quanti- 
 tative composition of alcohol. 
 
 In the vegetable kingdom alcohol is only found occasionally, 
 as ethyl butyrate, but in the animal kingdom it occurs in 
 various forms, e.g. in diabetic urine. It is also present in 
 small quantity in coal-tar, bone oil, wood spirit, and bread, 
 fresh English bread containing 0'3 per cent. 
 
 Formation. 1. From C 2 H 6 by conversion into C 2 H 5 C1 and 
 hydrolysis of the latter according to modes of formation 1 
 and 2. 
 
 2. Ethylene and concentrated H 2 S0 4 react at 160, yielding 
 ethyl hydrogen sulphate, 
 
 C 2 H 4 + H 2 S0 4 = C 2 H 5 HS0 4 ; 
 
76 III. MONOHYDRIC ALCOHOLS 
 
 and this when boiled with water gives ethyl alcohol. (See 
 pp. 44 and 70.) This method was discovered by Faraday, and 
 corroborated in 1855 by Berthelot. 
 3. By the reduction of acetaldehyde 
 
 CH 3 .CH:O + 2H = CH 3 .CH 2 -OH. 
 
 4. Preparation by the Alcoholic Fermentation of Sugar. Directly 
 from grape and fruit sugars, C 6 H 12 6 , and indirectly from cane- 
 sugar, C^H^Ojp after previous hydrolysis to two molecules of 
 C 6 H 12 6 ; also indirectly from malt-sugar, from starch, &c. 
 
 Fermentations are peculiarly slow decomposition-processes of 
 organic substances which are accompanied, as a rule, with libera- 
 tion of gas and evolution of heat, and which are induced by 
 micro-organisms, or by complex organic nitrogenous substances 
 (enzymes) of animal or vegetable origin. The alcoholic fer- 
 mentation of sugar, i.e. the fermentation which produces spirit, 
 is caused by the varieties of the genus Saccharomyces, the yeast 
 ferment, which forms small oval microscopic cells, multiplying 
 by gemmation. As plants, these require for their sustenance 
 inorganic salts, e.g. phosphates, potassium salts, and nitrogen 
 in the form of ammonium salts, but, as non-assimilating fungi, 
 no carbon dioxide. 
 
 In the vinous fermentation 94 to 95 per cent of the sugar 
 breaks up into alcohol and carbon dioxide, 
 
 C 6 H 12 6 = 2C 2 H 6 + 2C0 2 , 
 
 with 2-5 to 3-6 per cent glycerol, C 3 H 5 (OH) 3 , and 0'4 to 0*7 
 per cent succinic acid, C 4 H 6 4 , as invariable by-products. In 
 addition to these, most of the higher homologues of ethyl 
 alcohol are also formed the so-called fusel oil the latter re- 
 sulting largely from the presence of foreign micro-organisms. 
 
 The chief constituent of fusel oil is fermentation amyl 
 alcohol (isobutyl carbinol), C 5 H n OH, but it has also been 
 proved to contain the two propyl alcohols (chiefly isopropyl), 
 normal, iso, and tertiary butyl alcohols, normal and active 
 amyl alcohols, together with higher homologues and esters. 
 They can be separated by means of their hydrobromic esters. 
 
 Conditions of Fermentation. Fermentation can only go on 
 between the limits of 3 and 35, the most favourable tempera- 
 ture being between 25 and 30. The solution must not be 
 too concentrated, as the organism cannot live in a solution of 
 alcohol of greater concentration than 14 per cent; the presence 
 of air is not strictly necessaiy, but it has a favouring influence, 
 
ALCOHOLIC FERMENTATION 77 
 
 Yeast loses its activity upon the addition of any reagents 
 which destroy the cells, also when it is thoroughly dried, 
 when heated to 60, when treated with alcohol, acids, and 
 alkalis; the addition of small quantities of salicylic acid, 
 phenol, corrosive sublimate, &c., also prevents fermentation. 
 
 For a number of years it was thought that the presence of 
 the living yeast plant, or of some other similar organism, was 
 essential for the production of alcoholic fermentation. The 
 recent work of E. Buchner (B. 1897, 32, 2086, 2372; 1898, 
 33, 971, 2764) has shown that the fermentation is brought 
 about by an enzyme called Zymase, which is contained in the 
 cell. If the yeast cells are crushed with " Kieselgiihr " (a 
 siliceous earth) and water, so that the cell walls are broken, 
 and the mass then filtered through a Chamberland filter under 
 considerable pressure, an extract is obtained which, although 
 practically free from yeast cells, can yet induce alcoholic fer- 
 mentation. The zymase is relatively unstable and easily de- 
 composed, e.g. when the solution is heated or even kept for 
 some time, but it may be preserved by the addition of certain 
 antiseptic substances, such as chloroform, thymol, &c., which 
 readily kill the yeast plant itself. (Compare Chap. XL VIII.) 
 
 Buchner's researches indicate that fermentations induced by 
 organized ferments are probably due to certain unorganized 
 ferments (enzymes) contained in the cells of the organism. 
 
 The following materials are used for the preparation of 
 alcohol or of liquids containing alcohol: 
 
 (a) Grape-sugar, fruit-sugar, i.e. grapes and other ripe fruits, 
 for wine, &c. (b) Cane or beet sugar and molasses for brandy. 
 Solutions of cane-sugar are fermented by yeast, since ordinary 
 yeast always contains small amounts of an enzyme (invertase), 
 which can hydrolyse cane-sugar to glucose and fructose : 
 
 C 12 H 22 O n + H 2 = C 6 H 12 6 + C 6 H 12 6 , 
 
 and these are then directly fermented by the yeast organism, 
 (c) The starch of cereals for beer and corn brandy, and of 
 potatoes for potato brandy. The starch is first converted into 
 malt-sugar and dextrine under the influence of diastase, or 
 into grape-sugar, by boiling with dilute acids, and these sugars 
 are then fermented. 
 
 The transformation of starch into malt-sugar (maltose) and 
 dextrine is a typical example of fermentation by an enzyme, 
 the special enzyme in this case being diastase, a complex organic 
 nitrogen derivative produced during the germination of the 
 
78 III. MONOHYDRIC ALCOHOLS 
 
 barley in the process of malting. The transformation of the 
 starch into maltose, &c., is in reality a process of hydrolysis 
 induced by the ferment. The maltose C 12 H 22 O n in its turn 
 is hydrolysed by a second ferment (maltose) to grape-sugar, 
 CpHi 2 6 , which is then transformed into alcohol and carbon 
 dioxide. 
 
 A wine of medium strength contains 8J to 10 per cent 
 alcohol, port wine 15 per cent, sherry up to 21 per cent, 
 champagne 8 to 9 per cent, and beer an average of 2 to 6 
 per cent. 
 
 The different varieties of brandy or spirits obtained by 
 " burning ", i.e. by distilling fermented liquids, contain 30 to 
 40 per cent alcohol, and cognac even over 50 per cent. 
 
 Purification of alcohol. It is difficult to separate alcohol 
 completely from water by distillation, since their boiling-points 
 are only 22 apart from one another. Even after repeated 
 rectification the distillates are found to contain water. The 
 same reason applies to the difficulty of separating alcohol from 
 its higher homologues (fusel oil). From an alcohol containing 
 30 per cent of water the fusel oil can be extracted by chloro- 
 form. 
 
 On the large scale this separation is excellently effected by 
 the use of dephlegmators or fractionating columns, which are 
 based upon the principle of partial volatilization and partial 
 cooling of the vapours (Adam and JBerard; improved by Savalle, 
 Pistorius, Coffey, and others). In this way an alcohol containing 
 98 to 99 per cent can be obtained. 
 
 Aqueous alcohol can be deprived of the greater part of its 
 water by the addition of strongly heated carbonate of potash 
 or anhydrous copper sulphate, or by distillation over quick- 
 lime, and the last portions can be extracted by baryta, or by 
 several additions of metallic calcium and repeated distillation. 
 Alcohol containing water becomes turbid on being mixed with 
 benzene, carbon bisulphide, or liquid paraffin oil, and it gives 
 a white precipitate of Ba(OH) 2 on the addition of a solution 
 of BaO in absolute alcohol, and is capable of restoring the 
 blue colour to anhydrous copper sulphate. Alcohol free from 
 water is termed absolute alcohol. Ordinary absolute alcohol 
 usually contains at least 0*2 per cent of water.' 
 
 Contraction takes place on mixing alcohol and water 
 together, 53-9 volumes alcohol + 49 -8 volumes water giving, 
 not 103-7, but 100 volumes of the mixture. The percentage 
 pf alcohol in any spirit is determined either from its specific 
 
PROPERTIES OF ALCOHOL 79 
 
 gravity by reference to a specially -calculated table, or by 
 areometers of particular construction, or by its vapour tension 
 as estimated by Geissler's vaporimeter. 
 
 Properties. It is a colourless mobile liquid with character- 
 istic spirituous odour; boils at 78 - 3, or at 13 under 21 mm. 
 mercury pressure. Solidifies at 112'3, and has sp. gr. 0*79 
 at 15. It burns with an almost non- luminous flame, is 
 exceedingly hygroscopic, and miscible with water and with 
 ether in all proportions. Forms several cryo-hydrates with 
 water ( + 12Aq., + 3Aq., -j-JAq.). Is an excellent solvent 
 for many organic substances such as resins and oils, and also 
 dissolves sulphur, phosphorus, &c., to some extent. With 
 concentrated sulphuric acid it yields, according to the con- 
 ditions, ethyl hydrogen sulphate, ether, or ethylene. It dif- 
 fuses through porous membranes into a dry atmosphere more 
 slowly than water, and coagulates albumen, being therefore 
 used for preserving anatomical preparations. 
 
 It is very readily oxidized by the oxygen of the air, either 
 in presence of finely-divided platinum or in dilute solutions 
 in presence of certain ferments, first to aldehyde and then to 
 acetic acid; thus, beer and wine become sour, but not the 
 pure alcohol itself. K 2 O 2 O r or Mn0 2 + H 2 S0 4 oxidize it 
 in the first instance to aldehyde; fuming nitric acid attacks 
 it with explosive violence, yielding numerous products; but, 
 by the action of colourless concentrated HN0 3 , ethyl nitrate 
 can be obtained under suitable conditions; in dilute solution 
 glycollic acid is formed. Alkalis also induce a gradual 
 oxidation in the air; thus, alcoholic potash or soda solutions 
 quickly become brown with formation of aldehyde resin, this 
 latter resulting from the action of the alkali upon the alde- 
 hyde first produced. Alcoholic potash therefore frequently 
 acts as a reducing agent, e.g. upon aromatic nitro-compounds. 
 (See these.) Chlorine and bromine first oxidize alcohol to 
 aldehyde and then act as substituents. (See Chloral.) 
 Chlorinated alcohols can therefore only be prepared indirectly 
 (cf. Ethylene chlorhydrin). When the vapour of alcohol is 
 led through a red-hot tube, H, CH 4 , C 2 H 4 , C 2 H 2 , CgHg, C 10 H 8 , 
 CO, C 2 H 4 0, C 2 H 4 2 , &c., are formed. 
 
 Of the compounds containing alcohol of crystallization may 
 be mentioned, KOH + 2 C 2 H 6 0, LiCl + 4 C 2 H 6 0, CaCl 2 
 + 4C 2 H 6 0, and MgCl 2 + 6C 2 H 6 O. 
 
 Sodium ethoxide, C 2 H 5 ONa, is of special importance among 
 the alcoholates. It is formed by the action of sodium upon 
 
80 III. MONOHYDRIC ALCOHOLS 
 
 absolute alcohol. The crystals of C 2 H 5 -ONa + 2 C 2 H 6 0, at 
 first obtained, lose their alcohol of crystallization at 200 and 
 change into a white powder of C 2 H 5 ONa. (See also Bruhl.) 
 Sodium ethoxide is of especial value for syntheses, and can 
 frequently be employed in alcoholic solution. This compound 
 is sometimes termed sodium ethylate, but the better name is 
 ethoxide, in order to indicate its close relationship to sodium 
 hydroxide, NaOH. 
 
 When taken in small quantity alcohol acts as a stimulant, 
 in larger quantity as an intoxicant. Absolute alcohol is 
 poisonous, and quickly causes death when injected into the 
 veins. The presence of considerable amounts of fusel oil has 
 detrimental physiological effects. 
 
 Detection of Alcohol. 1. By the iodoform reaction* (see lodo- 
 form), when 1 part in 2000 of water can be recognized. 
 
 2. By means of benzoyl chloride, CgH 5 COCl, which yields 
 with alcohol the characteristically smelling ethyl benzoate; or 
 of jp-nitrobenzoyl chloride, which yields ethyl ^?-nitrobenzoate 
 melting at 57; the corresponding methyl ester melts at 97. 
 
 Propyl alcohols, C 3 H 7 OH. 
 
 1. Normal propyl alcohol, 1-Propanol, CH 3 . CH 2 . CH 2 OH 
 (Chancel, 1853), is obtained from fusel oil by means of its 
 hydrobromic ester (Fittig), or directly by fractionation. It 
 has also been obtained from propionic aldehyde and propionic 
 anhydride by reduction with sodium amalgam (Rossi). It is 
 a liquid with a pleasant spirituous odour, and boils 19 higher 
 than ethyl alcohol. It is miscible with water in all propor- 
 tions, but may be salted out on addition of calcium chloride. 
 Its constitution follows from that of propionic acid, into which 
 it is converted on oxidation. 
 
 Of the higher alcohols, w-butyl alcohol, CH 8 .CH 2 .CH 2 . 
 CH 2 'OH, may be obtained from the fusel oil formed when 
 certain special species of yeast (Saccharomyces ellipsoidius) are 
 used in the alcoholic fermentation. 
 
 Isobutyl carbinol, (CH 3 ) 2 :CH.CH 2 .CH 2 .OH, is the chief 
 constituent of the so-called " fermentation amyl alcohol " 
 obtained by fractional distillation of fusel oil, the other con- 
 stituent being secondary butyl carbinol, 
 
 C 2 H 6 .CH(CH 3 ).CH 2 .OH. 
 This latter, on account of its action on polarized light, is 
 
 * Acetaldehyde, acetone, and isopropyl alcohol also givo this reaction, 
 but not methyl alcohol. 
 
MONOHYDRIC UNSATURATED ALCOHOLS 81 
 
 fenerally known as active (i.e. optically active) amyl alcohol, 
 b is Isevo-rotatory, i.e. rotates the plane of polarization to the 
 left (cf. active valeric acid), and has [a] D 5 '9 at 20. 
 
 Normal hexadecyl- alcohol, or cetyl alcohol, forms as 
 palmitic ester the chief constituent of spermaceti. The cetyl 
 alcohol of commerce contains, in addition, a homologous alco- 
 hol, C 18 H 38 0. 
 
 Ceryl alcohol, Cerotin, C 26 H 63 OH, forms as cerotic ester 
 Chinese wax. 
 
 Melissic, or miricyl alcohol, C 30 H 61 OH or C 31 H 63 OH, is 
 present as palmitic ester in bees'-wax and in Carnauba wax, 
 and is most conveniently prepared from the latter. The 
 alcohols are obtained from all these esters (wax varieties) by 
 hydrolysis with boiling alcoholic potash. 
 
 B. Monohydrie Unsaturated Alcohols, CnH^OH 
 
 These are very similar to the saturated alcohols both in 
 physical properties and in general chemical behaviour, but are 
 sharply distinguished from the latter by the formation of addi- 
 tive compounds with hydrogen, halogens, halogen hydracids, 
 &c. 5 e.g.-. 
 
 CH 2 : CH CH 2 OH + Br 2 = CH 2 Br CHBr CH 2 OH. 
 
 They thus resemble the olefines owing to the presence of a 
 double bond, and the products are saturated alcohols or their 
 halide derivatives, the latter of which cannot be prepared 
 directly by substitution of the alcohols. These unsaturated 
 alcohols are to be considered as olefines in which an atom of 
 hydrogen is replaced by hydroxyl. 
 
 According to theory, the existence of alcohols which contain 
 the hydroxy-methylene group, :CH(OH), linked to a Carbon 
 atom by a double bond, might be predicted. To this class 
 belongs" vinyl alcohol (ethenol), CH:CH-OH, which occurs 
 in commercial ether, but which has not yet been isolated 
 (B. 22, 2863), although derivatives of it are known. By the 
 reactions in which one would expect it to be formed, its 
 isomer, CH 3 .CHO (acetaldehyde), is formed; in fact, the 
 grouping :C:CH-OH is usually unstable, passing as it does 
 into the more stable one, :CH-CH:0, a transformation which 
 is most readily explained upon the assumption that water is 
 taken up and again split off. Similarly, instead of the group 
 CH 2 :C(OH).CH 3 , we always get CH 3 .CO.CH 3 . 
 
 ( B 480 ) 
 
82 III. MONOHYDRIC ALCOHOLS 
 
 Allyl alcohol (l-Propene-3-ol), CH 2 :CH.CH 2 OH (Cahours 
 and Hofmann, 1856), is present to the extent of O'l to 0'2 per 
 cent in wood spirit, and is formed (1) from allyl iodide; (2) by 
 reduction of its aldehyde, acrolein (see this); (3) by heating 
 glycerol, C 3 H 5 (OH) 3 , with oxalic or formic acid and a little 
 ammonium chloride to 220. The reaction is somewhat 
 similar to the production of formic acid, and in both cases 
 the same product is first formed, viz. glyccryl monoformate 
 
 CH 2 -OH CH 2 .OH CH 2 .OH 
 
 CH-OH CH.:OH j CH 
 
 /"YD" ^\TT ^ITT ' /~\ "/"V^ 'TT* /^ITT 
 
 V^Jj-2 * vy-CL ^-^-2 * ^ * v/w ; Jtl; V^i2j 
 
 and this when heated to the required temperature, 220, 
 decomposes into C0 2 , H 2 0, and allyl alcohol. Allyl alcohol 
 is a mobile liquid of suffocating smell, having almost the same 
 boiling-point (97) as rc-propyl alcohol; like the latter, it is 
 miscible with water. It does not take up nascent hydrogen 
 directly, but chlorine, bromine, cyanogen, hypochlorous acid, 
 &c. If cautiously oxidized, it yields glycerol, but stronger 
 3xidation converts it into its aldehyde., acrolein, and acid, 
 acrylic acid, containing the same number of carbon atoms, 
 and it is therefore a primary alcohol; hence the above con- 
 stitutional formula. 
 
 C. Monohydrie Unsaturated Alcohols, Cyi^.g.OH 
 
 These alcohols are derivatives of acetylene and its homo- 
 logues. The compounds possess: (1) The characteristic pro- 
 perties of alcohols. (2) The properties of unsaturated com- 
 pounds. Each molecule of such an alcohol can combine with 
 1 or 2 molecules of a halogen or halogen hydracid. (3) Most 
 of them possess the further peculiarity of forming explosive 
 compounds with ammoniacal copper and silver solutions, 
 e.g. C 3 H 2 AgOH, the former being coloured yellow and the 
 latter white; acids decompose these compounds into the un- 
 saturated alcohol. Those of them which do not yield such 
 metallic compounds contain, not a triple bond, but two double 
 ones between the carbon atoms. The most important of these 
 alcohols is 
 
 Propargyl alcohol, OT propinyl alcohol (l-Propin-3-ol) t 
 
 C 3 H 3 OH, = CH-C-CHsOH, 
 
ETHERS 83 
 
 a mobile liquid of agreeable odour, lighter than water, and 
 boiling at 114, i.e. somewhat higher than normal propyl 
 alcohol. 
 
 For further examples of unsaturated alcohols, see Open- 
 chain Terpenes (Chap. XLI, A). 
 
 IV. DERIVATIVES OF THE ALCOHOLS 
 
 These may be classed in the following divisions : _ 
 
 A. Ethers of the alcohols, or alkyl oxides, e.g. C 2 H 5 .0C 2 H 5 , 
 ethyl ether. 
 
 B. Thio-alcohols and ethers, or alkyl hydrosulphides and 
 sulphides, e.g. C 2 H 5 -SH and (C 2 H 5 ) 2 S. 
 
 C. Nitrogen bases of the alcohol radicals. 
 
 D. Other metalloid compounds of the alcohol radicals. 
 
 E. Metallic compounds of the alcohol radicals, or organo- 
 metallic compounds. 
 
 A. Ethers Proper (Alkyl- or Alphyl-Oxides) 
 
 The ethers of the monohydric alcohols are compounds of 
 neutral character derived from the alcohols by elimination of 
 the elements of water (1 molecule water from 2 molecules 
 alcohol). They can frequently be prepared by treating the 
 alcohols with sulphuric acid, and are distinguished from the 
 latter by not reacting with acids to form esters, and by being 
 substituted and not oxidized by the halogens, &c. Only the 
 lowest member of the series is gaseous, most of them are 
 liquid, and the highest are solid. The more volatile ethers 
 are characterized by a peculiar odour which is not shown by 
 the higher members. 
 
 Constitution. The hydrogen atoms cannot be replaced by 
 sodium or other metallic radicals (see p. 18), and are all 
 presumably attached to carbon. 
 
 Their structure as alkyl oxides, or anhydrides of mono- 
 hydric alcohols (cf. metallic oxides), follows largely from 
 modes of formation 2 and 3, from the non-reactive character 
 of the hydrogen atoms, and from reactions 4 and 5, p. 85. 
 K;OH C 2 H 5 OH _ C 2 H 5 ^ 
 
 c 2 H 6 o;n - ^ 
 
 The alkyl groups contained in them may either be the 
 same, as in ordinary ether and in methyl ether, (CH 3 ) 2 0, in 
 
84 IV. DERIVATIVES OF MONOHYDRIC ALCOHOLS 
 
 which case they are termed "simple ethers"; or they may be 
 different, as in methyl-ethyl ether, CH 3 -0'C 2 H 5 , when they 
 are known as "mixed ethers". 
 
 Ethers derived from tertiary alcohols are not known. 
 
 Modes of Formation. 1. By heating the alcohols, C n H 2n+1 OH, 
 with sulphuric acid. The reaction proceeds in two phases, e.g.: 
 
 (a) C 2 H 5 .OH + OH-S0 2 .OH = OH.S0 2 .OC 2 H 5 + H-OH. 
 (6) OH.S0 2 .OC 2 H 6 +C 2 H 5 .OH = OH.S0 2 .OH 
 
 In phase a an alkyl hydrogen sulphate is formed, which, 
 when further heated with alcohol, as in b, yields ether and 
 regenerates sulphuric acid. The latter is therefore free to 
 work anew, and in this way to convert a very large quantity 
 of alcohol into ether. 
 
 This process is theoretically a continuous one, but practi- 
 cally it has its limits, through secondary reactions, such as the 
 formation of S0 2 , &c. A modification of the method consists 
 in heating the alcohol with benzene - sulphonic acid C 6 H 5 
 S0 2 OH in place of sulphuric acid. No sulphur dioxide is 
 formed, and the reaction becomes in reality continuous. The 
 method is only suitable for primary alcohols; secondary and 
 tertiary under similar conditions yield defines. Hydrochloric, 
 hydrobromic, and hydriodic, among other acids, act similarly tc 
 sulphuric acid; thus ether is obtained when alcohol is heated 
 with dilute hydrochloric acid in a sealed tube to 180, ethyl 
 chloride, C 2 H 5 C1, being formed as an intermediate product 
 When alcohol is heated with hydrochloric acid, a state of 
 equilibrium is established between the alcohol, ether, ethyl 
 chloride, hydrochloric acid, and water, after which the same 
 quantity of each of these products is destroyed as is formed 
 in unit of time. 
 
 2. By the action of alkyl halides on sodium -alky late, or 
 also upon alcoholic potash: 
 
 3. From alkyl halides and dry silver oxide, Ag 2 (also HgO 
 andNa 2 0): 
 
 2C 2 H 6 I 
 
 Modes of formation 1 and 2 yield mixed as well as simple 
 ethers, e.g.: 
 
 C 2 H 6 .S0 4 H + CH 3 -OH = C 2 H 5 .O.CH, + H 9 S0 4 . 
 CVE U I + CH 3 ONa = C 6 H U . O CH 3 -f Nal. 
 
ETHYL ETHER 85 
 
 Properties. 1. The ethers are very stable, e.g. ammonia, 
 alkalis, dilute acids, and metallic sodium have no action upon 
 them, nor has phosphorus pentachloride in the cold. 
 
 2. When superheated with water in presence of some acid, 
 such as sulphuric, the ethers take up water and are retrans- 
 formed into alcohols, the secondary more readily than the 
 primary; this change also proceeds, but extremely slowly, 
 at the ordinary temperature. 
 
 3. When warmed with concentrated sulphuric acid, alcohol 
 and ethyl hydrogen sulphate are formed : 
 
 .OH + C 2 H 6 .HS0 4 . 
 
 4. When saturated with hydriodic acid gas at 0, the ethers 
 yield alcohol and alkyl iodide : 
 
 C 2 H 6 .O.C 2 H 5 + HI = C 2 H 6 .OH + C 2 H 6 L 
 
 When the ethers are " mixed ", the iodine attaches itself to 
 the smaller alkyl group; further interaction yields, of course, 
 two molecules of alkyl iodide. 
 
 5. When heated with phosphorus halides the oxygen atom 
 is replaced by two halogen atoms, and two molecules of an 
 alkyl halide are formed. 
 
 6. Like the alcohols, the ethers are oxidized by nitric and 
 chromic acids, but halogens substitute in them and do not 
 oxidize; in this latter respect they resemble the hydrocarbons. 
 
 7. Many ethers form definite compounds with acids, especially 
 complex acids like H 4 FeC 6 N 6 (B. 190-1, 34, 2688); also with 
 bromine, with metallic salts, &c. (J. C. S. 1904, 85, 1106; Proc. 
 1904, 165). 
 
 Ethyl ether, Ethane-oxy-ethane, "Ether" (C 2 H 5 ) 2 0, was dis- 
 covered by Valerius Cordus about 1544, and possibly before 
 that time by Raymond Lully. It was also called " sulphuric 
 ether ", and " vitriol ether ", on account of its being supposed 
 to contain sulphur. Its composition was established by Saus- 
 sure in 1807, and Gay-lMssac in 1815, 
 
 Preparation. By the continuous process from ethyl alcohol 
 and sulphuric acid at 140, with gradual addition of the 
 alcohol, according to Boullay. It is freed from alcohol by 
 shaking with water, and dried by distillation over lime or 
 calcium chloride, and finally over metallic sodium. 
 
 Theories of the Formation of Ether. At first the action of the 
 sulphuric acid was considered to consist in an abstraction of 
 water. Later on, it was thought that the acid gave rise to 
 
86 IV. DERIVATIVES OF MONOHYDRIC ALCOHOLS 
 
 a contact action (Mitscherlich, Berzelius), but Liebig showed 
 that this view was incorrect, since ethyl hydrogen sulphate is 
 formed. Liebig assumed that the ethyl hydrogen sulphate 
 decomposed, when heated, into ether and S0 3 ; but Graham, on 
 the other hand, proved that the acid gives no ether when 
 heated alone to 140, but only when heated along with more 
 alcohol. 
 
 After this, Williamson propounded the theory of etheri- 
 fication at present held, a theory based on the opinion of 
 Laurent and Gerhardt that ether contains two ethyl radicals. 
 Its correctness was proved by mode of formation 2, and also 
 by the preparation of mixed ethers. 
 
 Properties. It is a mobile liquid with powerful ethereal 
 odour, and is very volatile, even at the ordinary temperature. 
 It melts at -113, boils at + 34'9, has specific gravity = 0'72 
 at 17 '4, and at 120 has a vapour pressure of 10 atmospheres. 
 It produces considerable lowering of temperature when evapo- 
 rated. It is easily inflammable, and therefore dangerous as a 
 cause of fire, from the dissemination of its very heavy vapour; 
 a mixture of it with oxygen or air is explosive. It is some- 
 what soluble in water (1 part in 10), and, conversely, 3 volumes 
 of water dissolve in 100 volumes of ether; the presence of 
 water can be detected by the milkiness which ensues upon the 
 addition of carbon disulphide. Ether is an excellent solvent 
 or extractive for many organic substances, and also for I 2 , 
 Br 2 , O0 3 , FeCl 3 , AuCl 3 , PtCl 4 , and other chlorides. It forms 
 crystalline compounds with various substances, e.g. the chlorides 
 and bromides of Sn, Al, P, Sb, and Ti, being present in them 
 as " ether of crystallization ". 
 
 When dropped upon platinum black it takes fire, and when 
 poured into chlorine gas an explosion results, hydrochloric acid 
 being set free. In the dark, however, and in the cold, sub- 
 stitution by chlorine is possible; the final product of the 
 substitution, perchloro- ether, C 4 C1 10 0, is solid and smells 
 strongly like camphor. 
 
 Ether was first employed as an anaesthetic by Simpson in 
 1848, but this property had been previously observed by 
 Faraday. It is further used as an extractive in the colour 
 industry, as Hofmann's drops when mixed with 1 to 3 volumes 
 of alcohol, for ice machines, and for the preparation of collo- 
 dion, &c. 
 
 Methyl ether, (CH 3 ) 2 (Dumas, Peligoi\ closely resembles 
 common ether, is gaseous at the ordinary temperature, but 
 
ISOMERISM OF ETHERS 87 
 
 liquid under 20, and is prepared on the large scale for 
 the production of artificial cold, 
 
 Ethyl-cetyl- and dicetyl ethers are solid at the ordinary 
 temperatures. 
 
 Several ethers with unsaturated alcohol radicals are also 
 known, e.g. allyl ether, (C 3 H 5 ) 2 0, and vinyl -ethyl ether, 
 C2H 3 .O.C 2 H 5 . B.-pt. 35-5. These can combine directly 
 with bromine. 
 
 Isomers. The general formula of the saturated ethers is 
 CnELjn+aO. Isomerie with each ether is a saturated alcohol, 
 thus C 2 H 6 = methyl ether or ethyl alcohol, C 4 H 10 = di- 
 ethyl ether or butyl alcohol. From C 4 H 10 on, however, 
 several different isomeric ethers are not only possible, but are 
 also known, e.g. di-ethyl ether, (C 2 H 5 ) 2 0, is isomeric with 
 methyl - propyl ether, CH 3 -0'C 3 H 7 ; similarly methyl -amyl 
 ether, CH 3 .O.C 5 H n , ethyl-butyl ether, C 2 H 5 .O.C 4 Hg, and 
 dipropyl-ether, C 3 H 7 0-C 3 H r , are all isomeric. Isomerism of 
 this kind depends upon the fact that the alkyl radicals and 
 hydrogen are homologous, so that if the numbers of carbon 
 atoms are equal, so also must be the numbers of hydrogen. 
 
 Such isomerism in which the compounds belong to the same 
 class and differ only in the nature of the alkyl group present 
 is termed metamerism. 
 
 The determination of the constitution of the ethers is based 
 upon (a) their syntheses according to modes of formation 1 or 2, 
 and (b) their decomposition by HI according to Keaction 4. 
 
 Varieties of Isomerism. The cases of isomerism which have 
 been mentioned up to now are of three kinds. The first was 
 the isomerism of the higher paraffins, which, since it is based 
 upon the dissimilarity of the carbon chains, is often termed 
 cham-isomerism. The isomerism between ethylene and ethyl- 
 idene chlorides or between primary and secondary propyl 
 alcohols depends upon the differences in position of the substi- 
 tuting halogen or hydroxyl in the same carbon chain, and is 
 termed position isomerism. In addition to these there is the 
 third kind, metamerism. Further cases will be spoken of 
 under the Benzene derivatives. 
 
 B. Thio-aleohols and -ethers 
 
 The relationship between oxygen and sulphur, indicated by 
 their positions in the periodic classification of the elements, is 
 supported by a study of their carbon derivatives. We have 
 
88 IV. DERIVATIVES OF MONOHYDRIC ALCOHOLS 
 
 a group of sulphur compounds analogous to the monohydric 
 alcohols. These are known as thio-alcohols or " thiols ". 
 Similarly a group corresponding with the ethers is known as 
 the thio- ethers or alkyl sulphides. These are liquids of a 
 most unpleasant and piercing odour, something like that of 
 leeks ; they are nearly insoluble in water, and the lower mem- 
 bers are very volatile. The higher homologues are not so 
 soluble in water, but continue to be soluble in alcohol and 
 ether, and their smell is less strong on account of the rise in 
 the boiling-point. They are readily inflammable. 
 
 The thio-alcohols, also called mercaptans or alkyl hydro- 
 sulphides, e.g. mercaptan, ethan-thiol, Q 7 H 5 SH, although of 
 neutral reaction, possess the chemical characters of weak acids 
 and are capable of forming salts, the " mercaptides ", especially 
 mercury compounds. The name " mercaptan " is derived from 
 " corpus mercurio aptum ". They are soluble in a strong solu- 
 tion of potash, and their boiling-points are distinctly lower 
 than those of the corresponding alcohols. The thio-ethers, 
 also termed alkyl sulphides, e.g. ethyl sulphide, (C 2 Hg) 2 S, are 
 on the other hand neutral volatile liquids without"acid char- 
 acter. 
 
 Both classes of compounds are derived from hydrogen 
 sulphide by the replacement of either one or both atoms of 
 hydrogen by alkyl groups, just as alcohol and ether are derived 
 from water: 
 
 The boiling-points are methyl mercaptan 6, ethyl mercap- 
 tan 36, methyl sulphide 37, ethyl sulphide 92. 
 
 The constitution of these compounds follows at once from 
 their modes of formation. 
 
 Formation. The mercaptans may be obtained 
 
 1. By warming an alkyl halide or sulphate with potassium 
 hydrosulphide in concentrated alcoholic or aqueous solution : 
 
 C 2 H 6 Br + KSH = C 2 H 6 .SH + KBr. 
 
 2. By heating alcohol with phosphorus pentasulphide, the 
 oxygen being thus replaced by sulphur (KekuU). 
 
 The thio-ethers are similarly obtained 
 1. From an alkyl halide or potassium alkyl sulphate and 
 normal potassium sulphide: 
 
 2C 2 H 5 .S0 4 K + 
 
THIO-ETHERS 89 
 
 2. By treating ethers with phosphorus pentasulphide. 
 " Mixed sulphides ", comparable with the " mixed ethers ", 
 can also be prepared,.^. methyl-ethyl sulphide, C 2 H 5 -S.CH 3 . 
 Behaviour. A. The Mercaptans. 
 
 1. Sodium and potassium act upon the mercaptans to form 
 sodium and potassium salts, white crystalline compounds, 
 which are decomposed by water. The mercury salts are ob- 
 tained by warming an alcoholic solution of mercaptan with 
 mercuric oxide, e.g. mercuric mercaptide, Hg(C 2 H 5 S) 2 (white 
 plates). With mercuric chloride sparingly soluble double com- 
 pounds are formed, e.g. (C 2 H 5 S)Hg Cl, a white precipitate. 
 The lead salts are yellow-coloured, and are formed when alco- 
 holic solutions of a mercaptan and of lead acetate are mixed. 
 
 2. When oxidized with nitric acid the mercaptans are 
 transformed into alkyl-.sulph.onic acids: 
 
 C 2 H 6 .SH + 30 = fSQ (ethyl-sulphonic acid). 
 
 3. The mercaptans in the form of sodium salts are oxidized 
 by iodine or by sulphury! chloride, S0 2 C1 2 (B. 18, 3178), and 
 also frequently in ammoniacal solution in the air to disulphides, 
 e.g. ethyl disulphide, (C 2 H 5 ) 2 S 2 , thus : 
 
 2C 2 H 6 S.Na + I 2 = C 2 H 6 .S.S.C 2 H 6 + 2NaI. 
 
 These are disagreeably-smelling liquids, which have much 
 higher boiling-points than the mercaptans. They are reduced 
 by nascent hydrogen, and with nitric acid yield disulphoxides, 
 e.g. ethyl disulphoxide, (C 2 H 5 ) 2 S 2 2 . 
 
 B. The Thio-ethers. 1. They yield additive compounds 
 with metallic salts, e.g. (C 2 H 5 ) 2 S, HgCl 2 , which can be crystal- 
 lized from ether. 
 
 2. They are capable of combining with halogen or oxygen. 
 Thus ethyl sulphide forms with bromine a dibromide, 
 (C 2 H 5 ) 2 S : Br 2 , crystallizing in yellow octohedra, and with 
 dilute nitric acid, diethyl sulphoxide, (C 2 H 5 ) 2 S:0, a thick 
 liquid soluble in water, which combines further with nitric 
 acid to the compound, (C 2 H 5 ) 2 SO, HN0 3 . Concentrated 
 nitric acid or potassic permanganate oxidizes the sulphides 
 or sulphoxides to sulphones, e.g. ethyl sulphide to (di)-ethyl 
 sulphone, (C.,H 5 ) 2 S0 2 , and methyl-ethyl sulphide to methyl- 
 ethyl sulphone, (CH 3 )(C 2 H 5 )S0 2 . The sulphones are solid 
 well -characterized compounds which boil without decom- 
 position. 
 
90 IV. DERIVATIVES OF MONOHYDRIC ALCOHOLS 
 
 The sulphoxides are reduced by nascent hydrogen to 
 sulphides, but not the sulphones. 
 
 3. The behaviour of the sulphides towards the alkyl haloids 
 is of especial interest. Thus the substances (CH 3 ) 2 S and CH 3 I 
 combine even in the cold to the white crystalline triinethyl- 
 sulphine iodide, (CH 8 ) 3 SI, or trimethyl-sulphonium iodide, as 
 it is now generally called in order to emphasize its similarity 
 to the ammonium salts; this is soluble in water, and when 
 heated is resolved into its components. It behaves exactly 
 like a salt of hydriodic acid, and yields with moist silver oxide 
 (but not with alkali) an oily base, trimethyl-sulphonium 
 hydroxide, (CH 3 ) 3 S-OH, which cannot be volatilized without 
 decomposition. This is as strong a base as caustic potash, 
 and resembles the latter so closely that it absorbs carbon 
 dioxide, cauterizes the skin, drives out ammonia, and gives 
 salts with acids even with hydrogen sulphide; these latter 
 closely resemble the alkali sulphides, e.g. they dissolve Sb 2 S 3 
 (Oefde, 1833; Cahours). 
 
 The compounds just described are of particular interest with 
 regard to the question of the valency of sulphur. 
 
 The readiness with which these sulphur compounds are 
 oxidized, and the ease with which they yield additive com- 
 pounds, is undoubtedly due to the readiness with which the 
 S atom passes from the di- to the tetra- or hexa-valent state; 
 for example: 
 
 ;;;:,, gg>S + Br, gives 
 The sulphoxides are 
 
 the sulphones 
 
 \ 
 
 the sulphonic acids 
 
 OH /OH 
 
 or 
 
 
 and the sulphonium compounds 
 
 s C 2 H 6 \ g /'C 2 H 6 
 
ESTERS OF INORGANIC ACIDS 91 
 
 Since in ethyl sulphide both the alkyl radicals are bound 
 to the sulphur, this will also be the case in ethyl sulphone, 
 otherwise the sulphones would manifestly be easily saponi- 
 fiable. (See Ethyl-hydrogen sulphite.) The sulphonium hy- 
 droxides also can only be explained very insufficiently as 
 molecular compounds, on the assumption of the divalence of 
 sulphur. The formula (CH 3 ) 2 S + CH 3 OH for trimethyl- 
 sulphine hydroxide does not indicate in the least the strongly 
 basic character of this substance, since it is not explicable why 
 the mere addition of the neutral methyl alcohol to the equally 
 neutral methyl sulphide should produce such an effect. 
 
 With respect to isomers, the same general conditions prevail 
 in the sulphur as in the corresponding oxygen compounds. 
 
 SULPHIDES OF UNSATURATED ALCOHOL RADICALS 
 
 Allyl sulphide, (C 3 H 5 ) 2 S (Wertlieim, 1844), present in the 
 oil of Allium sativum oil of garlic, in Thlasp arvense, &c., 
 may be prepared from allyl iodide and K 2 S (Hofmann, Cahours). 
 B.-pt. 140. 
 
 Analogous alkyl selenium and tellurium compounds are 
 also known. They are in part distinguished by their exces- 
 sively disagreeable, nauseous, and persistent odour. 
 
 C. Esters of the Alcohols with Inorganic Acids 
 and their Isomers 
 
 The esters or alkyl salts may be considered as derived from 
 the acids (see p. 74) by the exchange of the replaceable hy- 
 drogen of the latter for alkyl radicals, just as metallic salts 
 result by exchanging the hydrogen for a metallic radical: 
 KN0 3 . (C 2 H 6 )N0 3 . 
 
 ethyl chloride. 
 
 Monobasic acids yield only one kind of ester, "neutral or 
 normal esters", which are analogous to the normal metallic 
 salts of those acids. 
 
 Dibasic acids yield two series of esters (1) acid esters and 
 (2) neutral esters corresponding respectively with acid and 
 normal salts; thus, C 2 H 6 -HS0 4 and (C 2 H 5 ) 2 :S0 4 are the acid 
 
92 IV. DERIVATIVES OF MONOHYDRIC ALCOHOLS 
 
 and normal ethyl esters of sulphuric acid. Tribasic acids yield 
 three series of esters, &c. 
 
 The composition of the esters or alkyl salts is therefore 
 exactly analogous to that of metallic salts, so that in the 
 definition of polybasic acids their behaviour in the formation 
 of esters may also be included. 
 
 The normal esters are mostly liquids of neutral reaction, 
 and often of very agreeable odour, with relatively low boiling- 
 points, and volatilize, eventually in a vacuum, without decom- 
 position. Most of them are very sparingly soluble in water. 
 The acid esters, also called ester-acids, on the other hand, are 
 of acid reaction, without smell, usually very readily soluble 
 in water, much less stable than the neutral esters, and not 
 volatile without decomposition. They act as acids, i.e. form 
 salts and esters. 
 
 All esters are able to combine with water, and are by this 
 means resolved again into their components, namely, alcohol 
 and acid, e.g. 
 
 C 2 H 5 NO 3 + H 2 O = C 2 H 6 OH + HN0 3 . 
 
 This process occurs when the ester is boiled with alkalis or 
 acids, or when heated with steam to over 100, e.g. 150-1SO, 
 and is termed hydrolysis, or saponification, when alkalis are 
 used (see Soaps, p. 158). The reaction is usually conducted 
 in a flask fitted with a reflux condenser, but in a few cases the 
 reaction takes place when the ester is mixed with water at the 
 ordinary temperature. 
 
 General Modes of Formation. 1. The simplest method for 
 obtaining an ester is by the action of the acid on the alcohol, 
 water always being formed as a by-product. As the reactions 
 are reversible, 
 
 C 2 H 5 .OH + O:N-OH ^ C 2 H 5 .0-N:0 + H-OH, 
 
 it is essential that the water formed should be removed from 
 the sphere of action by the aid of concentrated sulphuric acid, 
 fused zinc chloride, &c., or that a large excess of acid should 
 be employed, otherwise after a short time a state of chemical 
 equilibrium is reached, all four compounds are present, and 
 the direct and reverse reactions are proceeding at the same 
 rate; even prolonged heating will then not transform any 
 further amounts of acid and alcohol into ester. 
 
 Esters are therefore often prepared by adding an excess of 
 
ESTERS OF NITRIC ACID 93 
 
 concentrated sulphuric acid to a mixture of the alcohol and 
 sodium salt of the acid. 
 
 2. The alcohol is heated with the acid chloride, thus : 
 
 -2C 2 H 6 .OH = 
 
 3. The silver salt of the acid is heated with an alkyl iodide; 
 this is a method of very general application, although it often 
 leads to isomers of the expected ester (see also p. 94): 
 
 CgHs-I + OiN-OAg = O:N-OC 2 H 5 -f Agl. 
 
 Besides the true esters, there are also included in this 
 division several other classes of acid derivatives isomeric with 
 them, but distinguished from them by not being readily 
 hydrolysed, i.e. by being more stable, e.g. nitre-compounds, 
 sulphonic and phosphinic acids, &c. The hydrocyanic deri- 
 vatives of the alcohols will also be described here for the sake 
 of convenience. These, also, are not hydrolysed in the normal 
 manner into alcohol and acid, but are decomposed in quite a 
 different manner. 
 
 ESTERS OF NITRIC ACID 
 
 Methyl nitrate, CH 3 ^0N0 2 , is a colourless liquid, boiling 
 at 66. Ethyl nitrate, C 2 H 5 .0-N0 2 (Millori), is a mobile 
 liquid of agreeable odour and sweet taste, but with a bitter 
 after-taste; it boils at 86, and burns with a white flame. Both 
 esters are soluble in water. The latter is prepared directly 
 from the alcohol and acid, with the addition of urea in order 
 to destroy any nitrous acid as fast as it is formed. 
 
 Nitric esters contain a large proportion of oxygen in a form 
 in which it is readily given up; they therefore explode when 
 suddenly heated. They are very readily hydrolysed to nitric 
 acid and the alcohol when boiled with alkalis. Tin and hydro- 
 chloric acid reduce them to hydroxylamine : 
 
 C 2 H 5 .O-N^ + 6H = C 2 H 6 -OH + H 2 N-OH + H 2 O. 
 
 These two reactions indicate that the nitrogen atom is not 
 directly united to carbon, as it is so readily removed either as 
 nitric acid or as hydroxylamine. 
 
94 IV. DERIVATIVES OF MONOHYDRIC ALCOHOLS 
 
 DERIVATIVES OF NITROUS ACID 
 
 The compound C 2 H 5 2 N exists in two isomeric forms, repre- 
 sented by the formula C 2 H 5 .0N:0 and C 2 H 5 -N^Q. The 
 
 former is termed ethyl nitrite, as it is the true ester of nitrous 
 acid, H0N:0; the isomeride is termed nitro-ethane, as it 
 
 contains the nitro group *N^/^ attached to carbon. 
 
 a. Alkyl nitrites. These are obtained by the action of 
 nitrous fumes (from arsenious oxide and nitric acid), or of 
 potassium nitrite and sulphuric acid, or of copper and nitric 
 acid upon the alcohols. They are neutral liquids of aromatic 
 odour, with very low boiling-points, and are readily hydrolysed 
 to the corresponding alcohol and acid. When reduced they 
 yield the alcohol, ammonia, and water. 
 
 Methyl nitrite is a gas; ethyl nitrite boils at 18, has a 
 characteristic odour, and in the impure state, as obtained 
 from alcohol, copper, and nitric acid, is used medicinally 
 under the name of "sweet spirits of nitre". 
 
 Amyl nitrite, C 5 H n -0N:0, is a pale-yellow liquid boiling 
 at 96, and is used in medicine; it produces expansion of the 
 blood-vessels and relaxation of the contractile muscles. 
 
 ft. The Nitro-derivatives are colourless liquids of ethereal 
 odour, practically insoluble in water, and boiling at tempera- 
 tures some 100 higher than their isomers. Like the latter 
 they distil without decomposition, and occasionally explode 
 when quickly heated. They are fundamentally distinguished 
 from the alkyl nitrites by not being readily hydrolysed, and 
 by yielding aniino-compounds (see these) on reduction, the 
 nitrogen remaining attached to carbon: 
 
 -6H = CH 3 .NH 2 + 2H 2 0. 
 
 Nitro-methane boils at 99-101. Nitro-ethane, C 2 H 5 -N0 9 
 (V. Meyer and Stub&r, 1872), boils at 113-114, burns with a 
 bright flame, and the vapour does not explode even at a high 
 temperature. 
 
 Formation. 1. The nitro -compounds may be obtained by 
 treating an alkyl iodide with solid silver nitrite (V. Meyer). 
 When methyl iodide is used nitro-methane alone is formed, 
 with ethyl iodide about equal weights of nitro-ethane and 
 ethyl nitrite, and the higher homologues in regularly decreas- 
 
NITRO-DERIVATIVES 95 
 
 ing amounts as compared with those of their isomers, from 
 which, however, they may be readily separated by distillation. 
 Tertiary alkyl iodides do not yield mtro-coinpounds : 
 
 Nitromethane is most readily prepared by the action of 
 sodium nitrite solution on sodium chloroacetate, carbon di- 
 oxide being eliminated, 
 
 2. The nitro-derivatives of the lower paraffins cannot be 
 obtained by the direct action of nitric acid on the hydro- 
 carbons, but with some of the higher derivatives this is pos- 
 sible, e.g. heptane, octane, &c. With decane a 30-per-cent 
 yield of a mono-nitro-derivative may be obtained by means of 
 fuming nitric acid. (W&rstall, Am. 1898, 20, 202; 1899, 21, 
 211; Konowalo/, Abs. 1905, i, 764; 1907, 1, 1.) This method 
 is largely employed in the aromatic series (see Nitrobenzene). 
 
 The constitution of the nitro-compounds is based on the fact 
 that they are not readily hydrolysed, and that the nitrogen is 
 not removed during reduction, but remains directly bound to 
 carbon in the resulting amines (see these). Consequently the 
 nitrogen of the nitro-compound is directly joined to the alkyl 
 radical i.e. to carbon; for instance: 
 
 / 
 CH 3 .N< I, or more probably CH 3 -N 
 
 .N< I 
 X) 
 
 Nitrogen which is attached directly to an alkyl radical is 
 therefore not removed by hydrolysing agents. Since the 
 nitrogen of the isomeric alkyl nitrites, on the other hand, is 
 easily split off from the alkyl radical either by hydrolysis or 
 by reduction, it is manifestly riot directly combined with the 
 carbon but with the oxygen. The alkyl nitrites, therefore, 
 receive the constitutional formula R-O-NiO, where R repre- 
 sents the alkyl radical. 
 
 From this follows for the hypothetical hydrated nitrous 
 acid the formula H-O-NrO, and for the anhydride the for- 
 mula (N0) 2 0. The aromatic hydrocarbons, e.g. benzene, C 6 Hg, 
 yield with nitric acid nitro-compounds, thus : 
 
 C 6 H 6 .H + HN0 3 = C 6 H 6 .N0 2 -f H 2 0. 
 
 Nitric acid, therefore, contains a nitro- group bound to 
 hydroxyl, corresponding with the formula H0N0 2 . 
 
 Behaviour. 1. They yield primary amines with acid reduc- 
 ing agents, e.g. iron and acetic acid, tin and hydrochloric acid, 
 
96 IV. DERIVATIVES OF MONOHYDRIC ALCOHOLS 
 
 &c., substituted hydroxylamines being formed as intermediate 
 products (V. Meyer, B. 1892, 25, 1714). 
 
 2. Primary (.CH 2 -N0 2 ) and secondary (:CH-N0 2 ) nitro- 
 compounds can yield metallic derivatives, and hence possess 
 certain acidic properties. For example, nitro-methane and 
 mtro-ethane react with alcoholic sodium hydroxide, yielding 
 sodium compounds, CH 2 Na.N0 2 and CH 3 CHNa N0 2 . It is 
 almost certain that these sodium salts are not true derivatives 
 of the nitro-compound, but are derived from an isomer, the 
 
 so-called iso-nitro- compound CH 2 :N^Vv TT, and thus sodic 
 
 nitro-methane has the constitutional formula CH 9 :NO'ONa 
 (Hcllemann, B. 1900, 33, 2913). The nitro-derivatives are 
 t/hus not true acids, but pseudo acids (Hantzsch, B. 1899, 32, 
 1)77; see also Phenylnitromethane)> These sodium salts are 
 crystalline solids, and are highly explosive. 
 
 Tertiary nitro-compounds (:C-N0 2 ) contain no hydrogen 
 joined to the carbon atom which is united to the nitro-group, 
 and they have not an acid character; the acidifying influence 
 of the nitro-group does not, therefore, extend to those hydrogen 
 atoms which are attached to other carbon atoms. 
 
 The hydrogen in the primary and secondary nitro-deriva- 
 tives, which is attached to the same carbon atom as the N0 2 
 group, can also be replaced by bromine. So long as hydrogen, 
 as well as this bromine and the nitro-group, remains joined to 
 the carbon atom in question, the compound is of a strongly 
 acid character; but when it also is substituted by bromine, 
 the compound becomes neutral, e.g. dibromo-nitro- ethane, 
 CH 3 -CBr 2 .N0 2 , is neutral. 
 
 The reactivity of the hydrogen atoms of the CH 2 X0 2 
 and ^>CHN0 2 groups, characteristic of primary and secon- 
 dary nitro-compounds, is exemplified in the reactions of 
 these compounds with aldehydes in the presence of sodium 
 carbonate. A primary nitro-compound can combine with 
 one or with two molecules of formaldehyde, yielding com- 
 pounds of the types - CH(N0 9 )CH 2 . OH and -C(N0 2 ) 
 (CH 2 .OH) 2 . 
 
 3. The primary nitro-compounds yield, with concentrated 
 hydrochloric acid at 140, acids of the acetic series containing 
 an equal number of carbon atoms, and hydroxylamine. 
 
 4. The reaction of the nitro-compounds with nitrous acid 
 is very varied, The primary yield nitrolic acids and the 
 
ESTERS OF SULPHURIC ACID 97 
 
 secondary pseudo-nitrols, while the tertiary do not react with 
 it at all. Thus from nitro-ethane, CH 3 .orfJ^ , ethyl- 
 
 TVT f"\"llT ^^^2 
 
 nitrolic acid, CH 3 .C^ N Q , an acid crystallizing in light- 
 yellow crystals and yielding intensely red alkali salts, is 
 formed. Normal nitro-propane acts similarly. Secondary 
 nitro- propane, (CH 3 ) 2 : CHN0 2 , gives, on the contrary, 
 propyl-pseudo-nitrol, (CH 3 ) 2 C(NO)(N0 2 ), a white crystalline, 
 indifferent, non-acid substance, which is blue either when 
 fused or when in solution. These reactions, which are only 
 given with compounds of low molecular weight (in the primary 
 up to C 8 , and in the secondary up to C 5 ), are specially appli- 
 cable for distinguishing between the primary, secondary, or 
 tertiary nature of an alcohol (see p. 74). The nitre-hydro- 
 carbons, which are readily prepared from the iodides, are dis- 
 solved in a solution of potash to which sodium nitrite is 
 added, the solution acidified with sulphuric acid and again 
 made alkaline, and then observed for the production of a 
 red coloration (primary alcohol), a blue coloration (secondary 
 alcohol), or no coloration (tertiary alcohol). 
 
 Chloropicrin, CC1 3 N0 2 , a heavy liquid of excessively suffo- 
 cating smell, b.-pt. 112, is formed from many hydrocarbon 
 coiri pounds by the simultaneous action of nitric acid and 
 chlorine, chloride of lime, &c. It is best obtained from jpicric 
 acid and bleaching-powder. 
 
 Polynitro -derivatives are also known. Dinitromethane, 
 CHo(N0 2 ).j, an unstable yellow oil; dinitroethane, CH 3 CH 
 (N0 2 ) 2 , obtained from CH 3 CHBr.N0 2 and potassium nitrite, 
 b.-pt. 185; trinitromethane or nitroform, CH(N0 2 ) 3 , colour- 
 less crystals, m.-pt. 15; tetranitromethane, C(N0 2 ) 4 , colour- 
 less crystals, m.-pt. 13 and b.-pt. 126, is prepared by the 
 action of nitric acid (D = T53) on acetic anhydride (Chatta- 
 way, J. C. S. 1910, 2100). Good yields (50 per cent) of dinitro- 
 compounds of the type N0 2 .[CH 2 ] n .N0 2 can be obtained from 
 the corresponding di-iodo-derivatives and silver nitrite (Fan 
 Bmun and SolecU, B. 1911, 44, ii526) provided n > 3. The 
 compounds are stable and react with bromine, nitrous acid, &c., 
 in much the same manner as mono-nitro-compounds. They 
 are accompanied by alkylene dinitrites, 0:N-0[CH 2 ] n .O'N:0, 
 and nitro-nitrites, N0 2 -[CH 2 ] n -O.N:0, from which they can 
 be separated by fractional distillation. The dinitro-compounds 
 can be used for the preparation of dialdehydes, since when 
 
 ( B 480 ) Q 
 
98 IV. DERIVATIVES OF MONOHVDRIC ALCOHOLS 
 
 reduced with stannous chloride they yield dioximes, and these 
 on hydrolysis give dialdehydes: 
 
 N0 2 .[CH 2 ] 5 -N0 2 -> OH.N:CH.[CH 2 ] 3 .CH:N.OH -> 
 
 1:5 Dinitro pentane : CH [CH 2 ] 3 CH : O 
 
 Glutaric aldehyde. 
 
 ESTERS OF SULPHURIC ACID 
 
 As a dibasic acid sulphuric acid can give rise to both neutral 
 or normal esters, e.g. (C 2 H 5 ) 2 S0 4 , and acid esters or alkyl 
 hydrogen sulphates, e.g. C 2 H 5 HS0 4 . 
 
 The neutral esters are formed by the three general methods : 
 (a) from fuming sulphuric acid and alcohol; (b) from silver 
 sulphate and alkyl iodide; (c) from sulphury! chloride and 
 alcohol : 
 
 S0 2 C1 2 + 2C 2 H 6 OH = S0 2 (OC 2 H 6 ) 2 + 2HC1 
 
 The acid esters of the primary alcohols are generally pre- 
 pared directly from their components. Secondary and tertiary 
 alcohols do not yield them. 
 
 Ethyl sulphate, (62115)2804, is a colourless oily liquid of 
 an agreeable peppermint odour, insoluble in water, and solidi- 
 fying on exposure to a low temperature. It boils at 208, is 
 quickly hydrolysed with boiling water, but only slowly with 
 cold water, yielding alcohol and sulphuric acid. 
 
 Methyl sulphate, (CH 3 ) 2 S0 4 , is a syrupy oil, b.-pt. 188, it 
 is extremely poisonous, does not adhere to glass, and is a 
 common reagent used instead of methyl iodide for the forma- 
 tion of methyl derivatives of phenols, alcohols, and amines (cf. 
 S. J., Exp. 127). 
 
 Ethyl hydrogen sulphate, C 2 H 5 O.S0 2 -OH (Dabit, 1802), 
 is obtained from a mixture of alcohol and sulphuric acid, but 
 not quantitatively, on account of the state of equilibrium that 
 ensues. It is also formed from ethylene and sulphuric acid 
 at a somewhat higher temperature. It differs from sulphuric 
 acid by its Ba-, Ca-, and Pb-salts being soluble, and it can 
 therefore be easily separated from the former by means of 
 BaC0 3 , &c. It yields salts which crystallize beautifully, e.g. 
 KC 2 H 5 S0 4 , but which slowly decompose into sulphate and 
 alcohol on boiling their concentrated aqueous solution, espe- 
 cially in presence of excess of alkali. 
 
 These salts are frequently used instead of ethyl iodide for the 
 preparation of other ethyl derivatives (process of ethylation). 
 
SULPHONIC ACIDS AND DERIVATIVES 99 
 
 The free acid ester is prepared by adding the requisite 
 amount of sulphuric acid to the barium salt. It is a colourless 
 oily liquid which does not adhere to glass, and which slowly 
 hydrolyses when its solution is evaporated or kept. When 
 heated alone it is decomposed into ethylene and sulphuric acid; 
 with alcohol it yields ethyl ether and sulphuric acid. 
 
 DERIVATIVES OF SULPHUROUS ACID 
 
 a. Alkyl Sulphites. Ethyl sulphite, S0 3 (C 2 H 5 ) 2 , is an 
 ethereal liquid of peppermint odour, which can be prepared 
 from alcohol and thionyl chloride, SOC1 2 , and which is rapidly 
 hydrolysed by water. It has b.-pt. 161, and its probable con- 
 stitution is: 0:S(OEt) 2 . 
 
 Ethyl Hydrogen Sulphite. The very unstable potassium 
 salt, OEt-S0 9 K, is formed by the action of dry sulphur di- 
 oxide on potassium ethoxide (Rosenheim, B. 1905, 38, 1301). 
 It is decomposed by water, yielding alcohol and potassium 
 sulphite. 
 
 The action of sodium hydroxide on ethyl sulphite does not 
 hydrolyse the ester to sodium ethyl sulphite, but to sodium 
 ethyl sulphomite, C 2 H 5 S0 2 ONa. (B. 1898, 31, 406.) 
 
 13. Sulphonic Acids. Sulphonic acids contain the mono- 
 valent group .S0 2 -OH. They are colourless oils or solids, 
 extremely hygroscopic, readily soluble in water, and are strong 
 monobasic acids. They are much more stable than the iso- 
 meric alkyl hydrogen sulphites; for example, they are not 
 hydrolysed when boiled with aqueous alkalis or acids, but are 
 decomposed when fused with potash. They are non-volatile 
 with steam, and when strongly heated decompose. 
 
 Ethyl-sulphonic acid, C 2 H 5 .S0 2 .QH (Lowig, 1839; H. Kopp, 
 1840), is a strong monobasic acid, and yields crystalline salts, 
 e.g. C 2 H 5 .S0 3 K + H 2 (hygroscopic), C 2 H 5 .S0 3 Na + H 2 0. 
 
 Methyl-sulphonic acid, CH 3 .S0 3 H, is a syrupy liquid, and 
 was prepared by Kolbe in 1845 from trichloro-methyl-sulphonic 
 chloride, CC1 3 .S0 2 C1 (produced from CS 2 , Cl, and H 2 0). 
 
 Modes of Formation. 1. From sodium or ammonium sulphite 
 and alkyl iodide (or alkyl hydrogen sulphate: 
 
 Sulphonic esters are formed by the action of alkyl iodides 
 on silver sulphite: 
 
 2C 2 H 5 I + Ag 2 S0 3 = (C 2 H 6 ) 2 S0 3 + 2AgI. 
 
100 IV. DERIVATIVES OF MONOHYDRIC ALCOHOLS 
 
 2. By the oxidation of mercaptans by KMn0 4 or HN0 3 : 
 C 2 H 6 -SH + 30 = C 2 H 5 -S0 3 H. 
 
 The sulphonic acids yield chlorides with PC1 5 , e.g. ethyl- 
 sulphonic acid gives ethyl-sulphonic chloride, C 2 H 5 'SOgCl, a 
 liquid which boils without decomposition at 177, fumes in 
 the air, and is reconverted by water into ethyl-sulphonic and 
 hydrochloric acids. Nascent hydrogen reduces it to mercaptan, 
 and with zinc dust it yields the zinc salt of a syrupy, readily 
 soluble acid, viz. ethyl-sulphinic acid, C 2 H 5 S0 2 H, which may 
 also be reduced to mercaptan. Sodium ethyl sulphinate yields 
 ethyl sulphone when treated with ethyl bromide, C 2 H 5 Br. 
 When esterified the acid forms an unstable ester, isomeric with 
 ethyl sulphone (B. 24, 2272). 
 
 Ethyl Ethyl-sulphonate, C 2 H 5 -S0 2 'OC 2 H 5 , is isomeric with 
 ethyl sulphite, and, being an ester of the more stable ethyl- 
 sulphonic acid, can only be partially hydrolysed. It is pre- 
 pared from silver sulphite and ethyl iodide. It boils at 213, 
 and the sulphonic esters generally have considerably higher 
 boiling-points than the isomeric alkyl sulphites. 
 
 Constitution. From the formation of the sulphonic acids 
 from mercaptans by oxidation, and the (indirect) reversibility 
 of this reaction, it follows that the sulphur in them is directly 
 attached to the alkyl radical; if, then, sulphur is regarded as 
 hexavalent, ethyl-sulphonic acid has the constitution 
 
 C 2 H 6 .S0 2 -OH = 
 
 This constitution is in perfect harmony with the reaction of 
 the acids with phosphorus pentachloride and also with their 
 monobasicity. From this we might conclude, assuming that 
 the conversion of metallic sulphites into sulphonic acid deriva- 
 tives is a simple exchange of alkyl and metallic radicals, that 
 the constitution of sodium sulphite is Na-S0 2 ONa, of the 
 hypothetical sulphurous acid HS0 2 OH, and of sulphuric 
 acid OH-S0 2 OH. The alkyl sulphites formed from thionyl 
 chloride probably have the alkyl groups attached to oxygen, 
 e.g. ethyl sulphite, SO(OC 2 H 6 ) 2 . 
 
 Esters of phosphoric acid PO(OK) 3 , PO(OE) 2 (OH), and 
 PO(OR)(OH) 2 , (K = alkyl), exist, as do also similar com- 
 pounds of phosphorous and hypophosphorous acids. The 
 phosphinic acids, &c., are related to the two last-mentioned 
 classes. Esters of boric and silicic acids are also known. 
 
REACTIONS OF NITRIDES; ; >>"h " ^^1 
 
 ALKYL DERIVATIVES OF HYDROCYANIC ACID 
 
 Hydrocyanic acid, HCN, yields two classes of derivatives 
 by the exchange of its hydrogen atom for alkyl radicals, 
 neither of which can be regarded as esters, in the sense that 
 they are hydrolysed to the acid and alcohol. 
 
 a. Alkyl Cyanides or Nitriles, E-C-N. These are either 
 colourless liquids, which volatilize without decomposition, or 
 solids, with an ethereal odour slightly resembling that of 
 leeks; they are lighter than water, and are relatively stable. 
 The lower members are miscible, with water, but the higher 
 ones not, and they boil at about the same temperatures as the 
 corresponding alcohols. 
 
 Formation. 1. By heating an alkyl iodide with an alcoholic 
 solution of potassium cyanide, or potassium ethyl -sulphate 
 with potassium ferrocyanide : 
 
 CH 3 I + KCN = Kl-f CH 3 . ON (methyl cyanide). 
 
 2. From fatty acids, e.g. acetic acid, CH 3 -CO.OH. The 
 ammonium salt when distilled loses water and yields the acid 
 amide, e.g. : 
 
 CH 3 .CO-ONH 4 = H 2 O + CH 3 .CO-NH 2 (acetamide). 
 
 The amide when heated with a dehydrating agent, e.g. P 4 10 , 
 loses a second molecule of water and yields the cyanide : 
 CH 3 -CO.NH 2 = H 2 O + CH 3 -C:N. 
 
 As a consequence of this mode of formation these com- 
 pounds are also termed nitriles of the monobasic acids, e.g. 
 CHg-CN, methyl cyanide or aceto-nitrile ; C 2 H 5 -CN, propio- 
 nitrile, &c. 
 
 3. The higher nitriles, in which C>5, are formed from the 
 amides of acids of the acetic series containing 1 atom of carbon 
 more in the molecule, and also from the primary amines with 
 the same number of carbon atoms, upon treatment^with bro- 
 mine and caustic-soda solution (Hofmann). See Amides. 
 
 4. From the oximes of the aldehydes, by warming with 
 acetic anhydride. See Aldoximes. 
 
 Reactions. The nitriles are chemically active. Most of the 
 reactions are of an additive nature, and are somewhat similar 
 to those characteristic of the olefines. These reactions are in 
 harmony with the constitutional formulae usually attributed 
 to the nitriles, e.g. R.C|N, according to which a triple bond 
 exists between a nitrogen and a carbon atom. 
 
102 . 'f.V.ERrtfATIYES OF "MONOHYDRIC ALCOHOLS 
 
 1. When hydrolysed with acids or alkalis, or superheated 
 with water, they take up water (2 mols.) and yield the 
 ammonium salts of fatty acids (with alkalis, the alkali salt, 
 and free ammonia). The reaction undoubtedly proceeds in 
 two distinct stages, and an acid amide is first formed: 
 
 CH 3 .CO-NH 2 -fH 2 = CH 3 .CO.ONH 4 . 
 
 It is generally impossible to stop the hydrolysis at the first 
 stage in the case of aliphatic nitriles, but this is readily 
 accomplished with aromatic cyanides. This is a reaction of 
 considerable interest, as it enables us to pass from a saturated 
 alcohol, C n H 2n+1 -OH, to the aliphatic acid, C n H ta+1 COOH, 
 which contains 1 atom of carbon more than the alcohol: 
 
 CH 3 .OH -> CH 3 I - CH 3 .CN CH 3 .COOH. 
 
 2. Just as acetamide is formed by the taking up of water, 
 so is thio-acetamide by the addition of sulphuretted hydrogen, 
 
 3. By the addition of hydrochloric acid, amido-chlorides or 
 imido-chlorides are formed ; by the addition of ammonia bases, 
 amidines. Halogens also form decomposable additive-products. 
 
 4. Primary amines are obtained by the reduction of nitriles 
 with sodium and alcohol (p. 106): 
 
 CH 3 .C!N + 4H = CH 3 .CH 2 .NH 2 (ethylaimne). 
 
 5. Metallic potassium or sodium frequently induces poly- 
 merization; thus methyl cyanide yields in this way cyan- 
 methine, a mono-acid base crj^stallizing in prisms. 
 
 Aceto-nitrile, Ethane-nitrile, CH 3 CN, b.-pt. 82 is present in 
 the products of distillation from the vinasse of sugar beet and 
 in coal-tar. Propio-nitrile; (Propane-nitrile), C 2 H 5 'CN, butyro- 
 nitrile, C 3 H 7 'CN, and valero-nitrile, C 4 H 9 CN, are liquids of 
 -agreeable bitter-almond-oil odour; palmito-nitrile, C 15 H 31 CN, 
 is like paraffin. 
 
 P. Isocyanides, Isonitriles or Carbylamines. These are 
 colourless liquids readily soluble in alcohol and ether, but 
 only slightly soluble in water. They have a feeble alkaline 
 reaction, an unbearable putrid odour, and poisonous proper- 
 ties, and boil somewhat lower than the isomeric nitriles. 
 
 Formation. 1. By heating an alkyl iodide with silver 
 cyanide instead of potassium cyanide (Gautier), a double com- 
 
 
CONSTITUTION OF CYANIDES AND ISOCYANIDES 103 
 
 pound with silver cyanide being first formed, according to 
 Wade : 
 
 Ag-N:C: + EtI = EtANzC: = AgI + Et-N:C: 
 
 I' (ethyl carbylamine). 
 
 2. In small quantity, along with the nitrile, when a potassium 
 alkyl-sulphate is distilled with potassium cyanide. 
 
 3. By the action of chloroform and alcoholic potash upon 
 primary amines (Hofmann, 1869) (see pp. 63 and 108): 
 
 CH 3 .NH 2 + CHC1 3 + 3KOH = CH 3 .N:C + 3KC1 + 3H 2 O. 
 
 Behaviour. 1 . The isonitriles differ fundamentally from the 
 nitriles in their behaviour with water or dilute acids. When 
 strongly heated with water, or with acids in the cold, they 
 decompose into formic acid and a primary amine containing 
 an atom of carbon less than themselves: 
 
 Unlike the nitriles, they are very stable towards alkalis. 
 
 2. The isonitriles are also capable of forming additive pro- 
 ducts with the halogens, HC1, H 2 S, &c., compounds different 
 from those given by the nitriles; thus, with HC1 they yield 
 crystalline salts which are rapidly decomposed by water into 
 amine and formic acid. 
 
 3. Some of the isonitriles change into the isomeric nitriles 
 when heated. According to Wade this change does not occur 
 at all readily in the fatty series if the carbylamines are 
 thoroughly dry. (J. C. S. 1902, 81, 1596.) 
 
 Methyl isocyanide, CH 3 -NC, boils at 58, and ethyl iso- 
 cyanide, C 2 H 5 NC, at 82. 
 
 Constitution of the Nitriles and Isonitriles. The constitution 
 of the nitriles follows from the readiness with which they can 
 be hydrolysed to acids of the acetic series. In acetic acid 
 we know that we have a methyl group directly attached to 
 a carbon atom, e.g. CH 3 CO OH, and since methyl cyanide 
 on hydrolysis yields acetic acid, it also presumably contains 
 the methyl group attached to carbon. The nitrogen atom, 
 on the other hand, is eliminated, and is thus probably not 
 directly bound to the alkyl radical. Consequently aceto-nitrile 
 has the constitution CH 3 C:N. 
 
 This constitutional formula is supported by a study of the 
 product formed on reduction, namely CH 3 CH 2 NH 2 . 
 
104 IV. DERIVATIVES OF MONOHYDRIC ALCOHOLS 
 
 In the case of the isonitriles, however, it is the nitrogen 
 which must be directly bound to the alkyl radical, as their 
 close connection with the amine bases shows, the amines being 
 easily prepared from and reconverted into the isonitriles. 
 The carbon atom of the cyanogen group, on the contrary, is 
 eliminated as formic acid on decomposition with acid, and is 
 consequently not directly united to the alkyl radical, but only 
 through the nitrogen. The constitutional formula of methyl 
 isocyanide is therefore either CH 3 N:C or CH 3 -N:C:, with 
 an unsaturated carbon atom (cf. Chap. LII). 
 
 D. Amines or Nitrogen Bases of the Alkyl Radicals 
 
 By the introduction of alkyl radicals in place of hydrogen 
 into the ammonia molecule, the important class of ammonia 
 bases or amines is formed. 
 
 The amines containing small alkyl groups bear the closest 
 resemblance to ammonia, and are even more strongly basic 
 than the latter. They have an ammoniacal odour, give 
 rise to white clouds with volatile acids, combine with hydro- 
 chloric acid, &c,, to salts with evolution of heat, and yield 
 platini- and auri-chlorides. Their aqueous solutions precipitate 
 insoluble hydroxides from solutions of the salts of the heavy 
 metals, and these precipitates are frequently soluble in excess. 
 
 The lowest members of this class are combustible gases 
 readily soluble in water. The next are liquids of low boiling- 
 point, also at first readily soluble; but the solubility in water, 
 and also the volatility, decrease with an increase in molecular 
 weight, until the highest members of the series, such as tricetyl- 
 amine, (C 16 H 33 ) 3 N, are at the ordinary temperature odourless 
 solids of high boiling-point, insoluble in water but soluble in 
 alcohol and ether, and readily combining with acids to form 
 salts. All amines are considerably lighter than water. 
 
 The quaternary ammonium hydroxides are solid and very 
 hygroscopic, and exceedingly like potash in properties. 
 
 Classification. The bases are divided into primary, secondary, 
 tertiary, and quaternary bases, according as they contain 1, 2, 
 3, or 4 alkyl radicals; the three first are derived from am- 
 monia, and the last from the hypothetical ammonium hy- 
 droxide, NH 4 .OH. Characteristic of primary amines is the 
 amino group, 'NHg, of secondary, the imino group, :NH, and 
 of tertiary, the N radical attached to three alkyl groups. 
 
FORMATION OF AMINES 105 
 
 The system of nomenclature is simple, as indicated by the 
 following examples: CH 3 NH 2 , methylamine ; C 3 H 7 'NH 2 , 
 propylamine; (C 2 H 5 ) 2 NH, di-ethylamine; (CH 3 ) 3 N, trimethyl- 
 amine; and N(C 2 H 5 ) 4 I, tetraethylammonium iodide. 
 
 The alkyl radicals may be either saturated or unsaturated. 
 
 Modes of Formation. 1. Primary amines, e.g. methylamine, 
 ethylamine, are obtained by heating alkyl cyanates with 
 potash solution (Wurtz, 1848), just as cyanic acid itself yields 
 ammonia and carbon dioxide : 
 
 2. By the direct' introduction of the alkyl radical into 
 ammonia by heating a concentrated solution of the latter with 
 methyl iodide, chloride, or nitrate, ethyl iodide, &c. In this 
 reaction an atom of hydrogen is first exchanged for an alkyl 
 radical, and then the base produced combines with the halogen 
 hydride, formed at the same time, to a salt, thus : 
 
 (I) NH 2 H + CH 3 I = NH 2 .CH 3 , HI. 
 
 From the methylamine hydriodide thus produced, free 
 methylamine can readily be obtained by distillation with 
 potash : 
 
 NH 2 (CH 3 ), HI + KOH = NH 2 (CH 3 ) + KI + H 2 O. 
 
 The methylamine can now combine further with methyl 
 iodide to hydriodide of dimethylamine : 
 
 (II) NH 2 (CH 3 ) + CH 3 I = NH(CH 3 ) 2 HI, 
 
 tthich, in its turn, yields the free base with potash. This 
 latter can again combine with methyl iodide: 
 
 (III) NH(CH 3 ) 2 + CH 3 I = N(CH 3 ) 3 HI, 
 
 the salt so produced yielding trimethylamine as before. 
 Finally, the trimethylamine can once more take up methyl 
 iodide : 
 
 (IV) N(CH 3 ) 3 + CH 3 I = N(CH 3 ) 4 I. 
 
 The compound obtained, tetramethylammonium iodide,^ is, 
 however, no longer a salt of an amine, but of an ammonium 
 base, and is not decomposed on distillation with potash solu- 
 tion. The velocities of formation of quaternary ammonium 
 iodides from tertiary amines and alkyl iodides have been 
 determiner! bv Menwhutkin. The reaction has been shown 
 
106 IV. DEBIVATIVES OP MONOHYDRIO ALCOHOLS 
 
 to be a bimolecular one. The velocity varies with the alkyl 
 iodide employed, decreasing as the alkyl group becomes more 
 complex. The solvent employed, for example, acetone, hexane, 
 methyl alcohol, &c., also affects the velocity of formation to 
 an enormous extent, e.g. the combination of ethyl iodide and 
 try-ethylamine takes place some 250 times as readily in ethyl 
 alcohol as in hexane solution. 
 
 Primary and secondary bases can also be transformed into 
 secondary and tertiary by warming with potassium alkyl- 
 sulphates (B. 1891, 24, 1678). 
 
 When, several alkyl iodides are used in place of methyl 
 iodide, mixed amines, i.e. amines containing different alkyl 
 
 ups in the molecule, are obtained, e.g. methyl-propylamine, 
 
 H(CH 3 )(C 3 H 7 ), methyl-ethyl-propy'lamine, N(CH 3 )(C 2 H 5 ) 
 (C 3 H r ). 
 
 The reactions I to IV given above do not in reality follow 
 each other in perfect order but go on simultaneously, the bases 
 being partly liberated from the hydriodides by the ammonia, 
 and so being free to react with more alkyl haloid. The pro- 
 duct obtained by distillation with potash is therefore a mixture 
 of all the three amines and ammonia. 
 
 These cannot be separated by fractional distillation, and so 
 their different behaviour with ethyl oxalate, OEt-CO-CO-OEt, 
 is made use of for the purpose. Methyl amine reacts with this 
 ester to form chiefly (1) dimethyl-oxamide, CH 3 NH. CO -CO- 
 NK CH 3 (solid), and (2) some methyl-oxamie ester, OEt CO 
 CO-NH-CH 3 (liquid); dimethylamine yields (3) the ethyl ester 
 of dimethyl-oxamic acid, OEt-CO-CO-N(CH 3 ) 2 (liquid), while 
 trimethylamine does not react with the ethyl oxalate. Upon 
 warming the product of the reaction on the water-bath, the 
 latter base distils over, and the remaining compounds can 
 then be separated by special methods (for which see B. 3, 776; 
 8, 760), and individually decomposed by potash, (1) and (2) 
 yielding methylamine, and (3) dimethylamine. 
 
 3. The nitro-compounds yield primary amines when treated 
 with acid reducing agents (see p. 95), thus : 
 
 CH 3 .N0 2 -f 6H = CH 3 .NH 2 + 2H 2 0. 
 
 4. The nitriles, including hydrocyanic acid, are capable of 
 taking up four atoms of hydrogen (see p. 102) and forming 
 primary amines (Menditis, 1862): 
 
 CH 3 .C:N + 4H = CH 3 -CH 2 .NH 2 (ethylamine). 
 
PROPERTIES OF AMINES 107 
 
 5. Primary amines, in which C < 6, are prepared according 
 to Hofmann's method, by the action of bromine and caustic- 
 soda solution upon the amides of acids containing 1 carbon 
 atom more than themselves (see Amides). 
 
 6. Primary amines likewise result from the reduction of 
 the oximes or hydrazones (see pp. 127 and 135): for example, 
 acetaldoxime : 
 
 CH 3 .CH:N.OH-]-4H = CH 3 .CH 2 .NH 2 + H 2 O. 
 
 7. See p. 463 for preparation of amines from phthalimide. 
 Isomers. Numerous isomers exist among the amines, as the 
 
 following table shows : 
 
 
 C 2 H 7 N. 
 
 C 3 H 9 N. 
 
 C 4 H n N. 
 
 Isomers 
 
 NH 2 (C 2 H 5 ) 
 NH(CH 3 ) 2 
 
 NH 2 (C 3 H 7 ) 
 NH(CH 3 )(C 2 H 6 ) 
 N(CH 3 ) 3 
 
 NHo(C 4 H 9 ) 
 NH(CH S )(C 8 H T ) and NH(C 2 H 5 ) 2 
 N(CH 3 ) 2 (C 2 H 6 ) 
 
 This kind of isomerism is the same as that of the ethers 
 (p. 87), i.e. metamerism. From (C 3 H r ) onwards, isomerism can 
 also occur in the alkyl radicals. According to theory, as many 
 amines C n as alcohols C n+1 are capable of existence. 
 
 Behaviour. 1. The amines combine directly with acids (or- 
 ganic or inorganic) to form salts in exactly the same way as 
 ammonia; the quaternary ammonium bases, however, react 
 with acids, forming salts and eliminating water like potassium 
 or ammonium hydroxide : 
 
 CH 3 .NH 2 + HC1 = CH 3 .NH 2 , HC1 = CH 3 .NH 3 CL 
 (CH 3 ) 4 N.OH + HC1 = (CH 3 ) 4 N.C1 + H 2 O. 
 
 The salts so obtained are white, crystalline compounds, 
 readily soluble in water, and frequently hygroscopic. The 
 chlorides form, with platinic chloride, sparingly soluble platini- 
 chlorides analogous to ammonium platinichloride, (NH 4 ) 2 PtCl 6 , 
 e.g. methylamine platinichloride, (CH 3 NH 3 ) 2 PtCl 6 . 
 
 The same applies to the aurichlorides, e.g. C 2 H 5 NH 3 AuCl 4 . 
 
 Strong alkalis, e.g. potassium hydroxide, decompose all the 
 salts with the exception of the quaternary ammonium com- 
 pounds yielding the free bases (and not ammonia). 
 
 2. Hydrolysing agents such as alkalis and acids do not 
 affect the nitrogen bases of the alcohol radicals. 
 
 3. The different classes of amines are distinguished from 
 
108 IV. DERIVATIVES OF MONOHYDRIC ALCOHOLS 
 
 each other by the primary having 2 hydrogen atoms, the 
 secondary 1, but the tertiary none replaceable by alkyl 
 groups; the same applies to acid radicals (acyl groups). The 
 ultimate products obtained from isomeric amines by the action 
 of methyl iodide are distinguished from one another by ana- 
 lysis. Thus of the three isomeric amines C 3 H 9 N, propylamine 
 gives with methyl iodide, C 8 H 7 .N(CH 3 ) 3 I, propyl-trimethyl- 
 ammonium iodide = C 6 H 16 NI; methyl-ethylamine gives C 2 H 5 
 N(CH 3 ) 3 I, ethyl-trimethylammonium iodide = C 5 H 14 NI; and 
 trimethylamine gives N(CH 3 ) 4 I, tetramethylammonium iodide 
 = C 4 H 12 NI. An iodine estimation in the final product would 
 immediately enable us to settle the constitution of the original 
 amine. 
 
 The primary bases further differ from the others in their 
 behaviour with chloroform, carbon disulphide, and nitrous acid. 
 
 4. Only the primary bases react with chloroform and alco- 
 holic potash, with formation of isonitriles (p. 103). 
 
 5. When warmed with carbon disulphide in alcoholic solu- 
 tion, the primary and secondary, but not the tertiary, bases 
 react to form derivatives of thiocarbamic acids. (See Carbonic 
 Acid Derivatives.) Should the amines be primary ones, the 
 characteristically smelling isothiocyanates are produced upon 
 heating the thiocarbamic derivatives with a solution of HgCl 9 
 (" Senfol " reaction). 
 
 6. Nitrous acid reacts with the primary amines, forming 
 alcohols, e.g. 
 
 A molecular rearrangement is occasionally met with, e.g. 
 the production of isopropyl alcohol from ?i-propylamine. 
 
 Secondary bases yield with nitrous acid nitroso-compounds, 
 e.g. " diinethyl-nitrosamine " : 
 
 (CH 3 ) 2 NH + NO.OH = (CH 3 ) 2 N.NO + H 2 0. 
 
 These nitrosamines are yellow-coloured volatile liquids of 
 aromatic odour (Geuther). When reduced with acid-reducing 
 agents, or when heated with alcohol and hydrochloric acid, 
 they regenerate the secondary amines. Weak reducing agents, 
 however, convert them into hydrazines (p. 112). The nitros- 
 amines are frequently of great service in the purification of 
 the secondary bases. 
 
 Nitrous acid has no action upon tertiary amines. 
 
 7. By the indirect action of nitric acid (B. 22, Ref. 295), 
 
PROPERTIES OF AMINES 109 
 
 nitr amines result, i.e. amines in which an amino-hydrogen atom 
 has been replaced by the nitro- group, e.g. CH 3 .NH.N0 2 , 
 methyl-nitramine. Similarly, by the indirect introduction of 
 an amino-group, hydrazines are formed, e.g. CH 3 NHNH 2 , 
 methyl-hydrazine. 
 
 8. While the amines are liberated from their salts by alkalis, 
 the free bases of the quaternary ammonium salts, e.g. tetra- 
 methylammonium iodide, cannot be prepared from these by 
 treatment with potash, because the products are soluble and 
 non-gaseous, and hence an equilibrium is attained. The salts 
 behave normally in aqueous solutions, for example, the iodides 
 yield precipitates with silver nitrate, and are good electrolytes, 
 The corresponding hydroxides, e.g. N(CH 3 ) 4 OH, are obtained 
 most readily by acting upon the iodides with moist silver 
 oxide. These hydroxides are extraordinarily like caustic 
 potash. They are colourless hygroscopic solids, readily soluble 
 in water, and abstract carbon dioxide from the air. The solu- 
 tions have strongly alkaline properties, are good electrolytes, 
 and precipitate metallic hydroxides from solutions of their 
 salts. When distilled they decompose, yielding the tertiary 
 base, the tetramethyl base yielding in addition methyl alcohol, 
 and the homologous bases olefine and water (Braun, A. 382, 1): 
 
 N(CH,),.OH = N(CH 3 ) 3 +CH 3 .OH. 
 N(C 2 H 6 ) 4 .OH = 
 
 They are of importance for the study of the valency of 
 nitrogen. Their formation and general properties are most 
 in harmony with the assumption of a penta- or quinque-valent 
 
 PTT / 3 
 nitrogen atom, e.g. 3 />N-CH 3 , and not as a so-called mole- 
 
 cular compound, N(CH 3 ) 3 , CH 3 I. (Cf. Trimethyl-sulphonium 
 hydroxide.) The fact that the salts N(CH 8 )(C 2 H 6 ) + C^Cl 
 and N(CH 3 )(C 2 H 5 ) 2 + CH 3 C1 are identical, is in agreement with 
 the former assumption. (Meyer and Lecco.) Lastly, optically 
 active isomers are met with among the quaternary ammonium 
 salts, a point which receives its readiest explanation from the 
 asymmetry of the molecule containing a quinquevalent nitrogen 
 atom. (See Stereochemistry of Nitrogen Derivatives.) 
 
 9. The quaternary iodides are resolved into tertiary base 
 and alkyl iodide when heated. They combine with 2 or 4 
 atoms of bromine or iodine to tri- and penta-bromides or 
 -iodides, e.g. N(CH 3 ) 4 .U 4 (dark needles), and N(C 2 H 5 ) 4 M 2 
 
110 
 
 IV. DERIVATIVES OF MONOHYDRIC ALCOHOLS 
 
 (azure-blue needles). Such periodides readily lose the excess 
 of iodine, and are hence relatively unstable. Hepta- and Ennea- 
 iodides also exist. 
 
 The following table gives the boiling-points of the various 
 
 amines:- 
 
 
 Primary. 
 
 Secondary. 
 
 Tertiary. 
 
 Methyl . . 
 
 6 
 
 7 
 
 3'5 
 
 Ethyl 
 
 19 
 
 56 
 
 90 
 
 ft-Propyl 
 
 49 
 
 98 
 
 156 
 
 w-Butyl . . 
 
 76 
 
 160 
 
 215 
 
 7i-0ctyl 
 
 180 
 
 297 
 
 366 
 
 
 
 
 
 Methylamine, CH 3 NH 2 , occurs in Mercurialis perennis 
 and annua (" mercurialin "), in the distillate from bones and 
 wood, and in herring brine. It is produced in many decom- 
 positions of organic compounds, e.g. from alkaloids, as when 
 caffeine is boiled with barium hydroxide; also by heating 
 trimethylamine hydrochloride to 285. 
 
 It is most readily prepared from acetamide, caustic soda, and 
 bromine. (B. 18, 2737.) It is more strongly basic and even 
 more soluble in water than ammonia, has a powerful ammo- 
 niacal and at the same time fishlike odour, and burns with a 
 yellowish flame. Its aqueous solution, like that of ammonia, 
 precipitates many metallic salts, frequently redissolving the 
 precipitated hydroxides; unlike ammonia, it does not dissolve 
 Ni(OH)2 and Co(OH),. 
 
 The hydrochloride, CH 3 NH 2 , HC1, forms large glistening 
 plates, is very hygroscopic and readily soluble in alcohol; the 
 platinichloride crystallizes in golden scales, and the sulphate 
 forms an alum. 
 
 Dimethylamine, (CH 3 ) 2 NH, occurs in Peruvian guano and 
 pyroligneous acid, and is formed by decomposing nitroso-di- 
 methyl-aniline by caustic-soda solution. 
 
 Trimethylamine, (CH 3 ) 3 N, is widely distributed in nature, 
 being found in considerable quantity in Chenopodium vulvariu, 
 also in Arnica montana, in the blossom of Cratcegus oxyacantlw, 
 and of pear, and in herring brine. (Werthdm.) 
 
 It is a decomposition product of the betaine of beet-root, 
 and therefore along with ammonia, dimethylamine, &c., 
 methyl alcohol and aceto - nitrile by the distillation of 
 
II YDBOXYL AMINES AND HYI'BAZISES 111 
 
 vinasse. It has an ammoniacal and pungent fishlike odour. 
 
 The tertiary amines can be oxidized by means of hydrogen 
 peroxide to compounds of the type (CH 3 ) 3 N : 0, trimethyl- 
 amine oxide, whijh are colourless crystalline bases. 
 
 Tetramethylammonium iodide, N(CH S ) 4 I, is obtained in 
 large quantity directly from IS[H 3 + CH 3 I. It crystallizes in 
 white needles or large prisms, and has a bitter taste. 
 
 Tetramethylammonium hydroxide, N(CH 3 ) 4 OH, crystallizes 
 in hygroscopic needles, and can be obtained by the action of 
 alcoholic potash on an alcoholic solution of its chloride; potas- 
 sium chloride is precipitated, and the hydroxide remains in 
 solution. It forms salts, e.g. a platinichloride, sulphide, poly-' 
 sulphide, cyanide, &c. 
 
 Ethylamine, C 2 H 6 NH 2 . Crude ethyl chloride (obtained as 
 a by-product in the manufacture of choral) is used for its pre- 
 paration. It has a strongly ammoniacal smell and biting taste, 
 mixes with water in every proportion, and burns with a yellow 
 flame. It dissolves A1(OH) 3 , but not Fe(OH) 3 ; also Cu(OH) 2 
 with difficulty, but not Cd(OH) 2 . With bleaching powder it 
 yields ethyl-dichloro-amme, C 2 H 5 'NC1 2 , as a yellow oil of a 
 most unpleasant piercing odour. 
 
 Tri-ethylamine, (C 2 H 5 ) 3 N, is an oily strongly alkaline liquid. 
 The precipitates which it gives with solutions of metallic salts 
 are mostly insoluble in excess of the precipitant. 
 
 HYDROXYLAMINES ; HYDRAZINES 
 
 The Alkyl-hydroxylamines, which are derived from hy- 
 droxylamine, NH 2 OH, just as the amines are from ammonia, 
 belong to two different series, in accordance with the constitu- 
 tion of hydroxylamine, thus : 
 
 NH 2 .OCH 3 and CHg-NH-OH 
 
 a-Methyl-hydroxylamine /3-Methyl-hydroxylamine. 
 
 The compounds of the first series, which are obtained from 
 the oxime ethers (p. 138), are as ethereal compounds toler- 
 ably stable, and do not reduce Fehling's solution. Those of 
 the second series, which likewise result from certain pxime 
 derivatives, but at the same time also from the reduction of 
 the nitro-hydrocarbons (p. 96), very readily undergo change, 
 reduce Fehling's solution even in the cold, and yield primary 
 amines when further reduced (B. 23, 3597; 24, 3528; 25, 1714). 
 
 E. Fischer (A. 190, 67; 199, 281, 294) has given the name 
 of hydrazines to a series of peculiar bases, mostly liquid and 
 
112 IV. DERIVATIVES OF MONOHYDRIO ALCOHOLS 
 
 closely resembling the amines, but containing two atoms oi 
 nitrogen in the molecule, and differing from the latter espe- 
 cially by their capability of reducing Fehling's solution, for the 
 most part even in the cold, and by the ease with which they 
 are oxidized. They are derived from "Diamide" or "Hydra- 
 zine", NH 2 -NH 2 (Curtius and Jay, J. pr. Oh. 1889, (2), 39, 27) 
 They are formed by the action of nascent hydrogen on the 
 nitrosamines (p. 108): 
 
 (CH 3 ) 2 N.NO + 4H = (CH 3 ) 2 N.NH 2 + H 2 0. 
 
 Primary, secondary, tertiary, and quaternary hydrazines are 
 known, according as 1, 2, 3, or 4 of the hydrogen atoms in 
 NH 2 NH 2 are replaced by alkyl groups. 
 
 The secondary hydrazines exist in two isomeric forms, 
 namely, NHR NHR arid NH 2 NR 2 , which are known respec- 
 tively as symmetrical and unsymmetrical secondary hydrazines. 
 
 Methyl-hydrazine, CH 3 .NH.NH 2 (cf. A. 1889, 253, 5). An 
 excessively hygroscopic liquid, which fumes in the air, and has 
 an odour similar to that of methylamine. B.-pt. 87. 
 
 Ethyl-hydrazine, C 2 H 5 .NH-NH 2 . When di-ethyl urea is 
 treated with nitrous acl J a nitroso-compound is formed, which, 
 on reduction with zinc dust and acetic acid, yields the so-called 
 " diethyl-semicarbazide ", and this decomposes, when heated 
 with hydrochloric acid, into carbon dioxide, ethylamine, and 
 ethyl-hydrazine : 
 
 2 H 6 
 
 N(NO).C 2 H 5 \N(NH 2 ).C 2 H 5 
 
 Di-ethyl-urea Nitroso-compound Diethyl-semicarbazide. 
 
 Ethyl-hydrazine is a colourless mobile liquid of ethereal 
 and faintly ammoniacal odour, boiling at 100. It is very 
 hygroscopic, forms white clouds with moist air, dissolves in 
 water and alcohol with evolution of heat, and corrodes cork 
 and caoutchouc. 
 
 Diethyl-hydrazine, (C 2 H 5 ) 2 N NH 2 , is prepared from di- 
 ethylamine by transforming it into diethyl-nitrosamine by 
 the nitrous-acid reaction, and then reducing the latter. It 
 resembles ethyl-hydrazine closely: 
 
 (C 2 H 5 ) 2 N-NO + 4H = 
 
 Tetra-ethyl-tetrazone, (C 2 H 5 ) 2 :N'N:N.N:(C 2 H 5 ) 2 , 
 
PHOSPHINES 113 
 
 colourless, strongly basic oil, volatile with steam, is formed 
 when diethyl-hydrazine is heated with mercuric oxide. 
 
 The constitution of the hydrazines follows from their modes 
 of formation. Since in diethyl-nitrosamine, (C 2 H 5 ) 2 NNO, 
 for instance, the nitroso-group NO must be attached to the 
 nitrogen of the amine and not to the carbon, judging from 
 the ease with which it can be separated (p. 108), so the same 
 linking of the atoms must be assumed in the hydrazines, 
 which are formed from the nitroso-compounds by reduction, 
 i.e. by exchange of for 2H. The readiness with which di- 
 ethyl-hydrazirie is oxidized to diethylamine, e.g. by alkaline 
 cupric oxide, is an agreement with such a formula. The 
 hydrazines are relatively stable towards reducing agents. 
 
 For aliphatic Diazo and Triazo Compounds, see Chap. LI. 
 
 E. Alkyl Derivatives of Phosphorus, Arsenic, &c. 
 
 1. PHOSPHORUS 
 
 Just as amines are derived from ammonia, so from phos- 
 phuretted hydrogen, PH 3 , are derived primary, secondary, 
 and tertiary phosphines by the exchange of hydrogen for 
 alkyl radicals, and to these must likewise be added quaternary 
 compounds, the phosphonium bases. The phosphines corre- 
 spond closely with the amines in composition and in some of 
 their properties, e.g. they are not saponifiable. But they differ 
 from them in the following points : 
 
 1. Like phosphuretted hydrogen itself, the alkyl phosphines 
 are only feebly basic; thus ethyl phosphine does not affect 
 litmus, and its salts are decomposed by water. The salts of 
 the secondary and tertiary compounds are not decomposed, 
 thus showing that the presence of alkyl radicals tends to 
 strengthen the basic properties of the compound. 
 
 2. Like phosphuretted hydrogen they are readily inflam- 
 mable, and they are consequently rapidly oxidized in the air 
 and readily take fire of themselves. 
 
 3. As the phosphorus atom in these compounds shows a 
 tendency to pass' from the ter- to the quinque-valent state, 
 many of the phosphines behave as unsaturated compounds; 
 they combine with oxygen, sulphur, halogens, &c., for ex- 
 ample, (CH 3 ) 3 PO, (CH 3 ) 3 PS, (CH 3 ) 3 PC1 2 , and a compound 
 (CH 3 ) 3 P, CS 2 , in the form of red plates. The products ob- 
 tained on oxidation are characteristic, and may be regarded 
 
 (B480) B 
 
114 IV. DERIVATIVES OF MONOHYDRIC ALCOHOLS 
 
 03 derived from phosphoric acid, 0:P(OH) 3 , by the replace- 
 ment of one or more OH groups by one or more alkyl radicals : 
 
 CHg-PHg, with nitric acid,, yields CH 3 -PO.(OH) 2 , methyl phos- 
 
 phonic acid. 
 (CH 3 ) 2 PH, with nitric acid, yields (CH 3 ) 2 PO OH, dimethyl phos- 
 
 phinic acid. 
 (CH 3 ) 3 P, on oxidation in the air, yields (CH 3 ) 3 PO, trimethyl phos- 
 
 phine oxide. 
 
 4. Corresponding with the disagreeable smell of phos- 
 phuretted hydrogen, they possess an excessively strong 
 stupefying odour; thus ethyl phosphine has a perfectly over- 
 powering smell, and excites on the tongue and deep down in 
 the throat an intensely bitter taste. 
 
 Formation. 1. The tertiary phosphines and quaternary 
 compounds are formed directly from phosphine and an alkyl 
 iodide. (Of. Amines, formation 2.) 
 
 PH 3 + 3C 2 H 6 I = P(C 2 H 6 ) 3 + 
 
 2. According to Hofmann (1871), primary and secondary 
 phosphines are formed by heating phosphonium iodide and an 
 alkyl iodide with zinc oxide, e.g. : 
 
 2C 2 H 6 I + 2PH 4 I -f ZnO = 2P(C 2 H 6 )H 2 , HI + ZnI 2 + H 2 0. 
 
 They can be separated from one another by decomposing 
 the salts of the primary phosphines by water, as already 
 mentioned. 
 
 3. The tertiary phosphines are produced from calcium 
 phosphide and an alkyl iodide, a reaction first observed by 
 Thenard in 1846; 
 
 4. Also from phosphorus trichloride and zinc methyl, or 
 magnesium alkyl iodides (Auger and Billy, C. 1904, 139, 597). 
 
 5. The phosphonium salts are formed by the combination 
 of tertiary phosphines with an alkyl haloid, and closely 
 resemble the corresponding ammonium compounds. 
 
 Tri-ethyl phosphine, P(C 2 H 5 ) 8 , has no alkaline reaction. 
 When concentrated it possesses a stupefying, and when dilute 
 a pleasant hyacinth-like odour. 
 
 Tetramethyl- phosphonium hydroxide, P(CH 8 ) 4 OH. Un- 
 like the analogous ammonium hydroxide, this compound de- 
 composes into trimethyl-phosphine oxide and methane when 
 heated: P(CH 3 ) 4 OH = P(CH 3 ) 3 O + CH 4 . 
 
 The tetra-ethyl compound decomposes in a similar manner. 
 
/,;_ ARSINES 115 
 
 2. ARSENIC 
 
 The similarity of arsenic to phosphorus and nitrogen is 
 further exemplified by the analogous compounds which it 
 forms with alkyl radicals. In virtue, however, of the more 
 metallic character of arsenic, it does not show the same ten- 
 dency to combine with alkyl radicals and hydrogen at the 
 same time, but forms derivatives containing alkyl groups and 
 electro -negative elements like chlorine or oxygen. Arsenic 
 analogues of methylamine have been recently prepared, and 
 are very unstable. Trimethyl-arsine, analogous to trimethyl- 
 amine and trimethylphosphine, is well known. As primary 
 and secondary compounds we have methyl-arsine dichloride, 
 CH 3 AsCl 2 , dimethyl-arsine chloride, (CH 3 ) 2 AsCl, and analo- 
 gous substances. They are colourless liquids of stupefying 
 odour, exerting in some cases an unbearable irritating action 
 upon the mucous membrane. They do not possess basic pro- 
 perties. In addition to these there exist also quaternary com- 
 pounds, arsonium salts, which are exactly analogous to the 
 quaternary phosphonium salts. 
 
 The halogen of the chlorine compounds is easily replaceable 
 by its equivalent of oxygen. Thus, corresponding with the 
 compound BAsCl 2 there is an oxide EAsO and a sulphide 
 R.AsS, and with the chloride E 2 AsCl an oxide (R 2 As) 2 0. 
 These oxides, liquid or solid, are compounds of stupefying 
 odour, and behave like basic oxides; hydrochloric acid recon- 
 verts them into the corresponding chlorides. 
 
 Here, also, the tendency of arsenic to change from the 
 tervalent to the quinquevalent state is especially marked. 
 The above chlorides and trimethyl-arsine itself all combine 
 with two atoms of chlorine to compounds of the type AsX . 
 The above oxygen compounds of the type AsX 3 and also tri- 
 methyl-arsine are consequently oxidizable to compounds con- 
 taining one atom or two OH groups more, acids or oxides 
 which are also formed from the chlorides of the type AsX 5 
 by exchange of halogen for or OH, e.g. cacodyl oxide, 
 
 (Me 2 As) 2 0, to cacodylic acid, Me 2 As<^ . These products 
 
 are therefore completely analogous to the phosphonic and 
 phosphinic acids and phosphine oxides already described. 
 
 The compounds As(CH 3 ) x Cl c _ x , of the type AsX 5 , when 
 heated, decompose into methyl chloride and compounds 
 As(CH 3 ) x . 1 Cl 4 _ x , of the type AsXg, this elimination of methyl 
 
116 IV. DERIVATIVES OF MONOHYDRIC ALCOHOLS 
 
 chloride taking place the more readily the fewer methyl 
 groups are present in the molecule; thus As(CH 3 ) 3 Cl 2 breaks 
 up when somewhat strongly heated, As(CH 3 ) 2 Cl 3 at 50, and 
 As(CH 3 )Cl 4 at 0, i.e. the last-named is only stable when in 
 a freezing -mixture. When, therefore, chlorine acts upon 
 As(CH 3 )Cl 2 at the ordinary temperature, the reaction appears 
 to be one of direct exchange of alkyl for chlorine, thus : 
 
 As(CH 3 )Cl 2 -f C1 2 = AsCl 3 + CHjCl. 
 
 It is interesting to note that, like free " methyl " (CH 3 ), 
 the radical As(CH 3 ) 2 has no separate existence; cacodyl pos- 
 sesses the doubled formula As 2 (CH 3 ) 4 (" Di-arsene-disnethyl rj ). 
 
 The tertiary arsines are formed : 
 
 1. From sodium arsenide and alkyl iodide (Cahours ard 
 Riche): 
 
 AsNa 3 -f SCgHfil = As(C 2 H 6 ) 3 + 3NaL 
 
 2. From arsenious chloride and (a) zinc alkyl (ffofmann),, 
 or (b) magnesium alkyl haloid (Pfeiffer, B. 1904, 37, 4620; 
 Sauvage, C. 1904, 139, 674). 
 
 Trimethyl-arsine, As(CH 3 ) 3 , and triethyl-arsine, As(C 2 H 5 ) 3 , 
 are liquids sparingly soluble in water. They fume in the air, 
 and are thereby oxidized to tri-methyl- or -ethyl-arsine oxide. 
 
 The secondary arsines are obtained from cacodyl and 
 cacodyl oxide, which are formed when a mixture of potassic 
 acetate and arsenious oxide is distilled (Cadet, 1760): 
 
 The distillate of cacodyl and cacodyl oxide so obtained, 
 and termed " alkarsin ", fumes in the air and is spontaneously 
 inflammable (Cadet's "fuming arsenical liquid"). Hydro- 
 chloric acid acts upon it to form cacodyl chloride (Bunsen, 
 1838), and caustic-potash solution gives pure cacodyl oxide, 
 As 2 (CH 3 ) 4 0, a liquid of stupefying odour which produces 
 nausea and unbearable irritation of the nasal mucous mem- 
 brane; it boils without decomposition, and is insoluble in 
 water and of neutral reaction. It yields salts with acids, 
 e.g. cacodyl chloride with hydrochloric acid: 
 
 0(AsMe 2 ) 2 + 2HC1 = 2 AsMe 2 Cl + H 2 O. 
 
 The chloride is a liquid of even more stupefying odour and 
 violent action than the oxide, and its vapour is spontaneously 
 
STIBINES 
 
 117 
 
 inflammable. When heated with zinc clippings in an atmos- 
 phere of carbon dioxide, it yields the free cacodyl, As 2 (CH 8 ) 4 
 (from /caKw&ys, "stinking"), a colourless liquid insoluble in 
 water and boiling undecomposed at 170, and of a horrible 
 nauseous odour which produces vomiting. It is as readily 
 inflammable in the air as the vapour of phosphorus, yielding 
 the oxide when slowly brought in contact with it, and also 
 combining directly with sulphur, chlorine, &c. Cacodyl 
 plays, therefore, even down to the most minute particulars, 
 the part of a simple electro-positive element; it is a true 
 "organic element" (Bunseri). 
 
 PTT O 
 
 Cacodylic acid, 3 x As \' is crvstalline > sduble in 
 
 water, odourless, and poisonous. It forms crystallizable salts. 
 
 SUMMARY 
 
 
 
 Compounds 
 with Chlorine. 
 
 Oxides. 
 
 Acids. 
 
 Primary .. 
 
 Methyl- 
 arsine 
 dichloride, 
 
 Methyl- 
 arsine tetra- 
 chloride, 
 
 Methyl- 
 arsine 
 oxide, 
 
 Methyl- 
 arsonic acid, 
 0:AsMe(OH) 2 . 
 
 
 AsMeCl 2 . 
 
 AsMeCl 4 . 
 
 AsMeO. 
 
 Solid plates. 
 
 
 B.-p. 133. 
 
 
 B.-p. 95. 
 
 
 Secondary 
 
 Cacodyl 
 chloride, 
 
 Cacodyl 
 trichloride, 
 
 Cacodyl 
 oxide, 
 
 Cacodylic 
 acid, 
 
 
 AsMe 2 Cl. 
 
 AsMe 2 Cl 3 . 
 
 (AsMe 2 ) 2 0. 
 
 O:AsMe 2 -OH. 
 
 
 B.-p. 100. 
 
 
 B.-p. 150. 
 
 Prisms. 
 
 
 
 
 
 M.-p. 200. 
 
 Tertiary... 
 
 Trimethyl- 
 
 Trimethyl- 
 
 Trimethyl- 
 
 
 
 arsine, 
 
 arsine 
 
 arsine 
 
 
 
 AsMe 3 . 
 
 dichloride, 
 
 oxide, 
 
 
 
 B.-p. 70. 
 
 AsMe 3 Cl 2 . 
 
 AsMe 3 O. 
 
 
 
 
 
 Solid. 
 
 
 3. ANTIMONY, BORON, AND SILICON COMPOUNDS 
 
 Antimony also forms compounds with the alkyls precisely 
 similar to those of arsenic; primary and secondary compounds 
 do not exist. Trimethyl-stibine, Sb(CH 3 ) 3 (Landolt), is a 
 highly disagreeable and spontaneously inflammable liquid of 
 onion-like smell; and Antimony pentamethyl, Sb(CH 8 ) 5 , an 
 oily liquid of weak odour, which can be distilled, and is not 
 
118 IV. DERIVATIVES OF MftOHYDRtC ALCOHOLS 
 
 spontaneously inflammable. Tetramethyl - stibonium - hy- 
 droxide, Sb(CHo) 4 OH, is very like caustic potash. 
 
 Bismuth yields tri-alkyl derivatives, e.g. Bi(CH 3 ) 3 , which 
 are relatively unstable. No bismuthonium compounds are 
 known. 
 
 Boron tri-ethyl, B(C 2 H 5 ) 3 (Frankland), is a spontaneously 
 inflammable liquid which burns with a green flame with 
 deposition of much soot; and boron trimethyl, B(CH 3 ) 3 , an 
 analogous gas of an unbearable stinking smell. 
 
 The silicon compounds (Friedel and Crafts), in contradis- 
 tinction to the foregoing, resemble methane and the paraffins 
 rather than the spontaneously inflammable silicon hydride, 
 and are very stable in the air. 
 
 Tetramethyl silicane, Si(CH 3 ) 4 , is a mobile liquid similar to 
 pentane, and floats on water. Tetraethyl silicane or Silico- 
 nonane, SiEt 4 , is also known, and gives rise to numerous 
 derivatives corresponding with those of tetraethyl methane, 
 e.g. SiC 8 H 19 Cl, SiC 8 H 19 .O.CO-CH 3 , SiC 8 H 19 -OH, Silicononyl 
 alcohol, &c. Compare B. 1911, 44, 2640. 
 
 F. Organo-Metallie Compounds 
 
 Most of the important metals form definite compounds with 
 alkyl groups. The composition of these organo-metallic or 
 metallo-organic compounds almost always corresponds with 
 that of the metallic chlorides from which they are derived 
 by the replacement of halogen by alkyl. They are colourless, 
 mobile liquids which boil without decomposition at relatively 
 low temperatures; they often decompose violently with water 
 and burn explosively in the air, but in other cases they are 
 stable, both in water and air. To the former category belong 
 the magnesium, zinc, and aluminium alkyls, and to the latter 
 the mercury, lead, and tin compounds. As most of the com- 
 pour^s are volatile, their molecular weights can be deter- 
 mined, and hence the valencies of the respective metals deter- 
 mined, as, the alkyl radicals are monovalent. Examples are : 
 ZnMe 2 , CdMe 2 , HgEt 2 , AlMe 3 , PbMe 4 , SnEt 4 , &c. 
 
 Compounds are also known which contain halogen as well 
 as alkyl radicals combined with a metal. They behave like 
 salts. The halogen in them can be replaced by hydroxyl, 
 whereby basic compounds result, compounds which are often 
 much more strongly basic than the corresponding metallic 
 hydroxides, in accordance with the electro-positive character 
 
O&GANO-METALLIC COMPOUNDS 119 
 
 of the alcohol radical. Such hydroxides or oxides cannot be 
 volatilized without decomposition. Compounds of this type, 
 e.g. CH 3 Mg-I, are very readily prepared from their com- 
 ments (Mg + CH 3 I) in dry ethereal solution, and are 
 ily made use of as synthetical reagents. 
 tie organo-metallic compound may be prepared 
 1. By treating the alkyl haloid with the metal in question- 
 In this way zinc-, magnesium-, and mercury-alky Is are got: 
 
 = Mg(CH 3 ) 2 + MgI 2 . 
 
 The mixed organo-metallic compounds (p. 121), e.g. CH 3 'Mg-I 
 or C 2 H 5 'Zn'I, are probably formed as intermediate products. 
 2. Numerous metallic compounds have been prepared by 
 double decomposition between zinc-alkyl and the metallic 
 chloride, or more recently by the action of the mixed mag- 
 nesium compounds on the metallic chloride. Pfeiffer (B. 1904, 
 37, 319, 1125, 4617) has prepared numerous tin, lead, and 
 mercury compounds by this method: 
 
 2Zn(C 2 H 5 ) 2 +SnCl 4 = Sn(C 2 H 5 ) 4 + 2ZnCl 2 . 
 2C 2 H 6 .Mg.I + HgCl 2 = Hg( 
 
 Potassium- and Sodium methide, K(CH 3 ) and Na(CH 3 ), and 
 Potassium- and Sodium ethide, K(C 2 H 5 ) and Na(C 2 H 5 ), are 
 not known in the free state. When metallic sodium is added 
 to zinc ethyl (or ethide), zinc separates out and a crystalline 
 compound of sodium ethide and zinc ethide is formed, from 
 which, however, the former cannot be prepared pure, since 
 decomposition sets in upon warming. On distilling in a stream 
 of carbon dioxide, the potassium methide combines with the 
 latter to form potassic .acetate; the ethyl compound behaves 
 in a similar way. 
 
 Zinc methyl or methide, Zn(CH 3 ) 2 (FranHand, 1849), is 
 prepared according to method 1: 
 (I) CH 3 I + Zn = Zn(CH 3 I); (H) 2Zn(CH 3 )I = Zn(CH 3 ) 2 + ZnI 2 . 
 
 The first stage is completed upon warming, and the second 
 upon distilling the resulting product. The zinc is conveniently 
 used in the form of the "copper-zinc couple", and the reaction 
 is facilitated by the addition of ethyl acetate, the reason for 
 this not being known. Zinc methyl is a colourless, mobile, 
 strongly refracting liquid of very piercing and repulsive smell. 
 
120 IV. DERIVATIVES OF MONOHYDRIC ALCOHOLS 
 
 B.-pt. 46; sp. gr. 1-39. It is spontaneously combustible, and 
 burns with a brilliant reddish-blue flame (the zinc flame), with 
 formation of zinc oxide, but may be distilled in an atmosphere 
 of carbon dioxide. When the supply of oxygen is limited, 
 zinc methoxide, Zn(OCH 3 ) 2 , is formed. It reacts violently 
 with water, yielding methane and Zn(OH) 2 , and with methyl 
 iodide gives ethane. It is employed in the preparation of 
 secondary and tertiary alcohols and of ketones. Iodine con- 
 verts it into zinc-methyl iodide, ZnCH 3 I, white plates (see 
 above), and methyl iodide; an excess of iodine yields zinc 
 iodide and methyl iodide. 
 
 Zinc ethyl, Zn(C 2 H 5 ) 2 , b.-pt. 118, sp. gr. 1-18, closely 
 resembles zinc methide. 
 
 The mercury compounds, HgMe 2 and HgEt 2 , are produced 
 by method of formation 1, also by method 2. They are 
 colourless liquids of peculiar sweetish and unpleasant odour, 
 and boil respectively at 95 and 159. They are permanent 
 in the air, but inflammable, and both especially the methyl 
 compound are very poisonous. 
 
 Aluminium methyl, A1(CH 8 ) 3 , is spontaneously inflammable 
 and decomposes violently with water. B.-pt. 130. For vap. 
 dens, see B. 22, 551. 
 
 Lead tetramethyl, Pb(CH 3 ) 4 , and ethyl, Pb(C 2 H 5 ) 4 (Cahours). 
 These are formed according to method 2, curiously with 
 separation of lead: 
 
 2PbCl 2 + 2Zn(CH 3 ) 2 = Pb(CH 3 ) 4 -f Pb + 2ZnCa,j. 
 
 They are stable in the air, and are interesting from the lead 
 in them being tetravalent. The hydroxide, Pb(CH 3 ) 3 .OH, 
 forms pointed prisms, smells like mustard, and is a strong 
 alkali; thus, it saponifies fats, drives out ammonia from its 
 salts, precipitates metallic salts, &c. The compound Pb 2 (C 2 H 5 ) 6 
 is also known. 
 
 The tin compounds are similar (Ladenburg, Frankland). 
 
 Tin tetramethyl, Sn(CH 3 ) 4 , Tin tetraethyl, Sn(C 2 H 5 ) 4 , Tin 
 triethyl, Sn 2 (C 2 H 5 ) 6 , Tin dimethyl, Sn 2 (CH 3 ) 4 , &c., are of in- 
 terest as indicating the tetravalence of tin. 
 
 For a number of years the zinc alkyl compounds were 
 largely used for the synthesis of various groups of compounds, 
 viz. hydrocarbons, tertiary alcohols, and ketones (see these). 
 To a large extent these compounds are now replaced by Gri- 
 gnard's reagents (C. 1900, 130, 1322; 1901, 132, 336, 558). 
 
V. ALDEHYDES AND KETONES 12l 
 
 Any alkyl haloid, when added to dry magnesium powder sus- 
 pended in pure anhydrous ether, yields a compound of the 
 type CHg'Mg'I. This reaction occurs in ethyl ether, amyl 
 ether, and in dimethylaniline, but not readily in solvents like 
 benzene unless ether or dimethylaniline is also present. It 
 would appear that the ether forms a definite compound, with 
 the magnesium alkyl compound, of the type CH 8 Mg-I, 
 
 (C 2 H 5 ) 2 0. Probably c 2 2 '>< 3 ( E ^ er and 
 B. 1902, 35, 1201). These Grignard compounds in ethereal 
 solution are extremely reactive. They have been largely made 
 use of for the preparation of hydrocarbons; primary, secondary, 
 and tertiary alcohols; aldehydes, acids, thio-acids, &c. (see 
 these); also for the detection and estimation of hydroxyl 
 groups (B. 1902, 35, 3912, and Hibbert and Sudborough, J. C. S. 
 1904, 85, 933) by measuring the volume of methane evolved 
 when a given weight of the hydroxyl compound is mixed 
 with an excess of the Grignard reagent dissolved in amyl ether. 
 They may also be used for differentiating between primary, 
 secondary, and tertiary amines (Sudb&rough and Hibbert, Proc. 
 1904, 20, 165). 
 
 V. ALDEHYDES AND KETONES, CJ3J) 
 
 The aldehydes and ketones are substances which are re- 
 spectively formed by the oxidation of the primary and 
 secondary alcohols, the oxidation consisting in the elimination 
 of two atoms of hydrogen from each molecule of alcohol. 
 
 The aldehydes are formed from the primary alcohols, and 
 are easily converted by further oxidation into the correspond- 
 ing acids containing an equal number of carbon atoms, oxygen 
 being taken up. They possess in consequence strongly reduc- 
 ing properties. 
 
 The ketones result from the oxidation of the secondary 
 alcohols, and are more difficult to oxidize further; they do 
 not possess reducing properties. Their oxidation does not 
 lead to acids containing an equal number of carbon atoms in 
 the molecule, but to others containing a smaller number, the 
 carbon chain being broken. 
 
 The lower members of both classes are neutral liquids of 
 peculiar smell, readily soluble i water and readily volatile, 
 only CH 2 being gaseous. As the number of carbon atoms 
 
122 V. ALDEHYDES AND KETONES 
 
 increases they become less soluble, and their odour becomes 
 less marked with rise of boiling-point until the highest mem- 
 bers are solid, odourless like paraffin, and only capable of being 
 distilled under reduced pressure. 
 
 The aldehydes closely resemble the ketones as regards modes 
 of formation and also in many of their properties. 
 
 Both groups of compounds contain the carbonyl :C:0 
 group, but in the aldehydes this is always attached to a hy- 
 drogen atom, and also to an alkyl group or a second hydrogen, 
 e.g. CHg.CO-H and H-CO-H, whereas in a ketone it is at- 
 tached to two alkyl groups, e.g. C 2 H 5 CO C 2 H 5 . 
 
 A. Aldehydes 
 
 The homologous series of the aldehydes, C n H 2n O, corre- 
 sponds exactly with that of the acids, G^H-^f)^ They form 
 a group of compounds exactly intermediate between the 
 primary alcohols and the fatty acids. Each primary alcohol 
 by the loss of hydrogen yields an aldehyde, and this by the 
 addition of oxygen yields a fatty acid : 
 
 H.CH,.OH 
 
 -2H +0 
 
 / 
 
 CH 3 .CH 2 -OH CH 3 .C CH 3 .C t , &c. 
 
 Their boiling-points are decidedly lower than those of the 
 corresponding alcohols, and rise, in the normal aldehydes, 
 at first by about 27 for each CH 2 , and later on by a less 
 amount. 
 
 Nomenclature. The name aldehyde is derived from alcohol), 
 <&%d(rogenatus), i.e. an alcohol from which hydrogen has 
 been removed. The various aldehydes are named accord- 
 ing to the acids to which they give rise on oxidation. For 
 example, H-CHO formaldehyde, CH 3 CHO, acetaldehyde, &c. 
 According to the Geneva Congress, the aldehydes receive 
 names ending in al, e.g. ethanal for acetaldehyde. 
 
 Modes of Formation. 1. By the regulated oxidation of the 
 primary alcohols, CnH^OH, by potassium dichromate or 
 manganese dioxide and dilute sulphuric acid; often slowly by 
 atmospheric oxygen, especially in the presence of bone-black 
 or platinum: 
 
ISOMERISM OF ALDEHYDES 123 
 
 2. From the acids of the acetic series, by distilling a mixture 
 of their calcium or barium salts with calcium or barium formate 
 (Limpricht). The foimic acid acts in this instance as a reduc- 
 ing agent, producing calcium carbonate, thus: 
 
 CHg-COOca -f- HCOOca = CH 3 .CHO + CaCOg. (ca = } Ca.) 
 
 3. From the dihalogen substitution products of the hydrotf 
 carbons containing the group tCHX 2 , by superheating with 
 water or by boiling with water and PbO: 
 
 CH 3 .CHC1 2 + H 2 O = CH 3 .CHO + 2HCL 
 
 4. From Grignard reagents (p. 120), and ethyl formate or 
 ethyl orthoformate. Also by heating alcohols with metals or 
 metallic oxides (Chap. XLIX). 
 
 Constitution. In the oxidation of the primary alcohols, 
 R.CH 2 OH, to their corresponding acids, R-CO-OH, the 
 alkyl radical R remains unaltered. It must consequently also 
 remain unchanged in the intermediate products of the oxida- 
 tion, viz. the aldehydes, which therefore possess the constitu- 
 tion R-CHO: 
 
 CH 3 .CH 2 -OH CH 3 .CHO CHg-CO-OH 
 
 Alcohol Aldehyde Acetic acid. 
 
 The aldehydes thus contain the group CHO, either -C-OH 
 or C^TT. The former is not correct, since the aldehydes do 
 
 not give the reactions characteristic of compounds containing 
 hydroxyl radicals. All their properties point to the presence 
 of the :C:0 group. The characteristic grouping of all alde- 
 hydes is thus the *C^Q group. This is confirmed by the fact 
 that an acid chloride R-C<Qj on reduction yields a primary 
 
 alcohol and undoubtedly an aldehyde as an intermediate 
 product: 
 
 
 homers. Isomerism in the aldehydes is caused solely by 
 isomerism in the alkyl radicals R, which are combined with 
 the group -CHO, and 'therefore contain an atom of carbon less. 
 Otherwise the aldehydes from C 3 H f) on are isomeric with 
 the ketones, with the oxides of the defines (e.g. aldehyde with 
 
124 V. ALDEHYDES AND KETONES 
 
 ethylene oxide, C 2 H 4 0), and with the alcohols of the allylic 
 series. 
 
 Behaviour. The aldehydes are distinguished by being 
 exceptionally chemically active. 
 
 1. The aldehydes are very readily oxidizable, slowly even 
 by the air alone, and quickly by chromic acid, salts of the 
 noble metals, &c. They consequently reduce an ammoniacal 
 solution of silver and often one of copper; this reaction is 
 characteristic and is especially delicate in the presence of 
 caustic-soda solution. (Formation of silver mirror.) 
 
 2. The aldehydes are easily reduced by nascent hydrogen, 
 e.g. sodium amalgam and dilute acid or zinc dust and glacial 
 acetic acid, to the primary alcohols from which they are 
 derived by oxidation, e.g.: 
 
 CH 3 .CHO + 2H = CH 3 .CH 2 .OH. 
 
 A glycol is formed as a by-product, e.g. butylene glycol, 
 C 4 H 8 (OH) 2 , from C 2 H 4 O. 
 
 3. Phosphorus pentachloride and trichloride convert the 
 aldehydes into ethylidene chloride and analogous dichloro- 
 substitution products of the hydrocarbons: 
 
 CH 3 -CHO - CH 3 .CHC1 2 . 
 
 4. Additive reactions. According to Perkin (J. C. S. 1887, 
 808), a solution of acetaldehyde in water contains a certain 
 amount of the hydrate, CH 3 -CH(OH) 2 . (Cf. Chloral hydrate.) 
 This compound is extremely unstable, and has never been iso- 
 lated in a pure form. In those reactions in which it might be 
 formed, its anhydride (acetaldehyde) is invariably produced, 
 e.g. CH 3 -CHC1 9 with alkali yields CH 3 .CH:0 as final product, 
 and not CH.uH(OH)j, although this is probably formed as 
 an intermediate substance. 
 
 Thus we conclude that two hydroxyl groups attached to the 
 same carbon atom cannot as a rule exist together, but a molecule 
 of water is eliminated, and an aldehyde or ketone is formed. 
 In particular cases only can compounds with two such hy- 
 droxyl groups exist (see Chloral). 
 
 If, in place of water, NaHS0 3 , NH 3 , HCN, &c., be employed, 
 direct addition to the aldehydes is readily observed, and in 
 all these reactions it is concluded that the addition occurs at 
 the expense of the doubly-united oxygen atom. A hydrogen 
 atom of the substance in question attaches itself to the oxygen 
 of the aldehyde, with formation of a hydroxyl group, while 
 
ADDITIVE COMPOUNDS OF ALDEHYDES 125 
 
 the residual X (e.g. NH 2 ), which was originally bound to the 
 afore-mentioned H atom, becomes united to the carbon: 
 
 CH 3 -CH: 
 
 Cf. additive reactions of the defines (p. 44). 
 The most important additive reactions are: 
 
 (a) Combination with water, which would lead to a dihydric 
 alcohol, does not as a rule take place, for the reasons already 
 given. Should the alkyl radical of the aldehyde, however, 
 contain several negative atoms, e.g. Cl, then the hydrates are 
 capable of existence, for instance chloral hydrate: 
 
 CC1 3 .CHO + H 2 O = CC1 3 .CH(OH)2. 
 
 But even in these cases the tendency for water to separate 
 is too great to allow of such hydrates behaving as dihydric 
 alcohols; they react rather, for the most part, exactly like the 
 aldehydes themselves. (Cf. Pyroracemic and Mesoxalic acids.) 
 
 (b) Occasionally, compounds with alcohol or acetic acid, e.g. 
 R.CH(OEt)(OH), or R.QH(OH)(OAc), are met with. They 
 are, however, extremely unstable. When the aldehyde is 
 heated with alcohol or acetic anhydride, stable ethers or esters 
 of the hypothetical glycols are obtained : 
 
 CH 3 .CHO + 2C 2 H 5 .OH = CH 3 .CH(OC 2 H 6 ) 2 + H 2 O. 
 CH 3 .CHO + (C 2 H 3 0) 2 = CH 3 .CH(OC 2 H 3 2 ) 2 . 
 
 The compounds obtained from alcohols, the so - called 
 "acetals" (see p. 129), are also formed by the partial oxidation 
 of primary alcohols, and are hydrolysed by sulphuric acid. 
 
 (c) The aldehydes combine wit^i sodium hydrogen sulphite, 
 NaHS0 3 , &c., to crystalline compounds, readily soluble in water 
 but sparingly in alcohol, e.g. C 2 H 4 0, NaHS0 3 , JH 2 0. These 
 are to be regarded as sulphite derivatives of the ethylidene 
 glycols, for instan^, CH 8 .CH(OH)(.O.S0 2 Na). They are 
 almost invariably decomposed when heated with alkalis or 
 acids and regenerate the aldehydes. They are, therefore, 
 of great importance for the separation of aldehydes from 
 mixtures. 
 
 (d) The aldehydes combine with ammonia to aldehyde- 
 ammonias, e.g. aldehyde-ammonia, (CH 3 .CHO,NH 3 ) 3 . These 
 are crystalline compounds, for the most part readily soluble m 
 water, sparingly in alcohol, and insoluble in ether. Like the 
 bisulphite compounds, they are advantageously used for the 
 
126 V. ALDEHYDES AND KETONES 
 
 purification of aldehydes, as they readily yield the aldehydes 
 when warmed with dilute acid. (See p. 128.) 
 
 (e) The aldehydes combine with hydrocyanic acid to form 
 nitriles of higher acids; thus, acetic aldehyde yields the com- 
 
 OTT 
 
 pound CH 3 CH<^Q^, ethylidene cyanhydrin. This reaction 
 
 is largely made use of in the preparation of certain hydroxy 
 acids, as the cyanhydrins, when hydrolysed, yield hydroxy 
 
 QTT 
 
 acids, e.g. CH 8 CH<^QQQTT, lactic acid. 
 
 (f) An interesting additive reaction is that between an 
 aldehyde and a Grignard compound (p. 121). Thus acetal- 
 
 dehyde and magnesium ethyl iodide yield Q j| ^>CH OMgl, 
 
 2 OFT 
 
 and this with water gives methy 1-ethyl-carbinol, Q T| ^>CH OH^, 
 
 (Cf. Secondary Alcohols.) 
 
 5. The aldehydes show great tendency to polymerize. (See 
 pp. 12 and 45.) In the case of formaldehyde this poly- 
 merization occurs spontaneously at the ordinary temperature. 
 Acetaldehyde is polymerized upon the addition of small quan- 
 tities of hydrochloric, sulphuric, or sulphurous acid, zinc 
 chloride, carbonyl chloride, &c., to para-aldehyde, C 6 H 12 3 , 
 = (C 2 H 4 0) 3 , at the ordinary temperature, and to meta-alde- 
 hyde, (C 2 H 4 0) 3 , at 0. Why the above-mentioned substances 
 should induce this polymerization is not known. 
 
 Another type of polymerization is the aldol condensation 
 (see pp. 127 and 131). 
 
 6. Towards alkalis the aldehydes behave differently. Alde- 
 hyde and several of its hornologues, when heated with caustic- 
 soda solution, are transformed into a reddish - brown resin 
 termed aldehyde-resin, a product insoluble in water but soluble 
 in alcohol, and possessing a peculiar odour. Other aldehydes 
 are transformed by alkalis into a mixture of equivalent amounts 
 of alcohol and acid, thus : 
 
 2ECOH -f H 2 = 
 
 7. The aldehydes show a great tendency to form condensation 
 products with aldehydes, ketones, acids, &c. (See Crotonic 
 Aldehyde, Cinnamic Acid, &c.) 
 
 (a) CHo.CHO + CHo.CHO = CEL-CHiCH-CHO + H 2 O. 
 (6) CH 3 .CO.CH 3 -f E-CHO = CH 3 .CO.CH:CHE + H 2 O. 
 
TESTS FOR ALDEHYDES 127 
 
 It is probable that in all these condensations direct addition 
 first occurs ; for example, in (a) aldol, CH 3 CH(OH) . CH 2 CHO, 
 is first formed, and then by the loss of- water forms croton 
 aldehyde, CH 3 - CH : CH ; CHO. (See p. 131.) 
 
 8. With hydroxylamine the aldehydes yield the so-called 
 Aldoximes, water being eliminated (V. Meyer , B. 15, 2778). 
 
 HaiN-OH = CH 3 .CH:N.OH -fH 2 O. 
 
 For the conditions under which oximes are formed, see B. 23, 
 2769. 
 
 9. The aldehydes react with hydrazines to form the so- 
 called Hydrazones, water being eliminated. Phenylhydrazine 
 is the reagent usually employed: 
 
 Hg.CHiO + Ha-N.NHCA = CH 3 .CH:N.NH.C 6 H 6 + H 2 O 
 
 Aldehyde-phenyl-hydrazone. 
 
 Most of the phenylhydrazones are somewhat sparingly 
 soluble in alcohol, crystallize very readily, and are made use 
 of in identifying different aldehydes. On reduction they 
 yield primary amines: 
 
 CH 3 .CH:N.NH.C 6 H 5 -f 4H = CH 3 .CH 2 .NH 2 + NH 2 .C 6 H 6 . 
 
 10. Moist chlorine and bromine act upon the aldehydes as 
 substituents; thus, from acetaldehyde chloral is obtained: 
 
 CH 3 .CHO + 3C1 2 = CClg-.CHO + 3HGL 
 
 11. Sulphuretted hydrogen converts the aldehydes into thio- 
 aldehydes. These are compounds of unpleasant aromatic 
 odour, which show the same peculiarities of polymerization as 
 the aldehydes (Klinger). (Cf. E. Baumann, B. 23, 60; 24, 
 1419, 3591.) 
 
 Eeactions 8 and 9 may also be regarded as condensations. 
 It is possible that in all these reactions direct addition first 
 occurs, and that water is subsequently eliminated. 
 
 Tests for aldehydes: 
 
 (1) Behaviour with ammoniacal silver-nitrate solution (p. 124, 
 and also B. 15, 1629). 
 
 (2) Behaviour with alkaline bisulphites (p. 125). 
 
 (3) Behaviour with phenyl - hydrazine and hydroxylamine 
 (see above). 
 
 (4) Aldehydes colour a solution of f uchsine which has been 
 
128 V. ALDEHYDES AND KBTONES 
 
 decolorized by sulphurous acid (Schi/'s reagent) an intense 
 violet-red; some ketones and chloral, but not chloral hydrate, 
 produce the same effect. (B. 13, 2343; Bull. Soc. Chim. 
 1894, 11, 692.) 
 
 Formaldehyde, Methanal, HCH:0, may be regarded as the 
 oxide of the divalent methylene radical, CH 2 :. It is obtained 
 dissolved in water and excess of methyl alcohol by leading the 
 vapour of the latter, mixed with air, over a glowing platinum 
 or copper spiral or platinum asbestos (Hofmann, 1869). Other 
 oxidizing agents lead directly to formic acid. 
 
 It is a gas, condensible by cold to a clear mobile liquid, 
 which boils at 21. A solution of about 40 per cent is an 
 article of trade, and is known as formalin. In solution it has 
 apparently the hydrate formula, CH 2 (OH) 2 , and is used as an 
 antiseptic and disinfectant. 
 
 Its chief polymeric forms are : 
 
 (1) Para-formaldehyde, probably (CH 2 0) 2 , a white mass 
 soluble in water; (2) trioxy-methylene, probably (CH 2 0) 8 , a 
 crystalline compound which passes into formaldehyde again 
 when volatilized; (3) formose (which see), a mixture of several 
 compounds of the nature of glucose. On account of this facility 
 for undergoing polymerization, formic aldehyde in all proba- 
 bility plays an important part in assimilation by plants. 
 
 It does not form an additive compound with ammonia, but con- 
 denses to the complex compound C 6 H 12 N 4 , hexamethyleneamine. 
 
 By its combination with hydrochloric acid, chloro -methyl 
 alcohol (chloro -metlianol), CH 2 C1(OH), and hydroxy-chloro- 
 methyl ether (cUoromethane-oxy-methanol), CH 2 C1 CH 2 OH, 
 are formed. Both of these are colourless liquids, which react 
 in many respects like formic aldehyde itself. 
 
 Methylal, CH 2 (OCH 3 ) 2 (see Acetals, p. 125), is frequently 
 made use of instead of formaldehyde, for carrying out conden- 
 sation reactions. It is employed in medicine as a soporific, 
 and is also used as an extractive for certain scents. B.-pt. 42. 
 
 Acetaldehyde, Ethanal, Aldehyde, CH 3 CHO, was formerly 
 termed "acetyl hydride", C 2 H 3 0H (Fourcroy and Vauquelin, 
 1800; composition established by LieUg in 1835). It is pre- 
 pared by passing ammonia gas into an ethereal solution of the 
 crude aldehyde, obtained by oxidizing alcohol with K 2 Cr 2 O r 
 -f- H 2 S0 4 and drying over CaCl 2 , washing the precipitated 
 aldehyde-ammonia with ether, and finally distilling it with 
 dilute sulphuric acid. It is obtained in large quantity as a by- 
 product in the first portions of the distillate " First Runnings " 
 
ACETAL, 'CHLORAL, ETC. 129 
 
 in the manufacture of spirit. For its production in place of 
 vinyl alcohol, C 2 H 3 OH, from acetylene, see pp. 50 and 81. 
 
 It is a colourless mobile liquid, boils at 21, and has sp. gr. 
 about 0'8. Its odour is aromatic and suffocating, and pro- 
 duces a kind of cramp in the chest when inhaled. It burns 
 with a luminous flame, dissolves sulphur, phosphorus, and 
 iodine, and is readily soluble in water, alcohol, and ether. 
 
 Para-aldehyde, C 6 H ]2 3 , is a liquid sparingly soluble in 
 water. It melts at 10, and boils at 124, i.e. more than 100 
 above that of aldehyde, and is used as a soporific. 
 
 Meta-aldehyde, (C 2 H 4 O 3 ) 8 , crystallizes in white prisms in- 
 soluble in water, j,nd sublimes at a little over 100, but is 
 partially reconverted into aldehyde. (B. 14, 2271; 40, 4341.) 
 
 Meta-aldehyde is changed back again into ordinary alde- 
 hyde by prolonged heating to 115 in sealed tubes, and also, 
 as is the case with para-aldehyde, by distillation with some- 
 what dilute sulphuric acid. Para-aldehyde reacts in the same 
 way as ordinary aldehyde with PC1 5 , but not with NH 3 , 
 NaHS0 3 , AgN0 3 , and NH 2 OH. The constitution of para- 
 aldehyde may be represented as: 
 
 (KdnM and Zincke). 
 
 (The union of three molecules of aldehyde by means of the 
 valencies of carbon atoms cannot be assumed, on account of the 
 readiness with which para-aldehyde breaks up into aldehyde.) 
 
 With regard to these and other polymeric compounds, the 
 general rule has been proved to hold that, in the case of bodies 
 of similar constitution, the one of simpler composition is the 
 more soluble, possesses the lower melting-point, and is the 
 more easily vaporized. 
 
 Acetal, CH 3 .CH(OC 2 H 5 ) 2 , boils at 104. It is usually ob- 
 tained by the partial oxidation of ethyl alcohol with man- 
 ganese dioxide and sulphuric acid, the acetaldehyde first 
 formed condensing with the alcohol with the production of 
 acetal. This, as well as methylal, is frequently used instead 
 of aldehyde for the carrying out of condensation reactions (see 
 p. 126). 
 
 Propylaldehyde, C 2 H 5 .CHO, is present in wood-tar. Nor- 
 mal heptylic aldehyde (cenanthol), C 7 H 14 0, is obtained by the 
 dry distillation of castor-oil under diminished pressure, &c. 
 
 Chloral, 2 - trichloro - ethanal, CC1 3 -CHO, is a liquid which 
 boils at 98, and which when impure easily changes into 
 
 (B480) J 
 
130 V. ALDEHYDES AND KETONES 
 
 a solid polymeric modification, meta-chloral, hut is regenerated 
 from this upon heating. It combines readily with water to 
 chloral hydrate, CC1 3 .CH(OH) 2 (see p. 125, a), and with 
 alcohol to chloral alcoholate, CC1 3 . CH(OH)(OC 2 H 5 ), and tri- 
 chloro-acetal, CC1 3 .CH(O.C 2 H 5 ) 2 . The end product of the 
 action of chlorine upon alcohol consists chiefly of the last three 
 substances. They are all colourless crystalline compounds, 
 which are converted into chloral by distilling with sulphuric 
 acid, and rectifying over lime. 
 
 Chloral is an oily liquid with a sharp, characteristic odour. 
 It combines with sodium bisulphite, ammonia, hydrocyanic 
 acid, and acetic anhydride, and reduces an ammoniacal solution 
 of silver oxide. It is readily oxidized to trichloracetic acid, 
 and decomposed by alkali into chloroform and an alkali for- 
 mate: 
 
 CC1 3 -CHO + HKO = CC1 3 H -f 
 
 Chloral hydrate, CC1 8 CH(OH) 2 , forms large colourless 
 crystals readily soluble in water, melting at 57, and boiling 
 with dissociation at 97. It acts as a soporific and antiseptic 
 Sulphuric acid converts it into chloral. 
 
 UNSATURATED ALDEHYDES 
 
 Acrolein, Acrylic aldehyde, propenal, CH 2 :CH'CHO, is pro- 
 duced by the oxidation of allyl alcohol, by the distillation of 
 fats, and by heating glycerol with potassium hydrogen sulphate. 
 It is a liquid boiling at 52, of pungent odour (the smell of 
 burning fat being due to it), and of violent action upon the 
 mucous membrane of the eyes. It unites in itself the proper- 
 ties of an aldehyde and of an unsaturated carbon compound, 
 and therefore combines with ammonia and with bromine; it 
 also unites with hydrogen bromide to bromopropyl aldehyde, 
 CH 2 Br.CH 2 .CHO. 
 
 When distilled, acrolein - ammonia yields picoline, C 6 H 7 N 
 (see Pyridine bases); and crotonic aldehyde-ammonia, by an 
 analogous reaction, collidine, C 8 H U N. 
 
 Acrolein can combine with two atoms of bromine to acrolein 
 dibromide (dibromopropyl aldehyde), CH 2 Br CHBr CHO, a 
 compound which is of importance in the synthesis of the 
 sugars. (See Synthesis of Monoses.) 
 
 Crotonic aldehyde, CH^CHiCH-CHO. When acetal- 
 dehyde is left for some time in contact with dilute hydro- 
 chloric acid or sodium hydroxide, polymerization occurs, and 
 
FORMATION OF KETONES 131 
 
 a substance termed aldol, or a-hydroxy-butyraldehyde, is 
 obtained, CH S CH(OH) . CH 2 . CHO. The constitution of 
 aldol follows from its properties. It cannot be readily con- 
 verted back into acetaldehyde, and in this respect differs from 
 the other polymeric forms, viz. meta- and para-aldehyde. This 
 difference is due to the fact that in the aldol condensation 
 the union of the molecules has been brought about between 
 carbon atoms, and hence the relative stability. Aldol when 
 distilled or in presence of dehydrating agents yields croton- 
 aldehyde, water being eliminated. 
 
 CH 3 .CH(OH).CH 2 .CHO = CH 3 .CH:CH.CHO + H 2 O. 
 On oxidation it yields crotonic acid. 
 
 B. Ketones 
 
 The lowest member of the series, Acetone, contains three 
 atoms of carbon. The higher members, from C 12 on, are solid. 
 They are all lighter than water; e.g. the sp. gr. of acetone is 
 0-81 at 0. 
 
 Occurrence. Acetone is present in urine, methyl-nonyl ketone 
 in oil of rue (Ruta graveolens). 
 
 Modes of Formation. 1. By the oxidation of secondary 
 alcohols; just as in the conversion of a primary alcohol to 
 an aldehyde, this oxidation consists in the withdrawal of 
 two hydrogen atoms from each molecule of the alcohol: 
 
 CH 3 .CH(OH).CH S + O = CH 3 .CO.CH 3 + H 2 
 
 Iiopropyl alcohol Acetone. 
 
 Many primary and secondary alcohols are decomposed into 
 hydrogen and aldehyde (or ketone) when heated in contact 
 with a catalyst (see Chap. XLIX). 
 
 2. By the dry distillation of the calcium or barium salts 
 of fatty acids, the metallic carbonate being also formed: 
 
 Some of the ketones of high molecular weight may be ob- 
 tained by heating fatty acids with phosphorus pentoxide 
 (Kipping): 
 
132 V. ALDEHYDES AND KETONES 
 
 When two different acids are employed, mixed ketones, i e, 
 ketones containing different alkyl radicals, are formed, thus : 
 
 Calcium acetate and propionate Methyl-ethyl ketone. 
 
 As a rule, in addition to the mixed ketone, the two simpl( 
 ketones, e.g. (CH 8 ) 2 CO and (C 2 H 5 ) 2 CO, are also formed. 
 
 3. From dichlorides containing the group CCC1 2 C: 
 
 (CH 3 ) 2 CC1 2 + H a O = (CH 3 ) 2 CO + 2HC1 
 
 Acetone chloride Acetone. 
 
 It is probable that the chlorine atoms are first replaces 
 by hydroxyls, yielding the glycol, CMe 2 (OH) 2 , which imme 
 diately eliminates H 2 0, yielding the ketone, CMe 2 0. 
 
 4. By the action of zinc alkyl upon an acid chloride, e.g 
 acetyl chloride, CH 3 -COC1. 
 
 X)ZnCH 3 
 An additive compound is first formed, CH 3 C^-CH 3 
 
 Cl 
 
 which must be quickly decomposed by water, otherwise ter 
 tiary alcohols are produced: 
 
 OH: 
 
 = CH 3 .CO-CH 3 + HCl-f CH 3 .Zn.OH. 
 
 \;Ci H; 
 
 This method of formation, which was devised by Freund ii 
 1861, allows of the preparation of any possible ketone by usinj 
 the requisite zinc alkyl and acid chloride. 
 
 At the same time it elucidates, together with method 2, tht 
 constitution of the ketones from the constitution of the corre 
 spending acids. Conclusions regarding constitution based 01 
 the latter method must be accepted with a considerable amoun 
 of reserve unless supported by other arguments, since in re 
 actions which occur at high temperatures intramolecular re 
 arrangements can readily occur. Theoretically, therefore 
 ketones are compounds which contain the carbonyl group 
 CO, linked on both sides with an alkyl radical, R-CO-E. I 
 the alcohol radicals are the same, "simple" ketones result 
 and if different, "mixed" ketones. A compound with les 
 than 3 C atoms is thus impossible, 
 
NOMENCLATURE OF KETONES 133 
 
 Ketones have been synthesised by the action of organo- 
 magnesium compounds on nitriles or acid amides, e.g.: 
 
 x + E'H, : ^ 
 
 and these with water yield R-CO-R'. (Blaise, C. 1901. 132, 
 38, 133, 299.) 
 
 5. From the ketonic acids or their esters, e.g. acetoacetic 
 ester, CH 3 CO - CH 2 CO OC 2 H 5 , by warming with moderately 
 dilute sulphuric acid or with dilute alkalis. This important re- 
 action will be treated of at greater length under acetoacetic ester. 
 
 6. By the addition of water to homologues of acetylene, 
 CH 3 .C:CH + H 2 = CH 3 .CO.CH 3 . This reaction occurs 
 at relatively high temperatures, or may be brought about 
 indirectly by the aid of sulphuric acid, or solutions of mercuric 
 salts. 
 
 homers. The ketones exhibit the same isomerism as the 
 secondary alcohols. This isomerism depends on the one hand 
 upon the isomerism within the alkyl groups, e.g. dipropyl 
 ketone and di-iso-propyl ketone, which are linked together by 
 the CO group, and on the other by the position of the oxygen 
 atom in the carbon chain (position isomerism) ; thus, C 4 H 9 CO 
 CH 3 is isomeric with C 3 H 7 CO C 2 H 5 . 
 
 The aldehydes containing an equal number of carbon atoms 
 in the molecule are always isomeric with the ketones, since 
 both classes of compounds are formed from isomeric alcohols 
 by the withdrawal of 2 H. 
 
 Further, acetone is isomeric with allyl alcohol. Such an 
 isomerism of a saturated with an unsaturated compound is 
 termed "saturation isomerism" (cf. p. 87). 
 
 Nomenclature. The usual name is formed by adding the 
 suffix ketone to the name of the alkyl groups present; e.g. 
 (C 2 H 5 ) 2 CO, diethyl ketone; CH 3 -CO.C 2 H 5 , methylethyl 
 ketone, &c. The names of the simple ketones are also derived 
 from the acids which yield them, e.g. "Valerone" (C 4 H 9 ) 2 CO, 
 from valeric acid. 
 
 The systematic names of the ketones are formed by taking 
 the name for the corresponding hydrocarbon, adding the suffix 
 one to indicate the O replacing "2 H, and then a number to 
 indicate the position of the atom, e.g. CH 8 .CO.CH 2 'CH 3 , 
 butan-2-one, &c. 
 
134 V. ALDEHYDES AND KETONES 
 
 Behaviour. 1. Reagents which give rise to nascent hydrogen 
 reduce the ketones to secondary alcohols : (CH 3 ) 2 CO + 2 H = 
 (CH 3 ) 2 CHOH. Small amounts of pinacones (see these) are 
 formed. at the same time. 
 
 2. Oxidizing agents, e.g. K 2 O 2 7 , and dilute H 2 S0 4 , slowly 
 convert the ketones into acids or ketones containing a smaller 
 number of carbon atoms in the molecule (not as in the case 
 of the aldehydes into acids containing an equal number), the 
 carbon chain being broken: 
 
 CH 3 .CO.CH 3 + 40 = C 
 
 Since the carbon atom is tetravalent, the CO group in the 
 ketone, being already linked to 2 alkyl radicals, can only yield 
 the COOH group, characteristic of acids (p. 140), by the re- 
 moval of one of the alkyl groups. In this process of oxidation 
 of a mixed ketone the molecule usually becomes ruptured in 
 such a manner that the CO group remains attached to the 
 smaller alkyl group. Thus CH 3 CO: C 3 IL on oxidation yields 
 mainly acetic CH 3 C0 2 H and propionic CoH 5 C0 2 H acids; but 
 at the same time a small amount is oxidized to a mixture of 
 carbonic and butyric acids (B. 25, R. 121). 
 
 Since the acids formed by oxidation bear no reciprocal 
 relation to the ketone, and the oxidation process is more 
 complicated than in the case of the aldehydes, it is easy to 
 understand why the ketones do not possess reducing pro- 
 perties. 
 
 3. Phosphorus pentachloride, PC1 5 , converts the ketones 
 into the corresponding dichlorides, acetone, for instance, into 
 acetone chloride, (CH 3 ) 2 CC1 2 . 
 
 4. Additive reactions, (a) The ketones do not as a rule 
 combine with water and alcohol, for the reasons given under 
 the aldehydes and at p. 132. 
 
 (b) With ammonia they yield complex condensation pro- 
 ducts, e.g. di - acetone - amine, C 6 H 13 NO, tri - acetone - amine, 
 CgH^NO (Heintz) ; this reaction is more complicated than that 
 with the aldehydes, 2 or 3 molecules of acetone combining 
 with 1 molecule of ammonia, with elimination of water. 
 
 (c) The ketones which contain the group CH 8 CO, and 
 a few other relatively simple ketones, combine with sodium 
 hydrogen sulphite to crystalline compounds, e.g. acetone tc 
 
 (CH 8 ) 2 C<\Q OQ -AT , H 2 0, which can be converted back intc 
 the ketone by distillation with sodium-carbonate solution. This 
 
REACTIONS OF KETONES 136 
 
 very important reaction is made use of in separating and puri- 
 fying the ketones. Stewart has recently (J. C. S. 1905, 87, 185) 
 studied the comparative rates at which some of these compounds 
 are formed. 
 
 (d) With hydrocyanic acid they yield hydroxy-nitriles, as 
 
 in the case of the aldehydes; e.g. (GE^fk^- 
 
 (e) Ketones readily form additive compounds with Grignartfs 
 reagents, and when decomposed with water these yield tertiary 
 alcohols (see p. 72) : 
 
 Me 2 CO + MeMgI 
 
 H = Me 3 C.OH + OH-Mg-I. 
 
 5. The ketones, unlike the aldehydes, do not possess the 
 property of polymerizing, but they form condensation products. 
 Just as aldehyde is converted into crotonic aldehyde, so is 
 acetone, by the action of many reagents e.g. CaO, KOH, HC1, 
 and H 2 S0 4 converted, with elimination of water, into mesityl 
 oxide, C 6 H 10 0, phorone, C 9 H U 0, or mesitylene, C 9 H 12 , accord- 
 ing to the conditions (see these substances): 
 
 203^0 = C 6 H 10 + H 2 O. . 3C 3 H 6 = C 9 H U O -}- 2H 2 O. 
 3C 3 H 6 O = C 9 H 12 + 3H 2 O. 
 
 Analogous condensations also ensue with other ketones or 
 aldehydes under the influence of dilute caustic soda or of 
 sodium ethoxide (B. 20, 655). In this way the more compli- 
 cated ketones are formed (A. 218, 121). 
 
 6. Sulphuretted hydrogen converts the ketones into thio- 
 compounds, e.g. acetone into thio-acetone, CH 3 -CS'CH 3 (B. 
 16, 1368), or their polymers. 
 
 7. Halogens give rise to substitution products. 
 
 8. Like the aldehydes, the ketones even C 35 react with 
 hydroxylamine, yielding oximes, which are termed Ketoximes 
 (V. Meyer, B. 15, 1324, 2778; 16, 823, 1784, &c.): 
 
 (CH 3 ) 2 C : p+'H 2 ;N.OH = H 2 O + (CH 3 ) 2 C:N.OH(acetoxime). 
 
 9. They react in an analogous manner with phenyl-hydrazine, 
 C 6 H 5 .NH.NH 2 (E. Fischer, B. 17, 572), with the formation of 
 phenyl-hydrazones (p. 127): 
 
 (CH 3 > 2 C:N.NH.C 6 H 6 + H 8 0. 
 
 Aceton e-phenyl-hy drazone. 
 
136 V. ALDEHYDES AND KETONES 
 
 Phenyl-hydrazine and hydroxylamine are therefore of great 
 value for the recognition of the aldehydic or ketonic character 
 of a substance. Semicarbazide, NH 2 .CO-NHNH 2 , reacts in 
 an analogous manner (A. 1898, 303/79), and it or its hydro- 
 chloride is now largely used as a reagent for aldehydes and 
 ketones, as the products (semicarbazones) crystallize well and 
 have definite melting-points: 
 
 (CH 3 ) 2 CO + NH 2 .NH.(X).NH 2 
 
 = H 2 + (CH 3 ) 2 C : N NH CO NH 2 . 
 
 Acetaldehyde-semicarbazone melts at 162, and acetone-semi 
 carbazone at 187. 
 
 10. Nitrous acid (ethyl nitrite and sodium ethylate) gives 
 rise to iso-nitroso-ketones, e.g. iso-nitroso-acetone, CH 3 -CO' 
 CH:NOH, by replacement of H 2 by the group :N*OH 
 (oximino). When hydrolysed, the :NOH group is replaced 
 by oxygen, and diketones or aldehydo-ketones are formed. 
 
 Acetone, 2-Propanone, CH 3 COCH 3 . The formula was 
 established by Liebig and Dumas in 1832. It is present in 
 very small quantity in normal urine, in the blood, in serum, 
 &c., but in much larger quantity in pathological cases such as 
 acetonuria and diabetes mellitus. It is produced, among other 
 ways, by the distillation of sugar, gum, cellulose, &c., and is 
 therefore present in wood spirit; also by the addition of water 
 oo allylene, C 3 H 4 (p. 50). On the large scale it is prepared by 
 the dry distillation of calcium acetate. 
 
 It is a liquid of peculiar pungent odour j boils at 56, and 
 has sp. gr. 0*81 at 0. It is soluble in water, but may be 
 salted out from its aqueous solution, and is also miscible with 
 alcohol and ether. KMn0 4 does not oxidize it in the cold, but 
 Cr0 3 converts it into acetic and carbonic acids. 
 
 Metallic sodium reacts with acetone, yielding the derivative 
 CH 8 .C(ONa):CH 2 . 
 
 Detection. Acetone may be detected by the formation of 
 indigo when its solution in sodium hydroxide is warmed with 
 o-nitro-benzaldehyde. 
 
 Sulphonal, (CH 3 ) 2 : C(S0 2 C 2 H 5 ) 2 , is formed when a mixture 
 of acetone and mercaptan is treated with hydrochloric acid, 
 and the mercaptol, (CH 3 ) 2 C(SC 2 H 5 ) 2 [a derivative of the 
 hypothetical acetone-glycol, (CH 3 ) 2 C(OH) 2 ], which is thus 
 formed, is oxidized by potassium permanganate to the corre- 
 sponding sulphone. It crystallizes in prisms, melts at 125 
 and acts as a soporific. 
 
ALDOXIMES AND KETOXIMES 137 
 
 Mesityl oxide, C 6 H 10 0, = CH 3 . CO OH : C(CH 3 ). 2 (Kane, 
 1838; Baeyer), is a liquid of aromatic odour, boiling at 132. 
 
 Phorone, C 9 H 14 0, = (CH 3 ) 2 C : CH . CO . CH : C(CH 3 ) 2 , forms 
 readily fusible yellow crystals. Both of these compounds are 
 obtained by saturating acetone with hydrochloric acid gas (A. 
 180, 1). 
 
 Methyl ethyl ketone (2-Butanone), CH 3 CO'C 2 H 5 , is present 
 in crude wood spirit, and is also formed by the oxidation of 
 secondary butyl alcohol. B.-pt. 81. 
 
 Pinacoline (2-Dimethyl-3-bufanone), methyl tertiary-butyl ketone, 
 CH 3 CO C(CH 3 ) 3 , is produced by the action of dilute sulphuric 
 acid upon pinacone (p. 193). This involves a characteristic 
 rearrangement known as the "pinacoline reaction". B.-pt. 
 106. 
 
 A number of ketones have been obtained from the higher 
 fatty acids. These have been converted by Krafft into the 
 corresponding paraffins, by first transforming them into the 
 chlorides, C n H 2n Cl 2 , by means of PC1 5 , and then heating the 
 latter with hydriodic acid and phosphorus. 
 
 ALDOXIMES AND KETOXIMES 
 
 The aldoximes and ketoximes are the compounds obtained 
 by the action of hydroxylamine on the aldehydes and ketones 
 respectively. They both contain the bivalent oximino group 
 ; N OH attached to carbon, e.g. : 
 
 CH 3 .CH:N.OH and (CH 3 ) 2 C:N.OH 
 
 Acetaldoxime Acetoxime. 
 
 They are either colourless crystalline compounds or liquids, 
 and are both basic and acidic in properties. With metallic 
 hydroxides they yield salts of the type CH 3 -CH:NOK; with 
 mineral acids they form salts in much the same manner as 
 ammonia does, e.g. CMe 2 :NOH, HC1. 
 
 The oximes are fairly readily hydrolysed by dilute acidjs, 
 yielding hydroxylamine and either an aldehyde or a ketone. 
 
 On reduction they all yield primary amines, :N OH-*NH 2 . 
 
 Dehydrating agents, e.g. acetic anhydride or acetyl chloride, 
 transform the aldoximes into nitriles, water being eliminated: 
 GH 8 .C;H;:Nv()BG = CH 3 .C:N + H 2 O. 
 
 The ketoximes with acetyl chloride undergo an interesting 
 intramolecular rearrangement known as the Bedcmann transfor- 
 mation, the final product being an acid amide or anilide. It 
 
138 V. ALDEHYDES AND KETONES 
 
 is probable that the hydroxyl group of the oxime changes 
 place with one of the alkyl groups attached to the carbon 
 atom, and this then leads to a wandering of a hydrogen atom 
 and a shifting of the double bond: 
 
 R-C-R' E.G. OH K.C:O 
 
 N.OH " N.R' NHR'. 
 
 Constitution. In the formation of the oximes the water 
 eliminated is undoubtedly formed from the oxygen of the 
 carbonyl group and the hydrogen atoms of the hydroxylamine, 
 otherwise the reaction would be of the type 
 
 H 2 O, 
 
 and an aminoketone would result. There are two possible* 
 ways in which water can be thus eliminated, yielding a com 
 
 pound CMe 2 :NOH or CMe 2 <J . That the first of these 
 two formulae is correct is demonstrated b the fact that when 
 
 an alkyl derivative, :C:NOR or :C\ | , is hydrolysed 
 
 X N-R 
 
 with hydrochloric acid an alkyl derivative of hydroxylamine, 
 NH 2 'OR, is obtained, and hence the alkyl group is presum- 
 ably attached to oxygen in the alkylated oxime, and the 
 oxime itself thus contains an OH group. This constitution 
 formula is in perfect harmony with the reactions character- 
 istic of oximes. 
 
 The oxime derived from an aldehyde or ketone often exists 
 in isomeric forms. This is especially true of those derived from 
 aromatic aldehydes and from mixed (unsymmetrical) ketones 
 of the aromatic series. According to Goldschmidt and V. Meyer, 
 these isomers are structurally identical, and are stereo-isomeric 
 (i.e. the isomerism is due to the spatial relationship of the 
 various atoms and radicals). 
 
 According to Hantzsch and Werner, the isomerism is readily 
 explicable if we assume that two of the three valencies of the 
 nitrogen atom, when N is united by a double bond to C, lie 
 in the same plane, but that the third valency lies outside this 
 plane. Thus R.C.H 
 
 N 
 
SATURATED MONOBASIC ACIDS 139 
 
 with the oxime derived from an aldehyde, if the two valencies 
 attaching N to C lie in a plane at right angles to the plane 
 of the paper, then the OH radical must fall either close to the 
 alkyl group R or to the H atom; in fact, two configurations 
 are possible, viz. : 
 
 R.C.H B-C.H 
 N.OH HO.N. 
 
 These are known (1) as sy?i-aldoximes when the H and OH 
 are close together, and as a rule they readily lose water, 
 yielding nitriles; (2) as anti-aldoximes when the H and OH 
 are far removed from one another. As a rule, these yield 
 acetyl derivatives, and not nitriles, on treatment with acetyl 
 chloride. 
 
 The oximes derived from unsymmetrical ketones also often 
 exist in stereo-isomeric forms, which can be explained in a 
 similar manner: 
 
 R-C-R' R-C-R' 
 
 N.OH HO-N. 
 
 No isomerism should occur, and so far none has been met 
 with, in the case of the oxime derived from a symmetrical 
 ketone when R = R'. The configurations of these isomeric 
 ketoximes are generally derived from a study of the Beckmann 
 transformation. 
 
 R.C-R' R.C-R' 
 
 gives R CO NHR' and || gives NHR CO R 
 N-OH OH-N 
 
 (See also Aromatic Aid oximes and Ketoximes.) 
 
 VI. MONOBASIC FATTY ACIDS 
 A. Saturated Acids, C.H.A, or CJWCO.H 
 
 (See Table, p. 140.) 
 
 The monobasic fatty acids are formed by the oxidation of 
 the saturated primary alcohols or of their corresponding 
 aldehydes. These acids are monobasic, i.e. contain in the 
 
140 
 
 VI. MONOBASIC FATTY ACIDS 
 
 molecule only one replaceable atom of hydrogen, since, as 
 a rule, they give rise to only one series of salts or of esters. 
 They are known as the fatty acids, because many of them 
 are contained in fats or are formed from fats by processes of 
 oxidation or hydrolysis. They are often spoken of as acids 
 of the aliphatic series. 
 
 The characteristic group of the monobasic acids is the 
 
 carboxylic group 'C^Q TTJ and it is the hydrogen of this 
 
 group which becomes replaced in the formation of salts. The 
 basicity of an acid, as a rule, depends on the number of such 
 carboxylic groups present in the molecule. 
 
 NORMAL FATTY ACIDS AND THEIR PHYSICAL DATA 
 i-COgH, where C^H^+i is a normal alkyl group. 
 
 
 
 Mclting-pt. 
 
 Boiling-pt. 
 
 
 CHnO. 
 
 8'3 
 
 101 
 
 Acetic acid. 
 
 C 9 H,O 
 
 17 
 
 118 
 
 Propionic acid 
 
 CoH.O, 
 
 36 
 
 141 
 
 Butyric acid 
 
 C 4 H 8 O 2 
 
 8 
 
 162 
 
 Valeric acid . . 
 
 aH, n o 9 
 
 
 186 
 
 Caproic acid 
 
 CH 
 
 + 8 
 
 205 
 
 Heptoic acid 
 
 CH 
 
 10 
 
 224 
 
 Caprylic acid 
 
 CcH ir O, 
 
 -1- 16 
 
 236 
 
 
 CH 
 
 12 
 
 254 
 
 
 r TT r? 
 
 31 
 
 269 
 
 TJndecylic acid 
 
 C^HgoOo 
 
 28 
 
 -{213 
 
 Laurie acid 
 
 C 19 H 9d O 2 
 
 - 43 
 
 {226 
 
 Tridecylic acid 
 
 C H 
 
 40 
 
 236 
 
 Mrristic acid . 
 
 
 54 
 
 248 
 
 Pentadecylic acid 
 
 
 51 
 
 257 
 
 Palmitic acid 
 
 
 63 
 
 (269 
 
 Margaric acid 
 
 p ic S 32 2 2 
 
 60 
 
 1277 
 
 Stearic acid 
 
 
 69 
 
 {287 
 
 Nondecylic acid 
 
 C,oHooOo 
 
 66 
 
 {298 
 
 A rachidic acid 
 
 p TT n 
 
 75 
 
 
 
 C H 
 
 83 
 
 
 Lignoceric acid 
 
 cXA 
 
 80 
 
 
 
 
 78 
 
 
 Melissic acid 
 
 C*HO! 
 
 90 
 
 
 
 
 
 
 The lower members of the series are liquids of pungent 
 
FORMATION OF FATTY ACIDS 111 
 
 odour and corrosive action, and boil without decomposition. 
 They dissolve readily in water, and the aqueous solutions exhibit 
 a strongly acid reaction, although most of the anhydrous acids 
 are without action on dry litmus paper. The intermediate 
 members have an unpleasant smell like that of rancid butter 
 or perspiration, and are oily and but slightly soluble in water. 
 Mobility, odour, and solubility diminish as the percentage of 
 carbon increases. The higher members, from C 10 , are solids, 
 like paraffin, insoluble in water, and can only be distilled 
 without decomposition in a vacuum. Their acid character no 
 longer finds expression in their reaction with litmus, but in 
 their capability of forming salts with bases. These higher 
 acids are readily soluble in alcohol, and especially in ether. 
 
 In this series the boiling-point rises regularly for each 
 increase in the number of atoms in the molecule. The 
 rise is roughly 19 for each increment of CH 2 . The melting- 
 points do not exhibit the same regularity: the melting-point of 
 any acid containing an even number of C atoms in the mole- 
 cule is higher than the melting-point of the acid with an odd 
 number of C atoms which immediately succeeds it. 
 
 Similar phenomena have been observed in other homologous 
 series. (See section on Physical Properties and Constitu- 
 tion.) 
 
 The specific gravity of the liquid acids is at first > 1, and 
 from C 3 onwards < 1, and it decreases continuously to about 
 0'8, the paraffin character of the hydrocarbon radical becoming 
 preponderant. 
 
 Occurrence. Many of the acids of this series are found in 
 nature in the free state, but more frequently as esters, viz. : 
 (a) esters of monohydric alcohols (see wax varieties), (b) esters 
 of glycerol or glycerides, in most of the vegetable and animal 
 fats and oils. For further particulars see pp. 157 and 158. 
 
 Formation. 1. By the oxidation of the primary alcohols, 
 
 R.CH 2 .OH, or their aldehydes, R.C<Q, by means of K 2 Cr 2 O r 
 
 or Mn0 2 and dilute H 2 S0 4 , or by the oxygen of the air in 
 presence of platinum or of nitrogenous substances, e.g. acetic acid 
 from alcohol. The acids thus formed contain the same number 
 of carbon atoms as the alcohol or aldehyde. Many complex 
 carbon compounds, e.g. ketones, unsaturated compounds, &c., 
 when oxidized yield acids containing a smaller number of 
 carbon atoms. The higher acids of this series are converted 
 into their lower homologues when oxidized. 
 
142 VI. MONOBASIC FATTY ACIDS 
 
 2. Several acids have been prepared from the halogen com- 
 pounds containing the group CX 8 , e.g. : 
 
 HCC1 3 + 4KOH = H-COaK + 3KC1 + 2H 2 O. 
 
 We should expect an exchange of the three chlorine atoms 
 for three hydroxyls, with formation of the intermediate com- 
 pounds CH(OH) 3 or RC(OH) 8 . Such compounds are, how- 
 ever, extremely unstable, and immediately eliminate water, 
 yielding the acids (cf. p. 124): 
 
 OH 
 
 :H = 
 
 But derivatives of these trihydric alcohols, or ortho-acids as 
 they are termed, are known; for example, ethyl ortho-formate, 
 HC(OC 2 H5) 3 , a neutral liquid of aromatic odour, insoluble in 
 water, and boiling at 146. 
 
 3. From the alkyl cyanides or nitriles, (^EL^CN. The 
 cyanides, which are prepared by warming the alkyl iodides 
 with cyanide of potassium, are converted into the fatty acids 
 and ammonia by hydrolysis with potassium hydroxide solu- 
 tion, with dilute or concentrated hydrochloric acid, or with 
 sulphuric acid diluted with its own volume of water. 
 
 The reaction may be regarded as the addition of two mole- 
 cules of water to each molecule of nitrile : 
 
 CH S .C:N CH S .(X).NH 2 CHa-CO-ONE^ 
 + H 2 +H,0 
 
 first yielding the acid amide, and then the ammonium salt of 
 the acid, which is decomposed by the hydrolysing agent 
 employed. The process, in the case of aromatic nitriles, can be 
 stopped at the point when the acid amide is formed, but in 
 the aliphatic series this is almost impracticable. The reaction 
 is the exact reverse of the formation of nitriles from the 
 ammonium salts of fatty acids: 
 
 CH 3 .CO-ONH 4 CH 3 .CO-NH 2 CH 3 .C:N. 
 -H 2 -H 2 O 
 
 The great importance of this reaction, by means of which 
 we can obtain an acid C n+1 from an alcohol C n , has been 
 already indicated (p. 101). And since the acids can be con- 
 verted indirectly by reduction into the corresponding alcohols, 
 
FORMATION OF FATTY ACIDS 143 
 
 it is thus possible to build up synthetically, step by step, the 
 alcohols richer in carbon from those poorer in carbon, a cir- 
 cumstance which is of especial importance in the case of the 
 normal alcohols (Lieben and Eossi). As an example: 
 
 qa 3 .OH CH 3 I CH 3 .CN CHg-COOH CHg-CHO 
 
 P and I KCN Hydrolysis With calcium 
 
 formate 
 
 CH 3 .QH 2 OH 
 
 Reduction. 
 
 4. The acids may be regarded as resulting from the par- 
 affins, e.g. acetic acid from CH 4 and C0 2 , and formic acid from 
 H 2 and C0 2 . The two components can be made to combine 
 indirectly; thus, carbon dioxide and sodium methyl (p. 119) 
 combine when heated together (Wanklyn)-. 
 
 CH 3 Na + C0 2 = CH 3 .C0 2 Na. 
 
 Formic acid is obtained in an analogous manner from 
 hydrogen and carbon dioxide, under the influence of the silent 
 electric discharge: 
 
 H 2 + CO, = H.C0 2 H; 
 
 or from hydrogen, potassium, and carbon dioxide, when the 
 potassium is placed in a bell-jar filled with moist carbon dioxide 
 (Kolbe and Schmitt, 1861); or by treating carbonate of am- 
 monia, &c., with sodium amalgam. 
 
 5. By passing carbon monoxide over heated caustic alkali 
 or alcoholate, thus: 
 
 CH 3 -ONa -f CO = CH 3 -C0 2 Na (at 160). 
 H-ONa + CO = H.C0 2 Na. 
 
 6. By the action of carbon dioxide on ethereal solutions of 
 organo-magnesium haloids, a magnesium compound, 
 
 C n H 2n+1 .Mg.I 
 
 is obtained, which gives the free acid on the addition of dilute 
 sulphuric acid (C. 1904, 138, 1048). 
 
 7. By the addition of hydrogen to unsaturated acids, e.g. 
 propionic acid, CH 3 -CH 2 .C0 2 H, from acrylic acid, CH 2 :CH- 
 C0 2 H. This addition of "hydrogen may be effected (a) directly 
 by hydriodic acid and phosphorus, sodium amalgam and water, 
 or by the aid of hydrogen and reduced nickel at a temperature 
 of about 100 (Abstr. 1903, 1, 547), or hydrogen and colloidal 
 
144 VI. MONOBASIC FATTY ACIDS 
 
 palladium at the ordinary temperature, Chap. XLIX; (b) in- 
 directly, by addition of hydrobromic acid and inverse substi- 
 tution. Unsaturated acids also yield saturated ones contain- 
 ing fewer carbon atoms when fused with potash, e.g. 1 mol. 
 crotonic acid, C,H 6 2 , yields 2 mols. acetic acid, C 2 H 4 2 . 
 
 8. From the nydroxy acids, by reduction with hydriodic 
 acid: 
 
 CH 3 .CH(OH).C0 2 H + 2HI = CH 3 .CH 2 .CO 2 H + I 2 -f H 2 O 
 
 Lactic acid Propionic acid. 
 
 9. From many polybasic acids, by the elimination of C0 2 , 
 for example, formic from oxalic, COOH;COOH, and acetic 
 from malonic, iC0 2 ;H CH 2 C0 2 H. 
 
 10. Aceto-acetic ester syntheses. The homologues 
 
 R.CH 2 .COOH and 
 
 can be prepared from acetic acid by first converting the latter 
 into aceto-acetic ester, CH 3 CO CH 2 COOC 2 H 5 , introducing 
 alkyl groups into this, and then decomposing the compound 
 so obtained by concentrated alcoholic potash. (Cf. Aceto- 
 acetic Ester, p. 228; and Malonic Ester, p. 238.) 
 
 Separation. Natural fats are nearly all glycerides, i.e. esters 
 derived from the trihydric alcohol, glycerol, and various fatty 
 and other acids, so that a mixture of acids is obtained when 
 any natural fat is hydrolysed. This mixture may be separated 
 into its components as follows : 
 
 (a) By fractional distillation in a good vacuum; (b) by 
 fractional precipitation of an alcoholic solution of the acids 
 by means of magnesium acetate, calcium chloride, &c., the 
 acids richer in carbon being precipitated first; (c) by frac- 
 tional solution: the dry barium salts of formic, acetic, pro- 
 pionic, and butyric acids are very differently soluble in alco- 
 hol, the solubility increasing rapidly with the number of 
 carbon atoms; (d) by fractional neutralization, and distillation 
 of the non-combined acid. 
 
 Behaviour. 1. Salts. The acids are monobasic, and thus 
 form normal salts, e.g. CHgC0. 2 Na. They also yield acid 
 salts the so-called per-acid salts from the existence of 
 which we might feel inclined to doubt their monobasic nature. 
 These salts can, however, be crystallized from a strongly acid 
 solution only; they decompose on the addition of water, and 
 a]so lose their excess of acid when heated. The formation of 
 
CONSTITUTION OF FATTY ACIDS 145 
 
 such acid salts is now usually regarded as being due to the 
 tetravalency of one of the oxygen atoms, e.g. : 
 
 All the other chemical characteristics of the acids go to prove 
 their monobasicity, especially the non-formation of acid esters. 
 
 2. The monobasic acids give rise to different groups of deri- 
 vatives in much the same manner as the monohydric alcohols. 
 The typical hydrogen atom is replaceable by an alkyl group 
 with formation of an ester or alkyl salt, e.g. CH 3 CO OC 2 H 5 , 
 ethyl acetate, or by a second acid radical with formation of an 
 anhydride ; the hydroxyl may further be replaced by halogen, 
 especially chlorine, to an acid chloride, by SH to a thio-aeid, 
 by NH 2 to an amide, &c. (See Acid Derivatives, p. 171.) 
 
 3. Halogens act upon the acids as substituents (see p. 167). 
 
 4. When the alkali salts are heated with soda lime, or fre- 
 quently when the silver salts are heated alone, carbon dioxide is 
 eliminated and*a paraffin formed (see e.g. Methane). Paraffins are 
 also formed when the alkali salts are electrolysed (see Ethane). 
 
 5. Most of the acids are relatively stable towards oxidizing 
 agents, formic acid alone being readily oxidized to carbonic 
 acid, and thus possessing strong reducing properties. 
 
 6. When the lime salts of the acids are heated with calcium 
 formate they are reduced to aldehydes, and when heated for 
 a lengthened period with hydriodic acid and phosphorus, tc 
 paraffins. 
 
 Qa. When the lime salts are distilled alone, or are heated 
 with phosphorus pentoxide, they are transformed into the 
 ketones, (C n _ 1 H 2n _ 1 ) 2 CO. 
 
 Constitution. It follows from their modes of formation, 
 especially 3, 4, and 6, and also from their behaviour (see 4 
 above), that acetic acid and its higher homologues contain 
 alkyl radicals. The conversion of the alcohols into acids 
 containing 1 atom of carbon more, by means of the cyanides, 
 is especially strong proof of this. The latter contain the 
 alkyl radical bound to the nitrile group CiN, and when 
 they are hydrolysed the alkyl radical remains unchanged, and 
 the tervalent nitrogen is replaced by 0" and (OH)', both of 
 these attaching themselves to the carbon atom of the original 
 cyanogen, and so forming the group 
 
 (B480) 
 
146 VI. MONOBASIC FATTY ACIDS 
 
 Consequently all the oxygen in the acid is united to a single 
 carbon atom in the form of the group C0 2 H. This group, 
 which is termed carboxyl, is characteristic of the existence of 
 acid properties. Further proof of the presence of the carboxyl 
 group is based largely on the reactions of the acids. The 
 alkyl group which they contain must be directly attached to 
 C, as it is not removed by the action of acids or alkalis. We 
 thus have C n H ?n+1 C. The presence of an OH group follows 
 from the reaction of the acids with PC1 3 or PC1 5 , when an 
 atom of and an atom of H become replaced by an atom of 
 Cl, and they must presumably therefore be present in the 
 form of the univalent 0H group. There is only 1 oxy- 
 gen atom left over to account for, and this is presumably 
 attached to the C by a double bond, and thus we have 
 
 The monobasic acids may therefore be re- 
 
 garded as compounds of the alkyl radicals with carboxyl, or, 
 in other words, as derived from paraffins by the replacement 
 of one hydrogen atom by a carboxyl group, thus : 
 
 Formic acid is, in this way, the hydrogen compound of 
 carboxyl, H-COoH. 
 
 The acids are distinguished as primary, secondary, or tertiary, 
 according as the alkyl radicals which they contain are pri- 
 mary, &c. Thus: 
 
 Primary Secondary Tertiary 
 
 E-CH 2 .CO 2 H EE'CH.C0 2 H EE'E"C-C0 2 H. 
 
 There is no room for doubt that it is the hydrogen atom of 
 the carboxyl group, the so-called "typical" hydrogen atom, 
 which is replaced by metals in the formation of salts, for the 
 foregoing acids are all monobasic, and consequently the number 
 of hydrogen atoms present in the alkyl radical is of no 
 moment for the acid character. In the di- and polybasic 
 acids, the presence of two or more carboxyls can usually be 
 demonstrated. 
 
 If the composition of the primary alcohols, E-CH 2 'OH, is 
 compared with that of the corresponding acids, E-COOH 
 (E = alkyl or hydrogen), the latter are seen to be derived 
 from the former by the exchange of two atoms of hydrogen 
 for one atom of oxygen] The character of the original 
 
FORMIC ACID 147 
 
 substance is thus completely changed by the entrance of the 
 electro- negative (acidifying) oxygen. 
 
 Nomenclature. The names for the first five acids are special; 
 from C 6 onwards, with a few exceptions, the names for the 
 normal acids indicate the number of carbon atoms, e.g. hexoic, 
 heptoic, or heptylic, &c. The systematic name (Geneva Con- 
 gress) of the normal compound is obtained by adding the word 
 acid to the name of the paraffin containing the same number 
 of carbon atoms, e.g. acetic acid = ethane acid. 
 
 The monovalent radicals left when OH is removed from 
 the molecule of each acid are often spoken of as acid or 
 acyl radicals. (Cf. Alkyl Eadicals.) The commonest of 
 these radicals are CH 3 CO., acetyl; C 2 H 5 CO., propionyl; 
 C 3 H r .CO., butyryl; &c. 
 
 The aldehydes may be looked upon as hydrogen compounds 
 of the acyl radicals, and the ketones as compounds of the latter 
 with alkyl radicals, thus : 
 
 (CH 3 .CO)H (aldehyde) (CH 3 .CO)CH 3 (acetone). 
 
 The constitution of aldehydes and ketones, and of compounds 
 derived from them, is based on the constitution of the mono- 
 basic acids. 
 
 homers. The acids of the acetic series show the same iso- 
 merism as the alcohols containing 1 atom of carbon less, since 
 they are formed from these by means of the cyanides. Thus 
 we have 1 propionic acid, 2 butyric acids corresponding with 
 the 2 propyl alcohols, 4 valeric acids corresponding with the 
 4 butyl alcohols, and so on. 
 
 Formic acid (Methane acid), acidum formidcum, CH 2 2 
 (Samuel Fisher and John Wray, 1670; Marggraf), occurs free 
 in ants, especially Formica rufa, in the processionary cater- 
 pillar (Bombyx processionea), in the bristles of the stinging 
 nettle, the fruit of the soap-tree (Sapindus saponaria), and in 
 tamarinds and fir cones; also in small quantity in various 
 organic liquids, in perspiration, urine, and the juice of flesh. 
 
 Formation. From HCN, CHClg, CH 3 OH, C0 2 , &c. (See 
 General Methods of Formation.) Its salts are obtained by 
 the reducing action of sodium amalgam upon ammonium 
 carbonate or solutions of the alkali hydrogen carbonates 
 (Lieben); the free acid by the dry distillation or oxidation of 
 many organic substances, e.g. starch (Scheele). 
 
 Preparation. 1. Sodium formate is obtained by absorbing 
 carbon monoxide in soda lime at 210 (Merz). 
 
148 VI. MONOBASIC FATTY ACIDS 
 
 2. When oxalic acid is heated, formic acid is obtained in 
 small quantity together with carbon monoxide, carbon dioxide, 
 and water, and the same effect is produced by the direct 
 action of sunlight upon its aqueous solution containing uranic 
 oxide : 
 
 C 2 H 2 4 = CO 2 + CH 2 O 2 . 
 
 This decomposition is best effected by heating crystallized 
 oxalic acid with glycerol to 100-110 (Berthelot, Loriri), the 
 formic acid produced combining with the glycerol to an ester, 
 monoformin (see Glyceryl Esters) : 
 
 CH 2 .OH CH 2 .OH 
 
 CH.OH = CH-OH -f H 2 O. 
 
 This remains behind in the flask, and practically only water 
 and carbon dioxide pass over. The monoformin is then hy- 
 drolysed either by boiling it with excess of water or by the 
 addition of more oxalic acid, the water of crystallization of 
 the latter acting as the hydrolysing agent. The formic acid 
 distils over with the water, and then the anhydrous oxalic 
 reacts again with the glycerol, yielding monoformin and 
 carbon dioxide, the process repeating itself time after time, 
 a very small amount of glycerol being thus sufficient to 
 convert considerable quantities of oxalic into formic acid. 
 (B. 15, 928.) The anhydrous acid is obtained by decompos- 
 ing the solid lead or copper salt with sulphuretted hydrogen. 
 
 Properties. It is a colourless liquid which solidifies in the 
 cold and fumes slightly in the air. M.-pt. +9; b.-pt. 101; 
 sp. gr. .1*22. It has a pungent acid and ant-like odour, acts 
 as a powerful corrosive, and produces sores on the soft parts 
 of the skin. It is a much stronger acid than acetic acid, is 
 a powerful antiseptic, and decomposes completely into carbon 
 monoxide and water when heated with concentrated sulphuric 
 acid: CH 2 2 = CO + H 2 0. 
 
 Salts. Potassium-, HC0 2 K, sodium-, HC0 2 Na, and am- 
 monium formate, HC0 2 NH 4 , form deliquescent crystals. The 
 first two yield oxalates when strongly heated, with evolution 
 of hydrogen (see Oxalates); the ammonium salt yields form- 
 amide and water at 180: 
 
 HC0 2 .NH 4 = H.C 
 
ACETIC ACID 149 
 
 The lead salt, Pb(HC0 2 ) 2 , forms glistening, sparingly soluble 
 needles, the copper salt, Cu(HC0 2 ) 2 + 4H 2 0, large blue mono- 
 clinic crystals, and _the silver salt colourless crystals. The 
 last-mentioned deposits silver when warmed, consequently a 
 solution of nitrate of silver is reduced when heated with formic 
 acid. 
 
 A solution of the soluble mercuric salt, Hg(HC0 2 ) 2 , evolves 
 carbon dioxide when gently warmed, and yields free formic 
 acid together with the sparingly soluble mercurous salt, 
 Hg 2 (HC0 2 ) 2 , which separates in white plates; on further 
 heating, carbon dioxide, formic acid, and metallic mercury 
 are obtained. Similarly an aqueous solution of mercuric 
 chloride is reduced by formic acid to the mercurous salt, 
 Hg 2 Cl 2 . 
 
 Formic acid is thus a strong reducing agent, and in this 
 respect differs from the other members of the series : 
 
 HCO-OH == C0 2 + 2H. 
 
 It decomposes into carbonic acid and hydrogen when heated 
 alone to 160, or when brought into contact with finely-divided 
 rhodium. 
 
 This power of reduction may be attributed to the alde- 
 hydic grouping contained in its constitutional formula, 
 H-O-CHrO. 
 
 Acetic acid (Ethane add), CH 3 COOH, was known in the 
 dilute form, as crude wine vinegar, to the ancients. Stahl 
 prepared the concentrated acid about 1700. Glauber mentions 
 wood vinegar (1648). Its constitution was established by 
 Berzelius in 1814. Salts of acetic acid are found in various 
 plant juices, especially those of trees, and in the perspiration, 
 milk, muscles, and excrementa of animals. Esters of acetic 
 acid also occur, e.g. triacetin in cro ton-oil (see p. 158, and also 
 under Grlycerol). 
 
 Formation (see p. 140 et seq.).It, is the final product of the 
 oxidation of a great many compounds, and also of their treat- 
 ment with alkalis. 
 
 The following synthesis is of historical interest: Perchloro- 
 ethylene, C 2 C1 4 , which is prepared from CC1 4 , i.e. from Cl and 
 CS 2 , yields with chlorine in presence of water in direct sun- 
 light trichloracetic acid, carbon hexachloride, C 2 C1 6 , being 
 obviously formed as intermediate product (Kolbe, 1843): 
 
 = CC1 3 .C0 2 H 
 
150 VI. MONOBASIC FATTY ACIDS 
 
 The latter acid is reduced to acetic by nascent hydrogen 
 (Melsens). 
 
 Preparation. 1. From alcohol. A dilute aqueous solution 
 of alcohol, containing up to 15 per cent, is slowly converted 
 into acetic acid on exposure to the oxidizing action of the air 
 and in presence of certain low forms of plant life known as 
 bacteria, especially Bacterium aceti. These organisms are con- 
 tained in the air, and hence become deposited in alcoholic 
 liquors exposed to the air, and thus produce the souring of 
 wines, &c. For the growth of the micro-organisms it is 
 essential that nitrogenous matter, phosphates, &c., shall be 
 present, and hence pure alcohol mixed with water does not 
 turn sour. In the "quick process" dilute alcoholic liquors 
 are allowed to trickle over beechwood shavings which have 
 been previously coated with the required bacteria (mother of 
 vinegar), and the temperature is kept at about 35. 
 
 Vinegar is an aqueous solution of acetic acid, usually con- 
 taining only 3 to 5 per cent, but containing also small quan- 
 tities of alcohol, of the higher acids, e.g. tartaric and succinic, 
 the ethyl esters of the acids, albuminoid matters, &c. 
 
 2. From wood. The dry distillation of wood, which is con- 
 ducted in cast-iron retorts, yields: (1) gases, e.g. hydrogen 
 15 per cent, methane 11 per cent, carbon dioxide 26 per cent, 
 carbon monoxide 41 per cent, and higher hydrocarbons 7 per 
 cent; (2) an aqueous solution known as pyroligneous acid, which, 
 in addition to acetic acid, contains methyl alcohol, acetone, 
 homologues of acetic acid, and strongly smelling combustible 
 products (empyreuma); and (3) wood-tar, which contains 
 compounds of the nature of carbolic acid. The pyroligneous 
 acid is worked up for acetic acid by converting it into the 
 sodium or calcium salt, heating these the former up to its 
 melting-point and the latter to 200 to get rid of empyreu- 
 matic substances, and then distilling with sulphuric acid. 
 
 Properties. Acetic acid is a strongly acid liquid of pungent 
 odour, which feels slippery to the touch and burns the skin, 
 and which solidifies on a cold day to large crystalline plates 
 melting at 17; (glacial acetic acid). It boils at 118, and its 
 vapour burns with a blue flame; sp. gr. at 15, 1*055. When 
 mixed with water, contraction and consequent increase in den- 
 sity ensue, the maximum point corresponding with the hydrate 
 CH 3 .C0 2 H -f H 2 0, = CH 3 -C(OH) 3 (ortho-acetic acid), which 
 contains 77 per cent acid and has a sp. gr. of 1'075 at 15*5; 
 after this, the specific gravity decreases with further addition 
 
ACETATES 161 
 
 of water, so that a 50-per-cent acid has almost the same density 
 as one of 100 per cent. The amount of acid present in a solu- 
 tion is determined either by its sp. gr., this contraction being 
 borne in mind, or by titration with standard alkali, using 
 phenolphthalein as indicator, or with very concentrated acid 
 by a careful determination of its melting- (freezing-) point in 
 the Beckmann apparatus. The vapour density near the boiling- 
 point is much higher than that required by theory, but is 
 normal above 250. The high values are due to the associa- 
 tion of the molecules at the lower temperatures, and in the 
 liquid state the molecular formula is undoubtedly (C 2 H 4 2 ) X , 
 &c. The acid is hygroscopic, and stable towards chromic acid 
 and cold permanganate of potash. It dissolves phosphorus, 
 sulphur, and many organic compounds, is corrosive, and gives 
 rise to painful wounds on tender parts of the skin. 
 
 Salts. All the normal acetates are soluble in water. The 
 following potassic salts are known : (a) KC 2 H 3 2 , (b) KC 2 H S 2 , 
 HC 2 H 3 2 , and (c) KC 2 H 3 O 2 , 2 HC 2 H 3 2 . 
 
 Sodium acetate, CH 3 COONa, 3 H 2 0, forms transparent 
 readily soluble rhombic prisms. Ammonium acetate, CH 3 - 
 CO ONH 4 , resembles the potassium salt. It is used in medi- 
 cine as a sudorific (liquor ammonii acetici). Its solution loses 
 ammonia on evaporation, and it yields acetamide when dis- 
 tilled. Ferrous acetate, Fe(C 2 H 3 2 ) 2 , is largely used in the 
 form of " iron liquor " as a mordant in dyeing. The normal 
 ferric salt, Fe (C 2 H 3 2 ) 3 , which is employed for the same pur- 
 pose, is obtained when a soluble ferric salt is mixed with sodium 
 acetate. Its solution is deep red in colour, and deposits the 
 iron as basic salt, CH 3 CO OFe(OH) 2 , when heated with 
 excess of water. It is used in medicine as "liquor ferri 
 acetici". The analogous aluminic acetate is known only in 
 solution, and finds a wide application as " red liquor " mordant 
 in calico printing and dyeing. Its use depends upon the fact 
 that it is readily hydrolysed by water, e.g. when exposed to the 
 action of steam, and on the insolubility of the compound 
 (lake) formed from the residual alumina and the colouring 
 matter. It is employed in small doses as an astringent in 
 cases of diarrhoea, &c. Lead salts. (1) Normal lead acetate 
 or sugar of lead, (CH 3 .COO) 2 Pb + 3H 2 0, is manufactured 
 from sheet-lead and acetic acid. It forms colourless lustrous 
 four-sided prisms, which are poisonous and of a ^ nauseous 
 sweet taste. It combines with lead oxide to (2) basic salts of 
 alkaline reaction, termed sub-acetates. 
 
152 VI. MONOBASIC FATTY ACIDS 
 
 The simplest basic salt has the composition OHPb0 
 CO-CH 3 , but there also exist others, e.g. OH-Pb-O-Pb-p- 
 CO-CHg, &c. Two molecules of acetic acid can combine 
 with as many as 5 molecules of lead oxide. These basic 
 acetates are used as Goulard's lotion, and on the large scale 
 for the preparation of white-lead, &c. 
 
 Cupric acetate, Cu(C 2 H 3 2 ) 2 + 2H 2 0, dark-green crystals, 
 also forms basic salts (verdigris). Silver acetate, AgC 2 H 3 2 , 
 forms characteristic glistening needles. 
 
 Detection of Acetic Acid. (1) When an acetate is heated with 
 alcohol and sulphuric acid, the pleasant-smelling ethyl acetate 
 is formed; (2) by means of the silver salt; (3) by the odour 
 of cacodyl produced upon heating the potassium or sodium 
 salt with arsenious oxide. (See p. 116.) 
 
 Propionic acid, CH 3 .CH 2 -C0 2 H (Gottlieb, 1844), may be 
 obtained by the reduction of acrylic or lactic acid (see pp. 
 143 and 144); also from lactate or malate of calcium by suit- 
 able Schizomycetes fermentation (Fitz). It is usually prepared 
 by the hydrolysis of ethyl cyanide (propionitrile) with alkalis. 
 (See pp. 101 and 142.) 
 
 Calcium chloride separates it from its aqueous solution in 
 the form of an oil, whence its name TT/OWTOS, the first, and TTIWV, 
 fat; the first oily acid. 
 
 Butyric acids, C 4 H 2 . 
 
 1. Normal butyric acid, butane add, ethylacetic acid, 
 CH 8 CH 2 CH 2 C0 2 H, occurs free in perspiration, in the 
 juice of flesh, in the contents of the large intestine, and in 
 the solid excrementa; as hexyl ester in the oil of the fruit 
 of Heracleum giganteum, as octyl ester in Pastinaca sativa, and 
 to the extent of 2 per cent as glyceride in butter (Chevreul, 
 1822). 
 
 Formation. (See also General Modes of Formation.) It 
 is produced (1) by the decay of moist fibrin and of cheese 
 (being therefore contained in Limburg cheese); (2) by a Schizo- 
 mycetes fermentation of glycerol, and of carbohydrates (Pelouzc 
 and Gelisj Fitz; see below); (3) by the oxidation of albu- 
 minoids with chromic acid, of fats with nitric acid, of coniine, 
 &c., and (4) by the dry distillation of wood. 
 
 Preparation. In the "butyric fermentation" of sugar or 
 starch by fission ferments (e.g. Bacillus butyUcus), CaC0 3 or 
 ZnO being added at the same time, to neutralize the acid 
 formed. 
 
 If the fermentation is brought about by impure material 
 
BUTYRIC AND VALERIC ACIDS 153 
 
 (decaying cheese, &c.), lactic acid is first produced by other 
 micro-organisms, this being then converted into butyric acid 
 by the butyric bacillus. 
 
 Properties. It is a thick liquid of unpleasant rancid odour, 
 in presence of ammonia like that of perspiration, is miscible 
 with water, and separates from its aqueous solution on the 
 addition of salts. B.-pt. 163. The calcium salt, Ca(C 4 H 7 2 ) 2 
 -f- H 2 0, forms glistening plates, and is characterized by being 
 more soluble in cold than in hot water; it therefore separates 
 on warming the concentrated cold aqueous solution. On pro- 
 longed heating of the solution, however, it is transformed into 
 the calcium salt of isobutyric acid. 
 
 2. Isobutyric acid, 2 - methyl - propane acid, dimethyl - acetic 
 acid, (CH 3 ) 2 : CH C0 2 H, is present in the free state in the 
 carob (Redtenbacher), in the root of Arnica montana, and as 
 esters in Pastinaca saliva and Roman chamomile oil. 
 
 It is obtained from isopropyl cyanide (Erlenmeyer), by the 
 oxidation of isobutyl alcohol, by the aceto-acetic ester syn- 
 thesis (p. 229), &c. It resembles w-butyric acid, but is more 
 sparingly soluble in water (1 in 5), and boils 9 lower, i.e. at 
 154. Unlike the latter, however, it is easily oxidized to 
 acetone or acetic acid, and carbonic acid. The calcium salt, 
 Ca(C 4 H 7 2 ) 2 , differs from its isomer in being more^oluble in 
 hot water than in cold. The solution is accompanied by a 
 slight absorption of heat, whereas the solution of the salt of 
 the 7i-acid is accompanied by a slight evolution of heat. 
 
 Valeric acid, C 5 H 10 2 , exists in the four different modifica- 
 tions which are theoretically possible: 
 
 1. Normal Valeric acid (Pentane acid), propyl-acetic acid, 
 CH 3 .(CH 2 ) 3 .C0 2 H, from normal butyl cyanide (Helen and 
 Rossi, 1871), is best prepared from propyl-malonic acid. (See 
 B. 21, Ref. 649; also malonic ester synthesis.) It boils at 185, 
 and is soluble in 27 parts of water. 
 
 2. Isovalerio acid, 3 -methyl -butane acid, isopropyl - acetic 
 acid, (CH 3 ) 2 : CH I CH 2 C0 2 H, is obtained from isobutyl 
 cyanide. It is found in the free state and in the form of 
 esters in the animal kingdom and in many plants, especially 
 (free) in the valerian root (Valeriana officinalis), and in the 
 angelica root (Angelica archangelica), from which it is obtained 
 by boiling with soda; further, in the blubber of the dolphin 
 (Chevreul, 1817), in the berries of Viburnum opulus, in the 
 perspiration from the foot, &c. The natural acid is usually 
 mixed with the active valeric acid, and is therefore optically 
 
154 VI. MONOBASIC FATTY ACIDS 
 
 active; the oxidation of fermentation amyl alcohol by chromic 
 acids yields a similar mixture. When pure it is optically in- 
 active, boils at 175, and has an unpleasant pungent acid 
 odour, like that of old cheese, and a corrosive action. It is 
 used in medicine. 
 
 3. Methyl -ethyl -acetic acid, active valeric add, 2- methyl- 
 
 /~1 TT 
 
 butane acid, Q jj 3 ^>CHC0 2 H, occurs in nature, as already 
 
 mentioned, and results from the oxidation of the active ( ) 
 amyl alcohol; it is in this case (+) optically active, while, 
 if prepared synthetically, e.g. by the aceto-acetic ester re- 
 action, it is optically inactive, but can be resolved by suitable 
 methods into a -j- valeric acid and a valeric acid. [For 
 determination of optical activity, see section on Physical 
 Properties.] 
 
 There are thus three distinct acids, one dextro-rotatory, 
 one Isevo - rotatory, and the third optically inactive, which 
 have to be represented by the same structural formula, viz.. 
 
 As regards their ordinary chemical and physical properties, 
 the two active acids are exactly alike, and differ only in their 
 action on* polarized light. This difference is not due to the 
 different arrangements of the molecules, as all three are liquids, 
 and in liquids the molecules are not usually regarded as having 
 definite arrangements. A further proof that the cause of 
 the activity, and hence of the isomerism, is to be sought for 
 in the molecules themselves, and not in any special arrange- 
 ments of the molecules, is the fact that the optical properties 
 of the acids in the gaseous state are similar to those in the 
 liquid. The investigations of Pasteur, Le Bel, and VaiHt Hoff 
 have shown that this kind of isomerism, which is now usually 
 termed stereo-isomerism, is due to the fact that the com- 
 pound contains a carbon atom to which 4 different radicals 
 are attached; in the case of valeric acid these are, H, CH 3 , 
 C 2 H 5 , C0 2 H. Such a carbon atom is usually termed an asym- 
 metric carbon atom. (This expression does not mean that the 
 carbon atom itself is asymmetric in shape, but that it is attached 
 to four distinct radicals, and as we shall see later this pro- 
 duces an asymmetric molecule.) 
 
 Varit Hoff showed that if we assume that these radicals are 
 arranged around the carbon atom, not in a single plane, but 
 in the three dimensions of space, then every compound con- 
 
STEREO-ISOMER1SM 
 
 155 
 
 taining a single asymmetric earbon atom should exist in the 
 modifications represented by the figures 1 and 2. 
 
 b I 
 
 I. 
 
 2. 
 
 Such modifications are not identical, since they cannot be 
 brought to superposition (this can be shown readily by the 
 aid of models), but they are very similar; in fact, they stand 
 in the relationship of the right to the left hand, or, in 
 other words, in the relationship of an asymmetric object to 
 its mirror image. 
 
 The spatial relationship of the radicals is often expressed 
 by stating that if the asymmetric carbon atom is situated 
 as the centre of a regular tetrahedron, then the four radicals 
 occupy the solid angles of the tetrahedron. The arguments 
 in favour of the spatial representation of the molecules of 
 carbon compounds are largely based on a consideration of 
 the number of isomeric forms in which simple carbon deriva- 
 tives occur. For example, no simple compound of the type 
 Caabb is known to exist in more than one modification. 
 If, however, the radicals and carbon atom were arranged in 
 a single plane, we should expect the two modifications: 
 
 b 
 
 but with the spatial or tetrahedral arrangement we can get 
 but the one modification. 
 
 a 
 
 
156 VI. MONOBASIC FATTY ACIDS 
 
 An examination of models* will clearly show that in what- 
 ever way we exchange the radicals a and b, we always arrive 
 at a figure which can be superimposed on the one depicted. 
 
 Similarly with regard to compounds C a a b c, in which 
 2 of the 4 radicals are alike. The tetrahedral arrangement 
 allows of one modification only, and in these cases only 
 one is actually known. When, however, all four radicals are 
 distinct, e.g. Cabcd, the spatial arrangement, as we have 
 already seen, admits of two configurations, which are in the 
 relationship of object to mirror image, and these two modifica- 
 tions undoubtedly represent the two optically active isomerides, 
 in which almost every compound of the type Cabcd has 
 been shown to exist. An examination of the models repre- 
 senting the two modifications shows that they are both asym- 
 metric, i.e. a plane of symmetry cannot be drawn through 
 them, and the optical activity which such compounds exhibit 
 when in the liquid state, or in solution, is undoubtedly con- 
 nected with the asymmetry of their molecules. Since the 
 two configurations contain the same radicals and are very 
 similar, in the one case containing the 4 radicals arranged 
 in what we may term a positive, and in the other, in the 
 opposite or negative direction, we should expect the molecules 
 of the two compounds to produce rotations of the polarized 
 ray equal in magnitude but of opposite sign. This is the case 
 with the two optically active valeric acids: the pure dextro- 
 acid has a rotation of + 17 '85, and the laevo-acid 17-85. 
 
 In addition to the two optically active modifications, a third 
 isomeride is usually known which is optically inactive. As it 
 can be synthesised by mixing together equal weights of the 
 d and I compounds, it follows that such a compound is either 
 a mixture or a definite compound of the two active isomerides, 
 i.e. its optical inactivity is owing to the fact that the two 
 components are present in equal quantities. Such isomerides 
 are often spoken of as racemic compounds, and are optically 
 inactive by external compensation. Such racemic compounds 
 may be resolved into their optically active components by 
 
 * In using models it must be remembered that the models are not sup- 
 posed to represent in the least the actual shapes of the atoms, but merely 
 their spatial relationships. It must also be borne in mind that the atoms 
 and radicals in the molecules are in a state of motion, and the fixed posi- 
 tion represented in the model may be supposed to represent the mean 
 position of the centre of gravity of any particular atom in its oscillatory 
 motion, or the position which the centre of gravity would occupy at absolute 
 zero. 
 
HIGHER FATTY ACIDS 157 
 
 several methods, most of which were devised by Pasteur. (See 
 Kacemic Acid.) 
 
 Relationship between Asymmetry of the Molecule and Optical 
 Activity. Since the two isomerides of the type Cabcd are 
 optically active, it should follow that any derivative of valeric 
 acid in which the four radicals attached to the central carbon 
 atom are still different should be also optically active, but 
 that a derivative in which two of the radicals become similar 
 should become inactive. This question has been examined by 
 Le Bel in the case of some forty derivatives of active amyl 
 
 C H H 
 
 alcohol, Q H^^^CH OH' ^ e a l c hl i ts chloride, amine, 
 
 all its esters, its oxidation product, viz. valeric acid, and 
 all its salts, esters, &c., are optically active: the hydrocarbon 
 C H H 
 
 Q jj^C^CH ^ ta ^ ne( ^ ky reducing the chloride is, however, op- 
 tically inactive, and cannot be resolved into active components. 
 
 4. Trimethyl-acetie acid, pivalic acid, (CH 3 ) 3 CC0 2 H, can be 
 prepared from tertiary butyl cyanide (Butleroff, 1873). It melts 
 at 35, boils at 164, and has an odour like that of acetic acid. 
 
 Of the hexylic acids, eight are theoretically possible, and 
 of these seven are already known. The most important among 
 them is normal caproic acid, CH 3 (CH 2 ) 4 - C0 2 H (Cheweul, 1 822), 
 which is found in nature, e.g. in cocoa-nut oil, Limburg cheese, 
 and as a glyceride in the butter made from goats' milk, and 
 is produced in the butyric fermentation of sugar, and by the 
 oxidation of albuminous compounds and of the higher fatty 
 acids, &c. Like valeric acid, it has a very unpleasant and per- 
 sistent odour of perspiration and rancid butter. B.-pt. 205. 
 
 The higher acids which are found in nature are all of 
 normal constitution, and contain for the most part an even 
 number of carbon atoms. Goats' butter contains the acids 
 C 6 , C 8 , and C 10 , hence the names caproic, caprilic, and capric 
 acids, and cocoa-nut oil in addition to those three the acid 
 C 12 . This last, lauric acid, is contained more especially in 
 oil" of laurels (Laurus nobilis) ; myristic acid, 0^ is present 
 in oil of iris and nutmeg butter (from Myristica moschata); 
 arachidic acid, C 20 , in the oil of the earth-nut (Arachis hypo- 
 gcea); behenic acid, C 22 , in oil of ben (Moringa oleifera); 
 cerotic acid, C 26 , forms in the free state the chief constituent 
 of bees'-wax, and as ceryl ester that of Chinese wax. Pal- 
 mitic acid, C 16 H 32 2 , and stearic acid, C 18 H 36 O 2 (pp. 158 and 
 161), are very widely distributed, being nearly always accom- 
 
158 VI. MONOBASIC FATTY ACIDS 
 
 panied by a third acid poorer in hydrogen, viz. oleic acid, 
 CjoH^Og (see Unsaturated Acids). 
 
 Most animal and vegetable fats and oils, e.g. tallow, suet, 
 butter, palm, olive and seal oils, consist almost entirely of a 
 mixture of the glyceryl esters of palmitic, stearic, and oleic 
 acids, these esters being termed, for the sake of brevity, 
 palinitin, C 3 H 5 (O.CO.C 15 H 31 ) 3 , stearin, C 3 H 5 (0 CO C ir H 35 ) 3 , 
 olein, C 3 H 5 (0 CO C ir H 33 ) 3 . Palmitin and stearin being solid 
 and olein liquid, the consistence of a fat or oil depends on the 
 preponderance or otherwise of the solid esters. The consti- 
 tution of the fats was elucidated by Chevreul in 1811. 
 
 Eancidity consists, in the case of many fats, of a partial sa- 
 ponification, whereby strongly smelling fatty acids are set free. 
 
 Most of the varieties of wax are, on the contrary, esters of 
 monohydric alcohols; thus bees'-wax consists of the melissic 
 ester of palmitic acid, C 30 H 61 CO C 15 H 31 , together with free 
 cerotic acid, Chinese wax (from Croton sebiferum, the tallow- 
 tree) of the ester C^H^O CO C 26 H 53 , and spermaceti (Ceta- 
 ceum, in the skull of Physiter macrocephalus) of the ester 
 C 16 H 33 O.CO.C 15 H 31 . 
 
 From all these esters the acids are obtained in the form of 
 potassium salts by saponification with alcoholic potash, thus : 
 
 C 3 H 6 (O.CO.C 17 H 36 ) 3 + 3KOH = 3C ir H a5 C0 2 K + C 3 H 6 (OH) 3 
 
 Stearin Potassic stearate Glycerol. 
 
 The separation of the acids is effected by fractional crystal- 
 lization, fractional precipitation with magnesium acetate, or by 
 fractional distillation either of the fats themselves or of their 
 esters in a vacuum. Oleic acid can be separated from palmitic 
 and stearic by taking advantage of the solubility of its lead 
 salt in ether. 
 
 The stearine candles of commerce consist of a mixture of 
 palmitic with excess of stearic acid, some paraffin or wax being 
 usually added to prevent them becoming crystalline. The 
 manufacture of candles depends upon the saponification of the 
 solid fats, especially of beef and mutton tallow, by means of 
 water and lime, of concentrated sulphuric acid, or of super- 
 heated steam. 
 
 Soaps consist of the alkaline salts of palmitic, stearic, and 
 oleic acids, hard soaps containing sodic salts, chiefly of the solid 
 acids, while soft soaps contain potassic salts, principally oleate. 
 By the addition of common salt to a solution of a potassic soap, 
 the latter is converted into a sodic soap, which is insoluble in 
 
SOAPS 159 
 
 a solution of sodic chloride. This process is usually termed 
 "salting out", and is analogous to the precipitation of sodic 
 chloride by the addition of hydric chloride to its saturated 
 solution. (Cf. Walker, "Phys. Chem.", p. 314.) These alkali 
 soaps dissolve to a clear solution in a little water, but with 
 excess of water are hydrolysed to a certain extent, yielding 
 free alkali and free fatty acid or acid salt, analogous to potassic 
 peracetate. The cleansing action of soap is usually attributed 
 to the presence of the small amount of free alkali thus formed : 
 
 + NaOH. 
 
 This hydrolysis is similar to that observed in the case of 
 inorganic salts derived from a feeble acid and a strong base, 
 and increases with increasing dilution. The production of 
 free alkali (or free hydroxyl ions) can be readily understood 
 by aid of the theory of ionization. The salt RC0 2 Na, when 
 dissolved in water, may be assumed to be ionized to a certain 
 
 extent in the normal manner, thus giving rise to cations Na 
 
 and anions RC0 2 . But water itself is ionized to a slight 
 
 + + 
 
 extent to H and OH ions, and we should thus have H and 
 
 RC0 2 ions in the same solution; the acid from which the 
 sodic salt is derived is a feeble acid, and hence shows little 
 
 tendency to ionize, and thus the H and R'C0 2 ions will unite 
 to form non-ionized molecules RC0 2 H. This implies removal 
 of hydrions from the sphere of chemical action, and a certain 
 number of water molecules will be ionized in order to supply 
 fresh hydrions ; these will again unite with the acid ions, and 
 the two reactions will proceed until a state of equilibrium 
 is established. In this state of equilibrium we shall have 
 
 R.C0 2 , Na, H, OH ions and R-C0 2 H and H 2 molecules; 
 but it is obvious that the OH ions will be largely in excess of 
 
 the H ions, since a considerable number of these latter have 
 been used up in forming non-ionized molecules of acid. The 
 solution, as a whole, will thus possess more or less pronounced 
 alkaline properties. (Cf. Walker, "Phys. Chem.", p. 290.) 
 The calcium, barium, and magnesium salts are insoluble in 
 water, but partly crystallizable from alcohol. The preci- 
 pitates produced by the action of hard waters on soaps consist 
 
160 VI. MONOBASIC FATTY ACIDS 
 
 largely of those insoluble salts. The lead salts are prepared 
 by boiling fats with lead oxide and water, and form the so- 
 called plaisters or lead plaisters. 
 
 The higher acids with an uneven number of carbon atoms, 
 C n , C 13 , C 15 , and C 17 , are prepared synthetically from the acids 
 containing 1 atom of carbon more, by transforming them into 
 the ketones C^H^^CO'CHa (p. 131), and oxidizing these, 
 when acids C n _ 2 H 2n _ 3 COOH are obtained. (Krafft.) 
 
 On these reactions a method for proving that the higher 
 fatty acids, e.g. palmitic and stearic, are normal in constitution 
 has been based. (See Caution, p. 132.) 
 
 The acid C 15 H 31 C0 2 H is converted into the ketone C 15 H 31 
 COCH 3 ; this on oxidation yields C 14 H 29 C0 2 H and acetic acid. 
 The conversion into ketone and subsequent oxidation is re- 
 peated, and an acid, C 13 H 27 -C0 2 H, obtained. The processes 
 are repeated until an acid, CH 3 (CH 2 ) 7 C0 2 H, ?i-nonylic acid, 
 is obtained. This can be shown to have a normal structure 
 by synthetical methods, and hence all the higher acids must 
 also have a normal structure, since if the acid C 13 H 2lr 'C0 2 H 
 had not a normal structure, but contained a side chain, e.g. 
 
 Q jj 3 ^>CHC0 2 H, on conversion into the ketone and sub- 
 sequent oxidation it would not yield the acid, C 12 H 25 -C0 2 H, 
 but a ketone, CH 3 CO C n H 23 , or the oxidation products of 
 this ketone. 
 
 Dissociation constant. One of the most characteristic 
 physical constants of the organic acids is what is termed the 
 dissociation or affinity constant K, which is derived from 
 
 the equation k = -, =, where v = volume of solution 
 
 v (1 a) 
 
 in litres containing 1 gram mol. of the acid, a is the amount 
 ionized, and 1 a the amount not ionized. This equation is 
 based on the law of mass action. In the case of any feeble 
 organic acid, e.g. acetic acid, where we have 1 gram molecule 
 dissolved in v litres of solution, a state of equilibrium repre- 
 sented by the equation + 
 CH 3 .COOH ^ CH 3 "COO + H 
 
 occurs. Then if ^ and Jc 2 represent the velocity constants of 
 the direct and reverse reactions, we have, according to Guld- 
 berg and Waage's law, at the stage of equilibrium: 
 
 *, X !^ = k X ? X or ^ = | = * 
 
 v v v v(l a} 
 
UNSATURATED ACIDS 
 
 161 
 
 The extent of ionization in a solution containing 1 grain 
 molecule in v litres is determined by electrical conductivity 
 
 determinations, a = , i.e. the degree of ionization at a 
 
 dilution v is the ratio of the molecular conductivity at this 
 dilution to the molecular conductivity at infinite dilution 
 when all the acid molecules are ionized. (Cf. Walker, pp. 
 232-235.) For a weak acid, k remains constant, and affords 
 a convenient measure of the strength of an organic acid. 
 As a rule, the constant is usually taken as 100 times k, or K 
 = 100 k. 
 
 Acid. 
 
 K. 
 
 Formic. Acetic. Propionic. 7i-Butyric. iso-Butyric. 
 0-0214 0-00180 0-00134 0'0015 0'00144 
 
 Formic acid is obviously much the strongest of the fatty 
 acids, but they are all comparatively weak acids compared 
 with the strong mineral acids. Close comparison cannot be 
 
 a? 
 drawn between the two groups, as the equation k = n__ a \ v 
 
 does not hold good for strong acids. 
 
 Palmitic acid (hexadecane acid), CH 3 '(CH 2 ) 14 .C0 2 II, is most 
 conveniently prepared from palm-oil, which is a mixture of 
 palmitin and olein; also by fusing oleic acid or cetyl alcohol 
 with potash. M.-pt. 60. 
 
 Stearic acid, CH 3 .(CH ? ) 16 'C0 2 H, is formed, among other 
 methods, by reducing oleic acid, and is also obtained from 
 the so-called shea-butter or from mutton suet. M.-pt. 68. 
 "Artificial ivory" consists of gypsum which has been saturated 
 with liquid stearic acid. 
 
 B. Unsaturated Acids, C u H 2n _A or CJL 
 
 
 
 Melting-pt. 
 
 Boiling-pt, 
 
 Acrylic acid CoH^Oo 
 
 
 7 
 
 140 
 
 
 (la 
 
 72 
 
 182 
 
 Crotonic acids, C 4 H 6 O 2 
 
 Jib 
 
 Li 
 
 15 
 16 
 
 172 
 160 
 
 Angelic acidl n TT n 
 Tiglicacid ) G 5 H 82- 
 
 
 45 
 65 
 
 185 
 198 
 
 Olpir* arirt (7 hi ()> 
 
 
 14 
 
 
 
 Erucic acid CXofJ^O? . 
 
 
 33 
 
 
 
 
 
 
 
 ( B 480 ) 
 
162 VI. MONOBASIC FATTY ACIDS 
 
 These acids are known as the acids of the oleic series. In 
 their physical properties they closely resemble the saturated 
 acids, apart from differences in melting-point, which are some- 
 times considerable. They have the chemical properties char- 
 acteristic of monobasic acids; they yield salts, esters, amides, 
 &c., in much the same manner as the saturated acids; but in 
 addition they resemble the olefines in the readiness with 
 which they yield additive compounds with hydrogen, halo- 
 gens, or halogen hydrides, thus forming fatty acids or their 
 substitution derivatives. Thus oleic acid, C 18 H 34 2 , when 
 treated with H 2 in presence of colloidal Pd, yields steanc 
 acid, C 18 H 36 2 , and with bromine, dibromo - stearic acid, 
 C 18 H 34 Br 2 2 . In this way they characterize themselves as 
 derivatives of the unsaturated hydrocarbons of the ethylene 
 series, from which we may imagine them to be formed by the 
 replacement of an atom of hydrogen by carboxyl. They may 
 therefore be termed olefine-carboxylic acids. 
 
 Upon the addition of halogen hydride, the halogen does not 
 always attach itself to that carbon atom to which the smaller 
 number of hydrogen atoms is united. 
 
 The presence of the double bonds renders them much more 
 sensitive to oxidizing agents than are the fatty acids. When 
 a very dilute oxidizing agent is employed, e.g. 1 per cent 
 permanganate, dihydroxy derivatives of fatty acids are ob- 
 tained : 
 
 CH 3 .CH:CH.C0 2 H + + H 2 = CH 3 .CH(OH).CH(OH).CO 2 H; 
 
 but if stronger oxidizing agents are employed, a rupture of 
 the molecule occurs at the position where the double bond 
 exists, and a mixture of acids is obtained: 
 
 CH 3 CH : CH CH 2 . CO 2 H CH 3 CO 2 H and C0 2 H CH 2 CO 2 H. 
 
 This affords an excellent method for determining the position 
 of the double bond in the molecule of the acid. Fusion with 
 caustic alkalis also causes a breaking up of the molecules, and 
 the formation of a mixture of fatty acids; but this reaction is 
 of no use for determining the position of the double bond, as 
 treatment with alkali tends to shift the double bond, if possible, 
 nearer to the carboxylic group. Fittig (B. 1891, 24, 82, &c.) 
 has studied the action of dilute alkalis on a number of un- 
 saturated acids, and always observed the same effect, e.g. 
 bydrosorbic aci4, CH 3 CH 2 CH : CH CH 2 COOH, passes into 
 
FORMATION OF UNSATURATED ACIDS 163 
 
 OH 3 CH 2 . CH 2 CH : CH . COOH (2 - hexene - 1 - add). Such 
 changes, which are termed " molecular transformations ", are 
 sxplained by the assumption that atoms or radicals (in this 
 sase the elements of water) are added on to the original 
 compound, and then eliminated in a different manner, e.g. : 
 
 CH 3 .CH:CH.CH 2 .CO 2 H GHo.CH 2 .CH(OH).CH 2 .C0 9 H 
 -> CH 3 .CH 2 .CH:CH.C0 2 H. 
 
 The presence of the double bond in the molecule has a con- 
 siderable effect upon certain properties of the acid; for ex- 
 ample, the dissociation constant and the rate of esterification 
 )y the catalytic method. 
 
 Fichter and Pfister have shown (Abs. 1904, i. 965) that the 
 ntroduction of a double bond usually increases the strength of 
 an acid, and that the effect is most marked when the double 
 xmd is in the /2-y-position, e.g. butyric acid, K = '00 154; cro- 
 ;onic acid, K = 0-00204; and for vinyl acetic, K = 0-00383. 
 
 Sudborough (J. C. S. 1905, 1840; 1907, 1033; 1909, 315, 
 975) has shown that the introduction of the double bond in 
 the a-position greatly retards esterification. The rates for 
 hydrocinnamic, C 6 H 5 GEL CH 2 C0 2 H, and for cinnamic acid, 
 
 6 H 6 .CH:CH.C0 2 H, are as 40:1. 
 
 Modes of Formation. 1. By oxidizing the corresponding 
 Icohols or aldehydes, e.g. acrylic acid from allyl alcohol or 
 acrolein. 
 
 CH 2 :CH-CH 2 .OH CH 2 :CH-CHO -> CH 2 :CH.C0 2 H. 
 
 2. From the unsaturated alcohols or their iodides, by con- 
 verting them into nitriles and hydrolysing these, e.g. crotonic 
 acid from allyl iodide (intramolecular rearrangement, p. 164). 
 
 CH 2 :CH.CH 2 I CH 3 .CH:CH.CN CH 3 -CH:CH.CO 2 H. 
 
 Both these methods of formation are analogous to those of 
 .he fatty acids. 
 
 3. From the monohalogen substitution products of the satu- 
 rated fatty acids, by warming with alcoholic potash, sometimes 
 upon simply heating with water. This reaction is analo- 
 gous to the formation of the olefines from alkyl haloids ; it 
 occurs in the case of those substituted acids which contain 
 the halogen in the ^-position to the carboxyl (see p. 167 
 
164 VI. MONOBASIC FATTY ACIDS 
 
 4. From the halogen substitution products of the unsati 
 rated acids by inverse substitution: 
 
 CH 3 .CH:CC1.CO 2 H CH 3 .CH:CH.C0 2 H. 
 
 5. By the elimination of water from hydroxy fatty acids. 
 
 CH 2 (OH).CH 2 .COOH = CH 2 :CH.(X) 2 H + H 2 O 
 
 Ethylene-lactic acid Acrylic acid. 
 
 This reaction corresponds with the formation of the olefine 
 from monohydric alcohols. 
 
 Constitution and homers. The constitution of the unsaturate< 
 acids, C n H 2n _2O2, follows from their behaviour as monobasi 
 acids and as unsaturated compounds, and the position of th 
 double bond is ascertained by the process of oxidation. Th 
 number of isomeric acids, C m K< im _i C0 2 H, is the same as th 
 number of isomeric unsaturated alcohols, C^H^^-OH. 
 
 Acrylic acid, propene acid, ethylene-carboxylic acid, CH 2 :CH 
 C0 2 H (Redtenbacher), is prepared by the oxidation of acrolei 
 by oxide of silver, or by the distillation of /3-iodopropioni 
 acid with oxide of lead. (Cf. mode of formation 3.) It i 
 very similar to propionic acid. Mixes with water and readil 
 polymerizes. It is reduced to propionic acid when warmei 
 with zinc and sulphuric acid, and is decomposed when fuse< 
 with alkali into acetic and formic acids. 
 
 Acids, C 4 H 6 2 . Four isomeric acids with this formula ar 
 known. 1. Ordinary or solid crotonic acid (2-Buten-l-acid] 
 CH 3 CH : CH C0 2 H, occurs along with isocrotonic aci< 
 in crude pyroligneous acid, and is prepared from allyl iodid 
 by means of the cyanide, which, instead of having the antici 
 pated formula, CH 2 : CH CH 2 CN, has the isomeric one 
 CH 3 'CH:CHCN; this affords another example of molecula 
 transformation. 
 
 It is also prepared by heating malonic acid with para 
 aldehyde and glacial acetic acid: 
 
 It crystallizes in large prisms, melts at 72, boils at 189, ha 
 an odour like that of butyric acid, and is fairly soluble ii 
 water. On reduction it yields ?i-butyric acid, and on carefu 
 oxidation, oxalic acid, hence the constitution. 
 
 2. Isocrotonic acid, CH 3 -CH:CH.C0 2 H, obtained by tin 
 
OLEIG AClt> 165 
 
 tction of sodium amalgam upon chloro-isocrotonic acid, melts 
 it 15, boils .at 172, and changes into ordinary crotonic acid 
 it 180. It is present in croton-oiL For preparation of the 
 mre acid see Morrell and Cellars, J. C. S. 1904, 345. 
 
 Isocrotonic acid was formerly regarded as CH 2 :CHCH 2 
 }0 2 H, but it shows almost the same chemical behaviour as 
 3rotonic acid, e.g. on reduction and oxidation, or on addition 
 )f hydrogen bromide, and is now regarded as having the same 
 .tructural formula as, but being stereo-isomeric with, solid 
 TO tonic acid. (Cf. Fumaric and Maleic acids.) 
 
 3. Meth-acrylic acid, 2-methyl-2-propene-l-actd, CH 2 : C<^QQ Vr, 
 
 s found in small quantity in Eoman chamomile oil, and may 
 be obtained by the withdrawal of HBr from bromo-isobutyr.c 
 icid: 
 
 t smells like decaying mushrooms, and melts at 15. 
 
 4. Vinyl-acetic acid, CH 2 : CH . CH 2 C0 2 H, 1-ButeneA-acid., 
 nay be obtained synthetically. 
 
 Angelic acid, CH 3 CH : C(CH 3 )C0 2 H, is present in the an- 
 gelica root, and, together with its stereo-isomer, tiglic acid, in 
 .ioman chamomile oil. (Cf. A. 250; 259, 24; 272, 1; 273, 127.) 
 PIC relationship of these two acids is exactly the same as that 
 of crotonic and isocrotonic acids. 
 
 Oleic acid, C 18 H 34 2 (Chevreul), is present as olein (glyceryl 
 oleate) in the fatty oils especially, e.g. olive, almond, and train 
 oils. It is a colourless oil, solidifies to white needles in the 
 cold, melts at 14, and cannot be volatilized without decom- 
 position. It is tasteless and odourless, and has no action 
 upon litmus, but quickly becomes yellow and acid by oxi- 
 dation in the air, and also acquires a rancid odour. Its lead 
 salt is soluble in ether, and by this means the acid ^ may be 
 separated from numerous other organic acids. It yields, on 
 fusion with potash, the saturated acids, palmitic and acetic. 
 Nitrous acid converts it into the stereo-isomeric crystalline 
 elai'dic acid, melting at 45. It contains a normal chain, 
 since on reduction it yields stearic acid. When carefully 
 oxidized, it yields pelargonic acid, CH 3 (CH 2 ) 7 C0 2 H, and 
 azelaic acid, C0 2 H.(CH 2 ) 7 -C0 2 H, and hence the constitu- 
 tional formula: 
 
 CH 3 .(CH 2 ) 7 -CH:CH.(CHo) 7 .C0 2 H. 
 
166 VI. MONOBASIC FATTY ACIDS 
 
 Erucic acid, C 22 H4 2 2 , occurs in rape-seed oil, melts at 33' 
 and on treatment" with nitrous acid yields the stereo-isomeri 
 brassidic acid, melting at 60. The constitution is probably : 
 
 CH 3 [CH 2 ] 7 CH : CH[CH 2 ] n CO 2 H. 
 
 iFor the stereo-chemistry of the unsaturated acids, see Fumari 
 <and Maleic acids. 
 
 C. Propiolic Acid Series, C n H 2u _/> 2 
 
 The acids of this series again contain two atoms of hydroge; 
 less than those of the former, and are to be regarded as cai 
 boxylic acids of the acetylene hydrocarbons, e.g. propiolic acid 
 CH:CC0 2 H, as acetylene-carboxylic acid. They can ac 
 cordingly be prepared by the addition of C0 2 to the sodiur 
 derivatives of the acetylenes (analogously to mode of formatioi 
 4 of the saturated acids, p. 143). 
 
 They closely resemble the unsaturated acids which have beei 
 already described, but differ from them by the fact that eac" 
 molecule of such an acid can combine with either 2 or 4 atom 
 of hydrogen, chlorine, bromine, &c., and can yield explosiv 
 compounds with ammoniacal silver and copper solutions 
 There are, however, acids of the formula C n H 2n _ 4 2 which d 
 not possess this last peculiarity, viz., those which are derived 
 not from the homologues of acetylene proper, but from thei 
 isomers, and which therefore contain two double bonds instea* 
 of a triple one. (Compare Acetylene Hydrocarbons, p. 51.) 
 
 The most important member of the series is propiolic o 
 propargylic acid, pi-opine add, CH:C-C0 2 H, which corn 
 sponds with propargyl alcohol, and is prepared by warmin 
 an aqueous solution of the acid potassium salt of acetylene-d 
 carboxylic acid, the latter being itself obtained from dibronu 
 succinic acid. (See p. 241, also B. 18, 677.) In its physic* 
 properties it resembles propionic acid, forms silky crystal 
 below 6, and boils at 144. It is readily soluble in wate 
 and alcohol, and becomes brown in the air. It gives, even i 
 dilute solution, the characteristic explosive silver precipitate, 
 
 Tetrolic acid, CH 3 'C:C-C0 2 H, is obtained from /3-chlor< 
 crotonic acid and aqueous potash, and melts at 76. 
 
 Sorbic acid, CH 3 .CH:CH.CH:CH.C0 2 H, is contained i 
 the juice of the unripe sorb apple (Sorbus Aucuparia), and ha 
 relatively high melting- and boiling-points. 
 
I 
 
 o 
 
 < 
 
 o 
 
 53 
 
 c3 
 ,Q 
 
 
 
 O 
 
 s 
 
 a 
 
 - 
 
 o 
 
 W "cc 
 
 1 g 
 
 I g 
 
 J> 
 
 fl ^ 
 O 
 
 !^ 2 
 
 S3 0} 
 
 5 "" 
 
 O5 CQ 
 
 ^^ r ^ 
 
 = ' 
 
 w ^ 
 
 S) J 
 
 -2 
 
 73 o 
 
 W g 
 
 1 
 
 O rt< 
 
 00 CO 
 
 i i O 00 O O i i 
 
 O 10 # CO . .t-r^O 
 
 <? T" f <? - 1 : :<?wp 
 
 o o o .-H o o o o 
 
 (M 
 
 O5 
 . . . O . 
 
 : : : p : eo 
 
 O CO 
 
 CO G> O) 
 
 G<J CT G^ ' 
 
 OOOOO 
 
 ,_, o o o o 
 
 CM CO 
 
 w 
 
 w 
 
 ^^S6 
 
 ,' <N' C* wPQ 
 
 MpcjMH 
 oooo 
 
 
 ^ cdfldooPgP 
 
 
 
 
 OP4so:j.tt^Qi.a aoa. 
 
 167 
 
168 VI. MONOBASIC FATTY ACIDS 
 
 The acids poorer in hydrogen also yield similar substitution 
 products, e.g. CH 2 : CC1 C0 2 H, a-chlor-acrylic acid; CHBr: 
 CH.C0 2 H, -brom-acrylic acid; CH 3 - CH : CC1 C0 2 H, a-chlor- 
 crotonic acid; CI:CC0 2 H, iodo-propiolic acid, &c. 
 
 All these halogen derivatires have the properties of mono- 
 basic acids; in many respects they resemble the parent sub-- 
 stances, but as a rule are much stronger acids. This is ex-* 
 tremely well shown in a comparison of the dissociation con- 
 stants K. (See table.) 
 
 Since their acid nature remains unaltered, they still contain 
 the carboxyl group; the halogen has therefore replaced the 
 hydrogen of the hydrocarbon radical. They may also be 
 looked upon as haloid substitution products of the hydro- 
 carbons, in which 1 atom of hydrogen is replaced by carboxyl : 
 
 CH 3 C1 (chloro-methane) CH 2 C1 C0 2 H (chlor-acetic acid). 
 
 The modes of formation and properties of these substituted 
 acids also coincide with this view. Tkus, while they show a 
 behaviour perfectly analogous to that of the non-substituted 
 acids, forming salts, esters, chlorides, anhydrides, and amides, 
 their halogen atoms are as readily exchangeable for OH, CN, 
 or S0 3 H, as are those of the substitution products of the 
 hydrocarbons. (See p. 61.) 
 
 homers and Constitution. While in each case only one mono-, 
 di-, &c., halide acetic acid exists, two isomeric monohaloid 
 propioni'c acids are known. This is readily explicable from 
 the fact that in propionic acid, CH 3 CH 2 C0 2 H, the two a-hy- 
 
 /3 a 
 
 drogen atoms are differently situated from the three /?- ones, 
 the former being attached to the carbon atom nearer to the 
 carboxyl, and the latter to that one farther from it. According 
 to theory, therefore, with which the observed facts agree, the 
 following two isomers are possible : 
 
 CH 3 .CHX.C0 2 H and CH 2 X.CH 2 -C0 2 H 
 
 a-Haloid-propionic acid jS-Haloid-propionic acid. 
 
 These acids yield two isomeric lactic acids by exchange of 
 their halogen for hydroxyl, thus : 
 
 GH 3 .CH(OH).C0 2 H and CH 2 (OH).CH 2 .CO 2 H 
 Common lactic acid Ethylene-lactic acid. 
 
 The constitution of both of these lactic acids follows from 
 their other modes of formation (see p. 207, et seq.). The 
 
FORMATION OF HALOID FATTY ACIDS 169 
 
 positions of the halogens in the a- and ft- substituted propionic 
 acids are thus also fixed. 
 
 Those substituted acids which contain the halogen attached 
 to the a-carbon atom, i.e. to the same carbon atom to which 
 the carboxyl group is united, are termed a-acids, and the others 
 /?, y, &c., acids, the successive carbon atoms in their order 
 from the carboxyl group being designated as a, /?, y, &c. 
 
 We thus distinguish, for instance, between a-, /3-, and y- 
 chloro-butyric acids, aa-, aft-, and fifi- dibromo-propionic acids, 
 &c. 
 
 Two stereo-isomeric forms of the a- or /?- mono-chloro- and 
 -bromo-crotonic acids are known (A. 248, 281), being derived 
 from crotonic and isocrotonic acids respectively. 
 
 Formation. (a) Of the saturated substituted acids. 
 
 1. Chlorine and bromine can substitute directly, the halogen 
 taking up the a-position to the carboxyl. 
 
 The reaction is often carried out in sunlight and in the 
 presence of a halogen carrier. One of the commonest methods 
 is to transform the acid into the acid bromide by the aid of 
 phosphorus and bromine, and then to brominate. The pro- 
 duct obtained, e.g. CH 3 CHBr COBr, on treatment with water 
 yields the a-bromo acid, CH 3 CHBr.C0 2 H. This is generally 
 known as the Hell-VoUmrd-Zelinsky method. Trimethyl acetic 
 acid, CMe 3 C0 9 H, which contains no a-hydrogen atom, cannot 
 be brominated in this manner (B. 1890, 23, 1594). 
 
 2. From hydroxy acids of the gly collie series by the action 
 of PC1 5 , HBr, &c., e.g. : 
 
 CH 3 .CH 2 .CH(OH).CO 2 H -> CH 3 .CH 2 .CHC1.C0 2 H. 
 
 3. By the addition of halogen or halogen hydride to the 
 unsaturated acids. 
 
 (b) Of the unsaturated substituted acids. These are often 
 prepared by the elimination of HC1, HBr, or HI from poly- 
 halogen derivatives of the fatty acids: 
 
 CH 3 - CHBr- CHBr- CO 2 H -> CHs-C 
 
 or by the addition of hydrogen halide to propiolic acids. 
 
 Behaviour. 1. For the replacement of chlorine, bromine, 
 and iodine by hydroxyl, see p. 206. This exchange takes 
 place with more difficulty in the a-monochloro-substituted 
 acids than in the corresponding bromine and iodine com- 
 pounds, but more easily than in the case of the alkyl 
 chlorides, and it is effected by means of moist silver oxide, 
 
170 VI. MONOBASIC FATTY ACIDS 
 
 or frequently by prolonged boiling with water alone (A. 200, 
 75). In this way monochlor-acetic yields glycollic acid: 
 
 CH 2 C1.C0 2 H + H 2 O = OH.<JE 2 .CO 2 H 
 
 /2-halogen acids, on the other hand, lose halogen hydride 
 when boiled with water, and yield unsaturated acids, together 
 with C0 2 and olefines C n _ 1 H 2n _ 2 . y-halogen acids break up 
 under these conditions (even with cold soda solution) into 
 HC1, &c., and a lactone, i.e. an anhydride of a y-hydroxy-acid 
 (see p. 217; cf. Fittig, A. 208, 116). 
 
 2. When boiled with an alcoholic solution of potassium 
 cyanide, cyano-fatty acids are produced: 
 CH 2 C1.C0 2 K 
 
 These compounds are on the one hand monobasic acids, 
 and on the other nitriles, and they consequently yield dibasic 
 acids when hydrolysed. In the above case malonic acid, 
 C0 2 H.CH 2 .C0 2 H, is formed. 
 
 3. They form sulphonic acids with sodium sulphite, e.g. : 
 
 CH 2 a.C0 2 Na + Na.S0 3 Na = NaSOj-GHj-OOjNa + NaCl. 
 
 These latter are compounds which, apart from the acid 
 character they derive from the carboxyl group, are actual sul- 
 phonic acids, like ethyl-sulphonic acid, and are thus dibasic. 
 Their sulpho-group can, however, be replaced by OH on boiling 
 with alkalis. 
 
 4. With AgN0 2 , under favourable conditions, nitro-deriva- 
 tives of the fatty acids are formed, and these yield amino- 
 acids on reduction, e.g. NH 2 - CH 2 C0 2 H. (B. 1910,43,3239.) 
 
 Chloroformic acid, Cl C0 2 H, has so far not been prepared, 
 although derivatives of it are known. (Cf. Chloro-carbonic 
 acid.) 
 
 The chlorinated acetic acids are formed by the direct sub- 
 stitution of acetic acid, or better, of acetyl chloride, chlori- 
 nated acetyl chlorides ensuing in the latter case as inter- 
 mediate products. 
 
 Monochlor-acetic acid (Chloro-ethane acid), CH 2 C1C0 2 H, 
 is prepared by chlorinating acetic acid, preferably in the pre- 
 sence of acetic anhydride, sulphur, or phosphorus. It forms 
 rhombic prisms or tables and corrodes the epidermis. Di- 
 chlor- acetic acid, CHC1 2 C0 2 H, is more conveniently ob- 
 tained by warming chloral hydrate with potassium cyanide 
 (B. 10, 2120), and trichlor- acetic acid, CC1 3 C0 2 H, by 
 
ACID DERIVATIVES 171 
 
 oxidizing chloral hydrate with nitric acid. The former de- 
 composes with boiling alkali to oxalic and acetic acids, and 
 the latter to chloroform and carbon dioxide. Inverse sub- 
 stitution reconverts tri-, di-, and monochlor-acetic acids into 
 acetic acid (Melsens, 1842). 
 
 Sulpho-acetic acid, S0 3 HCH 2 C0 2 H, forms deliquescent 
 prisms containing 1J mols. H 2 of crystallization. Its salts 
 crystallize well. Cyano-acetic acid, CN.CH 2 .C0 2 H, is a 
 crystalline substance melting at 65-66 and readily soluble 
 in water; it decomposes into aceto-nitrile, CH 3 CN, and C0 2 
 when heated, and yields malonic acid on hydrolysis. 
 
 a-Chloropropionic acid, CH 3 CHOI C0 2 H, is obtained by 
 the action of PC1 5 upon lactic acid, and decomposition of the 
 lactyl chloride, CH 3 CHC1 COC1, by water. /Modopro- 
 pionic acid, CH 2 I CH 2 C0 2 H, is prepared by acting upon 
 gly eerie acid, CH 2 (OH) . CH(OH) C0 2 H, with iodide of phos- 
 phorus (exchange of 2 OH for 21 and of I for H); also by 
 acting on acrylic acid with hydriodic acid. It forms colour- 
 less six-sided tables of a peculiar odour; m.-pt. 82. The two 
 cyanopropionic acids, C 2 H 4 (CN) C0 2 H, give the two succinic 
 acids when hydrolysed. 
 
 Chloro- and Bromo-crotonic acids, /3-Chloro-crotonic acid 
 (2-Chlwo-2-JButene acid) (m.-pt. 94) and the stereo -isomeric 
 /3-Isochloro-crotonic acid (m.-pt. 59-5) are formed by the 
 action of PC1 5 on ethyl acetoacetate, and treatment of the 
 product with water. The /3-chlor-iso-acid volatilizes with 
 steam, but the /?-chloro-acid does not. 
 
 VII. ACID DERIVATIVES 
 
 A general idea of the kind of derivatives to which acids 
 give rise is obtained by comparing these derivatives with cor- 
 responding derivatives of the saturated monohydric alcohols, 
 e.g. those of acetic acid with those derived from ethyl alcohol: 
 
 CH 3 -CH 2 .OH Alcohol. 
 CH 3 CH 2 ONa Sodium ethy late. 
 
 CH 3 CH 2 Cl Ethyl chloride. 
 CH S .CH 2 .SH Mercaptan. 
 CH 3 .CH 2 'NH 2 Ethylamine. 
 
 CH 3 CO OH Acetic acid. 
 CH S CO ONa Sodium acetate. 
 
 CH 3 *CH i X >0 Eth y 1 acetate - 
 (CH 8 -CO) 2 Acetic anhydride. 
 CH 8 CO Cl Acetyl chloride. 
 CH 8 - CO SH Thiacetic acid. 
 CHa-CO-NHz Acetamide. 
 
172 
 
 VII. ACID DERIVATIVES 
 
 It is seen that as regards formulae there is a close resem 
 blance, the acetyl group taking the place of the ethyl group. 
 Stated generally, the acid derivatives contain acyl radicals in 
 place of the alkyl groups contained in the corresponding 
 derivatives of alcohols. 
 
 These derivatives are obtained by methods many of which 
 are perfectly analogous to the modes of formation of the cor- 
 responding alkyl derivatives, but they differ characteristically 
 from these by being less stable towards hydrolysing agents. 
 
 A number of other derivatives, viz. amido- and imido- 
 chlorides, thiamides, imido-thio-compounds, and amidines, are 
 peculiar to the acids: 
 
 CH 8 CC1 2 - NHR*Amido-chlorides. 
 CH 8 CC1 : NR Imido-chlorides. 
 CH,.CS-NH 3 Thiamides. 
 
 CH 8 .C(NH)OH Iimno-compounds. 
 CH 8 .C(NH)SR Imino-thio- 
 CH 8 .C(NH)(NH 2 ) Amidines. 
 
 These compounds are also characterized by being readily 
 hydrolysed. 
 
 A. Esters of the Fatty Acids 
 
 We have already seen that mineral acids readily give rise to 
 esters by the replacement of their acidic hydrogen radicals by 
 alkyl groups, e.g. S0 2 (OH) 2 S0 2 (OEt) 2 . In exactly the 
 same manner the typical hydrogen of the fatty acids can be 
 replaced by alkyl groups, and we get esters derived from the 
 fatty acids, e.g. ethyl acetate, CH 3 C0 2 Et. Since these esters 
 correspond with the metallic salts, they are sometimes termed 
 alkyl salts. (Of. CHg . C0 2 K and CH 8 C0 2 Et. ) 
 
 Methods of Formation. 1. By direct esterification, i.e. by 
 direct action of the acid on the alcohol: 
 
 = CH 3 .(X).ONa -fH-OH 
 H = CH 3 .(X).OC 2 H 5 H- H-OH 
 
 Although the equation representing the reaction is analogous 
 to that representing the neutralization of acetic acid by an 
 alkali, the process of esterification differs from that of neutrali- 
 zation in two respects. 
 
 (1) The reaction proceeds but slowly; thus, in the esteri- 
 fication of acetic acid by ethyl alcohol the limit of the reaction 
 at the boiling-point is not reached until after the lapse of 
 
 * R signifies an alkyl radical either alphyl or aryl. 
 
ESTERIFICATION 173 
 
 several hours, and even then only two-thirds of the acid have 
 been transformed into ester. 
 
 (2) The reaction is a reversible or balanced one, and hence 
 is never complete. The water which is formed during the 
 process of esterification tends to hydrolyse the ester back into 
 acid and alcohol : 
 
 Thus, when equivalent quantities of acetic acid and ethyl 
 alcohol are employed, only some 66 per cent of the acid 
 becomes transformed into ester. It can readily be shown, by 
 aid of Guldberg-PFaage's law of mass action, that by employing 
 an excess of alcohol a larger proportion of acid will be con- 
 verted into ester. Thus, in the above equation, if the original 
 concentrations of the four substances expressed in gram mole- 
 cules be denoted by a, b, o and o, and the velocity constants 
 of the direct and reverse reactions by k^ and k 2 respectively, 
 then after time t equilibrium will be established; and if we 
 assume x gram molecules of acid have been esterified, then the 
 concentrations of the four substances will be a x, b x, 
 x and x. The rate of the direct reaction can be denoted by 
 &! (a x ) (b x), and that of the reverse by & 2 x 2 (Guldberg 
 and Waage). When equilibrium is established, the two 
 reactions will proceed at the same rate, and 
 
 k,(a-x}(b-x) = 2 * 2 , 
 
 or (ax) (bx) _ constant f or a gi ven temperature. 
 x- 
 
 In the case of acetic acid and ethyl alcohol, using gram 
 molecular proportions, i.e. a = b = 1, we find that equilibrium 
 is established when some two-thirds of acid are esterified. 
 Thus 
 
 (! i)(l-"f) = constant, 
 and the constant becomes equal to J. 
 
 Then, supposing we alter the proportions of acid and alcohol, 
 using 2 gram molecules of alcohol to 1 of acid, we have 
 
 4 
 = -85 (appro*.), 
 
174 VIL ACID DERIVATIVES 
 
 
 
 and thus 85 per cent of the acid will have been esterified in 
 place of the 66 per cent when only 1 gram. mol. of alcohol 
 was used. The reversible nature of the reaction is of especial 
 importance in the preparation of ethyl acetate, and in this 
 case the difficulty is overcome by the addition of a moderate 
 amount of concentrated sulphuric acid, which is ordinarily 
 supposed to react with the water, and thus prevent its hydro- 
 lysing the ester. (Compare also Wade, J. C. S. 1905, 1656.) 
 
 It is worthy of note that the limit of esterification does not 
 vary to any large extent with the temperature. Thus, in the 
 case mentioned above, the limit at 10 is 65 '2 per cent, and at 
 220 it is only 66*5 per cent. 
 
 With most of the higher esters, and more especially the 
 esters in the aromatic series, the limit of esterification is much 
 higher, as the esters are not so readily hydrolysable. In these 
 cases, however, the rates at which the esters are formed are 
 extremely slow, and a catalytic agent is therefore introduced. 
 The two common catalytic agents employed are: (1) A small 
 amount of dry hydrogen chloride. At one time it was cus- 
 tomary to saturate the boiling alcoholic solution of the acid 
 with hydrogen chloride, but the researches of E. Fischer and 
 Sprier (B. 1895, 28, 3201, 3252) have shown that the addition 
 of 3 per cent of dry hydrogen chloride to the alcoholic solu- 
 tion is quite sufficient. (2) A small amount of concentrated 
 sulphuric acid, which acts in much the same manner as the 
 hydrogen chloride. The use of these reagents is not to raise 
 the limit of esterification, but to accelerate the production. 
 In most cases, using the catalytic method at the boiling-point 
 of the alcohol, the reaction is complete after three hours, and 
 a 90-95 per cent yield of ester can be obtained by pouring 
 into water. 
 
 A number of researches have been made as to the influence 
 of the constitution of the acid and of the alcohol on the rate 
 of esterification, i.e. the amount of ester formed in unit time. 
 Menschutkin, who employed the direct esterification method 
 without a catalytic agent, i.e. the so-called auto -catalytic 
 method, found that primary acids, i.e. RCH 2 -C0 2 H, were 
 esterified most quickly; secondary acids, EE'CH-C0 2 H, were 
 intermediate; and tertiary acids, RR'R"C'C0 2 H, least readily 
 when the same alcohol was employed. Other researches tend 
 to show that strong acids react with alcohol more readily than 
 feeble acids in the absence of a catalyst. 
 
 The velocity of esterification has also been determined for 
 
ESTERIFICATION 175 
 
 a number of acids employing the catalytic metnod (HC1). 
 From the equation we should expect the reaction to be a 
 bimolecular reaction, or a reaction of the second order; by 
 altering the conditions, namely, by taking a large excess of 
 alcohol as compared with the acid, the concentration of the 
 alcohol may be regarded as constant, and the reaction then 
 becomes unimolecular (H. Goldschmidt) and may be studied 
 by the aid of the equation for unimolecular reactions, 
 
 K = - log. - ; where K = the velocity constant, t 
 
 time, a = concentration of the acid at the beginning of the ex- 
 periment expressed in c.c. of standard alkali, and a x con- 
 centration of the acid after the lapse of time t. 
 
 Using this method, it is found that the introduction of any 
 substituent (CH 3 , Cl, Br, I, C 6 H 5 , &c.) into the acetic acid 
 molecule always lowers the velocity of esterification, the 
 introduction of two such radicals, e.g. CHBr 2 C0 2 H, lowers 
 the constant to a still greater extent, and when all three 
 hydrogens are replaced by substituents, e.g. C(CH 3 ) 3 C0 2 H, 
 the acid is esterified very slowly indeed as compared with 
 acetic acid. 
 
 These examples afford an extremely good instance of what 
 is now generally termed steric retardation, or the retardation 
 of a chemical reaction by the spatial relationships of radicals 
 introduced into a molecule. 
 
 The common theory of the process of esterification is that 
 there is first direct union between a molecule of the acid and 
 of the alcohol : 
 
 + R'OH = 
 
 X)H, 
 
 yielding a dihydroxylic compound, which immediately elimi- 
 nates water, yielding the ester R-C<^J . The introduction 
 
 of radicals into the CH 3 group of the acetic acid molecule by 
 filling up the space renders the formation of such additive 
 compounds much more difficult, and hence the retardation of 
 esterification (Wegscheider). 
 
 The influence of the hydrogen chloride is purely catalytic; 
 it remains unchanged at the end of the reaction. Its catalys- 
 ing effect is undoubtedly due to to the hydrions it generates, 
 as strong acids (HC1, HBr) are much better catalysing agents 
 
176 VII. ACID DERIVATIVES 
 
 than weaker acids (picric acid). (Cf. Goldschmidt, B. 1895, 28, 
 3218; Sudborough and others, J. C. S. 1898, 81; 1899, 467; 
 1904, 534; 1905, 1840.) 
 
 2. By the action of an acid chloride upon an alcohol or its 
 sodium compound (cf. p. 179): 
 
 3. By the action of an alkyl haloid upon the salt of the 
 acid: 
 
 C 2 H 5 C1 + CH 3 CO.ONa = CH 3 .CO.OC 2 H 6 -f NaCl. 
 
 As a rule, an alkyl iodide and the silver salt of the acid are 
 employed. The ester can then be separated from the solid 
 silver iodide and distilled. Occasionally the potassium salt 
 and methyl sulphate are used. Reactions 2 and 3 are of very 
 general application, and are largely made use of when an ester 
 cannot readily be obtained by the catalytic method of esteri- 
 fication. 
 
 Properties. The esters are mostly neutral liquids which 
 volatilize without decomposition; only those which contain a 
 small number of carbon atoms in the molecule are soluble in 
 water, e.g. ethyl acetate (1:14). 
 
 1. "Hydrolysis. They are all hydrolysed (saponified), i.e. 
 resolved back into alcohol and acid, when heated, or better, 
 superheated, with water, or when boiled with aqueous solutions 
 of strong alkalis or mineral acids; with the simpler esters this 
 hydrolysis is complete when the ester is allowed to remain for 
 some time in contact with water or dilute alkali. 
 
 The hydrolysis of an ester under the infli^nce of water or 
 of mineral acids may be represented by the equation: 
 
 K.CO 2 B'4-H.OH = K-CO-jH + K'-OH, 
 
 and may be studied by the aid of the general equation for 
 
 a uni-molecular reaction, K = - log. , since the concen- 
 
 t a x 
 
 tration of the water, if a large excess is used, may be regarded 
 as constant. 
 
 The action of the mineral acid is purely catalytic. The 
 same result might ultimately be obtained by using water alone, 
 but is considerably accelerated by using a small amount of 
 a strong mineral acid (HC1, H 2 S0 4 ). Weak acids also ac- 
 celerate the hydrolysis of the ester, but to a less extent. Ifc 
 
HYDROLYSIS OF ESTEKS 177 
 
 has been found, using the same ester and equivalent quantities 
 of different acids, that the rate of hydrolysis is directly pro- 
 portional to the strength of the acid. In other words, the 
 catalysing influence of different acids is due to the hydrions. 
 The hydrolysis of an ester by alkalis is represented by the 
 equation: E . CO . OB' + NaOH = E-CO-ONa + R'-OH, 
 and as it is analogous to the preparation of soaps by the action 
 of alkalis on fats (p. 158), is commonly termed Saponification. 
 This is a bimolecular reaction, and if equivalent quantities of 
 ester and alkali are employed in solution, can be studied by 
 
 aid of the equation K = - 7 -^- r, where t = time, a = initial 
 t a(a x) 
 
 concentration of alkali and of ester, a x = concentration of 
 these after time t. The concentrations can readily be deter- 
 mined by direct titration with standard acid, and the number of 
 cubic centimetres of acid introduced directly into the equation. 
 
 It has been found that when different alkalis are employed, 
 their hydrolysing effect is proportional to their strengths, i.e. 
 is due to the free hydroxyl ions. Different esters are hydro- 
 lysed at very different rates by the same alkali; the rate 
 appears to depend on the complexity of the molecule, i.e. 
 the number of substituents present, and also on the nature 
 of these substituents, viz. whether they are of a positive or 
 negative nature. It has been found that CC1 3 C0 2 C 2 H 5 is 
 hydrolysed by alcoholic potash much more readily than ethyl 
 acetate itself, owing to the negative nature of the chlorine sub- 
 stituents. (Compare A. 228, 257; 232, 103; J. C. S, 1899, 482.) 
 
 In all cases it has been found that, comparing solutions of 
 equal strength, e.g. N/10, a strong alkali is a much better 
 hydrolysing agent than a strong acid. 
 
 2. A characteristic reaction of methyl and ethyl esters is 
 that they exchange OMe^methoxy) or OEt (ethoxy) groups 
 for NH 2 on treatment with strong ammonia, thus yielding 
 acid amides, e.g. CH 3 CO-NH 2 . 
 
 3. Phosphorus pentachloride decomposes most esters, yield- 
 ing an alkyl chloride and an acyl chloride, the of the OEt 
 group being replaced by two chlorine atoms 
 
 4. Ethyl esters are readily transformed into methyl esters, 
 R.COoEt >- R.C0 2 Me, by warming with methyl alcohol and 
 a catalyst (CH 3 ONa, HC1). The reaction is reversible, and is 
 termed alcoholysis. 
 
 5. Sodium methoxide combines with the esters to form un- 
 
 (B480) M 
 
178 VIL ACID DERIVATIVES 
 
 x 
 
 stable additive compounds, RC^-OCH,, which are derivatives 
 
 ' 
 
 of "ortho-acids". (See p. 142; also B. 20, 646.) 
 
 The odour and taste of many of the esters is so agreeable 
 that they are manufactured upon a large scale, and employed 
 as fruit essences. 
 
 Ethyl formate, H-CO.OC 2 H 5 , b.-pt. 55, is employed in 
 the manufacture of artificial rum or arrak. Ethyl acetate, 
 acetic ether, CH 3 .CO-OC 2 H r , b.-pt. 75, is used internally as 
 a medicine. Amyl acetate, CH 3 - CO. OC 5 H n , b.-pt. 148. The 
 alcoholic solution of this forms the essence of pears. Ethyl 
 butyrate, CH 3 (CH. 7 ) 2 CO'OC 2 H 5 , is the essence of pine-apples. 
 Iso-amyl iso-valerate, C 4 H 9 . CO OC 5 H n , b.-pt. 196, finds 
 application as apple oil or apple ether. Cetyl palmitate, 
 C 15 H 31 .CO.OC 16 H 33 , ceryl cerotate, C 2 ,H 51 CO OC 26 H 53 , and 
 melissic palmitate, C 15 H 81 CO0C3Ji 6 j, are constituents of 
 waxes. (See Wax Varieties, p. 158V) 
 
 When the esters of the acids of high molecular weight are 
 distilled under the ordinary pressure and not in a vacuum, they 
 decompose into an olefine and a fatty acid. (See p. 46.) 
 
 homers. All esters containing the same number of C atoms 
 in the molecule, and derived from the monohydric saturated 
 alcohols and the fatty acids, are isomeric. Thus methyl buty- 
 rate is isomeric not only with ethyl propionate but also with 
 propyl acetate' and with butyl formate. Further, all esters 
 are isomeric with the monobasic acids which contain an equal 
 number of carbon atoms, e.g. the esters just mentioned are 
 isomeric with the valeric acids. (See Metamerism, p. 87.) 
 
 Further cases of isomerism occur when the alcohol on the 
 one hand, or the acid on the other, is unsaturated, e.g. allyl 
 propionate and propyl acrylate. 
 
 B. Acid Chlorides, Bromides, &e. 
 
 Acid chlorides are the compounds derived from the acids by 
 the replacement of the hydroxyl group by chlorine : 
 
 B-CO-OH K-CO-C1. 
 
 1. They are usually prepared by the action of the chlo- 
 rides of phosphorus, PC1 3 and PC1 5 , upon the acids or their 
 salts : 
 
 C 3 H r CO.OH4-PCl 5 = 0^.00-01 + POC1, + HCL 
 
ACID CHLORIDES 179 
 
 The acid chloric^ is separated from the POC1 3 formed at the 
 same time by fractional distillation. In the case of acetic acid 
 PC1 3 is conveniently used : 
 
 3CH 3 .CO.OH + PC1 3 = SCHg-CO-Cl + POaHg. 
 
 Phosphorus oxychloride, POC1 3 , may also be allowed to act 
 upon the alkali salts of the acids; when the latter are present 
 in excess, acid anhydrides are produced (p. 180). Thionyl- 
 chloride, SOC1 2 , and the acid are frequently used, as the only 
 other product is S0 2 . 
 
 2. By the action of chlorine upon the aldehydes in the 
 absence of water: CH 3 .CHO + C1 2 = CH 8 .COC1 + HC1. 
 
 
 Properties. The acid chlorides are suffocating liquids which 
 fume in the air, distil without decomposition, and are recon- 
 verted by water, in many cases at the ordinary temperature, 
 into the corresponding acids and hydrochloric acid : 
 
 CHg.CO-Cl-f H 2 O = CH 3 .CO.OH-f HC1. 
 
 They are thus more readily decomposed than the alkyl 
 chlorides. When ,the chlorides are warmed with alcohols, the 
 chlorine is replaced by alkyloxy groups, e.g. OCH 3 , OC 2 H 5 , 
 and in this way esters are formed. With ammonia they yield 
 acid amides, E.CO-NH 2 . With the sodium salts of the fatty 
 acids they yield acid anhydrides. With organo-magnesium com- 
 pound they first form ketones, and then tertiary alcohols (see 
 p. 72). With silver cyanide acyl cyanides (e.g. CH 3 COCN, 
 acetyl cyanide) are formed, and thfs^on hydrolysis with 
 concentrated hydrochloric acid yield ketonic acids, CH 3 -CO- 
 COOH. 
 
 Formyl chloride is not known. 
 
 Acetyl chloride (Ethanoyl chloride), CH 3 -COC1, is a mobile, 
 colourless liquid of suffocating odour. Boils at 55, has a 
 sp. gr. 1-13 at 0, reacts extremely vigorously with water and 
 ammonium hydroxide, and is a reagent of exceptional im- 
 portance, since it serves for the conversion of the alcohols and 
 primary and secondary amines into their acetyl derivatives. 
 It is thus frequently used for detecting OH, NH 2 or NH 
 groups in organic compounds. The compound under exami- 
 nation is heated with acetyl chloride (or even better, acetic 
 anhydride), and the pure product either analysed or hydro- 
 lysed, and acetic acid tested for in the products of hydrolysis 
 (see p. 201). 
 
180 VII. ACID DERIVATIVES 
 
 The boiling-points of the acid chlorides are always con- 
 siderably lower than those of the corresponding acids. 
 
 Acid bromides and iodides are known and closely resemble 
 the chlorides. Their boiling-points are higher. 
 
 C. Acid Anhydrides ' 
 
 Corresponding with the monobasic fatty acids there are ;^^^ 
 hydrides, which may be regarded as derived from two molecul^M 
 of the acid by the elimination of a molecule of water, e.g.; 
 
 CH 3 .CO.OH _ CH 3 .CO\ 
 ~ 
 
 They may also be considered as acyl oxides. For instance, 
 (CH 3 .CO) 2 = acetyl oxide. 
 
 Preparation. 1. They cannot as a rule be obtained by the 
 direct withdrawal of water from the acids, but by the action 
 of acid chlorides upon the alkali salts of the acids: 
 
 CH 3 .CO.;Ci + Na;O.CO.CH 3 = (CH 3 -CO) 2 O + NaCl. 
 
 A very convenient method for preparing them is by the 
 action of phosphorus oxychloride on the sodium salts of the 
 acids, care being taken that sufficient of the dry sodium salt 
 is used to decompose the acid chloride first formed (see p. 179) : 
 
 = 2CH 3 -COC1 + NaCl + NaPO 3 . 
 
 2. By the action of phosgene on the acids (B. 17, 1286): 
 2CH 3 .CO.OH + COC1 2 = (CH 3 .CO) 2 + C0 2 
 
 3. The anhydrides of the higher acids are conveniently 
 prepared by the action of acetic anhydride on their sodium 
 salts. 
 
 Properties. The majority of the acid anhydrides are liquids, 
 but those of higher molecular weight solids, of neutral reaction, 
 and soluble in alcohol and ether. They are non-miscible with 
 water, but are gradually hydrolysed by it to the free acids. 
 Dilute alkalis decompose them readily. When warmed with 
 alcohols they yield esters; with ammonia, acid amides; and 
 with hydrogen chloride, free acid and acid chloride: 
 
 (CH 3 CO) 2 O + HC1 = CH 3 CO Cl + CH 3 CO OH. 
 The boilin fir-point of an acid anhydride is higher than that 
 
THIO-ACIDS 181 
 
 of the corresponding acid, although an ether boils at a lower 
 
 temperature than the corresponding alcohol, e.g. EtOH 78; 
 
 Et 2 35; AcOH 118; Ac 2 137. 
 
 Acetic anhydride, (CH 3 .CO) 2 0, is a mobile liquid of suffocat- 
 
 ing odour, boiling at 137, and having a sp. gr. of 1*073 at 20. 
 
 Like acetyl chloride it is a reagent of great importance, and 
 largely made use of in testing for and estimating hydroxyl 
 ups in carbon compounds, and for converting primary and 
 ndary amines into acetyl derivatives. 
 
 anhydrides containing two different acyl groups are 
 
 TT 
 
 also known (Gerhardt, Williamson), e.g. p, 2 ^ 3 n ^>0. When dis- 
 
 tilled they yield the two simple anhydrides. 
 
 Acyl peroxides have also been prepared. Acetyl peroxide, 
 (C 2 H 3 0) 2 2 , is a thick liquid insoluble in water, which acts as 
 a strong oxidizing agent and explodes when heated; it is 
 prepared by the action of barium peroxide, Ba0 2 , upon acetic 
 anhydride. 
 
 Numerous other peroxides have been prepared recently by 
 Baey&r and Tilliger (B. 1901, 34, 738) by means of hydrogen 
 peroxide in the presence of potassium hydroxide. Among the 
 simpler of these peroxides may be mentioned ethyl hydrogen 
 peroxide, C 2 H 5 .0.0-H, a colourless liquid; diethyl peroxide, 
 C 2 H 5 .0-O.C 2 H 5 , a liquid boiling at 65; acetone peroxide, 
 (C 3 H 6 2 ) 2 , boiling at 132; and triacetone peroxide, (C 3 H 6 2 ) 3 , 
 melting at 97. Many of these compounds are explosive. 
 
 D. Thio-aeids and Thio-anhydrides 
 
 Just as sulphur can replace oxygen in the alcohols and 
 ethers, giving rise to mercaptans and alkyl sulphides, so it 
 can replace oxygen in the carboxylic acids, giving rise to (1) 
 R-CO-SH, thiolic acids; (2) R.CS-OH, thionic acids; and (3) 
 R-CS-SH, thion-thiolic acids. 
 
 Thiacetic acid (Ethane-tUolic add), CH 3 .CO.SH, is a colour- 
 less liquid boiling below 100; it smells of acetic acid and 
 sulphuretted hydrogen, and is readily decomposed by water 
 into these two components. It is prepared from acetic acid 
 and phosphorus pentasulphide, P 2 S 6 . The other thio-compounds 
 are likewise readily hydrolysed, yielding acetic acid and hy- 
 drogen sulphide. 
 
182 VII. ACID DERIVATIVES 
 
 E. Acid Amides and Hydrazides 
 
 Amides. An acid amide is the compound derived from the 
 acid by the introduction of the amido* group in place of the 
 hydroxyl radical of the carboxylic group: 
 
 E-CO-OH E-CO.NH 2 . 
 
 They may also be regarded as derived from ammonia by-| 
 the replacement of a hydrogen atom by an acyl group, e.g. ^ 
 NH 2 CO CH 3 . Secondary and tertiary amides,' e.g. NH(CO 
 CH 3 ) 2 , and N(COCH 3 ) 3 , are known, but are of relatively 
 small importance. 
 
 Modes of Formation. 1. By the dry distillation of the 
 ammonium salts of the fatty acids: 
 
 CH 3 .CO-ONH 4 = CH 3 .(X).NH 2 + H 2 O. 
 
 2. By addition of water to the alkyl cyanides (nitriles) : 
 
 = CH 3 .CO.NH 2 . 
 
 This addition of water is frequently effected by dissolving 
 the nitrile in concentrated sulphuric acid, or in acetic and 
 concentrated sulphuric acids, or by shaking with concentrated 
 hydrochloric acid in the cold; also, and often quantitatively, 
 by hydrogen peroxide, H 2 2 , in alkaline solution. In some 
 cases a further addition of water occurs, and the ammonium 
 salt of the acid is formed. 
 
 3. By the action of acid chlorides or acid anhydrides upon 
 aqueous ammonia or solid ammonium carbonate; if amines 
 are employed here, in place of ammonia, alkylated amides 
 are formed: 
 
 CH 3 .COCl-f2NH 3 = OE 3 .CONH 2 -J-NH 4 C1. 
 
 4. By heating esters with ammonia solution, sometimes even 
 on shaking in the cold: 
 
 CH 3 .CO-OC 2 H 6 + NH 3 = CH 3 .00-NH 2 -f C 2 H 6 OH. 
 
 Properties. 1. With the exception of formamide they are 
 colourless crystalline compounds, volatile without decomposi- 
 tion, but with relatively high boiling-points. The following 
 
 * The NH 4 group it usually termed an amino group when present in a 
 primary amine, l>ut an amido group when present in an acid amide. 
 
ACID AMIDES 183 
 
 comparison of boiling-points is interesting, as the order is the 
 same for most groups: 
 
 Acetyl Ethyl Acetic Acetic 
 
 chloride. acetate. acid. anhydride. Acetamide. 
 
 Boiling-point 55 78 117 137 222 
 
 2. The lower members are soluble in water, and although 
 derivatives of ammonia are, unlike most amines, practically 
 neutral, the strongly positive character of the hydrogen atoms 
 of the ammonia being cancelled by the entrance of the nega- 
 tive acyl radical. Still, the primary amides are capable of 
 forming additive compounds with some acids, e.g. acetamide 
 yields the compound (C 2 H 3 NH 2 ) 2 HC1, "acetamide hydro- 
 chloride"; these are, however, unstable, and are decomposed 
 for the most part by water alone. On the other hand, the 
 hydrogen of the amido group can be replaced by particular 
 metals, especially mercury (also sodium; cf. B. 23, 3037; 28, 
 2353), the amides, therefore, playing the part of weak acids 
 in the compounds so obtained, e.g. mercury acetamide, (CH 3 
 CONH) 2 Hg. 
 
 3. The amides are readily hydrolysed, more especially by 
 alkalis, to the free acid and ammonia. Alkylated amides on 
 hydrolysis yield the acid (or sodium salt) and an amine (not 
 ammonia). Amines are not decomposed by alkalis. 
 
 CH 3 .CO.NHC 2 H 5 + NaOH = CHg-CO-ONa + C 2 H 6 NH 2 . 
 
 Hydrolysis of Acid Amides. The velocity of hydrolysis of 
 the amides of the common fatty acids has been determined by 
 Crocker and Lowe (J. C. S. 1907, 91, 593 and 952), using an 
 electro-conductivity method. With sodium hydroxide and also 
 hydrochloric acid, formamide is hydrolysed most readily, and 
 valeramide least readily. 
 
 4. Nitrous acid converts the primary amides into the corre- 
 sponding acids, with liberation of nitrogen : 
 
 CH 3 .CO.NH 2 + N0 2 H = CHg-CO-OH + N, + H 2 O. 
 
 This reaction is a general one, and corresponds exactly with 
 the action of nitrous acid upon the primary amines (p. 108). 
 
 5. Nitriles (see p. 101) are formed by heating with P 4 10 , 
 P 2 S 5 , and PC1 5 (see pp. 185 and 186). 
 
 6. If bromine in the presence of alkali is allowed to act 
 upon primary amides, bromamides, BCONHBr, e.g. CH 3 - 
 CO.NHBr, aceto-bromamide (colourless rectangular plates), 
 are first formed, and these are decomposed by the alkali into 
 
184 VII. ACID DERIVATIVES 
 
 a primary amine, carbon dioxide and potassium hydroxide. 
 If less bromine is used, urea derivatives are formed, e.g. methyl- 
 acetyl-urea, CH 3 .NH.CO.NH.CO.CH 3 , which react with ex- 
 cess of alkali, yielding primary amines in this case CH 3 NH 2 
 containing 1 atom of carbon less than the original amide. 
 This is an excellent method for the preparation of amines 
 from Cj to C 6 , but less valuable for those from C 6 onwards, 
 as in the case of the higher compounds the production of amine 
 diminishes, a nitrile being formed instead by the further action 
 of the bromine (see below). Such nitriles C n H 2n+1 CN, in 
 which n > 4, can therefore be obtained directly from the amine 
 by the action of bromine and alkali upon it, thus : 
 
 C 7 H 16 .CH 2 .NH 2 + 2Br 2 = CVH 15 .CH 2 .NBr 2 + 2HBr 
 
 (Reversal of the Mendius reaction, p. 106; cf. Hofmann, B. 15, 
 407, 752; 17, 1407, 1920; 18, 2737.) 
 
 Since these nitriles on hydrolysis yield acids containing 
 1 atom of carbon less than the amide originally taken, this 
 reaction renders it possible to descend in the series successively 
 from one acid to another (compare p. 160), e.g. : 
 
 C H 13 .CH 2 .C0 2 H C 6 H 13 .CH 2 .CO.NH 2 C 6 H ir CH 2 .NH 2 
 C 6 H 13 .CH 2 .NBr 2 C 6 H 13 .CN C 6 H 13 .CO 2 H. 
 
 This has been done in the case of the normal acids from C 14 
 to Cp and it furnishes a further proof of their normal con- 
 stitution. 
 
 Constitution. Most of the methods of formation and many 
 of the properties of the amides point to the constitutional for- 
 mula (I). A second formula is possible (II), in favour of which 
 certain arguments have been adduced (B. 22, 3273; 23, 103; 
 25, 1435): 
 
 (I) R.C (II) 
 
 This last formula easily passes into the first by the migration 
 of a hydrogen atom, and most of the reactions of the simple 
 amides are explicable almost equally well by either formula. 
 (Cf. Titherley, J. C. S. 1897, 468; 1901, 407.) 
 
 We thus have a single compound which appears to possess, 
 according to its reactions, two distinct formulae. Such a sub- 
 stance is usually termed a tautomeric substance. 
 
AMIDO- AND IMIDO-CHLORIDES 185 
 
 On alkylation, under different conditions, it is possible to 
 obtain two distinct types of mono-alkylated amides, viz.: 
 
 and (n) 
 
 These differ as regards physical and chemical properties; 
 they are isomeric. Compounds of type I closely resemble the 
 original amides; compounds of type II are usually known as 
 imino ethers, and differ to a large extent (p. 187). 
 
 In many other cases we find that a tautomeric substance 
 gives rise to two distinct groups of alkyl derivatives (see 
 Cyanogen Derivatives). 
 
 Formamide (Methane-amide), HCO-NH 2 , is a liquid readily 
 soluble in water and alcohol. It boils with partial decom- 
 position at about 200. When quickly heated it decomposes 
 into CO and NH 3 , and with phosphorus pentoxide it yields 
 hydrocyanic acid. 
 
 Acetamide, Ethane-amide, CH 3 -CO'NH 2 , forms long needles, 
 readily soluble in water and alcohol. It melts at 82, boils at 
 222, and when pure has no odour. 
 
 Di-acetamide, (C 2 H 3 0) 2 NH. M.-pt. 78; b.-pt. 223. 
 
 HYDRAZIDES 
 
 Just as ammonia by the introduction of acyl groups yields 
 the acid amides, so hydrazine yields the acid hydrazides, e.g. 
 acetyl hydrazine or acet-hydrazide, CH 3 CO NH NH 2 . They 
 are formed by the action of esters on hydrazine. They are 
 basic in character, are readily hydrolysed, and possess reduc- 
 ing properties. With nitrous acid they yield acid azides, e.g. 
 
 || , which are acyl derivatives of hydrazoic acid, 
 
 , 
 ^ || 
 
 (N 3 H). 
 
 All 4 hydrogen atoms in hydrazine can be replaced by acyl 
 radicals in much the same manner as the 3 hydrogen atoms in 
 the ammonia molecule can. The products are termed di-, tri-, 
 and tetra-hydrazides, e.g. tetra-acet-hydrazide, Ac 2 N-NAc 2 . 
 
 F. Amido-ehlorides and Imido-ehlorides 
 
 By the action of PC1 5 upon the primary amides an ex- 
 change of C1 2 for O takes place, giving rise in the first in- 
 stance to the so-called amido-chlorides, e.g. acetdichloroamide, 
 
186 VII. ACID DERIVATIVES 
 
 CH 3 'CC1 2 NH 2 ; these are extremely unstable compounds, 
 being converted by water into amide and hydrochloric acid, 
 and readily giving up HC1, with formation of imido-chlorides, 
 e.g. CH 3 CC1:NH, acetchloroimide. The imido-chloroides are 
 also relatively unstable, yielding with water the amide and 
 hydrochloric acid. When heated, they break up into nitrile 
 and hydrochloric acid. 
 
 The alkylated amides (p. 182) also yield chloroamides, e.g. 
 CH 3 .CO.NH.C 2 H 5 gives CH 3 .CC1 2 .NH.C 2 H 5 , ethyl acet- 
 chloroamide, and CH 3 .CO-NK 2 gives CH 3 .CC1 2 .NK 2 ; if 
 these still contain amido-hydrogen, they readily yield imido- 
 chlorides, e.g. CH 3 CC1:NC 2 H 5 , ethyl acetchioroimide. 
 
 The chlorine in these compounds is chemically active; it 
 can be exchanged for sulphur or for an amino group. 
 
 G. Thiamides and Imido-thio-ethers 
 
 Thiamides are compounds derived from the amides by the 
 exchange of oxygen for sulphur, e.g. CHo'CS-NH 2 , thiacet- 
 amide (ethane-thion-amide), CH 3 -CS'NHC 6 H 5 , thiacetanilide. 
 They are mostly crystalline compounds, and result from the 
 addition of H 2 S to the nitriles (CaJwurs), e.g.: 
 
 = CH 3 .CS.NH 2 ; 
 
 by treating acid amides with P 2 S 5 ; from the amido-chlorides, 
 as given above; and by the action of H 2 S or CS 2 upon the 
 amidines. Both simple and alkylated thiamides are known. 
 
 When heated alone, they yield a nitrile and sulphuretted 
 hydrogen (compare Elimination of Water from Amides). 
 When hydrolysed with alkalis, they yield the corresponding 
 acid, ammonia (amine) and H 2 S, thus: 
 
 K.CS-NHR + 2H 2 o = K-CO-OH + H 2 s + NH 2 .R 
 
 They are rather more acid in character than the amides, 
 and thus many of them are soluble in alkali and yield metallic 
 derivatives. Consequently, for them, as well as for the amides, 
 
 the iso-formula R-C-TT is taken into consideration. From 
 
 this pseudo form R'C^Mtn iso-thio acid amides, are derived 
 
 a number of compounds, the Imino-thio -ethers, by the re- 
 placement of one or both the hydrogen atoms by alkyl groups, 
 
AMtDlNttS 187 
 
 acetimido-thiomethyl, CH 3 .G< H S; methyl iso-thio-acet- 
 
 QI /""'TIT iN 1. 
 
 anilide, CH 3 C^-^ Q j| . They are decomposed by hydro- 
 chloric acid into esters of thiacetic acid, thus: 
 
 CH 3 .qNH).SCH 3 -f H 2 = CH 3 .CO.SCH S + NHg. 
 
 These imino-thio-ethers are prepared by the action of mer- 
 captans upon nitriles in presence of hydrochloric acid gas 
 (Pinner), and by the action of alkyl iodides upon thiaraides 
 (Wallach, Bernthsen)-. 
 
 Imino-ethers, RC^-,, which are the oxygen compounds 
 
 corresponding to the above imino-thio-ethers, and which are 
 isomeric with the alkylated amides, are also known (Pinner), 
 They are derived from the pseudo form of the acid amides, 
 
 hypothetical compounds unknown in the free 
 
 state, which are isomeric with the simple amides. They are 
 formed by the combination of a nitrile with an alcohol under 
 the influence of hydrochloric acid gas, and in certain cases by 
 alkylating amides; some of them are liquids which boil with- 
 out decomposition, but others are only known in the form of 
 salts. 
 
 H. Amidines 
 
 Amidinesare compounds derived from the amides, R- CO 'NH 2 , 
 R-CO-NHR', and R.CO-NR' 2 , by the replacement of oxygen 
 by the bivalent imido-residue NH or (NR) : 
 
 Acetamidine (ethane-amidine) Ethenyl-diphenyl amidine. 
 
 The amidines are well-defined crystalline bases, and form 
 stable salts. Like all acyl derivatives, they are readily hydro- 
 lysed, and thus differ from the amines. 
 
 Formation. I. By heating the amides with amines in pre- 
 sence of PC1 3 (Hofmann) : 
 
 H 2 O. 
 
188 VIII. POLYSYDRIC ALCOHOLS 
 
 2. By treating the imido-chlorides, thiamides, and iso-thi- 
 amides with ammonia or with primary or secondary amines 
 (Wallach, Bernthseri), thus: 
 
 = E-C(NH)(NHB') + H 2 S; 
 = R-C(NH)(NH 2 ) + RSH. 
 
 3. By heating the nitriles with (primary or secondary) amine 
 hydrochloride; this is a particularly easy method when aromatic 
 amines are used, but not in the case of ammonium chloride 
 (Bernthsen) : 
 
 CH 3 .CN-f NH 2 .R = CH 3 .C(NH)(NHR). 
 
 4. By the action of amine bases or ammonia upon imino- 
 ethers. 
 
 Behaviour. 1. They decompose into ammonia or amine and 
 acid when boiled with acids or alkalis (see above), and into 
 ammonia and amide upon boiling with water. 
 
 2. The dry compounds, when heated, readily yield am- 
 monia or amine and acid nitrile, so long as the imido-hydrogen 
 atom has not been replaced by alkyl groups. 
 
 Amidoximes are the compounds formed by the addition of 
 hydroxylamine to nitriles, and, from this mode of formation 
 and from their properties, appear to be amidines in which an 
 amido- (imido-) hydrogen atom is replaced by hydroxyl: 
 
 R.CN-f NH 2 OH = R.C 
 
 Such an amidoxime is, for instance, isuret, NH 2 CH : N OH, 
 also termed methenyl amidoxime, which is prepared from 
 hydrocyanic acid and hydroxylamine; it is isomeric with carb- 
 amide or urea; also ethenyl amidoxime, CH 3 'C(NOH)(NH 2 ). 
 These compounds are hydrolysed in much the same manner as 
 amidines. 
 
 VIII. POLYHYDRIC ALCOHOLS 
 
 A. Dihydric Alcohols or Glyeols, C n H 2n (OH) 2 
 
 The dihydric alcohols may be regarded as derived from the 
 paraffins by the replacement of two hydrogen atoms by two 
 hydroxyl groups. 
 
 As the monohydric alcohols are often compared with the 
 hydroxides derived from the monovalent jnetals, we may 
 
OLYCOLS 189 
 
 compare the glycols with the hydroxides derived from the 
 bivalent metals, e.g. C 2 H 4 (OII) 2 with Pb(OH) 2 . In the satu- 
 rated dihydric alcohols we have the hydroxyl groups attached 
 to a bivalent alkylene radical, e.g. C 2 H 4 ", C 3 H ", &c. 
 
 In many respects they resemble the monohydric alcohols, 
 but they possess these properties in duplicate. Just as, e.g., 
 plumbous hydroxide, Pb(OH) 2 , can give rise to two series of 
 salts, e.g. the basic chloride, OH-Pb-Cl, and the normal 
 chloride, PbCl 2 , so glycol, C 2 H 4 (OH) 2 , can give rise to two 
 chlorides, OHC 2 H 4 .C1 and C 2 H 4 C1 2 , known respectively as 
 glycol monochlorhydrin and glycol dichlorhydrin or ethylene 
 dichloride. Similarly, with the acetates and amines derived 
 from glycol we have 
 
 OH.C 2 H 4 .O.CO.CH 3 and C 2 H 4 (O.CO.CH 3 ) 2 
 
 Mono-acetate Di-acetate, 
 
 OH.C 2 H 4 .NH 2 and C 2 H 4 (NH 2 ) 
 
 Hydroxyethylamine Ethylene diamine, 
 
 and similarly with other glycols. 
 
 The glycols, as alcohols, give rise to every class of alcoholic 
 derivative; but when, for example, the formation of an ester 
 such as glycollic monoacetate has taken place, this still behaves 
 as a monohydric alcohol, yielding, e.g., with a second molecule 
 of acid, a new ester; it is therefore termed an ester-alcohol. 
 
 It is not necessary that both the groups which replace 
 the hydrogen or hydroxyl should be of the same nature; 
 thus we know a mixed derivative of the composition 
 NH 2 C 2 H 4 S0 2 OH, which possesses at one and the same 
 time the character of an amine and of a sulphonic acid. 
 
 The glycols are mostly thick liquids of sweetish taste, a few 
 only being solid crystalline compounds; they dissolve readily 
 in water and alcohol, but are only sparingly soluble in ether. 
 It will be found that the solubility of a compound in water 
 tends to increase, and its solubility in ether to decrease, with 
 the number of hydroxyl groups present in the molecule of the 
 compound. Their boiling-points are much higher than those 
 of the corresponding monohydric alcohols, just as these latter 
 possess considerably higher boiling-points than the hydro- 
 carbons from which they are derived. 
 
 Constitution. As already stated, the glycols contain two 
 hydroxyl groups in each molecule; the arguments in favour 
 of the presence of these hydroxyl groups are exactly similar 
 to those used in the study of the constitution of ethyl alcohol, 
 
190 VIII. POLYHYDRIC ALCOHOLS 
 
 and are btased mainly on certain methods of formation, and on 
 the chief chemical characteristics of the compounds. 
 
 Glycols which contain two hydroxyls linked to the same 
 carbon atom are, as a rule, incapable of existence, and are 
 only known in derivatives (see p. 64). Instead of the glycols 
 CH 2 (OH) 2 and CH 3 -CH(OH) 2 , we always obtain the corre- 
 sponding aldehydes, CH 2 : and CH 3 CH : O. All glycols con- 
 tain their hydroxyls attached to two different carbon atoms. 
 Glycol itself has thus the constitution OH CH 2 CH 2 OH, 
 which can be proved directly by transforming it, by means of 
 hydrochloric acid, into glycol chlorhydrin, CH 9 C1 CH 2 OH, 
 and oxidizing the latter to monochloracetic acid, Cll 2 Cl CO OH. 
 In this last compound the chlorine and hydroxyl are united to 
 different carbon atoms, and consequently the same applies to 
 glycol chlorhydrin and to the two hydroxyl groups of glycol. 
 (Cf. p. 62.) 
 
 The monohydric alcohols are distinguished as primary, 
 secondary, and tertiary. The glycols may in the same way 
 be characterized as di-primary when they contain the group 
 CH 2 OH twice, as in glycol; as primary- secondary when they 
 contain the group CH 2 'OH together with the group CHOH, 
 as in propylene glycol, CH 3 .CH(OH) CH 2 OH; further as 
 di-secondary, primary-tertiary, secondary-tertiary, and di- 
 tertiary. The structure of a glycol is usually determined by an 
 examination of its oxidation products. (See pp. 192, 203, et seq.) 
 
 Modes of Formation. 1. From the di- halogen -substituted 
 derivatives of the paraffins, in which the two halogen atoms are 
 attached to two different carbon atoms, e.g. ethylene bromide: 
 
 (a) By transformation into the di-acetates by means of 
 silver or potassium acetate, and hydrolysis of the ester so 
 produced by potash or baryta water: 
 
 CH 2 Br CH 2 Br -f 2 CH 3 CO O Ag 
 
 = CH 3 .CO.O.CH 2 .CH 2 .O.CO.CH 3 4-2AgBr, 
 
 GH 3 .CO.O.CH 2 .CH 2 .0.(X).CH 3 
 
 = OH.CH 2 .CH 2 -OH + 2CH 3 .COOK. 
 
 In the actual preparation of glycol from ethylene bromide, 
 potassium acetate and alcohol (Demole), this saponification 
 ensues directly upon prolonged boiling of the mixture. 
 
 (b) By boiling with water and lead oxide or potassium 
 carbonate. These reagents serve to neutralize the acid as it 
 is formed, and so the reaction is facilitated: 
 
 ^-f 2HOH ^ C 2 H 4 (OH) 2 + 2HBr. 
 
PROPERTIES OF GLYCOLS 191 
 
 2. In the reduction of ketones to secondary alcohols, the 
 so-called pinacones, i.e. di-tertiary glycols, are obtained as by- 
 products (see pp. 72 and 134), thus: 
 
 CMe 2 :0 CMe 2 .OH 
 
 -f 2H = . (pmacone). 
 
 CMe 2 :O CMe 2 .OH * 
 
 3. By the careful oxidation of olefines by means of very 
 dilute KMn0 4 (p.. 45): 
 
 CH 2 :CH 2 + O + H 2 O = OH.CH 2 .CH 2 .OH. 
 
 Behaviour. 1. As in the case of the monohydric alcohols, 
 the hydrogen of the hydroxylic groups is directly replaceable 
 by potassium or sodium, with the formation of alcoholates, e.g. 
 OH C 2 H 4 ONa and C 2 H 4 (ONa) 2 , sodium and di-sodium glycols. 
 
 2. The metal in these compounds may be exchanged for 
 new alkyl groups by treatment with alkyl iodide, when gly- 
 collic ethers are obtained: 
 
 C 2 H 4 (ONa) 2 + 2C 2 H 6 I = 
 
 Glycol di-ethyl ether. 
 
 These ethers, like those of the monohydric alcohols, are stable, 
 and cannot be hydrolysed by dilute mineral acids or alkalis. 
 
 3. Acids act upon them to produce esters, which are either 
 normal esters or ester-alcohols (see p. 189). 
 
 The halogen esters of the glycols are termed chlor-, brom-, 
 or iodhydrins, e.g. glycol chlorhydrin, C 2 H 4 C1(OH), glycol di- 
 chlorhydrin, C 2 H 4 C1 2 , &c. The ester-alcohols which are formed 
 by the action of halogen hydride may also be regarded as 
 mono-substitution products of the monohydric alcohols, which 
 cannot be prepared by direct chlorination, e.g. C 2 H 4 C1(OH), 
 monochlorethyl alcohol. Similarly the di- halogen esters, 
 CHgCl-CHgCl, CH 2 Br.CH 2 Br, &c., are the di-substitution pro- 
 ducts of the paraffins, viz. ethylene dichloride and dibromide. 
 
 4. As the halogen atoms in the chlor-, brom-, and iodhy- 
 drins are readily replaceable, just as in C 2 H 5 C1 or C 2 H 5 I, 
 these compounds may be used for the preparation of most of 
 the other glycol derivatives; thus they yield thio-glycols with 
 potassium hydrosulphide, amines with ammonia, sulphonic acids 
 with sodic bisulphite, and nitriles with potassic cyanide. 
 
 5. Alkalis react with the glycol monochlorhydrins, and by 
 the elimination of HC1 yield cyclic anhydrides, e.g. ethylene 
 
 PTT 
 
 oxide, 2 J>0. It is interesting to note that these anhydrides 
 CJBL/ 
 
192 VIII. POLYHYDRIC ALCOHOLS 
 
 cannot be obtained by the elimination of water from the glycols 
 themselves. When ethylene glycol is heated with zinc chloride 
 at 230 water is eliminated, and the product obtained is acet- 
 aldehyde (or a polymer). This reaction is explained by assum- 
 ing the intermediate formation of unsaturated alcohols which 
 are not in themselves capable of existence, e.g. CH 2 :CH(OH), 
 but which immediately undergo transformation into the iso- 
 meric aldehydes or ketones: 
 
 CH 2 :CH.OH = CH 3 -CH:O. 
 
 6. As alcohols the glycols are readily oxidized. If they 
 contain the primary alcoholic group, they can yield aldehydes 
 and acids containing the same number of carbon atoms. If they 
 contain a secondary alcoholic group, they yield ketones, e.g. : 
 
 CH 2 OH.CH 2 OH CHO.CH 2 OH 
 
 and COOH.CH 2 OH COOH-COOH 
 
 CH 3 .CH(OH).CH 2 OH > CH 3 .CH(OH).COOH 
 
 CH 3 .CO.COOH, &c. 
 
 Methylene- and Ethylidene-glycols. (See Aldehydes.) 
 Ethylene glycol (glycol), OH.CH 2 .CH 2 .OH (Wurtz, A. 100, 
 110), is prepared from ethylene bromide by means of potas- 
 sium acetate in alcoholic solution (Demole), or of potassium 
 carbonate in aqueous solution, as given above (A. 192, 250). 
 For properties, see above. Its formula has been corroborated 
 by the determination of its vapour density. Oxidizing agents 
 transform it into gly collie acid, OH CH 2 CO OH, and oxalic 
 acid, OH- CO- CO- OH. 
 
 Propylene glycol is known in two isomeric forms, viz. : 
 
 (a) Trimethylene glycol, /3-Propylene glycol, Propa7ie-l:3- 
 diol, OH-CHg.CH^.CHg.OH, which is prepared from tri- 
 methylene bromide, and is a di-primary glycol boiling at 216. 
 It is also produced by the Schizomycetes fermentation of gly- 
 cerol (B. 14, 2270). 
 
 (b) a-Propylene glycol, Propane - 1 : 2 - diol, CH 3 -CH(OH). 
 CH 2 OH, can be prepared from propylene bromide in an 
 analogous manner, but is more easily obtained by distilling 
 glycerol with caustic soda. It boils at 188. It contains an 
 asymmetric carbon atom in the molecule, and becomes opti- 
 cally ( ) active when fermented, i.e. fission fungi destroy the 
 dextro modification more rapidly than the laevo. 
 
DERIVATIVES OF GLYCOLS 193 
 
 Four butylene glycols, and various amylene- and hexylene- 
 glycols, &c., are also known. Of these, the y-glycols (in which 
 the hydroxyls are in the positions 1:4, and which therefore 
 contain the grouping G(OH) C C C(OH) ) yield compounds 
 
 of the furane series by the formation of anhydrides (B. 22, 
 2567), and therefore stand in close relation to thiophene and 
 pyrrole. 
 
 Pinacone, Tetramethyl - ethylene glycol (2:3- Dimethyl - 
 butane-2:3-diol), (CH 3 ) 2 : C(OH) C(OH) : (CH 3 ) 2 . The hydrate, 
 (+ 6H 2 0), forms large quadratic tables; in the anhydrous 
 state it is a crystalline mass melting at 38 and boiling at 
 172. When warmed with dilute sulphuric or hydrochloric 
 acid it yields pinacoline, CH 3 CO C(CH 3 ) 3 , methyl tertiary- 
 butyl ketone or 2:2-dimethyl-butan-3-one (see p. 137): 
 
 In this reaction. an interesting intramolecular rearrangement 
 occurs, together with the elimination of water. 
 
 Numerous other pinacones are known. They may be ob- 
 tained by reducing ketones or synthetically (Lieben, M. 17, 68; 
 19, 16), and with acids yield the corresponding pinacolines. 
 
 DERIVATIVES OF THE GLYCOLS 
 
 The ethers, e.g. C 2 H 4 (OCH 3 ) 2 , are mostly colourless liquids 
 with ethereal odours, and have lower boiling-points than the 
 glycols. (Cf. Ether and Ethyl Alcohol.) They cannot be 
 readily hydrolysed. 
 
 The esters, e.g. C 2 H 4 (0 CO CH 8 ) 2 , are also mostly liquids, 
 and are readily hydrolysed. 
 
 The following esters of inorganic acids are interesting: 
 
 Glycol chlorhydrin, CH 2 C1.CH 2 -OH, obtained by passing 
 hydrogen chloride into warm glycol, or by the addition of 
 hypochlorous acid to ethylene, is a liquid miscible with water, 
 and boiling at 130; in this last respect differing from its corre- 
 sponding alcohol to almost the same extent as ethyl chloride 
 does from alcohol. 
 
 Glycollic di-nitrate, CoH 4 (N0 8 ) 2 , is prepared by acting on 
 glycol with sulphuric and nitric acids: 
 
 C 2 H 4 (OH) 2 + 2N0 2 .OH = C 2 H 4 (0-N0 2 ) 2 + 2H 2 O. 
 
 It is a yellowish liquid, insoluble in water, is readily hydro- 
 
 (3480) N 
 
194 VIII. POLYHYDRIO ALCOHOLS 
 
 lysed by alkalis to glycol and nitric acid, and hence the con- 
 stitution. The formation of such nitric esters, which are 
 highly explosive, is characteristic of the polyhydric alcohols 
 (see Nitroglycerine). 
 
 Ethylene cyanide, CN CH 2 CH 2 ON, obtained by the 
 action of potassium cyanide on ethylene dibromide, is a 
 crystalline solid, and on hydrolysis with alkalis yields 
 CO 2 H CH 2 CH 2 C0 2 H, succinic acid, and hence may be 
 regarded as succinonitrile. 
 
 Glycol monochlorhydrin with potassium cyanide yields 
 ethylene cyanhydrin, or the nitrile of /3-lactic acid, OHCH 2 . 
 CH 2 CN. Isomeric with it is ethylidene cyanhydrin, 
 CH 3 CH(OH)CN, the additive product of hydrocyanic acid 
 and aldehyde (p. 126). 
 
 Ethylene oxide, C 2 H 4 (Wurtz\ obtained by distilling 
 glycol chlorhydrin with caustic -potash solution, is a mobile 
 liquid of ethereal odour boiling at 13 -5. It is miscible with 
 water, and slowly converted into the glycol. 
 
 It has many of the properties of an unsaturated compound, 
 e.g. with HC1 it yields the chlorhydrin, with NH 8 the amino 
 alcohol, OH.CHg.CHg.NH^ and with chlorine ethylene di- 
 chloride. 
 
 It is largely owing to the last reaction that the ring consti- 
 
 s. 
 
 tution, i-. /O, and not the open-chain formula, CH 2 :CHOH, 
 CHy 
 
 is given to the compound. The formation of additive com- 
 pounds is accompanied by the rupture of the ring. Some of 
 the higher homologues of ethylene oxide are much more 
 stable, and do not yield additive compounds; this is due to 
 the fact that the ring is more stable and therefore less easy to 
 rupture (compare Polymethylene Compounds). 
 
 AMINES OF THE DIHYDRIO ALCOHOLS 
 
 These are derived from glycols by the replacement of one or 
 both hydroxyl groups by amino groups : 
 
 OH.CH 2 .CH 2 .NH 2 and NH 2 .CH 2 .CH 2 -NH 2 
 
 Hydroxy ethylamine Ethylene diamine. 
 
 In the former case compounds are obtained wnich possess 
 the properties of an amine in addition to those of an alcohol; 
 in the latter, diamines free from oxygen, which are analogous 
 to ethylamine, but are di-acid and not mono-acid bases. 
 
DIAMINES 195 
 
 Secondary and tertiary diamines corresponding with the 
 primary amiiie, NH 2 -CH 2 .CH 2 .NH 2 , are known, e.g.: 
 
 The methods by means of which these diamines can be 
 obtained are analogous to those described for the monamines, 
 viz. : 
 
 1. By heating ethylene bromide, &c., with alcoholic am- 
 monia to 100 (Hofmanri): 
 
 C 2 H 4 Br 2 + 2NH 3 = C 2 H 4 (NH 2 ) 2 + 2HBr; 
 C 2 H 4 (NH 2 ) 2 + C 2 H 4 Br 2 = (C 2 H 4 ) 2 N 2 H 2 + 2HBr; 
 (C 2 H 4 ) 2 N 2 H 2 + C 2 H 4 Br 2 = (CgH^N, + 2HBr. 
 
 The primary, secondary, and tertiary bases, which are formed 
 simultaneously, can be separated by fractional distillation. 
 
 The hydroxy amines (or alkines, Ladenburg) are obtained in 
 an analogous manner by using ethylene chlorhydrin, thus: 
 
 C 2 H 4 (OH)C1 -f NH 3 
 
 In this case also primary, secondary, and tertiary bases are 
 produced at the same time, and are separated by the fractional 
 crystallization either of their hydrochlorides or of their platini- 
 chlorides. 
 
 Ethylene chlorhydrin yields choline chloride (p. 196) with 
 trimethylamine. 
 
 2. Primary diamines are formed by the reduction of the 
 nitriles, C n H 2n (CN) a , e.g. by adding metallic sodium to the 
 hot alcoholic solution: 
 
 CN.CH 2 .CH 2 .CN-f 8H 
 
 Butylene diaraine. 
 
 Ethylene diamine, C 2 H 4 (NH 2 ) 2 , Diethylene diamine, 
 (C 2 H 4 ) 2 N 2 H 2 , &c., are colourless liquids distilling without de- 
 composition. The former boils at 123, and has an ammoni- 
 acal odour; the latter melts at 104 and boils at 146, and 
 
 is identical with piperazine, i.e. hexahydro-pyrazine. Hence 
 
 /~ITT r^TT 
 it possesses the constitutional formula NH<^QTT 2 ^Tr^NH, 
 
 and has a closed-chain constitution (Hofmann, B. 23, 3297). 
 
 Tetr amethylene - diamine, Butane -1:4- diamine, putrescine, 
 butylene-diamine, NH 2 CH 2 CH 2 CH 2 CH 2 . NH 2 , is prepared 
 according to method 2, and is also formed during the putre- 
 
196 VIII. POLYHYDRIC ALCOHOLS 
 
 faction of flesh. As a " y-diamine ", i.e. the diamine of a 
 y-glycol, it is closely related to pyrrole, from which it is 
 formed by the action of hydroxylamine (whereby a dioxime 
 is first produced), and subsequent reduction (B. 22, 1968). 
 
 Pentamethylene diamine, cadaverine, NH 2 (CHA'NHo, is 
 formed by the reduction of trimethylene cyanide, CN (CH 2 ) 3 
 CN, which on its part is prepared from trimethylene bromide 
 CH 2 Br.CH 2 .CH 2 Br, and KCN (Ladenburg). It is a colourless 
 syrupy liquid of very pronounced spermaceti and piperidirie 
 odour, solidifies in the cold, and boils at 178-179. It possesses 
 especial interest, because, being a S-diamine, it gives up ammonia 
 
 CH CH 
 
 and yields the cyclic base piperidine, C ' 
 
 (see this). 
 
 Many of these poly acid bases are found in decaying albumen 
 and in corpses, and are designated ptomaines or toxines (cf 
 e.g. B. 19, 2585). 
 
 Choline, bilineurine, ethykl - trimethyl - ammonium hydroxide, 
 OH.CH 2 .CH 2 .NMe 3 .OH (Strecker), is found in the bile 
 (x^?> bile), brain, yolk of egg, &c., being present in these 
 combined with fatty acids and gly eery 1- phosphoric acid as 
 lecithin. It is also found in herring brine, hops, beer, and 
 in many fungi, &c., and is obtained by boiling sinapine with 
 alkalis (the old name for this product was " Sincaline "). 
 Choline is a strong, deliquescent base, and readily absorbs 
 carbon dioxide from the air. It is not poisonous. The 
 chloride has the formula OH 'CoH^NMegCl. Concentrated 
 HN0 3 oxidizes choline to muscarine, C 5 H 15 N0 3 = (OH) 2 CH- 
 CH 2 NMe a OH, an excessively poisonous base, which is 
 present in toad-stool, Agaricus muscarius. 
 
 By transforming choline, by means of hydriodic acid, into 
 its iodide, CH 2 I-CH 2 'NMe 3 I, and treating the latter with 
 moist oxide of silver, and also from the putrefaction of choline, 
 neurine (vevpov, nerve), trimethyl -vinyl -ammonium hydroxide, 
 CH 2 :CHNMe 3 -OH (Hofmann), is obtained. This base, con- 
 taining the unsaturated radical " vinyl ", C 2 H 3 , is very similar 
 to choline, and can also be prepared from brain substance; it 
 is only known in solution, and is very poisonous. It can be 
 re-transformed into choline. (For this, and also for deriva- 
 tives, see e.g. A. 267, 249; 268.) 
 
 Another natural compound related to hydroxy ethylamine 
 is taurine, C 2 H 7 NS0 3 (Gmelin), which is present in combina- 
 tion with choljc acid as tauroeholic acid in the bile of oxen 
 
 
TRIHYDRIC ALCOttOLS 19? 
 
 and many other animals, also in the kidneys, lungs, &c. It 
 crystallizes in large monoclinic prisms, is readily soluble in hot 
 water, but insoluble in alcohol, and decomposes when strongly 
 heated. Its constitution follows from its synthesis. 
 
 Isethionic acid, hydroxy-ethyl-sulphonic acid, OH GEL* 
 CH 2 S0 2 OH, is obtained when carbyl sulphate, C 2 H 4 S 2 6 
 (from C 2 H 4 and S0 3 ), is boiled with water; its constitution 
 follows from its properties, and also from the fact that it 
 may be obtained by the oxidation of the hydroxymercaptan, 
 OH-CH^CEL-SH. Isethionic acid with PC1 5 yields the 
 chloride CH 2 C1 CH 2 S0 2 C1, and this with water gives chloro- 
 ethyl-sulphonic acid, CH 2 C1 CH 2 S0 2 OH, which with am- 
 monia yields taurine; its constitution must, therefore, be 
 NH 2 .CH 2 .CH 2 -S0 2 .OH, amino-ethyl-sulphonic acid, and in 
 accordance with this constitution it unites in itself the pro- 
 perties of an alcoholic amine and a sulphonic acid, and is 
 therefore at the same time a base and an acid. It forms 
 unstable salts with alkalis, but not with acids, the groups 
 NH 2 and S0 3 H in the molecule practically neutralizing one 
 another, so that its reaction is neutral. Nitrous acid converts 
 it into isethionic acid, a reaction analogous to the decom- 
 position of the primary amines by this reagent. As an alky 1 
 sulphonic acid, it is not hydrolysed by boiling with alkalis and 
 acids. It is sometimes represented as a cyclic ammonium salt, 
 
 CH 2 .NH 3 
 CH 2 -SO 3 . 
 
 B. Trihydric Alcohols 
 
 The molecule of each trihydric alcohol contains three hy- 
 droxyl groups, each attached to a different carbon atom. They 
 may be regarded as analogous to the hydroxides of tervalent 
 meteU e.g. C S H 6 (OH) 8 arid A1(OH) 3 . They can give rise to 
 three distinct groups of derivatives according as one, two, or 
 three of the hydroxyls react, e.g. chlorides C 3 H 5 C1(OH) 2 , 
 monochlorhydrin; C 3 H 5 C1 2 -OH, dichlorhydrin; and C 3 H 5 C1 3 , 
 trichlorhydrin of glycerol. Similarly for acetates, amino- 
 derivatives, &c. 
 
 Although the compound CH(OH) 3 , ortho-formic acid, is not 
 known, derivatives, e.g. ethyl ortho-formate, CH(OEt) 3 , (p. 142), 
 and similarly ethyl ortho-acetate, CH 8 -C(OEt)3, can readily be 
 prepared. 
 
19$ Vtlt. fOLYHYDHIC ALCOHOLS 
 
 Glycerine, glycerol, propane-I:2:3-triol, OH CH 2 . CH(OH) 
 CH 2 -OH. (Scheek, 1779; formula established by Pelouze in 
 1836, and constitution by Berthelot and Wurtz.) 
 
 Synthesis. By heating 1 : 2 : 3-trichlorpropane with water tc 
 170: 
 
 CH 2 C1 CH 2 .OH 
 
 CHC1 +3H-OH = CH-OH + 3HC1. 
 CH 2 C1 CH 2 .OH 
 
 The trichlorpropane is itself obtainable from isopropyl iodide 
 (which can also be prepared synthetically) by conversion into 
 propylene, addition of C1 2 , and heating the propylene dichloride 
 thus formed with iodine chloride (Friedel and Silva, Bull. Soc. 
 Chim. 20, 98): 
 
 CH 3 .CHI.CH 3 CH 3 .CH:CH 2 
 
 CH 3 .CHC1-CH 2 C1 CH 2 C1.CHC1.CH 2 C1. 
 
 Glycerol is also produced when allyl alcohol is oxidized with 
 very dilute potassium permanganate : 
 
 CH 2 :CH-CH 2 .OH OH.CH 2 .CH(OH).CH 2 .OH. 
 
 The constitution of glycerol follows from these syntheses and 
 also from its relation to tartronic acid (p. 199); each of the 
 three hydroxyls is attached to a separate carbon atom. 
 
 Preparation. Glycerol is usually prepared by hydrolysing 
 the natural fats and oils (especially olive-oil), which are the 
 glyceryl salts of fatty and other acids (p. 158). The hydro- 
 lysis may be effected by means of superheated steam, by 
 heating with lime and water, or with sulphuric acid. They 
 are thus resolved into their components, glycerol and acid; 
 the glycerol distils over with the superheated steam, and may 
 be purified by animal charcoal. Hydrolysis by means of an 
 enzyme contained in castor-oil seeds is used commercially. 
 
 In the manufacture of stearic acid (p. 161) the fats are 
 hydrolysed with sulphuric acid, when the glycerol is con- 
 verted into glyceryl-sulphuric acid, C 3 H 5 (OH) 2 (0*S0 3 H), from 
 which it can be obtained by boiling with water or with lime. 
 In the preparation of plaister, by boiling fats with lead oxide 
 and water (p. 160), an aqueous solution of glycerol is obtained 
 together with the insoluble lead plaister. 
 
 Large quantities of glycerol are now recovered from the 
 liquors from which the hard soaps (p. 158) have separated. 
 
 Properties. It is a thick, colourless syrup, of specific gravity 
 
GLYCEROL 199 
 
 1-27, solidifies, when strongly cooled, to crystals like those of 
 sugar-candy, which melt at 17. It boils at 290, but, when 
 impure, can be distilled without decomposition under diminished 
 pressure only, viz. at 170 under 12 mm. It is very hygro- 
 scopic, and mixes with water and alcohol in all proportions, 
 but is insoluble in ether. 
 
 Uses. In the manufacture of liqueurs, fruit preserves, wine, 
 &c.; for non-drying stamp colours and blacking; when mixed 
 with glue, in book printing; as a healing ointment for external 
 use; but especially in the manufacture of nitro-glycerine and 
 in the colour industry. 
 
 Behaviour. 1. With alkalis and other metallic hydroxides 
 it forms alcoholates, which are readily decomposed again into 
 their components. 
 
 2. As a trihydric alcohol the hydrogen atoms of the OH 
 groups can be replaced by alkyl radicals yielding ethers, e.g. 
 mono-ethylin, C 3 H 5 (OH) 2 (OC 2 H 5 ),and triethylin, C 3 H 5 (OC 2 H 5 ) 3 , 
 liquids which boil without decomposition. 
 
 3. As an alcohol it forms the most various esters : thus, with 
 sulphuric acid, the easily saponifiable glyceryl-sulphuric acid, 
 C 3 H 5 (OH) 2 (0 S0 3 H); with phosphoric acid, glyceryl-phosphoric 
 acid, C 3 H 5 (OH) 2 (O.P0 3 H 2 ); with nitric acid, glyceryl trini- 
 trate, C 3 H^(0'N0 2 ) 3 ; with hydrochloric acid the chlornydrins ; 
 and with the higher fatty acids the fats. For its behaviour 
 with hydriodic acid, or iodine and phosphorus, see p. 60. 
 
 4. It yields compounds of a mercaptan or aminic character 
 by exchange of OH for SlTor NH 2 . 
 
 5. When distilled with dehydrating agents, e.g. phosphorus 
 pentoxide, or, better, anhydrous potassium hydrogen sulphate, 
 two molecules of water are eliminated from each molecule of 
 glycerol, and acrolein (p. 130) is formed. By the indirect sepa- 
 ration of one mol. H 2 0, glycide alcohol, C 3 H 6 2 , is obtained. 
 
 6. Oxidizing agents convert it, according to circumstances, 
 either into glyceric, OH CH 2 . CH(OH) . C0 2 5, tartronic, 
 C0 2 H.CH(OH).C0 2 H, or mesoxalic acid, C0 2 JB^ CO . CO JEt, 
 or acids with a smaller number of carbon atoms. The for- 
 mation of the three above-mentioned acids indicates that 
 glycerol molecule must be built up of two primary and one 
 secondary alcoholic groups, as represented in the formula 
 already given. Halogens oxidize and do not substitute. 
 
 7. It yields 'normal butyl alcohol, caproic acid, and butyric 
 acid by certain fermentations. (Cf. B. 16^ 884.) 
 
 8. It is largely used in the preparation of allyl alcohol (p. 82), 
 
200 VIII. POLYttYDRIC ALCOHOLS 
 
 acrolein (p. 130), allyl iodide (p. 65), isopropyl iodide (p. 60), 
 and formic acid (p. 148). 
 
 DERIVATIVES 
 
 Chlorhydrins (hydrochloric esters). Mono- and dichlor- 
 hy drills are formed by the action of hydrochloric acid on 
 glycerol, and trichlorhydrin by the action of phosphorus 
 pentachloride on the mono- or di-compounds. Each of the 
 two first-named exists in two isomeric modifications. 
 
 a-Monochlorhydrin, S-Chloro-propane-l-.Z-diol, CH 2 (OH)' 
 CH(OH).CH 2 C1, is formed from epichlorhydrin, C 3 H 5 O.C1, 
 (see below), and water; a-dichlorhydrin, I:3-dichloro-propane-2-ol, 
 CH 2 C1 CH(OH) . CH 2 C1, from epichlorhydrin and HC1; /3-mono- 
 chlorhydrin, CH 2 (OH).CHC1-CH 2 (OH), and ^-dichlorhydrin, 
 CH 2 C1.CHC1-CH 2 .OH, by the addition of hypochlorous acid 
 to allyl alcohol or to allyl chloride. 
 
 The chlorhydrins are liquids sparingly soluble in water, and 
 readily soluble in alcohol and ether. Their boiling-points are 
 much below that of glycerol. 
 
 Glycide Compounds. By the elimination of water from 
 glycerol a compound is obtained which unites within itself 
 the properties of ethylene oxide and of a monohydric alcohol, 
 viz. glycide alcohol, 
 
 OH-CHjj.CH.OH OH.CH 2 .CH\ 
 
 CHj-OH " CH2/' 
 
 which is isomeric with propionic acid. 
 
 It may be prepared by the abstraction of HC1 from a-mono- 
 chlorhydrin by means of baryta, just as ethylene chlorhydrin 
 yields ethylene oxide. It is a colourless liquid, boiling at 162, 
 and miscible with water, alcohol, and ether. It combines with 
 H 2 0, yielding glycerol, and with HC1 yielding the chlorhydrin, 
 and, as an alcohol, forms esters (glycide esters), &c. Its hydro- 
 chloric ester is epichlorhydrin, 
 
 CH 2 C1- 
 
 isomeric with chlor-acetone and propiony) chloride, a mobile 
 liquid of chloroform odour, boiling at 117, which is formed by 
 the elimination of HC1 from either of the dichlorhydrins. Like 
 ethylene oxide it is capable of combining with ELO, HC1, &c. 
 Esters of Nitric Acid. Mononitrin, C 3 H 6 (OH) 2 (O 
 
POLYHYDRIC ALCOHOLS 201 
 
 and trinitrin or nitre-glycerine, C 3 H 5 (0'N0 2 ) 3 , are known. 
 The latter is prepared by treating glycerol with a cold mix- 
 ture of concentrated nitric and sulphuric acids (B. 1899, 32, 
 1444). It is a colourless oil, insoluble in water, poisonous, 
 and of a sweet, burning, aromatic taste. Sp. gr. 1*6. M.-pt. 
 about 11-12. It burns without explosion, but explodes with 
 terrible violence when quickly heated or when struck (Nulel's 
 explosive oil). When mixed with kieselguhr in the proportion 
 of three parts to one it forms dynamite (Nobel, 1867), which 
 is exploded by fulminate of mercury with frightful force. It 
 is hydrolysed by alkalis and by ammonium sulphide, yielding 
 
 glycerol and nitric acid, and hence its constitution as a nitrate, 
 3 H 5 (0 N0 2 ) 3 , and not a nitro-derivative, e.g. C 3 H 2 (N0 2 ) 3 (OH) 3 . 
 
 The esters derived from glycerol and the fatty acids are 
 largely met with in vegetable and animal oils and fats. Most 
 of these are the normal esters, e.g. glyceryl tripalmitate, tripal- 
 mitin, C 3 H 5 (0 CO C 15 H 31 ) 3 , tristearin, &c. (see p. 158, et seq.). 
 
 These esters can also be obtained artificially, as can also the 
 mono- arid dihydric esters, e.g. monopalmitin, (OH) 2 C 3 H 5 .O 
 CO.C 15 H 31 , and dipalmitin, OH . C 3 H 5 (0 CO C 15 H 31 ) 2 . 
 
 Most are wax-like solids, and, on hydrolysis, yield as ulti- 
 mate products glycerol and the fatty acid. With the normal 
 esters this hydrolysis occurs in stages yielding the mono- 
 hydroxy ester, then the dihydroxy, and finally glycerol. 
 
 C. Tetra-, Penta-, and Hexahydric Alcohols 
 
 These alcohols can react respectively with 4, 5, or 6 mole- 
 cules of a monobasic acid to form neutral esters, and conse- 
 quently 4, 5, or 6 alcoholic hydroxyls are to be assumed as 
 present in their molecules. 
 
 The number of hydroxyls present in an alcohol is usually 
 
 determined from the number of acetyl groups present in the 
 
 ester which is formed when the alcohol is heated with acetic 
 
 anhydride and anhydrous sodic acetate, thus: 
 
 C 6 H 8 (OH) 6 + 6(CH 3 .CO) 2 = C 6 H 8 (0-CO.CH 3 ) 6 + 6CH..CO.H. 
 
 One of the simplest methods of determining the number of 
 acetyl groups is to hydrolyse the acetate by distilling with ben- 
 zene sulphonic acid in steam, and to titrate the acetic acid in 
 the distillate with standard barium hydroxide, using phenol- 
 phthalein as indicator (Sudborough and Thomas, J. C. S. 1905, 
 1752). 
 
202 VIII. POLYHYDRIC ALCOHOLS 
 
 The ester of any alcohol in question may also be prepared by 
 the aid of an acid containing halogen, bromo-benzoic acid being 
 especially suitable for this; and from the percentage of bromine 
 found in the ester, the number of acid radicals which have entered 
 the molecule, i.e. the number of hydroxyls, can be deduced. 
 
 The polyhydric alcohols are solid crystalline compounds of 
 sweet taste. Many occur as natural products, and they may 
 be obtained by the reduction of the corresponding hydroxy 
 aldehydes, hydroxy ketones, or hydroxy monobasic acids (man- 
 nonic acid, &c.) by sodium amalgam. (E. Fischer, B. 22, 2204.) 
 Conversely, cautious oxidation by bromine water transforms 
 them first into sugars (hydroxy aldehydes), and then into the 
 corresponding acids. As a rule they cannot be volatilized 
 without decomposition. Their derivatives are exactly analo- 
 gous to those of glycol and glycerol. 
 
 Their constitution follows from the generalization already 
 repeatedly referred to, viz. that not more than one hydroxyl 
 group can be attached to the same carbon atom without the 
 immediate separation of water, so that a tetrahydric alcohol 
 must contain at least 4, and a hexahydric alcohol at least 6, 
 atoms of carbon. The tetrahydric alcohol erythritol, C 4 H 6 (OH) 4 , 
 has thus the formula: 
 
 OH CH 2 CH(OH) CH(OH) CH 2 OH, 
 
 and mannitol, the simplest of the hexahydric alcohols, C 6 H 8 (OH) 6 , 
 the formula: 
 
 OH.CH 2 (CH.OH) 4 .CH 2 .OH. 
 
 All the common polyhydric alcohols have a normal carbon 
 chain, as on reduction with hydriodic acid they yield normal 
 secondary iodides, e.g. erythritol yields 2-iodo-butane, CH 3 - 
 CHI.CH 2 .CH 3 . 
 
 1. Tetrahydric Alcohols. Ortho-carbonic ether, C(OC 2 HJ 4 , 
 is to be regarded as the ether of the hypothetical alcohol, C(OH) 4 , 
 which may be looked upon as the hydrate of carbonic acid, 
 but is itself incapable of existence. It is a liquid of ethereal 
 odour, boiling at 159. 
 
 Erythritol (Butane-tetrol) occurs in the free state in Proto- 
 coccus vulgaris, and combined with orsellinic acid as an ester 
 (erythrin), in many lichens and algas. It forms large quad- 
 ratic crystals, sparingly soluble in alcohol arid insoluble in 
 ether. M.-pt. 112; b.-pt. about 300. 
 
 2. Pentahydric Alcohols, Arabitol, OH . CH 2 . (CH - OH) 3 . 
 
HEXAHYD&IC ALCOttOLS 203 
 
 CH 2 OH (from arabinose by reduction). Xylitol, by the 
 reduction of xylose, is stereo - isomeric ; and rhamnitol, 
 OH CH 2 (CH . OH) 4 . CH 8 , m.-pt. 121, from rhamnose, is 
 homologous. 
 
 3. Hexahydric Alcohols, Mannitol, OH.CH 2 .(CH.OH) 4 . 
 CH 2 OH (Proust, 1800), is found in many plants, for instance 
 in the larch, in Viburnum Opulus, in celery, in the leaves of 
 Syringa vulgaris, in sugar-cane, in Agaricus integer (of the dry 
 substance of which it forms 20 per cent), in rye bread, and 
 especially in the manna ash, Fraxinus ornus, the dried juice 
 of which constitutes manna. It can be prepared from grape- 
 sugar, or still better from fruit sugar, from which it only 
 differs in composition by containing two atoms of hydrogen 
 more in the molecule, by reduction with sodium amalgam. 
 
 It crystallizes in fine needles or rhombic prisms, and is 
 readily soluble in cold water and boiling alcohol. It is 
 dextro-rotatory, but a laevo-rotatory and an inactive modi- 
 fication are also known. (See Mannonic Acid.) M.-pt. 166. 
 When heated it is converted into its anhydrides, mannitan, 
 C 6 H 12 5 , and mannide, C 6 H 10 4 . Cautious oxidation converts 
 mannitol into a mixture of mannose, OH CH 2 (CH OH) 4 CHO, 
 and fructose, OH.CH 2 (CH.OH) 3 .CO.CH 2 .OH. Nitric acid 
 oxidizes it to saccharic acid, C0 2 H . (CH OH) 4 COJE ; hydri- 
 odic reduces it to secondary hexyl iodide, CH 3 CHI (CH 2 ) 3 
 CH 8 (p. 59). 
 
 The molecule of mannitol contains 4 asymmetric carbon 
 atoms, e.g. : 
 
 OH.CH 2 .CH(OH).CH(OH).CH(OH).OH(OH).CH 2 OH, 
 
 and hence a number of stereo-isomerides are known, e.g. d-, 1-, 
 and r-mannitol, d-, 1-, ?--sorbitol, and dulcitol, which is optically 
 inactive owing to the fact that its molecule is symmetrical in 
 configuration. (See Stereochemistry of the Sugars.) 
 
 The sugars are closely related to the penta- and hexa- 
 hydric alcohols, being the corresponding polyhydric aldehydes 
 or ketones. The alcohols as a rule are not fermented by 
 yeast, and do not reduce an alkaline cupric solution, dulcitol 
 excepted. 
 OXIDATION PRODUCTS OF THE POLYHYDRIC ALCOHOLS 
 
 Just as the monohydric alcohols are oxidized to aldehydes, 
 ketones, and acids, so the polyhydric alcohols pass, on oxida- 
 tion, into aldehydes, ketones, and polybasic acids. 
 
204 
 
 VIII. POLYHYDRIC ALCOHOLS 
 
 Further, by this oxidation of the polyhydric alcohols we 
 obtain not only aldehydes, ketones, and acids, but also 
 numerous compounds which possess a double chemical char- 
 acter in so far as they unite in themselves the properties of 
 more than one of these classes of compounds. These are the 
 hydroxy aldehydes, which are at the same time aldehyde and 
 alcohol, the hydroxy ketones, at the same time ketone and 
 alcohol, the hydroxy acids, aldehyde acids, ketone acids, and 
 ketone aldehydes. 
 
 An aldehyde acid, for instance, is capable, as an acid, of 
 forming salts, esters, and amides on the one hand; and on the 
 other, as an aldehyde, it is able to reduce an ammoniacal 
 silver solution, to combine with NaHS0 3 , and to react with 
 hydroxylamine, &c. 
 
 SUMMARY OF THE OXIDATION PRODUCTS 
 (a) Of the di-primary alcohols. 
 CHO 
 
 CH 2 -OH 
 
 CH 2 -OH 
 Glycol 
 
 CH 2 -OH 
 
 "^CHO 
 
 Glycollic aldehyde 
 
 CHO 
 
 Glyoxal 
 
 CH 2 -OH 
 CO-OH 
 
 Glycollic acid 
 
 ^ CHO 
 
 * CO-OH^ 
 
 Glyoxalic acid. 
 
 CO- OH 
 CO-OH 
 
 Oxalic acid 
 
 Possible products: Di-aldehydes, dibasic acids, hydroxy 
 aldehydes, hydroxy acids, aldehyde acids. 
 
 (b) Of the hydroxy primary-secondary alcohols. 
 
 CH, 
 
 Methyl-glyoxal 
 
 CH 2 -OH 
 
 -Propylene 
 glycol 
 
 CH-OH - 
 CHO 
 
 (Lactic aldehyde, 
 unknown) 
 
 CH 3 
 CH-OH 
 CO- OH 
 
 Lactic acid 
 
 CO- OH 
 
 .=0 
 
 If 
 
 I! 
 
MONOHYDROXY FATTY ACIDS 205 
 
 Possible products: hydroxy aldehydes, hydroxy ketones, 
 ketone aldehydes, hydroxy acids, ketone acids. 
 
 (c) Of the di-secondary alcohols: hydroxy ketones, di- 
 ketones. (No dibasic acids or alcohol acids, C n .) e.g. : 
 
 CHg-CH-OH CH 3 .CH.OH CH 3 .CO 
 
 CH 3 .CH.OH " " CH 3 .CO ' CH 3 .CO 
 
 Di-secoudary butylene glycol Dimethyl-ketol Di-acetyl. 
 
 (d) The tri- and polyhydric alcohols are capable of yielding 
 the most various products upon oxidation, especially poly- 
 hydroxy ketones, polyhydroxy acids, keto-acids, and polybasic 
 acids. 
 
 Of all these oxidation products, the most important are the 
 hydroxy acids, the polybasic acids, and the keto-acids. For 
 the sake of convenience the hydroxy monobasic acids will be 
 treated of first. 
 
 IX. HYDROXY MONOBASIC ACIDS AND COM- 
 POUNDS RELATED TO THEM 
 
 A. Monohydroxy Fatty Acids 
 
 These compounds may be regarded as monohydroxy deri- 
 vatives of the fatty acids, e.g. OH-CHg-COnH, hydroxy acetic 
 acid, or glycollic acid, OH CH 2 CH 2 C0 2 H, ^-hydroxy pro- 
 pionic acid, or /2-lactic acid, &c. 
 
 They combine within themselves the properties of a mono- 
 basic acid and of an alcohol, and are consequently capable 
 of forming derivatives as alcohols, as acids, and as both 
 together. 
 
 The lowest members of the series, which are the most im- 
 portant, are glycollic acid and lactic acid, both syrupy liquids 
 which solidify to crystalline masses in the desiccator, and readily 
 give up water to form anhydrides. They cannot be volatilized 
 without decomposition; and are readily soluble in water, and 
 for the most part also in alcohol and ether. 
 
 Formation. 1. By the regulated oxidation of the glycols. 
 (See Summary, p. 204.) 
 
 2. From the fatty acids, through their monohaloid substi- 
 tution products, the halogen of these being easily replaced by 
 
206 IX. HTDROXY MONOBASIC ACIDS 
 
 hydroxyl, either by means of moist oxide of silver or often by 
 prolonged boiling with water alone: 
 
 CH 2 C1.C0 2 H + H 2 = CH,(OH).C0 2 H 
 
 This reaction is conditioned by the halogen having the 
 a-position with respect to the carboxyl (cf. pp. 169 and 170). 
 
 For a reaction of these haloid-substitution products in a 
 different direction, see fi- and y-hydroxy acids. 
 
 3. From the aldehydes and ketones containing 1 atom of 
 carbon less, by the preparation of their hydrocyanic acid com- 
 pounds, cyanhydrins (see pp. 126 and 135), and hydrolysis 
 of the latter. Thus, irom aldehyde is produced ethylidene 
 cyanhydrin, and from this a-lactic acid: 
 
 CH 3 .CH(OHXCN) + 2H 2 = CH 3 .CH(OH).CO 2 H + NH 3 . 
 
 Since the aldehydes and ketones are easily obtained from 
 the corresponding alcohols, this reaction furnishes a means of 
 preparing the acids, C n H 2n (OH) (C0 3 H), from the alcohols, 
 C n H 3n+l (OH), i.e. of introducing carboxyl into the latter in 
 place of hydrogen; this is a most important synthesis. 
 
 4. From the glycollic cyanhydrins by saponification, e.g. 
 /2-lactic acid from ethylene cyanhydrin: 
 
 OH.CH 2 .CH 2 .CN + 2H 2 = OH-CH^CHa-CO.^ -f NH 3 . 
 
 As the cyanhydrins can be readily obtained from the glycols 
 (p. 191), this formation of hydroxy acids represents an exchange 
 of a hydroxyl of the glycol for carboxyl, and is analogous to 
 the formation of acetic acid from methyl alcohol. Thus : 
 
 OH.CH 2 .CH 2 -OH OH-CH 2 .CHoCl 
 
 OH.CH 2 -CH 2 .CN OH.CH 2 .CH 2 .C0 2 H 
 
 and CHj-OH CH 3 C1 CH 3 .CN CH 3 .CO 2 H. 
 
 5. By the reduction of aldehyde acids or ketonic acids, e.g. 
 lactic from pyruvic acid (p. 225). This reaction corresponds 
 with the formation of the alcohols from the aldehydes or 
 ketones by reduction. 
 
 6. By the action of nitrous acid upon amino acids (see Gly- 
 cocoll); a reaction analogous to the formation of alcohols from 
 amines (p. 108). 
 
 7. Hydroxy acids of the fatty series containing an equa] 
 number of carbon atoms result by direct oxidation, if a CH 
 
NOMENCLATURE OF HYDROXY ACIDS 207 
 
 group, i.e. a "tertiary" hydrogen atom, is present in the 
 original acid (E. Meyer, B. 11, 1283; 12, 2238): 
 
 (CH 3 ) 2 CH.C0 2 H 
 
 laobutyric acid a-Hydroxy-isobutyric acid. 
 
 Constitution and Isomers. As hydroxy compounds of the 
 fatty acids, the acids of the foregoing series can exist in as 
 many modifications as the monohaloid fatty acids. Thus there 
 is only one glycollic acid, corresponding with monochloracetic 
 acid, but two lactic acids corresponding with a- and /2-chloro- 
 propionic acids are possible, and both actually exist; they 
 are designated as a- and /3-hydroxy propionic acids: 
 
 O^ (a-chloro-propionic acid). 
 CH 3 CH(OH)-CO^[ (a-hydroxy -propionic acid or common lactic 
 
 acid). 
 
 CH 2 ICH 2 -CO 2 H (/3-iodo-propionic acid). 
 OH-CH 2 -CH 2 -CO 2 H (jS-hydroxy propionic acid or /3-lactic acid) 
 
 From the two butyric acids can be theoretically derived: 
 
 (a) From the normal acid: 
 
 CH 3 .CH 2 .CH 2 .CO 2 H, 
 
 y ft 
 
 an a-, ft-, and y-hydroxy butyric acid. 
 
 (b) From isobutyric acid : 
 
 an a- and /3-hydroxy isobutyric acid. 
 
 Systematic Nomenclature. OH . CH 2 CH 2 C0 2 H, Propane-3- 
 jlrl-acid; (CH 3 ) 2 C(OH) C0 2 H, 2 -Methyl-propane- 2 -ol-l-add] 
 OH.CH 2 .CH 2 .CH 2 .C0 2 H, Butane4-ol-\-add, &c. 
 
 The constitution of these hydroxy acids can often be deduced 
 from their methods of formation. Thus the preparation of 
 common lactic acid from aldehyde, CH 3 -CHO, according to 
 method 3, shows that it contains the group CH 3 -CH:, "ethy- 
 lidene"; it is therefore termed "ethylidene lactic acid" On 
 the other hand, the formation of /3-hydroxy propionic acid 
 from glycol cyanhydrin, according to 4, is a proof of its con- 
 taining the group .CH 2 .CH 2 ., "ethylene"; hence the name 
 "ethylene lactic acid". 
 
 The constitution can also frequently be deduced from a 
 study of their oxidation products; if they can be oxidized, 
 for instance, to dibasic acids (which contain two carboxyls), 
 
208 IX. HYDROXY MONOBASIC ACIDS 
 
 then they must contain a primary alcohol group, CH 2 OH, 
 since only such a group yields a new carboxyl on oxidation. 
 Ethylene lactic acid is therefore a "primary" alcohol acid. 
 Its isomer, ethylidene lactic acid, is similarly a "secondary" 
 alcohol acid, while a-hydroxy isobutyric acid is a " tertiary 
 alcohol acid, i.e. acid and tertiary alcohol at the same time. 
 
 Behaviour. 1. The double chemical character of the hydroxy 
 acids will be dealt with more in detail under Glycollic Acid. 
 As acids they form salts, esters, and amides; as alcohols they 
 yield ethers, amines, &c. Of these derivatives the alcoholic 
 amines of the acids, the so-called amino acids, are of especial 
 interest. (See Glycocoll, p. 211.) 
 
 2. The hydroxy acids form different kinds of anhydrides, 
 viz.: (a) as alcohols (see Di-glycollic Acid); (b) one molecule 
 as alcohol forms with a second molecule as acid an ester, with 
 elimination of H 2 (see Glycollic Anhydride); (c) operation b 
 is repeated, the first molecule acting as acid, and the second 
 as alcohol (see Glycolide); (d) one molecule loses H 2 0, with 
 formation of an " intramolecular " anhydride, a so-called ladone 
 (see p. 217). 
 
 3. For behaviour upon oxidation see p. 207, and also the 
 individual compounds. 
 
 4. Just as the alcohols readily give up water, yielding 
 olefines, so many of the hydroxy acids, especially the ft-, can 
 be transferred into unsaturated monobasic acids. (See Hydra 
 cry lie Acid, p. 216.) 
 
 5. When warmed with hydriodic acid, the hydroxy acids 
 are reduced to the corresponding fatty acids, just as the 
 alcohols are converted by this reagent into hydrocarbons. 
 
 6. When the a-hydroxy acids are warmed with dilute sul- 
 phuric acid, formic acid is produced together with the alde- 
 hyde or ketone which would give rise to the acid, according 
 to method 3. The /2-hydroxy acids, on the other hand, decom- 
 pose into water and acids of the acrylic series. Thus : 
 
 CH 3 .CH:0-f H- 
 OH.CH 2 .CH 2 .CO 2 H = CH 2 :CH.CO 2 H + 
 
 The a-, /?-, -y-, &c., hydroxy acids also differ from each 
 other in the facility with which they form anhydrides. (See 
 Lactones, p. 217.) 
 
GLYCOLLIC ACID 209 
 
 Glycollic Acid, Hydroxy-acetic acid, Ethanolic add, OH-CH 2 . 
 C0 2 H (Strecker, 1848), occurs in unripe grapes, in the leaves of 
 the wild vine, &c. 
 
 Formation. 1. By the oxidation of glycol with dilute HN0 3 
 ( Wurtz). 
 
 2. Together with glyoxal and glyoxylic acid, by the oxida 
 tion of alcohol with dilute HN0 3 . 
 
 3. By the reduction of oxalic acid with Zn + H 2 S0 4 . 
 
 4. From formic aldehyde synthetically, according to method 
 3, y. 206. 
 
 5. It is usually prepared by boiling chloro-acetic acid with 
 water in the presence of marble, the marble serving to 
 neutralize the HC1 formed in the reaction (A. 200, 76): 
 
 CH 2 C1.C0 2 H + H 2 ^ OH.CH 2 .C0 2 H + HC1. 
 
 Properties. It forms colourless needles or plates, is readily 
 soluble in water, alcohol, and ether, and melts at 80. Nitric 
 acid oxidizes it to oxalic acid. The alkaline salts are hygro- 
 scopic, the calcium salt and the magnificent blue copper salt 
 are sparingly soluble in water. K = 0*0152. 
 
 Derivatives. (See table, p. 210.) As an acid, gly collie acid 
 forms salts, esters e.g. ethyl glycollate a chloride, glycollyl 
 chloride, and glycollamide, all of which are readily hydro- 
 lysed, some of them even on warming with water. All those 
 derivatives still retain their alcoholic character. If, on the 
 other hand, glycollic acid forms derivatives as an alcohol, the 
 properties of the alcoholic derivatives in question are combined 
 with those of an acid, since the hydroxyl of the alcoholic 
 group, -CHg-OH, enters into reaction, while the carboxyl 
 group remains unchanged. These derivatives are either 
 ethers, such as ethyl-glycollic acid (see table), or e.g. amines, 
 such as glycocoll, and, as alcoholic derivatives, they are not 
 readily hydrolysed; or they are esters ^f glycollic acid, as 
 alcohol, e.g. acetyl-glycollic acid, CH 2 (0 . CO CH 3 ) . C0 2 H, or 
 monocMoracetic acid, CH 2 C1-C0 2 H (the hydrochloric ester 
 of glycollic acid), and then they are of course saponifiable. 
 These latter compounds still retain their acid character, and 
 therefore form, on their part, esters, chlorides, and amides, 
 which are also readily hydrolysed. The following table gives 
 a summary of the more important derivatives of glycollic 
 acid : 
 
 (B480) 
 
210 
 
 IX. HYDROXY MONOBASIC ACIDS 
 
 Acid Derivatives 
 
 Alcoholic Derivatives. 
 
 Mixed Derivatives. 
 
 HO.CH 2 .CO-ONa 
 
 Sodium glycollate. 
 
 
 NaO.CH 2 .CO-ONa 
 Di-sodium glycollate. 
 Hygroscopic; decomp. 
 by H^.0 into Na salt 
 and NaOH. 
 
 HO.CH 2 .CO-OC 2 H 5 
 Ethyl glycollate. 
 Liquid, b.-pt. 160. 
 
 OCiHs-CHa-CO-OH 
 
 Ethyl-glycollio acid. 
 Liquid, b.-pt. 206. 
 
 C 2 H S .O.CH 2 .CO.OC 2 H 5 
 Ethylic ethyl-glycollate. 
 Liquid, b.-pt. 152. 
 
 HO-CH 2 .CO.C1 
 
 Glycollyl chloride. 
 Oil ; decomposes on 
 volatilizing. 
 
 CH 2 C1.CO.OH 
 Moiiochloracetic 
 acid. 
 
 CH 2 C1-COC1 
 
 Mon ochloracety 1 
 chloride. Liquid, b.-pt. 
 120, of suffocating 
 odour. 
 
 HO.CH 2 .CO.NH S 
 
 Glycollamide. 
 Crys. M.-pt. 120; 
 does not form salts 
 with bases. 
 
 NH 2 .CH 2 .CO-OH 
 
 Glycocoll. 
 Crys. M.-pt. 236. 
 Forms salts with 
 acids and bases. 
 
 NH 2 .CH 2 .CO.NH 2 
 Glycocollamide. 
 Crys. 
 
 It is easy to see that the corresponding derivatives of the 
 first and second vertical rows are always isomeric. 
 
 Anhydrides of Glycollic Acid. 1. Glycollic acid can yield 
 different types of anhydrides: (1) the elimination of one mol. 
 of water from the alcoholic hydroxyls of two molecules of the 
 acid produces diglycollic acid, 
 
 2 -CO 2 H 
 2 -C0 2 H, 
 
 which is obtained by boiling monochloracetic acid with lime. 
 It forms large rhombic prisms, is a dibasic acid, and, as an 
 ether, is not saponified when boiled with alkalis, but is decom- 
 posed when heated with concentrated hydrochloric acid to 120. 
 2. Diglycollic acid loses water when heated, yielding the 
 diglycollic anhydride, 
 
 3. Glycollic anhydride, OH.CH 2 .CO.O.CH 2 .CO 2 H, is an 
 ester, which is formed when glycollic acid is heated at 100. 
 It becomes hydrated again when boiled with water, and may 
 be regarded as an ester derived from glycollic acid acting as 
 an alcohol and as an acid. 
 
 
GLYCOCOLL 211 
 
 CH 2 .O.CO 
 
 4. Glycohde, - . , is also an ester anhydride, and 
 
 OU U Oiig 
 
 is isomeric with 2 (and with fumaric acid). It is formed when 
 sodium bromo-acetate is distilled in a vacuum. Lustrous 
 plates; m.-pt. 87. It becomes hydrated again when boiled 
 with water. 
 
 Glycocoll (Ammo -ethane acid), glycine, amino- acetic add., 
 NH 2 .CH 2 .C0 2 H (Braconnot, 1820). This is the simplest 
 representative of the important class of amino acids, so called 
 because they are derived from the fatty acids by the exchange 
 of a hydrogen atom of the hydrocarbon radical for an amino 
 group, e.g. CH 3 .C0 2 H, acetic acid; CH 2 (NH 2 ) C0 2 H, amino- 
 acetic acid. 
 
 Formation. 1. By the action of concentrated ammonia upon 
 monochloracetic acid (Heintz, A. 122, 261; Kraut, A. 266, 292): 
 
 CH 2 C1.C0 2 H 
 
 (cf. also B. 23, Eef. 654). Di- and triglycollamic acids, 
 NH(CH 2 .C0 2 H) 2 and N(CH 2 . C0 2 H) 3 , are produced at the 
 same time. 
 
 a-Chloropropionic acid in like manner yields alanine with 
 ammonia (see Lactic Acid). The method is a general one 
 for the production of amino acids. 
 
 2. By boiling glue with alkalis or acids. 
 
 3. Together with benzoic acid, by decomposing hippuric acid, 
 i.e. benzoyl-glycocoll, with concentrated hydrochloric acid: 
 
 Properties. Glycocoll forms large colourless rhombic prisms, 
 readily soluble in water, but insoluble in absolute alcohol and 
 ether. It has a sweet taste, hence the name " glue sugar " or 
 
 glycocoll (yXvKvs, sweet, KoAXa, glue). It melts and decom- 
 poses at 236. Glycocoll, like all the amino acids, possesses 
 the properties of both an amine and an acid. It therefore 
 forms salts with acids as well as with bases, e.g. glycocoll 
 hydrochloride, C 2 H 5 N0 2 HC1, which crystallizes in prisms, and 
 the characteristic copper salt, copper glycocoll, (C 2 H 4 N0 2 ) 2 Cu 
 + H 2 > which crystallizes in blue needles, the latter being 
 obtained by dissolving cupric oxide in a solution of glycocoll. 
 Most of the other amino acids also form characteristic copper 
 salts of this nature, which serve for their separation. Glycocoll 
 
212 IX. HYDROXY MONOBASIC ACIDS 
 
 also yields compounds with salts, and, as an acid, forms an 
 ethyl ester, an amide, &c. (see table, p. 210). When heated 
 with BaO it is decomposed into methyl-amine and C0 2 , while 
 nitrous acid converts it into glycollic acid (the normal reaction 
 of the primary amines). With ferric chloride it produces an 
 intense red, and with copper salts a deep-blue coloration. 
 Ethyl armno-acetate (b.-pt. 43/ll mm.) and nitrous acid 
 
 N \ 
 yield the interesting ethyl diazo-acetate, || yCH'CO'OC 2 H 5 , 
 
 from which hydrazine, NH 2 NH 2 , and its hydrate were first 
 prepared; and from the latter the remarkable compound, 
 hydrazoic acid, N 3 H (Curtius, J. pr. Ch. (2) 38, 396, 472; 43, 
 207; B. 24, 3341; 29, 759; 33, 58). See also Di and Triazo 
 Derivatives, Chap. LI. 
 
 Constitution (see B. 16; 2650). Free glycocoll may possibly 
 be an intramolecular salt, corresponding with the formula 
 
 CH 2 <Q^ 3 > (see Taurine, p. 197, and Betaine below). 
 Alkyl and Acyl Derivatives of Glycocoll: 
 
 Methyl-glycocoll Trimethyl-glycocoll Acetyl-glycocoll 
 or Sarcosine, or Betaine, or Aceturic Acid, 
 
 CH 2 .NHCH 3 CH 2 .N(CH 3 
 
 00- OH CO-0 - ' CO-OH. 
 
 Most of these alkyl derivatives are interesting, as they 
 either occur as such in natural products, or may be obtained 
 by the decomposition of certain natural compounds. Sar- 
 cosine is obtained by the decomposition of the complex 
 natural substances creatine or caffeine. Betaine occurs in 
 beet-root, and is present in large quantities in the molasses 
 from beet-root sugar. It crystallizes with 1 H 2 0, which it . 
 readily gives up on heating. This hydrate may possibly be 
 C0 2 H CH 2 NMe 3 OH. When heated at 293 betaine is 
 transformed into the isomeric methyl ester of dimethylamino- 
 acetic acid, NMe 2 -CH 2 .COOMe; at higher temperatures it 
 yields trimethylamine. It has been synthesised by the action 
 of trimethylamine on monochloracetic acid (B. 1902, 35, 603): 
 
 d-CHj-COOH -> (CH 3 ) 3 N(C1).CH 2 .CO.OH (CH 3 ) 3 N.CH 2 .CO. 
 
 Numerous other compounds of a similar type are known, and 
 are all usually termed betaines. 
 
LACTIC ACIDS 
 
 213 
 
 Lactic Acids (Hydroxy-propionic acids). (Wislicenus, A. 128, 
 1; 166, 3; 167, 302, 346.) As has been already mentioned, 
 two isomeric lactic acids are theoretically possible, viz. a- and 
 /3-hydroxy-propionic acids, a- and /?-lactic acids, or ethylidene- 
 and ethylene-lactic acids, and both of these are known. 
 
 The minute investigation of the different lactic acids has 
 been of very great importance for the development of chemical 
 theory; they were formerly held to be dibasic, and the recog- 
 nition of their hydroxy-monobasic nature has materially con- 
 tributed to the acceptation of the theory of the linking of 
 atoms. 
 
 The molecule of a-hydroxy-propionic acid contains an 
 asymmetric carbon atom, 
 
 CHo-CH 
 
 II 
 
 and hence should exhibit exactly the same kind of isomerism 
 as was met with in the case of active valeric acid. 
 
 In reality two optically active a-lactic acids are known, one 
 of which is dextro (d\ and the other laevo (I) rotatory. These 
 two acids are identical in all their properties, with the excep- 
 tion of optical activity. A mixture (or compound) of the 
 two in equal quantities is optically inactive, and is known as 
 inactive (dl) or racemic (r) lactic acid. 
 
 The molecule of /?-hydroxy-propionic acid does not contain 
 an asymmetric carbon atom, and hence exists in only one 
 modification, which is optically inactive. 
 
 i 
 Modes of Formation. 
 
 Fermentation Lactic Acid. 
 
 Ethylene-lactic Acid. 
 
 i 
 1. By the regulated! 
 oxidation of / 
 
 a-Propylene glycol, 
 CH 3 .CH(OH).CH 2 OH. 
 
 jS-Propylene glycol, 
 OH.CH 2 .CH 2 .CH 2 OH 
 
 2. By the exchange"! 
 of halogen for >- 
 
 a-Chloro-propionic 
 acid, 
 
 S-Iodo-propionic acid, 
 CH 2 I.CH 2 .CO.OH. 
 
 hydroxyl in J 
 
 CH 3 .CHC1.CO-OH. 
 
 
 3. By hydrolysis of-! 
 
 Aldehyde-cyanhydrin, 
 CH 3 .CH(OH)-CN. 
 
 E t hy lene-cy anhy drin , 
 OH.CH 2 .CH 2 -CN. 
 
 4. B}f action of ni-\ 
 
 Alanine, 
 
 
 irons acid upon/ 
 
 CH 3 .CH(NH 2 ).CO.OH. 
 
 
 5. By the reduction! 
 
 Pyro-racemic acid, 
 
 
 of 
 
 CHs-CO-CO-OH. 
 
 
 6. By the lactic fermentation of sugar, etc. 
 
 
214 IX. HYDROXY MONOBASIC ACIDS 
 
 1. dl-Ethylidene- lactic Acid (Propane-2-ol-l-acid), ordinary 
 fermentation lactic acid, CH 3 CH (OH) C0 2 H. Discovered by 
 Scheele, and recognized as hydroxy-propionic acid by Kolbe. 
 Occurs in opium, sauerkraut, and in the gastric juice. 
 
 Preparation. This depends upon the so-called lactic fer- 
 mentation of sugars, e.g. milk, cane- and grape-sugars, and of 
 substances related to them, such as gum and starch; it is 
 induced by certain species of bacteria commonly spoken of as 
 the lactic bacilli. The fermentation proceeds best at a tempera- 
 ture of 34-35 in a nearly neutral solution, this last condition 
 being attained by the addition of chalk or zinc-white to the 
 fermenting mixture. The free acid can then be liberated 
 from the lactate of zinc by sulphuretted hydrogen. When 
 a non-homogeneous ferment (e.g. decaying cheese) is used, the 
 lactic acid at first produced is readily transformed by other 
 organisms into butyric acid (p. 152). 
 
 Lactic acid is also produced in large quantity by heating 
 grape- or cane-sugar with caustic-potash solution of a certain 
 degree of concentration (B. 15, 136). The relations of lactic 
 acid to the sugar varieties appear, at a superficial glance, to 
 be very simple; thus grape-sugar, C 6 H 12 6 , and lactic acid, 
 C 3 H 6 3 , are polymers. 
 
 Lastly, the inactive acid is produced by mixing equal quan- 
 tities of the two active modifications. In syntheses the latter are 
 formed in equal amounts, and hence the inactive acid is obtained. 
 
 Properties. When its solution is evaporated in a desiccator, 
 a thick, non-crystallizing and hygroscopic syrup is obtained, 
 which is miscible with water, alcohol, and ether, and which 
 gradually loses water, yielding the solid lactic anhydride, 
 C 6 H 10 5 , before all the water of solution has been got rid of. 
 To obtain the pure acid it is necessary to distil under very 
 low pressures, when a crystalline solid melting at 18 is 
 obtained. K = O0138. When heated, it is partially con- 
 verted into the anhydride, lactide, C 6 H 8 4 , and partially into 
 aldehyde, CO, and H 2 0. Similarly it decomposes into alde- 
 hyde and formic acid when heated with dilute sulphuric acid 
 to 130, concentrated sulphuric giving rise to carbon monoxide 
 instead of formic acid : 
 
 CH 3 .CH(OH).CO 2 H = CH 3 .CHO + HCO 2 H. 
 
 When oxidized, it yields acetic and carbonic acids; hydro- 
 bromic acid converts it into a-bromo-propionic acid, and boiling 
 hydriodic acid into propionic acid itself. 
 
LACTIC ACIDS 2l5 
 
 The inactive acid is split up into the two active modifications 
 by the crystallization of the strychnine salts (Purdie and 
 Walker, J. C. S. 1892, 754); further, when green mould, Peni- 
 cillium glaucum, is sown in a solution of the ammonium salt 
 of the inactive acid, the Isevo-acid is assimilated more rapidly 
 than the dextro-, and the solution thus becomes optically 
 active (Linossier, B. 1891, 24, 660). A very simple resolution 
 has been accomplished by Purdie (J. C. S. 1893, 1143) by crys- 
 tallizing the zinc ammonium salt, ZnC 6 H 10 6 , NH 4 C 3 H 5 3 , 
 2H 2 0. (Cf. Eesolution of Racemic Acid.) 
 
 A number of well-defined salts are known, e.g. Calcium 
 lactate, (C 3 H 5 3 ) 2 Ca + 5H 2 0; zinc lactate, (C 3 H 5 3 ) 2 Zn 
 + 3H 2 0; ferrous lactate, (C 3 H 5 3 ) 2 Fe + 3H 2 0. When 
 sodium lactate is heated with sodium, di- sodium lactate, 
 CH 3 CH(ONa) C0 2 Na, which is at the same time a salt 
 and an alcoholate, is formed. 
 
 The derivatives of lactic acid are derivatives of it either as 
 acid or as alcohol, and are perfectly analogous to those of 
 glycollic acid (see table, p. 210). Thus ethyl-lactic acid, 
 a-ethoxy-propionic acid, CH 3 CH(OC 2 H 5 ) C0 2 H, a thick acid 
 liquid which boils almost without decomposition, corresponds 
 with ethyl-glycollic acid; ethyl lactate, which can be distilled 
 without decomposition, with ethyl glycollate; lactamide, 
 CH 3 .CH(OH).CO.NH 9 , with glycollamide; and alanine, 
 CH 3 .CH(NH 2 ).CO.OS, with glycocoll. 
 
 By the action of PC1 5 , lactyl chloride, CHg-CHCl-CO-Cl 
 (p. 171), is formed; as the chloride of a-chloro-propionic acid 
 it is decomposed by water, yielding the latter acid and HC1. 
 
 The following anhydrides of lactic acid are known : 
 
 (1) Lactylic acid or Lactic anhydride, C 6 H 10 5 , which is 
 analogous to glycollic anhydride, and forms a yellow amor- 
 phous mass. (2) Lactide, C 6 H 8 4 , analogous to glycolide 
 (plates melting at 125). (3) Dilactic acid, C 6 H 10 5 , the 
 alcoholic anhydride, analogous to diglycollic acid. 
 
 2. d-Ethylidene-lactic acid, Sarco-ladic add, para-lactic acid 
 (Liebig). This occurs in the juice of flesh, and is therefore to 
 be found in Liebig's extract of meat. It results from certain 
 fermentations. Its chemical properties are exactly similar to 
 those of ordinary lactic acid; thus it readily yields lactide or 
 aldehyde. Its salts differ to some extent, however, from those 
 of the latter; thus, the zinc salt, + 2H 2 0, is much more easily 
 soluble, and the calcium salt + 4H 2 0, much more sparingly 
 soluble than the corresponding common lactates. Such differ- 
 
216 ix. HYDROXY MONOBASIC ACIDS 
 
 ences are usually met with between d- and ^-compounds on 
 the one hand, and their r-isomeride on the other. 
 
 3. 1-Ethylidene-lactic acid is obtained from the fermenta- 
 tion of cane-sugar by means of the l-ladic bacillus. Its salts 
 correspond exactly with the salts of d-lactic acid. They have 
 the same formulae, same solubilities, &c. 
 
 4. Ethylene-lactie acid (Propane-3-ol-l-acid), hydracrylic acid 
 (Wislicmus, A. 128, 1), forms a syrupy mass. It differs from 
 lactic acid (a) by its behaviour upon oxidation, yielding car- 
 bonic and oxalic acids, and not acetic; (b) by not yielding an 
 anhydride when heated, but by breaking up into water and 
 acrylic acid, hence the name hydracrylic acid: 
 
 CH 2 (OH).CH 2 .COOH = CH 2 :CH.COOH + H 2 0; 
 
 (c) in solubility, and in the amount of water of crystallization 
 of its salts (e.g. zinc salt, + 4H 2 0, very readily soluble in water; 
 calcium salt, + 2 H 2 0). It is not so strong an acid as a-lactic 
 acid. K = 0-00311. 
 
 It may be synthesised from ethylene by means of the fol- 
 lowing series of reactions: (a) the addition of hypochlorous 
 acid, (b) conversion of the chlorhydrin into the corresponding 
 nitrile, and (c) hydrolysis, e.g. : 
 
 CH 2 :CH 2 * OH.CH 2 .CH 2 C1 -* OH.CH 2 .CH 2 .CN 
 -^ OH.CH 2 .CH 2 .C0 2 H. 
 
 Hydroxy-caproic Acids, Leucine or a-Amino-caproic acid, 
 CH 3 .CH 2 .CH 2 .CH 2 .CH(NH 2 ).C0 2 H, is a derivative of a-hy- 
 droxy-caproic. It forms glistening plates, and, like other 
 amino acids, is closely related to albumen. It is found in old 
 cheese, also abundantly in the animal organism in the gastric 
 gland, and in the shoots of the vetch and gourd, &c. It forms, 
 along with tyrosine, a constant product of the digestion of al- 
 bumen in the small intestine and of the decay of albuminous 
 substances, and is formed when the latter are boiled with alkalis 
 or acids. It has also been prepared synthetically. It closely 
 resembles glycocoll, and forms a characteristic sparingly soluble 
 blue copper salt. Leucine is dextro-rotatory. A laevo- and an 
 inactive modification are also known (B. 24, 669). 
 
 LeSueur (J. C. S. 1904, 827; 1905, 1888) has prepared several 
 hydroxy derivatives of the higher fatty acids, e.g. a-hydroxy- 
 margaric and a-hydroxy-stearic acids, and has found that a 
 good yield (35-60 per cent) of an aldehyde can be obtained 
 when the acid is heated to 240-250. The molecule of the 
 
LACTONES 217 
 
 aldehyde so obtained contains a carbon atom less than the 
 molecule of the hydroxy acid, and water, formic acid, carbon 
 monoxide, and a lactide are obtained as by-products. 
 
 LACTONES 
 
 All hydroxy acids tend to lose water under certain con- 
 ditions, yielding anhydro-compounds. 
 
 The manner in which this water is eliminated is very 
 different in the various types of hydroxy acids. 
 
 1. In the case of the a-hydroxy acids, 1 or 2 mols. of water 
 are usually eliminated from 2 molecules of the acid, yielding 
 compounds of the type of diglycollic acid, glycollic anhydride, 
 &c. 
 
 2. In /2-hydroxy acids 1 molecule of water is usually elimi- 
 nated from 1 molecule of the acid, and an a-/3-unsaturated acid 
 is formed, e.g. : 
 
 CH 3 .CH(OH).CH 2 .C0 2 H -> CH 3 .CH:CH.C0 2 H (crotonic acid). 
 
 3. In the case of y-hydroxy acids, e.g. y-hydroxy-butyric 
 acid, OH.CH 2 .CH 2 .CH 2 l .C0 2 H, 1 molecule of water is elimi- 
 nated from 1 molecule of the acid, and an inner anhydride or 
 lactone is formed, 
 
 2 2 
 
 = butyro-lactone or butanolid. 
 CH 2 CO / 
 
 The formation of such a lactone is characteristic of y-hydroxy 
 acids. Many of these acids are so unstable in the free state, 
 that when mineral acid is added to their salts the lactones and 
 not the free acids are obtained. 
 
 The "y-lactones" are for the most part neutral liquids of 
 faint aromatic odour, readily soluble in alcohol and ether, and 
 distilling without decomposition. They dissolve in alkalis, 
 yielding the salts of the corresponding hydroxy acids, and form 
 brominated fatty acids with HBr, and amino acids or amides 
 of y-hydroxy acids with NH 3 (B. 23, Ref. 234). 
 
 8- and /?-, but only a few a-lac tones, from 8-, /?-, and a-hy- 
 droxy acids, are also known. They show marked differences 
 in the ease with which they are formed and in their stability, 
 the y-lactones being the most stable. (For a-Lactones, see B. 
 1891, 24, 4070; for ft-, B. 1897, 30, 1954.) 
 
 The formation of lactones by warming the isomeric unsatu- 
 rated acids, CJI^f)^ which contain the double bond in the 
 
218 IX. HYDHOXY MONOBASIC ACIDS 
 
 /?-y or 7-8 position, with HBr or with moderately concentrated 
 H 2 S0 4 , is worthy of note, e.g. : 
 
 E.CH:CH.CH 2 .CO 2 H -* K.CH.CH 2 .CH 2 .Cp. 
 
 (For details, see Fittig and his pupils, A. 208, 37, 111; 216, 
 26; 255, 1, 275; 256, 50; 268, 110.) 
 
 The reaction is generally regarded as the addition of HBr 
 or H 2 O to the double bond, and then the elimination of the 
 Br or OH in the y-position with the H of the carboxyl group. 
 
 B. Polyhydrie Monobasic Acids 
 
 Just as glycol on oxidation can yield the monohydroxy 
 monobasic acid, glycollic acid, so the polyhydric alcohols on 
 careful oxidation with nitric acid can yield polyhydroxy 
 monobasic acids, e.g.: 
 
 OH.CH 2 .CH(OH).CH 2 .OH OH.CH 2 .CH(OH).C0 2 H. 
 
 They are usually designated according to the number of 
 alcoholic hydroxyl groups present. This number can be 
 determined by converting the acid, or better, its ester, into 
 the acetyl derivative, and estimating the number of acetyl 
 groups by analysis or by hydrolysis (p. 201). 
 
 In none of these acids do we find more than one OH group 
 attached to the same carbon atom. All have the properties of 
 monobasic acids and, in addition, the properties of polyhydric 
 alcohols. Those which contain a hydroxyl group in the 
 y-position yield lactones. 
 
 Most of the compounds belonging to this class either crys- 
 tallize badly or are gum-like. A number of these acids are 
 formed by the cautious oxidation of the sugars or of the 
 unsaturated acids, CJi^.flz (see p. 162). 
 
 I. DIHYDROXY MONOBASIC ACIDS 
 
 Glyceric acid (Propane-2:3-diol-l-acid), OH.CH 2 -CH(OH). 
 C0 2 H, is a syrupy liquid which is obtained by the cautious 
 oxidation of glycerol. The molecule contains an asymmetric 
 carbon atom, the artificial acid is optically inactive, but a d- 
 and an /-modification are known (Frankland, J. 0. S. 1891, 96). 
 
 Various compounds obtained from natural sources are closely 
 related to the dihydroxy acids, viz. serine, a-amino-^-hydroxy 
 
POLYHYDRIC MONOBASIC ACIDS 219 
 
 propionic acid, obtained by boiling silk glue with dilute acids; 
 ornithine, aS-diamino- valeric acid; and lysine, ae-diamino- 
 caproic acid, obtained by the hydrolysis of casein. 
 
 II. TETBA- AND PENTAHYDROXY MONOBASIC ACIDS 
 
 The tetra- and pentahydroxy acids, e.g. OH CH 2 (CH OH), 
 C0 2 H and OH.CH 2 .(CH.OH) 4 .C0 2 H, are of particular im- 
 portance, on account of their close connection with the simple 
 sugars. They are obtained either by the cautious oxidation 
 of the corresponding sugars, e.g. by means of bromine water : 
 or by the reduction of the corresponding dibasic acids (sac- 
 charic acid, &c.); or, lastly, by the addition of hydrocyanic 
 acid to the polyhydroxy aldehydes or ketones, just as lactic 
 acid is formed from aldehyde. Conversely, the acids, in the 
 form of their lactones, are on the one hand reconverted into 
 the sugars by reduction with sodium amalgam; while, on the 
 other hand, they are oxidized by nitric acid to the correspond- 
 ing dibasic acids. 
 
 The acids are named according to the sugar to which they 
 are related: Arabinose -> Arabonic Acid, 
 Glucose * Gluconic Acid. 
 
 (See Sugars, p. 300, &c.) 
 
 Some of the acids are known in the form of their lactones 
 only. The phenyl-hydrazones are frequently made use of for 
 their isolation. 
 
 A number of different acids, e.g. mannonic, gluconic, gulonic, 
 galactonic, and talonic acid, have been obtained by the oxida- 
 tion of the hexoses (p. 307) and by other methods. Inves- 
 tigation has shown that those acids all possess the same 
 structural formula, 
 
 OH CH 2 . CH(OH) CH(OH) . CH(OH) CH(OH) CO 2 H, 
 
 which is seen to contain 4 distinct asymmetric carbon atoms. 
 
 The acids are thus stereo-isomeric ; their differences depend 
 on the arrangement in space of the different radicals (cf. the 
 Sugars). 
 
 The number of stereo-isomerides possible is the same as for 
 the sugars (the corresponding aldo-hexoses), viz. eight pairs 
 of optically active isomerides and eight racemic compounds. 
 Most, but not all, of these have been obtained. 
 
 Three extremely important methods have been employed 
 (mainly by E. Fischer) for the preparation of these acids: 
 
220 IX. HYDROXY MONOBASIC ACIDS 
 
 1. Oxidation of the corresponding aldehyde (a sugar), e.g. 
 ordinary glucose when carefully oxidized with chlorine- or 
 bromine- water yields d-gluconic acid: 
 
 OH.CH 2 .(CH-OH) 4 .CH:O -> OH.CH 2 .(CH.OH) 4 .CO-OH. 
 
 2. From a stereo-isomeric acid by intramolecular transfor- 
 mation under the influence of high temperature, and generally 
 in the presence of an organic base, e.g. d-gluconic heated with 
 quinoline and water yields d-mannonic; galactonic * talonic. 
 
 The reaction is a reversible one, and hence the final product 
 is a mixture of the two acids, which can be separated by the 
 difference in solubility of certain of their salts. 
 
 3. The addition of hydrogen cyanide to a polyhydric alde- 
 hyde or ketone and subsequent hydrolysis, e.g. : 
 
 -OHVCHO OH-CH 2 .(CH.OH) 3 .CH(OH).CN 
 OH.CH 2 .(CH.OH) 3 .CH(OH).C0 2 H. 
 
 It is obvious that an additional asymmetric carbon atom is 
 introduced by the addition of the HCN, and thus a mixture 
 of two stereo-isomeric nitriles is formed, and on hydrolysis a 
 mixture of two stereo-isomeric acids, e.g. : 
 
 7 A ,1 . _ __ -Z-Glucomc acid 
 -^-Mannonic acid. 
 
 This reaction is somewhat similar to the addition of HCN 
 to acetaldehyde, the main difference is that the original com- 
 pound is optically active, and hence its molecule is asymmetric. 
 By the addition of HCN two compounds are obtained, as a 
 rule not in equal amounts, both of which are optically active, 
 but do not stand in the relationship of object to mirror image. 
 
 This reaction has been extended, and hydroxy acids con- 
 taining 7, 8, and 9 carbon atoms have thus been obtained. 
 
 C. Hydroxy Aldehydes 
 
 As examples, we have glycollic aldehyde, OH CH 2 CH : 0, 
 aldol, CH 3 .CH(OH).CH2-CH:0 (see p. 131), and glyceric 
 aldehyde, OH.CH 2 .CH(OH).CH:O. The last-named is con- 
 tained in glycerose, a product obtained by oxidizing glycerol 
 with bromine water. Alkalis convert it into a mixture of 
 sugars, C 6 H 12 6 (see a-Acrose). (For further examples of hy- 
 droxy aldehydes and ketones, see Sugars, p. 300.) 
 
DIKETONES 221 
 
 D. Dialdehydes (cf. p. 97) 
 
 Glyoxal (Ethane-dial), CHO-CHO (Debus, 1856), is formed 
 by the careful oxidation of alcohol, or better, of aldehyde; it 
 possesses all the characteristic properties of aldehydes; one 
 molecule of the aldehyde is capable of combining with two 
 of hydrogen cyanide or of sodium hydrogen sulphite. 
 
 E. Diketones 
 
 1. Diacetyl, Butane-dione, a-diketo-butane, CH 3 COGOCH 3 , 
 b.-pt. 87-88. This can be prepared by boiling iso-nitroso- 
 methyl acetone, CH 3 - C( : N OH) CO CH 3 , a product obtained 
 by the action of nitrous acid on methyl ethyl ketone, with 
 dilute H 2 S0 4 , when the oximino group is replaced by oxygen. 
 It is a yellow-green liquid, its vapour having the colour of 
 chlorine, and an odour similar to that of quinone (v. Pechmann, 
 B. 20, 3162; 24, 3594; Fittig and his pupils, A. 249, 182). 
 Reduction converts it into dimethyl-ketol. Homologues are 
 known (cf. B. 22, 2115). 
 
 2. Acetyl-acetone, CH 3 .CO.CH 2 .CO-CH 3 , is formed by 
 the action of aluminic chloride upon acetyl chloride and sub- 
 sequent decomposition of the aluminium compound, or better 
 (B. 22, 1009), by the action of sodium upon a mixture of 
 ethyl acetate and acetone (see Aceto-acetic ester synthesis, 
 p. 224): 
 
 CH 3 .CO-OC 2 H 6 + CHo-CO 
 
 It is a liquid which boils at 137. 
 
 3. Acetonyl- acetone, y-diketo-hexane, CH 3 COCH 2 CH 2 ' 
 CO-CH 3 , may be prepared from monochlor-acetone and ethyl 
 aceto-acetate (B. 17, 2756); also from diaceto-succinic ester 
 (B. 22, 168, 2100). It is a liquid of pleasant odour, and 
 boils at 188. 
 
 These three compounds are the simplest representatives of 
 the a-, ft-, and y-diketones, or of the 1:2-, 1:3-, and l:4-di- 
 ketones, i.e. of those diketones whose carbonyl groups are 
 either next to one another (a-position), or separated by ona 
 carbon atom (^-position), or separated by two (y-position). 
 
 As diketones they yield mono- and dioximes, and also 
 mono- and dihydrazones. Such dihydrazones, and also those 
 
222 IX. HYDROXY MONOBASIC ACIDS 
 
 from the dialdehydes, are termed osazones, e.g. diacetyl 
 osazone. 
 
 C 6 H 6 .NH.N:CMe.CMe:N.NH.C 6 H 6 . 
 
 Osazones are also formed by the action of phenylhydrazino 
 on polyhydroxy aldehydes or ketones, e.g. glucose and fructose, 
 an atom of oxygen being at the same time taken up; they are 
 mostly yellow in colour (cf. the phenyl-hydrazine compounds 
 of the carbohydrates). 
 
 The diketones show the most varied behaviour on condensa- 
 tion. By the action of alkali on the a-diketones, they yield 
 benzene derivatives (see Quinone); the /3-diketones readily 
 pass into pyrazole and isoxy-azole derivatives, and serve for 
 the synthesis of derivatives of quinoline; while the y-diketones 
 are easily converted into derivatives of pyrrole, furane, and 
 thiophene, and the S-diketones into derivatives of pyridine and 
 tetrahydrobenzene. 
 
 The constitution of the above compounds is usually deduced 
 directly from their mode of formation, but as certain of them 
 react as tautomeric substances (cf. Ethyl Aceto-acetate) special 
 physical methods have also been used (cf. W. H. Perkin, J. C. S. 
 1892, 800). 
 
 F. Aldehydic Monobasic Acids 
 
 Glyoxalic acid (Ethanal add), glyoxylic acid, CHOC0 2 H, 
 occurs in unripe fruits such as grapes, gooseberries, &c., and 
 may be prepared by superheating dichloracetic acid, CHC1 2 - 
 C0 2 H, with water, 2C1 being here exchanged for 2 (OH), and 
 water being eliminated. It crystallizes in rhombic prisms, 
 dissolves readily in water, and is volatile with steam. The 
 acid and most of its salts contain one molecule of water of 
 crystallization, which points to the formula CH(OH) 2 C0 2 H, 
 analogous to that of chloral hydrate. 
 
 Glycuronic acid, CHO [CH(OH)] 4 C0 2 H. The lactone of 
 this acid forms colourless crystals, which melt at about 175. 
 The acid itself is obtained from saccharic acid by reduction 
 with sodium amalgam. It is found as a camphor compound in 
 the urine of dogs after camphor is administered to them. 
 
 G. Monobasic Ketonie Acids 
 
 Ketonic acids are compounds which contain both a carbonyl 
 and a carboxylic group; they react as acids, and also as ketones; 
 
KETONIC ACIDS 223 
 
 thus, besides being capable of forming salts, esters, &c., they 
 also combine with sodium bisulphite, yield oximes with hy- 
 droxylamine hydrochloride (see p. 135), are reduced by nascent 
 hydrogen to hydroxy acids, and so on. The most important 
 members of this class are pyroracemic acid, CH 3 COC0 2 H, 
 aceto-acetic acid, CH 3 CO - CH 2 C0 2 H, and Isevulic acid, 
 CH 3 .CO.CH 2 .CH 2 .C0 2 H. 
 
 Constitution and Nomenclature. The ketonic acids are charac- 
 terized theoretically by the presence of carboxyl and of car- 
 bonyl, the latter being linked to carbon on both sides. They 
 may be regarded either as fatty acids, in which a hydrogen 
 atom of the alkyl group has been replaced by acyl, ECO-, as 
 indicated in the name aceto-acetic acid; laevulic acid is then 
 /5-aceto-propionic acid, and pyroracemic acid is aceto-fonnic 
 acid ; or they may be regarded as derived from the fatty acids 
 by the replacement of the two hydrogen atoms of a CH 2 
 group by an atom of oxygen. 
 
 In the latter case aceto-acetic acid is to be designated 
 j3-ketobutyric acid, or butane-3-one-l-acid. This last is the sys- 
 tematic name (Geneva Congress); the expression one indicates 
 the presence of a ketonic group, and the number indicates the 
 relative positions of the ketonic and carboxylic groups. 
 
 The constitution of a ketonic acid is, as a rule, easy to deter- 
 mine, either from its synthesis or from its transformation into 
 the corresponding hydroxy acids of known constitution by 
 means of nascent hydrogen. 
 
 The ketonic acids are usually divided into a, /?, and y, or 
 1, 2, and 3 ketonic acids, according to the relative^positions of 
 the carbonyl and carboxylic groups. CH 3 'CO'C0 2 H, pyro- 
 racemic or pyruvic acid, is a type of an a-acid; CH 3 'CO 
 CH 2 .C0 2 H, aceto-acetic acid, is a type of a /3-acid; and 
 CH 3 .CO.CH 2 .CH 2 .C0 2 H, Isevulic acid, is a type of ay-acid. 
 The a- and y-acids are relatively stable; many can be distilled 
 without undergoing decomposition; but the /3-acids are remark- 
 ably unstable, and readily lose carbon dioxide, yielding ketones. 
 All the ketonic acids on careful reduction yield hydroxy acids. 
 
 Modes of Formation. I. a-Ketonic acids are formed when 
 the acyl cyanides are hydrolysed (Claisen and SJiadwell) (cf 
 p. 179 and B. 1898, 31, 1023): 
 
 CH 3 .CO.CN + 2H 2 = CH 3 .(X).C0 2 H4-NH 3 
 
 Acetyl-cyanide Pyroracemic acid. 
 
 The constitution follows from this method of formation. 
 
224 IX. HYDROXY MONOBASIC ACIDS 
 
 2. Aceto-acetic and other /3-ketonic acids are obtained as 
 esters by the action of sodium or sodium ethoxide on ethyl 
 acetate and its homologues: 
 
 2(CH 3 .CO.OC 2 H 5 ) = CH 3 .CO.CH 2 .CO.OC 2 H 5 + C 2 H 6 OH. 
 
 According to Claisen and Lowman (B. 20, 651; 26, 2130; 
 38, 713), the ethyl acetate is first converted by the sodium 
 ethoxide into an additive compound: 
 
 -C 2 H 
 
 Na 
 
 a derivative of ortho-acetic acid (p. 142), which then reacts 
 with another molecule of ethyl acetate, thus: 
 
 CH 3 
 
 = CH 3 . C(ONa) : CH . CO 2 Et+2EtOH 
 
 CH 3 .C(OH):CH.C0 2 Et CH 3 .CO.CH 2 .CO 2 Et. 
 
 From the sodium salt thus obtained, the aceto-acetic ester 
 can be liberated by acetic acid, probably first as the enolic com- 
 pound, which is immediately transformed into the ketonic. 
 
 As shown in the above formation of aceto-acetic ester, one 
 molecule of ethyl acetate reacts with a second molecule. Many 
 reactions of an analogous nature, in which the two reacting 
 molecules are different, may be brought about in the same 
 way by the aid of sodium ethoxide (W. Wislicenus, A. 246, 306). 
 Thus ethyl oxalate and ethyl acetate react in the presence of 
 sodium ethoxide, yielding the sodio derivative of ethyl oxal- 
 acetate: 
 
 (X) 2 Et.O);pEt+KCH 2 .CO 2 Et = C0 2 Et.CO.CH 2 .CO 2 Et-f EtOH. 
 
 Esters also readily react with ketones, with the formation of 
 diketones (L. Claisen): 
 
 CH 3 .CO-OEt + CH 3 .CO.CH 3 = CH 3 .CO-CH 2 .CO.CH 3 + EtOH 
 
 Acetyl-acetone. 
 
 When ethyl formate is employed, ketonic aldehydes are not 
 obtained, but their structural isomers, hydroxy-methylene 
 compounds; with acetone, for example, hydroxy-methylene- 
 acetone, thus: 
 
 H CO OC 2 H 5 +CH 3 CO CH 3 = CH(OH) : CH CO - CH 3 +C 2 H 5 OH 
 
 Ethyl formate Hydroxy-methylerie-acetone. 
 
 
a-KETONIC ACIDS 225 
 
 This condensation between esters, or between esters and 
 ketones, in the presence of sodic ethoxide is usually known as 
 Claisen's reaction, and is of extreme importance as a synthe- 
 tical process. (For summary see B. 1905, 38, 709.) 
 
 In all cases, according to Claisen, the condensation is pre- 
 ceded by the formation of an additive compound between the 
 sodium ethoxide and the ester. As a rule, metallic sodium 
 and not sodium ethoxide is added to the ester (e.g. to ethyl 
 acetate in the preparation of ethyl aceto-acetate), but the 
 reaction only proceeds when the ester contains free alcohol, 
 and can thus give rise to sodic ethoxide. Quite recently (Ber. 
 1905, 38, 693) the same chemist has shown that sodamide, 
 NaNH 2 , may be used in place of sodic ethoxide. 
 
 Michael (B. 1900, 33, 3731, and 1905, 38, 1922) considers 
 that the Claisen condensation proceeds in a different manner, 
 and that it may be compared with the aldol condensation. 
 Compare also Stoermer and Kippe (B. 1905, 38, 1953). 
 
 3. Higher homologues of aceto-acetic ester (/3-ketonic acids) 
 are easily obtained from it by the action of sodium ethoxide 
 and alkyl halides (p. 228). 
 
 4. Ketonic acids are produced by the cautious oxidation of 
 hydroxy acids containing the secondary alcoholic group: 
 
 CH 3 .CH(OH).CO.OH + = CH^CO-CO-OH + 
 
 Lactic acid Pyroracemic acid. 
 
 a-Ketonic Acids, Pyruvic or pyroracemic acid, GEL- CO* 
 C0 2 H, is a liquid which is readily soluble in water, alcohol, 
 and ether, boils with slight decomposition at 165-170, and 
 smells of acetic acid and extract of beef. It is formed by the 
 dry distillation either of tartaric or of racemic acid, hence its 
 name. 
 
 In this decomposition carbon dioxide is probably first 
 evolved and gly eerie acid formed: 
 CO ? :H.CH(OH).CH(OH).C0 2 H -> CH 2 (OH).CH(OH).GX3 2 H. 
 
 This then loses water, yielding pyruvic acid. 
 
 It may also be obtained by methods 1 and 4. 
 
 Pyroracemic acid has a tendency to polymerize. Nascent 
 hydrogen reduces it to ethylidene-lactic acid: 
 
 CH 3 .CO.C0 2 H + 2H = CH 3 .CH(OH).C0 2 H. 
 It is a relatively strong acid owing to the negative nature 
 
 (B480) ? 
 
226 IX. HYDROXY MONOBASIC ACIDS 
 
 of the CO group, K = 0*56. It reacts as a ketone with 
 phenyl-hydrazine, hydroxylamine, and hydrogen cyanide. 
 
 The phenyl-hydrazone crystallizes readily, melts at 192 
 when quickly heated, and is largely made use of in detecting 
 the acid. The acid also resembles the ketones in the readiness 
 with which it forms condensation products, yielding either 
 benzene derivatives (B. 5, 956), or in presence of ammonia 
 those of pyridine. 
 
 The electrolysis of a concentrated solution of the potassium 
 salt proceeds in the normal manner, the CH 3 CO COO 
 groups formed at the anode yield diacetyl and carbon dioxide 
 (cf. Electrolysis of potassium-acetate solution), but secondary 
 reactions also occur, and acetic acid is formed to a certain 
 extent. 
 
 /2-Ketonic Acids. Aceto-aeetic acid, CH 3 .CO.CH 2 -C0 2 II, 
 is a strongly acid liquid, miscible with water, and breaking up 
 into acetone and carbonic acid when warmed. It is prepared 
 by the cautious hydrolysis of its ethyl ester (B. 15, 1376, 1871). 
 Its aqueous solution is coloured violet-red by ferric chloride. 
 The Na- or Ca-salt is sometimes contained in urine (B. 16, 
 2314). Its constitution as acetone-carboxylic acid follows from 
 the products of decomposition. 
 
 The ethyl ester, ethyl aceto-acetate, or commonly called 
 aceto -acetic ether, is prepared by the Claisen condensation 
 method (general method 2). It is liberated from the sodium 
 derivative by the addition of acetic acid, and purified by 
 distillation under reduced pressure. It boils at 181, or at 
 71 under 12'5 mm. pressure, is only slightly soluble in water, 
 but readily in alcohol and ether, and has a pleasant fruity 
 odour. Ferric chloride colours its aqueous solution violet-red. 
 Extremely characteristic are the products to which it can give 
 rise on hydrolysis. 
 
 1. Normal Hydrolysis. As an ester, it can be hydrolysed 
 to the corresponding acid and alcohol, viz. aceto -acetic acid 
 and ethyl alcohol. This reaction occurs only when the ester 
 is extremely carefully hydrolysed in the cold with dilute 
 alkali. 
 
 2. Ketonic Hydrolysis. This hydrolysis is best accomplished 
 by the aid of dilute sulphuric acid or baryta water, 
 
 CH 3 .CO.CH 2 .:COOiC 2 H 6 
 H; iOH, 
 
 the products being acetone, carbon dioxide, and ethyl alcohol 
 
ETHYL ACETO-ACETATE 227 
 
 3. Add Hydrolysis. This takes place most readily when the 
 ester is heated with concentrated alcoholic potash or soda, 
 
 CH 3 .CO: .CH 2 .COO : C 2 H 5 
 
 HO;H Hiofe, 
 
 the products being acetic acid and ethyl alcohol. 
 
 Ethyl aceto-acetate has been represented by the formula 
 CH 3 CO CH 2 C0 2 Et, and undoubtedly numerous arguments 
 can be brought forward in favour of this constitution; e.g. it 
 reacts with sodic-hydric sulphite, with hydrogen cyanide, and 
 with hydroxylamine as a ketone, and hence should contain 
 the C-CO'C group; a further argument for the ketonic con- 
 stitution is to be found in the decomposition of the acid into 
 acetone and carbon dioxide ; on the other hand, with ammonia 
 or amines it gives /5-amino, or substituted /3-amino crotonic 
 acids, e.g. CH 3 CH(NH 2 ) : CH C0 2 H, and with phosphorus 
 pentachloride it yields /5-chloro-crotonic acid, CH 3 -CC1:CH- 
 C0 2 H. These latter reactions could be most readily explained 
 by assuming the constitution CH 3 C(OH) : CH C0 2 Et, i.e. ethyl 
 /3-hydroxy-crotonate for ethyl aceto-acetate. The ester is thus 
 a typical tautomeric substance, reacting as though it possessed 
 two distinct constitutions, and a study of the chemical proper- 
 ties alone will not, as a rule, permit us to settle with certainty 
 which of the two is the more probably correct. 
 
 The following suggestions have been made to account for 
 the tautomerism: 
 
 (a) The ester is really a mixture of the two distinct com- 
 pounds. 
 
 (b) The pure ester is unstable, and although it may have 
 the one constitution, e.g. ethyl aceto-acetate or ketonic con- 
 stitution, in the presence of various reagents it is readily 
 transformed into the isomeric compound with the enolic con- 
 stitution, i.e. ethyl /3-hydroxy crotonate. This type of tauto- 
 merism is thus often spoken of as keto-enolic tautomerism^ 
 and is frequently met with (see Phloroglucinol, &c.). Accord- 
 ing to this view, it consists in the wandering of a hydrogen 
 atom and a change in position of a double bond (desmotropism). 
 
 (c) According to Van Laar, the tautomerism is due to an 
 oscillatory hydrogen atom, which cannot be regarded as per- 
 
228 IX. HYDROXY MONOBASIC ACIDS 
 
 manently attached to C or to 0, but as continually oscillating 
 between the two. 
 
 Physical methods have been used for elucidating the consti- 
 tution of such compounds. The most important of these are 
 the molecular refraction (Gladstone, Bruhl), the molecular mag- 
 netic rotation (W. H. Perkin, Sen., J. C. S. 1892, 800), and 
 the absorption of electric waves (Drude, B. 1897, 30, 940). 
 [Compare chapter on Relationship between Physical Properties 
 and Chemical Constitution.] The conclusions arrived at from 
 such a study are (a) that ethyl aceto-acetate is a mixture in 
 chemical equilibrium of the ketonic and enolic forms, but con- 
 sists mainly of the ketonic compound, and (b) that a rise of 
 temperature favours the ketonic form. (See also Baly and 
 Desch, J. C. S. 1904, 1029; 1905, 766.) 
 
 The metallic derivatives are enolic compounds. 
 
 1. Ethyl Aceto-acetate as a Synthetical Reagent. One 
 atom of hydrogen in the aceto-acetic ester molecule is readily 
 replaceable by metals (Geuther; Conrad, A. 188, 269). The sodio 
 derivative is formed together with hydrogen on the addition 
 of sodium, and also when an alcoholic solution of the ester 
 is mixed with the calculated amount of sodium ethoxide in 
 absolute alcohol: 
 
 CH 3 .CO.CHNa.CO 2 Et or CH 3 .C(ONa):CH.CO 2 Et. 
 
 This sodio derivative forms long needles or a faintly lustrous 
 loose white mass. The copper salt crystallizes in bright-green 
 needles. 
 
 The sodium is readily replaced by alkyl radicals when the 
 sodio derivative is heated with an alkyl bromide or iodide; 
 sodium bromide or iodide is thus formed together with alky- 
 lated aceto-acetic esters, which are of great interest in various 
 syntheses, e.g.: ethyl methylacetoacetate, CH 3 -CO.CH(CH) 3 . 
 C0 2 C 2 H 5 , and the corresponding ethyl- and propyl-acetoacetic 
 esters, &c. In these compounds the hydrogen atom of the CH 
 
 rup may be again replaced by Na, and this again substituted 
 alkyl, with the production of dialkylated aceto-acetic esters, 
 e.g.: dimethylacetoacetic ester or ethyl dimethylacetoacetate, 
 CH 3 .CO.C(CH 3 ) 2 .C0 2 C 2 H 5 ; methylethylacetoacetic ester, 
 CH 3 .CO.C(CH 3 )(C 2 H 5 ).C0 2 C 2 H 5 , and so on. 
 
 These alkylated aceto-acetic esters exactly resemble the 
 mother substance, especially in the manner in which they 
 can be decomposed by either the "ketonic hydrolysis" or 
 the "acid hydrolysis" (cf. p. 226). The formation of ketone 
 
ACYL DERIVATIVES OF ETHYL ACETO ACETATE 2^9 
 
 largely predominates when dilute acid is employed, and of 
 fatty acids when concentrated alkali is used. 
 
 In the ketonic hydrolysis the alkyl groups introduced are 
 left attached to a carbon atom of the acetone molecule, e.g. : 
 
 _ = EtOH + C0 2 + CH 3 .CO.CHMeEt. 
 
 This affords a very general method for the synthesis of some 
 of the higher ketones. 
 
 In the acid hydrolysis the alkyl groups remain attached to 
 a carbon atom, which is united to a carboxylic group, e.g. : 
 
 EtOH. 
 
 This affords a simple method for synthesising any mono- or 
 dialkylated acetic acid, e.g.: CH 3 CH 2 C0 H ; C 2 H 5 -CH 2 . 
 C0 2 H; (CH 3 )(C 2 H 5 )CH.C0 2 H; (CH 3 )(C 3 H r )CH . C0 2 H. (Cf. 
 Ethyl malonate synthesis, p. 237; also Wislicenus and his 
 pupils, A. 186, 161.) 
 
 2. Acyl groups may be introduced in place of alkyl radi- 
 cals into aceto-acetic ester by similar methods, e.g. from acetyl 
 chloride, diaceto- acetic ester, (CH 3 . CO) 2 CH . C0 2 C 2 H 5 . The 
 product obtained varies with the conditions. When an acyl 
 chloride reacts with the sodio-derivative of ethyl acetoacetate 
 the chief product is the C-acyl derivative, viz. (CH 3 CO) 
 (R.CO)CH-C0 2 Et, but when the free ester is treated with 
 an acyl chloride in the presence of pyridine the isomeric 0-acyl 
 derivative is obtained, e.g. R . CO . C . CMe : CH - C0 2 Et. The 
 0-derivatives, when heated or when warmed with potassium 
 carbonate, are transformed into the isomeric C-compounds. 
 
 Ethyl chlorocarbonate and the sodio-derivative yield the 
 0-derivative CH 3 . C(0 C9 2 Et) : CH - C0 2 Et together with a 
 small amount of the C-derivative, aceto-malonic ester, (CH 3 * 
 CO) CH(C0 9 CJEL) 9 ; from monochloracetic ester, CH 2 C1 
 C0 2 C 2 H 5 , aceto-succinic ester, CH 3 .CO.CH(CH 2 .C0 2 C 2 H 5 ) 
 (C0 2 C 2 H 5 ) may be similarly obtained (see Malonic and Suc- 
 cinic acids, and also the Synthesis of dibasic acids), &c. 
 
 3. Iodine acts upon sodio-aceto-acetic ester, yielding diaceto- 
 succinic ester: 
 
 CH 3 .CO.CHNa.C0 2 C 2 H 5 CH 3 .O).CH.C0 2 C 2 H 6 
 
 + l2 "" GH.-CO.CH.CO.C.H. 
 
230 IX. HYDKOXY MONOBASIC ACIDS 
 
 4. In addition to the above-mentioned simple syntheses, d 
 number of more complex syntheses may be effected by means 
 of ethyl acetoacetate. Many of these lead to the formation of 
 closed-chain compounds, and will be described in connection 
 with the various groups of ring compounds. The following 
 may be mentioned as the more important: 
 
 (a) Hantzsch's synthesis of pyridine derivatives, e.g. ethyl 
 dihydrocollidine dicarboxylate, 
 
 <Me:C(C0 2 Et) >CHMe) 
 
 !:C(C0 2 Et) 
 
 by heating ethyl acetoacetate with aldehyde ammonia. 
 
 (b) The formation of oxyuvitic acid (a benzene derivative), 
 C 6 H 2 (CH 3 )(OH)(C0 2 H) 2 , by the action of chloroform on the 
 sodio-derivative. 
 
 (c) The formation of methyluracyl by the condensation of 
 ethyl acetoacetate with urea, 
 
 * nn^ NH 2 i Et OOxnTT nn/ NH CO v nTT 
 
 ^vXTTT T OTT CV^s^^ 2 " ^-^\"\TTT rVr~<TT\ *&***" 
 ^1 X 2 vXlg \j\J' ^1> 1 \j\\jl)^ 
 
 (See p. 287 and Synthesis of Uric Acid, p. 291.) 
 
 (d) The production of furane and pyrrole derivatives by 
 heating ethyl diacetosuccinate (see Synthesis 3) with acids 
 or with ammonia and amines. 
 
 (e) The synthesis of 
 
 Phenylmethylpyrazolone Phenyldimethylpyrazolone 
 
 by the condensation of ethyl acetoacetate with phenylhydra- 
 zine and methylphenylhydrazine respectively. 
 
 Chlor- and dichlor-aceto-acetic esters, which are very active 
 chemically, are produced by the replacement of the H of the 
 methylene group by Cl. The two methylene hydrogen atoms 
 are also replaceable by the isonitroso group, :N'OH (by the 
 action of NoOA and by the imido group, :NH (cf. A. 226. 
 294; B. 28, 2683). 
 
 Laevulic acid, CH 3 . CO CH 2 . CH 2 C0 2 H, forms crystalline 
 plates, melts at 33, and boils at 239. It is formed by the 
 action of acids upon cane-sugar, laevulose, cellulose, gum, 
 starch, and other carbohydrates (A. 175, 181; 206, 207), and 
 has also been prepared synthetically. (For its constitution, 
 cf. A. 256, 314.) It is employed in cotton printing and for 
 the preparation of anti-thermine, &c. 
 
DIBASIC ACIDS 
 
 231 
 
 X. DIBASIC ACIDS 
 
 Dibasic acids are those which are capable of forming two 
 series of salts, viz. acid and normal, and likewise two series of 
 esters, chlorides, amides, &c. They are characterized by the 
 presence of two carboxyl groups in the molecule. 
 
 A. Saturated Dibasic Acids, C U H 2U _ 2 4 > OP Acids 
 of the Oxalic Series 
 
 Name. 
 
 Formula. 
 
 Melting-pt. 
 
 K. 
 
 Oxalic 
 
 CO 2 H- 
 
 C0 2 H- 
 CO 9 H- 
 COgH- 
 CO,H. 
 
 CO^H. 
 
 C0 2 H. 
 
 C0 2 H 
 
 CH 9 . 
 [CHlo] 
 
 cnr 
 'CH; S 
 
 'CH 2 
 
 ;cH 2 . 
 
 C0 2 H 
 2-CO 2 H 
 3 .C0 2 H 
 4 -CO 2 H 
 5 -CO 2 H 
 6 -C0 2 H 
 
 )' Sublimes 1 
 \ 150-160 J 
 132 
 185 
 97'5 
 149 
 105 
 140 
 
 10-0 
 
 0-016 
 0-0065 
 0-0047 
 0-00371 
 0-00323 
 0-00258 
 
 Malonic 
 
 Succinic 
 
 Grluteivic 
 
 Adipic 
 Pimelic 
 
 Suberic . . 
 
 
 The above are solid crystalline compounds of strongly acid 
 character, and most of them are readily soluble in water. 
 When heated, they either yield an anhydride, or carbon di- 
 oxide is eliminated and a monobasic acid formed; but most of 
 them can be volatilized in vacuo. 
 
 Formation. 1. By the oxidation of the di-primary glycols. 
 (See table, p. 204.) 
 
 la. By the oxidation of hydroxy-acids and, generally, of 
 many complex compounds, such as fats, fatty acids, and carbo- 
 hydrates. 
 
 2. By the hydrolysis of the corresponding nitriles; thus, 
 oxalic acid is formed from cyanogen, and succinic acid from 
 ethylene cyanide: 
 
 (CN) 2 + 4H 2 = (C0 2 H) 2 + 2NH 3 . 
 ) 2 .CN + 4H 2 = C0 2 H.(CH 2 ) 2 -C0 2 H. 
 
 CN.(CH 2 ) 2 . 
 
 Since ethylene cyanide is a glycol derivative, its conversion 
 into succinic acid represents the synthesis from a glycol of an 
 acid containing two atoms of carbon more than itself, i.e. the 
 oxcnange of 2 (OH) *or 2'/XX,H), or the indirect combination 
 of ethylene with 2(CO ? H/. 
 
232 x. bl&Aslo 
 
 3. By the hydrolysis of the cyano-fatty acids (p. 170), and 
 consequently from the halogen fatty acids also. Thus chloro- 
 or cyaho-acetic yields malonic acid, /3-iodo- (or cyano-) propionic 
 acid, common succinic acid, and a-iodo- (or cyano-) propionic 
 acid, methyl malonic acid. 
 
 A dibasic acid can therefore be formed from each hydroxy- 
 acid by the exchange of OH for C0 2 H, or indirectly from a 
 fatty acid by the replacement of H by C0 2 H. Thus : 
 
 2H-- CH 2 (CN).C0 2 H-> CH 2 (C0 2 H) 2 . 
 
 4. The homologues of malonic acid can be prepared from 
 malonic acid itself by a reaction exactly analogous to the aceto- 
 acetic ester synthesis (the "Malonic ester synthesis", p. 238). 
 
 The dibasic acids are also obtained by means of the aceto- 
 acetic ester synthesis. Aceto-malonic and aceto-succinic acids, 
 which have already been mentioned at p. 229, yield respec- 
 tively malonic and succinic acids by the elimination of acetyl 
 (" acid decomposition "). 
 
 5. Higher homologues are obtainable by the electrolysis of 
 the ethyl potassium salts (p. 234) of the simpler dibasic acids, 
 e.g. adipic acid from potassium ethyl succinate. 
 
 The reaction is exactly analogous to the formation of ethane 
 by the electrolysis of potassium acetate. For example, with 
 
 potassium ethyl succinate the anions C0 2 Et CH, CH 2 C0, 2 
 
 + 
 
 and kations K are present. When these become discharged at 
 the electrodes during electrolysis, each C0 2 Et CH 2 CH 2 C0 2 
 group splits up into carbon dioxide and the monovalent radical 
 CO 2 Et CH 2 CH 2 . Two such radicals then combine, yielding 
 ethyl adipate, C0 2 Et CH 2 CH 2 CH 2 CH 2 C0 2 Et. The potas- 
 sium formed at the cathode reacts with the water, yielding 
 hydrogen and potassium hydroxide. 
 
 The constitution of the acids C n H 2n _ 2 4 is, as a rule, very 
 easy to determine from the above-mentioned modes of for- 
 mation, especially 2, 3, and 4. According to these, one has 
 to decide between the malonic acids proper, i.e. malonic acid 
 and its alkyl derivatives (p. 238), whose two carboxyl groups 
 are both linked to one carbon atom: 
 
 CH 2 (CO 2 H) 2 , E - CH(CO 2 H) 2 , EE'C(CO 2 H) 2 , 
 
 and ordinary succinic acid and its homologues, which contain 
 the carboxyls bound to two different carbon atoms. 
 
PROPERTIES OF DIBASIC ACIDS 233 
 
 The bivalent acid residues, C 2 2 = oxalyl, C 3 H 2 2 = malonyl, 
 and C 4 H 4 2 = succinyl, which are combined with the two hy- 
 droxyls, are termed the radicals of the dibasic acids, and are 
 examples of bivalent acyl radicals. 
 
 homers. Isomers of oxalic and malbnic acids ate neither 
 theoretically possible nor actually known. We know, how- 
 ever, two succinic acids, viz. : 
 
 CX) 2 H.CH 2 .CH 2 .C!O 2 H and CH 3 .CH(CO 2 H) 2 . 
 
 The former corresponds with ethylene chloride and the latter 
 with ethylidene chloride, from which they are respectively 
 derived by the exchange of two chlorine atoms for two car- 
 boxyls. Hence the names ethylene- and ethylidene-succinic 
 acids, or more commonly succinic acid and methylmalonic acid. 
 
 Since ethylene cyanide can be prepared from the chloride, 
 the above derivation of ethylene-succinic acid is also an experi- 
 mental one. This is not the case, however, with the isomeric 
 acid, since, as a rule, when several chlorine atoms are bound 
 to the same carbon atom, as in ethylidene chloride, they cannot 
 be exchanged for cyanogen. 
 
 Behaviour. Many of the dibasic acids, in the molecules of 
 which the carboxyls are attached to different carbon atoms, 
 yield intramolecular anhydrides by the elimination of a mole- 
 cule of water from one of the acid. These anhydrides may 
 be obtained either (1) by heating the acids alone, or (2) more 
 generally by the action of phosphorus pentachloride, acetyl 
 chloride, or carbonyl chloride upon the acids (B. 10, 1881; 17, 
 1285). They recombine slowly with water to form the free 
 acids. This formation of anhydride is favoured by the presence 
 of substituents in the molecule (B. 23, 101, 620; 26, 1925). 
 
 The elimination of water occurs most readily with succinic 
 and glutaric acids and their substituted derivatives; in fact, 
 with the acids containing a chain of 4 or 5 carbon atoms : 
 
 C0 2 H.C.C.C0 2 H and C0 2 H.C.C.C. 
 
 This is undoubtedly to be attributed to the spatial relation- 
 ships of the atoms within the molecule. Assuming that the 
 four valencies of a carbon atom are symmetrically distributed 
 in space (i.e. directed towards the solid angles of a tetra- 
 hedron), then it can be readily seen by the aid of models that 
 in acids of the above types the C0 2 H groups are brought 
 
234 
 
 X. DIBASIC ACIDS 
 
 sufficiently near to one another for water to be eliminated, 
 and for a closed ring to be formed (compare Polymethylene 
 Derivatives). 
 
 The derivatives of the dibasic acids, i.e. their esters, amides, 
 &c., show precisely the same characteristics as the analogous 
 derivatives of the monobasic acids, especially in the readiness 
 with which they are hydrolysed. 
 
 DERIVATIVES OF DIBASIC ACIDS 
 
 Derivatives. 
 
 Salts. 
 
 Esters. 
 
 Chlorides. 
 
 Amides. 
 
 
 CO-ONa 
 
 CO-OC 2 H 6 
 
 CO -01 
 
 CO-NH 2 
 
 Acid. 
 
 CO- OH 
 
 Acid sodium 
 oxalate. 
 
 CO- OH 
 
 Ethyl-oxalic 
 acid. 
 
 CO-O(H) 
 
 (only known in 
 derivatives). 
 
 CO- OH 
 
 Oxamic 
 acid. 
 
 Neutral 
 or 
 normal. 
 
 CO-ONa 
 
 CO-ONa 
 
 Neutral sodium 
 oxalate. 
 
 CO-OC 2 H 5 
 
 CO-OC,H 6 
 Ethyl 
 oxalate. 
 
 CO-C1 
 
 CO-C1 
 Oxalyl 
 chloride. 
 
 CO-NH 2 
 
 'CO-NH 2 
 
 Oxamide. 
 
 As in the case of the glycols, complications arise from the 
 formation of mixed derivatives, e.g. partly ester and partly 
 amide, as in the case of ethyl oxamate (p. 237), and also from 
 the fact that many of the acids form imides. Such imides are 
 derived from the hydrogen-ammonium salts of the acids by 
 the elimination of two molecules of water, thus: 
 
 Succinic acid 
 
 Succinimide. 
 
 Like the amides they are readily hydrolysed (cf. Succini- 
 mide). 
 
 Oxalic acid (Ethane diadd), (C0 2 H) 2 , 2H 2 0, is one of the 
 oldest known organic acids, and occurs as its acid potassium 
 salt in many plants, especially in Oxalis Acetosella (wood-sorrel), 
 and in varieties of Rumex, and as the free acid in varieties of 
 Boletus, as normal sodium salt in varieties of Salicornia, and 
 as calcium salt in rhubarb root, &c. 
 
 It may be prepared by a variety of different reactions. 
 
 at 360 C 
 
 the direct co bination of carbon dioxide with sodium 
 
 4 Na 2 . 
 
OXALIC ACID 235 
 
 2. By quickly heating sodium formate to a high tem- 
 perature: 2HC0 2 Na = H 2 + C 2 4 Na 2 . 
 
 3. It is often met with as an oxidation product of relatively 
 complex carbon compounds, e.g. by the oxidation of alcohol 
 by permanganate, and of sugar, starch, wood, &c., by nitric 
 acid. The oxidation of cane-sugar with concentrated nitric 
 acid is often employed for the preparation of pure oxalic acid. 
 The crystallized acid readily separates when the liquid is 
 cooled or evaporated. 
 
 4. On the commercial scale, oxalic acid is manufactured by 
 the fusion of cellulose (see Carbohydrates) in the form of saw- 
 dust with a mixture of sodium and potassium hydroxides at 
 200-220 in flat iron pans. The sodium and potassium oxalates 
 are extracted with water, then precipitated as calcium oxalate, 
 and finally converted into the acid by treatment with the 
 requisite amount of sulphuric acid. 
 
 It crystallizes from water in large, transparent, monoclinic 
 prisms containing two molecules of water of crystallization. 
 They slowly effloresce in the air, and readily become an- 
 hydrous when heated at 100. At higher temperatures the 
 acid partly decomposes into carbon dioxide and formic acid, 
 and partly sublimes unaltered. 
 
 The acid is readily soluble in water, moderately in alcohol, 
 and somewhat sparingly in ether. The aqueous solution de- 
 composes when exposed to light. 
 
 Concentrated sulphuric acid decomposes it into carbon mon- 
 oxide, carbon dioxide, and water: 
 
 C 2 H 2 O 4 = CO 2 
 
 Oxalic acid is stable as regards nitric acid and chlorine, but 
 permanganate of potash or manganese dioxide in acid solution 
 oxidizes it to carbonic acid: 
 
 C 2 H 2 4 + = 2C0 2 + H 2 O. 
 
 It is reduced by nascent hydrogen to glycollic acid. 
 
 The strength of an aqueous solution of the acid may bo 
 determined by titration with standard alkali, using phenol 
 phthalein as indicator, or by means of standard permanganate 
 in the presence of sulphuric acid. 
 
 Its salts are known as oxalates. The alkaline salts, both acid 
 and normal, are readily soluble in water, the normal sodium 
 
236 fc. DIBASIC 
 
 salt being the least so. The " salt of sorrel " of commerce is 
 a mixture of C 2 O 4 HK and a salt, C 2 4 HK + C 2 4 H 2 + 2H 2 
 (cf. p. 144). The calcic salt, C s 4 0a + H 2 (or 3H 2 0), is 
 insoluble in water arid acetic acid, and serves for the recog- 
 nition of oxalic acid. Ferrous-potassic oxalate, (C 2 4 ) 2 FeK 2 
 + H 2 0, finds application in photography as a powerful reduc- 
 ing agent (the "oxalate developer ). 
 
 Ethyl oxalate, (COOC 2 H 6 ) 2 , which can be directly pre- 
 pared from the anhydrous acid and ethyl alcohol without a 
 catalytic agent, is liquid, while methyl oxalate, (COOCH 3 ) 2 , 
 is a solid, crystallizing in plates which melt at 54; both of 
 them possess an aromatic odour, distil without decomposition, 
 and are extremely readily hydrolysed. Partial hydrolysis, with 
 alcoholic potash solution, produces potassium ethyl-oxalate, 
 COOK-COOC 2 H 5 , from which the free ethyl -oxalic acid, 
 COOH COOC 2 H 5 , which is readily hydrolysed, and its 
 chloride, ethyl-oxalyl chloride, COC1 . COOC 2 H 5 , can easily 
 be prepared. Oxalic ester yields, with an excess of ammonia, 
 oxamide, and with one equivalent the mixed derivative, am- 
 monic oxamate, COONH 4 .CQ.NH 2 . 
 
 Oxalyl chloride, (COC1) 2 , has been obtained by the action of 
 excess of phosphorus pentachloride on ethyl oxalate. It is a 
 liquid, b.-pt. 70, and has a pungent odour (B. 41, 3558). 
 
 Oxamide, NH 2 COCONH 2 , the normal amide of oxalic 
 acid, is obtained, among other methods, by the distillation of 
 ammonium oxalate, by the partial hydrolysis of cyanogen, 
 but is most readily obtained by the addition of ammonium 
 hydroxide solution to ethyl oxalate. It is a white crystalline 
 powder, is readily hydrolysed, and by the abstraction of water 
 may be converted into cyanogen. When heated it sublimes 
 unchanged. 
 
 Oxamic acid, NH 2 CO CO OH, the amic acid correspond- 
 ing with oxalic acid, is prepared by heating ammonium hy- 
 drogen oxalate. It is a crystalline powder, sparingly soluble 
 in cold water, possesses acid properties, and yields salts, esters, 
 &c. It melts and decomposes at 210. 
 
 Ethyl oxamate, oxamethane, NH 2 CO CO OC 2 H 5 , is a crys- 
 talline compound, and melts at 114-115. The action of 
 PC1 5 on this compound is first to form NH 2 CC1 2 - CO OC 2 H 5 , 
 ethyl-examine chloride, which re,-idily loses hydrogen chlo- 
 ride yielding NH : CC1 CO . OC 2 H 5 and finally NjC-Cp. 
 OC 2 H 5 , cyano- carbonic ester. Corresponding with oxamide 
 we have dimethyl-oxamide, CH 3 . NH . CO . CO . NHCH 3 , and 
 
MALONICJ ACID 237 
 
 r 
 
 corresponding with oxamethane, ethyl - dimethyl - oxamate, 
 (CH 3 ) 2 N CO CO OCgHg, both of which were mentioned at 
 p. 106. 
 
 Oximide, -^NH, is prepared by the action of PC1 5 upon 
 
 oxamic acid. It forms colourless prisms readily soluble in 
 water and of neutral reaction, is quickly hydrolysed by hot 
 water, and is transformed into oxamide by the action of am- 
 monia (B. 19, 3228). 
 
 Cyanogen, N:C-C:N, is the nitrile corresponding with oxalic 
 acid (see p. 265). 
 
 Malonic acid, Propane diadd, CH 2 (C0 2 H) 2 , occurs in beet- 
 root as its calcium salt, and may be obtained by the following 
 methods : 
 
 ^(1) By the oxidation of malic acid by means of chromic 
 acid, hence its name; (2) by the hydrolysis of malonyl-urea 
 (p. 288), (Baeyer}-, (3) by the hydrolysis of cyano-acetic acid 
 (Kolbe, Milllei-, A. 131, 348; 204, 121): 
 
 CN.CH 2 .C0 2 H + 2H 2 = CH 2 (CO 2 H) 2 + NH 3 . 
 
 It crystallizes in large plates, dissolves readily in water, 
 alcohol, and ether, melts at 132, and decomposes when heated 
 to a slightly higher temperature. 
 
 Ethyl malonate, malonic ester, CH 2 (CO OC 2 H 5 ) 2 , is usually 
 obtained by passing hydrogen chloride into a solution of cyano- 
 acetic acid (from chloracetic acid) in absolute alcohol. It is 
 a liquid of faint aromatic odour boiling at 198, and having a 
 remarkable similarity to aceto-acetic ester. Thus the hydro- 
 gen of the methylene group is replaceable by sodium, through 
 the influence of the carbonyl groups CO, which are also bound 
 to the methylene; and the resulting sodio-malonic ester readily 
 exchanges the metal for alkyl when treated with an alkyl 
 iodide. By this means the higher homologues of ethyl 
 malonate, e.g. methyl-, ethyl-, propyl-, &c., malonic esters, are 
 obtained. Further, the second hydrogen atom in these can 
 be exchanged in exactly the same manner for sodium and 
 then for alkyl, whereby dialkyl malonic acids are formed. 
 This so-called "malonic ester" synthesis is an important 
 method for the preparation of the higher dibasic acids, being 
 applicable even in complicated cases. (Cf. Conrad and Bischoff, 
 A. 204, 121.) It is also of importance for the preparation of 
 some of the higher fatty acids, as the substituted malonic 
 
238 X. DIBASIC ACIDS 
 
 acids when heated above their melting-points lose carbon 
 dioxide and yield fatty acids: 
 
 When ethyl malonate is heated with its sodium compound, 
 a derivative of phloroglucinol is formed. (See this.) 
 
 Malonic anhydride, carbon suboxide, C 3 2 , 0:C:C:C:0, 
 is formed when malonic acid is heated in a suitable apparatus 
 at 140-150. (Diels and Wolf, B. 1907, 40, 355; cf. also 1906, 
 39, 689; Standinger and St. Bereza, B. 1908, 41, 4461.) The 
 yield is only 10-12 per cent, and acetic acid and carbon dioxide 
 are also formed. It is a colourless liquid, b.-pt. -\- 7, m.-pt. 
 107, and Dj I'll. It reacts readily with water, hydrogen 
 chloride, dry ammonia, and aniline, yielding respectively mal- 
 onic acid, malonyl chloride, malonamide, and malonanilide. It 
 is stable at low temperatures, but decomposes rapidly at 100. 
 
 Succinic acid, Butane diacid, ethylene-succinic add, symmetriwl 
 ethane-dicarboxylic acid (from succinum = amber), C0 2 HCH 2 - 
 CH 2 C0 2 H. This acid has been known for a long time; its 
 composition was determined by Berzelius. It exists in amber, 
 in various resins and lignites, in many Composite, in Papa- 
 veraceae, in unripe wine grapes, urine, blood, &c. 
 
 It may be obtained by most of the general methods described 
 on p. 231, e.g.-. 1. By the hydrolysis of ethylene cyanide. This 
 is an extremely important method, as it affords a synthesis of 
 succinic acid and also establishes its constitution, since it can 
 be shown that in ethylene dibromide the two bromine atoms 
 are attached to distinct carbon atoms: 
 
 CH 2 :CH 2 CH 2 Br.CH 2 Br CN-CHo-CHo-CN 
 ^* C0 2 H.CH 2 .CH 2 .C0 2 H. 
 
 2. From ^-iodo-propionic acid by conversion first into 
 /5-cyano-propionic acid and subsequent hydrolysis. 
 
 3. By the reduction of f umaric and maleic acids, C0 2 H CH : 
 CII-C0 2 H. 
 
 4. By heating its hydroxy- acids, malic or tartaric, with 
 hydriodic acid: 
 
 = C0 2 H.CH 2 .CH 2 .CO 2 H+I 2 . 
 
 5. It may also be obtained by the fermentation of the salts 
 of these hydroxy-acids by means of certain micro-organisms, 
 e.g. certain species of bacteria, 
 
SUCCINIO ACID 239 
 
 It is also formed in small quantities as a by-product in the 
 alcoholic fermentation of sugar, and by the oxidation of fats, 
 fatty acids, and paraffins by means of nitric acid. 
 
 It is usually prepared from calcic malate according to 5, 
 or by the distillation of amber. 
 
 6. It may also be synthesised from ethyl malonate. The 
 sodio- derivative of this ester reacts not merely with alkyl 
 iodides or bromides, but also with the esters of haloid fatty 
 acids, e.g. ethyl bromoacetate. 
 
 (C0 2 Et) 2 CHNa + Br.CH 2 .CO 2 Et 
 
 = NaBr + (CO 2 Et) 2 . CH . CH 2 . CO 2 Et. 
 
 The product is ethyl ethane-tricarboxylate, and when this 
 is hydrolysed, alcohol, carbon dioxide, and succinic acid are 
 formed. This method is of general interest, as various sub- 
 stituted succinic acids may be synthesised by this method. 
 In place of sodio-ethyl malonate, the sodio-derivatives of esters 
 of mono-substituted malonic acids may be used, and in place 
 of ethyl bromo-acetate the esters of other halogen fatty acids, 
 e.g. ethyl iodo-propionate or ethyl bromo-valerate. It has 
 recently been shown (Bone and Sprankling, J. C. S. 1899, 839) 
 that better yields can be obtained by using ethyl cyano-acetate 
 and its derivatives in place of ethyl malonate and its derivatives. 
 
 Properties. It crystallizes in monoclinic prisms or plates 
 with an unpleasant faintly acid taste, is readily soluble in 
 water, melts at 185, and boils at 235, but is at the same 
 time partially converted into its anhydride. (For its electro- 
 lysis, see pp. 46 and 232.) Is very stable towards oxidizing 
 
 Of the salts of succinic acid, the basic ferric salt, obtained 
 by the addition of a ferric salt to ammonium succinate, is 
 used in analysis for the separation of the ferric and aluminic 
 radicals. The calcic salt is soluble in water. 
 
 The derivatives of succinic acid correspond closely with 
 those of oxalic, e.g. succinamic acid, NH 2 CO CH 2 CH 2 
 CO -OH, is analogous to oxamic acid, and succinamide, 
 NH 2 CO CH 2 CH 2 CO NH 2 , to oxamide. There also exists, 
 as in the case of other dibasic acids, an imide, succinimide, 
 
 C 2 H 4 <f!c)>NH. The latter crystallizes in rhombic plates, 
 and is formed by heating ammonium hydrogen succinate. 
 The basic properties of the NH are so modified by the two 
 carbonyl groups of the acid radical that the imido-hydrogen is 
 
240 X. DIBASIC ACIDS 
 
 replaceable by metals, such as K, Ag, &c. (Cf. B. 25, Kef. 
 283.) Succinyl chloride reacts as though it were dichloro- 
 
 butyro-lactone, C 2 H 4 ^QQ_^>0. It is a colourless liquid 
 
 boiling at 190, and is obtained by the action of phosphorus 
 pentachloride (2 mols.) on the acid, or of 1 mol. on the anhy- 
 dride. In many of its properties it resembles the acid chlorides, 
 but on reduction yields butyro-lactone ; with benzene and alu- 
 minium chloride it yields mainly y-diphenyl-butyro-lactone, 
 
 PPh 
 
 , and with zinc ethyl y-diethyl-butyro-lactone. 
 
 The chloride is probably a mixture of dichloro-butyro-lactone 
 with a small amount of the normal chloride. Succinic an- 
 
 PO 
 hydride, C 2 H 4 <^pQ^>0, is best obtained by the action of acetic 
 
 anhydride on the acid. It crystallizes in glistening plates, 
 melts at 120, and distils without decomposition. It slowly 
 combines with water, yielding the acid; more readily with 
 alkalis, and also with alcohols at a higher temperature, yield- 
 ing the acid esters, e.g. HO.CO-CH 2 .CH 2 .CO.OEt. This is 
 the most convenient method for the preparation of acid esters. 
 The other methods sometimes employed are: (a) the partial 
 hydrolysis of the neutral ester, and (b) the partial esterifi- 
 cation of the acid by means of very dilute solution of hydrogen 
 chloride in the requisite alcohol (Bone, Sudborough, and Spunk- 
 ling, J. C. S. 1904, 534). 
 
 Of the higher acids the following are of interest : 
 Glutaric acid, Pentane diacid, C0 2 H-CH 2 .CH 2 .CH 2 .C0 2 H. 
 It may be obtained from glutamic acid (p. 249), and also by 
 condensing formaldehyde with ethyl malonate in the presence 
 of a small amount of diethylamine : 
 
 CH 2 :O + 2H-CH(C0 2 Et) 2 
 
 (CO 2 Et) 2 .CH.CH 2 .CH(CO 2 Et) 2 . 
 
 This is a further example of the readiness with which alde- 
 hydes condense with compounds containing a methylene group 
 adjacent to carbonyl or negative groups. The product, ethyl 
 propane-tetracarboxylate, on hydrolysis yields ethyl alcohol, 
 carbon dioxide, and glutaric acid. The last crystallizes in 
 prisms, melts at 97, is readily soluble in water, and yields 
 an anhydride, an imide, &c. The imide can be obtained 
 when piperidine is oxidized with hydrogen peroxide, and when 
 distilled with zinc dust yields a small amount of pyridine, 
 
UNSATURATED DIBASIC ACIDS 241 
 
 Isomeric with glutaric acid is methyl-succinic or pyro- 
 tartaric acid, C0 2 H . CHMe CH 2 C0 2 H, an acid closely 
 resembling succinic acid, and obtained by dry distillation of 
 tartaric acids. 
 
 The s- dimethyl- and s-dibromo- succinic acids, C0 2 H 
 CHBr'CHBrC0 2 H, occur in the same number of stereo- 
 isomeric modifications as the tartaric acids (p. 249). 
 
 Mono- and dibromo-succinic acids, C 2 H 3 Br(C0 2 H) 2 and 
 C 2 H 2 Br 2 (C0 2 H) 2 , are easily prepared, and are valuable for the 
 syntheses of the hydroxy-succinic acids. 
 
 Sodium reacts with ethyl succinate, yielding ethyl succinylo- 
 succinate, a compound related to benzene. 
 
 Isosuccinic acid, Methyl - propane diacid, ethylidene - succinic 
 add, or methyl -malonic acid, CH 3 CH(C0 2 H) 2 , is formed by 
 the malonic ester synthesis, or from a-chloro- (or iodo-) pro- 
 pionic acid (pp. 237 and 232). It is a solid, when heated 
 decomposes into C0 2 and propionic acid, and yields no an- 
 hydride (p. 234). 
 
 Relative strengths of the dibasic acids: 
 
 K 
 
 Oxalic 10-0 (about) 
 
 Malonic 0'163 
 
 Succinic 0'0066 
 
 Glutaric 0'0047 
 
 The strengths of alkylated succinic acids are not so very 
 different from that of succinic acid, and those of alkyl glutaric 
 acids are of the same order as that of glutaric. 
 
 B. Unsaturated Dibasic Acids 
 
 The unsaturated acids stand in the same relation to the 
 saturated dibasic acids as acrylic acid does to propionic. As 
 dibasic acids they yield derivatives analogous to those of oxalic 
 acid, while as unsaturated compounds each molecule possesses, 
 in addition, the property of combining with two atoms of hy- 
 drogen or halogen, or with one molecule of halogen hydride. 
 
 Common Methods of Formation. 1. By the elimination of 
 water from the hydroxy dibasic-acids. Thus malic acid when 
 distilled yields water and maleic anhydride, which volatilizes, 
 and also fumaric acid, which remains behind : 
 
 CO 2 H.CH(OH).CH 2 .CO 2 H - H 2 O = CO 2 H.CH:CH.CO 2 H. 
 
 The actual product obtained by the elimination of water 
 
 (U480) Q 
 
242 X. DIBASIC ACIDS 
 
 from malic acid varies considerably with the conditions of 
 the experiment. Thus, when malic acid is maintained at a 
 temperature of 140-150 for some time, the chief product is 
 fumaric acid; when the malic acid is rapidly -heated at a 
 higher temperature, maleic anhydride is largely formed. 
 
 Citric acid yields, in a similar way, C0 2 , H 2 0, itaconic acid, 
 CH 2 :C(C0 2 H).CH 2 .C0 2 H, and citraconic anhydride (methyl- 
 maleic anhydride). 
 
 2. By the separation of halogen hydride from the mono- 
 haloid derivatives of succinic acid arid its homologues, e.g. 
 monobromo-succinic acid yields fumaric, thus: 
 
 CO 2 H.CHBr.CH 2 .CO 2 H-HBr = CO 2 H.CH:CH.CO 2 H. 
 
 3. Fumaric acid has been prepared synthetically from 
 acetylene di-iodide, just as succinic acid has been from ethy- 
 lene dibromide. 
 
 Constitution. The acids of this series may be regarded as 
 dicarboxylic acids of the olefines, e.g. fumaric and maleic acids, 
 C 2 H 2 (C0 2 H) 2 , as those of ethylene. Their mode of formation 
 
 1 corresponds exactly with the production of ethylene from 
 alcohol, or with that of acrylic from ethylene lactic acid, while 
 
 2 agrees with that of ethylene from ethyl iodide. 
 
 Maleic acid (ds-Butene diacid), C0 2 H.CH:CH.C0 2 H, crys- 
 tallizes in large prisms, possesses a grating, nauseous acid 
 taste, and is very readily soluble in cold water. It distils 
 unchanged, excepting for partial transformation into maleic 
 anhydride. It is conveniently prepared by heating the acetyl 
 derivative of malic acid (see p. 247), or from fumaric acid and 
 POC1 8 (A. 268, 255). 
 
 Fumaric acid (trans-Butene diacid), C 2 H 2 (C0 2 H) 2 , crystallizes 
 in small prisms with a strong, purely acid taste, and is almost 
 insoluble in cold water. It does not melt, but sublimes at about 
 200 with formation of maleic anhydride. It occurs in Fumaria 
 offidnalis, various fungi, truffles, Iceland moss, &c., and is 
 obtained from maleic acid either by prolonged heating of the 
 latter at 130, or by the action upon it of hydrobromic or 
 other acids. (For its preparation, see A. 268, 255.) 
 
 Both acids are converted into esters when their silver salts 
 are heated with alkyl iodide, and these esters stand in very 
 close relationship to one another, as do the free acids; thus 
 ethyl maleate is changed into ethyl fumarate when warmed 
 with iodine, and the latter ester is formed by saturating an 
 alcoholic solution of maleic acid with dry hydrogen chloride. 
 
STEREO-CHEMISTRY OF UNSATURATED DIBASIC ACIDS 243 
 
 Isomerism of Funiaric and Maleic Acids. The isomerism 
 of these two acids is a problem which has attracted the atten- 
 tion of numerous chemists. Attempts were first made to 
 account for the difference by polymerism or structural iso- 
 merism, e.g. Fittig has suggested 
 
 CO 2 H.CH:CH.CO 2 H and C0 2 H.CH 2 .C-C0 2 H; 
 
 A 
 
 but isomerism of this type is impossible, since both acids 
 when oxidized yield one or other of the tartaric acids C0 2 H 
 CH(OH) CH(OH) . C0 2 H. 
 
 Anschutz has brought forward the formulae 
 
 CH-CO , 
 
 CO 2 H.CH:CH.CO 2 H and || >O. 
 
 CH.C(OH)/ 
 
 Such a formula as the latter is not at all probable, as in this 
 case maleic acid, which is the stronger acid (K = 1'17, and 
 for fumaric K = 0'093), would not possess a carboxylic, but 
 merely a hydroxy lactone structure (PFegscheider, B. 1903, 
 36, 1543). This formula is also found to be quite unten- 
 able when the products of bromi nation and of oxidation are 
 considered. 
 
 The fact that the two acids are structurally identical, and 
 must both be represented as ethylene dicarboxylic acids, is now 
 generally recognized, and the conclusion is largely based on 
 the following facts: (1) Both acids when reduced with 
 sodium amalgam yield ordinary succinic acid. (2) Both acids 
 combine with hydrogen bromide, yielding the same bromo- 
 succinic acid. (3) Both acids combine with water at moderate 
 temperatures, yielding the same malic acid. In most of these 
 additive reactions the maleic acid reacts somewhat more readily 
 than the fumaric, and is at the same time partially transformed 
 into fumaric. (4) When carefully oxidized, the two acids 
 yield stereo-isomeric tartaric acids, maleic being transformed 
 into meso-tartaric, and fumaric into racemic acid.^ (5) Simi- 
 larly, on addition of bromine they yield stereo-isomeric di- 
 bromo-succinic acids. 
 
 As the two acids are structurally identical, the isomerism 
 can only be accounted for by a different spatial relationship 
 of the atoms within the molecule. The stereo-isomerism of 
 these unsaturated compounds is quite distinct from that of 
 the saturated compounds, such as lactic and tartaric acids. 
 
244 X. DIBASIC ACIDS 
 
 We are forced to assume that in saturated compounds where 
 two C atoms are united by a single bond, there is free rotation 
 around the axis represented by the bond; otherwise, the 
 number of isomerides Cabc-Cdef, or even Caab-Caab, 
 would be much greater than what is actually found. When, 
 however, the two carbon atoms become united by a so-called 
 double bond, free rotation is completely prevented, and we 
 have the centres of gravity of the two C atoms and of the 
 four substituents all lying in the same plane, viz. the plane 
 of the paper, e.g. C 2 H 4 may be represented as 
 
 H-C-H 
 
 H.C.H. 
 
 No stereo-isomerism is possible with such a compound, nor 
 yet with any compound in which the 2 radicals attached to 
 the one carbon atom are the same, e.g. CH 2 :CC1C0 2 H; but 
 immediately each carbon atom has 2 different radicals attached 
 to it, isomerism is theoretically possible, e.g. crotonic acid, 
 CH 3 .CH:CH.C0 2 H, and maleic acid, C0 2 H . CH : CH . C0 2 H, 
 viz.: 
 
 CH 3 .C-H CH 3 .C-H 
 
 C0 2 H.C.H H.C.C0 2 H, 
 
 C0 2 H-C.H C0 2 H.C.H 
 
 C0 2 H.C.H H.C.C0 2 H; 
 
 and similarly for oleic and elaidic acids, erucic and brassidic 
 acids, cinnamic and allocinnamic acids and its derivatives, and 
 also for numerous other compounds. 
 
 As the centres of gravities of the carbon atoms and of their 
 substituents all lie in one plane, the molecules are not perfectly 
 asymmetric, and therefore possess no optical activity, and 
 cannot be resolved into optically active components. 
 
 The two isomerides are not so closely related to one another 
 as d- and /-valeric acids, or as d- and Z-tartaric acids; as a rule, 
 they differ entirely as regards their ordinary physical pro- 
 perties, e.g. crystalline form, solubility, melting-point, water 
 of crystallization, dissociation constant, &c., and in many cases 
 considerable differences in chemical properties are met with, 
 e.g. maleic acid yields an anhydride and fumaric acid does not. 
 As a rule, one of the isomerides is less stable than the other, 
 and under suitable conditions, e.g. influence of (a) heat, 
 
STEREO-CHEMISTRY OF UNSATURATED DIBASIC ACIDS 245 
 
 (b) light, (c) chemical reagents, especially small amounts of 
 halogens or halogen hydracids, the labile compound is trans- 
 formed into the stable. With certain pairs of isomerides the 
 transformation is mutual, so that whichever of the two we 
 start with we obtain, under the conditions enumerated above, 
 a mixture of the two in chemical equilibrium. 
 
 As examples of the transforming action of heat we have the 
 following : Fumaric -* maleic; allocinnamic cinnamic; 
 angelic tiglic, and either chloro-fumaric, C0 2 H-CC1:CH. 
 C0 2 H, or chloro-maleic acid heated separately yields a mixture 
 of the two. The effect of exposure to sunlight is often identical 
 with the action of heat, but not always so, e.g. ethyl benzyl- 
 
 aminocrotonate, Q H p h ^ -^ j|^>C : CH C0 2 Et, exists in two 
 
 stereo-isomeric modifications melting at 79 and 21; the effect 
 of heat is to transform the higher melting ester into the lower 
 melting, and the effect of sunlight is the exact opposite. As 
 examples of the influence of chemicals, we have the action 
 of small amounts of nitrous acid in transforming oleic into 
 elaidic and erucic into brassidic acids. Similarly, small 
 amounts of bromine will transform dimethyl maleate into 
 dimethyl fumarate. 
 
 Skraup has shown that either sulphur dioxide or hydrogen 
 sulphide alone is unable to transform maleic into fumaric, but 
 that a mixture of the two will bring about the transformation. 
 The chemical reaction between the H 2 S and S0 2 may be re- 
 garded as a type of detonator which starts the transformation 
 in the maleic acid. All chemical reactions, however, cannot 
 act in the same manner as catalysts. It has also been shown 
 that the salts of maleic acid, e.g. copper maleate, when decom- 
 posed by hydrogen sulphide yield fumaric acid or a mixture 
 of fumaric and maleic acids, although, as stated above, the 
 sulphide itself is incapable of transforming free maleic acid 
 into fumaric. 
 
 The exact method of transformation is not known. It may 
 be (a) that the two radicals attached to the one carbon atom 
 actually exchange positions directly; (b) the two carbon atoms 
 may not be entirely unable to rotate round their common 
 axis, but may only be in a state of strain, and under the 
 influence of light, heat, &c., a rotation through an angle of 
 180 may occur; or (c) in the case of change brought about by 
 chemical agents it is possible that the agent employed first 
 forms an additive compound and is subsequently removed, 
 
246 X. DIBASIC ACIDS 
 
 but this view has been shown to be impossible in many cases 
 by Anschiitz, Fittig, and Michael. 
 
 The system of nomenclature adopted to distinguish between 
 the two isomerides is to term the compound in which two 
 similar substituents are on the same side of the molecule the 
 cis compound, and the isomeride in which the two similar 
 radicals are on opposite sides of the molecule the trans: 
 
 C0 2 H.C-H C0 2 H.C-H 
 
 C0 2 H.C-H H.C.C0 2 H 
 
 cw-Ethylene dicarboxylic acid trans-Ethylene dicarboxylic acid. 
 
 In cases where it has not been found possible to ascertain 
 which of the two known compounds has the cis configuration 
 and which the trans, the ordinary name is given to the one 
 and the prefix iso, or better, allo, to the other, e.g. crotonic and 
 isocrotonic acids, cinnamic and allocinnamic acids. 
 
 Determination of Configuration. In the case of fumaric and 
 maleic* acids this has been accomplished with a considerable 
 degree of certainty. The arguments used for the cis con- 
 figuration of maleic and the trans configuration of fumaric are 
 briefly : (a) Maleic acid when heated, or treated with dehydrat- 
 ing agents, readily yields an anhydride (cf. Succinic anhydride), 
 
 CH-CCK 
 
 />0, which can combine with water to re-form maleic 
 
 acid. Fumaric acid yields no distinct anhydride of its own. 
 (b) Maleic acid when oxidized yields meso-tartaric acid, whereas 
 fumaric acid yields racemic acid (see p. 252) : 
 
 CO 2 H 
 
 H.C.C0 2 H H-j-OH 
 
 H.n.C0 2 H H4-OH 
 
 C0 2 H. 
 
 CO 2 H CO 2 H 
 
 H.C.C0 2 H HfOH d OH-J-H 
 
 C0 2 H.C.H C0 2 H-M)E OH-f(X) 2 H 
 
 Th3 configurations of other pairs of olefine stereo-isomerides 
 have not been determined with the same degree of certainty, 
 and many of the methods described in text-boots as being 
 available for this purpose cannot be relied on, e.g. of two 
 
HYDftOXY DIBASIC ACIDS 247 
 
 stereo-isomeric a- or /Mialogenated compounds, the one which 
 has the halogen in the czs-position with respect to a hydrogen 
 atom will lose halogen hydracid more readily under the 
 influence of alkali, e.g. : 
 
 CH 3 .C.Br CH 3 .C.Br 
 
 H.C.C0 2 H 
 
 In many cases it is probable that exactly the reverse holds 
 good. 
 
 An admirable account of the stereochemistry of olefine 
 derivatives will be found in Werner's " Stereochemie ", 1904 
 pp. 179-227. 
 
 For higher homologues, see Fittig, B. 26, 40. 
 
 Acetylene-dicarboxylic acid, Butine diacid, C0 2 HC:C' 
 C0 2 H, is a type of an acetylenic acid; it is obtained by the 
 elimination of two molecules of hydrogen bromide from one of 
 dibromo-succinic acid. It possesses the characteristic proper- 
 ties of a dibasic acid, and also of an unsaturated compound, 
 but does not yield metallic derivatives of the type of silver 
 acetylene. It readily loses carbon dioxide, yielding propargylic 
 acid, CH:C-C0 2 H. Diacetylene-dicarboxylic acid, C0 2 H- 
 C:C'CiCC0 2 H, and tetracetylene-dicarboxylic acid, Deca- 
 tetrine diacid, C0 2 H .CiC-CiC-CiC-CiO. C0 2 H, have been 
 prepared by Baeyer (B. 18, 678 and 2269). With increasing 
 length of chain they show an increasing tendency to explode. 
 (For Baeyet's theory of explosions, see B. 18, 2277.) 
 
 C. Hydroxy Dibasic Acids 
 
 1. Tartronic acid, Propanol diacid, hydroxy-malonic acid, OH- 
 CH.(C0 2 H) 2 , forms large prisms (-f ^H 2 0), and is ^ easily 
 soluble in water, alcohol, and ether. It cannot be distilled 
 unchanged, since it breaks up on heating into carbon dioxide 
 and glycolide. As hydroxy-malonic acid it may be prepared 
 by the action of moist silver oxide on chloromalonic acid. It 
 may also be obtained by the reduction of the corresponding 
 ketonic acid, mesoxalic acid, CO(C0 2 H) 2 , and also by the 
 oxidation of glycerol with permanganate. 
 
 2. Malic acid, Butanol diacid, hydroxy-succinic acid, C0 2 H- 
 CH 2 .CH(OH).COJS (Scheele, 1785), is very widely distributed 
 in the vegetable kingdom, being found in unripe apples, sorb- 
 apples, grapes, barberries, mountain-ash berries, quinces, &c. 
 
248 X. DIBASIC ACIDS 
 
 Some of the simpler methods of formation are quite analogous 
 to those employed in the case of hydroxy monobasic acids, e.g. 
 
 (1) by the action of moist silver oxide on bromo-succinic acid; 
 
 (2) by the reduction of tartaric or racemic acid with HI, and 
 of oxal-acetic acid (pp. 224 and 260) with sodium-amalgam; 
 
 (3) by the action of nitrous acid on the corresponding amino 
 acid, aspartic acid; and (4) by the addition of the elements of 
 water to fumaric or maleic acid under the influence of aqueous 
 sodic hydroxide. 
 
 It crystallizes in hygroscopic needles, is readily soluble in 
 water and alcohol, but only sparingly in ether. It melts at 
 100, and when it is distilled, maleic anhydride passes over 
 and fumaric acid remains in the retort (p. 241). K = 0'04. 
 
 The molecule of malic acid contains an asymmetric carbon 
 atom, and thus the acid should exist in two optically active 
 and a racemic modification. The acid obtained from natural 
 sources, Z-malic acid, is Ia3vo-rotatory in dilute solution, but the 
 rotation diminishes as the concentration increases. With a 
 34-per-cent solution at 20 no optical activity is shown, and with 
 more concentrated solutions dextro-rotation is exhibited. The 
 acid obtained synthetically is optically inactive and constitutes 
 the racemic form, and it has been resolved into optically active 
 modification by the usual methods (p. 254), (B. 1898, 31, 528). 
 
 The alkali salts and the acid calcium salt of malic acid are 
 readily soluble in water, while the normal calcium salt is only 
 sparingly soluble. 
 
 The constitution follows from its methods of preparation, 
 from the fact that it is readily reduced to succinic acid, and 
 that its esters react with acetic anhydride, yielding mono- 
 acetyl derivatives. 
 
 Amides and Amines of Malic Acid. Like glycollic acid, 
 malic acid forms as an acid amides (saponifiable), and as 
 an alcohol an amine (not saponifiable). The amides are: 
 
 Malamide, NH 2 .CO.CH(OH).CH 2 .CO.NH 2 , crystallizing 
 in prisms, and malamic acid, C0 2 H.CH 2 .CH(OH).Cp-NH 2 , 
 the latter being only known as ethyl ester. The amino-acid, 
 aspartic acid, C0 2 H CH(NH 2 ) - CH 2 CO 2 H, unites in itself, 
 like glycocoll, the properties of a base and of an acid, but 
 the acid character predominates. Its acid amide, asparagine, 
 CO 2 H.CH(NH 2 ).CH 2 .CO.NH 2 , which is isomeric with mal- 
 amide, is very widely distributed in the vegetable kingdom, 
 being present in the young leaves of trees, in beet-root, 
 potatoes, the shoots of peas, beans, and vetches, and in 
 
ASPARTIC ACID. TARTARIC ACID 249 
 
 asparagus; it was first found in the last-named vegetable in 
 the year 1805. It forms glistening rhombic prisms (+ H 2 0), 
 is readily soluble in hot water, but insoluble in alcohol and 
 ether, and yields aspartic acid when hydrolysed. It is leevo- 
 rotatory. 
 
 A dextro-rotatory asparagine has likewise been obtained 
 from the shoots of vetches (B. 20, Ref. 510); it possesses a 
 sweet taste, and unites with the laevo-rotatory compound to 
 an inactive modification. For the synthesis of the asparagines 
 and their constitution, see Piutti, B. 22, Ref. 241 and 243. 
 
 Aspartic acid, amino-succinic add, is present in beet molasses, 
 and forms an important product of the decomposition of 
 proteids with acids or alkalis. It has been synthesized, e.g. 
 from bromo-succinic acid and ammonia, and crystallizes in 
 small rhombic plates readily soluble in hot water. It exists 
 in optically active modifications, which differ in taste and 
 are convertible the one into the other (B. 20, R. 510). 
 Nitrous acid transforms both aspartic acid and asparagine 
 into malic acid. 
 
 Glutainic acid, a-amino-glutaric acid, C0 2 H CH(NH 2 ) CH 2 
 CH 2 ^C0 2 H, and glutamine correspond with aspartic acid and 
 asparagine. The former is found in beet-root and in the 
 shoots of the vetch and gourd, while the latter is produced, 
 together with aspartic acid and leucine, by boiling proteids 
 with dilute sulphuric acid. 
 
 D. Dihydroxy Dibasic Acids 
 
 These acids are characterized by the presence of two hy- 
 droxyl radicals in the molecule in addition to two carboxyls. 
 
 Tartaric acid, Butane -diol diacid, dihydroxy - succinic add, 
 C0 2 H . CH(OH) . CH(OH) (C0 2 H), exists in four distinct 
 modifications. 
 
 1. d- or Dextro-tartaric acid, m.-pt. 170. 
 
 2. /- or Laevo-tartaric acid, anti-tartaric add, m.-pt. 170. 
 
 3. Racemic acid, d-l-tartaric add, para-tartaric add, m.-pt. 
 206. 
 
 4. i- or Inactive tartaric acid, meso-tartaric add, m.-pt. 143. 
 
 The constitution of these acids follows from their relation- 
 ship to succinic acid, from their methods of formation, and 
 from the fact that their esters with acetic anhydride yield 
 diacetyl derivatives. 
 
 Solutions of equal concentration of the two first of these 
 
250 X. DIBASIC ACIDS 
 
 acids turn the plane of polarization of light in an equal 
 degree, but in opposite directions. By their union the in- 
 active racemic acid is formed, and this can, conversely, bo 
 separated into its components. The fourth tartaric acid, 
 likewise inactive, cannot be resolved in this way. 
 
 The common tartaric acid found in nature is optically 
 active, and is the ^-tartaric acid, whereas the acids obtained 
 synthetically are optically inactive, viz. racemic acid or meso- 
 tartaric acid, or a mixture of both, e.g. dibromo-succinic acid 
 with moist silver oxide yields a mixture of racemic and meso- 
 tartaric acids. 
 
 Fumaric acid when oxidized with permanganate is converted 
 into racemic acid, and maleic acid by a similar process into 
 meso-tartaric acid (p. 246). Glyoxal cyanhydrin (p. 221) when 
 hydrolysed yields racemic acid, and finally, mannitol when 
 oxidized with nitric acid yields racemic acid, and sorbitol 
 meso-tartaric acid. 
 
 Synthesis : 
 
 CH 2 :CH 2 - CH 2 Br.CH 2 Br - CN.CH 2 .CH 2 -CN 
 Br KCN 
 
 C0 2 H.CHBr.CHBr.C0 2 H 
 Hydrolysis Br 2 
 
 C0 2 H.CH(OH).CH(OH).C0 2 H. 
 AgOH 
 
 Stereo-isomerism of the Tartaric Acids. The isomerism of 
 the tartaric acids is of much the same type as that discussed 
 in the case of active valeric and of a-lactic acid. A glance at 
 the constitutional formula for the acids shows the presence of 
 2 asymmetric carbon atoms; to each of these 2 atoms are 
 attached the radicals H, OH, and C0 2 H, and the remaining 
 valency of each carbon is employed in attaching it to the other 
 carbon atom. 
 
 A compound of this general type, C(a, b, c) C(a, b, c), is 
 known as a compound containing 2 similar asymmetric carbon 
 atoms. If one valency of each carbon is employed in uniting 
 the 2 carbon atoms together, then the 3 radicals, a, b, c, which 
 are attached to the remaining three valencies of a carbon atom, 
 
 may be arranged in two distinct ways, viz. a ~^ , positive order, 
 and V' , negative order. 
 
STEREO-CHEMISTRY OF TARTARIC ACIDS 
 The following combinations are thus possible: 
 
 251 
 
 But Nos. 3 and 4 must be identical, as the radicals attached 
 to the 2 asymmetric carbon atoms are identical. 
 These spatial relationships may be represented: 
 
 where a = H, b = OH, and c = C0 2 H. 
 
 Note. At first sight it appears as though the radicals a, b, c 
 in the lower half of fig. 1 were arranged in the and not the 
 -f- order, as indicated. It must be remembered, however, that 
 each part of the molecule must be looked at from the same 
 point of view; and if we take the order of the radicals in the 
 upper tetrahedron when arranged so that the solid angle 
 which represents the point of attachment to the second tetra- 
 hedron is pointed down, then we must regard the second 
 tetrahedron from the same point of view, i.e. we must turn 
 the figure upside down. It is then seen that the arrangement 
 in the lower half of the molecule is the -f . 
 
 Instead of using the above cumbrous figures, it is usual to 
 regard such models as projected upon a plane surface, and to 
 use the projections thus obtained (E. Fischer, B. 1891, 24, 2684): 
 
 a C-b 
 u C a 
 
 \y 
 
 )_C a b C a 
 
 Jw 
 
 a U b 
 
 i 
 e 
 
 I 
 b C-a 
 
 I 
 
 e 
 
252 X. DIBASIC ACID8 
 
 or c c 
 
 a-Lb b-fa b-U 
 
 b-U a-Lb b-L-a 
 
 Note. The manner in which these projection formulae are 
 obtained can be best seen by means of models. 
 
 A comparison of the three configurations at once shows that 
 Nos. I and II are perfectly asymmetric, and are related to 
 one another as object to mirror image; they should therefore 
 represent the two optically active tartaric acids, and the 
 compound of the two should represent the molecule of racemic 
 acid. No. Ill has a plane of symmetry, and should therefore 
 represent the non-resolvable, inactive acid meso-tartaric acid. 
 
 The question as to whether No. I represents d- or /-tartaric 
 acid has been settled by Fischer (B. 1896, 29, 1377) in favour 
 of the d-acid. We thus have : 
 
 CO 2 H CO 2 H CO 2 H 
 
 H-[-OH OH-Ln OH-j-H 
 
 OH-j-H H-K)H OH-f-H 
 
 C0 2 H C0 2 H C0 2 H 
 
 d I meso 
 
 1. Dextro-tartaric acid, acidum tarlaricum, is the tartaric 
 acid found in nature. It was discovered by Scheele in 1769. 
 It occurs in the free state, but chiefly as acid potassium salt, 
 in various fruits, especially in the juice of grapes, from which 
 potassic hydric tartrate (cremor tartari) separates in crystals 
 during fermentation. When this is boiled with chalk and 
 chloride of calcium it is transformed into the neutral calcium 
 salt, from which the acid is liberated on addition of H 2 S0 4 . 
 
 It crystallizes from water in large transparent monoclinic 
 prisms, of a strong and purely acid taste, is readily soluble in 
 water, also in alcohol, but almost insoluble in ether. It melts 
 at 170, and its aqueous solution reduces an ammomacal silver 
 solution upon warming. When melted, it is changed into an 
 amorphous modification, and then into an anhydride, and when 
 heated more strongly it carbonizes with the dissemination of 
 a characteristic odour and formation of pyro-racemic and pyro- 
 tartaric acids. Oxidation converts it either into dihydroxy- 
 tartaric (p. 260) or tartronic acid, and then into formic and 
 carbonic acids, &c. It is employed in medicine, dyeing, &c. 
 
TARTARIC ACID DERIVATIVES 253 
 
 Normal potassic tartrate, C 4 H 4 6 K + JH 2 O, forms mono- 
 clinic prisms easily soluble in water. "Acid potassic tartrate, 
 tartar, or cremor tartari, C 4 H 5 6 K, small rhombic crystals 
 of acid taste, sparingly soluble in water, is much used in 
 dyeing, medicine, &c. Potassic sodic tartrate, Rochelle or 
 seignette salt, C 4 H 4 6 KNa + 4H 2 (1672), forms magnificent 
 rhombic prisms. Calcic tartrate, C 4 H 4 6 Ca -f 4H 9 0, is a 
 powder insoluble in water, but soluble in cold caustic-soda 
 solution; on warming the solution it separates as a jelly, 
 which redissolves upon cooling. Potassic antimonyl-tartrate, 
 tartar emetic, C 4 H 4 6 (SbO)'K + JH 2 (see B. 15, 1540), is 
 obtained by heating cream of tartar (cremor tartari) with anti- 
 mony oxide and water. It crystallizes in rhombic efflorescent 
 octahedra, readily soluble in water. It is poisonous and acts 
 as an emetic, and is used as a mordant in dyeing. 
 
 Fehling's solution is a solution of cupric sulphate mixed with 
 alkali and Eochelle salt, and is largely used as an oxidizing 
 agent. Thus with various carbon compounds, such as formal- 
 dehyde, glucose, fructose, &c., it readily yields a precipitate of 
 cuprous oxide. 
 
 The diethyl ester is a thick oil, while the monoethyl ester 
 crystallizes in prisms. Aceto-tartaric acid and amides of 
 tartaric acid are known, and also various anhydrides. As an 
 alcohol, it forms with nitric acid a dinitric ester, the so-called 
 nitro-tartaric acid, C 2 H 2 (O N0 2 ) 2 (C0 2 H) 2 , which is readily 
 hydrolysed, yielding dihydroxy-tartaric or tartronic acid. 
 
 2. Laevo-tartaric acid is identical in its chemical and also 
 in almost all its physical properties with ordinary tartaric acid, 
 but differs from it in that its solutions turn the plane of polar- 
 ization of light to the left, in a degree equal to that in which 
 the other turns it to the right. The crystallized salts show 
 hemihedral faces like the salts of dextro-tartaric acid, but 
 oppositely situated (see p. 254). When equal quantities of 
 both acids are mixed together in aqueous solution, the solu- 
 tion becomes warm, and we obtain: 
 
 3. Eacemic acid, (C 4 H 6 6 ) 2 , 2H 2 0, the composition of 
 which was first established by Berzelius, who recognized it as 
 being different from tartaric acid, and who developed the idea 
 of isomerism from this first example in 1829. Racemic acid is 
 obtained from tartar mother liquor. It differs from dextro 
 tartaric acid in that its crystals are rhombic and efflorescent, 
 and also less soluble in water than the former; further, the free 
 acid is capable of precipitating a solution of calcium chloride 
 
254 
 
 X DIBASIC ACIDS 
 
 and is optically inactive (see below). The salts, which are 
 termed racemates, and also the esters (B. 21, 518), show small 
 differences from the tartrates in the proportions of their water 
 of crystallization, in solubility, and melting-point or boiling- 
 point. Molecular- weight determinations of dilute aqueous 
 solutions of racemic acid indicate that under these conditions 
 it is completely resolved into d- and Z-tartaric acids. 
 
 4. Meso-tartaric acid, a fourth tartaric acid, is inactive like 
 the foregoing, but non-resolvable into the active acids. When 
 heated with water at 170 it is partially transformed into 
 racemic acid, which can then be resolved. It differs from 
 racemic acid and also from the active acids in all its physical 
 properties. It crystallizes in efflorescent rectangular plates, 
 m.-pt. 143. The acid-potassium salt is readily soluble in water. 
 
 Racemic Compounds. Resolution of Racemic Compounds into 
 their Optically Active Components. Racemic acid has been re- 
 solved by three distinct methods, all due to Pasteur; and as 
 they are also applicable to the resolution of other racemic 
 compounds, they are given below. 
 
 1. When a solution of sodium-ammonium racemate, 
 
 Na(NH 4 )C 4 H 4 6 , 2H 2 O, 
 
 is evaporated, beautiful rhombic crystals having the compo- 
 sition NaNH 4 C 4 H 4 O 6 , 4H 2 and showing hemihedral faces* 
 
 * Hemihedral Faces. These are small faces which are not perfectly 
 symmetrically situated with respect to the other crystalline faces; they 
 occur in only half the positions where they might be expected, and thus 
 give the crystals a non-symmetric structure. 
 
 The following figs, represent crystals of the d- and Z-sodic ammonic 
 tartrates : 
 
 The faces a and b are the hemihedral faces, and it will be noticed that 
 the two crystals are non-superposable, but stand in the relationship of 
 object to mirror-image. 
 
RESOLUTION OF RACEMIC COMPOUNDS 255 
 
 are obtained. Pasteur observed that these faces were not 
 always similarly situated, but that certain crystals were 
 dextro-hemihedral, while others were Isevo-hemihedral, so 
 that one crystal formed the reflected image of the other. 
 The Isevo-hemihedral crystals when dissolved exhibit dextro- 
 rotation, and vice versa. If now the two kinds of crystals be 
 separated from one another mechanically, and the free acid 
 liberated from each, this will be found to consist, not of racemic 
 acid, but in the one case of dextro- and in the other of Isevo- 
 tartaric acid. 
 
 In the process of crystallization it is essential that the tem- 
 perature should be below 27, as otherwise, in place of the 
 enantiomorphously related crystals of sodic-ammonic d- and 
 /-tartrates, it is found that the crystals are all alike, possess 
 no hemihedral faces, and consist of sodic-ammonic racemate. 
 This temperature is termed the transition point, and for each 
 racemic compound there is a definite transition temperature. 
 Thus for sodic-potassic racemate it is 3, for rubidic racemate 
 40 '4, for ammonic-hydric malate 74. 
 
 In the case of sodic-ammonic racemate the transition tem- 
 perature may be determined by means of a dilatometer (Varit 
 Hoff and Deventer, Zeit. Phys., 1887, 1, 173). This is a large 
 thermometer, the bulb of which is filled with an equimolecular 
 mixture of the two active salts and covered with oil, the level 
 of which can be read off on the stem. As the temperature of 
 the dilatometer is raised gradually, a considerable increase in 
 volume is noticed at 27, due to the change expressed by the 
 equation : 
 
 NaNH 4 C 4 H 4 6 , 4H 2 O + NaNH 4 C 4 H 4 6 , 4 H 2 O 
 
 = (NaNH 4 C 4 H 4 6 ) 2 , 2H 2 O + 6H 2 O. 
 
 Other racemic compounds have been resolved by this simple 
 method of crystallization. In all cases the temperature em- 
 ployed must be below the transition temperature of the given 
 substance, i.e. below the temperature at which the mixture 
 of active components becomes transformed into the racemic 
 compound. In this method of resolution no differences in 
 solubility of the two components are met with, and hence no 
 process of fractional crystallization can be employed; the two 
 salts are deposited side by side, and must be picked out indi- 
 vidually. The resolution of zinc ammonic lactate has already 
 been mentioned (p. 215); further examples are sodic-potassic 
 racemate, asparagin, and camphoric acid. 
 
256 X. DIBASIC ACIDS 
 
 2. A very common method of resolving racemic acids is by 
 combination with an optically active base, e.g. an alkaloid. In 
 the case of racemic acid itself, Pasteur used /-cinchonine. The 
 two salts formed are (a) d-acid -f- /-base, (b) /-acid + /-base. 
 As these two salts are not enantiomorphously related, i.e. 
 their molecules do not stand in the relationship of object to 
 mirror-image, they possess different solubilities, and may be 
 separated by fractional crystallization. 
 
 The following is a list of some simple racemic compounds 
 which have been resolved by this method; the salt named is 
 the less soluble of the two, and crystallizes first. 
 
 Acids. Quinine: d-tartrate. Strychnine: /-lactate, d-methyl- 
 succinate, ^-methoxy-succinate, c/-phenyldibromo-propionate. 
 Cinchonine: /-tartrate, d^-malate, d-mandelate. Brucine: d-tar- 
 trate, /-valerate, /-aspartate. 
 
 Racemic bases may be resolved by a similar process, viz. 
 by combination with an optically active acid, e.g. d-tartaric, or 
 even better, d-bromocamphor-sulphonic acid, and separating 
 the two salts thus obtained by fractional crystallization. Thus 
 ethyl-piperidine and coniine have been resolved by Ladenburg 
 by using d-tartaric acid (A. 1888, 247, 85; cf. also Pope and 
 Harvey on resolution of tetrahydro-/3-naphthylamine, J. C. S. 
 1901, 74; also Pope and Peachey, ibid. 1899, 1066 and 1105). 
 
 3. The third method consists in subjecting a solution of an 
 ammonium salt of the acid to the action of some of the lower 
 plant organisms, e.g. moulds, bacteria, yeasts, &c. Different 
 organisms are required in different cases. Pasteur found that 
 ordinary green mould Penicillium glaucum when grown in a 
 solution of ammonium racemate, destroys the salt of the c?-acid 
 and leaves a solution of the salt of the ^acid. If, however, the 
 decomposition is allowed to proceed, the /-salt is also destroyed ; 
 the reaction is a preferential decomposition, and, if stopped at 
 a suitable time, practically all d-salt will have disappeared. It 
 is obvious that in this method one of the active components is 
 lost; but by using two distinct organisms in separate solutions 
 it is sometimes possible to obtain both d- and /-compounds. 
 Thus Penicillium glaucum grown in a solution of a salt of d-l- 
 mandelic acid leaves the d-salt, and Saccharomyces ellipsoideus 
 leaves the /-salt. 
 
 Among other resolutions which have been effected by this 
 method may be mentioned the destruction of /-lactic, /-mandelic, 
 d-glyceric, /-ethoxy-succinic acids, and of d-methylpropyl-car- 
 binol by Penicillium glaucum, and the destruction of d-mandelic, 
 
RACEMIG COMPOUNDS 257 
 
 ?-phenyldibromo-propionic acids and of ^-glucose, d-fmctose, 
 and ^-manno.se by yeast (different species). 
 
 4. Markwald and M'Kenzie (B. 1901, 34, 469) have suggested 
 another method of resolution, viz. by esterifying the racemic 
 acid with an optically active alcohol. They used r-mandelic 
 acid and Z-menthol, and found that the ^-component of the 
 racemic acid was esterified somewhat more rapidly than the /. 
 (Of. also Mackenzie, J. C. S. 1904, 378.) 
 
 5. Ostromisslensky (B. 1908, 41, 3035) has shown that a mix- 
 ture of d- and /-isomerides can be easily separated if a super- 
 saturated solution of the mixture is impregnated with a crystal 
 of a suitable active material, thus a crystal of /-asparagine 
 (p. 248) immediately produces the deposition of d-sodium am- 
 monium tartrate from a supersaturated solution containing the 
 d- and /-salts. A crystal of any optically active tartrate or of 
 any isomorphous substance will also cause a separation of one 
 of the active sodium ammonium tartrates, the actual salt de- 
 posited depending on the activity of the crystal used, e.g. 
 c?-sodium tartrate always deposits c?-sodium ammonium tar- 
 trate. It is not necessary that the impregnating substance 
 should be optically active; it must, however, be isomorphous 
 or isodimorphous. Thus a crystal of glycine can cause the 
 deposition of Z-asparagine from a supersaturated solution of 
 d-l asparagine. 
 
 This method of resolution cannot be used when the super- 
 saturated solution contains a definite racemic compound of the 
 d-l isomerides, and can thus be used as a method for deter- 
 mining whether the given substance exists in solution as a 
 d-l conglomerate or as a true racemic compound. 
 
 Racemisation. When d-tartaric acid is heated with a small 
 amount of water at 175 racemic acid is formed, together with 
 a small amount of the meso acid. This conversion of an 
 optically active compound into its racemic isomeride is usually 
 termed racemisation, and is to be attributed to the transforma- 
 tion of 50 per cent of the original active acid into its optical 
 isomer. As further examples of racemisation, may be men- 
 tioned the heating of d- valeric acid with concentrated sul- 
 phuric acid and of amyl alcohol with sodium hydroxide. 
 When valeric acid is boiled for eighty hours partial racemi- 
 sation occurs, as is indicated by a slight diminution in its 
 rotatory power. Racemisation often occurs during a chemical 
 reaction; thus Z-mandelic acid, C 6 H 5 -CH(OH).C0 2 H, and 
 hydrobromic acid at 50 yield not /-phenylbromo-acetic but 
 
 (B480) $ 
 
258 
 
 X. DIBASIC ACIDS 
 
 r-phenylbromo-acetic acid. (Cf. also Easterfield, J. C. S. 1891, 
 72; Pope, ibid. 1901, 81, and P. 1900, 116.) 
 
 Occasionally the racemisation occurs at the ordinary tem- 
 perature, and is then termed autoracemisation; thus d-phenyl- 
 bromo-acetic acid when kept in benzene solution for some 
 three years becomes quite inactive, and ethyl d-bromo-suc- 
 cinate in the course of four years diminishes in rotatory power 
 from +40-96 to +9 (Walden, B. 1898, 31, 1416). 
 
 Criteria for Determining the Nature of the Racemic Compound. 
 The racemic substance may be one of the following: (a) A 
 definite compound of 1 molecule of the ^-component with 1 of 
 the I. (b) An ordinary mixture of the two in molecular pro- 
 portions, (c) Mixed crystals, i.e. a solid solution of the two 
 isomorphous antipodes without chemical combination. The 
 first are termed racemic compounds proper, the second inactive 
 conglomerates, and the third pseudoracemic compounds (Kip- 
 ping and Pope, J. C. S. 1897, 989). 
 
 A true racemic compound cannot be recognized by mole- 
 cular-weight determinations, as in the gaseous form or in 
 solution it is usually resolved into its components. In certain 
 cases the recognition of the substance as a racemic compound 
 is simple, e.g. sodic-ammonic racemate, which crystallizes in 
 a different crystallographic system, and contains a different 
 amount of water of crystallization from the active isomers, 
 and possesses a definite transition point. 
 
 When such simple criteria are of no use, Backhuis Eoozeboom 
 (Zeit. Phys. 1899, 28, 494) recommends a study of the 
 melting-point curves. These are obtained by taking the 
 melting-points of mixtures of the compounds in different 
 proportions, and then plotting the melting-points against 
 the composition. The following types of curves are met 
 with: 
 
 Conglomerates, fig. 1. Racemic compounds, figs. 2 and 3. 
 Mixed crystals, figs. 4, 5, and 6. 
 
 B 
 
POLYHYDROXY DIBASIC ACIDS 
 C 
 
 B 
 
 B 
 
 259 
 
 A represents the melting-point of the pure ^-compound, B that 
 of the pure I, and C that of the racemic compound or mixture. 
 These curves should be studied by aid of the Phase rule. 
 
 E. Polyhydroxy Dibasic Acids 
 
 Trihydroxy - glutaric acid, C0 2 H CH(OH) CH(OH) 
 CH(OH) C0 2 H, and the stereo -isomeric acids saccharic, 
 mucic, and isosaccharic acid C0 2 H CH(OH) CH(OH) 
 CH(OH).CH(OH).C0 2 H, are the best-known examples. 
 
 Many of these acids form lactones (p. 217), the so-called 
 lactonic acids, and some of them also double lactones (cf. Fittig, 
 A. 255, 1, et seq.). 
 
 Trihydroxy-glutaric acid, C0 2 H.(CH.OH) 3 .C0 2 H, is a fre- 
 quent oxidation-product of sugar varieties, e.g. of xylose and 
 arabinose. According to theory, four stereo-isomers should 
 exist, and four are actually known; they may be represented 
 by the following projection formulae, where X = C0 2 H: 
 
 ^\. 
 
 OH4-H 
 H-j-OH 
 H-j-OH 
 
 X 
 
 H-^OH 
 HO4-H 
 HO-j-H 
 
 X 
 
 H-OH 
 H-hOH 
 
 HOHE 
 H-K)H 
 
 X 
 
 Nos. 1 and 2 are enantiomorphously related and optically 
 active, and can form a racemic compound. Compounds 3 and 
 4 are inactive substances of the type of mesotartaric acid. 
 
 Saccharic acid is produced by the oxidation of cane-sugar, 
 glucose, gulose, gulonic acid, mannitol, or starch by nitric 
 acid, and exists in the d-, Z-, and r-forms (see Glucoses); (/-sac- 
 charic acid when reduced yields glycuronic acid (see p. 222). 
 All the three varieties are deliquescent. 
 
 Mucic acid is formed by oxidizing dulcitol, the gums, muci- 
 
260 X. DIBASIC ACIDS 
 
 lages, and milk-sugar. It is a sparingly soluble, colourless, 
 crystalline powder. The molecule being symmetrical in struc- 
 ture, it is optically inactive. It is easily converted into deri- 
 vatives of furane (see this). 
 
 Isosaccharic acid is obtained by the oxidation of glucos- 
 amine, C 6 H n 6 (NH 2 ). 
 
 Theoretically, ten stereo -isomeric acids of the formula 
 C0 2 H-[CH.OH] 4 .CO 2 H are possible, most of which (e.g. el- 
 and i-manno-saccharic acids, talomucic acid, &c.) have been 
 prepared by E. Fischer (B. 24, 539, 2137, 3622). For their 
 relations to the hexoses, see the table appended to these. 
 
 F. Dibasic Ketonic Acids 
 
 Dibasic ketonic acids unite in themselves the properties of a 
 ketone and of a dibasic acid. The following are known : 
 
 1. Mesoxalic acid, CO(C0 2 H) 2 or C(OH) 2 (C0 2 H) 2 (see p. 
 199), is prepared from dibromo-malonic acid, CBr 2 (C0 2 H) 2 , 
 and baryta water or oxide of silver, thus: 
 
 CBr 2 (C0 2 H) 2 + H 2 = CO(CO 2 H) 2 + 2HBr; 
 
 also by boiling alloxan (p. 288) with baryta water. It crys- 
 tallizes in deliquescent prisms (-f ILO). 
 
 As a ketone it combines with NaHS0 3 , reacts with hy- 
 droxylamine, and is reduced by nascent hydrogen to tar- 
 tronic acid: 
 
 O) 2 H.CO.CO 2 H + 2H = CO 2 H.CH(OH).CO 2 H. 
 
 Since the acid and its salts still retain a molecule of water 
 at temperatures above 100, this may be united in much the 
 same manner as the water in chloral hydrate, corresponding 
 with the formula C(OH) 2 (C0 2 H) 2 , " dihydroxy-malonic acid ". 
 In fact, two modifications of the ethyl ester are known, viz. 
 C(OH) 2 (C0 2 C 2 H 5 ) 2 and CO(C0 2 C 2 H 5 ) 2 . 
 
 2. Oxal-acetic acid, Butanone diacid, C0 2 H CH 2 CO C0 2 H, 
 is an acid corresponding in many respects with aceto-acetic acid. 
 Its ethyl ester is prepared by the action of sodium ethoxide 
 upon a mixture of ethyl oxalate and acetate (p. 224), and 
 also by the action of concentrated sulphuric acid upon ethyl 
 acetylene-dicarboxylate. It is a colourless oil, but the alco- 
 holic solution gives an intense dark-red coloration with ferric 
 chloride. It is of importance as a synthetical reagent, as the 
 hydrogen atoms of the methylene group can be replaced by 
 
POLYBASIC ACIDS 261 
 
 Sodium, and hence by various alkyl and acyl radicals (W. 
 fPislicenus). 
 
 3. Acetone -dicarboxylic acid, Pentanone diatid, CO(CH 2 
 C0 2 H) 2 , obtained by treating citric acid with concentrated 
 H 2 S0 4 , readily decomposes into acetone and 2C0 2 (see A. 261, 
 151). 
 
 4. Dihydroxy-tartaric acid, C0 2 H . CO - CO C0 2 H, or pro- 
 bably C0 2 H.C(OH) 2 .C(OH) 2 .C0 2 H, is formed from pyro- 
 catechol and nitrous acid, and by the gradual decomposition 
 of nitro-tartaric acid. It melts at 98. The characteristic 
 sparingly soluble sodium salt decomposes readily into carbon 
 dioxide and sodium tartronate. 
 
 CH 8 .CO.CH.CO,H 
 
 5. Diaceto-succmic acid, ^^^^^ (see p. 229). 
 
 The ester of this is closely related to acetonyl-acetone, the 
 latter being readily obtainable from the former by the action 
 of caustic-soda solution ("Ketonic decomposition": cf. B. 33, 
 1219). 
 
 6. Diacetoglutaric acid, (X) 2 H . CHAc CH 2 CHAc CO S H. 
 The ester of this acid is formed by condensing ethyl aceto- 
 acetate with formaldehyde in the presence of diethyl amine, 
 and is readily converted into derivatives of tetrahydrobenzenf 
 or pyridine (Knoewnagel, A. 281, 94; cf. also B. 31, 1388). 
 
 Most of these ketonic acids exhibit keto-enolic tantomerism, 
 thus 5 isomerodes of diacetyl-succinic acid are known (Knorr, 
 A. 1899, 306, 332). 
 
 XL POLYBASIC ACIDS 
 
 The polybasic acids contain two or more carboxylic groups 
 in the molecule. The tribasic acids, like phosphoric acid, can 
 give rise to three series of salts normal, monoacid, and di- 
 acid. Both saturated and unsaturated acids are known, and 
 also substituted derivatives. 
 
 A. Saturated and Unsaturated Polybasic Acids 
 
 A simple tribasic acid is tricarballylic acid, symmetrical pro- 
 pane -tricarboxylic acid, C0 2 H.CH 2 .CH(C0 2 H).CH 2 .C0 2 H. 
 It occurs in unripe beet, and is prepared (a) by the addition 
 of hydrogen to aconitic acid, (b) by heating citric acid with 
 hydriodic acid, and (c) synthetically from glycerol by trans- 
 forming it into the tribromhydrin, C 8 H 6 Br 8 , treating this with 
 
262 XL POLYBASIC ACH>S 
 
 KCN, and hydrolysing the cyanide formed, C 3 H 5 (CN) 3 . Since 
 the three hydroxyls in glycerol are distributed among three 
 carbon atoms, the same holds good for the carboxyls in the 
 acid, which has, therefore, the symmetrical constitution: 
 
 C0 2 H CH 2 CH(C0 2 H) . CH 2 . CO 2 H. 
 
 This acid is of importance in determining the constitution 
 of citric acid, from which, as already seen, it can be- obtained 
 by reduction with HI. It crystallizes in rhombic prisms, is 
 readily soluble in water, and melts at 166. 
 
 An unsaturated tribasic acid closely related to tricarballylic 
 acid is aconitic acid, C0 2 H.CH:C(C0 2 H).CH 2 .C0 2 H, which 
 contains two atoms of hydrogen less than tricarballylic acid. 
 It is found in nature, in Aconitum Napellus, shave-grass, sugar- 
 cane, beet-root, &c., and is prepared by heating citric acid, 
 C 6 H 8 7 , when the elements of water are eliminated. It is a 
 strong acid, crystallizable, readily soluble in water, melts at 
 191, and is reduced by nascent hydrogen to tricarballylic 
 acid, hence its constitution. 
 
 B. Hydroxy Polybasic Acids 
 
 Citric acid, acidum citricum, hydroxy-tricarballylic acid, C0 2 H 
 CH 2 .C(OH)(C0 2 H).CH 2 .CO 2 H (Sdieele, 1784; recognized as 
 tribasic by Liebig in 1838), occurs in the free state in lemons, 
 oranges, and red bilberries, and mixed with malic acid in 
 gooseberries, &c., also as calcium salt in woad, potatoes, beet- 
 root, &c. It is usually prepared from the juice of lemons by 
 means of the lime salt. It crystallizes in large rhombic prisms 
 ( + H 2 0), is readily soluble in water, moderately in alcohol, 
 but only sparingly in ether. It loses its water of crystal- 
 lization at 130, melts at 153, and breaks up at a higher 
 temperature first into aconitic acid and water, and then into 
 carbon dioxide, itaconic acid, citraconic anhydride, and acetone. 
 Oxidizing agents effect a verv thorough decomposition. 
 
 Calcium citrate is precipitated as a white sandy powder 
 when a mixture of calcium chloride and alkali citrate solutions 
 is boiled. The three series of salts are well characterized; the 
 alkali salts are soluble in water, the others mostly insoluble. 
 Among the derivatives may be mentioned mono-, di-, and' tri 
 ethyl citrates and triethyl aceto-citrate, 
 
 CO 2 Et GH, 0(0 - CO CHaXCOgEt) CH S . CO a Et. 
 
CYANOGEN COMPOUNDS 263 
 
 The formation of this last is a direct proof of the alcoholic 
 character of citric acid. The amides of citric acid are con- 
 verted by concentrated H 2 S0 4 into citrazinic acid, C 6 H 5 N0 4 , 
 a pyridihe derivative (B. 17, 2681). 
 
 The constitution of citric acid is arrived at (a) from its con- 
 version into aconitic acid by the elimination of water, (b) from 
 its reduction to tricarballylic acid, and (c) from its synthesis 
 from 1 : 3 dichloroacetone, e.g. : 
 
 CH 2 C1.CO.CH 2 C1 + HCN CH 2 C1.C(OH)(CN).CH 2 C1 
 
 CN.CH 2 .C(OH)(CN).CH 2 .CN 
 CX) 2 H.CH 2 .C(OH)(C0 2 H).CH 2 .C0 2 H. 
 
 The acid has been synthesised by Lawrence (J. C. S. 1897, 
 71, 457) by an application of Eeformatsky's reaction, i.e. the 
 condensation of a halogen derivative with a ketone in the 
 presence of zinc. The substances used were ethyl bromacetate, 
 ethyl oxalacetate, and pure zinc turnings : 
 
 _ CO 2 Et-CH 2 .C(OZnBr).CO 2 Et 
 CH 2 .CO 2 Et. 
 
 This condensation product reacts with water, yielding ethyl 
 citrate, C0 2 Et.CH 2 .C(OH)(C0 2 Et).CH 2 .C0 2 Et, zinc oxide, 
 and hydrogen bromide. 
 
 Citric acid is also formed when solutions of glucose are fer- 
 mented by certain moulds, e.g. Citromycetes pfefferianus and 
 C. glaber (Wehner, Bull. Soc. Chim. 1893 [III], 9, 728). 
 
 Acids containing more than three carboxylic groups do not, 
 as a rule, occur in nature,^ but a number of esters of such acids 
 have been prepared by means of the aceto-acetic ester and 
 malonic ester syntheses. 
 
 XII. CYANOGEN COMPOUNDS 
 
 Under the name of the cyanogen compounds is included a 
 group of substances which are derivable from cyanogen, C 2 N 2 . 
 Cyanogen itself is a gas of excessively poisonous properties 
 which behaves in many respects like a halogen; and its 
 hydrogen compound, hydrocyanic acid, HCN, is an acid re- 
 
264 XII. CYANOGEN COMPOUNDS 
 
 sembhng hydrochloric acid to a certain extent. In many 
 cyanogen compounds the monovalent group (CN) plays the 
 part of an element; cyanogen is to be regarded as the isolated 
 radical (CN), which, however, possesses the double formula 
 C 2 N 2 , just as a molecule of chlorine (C1 2 ) is made up of two 
 atoms. The cyanogen group is further capable of combining 
 with the halogens, hydroxyl, sulphydril (SH), amidogen, &c. 
 From the compounds so obtained numerous others are derived 
 by the entrance of alkyl radicals in place of hydrogen. Such 
 derivatives invariably exist in two isomeric forms, sharply 
 distinguished from one another by their properties. They 
 are often termed normal and iso compounds, and the isomerism 
 is of very great interest. (See table, p. 265.) 
 
 Polymeric modifications of most of those compounds also 
 exist. The number of cyanogen compounds known is thus a 
 very large one. 
 
 Carbon and nitrogen do not combine directly except in the 
 presence of an alkali, and then a metallic cyanide is formed. 
 As examples of this reaction, we have the following: 
 
 1. When nitrogen is led over a red-hot mixture of coal and 
 carbonate of potash, potassium cyanide, KCN, is formed, espe- 
 cially under a high pressure. 
 
 2. Ammonium cyanide is formed when ammonia is passed 
 over red-hot coal. 
 
 3. Potassium cyanide is formed when nitrogenous organic 
 compounds such as leather, horn, claws, wool, blood, &c., are 
 heated with potashes. 
 
 4. Hydrocyanic acid is formed when electric sparks are 
 passed through a mixture of acetylene and nitrogen, and also 
 by the action of the silent electric discharge on a mixture 
 of cyanogen and hydrogen. It is also formed (commercial 
 method) when a carefully dried mixture of hydrogen, am- 
 monia, and a volatile carbon compound (CO, C0 2 , C 2 H 2 , &c.) 
 is passed over heated platinized pumice. (For further modes 
 of formation, see p. 266 et seq.) 
 
 The original material for the preparation of most of the 
 cyanogen compounds is potassium ferrocyahide, which is manu- 
 factured on the large scale and possesses the great advantage 
 over potassium cyanide of being stable in the air and compara- 
 tively non-poisonous. 
 
I 
 
 CYANOGEN COMPOUNDS 
 SUMMARY OF THE CYANOGEN COMPOUNDS 
 
 Relation to carbonic acid, &c. 
 (&ee p. 279.) 
 
 Name. 
 
 Formula. 
 
 Nitrile of oxalic acid, 
 
 Cyanogen, 
 
 N:C-C:N 
 
 Nitrile of formic acid, 
 
 Hydrocyanic acid, 
 Alkyl derivatives: 
 (a) Nitriles, 
 (6) Isonitriles, 
 
 NiC.H 
 
 R.CiN 
 R-N:C 
 
 
 Cyanogen chloride, 
 bromide, iodide, 
 
 N-C-Cl 
 
 CO 3 H 2 + NH 3 -2H 2 O, 
 
 (Nitrile of carbonic acid, 
 eventually Carbiinide), 
 
 Cyanic acid, 
 Alkyl derivatives: 
 (a) Methyl cyanate, 
 (6) isocyanate, 
 
 N-C-OH 
 
 N:C-O.CH 3 
 O:C:N.CH 3 
 
 
 Thiocyanic acid, 
 Alkyl derivatives : 
 (a) Ethyl thiocyanate 
 (6) Allyl isothio- 
 cyanate, 
 
 N-C-SH 
 
 N:C.S.C 2 H 5 
 S:C:NC 3 H 6 
 
 CO 3 H 2 -f 2NH 3 3H 2 O, 
 (Nitrile and amide of car- 
 bonic acid, eventually 
 Carbo-di-imide, see p. 
 277), 
 
 Cyanamide, 
 Alkyl derivatives: 
 (a) Alkyl cyana- 
 mide, 
 (6) Carbo-di-imide, 
 
 N:C-NH 2 
 
 NiC-NH-K 
 RN:C:NK* 
 
 The amic acid of car- 
 bonic acid, 
 
 Carbamic acid, 
 
 NH 2 .CO-OH 
 
 The amide of carbonic 
 acid, 
 
 Urea, 
 
 CO(NH 2 ) 2 
 
 
 Thio-urea, 
 Alkyl derivatives : 
 (a) Alkyl-thio-ureas, 
 (6) Imido-thio-carba- 
 mine compounds, 
 
 CS(NH 2 ) 2 
 
 NH 2 .CS.NHR 
 NH:< 2 
 
 CO 3 H 2 + 3NH 3 -3H 2 O, 
 (Amidine), 
 
 Guanidine, 
 
 HNlCKNHj)., 
 
 
 * R = alkvl radical. 
 
266 XII. CYANOGEN COMPOUNDS 
 
 A. Cyanogen and Hydrocyanic Acid 
 
 Cyanogen, N-C-CjN, which was discovered by Gay-Lussac 
 in 1815, occurs in the gases of blast-furnaces and in coal gas. 
 
 As the nitrile of oxalic acid, it may be obtained by the 
 abstraction of the elements of water from ammonium oxalate 
 by means of P 4 10 ; also in the same way from the intermediate 
 product of this reaction, oxamide : 
 
 NH 4 0-CO.CO.ONH 4 -4H 9 O = N:C-C:N, 
 NH 2 .CO.CO.NH 2 -2H 2 = N:C-C:N. 
 
 It is usually prepared by heating dry silver cyanide, AgCN, 
 or mercuric cyanide, Hg(CN) 2 , strongly : 
 
 Hg(CN) 2 = Hg + C 2 N 2 ; 
 
 or by heating a solution of cupric sulphate with potassium 
 cyanide (B. 18, Kef. 321). 
 
 Cyanogen is a colourless gas of a peculiar unpleasant odour 
 resembling that of bitter almonds, and is terribly poisonous. 
 It is easily liquefied and solidified (sp. gr. 1*8 of the liquid; 
 m.-pt. 34; b.-pt. 21), is soluble in 0'25 vol. of water and 
 in even less alcohol. The solutions become dark upon stand- 
 ing, with separation of a brown powder ("Azulmic acid"), 
 while oxalic acid, ammonia, formic acid, hydrocyanic acid, and 
 urea are to be found in the liquid. The formation of the 
 oxalic acid and ammonia is due to normal hydrolysis, and that 
 of formic acid to the hydrolysis of the hydrocyanic acid formed 
 as an intermediate product. In presence of a minute quantity 
 of aldehyde, oxamide is formed as the result of the addition of 
 water. Cyanogen combines with heated potassium to KCN, 
 and dissolves in aqueous potash to form KCN and KCNO. 
 
 Paracyanogen, (CN) X , is a polymer of cyanogen. It is an 
 amorphous brown powder which is formed as a by-product 
 when mercuric cyanide is heated; upon further heating, it is 
 transformed into cyanogen. 
 
 Hydrocyanic acid, pmssic acid, CNH, was discovered about 
 the year 1782 by Scheele, and investigated closely by Gay- 
 Lussac. 
 
 Some of the more interesting methods of formation are the 
 following : 
 
 1. It is readily liberated from its salts by the action of 
 almost any other acid, even carbonic acid; and even complex 
 
HYDROCYANIC ACID 267 
 
 cyanides, e.g. potassium ferrocyanide, when distilled with 
 moderately dilute sulphuric acid yield hydrogen cyanide: 
 
 K 4 Fe(CN) 6 + 5H 2 S0 4 = 6HCN + FeSO 4 + 4KHSO 4 . 
 
 The ferrous sulphate produced reacts with more ferrocyanide 
 to form potassium ferrous ferrocyanide, FeK 2 (FeC 6 N 6 ), which is 
 not affected by dilute acids (see p. 269); consequently only half 
 of the cyanogen present is converted into hydrocyanic acid. 
 When concentrated sulphuric acid is employed in place of the 
 dilute, carbon monoxide and not hydrocyanic acid is obtained. 
 
 2. As the nitrile of formic acid, it may be prepared by the 
 action of dehydrating agents on ammonium formate or form- 
 amide : 
 
 H.CO-ONH 4 = H.CO.NH 2 + H 2 O = HGN + 2H 2 O. 
 
 3. Together with oil of bitter almonds, C 6 H 5 .CHO, and 
 grape-sugar, C 6 H 12 6 , by the hydrolysis of the glucoside 
 amygdalin under the influence of the enzyme " emulsin " (see 
 Benzaldehyde) : 
 
 SH0 = 
 
 The oil of bitter almonds and its aqueous solution (aqua 
 amarum amygdalarum) prepared from the almonds them- 
 selves consequently contain HCN. 
 
 The acid occurs in the free state in the tree Pangium edule, 
 found in Java, more particularly in the seeds. It exists in 
 the form of glucosides in various plants (C. C. 1906, ii, 1849: 
 1909, i, 387). 
 
 4. By the action of ammonia and chloroform on alcoholic 
 potash under pressure. Cf. p. 103. 
 
 For other syntheses, see p. 264. 
 
 Hydrogen cyanide is a colourless liquid boiling at 25 
 and solidifying at 12. Sp. gr. 0'70. It has a peculiar 
 odour and produces an unpleasant irritation in the throat, is 
 miscible with water, and burns with a violet flame. Like 
 potassium cyanide, it is one of the most terrible of poisons. 
 The best antidotes are stated to be hydrogen peroxide or 
 small quantities of chlorine mixed with air. When absolutely 
 pure it can be preserved unchanged, but it decomposes in 
 presence of traces of water or ammonia, with separation of 
 a brown mass and formation of ammonia, formic acid, oxalic 
 acid, &c. The addition of minute quantities of mineral acids 
 renders the aqueous solution more stable. 
 
268 XII. CYANOGEN COMPOUNDS 
 
 Liquid hydrocyanic acid is a good solvent for many salts, 
 and has a high ionizing power. Acids (sulphuric and trichloro- 
 acetic), however, do not appear to dissociate when dissolved 
 in the liquid. 
 
 The acid has many properties of an unsaturated compound. 
 It is readily reduced by nascent hydrogen to methylamine. 
 In the presence of hydrochloric acid it combines with water 
 yielding formamide. With diazomethane (Chap. LI) it yields 
 methyl cyanide together with methyl carbylamine. With 
 hydrogen chloride it gives iminoformyl chloride, NHrCHCl, a 
 compound of importance in the synthesis of aromatic alde- 
 hydes (A. 1906, 347, 347); but has not been isolated. From 
 ethyl acetate solution a product 2HCN, 3HC1 = NH:CH-NH- 
 CHC1 2 , HC1, dichloromethyl formamidine hydrochloride is 
 obtained. It combines directly with most aldehydes and 
 ketones, yielding cyanhydrins (nitriles of hydroxy acids), 
 (p. 206), and also with certain unsaturated compounds, espe- 
 cially in the presence of potassium cyanide, yielding saturated 
 nitriles (Lapworth, J. C. S. 1903, 995; 1904, 1214; Knoe- 
 venagel, B. 1904, 37, 4065); e.g. a-phenylcinnamo-nitrile, 
 CHPh:CPh.CN, yields diphenylsuccinylo-nitrile, CN-CHPh- 
 CHPh-CN. 
 
 Hydrocyanic acid is an extremely weak monobasic acid 
 (K = 0*0013 x 10~ 6 ), and its salts are decomposed even by 
 carbonic acid. It is a typical tautomeric compound. Its 
 reduction to an amine and its hydrolysis to formic acid are 
 similar to the corresponding reactions of methyl cyanide, and 
 it might be urged that these reactions favour the nitrile for- 
 mula HCjN Both reactions are, however, compatible with 
 the view that it has the carbylamine structure H-N:C. The 
 salts are usually regarded as carbylamine derivatives (see 
 derivatives of divalent carbon, Chap. L, D), and it might be 
 argued that the free acid has a similar structure. Such an 
 argument is, however, unsound, as numerous examples are 
 known where salts have a structure quite different from that 
 of the acid from which they are prepared (cf. ethyl aceto- 
 acetate and pseudo acids). 
 
 Hydrocyanic acid can be detected by converting it either 
 into Prussian blue or into ferric thiocyanate. In the former 
 case the solution to be tested is treated with excess of caustic 
 soda and some ferrous and ferric salt, boiled, and acidified, 
 when Prussian blue results; in the latter the solution is 
 evaporated to dryness together with a little yellow sulphide 
 
FERROCYANIDES AND FERRICYANIDES 269 
 
 of ammonium, the residue taken up with water and ferric 
 chloride added, when the blood -red colour of ferric thio- 
 cyanate is obtained. 
 
 Trihydrocyanic acid, (CNH) X , results from the polymer- 
 ization of hydrocyanic acid under certain specified conditions. 
 It forms white, acute-angled crystals, which readily yield hy- 
 drogen cyanide when heated above 180. Its molecular weight 
 is still unknown. 
 
 Cyanides. The cyanides of the alkali and alkali -earth 
 metals are soluble in water, and the solutions have a strongly 
 alkaline reaction due to the hydrolysing action of the water 
 (cf. Soaps, p. 159). The salts of the heavy metals, with the 
 exception of mercuric cyanide, are insoluble in water. 
 
 Potassium cyanide, KCN, forms colourless deliquescent 
 cubes, sparingly soluble in alcohol. The commercial product 
 usually contains large amounts of potassium carbonate due to 
 the action of atmospheric carbon dioxide. It is formed when 
 potassium ferrocyanide is fused, and the product extracted 
 with water: 
 
 K 4 FeC 6 N 6 = 4KCN + FeC 2 + N 2 . 
 
 Large quantities are manufactured by Beilby's process, which 
 consists in treating a fused mass of potassium carbonate and 
 carbon with ammonia, the product being a molten cyanide of 
 high strength. The pure salt can be prepared by passing 
 hydrogen cyanide into an alcoholic solution of potassium 
 hydroxide. It reacts with hydrogen peroxide in two different 
 ways (cf. Masscrn, J. C. S. 1907, 1449): 
 
 1. 80 % KCN -f H 2 O 2 KCNO + H 2 and 
 
 KCNO + 2H 2 NH 3 + KOH + C0 2 ; 
 
 2. 20 % KCN + 2H 2 O > NH 3 + H-COOK. 
 
 Mercuric cyanide, Hg(CN) 2 , crystallizes in colourless prisms, 
 is stable in the air, readily soluble in water, and excessively 
 poisonous. Its aqueous solution is a non-conductor of the 
 electric current, and does not give the ordinary reactions for 
 a mercuric salt or for a cyanide (cf. B. 1908, 41, 317). 
 Argentic cyanide, AgCN, forms a white flocculent precipitate 
 closely resembling argentic chloride in appearance, but is 
 soluble in hot concentrated nitric acid. 
 
 Complex Cyanides. The double cyanides, which are pro- 
 duced by dissolving the insoluble metallic cyanides in a solu- 
 tion of potassium cyanide, are divided into two classes. Th(j 
 
270 XII. CYANOGEN COMPOUNDS 
 
 members of the one class are decomposed again on the addition 
 of dilute mineral acids, with separation of the insoluble cyanide 
 and formation of hydrocyanic acid, e.g. KAg(CN) 2 ; K 2 Ni(CN) 4 . 
 The members of the other class are much more stable, do not 
 evolve hydrocyanic acid, and comport themselves as salts of 
 particular acids; to this class belong potassium ferrocyanide, 
 K 4 Fe(CN) 6 , [Fe(CN) 2 , 4KCN], and potassium ferricyanide, 
 K 3 Fe(CN) 6 , [Fe(CN) 3 , 3KCN]. The members of this second 
 class are often termed complex salts, and are the metallic salts 
 of complex acids, e.g. hydroferrocyanic acid, H 4 FeC N 6 , and 
 hydroferricyanic acid, H 3 FeC 6 N 6 , which are formed when the 
 salts are decomposed with mineral acids. Certain salts of the 
 latter acid are not decomposed at all by dilute acids, for in- 
 stance Prussian blue, but they are by caustic potash (which 
 converts Prussian blue into Fe(OH) 3 arid K 4 FeC 6 N 6 ). 
 
 These complex salts, as a rule, do not give the reactions 
 characteristic of simple cyanides, e.g. white precipitate with 
 silver-nitrate solution, owing to the fact that in solution they 
 
 do not yield the simple cyanide ions CN but the more complex 
 
 anions FeC 6 N 6 and FeC 6 N 6 . 
 
 Potassium ferrocyanide, yellow prussiate of potash, K 4 Fe(CN) 6 
 -f- 3H 2 0, may be obtained by adding excess of potassium 
 cyanide to a solution of ferrous sulphate, or by dissolving 
 iron in a solution of cyanide of potassium, when hydrogen is 
 evolved, thus: 
 
 2KCN + Fe + 2H 2 O = Fe(CN) 2 + 2KOH -f H 2 ; 
 Fe(CN) 2 -f 4KCN = K 4 Fe(CN) 6 . 
 
 The old commercial method consisted in fusing together 
 scrap-iron, nitrogenous organic matter, and crude potassic 
 carbonate. 
 
 It is now usually manufactured from the hydrogen cyanide 
 present in crude coal gas or the gas from coke ovens. The 
 spent oxide used in the purification of coal gas contains Prus- 
 sian blue (ferric ferrocyanide, p. 271). The spent oxide is 
 heated with hot milk of lime, and the Prussian blue thus 
 transformed into calcium ferrocyanide, from which the potas- 
 sium salt can be prepared. 
 
 Another method consists in passing the coal gas, before it 
 has been subjected to dry purification, through an alkaline 
 solution containing an iron salt. The sulphuretted hydrogen 
 reacts with the iron salt, forming ferrous sulphide, and this 
 
FORROCYANIDES AND FERRICYANIDES 
 
 271 
 
 with the hydrogen cyanide and alkali (potassium carbonate) 
 yields potassium f errocyanide : 
 
 FeS + 6HCN + 2K 2 CO 3 = K 4 FeC 6 N 6 + H 2 S + 2CO 2 + 2H 2 O. 
 
 It forms large, lemon-coloured monoclinic plates, which are 
 stable in the air and easily soluble in water, but insoluble in 
 alcohol. Concentrated HC1 yields hydro-ferrocyanic acid, 
 H 4 FeC 6 Ng, in the form of white needles. With a solution 
 of CuS0 4 , a red-brown precipitate of cupric ferrocyanide, or 
 Hatchetfs brown, CuJFeCgNg, is thrown down, and with solu- 
 tions of ferrous and ferric salts the well-known characteristic 
 precipitates (see below). Chlorine oxidizes it to 
 
 Potassium ferricyanide, red prussiate of potash, K 3 FeC 6 N G , 
 thus : 
 
 2K 4 FeC 6 N 6 + C1 2 = 2K 3 FeC 6 N 6 + 2KC1. 
 
 This crystallizes in long, dark-red, monoclinic prisms which 
 are readily soluble in water. The solution decomposes when 
 kept, and acts as a strong oxidizing agent in the presence of 
 alkali, potassium ferrocyanide being reproduced. 
 
 Hydro-ferricyanic acid, H 3 FeC 6 N 6 , forms brown needles, 
 and is easily decomposed 
 
 FERRO- AND FERRI-CYANIDES OF IRON 
 
 
 Ferrocyanides. 
 
 Ferricyanides. 
 
 Ferrous salts, 
 
 Potassium-ferro-ferrocyanide, 
 K 2 Fe(FeCgN 6 )*, fromFeS0 4 
 + KjFeCsNe; white, becom- 
 ing rapidly blue in the air 
 from conversion into 
 
 TurribulVs blue, 
 Fe 3 ii (FeC 6 N) 2 iil , from 
 FeS0 4 (excess) + 
 
 i 
 
 Ferric salts, 
 
 Potassium -ferri - ferrocyanide, 
 KFe^FeCeNe), or soluble 
 Prussian blue, which is also 
 formed from ferrous sul- 
 phate with an excess of 
 potassic ferricyanide. 
 
 (FeCls-t- K 3 FeC 6 Ngive 
 no . precipitate, but 
 only a brown color- 
 ation.) 
 
 
 Insoluble Prussian blue 
 or Williamson's blue, 
 Fe 4 iii (FeC 6 N 6 ) 3 iv , from FeCl 8 
 + K 4 FeC 6 N 6 ; blue powder 
 with a copper glance. 
 
 
272 XII. CYANOGEN COMPOUNDS 
 
 The formation of Prussian blue was first observed by 
 Diesbach about the year 1700. 
 
 As regards the constitution of hydro-ferro- and hydro-ferri- 
 cyanic acids, one may make the assumption that they contain 
 the tervalent radical, (C 3 N 3 ) Ui , " tricyanogen ", of cyanuric 
 acid (see p. 272): 
 
 Potassium ferrocyanide Potassium ferricyanide. 
 
 Turnbull's blue. 
 
 When ferrocyanide of potassium is oxidized by nitric acid, 
 nitro - prussic acid is formed, the sodium salt of which, 
 
 -+- 2H 2 0, crystallizes in red prisms soluble 
 in water. It forms a valuable reagent for the detection of 
 sulphuretted hydrogen, an alkaline solution yielding with the 
 latter a splendid but transient violet coloration. 
 
 B. Halogen Compounds of Cyanogen 
 
 Cyanogen chloride, C1N:0 (Berthollet), is a colourless con- 
 densable gas of a most obnoxious pungent odour, is somewhat 
 soluble in water, and boils at 15 -5. It is prepared by the 
 action of chlorine upon mercuric cyanide or upon dilute 
 aqueous hydrocyanic acid, CNH + C1 2 = CNC1 + HC1. It 
 polymerizes readily to cyanuric chloride, and yields sodium 
 chloride and cyanate with aqueous sodium hydroxide: 
 
 CN.Cl + 2NaOH = CN-ONa + ClNa -f H 2 O. 
 
 Cyanogen bromide, CNBr, forms transparent prisms, and 
 is prepared by the action of sulphuric acid on a mixture of 
 bromate, bromide, and cyanide of sodium: 
 
 5HBr-f 3HCN = SBrCN + 3HBr + 3H 2 O. 
 
 Cyanogen iodide, ONI, forms beautiful white prisms, smelling 
 intensely both of cyanogen and iodine, and subliming with the 
 utmost ease. (For constitution cf. Chattaway and PFadmore, 
 J. C. S. 1902, 191.) 
 
 Cyanuric chloride, trichlorocyanogen, (CC1) 3 N 3 , is obtained 
 from cyanogen chloride, or from hydrocyanic acid and chlor- 
 ine in ethereal solution. It forms beautiful white crystals of 
 a.n unpleasant pungent odour, melts at 145, and boils at 
 
CYANIC AND CYANURIC ACIDS 273 
 
 190. Boiling water decomposes it with formation of hydro- 
 gen chloride and cyanuric acid 
 
 C. Cyanic and Cyanurie Acids 
 
 Cyanuric acid is formed when urea is heated, either alone 
 or in a stream of chlorine gas; and when this acid is distilled, 
 and the vapour condensed in a freezing-mixture, cyanic acid, 
 CNOH, is obtained as a mobile liquid of a pungent odour: 
 
 CaNsOaHg = 3 CNOH 
 
 It is exceedingly unstable; when taken out of the freezing- 
 mixture it changes, with explosive ebullition, into a white 
 porcelain-like mass which consists of cyanuric acid 70 per cent, 
 and cyamelide 30 per cent. Potassium cyanate, CNOK, fre- 
 quently also termed potassium isocyanate, is prepared by the 
 oxidation of an aqueous solution of potassium cyanide b" 
 means of permanganate (A. 259, 377); or by fusing potassium 
 cyanide or yellow prussiate of potash with Pb0 2 or Mn0 2 : 
 (CNK + = CNOK). It crystallizes in white plates, readily 
 soluble in water and alcohol. Ammonium cyanate, CNO 
 (NH 4 ), forms a white crystalline mass, and is of especial 
 interest on account of the readiness with which it changes 
 into the isomeric urea, CO(NH 2 ) 2 (p. 281). 
 
 When these salts are decomposed with mineral acids, free 
 cyanic acid is not formed, but its products of hydrolysis, viz. 
 carbon dioxide and ammonia : 
 
 CONH + H 2 = C0 2 + NH 3 . 
 
 This decomposition is avoided by the addition of dilute acetic 
 acid (instead of hydrochloric), but in the latter case the cyanic 
 acid changes into its polymer cyanuric acid, and the hydrogen- 
 potassium salt of the latter slowly crystallizes out. 
 
 When the hydrogen atom in the cyanic acid molecule is 
 replaced by alkyl radicals, two distinct groups of compounds 
 are possible. The derivatives which are constituted on the 
 type N;CCKR are termed the normal, and those on the type 
 0:C:NR the iso-compounds. 
 
 Ethyl isocyanate, cyanic ether, : C : N CH 2 CH 3 , obtained 
 when potassium cyanate is distilled with ethyl iodide or 
 potassium ethyl-sulphate, is a colourless liquid of suffocating 
 odour, distilling at 60, and is decomposed by water. It does 
 
 (B480) S 
 
274 XIL CYANOGEN COMPOUNDS 
 
 not behave as a typical ester, since when hydrolysed with acids 
 or alkalis it yields ethylamine and carbon dioxide: 
 
 Water, which acts in a similar manner, gives rise to the 
 more complicated urea derivatives; ammonia and amines also 
 produce derivatives of urea, and alcohol yields derivatives of 
 carbamic acid (see Carbonic Acid Derivatives). 
 
 The production of ethylamine as one of the products of 
 hydrolysis is usually regarded as a strong argument in favour 
 of the view that in the original isocyanate the ethyl group 
 is attached to nitrogen and not to oxygen, e.g. 0:C:N-Et. 
 It is questionable, however, whether free cyanic acid and 
 cyanate of potassium possess analogous constitutions, since 
 frequent observations have shown that the normal cyanic 
 compounds readily change into the iso- (see below) ; theoretical 
 considerations indeed make it more probable that cyanic acid 
 has the constitution N|COH, according to which it appears 
 as the normal acid, with cyanogen chloride as its chloride. 
 
 Normal cyanic esters are not known (cf. A. 287, 310). 
 
 Cyanuric acid, C 3 N 3 3 H 3 , = (CN) 3 (OH) 3 (Scheele), obtained 
 by heating urea, or by the action of water on cyanuric chloride, 
 forms transparent prisms containing two molecules of water of 
 crystallization. It effloresces in the air, and dissolves readily 
 in hot water. It is a tribasic acid. The sodium salt is spar- 
 ingly soluble in cone. NaOH; the (Cu-NH 4 ) salt possesses a 
 characteristic beautiful violet colour. Upon prolonged boiling 
 with hydrochloric acid it is hydrolysed to C0 2 and NH 3 , while 
 phosphorus pentachloride converts it into cyanuric chloride. 
 
 Only one cyanuric acid is known, and owing to the fact 
 that the N-methyl derivative is obtained by the action of 
 diazo-methane is represented by the iso-structure : 
 
 (Compare also Hantzsch, B. 1906, 39, 139). 
 
 Cyanuric acid is a pseudo acid, as its salts and also chloride 
 have the normal structure. The mercuric salt exists in two 
 isomeric forms. 
 
 Two distinct groups of alkyl derivatives are, however, 
 known normal cyanuric esters, e.g. ethyl cyanurate, 
 
ISO-THIOCYANATES 275 
 
 which is formed by the action of ethyl iodide on silver cyanu- 
 rate at the ordinary temperature, or by the action of sodium 
 ethoxide on cyanogen chloride or cyanuric chloride, is readily 
 changed into an isocyanuric ester, e.g. ethyl isocyanurate, 
 
 These isocyanurates are often formed instead of the normal 
 compounds if the temperature is not kept low, e.g. when a 
 cyanurate is heated with potassium ethyl-sulphate. They are 
 further formed by the polymerization of the isocyanic esters, 
 oeing thus obtained as by-products in the preparation of the 
 latter. 
 
 The constitution of the normal compounds is largely based 
 on the fact that on hydrolysis they behave as normal esters 
 and yield ethyl alcohol and cyanuric acid. The isocyanurates, 
 on the other hand, usually yield primary amines, e.g. ethyl- 
 amine, and hence presumably the alkyl group is attached to 
 nitrogen in the isocyanurate molecule. 
 
 For mixed normal iso-esters, see Hantzsch and Bauer, B. 
 1905, 38, 1005. 
 
 D. Thioeyanic Acid and its Derivatives 
 
 Nearly every oxygen derivative of cyanogen has a sulphu r 
 analogue. As examples, we have the salts of thiocyamc 
 acid. 
 
 Potassium thiocyanate, -sulphocyanate, -sulphocyanide, -rhod- 
 anide, CNSK, is readily formed when potassium cyanide is 
 fused with sulphur, or when an aqueous solution of KCN 
 is evaporated with yellow ammonium sulphide. 
 
 It is usually prepared by fusing potassium ferrocyanide with 
 sulphur and potashes. It forms long colourless deliquescent 
 prisms, extremely soluble in water with absorption of much 
 heat, and also readily soluble in hot alcohol. Ammonium 
 thiocyanate, CNS(NH 4 ), is formed when a mixture of carbon 
 disulphide, concentrated ammonia, and alcohol (Millori) is 
 heated, dithiocarbamate and trithiocarbonate of ammonia 
 being formed as intermediate products: 
 
 = CNSH + H 2 S. 
 
 It forms colourless deliquescent plates, readily soluble in 
 alcohol, and when heated to 130-140 is partially transformed 
 
276 XII. CYANOGEN COMPOUNDS 
 
 into the isomeric thio-urea, just as ammonium cyanate is into 
 urea. It precipitates silver thiocyanate, CNSAg (white), from 
 solutions of silver salts, and is therefore employed in the 
 titration of silver, with ferric sulphate as indicator; and it 
 gives with ferric salts a dark blood -red coloration of am- 
 monium ferrithiocyanate, 2Fe(CNS) 8 , 9NH 4 CNS, 4H 2 0. 
 This last reaction is exceedingly delicate. Mercurous thio- 
 cyanate, HgCNS, is a white powder insoluble in water, which 
 increases enormously in volume upon being burnt (Pharaoh's 
 serpents). The free thiocyanic acid, CNSH, as obtained by 
 decomposing the mercurous salt with hydrochloric acid, is a 
 pale-yellow liquid of pungent odour, but when pure is a 
 colourless solid, m.-pt. 5. The acid and its salts appear to 
 have the normal structure HS'C|N. At the ordinary tem- 
 perature it polymerizes to a yellow amorphous substance, and 
 decomposes in concentrated aqueous solution, with formation 
 of persulphocyanic acid, C 2 N 2 S 3 H 2 (yellow crystals). 
 
 Concentrated sulphuric acid decomposes the thiocyanates 
 with formation of carbon oxy - sulphide : CNSH + H 2 
 = COS-f NH 3 ; sulphuretted hydrogen decomposes them into 
 carbon disulphide and ammonia : CNSH + H 2 S = CS 2 + NH 3 . 
 
 The alkyl derivatives of thiocyanic acid exist in two distinct 
 forms, corresponding with the normal and iso-cyanates. 
 
 Normal Thiocyanates. Ethyl thiocyanate, N:C-S.CH 2 . 
 CH 3 , is obtained either (1) by the distillation of potassium 
 ethyl -sulphate with potassium thiocyanate, or (2) by the 
 action of cyanogen chloride upon ethyl mercaptide. It is a 
 colourless liquid with a peculiar pungent odour of leeks, boils 
 at 142, and is almost insoluble in water. Alcoholic potash 
 hydrolyses it in the normal manner, yielding ethyl alcohol 
 and potassium thiocyanate; in other reactions, however, the 
 alkyl radical remains united to sulphur; thus nascent hydro- 
 gen reduces it to mercaptan, and fuming nitric acid oxidizes it 
 to ethyl-sulphonic acid. 
 
 These reactions, combined with its formation from a mer- 
 captide, indicate that the ethyl group is directly attached to 
 sulphur, viz. C 2 H 5 -S-C:N. 
 
 Allyl thiocyanate, NjCSC 3 H 5 , is a colourless liquid smell- 
 ing of leeks. It boils at 161, and when distilled is converted 
 into the isomeric mustard oil. 
 
 The iso-thiocyanates are usually known as mustard oils, 
 and are more stable than the normal thiocyanates. They 
 contain the alkyl radical attached to nitrogen, and not to 
 
CYANAMIDE AND ITS DERIVATIVES 277 
 
 sulphur (cf. Isocyanates), since on hydrolysis they yield 
 primary amines, e.g. : 
 
 S:C:NEt + 2H 2 = H 2 S + C0 2 + NH 2 Et, 
 and also on reduction: 
 
 S:C:NEt-f 4H = NH 2 Et + CH 2 S. 
 
 The thiomethylene formed in this last reaction immediately 
 polymerizes to (CH 2 S) 3 . The commonest iso-thiocyanate is 
 allyl mustard oil, commonly known as mustard oil, since the 
 odour and taste of mustard seeds (Sinapis niger) are due to 
 this compound. It does not exist as such in the seeds, but 
 is formed from a glucoside, potassium myronate, when the 
 seeds are pulverized and left in contact with water. The 
 reaction is a process of fermentation, and is due to the 
 presence of an enzyme, myrosin, in the seeds: 
 
 C 10 H 18 10 NS 2 K = C 6 H 12 O fl + KHS0 4 + SCNC 3 H 6 . 
 
 It is a liquid sparingly soluble in water and of exceedingly 
 pungent odour, which produces blisters on the skin, and boils 
 at 151. It is also obtained by distilling allyl thiocyanate, 
 owing to a molecular rearrangement, or by the action of 
 carbon disulphide upon allylamine: 
 
 CS 2 + NH 2 .C 3 H 6 = CS:N.C 3 H 6 + H 2 S. 
 
 This reaction proceeds in two stages, a dithiocarbamate, 
 C 3 H 5 NH.CS.SNH 3 C 3 H 5 , the allylamine salt of allyl-dithio- 
 carbamic acid being first formed, and this is changed into allyl 
 iso-thiocyanate when distilled with mercuric chloride. (See 
 Dithiocarbamic acid, p. 296.) 
 
 Ethyl iso-thiocyanate, C 2 H 5 N:CS (b.-pt. 134), and methyl 
 iso-thiocyanate, CH 3 N:CS (solid, m.-pt. 34, b.-pt. 119), &c., 
 closely resemble the allyl compound, and are obtained in an 
 analogous manner by the action of carbon disulphide upon 
 ethylamine, methylamine, &c. 
 
 The mustard oils are also obtained by distilling alkylated 
 thio-ureas (p. 297) with syrupy phosphoric acid (Hofmann, 
 B. 15, 985), or with concentrated hydrochloric acid. 
 
 E. Cyanamide and its Derivatives 
 
 The Amide of Cyanic Acid. Cyanamide, N;C.NH 2 , is 
 formed by leading cyanogen chloride into an ethereal solution 
 
278 XII. CYANOGEN COMPOUNDS 
 
 of ammonia, CNC1 + 2NH 8 = CN-NH 2 + NH 4 C1, or by 
 the action of HgO upon thio-urea in aqueous solution ("de- 
 sulphurization"), NH 2 .CS-NH 2 - NC-NH^ + H 2 S. 
 
 It is a colourless crystalline hygroscopic mass, readily 
 soluble in water, alcohol, and ether. It melts at 40, and 
 when heated to 150 changes into the polymeric dicyan-diamide 
 with explosive ebullition; the same change occurs on evaporat- 
 ing its solution or allowing it to stand. Dilute acids cause it 
 to take up the elements of water, with formation of urea : 
 
 N:C-NH 
 
 NH 2 ; 
 
 and it combines in an analogous manner with hydrogen sul- 
 phide to thio-urea. When heated with ammonium salts, it 
 yields salts of guanidine. 
 
 Cyanamide behaves as a weak base, forming crystalline, 
 easily decomposable salts with acids and, at the same time, 
 as a weak acid, yielding a sodium salt, CNNHNa, a lead 
 and a silver salt, &c. The last is a yellow powder, and has 
 the composition CN 2 Ag 2 . 
 
 The calcium derivative of cyanamide, N;CNOa, is manu- 
 factured for use as a fertilizer, as, in the soil, the nitrogen be- 
 comes available for the plant in the form of ammonia. It is 
 manufactured by passing air or nitrogen over calcium carbide 
 at about 800-1000, 
 
 CaC 2 + N 2 = CaCN 2 + C, 
 
 or by passing nitrogen over a mixture of lime and carbon 
 heated to 2000. An excess of carbon is used, and the crude 
 product, which forms a black powder, contains 14-23 per cent 
 of nitrogen (cf. Abs. 1904, i. 562). The presence of a small 
 amount of calcium chloride accelerates the absorption of nitro- 
 gen by calcium carbide. 
 
 Cyanamide also gives rise to two isomeric series of alkyl 
 derivatives. 
 
 1. Methyl- and ethyl-cyanamides are prepared from methyl 
 and ethyl thio-urea. Diethyl-cyanamide, CN 2 (C 2 H 5 ) 2 , and its 
 homologues are obtained by the action of alkyl iodides or sul- 
 phates on crude calcium cyanamide (B. 1911, 44, 3149). Acids 
 hydrolyse the ethyl compound to C0 2 , NH 3 , and NH(C 2 H 5 ) 2 , 
 hence it possesses the constitution N C N(C 2 H 6 ) 2 : 
 
 N!C.N(C 2 H 6 ) 2 + 2H 2 = NH 3 + C0 2 + NH(C 2 H 5 ) 2 . 
 
CARBONIC ACID DERIVATIVES 279 
 
 2. Other cyanamide derivatives, which are chiefly known in 
 the aromatic series, are derived from a hypothetical isomer 
 of cyanamide, viz. carbo-di-imide, NH:C:NH; for instance, 
 diphenyl-carbodiimide, CN 2 (C 6 H 5 ) 2 . Boiling with acids like- 
 wise decomposes them into C0 2 and an amine, but the latter 
 can only be a primary one. 
 
 XIII. CARBONIC ACID DERIVATIVES 
 
 Carbonic acid is a dibasic acid, forming two series of 
 salts, e.g. Na 2 C0 3 and NaHC0 3 . The acid itself, C0 3 H 2 , 
 
 = 0*XVvTT, is unknown, but may be supposed to exist 
 
 in the aqueous solution. It is the lowest hydroxy-acid 
 C n H 2n 3 , i.e. it is homologous with gly collie acid, and may 
 be regarded as hydroxy-formic acid. As both hydroxyls are 
 linked to the same carbon atom, the non-existence of the free 
 hydrate is readily understood (see p. 124, &c.). 
 
 The salts of carbonic acid and several simple derivatives of 
 carbon are usually treated of under inorganic chemistry. The 
 esters, chlorides, and amides of carbonic acid, like the salts, 
 form two series. The normal compounds, e.g. CO(OC 2 H 5 ) 2 , 
 ethyl carbonate, COCL, carbonyl chloride, and CO(NH 2 ) 2 , 
 carbamide or urea, are well characterized, and are very similar 
 to those of oxalic or succinic acid; the acid compounds, e.g. 
 OH.CO.OC 2 H 5 , ethyl hydrogen carbonate, OH.CO.C1, chloro- 
 carbonic or chloroformic acid, and OH-CO-NH 2 , carbamic 
 acid, on the other hand, are unstable in the free state, but 
 form stable salts. Many mixed derivatives are known, e.g. 
 ethyl carbamate, NH 2 CO OEt, which is an ester and an 
 acid amide, analogous to oxamethane (p. 236); C1-CO'OC 2 H 5 , 
 ethyl chloro-carbonate, which is an ester and an acid chloride. 
 
 A. Esters 
 
 Ethyl carbonate, CO(OC 2 H 5 ) 2 , is formed by the action of 
 ethyl iodide upon silver carbonate, or by the action of alcohol 
 upon ethyl chloro-carbonate, and therefore indirectly from 
 carbon oxy-chloride and alcohol: 
 
 CO(OC 2 H 6 ) 2 + 
 
280 XIII. CARBONIC ACID DERIVATIVES 
 
 It is a neutral liquid of agreeable odour, lighter than water, 
 and boils at 126. 
 
 Analogous methyl and propyl esters are known, and also 
 esters containing two different alkyl groups. It is a matter 
 of no consequence which of these radicals is introduced first 
 into the molecule, a proof of the symmetrical arrangement of 
 the two hydroxyls. 
 
 Ethyl hydrogen carbonate, HO CO C 2 H 5 , a type of an 
 acid ester, corresponds exactly with ethyl hydrogen sulphate, 
 but is much less stable, and only known in its salts. Potas- 
 sium ethyl carbonate, KO'COOC 2 H 5 , is obtained by passing 
 C0 2 into an alcoholic solution of potassic ethoxide: C0 2 
 + KOC 2 H 5 = CO S (C 2 H 5 )K. It crystallizes in glistening 
 mother-of-pearl plates, but is decomposed by water into 
 potassium carbonate and alcohol. 
 
 B. Chlorides of Carbonic Acid 
 
 Carbon oxy - chloride, Carbonyl chloride, phosgene, COC1 2 
 (/. Davij), is the true chloride of carbonic acid and is analogous 
 to sulphuryl chloride, S0 2 C1 2 . It is obtained by the direct 
 combination of carbon monoxide and chlorine in sunlight, and 
 also by the oxidation of chloroform by means of chromic acid. 
 It is a colourless gas, condensing to a liquid below +8, of 
 exceptionally suffocating odour, and is readily soluble in 
 benzene or toluene. As an acid chloride it decomposes 
 violently with water into C0 2 and HC1. It therefore trans- 
 forms hydrated acids into their anhydrides, with separation 
 of water, and converts aldehyde into ethylidene chloride. It 
 yield urea derivatives with secondary amines of the fatty 
 series, and carbamic chlorides with secondary amines of the 
 aromatic (B. 20, 783). 
 
 Chloro-carbonic acid, Chloro-formic acid, Cl-CO-OH, the 
 half acid chloride of carbonic acid, is analogous to chloroxalic 
 acid (p. 234), but is so unstable that it is unknown in the free 
 state. Its esters, however, e.g. ethyl chloro-carbonate, ethyl 
 chloro-formate, C1.CO-OC 2 H 5 , may be prepared by the action 
 of carbon oxy-chloride upon alcohols (Dumas, 1833): 
 
 COC1 2 + C 2 H 6 OH = C1.CO.OC 2 H 6 
 
 The ethyl ester is a volatile liquid of very pungent odour, 
 which boils at 93. It reacts as an acid chloride, being decom- 
 

 AMIDES OF CARBONIC ACID 281 
 
 posed by water, and is specially fitted to effect the synthetical 
 entrance of the carboxyl group into many compounds. 
 
 The esters and acid chlorides just described are derived 
 from ordinary carbonic acid, H 2 C0 3 , the analogue of meta* 
 silicic acid, H 2 Si0 3 . Although an ortho-carbonic acid itself, 
 C(OH) 4 , is unknown, certain derivatives are readily prepared. 
 Carbon tetrachloride may be regarded as the chloride of 
 ortho-carbonic acid. It is much more stable than ordinary 
 acid chlorides, and at high temperatures only is it decomposed 
 by alkalis, yielding alkali chloride and carbonate. 
 
 The esters of ortho-carbonic acid, e.g. ethyl ortho-carbonate, 
 C(OC 2 H 5 ) 4 , are readily obtained by the action of sodium alco- 
 holates on chloropicrin (p. 97). They are colourless oils with 
 fragrant odours. The ethyl ester boils at 158, and the propyl 
 at 224. When hydrolysed, they yield an alkali carbonate and 
 the alcohol. 
 
 C. Amides of Carbonic Acid 
 
 The normal amide of carbonic acid is urea or carbamide, 
 NH 2 'CO'NH 2 , the amic acid is carbamic acid, HOCONH 2 . 
 Imido-carbonic acid, HN:C(OH) 2 , would be an imide of car- 
 bonic acid, but it is only known in its derivatives (Sandmeyer, 
 B. 19, 862). 
 
 The amidine of carbonic acid is guanidine. The "ortho- 
 amide" of carbonic acid, which would possess the formula 
 C(NH 2 ) 4 , is unknown; when it might be expected, guanidine 
 and ammonia are formed instead. 
 
 The modes of formation of urea and of carbamic acid are 
 exactly analogous to those of the amides in general: 
 
 1. By the action of ammonia upon ethyl carbonate: 
 
 CO(OC 2 H 6 ) 2 + 2NH 3 = CO(NH 2 ) 2 + 2C 2 H 6 -OH. 
 CO(OC 2 H 5 ) 2 + NH 3 
 
 2. By the abstraction of the elements of water from car- 
 bonate or carbamate of ammonia. Dry carbon dioxide and 
 ammonia combine together directly to ammonium carbamate, 
 the so-called anhydrous carbonate of ammonia, NH 2 .COj 
 ONH 4 , which is transformed into urea when heated to 135, 
 or when exposed to the action of an alternating current of 
 electricity : 
 
 NH 2 .CO-ONH 4 = CO(NH 2 ) 2 + H 2 0. 
 
282 XIII. CARBONIC ACID DERIVATIVES 
 
 3. By the action of ammonia upon carbonyl chloride and its 
 derivatives : 
 
 COCl 2 -f4NH 3 = CO(NH 2 ) 2 + 2NH 4 C1. 
 CO(OC 2 H 6 )C1 + 2NH 3 = CO(OC 2 H 5 )NH 2 + NH 4 C1. 
 
 Carbamic acid, NH 2 .COOH, is known only in the form 
 of derivatives; the ammonium salt, NH 2 CO'ONH 4 , forms a 
 white mass, and dissociates at 60 into 2NH 3 + C0 2 . Its 
 aqueous solution does not precipitate a solution of calcic 
 chloride at the ordinary temperature, since calcic carbamate 
 is soluble in water; but when boiled it is hydrolysed to the 
 carbonate, and calcic carbonate is then thrown down. 
 
 Urethane, Ethyl carbamate, NH 2 CO OC 2 H 5 , is formed 
 according to method 3, and by the direct union of cyanic 
 acid with alcohol; also from urea nitrate and sodium nitrite 
 in presence of alcohol. It forms large plates, is readily 
 soluble in water, melts at 50, and boils at 184. It acts 
 as a soporific, and on hydrolysis with alkali yields the alkali 
 carbonate, ammonia and ethyl alcohol. One of its hydrogen 
 atoms is replaceable by sodium. Urethane may be employed 
 instead of cyanic acid for certain synthetic reactions (B. 23, 
 1856). 
 
 Analogous methyl and propyl esters of carbamic acid are 
 known, and are also termed urethanes. 
 
 Carbamic chloride, NH 2 'COC1, obtained by the action of 
 hydrogen chloride upon cyanic acid (Wohler, A. 45, 357), and 
 of carbonyl chloride upon ammonium chloride at 400, forms 
 long, compact, colourless needles of pungent odour. M.-pt. 50, 
 b.-pt. 61-62. It reacts violently with water, amines, &c., and 
 serves for the synthesis of organic acids (see these). 
 
 Ethyl imido-dicarboxylate, NH(C0 2 C 2 H 5 ) 2 , is the imide 
 corresponding with the amide urethane. It may be prepared 
 from the sodium compound of urethane and ethyl chloro- 
 carbonate. It forms colourless crystals, melting at 50. By 
 the exchange of one ethoxy (OC 2 H 5 ) group for an amido (NH 2 ) 
 group, it gives rise to allophanic ester, and by the exchange of 
 two, to biuret (see p. 289). 
 
 Urea, Carbamide, CO(NH 2 )2, was first found in urine in 
 1773. It is contained in the urine of mammals, birds, and 
 some reptiles, and also in other animal fluids. An adult man 
 produces about 30 gms. daily, and it may be regarded as the 
 final decomposition product formed by the oxidation of the 
 nitrogenous compounds in the organism. 
 
tJREA 283 
 
 It may be prepared by the action of ammonia on ethyl car- 
 bonate, ethyl carbamate, or phosgene, and synthetically by the 
 molecular transformation of ammonium cyanate, by warming 
 its aqueous solution or allowing it to stand (cf. pp. 1 and 273): 
 
 N:C-ONH 4 ^ 
 
 The reaction is reversible, and hence the process is never 
 complete. When equilibrium is reached, only a very small 
 amount of untransformed cyanate is left, and the equilibrium 
 is practically independent of the temperature. The reaction 
 has been shown to be a typical bimolecular one (Walker and 
 Hambly, J. C. S. 1895, 746). 
 
 The reaction is represented as follows by Chattaway (P. 1911. 
 27, 281): 
 
 NH 4 -N:C:O -* HN:C:0 + 
 
 HN:C(OH)NH 2 -* 
 
 It is usually prepared by mixing a solution of potassium 
 cyanate (from the ferrocyanide) with ammonium sulphate and 
 evaporating the mixture (ammonium cyanate is first formed 
 and gradually changes to urea), or by evaporating urine, add- 
 ing nitric acid, and decomposing the separated and purified 
 nitrate of urea by barium carbonate. 
 
 It is also formed by heating a solution of carbon monoxide 
 in ammoniacal cuprous chloride: 
 
 CO + 2NH 3 -{- Cu 2 Cl 2 = CO(NH 2 ) 2 + 2HC1 + 2Cu. 
 
 It crystallizes in long rhombic prisms or needles, has a 
 cooling taste, is very readily soluble in water, also in alcohol, 
 but not in ether. It melts at 132, sublimes in vacuo without 
 decomposition, and when strongly heated yields ammonia, 
 cyanuric acid, biuret, and ammelide. As an amide it is 
 readily hydrolysed by boiling with alkalis or acids, or by 
 superheating with water (cf. Fawsitt, J. C. S. 1904, 1581; 
 1905, 494): 
 
 CO(NH 2 ) 2 
 
 Nitrous acid reacts with it to produce carbon dioxide, 
 nitrogen, and water: 
 
 CO(NH 2 ) 2 + 2N0 2 H = C0 2 + 2N 2 + 3H 2 0. 
 
 Sodium hypochlorite and hypobromite act in a similar 
 manner (Davy, Knop). Hufner's method of estimating urea 
 quantitatively depends upon the measurement of the nitrogen 
 
284 XIII. CARBONIC ACID DERIVATIVES 
 
 thus obtained (J. pr. Ch., [2], 3, 1 ; cf. also B. 24, Ref. 330). 
 Urea also reacts with bromine and alkalis in much the same 
 manner as the lower acid amides (Hofmann reaction, p. 184), 
 yielding carbon dioxide and the corresponding amine, hydra- 
 zine (C. C. 1905, i, 1227), which is best removed by the addi- 
 tion of benzaldehyde. 
 
 Urea reacts with an aqueous solution of chlorine, yielding 
 the dichloro-derivative CO(NHC1) 2 . With acids this forms 
 nitrogen trichloride, and with ammonia it yields diurea or 
 
 paraurazine, CO^^ 00 ( Chattawa y> J - c - s - 1909 > 
 
 129, 235). When warmed with alcoholic potash to 100, urea 
 is converted into cyanate of potassium and ammonia. 
 
 The basic character of the amino groups is greatly weakened 
 in urea by the presence of the negative carbonyl. Among 
 the salts of urea with acids may be mentioned urea nitrate, 
 COISr 2 H 4 , HN0 3 , which crystallizes in glistening white plates, 
 readily soluble in water, but only slightly in nitric acid; also 
 the chloride, oxalate, and phosphate. But like acetamide, 
 urea also forms salts with metallic oxides, especially with mer- 
 curic oxide, e.g. CON 2 H 4 , 2HgO; finally, it yields crystalline 
 compounds with salts, e.g. urea sodium chloride, CON 2 H 4 , 
 NaCl, H 2 (glistening prisms), and urea silver nitrate, 
 CON 2 H 4 , AgN0 3 (rhombic prisms). The precipitate which 
 is obtained on adding mercuric nitrate to a neutral aqueous 
 solution of urea has the formula 2CON 2 H 4 , Hg(N0 3 ) 2 , 3HgO; 
 upon its formation depends Liebig's method for titrating urea. 
 (See the memoirs of Pfluger and Boliland on the subject, e.g. 
 Pflilger, Arch. f. Phys. 38, 575.) 
 
 Isomeric with urea is the amidoxime, isuret or methane 
 amidoxime, NHiCH-NH-OH, which is obtained from HCN 
 and NH 2 OH; it crystallizes in prisms (see p. 188). 
 
 Closely related to carbamide, NH 2 CO'NH 2 , is semicar- 
 bazide or semihydrocarbazide, NH 2 CO-NH-NH 2 , which is 
 the half amide and half hydrazide of carbonic acid. It may 
 be prepared from potassium cyanate and hydrazine hydrate. 
 It is a basic substance, melts at 96, and is usually met with 
 in the form of its hydrochloride. It reacts with aldehydes 
 and ketones in much the same manner a^ phenyl-hydrazine, 
 yielding condensation products known as semicarbazones : 
 
 H 2 O + C 6 H 6 . C(CH 3 ) : N - NH CO NH 2 , 
 

 UREIDES 285 
 
 which crystallize well, and have well-defined melting-points 
 (see p. 136). 
 
 Alkylated ureas are obtained by the exchange of the amido 
 hydrogen atoms for one or more alkyl radicals. 
 
 They are produced by Wohler's synthetical method, viz. by 
 the combination of cyanic acid with amines, or of cyanic esters 
 with ammonia or amines, thus : 
 
 CO-NC 2 H 6 + NH 2 .C 2 H 6 = CO(NH.C 2 H 6 ) 2 . 
 
 Also from amines and carbon oxy-chloride. As examples may 
 be mentioned: 
 
 Methyl urea, OCX^j a-Diethyl urea, 
 Ethyl urea, CO; ^Diethyl urea, 
 
 Certain of them closely resemble urea; others, however, are 
 liquid and volatilize without decomposition. Their constitution 
 follows very simply from the nature of the products which 
 are formed on hydrolysis; thus a-diethyl urea breaks up into 
 carbon dioxide and ethylamine, and the /?- compound into 
 carbon dioxide, ammonia, and diethylamine, in accordance 
 with the generalization enunciated on p. 95, that alkyl radi- 
 cals which are directly united to nitrogen are not separated 
 from it on hydrolysis. 
 
 Acyl Derivatives. By the entrance of acyl radicals into 
 urea, its acid derivatives or ureides are formed. These are 
 formed by the action of acid chlorides or anhydrides upon 
 urea, or by the action of phosphorus oxy-chloride upon the 
 salts of urea with organic acids. The simple ureides correspond 
 in many respects with acid amides or anilides, have neither 
 distinctly acid nor basic properties, and may be hydrolysed to 
 the acid and urea or its products of decomposition (p. 283). 
 To this class belong acetyl urea, NH 2 .CO.NH.(X).CH 3 , and 
 allophanic acid, NH 2 -CO-NH.C0 2 H. Hydroxy- monobasic 
 acids also form ureides, not only in virtue of their acidic 
 nature, but as alcohol and acid at the same time, thus: 
 
 Hydantoic acid, nn^-- 2'C0 2 H 
 
 .NH-CH.CH, 
 
 . NH -CH 2 Dactyl urea, CO< A O 
 Hydantom, OX' 
 
 Hydantoi'n or glycolyl urea (needles, neutral) and hydantoic 
 
286 XIII. CARBONIC ACID DERIVATIVES 
 
 acid or glycoluric acid (prisms), are derivatives of glycollic acid ; 
 the former on hydrolysis yields hydantoic acid, which in its 
 turn is broken up into C0 2 , NH 3 , and glycocoll. They are 
 obtained from certain uric acid derivatives (e.g. allantom) by 
 the action of hydriodic acid, and also synthetically, for in- 
 stance, hydantoic acid from glycocoll and cyanic acid. A 
 methyl-hydanto'in, C 3 H 3 (CH 3 )N 2 2 , results from the partial 
 hydrolysis of creatinine (p. 298), NH being here replaced by 0. 
 Just as the dibasic acids oxalic, malonic, tartronic, and 
 mesoxalic yield amides with ammonia, so with urea they 
 form compounds of an amidic nature. In such reactions 
 either two molecules of water are eliminated, so that no car- 
 boxyl radical remains in the compound, or only one molecule 
 is eliminated and a carboxyl group is retained. In the former 
 case the so-called cyclic ureides are obtained, and in the latter 
 the ureido-acids, e.g. from oxalic acid, parabanic and oxaluric 
 acids : 
 
 CO-OH co^ 1111 ' 00 co/ NH 3 
 
 CO-OH X NH-CO \NH.CO.OO,H 
 
 Oxalic acid Cyclic ureide (parabanic acid) Ureido-acid (oxaluric acid). 
 
 In an analogous manner the ureide barbituric acid, 
 C 4 H 4 No0 3 , is derived from malonic acid, the ureide dialuric 
 acid, Cf 4 H 4 N 2 4 , from tartronic acid, arid the ureide alloxan, 
 C 4 H 2 N 2 4 , and ureido-acid alloxanic acid, C 4 H 4 N 2 5 , from 
 mesoxalic acid. 
 
 These are solid and, for the most part, beautifully crystal- 
 lizing compounds of a normal amidic character, and therefore 
 readily hydrolysed to urea (or C0 2 and NH 3 ) and the respec- 
 tive acid. The ureido-acids may be regarded as half-hydro- 
 lysed ureides, and may be prepared from the latter in this 
 manner. As they contain a carboxyl group, they still possess 
 acidic properties. 
 
 The constitution of the various cyclic ureides and ureido- 
 acids follows in most cases from the products they yield on 
 hydrolysis, and also from their synthetical methods of for- 
 mation and their relationships to one another. 
 
 Some of these ureides are obtained synthetically from urea 
 and the requisite acid often in the presence of phosphorus 
 oxy-chloride, e.g. malonyl urea (barbituric acid), 
 
 from urea and malonic acid. Many can be obtained by the 
 
PARABANIC ACID. METHYL URACYL 287 
 
 oxidation of various complex natural products, e.g. alloxan or 
 parabanic acid by oxidizing uric acid with nitric acid. 
 
 Most of the ureides have the character of more or less 
 strong acids. Since this acid character is not to be explained, 
 as in the case of the ureido-acids, by the presence of carboxyl 
 groups, one must assume that it depends upon reasons similar 
 to those which apply in the case of cyanic acid and of suc- 
 cinimide, viz. that the replaceable hydrogen atoms are imido- 
 hydrogen atoms, the acidic nature of which is determined by 
 the adjacent carbonyl groups. This explains, for instance, why 
 parabanic acid is a strong dibasic acid. 
 
 Only a few of the more important among these compounds 
 can be discussed here. The names given to the majority of 
 them have no relationship to their constitution, and were as- 
 signed to them before the constitutions had been determined. 
 
 Parabanic acid, Oxalyl urea, C0<^ , is prepared 
 
 by the action of nitric acid upon uric acid, and crystallizes 
 in needles or prisms soluble in water and alcohol. The salts, 
 e.g. C 3 HKN 2 3 , C 3 Ag 2 N 2 3 , are unstable, being converted by 
 water into salts of the monobasic oxaluric acid, NH 2 -CO 
 NH.CO.C0 2 H, which crystallize well. 
 
 A methyl - parabanic acid, CO , and a di- 
 
 methyl - parabanic acid, the so-called " cholestrophane ", 
 , are also known. The former is prepared 
 
 by the action of nitric acid upon methyl-uric acid, and crystal- 
 lizes in prisms, while the latter is obtained from theine with 
 nitric acid or chlorine water, and also by the methylation of 
 parabanic acid, i.e. from the silver salt and methyl iodide. It 
 crystallizes in plates and distils without decomposition. 
 
 Methyl- iiracyl, CO<^;^^>CH, is produced by 
 
 the action of urea upon acetoacetic ester, water and alcohol 
 being eliminated (Behrend, A. 229, 1, and p. 230). When it 
 is treated with nitric acid, a nitro-group enters the molecule, 
 and the methyl-group is oxidized to carboxyl, thus forming 
 5-nitro-uracyl-4-carboxylic acid, 
 
288 XIII. CARBONIC ACID DERIVATIVES 
 
 This in its turn can give up carbon dioxide and pass into 
 5-nitro-uracyl, 
 
 which yields upon reduction with tin and hydrochloric acid 
 5-amino-uracyl and isobar bituric acid, 5-hydroxy-uracyl, 
 
 This last is oxidized by bromine water to isodialuric acid, 
 
 from which uric acid may be synthesised by warming with 
 urea and sulphuric acid (see p. 291). 
 
 Barbituric acid, Malonyl urea, CO<;>CH 2 , crys- 
 
 tallizes in large colourless prisms (+ 2H 2 0). The hydro- 
 gen atoms of the methylene group are reactive (cf. ethyl 
 malonate), and can be replaced by bromine, -NOg, :N-OH, 
 metals, &c. The metallic radicals in their turn can be 
 replaced by alkyl groups. The dimethyl derivative when 
 hydrolysed yields carbon dioxide, ammonia, and dimethyl- 
 malonic acid, thus indicating that the methyl groups have 
 replaced the methylene hydrogen atoms. The e'so-nitroso 
 
 derivative, CO<^;^>C:N.OH, violuric acid, can also 
 
 be obtained by the action of hydroxylamine on alloxan, and 
 on reduction yields ammo-barbituric acid (uramil), from which 
 pseudouric and uric acids have been synthesised (p. 291). 
 Diethylbarbituric acid (veronal) is used as a soporific. 
 
 Dialuric acid, Tartronyl urea, CO<^;^Q>CH.OH, crys- 
 
 tallizes in colourless needles or prisms which redden in the 
 air. It is a strong dibasic acid, and on oxidation yields allox- 
 an tin. 
 
 Alloxan, Mesoxalyl urea, C0< ' ^^' ma ^ ^ e P re ~ 
 
 pared from uric acid by oxidation with cold HNO 3 . It forms 
 large colourless glistening rhombic prisms ( + 4H 2 0), is readily 
 soluble in water, and has strongly acidic properties. It colours 
 the skin purple-red, and with ferrous sulphate solution pro- 
 duces an indigo-blue colour. It combines with NaHSOg, and 
 
** MUREXIDE. ALLANTOIN 289 
 
 readily changes into alloxantin. The corresponding ureido- 
 acid, alloxanic acid, NH 2 CO NH . CO CO C0 2 H, which 
 alloxan yields even with cold alkali, forms a radiating crys- 
 talline mass readily soluble in water. Methyl- and di- 
 methyl alloxan are also known, and may be obtained by 
 the action of nitric acid upon methyl-uric acid and caffeine 
 respectively. 
 
 The diureide alloxantin, C 8 H 4 7 N 4 , stands midway in 
 composition between tartronyl- and mesoxalyl-urea, by the 
 combination of which it is formed. It may also be obtained 
 by the action of H 2 S on alloxan, or directly from uric acid 
 and HN0 3 . It crystallizes in small hard prisms (+ 3H 2 0), 
 which become red in air containing ammonia, their solution 
 acquiring a deep-blue colour on the addition of ferric chloride 
 and ammonia. The tetramethyl derivative, amalic acid, 
 C 8 (CH 3 ) 4 N 4 7 , is obtained by oxidizing theine with chlorine 
 water, and forms colourless crystals which redden the skin 
 and whose solution is turned violet-blue by alkali. Both these 
 compounds yield, upon oxidation, first alloxan or its dimethyl 
 derivative, and then parabanic or dimethyl -parabanic acid. 
 Alloxantin probably has the constitution: 
 
 When heated with ammonia it is converted into murexide, 
 the acid ammonium salt of purpuric acid, C 8 H 5 N 6 5 , which is 
 the acid form of barbituryl iminoalloxan : 
 
 NH.CO 
 
 (J. pr. 1905, [ii], 73, 449), which is formed when uric acid is 
 evaporated with dilute nitric acid, and ammonia added to the 
 residue; this constitutes the "murexide test" for uric acid. 
 Murexide crystallizes in four-sided plates or prisms (+ H 2 0) 
 of a golden-green colour, which dissolve to a purple-red solu- 
 tion in water and to a blue one in potash. The free acid is 
 incapable of existence. 
 
 Allantoi'n is a diureide of glyoxylic acid, of the constitution 
 
 . 
 
 ra-co, 
 
 and is found in the allantoic liquid of the cow, the urine of 
 
 (B480) 
 
290 XIII. CARBONIC ACID DERIVATIVES 
 
 sucking calves, &c. It forms glistening prisms, and can be 
 synthesised from its components. 
 
 Biuret, NH 2 .CO.NH.(X).NH 2 , is obtained by heating urea 
 at 160: 
 
 2NH 2 .(X).NH 2 = NH 3 + NH(CO-NH 2 ) 2 . 
 
 It crystallizes in white needles ( -f H 2 0), and is readily 
 soluble in water and alcohol. The alkaline solution gives a 
 beautiful violet-red coloration on the addition of a little cupric 
 sulphate the "biuret reaction". Biuret is also formed by 
 the action of ammonia upon the allophanic esters, crystalline 
 compounds sparingly soluble in water, which are prepared 
 from urea and chloro-carbonic esters, thus: 
 
 CO(NH 2 ) 2 + C1.C0 2 C 2 H 5 = NH 2 .CO-NH.CX) 2 C 2 H 6 + HC1. 
 
 Allophanic acid itself is not known in the free state, as it 
 immediately breaks up into urea and carbon dioxide. Biuret 
 may be regarded as its amide. 
 
 The Purine Group (E. Fischer, B. 1899, 32, 435; 35, 2564). 
 A number of relatively complex cyclic diureides derived from 
 1 molecule of hydroxy dibasic acids and 2 of urea are known. 
 One of the most important of these is uric acid. 
 
 The parent substance of this group of compounds is purine 
 (E. Fischer, B. 1899, 32, 449). 
 
 Purine : 
 
 2CH5C.NEK8 
 
 4 9 
 
 is usually obtained from uric acid : 
 NH-CO 
 
 co r 
 
 NH.! 
 
 which reacts with phosphorus oxy-chloride as the tautomeric 
 trihydroxy purine: 
 
 N = C-OH 
 
SYNTHESIS OF URIC ACID 291 
 
 yielding the corresponding trichlorpurine : 
 N = CC1 
 
 and this on reduction yields purine itself. It is a colourless 
 crystalline compound, melts at 216, and is both an acid and a 
 base. It dissolves readily in water, and is not easily oxidized. 
 The atoms of the ring are usually numbered as indicated. 
 
 Uric acid is the keto form of 2:Q:8-trihydroxy-purine, and 
 has the constitutional formula: 
 
 NH-CO 
 CO ' 
 NH-< 
 
 Uric acid and many other compounds containing the 
 NHCO group, as tautomeric substances, behave in certain 
 reactions as ketonic compounds and in other reactions as hy- 
 droxylic derivatives, i.e. they exhibit keto-enolic tautomerism. 
 
 It is a common constituent of the urine of most carnivorous 
 animals, whereas that of herbivorous animals contains hippuric 
 acid. It is also found in the blood and muscle juices of the 
 same animals, and would appear to be the oxidation product 
 of the complex nitrogenous compounds contained in the 
 organism. It is also contained in the excrement of birds, 
 serpents, and insects, and in guano. 
 
 Syntheses. 1. By heating glycocoll with urea (HorlaczewsU, 
 B. 15, 2678). 
 
 2. By heating isodialuric acid (p. 288) with urea and concen- 
 trated sulphuric acid (R. Behrend and 0. Roosen, A. 251, 235) : 
 
 NH-CO NH-CO 
 
 CO C-OH + H 2 N >CQ m 00 9/ NH \ CO + 2H 2 0. 
 
 NH-C.OH ^ H^/ NH-C.NH/ 
 
 3. By heating cyano-acetic acid with urea (Traube, B. 1891, 
 24, 3419; 1900, 33, 3035). 
 
 4. By heating pseudouric acid with hydrochloric acid when 
 water is eliminated (K Fischer, B. 1897, 30, 559): 
 
 NH-CO NH-CO 
 
 CO CH.NH-CO-NH 2 = H 2 O + CO C-NH\ C() 
 
 NH-CO ' 
 
292 XIII. CARBONIC ACID DERIVATIVES 
 
 The pseudo acid is obtained as the potassic salt by the 
 condensation of amino-barbituric acid (p. 288) with potassic 
 cyanate : 
 
 NH.CO NH-CO 
 
 CO CH-NH 2 -f HCNO = CO CH-NH-CO-NH,, (Baeyer). 
 
 NH-CO NH.CO 
 
 It is usually prepared from guano and the excrement of 
 serpents, and crystallizes in small plates; is almost insoluble 
 in water, and quite insoluble in alcohol or ether. Uric acid 
 is a weak dibasic acid; its common salts are the acid ones, 
 e.g. C 5 H 3 3 N 4 K, a powder sparingly soluble in water. The 
 lithium and piperazine salts are somewhat more soluble, and 
 hence are used in medicine for removing uric acid from the 
 human system. 
 
 When the two lead salts are treated with methyl iodide, 
 methyl- and dimethyl uric acids are obtained, both of which 
 also are weak dibasic acids, since they still contain replaceable 
 imido-hydrogen atoms. 
 
 Constitution. The constitutional formula, given above, was 
 first proposed by Medicus, and afterwards proved to be correct 
 by E. Fischer (A. 215, 253). The more important arguments 
 used were: (1) Uric acid yields alloxan and urea when 
 cautiously oxidized, this proving that we have to deal here 
 with a carbonic acid derivative and a carbon chain, CCC; 
 (2) uric acid contains four imido groups, since, by the intro- 
 duction of four methyl groups, one after the other, four mono- 
 methyl, various di- and trimethyl, and one tetramethyl uric 
 acids are obtained. When the tetramethyl acid is hydrolysed 
 with concentrated hydrochloric acid all the nitrogen is elimi- 
 nated as methylamine, and thus each methyl group is probably 
 attached to a nitrogen atom; (3) dimethyluric acid yields 
 methylalloxan and methylurea on oxidation. 
 
 Uric acid is usually recognized by its sparing solubility, and 
 by its giving the murexide test. 
 
 Xan thine, 2:Q-Dihydroxy-purine, or the corresponding keto 
 form: 
 
 NH-CO NH.CO 
 
 co C.NH\ CH C.NH\ 
 
 NH-C-N/ C N_C-N/ H ' 
 
 Xanthine Hypoxantkiue 
 
DERIVATIVES 293 
 
 may be obtained by the reduction of uric acid with sodium 
 amalgam, or by the action of nitrous acid on guanine (amino 
 hypoxanthine). It is a white amorphous mass, and is both 
 basic and acidic. The lead salt, C 5 H 2 PbN 4 2 , is converted 
 into theobromine by methyl iodide. (Of. B. 1897, 30, 2235; 
 1900, 33, 3035.) When oxidized it yields the same products 
 as uric acid. 
 
 Hypoxanthine, Sarcine, or Q-oxy-purine, is sparingly soluble 
 in water and closely resembles xanthine, 
 
 Theobromine, 3 : 1-Dimethyl-xanthine, 
 
 NH CO NMe-00 
 
 CO C-NMex CO C.NMe\ 
 
 NMe C N/ NMe . C N/ ' 
 
 Theobromine Caffeine 
 
 occurs in the beans of cacao; it is a crystalline powder of 
 bitter taste, and is only sparingly soluble in water and alcohol. 
 It forms salts both as a base and as an acid. The silver salt, 
 C r H 7 AgN 4 2 , when treated with CH 3 I, yields caffeine or 
 theine, I:3:7-trimethyl-xanthine, which occurs in tea (2-4 per 
 cent), coffee, and various plants. (For synthesis from dimethyl 
 urea and malonic acid, see Fischer, B. 1895, 28, 3137; 1899, 
 32, 435; from cyanoacetic acid, 1900, 33, 3035.) It crystal- 
 lizes (+ H 2 0) in beautiful long glistening silky needles of 
 faintly bitter taste, which are sparingly soluble in cold water 
 and alcohol, and can be sublimed. The salts are readily de- 
 composed by water. Chlorine oxidizes it to dimethyl alloxan 
 and monomethyl urea. Theophylline, 1 : 3-dimethyl-xanthine, 
 also occurs in tea. 
 
 Guanine, 2-amino-Q-oxy-purine, or 2-amino-hypoxanthine, and 
 adenine, Q-amino-purine, both contain amino-groups, and are 
 thus basic substances. Both compounds, together with xan- 
 thine and hypoxanthine, are formed by the decomposition of 
 the nucleic acids and other complex compounds contained in 
 the animal system. The constitution follows largely from 
 (1) basic properties, (2) their conversion respectively into 
 xanthine and hypoxanthine by the aid of nitrous acid, and 
 (3) from their oxidation products. 
 
 A summary of some of the more important ureides which 
 can be obtained from uric acid are tabulated here: 
 
t-t 
 
 o 
 
 X 
 
 W 
 
 o 
 
 A 
 
 w 
 
 g 
 
 -.8 
 
 
 v 
 
 o 
 o 
 
 V 
 
 o 
 
 si^ill^ljssi 
 
 8 
 
SULPHUR DERIVATIVES OF CARBONIC ACID 295 
 
 D. Sulphur Derivatives of Carbonic Acid 
 
 In addition to most of the carbonic acid derivatives which 
 have been described, there exist analogous compounds in which 
 the oxygen is wholly or partially replaced by sulphur. Many 
 or these again are unstable in the free state, from the fact of 
 their being too readily hydrolysed to C0 2 , COS, or CS 2 , but 
 they are known as salts, or at least as esters. The latter are 
 often not real esters, in so far that those which contain an 
 alkyl radical linked to sulphur do not yield the corresponding 
 alcohols on hydrolysis, but mercaptans, in accordance with the 
 intimate character of this linking. 
 
 Various mono-, di-, and tri-thio-derivatives of carbonic acid 
 are known, according as 1, 2, or 3 of the oxygen atoms are 
 replaced by sulphur. 
 
 Many of the thio-acids react as tautomeric substances, and 
 give rise to isomeric alkyl derivatives in exactly the same 
 manner as hydrocyanic, cyanic, and thiocyanic acids. 
 
 Thiophosgene, Thiocarbonyl chloride, CSC1 2 . When chlorine 
 is allowed to act upon carbon disulphide, there is first formed 
 the compound CC1 3 'SC1, which is converted into thiophosgene 
 by SnCl 2 . It is a red, mobile, strongly fuming liquid of 
 sweetish taste, which attacks the mucous membrane, and boils 
 at 73. In its chemical behaviour it closely resembles phosgene, 
 but is much more stable towards water than the latter, being 
 only slowly decomposed even by hot water. With ammonia it 
 yields ammonium thiocyanate and not thiocarbamide. 
 
 Thiocarbonic Acids. Tri-thiocarbonic acid is made up of 
 the constituents CS 2 + H 2 S, so that carbon disulphide is its 
 thio-anhydride, while the di-thiocarbonic acids contain the 
 elements of CS 2 + H 2 or of COS + H 2 S, and the mono- 
 acids those of COS + H 2 or of C0 2 + H 2 S. We find 
 accordingly that CS 2 combines with Na 2 S to CS 3 Na 2 , sodic tri- 
 thiocarbonate, with KSC 2 H 5 to CS(SC 2 H 5 )SK, with KOC 2 H 5 
 (i.e. an alcoholic solution of potash) to CS(OC 2 H 5 )SK, potas- 
 sium xanthate. In a similar manner COS and CSC1 2 combine 
 with mercaptides and alcoholates. 
 
 Tri-thiocarbonic acid, CS 3 H 2 , is a brown oil, insoluble in 
 water, and readily decomposed, and its ethyl ester, 
 S:C(SC 2 H 5 ) 2 , a liquid boiling at 240. 
 
 Potassium xanthate, S:C<g^ H5 , obtained by the action 
 of potassic ethoxide, (KOH + C 2 H 6 OH), on carbon disulphide, 
 
296 XIII. CARBONIC AClt> DERIVATIVES 
 
 crystallizes in beautiful colourless needles, very readily soluble 
 in water, less so in alcohol. A solution of cupric sulphate 
 throws down cupric xanthate as a yellow unstable precipitate, 
 hence the name. It is employed in indigo printing. The free 
 xanthic acid, or ethyl hydrogen dithiocarbonate, CS(OC 2 H 5 )SH, 
 is an oil insoluble in water, and decomposes at so low a tem- 
 perature as 25 into carbon disulphide and alcohol. 
 
 Thiocarbamic Acids. Di-thiocarbamic acid, NH 2 CS-SH, 
 is formed as ammonic salt by the combination of CS 2 and NH 3 
 in alcoholic solution : 
 
 CS 2 + 2NH 3 = NH 2 .CS-SNH 4 . 
 
 The free acid is a reddish oil which easily decomposes into 
 thiocyanic acid and sulphuretted hydrogen: 
 
 NH 2 .CS-SH = CSNH + SELj. 
 
 Carbon disulphide combines in an analogous manner with 
 primary amines to form the aminic salts of alkylated di-thio- 
 carbamic acids; thus ethylamine yields ethylamine ethyl-di- 
 thiocarbamate, C 2 H 5 NH.CS.SNH 3 C 2 H 5 . When such salts 
 are heated above 100, H 2 S is evolved and a dialkyl-thio- 
 urea left behind, e.g. diethyl-thio-urea, CS(NHC 2 H 5 ) 2 ; when 
 HgCl 2 or AgN0 3 is added to their solutions, the Hg or Ag 
 salts of the acids are precipitated, and these decompose on 
 boiling with water into HgS or Ag 2 S and the corresponding 
 mustard oil (cf. p. 275): 
 
 2CS(NHC 2 H 5 ).SAg = 2CSNC 2 H 5 + Ag 2 S + H 2 S. 
 
 Secondary amines also give rise to alkylated di-thiocarbamic 
 acids, but the latter do not yield mustard oils. 
 
 Thiocarbamide, Thio-urea, sulpho-urea, S:C(NH 2 ) 2 (Reynolds), 
 is the analogue of urea, and its modes of formation are exactly 
 similar to those of the latter. Thus it is formed from am- 
 monium thiocyanate just as urea is from the cyanate: 
 
 N:C.SNH 4 ^ CS(NH 2 ) 2 . 
 
 To effect this molecular transformation a temperature of 
 at least 130 is required, and it is only partial, as the reaction 
 is reversible. At 170 equilibrium is attained after 45 minutes, 
 and the mixture then contains only 25 per cent of thiocarba- 
 mide (Reynolds and Werner, P. 1902, 207). It may also be 
 
AMIDINES OF CARBONIC ACID 297 
 
 formed by the direct union of sulphuretted hydrogen with 
 cyanamide: CN.NH 2 + SH 2 = CS(NH 2 ), 
 
 Thiocarbamide crystallizes in rhombic six-sided prisms, or 
 if not quite pure in long silky needles, readily soluble in 
 water and alcohol. M.-pt. 172. It is easily hydrolysed to 
 C0 2 , H 2 S, and 2NH 3 . HgO abstracts H 2 S from it, with for- 
 mation of cyanamide. Cold permanganate of potash solution 
 oxidizes it to urea. As a weak base it forms salts with acids, 
 but at the same time it yields salts with HgO and other 
 metallic oxides; it also combines with salts, such as AgCl, 
 PtCl 4 , &c. When heated with alcoholic potash to 100, it is 
 reconverted into (the potassium salt of) thiocyanic acid and 
 ammonia. 
 
 Thiocarbamide gives rise to alkyl derivatives (normal and 
 pseudo), acyl derivatives, cyclic ureides, &c., in much the 
 same manner as urea itself. 
 
 E. Amidines of Carbonic Acid 
 
 Guanidine, or Imino-carbamide, NH:C(NH 2 ) 2 (Strecker, 
 1861), may be obtained by the oxidation of guanine, also by 
 heating cyanamide with ammonium iodide, and therefore from 
 cyanogen iodide and ammonia: 
 
 = CN 3 H 5 ,HI. 
 
 It is usually prepared by heating thio-urea with ammonium 
 thiocyanate to 180-190, and therefore from the thiocyanate 
 alone at this temperature ( Volhard) : 
 
 CS(NH 2 ) 2 + NH 4 -CNS = C(NHXNH 2 ) 2 , CNSH + H 2 S 
 
 Guanidine isothiocyanate. 
 
 Guanidine crystallizes well, is readily soluble in water and 
 alcohol, deliquesces in the air, and is a sufficiently strong 
 monoacid base to absorb carbon dioxide. Guanidine car- 
 bonate, (CN 3 H 5 ) 2 , H 2 C0 3 , crystallizes beautifully in quadratic 
 prisms. The base is readily hydrolysed, at first to urea and 
 ammonia, and finally to ammonia and carbon dioxide. 
 
 By the action of a mixture of nitric and sulphuric acids 
 upon guanidine nitrate, nitro-guanidine, NH 2 'C(NH)NHN0 2 , 
 is obtained, which is readily reduced to amino-guanidine, 
 NH 2 C(NH)NH NH 2 . The latter, when boiled with alkalis or 
 acids, breaks up into hydrazine, N H 4 , ammonia, and carbon 
 
298 XIII. CARBONIC ACID DERIVATIVES 
 
 dioxide, and it yields with nitrous acid diazo - guanidine, 
 NH 2 C(NH)NHN:N-OH, which in its turn is decomposed by 
 alkalis into water, cyanamide, and hydrazoic add, N 3 H 
 (Curtius, A. 1900, 314, 339). 
 
 By the direct combination of cyanamide with glycocoll 
 there is formed glycocyamine : 
 
 NH;C \NH 2 .CH 2 .C0 2 H, 
 which readily loses water with formation of glycocyamidine : 
 
 If, instead of glycocoll, its methyl derivative, sarcosine, is used, 
 we obtain in an analogous manner creatine and ereatinine 
 (Folhard): 
 
 e.CH 2 .C0 2 H 
 
 Creatine Creatinine. 
 
 Creatine is present in the juice of muscle, and is prepared 
 from extract of meat (LieUg). It crystallizes in neutral 
 prisms (+ H 2 0) of a bitter taste, is moderately soluble in 
 hot water, but only slightly in alcohol. When heated with 
 acids it loses water and yields ereatinine, which is an invari- 
 able constituent of urine, and which forms a characteristic 
 double salt with zinc chloride, 2C 4 H r N 3 + ZnCl 2 . It is a 
 strong base and much more readily soluble than creatine. 
 
 Creatinine is the methyl derivative of imino-hydantoin, and 
 as such yields, when carefully hydrolysed, ammonia and methyl- 
 hydantoi'n. 
 
 XIV. CARBOHYDRATES 
 
 Most of the carbohydrates which occur in nature have been 
 known for a long time. Cane-sugar was found in the sugar- 
 beet by Marggrafm 1747, and dextrose in honey by Glauber. 
 The transformation of starch into glucose (p. 309) was first 
 observed by Kirchoff in 1811. 
 
 The name carbohydrate was formerly applied to certain 
 substances which occur naturally in large quantities in the 
 vegetable and animal kingdom, and which could be repre- 
 
CARBOHYDRATES 299 
 
 sented by the general formula C x (H 2 0) y , where x = 6 or a 
 multiple of 6, ..^dextrose ,C 6 (H 2 0) 6 or C 6 H 6 , cane-sugar, 
 C i 2 (H 2 0) n or C ]2 H 22 O n , and starch [C fl (H 2 0)J x . In addition 
 to these natural products, the group at the present time 
 includes a number of compounds which have only been ob- 
 tained synthetically, mainly as a result of the researches of 
 E. Fischer. The number of carbon atoms in these varies 
 considerably. Carbohydrates are now known in which the 
 hydrogen and oxygen are not present in the proportions of 
 2 atoms of hydrogen to 1 of oxygen, e.g. rhamnose, C 6 H 12 5 . 
 
 The carbohydrates are usually divided into the three fol- 
 lowing groups, according to their relative complexity: 
 
 A. Monosaceharoses. This is the simplest group of the 
 carbohydrates, and the members are all polyhydroxy alde- 
 hydes or ketones containing from 3-9 carbon atoms. The 
 group includes the common substances arabinose, C 5 H 10 5 , 
 and the isomeric compounds, C 6 H 12 6 , glucose or grape-sugf.r, 
 and fructose or fruit-sugar. As a rule, the compounds are 
 readily soluble in water, have a sweet taste, and do not 
 crystallize very readily. 
 
 B. Bi- and Trisaccharoses. These compounds may be 
 regarded as anhydrides of the monoses, usually derived by 
 the elimination of 1 molecule of water from 2 mols. of a 
 monose, or of 2 mols. of water from 3 of a monose. It is not 
 necessary that the 2 or 3 molecules of monose should be iden- 
 tical in structure, e.g. cane-sugar is the anhydride produced by 
 the elimination of 1 mol. of water from 1 mol. of glucose and 
 1 of fructose. As anhydro-derivatives they are readily hydro- 
 lysed by mineral acids, yielding the monoses, from which they 
 may be regarded as being derived. 
 
 Most of the di- and trioses are soluble in water, crystallize 
 very well, and also possess a sweet taste. Examples are cane- 
 sugar, maltose, and milk-sugar. 
 
 C. Polysaccharoses or Polyoses, This group includes the 
 complex carbohydrates, such as starch, cellulose, &c. They 
 may be regarded as derived from the monoses by the elimi- 
 nation of x mols. of water from x mols. of a monose, e.g. : 
 
 #C 6 H 12 6 - #H 2 = (C 6 H 10 6 ) X . 
 
 In conformity with such a structure they are fairly readily 
 hydrolysed, yielding as the ultimate product a monose. As 
 a rule, they do not dissolve in water, possess no sweet taste, 
 and have not been obtained in a crystalline form. 
 
300 XIV. CARBOHYDRATES 
 
 A. Monosaeeharoses 
 
 These are all open-chain polyhydroxy-aldehydes or ketones, 
 
 OH CH 2 CH(OH) . CH(OH) CH(OH) - OH : O Arabinose, 
 
 OH CH 2 CH(OH) CH(OH) CH(OH) CO CH 2 OH Fructose, 
 
 and are divided into the two main groups aldoses and ketoses, 
 according to their aldehydic or ketonic constitution. As a 
 rule, several hydroxyl groups are present in addition to the 
 
 aldehydic 'C^ or ketonic ^>C:0 group, and invariably one 
 
 of these hydroxyl groups is in the a-position with respect to 
 the aldehydic or ketonic group. 
 
 The monoses are usually divided into sub-groups, according 
 to the number of oxygen atoms present in the molecule, e.g. : 
 
 Trioses, OH.CH 2 .CH(OH).CH:0 and OH.CH 2 .CO-CH 2 .OH; 
 Tetroses, OH.CH 2 .(CH.OH) 2 .CH:0; 
 
 Pentoses, OH.CH 2 .(CH.OH) 3 .CH:O and CH 8 .(CH.OH) 4 .CH:0; 
 Hexoses, OH.<JE 2 .(CH.OH) 4 .CH:O and 
 
 OH.CH 2 .(CH.OH) 3 .CO-CH 2 .OH; 
 Heptoses, OH CH 2 (CH OH) 5 CH : O ; 
 Octoses, OH.CH 2 .(CH.OH) 6 .CH:0; 
 Nonoses, OH-CH 2 .(CH-OH) 7 .CH:O. 
 
 As a rule, the molecule of any single monose contains several 
 asymmetric carbon atoms, e.g. a hexose, OHCH 2 (CH-OH) 4 
 CH:0, contains 4 asymmetric carbon atoms, and hence 
 should exist in 2 4 , i.e. sixteen distinct optically active modi- 
 fications, in addition to eight racemic forms. In most cases 
 all the possible stereo-isomeric modifications are not known, 
 but the number of such compounds known has been largely 
 increased within recent years owing to the brilliant researches 
 of Emil Fischer (B. 1890, 23, 2114; 1894, 27, 3189). 
 
 General Characteristics of Aldoses. As aldehydes the 
 aldoses possess most of the properties already described as 
 characteristic of fatty aldehydes. 
 
 They are readily reduced by ordinary alkaline reducing 
 agents, yielding polyhydric alcohols: 
 
PROPERTIES OF ALDOSES 301 
 
 When oxidized, they yield first mono- and then dibasic acids, 
 containing the same number of carbon atoms : 
 
 OH.eH 2 .(CH.OH) 4 .CH:0 OH.CH 2 .(CH.OH) 4 .CO.OH 
 COOH.(CH.OH) 4 .COOH. 
 
 These reactions are of considerable importance as direct 
 evidence of the aldehydic nature of the aldoses. The first 
 stage of the oxidation is effected by mild oxidizing agents, 
 such as chlorine, bromine water, silver oxide, or ammoniacal 
 solutions of cupric salts. The last-mentioned reaction is the 
 basis of the usual volumetric method for the estimation of 
 glucose and other aldoses. The aldose solution is added to a 
 given volume of a standard Fehlintfs solution (a solution con- 
 taining cupric sulphate, sodic ammonic tartrate, and sodic 
 hydroxide (p. 253) ) until the blue colour just disappears on 
 boiling. An even more exact method is to weigh the cuprous 
 oxide (as such, as metallic copper, or as cupric oxide) formed 
 by reducing a given volume of the sugar solution with an 
 excess of Fehling's solution. 
 
 The oxidation to a dibasic acid requires somewhat stronger 
 oxidizing agents, e.g. nitric acid. 
 
 Although the aldoses do not combine directly with ammonia 
 or sodic hydric sulphite, they readily form additive compounds 
 with hydrogen cyanide : 
 
 OH CH 2 (CH OH) X CH : + HCN 
 
 = OH.CH 2 (CH.OH) X .CH(OH).CN. 
 
 This is an extremely important reaction as being the basis 
 of a method for passing from a tetrose to a pentose, or from a 
 pentose to a hexose (see p. 304). 
 
 They react normally with hydroxylamine, yielding oximes, 
 more especially in alcoholic solution, and the oximes thus 
 obtained may be converted into a monose containing a smaller 
 number of oxygen atoms (p. 305). 
 
 They can also react normally with phenyl-hydrazine, yield- 
 ing phenyl-hydrazones, which, as a rule, are sparingly soluble, 
 colourless, crystalline compounds with definite melting-points. 
 These are readily transformed back into the aldoses by treat- 
 ment with hydrolysing agents or with benzaldehyde (A. 1895, 
 288, 140). One of the most characteristic properties of 
 monoses is the formation of osazones or diphenyl-hydrazones. 
 This reaction may be regarded as taking place in three distinct 
 stages: (a) Formation of a phenyl-hydrazone, XCH(OH) 
 
304 XIV. CARBOHYDRATES 
 
 The ketoses also form metallic derivatives and acetyl deriva- 
 tives. 
 
 Alcoholic Fermentation of Monosaccharoses. Many of the 
 natural products, e.g. d-glucose and ^-fructose, are readily fer- 
 mented by yeast (Saccharomyces), yielding as chief products 
 ethyl alcohol and carbon dioxide (p. 76). This decomposition 
 is undoubtedly due to the presence of an enzyme, Buchner's 
 zymase, which is contained in the cells of the organism. 
 Fischer's researches have shown that all monoses cannot be 
 fermented, only certain of those containing 3 or a multiple of 
 3 carbon atoms. Even such monoses are not all readily fer- 
 mented, e.g. ^-glucose is fermented more readily than /-glucose, 
 and the isomeric guloses cannot be fermented by yeast. There 
 appears to be an intimate relationship between the configura- 
 tion of the monose molecule and of the ferment (enzyme) 
 which is capable of decomposing it. Fischer has compared 
 this relationship to that of a lock and its corresponding key. 
 
 Conversion of an Aldose into an Isomeric Ketose. This is 
 an interesting transformation due to E. Fischer, and consists 
 in converting the aldose into its osazone, which on hydrolysis 
 with hydrochloric acid yields phenyl-hydrazine and a poly- 
 hydroxy-ketonic aldehyde, usually known as an osone. When 
 the osone is reduced, the aldehydo-group is converted into a 
 primary alcoholic radical, and a hydroxy-ketone (ketose) iso- 
 meric with the original aldose is obtained, e.g. : 
 
 X-CH(OH).CH:0 X.C(:N-NHPh).CH:N.NHPh 
 
 X.CO-CEVOH - X.CO-CH-.O. 
 
 By this means d-glucose can be transformed into ^-fructose. 
 
 Synthesis of a Mono saccharose from a Simpler Mono- 
 saccharose. The aldose is converted into its cyanhydrin by- 
 means of hydrogen cyanide (Kiliani): 
 
 X.CH(OH).CH(OH).CH:0 
 
 As this reaction involves the introduction of a further 
 asymmetric carbon atom into the molecule, two distinct 
 optically active nitriles will be formed. As the two com- 
 pounds are not related to one another as object to mirror 
 image, they will not be optical antipodes, and will not neces- 
 sarily be formed in equal amount. The mixture of cyanides is 
 hydrolysed, the resulting hydroxy acids converted into lactones 
 
CONVERSION OF A MONOSE INTO OTHER MONOSES 305 
 
 and then reduced with sodium amalgam, when a mixture of 
 two sugars is obtained: 
 
 X.CH(OH).CH(OH).CH(OH).C0 9 H 
 
 -^ X.CH.CH(OH).CH(OH).CO 
 
 I 
 
 X.CH(OH).CH(OH).CH(OH).CH:0. 
 
 As examples of this we have : 
 
 /3-Galaheptose. 
 
 By similar methods E. Fischer has succeeded in preparing 
 octoses and nonoses. 
 
 Conversion of a Monosaccharose into a Simpler Mono- 
 saccharose (Wohl, B. 1893, 26, 730). The aldose is converted 
 into its oxime, which reacts with acetic anhydride, yielding an 
 acetylated hydroxy-nitrile, e.g.: 
 
 OH.CH 2 .[CH.OH] 4 .CH:N.OH 
 OAc.CH 2 .[CH.OAc] 4 .CN. 
 
 The nitrile when treated with ammoniacal silver nitrate solu- 
 tion loses hydrogen cyanide and yields the acetyl derivative of 
 a lower monose, e.g. : 
 
 Ac CH 2 [CH O Ac] 3 . CHO, 
 
 from which the monose itself is readily obtained. 
 
 Another method has been worked out by Buff (B. 1898, 31, 
 1573; 1902, 35, 2360). This consists in oxidizing the aldose 
 to the corresponding monobasic acid, and then oxidizing the 
 calcic salt of this with ferric acetate and hydrogen peroxide. 
 In this way carbonic acid is split off and an aldose obtained : 
 
 OH.CH 2 .(CH.OH) 3 .CH.(OH).CO-OH + O 
 
 = OH.CH 2 (CH.OH) 3 .CH:0 + H 2 C0 3 . 
 
 The aldose can be isolated as its phenylhydrazone, and this 
 with benzaldehyde yields the free aldose. 
 Trioses. When glycerol is oxidized with dilute nitric acid 
 
 (B480) U 
 
306 XIV. CARBOHYDRATES 
 
 or other oxidizing agents, a product C 3 H 6 3 is obtained, 
 which has been termed glycerose. This has been shown to 
 consist of the ketone, dihydroxyacetone, OH-CH 2 COCH 2 - 
 OH, with a small amount of the isomeric aldehyde, glycer- 
 aldehyde, OH . CH 2 . CH(OH) . CH : 0, and may be regarded 
 as the simplest monose. It is a syrup, possesses most of the 
 characteristic properties of the monoses, and when warmed 
 with alkalis undergoes condensation and yields a hexose 
 (o-acrose) (p. 312) which closely resembles fructose. 
 
 Tetroses, C 4 H 8 O 4 . A tetrose, erythrose, can be obtained 
 by the oxidation of erythritol, OH CH 2 [CH OH] 2 CH 2 OH, 
 with nitric acid, and is probably a mixture of an aldose and 
 ketose. Other tetroses can be obtained from the pentoses by 
 the general methods described on p. 305. 
 
 Pentoses. The pentoses are characterized by the fact that 
 they yield furfuraldehyde or methyl-furfuraldehyde upon pro- 
 longed boiling with hydrochloric acid, water being eliminated. 
 This reaction is largely made use of for their quantitative esti- 
 mation (B. 1892, 25, 2912; 1898, 30, 2570). Arabinose gives 
 furfuraldehyde itself, while its homologue, rhamnose, gives 
 methyl-furfuraldehyde. When warmed with hydrochloric acid 
 and phloroglucinol, cherry-red colorations are produced. The 
 pentoses do not appear to exist free in the animal or vegetable 
 kingdom, but are readily formed by the hydrolysis of various 
 natural gummy carbohydrates. 
 
 J-Arabinose, C 5 H 10 5 , = OH.CH 2 .[CH.OH] 3 .CH:0, is pro- 
 duced by boiling gum-arabic, cherry gum, or beet-root chips 
 with dilute sulphuric acid, and forms prisms which dissolve 
 in water to a dextro-rotatory solution. It combines with 
 hydrogen cyanide, and thus yields the nitriles of two stereo- 
 isomeric hydroxy-caproic acids, viz. Z-mannonic acid (Kiliani, 
 B. 20, 339, 1233) and Z-gluconic acid (E. Fischer). In addition 
 to /-arabinose, a d-arabinose and a d-l- or racemic arabinose 
 are also known. They are related to one another in exactly 
 the same manner as /-, d-, and r-tartaric acid. The corre- 
 sponding alcohol is arabitol. 
 
 /-Xylose, or Wood-sugar, is stereo-isomeric with arabinose. 
 and is prepared by boiling wood-gum, straw, and jute with 
 dilute sulphuric acid, and is very similar to arabinose. (Foi 
 its constitution, see B. 24, 537.) The corresponding alcohol is 
 xylitol. Ribose (B. 1891, 24, 4214) and Lyxose (B. 1899, 
 33, 1798) are stereo-isomeric with arabinose. 
 
 Rhamnose, or Isodulcite, C 6 H 12 6 , = CH 3 . [CH OH] 4 . CH : 0, 
 
ALDOHEXOSES 307 
 
 is obtained from several glucosides, e.g. quercitrin or xantho- 
 rharanin (yellow needles, present in French berries, Ehamnus 
 tinctoria, &c.), by the action of dilute sulphuric acid. It forms 
 colourless crystals which contain 1H 2 0, melts at 93, and 
 when distilled with sulphuric acid yields a-methyl-furfuralde- 
 hyde. 
 
 Several isomerides of rhamnose are known, e.g. fucose from 
 sea-weed, quinovose, rhodeose, and isorhamnose. 
 
 Hexoses. The hexoses constitute the most important 
 group, as they contain all the more common natural mono- 
 saccharoses, e.g. d-glucose, ^-fructose, d-galactose, &c. These 
 occur in the free state in the juices of ripe fruits, and 
 are also found combined with acids and other compounds in 
 the ether- or ester-like compounds known as glucosides. They 
 are also formed by the hydrolysis of more complex carbo- 
 hydrates, e.g. cane-sugar, maltose, milk-sugar, or starch, either 
 under the influence of mineral acids or of enzymes. They are 
 sweet and for the most part crystalline compounds readily 
 soluble in water, sparingly in absolute alcohol, and insoluble in 
 ether. They possess the chemical properties of pentahydroxy- 
 aldehydes and ketones. 
 
 Aldohexoses. The common aldohexoses have the con- 
 stitution represented by the formula: 
 
 In this formula the 4 carbon atoms contained within the 
 brackets are asymmetric carbon atoms, and hence such a 
 compound should exist in numerous stereo-isomeric forms, 
 It can be shown that in this case the number of optically 
 active isomerides theoretically possible is sixteen; of these 
 some eleven are actually known, namely: 
 
 Dibasic Acid, M.-p. of 
 
 Aldohexose. Monobasic Acid. COaH[CH-OHVCO a H. Alcohol. Osazone. 
 
 d- & J-Mannose d- & Z-Mannonic acid d- & Z-Mannosaccharic d- & Z-M annitol 206* 
 
 d-&Z-Glucose d-&Z-Gluconic acid d-&Z-Saccharic d-&Z-Sorbitol Ibid 
 
 d-&J-Gulose d-&l-Gnlouic acid d-&Z-Saccharic d-&Z-Sorbitol 157-159* 
 
 d-&Mdose d-&Mdonic acid Idosaccharic d-&Mditol 193' 
 
 d-&Z-Galactose d-&Z-Galactonicacid t-Mucic i-Dulcitol 193" 
 
 d-Talose d-Talonic acid Talomucic d-Talitol 193* 
 
 All of these hexoses have to be represented by the same 
 structural formula, and only differ as regards the spatial 
 arrangements of the various radicals within the molecule. 
 All are optically active in solution, and the majority form 
 
308 XIV. CARBOHYDRATES 
 
 pairs of optical antipodes, e.g. d- and Z-glucose, which are 
 related in exactly the same manner as d- and Z-tartaric acids. 
 The members of such a pair are identical as regards their 
 ordinary chemical and physical properties, with the exception 
 of their effects on polarized light, and their behaviour towards 
 enzymes or ferments generally. As a rule, one of the two 
 compounds exists naturally, e.g. d-glucose, and the second 
 must be prepared by artificial means. The two are able to 
 form a racemic compound, which differs as regards its physical 
 properties from the active components. 
 
 The determination of the configuration of each aldohexose 
 has been accomplished by E. Fischer largely from a study of 
 the following points: (a) The relationship of the aldohexose 
 to the aldopentoses, e.g. Z-arabinose can be transformed into a 
 mixture of /-glucose and /-mannose, and hence in all three 
 compounds the configuration of the following part of the 
 molecule 
 
 OH CH 2 CH(OH) CH(OH) . CH(OH>- 
 
 must be identical, (b) The nature of the dibasic acid formed 
 on oxidation, or of the alcohol formed on reduction. When 
 reduced, ^-galactose yields an inactive hexahydric alcohol, viz. 
 i-dulcitol, and from this it follows that in the ^-galactose 
 molecule the H and OH radicals must be so spatially arranged 
 that when the -CHiO group is converted into a CH 2 -OH 
 group a symmetrical molecule is obtained (see formula below), 
 (c) The nature of the osazone; e.g. ^-glucose and d-mannose 
 both give rise to the same osazone d-glucosazone and hence 
 the spatial arrangements of the two molecules must be identical, 
 with the exception of the part CH(OH) CH : 0. 
 
 As the result of such methods, the following configurations 
 have been arrived at for some of the commoner aldohexoses 
 (B. 1891, 24, 2683; 1894, 27, 3211): 
 
 CHO CHO CHO CHO 
 
 HO-C.H H-C.OH H-C-OH H-C-OB 
 
 HO-C.H H.C-OH HO-C.H HO-C.H 
 
 H.C-OH HO-C.H H-C-OH HO-C.H 
 
 H-C-OH HO-C-H H-C-OH H-C-OH 
 CH 2 .OH CH 2 OH CH 2 OH CH 2 OH 
 
 d-Mannose i-Mannose cZ-Glucose <2-Galactose, 
 
309 
 
 E. Fischer has suggested the following system of nomen- 
 clature. According to the Geneva Congress, the name for glu- 
 cose is hexanepentolal. Fischer suggests that the asymmetric 
 carbon atoms be numbered with respect to the CHO group, 
 and that when the H is to the left and OH to the right of an 
 asymmetric carbon atom, it is termed -f and the reverse 
 Thus: 
 
 e?-Glucose is hexanepentolal, -j \- -f- 
 
 Z-Glucose 1 
 
 c?-Mannose J- -}- 
 
 rf-Galactose -\ \- 
 
 d-Gulose 1 
 
 rf-Idose + - + - 
 d-Talose \- 
 
 d-Glucose, Grape-sugar or dextrose, C 6 Hj 2 6 + H 2 0, occurs 
 together with ^-fructose in most sweet fruits, in honey, also in 
 diabetic urine. It is prepared by the hydrolysis of more com- 
 plex carbohydrates, e.g. sucrose or starch. The usual method, 
 the hydrolysis of starch with dilute sulphuric acid, yields 
 a product which contains, in addition to dextrose, dextrine 
 and unfermentable substances. It crystallizes from water in 
 nodular masses made up of six-sided plates which melt at 86, 
 and from methyl alcohol in small anhydrous prisms free from 
 water; m.-pt. 146. It is dextro-rotatory, [a] D = 52-6, hence 
 the name " dextrose ". 
 
 A freshly-prepared solution turns the plane of polarization 
 almost twice as much as one which has been kept or heated 
 to boiling, a phenomenon which is known as "bi-, multi-, or 
 muta-rotation ". (For explanation, cf. chapter on Physical 
 Constants and Constitution.) The strength of a solution of 
 glucose is usually determined polarimetrically from its specific 
 rotatory power, or gravimetrically by determining the weight 
 of cuprous oxide obtained by the reduction of Fehling's solution 
 with a given volume of the solution (cf. p. 301). 
 
 d-Glucose-plienyl-hydrazone, C 12 H 18 N 2 5 , forms fine crys- 
 tals which melt at 115. Another modification melts at 
 144. d-Phenyl-glucosazone crystallizes in sparingly soluble 
 needles. The rotation produced by the hydrazones and osa- 
 zones may be the opposite of that of the mother substance. 
 It is an important point for the recognition of the latter. 
 d-Pentacetyl- glucose, VJLMQC&jS)* melts at 111. 
 d-Glucosone, CH 2 (OH).[CH(OH)] 3 .t50.CHO, forms a syrup 
 which does not ferment with beer yeast, and which yields 
 
310 XIV. CARBOHYDRATES 
 
 the osazone immediately with phenyl-hydrazine. Methyl 
 glucoside, 
 
 OH.CH 2 .CH(OH).CH.(CH.OH) 2 .CH.OCH3, 
 
 exists in two stereo-isomeric modifications, melting at 165 
 and 107. /-Glucose resembles e-glucose closely, excepting 
 that it turns the plane of polarization as strongly to the left 
 as the latter does to the right. i-Glucose, from i-gluconic 
 acid, is a colourless syrup. The osazone, i-glucosazone, melts 
 at 216, and, apart from rotatory power, is deceptively like 
 the d- and -osazones. 
 
 Constitution of ^-Glucose, Its constitution as a penta- 
 bydroxy aldehyde follows from the formation of a pentacetyl 
 derivative, and from its oxidation first to a monobasic acid 
 (gluconic acid) and then to a dibasic acid (saccharic acid), 
 both of which contain the same number of carbon atoms as 
 glucose. A proof both of its aldehydic nature and of the 
 normal structure was afforded by Kiliani (B. 1886, 19, 767), 
 who prepared the cyanhydrin, hydrolysed this to the hexa- 
 hydroxy-carboxylic acid, and, by reducing this with hydriodic 
 acid and phosphorus, obtained w-heptylic acid : 
 
 OH.CH 2 .(CH.OH) 4 .CH:O OH.CH 2 .(CH.OH) 4 -CH(OH).CN 
 CH 3 .(CH 2 ) 5 .C0 2 H OH.CH 2 .(CH.OH) 6 .C0 2 H 
 
 a product which could not have been produced if the glucose 
 had possessed either a ketonic or an iso-chain (cf. Fructose). 
 (For configuration, see p. 308.) 
 
 rf-Mannose is stereo-isomeric with d-glucose, and is formed 
 together with e-fructose by the cautious oxidation of mannitol, 
 also by boiling the reserve cellulose of the seed of the Brazil- 
 nut with dilute hydrochloric acid, and by reducing mannonic 
 acid lactone with sodium amalgam. It forms a colourless 
 amorphous mass readily soluble in water, is dextro-rotatory, 
 [alp = +14 *36, and yields the same osazone as ^-glucose. 
 When treated with sodium amalgam it passes readily into 
 d-mannitol. The hydrazone melts at 195, and is sparingly 
 soluble in water. z-Mannose forms a colourless syrup. The 
 osazone is identical with that from t-fructose. /-Mannose is 
 not so readily fermented as the ^-isomeride. 
 
 d-Galactose is formed together with ^-glucose by the hydro- 
 lysis of milk-sugar with dilute acid, and also from certain 
 gums. It crystallizes in slender needles, melts at 166, is 
 
KETOHEXOSES 311 
 
 dextro-rotatory, [a] D = +80-3, and readily fermented. Its 
 pentacetyl derivative melts at 143, a-methylgalactoside at 
 111, and the stereo-isomeric /^-compound at 173-175. 
 
 Talose is a syrup. The phenyl-hydrazone is very readily 
 soluble in water (difference from galactose). 
 
 Ketohexoses, OH.CH 2 .[CH.OH] 3 .CO.CH 2 .OH, are struc- 
 turally isomeric with the aldohexoses. As ketones they can- 
 not be oxidized to acids containing the same number of carbon 
 atoms (cf, pp. 68 and 303). The formula contains 3 asym- 
 metric carbon atoms, and hence numerous stereo-isomerides 
 are theoretically possible. 
 
 ^-Fructose, Fruit-sugar or Icevulose, C 6 H 12 6 , is almost invari- 
 ably found along with d-glucose in the juice of sweet fruits 
 and also, together with the latter, in honey. It is formed 
 along with d-glucose by the inversion of cane -sugar, and 
 together with d-mannose by the cautious oxidation of d-man- 
 nitol; also from d-phenyl-glucosazone, and therefore indirectly 
 from d-glucose. It is most easily prepared by heating inulin 
 (p. 319) with very dilute acid (B. 23, 2084); is somewhat diffi- 
 cult to obtain crystalline, and then forms hard, anhydrous, 
 rhombic crystals melting at 95. It is laevo-rotatory, although 
 belonging genetically to the ^-series. Its power of rotation is 
 almost double that of /-glucose. It may be separated from 
 ^-glucose by means of its sparingly soluble lime compound. 
 
 Its close relationship to ^-glucose is shown by the fact that 
 it yields the same osazone, and on reduction yields a mixture 
 of d-mannitol and d-sorbitol. On oxidation it yields glycollic 
 and tartaric acids, or glycollic and trihydroxy-butyric acids. 
 With methyl-phenyl-hydrazine it yields a colourless osazone. 
 It is fermentable, but not so readily as d-glucose. 
 
 I- Fructose closely resembles d- fructose, but is dextro- 
 rotatory, and as it is not readily fermented, can easily be 
 obtained from i-fmctose, which is a syrup. 
 
 Constitution of ^-Fructose. The general properties point to 
 its ketonic structure, and this was further proved by Kiliani, 
 who hydrolysed the cyanhydrin, and then reduced the hydroxy- 
 acid thus obtained with hydriodic acid and phosphorus, and 
 obtained methvl-butyl-acetic acid: 
 
 /OH 
 OH.CH 8 .(CH.OH) 3 .CO.CH 2 .OH OH.CH 2 .(CH.OH) 8 .C<-CN 
 
 I NO-tljUli 
 
312 XIV. CARBOHYDRATES 
 
 Its configuration as Jiexanepentol-2-one f- + follows from 
 
 its close relationship to ^-glucose. 
 
 CHO CH 2 -OH 
 
 d-Glucose, fl-C-OH rf-Fructose, CO 
 
 HO-C-H HO-C-H 
 H-C.OH H.C-OH 
 
 H.C-OH H.C.OH 
 
 CH 2 -OH CH 2 OH, 
 
 since both yield the same osazone. 
 
 Other stereo-isomeric ketohexoses are d-tagatose, obtained 
 by the action of potassic hydroxide solution on d-galactose. 
 It melts at 124, and yields the same osazone as d-galactose. 
 d-Sorbose, obtained by oxidizing d-sorbitol; and /-sorbose, 
 obtained as a by-product in the preparation of d-tagatose. 
 
 Synthesis of Hexoses. 0. Loew obtained, by the action of 
 lime-water on formaldehyde, a substance which he termed 
 formose, C 6 H 12 6 , but which has since been shown to be a 
 mixture of hexoses containing a-acrose. Butleroff has ob- 
 tained a similar product from trioxymethylene. Fischer and 
 Tafel (B. 1887, 20, 1093, 3384; 1889, 22, 97) obtained a 
 mixture of sugars by the action of baryta water on glycerose 
 (p. 306). Among these sugars was a-acrose, which is the 
 starting-point for the synthesis of most other hexoses. The 
 a-acrose is converted into its osazone; this is hydrolysed to 
 the osone, and then reduced to the ketose, when d-Z-fructose 
 is obtained. According to Neuberg (B. 1902, 35, 2626) the 
 original a-acrose is d-Z-fructose, since it reacts with methyl- 
 phenyl-hydrazine, yielding methyl-phenyl-fructosazone. The 
 scheme (p. 313) gives a rtsumb of the steps involved in the 
 synthesis of the other hexoses from a-acrose. 
 
 The action of alkalis on hexoses has been studied by Lobry 
 de Bruyn (B. 28, 3078), who has shown that glucose, mannose, 
 and fructose are partially transformed into each other under 
 the influence of dilute alkalis: 
 
 Glucose ^= fructose ^z mannose. 
 
 Fructose appears to be formed as an intermediate product 
 in the conversion of glucose into mannose. The transfor- 
 mation is only partial, and is accompanied by a change in 
 rotatory power 
 
SYNTHESIS OF HEXOSES 
 
 311 
 
 -3 " 
 
 S X 
 
 I 
 
 jli= 
 
 
 *o_ 
 
 """3 
 
 2 
 
 if 
 
 I 
 
31 4 XIV. CARBOHYDRATES 
 
 B. Di- and Trisaeeharoses 
 
 This group comprises those carbohydrates which may be 
 regarded as derived from 2 or 3 molecules of a monose by 
 the elimination of 1 or 2 mols. of water respectively. As 
 such anhydrides, they are all readily hydrolysed when boiled 
 with dilute acids, yielding monoses, usually hexoses. Thus 
 cane-sugar yields a mixture of d-glucose and d-fructose; mal- 
 tose yields ^-glucose only; milk-sugar yields ^-glucose and 
 d-galactose : 
 
 C 12 H 22 O n + H 2 = 2C 6 H 12 6 . 
 
 Raffinose or melitriose is a type of a trisaccharose, and on 
 hydrolysis yields melibiose and d-fructose. The hydrolysis in 
 most of these cases can not only be effected by means of acids, 
 but also by means of enzymes, e.g. diastase and invertase 
 hydrolyse cane-sugar, maltase malt-sugar, &c. 
 
 The disaccharoses are thus ethereal anhydrides of the hex- 
 oses, e.g. cane-sugar is d-glucose-d-fructose anhydride, and malt- 
 sugar d-glucose anhydride, &c. In this anhydride formation 
 8 of the original 10 OH groups have remained intact, as the 
 bioses readily yield octacetyl derivatives: 
 
 2C 6 H r O(OH) 5 = [C 6 H 7 0(OH) 4 ] 2 + H 2 O. 
 
 The compounds possess for the most part a sweet taste, and 
 crystallize more readily and are more stable than the monoses, 
 but resemble the latter in solubility. They are not directly 
 fermentable, but are readily fermented after hydrolysis to 
 monoses. All those which occur naturally are optically 
 active. Cane-sugar does not reduce Fehling's solution, but 
 milk- and malt-sugars do. 
 
 Cane-sugar or Sucrose, SaccharoUose, C 12 H ?2 O n> occurs in red 
 beet (Beta), in the sugar-cane (Saccharum), in the sugar-maple 
 (Sorghum), and in many other plants, chiefly in the stem. 
 
 Preparation. (a) From sugar-cane by expressing .the juice 
 and evaporating it until crystallization begins. (&) From 
 sugar-beet by a systematic extraction of the pulp with water, 
 e.g. by the "diffusion process". The impure juice is then 
 treated with lime ("defecation"), the excess of the latter 
 thrown down by carbon dioxide ("saturation"), and the syrup 
 filtered through animal charcoal, and evaporated in vacuo to 
 crystallization. From the mother-liquid of molasses the crys- 
 tallizable sugar still present can be obtained as the sparingly 
 
CANE-SUGAR, MILK-SUGAR, AND MALTOSE 315 
 
 soluble strontium saccharate, C 12 H 22 O n , SrO, which is then 
 suspended in water and decomposed by carbon dioxide ("de- 
 sugarizing of molasses"), 
 
 Cane-sugar crystallizes in large monoclinic prisms, as is well 
 seen in sugar-candy, and is soluble in one-third of its weight of 
 water. It is not turned brown when heated with potash, and 
 yields saccharates with lime and strontia, e.g. C 12 H. 2Z U + CaO 
 + 2H 2 0; C 12 H 22 O n + 2CaO; C 12 H W U + 3CaO. Concen- 
 trated sulphuric acid produces charring (difference from 
 ^-glucose). Cane-sugar melts at 160, and remains in the 
 amorphous condition for some time after cooling (barley- 
 sugar); when heated more strongly, it becomes brown from 
 the formation of caramel or sugar dye, and finally chars. 
 
 The percentage of sugar in a solution of unknown strength 
 can be determined from the specific rotatory power ([a] 2 D = 
 4-66-5) by measuring the angle (a) through which the plane 
 of polarization is turned when a ray of polarized light is passed 
 through a layer of the solution of known length (cf. p. 309). 
 This is known as saccharimetry. 
 
 It is readily hydrolysed by acids, and this process is com- 
 monly spoken of as the inversion of cane-sugar, and the pro- 
 duct as invert sugar. These names are due to the fact that 
 the hydrolysis is accompanied by a change in the optical 
 activity of the solution. The solution of cane-sugar is dextro- 
 rotatory, but after hydrolysis (or inversion) it becomes laevo- 
 rotatory, as ^-fructose is more strongly laevo- than d-glucose is 
 dextro-rotatory. 
 
 Sucrose itself does not reduce Fehling's solution, but after 
 inversion readily reduces. This would indicate that in the 
 anhydride formation the aldehydic group of ^-glucose and the 
 ketonic group of ^fructose have been destroyed. The con- 
 stitutional formula suggested by E. Fischer (B. 1893, 26, 
 2405) is: 
 
 This formula readily accounts (a) for the formation of an 
 -octacetyl derivative (m.-pt. 67); (b) for the absence of all 
 reducing properties; (c) for the readiness with which it can 
 be hydrolysed, since the two hexose molecules are united by 
 means oi an atom of oxygen; (d) for the non-formation of a 
 hydrazdrie. 
 Milk-sugar or Lactose, Lactobiose, C 12 H 22 O n + H 2 0, occurs 
 
316 XIV. CARBOHYDRATES 
 
 in milk, and only occasionally in the vegetable kingdom. It is 
 obtained by evaporating sweet whey. It crystallizes in hard 
 rhombic prisms, and is much less sweet than cane-sugar, and 
 also much less soluble in water. It is converted into " lacto- 
 caramel" at 180. It shows muta-rotation (p. 309), and reduces 
 Fehling's solution. 
 
 Maltose or Malt-sugar, Maltobiose, C ]2 H 22 O n -f H 2 0, is 
 formed by the action of diastase upon starch during the ger- 
 mination of cereals (preparation of malt). It forms a hard 
 white crystalline mass, very similar to grape-sugar, and 
 strongly dextro-rotatory. It reduces Fehling's solution, but 
 only to about two-thirds the extent to which ^-glucose does. 
 
 Lactose and maltose resemble one another very closely, and 
 are probably stereo-isomeric. Since they both possess reduc- 
 ing properties, yield hydrazones, cyanhydrins, and can be 
 oxidized to monobasic acids containing the same number of 
 carbon atoms, it is obvious that they must contain an alde- 
 hydo- group, and the following structural formula has been 
 given to both by E. Fischer (B. 1893, 26, 2405): 
 
 OH.CH 2 .CH(OH).CH.(CH.OH) 2 .CH.O.CH 2 .(CH.OH) 4 .CH:0 
 
 Raffinose or Melitriose, C 18 H 32 O 16 -f 5 !!./), is found in the 
 sugar-beet, and therefore in molasses, in the manna of the 
 eucalyptus, and in cotton-seed cake, &c. It is very like cane- 
 sugar but tasteless, is strongly dextro-rotatory, and does not 
 i'educe Fehling's solution. When inverted, it yields in the first 
 instance d-fructose and "melibiose", the latter then breaking 
 up into galactose and d-glucose. (For its constitution, see 
 B. 1889, 22, 3118; also A. 232, 169.) 
 
 Isomaltose is a biose obtained synthetically by Fischer 
 (B. 1895, 28, 3024) by the condensing action of hydrochloric 
 acid on glucose. It is non-fermentable. 
 
 C. Polysaccharoses 
 
 The empirical formula of the members of this series is 
 CgHjQpg, but they all possess a much higher molecular weight, 
 e.g. (CgHjoO,^. They are for the most part .amorphous and 
 tasteless, insoluble in alcohol and ether; a few are soluble in 
 cold water, but the majority not; thus cellulose is insoluble 
 and also mucilage, the latter merely swelling up with water, 
 while starch forms a jelly with hot water. When boiled with 
 
CELLULOSE 317 
 
 dilute acids or subjected to the action of enzymes, they are 
 hydrolysed to mono- or di-saccharoses, generally to hexoses 
 e.g. r C 6 H 10 (X + II = C 6 H 1? 6 . The formation of pentoses 
 is frequently to be noticed in this decomposition. 
 
 Like the foregoing compounds, therefore, the members of 
 this group are to be regarded as the anhydrides of hexoses or 
 pentoses. Consequently they still possess an alcoholic character 
 and yield acetic and nitric esters, &c. Most of them are opti- 
 cally active. With dilute nitric acid they yield the same oxida- 
 tion products as are obtained from the corresponding hexoses 
 or pentoses, and iodine frequently gives characteristic colora- 
 tions. 
 
 Cellulose, (CgH^O^, is widely distributed in nature as the 
 membrane of plant cells; cotton, elder pith, wood, &c., consist 
 of cellulose in a more or less pure state. It can be prepared 
 by extracting cotton-wool or Swedish filter-paper with caustic 
 potash, hydrochloric acid, water, alcohol, and ether succes- 
 sively, or by treating pine wood with sulphuric and a little 
 nitric acid. It forms a white amorphous powder, insoluble in 
 the ordinary reagents, but soluble in an aminoniacal solution 
 of cupric oxide, from which it is again thrown down by acids. 
 
 When boiled with dilute sulphuric acid, it yields dextrine 
 and d-glucose, while the concentrated acid converts it first 
 into amyloid, an amorphous mass which is turned blue by 
 iodine, and finally into dextrine. Parchment paper is simply 
 unglazed paper which has been transformed superficially into 
 amyloid by sulphuric acid. 
 
 Many cellulose derivatives are compounds of commercial 
 importance. The nitric esters, so called mtro-celluloses, are 
 used for a variety of purposes, and are usually prepared by 
 the action of a mixture of nitric and sulphuric acids on the 
 carbohydrate. The nature of the product depends largely on 
 the concentration of the acid mixture and upon the tempera- 
 ture. In order to render the products stable, it is necessary to 
 remove all traces of free acid. Collodion, a tetranitrate, is 
 soluble in a mixture of alcohol and ether (1:7), and the solu- 
 tion is largely used for coating materials and rendering them 
 air-tight. It is also used for the manufacture of artificial silk 
 and in photography. When mixed with camphor (various 
 other substitutes, such as phenolic esters, are now used) it 
 forms ordinary celluloid. Gun-cotton, pyroxiline, is probably 
 a hexanitrate; in appearance it resembles cotton wool, but is 
 not so soft. It burns readily and explodes when struck or 
 
318 XIV. CARBOHYDRATES 
 
 strongly heated. It is largely used for making smokeless 
 powders, and is often met with in the form of compressed 
 cakes. 
 
 Practically all artificial silks are cellulose derivatives. The 
 oldest method (Chardonnel) consisted in dissolving cellulose 
 nitrates in a mixture of alcohol and ether (3:2), and forcing 
 the solution under pressure from a copper vessel through small 
 capillary tubes into water. The thread thus obtained was 
 stretched to about the thickness of natural silk, and as it be- 
 came hard was wound, dried, and denitrated by treatment 
 with a reducing agent, such as ammonium sulphide or cuprous 
 chloride and hydrochloric acid. 
 
 Other methods which are now adopted consist in (a) the use 
 of cellulose acetates obtained by the action of acetyl chloride 
 and zinc acetate or quinoline, or of acetic anhydride and a 
 mineral acid on cellulose. The solution of the acetate is 
 squirted into alcohol through small holes, (b) The use of a 
 solution of cellulose in ammoniacal cupric oxide, and forcing 
 the solution through small holes into dilute acid (Thiele silk), 
 (c) Use of viscose. Artificial, human, and horse hair are manu- 
 factured by similar methods. The artificial silks are used for 
 the manufacture of fabrics, and also for insulating metallic 
 wires. Viscose (Cross and Bevari) is the sodium salt of cellu- 
 lose xanthate. Cotton fibre is allowed to swell by treatment 
 with sodium hydroxide solution, and is then shaken with car- 
 bon disulphide. Its solution in water forms a gelatinous mass 
 which can be moulded. When exposed to the air it shrinks 
 and hardens to a horn-like mass. It is used as a substitute 
 for glue, celluloid, horn, ivory, &c. When used for the manu- 
 facture of artificial silk it is necessary to purify it; this is done 
 by acidifying with a weak acid (acetic or lactic), precipitating 
 with alcohol or brine, and washing. 
 
 Viscoid is a mixture of viscose with clay or zinc oxide, and 
 sets to an extremely hard mass. 
 
 Starch or Amylum, (C 6 H 10 6 ) r , is present in all assimilating 
 plants, being built up by the chlorophyll granules from the 
 carbon dioxide absorbed, and is found especially in the nutri- 
 ment reservoirs of the plants, e.g. in the grains of cereals, in 
 perennial roots, potatoes, &c. It is converted into sugar 
 during the transference of the sap. It forms a white velvety 
 hygroscopic powder which consists of round or elongated 
 granules built up of concentric layers, and insoluble in cold 
 water. The interior of these granules consists of " granulose " 
 
GUMS AND DEXTRINES 319 
 
 and their husk probably of cellulose. When they are wanned 
 with water, the latter is broken open and the granulose dis- 
 solves; if the solution is moderately dilute, it can be filtered 
 and a clear solution obtained, from which alcohol precipitates 
 " soluble starch ". Both the granules of starch and its jelly are 
 coloured an intense blue by iodine and bright yellow by bro- 
 mine, from the formation of loose additive compounds, "iodide 
 and bromide of starch ". The colour of the iodide of starch 
 vanishes on heating, but reappears on cooling. Ordinary air- 
 dried starch contains some 10-20 per cent of water, which can 
 be removed by heating to 105. 
 
 The so-called " soluble starch " is formed (a) when starch is 
 heated with glycerol, (b) when starch is boiled with water con- 
 taining sulphuric acid, (c) by the action of diastase or starch. 
 Further treatment with acid converts it into dextrine and 
 ^-glucose, and with diastase into dextrine and maltose and 
 isomaltose (B. 1893, 26, 2533). Warming with very little 
 dilute nitric acid to 110 yields dextrine. 
 
 Lichenin, or Moss starch, present in many lichens, e.g. in 
 Iceland moss (Cetraria islandica), is coloured a dirty blue by 
 iodine; and inulin, present in the roots of the dahlia and 
 many composites (Inula Helenium), is coloured yellow by 
 iodine and converted into ^-fructose when boiled with water. 
 
 Glycogen, or Animal starch, Liver starch, is present, e.g. in 
 the livers of the mammalia. It is a colourless amorphous 
 powder which is turned wine-red by iodine; after the death 
 of the animal it rapidly changes into d-glucose, the same 
 conversion being effected by boiling with dilute acids, while 
 enzymes transform it into maltose. 
 
 Dextrine, or Starch gum, is a comprehensive name applied to 
 intermediate products obtained in the transformation of starch 
 into maltose and d-glucose. It may be prepared (a) by heating 
 starch either alone or with a little nitric acid, (b) together with 
 d-glucose by boiling starch with dilute sulphuric acid, and (c) 
 together with maltose by the action of diastase on starch. The 
 dextrines are soluble in water, and are precipitated by alcohol. 
 They are often named according to their reaction with iodine, 
 e.g. amylo-dextrine blue, erythro-dextrine red, and achroo- 
 dextrine no colour. They do not reduce Fehling's solution 
 even when warmed, and are not directly fermentable by yeast 
 but only after the prolonged action of diastase, glucose being 
 formed as an intermediate product. 
 
 Synthesis of Sugars. The sugars are extremely important 
 
320 XIV. CARBOHYDRATES 
 
 from the point of view of plant physiology. The plant ab- 
 sorbs carbon dioxide and water, and with the aid of sunlight 
 is capable, in the presence of chlorophyll, of transforming these 
 into glucose and even more complex carbohydrates. Various 
 speculations have been made with regard to the manner in 
 which these complex compounds Are formed. Baeyer has sug- 
 gested that the carbon dioxide is first reduced to formaldehyde, 
 and this then polymerizes as in Loew's experiments, yielding 
 carbohydrates, 
 
 C0 2 H.C -> (H 2 C:0) 6 = C 6 H 12 O 6 . 
 
 For many years the important link in this chain, viz. the 
 reduction of carbon dioxide to formaldehyde, was missing; 
 the reaction could not be accomplished in the laboratory. 
 Fenton has recently shown (J. C. S. 1907, 91, 687) that when 
 carbon dioxide is passed into water in which sticks of mag- 
 nesium are immersed, a small amount of the gas is reduced to 
 formaldehyde, especially in the presence of ammonia or phenyl- 
 hydrazine. Lob has also found that moist carbon dioxide 
 yields formaldehyde under the influence of the silent electric 
 discharge (Zeit. Electrochemie,'1905, 11, 745; 1906, 12, 282). 
 
CLASS II CHEM18TE.Y OF THE CYCLIC 
 COMPOUNDS 
 
 XV. INTRODUCTION 
 
 The compounds which have been treated of in Sections I to 
 XIV are derivable from the homologous hydrocarbons C n H 2n+2 , 
 C n H 2n , C n H 2n _ 2 , &c., by the exchange of hydrogen for halogen, 
 hydroxyl or oxygen, amidogen, carboxyl, &c. ; and since all the 
 hydrocarbons already mentioned may also be regarded as deri- 
 vatives of methane (e.g. C 2 H 6 = CH 3 (CH 3 ) = methyl-methane, 
 C 3 H 8 = CH 2 (CH 3 ) 2 = dimethyl-methane, C 2 H 4 = CH 2 :CH 2 
 = methylene-methane, C 2 H 2 = CHjCH = methine-methane, 
 &c.), we may term the compounds which have been described 
 in the foregoing portion of this book methane derivatives. 
 
 As nearly all these compounds have open-chain formulae, 
 they are spoken of as open- chain compounds, or often ali- 
 phatic compounds. 
 
 But in addition to this first class of organic compounds 
 there is a second great class, viz. that of the closed-chain com- 
 pounds. The old classification was into aliphatic or methane de- 
 rivatives and aromatic or benzene derivatives. The expression 
 "aromatic" is historical, but no longer justified by facts, since 
 compounds of agreeable as well as unpleasant odour are to be 
 found in both classes. The members of this second class which 
 are derivable from the hydrocarbon benzene, C 6 H 6 (and also 
 from more complicated hydrocarbons such as anthracene, naph- 
 thalene, &c., which are themselves derivatives of benzene), just 
 as the methane derivatives are from methane, are designated 
 benzene derivatives. 
 
 Eecent investigations have led to the discovery of numerous 
 other cyclic compounds which cannot be regarded as simple 
 derivatives of benzene, e.g. : 
 
 CH CH:CH\ 
 
 7 
 
 (B480) 321 
 
322 XVI. POLYMETHYLENE DERIVATIVES 
 
 and hence the modern classification of the cyclic compounds is 
 into: 
 
 A. Carbocyclic or Isocyclic. In all these compounds the 
 ring or closed chain is composed entirely of carbon atoms. 
 The carbocyclic compounds are usually divided into 
 
 (i) Polymethylene derivatives or naphthenes. 
 (ii) Benzene derivatives or aromatic compounds, including 
 the allied compounds naphthalene, anthracene, &c. 
 
 B. Heterocyclic Compounds. In these compounds the closed 
 ring is formed partly of carbon atoms and partly of atoms of 
 other elements. Well-known examples are: 
 
 CH:CH\ CH:CH\ 
 
 >O (furane), >S (thiophene), 
 
 mr.r<TT/ mr-mr/ 
 
 V/JCL yy Ji- t^Ji . VyJd' 
 
 \NH (pyrrole), CH<^SS;S5^N (pyridine), &c. 
 vv-tL 1 Oxi.' 
 
 CAKBOCYCLIC COMPOUNDS 
 
 XVI. POLYMETHYLENE DERIVATIVES 
 
 The hydrocarbons from which all these compounds are 
 derived consist of three or more methylene groups united 
 together to form a closed ring. The names for the specific 
 hydrocarbons indicate the number of such groups, e.g. : 
 
 2 ^-tl-2 * ^-^-2 
 
 (trimethylene), | J_ (tetramethylene), 
 
 /CH 2 2 ^nr PTT v. 
 
 CH 2 < | (pentamethylene), CH 2 <X^ 2 ' 2NCH 2 (hexamethylene). 
 
 x!H.CH ^L 2 'V,n 2 
 
 The systematic names for these compounds are cyclo-pro- 
 pane, cyclo-butane, &c., although the compounds are isomeric 
 with the defines, and have the same general formula, C n H2 n . 
 The above names indicate the fact that the compounds are in 
 a sense saturated. 
 
 Eelative Stability of Polymethylene Compounds. It has 
 been found that the majority of trimethylene derivatives are 
 relatively unstable; to a certain extent they resemble ethylene. 
 
FORMATION OF POLYMETHYLENE COMPOUNDS 323 
 
 oxide, and are capable of forming additive products by the 
 rupture of the ring. Thus bromine slowly transforms tri- 
 methylene under the influence of sunlight into trimethylene 
 dibromide : 
 
 CK/ I . CH 2 Br.CH 2 .CH 2 Br. 
 
 Tetramethylene derivatives are somewhat more stable, and 
 penta- and hexa-methylene derivatives are remarkably stable 
 and show little or no tendency towards the rupture of the 
 molecule. 
 
 These facts are in harmony with Ba&yer's tension theory. 
 If the four valencies of the tetravalent carbon atom are 
 assumed to be symmetrically distributed in space around the 
 carbon atom, it is found that ring formation in the case of a 
 
 / 2 
 compound CH 2 <\ | can only take place by the exercise of 
 
 CH 2 
 
 a considerable strain in the molecule; hence when the ring 
 formation is completed there is considerable tendency for it to 
 spring apart or rupture at some point. With penta- and hexa- 
 methylene compounds, on the other hand, it can be seen by 
 the aid of models that practically no strain is required to com- 
 plete the ring formation, and thus the rings when once formed 
 are relatively stable. 
 
 GENERAL METHODS OF FORMATION 
 
 1. By the action of sodium on dihalogen derivatives of the 
 paraffins (Freund). The two halogen atoms must not be 
 attached to the same or to adjacent carbon atoms. 
 
 CH 2 .CH 2 Br CH 2 .CH 2 
 
 + 2Na = 2NaBr + I 
 CH 2 -CH 2 Br 
 
 2. Acids and their esters can be obtained by the conden- 
 sation of ethyl sodio-malonate with ethylene dibromide and 
 other dihalogen derivatives (W. H. Perkin, Jun.): 
 
 fNa 2 C(C0 2 Et) 2 = 
 
324 XVI. POLYMETHYLENE DERIVATIVES 
 
 and the ester on hydrolysis yields trimethylene-dicarboxylic 
 acid. 
 
 Ethyl acetoacetate may be substituted for ethyl malonate. 
 
 3. By the action of halogens (bromine, or preferably iodine) 
 on the sodio-derivatives of certain esters, e.g. sodio-derivative 
 of ethyl butane-tetracarboxylate (W. H. Perkin, Jun.): 
 
 CH 2 .CNa<C0 2 Et) 2 CH 2 -C(CO 2 Et) 2 
 
 CH 2 .CNa(C0 2 Et) 2 2 * CH 2 .C(CO 2 Et) 2 . 
 
 4. By intramolecular pinacone formation. Just as ketones 
 on reduction yield pinacones : 
 
 (CH3) 2 .C:0 , 
 (CH 3 ) 2 .C:0 + - 
 
 (cf. p. 191), so certain diketones on reduction yield cyclic 
 pinacones, i.e. dihydric alcohols derived from the polymethy- 
 lene hydrocarbons: 
 
 H.CO.CH 3 H xCH 2 .C(OH).CH 3 
 
 O.CH 3 + ' H2 \CH 2 .C(OH).CH 3 
 
 1 : 2-Dimethyl-l : 2-dihydroxy 
 cyclo-pentane. 
 
 5. A number of ketones derived from the polymethylenes 
 have been obtained by the dry distillation of the calcium salts 
 of the higher dibasic acids of the oxalic series (/. Wislicenus\ 
 e.g. calcium adipate yields keto-pentamethylene : 
 
 CH 2 CH 2 CO O\ CH 2 CH 
 
 ; . CH 2 .CH 2 .CO.O> = Ca 
 
 and this can be reduced to pentamethylene. The constitution 
 of the keto-derivative follows from the fact that on oxidation 
 the ring is ruptured and glutaric acid is formed. 
 
 Keto-hexamethylene and keto-heptamethylene or suberone 
 have been obtained by similar methods, but the yield is not so 
 good in these two cases. 
 
 6. Hexamethylene compounds are often obtained by the 
 reduction of benzene derivatives with sodium and alcohol: 
 
 General Properties. On the whole these compounds some- 
 what closely resemble the paraffins as regards their chemical 
 
ISOMERISM OF POLYMETHYLENE COMPOUNDS 325 
 
 properties, hence the names cyclo-pentane for pentamethylene, 
 cyclo-hexane, &c. 
 
 The trimethylene compounds, however, resemble the de- 
 fines, e.g. (a) they can combine with bromine to form additive 
 compounds; (b) they are slowly oxidized by permanganate. 
 In neither of these reactions do they take part so readily as 
 ;iae simpler olefines, and in all cases the products obtained are 
 formed at the expense of the rupture of the ring. 
 
 The fact that the majority of the hydrocarbons of this series 
 resemble paraffins indicates that the formation of a closed chain 
 does not affect to any considerable extent the properties of 
 a compound (cf. Benzene). 
 
 In their chemical properties the compounds closely resemble 
 the corresponding derivatives of the paraffins, e.g. the acids 
 resemble to a large extent the fatty acids, yielding salts, esters, 
 acid chlorides, amides, &c. 
 
 Isomerism. (a) Position Isomerism. No examples of iso- 
 merism have been met with in the case of mono-substituted de- 
 rivatives, e.g. only one tetramethylenecarboxylic acid is known. 
 Position isomerism can occur in the case of di- and poly-sub- 
 stituted derivatives, e.g. tetramethylene-1 :l-dicarboxylic acid 
 and isomeric 1 : 2 and 1 : 3 acids. 
 
 4 ' l:2-Dicarboxylic acid 
 
 l:l-Dicarboxylic acid 
 
 COoH-C 
 
 ^V^-LJ-2' 
 
 l:3-Dicarboxylic acid. 
 
 The number of isomerides possible in each case can be worked 
 out by the student (cf. Benzene Derivatives). 
 
 (b) Stereo -isomerism. Certain di- substituted derivatives 
 have been found to exist in isomeric forms which are struc- 
 turally identical. These must therefore be stereo-isomeric. 
 Some of the simplest examples of this stereo-isomerism are 
 met with in the dibasic acids. For example: 
 
 Tetramethylene-l:2-dicarboxylic acid exists in two isomeric 
 forms. In both acids the 2C0 2 H groups are Attached to the 
 carbon atoms 1 and 2, and the only difference is in the relative 
 spatial relationships of the groups. If the plane of the paper 
 represents the plane in which the centres of gravity of 
 
326 XVI. POLYMETHYLKNE DERIVATIVES 
 
 the four carbon atoms of the ring lie, then the possibilities 
 are 
 
 H C0 2 H 
 
 (I) cis. 
 
 (I) That the two C0 2 H groups lie in the same plane either 
 above or below the plane of the paper (this is known as the tis 
 acid) ; and (II) that the two C0 2 H groups lie in different planes, 
 one above and one below the plane of the paper (this is 
 known as the trans acid). As a rule, the cis acids yield inner 
 
 f^O 
 anhydrides, e.g. C 4 H 6 <^QQ^>0, more readily than the stereo- 
 
 isomeric trans acids, and the cis acids are generally transformed 
 into the corresponding trans acids when heated with hydro- 
 chloric acid at 190. (Cf. Perkin, Jun., J. C. S. 1894, 572.) 
 
 A simple method of depicting these isomerides is due to 
 Aschan (B. 1902, 35, 3389). 
 
 The plane of the carbon atoms of the ring is represented 
 by a straight line. The unsubstituted hydrogen atoms are 
 not denoted, only those which have been replaced by sub- 
 stituents. It has been found that the symmetry of such pro- 
 jections corresponds with the symmetry of the molecules 
 projected. For the cis dicarboxylic acids, for example, if 
 C0 2 H = X, we have: 
 
 X_* and ^_ _^ 
 
 (I) cis. (H) trans. (III). 
 
 The cis compound (I) is not perfectly asymmetric, whereas 
 the trans compound (II) is. Corresponding with (II) is a third 
 isomeride, which stands in the same relationship to (II) as an 
 object to its mirror image, or as d- to Z-lactic acids. Both 
 should therefore be optically active (one d and the other I to 
 the same extent), and should be capable of combining to yield 
 a racemic compound. All the trans compounds prepared arti- 
 ficially are optically inactive, and are presumably therefore 
 racemic compounds of (II) and (III), although so far very few 
 have been resolved into optically active components. 
 
fcENZENE DERIVATIVES 32^ 
 
 Intermediate between the polymethylene compounds and 
 benzene derivatives are the reduction products of benzene 
 and its derivatives, e.g. di- and tetra-hydrobenzene, tetrahydro- 
 phthalic acid, &c., C 6 H 8 , C 6 H 10 , C 6 H 8 (C0 2 H) 2 . These will be 
 discussed along with the benzene compounds," from which they 
 are derived. 
 
 XVII. BENZENE DERIVATIVES. INTRODUCTION 
 
 Benzene is, as its formula C 6 H 6 shows, a compound much 
 poorer in hydrogen than the paraffins, containing 8 hydrogen 
 atoms less than hexane, C 6 H J4 ; in the same way all benzene 
 derivatives are much poorer in hydrogen, i.e. richer in carbon 
 than the analogous methane derivatives, as is seen by com- 
 paring e.g. benzoic acid, C r H 6 2 , with heptoic acid, C 7 H 14 2 , 
 or aniline, C 6 H 7 N, with ethylamine, G 2 H 7 N, &c. 
 
 The hydrogen atoms of benzene are, like those of methane, 
 replaceable by numerous types of radicals. By the entrance 
 of halogens, halide substitution products are formed, by the 
 entrance of NH 2 , aromatic bases, of OH, phenols, of N0 2 , 
 nitro-compounds, and of CH 3 , &c., the homologues of benzene; 
 there are, in addition to these, aromatic alcohols, aldehydes, 
 acids, &c. 
 
 These benzene derivatives are partly analogous in their 
 properties to the methane derivatives of corresponding com- 
 position; in part, however, they show new and peculiar pro- 
 perties of their own (see pp. 328 et seq.). One distinguishes 
 between mono-, di-, tri-, &c., substituted benzene derivatives 
 according as 1, 2, or more hydrogen atoms are replaced by 
 the various radicals; thus, for instance, toluene, C 6 H 5 CH 3 , 
 and chloro-benzene, C 6 H 5 -C1, are mono-derivatives, dimethyl- 
 benzene, C,H 4 (CH 3 ) 2 , and dichloro-benzene, C 6 H 4 C1 2 , di-deri- 
 vatives, and so on. It is not necessary that the substituents 
 should be identical, so that innumerable compounds are known 
 containing various substituents, e.g. OHC 6 H 4 -N0 2 , nitro- 
 
 Shenol; C 6 H 4 BrS0 3 H, bromobenzene-sulphonic acid; CH 3 
 6 H 3 (NO 2 ) 2 , dinitro-toluene. Such compounds have usually 
 some of the characteristics of all those mono-derivatives which 
 result from benzene by the exchange of one hydrogen atom 
 for one of these substituents. 
 
 All the derivatives of benzene can be converted either into 
 benzene itself or into very closely allied compounds by rcla- 
 
326 XVI. POLYMETHYLENE DERIVATIVES 
 
 the four carbon atoms of the ring lie, then the possibilities 
 are 
 
 H 
 
 (I) cis. 
 
 (I) That the two C0 2 H groups lie in the same plane either 
 above or below the plane of the paper (this is known as the cis 
 acid); and (II) that the two C0 2 H groups lie in different planes, 
 one above and one below the plane of the paper (this is 
 known as the trans acid). As a rule, the cis acids yield inner 
 
 anhydrides, e.g. C 4 H 6 <^pQ^>0, more readily than the stereo- 
 
 isomeric trans acids, and the cis acids are generally transformed 
 into the corresponding trans acids when heated w r ith hydro- 
 chloric acid at 190. (Cf. Perkin, Jun., J. C. S. 1894, 572.) 
 
 A simple method of depicting these isomerides is due to 
 Aschan (B. 1902, 35, 3389). 
 
 The plane of the carbon atoms of the ring is represented 
 by a straight line. The unsubstituted hydrogen atoms are 
 not denoted, only those which have been replaced by sub- 
 stituents. It has been found that the symmetry of such pro- 
 jections corresponds with the symmetry of the molecules 
 projected. For the cis dicarboxylic acids, for example, if 
 C0 2 H = X, we have: 
 
 ^^ and ^_ __* 
 
 (I) cis. (II) trans. (III). 
 
 The cis compound (I) is not perfectly asymmetric, whereas 
 the trans compound (II) is. Corresponding with (II) is a third 
 isomeride, which stands in the same relationship to (II) as an 
 object to its mirror image, or as d- to /-lactic acids. Both 
 should therefore be optically active (one d and the other / to 
 the same extent), and should be capable of combining to yield 
 a racemic compound. All the trans compounds prepared arti- 
 ficially are optically inactive, and are presumably therefore 
 racemic compounds of (II) and (III), although so far very few 
 have been resolved into optically active components. 
 
6ENZENE DERIVATIVES 32 1 
 
 Intermediate between the polymethylene compounds and 
 benzene derivatives are the reduction products of benzene 
 and its derivatives, e.g. di- and tetra-hydrobenzene, tetrahydro- 
 phthalic acid, &c, C 6 H 8 , C 6 H 10 , C 6 H 8 (C0 2 H) 2 . These will be 
 discussed along with the benzene compounds, from which they 
 are derived. 
 
 XVII. BENZENE DERIVATIVES. INTRODUCTION 
 
 Benzene is, as its formula C 6 H 6 shows, a compound much 
 poorer in hydrogen than the paraffins, containing 8 hydrogen 
 atoms less than hexane, C 6 H J4 ; in the same way all benzene 
 derivatives are much poorer in hydrogen, i.e. richer in carbon 
 than the analogous methane derivatives, as is seen by com- 
 paring e.g. benzoic acid, C r H 6 2 , with heptoic acid, C 7 H 14 2 , 
 or aniline, C 6 H 7 N, with ethylamine, C 2 H r N, &c. 
 
 The hydrogen atoms of benzene are, like those of methane, 
 replaceable by numerous types of radicals. By the entrance 
 of halogens, halide substitution products are formed, by the 
 entrance of NH 2 , aromatic bases, of OH, phenols, of N0 2 , 
 nitro-compounds, and of CH 3 , &c., the homologues of benzene; 
 there are, in addition to these, aromatic alcohols, aldehydes, 
 acids, &c. 
 
 These benzene derivatives are partly analogous in their 
 properties to the methane derivatives of corresponding com- 
 position; in part, however, they show new and peculiar pro- 
 perties of their own (see pp. 328 et seq.). One distinguishes 
 between mono-, di-, tri-, &c., substituted benzene derivatives 
 according as 1, 2, or more hydrogen atoms are replaced by 
 the various radicals; thus, for instance, toluene, C 6 H 5 'CH 3 , 
 and chloro-benzene, C 6 H 5 -C1, are mono-derivatives, dimethyl- 
 benzene, C,H 4 (CH 3 ) 2 , and dichloro-benzene, C 6 H 4 C1 2 , di-deri- 
 vatives, and so on. It is not necessary that the substituents 
 should be identical, so that innumerable compounds are known 
 containing various substituents, e.g. OH .C 6 H 4 -NO 2 , nitro- 
 phenol; C 6 H 4 BrS0 3 H, bromobenzene-sulphonic acid; CH 3 . 
 C 6 H 3 (N0 2 ) 2 , dinitro-toluene. Such compounds have usually 
 some of the characteristics of all those mono-derivatives which 
 result from benzene by the exchange of one hydrogen atom 
 for one of these substituents. 
 
 All the derivatives of benzene can be converted either into 
 benzene itself or into very closely allied compounds by rela- 
 
328 XVII. BENZENE DERIVATIVES. INTRODUCTION 
 
 lively simple reactions. Thus all the carboxylic acids of ben- 
 zene (benzoic, phthalic, mellitic, &c.) yield benzene on dis- 
 tillation with lime, while other acids, such as salicylic, evolve 
 C0 2 and yield phenol; the last-named compound is converted 
 into benzene when distilled with zinc dust. The homologues 
 of benzene are converted by oxidation into benzene-carboxylic 
 acids, which yield benzene when heated with lime. 
 
 The relationship of a benzene derivative to its mother substance is 
 therefore a very simple one. 
 
 This circumstance is one particularly worthy of note, since 
 the atomic group C 6 H 6 is already a tolerably complicated 
 molecule in itself, and also because benzene cannot by any 
 means be transformed into a simpler hydrocarbon containing 
 5, 4, or 3 carbon atoms; when oxidized, which is a matter of 
 difficulty, it yields carbonic or similar simple organic acids. 
 
 The benzene derivatives are connected with one another by 
 the most varied reactions. The N0 2 group is readily con- 
 vertible into NH 2 , and the latter is replaceable by halogen, 
 hydrogen, and hydroxyl; the halogen is also replaceable by 
 methyl, carboxyl, &c. 
 
 As a rule, the group of 6 carbons with the hydrogens is 
 spoken of as the benzene nucleus, and all substituents are 
 spoken of as side chains. Thus in C 6 H 5 -CHO, C 6 H 4 *(CH 3 ) 2 , 
 
 C 6 H 5 NH 2 the radicals underlined are the side chains. 
 
 o 
 
 CHARACTERISTIC PROPERTIES OF BENZENE DERIVATIVES 
 
 In many chemical properties benzene and its derivatives 
 differ markedly from the paraffins or unsaturated open-chain 
 hydrocarbons. 
 
 1. The aromatic hydrocarbons and their derivatives are 
 readily attacked by concentrated nitric acid, yielding nitro- 
 derivatives : 
 
 Certain of the higher paraffins also yield nitro-derivatives 
 when heated with nitric acid (p. 95). 
 
 2. Sulphonic acids are readily formed by the action of con- 
 centrated or fuming sulphuric acid : 
 
 2 .OH = H 2 + C C H 5 .S0 2 .OH. 
 This type of reaction is never met with in the aliphatic series. 
 
tSOMERISM OF BENZEKE DERIVATIVES 329 
 
 3. The homologues of benzene differ from the paraffins 
 especially as regards oxidation; while the latter are only 
 attacked with difficulty by oxidizing agents, the former are 
 readily converted into benzene-carboxylic acids: 
 
 C 6 H 5 .CH 3 C 6 H 6 .C0 2 H. 
 
 4. The halogens chlorine and bromine can react with ben- 
 zene in two distinct ways : (a) yielding substituted derivatives, 
 e.g. C^Hg + Br 2 = C 6 H 5 Br + HBr, or (b) yielding additive 
 products, e.g. C 6 H 6 Br 6 . 
 
 The process of substitution is the more important and the 
 commoner of the two reactions. 
 
 5. There are not wanting other distinguishing characteristics 
 between the aromatic hydrocarbons and the paraffins. Thus 
 the halogen compounds C 6 H 5 X are chemically less active, and 
 the hydroxyl compounds, e.g. C 6 H 5 (OH), are of a more acidic 
 nature than the corresponding fatty bodies. The phenyl radical, 
 C 6 H 5 , is therefore more acid or " negative " in character than 
 the ethyl, C 2 H 5 (cf. V. Meyer, B. 20, 534, 2944; A. 250, 118). 
 
 6. Diazo-compounds are far more common in the aromatic 
 series than in the aliphatic. 
 
 ISOMERIC RELATIONS 
 
 1. While several isomeric mono-derivatives are both theo- 
 retically possible and have been actually obtained from each 
 hexane, CgH^, benzene is only capable of forming a single 
 mono -derivative in each case; isomeric mono -derivatives of 
 benzene are unknown. The six hydrogen atoms of benzene thus 
 possess an equal value, or are similarly situated within the molecule. 
 This is not merely an empirical law, but one which has been 
 proved experimentally. 
 
 PROOF OF THE EQUAL VALUE OF THE SIX HYDROGEN 
 
 ATOMS 
 
 Let the 6 H atoms be designated as a, b, c, d, e, and / 
 respectively. 
 
 (1) Phenol, C 6 H 5 (OH), whose hydroxyl may have replaced 
 the H atom a, may be converted into bromo-benzene, C 6 H 5 Br, 
 and this latter into benzoic acid, C 6 H 5 (C0 2 H). The carboxyl 
 in the latter has therefore also the position a, i.e. it has re- 
 placed the H atom a. 
 
330 XVII. BENZENE DERIVATIVES. INTRODUCTION 
 
 (2) Three hydroxy-benzoic acids, C 6 H 4 (OH)(C0 2 H), can 
 either be prepared from benzoic acid or converted into it; 
 their carboxyl therefore has the position a, and consequently 
 their hydroxyl must replace some one of the other H atoms, 
 be it 5, c, or d. 
 
 (3) Each hydroxy-benzoic acid can be decomposed, yielding 
 carbon dioxide and ordinary phenol, C 6 H 6 OH: 
 
 C 6 H 4 (OH)(C0 2 H) = C 6 H 5 (OH) + C0 2 . 
 
 And since the latter compound contains the hydroxyl in 
 position a, according to (1), while the hydroxyl in the hy- 
 droxy-benzoic acids replaces the H atoms b, c, and d, it follows 
 that the hydrogen atoms a, b, c, and d are of equal value. 
 
 (4) Now, as will be explained on p. 331, for each H atom 
 there are present two other pairs of symmetrical hydrogen 
 atoms, i.e. pairs of which either the one or the other atom 
 may be replaced by any given radical without different sub- 
 stances resulting. But the atoms of such a pair cannot both 
 be present in the positions a, b, c, and d, as in this case three 
 hydroxy-benzoic acids could not exist. It must therefore be 
 the remaining H atoms e and / which are respectively in posi- 
 tions symmetrically situated to two of the former, and which 
 are therefore of equal value with them, i.e. e = c, f = b. Since, 
 however, a = b = c = d, it follows that all the 6 hydrogen 
 atoms are of equal value (Ladenburg, B. 7, 1684). 
 
 2. With di-substituted derivatives of benzene it has been 
 found that in each case three distinct isomeric forms exist. 
 The two substituents may be alike, or they may be dis- 
 similar, e.g. three dichloro-benzenes, C 6 H 4 C1 2 , three diamino- 
 benzenes, C 6 H 4 (NH 2 ) 2 , three dimethyl-benzenes, C 6 H 4 (CH 3 ) 2 , 
 three hydroxy-benzoic acids, C 6 H 4 (OH)(C0 2 H), are known. 
 In no case have more than three such isomerides been found. 
 
 It can be shown that with respect to each H atom of ben- 
 zene, e.g. for a, two pairs of other H atoms, e.g. b and /, c and e, 
 are symmetrically situated, so that it makes no difference 
 whether, after a is replaced, the second substituent replaces 
 the one or the other of the symmetrically placed hydrogen 
 atoms, say b or /. According to the above notation, there- 
 fore, ab = af t and ac = ae. On the other hand, the com- 
 binations ab and ac are not equivalent, but represent isomers; 
 the combination ad, the only remaining case, represents the 
 third isomer. 
 
CONSTITUTION OF BENZENE 331 
 
 PROOFS THAT FOR EVERY H ATOM (a) TWO OTHER PAIRS 
 OF SYMMETRICALLY LINKED H ATOMS EXIST 
 
 1. According to Hubner and Petermann (A. 149, 129; cf. 
 also Hubner, A. 222, 67, 166), the (so-called meta-) bromo- 
 benzoic acid, which is obtained by brominating benzoic acid, 
 and whose Br atom may be in position c and C0 2 H in posi- 
 tion a, yields with nitric acid two nitrobromo-benzoic acids, 
 C 6 H 3 Br(N0 2 )(C0 2 H), the N0 2 being, say, in positions b and/. 
 These are both reduced by nascent hydrogen to the same (so- 
 called ortho-) amino-benzoic acid, C 6 H 4 (NH 2 )(C0 2 H), the N0 2 
 being here changed to NH 2 and the Br replaced by H. Since 
 the same amino-benzoic acid is formed in both cases, notwith- 
 standing that the nitro-groups must be in the place of different 
 H atoms, say b and /, from the fact of the two nitro-acids 
 being dissimilar, it follows that b and / must be arranged sym- 
 metrically as regards the H atom a, i.e. ab af. 
 
 2. In an analogous manner salicylic acid, C 6 H 4 (OH)(C0 2 H), 
 which can be prepared from the above-mentioned amino-ben- 
 zoic acid, yields two nitro-derivatives, C 6 H 3 (OH)(N0 2 )(C0 2 H). 
 If, however, the hydroxyl in these is replaced by hydrogen (a 
 reaction which can be effected by indirect methods), the nitro- 
 benzoic acids thus obtained, C 6 H 4 (N0 2 )(G0 2 H), are identical, 
 and therefore the H atoms which have been replaced by 
 N0 2 are in position^ symmetrical to a. When this nitro- 
 benzoic acid is in its turn reduced to amino-benzoic acid, 
 C 6 H 4 (NH 2 )(C0 2 H), it is not the above (ortho-) amino-acid 
 (where ab = af) which is obtained, but an isomer. The N0 2 
 groups cannot therefore here be in the positions b and /, but 
 must replace two other H atoms which are likewise symmetric 
 towards a, say c and e, i.e. ac ae (Hubner, A. 195, 4). 
 
 Thus two pairs of H atoms are symmetrically situated as 
 regards the H atom a: ab = afj ac = ae. There remains 
 only the third possible combination ad] the sixth H atom d 
 is situated towards the first a in a position of its own, i.e. in 
 one to which there is no corresponding position. 
 
 For further particulars, cf. Ladenburg, "Theorie der aromat. 
 Verbindungen ", Braunschweig, 1876; WroUewsky, A. 168, 
 153; 192, 196; B. 8, 573; 9, 1055; 18, Ref. 148. Noelling, 
 B. 1904, 37, 1015, gives a very simple proof. 
 
 It has been assumed in the considerations just detailed 
 that when one compound is converted into another by tho 
 
332 XVII. BENZENE DERIVATIVES. INTRODUCTION 
 
 exchange of atoms or radicals (NH 2 for N0 2 , H for OH), this 
 exchange is effected without a so-called " molecular rearrange- 
 ment" taking place at the same time (see p. 132). Experience 
 has proved that this may be taken for granted in a large 
 number of reactions which proceed with relative smoothness 
 and at comparatively low temperatures. Those instances in 
 which a molecular rearrangement ensues are now well known ; 
 especially is this the case in the fusion of sulphonic acids 
 with potash (exchange of S0 3 H for OH), a reaction which 
 takes place at relatively high temperatures only, and which 
 frequently leads to isomers of the compounds expected. In 
 other reactions which occur at high temperatures a rearrange- 
 ment of the atoms in the molecule can also take place. Thus, 
 when potassium ortho-hydroxy-benzoate is heated to 220, the 
 potassium salt of the para-acid is formed; the three isomeric 
 bromo-benzene-sulphonic acids, C 6 H 4 Br(S0 3 H), and the three 
 bromo-phenols, C 6 H 4 Br(OH), yield only meta-dihydroxy -benzene 
 (resorcinol), C 6 H 4 (OH) 2 , when fused with potash, and not the 
 three isomeric dihydroxy -benzenes; ortho- phenol -sulphonic 
 acid, C 6 H 4 (OH)S0 3 H, yields the para-acid when heated. Re- 
 actions of this nature probably arise from the successive taking 
 up and splitting off of atoms or atomic groups. 
 
 CONSTITUTION OF BENZENE 
 
 The formula C 6 H 6 at once indicates that benzene cannot be 
 a saturated open-chain compound. The possibility that it is 
 an open-chain unsaturated compound containing several double 
 or triple bonds has been shown to be untenable, e.g. dipro- 
 pargyl (p. 53), CH:C.CH 2 .CH 2 .CiCH, although resembling 
 benzene in physical properties, is quite different as regards 
 most of its chemical properties; it combines readily with bro- 
 mine, yielding additive compounds with 2, 4, 6, or 8 atoms of 
 bromine, and it is also oxidized with the greatest readiness. 
 Benzene combines with bromine only slowly and under specific 
 conditions, and then yields C 6 H 6 Br 6 ; it is, further, extremely 
 stable towards oxidizing agents. The equivalency of the 
 6 hydrogen atoms in the benzene molecule is a further strong 
 argument against such open-chain formulae. KehiU was the 
 first to suggest a closed -chain, cyclic, or ring formula for 
 benzene. 
 
 In order to account for the existence of only one mono- 
 substituted derivative, C 6 H 6 X, but of three isomeric di-sub 
 
ISOMERISM OF BENZENE DERIVATIVES 333 
 
 stituted derivatives, C^H^Xg, it is necessary to assume that 
 a single hydrogen atom is attached to each carbon atom. 
 
 CH 
 
 This formula is usually known as the benzene ring. 
 
 In the above formula the six hydrogen atoms are symmetri- 
 cally placed with respect to one another, and thus in the for- 
 mation of a mono-substituted derivative it is immaterial which 
 one of the six hydrogens is replaced; only one compound, 
 C 6 H 5 X, can be formed. 
 
 With di-substituted derivatives three isomerides are theo- 
 retically possible, viz.: 
 
 the 1:2 or ortho-compound, 1:3 or meta-compound, and the 
 1:4 or para-compound. 
 
 The compound 1:5 is identical with 1:3, and 1:6 is identical 
 with 1:2. Cf. JPohl, B. 1910, 43, 3474. 
 
 The hydrogen atoms in positions 2 : 6 form one pair of sym- 
 metrical hydrogen atoms mentioned on p. 329, and those in 
 positions 3:5 form the second pair, whereas the hydrogen in 
 position 4 has no other hydrogen atom corresponding with it. 
 
 Similarly, three tri-substituted derivatives, C 6 H 3 X 3 , are 
 known, and only three are possible with such a ring formula, 
 viz. : 
 
 XXX 
 
 (III) 
 
 (I) 1:2:3 or adjacent tri-derivative. 
 
 (II) 1 : 3 : 5 or sym. tri-derivative. 
 
 (III) 1:2:4 or unsym. tri-derivative. 
 
 Any other combination is identical with one of these, 2:4:6 
 = 1:3:5, and 1:4:6 = 1:2:4. 
 
334 XVII. BENZENE DERIVATIVES. INTRODUCTION 
 
 The number of isomerides is considerably increased when 
 the three substituents are not similar, e.g. in a compound, 
 
 ith a tetra-substituted derivative, C 6 H 2 X 4 , where all four 
 substituents are alike, only three isomerides are possible, 
 namely those corresponding with the 0-, m-, and |?-di-deriva- 
 tives : 
 
 X 
 
 And with a penta-substituted derivative, C 6 HX 5 , only one 
 form is possible. 
 
 The number of isomerides actually found in each case is in 
 perfect harmony with these theoretical deductions. 
 
 The ring formula for benzene, given above, represents each 
 carbon atom as tervalent; the difficulty of accounting for the 
 fourth valency can be overcome in several ways. 
 
 The first method, suggested by KeJcuU, was to suppose 
 alternate double and single bonds between the 6 carbon 
 atoms, e.g.: 
 
 CH 
 
 This formula is in perfect harmony with the formation of 
 benzene from acetylene, and of trimethyl-benzene from acetone. 
 It also largely accounts for the formation of additive com 
 pounds by benzene and its derivatives, e.g. : 
 
 CH* CHC1 
 
 1 
 
 Hdl H H( 
 
 HC1 
 
 Dihydro-benzeue Tetrahydro-benzene Benzene hexachloride. 
 
 Two arguments which have been brought forward against 
 this formula are 
 
CONSTITUTION OF BENZENE 335 
 
 (a) Two ortho-disubstituted derivatives should be possible, 
 
 namely, those represented by the formulae: 
 
 In formula (I) the 2 carbon atoms to which the substituents 
 are attached are united by a double bond, and in formula (II) 
 by a single bond. KekuU has suggested that the single and 
 double bonds may be continually changing, so that positions 
 2 and 6 are really symmetrical with respect to 1. 
 
 (b) The stability of benzene towards oxidizing agents has 
 been used as an argument against such a formula containing 
 three double bonds in the molecule. Di- and tetrahydro- 
 benzenes obtained by the reduction of benzene which con- 
 tain respectively two and one double bonds in their molecules, 
 are readily oxidized, and also readily yield additive compounds 
 with halogens. It has been suggested that the peculiar sym- 
 metrical structure of the benzene molecule may account for 
 its stability. 
 
 (II) A second method of accounting for the fourth valency 
 of each carbon atom is that first suggested by Armstrong, and 
 afterwards developed by Baeyer: 
 
 (IlA) 
 
 It represents the fourth valency of each carbon atom as 
 directed towards the centre of the molecule, where the 6 are 
 kept in equilibrium. This centric formula for benzene repre- 
 sents a method of linking which is unknown in the fatty 
 series. When reduced to dihydro-benzene, four of the six 
 centric bonds form two double bonds. 
 
336 
 
 XVII. BENZENE DERIVATIVES. INTRODUCTION 
 
 This readily accounts for the great difference between the 
 chemical properties of benzene and of its reduction products. 
 
 Various other formulae have been suggested for benzene, 
 e.g. Ladenburg's prism formula, Claus's diagonal formula, and 
 Dewar's formula. 
 
 (in) 
 
 (IV) 
 
 (V) 
 
 Dewar 
 
 Claus 
 
 A strong objection to the prism formula and to any other 
 three-dimension space formula is that the molecules of certain 
 substituted derivatives would be perfectly asymmetric, and 
 should therefore exist in optically active modifications. No 
 benzene derivative which occurs naturally is optically active, 
 and attempts to resolve substituted benzene derivatives, e.g. 
 C 6 H(OH)(C0 2 H)(CH 3 )(C 3 H 7 )(N0 2 ), nitrothymotic acid, have 
 been unsuccessful. Rugheimer (B. 1896, 29, 1967) states, 
 however, that he has obtained w-methyl-jp-hydroxy-benzoic 
 acid in an optically active form. 
 
 Other objections to the prism formula are (a) the difficulty 
 of accounting for the reduction products of benzene, and (b) 
 the fact that when benzene is oxidized by various methods no 
 compound is met with which contains a carbon atom attached 
 to 3 other carbon atoms, as is the case in the prism formula. 
 
 Researches upon the constitution of benzene and its deriva- 
 tives by Baeyer (A. 245, 251, 256, 258, 269, 176), and upon 
 similar (and also nitrogen) ring-systems by Bamberger (A. 257, 
 1), have shown that the nature of the groups entering the 
 benzene molecule has an influence upon the special (fourth) 
 linking of the atoms ; so that the constitution of the ring in all 
 benzene derivatives is not to be taken as established without 
 further investigation because a particular formula applicable 
 to benzene itself has been arrived at. On the contrary, 
 KeTcaU's formula (I) might suit for certain compounds (as 
 has been proved by Biwyer for phloroglucinol [B. 24, 2687]), 
 and formula (IL\) for others. 
 
 Compare also A. 274, 331; 279, 1; B. 30, 2975; A. 306. 
 125; Kauffmann, Ahren's Sammlung, 1907, 12, 79. 
 
ISOMERISM OF BENZENE DERIVATIVES 
 
 337 
 
 METHODS FOR DETERMINING WHICH OF THREE ISO- 
 MERIC COMPOUNDS IS THE ORTHO, WHICH MET A, 
 AND WHICH PARA. 
 
 1. A method worked out by Korner (1875) for the three 
 dibromobenzenes. One of these (a) is a solid melting at 89; 
 a second (b) is a liquid which boils at 224, and when solidified 
 melts at 1; and the third (c) is a liquid boiling at 219 and 
 melting at +1. When further brominated, the compound a 
 yields only one tribromobenzene; compound b, under similar 
 conditions, yields a mixture of two isomeric tribromobenzenes; 
 and compound c a mixture of three. 
 
 Br Br Br 
 
 From a glance at the above formulae, it is obvious (1) that 
 the para- or l:4-compound could give rise to only one tri- 
 bromobenzene, (2) that the ortho- or l:2-compound could give 
 a mixture of two isomeric tribromobenzenes, and (3) that the 
 meta- or l:3-compound could give a mixture of three isomeric 
 tribromobenzenes. 
 
 The compound melting at 89 is therefore ^-dibromobenzene, 
 the one boiling at 224 is the ortho-, and the one boiling at 
 219 and melting at +1 is the meta-compound. 
 
 Incidentally, this gives us a method for determining which 
 of the three tribromobenzenes is the adj., which the sym., and 
 which the unsym. A glance at the formulae indicates that the 
 sym.-tribromobenzene is the one which is formed from the 
 m-dibromobenzene only. The adj. is the one formed from 
 both ortho- and meta-, and the unsym. is the one which is 
 formed from ortho-, meta-, and para-dibromobenzenes. 
 
 Similar results are obtained by examining the nitro-dibromo- 
 benzenes obtained by nitrating the dibromobenzenes. 
 
 The p-compound yields only one nitre-derivative; the 0-com- 
 
 (B480) Y 
 
338 XVII. BENZENE DERIVATIVES. INTRODUCTION 
 
 pound yields two nitro-derivatives; the ra-compound yields 
 three nitro-derivatives : 
 
 Br 
 
 but the nitro-dibromobenzenes thus formed are all different. 
 
 Similar methods may be adopted for determining the 
 constitutions of the three diamino-benzenes, C 6 H 4 (NH 2 ) 2 , by 
 determining from how many of the six diamino-benzoic acids 
 each of the three can be obtained by elimination of carbon 
 dioxide. 
 
 The m-compound is the one which is formed from three 
 distinct acids, the ortho- from two, and the para- from one 
 only (Griess). 
 
 The relationships between the three xylenes, C 6 H 4 (CH 3 ) 2 , 
 and the six nitro -xylenes are exactly analogous to those 
 between the three dibromobenzenes and their six nitro-deri- 
 vatives. 
 
 2. When the constitution of several groups of compounds, 
 e.g. the dibromobenzenes, the xylenes, and the diamino-ben- 
 zenes have been settled, then the constitutions of other com- 
 pounds can be determined by conversion into one of the 
 compounds of known constitution, e.g. the dinitro-benzene 
 which yields m-diamino-benzene on reduction is the m-dinitro- 
 compound, or the acid obtained by the oxidation of o-xylene 
 must be the 0-dicarboxylic acid. 
 
 This constitution is confirmed by the fact that this acid 
 is the only one of the three ibomeric benzene-dicarboxylic 
 
ISOMERISM OF BENZENE DERIVATIVES 339 
 
 acids which yields an inner anhydride, phthalic anhydride, 
 ), and hence the two C0 2 H groups are probably 
 
 attached to two adjacent carbon atoms. 
 
 3. The constitution of certain di-substituted derivatives is 
 based on Ladenburg's proof (A. 179, 174) of the equivalence 
 of the three unsubstituted hydrogen atoms in mesitylene, 
 C 6 H 3 (CH 3 ) 3 ; in other words, on the fact that mesitylene is 
 sym.-trimethyl-benzene, e.g. the constitution of w-xylene is 
 based on the following reactions: 
 
 GEL 
 
 C0 2 
 
 Ladenburg's proof is briefly as follows : Mesitylene yields a 
 dinitro-derivative, C 6 H(CH 3 ) 3 (N0 2 ) 2 , in which two of the three 
 nucleus hydrogen atoms (a and b) are replaced by nitro-groups. 
 From this we get, by the three processes of reduction, acety 
 lation, and nitration, a dinitro-acetamino-mesitylene : 
 
 C 6 H(CH 3 ) 3 (N0 2 )(NH 2 ) C 6 H(CH 3 ) 3 (N0 2 )(NHAc) 
 
 a b 
 
 C 6 (CH 3 ) 3 (N0 2 ) 2 (NHAc), 
 
 in which the third hydrogen (c) is replaced by N0 2 ; on hydro- 
 lysis, this yields C 6 (CH 3 ) 3 (N0 2 ) 2 (NH 2 ), and on elimination of 
 the amino-group, C 6 H(CH 3 ) 3 (N0 2 ) 2 , a olinitro-mesitylene, which 
 is identical with the original dinitro-compound started with. 
 Hence two of the hydrogen atoms (say b and c) are similarly 
 situated. The nitro-amino-mesitylene, C 6 H(CH 3 ) 3 (N0 2 )(NH 2 ), 
 
 a ' b 
 
 in which the nitro-group is in position a and the amino- in 
 position b t yields C 6 H 2 (CH 3 ) 3 N0 2 , and this, when reduced, 
 
 a 
 
 acety lated, nitrated, and hydrolysed: 
 
 C 6 H 2 (CH 3 ) 3 NH 2 C 6 H 2 (CH 3 ) 3 .NHAc 
 a a 
 
 & or c a 6 or c 
 
 a nitro-amino-mesitylene which is identical with the original 
 nitro-amino-mesitylene, and hence the position a is similarly 
 situated to either b or c, but in the first part of the argument 
 it was shown that b = c, .*. a = b = c. 
 
340 XVII. BENZENE DERIVATIVES. INTRODUCTION 
 
 Other Types of Isomerism. 1. In addition to the cases of 
 isomerism dealt with in the preceding pages (isomerism due to 
 the positions of the substituents in the nucleus), other types of 
 isomerides are met with. A frequent example is the isomerism 
 of a compound containing a substituent in the nucleus with a 
 compound containing the same substituent in the side chain; 
 well-known examples are C 6 H 4 C1 CH 3 and C 6 H 5 CH 2 C1, 
 
 and C 6 H 5 -CH 2 .NH 2 . Isomerism of this type is 
 
 usually accompanied by considerable difference in chemical 
 properties. 
 
 2. " Side-chain isomerism " is the name given when the iso- 
 merism is confined to the side chain, e.g. : 
 
 C 6 H 6 .CH 2 .CH 2 .CH 3 and C 6 H 5 .CH(CH 3 ) 2 
 
 Normal- and Isopropyl-benzene. 
 
 Stereo-isomerism. When the side chain contains an asym- 
 metric carbon atom, e.g. C 6 H 5 CH(OH)(C0 2 H), mandelic acid, 
 stereo-isomerism of the type of the active lactic acids is met 
 with. Stereo-isomerism of the type of the crotonic acids is 
 met with in unsaturated compounds like cinnamic acid, C 6 H 5 
 CH:CHC0 2 H, and stereo-isomerism analogous to that de- 
 scribed in the case of polymethylene derivatives is met with 
 among the reduced benzene derivatives, e.g. di-, tetra-, and 
 hexahydrophthalic acid (p. 466). 
 
 OCCURRENCE OF THE BENZENE DERIVATIVES 
 
 Many benzene derivatives occur in nature, e.g. oil of bitter 
 almonds, benzoic acid, salicylic acid, and hippuric acid, while 
 others are obtained from the destructive distillation of organic 
 substances, especially of coal. 
 
 The destructive distillation of coal yields (a) gases (illumi- 
 nating gas); (b) an aqueous distillate containing ammonia and 
 its salts, &c.; (c) tar; and (d) coke. 
 
 The various fractions obtained by distilling coal-tar contain : 
 
 (a) Fatty hydrocarbons in small amount. 
 
 (b) Aromatic hydrocarbons, the most important of which 
 are the following: Benzene, C 6 H 6 , toluene, CgH^CHg, and 
 many homologues of benzene containing methyl substituents, 
 e.g. mesitylene, C 6 H 3 (CH 3 ) 3 , durene and isodurene, C 6 H 2 (CH 3 ) 4 . 
 More complex hydrocarbons : cinnamene, C 6 H 5 CH : CH 2 ; 
 naphthalene, C 10 H 8 ; diphenyl, C 12 H 10 ; acenaphthene, C 12 H 10 ; 
 
FORMATION OF BENZENE DERIVATIVES 341 
 
 fluorene, C 13 H 10 ; anthracene, C 14 H 10 ; phenanthrene, C U H 10 ; 
 pyrene, C 16 H 10 ; chrysene, C 18 H 12 . 
 
 (c) Other neutral substances, e.g. alcohol (in very small 
 quantity), benzonitrile, cumarone, CgHgO. 
 
 (d) Phenols: e.g. phenol or carbolic acid, C 6 H 5 OH; o-, m-, 
 and ^>-cresol, CH 3 C 6 H 4 OH. 
 
 (e) Bases: pyrrole, C 4 H 5 N; pyridine, C 5 H 5 N, and its homo- 
 logues; aniline, CgH 5 NH 2 ; quinoline, C 9 H 7 N, and its homo- 
 logues; acridine, C 13 H 9 N. (See Schultz, "Chemie des Stein- 
 kohlentheers ", Braunschweig, 1886.) 
 
 All these compounds are not present in the original coal, but 
 are formed during the process of distillation. The compounds 
 formed, and also their relative amounts, depend on numerous 
 factors, e.g. nature of coal, temperature and pressure of distil- 
 lation, kind of retort used, &c. 
 
 The presence of the hexahydro-compounds of benzene and 
 its homologues has been proved in most natural petroleums, 
 especially in those from the Caucasus (J. pr. Ch. (2) 45, 561; 
 cf. p. 41). 
 
 FORMATION OF BENZENE DERIVATIVES FROM 
 OPEN-CHAIN COMPOUNDS 
 
 The benzene derivatives can be produced from the fatty 
 compounds by a relatively small number of reactions only. 
 
 1. Many methane derivatives, e.g. alcohol, yield a mixture 
 containing a large number of the derivatives of benzene when 
 their vapours are led through red-hot tubes. Acetylene, C 2 H 2 , 
 polymerizes at a low red heat to benzene, C 6 H 6 (Berthelot): 
 
 CH CH 
 
 HC CH HC CH 
 
 HC CH HC CH 
 
 V 
 
 In an analogous manner allylena CH 3 'C':CH, yields mesity- 
 lene or 1:3:5 trimethyl-benzene, C 6 H 3 (CH 3 ) 3 , when distilled 
 with dilute sulphuric acid, while crotonylene, CH 3 C:CCH 3 , 
 yields hexamethyl -benzene, C 6 (CH 3 ) 6 ; bromo- acetylene and 
 iodo-acetylene polymerize to s-tribromo- and ^tn-iodo-benzene 
 when exposed to light; propiolic acid, CH*:C'C0 2 H, poly- 
 merizes to trimesic acid, C 6 H 3 (C0 2 H) 3 . 
 
342 XVII. BENZENE DERIVATIVES. INTRODUCTION 
 
 2. Ketones condense to benzene hydrocarbons when dis- 
 tilled with dilute sulphuric acid, e.g. acetone yields mesitylene 
 (Kane, 1838) and methylethyl ketone, triethyl-benzene: 
 
 CH 3 CH 3 
 
 C(C C 
 
 (H 2 )CH CH(H) 2 HC CH 
 
 | -* I' 1 +3H 2 0. 
 
 CH 3 .C(0) 0(0). CH 3 CH 3 -C CJ.CH 3 
 
 (H 2 )CH C 
 
 3 mols. Acetone H 
 
 Mesitylene 
 
 3. Certain 1 : 2-diketones, aldehyde acids, and keto-aldehydes 
 are transformed in an analogous manner into benzene deri- 
 vatives by suitable "condensing" agents; diacetyl, CH 3 
 CO'CO'CH 3 , is transformed by alkalis into xylo-quinone, 
 C 6 H 2 2 (CH 3 ) 2 (B. 21, 1411), and ethyl /3-hydroxyacrylate into 
 the ethyl ester of trimesic acid (B. 20, 2930). 
 
 4. Certain 1 : 5 diketones react with hydrochloric acid, yield- 
 ing reduced benzene derivatives, which can readily be trans- 
 formed into benzene derivatives, e.g. ethylidene-diacetoacetic 
 ester (from acetaldehyde and acetoacetic ester) yields dimethyl- 
 
 QQ QTT 
 
 cyclo-hexenone, CH<Tr<\T XtrOOHMe, the dibromide of 
 
 ^L/ivie-urig 
 
 which is converted into sym.-xylenol, 
 (Knoevenagel). 
 
 5. By the action of methylene iodide upon the sodium com- 
 pound of ethyl pentane-tetracarboxylate and subsequent hy- 
 drolysis, hexahydro-isophthalic acid is formed (W. H. Perkln, 
 jun., J. C. S. 1891, 59, 798): 
 
 CH 9 CH, 
 
 2 C CH.' 
 
 H 2 C C(C0 2 Et) 2 H 2 C CH-C0 2 H 
 
 | \ N +CH 2 I 2 | | 
 
 H 2 C Na 1 H 2 C CH 2 
 
 )(C0 2 Et) 2 CH.C0 2 H 
 
 Sodium compound of ethyl Hexahydro-isophthalic 
 
 pentane-tetracarboxylate acid. 
 
 6.' By the action of sodium upon ethyl succinate (Herrmann, 
 A. 211, 306; B. 16, 1411), or upon ethyl bromo-acetoacetate 
 (Duisberg), ethyl snccinylo- succinate, "ethyl diketo-hexa- 
 
DECOMPOSITION Of BENZENE COMPOUNDS 343 
 
 methylene-dicarboxylate ", is obtained, and is readily trans- 
 formed into ethyl dihydroxy-terephthalate and then into quinol: 
 
 EtO;CO CO 
 
 CO 2 Et.HC;H j CH 2 C0 2 Et-HC CH 2 
 
 H 2 C i H;CH.CO 2 Et H 2 C CH'COaEt 
 
 COiOEt CO 
 
 2 mols. Ethyl succinate Ethyl succinylo-succinate. 
 
 7. When ethyl sodio-malonate, CHNa(C0 2 Et) 2 , is heated, 
 ethyl phloroglucinol-dicarboxylate is formed, and this on hy- 
 drolysis yields phloroglucinol. (Cf. p. 420.) 
 
 8. Hexyl iodide, C 6 H 13 I, is converted into hexachloro-ben- 
 zene, C 6 C1 6 , when heated with IC1 3 , and into hexabromo-ben- 
 zene, C 6 Br 6 , by bromine at 260; the latter compound can also 
 be obtained by heating CBr, to 300. 
 
 9. Mellitic acid, C 6 (C0 2 H) 6 , is produced by the oxidation 
 of graphite or lignite by means of KMnO 4 . 
 
 10. Potassium carboxide, which is formed by the action of 
 carbon monoxide upon potassium, is the potassium compound 
 of hexahydroxy-benzene, C 6 (OH) 6 . 
 
 THE CONVERSE TRANSFORMATION OF BENZENE DERI- 
 VATIVES INTO FATTY COMPOUNDS 
 
 1. When the vapour of benzene is passed through a red-hot 
 tube it is partially decomposed into acetylene. 
 
 2. Benzene is oxidized by chloric acid to " trichloro-pheno- 
 malic acid", i.e. /3-trichloraceto-acrylic acid, CC1 8 'COCH: 
 CH.C0 2 H (KekuU and Strecker, A. 223, 170). 
 
 When chlorine is allowed to act upon phenol in alkaline 
 solution, the benzene ring is broken, and the acids, C 6 H 6 CloO 4 , 
 C 6 H 5 C10 4 , &c., are produced (Hantzsch, B. 20, 2780). Catechol, 
 resorcinol, and phloroglucinol are also ultimately converted 
 into fatty compounds by treatment with chlorine and the sub- 
 sequent action of alkalis, e.g. resorcinol (m-dihydroxybenzene) 
 yields dichloro-maleic acid (B. 1894, 27, 3364). Bromine, acting 
 upon bromanilic acid, yields perbromo-acetone, CBr 8 COCBr 3 . 
 
 3. Nitrous acid converts catechol into dihydroxy-tartaric 
 acid (see p. 260), while permanganate of potash, acting upon 
 phenol, gives rise to inactive tartaric acid and oxalic acid 
 (Dobner, B. 24, 1753). 
 
344 XVIII. BENZENE HYDROCARBONS 
 
 4. Oxidizing agents which are capable of rupturing the 
 benzene ring yield, as a rule, carbonic, formic, and acetic 
 acids. 
 
 5. The hexahydro- benzenes are transformed into hydro- 
 carbons of the methane series when heated with hydriodic 
 acid at 280 (Berthelot, A. 278, 88; 302, 5). This decom- 
 position appears, however, to be very difficult of accomplish- 
 ment. 
 
 6. When reduced with metallic sodium and amyl alcohol, 
 0-hydroxy-benzoic acid is converted into pimelic acid: 
 
 CH 
 
 XVIII. BENZENE HYDROCARBONS 
 A. Homologues of Benzene, 
 
 The benzene hydrocarbons are for the most part colourless 
 liquids, insoluble in water, but readily soluble in alcohol and 
 ether (durene and penta- and hexamethyl-benzenes are crys- 
 talline). They distil without decomposition, possess a peculiar 
 and sometimes pleasant ethereal odour, and burn with a very 
 smoky flame. Many, especially benzene and its methyl deriva- 
 tives, occur in the lower fractions from coal-tar; others are 
 prepared synthetically by Fittig's or Friedel-Crafts' methods. 
 
 Modes of Formation. 1. Fittig's Synthesis. By treating a 
 mixture of a brominated benzene hydrocarbon and an alkyl 
 iodide or bromide with sodium in the presence of dry ether 
 (A. 131, 303): 
 
 Br + CH 3 I +2Na == C 6 H 6 .CH 3 -f Nal + NaBr; 
 
 66 3 == 66 . 3 - a r; 
 
 C 6 H 4 Br(0 2 H 5 ) + C 2 H 6 I + 2Na = C 6 H 4 (C 2 H 5 ) 2 -f Nal + NaBr. 
 
BENZENE AND ITS HOMOLOGUES 
 
 345 
 
346 XVIII. BENZENE HYDROCARBONS 
 
 Jannasch synthesised ^?-xylene, durene, and isodurene by this 
 method. 
 
 2. Friedel^ and Crafts 1 Synthesis (1877). By the action of 
 alkyl chlorides (bromides or iodides) on aromatic hydro- 
 carbons in the presence of anhydrous aluminic chloride, 
 (A1C1 3 ): 
 
 C 6 H 6 + CH 3 C1 = C 6 H 6 .CH 3 +HC1; 
 C fl H 6 + 2CH 3 C1 = C 6 H 4 (CH 3 ) 2 + 2HC1, &c. 
 
 This reaction is, like the preceding one, capable of very 
 wide application; by means of it all the hydrogen atoms in 
 benzene can be gradually replaced by methyl. The best 
 yields are often obtained by the addition of carbon bisulphide, 
 which serves as a diluent, and also prevents the temperature 
 rising to any appreciable extent, and thus largely avoids the 
 decomposing or differentiating action of the chloride on the 
 homologues first formed. At higher temperatures, for ex- 
 ample, C 6 H 5 'CH 3 would be transformed to a large extent 
 into C 6 H 6 and C 6 H 4 (CH 3 ) 2 (B. 1894, 27, 1606, 3235). 
 
 Zinc and ferric chlorides (Nencki, B. 1899, 32, 2414) act in 
 the same way as chloride of aluminium, while ethyl chloride 
 and other haloid compounds, such as chloroform and acid 
 chlorides, may replace methyl chloride. (See respectively 
 triphenyl-methane and the ketones; cf. also B. 14, 2624; 16, 
 1744; Ann. de chim. et phys. [6] \ 419; B. 30, 1766.) The 
 metallic chloride forms additive compounds with the acyl 
 chloride or alkyl derivative, e.g. CEL COC1, A1C1 3 , and also 
 with the condensation product, e.g. C 6 H 5 CO CH 3 , A1C1 3 (Per- 
 rier, B. 1900, 33, 815). The reaction is a unimolecular one, 
 except when an excess of A1C1 3 is used. 
 
 For a summary of the Friedel- Crafts' reaction, see Steele, 
 J. C. S. 1903, 1470. 
 
 Alcohols also, like their haloid esters, are capable of react- 
 ing in an analogous manner in presence of ZnCl 2 : 
 
 C 6 H 6 + C 4 H 9 OH = C 6 H 6 .C 4 H 9 + H 2 O. 
 
 3. A method of formation somewhat analogous to the Fittig 
 synthesis is the action of alkyl iodides or methyl sulphate on 
 organo-magnesium haloids (Grignard's compounds) in toluene 
 solution (Houben, B. 1903, 36, 3083; 1904, 37, 488; Werner, 
 ibid., 2116, 3618): 
 
 CH 3 .C 6 H 4 .MgBr + C 2 H 6 Br = CH 3 .C 6 H 4 .C 2 H 6 + MgBr 2 . 
 
FORMATION Of BENZENE HYDROCARBONS 347 
 
 4. The benzene hydrocarbons are formed when their carb- 
 oxylic acids are distilled with soda-lime: 
 
 C 6 H 5 .C0 2 H = C 6 H 6 + C0 2 ; 
 CH 3 .C 6 H 4 .C0 2 H = C 6 H 6 6 .CH 3 4-00 2 . 
 
 5. From sulphonic acids (p. 402) by the elimination of the 
 S0 3 H group: 
 
 C 6 H 3 (CH 3 ) 2 S0 3 H + H 2 = C 6 H 4 (CH 3 ) 2 -t-H 2 S0 4 . 
 
 This reaction can be effected by dry distillation, by heating 
 with concentrated hydrochloric acid to 180, by distillation of 
 the ammonium salt (Caro), or by treatment with superheated 
 steam, e.g., in presence of concentrated sulphuric acid (Arm- 
 strong, W. Kelbe); also by heating with concentrated phosphoric 
 acid (B. 22, Kef. 577). 
 
 6. From the amino-compounds by transforming these into 
 diazonium-compounds (p. 387), and boiling the latter with ab- 
 solute alcohol or with an alkali stannite solution (B. 22, 587). 
 Griess reaction. 
 
 7. By distillation of the phenols (or ketones) with zinc dust. 
 homers and Constitution. The table given on p. 345 shows 
 
 that the benzene hydrocarbons, from C 8 H 10 on, exist in many 
 isomeric modifications; thus, isomeric with the three xylenes 
 we have ethyl-benzene, with the three trimethyl-benzenes 
 the three methylethyl-benzenes and the two propyl-benzenes, 
 with durene, isodurene, cymene, &c. 
 
 The constitution of these hydrocarbons follows very simply 
 from their modes of formation. A hydrocarbon C ]0 H 14 , for 
 instance, which is obtained from benzene and methyl chloride 
 by the Friedel-Crafts' reaction, can only be a tetramethyl-ben- 
 zene; another of the same molecular formula C 10 H 14 , which has 
 been prepared from bromo-benzene, butyl bromide and sodium, 
 must be a butyl-benzene ; while a third, from j9-bromo-toluene, 
 normal propyl iodide and sodium, must be a jp-propyl-toluene 
 (p-methyl-7i-propyl-benzene), &c. The synthesis therefore de- 
 termines the constitution. 
 
 The groups CH 3 , C 2 H 5 , &c., which replace hydrogen in 
 benzene, are termed "side chains". 
 
 When oxidized, the hydrocarbons yield a benzene-mono-, 
 di-, or tri-, <fec., carboxylic acid, e.g. benzoic acid, C 6 H 5 C0 2 H, 
 0-, m-, >-phthalic acid, C 6 H 4 (C0 2 H) 2 , according to the number 
 of side chains present in the hydrocarbon; and a further proof 
 of the constitution of the compound is thus afforded. 
 
348 XVIII. BENZENE HYDROCARBONS 
 
 If, for example, a hydrocarbon C 9 H 12 yields a benzene-tri- 
 carboxylic acid, C 6 H 3 (C0 2 H) 3 , upon oxidation, it must contain 
 three side chains, i.e. must be a trimethyl-benzene; should a 
 phthalic acid, on the other hand, result, then it can only be 
 an ethyl-toluene. Since cymene yields p- (or tere-) phthalic 
 acid, C 6 H 4 (C0 2 H) 2 , on oxidation, its two side chains must be 
 in the ^-position towards one another. 
 
 The respective isomers resemble each other closely in 
 physical properties, their boiling-points, for example, lying 
 very near together. The ortho-derivatives often boil at about 
 5, and the meta- at about 1 higher than the para-compounds; 
 the boiling-point rises with an increasing number of methyl 
 groups. (Of. B. 19, 2513.) 
 
 Behaviour. 1. The benzene hydrocarbons are, as a rule, 
 readily nitrated and sulphonated, mono-, di-, and even tri- 
 derivatives being all usually capable of preparation, according 
 to the conditions. As a rule, it is only the hydrogen atoms 
 of the benzene nucleus which are replaced, the side chains 
 reacting as paraffin residues. Hexamethyl-benzene can thus 
 neither be nitrated nor sulphonated. Exceptions to this 
 generalization are met with, e.g. mesitylene yields a nitro- 
 derivative, C 6 H 3 (CH 3 ) 2 .CH 2 .N0 2 . 
 
 2. Oxidation. Benzene itself is not readily oxidized; per- 
 manganate of potash converts it slowly into formic and oxalic 
 acids, some benzoic acid and phthalic acid being produced at 
 the same time. These doubtless result from some previously 
 formed diphenyl. 
 
 The homologues of benzene, on the other hand, are readily 
 oxidized to carboxylic acids, the benzene nucleus remaining 
 unaltered, and each side chain no matter how many carbon 
 atoms it may contain being converted, as a rule, into carb- 
 oxyl. 
 
 Nitric acid allows of a successive and often a partial oxi- 
 dation of individual side chains, chromic acid mixture (K 2 Cr 2 7 
 + H 2 S0 4 ) acts more energetically, converting all the side chains 
 in the p- and m-compounds into carboxyl, and completely 
 destroying the o-compounds. The latter may be oxidized to 
 the corresponding carboxylic acids by KMn0 4 . 
 
 When a hydrocarbon is selectively oxidized, the longest side 
 chain, as a rule, is most readily oxidized; thus C 3 H 7 C 6 H 4 - 
 CH 3 yields first C0 2 H . C 6 H 4 . CH 3 , and then C 6 H 4 (C0 2 H) 2 . 
 
 3. Reduction. The benzene hydrocarbons and most of their 
 derivatives are capable of taking up six atoms of hydrogen. 
 
REDUCED BENZENE DERIVATIVES 349 
 
 Benzene itself is only converted into hexahydro-benzene, C 6 H 12 , 
 with difficulty, but toluene, xylene, and mesitylene combine 
 with hydrogen more easily when they are heated with phos- 
 phonium iodide, PH 4 I, at a rather high temperature, the com- 
 pounds C 7 H 8 H 2 , C 8 H 10 H 4 , and C 9 H 12 H 6 being formed. The 
 two former can then be made to take up more hydrogen by 
 energetic reaction. 
 
 An interesting method of formation of C 6 H 12 is by the action 
 of freshly reduced nickel on a mixture of hydrogen and ben- 
 zene or its homologues at moderate temperatures. 
 
 Hexahydro-benzene and its analogues, C^H^, are colourless 
 liquids insoluble in water, and of somewhat lower boiling-point 
 than their mother compounds, into which they can be readily 
 retransformed by oxidation, either by heating with sulphur or 
 by means of fuming nitric acid, nitration also taking place in 
 the latter case; e.g. hexahydro-benzene yields nitro-derivatives 
 of benzene. They are found in petroleum, especially in that 
 from the Caucasus (Eeilstein, Kurbatow), and differ from the 
 isomeric defines by being insoluble in sulphuric acid, and by 
 not forming additive products with bromine (cf. B. 20, 1850; 
 A. 234, 89; 301, 154). 
 
 They are identical with hexamethylene and its derivatives, 
 and react as saturated compounds. The partially reduced 
 benzene derivatives, on the other hand, behave more like 
 olefines. 
 
 The dihydro-benzenes, C 6 H 8 , readily combine with two or 
 four atoms of bromine, and are readily oxidized by alkaline 
 permanganate, as .might be inferred from the presence of 
 double bonds in the molecule. Two isomeric compounds, 
 A 1 : 3-dihydro-benzene and A 1 : 4-dihydro-benzene, are known: 
 
 L 2 
 
 Cyclohexa-1 : 4-diene 
 
 Tetrahydro-benzene, , which exists in one form 
 
 H 2 k/H 2 
 
 H 2 
 
 Cyclohexene 
 
350 XVIII. BENZENE HYDROCARBONS 
 
 only, is readily oxidized, combines with two atoms of chlorine 
 and bromine or with a molecule of hypochlorous acid. All are 
 colourless, volatile liquids. 
 
 4. Behaviour with Halogens. Chlorine and bromine react 
 differently, according to the conditions. In direct sunlight 
 they yield with benzene the additive products C 6 H 6 C1 6 and 
 C 6 H 6 Br 6 , while in diffused daylight, especially in presence of a 
 little iodine, SbCl 3 or MoCl 5 , they give rise to the substitution 
 products C 6 H 5 C1, C 6 H 6 Br, &c. (For further details, and for 
 substitution by iodine, see pp. 57 and 356.) 
 
 5. Chromium oxychloride, Cr0 2 Cl 2 , converts the methylated 
 benzene hydrocarbons into aromatic aldehydes (p. 423; cf. B. 
 23, 1070). (Etard's reaction.) 
 
 6. The numerous " condensations " which benzene, &c., can 
 undergo with oxygenated compounds in presence of ZnCl 2 , 
 P 4 10 , or H 2 S0 4 , and with chlorinated compounds in presence 
 of A1C1 3 , are of great interest; thus benzene yields diphenyl- 
 ethane with aldehyde and sulphuric acid, and benzophenone 
 with benzoic acid and phosphorus pentoxide. 
 
 7. In presence of aluminic chloride, oxygen can be intro- 
 duced into benzene, yielding phenol; sulphur, yielding phenyl 
 sulphide; ethylene, yielding ethyl-benzene; carbon dioxide, 
 yielding benzoic acid. 
 
 Benzene, C 6 H 6 , was discovered by Faraday in 1825, and 
 detected in coal-tar by Hofmann in 1845. It is obtained from 
 the portion of coal-tar which boils at 80-85 by fractionating 
 or freezing. It may be prepared chemically pure by distilling 
 a mixture of benzoic acid and lime. The ordinary benzene of 
 commerce usually contains thiophene, and thus gives a char- 
 acteristic deep-blue coloration when shaken with a solution of 
 isatin in concentrated sulphuric acid; but it may be freed 
 from the impurity by repeated shaking with small quantities of 
 sulphuric acid, which converts the thiophene into a sulphonic 
 acid. It burns with a luminous smoky flame, and is a good 
 solvent for resins, fats, iodine, sulphur, phosphorus, &c. When 
 its vapour is led through a red-hot tube, diphenyl is obtained. 
 
 C 7 H 8 . Toluene, C 6 H 5 -CH 3 . Discovered in 1837. Formation: 
 by the dry distillation of balsam of Tolu and of many resins. 
 Synthesis according to Fittig (see above). Preparation-, from 
 coal-tar, in which it is found accompanied by thio-tolene. 
 Toluene is very similar to benzene. It boils at 110, and is 
 still liquid at 28. Cr0 2 Cl 2 converts it into benzaldehyde, 
 and HN0 3 or Cr0 8 into benzoic acid. 
 
XYLENES 351 
 
 C 8 H 10 . (a) o-, m-, and ^-Dimethyl-benzenes or Xylenes, 
 C 6 H 4 (CH 3 ) 2 . The xylene of coal-tar consists of a mixture of 
 the three isomers, m-xylene being present to the extent of 70 
 to 85 per cent. These cannot be separated from one another 
 by fractional distillation. wi-Xylene is more slowly oxidized 
 by dilute nitric acid than its isomers, and can thus be obtained 
 with relative ease. 
 
 For the separation of these isomers by means of H 2 S0 4 see 
 B. 10, 1010; 14, 2625; 17, 444; 25, Kef. 315; and for their 
 recognition see B. 19, 2513. Benzene and toluene yield chiefly 
 ortho-, together with a little para-xylene, when subjected to 
 the Friedel-Crafts synthesis (B. 14, 2627). 
 
 1. o- Xylene, which can be prepared synthetically from 
 0-bromo-toluene, methyl iodide, and sodium, is oxidized to 
 carbonic acid by chromic acid mixture, and to 0-toluic acid, 
 C 6 H 4 (CH 3 )C0 2 H, by dilute nitric acid; it is difficult to 
 nitrate. 
 
 2. m-Xylene or iso-xylene can also be prepared from mesity- 
 lene, C 6 H 3 (CH 3 ) 3 , [1:3:5], by oxidation to mesitylenic acid, 
 CgH 3 (CH 3 ) 2 C0 2 H, and subsequent distillation with lime. 
 Dilute nitric acid only oxidizes it at a temperature of 120, 
 while chromic acid mixture converts it into isophthalic acid, 
 C 6 H 4 (C0 2 H) 2 . It yields tetra- and hexahydro- derivatives, 
 C 8 H 14 and C 8 H 16 ; the latter is present in Caucasian petroleum, 
 and boils at 11 9. 
 
 3. ^-Xylene is prepared from j?-bromo-toluene, or better, 
 ;?-dibromo-benzene, methyl iodide, and sodium (B. 10, 1356; 
 B. 17, 444). M.-pt. 13. Dilute nitric acid oxidizes it to 
 0-toluic acid, C,H 4 ( GIL )C0 2 H, and terephthalic acid, 
 C 6 H 4 (C0 2 H) 2 . 
 
 Dihydro-^-xylene can be prepared from ethyl succinylo-suc- 
 cinate. Liquid; b.-pt. 133. It has an odour of turpentine, and 
 is closely related to the terpenes. (Cf. Baeyer, B. 25, 2122.) 
 
 Jb) Ethyl-benzene, C 6 H 5 .0 2 H 5 , is obtained from C 6 H 5 Br 
 CoH 5 Br by the Fittig reaction; from cinnamene, CJ3 5 
 CH:CH 2 , on reduction with HI; and from C 6 H 6 and C 2 H 5 C1 
 by the Friedel-Crafts reaction. It is found in small quantity 
 in the xylene from tar, and when oxidized yields benzoic acid. 
 C 9 H 12 . (a) Trimethyl-benzenes, 1. Mesitylene, l:3:5-tfn- 
 methyl-benzene, C 6 H 3 (CH 3 ) 3 . This is contained in coal-tar 
 along with the two other isomeric trimethyl-benzenes ("tar- 
 cumene "), and can be synthesised from acetone or allylene. 
 It is a liquid of agreeable odour. Nitric acid oxidizes the 
 
352 XVIII. BENZENE HYDROCARBONS 
 
 side chains one by one, while chromic acid mixture decom- 
 poses it completely. (For constitution, see p. 339.) 
 
 2. Pseudo-cumene, l-.Z-A-trimethyl-benzene, is separated from 
 mesitylene, not by fractional distillation, but by taking ad- 
 vantage of the sparing solubility of pseudo-cumene-sulphonic 
 acid (B. 9, 258). Its constitution follows from its formation 
 from bromo-j^-xylene [1:4:2], and also from bromo-w-xylene 
 [1:3:4], by the Fittig reaction. Nitric acid oxidizes the side 
 chains successively. 
 
 3. Hemellithene, l:2:3-trimethyll)enzene (see B. 15, 1853), is 
 present in coal-tar (B. 20, 903). 
 
 (b) Pr opyl- benzenes, 1. w-Propyl- benzene, C 6 H 5 .CH 2 - 
 CH 2 'CH 3 , is obtained from bromo-benzene and normal propyl 
 iodide by the Fittig reaction, and also from benzyl chloride, 
 C 6 H 5 .CH 2 C1, and zinc ethyl. 
 
 2. Isopropyl-benzene or Cumene, CgH 5 CH(CH 3 ) 2 , is pro- 
 duced by the distillation of cumic acid, C 6 H 4 (C 3 Hf)(C0 2 H), 
 with lime; from benzene and iso- or normal propyl iodide by 
 means of A1C1 3 , in the latter case with molecular rearrange- 
 ment (p. 132); and from benzylidene chloride, C 6 HCHC1 2 , 
 and zinc methyl, this last method furnishing proof of its con- 
 stitution. On oxidation, both n- and iso-compounds yield ben- 
 zoic acid. 
 
 Cj H 14 . (a) Durene, 1:2:4:5- or s-tetramethyl-benzene, 
 C 6 H 2 (CH 3 ) 4 , has been found in coal-tar, and can be prepared 
 from toluene and methyl chloride by the Friedel-Crafts reaction, 
 or from dibromo-m-xylene (from coal-tar xylene), methyl iodide, 
 and sodium (A. 216, 200). It is a solid, and possesses a camphor- 
 like odour. (For its constitution see B. 11, 31.) Both of its 
 isomers are known. 
 
 (b) Methyl-propyl-benzenes, C 6 H 4 (CH 3 )C 3 H 7 . The most 
 important of these is cymene or isopropyl-p-methyl-benzene. 
 It is found in Eoman cummin oil (Cuminum cyminum), in 
 eucalyptus oil, &c., and is formed when camphor is heated 
 with PgSg, or better, P 4 10 , also when oil of turpentine is 
 heated with iodine, &c. It has been synthetically prepared 
 from ^7-bromo-isopropyl-benzene, methyl iodide, and sodium; 
 and also from j9-bromo-toluene, n-propyl iodide, and sodium, 
 the %-propyl- changing here into the isopropyl group. It is a 
 liquid of agreeable odour. 
 
 Cymene was formerly regarded as 7i0maZ-propyl-^>-methyl- 
 benzene, but its synthesis from ^?-brom-w0-propyl-benzene, 
 methyl iodide, and sodium established its constitution as an 
 
UNSATURATED BENZENE HYDROCARBONS 353 
 
 isopropyl derivative (cf. JVidman, B. 24, 439). When oxidized, 
 it yields either ^7-toluic acid, terephthalic acid, cumic acid, or 
 />-tolyl-methyl-ketone, according to the conditions. 
 
 C 12 H 18 . Hexamethyl- benzene, Mellitene, C 6 (CH 3 ) 6 , crys- 
 tallizes in prisms or plates which melt at 164. It can neither 
 be sulphonated nor nitrated (see p. 347). KMn0 4 oxidizes it 
 to mellitic acid, C 6 (C0 2 H) 6 . 
 
 B. Unsaturated Benzene Hydrocarbons 
 
 The benzene hydrocarbons containing less hydrogen comport 
 themselves, on the one hand, like benzene itself, and on the 
 other like the un saturated hydrocarbons of the fatty series, 
 combining readily with hydrogen, halogen, halogen hydride, 
 &c. They are derived from the olefines or acetylenes by the 
 exchange of H for C 6 H 5 , thus: C 6 H 5 'CH:CH 2 , cinnamene, 
 styrene, or phenyl-ethylene; C 6 H 5 .C|CH, phenyl-acetylene. 
 They are formed by the elimination of C0 2 from the corre- 
 sponding acids, by the elimination of HBr from compounds of 
 the type C 6 H 5 CH 2 CH 2 Br, and by the elimination of water 
 from certain secondary and tertiary alcohols (C. R. 1901, 132, 
 1182). 
 
 Cinnamene, C 6 H 5 -CH:CH 2 , occurs along with other com- 
 pounds in storax (Styrax officinalis), in the juice of the bark of 
 Liquidambar orientate, and in coal-tar (being in this last case 
 probably a degradation product of certain acids). It is formed 
 when cinnamic acid is slowly distilled or heated with water to 
 200 (B. 1890, 23, 3269): C 6 H 5 CH : CH :COO;H. 
 
 It is also obtained when benzene vapour and ethylene are 
 passed through a red-hot tube, or when a-bromo-ethyl-benzene, 
 C 6 H 5 'CH 2 'CH 2 Br (by action of bromine on ethyl-benzene), is 
 heated. It is a liquid, has a characteristic odour, and boils at 
 140. It changes on keeping into the polymeric meta-styrene, 
 an amorphous transparent mass, and yields ethyl-benzene when 
 heated with hydriodic acid. Addition of HBr converts it into 
 a-bromo-ethyl-benzene, C 6 H 5 CH 2 CH 2 Br. By the conden- 
 sation of styrene with toluene, in presence of concentrated 
 sulphuric acid, and on subsequent superheating, anthracene is 
 formed (Kramer, Spilker, B. 23, 3169). 
 
 Phenyl-acetylene, CyHg.CjCH, is produced by the separa- 
 tion of C0 2 from phenyl-propiolic acid. 
 
 It is a pleasant-smelling liquid boiling at 142, and as an 
 acetylene derivative yields white and pale-yellow explosive 
 
 (B4SO) Z 
 
354 XIX. HALOGEN DERIVATIVES 
 
 metallic compounds with solutions of silver and cuprous 
 oxides. It combines with water to aceto-phenone, C 6 H 6 CO 
 CH 3 , when it is dissolved in sulphuric acid, and the solution 
 is diluted with water, or when heated with water to 300. 
 
 XIX. HALOGEN DERIVATIVES 
 
 SUMMAKY 
 
 Cl Br I 
 
 M.-p. B.-p. M.-p. B.-p. M.-p. B.-p. 
 
 C 6 H 6 C1 ............... -45 132 -31 157 -30 188 
 
 C 6 H 4 C1 2 o ......... liq. 179 -1 224 +27 286 
 
 m ......... liq. 172 liq. 220 +40 285 
 
 p ......... +56 173 +87 219 +129 285 
 
 CH 3 .C fl H 4 Clo ... 34 159 -26 181 liq. 211 
 
 m ... 48 162 40 184 liq. 204 
 
 p ... +7'4 162 28 185' +35 211'5 
 
 C 6 H 6 .CH 2 C1 ........ -48 175 ... 198 +24 decomposes 
 
 C 6 Cl 6 (Br 6 ,I fl ) ....... 229 326 
 
 Benzene and its homologues can give rise to (A) additive 
 compounds with bromine or chlorine, or (B) substituted deri- 
 vatives. 
 
 A. Additive Compounds 
 
 These are of comparatively little importance, and are formed 
 when the hydrocarbon is exposed for some time to chlorine or 
 bromine vapour in bright sunlight. 
 
 Benzene hexachloride, C 6 H 6 C1 6 , exists in two stereo-isomeric 
 modifications; the one melts at 157, and the other sublimes at 
 310. When warmed with alkali, they yield trichloro-benzene 
 and HC1. The isomerism is probably due to the different 
 arrangement of the halogen atoms on either side of the plane 
 of the benzene ring in the two compounds. The hexabromide 
 (Matthews, J. C. S. 1901, 79, 43) melts at 212. 
 
 B. Substituted Derivatives 
 
 Haloid substitution products in immense number are derived 
 from the benzene hydrocarbons by the exchange of hydrogen 
 for halogen. They are either colourless mobile liquids or 
 
SUBSTITUTED HALOGEN DERIVATIVES 855 
 
 crystalline solids, insoluble in water but readily soluble in 
 alcohol and ether, distil unchanged, and are distinguished by 
 their peculiar odour and also, in part, by their irritant action 
 upon the mucous membrane. They are heavier than water. 
 
 The substitution products of benzene and its homologues 
 may be arranged in two distinct groups. In one the halogen 
 is bound very firmly, far more so than in methyl chloride, 
 ethyl iodide, &c.; it cannot be exchanged for OH (by means 
 of AgOH), or for NH 2 (by NH 3 ), &c., but reacts with sodium 
 (see the Fittig reaction, p. 344) ; A. 332, 38 ; for an exception, 
 see B. 1892, 25, 1499; 1895, 28, 2312; and magnesium (see 
 below). All the substituted derivatives of benzene and many 
 common derivatives of its homologues belong to this class. 
 
 In the second group, of which benzyl chloride is a good 
 type, the halogen atoms enter into reaction as readily as do 
 those of the haloid substitution products of the methane series. 
 
 When the members of the first group are subjected to oxi- 
 dation, a process which converts side chains into carboxylic 
 groups, chloro-derivatives of benzoic and other acids are ob- 
 tained. The members of the second group, when subjected to 
 similar treatment, yield aromatic acids which are free from 
 halogen, e.g. benzoic acid, C 6 H 5 C0 2 H, phthalic acid, 
 C 6 H 4 (C0 2 H) 2 . From this it follows that the halogen is 
 present in the first case in the benzene nucleus, and in the 
 second in the side chain. Chloro-toluene is C 6 H 4 C1CH 3 , and 
 benzyl chloride C 6 H 5 .CH 2 C1. 
 
 When the halogen atoms replace hydrogen atoms of the 
 benzene nucleus, the products are extremely stable, and the 
 halogen cannot readily be removed from the molecule. On 
 the other hand, when the halogen replaces hydrogen atoms of 
 a side chain (methyl or ethyl groups), the compound is ex- 
 tremely reactive, and closely resembles the halogen derivatives 
 of the fatty series. In this way it is always easy to arrive 
 at the constitution of a compound from the behaviour of its 
 halogen atoms and from its products of oxidation. Thus a 
 compound C 7 H 6 C1 2 , which yields monochloro-benzoic acid upon 
 oxidation, has manifestly the formula C 6 H 4 C1 CH 2 C1 (chloro- 
 benzyl chloride). 
 
 The majority of aromatic halogen derivatives, independently 
 of the position of the halogen in the side chain or nucleus, 
 react in dry ethereal solution (or in benzene in presence of a 
 little dimethyl-aniline) with dry magnesium powder, yielding 
 organo-magnesium compounds, e.g. C 6 H 5 -MgBr, phenyl-mag- 
 
356 XIX. HALOGEN DERIVATIVES 
 
 nesium bromide, C 6 H 5 CH 2 Mg Cl, benzyl-magnesium chloride, 
 &c. These compounds Cmgnard's compounds are chemically 
 extremely active, and, like the analogous aliphatic compounds 
 (p. 120), can be employed for the syntheses of saturated and 
 unsaturated hydrocarbons, primary, secondary, and tertiary 
 alcohols, thiophenols, aldehydes, ketones, acids, &c., e.g.: 
 
 1. C 6 H 6 .Mg.Br + Br.C 2 H 6 = MgBr 2 + C 6 H 6 .C 2 H 6 . 
 
 a C 6 H 5 .Mg.Br + = C 6 H 6 .O.MgBr. 
 
 2 - C 6 H 6 .0-MgBr + H 2 = C 6 H 6 .QH + Br-Mg-OH. 
 
 , C 6 H 6 .Mg.Br + C0 2 = C 6 H 6 .CO 2 .MgBr. 
 
 * C 6 H 6 .CO 2 MgBr + H.OH = C 6 H 6 -CO 2 H + OH-Mg.Br. 
 
 and with water (C 6 H 6 ),C OH. 
 
 The Grignard compounds may also be used for converting a 
 bromo-derivative into the corresponding iodo-compound, e.g. : 
 
 C 6 H 6 Br C 6 H 5 -M g .Br C 6 H 6 I + MgBrl. 
 Mg I, 
 
 The boiling-points of the isomeric halogen substitution pro- 
 ducts differ but little from one another (cf. 0-, m- t ^?-chloro- 
 benzene and benzyl chloride). 
 
 The influence of the introduction of F, Cl, Br, or I in place 
 of hydrogen on the boiling-point of a hydrocarbon is similar 
 to that noted in the fatty series. Iodine raises the boiling- 
 point to the greatest extent, and fluorine to the least. 
 
 The halogen derivatives may be nitrated, sulphonated, &c., 
 in much the same manner as benzene itself. 
 
 Modes of Formation. 1. By the action of chlorine or bromine 
 upon aromatic hydrocarbons there are formed, according to 
 the conditions, either additive or substitution products, the 
 latter class especially in presence of iodine or some other 
 halogen carrier. The function of the halogen carrier, e.g. I, 
 P, Fe, &c., is probably to form an additive compound with 
 the halogen, e.g. IC1 3 , PC1 5 , FeCl 3 , then to give up part or 
 the whole of the halogen in the nascent state to the hydro- 
 carbon, and then to be immediately converted back into the 
 above compounds again. (Cf. p. 56, also B. 18. 607.) Iodine 
 only substitutes directly under the conditions detailed at p. 57. 
 From benzene most of the chlorinated derivatives up to 
 C 6 C1 6 can be obtained in succession; the last-named compound 
 is formed with the aid of MoCl 5 , IC1 3 , &c., at a somewhat 
 high temperature. A hexabromo-benzene and a hexa-iodo-com 
 
FORMATION OF HALOGEN DERIVATIVE^ 357 
 
 pound also exist. In the case of toluene and its hdniologues 
 the halogen enters the benzene nucleus alone if the operation 
 is performed in the cold, with the exclusion of direct sunlight 
 or with the addition of iodine; while if the gas is led into the 
 boiling hydrocarbon, or if the experiment is conducted in sun- 
 light and without addition of iodine, it goes almost exclusively 
 into the side chain (Beilstein; Schramm; see also B. 13, 1216). 
 
 2. From compounds containing oxygen (the phenols, aro- 
 matic alcohols, aldehydes, ketones, and acids), by the action 
 of phosphorus pentachloride or bromide: 
 
 C 6 H 5 .OH + PC1 5 = C 6 H 6 C1 + POC1 3 + HC1; 
 C 6 H 6 .CH:O + PC1 5 = C c H 6 .CHCl 2 -f POC1 3 . 
 
 3. From the primary amines. The amine is first converted 
 into a diazonium salt (p. 385), and this is then warmed with solu- 
 tions of cuprous chloride or bromide, when the corresponding 
 chlorine or bromine compound is obtained. If the diazonium 
 salt is warmed with potassium iodide solution, iodo-substitution 
 products are obtained: 
 
 C 6 H 5 .N(C1):N 
 
 C 6 H 6 .N(C1):N + KI = C 6 H 6 I + N 2 + KC1. 
 
 Gattermann 's modification consists in transforming the amine 
 into the diazonium chloride, bromide, or iodide, and then de- 
 composing this with finely-divided copper powder (Sandmeyw,, 
 B. 17, 1633, 2650; Gattermann, B. 23, 1218): 
 
 C 6 H 6 .NI:N = C 6 H 6 I + N 2 . 
 
 The method is largely used for the preparation of halogen de- 
 rivatives of benzene homologues, especially for iodo-derivatives, 
 
 ^-Dibromo-benzene is obtained, together with bromo-ben- 
 zene, by bromination of benzene in presence of a little iron. 
 
 The trichloro-benzene which results by direct substitution 
 has the (asymmetric) constitution 1:2:4. It may also be 
 formed by the separation of 3HC1 from C 6 H 6 C1 6 . 
 
 Hexachloro- and hexabromo-benzenes are produced by the 
 prolonged chlorination or bromination of benzene, toluene^ 
 naphthalene, &c., and also from carbon tetrachloride and 
 bromide, as given at p. 343. They are solid and can be 
 distilled. 
 
 When toluene is chlorinated or brominated, as given on 
 p. 356, the para- and ortho-compounds are formed in approxi- 
 mately equal quantities. ra-Chloro-toluene is obtained from 
 
358 XIX. HALOGEN DERIVATIVES 
 
 chloro-^-toluidine, C 6 H 3 C1(NH 2 )CH 3 (from ^-toluidine and Ci), 
 according to method 3. Oxidation by HN0 3 , Cr0 3 , or KMn0 4 
 converts them into the haloid-benzoic acids, but chromic acid 
 mixture must only be used in the case of the p- and m-, and 
 not in that of the 0-compounds, as it completely disintegrates 
 the latter. 
 
 Benzyl chloride, C 6 H 5 -CH 2 C1 (Cannizaro), is prepared by 
 chlorinating boiling toluene, and benzyl bromide in an analo- 
 .gous manner; the latter can be converted into benzyl iodide 
 by potassium iodide solution. The behaviour of these com- 
 pounds shows them to be the haloid esters of benzyl alcohol, 
 1 C 6 H 5 CH 2 OH, from which they may be obtained by the 
 action of halogen hydride, or of halogen derivatives of phos- 
 phorus, and into which they are transformed by prolonged 
 boiling with water, or better, with a solution of potassium 
 carbonate. When boiled with potassium acetate, the chloride 
 yields benzyl acetate, with potassium sulph-hydrate the mer- 
 captan, and with ammonia the amine. 
 
 The compounds containing halogen in the side chain irritate 
 the mucous membrane of the nose and eyes exceedingly, and 
 on oxidation yield benzoic acid. Benzyl chloride is used on 
 the large scale for the preparation of oil of bitter almonds and 
 also of certain dyes. 
 
 Benzal chloride, Benzylidene chloride, C 6 H 5 CHC1 2 , and 
 benzo-trichloride, C 6 H 5 CC1 3 , are produced by the further 
 chlorination of boiling toluene and also by the action of PC1 5 
 upon the corresponding oxygen compounds, benzaldehyde, 
 C 6 H 6 CHO, benzoic acid, C 6 H 5 C0 2 H, and benzoyl chloride, 
 C 6 H 5 COC1. They are liquids resembling benzyl chloride, 
 and are reconverted into the original oxygen compounds by 
 superheating with water, and into benzoic acid by oxidizing 
 agents. 
 
 Chlorobromo-benzenes, C 6 H 4 ClBr, chlor-iodo-benzenes, and 
 other mixed derivatives also exist in large number. 
 
 Substitution compounds of unsaturated hydrocarbons are 
 likewise known, e.g. /3-bromo-styrene, C 6 H 5 CBr : CH 2 , a- 
 bromo-styrene, C 6 H 5 CH : CHBr, &c. 
 
 Iodine Derivatives containing a Polyvalent Iodine Atom. 
 The iodine atom attached to the nucleus may in many cases 
 unite with other atoms, and thus exercise a higher valency. 
 The compounds thus obtained have but few analogues in the 
 fatty series. 
 
 Phenyl-iodide dichloride, C 6 H 5 I:C1 2 (Willgerodt), is formed 
 
NITRO-COMPOUNDS 359 
 
 as a yellow crystalline compound when dry chlorine is led 
 into a chloroform solution of phenyl iodide. The chlorine is 
 loosely combined, and may be removed on warming, or by the 
 action of potassium iodide. Alkalis transform the dichloride 
 into iodoso- benzene, CgH 5 -I:0, a yellow amorphous sub- 
 stance which dissolves in acids, yielding salts, e.g. acetate, 
 C 6 H 5 .I(C 2 H 3 2 ) 2 , nitrate, C 6 H 6 .I(0-NO ? ) 2> &c. It decom- 
 poses when heated, oxidizes potassium iodide solution, and 
 when kept or when distilled in steam is converted into phenyl 
 iodide and iodoxy-benzene, C 6 H 5 -I0 2 . This latter is crystal- 
 line, explodes when heated, is not basic, and resembles per- 
 oxides. It may also be prepared by oxidizing the iodoso- 
 compound with Card's reagent. 
 
 lodonium compounds (Hartmann and V. Meyer, B. 27, 1592), 
 e.g. diphenyl-iodonium iodide, (0 6 H 5 ) 2 II, and the correspond- 
 ing hydroxide, (C 6 H 5 ) 2 I OH, can be obtained when a mixture of 
 iodoso- and iodoxy-benzene is shaken with moist silver oxide: 
 
 H = (C 6 H 6 ) 2 I.OH + AgIO 3 . 
 
 The hydroxide which is only known in solution has strongly 
 alkaline properties. The salts, which crystallize well, closely 
 resemble the thallium salts. It is highly probable that the 
 three valencies of the polyvalent iodine atom in these iodo- 
 nium salts lie in the same plane, as, according to Peters and 
 Kipping (J. C. S. 1902, 1350), stereo-isomerides of the form 
 RR'I X do not appear to exist, and no resolution into optically 
 active components can be effected. 
 
 XX. NITRO-SUBSTITUTION PKODUCTS OF THE 
 AROMATIC HYDROCARBONS 
 
 When benzene and its derivatives are treated with concen- 
 ;rated nitric acid, most of them are easily dissolved, with evo- 
 ution of heat, and transformed into mtro-compounds which 
 re precipitated on the addition of water. According to the 
 onditions of the experiment and the nature of the compound 
 ;o be nitrated, one or more nitro-groups enter the molecule 
 see, e.g., phenol). The nitro-groups substitute in the nucleus, 
 nd only very seldom in the side chain (cf. p. 363). 
 
 Very often fuming nitric acid or a mixture of fuming nitric 
 nd concentrated sulphuric (or fuming sulphuric) acid is used. 
 
360 XX. AROMATIC NITRO-COMPOUNDS 
 
 The advantage of the addition of sulphuric acid is to absorb 
 the water formed during nitration, and thus to keep the nitric 
 acid from becoming too dilute. The stronger the acid and 
 the higher the temperature, the larger the number of nitro- 
 groups introduced. The homologues of benzene are, as a rule, 
 nitrated more readily than benzene itself. 
 
 SUMMARY 
 
 CH^NO> 
 
 Nitro-benzene . . 
 
 Positions of 
 Substituents. 
 
 M.-p. 
 
 +3 
 
 B.-p. 
 908 
 
 Sp. 
 gr. 
 1.204 
 
 C fl H 4 (N0 2 ) 2 . .. 
 
 o-Dinitro-benzene.... 
 
 1:2 
 
 117 
 
 319 
 
 
 C 6 H 8 (N0 2 ) 8 
 CHs-CeH^NO.,... 
 
 m-Dinitro-benzene ... 
 2>-Dinitro-benzene ... . 
 s-Trinitro-benzene . . . 
 os-Trinitro-benzene . 
 o-Nitro- toluene 
 wi-Nitro-toluene . 
 
 1:3 
 1:4 
 1:3:5 
 1:2:4 
 *1:2 
 1:3 
 
 90 
 172 
 122 
 57-5 
 -10-5 
 + 16 
 
 302 
 299 
 
 t 
 
 218 
 ?30 
 
 1-168 
 1-168 
 
 
 ^?-Nitro-toluene 
 
 1:4 
 
 51 
 
 934 
 
 f 1-123 
 
 CH8.C 6 H V (N0 2 ) 2 
 (CH 8 )2 C 6 H 8 N0 2 
 
 2:4-Dinitro-toluene . . . 
 2:6-Dinitro-toluene . . . 
 4-Nitro-xylene . . . 
 
 . 1:2:4 
 . 1:2:6 
 . 1:3:4 
 
 70 
 66 
 
 +2 
 
 t 
 946 
 
 \ (54) 
 1 -135 
 
 (CH^CJL.NO,.. 
 
 Nitro-mesitvlene. . . , 
 
 . 1:3:5:2 
 
 44 
 
 255 
 
 
 Nitro-compounds are also produced by the action of nitrous 
 acid upon diazonium compounds in the presence of cuprous 
 oxide (Sandmeyer, B. 20, 1494): 
 
 C 6 H 6 NC1:N + HN0 2 = C 6 H fi .N0 2 + HC1 + N 2 , 
 
 and also by the oxidation of primary aromatic amines : 
 C 6 H 5 .NH 2 C C H 6 .N0 2 
 
 (Bamberger, B. 1893, 26, 496). These reactions, however, are 
 mainly of theoretical interest. 
 
 They cannot, however, be prepared according to mode of 
 formation 1 for nitro-methane (p. 94), i.e. by the action of 
 AgN0 2 on C 6 H 5 C1, &c. 
 
 The nitro-compounds are, for the most part, pale-yellow 
 liquids which distil unchanged and volatilize with water 
 vapour; some form colourless or pale-yellow crystals; some- 
 times they are also of an intense yellow or red colour. Many 
 
 * The positions of CH 3 group, or groups, are always given first. 
 t Most of the polynitro-compounds are not volatile, but decompose 
 when heated. 
 
#ALOir> NITRO-COMPOUNDS 361 
 
 of them explode when heated. They are heavier than water, 
 and insoluble in it; but most of them are readily soluble in 
 alcohol, ether, and glacial acetic acid. 
 
 The nitro-group in most aromatic nitro-compounds is bound 
 very firmly, as in the case of the nitre-methanes, and is not 
 exchangeable for other groups. Like the latter compounds 
 also, they are readily reduced in acid solution to the corre- 
 sponding amines; in alkaline solution they are converted into 
 azoxy-, azo-, and hydrazo- compounds (see these), and in 
 neutral solution into hydroxylamine derivatives. 
 
 When reduced electrolytically, nitro -benzene can yield 
 either phenyl-hydroxylamine, C 6 H 5 NH-OH, which is imme- 
 diately transformed into p-amino- phenol, OHC 6 H 4 NH 2 
 (Gattermann, B. 1893, 26, 1814; 1894, 27, 1927), or it can 
 yield aniline. Other nitro-compounds can be reduced in a 
 similar manner. When hydrogen is passed into an alcoholic 
 solution of nitro-benzene containing colloidal palladium, aniline 
 is formed. 
 
 Nitro-benzene, C 6 H 5 (N0 2 ) (Mitscherlich, 1834), is formed 
 when a mixture of sulphuric and the calculated quantity of 
 nitric acid is added to benzene. It is a yellowish liquid with 
 an intense odour of oil of bitter almonds, which solidifies in 
 the cold, and melts at +5. 
 
 Dinitro-benzenes, C 6 H 4 (N0 2 ) 2 are produced when benzene 
 is boiled with fuming nitric acid; in this, as in all analogous 
 cases, the two nitro groups take up the meta-position to one 
 another, very little of the o- and ^-compounds being formed, 
 and after crystallizing from alcohol, pure m-dinitro-benzene is 
 obtained in long colourless needles. 
 
 The 0-compound crystallizes in plates and the ^-compound 
 in needles, both being colourless; they are prepared indirectly 
 by eliminating NH 2 from the corresponding di-nitranilines. 
 
 When reduced, they yield first the three nitranilines, and 
 then the phenylene-diamines (pp. 374 and 380). 
 
 o-Dinitro-benzene exchanges a nitro-group for hydroxyl when 
 boiled with caustic soda, and for an amino-group when acted 
 on by ammonia, yielding o-nitro-phenol, C 6 H 4 (N0 2 )(OH), and 
 0-nitraniline, C 6 H 4 (N0 2 )(NH 2 ), respectively. These reactions 
 appear to be characteristic of all compounds containing two 
 nitro-groups in ortho-positions. The ?w-compound is oxidiz- 
 able by K 3 FeC 6 N 6 to a- and /3-dinitro-phenol. 
 
 s-Trinitro-benzene crystallizes in colourless plates, melts at 
 122, and forms additive compounds with aromatic hydro- 
 
362 XX. AROMATIC NITRO-COMPOUNDS 
 
 carbons, phenols, and especially with aromatic bases, e.g. ani- 
 line, naphthylamine. Most of these are well-defined crystal- 
 line compounds of red, reddish-brown, or black colour, and are 
 readily resolved into their components by warm mineral acids 
 (A. 1882, 215, 344; J. C. S. 1901, 522; 1903, 1334; 1906, 
 583; 1910, 773). 
 
 Nitro-toluen.es, CH 3 C 6 H 4 N0 2 . When toluene is nitrated, 
 the p- and 0-compounds, with very little wi-compound, are 
 formed. The first is solid, crystallizing in large prisms, and 
 the second liquid, the latter being used as a perfume under 
 the name of " oil of mirbane"; both are employed in the colour 
 industry. m-Nitro- toluene can be prepared indirectly from 
 m-nitro-^-toluidine, C 6 H 3 (CH 3 )(NO 2 )(NH 2 ), by the elimination 
 of the ammo-group (p. 387). Further nitration gives rise to: 
 
 Dinitro- toluenes, CH 3 C 6 H 3 (N0 2 ) 2 , of the constitution 
 OH 3 :N0 2 :N0 2 = 1:2:4 and 1:2:6, the two nitro-groups 
 being again in the m-position to one another in both cases. 
 (Cf. p. 361.) 
 
 Most of these nitro-compounds are of great technical im- 
 portance, on account of the readiness with which they are 
 reduced to amines. 
 
 Trinitro-tertiary-butyl-toluene, C 6 H(CH 3 )[C(CH 3 ) 3 ](N0 2 ) 3 , 
 is used as "artificial musk". 
 
 Chloro- and Bromo-nitro-benzenes, When chloro- or bromo- 
 benzene is nitrated, ^-chloro- (or bromo-) nitro-benzene is 
 formed, together with smaller quantities of the o-compounds. 
 The ra-compounds "must be prepared indirectly by replacing 
 an amino-group in m-nitraniline by halogen. The ^-deriva- 
 tives have a higher melting-point than their isomers, and the 
 m-compounds for the most part a higher one than the 0-deri- 
 vatives, this law frequently repeating itself in other cases also. 
 The p-derivatives are usually also less soluble in alcohol. The 
 o- and ^-compounds, but not the w-, exchange halogen for 
 hydroxyl when boiled with potash, and for the amino-group 
 when heated with ammonia. 
 
 In s-trinitro-chloro-benzene, C 6 H 2 (N0 2 ) 3 C1, and in 1-chloro- 
 2 : 4-dinitro-benzene the chlorine atoms have been rendered so 
 readily exchangeable, that the compounds behave as alkyl 
 chlorides, or even as acid chlorides; hence the name "picryl 
 chloride", the chloride of picric acid (p. 414), for the former 
 compound. 
 
 0-, m- y and ^-Nitro-cinnamenes, C0H 4 (N0 2 )(C 2 H 3 ), can be 
 prepared by indirect methods. a-Nitro-styrene, C 6 H 6 -CH; 
 
PHENYL-NITRO-METHANE 363 
 
 CH'N0 2 , which is formed by the action of nitrous acid on 
 cinnamene, contains the nitro-group in the side chain, since it 
 can be prepared from benzoic aldehyde and nitro-methane by 
 means of zinc chloride, thus: 
 
 C 6 H 6 CHO + CH 3 NO 2 = C 6 H 6 . CH : CH . NO 2 + H 2 O. 
 
 o-Nitro-phenyl- acetylene, N0 2 C 6 H 4 C CH, is formed 
 when o-nitro-phenyl-propiolic acid is boiled with water. It 
 crystallizes in colourless needles. 
 
 Phenyl-nitro-methane, C 6 H 5 CH 2 N0 2 , isomeric with the 
 nitro-toluenes, is the most typical of the aromatic nitro-deriva- 
 tives with a nitro-group in the side chain. It is formed by the 
 action of nitric acid (D 1-12) on toluene under pressure, and 
 also by the action of benzyl halides on silver nitrite (cf. Nitro- 
 methane). It is a true nitro-derivative, and not an alkyl 
 nitrite (benzyl nitrite, C 6 H B .CH 2 .O.N:0), as it is not readily 
 hydrolysed, and when reduced yields benzylamine, C 6 H 5 
 CH 2 -NH 2 . It exists in two distinct modifications, which are 
 readily transformed into each other. As generally prepared, 
 it is a colourless liquid with a characteristic odour, boils at 
 225-227, and dissolves to a certain extent in water, yielding 
 a solution which does not give a coloration with ferric chloride. 
 The second modification, which is a crystalline solid melting 
 at 84, is formed when the sodium derivative obtained from 
 the oily compound is decomposed in the cold by hydrochloric 
 acid. The solid modification is relatively unstable, and when 
 kept, gradually passes over into the oily form. The solid is 
 probably a hydroxy-compound, since (a) its aqueous solution 
 gives a red-brown coloration with ferric chloride, (b) it reacts 
 with phenyl-carbimide, (c) it reacts with PC1 5 , and (d) with 
 benzoyl chloride it gives dibenzhydroxamic acid, 
 
 C 6 H 6 .CO.NH.O.COC 6 H 5 (from 
 
 The solid would thus be represented by the formula: 
 C 6 H 6 .CH:NO-OH or perhaps C 6 H 5 .CH-N.OH, 
 
 O 
 
 -an &09ulr0-fonnula, the sodium salt by C 6 H 5 CH:NO'ONa, 
 and the oil by C 6 H 5 -CH 2 -N0 2 . The tendency to form iso- 
 nitro-compounds is also shown by certain aliphatic nitre-com- 
 pounds. 
 
364 XX. AROMATIC NITRO-COMPOUND8 
 
 The oily compound, although it gives rise to a sodium salt, 
 is, strictly speaking, not an acid ; it is what is termed a pseudo- 
 acid, and before it yields a sodium salt it undergoes intra- 
 molecular rearrangement, yielding the true acid the isomtro- 
 compound. When the sodium salt is treated with a mineral 
 acid, the fsonitro-compound, or true acid, is first formed; but 
 as this is unstable, it gradually changes over into the true 
 nitro- or pseudo-acid form. Numerous examples of pseudo- 
 acids, i.e. compounds which on formation of metallic salts 
 undergo intramolecular rearrangement so that the original 
 substance has a structure different from that of the salt, have 
 been investigated by Hantzsch (B. 1899, 32, 575; 1902, 35, 210, 
 226, 1001; 1906, 39, 139, 1073, &c.), who describes the following 
 as some of the most characteristic criteria of pseudo-acids: 
 
 1. The compound is a pseudo-acid if it gradually neutralizes 
 an alkali. The pseudo-acid, as such, does not neutralize the 
 base, but is first transformed into the isomeric true acid, 
 which then neutralizes the alkali. If the transformation is 
 slow, then the process of neutralization is also slow. Similarly, 
 if when a solution of a salt of the acid is decomposed by an 
 equivalent quantity of a mineral acid, the electrical conductivity 
 gradually falls to that required for the metallic salt of the 
 mineral acid, it indicates that the acid is a pseudo-acid, e.g. 
 barium esonitro-methane +HC1 give isonitro-methane +BaCl 2 , 
 and then nitro-methane -f-BaCl 2 . Isonitro-methane is a fairly 
 strong acid, and hence is dissociated to an appreciable extent; 
 as it becomes transformed into nitro-methane (the pseudo- 
 acid) the conductivity will diminish, as nitro-methane is an 
 extremely feeble acid scarcely ionized. 
 
 2. If the original compound is extremely feebly acidic, and 
 yet yields a sodium derivative which dissolves in water yield- 
 ing a practically neutral solution, then the compound must be 
 a pseudo-acid. It is a well-known fact that only sodium salts 
 derived from comparatively strong acids, e.g. NaCl, Na 2 S0 4 , 
 Nal, &c., dissolve in water to neutral solutions, i.e. are not 
 hydrolysed by water. The sodium salts derived from feeble 
 acids are always appreciably hydrolysed, e.g. Na 2 C0 8 , CH 3 
 COONa, &c. Hence if the sodium salt is not hydrolysed to 
 an appreciable extent, the salt must be derived from a strong 
 acid (the true acid), and the non- or feebly acidic compound 
 must be the pseudo-acid. 
 
 3. If the compound in question will not yield a salt with 
 ammonia in an anhydrous solvent, e.g. dry benzene, but will 
 
NITROSO-DERIVATIVES 365 
 
 do so in the presence of water, e.g. in moist ether, then the 
 substance is a pseudo-acid. The formation of a salt in dry 
 ether does not necessarily indicate that the substance is a 
 true acid. 
 
 4. If the compound dissolves in water or in other dissociating 
 (ionizing) media to a colourless solution, but yields a coloured 
 solid salt or coloured ions when dissolved in alkalis, it is a 
 pseudo-acid. 
 
 5. An abnormally high temperature coefficient for the elec- 
 trical conductivity and an increase in the coefficient with rise 
 of temperature are further indications of pseudo-acids. 
 
 Nitro- methane, bromo-nitro-methane, dibromo-nitro-meth- 
 ane, nitro-ethane, phenyl-nitro-methane, phenyl-bromo-nitro- 
 methane, in addition to numerous other organic compounds, 
 e.g. cyanuric acid, react as pseudo-acids. 
 
 NITROSO-DERIVATIVES OF THE HYDROCARBONS 
 
 Nitroso-benzene, C 6 H 5 .N:0, an aromatic compound which 
 contains the nitroso-group, N:0, in place of a benzene hy- 
 drogen atom, is produced by the action of nitrosyl chloride, 
 NO'Cl, upon mercury diphenyl dissolved in benzene; it is 
 also obtained by the oxidation of diazo-benzene with alkaline 
 permanganate, and most readily by the oxidation of phenyl- 
 hydroxylamine with chromic acid or ferric chloride. It forms 
 colourless plates, melts at 68, yields green solutions, and pos- 
 sesses a powerful odour similar to that of cyanic acid. When 
 reduced it yields aniline, and when oxidized nitro-benzene. 
 It readily condenses with different compounds, e.g. with ani- 
 line in the presence of acetic acid to azo-benzene: 
 
 C C H 5 .N:0 + H 2 N.C 6 H 6 = H 2 O + C 6 H 5 .N:N.C 6 H fi) 
 
 and with phenyl-hydroxylamine to azoxy-benzene. 
 
 Nitroso-derivatives of tertiary amines are obtained directly 
 by the action of nitrous acid upon the latter. (See Nitroso- 
 dimethyl-aniline, NQ.C 6 H 4 .N(CH 3 ) 2 , p. 378.) 
 
366 XXI. ARYLAMINKS 
 
 XXL AMINO-DERIVATIVES OR ARYLAMINES* 
 
 (See Table, p. 367.) 
 
 Aniline, the simplest of the aromatic bases, may be regarded 
 (1) as benzene in which a hydrogen atom is replaced by the 
 amino-group ("amino-benzene"), or (2) as ammonia in which 
 a hydrogen atom is replaced by phenyl, C 6 H 5 , ("phenyl- 
 amine"). According to the former view, ammo-compounds 
 can be derived from all the benzene hydrocarbons, and not 
 only monamines (containing NH 2 ), but also diamines (2NH 2 ), 
 triamines, &c.; according to the latter, the phenyl group 
 may enter anew with the formation of secondary or tertiary 
 amines. Secondary and tertiary amines, and even quaternary 
 ammonium compounds, may also result from the entrance of 
 alky 1- radicals into the above monamines, diamines, &c. 
 Amines are also known in which the NH 2 group is attached 
 to a carbon atom of a side chain, e.g. C 6 H 5 CH 2 NH 2 . These 
 compounds differ in many respects from aniline and its homo- 
 logues. 
 
 An extraordinarily large number of aromatic bases are thus 
 theoretically possible, and also actually known. In certain 
 respects they closely resemble the aliphatic amines, e.g. they 
 form salts with acids, e.g. (XH 5 NH 2 , HC1, and complex salts, 
 e.g. platinichlorides and auricnlorides, 2C 6 H 5 NH 2 , H 2 PtCl 6 and 
 C 6 H 6 NH 2 , HAu01 4 ; they possess a basic odour, give rise to 
 white clouds with volatile acids, and distil for the most part 
 unchanged, &c. As a rule, however, they are weaker bases 
 than the aliphatic amines, since the phenyl group, C 6 H 5 , pos- 
 sesses a negative character, and not like the alphyl radicals 
 a positive; thus the salts of diphenylamine are decomposed 
 even by water, and triphenylamine no longer possesses basic 
 properties, while dimethyl-aniline has a strongly-marked basic 
 character. 
 
 * To distinguish between monovalent alcoholic or hydrocarbon radicals 
 of the fatty and aromatic series the following system has been suggested : 
 The term alkyl group comprises all such monovalent radicals whether of 
 the aliphatic series, e.g. CH 8 , C 2 H 5 , or of the aromatic, e.g. CH fc CH s .C 6 Ht, 
 C 6 H 5 'CHo, &c. The purely aliphatic alkyl radicals are termed alphyl 
 groups, and the aromatic, aryl ( Vorlander, J. pr. [2], 69, 247). Thus anil/ ue 
 is often spoken of as a type of the arylamines. 
 
PRIMARY MONAMINES 
 
 367 
 
 The diamines have a more strongly basic character than the 
 monamines, and are more readily soluble in water. 
 
 ANILINE AND ITS HOMOLOGUES 
 
 Formula. 
 C fl H,.NH 9 .. 
 
 Name. 1 
 
 Positions of 
 iubstituents 
 NH 2 in 1. 
 
 M.-p. B.-p. 
 
 8 183 
 
 M.-p. of 
 Acetyl 
 Derivative. 
 
 115 
 
 CJELMe-NH,.. 
 
 o-Toluidine 
 
 1-2 
 
 liq 199 
 
 110 
 
 
 
 1:3 
 
 liq. 199 
 
 65'5 
 
 
 #-Toluidine ... 
 
 1:4 
 
 42 '8 198 
 
 153 
 
 C 6 H 3 Me 2 -NH 2 .. 
 
 ac?/.-0-xylidene .... 
 wnsywi.-o-xylidene 
 ac^'.-m-xylidene. . . 
 -xylidene 
 
 1:2:3 
 1:3:4 
 1:2:6 
 1:2:5 
 
 liq. 223 
 49 226 
 liq. 215 
 15'5 215 
 
 134 
 99 
 176 
 139 
 
 C 6 H 2 Me 3 NH 2 . 
 
 Mesidine 
 
 1-2-4-6 
 
 liq 233 
 
 216 
 
 C 6 H 6 -NHMe... 
 C 6 H 6 .NMe 2 
 
 Pseudo-cumidine . 
 
 Methyl-aniline.... 
 Dimethyl-aniline . 
 
 1:2:4:5 
 
 68 234 
 
 ... 192 
 ... 192 
 ... 204 
 
 164 
 101-102 
 
 54'5 
 
 (lld-NEt, 
 
 Diethyl-aniline . . 
 
 
 213 
 
 
 
 
 
 183 
 
 60 
 
 A. Primary Monamines 
 
 Isomers. The isomerism of the aromatic is in part analogous 
 to that of the fatty amines (p. 107), e.g. dimethyl-aniline is 
 isomeric with the methyl-toluidines and the xylidines. Cases 
 of isomerism are also caused by the amino-group being present 
 in the benzene nucleus in the one case, and in the side chain 
 in the other. Finally, position isomerides are frequently met 
 with, e.g. 0-, m-, and ^-toluidines, CH 3 C 6 H 4 NH 2 . 
 
 Constitution. As already seen at pp. 108 et seq., amines are 
 very easy to characterize as primary, secondary, &c. In 
 addition, their modes of formation, and also their behaviour, 
 show whether the amino-group of a primary amine is present 
 in the benzene nucleus or in the side chain. 
 
 Modes of Formation. 1. The most important mode of pre- 
 paration of the primary arylamines, whether mono- or di-, &c., 
 is the reduction of the corresponding nitro-compounds : 
 
 C 6 H 6 .N0 2 
 
 Nitro-benzene 
 
 C 6 H 4 (N0 2 ) 2 H 
 Diuitro-benzene 
 
 Aniline. 
 
 4H 2 + C 6 H 4 (NH 2 ) 2 
 
 Phenylene-diamine. 
 
368 XXI. ARYLAMINES 
 
 The usual method of introducing an ammo-group into a 
 benzene hydrocarbon is to first nitrate and then reduce. An 
 interesting direct method for the introduction of the NH 
 group is by the action of ferric or aluminic chloride on a 
 mixture of the hydrocarbon and hydroxylamine hydrochloride 
 (B. 1901, 34, 1778): 
 
 NH.OH = 
 
 The reduction of nitro- to amino-compounds takes place 
 most readily in acid solution, e.g. by the gradual addition of 
 the former to a warm mixture of tin or stannous chloride 
 and hydrochloric acid. On a manufacturing scale, iron and a 
 limited amount of hydrochloric acid are used (Be~champ\ also 
 frequently zinc dust and hydrochloric or acetic acid. Am- 
 monium sulphide (Zinin), ferrous sulphate, and baryta water, 
 &c., also effect the reduction. (See Aniline and chapter on 
 Eeduction.) 
 
 Aniline and its homologues may also be obtained by the 
 electrolytic reduction of nitro-compounds. 
 
 Ammonium sulphide acts more mildly than tin and hydro- 
 chloric acid, and is therefore of special value for the partial 
 reduction of dinitro-compounds (see Nitraniline). An alcoholic 
 solution of stannous chloride containing hydrochloric acid may 
 also be used for this purpose (B. 19, 2161). 
 
 Amines are also formed when nitroso-compounds and aryl- 
 hydroxylamines are reduced. 
 
 2. By heating phenols with the compound of zinc chloride 
 and ammonia, or of calcium chloride and ammonia, to 300 
 (Merz), secondary amines being formed at the same time: 
 
 C 6 H 6 .iOH"+H;NH 2 = 
 
 This reaction proceeds more easily in the presence of nega- 
 tive groups, e.g. with the mtro-phenols (B. 19, 1749). 
 
 3. By distilling amino-acids with lime, sometimes by merely 
 heating them alone : 
 
 NH 2 .C 6 H 4 .C0 2 H = C 6 H 6 .NH 2 -hC0 2 . 
 
 4. When the hydrochlorides of secondary and tertiary 
 amines of the type of mono- and di-methyl-aniline are heated 
 in sealed tubes, the methyl groups wander from the nitrogen 
 atom to a carbon atom of the benzene nucleus, e.g. methyl- 
 aniline hydrochloride at 335 yields toluidine hydrochloride: 
 
 C fl H 6 .NHCH 3 ,HCl ^ CH 3 .C C H 4 .NH 2 ,HCL 
 
PROPERTIES OF PRIMARY ARYLAMINES 369 
 
 The methyl groups invariably take up the o- or p-, and not 
 the m- position, with respect to the amino-group. Q 
 
 Similarly, the final product obtained by heating phenyl- 
 trimethylammonium iodide, C 6 H 5 'NMe 3 I, is mesidine hy- 
 driodide, C fl H 2 Me 8 NH 2 [NH 2 : Me 3 = 1 : 2 : 4 : 6*J. ftiphenyl- 
 amine hydrochloride does not behave in a similar manner. 
 
 This reaction, often known as the Hofmann reaction, is of 
 considerable service in obtaining the higher homologues of 
 aniline from aniline, toluidine, &c. Aniline is readily con- 
 verted into dimethyl-aniline, and when the hydrochloride of 
 this is heated to about 300 the methyl groups wander from 
 the side chain into the nucleus: 
 
 C 6 H 6 .NMe 2 C G H 3 Me 2 .NH2. 
 
 5. Primary amines can be obtained from acid amides by 
 Hofmann' s reaction (cf. p. 183), viz. treatment with bromine 
 and alkali, or from acid azides, K-CO'N 3 . When boiled with 
 alcohol the azide yields nitrogen and, by molecular rearrange- 
 ment, a urethane, RNH'COOEt, and this on hydrolysis 
 gives a primary amine, RNH 2 . 
 
 6. The aromatic amines cannot, as a rule, be obtained by 
 heating chloro-benzene, &c., with ammonia unless there is a 
 nitro-group in the ortho- (or para-) position with respect to 
 the halogen. Benzylamine, however, and all analogously 
 constituted bases, which contain the NH 2 group in the side 
 chain, can be obtained by the methods employed for the pre- 
 paration of aliphatic amines. Thus benzylamine is formed by 
 the action of ammonia, or better, of acetamide upon benzyl 
 chloride (the latter method gives acetyl-benzylamine, which 
 can be readily hydrolysed). 
 
 Properties. The primary monamines are either liquid or 
 solid crystalline bases. They are colourless when pure, but 
 readily become brown when exposed to the air, largely 
 owing to the presence of small amounts of impurities, and 
 possess a weakly basic though not disagreeable odour. Ani- 
 line is somewhat soluble in water (1:31), its homologues 
 less so. 
 
 Behaviour. 1. With acids most of them form crystalline 
 salts, the majority of which are readily soluble in water. 
 They do not, however, unite with very weak acids, such as 
 
 * The numbers 1:2:4:6 indicate the relative positions of the amino- and 
 three methyl -radicals in the benzene ring. 
 
 (B480) ?A 
 
370 XXI. ARYLAMINES 
 
 carbonic, and they are therefore separated from their salts in 
 the free state by sodium carbonate, and in some cases even by 
 sodium acetate (when no acetates exist). They yield com- 
 plex salts, such as platinichlorides, (C 6 H 5 NH 2 ) 2 , H 2 PtCl 6 , ami- 
 chlorides, C 6 H 5 NH 2 , HAuCl 4 , ami similar compounds with stan- 
 nous, stannic, and zinc chlorides. The platinum double salts 
 are often sparingly soluble, and therefore suited for the isolation 
 of the bases. 
 
 All salts of the bases are readily decomposed by strong 
 alkalis, and the free bases are regenerated. Even in aqueous 
 solution the salts are largely split up into free acid and free 
 base; the result is that the strength of a solution of aniline 
 hydrochloride may be determined by titrating the hydrochloric 
 acid present by standard alkali hydroxide, using phenol- 
 phthalein as indicator. This is not due to the fact that the 
 salt is completely hydrolysed in aqueous solution; in reality 
 there is a state of equilibrium represented by the equation: 
 C 6 H 6 .NH 3 C1 ^ C 6 H 6 NH 2 + HC1, 
 
 and as the HC1 is neutralized by the addition of alkali, more 
 of the aniline salt is decomposed in order to restore the equi- 
 librium. This continues until the whole of the salt is decom- 
 posed, and the HC1 neutralized by the alkali. 
 
 The amines also form additive compounds with numerous 
 metallic salts, e.g. 2C 6 H 7 N + ZnCl 2 , 2C 6 H 7 N + HgCl 2 , &c. 
 
 2. When aniline is heated with potassium or sodium, the hy- 
 drogen is replaced by metal with formation of the compounds 
 CgH 5 NHK and C 6 H 5 NK 2 . These yield di- and tri-phenylamine 
 with bromobenzene, and decompose immediately with water. 
 
 3. The primary arylamines react with methyl iodide, benzyl 
 chloride, &c., yielding secondary, tertiary, and even quaternary 
 compounds : 
 
 = C 6 H 5 .NH(CH 3 ),HI; 
 
 C 6 H 5 .NH(CH 3 ) + CH 3 I = QgHs-NC 
 C 6 H 6 .N(CH 3 ) 2 + CH 3 I = C 6 H 5 .N(CH 3 ) 3 I. 
 
 The secondary and tertiary bases can be liberated from their 
 hydriodides by soda, but moist oxide of silver must be used in 
 the case of the ammonium bases (see p. 109). 
 
 4. Just as the ammonium salts of acids can eliminate water, 
 yielding amides, so the aniline salts can yield anilides, e.g. 
 aniline acetate gives acetanilide: 
 
 CH 3 .CO-ONH 3 C 6 H 6 = CH 3 .CO-NHC 6 H 6 -fH a O. 
 
ANILIDES. ISONITRILES 371 
 
 These anilides may be looked upon either as acetylated 
 amines or as phenylated amides, the formula CH 3 CO- 
 NHC 6 H 5 corresponding with the latter view. They are in 
 every respect analogous in their chemical behaviour to the 
 ordinary amides, especially to the alkylated amides (p. 182), 
 being hydrolysed to the acid and aniline by alkalis, and being 
 formed by analogous methods, e.g. by heating the acid, or 
 better, its anhydride or chloride, with the amine in question, 
 thus : 
 
 CH 3 C 6 H 4 NH 2 + CH 3 COC1 = CH 3 C 6 H 4 . NH CO CH 3 + HC1. 
 
 Toluidiue Acet-toluidide 
 
 5. Aliphatic aldehydes react with the primary bases, with 
 elimination of water, thus: 
 
 CH 3 .CHO-f 2C 6 H 6 .NH 2 = CH 3 .CH(NH.C 6 H 5 ) 2 -f H 2 O. 
 
 Ethylidene-diphenyl-diamine 
 
 Aromatic aldehydes, however, react as follows : 
 C 6 H 5 CHO + NH 2 C 6 H 6 = C 6 H 6 . CH : N C 6 H 6 + H 2 0. 
 
 In this case an additive compound appears to be first formed, 
 C 6 H 5 .CH(OH).NH-C 6 H 5 , and this loses water, yielding ben- 
 zylidene aniline, C 6 H 5 CH : N C 6 H 5 . 
 
 Condensation products of this latter kind (Schiff's bases) 
 can also be obtained with the fatty aldehydes, but they poly- 
 merize readily (v. Miller, Plochl, B. 25, 2020). 
 
 6. When warmed with chloroform and alcoholic potash, the 
 primary bases, like those of the fatty series, yield isonitriles 
 of stupefying odour. When they are warmed with carbon 
 disulphide, thio-ureas are formed, and from the latter isothio- 
 cyanates (mustard oils) by treatment with phosphoric acid (cf. 
 pp. 276 and 296). 
 
 7. Bromine and chlorine, especially in the form of sodium 
 hypochlorite or hypobromite, react with amines, forming sub- 
 stituted derivatives of the type C 6 H 5 -NHBr, in which the 
 halogen is attached to nitrogen. These compounds are ex- 
 tremely unstable, can only be kept at low temperatures, and 
 the halogen atom readily passes from the side chain into the 
 benzene nucleus: 
 
 C fl H 6 .NHBr 
 
 usually into the para-position (Chattaway and Orton, J. C. S. 
 1899, 1046; 1900, 134, 152, 789, 797). 
 
372 XXI. AR FAMINES 
 
 8. Nitrous acid converts the primary aromatic amines in 
 acid solution into diazonium salts (p. 385), and in the absence 
 of acids into diazo-amino-compounds (p. 392). 
 
 9. The oxidation products of the primary bases are very 
 various, azo-benzene, nitro-benzene, ^-amino-phenol, phenols, 
 quinones, azo-compounds, aniline black, &c., resulting accord- 
 ing to the conditions; a mixture of aniline and toluidine yields 
 magenta (fuchsine) (see Triphenylmethane dyes). 
 
 10. The bases which contain the amino-group in the side 
 chain possess, in contradistinction to the purely aromatic 
 amines, the character of the amines of the fatty series, and 
 cannot, therefore, be diazotized. 
 
 Aniline, ammo-benzene, Phenylamine, C 6 H 5 NH 2 , was first 
 obtained in 1826 by Unverdorben from the dry distillation of 
 indigo, and termed by him "crystalline"; then Eunge found 
 it in coal-tar in 1834, and called it "cyanol". In 1841 
 Fritsche prepared it by distilling indigo with potash, and gave 
 it the name of aniline; while in 1842 Zinin obtained it by the 
 reduction of nitro-benzene, and called it " benzidam ". It was 
 accurately investigated by A. W. Hofmann in 1843, and he 
 was able to show that all the above products are identical. 
 
 It is present in small quantities in coal-tar and also in bone- 
 oil. 
 
 Preparation. Since 1864 aniline has been prepared on a 
 manufacturing scale by reducing nitro-benzene with iron 
 filings and a regulated quantity of hydrochloric acid, and 
 distilling with steam after the addition of lime. The amount 
 of hydrochloric acid actually employed is only about j^th of 
 that required by the equation: 
 
 = C 6 H 6 -NH 2 + 2H 2 + 3FeCl 2 . 
 
 This is probably due to the fact that water and metallic iron, 
 in the presence of ferrous chloride, can act as reducing agents. 
 It is a colourless, oily, strongly refracting liquid of peculiar 
 odour, which quickly turns yellow or brown in the air, and is 
 finally converted into a resin. It dissolves in 31 parts of 
 water, has no action upon litmus, and is a weaker base than 
 ammonia, although it can displace the latter at higher tem- 
 peratures. It is poisonous, burns with a smoky flame, and is 
 a good solvent for many compounds which are otherwise not 
 readily dissolved, e.g. indigo and sulphur. Aqueous solutions 
 of the salts have a distinct acid reaction. 
 
 The behaviour of aniline has been investigated with the 
 
ANILINE 373 
 
 utmost care. Oxidation in alkaline solution leads to azo- 
 benzene, while arsenic acid produces chiefly violaniline, a 
 violet colouring-matter. A solution of free aniline is tem- 
 porarily coloured violet by one of bleaching- powder, this 
 reaction being an extremely delicate one. A solution in con- 
 centrated H 2 S0 4 is first coloured red and then blue by a small 
 grain of potassium dichromate. A solution of K 2 O 2 7 pro- 
 duces in an acid solution of aniline sulphate a dark-green and 
 then a black precipitate of aniline black (Willstdtter, B. 1907, 
 40, 2665; 1910, 43, 2976; Green, J. C. S. 1910, 2388; B. 1911, 
 44, 2570), and ultimately quinone, C 6 H 4 2 . A mixture of 
 aniline and toluidine may be oxidized to magenta, mauveine, 
 &c., and a mixture of aniline and j9-diamines to safranines (see 
 these). When reduced, aniline yields amino-hexamethylene, 
 boiling at 134. 
 
 Salts. Aniline hydrochloride, C 6 H 5 *NH 2 , HC1, forms large 
 colourless plates which become greenish-grey in the air and 
 distil unchanged, and aniline sulphate, (C 6 H 7 N) 2 , H 2 S0 4 , beau- 
 tiful white plates, sparingly soluble in water. The platini- 
 chloride, (C 6 H 7 N) 2 , H 2 PtCl 6 , crystallizes in yellow plates, which 
 are sparingly soluble. 
 
 Substitution Products Halogen 'Derivatives. Aniline is much 
 more readily substituted by halogens than benzene, chlorine 
 or bromine causing substitution of as many as three atoms 
 of hydrogen, yielding s?/w-trichlor- or -tribrom-aniline, while 
 iodine produces mono-iodoaniline. In the chlorination of ani- 
 line it is necessary to use a solvent free from water (e.g. 
 chloroform or glacial acetic acid), otherwise oxidation and not 
 substitution occurs. In bromination the simplest method is to 
 aspirate air saturated with bromine vapour through an acid solu- 
 tion of aniline. In all these reactions the halogen probably 
 first substitutes H of the NH 2 group (see p. 371). In the 
 preparation of monochlor-aniline, the aniline must be "pro- 
 tected" by using it in the form of its acetyl derivative, 
 acetanilide. When this is suspended in water, it is mostly 
 transformed by chlorine into p - chlor - acetanilide, which 
 readily yields p-chlor-aniline on hydrolysis ; the latter forms 
 colourless crystals, m.-pt. 71, b.-pt. 231. The o- and m-com- 
 pounds, which are both liquid, are prepared indirectly, e.g. by 
 the reduction of o- or m-chloro-nitro-benzene. 
 
 The basic character is weakened in the mono-chlor-anilines 
 by the entrance of the halogen, this being the case particularly 
 in the 0-compounds. It is still more striking in s-tri chlor- 
 
374 XXI. ARYLAMINJCS 
 
 aniline, C 6 H 2 C1 3 (NH 2 ) (crystals, volatile without decomposi- 
 tion), which no longer combines with acids in presence of 
 water, o- and ^-Chlor-anilines are only capable of taking up 
 two more atoms of chlorine with the formation of trichlor- 
 aniline: [NH 2 : Cl : Cl : Cl = 1.2.4.6]; ra-chlor-aniline, on the 
 other hand, can be further chlorinated to tetra- and penta- 
 chlor-aniline. 
 
 The bromo-derivatives of aniline closely resemble the chlor- 
 anilines, and may be prepared by similar methods. The best- 
 known compound is s-tribrom-aniline, which is formed by the 
 action of bromine water on a solution of aniline hydrochloride. 
 It crystallizes from alcohol in needles, and melts at 119. 
 
 As an example of the methods sometimes employed for the 
 preparation of halogen derivatives may be cited the prepara- 
 tion of 2 : 6-dibrom-aniline from sulphanilic acid, 1-amino-ben- 
 zene-4-sulphonic acid. When carefully brominated, this yields 
 the 2 : 6-dibromo-derivative ; and when this is superheated with 
 steam at 170 the sulphonic acid group is removed, and 2:6- 
 dibrom-aniline, melting at 84, is formed. 
 
 Nitranilines. Aniline is likewise attacked far more vio- 
 lently than benzene by concentrated nitric acid, and therefore 
 when it is wished to prepare the mono-nitro-compounds, the 
 aniline must again be " protected ", either by using its acetyl 
 compound, or by nitrating in presence of excess of concen- 
 trated sulphuric acid. In the latter case all three nitranilines 
 result, the m-compound preponderating. When acetanilide is 
 nitrated, p-nitr acetanilide, N0 2 .C 6 H 4 -NHCO.CH 3 , and a 
 little of the o-compound, are formed, and both are readily 
 hydrolysed by potash or hydrochloric acid. 
 
 The nitranilines are further obtained by the partial reduc- 
 tion of the corresponding dinitro-benzenes, e.g. by means of 
 ammonium sulphide; this is the method usually employed for 
 the preparation of m-nitraniline. (For mechanism of the re- 
 action, see Cohen and M'Candlish, J. C. S. 1905, 1257.) 
 
 The o- and ^-compounds are also formed when o- and p- 
 C 6 H 4 C1.N0 2 , C 6 H 4 Br.N0 2 , OH.C 6 H 4 .N0 2 , or OEt.C 6 H 4 .NO ? 
 are heated with ammonia at 180, and conversely the o- and 
 p-nitranilines are converted into nitro-phenols when boiled 
 with alkalis, the former more easily than the latter, thus: - 
 
 C fl H 4 (N0 2 )(NH 2 ) -f H-OH = C 6 H 4 (N0 2 )OH + NH 3 . 
 
 These are all further examples of the remarkable influence of 
 nitro- groups on other substituents, e.g. Cl, Br, OH, 
 
TOLUIDINE! 375 
 
 &c., in the o- and p-, but not in the m-position. (Cf. Picryl 
 Chloride and Picramide.) 
 
 The three ni tramlines crystallize in yellow needles or 
 prisms, and are readily soluble in alcohol, but only very 
 slightly in water. They melt respectively at 71, 114, 147, 
 and their acetyl derivatives at 92, 142, and 207. The o- 
 and m-compounds are volatile with steam, but not ^-nitraniline. 
 When reduced, they yield phenylene-diamines. 
 
 Di- and trinitranilines, 
 
 C 6 H 3 (N0 2 ) 2 (NH 2 ) and *-C 6 H 2 (NO 2 ) 3 (NH 2 ), 
 
 are likewise known; the latter, which is termed picramide, 
 and which crystallizes in yellow needles, m.-pt. 188, comports 
 itself as the amide of picric acid, since it is readily transformed 
 into the latter compound on hydrolysis. 
 
 (For alkyl derivatives, see under Secondary and Tertiary 
 Monamines.) 
 
 Homologues of Aniline. Of the three toluidines, CH 3 
 C 6 H 4 NH 2 , the o- and ^-compounds are obtained by the 
 reduction of the corresponding nitro-compounds. The o- is 
 liquid and the p- solid. 
 
 m-Toluidine, which is liquid, may be prepared from wi-nitro- 
 toluene or ra-nitro-benzaldehyde (cf. B. 15, 2009). 
 
 The boiling-points of the three isomeric toluidines are almost 
 identical, but the melting-points of their acetyl compounds 
 differ widely (see table, p. 367) ; these are, therefore, of value 
 for the characterization ot the toluidines. o-Toluidine is 
 coloured violet by a solution of bleaching-powder, and blue by 
 sulphuric and nitrous acids and also by ferric chloride, but not 
 >-toluidine. For their conversion into fuchsine, see Triphenyl- 
 methane dyes. If during oxidation the amino-group be pro- 
 tected by the introduction of acetyl, the methyl radical can 
 be oxidized to carboxyl and an acetyl derivative of amino- 
 benzoic acid obtained. When oxidized with KMnO 4 , the 
 amino-compounds are transformed into azo-compounds. 
 
 (For higher homologues, see table, p. 367.) 
 
 B. Secondary Monamines 
 
 We have purely aromatic secondary amines, such as di- 
 phenylamine, (C 6 H 5 ) 2 NH, and mixed secondary bases, which 
 contain both an alphyl and an aryl group, e.g. methylaniline. 
 C tt H 6 .NH.CH 8 . 
 
376 XXI. ARYLAMINES 
 
 Modes of Formation. 1. Mixed secondary amines are formed 
 when the primary amines are heated with alphyl iodides (Hof- 
 mann) (see p. 105). 
 
 This reaction does not usually stop short with the intro- 
 duction of one alphyl radical, but extends further with the 
 formation of tertiary bases. In order to avoid this, the alphyl 
 iodide, &c., may be allowed to act upon the acetylated primary 
 bases, e.g. acetanilide [or upon their sodium compounds (Hepp}\ 
 and the resulting acetyl compound hydrolysed : 
 
 C 6 H 6 .NH.CO-CH 3 -f-CH 3 I = C 6 H 6 .N(CH 3 )CO.CH 3 + HI. 
 
 The secondary bases are separated from the tertiary by 
 treatment with nitrous acid (see below, under Nitrosamines). 
 
 2. The purely aromatic secondary amines are obtained when 
 the primary arylamines are heated with their hydrochlorides : 
 
 NH 3 . 
 
 Twodiffsrent aryl radicals maybe introduced, <?.</. (C 6 H 6 )(CH 3 
 C 6 H 4 )NH, phenyl-tolylamine. 
 
 Behaviour. 1. The mixed secondary bases have strongly- 
 marked basic properties, while the purely aromatic are feebler 
 bases than the primary arylamines (cf. p. 366). 
 
 2. For the migration of the alphyl group from the side 
 chain into the nucleus, see p. 369. 
 
 3. The hydrogen of the imino-group is replaceable by an 
 alkyl or acyl radical, and also by potassium or sodium: 
 
 (C 6 H 6 ) 2 NH + CH 3 I = HI + (C 6 H 5 ) 2 NCH 3 
 
 Methyl-diphenylamine. 
 
 (CeH^H + CCHg-CO^O = CH 3 .CO 2 H + (C 6 H 5 ) 2 N.CO.CH 3 
 
 Acetyl-diphenylamine. 
 
 4. The secondary bases give neither the isonitrile nor the 
 "mustard oil" reaction (p. 108). 
 
 5. With nitrous acid, nitrosamines are formed (cf. p. 108): 
 
 C 6 H 6 NHCH 3 + NO.OH = H 2 O + C 6 H 6 .N(NO).CH 3 
 
 Pheuyl-methyl-nitrosamine. 
 
 These nitrosamines are neutral oily liquids insoluble in 
 water, and they regenerate the secondary bases when heated 
 with stannous chloride or with alcohol and hydrochloric acid. 
 With mild reducing agents they yield hydrazines. 
 
 They serve for the preparation of the pure secondary bases, 
 
TERTIARY MONAMINES 377 
 
 since they alone are precipitated by sodium nitrite as non- 
 basic oils from the acid solution of a mixture of primary, 
 secondary, and tertiary bases. When such nitrosamines are 
 digested with alcoholic hydrochloric acid, a molecular re- 
 arrangement takes place, and compounds of the nature of 
 nitroso-dimethyl-aniline (p. 378) are formed, the nitroso-group 
 becoming attached to a carbon atom of the nucleus (0. Fischer 
 and Hepp, B. 19, 2991; 20, 1247): 
 
 C 6 H 6 .N(NO).CH 3 = NO.C 6 H 4 .NHCH 3 . 
 
 All nitrosamines give Liebermann's reaction (p. 409). 
 
 Methyl aniline, C 6 H 5 -NHMe, is a colourless oil lighter than 
 water. It is a stronger base than aniline; its sulphate does 
 not crystallize, and is soluble in ether. With bleaching-powder 
 it gives a brown coloration. 
 
 (For the oxidation of ethylaniline, see Bamberger, Abstr. 
 1902, 1, 275.) 
 
 Diphenylamine, NHPh 2 , crystallizes in colourless plates, 
 melts at 54, distils at 302, and its solution in sulphuric acid 
 yields an intense blue colour with a trace of nitric acid (deli- 
 cate test). It is prepared by heating aniline and aniline 
 hydrochloride at 210-240. The nitrosamine, NPh 2 -NO, 
 forms yellow plates melting at 6 6 '5, and the acetyl-deriva- 
 tive, NPho-CO-CHg, melts at 103. Numerous nitro-deriya- 
 tives are Jmown, e.g. [C 6 H 2 (N0 2 ) 3 ] 2 NH, which is feebly acidic 
 in properties; its ammonium salt, C 12 H 4 (N0 2 ) 6 NNH 4 , is the 
 dye aurantia. 
 
 C. Tertiary Monamines 
 
 These also are either purely aromatic or mixed (alphyl- 
 arylamines). 
 
 Modes of Fwmation. 1. The latter are formed when the 
 primary or secondary bases are alkylated (cf. p. 376). Methyl 
 bromide, iodide or sulphate are often used on the small scale, 
 but on the manufacturing scale methyl alcohol and hydro- 
 chloric acid under pressure. 
 
 A convenient laboratory method is that due to Noelting 
 (B. 1891, 24, 563; J. C. S. 1904, 85, 236). The primary 
 amine is heated on the water-bath with a slight excess of the 
 alkyl iodide and sodium carbonate solution, and in many cases 
 an almost theoretical yield of the tertiary amine is formed. 
 Tertiary bases are also formed when the quaternary salts are 
 strongly heated. 
 
S?8 XXI. ARYLAMlNtiS 
 
 2. Triphenylamine, a purely aromatic base, is formed by 
 the action of bromobenzene upon dipotassium-aniline : 
 
 C C H 5 NK 2 + 2C 6 H 6 Br = (C 6 H 6 ) 3 N + 2KBr. 
 
 Behaviour. 1. Unlike the alphyl-arylamines, the purely aro- 
 matic tertiary amines are incapable of forming salts. 
 
 2. They do not yield isonitriles with CHC1 3 , isothiocyanates 
 with CS 2 , or acyl derivatives with acid chlorides, but most of 
 them yield quaternary compounds with methyl iodide. 
 
 3. Nitrous acid reacts with the tertiary aromatic bases 
 (which thereby differ from the tertiary bases of the fatty 
 series), yielding coloured nitroso-compounds which contain 
 the NO-group linked to the benzene nucleus: 
 
 C 6 H 6 .N(CH 3 ) 2 + NO.OH = NO.C 6 H 4 .N(CH 3 ) 2 + H 2 O. 
 
 2>-N itroso-d imethyl-aniline 
 
 Such nitroso- derivatives are, in contradistinction to the 
 nitrosamines already mentioned, converted into diamines on 
 reduction, and when hydrolysed yield nitroso-phenols. 
 
 4. The tertiary amines, when oxidized with hydrogen per- 
 oxide, yield unstable oxides, e.g. dimethyl-phenylamine oxide, 
 CgHg'NMeolO, feebly basic compounds soluble in water, and 
 decomposed at high temperatures. (B. 1899, 32, 346; Abstr. 
 1901, 1, 200.) 
 
 5. Tertiary amines in which the three substituents are 
 different, e.g. methyl-ethyl-aniline or benzyl-phenyl-hydrazine, 
 do not exist in isomeric forms, and cannot be resolved into 
 optically active components (Kipping and Salway, J. C. S. 1904, 
 438; H. 0. Jones and Millington, C. C. 1904, 2, 952). The 
 centres of gravity of the nitrogen atom and of the three sub- 
 stituents would therefore appear to lie in one plane. 
 
 Dimethyl-aniline, C 6 H 5 N(CH 3 ) 2 , is an oil of sharp basic 
 odour, solidifying in the cold; its salts do not crystallize well. 
 It combines with methyl iodide, even in the cold, to the com- 
 pound N(C 6 H 5 )(CH 3 ) 3 I, phenyl-trimethyl- ammonium iodide, 
 which breaks up into its components when distilled. With 
 nitrous acid it yields ^-nitroso-dimethyl-aniline, which crystal- 
 lizes in green plates, melting at 85; the hydrochloride crys- 
 tallizes in yellow needles. When oxidized with permanganate 
 the nitroso-compound yields ^-nitro-dimethyl-aniline (m.-pt, 
 162), when reduced ^-amino-dimethyl-anilme, and when hy- 
 drolysed with alkali ^-nitroso-phenol (p. 412) and dimethyl- 
 
THE QUATERNARY BASES 379 
 
 amine. (For condensations, see Malachite green, p. 483.) 
 Bleaching-powder colours dimethyl-aniline only a pale-yellow. 
 Dimethyl-aniline yields compounds of somewhat complex com- 
 position with acid chlorides, aldehyde, &c.; for example, tetra- 
 methyl-diamino-benzophenone or, finally, methyl violet with 
 carbonyl chloride, leuco-malachite green with benzoic alde- 
 hyde, &c. Mild oxidizing agents, such as chloranil, convert it 
 into methyl violet. 
 
 Diethyl-aniline boils at 213; its nitroso-derivative melts 
 at 84. 
 
 Triphenyl-amine, NPh 3 , melts at 127, and yields no salts. 
 
 D. The Quaternary Bases 
 
 correspond entirely with the quaternary bases of the fatty series. 
 Trimethyl-phenyl-ammonium hydroxide, C 6 H 5 N(CH 3 ) 3 OH, 
 for instance, is a colourless, strongly alkaline, bitter substance 
 which breaks up into dimethyl -aniline and methyl alcohol 
 when heated. Most of the tertiary amines, however, which 
 contain substituents in the two ortho- positions with respect 
 to the alphylated NH 2 group, are incapable of yielding quater- 
 nary ammonium salts, e.g. : 
 
 N(CH 3 ) 2 
 
 (E. Fischer, B. 1900, 33, 345, 1967). This is an example of 
 steric retardation or inhibition (cf. p. 175). 
 
 The readiness with which a given quaternary salt is formed 
 depends to a large extent on (a) the order in which the 
 radicals are introduced, (6) the nature of the alkyl haloid 
 used, e.g. chloride bromide or iodide, the last reacting most 
 readily, (c) the solvent (p. 106), and (d) temperature (cf. Wede- 
 kind, A. 1901, 318, 90; Jones, B. A. Kep. 1904, 179). It has 
 been found that in the preparation of phenyl-dimethylethyl 
 ammonium iodide a 100 -per -cent yield is obtained when 
 methylethyl-aniline is combined with methyl iodide, but only 
 a 15-per-cent when dimethyl -aniline is combined with ethyl 
 iodide under similar conditions. 
 
380 XXI. ARYLAMINES 
 
 E. Diamines, Triamines, &c. 
 
 Polyamino-derivatives may be obtained by reducing poly- 
 nitro-hydrocarbons or nitro-amino-compounds, e.g. : 
 
 C 6 H 4 (N0 2 ) 2 * C 6 H 4 (NH 2 ) 2 (plienylene-diamine). 
 
 The o- and ^-diamines are best obtained from the o- and 
 p-nitro-amino-compounds. Tetramino- benzene is formed in 
 an analogous manner by reducing dinitro-m-diamino-benzene. 
 
 A new amino-group can be introduced in the ^-position 
 into an arylamine, especially a secondary or tertiary, such as 
 C 6 H 5 N(CH 3 ) 2 , by first transforming the latter into an azo- 
 dye (e.g. benzene-azo-dimethyl-aniline, C 6 H 6 -N:NC 6 H 4 NMe) 
 by coupling it with benzene-diazonium chloride, and decom- 
 posing this by reduction. (See the Azo-compounds.) 
 
 Diamines are also formed by the reduction of the nitroso- 
 compounds of tertiary amines; amino-dimethyl-aniline, NH 2 - 
 CglBL-N^Hg)^ from ^-nitroso-dimethyl-aniline. 
 
 The polyamines are solid compounds which crystallize in 
 plates and distil unchanged, and are soluble in warm water. 
 Though originally without colour, most of them quickly 
 become brown in the air, their instability increasing with the 
 number of amino-groups present. In accordance with the 
 readiness with which they are oxidized, they frequently yield 
 characteristic colorations with ferric chloride, e.g. 0-phenylene- 
 diamine a dark-red, and 1 : 2 : 3-triamino-benzene a violet and 
 then a brown colour. 
 
 The three isomeric groups of diamines differ materially in 
 their behaviour: (a) Ortho-cLLamines. 1. Ferric chloride yields 
 a yellowish-red crystalline precipitate of diamino-phenazine 
 hydrochloride with a solution of o-phenylene-diamine. 
 
 2. The mono-acyl compounds of the o-diamines change into 
 derivatives of imido-azole (A. 273, 269), the so-called "JBenz- 
 imido-azoles " or " Anhydro-lases ", through the formation of in- 
 tramolecular anhydrides; thus o-nitracetanilide, when reduced 
 with tin and hydrochloric acid, yields methyl-benzimido-azole 
 or phenylene-ethenyl-amidine (A. 209, 339): 
 
 Compounds of this nature are also obtained by heating 
 o-diamines with acids. 
 
ACYL DERIVATIVES 381 
 
 3. Glyoxal and many of the a-diketones yield qumoxaline 
 and its derivatives with 0-diamines : 
 
 ON;n a ""o;c.R 
 N;H 2 OJC-R 
 
 and the a-ketonic alcohols react in an analogous manner, e.g. 
 benzoin yields dihydro-diphenyl-quinoxaline. 
 
 4. Nitrous acid converts the o-diamines into the so-called 
 ." azimido-compounds ", compounds which contain three atoms 
 of nitrogen, e.g. 0-phenylene-diamine into azimido- benzene 
 
 = imido-azo-phenylene, CgH^^N (B. 9, 219, 1524; 15, 
 
 1878, 2195; 19, 1757). 
 
 (b) Meta-diamino-bases. 1. These form yellow-brown dyes 
 with nitrous acid, even when only traces of the latter are 
 present. (See Bismarck Brown, p. 401). 
 
 2. They yield azo-dyes with benzenediazonium chloride (see 
 Chrysoidine, p. 401.) 
 
 3. With nitroso-dimethyl-aniline, or on oxidation together 
 with para-diamines, blue colouring-matters (indamines) are ob- 
 tained, and these when boiled yield red dyes (see Toluylene red). 
 
 (c) Para-diamino-compounds. 1. When warmed with ferric 
 chloride, or better, with Mn0 2 + H 2 S0 4 , quinone, C 6 H 4 2 (or 
 a homologue), is formed, and may be recognized by its odour. 
 
 2. By oxidizing para-diamines, containing one amino-group, 
 together with a monamine or a meta-diamine, indamines are 
 produced. 
 
 ACYL DERIVATIVES OF ABYLAMINES. ANILIDES, &c. 
 
 Practically all primary and secondary arylamines but not 
 tertiary react with acids, or better, acid anhydrides or acid 
 chlorides, yielding acyl derivatives, the most characteristic 
 of which are the acetyl derivatives, e.g. C 6 H 5 NH CO CH 3 , 
 CH 3 .C 6 H 4 .NH.CO.CH 3 , (C 6 H 5 ) 2 N CO . CH 3 , &c. The acyl 
 products formed from aniline are termed anilides (p. 370), e.g. 
 acetanilide, benzanilide, oxanilide; they are really phenylated 
 acid amides (see p. 182 et seq.), and as such may be hydrolysed, 
 although not so readily as the amides, by means of acids or 
 alkalis, to aniline and the corresponding acid. 
 
 The dibasic acids like oxalic acid can give rise not merely 
 to anilides, e.g. C 6 H 5 .NHCO.CO.NH.C 6 H 5 , oxanilide, but 
 
382 XXI. ARYLAMINES 
 
 also to half anilides, the anilic acids, which correspond with 
 the amic acids, e.g. oxanilic acid, C 6 H 5 NH CO CO OH. 
 These are monobasic acids, and can also be hydrolysed to 
 their components. 
 
 Similarly, the toluidines give rise to toluidides, e.g. acetolui- 
 dide, CH 3 .C 6 H 4 .NH.CO.CH 3 , the xylidines to xylidides, &c. 
 
 The acetyl derivatives are frequently used for the identi- 
 fication of the various primary and secondary arylamines, 
 since they crystallize well and have definite melting-points. 
 As a rule, it is sufficient to mix the amine with a slight excess 
 of acetic anhydride and warm for two minutes, and then to 
 pour into water. After a short time the solid (or oily) acetyl 
 derivative is obtained. 
 
 Formanilide, C 6 H 6 NHCH:0, from aniline and formic 
 acid, is worthy of note, because its sodium salt reacts accord- 
 ing to the formula C 6 ILNNaCH:0, but its silver salt ac- 
 cording to the formula C 6 H 5 N : CH Ag. (Cf. B. 23, 2274, 
 Ref. 659.) The latter corresponds to those isomers of the 
 amides, the imido-hydrates and imino-ethers (p. 187). 
 
 Acetanilide, C 6 H 5 NHCO'CH 3 , is most conveniently pre- 
 pared by boiling aniline with glacial acetic acid for twenty- 
 four hours. It crystallizes in beautiful white prisms which are 
 readily soluble in hot water or alcohol, less readily in ether 
 and benzene. It melts at 115, and boils at 304. In the 
 absence of water it can form a hydrochloride, C 7 H 9 ON, HC1. 
 Acetanilide is used, under the name of " antif ebrine ", as a 
 medicine in cases of fever. 
 
 Thio-acetanilide, C 6 H 5 NH.CS.CH 3 , is formed when acet- 
 anilide is heated with P 2 S 5 , and from it imido-thio-com- 
 ponnds, amidines, &c., can be prepared. Methyl-acetanilide, 
 C 6 H 5 .N(CH 8 )(CoH 3 0), is used as a specific against headache. 
 
 Oxanilide, C 6 H 5 - NH . CO . CO NH . C 6 H 5 , is obtained when 
 aniline oxalate is heated at 160-180. It melts at 252, boils 
 without decomposition, and is best hydrolysed by fusion with 
 potash. 
 
 The half anilide, oxanilic acid, COOH CO NH C 6 H 5 , is 
 formed when aniline oxalate is heated at 130-140. It melts 
 at 149-150, is soluble in hot water, has the properties of a 
 monobasic acid, and with phosphorus pentachloride yields 
 phenyl carbimide (phenyl isocyanate): 
 
 C 6 H 6 .NH.CO.OH C 6 H 6 .NH.CO.C1 C 6 H 5 .N:C:O. 
 Diacyl derivatives of aniline and its homologues are also 
 
DIACETANILIDE. PRIMARY AMINES 383 
 
 known, e.g. C 6 H 5 N(CO CH 3 ) 2 , diacetanilide. This is formed, 
 together with acetanilide, when aniline is boiled for an hour 
 with excess of acetic anhydride, or when the amine is heated 
 to a high temperature with acetyl chloride. The two may be 
 separated by fractional distillation under diminished pressure. 
 The diacetanilide crystallizes in colourless prisms, melts at 
 37, and, unlike acetanilide, is readily soluble in benzene or light 
 petroleum. On hydrolysis with dilute alkali, one acetyl group 
 is split off more readily than the second. 
 
 The presence of one or two substituents in the o-position 
 with respect to the amino-group of aniline facilitates the for- 
 mation of diacetyl derivatives, e.g. o-toluidine yields a diacetyl 
 derivative more readily than aniline, and s-tribrom-aniline 
 yields a diacetyl derivative with the greatest readiness 
 (J. C. S. 1901, 533). 
 
 In nearly all those compounds of the fatty series which 
 are amino- or imino-derivatives of alcohols, acids, or hydroxy- 
 acids, the unreplaced ammoniacal hydrogen can be substituted 
 indirectly either wholly or partially by phenyl. The number 
 of these phenylated (tolylated, xylylated, &c.) compounds is 
 thus extremely large. Among them may be mentioned: 
 Phenyl-glycocoll, Phenyl-glydne, C 6 H 5 - NH . CH 2 . C0 2 H, from 
 chloracetic acid and aniline; phenyl-imino-butyric acid, CH 3 
 C(:NCgH 5 )-CH. 2 -C0 2 H, from aniline and aceto-acetic ester; 
 carbanilide or diphenyl-urea, CO(NHC 6 H 5 ) 2 , from aniline and 
 carbon oxy chloride (cf. p. 280); phenyl isocyanate, phenyl 
 carbimide, COiN-CgHg, from COC1 2 and fused aniline hydro- 
 chloride, a sharp-smelling liquid exactly analogous to the iso- 
 cyanic esters its vapour gives rise to tears; phenyl isothio- 
 cyanate, C 6 H 5 N:CS (b.-pt. 222), a liquid possessing all the 
 characteristics of the mustard oils (p. 275); diphenyl thio- 
 urea, CS(NHC 6 H 6 ) 2 , from aniline and carbon disulphide (forms 
 glistening plates, melting at 154; it is decomposed into phenyl 
 isothiocyanate and aniline when hydrolysed with concentrated 
 HC1). 
 
 PRIMARY AMINES WITH THE AMINO-GROUP IN THE 
 SIDE CHAIN 
 
 These compounds resemble the primary alphylamines much 
 more closely than aniline. As an example, we have benzyl- 
 amine, C 6 H 5 CH 2 NH 2 , the amine corresponding with 
 benzyl alcohol; it is a colourless liquid which distils un- 
 changed. The acetyl compound, C 6 H 5 .CH 2 .NH-CO.CH 2 , 
 
384. XXII. DIAZO- AND AZO-COMPOUNDS 
 
 is formed by heating benzyl chloride, CpH 5 CH 2 Cl, with acet- 
 amide. Benzylamine is formed, together with di- and tri- 
 benzylamines, by the action of alcoholic ammonia on benzyl 
 chloride; it is also readily obtained by reducing the phenyl- 
 hydrazone of benzaldehyde : 
 
 C 6 H 6 .CH:N- NHC 6 H 6 - 
 H H 2 i H 
 
 It may also be prepared from benzyl chloride and potassium 
 phthalimide (cf. p. 465). Its behaviour is entirely analogous to 
 that of methylamine, as the phenyl derivative of which it is 
 to be regarded. It dissolves in water, and the solution thus 
 formed is alkaline. Conductivity determinations show that it 
 is about as strong a base as ammonia, and thus differs materi- 
 ally from aniline. 
 
 It possesses all the characteristic properties of a primary 
 amine, but as the NH 2 is attached to a side chain and not to 
 the benzene nucleus it cannot be diazotized, and on treatment 
 with nitrous acid it immediately yields benzyl alcohol. 
 
 XXII. DIAZO- AND AZO-COMPOUNDS; 
 HYDEAZINES 
 
 A. Diazo-eompounds 
 
 The primary arylamines differ characteristically from the 
 primary alphylamines in their behaviour towards nitrous acid. 
 The latter are converted into alcohols without the formation 
 of intermediate products (cf. p. 108): 
 
 The aromatic amines can undergo an analogous transfor- 
 mation; but if the temperature is kept sufficiently low, well- 
 characterized intermediate products, the so-called diazo-eom- 
 pounds or diazonium salts, e.g. benzene diazonium chloride, 
 C 6 H 5 N 2 C1, are obtained, which are of especial interest both 
 scientifically and technically (cf. Azo-dyes, p. 389). They were 
 discovered by P. Griess in 1860, and were carefully investigated 
 by him (A. 121, 257; 137, 39). 
 
 The diazo-compounds are usually divided into (1) the diazo- 
 
 r^ FT 
 nium salts, e.g. 6 p>NjN, compounds which are analogous 
 
DIAZONIUM COMPOUNDS <385 
 
 to ammonium salts; (2) the true diazo-compounds, which con- 
 tain the grouping N : N . 
 
 I. Diazonium Compounds, The diazonium salts, as a rule, 
 #re not obtained in the solid state, as they themselves are of 
 little commercial value, but are of importance as intermediate 
 products in various decompositions. 
 
 Solutions are usually prepared by the addition of an 
 aqueous solution of sodium nitrite to a solution of the amine 
 in an excess of the requisite acid (V. Meyer}. The essentials 
 are (1) The solution must be kept cool, at or only a few 
 degrees above, otherwise a phenol is formed and nitrogen 
 evolved. (2) An excess of acid must be used, otherwise 
 diazo-amino-compounds are formed. (3) As a rule, it is 
 advisable not to use an excess of nitrous acid. This is 
 avoided by testing for free nitrous acid by means of potassium 
 iodide starch paper. 
 
 This conversion of amino- into diazo-compounds is termed 
 " diazotizing ". 
 
 The crystalline salts, e.g. benzene-diazonium chloride, may 
 be obtained by adding concentrated hydrochloric acid to an 
 alcoholic solution of aniline hydrochloride, and then amyl 
 nitrite (Knoevenagel). They may also be obtained by the 
 addition of alcohol and ether to their aqueous solutions. 
 
 Constitution. The N. 2 X group can be attached to only one 
 carbon atom of the benzene nucleus, since (1) when the salts 
 undergo decomposition the products formed contain groups, 
 e.g. Cl, OH, CN, &c., which are attached to a single carbon 
 atom; (2) penta- substituted anilines, e.g. S0 3 H-C 6 Br 4 NH 2 , 
 can be diazotized, hence Griess' formulae, e.g. C 6 H 4 N 2 , HC1, 
 where the diazo-radical replaces two hydrogen atoms of the 
 nucleus, are untenable. 
 
 For many years the constitutional formula given to these 
 compounds was that suggested by KekuU, viz. C 6 H 5 *N:NC1, 
 for the chloride; this represents them as analogous to the 
 azo-compounds. This formula readily explains the reduction 
 of the diazonium salts to hydrazines, CVH 5 NHNH 2 , and their 
 conversion into azo-dyes, e.g. C 6 H 5 N : N C 6 H 4 OH. Within the 
 last few years a constitutional formula which was suggested by 
 Blomstrand in 1875 has become generally accepted. This repre- 
 sents the molecule of a diazonium salt as containing a quinque- 
 
 O TT 
 valent nitrogen atom, e.g. 6 Q->N:N. The chief arguments 
 
 in favour of the Blomstrand formula are briefly: 
 
 (B480) 2P, 
 
386 XXII. DIAZO- AND AZO-COMPOtTNDS 
 
 
 
 1. It indicates the resemblance between the diazonium and 
 ammonium salts, as both thus contain quinquevalent nitrogen : 
 
 and 
 
 The resemblance between the two groups of compounds is 
 marked. The diazonium salts are colourless crystalline com- 
 pounds readily soluble in water; those derived from strong 
 acids, e.g. the chlorides, nitrates, and sulphates, are neutral in 
 solution, cf. NH 4 C1; whereas those derived from feeble acids, 
 e.g. carbonic acid, are partially hydrolysed in aqueous solution, 
 and hence give an alkaline reaction, cf. Na.,C0 8 or (NH 4 ) 2 C0 3 . 
 In addition they form sparingly soluble platinichlorides, 
 (C 6 H 5 N 2 ) 2 PtCl 6 , and aurichlorides, C 6 H 5 N 2 AuCl 4 , comparable 
 with the ammonium compounds. The aqueous solutions of 
 the salts are ionized to much the same extent as the corre- 
 sponding quaternary ammonium salts. This resemblance of 
 the diazonium ions to the quaternary ammonium ions is 
 further established by a comparison of migration values. 
 The free base, benzene -diazonium hydroxide, corresponding 
 with ammonium hydroxide, is obtained by the action of moist 
 silver oxide on the chloride; it dissolves readily in water, 
 yielding strongly alkaline solutions, but is very unstable, and 
 gradually decomposes. When neutralized with acids, it yields 
 the above-mentioned diazonium salts. 
 
 2. The conversion of aniline and its homologues into diazo- 
 nium salts is rendered somewhat more simple by such a for- 
 mula: 
 
 HO 
 
 3. The elimination of nitrogen and the formation of mono- 
 Bubstituted compounds, e.g. C 6 H 5 -OH, C 6 H 6 Br, &c., is readily 
 explicable: 
 
 Cain (J. C. S. 1907, 91, 1049) has suggested a new consti- 
 tutional formula for diazonium salts, e.g. benzene-diazonium 
 chloride, 
 
 :N.C1 
 
 -N 
 is claimed that the double linkage between nitrogen and 
 
REACTIONS OP DIAZONIUM SALTS 387 
 
 carbon atom of the benzene nucleus is more in harmony with 
 the readiness with which the nitrogen is eliminated from the 
 molecule. It also accounts for the fact that in a ^-diamine 
 only one amino-group can be diazotized. 
 
 Reactions. 1. The reaction characteristic of the diazonium 
 salts is the readiness with which nitrogen is eliminated and 
 monovalent groups introduced into the molecule in place of 
 the N 2 X radical, and for this reason the diazonium compounds 
 are frequently made use of in the laboratory for the prepara- 
 tion of various substituted benzene derivatives. As examples 
 of this type of reaction, we have 
 
 (a) Replacement of N 2 X by OH. An aqueous solution of 
 a diazonium salt, especially one containing sulphuric acid, 
 evolves all its nitrogen in the form of gas when warmed, and 
 a phenol is formed : 
 
 |N:N = Cfl H 6 .OH + N 2 -f HCI. 
 
 This reaction, which is of very universal application, there- 
 fore allows of the exchange of NH 2 for OH. The only excep- 
 tions appear to be those salts containing numerous negative 
 substituents in the benzene nucleus, e.g. C 6 H 2 Br 3 N 2 C1. 
 
 For the effect of light on the decomposition of solutions 
 of diazonium salts, see Orton, Coates, and Burdett, P. 1905, 
 168. 
 
 (b) Replacement by H. When diazonium-compounds, either 
 in the solid state or dissolved in concentrated sulphuric acid, 
 are heated to boiling with absolute alcohol, the diazo-group is 
 generally replaced by hydrogen. In this reaction the alcohol 
 gives up two hydrogen atoms, and is oxidized to aldehyde : 
 
 This affords a simple method for the replacement of NH 
 by H. 
 
 Instead of this reaction, there occurs in many cases an ex- 
 change of the diazo-group for the ethoxy-radical,*0'C 2 H 5 , with 
 the formation of ethyl ethers of phenols; thus from chlorinated 
 toluidines ethyl ethers of chloro-cresols are formed, and not 
 chloro-toluenes (B. 17, 2703; 22, Ref. 658; 34, 3337). 
 
 Under certain conditions stannous chloride in alkaline solu- 
 tion acts in an analogous manner (B. 22, Ref. 741), while 
 under others it gives rise to hydrazines (p. 397). In 
 
388 XXII. DIAZO- AND AZO-COMPOUNDS 
 
 manner NH 2 may be replaced by H, by first converting an 
 amino-compound into a hydrazine, and then decomposing the 
 latter with CuS0 4 (Baeyer, B. 18, 89). 
 
 (c) Replacement by Halogen Sandmeyer's Reaction. When a 
 diazonium-compound is warmed with a concentrated solution 
 of cuprous chloride in hydrochloric acid, the diazo-group is 
 replaced by chlorine (Sandmeyer, B. 17, 1633; 23, 1218, 1628; 
 A. 272, 143). The same reaction takes place on distilling the 
 diazonium platinichloride with soda, and sometimes on simply 
 treating the diazo-compound itself with fuming hydrochloric 
 acid, or with hydrochloric acid in presence of copper dust 
 (Gattermann) : 
 
 Warming with cuprous bromide yields, in the same way, a 
 bromo-derivative (Sandmeyer, B. 18, 1482), and treatment with 
 hydriodic acid or potassium iodide an iodo-compound : 
 
 2C 6 H 6 .N 2 .C1 + CuJBro = 2C 6 H 5 Br + Cu 2 CL + N 2 ; 
 C 6 H 6 N 2 Cl + KI = C C H 5 I + KC1 + N 2 . 
 
 The ammo-group may further be exchanged for bromine by 
 boiling the diazonium perbromides (see Benzene-diazonium per- 
 bromide) with absolute alcohol. 
 
 (d) ^Replacement by C]N. This is accomplished by adding 
 the diazotized solution to a warm solution of potassium cuprous 
 cyanide : 
 
 C 6 H 6 .N 2 C1 C 6 H 6 N 2 CN C 6 H 5 -CN. 
 
 This reaction is of importance, as the product obtained is a 
 nitrile, and can be hydrolysed to an acid. 
 
 (e) Phenyl sulphide is formed by the action of hydrogen 
 sulphide on benzene-diazonium chloride (cf. B. 15, 1683); 
 nitro- benzene is formed by the action of nitrous acid in 
 presence of cuprous oxide; benzenesulphonic acid from sul- 
 phurous acid; phenyl thiocyanate from thiocyanic acid; and 
 phenyl cyanate from cyanic acid, &c. (cf. B. 23, 738, 1218, 
 1454, 1628; 25, 1086; 26, 1996). 
 
 (/) When oxidized in alkaline solution, benzene-diazonium 
 hydroxide yields together with other products nitroso-ben- 
 zene (p. 365), and much benzene-diazoic acid, C 6 H 5 'N -NO- 
 OK, or its isomeride, phenyl - nitramine, C 6 H 5 NHNO,, 
 (m.-pt. 46; explodes at 98) (see B. 26, 471; 2?, 584, 915). 
 
REACTIONS OF DIAZONIUM SALTS 389 
 
 2. When a solution of a diazonium compound reacts with a 
 primary or secondary amine, or when nitrous acid acts upon 
 such an amine in the absence of free mineral acid, diazo- 
 amino-compounds are formed, and these readily change into 
 amino-azo-compounds : 
 
 Diazo-amiuo-benzene. 
 
 3. Azo-dyes. The diazonium salts readily react with ter- 
 tiary amines or with phenols, yielding derivatives of azo- 
 benzene, e.g. : 
 
 C 6 H 6 .N 2 C1 + C 6 H 6 N(CH 3 ) 2 = HC1 + C 6 H 6 .N:N.C 6 H 4 .N(CH 3 ) 2 
 
 Dirnethyl-amino-azobenzene. 
 
 C 6 H 6 .N 2 C1 + C 6 H 5 .OH = HC1 + C 6 H 5 -N:N.C 6 H 4 .OH 
 
 Hydroxy-azobenzene. 
 
 Such derivatives possess basic or acidic properties, are 
 usually coloured yellow, red, or brown, and are known as 
 azo-dyes. 
 
 The formation of such an azo-dye is largely made use of as 
 a test for a primary aromatic amine with the NH 2 in the 
 nucleus. The amine is dissolved in acid, diazotized, and then 
 mixed with an alkaline solution of a phenol (preferably 
 /3-naphthol), when an orange-red dye is precipitated. The 
 process is commonly spoken of as the "coupling" up of a 
 diazonium salt with an amine or a phenol. 
 
 It has been proposed to use diazo-compounds, sensitive to 
 light, in photography (B. 23, 3131; 34, 1668). 
 
 4. The diazonium salts react in alkaline solution with com 
 pounds containing the grouping CH 2 'CO, yielding azo-com- 
 pounds or phenylhydrazones, e.g. : 
 
 PIT rn PTT rn ^ 
 /H3C 
 
 Cf. B. 1888, 21, 1697. For the azo or hydrazone constitution 
 of such compounds, compare Auwers (Abstr. 1908, i, 477; 
 1911, i, 168, 585). 
 
 Benzene-diazonium perbromide, C 6 H 5 N 2 Br, Br 2 , is a dark- 
 brown oil, solidifying to yellow crystalline plates, and is pre- 
 pared by the addition of HBr or KBr and bromine water to 
 diazonium salts. Two of its atoms of bromine are only loosely 
 linked. Ammonia converts it into benzene-diazo-imide, which 
 
390 XXII. DlAZO- AND A20-COMPOtJN&S 
 
 is to be regarded as the phenyl derivative of hydrazoic acid, 
 N 3 H, thus: 
 
 C 6 H 6 N(Br) : N + Br 2 = C 6 H 6 NBr 2 : NBr [Beuzene-diazonium perbromide]. 
 
 a XT 
 [Benzene-diazo-imide]. 
 
 In accordance with this, dinitro-benzene-diazo-imide (from 
 dinitro-aniline) is decomposed by alcoholic potash into dinitro- 
 phenol and hydrazoic acid a method of obtaining this latter 
 substance by means of organic compounds (see p. 298). 
 
 II. Diazo- compounds. These contain the grouping R-N: 
 NX, where R = an aryl radical and X an acid radical or 
 OH or OK. When a benzene-diazonium salt is mixed with 
 an excess of alkali, a potassium salt, normal potassium diazo- 
 benzene oxide, C 6 H 5 N 2 OK, is precipitated. It crystallizes in 
 white plates, and can be quantitatively converted into ben- 
 zene-diazonium chloride; it yields ethers, and on oxidation 
 gives nitroso-benzene and benzene-diazoic acid: 
 
 C 6 H 6 .N:N< H or CflH^NH-NOj, 
 
 The acid, C 6 H 5 N 2 OH, which corresponds with the potassium 
 salt, is not known in a pure form. When the normal potas- 
 sium salt is heated with concentrated potash at 130-135, it 
 is transformed into potassium isodiazo-benzene oxide (Schraube 
 and Schmidt, B. 1894, 27, 520). When this is acidified with 
 acetic acid, the free hydroxide is obtained as a colourless oil 
 which is very unstable. 
 
 Similar normal and isopotassium derivatives have been ob- 
 tained from other diazonium salts, and it has been found that 
 the presence of negative radicals (Br, N0 2 ) facilitates the for- 
 mation of the iso-compound, in fact to such an extent that 
 certain diazonium salts, when added to an alkali, immediately 
 yield the isodiazo-compounds. Considerable controversy has 
 taken place regarding the constitutional formulae of these two 
 groups of compounds. At one time the isodiazo-oxides were 
 regarded as derivatives of phenyl-nitrosamine, viz. C 6 H 5 -NK 
 NO, and the normal compounds as true diazo-oxides, C 6 H 6 
 N:NOK. The researches of Hantzsch have proved that the 
 two compounds are very similar as regards chemical properties. 
 For example, both "couple" with alkaline solutions of phenols, 
 yielding azo-dyes (p. 389), but as a rule the normal more 
 readily than the iso-compounds. Both compounds, on reduc- 
 
STEREO-ISOMERIC DIAZO-HYDROXtDES 391 
 
 tion with sodium amalgam in the presence of a large excess of 
 alkali, yield phenyl-hydrazine, and both compounds, on oxi- 
 dation in alkaline solution, yield potassium benzene-diazoate, 
 C 6 H 5 N : NO OK. Similarly, both compounds yield the same 
 benzoyl derivative by the Schotten-Baumann method. Hantzsch 
 draws the conclusion that the two compounds are structurally 
 identical and stereo-isomeric. As the w-diazo-oxide can be syn- 
 thesised by the action of hydroxylamine on nitroso-benzene in 
 alkaline solution (B. 38, 2056): 
 
 N.OH = H 2 + C 6 H 6 .N:N-OH, 
 
 it is probable that both normal and iso-compound are true 
 diazo-derivatives, and that they are stereo-isomeric in much 
 the same manner as the oximes (p. 138). According to 
 Hantzsch, the normal compound has the syn- and the iso- the 
 <w&'-configuration : 
 
 C 6 H 5 -N C 6 H 6 .N 
 
 KO-N N-OK, 
 
 Potassium benzene syn diazo-oxide anti 
 
 as the normal compounds evolve nitrogen very readily, whereas 
 the iso-compotinds are more stable. (Ber. 1894, 27, 1702; 
 1895, 28, 676, 1734; 36, 4054; 37, 1684.) 
 
 The isodiazo-oxides can almost undoubtedly react as tauto- 
 meric compounds, viz. as nitrosamine derivatives, C 6 H 5 -NK 
 NO, since the potassium salt yields an N-ether, C 6 H 5 'NEt-NO, 
 whereas the silver salt yields an O-ether, C 6 H 5 N : N OEt. 
 Bamberger has suggested that the normal diazo-oxides may 
 have a diazonium constitution C 6 H 5 N(OK)jN, whereas the 
 iso-compound has the diazo-constitution C 6 HgN:NOK; but 
 Hantzsch has pointed out that the diazonium hydroxides, 
 from which the true diazonium salts are formed, must be 
 extremely strong bases, and could not possibly therefore pos- 
 sess sufficiently acidic properties to give rise to stable potas- 
 sium salts which are only partially hydrolysed in aqueous 
 solution. 
 
 Certain diazo-hydroxides, RN 2 OH, have been isolated as 
 colourless solids with acidic properties ; the majority, however, 
 are extremely unstable, and pass over into the isomeric nitros- 
 amines R-NH-NO, yellow compounds with neutral properties 
 (B. 35, 2964; 36, 4054; 37, 1084). 
 
 Corresponding with the normal and isodiazo-oxides, Hantzsch 
 
392 XXII. DIAZO- AND AZO-COMPOUNDS 
 
 has discovered two groups of sulphonates and of cyanides, 
 which he also regards as being stereo-isotneric in the same 
 sense, e.g.: 
 
 E-N K-N 
 
 In the case of j0-anisidine, evidence of the existence of three 
 isomeric diazo-cyanides has been obtained. The one is colour- 
 less and is an electrolyte, and hence is regarded as the diazo- 
 nium salt, OMe-C 6 H 4 -N(CN)jN; the other two are reddish- 
 coloured solids and non-electrolytes. The syw-compound is 
 unstable, and melts at 51; it gradually passes over into the 
 more stable an ^'-compound, which melts at 121. 
 
 It is probable that when a syn diazo-cyanide is dissolved in 
 water it is largely transformed into the ionized diazonium 
 cyanide : 
 
 Compare also Armstrong and JRobertson, J. C. S. 1905, 1280; 
 Hantzsch, P. 1905, 287. An account of the chemistry of diazo- 
 compounds will be found in B. A. Rep. 1902, 181 (G. T. Morgan), 
 and in Ahrens Sammlungt 1902, 8, pp. 1-82 (Hantzsch). 
 
 B. Diazo-amino-eompounds 
 
 The diazo-amino-compounds are pale-yellow crystalline sub- 
 stances which are stable in the air, and do not combine with 
 acids. They are obtained by the action of a primary or 
 secondary amine on a diazonium salt, and also when nitrous 
 acid reacts with a free primary aromatic amine instead of with 
 its hydrochloride, probably : 
 
 C 6 H 5 NH 2 -f-O:N.OH = C 6 H 6 -N:N.OH + H 2 O and 
 C 6 H 5 .N:N.OH + C 6 H 6 NH 2 = C 6 H 6 .N:N.NHC 6 H 6 + H 2 O. 
 
 Diazo-amino compounds have been synthesised by the action 
 of Grignard compounds on alkyl or acyl derivatives of hydra- 
 zoic acid, and decomposing the products with water: 
 
 RN 3 + B'Mgl RN(MgI)-N:NR' 
 RN(MgI).N:NR' + H 2 O R-NH-NiN-R' + Mgl-OH 
 
 In this manner not merely aromatic but aliphatic aromatic 
 
blAZO-AMINO-COMPOtJNDS 393 
 
 Compounds of the types C 6 H 6 -NH.N:N.CH 3 and C 6 H 5 CH 2 - 
 NH N : N CH 3 have been prepared. 
 
 Reactions. 1. They are not bases, and hence do not form 
 salts with acids. 
 
 2. They behave in much the same way as the diazo-com- 
 pounds, since they are usually decomposed in the first instance 
 into their components, a diazonium salt and an amine, the 
 former then entering into reaction. Thus diazo-amino-ben- 
 zene, for example, yields phenol and aniline when boiled 
 with water or hydrochloric acid, while with hydrobromic 
 acid it gives bromobenzene and aniline. These reactions 
 are easy to recognize from the accompanying evolution of 
 nitrogen. 
 
 3. By the renewed action of nitrous acid in acid solution 
 they are completely transformed into diazonium salts: 
 
 C 6 H 6 .N 2 .NH.C 6 H 5 + NO 2 H + 2HC1 = 2C 6 H 5 .N 2 .C1 + 2H 2 O. 
 
 4. Most of them readily undergo molecular transformation 
 into the isomeric amino-azo-compounds (KekuU): 
 
 C 6 H 6 .N:N-NH/ \H C 6 H 6 .N:N/ 
 
 This molecular rearrangement takes place most readily in 
 presence of an amine hydrochloride, which acts as a catalytic 
 agent. The amino-group always takes up the para-position 
 with regard to the azo-group (N:N) if this is free. If, how- 
 ever, this is already substituted, as in the diazo-amino-com- 
 pound from |?-toluidine, then the transformation occurs much 
 more slowly, and the NH 2 takes up the o-position with respect 
 to the N : N group. The velocity of transformation has been 
 investigated by H. Goldschmidt, and the reaction has been 
 shown to be unimolecular. Only a relatively small amount 
 of aniline salt is required, and the velocity is proportional to 
 the strength of the acid, the aniline salt of which is used (B. 
 1896, 29, 1899). For similar transformations, see Benzidene 
 (p. 395) and Azoxy-benzene (p. 395). 
 
 5. The imino- hydrogen of the diazo-amino-compounds is 
 replaceable by metallic radicals, and also by acyl groups. 
 
 Constitution. By the action of benzene-diazonium chloride 
 upon ^-toluidine, " diazo-benzenef>-toluidide " is formed, and 
 would appear to possess the formula: 
 
 (I). 
 
394 XXII. DIAZO- AND AZO-COMPOUNDS 
 
 But the same compound is also obtained from a mixture 
 of ^-toluene-diazonium chloride and aniline, a reaction which 
 would indicate its constitution to be: 
 
 C 6 H 6 .NH.N:N.CVH 7 (II). 
 
 It is all the more difficult to decide which of these two 
 formulae is the right one, from the fact that most of those 
 " mixed diazo-amido-compounds " react as if they had both of 
 the above constitutions. Thus, when the compound just men- 
 tioned is boiled with dilute sulphuric acid, it yields not only 
 phenol and ^-toluidine (according to I), but also aniline and 
 ^?-cresol (according to II). Such diazo-ami no-compounds are 
 thus typical tautomeric substances. (Cf. e.g. B. 19, 3239; 20, 
 3004; 21, 548, 1016, 2557; J. C. S. 1889, 55, 412, 610, &c.) 
 
 Diazo-amino- benzene, C 6 H 5 N : N NHC 6 H 5 (Griess), is 
 usually prepared by adding NaN0 2 (1 mol.) to the solution 
 of aniline (2 mols.) in HC1 (3 mols.), and saturating with 
 sodium acetate (B. 1884, 17, 641; 1886, 19, 1952). It crystal- 
 lizes in bright-yellow lustrous plates or prisms, is insoluble in 
 water, but readily soluble in hot alcohol, ether, and benzene, 
 melts at 98, and is far more stable than the diazo-compounds. 
 
 C. Azo-compounds, and Compounds intermediate 
 between the Nitro- and Ammo-compounds 
 
 While the reduction of nitro-compounds in acid solution leads 
 to the aromatic amines, the use of alkaline reducing agents, 
 such as sodium amalgam, zinc dust and caustic soda, and also 
 potash and alcohol, gives rise for the most part to intermediate 
 products, the azoxy-, azo-, and hydrazo-compounds : 
 
 C 6 H 5 .N0 2 C 6 H 6 .iST.N.C 6 H 5 C 6 H 5 .N:N.C 6 H 5 
 
 Nitro-benzene \/ Azo-benzene 
 
 Azoxy-benzene 
 C C H 6 NH NHC 6 H 5 C 6 H 6 . NH 2 ; 
 
 Hydrazo-benzene Aniline 
 
 and reduction in neutral solution yields pheriyl-hydroxyl- 
 amines, C 6 H 5 -NH.OH. 
 
 Of these the azo-compounds are the most important 
 
 1. AZOXY-COMPOUNDS 
 
 The azoxy-compounds are mostly yellow or red crystalline 
 substances which v are obtained by the action of alcoholic 
 
HYDRAZO-COMPOtlNDS 396 
 
 potash, and especially of potassium methoxide (B. 15, 865), 
 upon the nitro-compounds. Many of them may also be 
 obtained by the oxidation of azo-compounds. They are of 
 neutral reaction, and are very readily reduced to azo-com- 
 pounds. 
 
 Azoxy - benzene, (C 6 H 5 ) 2 N 2 (Zinin), forms pale -yellow 
 needles melting at 36, is insoluble in water, but dis- 
 solves readily in alcohol and ether. Concentrated sulphuric 
 acid transforms it into the isomeric ^?-hydroxy-azo-benzene, 
 C G H 5 N:N.C 6 H 4 .OH. 
 
 2. HYDRAZO-COMPOUNDS 
 
 These are colourless crystalline neutral compounds, and, 
 like the azo-compounds, cannot be volatilized without decom- 
 position; e.g. hydrazo- benzene decomposes into azo-benzene 
 and aniline when heated. They are obtained by the reduction 
 of azo-compounds with ammonium sulphide or zinc dust and 
 alkali, or by sodium hyposulphite. Oxidizing agents, such as 
 ferric chloride, readily transform them into azo-compounds, a 
 reaction which also occurs when the hydrazo-compounds are 
 exposed to the air. Stronger reducing agents, e.g. sodium 
 amalgam, convert them into amino-compounds. 
 
 Strong acids cause them to change into the isomeric deriv- 
 atives of diphenyl (p. 472); thus from hydrazo-benzene and 
 hydrochloric acid we obtain benzidine hydrochloride (the 
 hydrochloride of ^/-diamino-diphenyl, p. 472): 
 
 > NIL, 
 
 This rearrangement is typical, and is often observed in the 
 case of aromatic compounds. It may be regarded as the 
 shifting or wandering of a radical in this case the relatively 
 complex CgH 5 NH from attachment to the side chain to 
 direct attachment to the benzene nucleus, or, in other words, 
 the NH'CgHg group exchanges place with the hydrogen atom 
 in the ^-position in the nucleus: 
 
396 XXII. DIAZO- AND AZO-COMPOUNDS 
 
 The operation is repeated, 
 
 and j^'-diamino-diphenyl is formed. 
 
 Other well-known examples of this are the transformation of 
 methyl-aniline or dimethyl-aniline into o-toluidine and xylidene, 
 and ultimately into mesidene (Hofmann, p. 368); the transforma- 
 tion of N-brominated amines or anilides, e.g. C 6 H 5 NBr COCH 3 
 into C 6 H 4 Br-NH.COCH 3 (Chattaway and Orion, p. 370), of dia- 
 cetylated amines, C 6 H 5 N(COCH 3 ) 2 , into ketonic substances, 
 CH 3 CO - C 6 H 4 NH - CO CH 3 (Chattaway, J. C. S. 1 904, 386, 589, 
 1663), of phenyl-hydroxylamine into ^-amino-phenol (p. 395), 
 and of diazo-amino-benzene into amino-azo-benzene (p. 391). 
 
 This molecular rearrangement does not take place if the 
 hydrogen which occupies the para-position to the imino-group 
 is replaced by other groups. In such cases a partial re- 
 arrangement only occurs, and derivatives of diphenylamine 
 are formed (B. 25, 992, 1013, 1019); thus ^-hydrazo-toluene, 
 CH 3 C 6 H 4 NH NH C 6 H 4 - CH 3 , yields o-amino-di-^-toly lamine, 
 
 CH 8 .C 6 H 4 .NH-C 6 H 8 <0|k (Cf. Jacobson, B. 1893, 26, 700; 
 
 1898, 31, 890; A. 1895, 28 3 7, 98.) 
 
 Hydrazo-benzene, sym.-Diphenyl-hydrazine, C 6 H 5 NHe * : I 1 
 CgH 5 (Hofmann), forms colourless plates of camphor- like 
 odour, which are only slightly soluble in water, but dissolve 
 readily in alcohol and ether; m.-pt. 131. The imino-hydrogen 
 atoms are replaceable by acetyl- or nitroso-groups. 
 
 3. AZO-COMPOUNDS 
 
 The azo-compounds are red or yellowish -red, crystalline, 
 neutral substances, insoluble in water, but soluble in alcohol; 
 some of them may be distilled without change. Azo-benzene 
 itself (benzene-azo-benzene, C 6 H 5 N:NC 6 H 5 ) crystallizes in 
 large red plates, melts at 68, and distils at 293. Oxidizing 
 agents convert them into azoxy-, and reducing agents into 
 hydrazo- or amino-compounds. Chlorine and bromine act as 
 substituents. 
 
 The so-called "mixed" azo-compounds, which contain both 
 
ft PHENYL-HYDROXYLAMINE 397 
 
 an alphyl and an aryl radical, are also known, e.g. azo-phenyl- 
 
 ethyl, C 6 H 5 .N:N.C 2 H 5 , a bright-yellow oil (B. 1897, 30, 793). 
 
 Modes of Formation. 1. By the cautious reduction of nitro- 
 
 or azoxy-compounds, e.g. by means of sodium amalgam or of 
 
 an alkaline solution of stannous oxide (B. 18, 2912). 2. By 
 
 distilling azoxy-benzene with iron filings. 3. By the oxidation 
 
 of hydrazo-benzene. 4. By the oxidation of amino-compounds, 
 
 e.g. together with azoxy-compounds by means of KMnO 4 : 
 
 2C 6 H 6 .NH 2 + 20 
 
 5. By the action of nitroso- upon amino-compounds in pre- 
 sence of acetic acid. In this way azo-benzene is obtained from 
 nitroso-benzene and aniline acetate : 
 
 C 6 H 5 .NO + NH 2 .C 6 H 5 = C 6 H 5 .N:N-C 6 H 5 + H 2 0. 
 
 Ammo- and hydroxy-derivatives of azo-benzenes are known, 
 thus : 
 
 C 6 H 6 .N:N.C 6 H 4 .NH 2 C 6 H 6 .N:N.C 6 H 4 .QH 
 
 Amino-azo-benzene Hydroxy-azo-benzene. 
 
 The former are at the same time bases and azo-compounds, 
 and the latter azo-compounds and phenols (i.e. weak acids). 
 (Cf. Azo-dyes, p. 399.) 
 
 /2-Phenyl-hydroxylamine, C 6 H 5 .NH-OH, is formed when 
 nitro-benzene is reduced with zinc dust and water, more 
 especially in the presence of a mineral salt, e.g. CaCl 2 . It is 
 a colourless crystalline substance melting at 81, and is 
 rela f ' ly^unstable. Aqueous solutions rapidly undergo oxi- 
 dation on exposure to the air, yielding azoxy-benzene; oxidiz- 
 ing agents generally yield nitroso-benzene. Mineral acids 
 immediately cause molecular rearrangement into p-amino- 
 phenol, NH 2 -C 6 H 4 .OH (cf. p. 394). All the arylated /3-hy- 
 droxylamines corresponding with phenyl-hydroxylamine reduce 
 Fehling's solution, and this affords a test for an aromatic nitro- 
 compound. If, after warming with water and zinc dust, a solu- 
 tion is obtained which reduces FeMing's solution, the presence 
 of a nitro-group in the original compound can be inferred. 
 
 D. Hydrazines 
 
 The aromatic hydrazines (E. Fischer) entirely correspond 
 with those of the fatty series (cf. p. 111). 
 
 Phenyl-hydrazine, C G H 5 NH NH 2 , s-diphenyl-hydrazine or 
 hydrazo-benzene, C 6 H 6 NH NH C e H 6 ; unsym.-diphenyl- 
 
398 XXII. DIAZO- AND AZO-COMPOUNDS 
 
 hydrazine, (C 6 H 5 ) 2 N NEL and phenylmethyl - hydrazine, 
 (C 6 H 5 )(CH 3 )N.NH 2 , are all known. 
 
 Phenyl-hydrazine, C 6 H 5 NHNH 2 , forms a colourless crys- 
 talline mass, melting at 23 to a colourless oil, which quickly 
 becomes brown from oxidation, and which is best distilled 
 under reduced pressure. When kept or when heated it under- 
 goes slow decomposition (Chattaway). It forms salts with 
 mineral acids, e.g. the hydrochloride, C 6 H 5 N 2 H 3 , HC1 (plates). 
 Like all hydrazines, it has strong reducing power, reducing 
 Fehling's solution even in the cold. It is readily destroyed by 
 oxidation (Chattaway, C. N. 1911, 103, 217), but is stable to- 
 wards mild reducing agents. Energetic reducing agents con- 
 vert it into aniline and ammonia. Gentle oxidation of the 
 sulphate by means of HgO converts it into benzene-diazonium 
 sulphate. It is prepared: (a) by reducing benzene-diazonium 
 chloride with the calculated quantity of SnCl 2 and HC1: 
 
 C 6 H 6 N 2 C1 + 4H = C 6 H 6 .NH.NH 2 ,HC1; 
 
 (b) by reducing potassium diazo- benzene -sulphonate, C 6 H 5 - 
 NrN-SOgK (from 6 H 5 N 2 C1 and K 2 SO ? ), with zinc dust and 
 icetic acid to potassium phenyl-hydrazine-sulphonate, C G H 5 
 NHNHS0 3 K, which is then hydrolysed to phenyl-hydrazine 
 and sulphuric acid : 
 
 CcH 5 .NH-NH.S0 8 K + HC1 + H 2 = CeHj-NH-NHa, HC1 + KHS0 4 . 
 
 Alkyl and acyl derivatives of phenyl-hydrazine are known; 
 the former (mono-alky lated derivatives only) are obtained by 
 the action of alkyl iodides on the base or its metallic deriva- 
 tives. Phenyl-methyl-hydrazine, which can be obtained in 
 this way, is largely used for differentiating ketoses and aldoses 
 (p. 302); its constitution follows from its formation by the 
 
 /~1 TT 
 
 reduction of nitroso-methyl-aniline, Q|J 6 ^>NNO. Both mono- 
 
 and diacyl derivatives are known. The mono-acyl derivatives 
 or hydrazides (cf. Amides, Anilides) are obtained by the 
 action of the acid or acid anhydrides on the base; they give 
 a violet-red coloration with sulphuric acid and dichromate of 
 potash, and can be used for isolating acids which are readily 
 soluble (B. 22, 2728), e.g. acetylphenyl-hydrazide, C 6 H 5 -NH. 
 NH.CO-CH 8 ; m.-pt. 128. 
 
 The base is an important and often an exceedingly delicate 
 reagent for aldehydes and ketones, combining with them to 
 hydrazones, with elimination of water (cf. pp. 127 and 135). 
 
AZO-DYE8 399 
 
 Most of these compounds are solid and crystalline, and are 
 therefore eminently suited for the recognition of aldehydes 
 and ketones. With certain sugars it yields phenyl-hydrazones, 
 but with an excess of the base, osazones (p. 301) are formed. 
 Diketones, keto-aldehydes, &c., also yield osazones. 
 
 With ethyl aceto- acetate, phenyl-hydrazine forms pyrazole 
 derivatives, &#. phenyl-methyl-pyrazolone, the methyl deriva- 
 tive*of whrch is antipyrine (see p. 230). 
 
 Drphenyl-hydrazine, (CgH 5 ) 2 NNH 2 , is an oily base which 
 boils without decomposition, and, like phenyl-hydrazine, is 
 easily oxidized; it only reduces Fehling's solution, however, 
 when warmed. It is obtained by reducing diphenyl-nitros- 
 amine, (C 6 H 5 ) 2 N-NO, with zinc dust and acetic acid. M.-pt. 
 34. Like phenyl-hydrazine, it yields characteristic hydra- 
 zones and osazones with the sugars. 
 
 ^-Bromo-phenyl-hydrazone, C 6 H 4 Br*NHNH 2 , and|?-nitro- 
 phenyl-hydrazine are often used in isolating ketones, &c., as 
 the phenyl-hydrazones thus obtained crystallize well (B. 1899, 
 32, 1806). 
 
 E. Azo-dyes 
 
 A number of compounds derived from azo-benzene and its 
 homologues are largely used as dyes, under the name of azo- 
 dyes. These compounds are either basic and contain NH 2 or 
 N(CH 3 ) 2 groups, or are acidic and then contain either phenolic, 
 OH, or sulphonic, S0 2 OH, and phenolic groups. Azo-benzene 
 itself is a highly-coloured substance, but is not a dye. In 
 order that a coloured substance shall be a dye, it is essential 
 that the colour it imparts to a fabric shall not be removed by 
 washing or treatment with soap. According to 0. Witi> when 
 certain characteristic groups known as chromophores, among 
 which are N:N and N0 2 , are present, the compound is 
 coloured or is a chromogene ; and when, in addition to the 
 chromophore, a strongly basic (e.g. NH 2 ) or acidic group (e.g. 
 OH or S0 2 OH) is also present, we obtain a dye, e.g. : 
 
 Chromogeues. Dyes. 
 
 Nitre-benzene Nitraniline, N0 2 < C 6 H 4 -NH 2 ; 
 
 Nitro-benzene Picric acid, (NO 2 ) 3 .C 6 H 2 .OH; 
 
 ^.zo-benzene >-Hydroxy-azo-benzene, C 6 H 6 -N:N-C 6 H 4 'OH. 
 
 The majority of dyes, when reduced, yield colourless com- 
 pounds leuco-compounds which on oxidation are converted 
 into the original dyes. 
 
 With regard to the theory of the process of dyeing fabrics, 
 
400 XXII. DIAZO- AND AZO-COMPOUNDS 
 
 there are still two distinct schools. According to one, the process 
 consists in the formation of definite compounds of the basic or 
 acidic dye with acidic or basic constituents of the fabric dyed. 
 According to the other, the operation is largely a physical one, 
 and the dyed fabric may be regarded as a solid solution. 
 
 In most cases, silk and woollen and in a few cases cotton 
 fabrics can be dyed by direct immersion in a solution of the 
 dye; but, as a jule, cotton will not dye directly, but recmires 
 previous treatment with a mordant. The object of fehPmor- 
 dant is to deposit some substance on the fabric which will 
 afterwards combine with or fix the dye. The chief mordants 
 employed for acid dyes are the feeble bases aluminic, chromic, 
 or ferric hydroxides, obtained by immersing the fabric in a 
 solution of the metallic acetate, and then subjecting to the 
 action of steam. The product formed by the action of the 
 dye on the mordant is known as a lake, and the same dye can 
 give rise to different-coloured lakes, according to the mordant 
 used. When basic dyes are employed for cotton goods, the 
 fabric is usually mordanted with tannic acid. Stannic hy- 
 droxide obtained from such a salt as SnCl 4 , 2NH 4 C1 is also 
 used as a mordant. 
 
 ^-Amino-azo-benzene is the parent substance of the dyes 
 known as chrysoidines. It may be obtained (1) by nitrating 
 azo-benzene and then reducing (this indicates its constitution 
 as an amino-derivative of azo-benzene); (2) by molecular re- 
 arrangement of diazo-amino-benzene (p. 393): 
 
 ; gives NH 2 .C 6 H 4 .N:N.C 6 H 5 , 
 
 another example of the wandering of a radical from a side 
 chain into the benzene nucleus. The amino-group occupies 
 the ^-position with respect to the azo-group. 
 
 Substituted amino-azo-benzenes, e.g. dimethyl-amino-azo- 
 benzene, are obtained directly by the action of a diazonium 
 salt on a tertiary amine: 
 
 = C 6 H 5 .N:N.C 6 H 4 .N(CH 3 ) 2 + HC1. 
 
 Assuming the Blomstrand formula for the diazonium sait, 
 the reaction is probably first additive, and then HC1 is 
 eliminated : 
 
CHRYSOIDINES AND TROP^OLINES 401 
 
 The azo-group always takes up the ^-position with respect 
 to the substituted amino-group if this position is free. If, 
 however, the jo-position is already substituted, a dye is not 
 formed, or is formed very incompletely, and the o-position is 
 taken up. 
 
 The chrysoidines are coloured yellow to brown, and, as they 
 contain amino- or substituted amino-groups in the molecule, 
 are basic, and form well-defined salts with mineral acids. 
 
 Among the simplest chrysoidines we have : 
 
 Aniline yellow, the hydrochloride of j;-amino-azo-benzene. 
 It is now very little used. 
 
 Chrysoidine, or 2-A-diamino-azobenzene hydrochloride, C r H 5 
 N : N . C 6 H 3 (NH 2 ) 2 , HC1 [N 2 : (NH 2 ) 2 = 1:2:4]. It dyes silk and 
 wool directly an orange-red colour. 
 
 Bismarck brown, or 3':Z'A-triamino-azo-benzene hydrochloride, 
 NH 2 .C 6 H 4 .N:N.C 6 H 3 (NH 2 ) 2 ,HC1, is obtained by diazotizing 
 w-phenylenediamine and coupling the diazonium salt with a 
 second molecule of the base. 
 
 The brown coloration obtained by the addition of a few 
 drops of dilute nitrous acid solution to m-phenylenediamine 
 is due to the formation of Bismarck brown or a related sub- 
 stance. The hydrochloride crystallizes in reddish - brown 
 plates. 
 
 Many of the chrysoidine dyes are sulphonated derivatives 
 of amino-azo-benzene. As an example, we have methyl orange, 
 which is the sodium salt of helianthine or jp-dimethamino-azo- 
 benzene-^-sulphonic acid, (CH 3 ) 2 N.C 6 H 4 .N:N.C 6 H 4 .S0 2 .OH. 
 It is largely made use of as an indicator in volumetric analysis, 
 as it is not affected by weak acids, e.g. carbonic, but is an ex- 
 tremely delicate reagent for the feeblest alkalis. 
 
 The dyes known as tropaeolines are derivatives of ^-hydroxy- 
 azo-benzene. Such compounds are obtained by adding the cold 
 diazotized solution to an alkaline solution of a phenol. The 
 dye is then salted out by the addition of sodium chloride and 
 collected. The reaction is often made use of in testing for a 
 primary aromatic amine (p. 389), as the precipitates produced 
 are usually coloured bright red. The azo-group invariably 
 occupies the p-position with respect to the OH group, unless 
 this is already substituted. 
 
 ^-Hydroxy-azo-benzene crystallizes in brick-red prisms, and 
 is a yellowish-red dye. 
 
 Resorcin yellow, OH.S0 2 .C 6 H 4 .N:N ; C 6 H 3 (OH) 2 , 2A-di- 
 hydroxy-azo -benzene- 4' '-sulphonic acid, obtained by coupling a 
 
 (B480) 2C 
 
402 XXII. DIAZO- AND AZO-COMPOUNDS 
 
 diazotized solution of sulphanilic acid with an alkaline solu- 
 tion of resorcinol, is known as Tropseolin 0. 
 
 The constitution of an azo-dye can usually be determined by 
 an examination of its decomposition products, especially the 
 products formed by energetic reduction ; e.g. Bismarck brown, 
 on reduction with tin and hydrochloric acid, yields a mixture 
 of 1 : 3-diamino- and 1:2: 4-triamino-benzene : 
 
 NH 2 : NH, 
 
 <( \N:|N 
 N / 2H ; 2I_ 
 
 Bis-azo-dyes. Certain well-known dyes, e.g. Biebrich scarlet, 
 contain two azo-groups. Such can be obtained by diazotizing 
 an amino-derivative of azo-benzene, and then coupling it with 
 a tertiary amine or with a phenol, and we thus obtain com- 
 pounds of the type C g H 5 .N:N.C 6 H 4 .N:N.C 6 H 4 .OH. 
 
 Another type of bis-azo-compound is formed by coupling a 
 diamine or dihydric phenol with 2 mols. of a diazonium salt. 
 
 Many amino- and hydroxy-azo-derivatives react as tauto- 
 meric substances, especially those which contain an NH 2 01 
 OH group in the ortho - position with respect to the N 2 
 radical. These react as though they were quinone hydra- 
 zones or quinone-imide derivatives, e.g.: 
 
 C 6 H 5 .N:N.C 6 H 4 .OH C 6 H 6 NH.N:C 6 H 4 :O, 
 C 6 H 6 .N:N.C 6 H 4 .NH 2 C 6 H 6 .NH.N:C 6 H 4 :NH. 
 
 For a general summary compare Auwers (A. 1908, 360, 11). 
 The general conclusion drawn is that all the compounds, both 
 para and ortho, are true hydroxy-azo-compounds. 
 
 According to Hantzsch, many of the hydroxy-azo-compounds 
 are pseudo-acids (p. 363), i.e. the hydrogen compound is the 
 quinone hydrazone; but in the formation of a salt, intra- 
 molecular rearrangement occurs, and the salt thus has a con- 
 stitution quite different from that of the parent substance, e.g.: 
 
 C 6 H 5 .NH.N:C 6 H 4 :0 - 
 
 F. Phosphorus Compounds, &c.; Org-ano-Metallie 
 Derivatives 
 
 The phosphorus, &c., compounds of the fatty series have 
 their analogues in corresponding compounds of the aromatic; 
 these latter have been investigated by Michaelis and his 
 pupils (A. 181, 188, 201, 212, and 229 ; B. 28, 2205): for 
 
SULPHONIC ACIDS 403 
 
 instance, phenyl phosphine, C G H r .PH 2 ; phenyl phosphinic 
 acid, C 6 H 5 PO(OH) 2 ; phosphenyl chloride, C tf H 5 -PCl 2 ; phos- 
 phino-benzene, C 6 H 5 P0 2 ; and phospho -benzene, C 6 H 5 P:P 
 C 6 H 5 (these two last being analogous to nitro- and to azo- 
 benzene). Some of those compounds are solid, and they are 
 less volatile and more stable than the corresponding aliphatic 
 compounds. Corresponding derivatives of arsenic are also 
 known. 
 
 Aromatic Organo - Metallic Compounds. Mercury, tin, 
 lead, tellurium, and magnesium yield phenyl derivatives. 
 Mercury phenyl, Hg(C 6 H 5 ) 2 , is obtained by the action of 
 sodium amalgam of bromobenzene. It is relatively stable. 
 Numerous compounds of the type of phenyl magnesium 
 bromide, C 6 H 5 -Mg-Br, have been prepared, and are used as 
 synthetical reagents (cf. p. 356). 
 
 XXIII. ABOMATIC SULPHONIC ACIDS 
 
 The aromatic sulphonic acids are very similar in properties 
 to the sulphonic acids of the fatty series, but can be obtained 
 much mofe readily. One of the characteristic properties of 
 benzene and its derivatives is the readiness with which they 
 react with concentrated sulphuric acid, yielding sulphonic 
 acids. In some cases fuming sulphuric acid is used; in others 
 sulphuryl chloride, OH-SO^Cl. 
 
 Benzene-sulphonic acid, C 6 H 5 .S0 2 OH (Mitscherlich, 1834), 
 is formed when benzene is heated with concentrated sulphuric 
 acid for some hours : 
 
 C 6 H 6 + S0 2 (OH) 2 = C 6 H 5 .S0 2 .OH + H 2 0. 
 
 As in the case of ethyl hydrogen sulphate, advantage is 
 taken of the solubility of its barium, calcium, or lead salt to 
 separate it from the excess of sulphuric acid; or its sodium 
 salt is separated by the addition of sodium chloride. 
 
 It crystallizes in small plates containing 1JH 2 0, deliquesces 
 in the air, and is readily soluble in alcohol. The barium salt 
 crystallizes in glistening mother-of-pearl plates containing 1H 2 O. 
 
 It is very stable, and is not hydrolysed when boiled with 
 alkalis or acids (cf. Ethyl hydrogen sulphate). It is, however, 
 
404 XXIII. AROMATIC SULPHONIC ACIDS 
 
 decomposed into benzene and sulphuric acid when heated with 
 hydrochloric acid at 150, or with water vapour at a high 
 temperature (cf. p. 347): 
 
 C 6 H 5 .S0 2 .OH + H 2 = C 6 H 6 + S0 2 (OH) 2 . 
 
 When fused with alkali, it yields phenol in the form of its 
 potassium salt: 
 
 C 6 H 5 .S0 3 K + 2KOH =- C 6 H fi .OK + S0 3 K 2 + H 2 0, 
 
 and when distilled with potassium cyanide, it yields benzo- 
 nitrile: 
 
 C 6 H 6 .SO 3 K + CNK = C 6 H 6 .CN + S0 3 K 2 . 
 
 With PC1 5 the OH group present in the sulphonic acid 
 radical is replaced by chlorine, and benzene-sulphonic chloride 
 is formed: 
 
 C 6 H 6 .S0 2 OH-f PC1 6 = C 6 H 5 -S0 2 C1-|-POC1 3 + HC1. 
 
 This is an oil, insoluble in water; it melts at 14-5, and boils 
 at 120 (under 10 mm. pressure); as an acid chloride it is 
 reconverted into sulphonic acid by hot water, into the corre- 
 sponding esters by alcohols, and into benzene-sulphonamide, 
 C 6 ELS0 2 NH 2 (lustrous mother-of-pearl plates melting at 
 150), by ammonia. This compound can be sublimed, and 
 corresponds with other amides in its properties. The amido- 
 group, however, is so affected by the strongly acidifying action 
 of the S0 2 group that its hydrogen is replaceable by metals, 
 and the sulphonamides consequently dissolve in aqueous solutions 
 of alkali hydroxides. 
 
 The sulphonamides are largely made use of in distinguish- 
 ing the various sulphonic acids. These acids themselves are 
 difficult to purify, as a rule do not crystallize well, and have 
 no definite melting-point. The sulphonamides, on the other 
 hand, crystallize readily, and have sharp melting-points. The 
 sodium salt of the acid is treated with PC1 5 , and the chloride 
 thus obtained is warmed with ammonium carbonate. 
 
 Benzene-sulphonic chloride likewise yields sulphonamides 
 with primary and secondary amines, C 6 H 5 'S0 2 NHR and 
 C 6 H 5 'S0 2 NRB/, the former of these being soluble in alkali, 
 but the latter insoluble. Tertiary amines do not, of course, 
 give sulphonamides. This serves as the basis of a method for 
 separating primary, secondary, and tertiary bases, especially 
 
AMINO-SULPHONIC ACIDS 405 
 
 when /3-anthraquinone sulphonic chloride is used (Hinsberg, 
 B. 23, 2962; 1900, 33, 477, 557, 3526; 38, 906). 
 
 When benzene-sulphonic chloride is treated with zinc dust, 
 zinc benzenesulphinate is formed : 
 
 2C 6 H 6 .S0 2 Cl + 2Zn = (C 6 H 6 S0 2 ) 2 Zn + ZnCl 2 . 
 
 An alkaline sulphinate is also produced (along with phenyl 
 disulphide as by-product) when benzene-sulphonic chloride is 
 treated with thio-phenol in presence of alkali. 
 
 Benzene-sulphuric acid crystallizes in large glistening prisms, 
 readily soluble in hot water, alcohol, and ether. It possesses 
 reducing properties, and is itself converted into thio-phenol by 
 nascent hydrogen: 
 
 C 6 H 6 .S0 2 H + 4H = C 6 H 6 SH -f 2H 2 0. 
 
 Substitution may be effected in benzene-sulphonic aoid by 
 chlorine, bromine, and the groups N0 2 and NH 2 . 
 
 The nitro-benzene-sulphonic acids, N0 2 C 6 H 4 S0 3 H, are 
 obtained by nitrating benzene-sulphonic acid or by sulphonat- 
 ing nitro-benzene, the w-compound preponderating. Reduc- 
 ing agents convert them into the 
 
 Amino- benzene -sulphonic acids, NH 2 'C 6 H 4 S0 3 H. The 
 ^-compound, which is termed sulphanilic acid, is obtained by 
 heating aniline sulphate at 180-200 (Gerhardt, 1845); also by 
 reducing ^-nitro-benzene-sulphonic acid. The conversion of 
 aniline sulphate into sulphanilic acid proceeds in the following 
 stages : 
 
 NH 3 HSO 4 NH.SO 2 -OH 
 
 Aniline hydrogen Phenylsulphonamto 
 sulphate acid 
 
 
 SO 2 'OH Aniline 
 
 Sulphanilic acid o-siilphonic acid. 
 
 (Of. Eamberger, B. 1897, 30, 2274.) It crystallizes in rhombic 
 plates (+ H 2 O), sparingly soluble in water, forms metallic salts, 
 
406 XXIII. AROMATIC SULPHONIC ACIDS 
 
 e.g. sodium sulphanilate, NH 2 C 6 H 4 S0 8 Na + 2H 2 (large 
 plates), but does not combine with acids. The formula 
 
 C 6 H 4 <^qQ 3 /> possibly expresses the constitution of sulph- 
 
 anilic acid. The m-acid, also termed metanilic acid, is em- 
 ployed in the preparation of azo-dyes, e.g. metaniline yellow; 
 it crystallizes in fine needles or prisms. 
 
 Diazo-benzene-sulphonic acid, C 6 H 4 <^gQ ^> (the anhydride 
 of C 6 H 4 <^Q TT Y is obtained by adding a mixture of sul- 
 
 phanilate and nitrite of sodium to dilute sulphuric acid. It 
 forms colourless needles, sparingly soluble in water, shows all 
 the reactions of the diazo-compounds, and is of great impor- 
 tance for the preparation of azo-dyes. 
 
 Benzene-disulphonic acids, C 6 H 4 (S0 3 H) 2 (principally meta-), 
 and benzene-trisulphonic acids, C 6 H 3 (S0 3 H) 3 , result from the 
 energetic sulphonation of benzene with fuming sulphuric acid. 
 The former exist, of course, in three isomeric modifications. 
 "When they are distilled with KCN, they yield the compounds 
 C 6 H 4 (CN) 2 , the nitriles of the phthalic acids; when fused with 
 KOH, the m-disulphonic acid changes into resorcinol (m-di- 
 hydroxy-benzene), G 6 H 4 (OH) 2 . 
 
 Almost all the homologues of benzene, with the exception 
 of hexamethyl-benzene, yield sulphonic acids. From toluene 
 are obtained the o-, m-, and ^-toluene sulphonic acids, CH 3 - 
 C 6 H 4 .S0 3 H (Hollemann and Caland, B. 1911, 44, 2504). Of 
 these it is the p-acid which is formed in largest quantity 
 directly; its potassium salt crystallizes beautifully. 
 
 The sulphonic acids of the three xylenes, the xylene-sul- 
 phonic acids, C 6 H 3 (CH 3 \ 2 S0 3 H, serve for the separation of 
 these isomers from each other; and the power of crystalliza- 
 tion of the salts or amides of the sulphonic acids of the higher 
 benzene homologues is frequently made use of for the recog- 
 nition and separation of these hydrocarbons. 
 
 The above instances are sufficient to show that sulphonic 
 acids may be obtained from the most complicated aromatic 
 compounds. This is of especial importance if the latter are 
 dyes whose application is hindered by their insolubility in 
 water, as in the case, e.g., of indigo, amino-azo-benzene, &c. 
 The sulphonated dyes, however, are usually inferior to their 
 originals in colouring power arid purity, e.g., they do not stand 
 the effects of light so well. 
 
XXIV. PHENOLS 407 
 
 XXIV. PHENOLS 
 
 The hydroxylic derivatives of benzene and its homologues 
 are usually divided into (a) phenols and (b) aromatic alco- 
 hols. The phenols all contain the hydroxyl group or groups 
 directly attached to the benzene nucleus, e.g. C 6 H 5 (OH), 
 C 6 H 4 (OH) 2 , whereas in the alcohols the hydroxyl group is 
 present in a side chain, e.g. C 6 H 5 CH 2 -OH. 
 
 One important point of difference between the phenols and 
 alcohols is the more pronouncedly acidic nature of the phenol. 
 The aromatic alcohols closely resemble those of the aliphatic 
 series, but the phenols react as feeble acids, the hydroxylic 
 hydrogen being displaced by the action of sodium or potassium 
 hydroxide. 
 
 The phenols are either liquid or solid compounds, and are 
 often characterized by a peculiar odour, e.g. carbolic acid and 
 thymol. Most of them can be distilled without decomposition, 
 and all are readily soluble in alcohol or ether; some dissolve 
 easily in water, others less readily, the solubility tending to 
 increase with the number of hydroxyl groups present in the 
 molecule. Many of them are antiseptics, e.g. phenol, creosol, 
 and resorcinol. . 
 
 The phenols are usually divided into mono-, di-, tri- or tetra- 
 hydric, according to the number of OH groups present in the 
 molecule. 
 
 Behaviour. 1. Like the alcohols, the phenols are capable 
 of forming ethers such as anisole, C 6 H 5 0-CH 3 , esters, e.g. 
 phenyl acetate, C 6 H 5 CO CH 3 , and phenyl hydrogen 
 sulphate, C 6 H 6 S0 2 OH, thio-coinpounds, e.g. thiophenol, 
 C 6 H 5 .SH, &c. 
 
 They can only be compared with the tertiary alcohols, since 
 they cannot, like the primary or secondary alcohols, yield acids 
 or ketones containing an equal number of carbon atoms in the 
 molecule upon oxidation. 
 
 2. The phenols are weak acids, and form salts known as 
 phenates or phenoxides, e.g. C 6 H 5 OK, potassium phenate or 
 potassium phenoxide; most of the salts are readily soluble in 
 water, and far more stable than the alcoholates, with which 
 they correspond. 
 
 In aqueous solutions the salts are largely hydrolysed, and 
 are decomposed by carbon dioxide, as the phenols are ex- 
 tremely feeble acids comparable with hydrocyanic acid (cf. 
 Walker, Phys. Chem., chapter xxiv). The acid character of the 
 
408 
 
 XXIV. PHENOLS 
 
 J^O) 
 
 CD Ci 
 
 66 
 
 o o o o o 
 CO (N Oi ^ l>- 
 i i CM O CO CO 
 CM (N <?q CM <M 
 
 o I-H 
 
 o 2 
 
 cq o cq 
 co -^ I 
 
 CM 
 
 W 
 
 S 1 
 
REACTIONS OF PHENOLS 409 
 
 phenols is considerably increased by the entrance of negative 
 groups, especially N0 2 , into the molecule. (See Picric acid; 
 also Abst. 1903, 1, 754.) 
 
 3. The presence of NH 2 or OH groups in the benzene 
 nucleus renders compounds much more reactive towards halo- 
 gens, nitric acid, sulphuric acid, oxidizing agents, &c. With 
 polyamines and aminophenols the reactivity is such that the 
 compounds undergo spontaneous oxidation on exposure to the 
 air. The reactivity with chlorine is so great that frequently 
 compounds of this type cannot be chlorinated by the usual 
 methods. Orton and King (J. C. S. 1911, 1185) have introduced 
 a method based upon the fact that the reversible reaction: 
 
 K-NClAc + HCl ^ B-NHAc 
 
 proceeds from left to right in the presence of glacial acetic 
 acid, and thus by taking very dilute solutions of hydrochloric 
 acid, e.g. 0*021 N, the concentration of the chlorine is kept so 
 low that chloro-derivatives are obtained free from products of 
 oxidation. Cresols can be chlorinated in the same manner. 
 The acetyl derivative generally used is 2 : 4-dichloro-acetyl- 
 chloranilide, and if the theoretical amount of this compound is 
 used the reaction proceeds to completion, as hydrogen chloride 
 is formed by the action of the chlorine on the amine or phenol. 
 
 4. Many phenols give characteristic colorations with ferric 
 chloride in neutral solution, e.g. phenol and resorcinol violet, 
 catechol green, and orcinol blue-violet; while pyrogallol yields 
 a blue colour with ferrous sulphate containing a ferric salt, 
 and a red one with ferric chloride. Bleaching-powder and 
 iodine solution, in certain cases, also give particular coloration. 
 
 5. Liebermann's Reaction. When the phenols are mixed 
 with concentrated H 2 S0 4 and a drop of nitrite solution or of 
 a nitrosamine, they yield intensely coloured solutions which 
 turn to a deep-blue or green when diluted and rendered 
 alkaline with potash. 
 
 6. The sodium and potassium salts of the phenols react 
 with C0 2 (Kolbe) or with COC1 2 , with formation of aromatic 
 hydroxy-acids, e.g. salicylic acid (see this). 
 
 For further methods of preparation of hydroxy-acids and 
 aldehydes, see Tiemann-Reimer reaction (pp. 430 and 440). 
 
 7. The phenols couple with diazonium salts to form azo- 
 dyes (p. 389); when heated with benzo-trichloride, CgHyCC^, 
 they yield yellow-red dyes (see Aurin), and with phthalic acid, 
 the phthaleins (see Phenol-phthalein). 
 
410 XXIV. PHENOLS 
 
 8. When heated with zinc dust, the phenols are converted 
 into the corresponding hydrocarbons (Baeyer). 
 
 9. When heated with the additive compounds of zinc chloride 
 and ammonia or calcic chloride and ammonia, the OH is replaced 
 by NH 2 (cf. p. 368; also B. 19, 2901). 
 
 10. Heating with phosphorus pentachloride partially con- 
 verts the phenols into chlorinated hydrocarbons, and heating 
 with P 2 S 5 into thio-phenols. 
 
 Occurrence. Many individual phenols are found in the 
 vegetable and animal kingdoms, and also in coal-tar. 
 
 Constitution. The hydroxyl-groups in phenol, C 6 H 5 OH, and 
 in the di- and polyhydroxy-benzenes, containing six carbon 
 atoms, are linked to the benzene nucleus. That this is also 
 the case in the homologues of these compounds follows: 
 (a) from their completely analogous reactions; (b) from their 
 behaviour upon oxidation. Thus, when oxidized, w-cresol 
 yields m-hydroxy-benzoic acid, and hence the OH is present 
 in the benzene nucleus and not in the side chain, and must 
 be in the m-position with respect to the methyl group. 
 
 A. Monohydrie Phenols 
 
 Modes of Formation. 1. Many phenols are formed during 
 the destructive distillation of the more complex carbon com- 
 pounds, especially of wood and coal; they are therefore 
 present in wood- and coal-tars. The latter contains more 
 especially phenol and its homologues, cresol, &c.; the former, 
 among other products, the methyl ethers of polyhydric phenols, 
 e.g. guaiacol, C 6 H 4 (OH)(0CH 3 ), and its homologue creosol, 
 C 6 H 3 (CH 3 )(OH)(O.CH 3 ). 
 
 The phenols are isolated from coal-tar, &c., by shaking with 
 sodic hydroxide solution, in which they dissolve, saturating 
 the alkaline solution with hydrochloric acid, and purifying the 
 precipitated phenols by fractional distillation. 
 
 2. Phenols are formed together with an alkali sulphite when 
 salts of sulphonic acids are fused with potassic or sodic hy- 
 droxides (KekuU, Wurtz, Dusart, 1867): 
 
 C 6 H 6 .S0 3 K + 2KOH = C 6 H 6 .QK + SO 3 K 2 + H 2 O. 
 
 In the laboratory nickel or silver basins are used for this 
 fusion, and on the large scale iron boilers, c. The alkali 
 salts of the phenols are formed, and the free phenols may be 
 liberated, by the addition of mineral acid. The chlorinated 
 
PREPARATION OF PHENOLS 411 
 
 sulphonic acids and the chlorinated phenols also exchange the 
 halogen for hydroxyl when fused with potash: 
 
 C 6 H 4 C1(SO 3 K) -f 4KOH = C 6 H 4 (OK) 2 + SO 3 K 2 -f KC1 + 2H 2 0. 
 
 In certain cases intramolecular rearrangement occurs during 
 this fusion, e.g. all three bromo-benzene-sulphonic acids, the 
 ortho-, meta-, and para-, yield m-dihydroxy-benzene (resorcinol) 
 when fused with potash. 
 
 3. They are formed when aqueous solutions of diazonium 
 salts are heated (Griess-, cf. p. 387). As a rule, a very dilute 
 sulphuric acid solution is employed: 
 
 C 6 H 4 C1(N 2 C1) -f- H 2 O = C c H 4 Cl-OH + N 2 -f HC1. 
 
 4. Phenol is produced from benzene by the action of ozone 
 or hydrogen peroxide, and also by that of the oxygen of the 
 air in presence of caustic soda solution or of aluminium 
 chloride. In an analogous manner di- and even trihydroxy- 
 benzene may be obtained by fusing phenol with potash : 
 
 C C H 6 .OH + = C 6 H 4 (OH) 2 . 
 
 5. The phenols cannot be prepared from chloro-, bromo-, or 
 iodo-benzene in the same way as the alcohols from alkyl 
 chlorides, bromides, or iodides, the halogen being bound too 
 firmly to the benzene nucleus. If, however, nitro-groups are 
 present in o- or ^-positions, an exchange of this kind can be 
 effected by heating with aqueous sodium or potassium hy- 
 droxides; trinitro-chloro-benzene indeed reacts with water 
 alone : 
 
 C C H 2 C1(N0 2 ) 3 + HOH = C 6 H 2 (OH)(N0 2 ) 3 + HC1. 
 
 Similarly, the amino-group in amino-compounds may be 
 replaced by hydroxyl by means of boiling alkalis, provided 
 nitro-groups are also present in certain position; thus o- and 
 p- (not m-) dinitro-aniline yield dinitro-phenols, a reaction 
 which corresponds with the saponification of the amides (cf. 
 pp. 362 and 374). 
 
 6. Phenols are also formed when salts of the aromatic 
 hydroxy-acids are distilled with lime, or when their silver 
 salts are carefully heated: 
 
 C C H 2 (OH) 3 .C0 2 H = C0 2 -hC G H 3 (OH) 3 
 
 Gallic acid Pyrogallol. 
 
 Phenol, Carbolic acid, hydroxy -benzene, C 6 H 5 OH, was dis- 
 
412 XXIV. PHENOLS 
 
 covered in 1834 by Runge in coal-tar. It occurs in the urine 
 of the herbivora and in human urine as phenyl hydrogen sul- 
 phate, also in castoreum, and in bone-oil. It forms a colourless 
 crystalline mass consisting of long needles, melts at 42, boils 
 at 181, is soluble in fifteen parts of water at 16, and itself 
 dissolves some water, a small percentage of the latter sufficing 
 to liquefy the crystalline phenol. Alcohol and ether dissolve it 
 readily. It is hygroscopic, and acquires a reddish colour in the 
 air owing to the presence of impurities, possesses a character- 
 istic odour and burning taste, is poisonous, acts as a splendid 
 antiseptic, and exerts a strongly corrosive action upon the skin. 
 As a very feeble acid it dissolves readily in caustic potash 
 solution, but not in the carbonate. Ferric chloride colours the 
 aqueous solution violet, while a pine shaving moistened with 
 hydrochloric acid is turned greenish-blue by phenol. 
 
 Hexahydro-phenol, 6 H U OH, prepared from quinitol (cyclo- 
 hexane-1 : 4-diol) (B. 26, 229), is a liquid with an odour resem- 
 bling that of fusel oil. 
 
 Anisole, or Phenyl methyl ether, C 6 H 5 CHg, and phenetole, 
 or phenyl ethyl ether, C 6 H 5 C 2 H 6 , are best obtained by heat- 
 ing phenol and caustic potash with methyl or ethyl iodide in 
 alcoholic solution : 
 
 C 6 H 5 .OK + CH 3 I = C 6 H 5 .OCH 3 -}-KIj 
 
 the former is also obtained by distilling anisic acid with lime. 
 They are liquids of ethereal odour which boil at a lower 
 temperature than phenol, just as ether has a lower boiling- 
 point than alcohol. They are very stable neutral compounds, 
 which are not readily hydrolysed by acids or alkalis; when 
 heated with HI to 140, or with HC1 to a higher temperature, 
 or with aluminium chloride, they are decomposed, yielding 
 phenol : 
 
 Phenyl ether, Diphenyl oxide, (C 6 H 5 ) 2 0, is formed when 
 phenol is heated with ZnCl 2 or AlClg, but not with H 2 S0 4 . 
 It crystallizes in needles, and is not decomposed by hydriodic 
 acid. 
 
 Esters. Phenyl hydrogen sulphate, C 6 H. S0 2 OH (cf. 
 Ethyl hydrogen sulphate), is only capable of existence in the 
 form of salts, being immediately hydrolysed into phenol and 
 sulphuric acid when attempts are made to isolate it. The 
 potassium salt, C 6 H 6 0S0 2 .OK (plates, sparingly soluble in 
 
THIO-PHENOL 413 
 
 water), is found in the urine of the herbivora and also in 
 human urine after the consumption of phenol, and it may 
 be prepared synthetically by heating potassium phenate with 
 potassic pyro-sulphate in aqueous solution (Baumann). It is 
 very stable towards alkalis, but is saponified by hydrochloric 
 acid. 
 
 Phenyl acetate, C,HLO CO CH 3 , obtained from phenol, 
 acetic anhydride, and dry sodic acetate, is a liquid which 
 boils at 193, and is readily hydrolysed (cf. Ethyl acetate). 
 
 Thio-phenol, Phenyl hydrosulphide, C 6 H 5 SH, is prepared 
 from benzene-sulphonic chloride, C 6 H 5 'S0 2 C1, as given at 
 p. 405, or by heating phenol with P 2 S 5 . It is a liquid of 
 most unpleasant odour and of pronounced mercaptan char- 
 acter (see p. 89). It yields, for instance, a mercury com- 
 pound, (C 6 H 6 S) 2 Hg, crystallizing in glistening needles, and 
 also salts with other metals. When warmed with concen- 
 trated H 2 S0 4 , a cherry-red and then a blue coloration is 
 produced. 
 
 Closely related to the above are: (a) phenyl sulphide, (C 6 H 5 ) 2 S, 
 which is formed by the action of benzene-diazonium chloride 
 upon thio-phenol (B. 23, 2469): 
 
 It is a liquid smelling of leeks, and is oxidizable to phenyl 
 sulphone, (C 6 H 5 ) 2 S0 2 ; (b) phenyl disulphide, (C 6 H 5 ) 2 S 2 (glisten- 
 ing needles, m.-pt. 60), which is very easily prepared by the 
 action of iodine upon the potassium compound of thio-phenol, 
 or by exposing an ammoniacal solution of the latter to the air. 
 It is readily reduced to thio-phenol, and may be indirectly 
 oxidized to benzene-disulphoxide, (C 6 H 5 ) 2 S 2 2 . (Cf. the cor- 
 responding compounds of the fatty series, p. 89, et seq.) 
 
 SUBSTITUTED PHENOLS 
 
 Chloro- and Bromo-phenols. When chlorine is led into 
 phenol, o- and j?-chloro-phenols are formed. These, and also 
 the m-compound, may be obtained by reducing and diazotizing 
 the haloid nitro-benzenes. 
 
 Of the isomeric di-derivatives, the ^-compounds have the 
 highest melting-point and the o- the lowest; thus 0-chloro- and 
 bromo-phenols are liquid and the ^-compounds solid. When 
 fused with caustic potash they yield dihydroxy - benzenes 
 (p. 411), often with a molecular rearrangement. The chloro- 
 
414 XXIV. PHENOLS 
 
 phenols have a sharp, persistent odour. All the 5 hydrogen 
 atoms of phenol can be replaced by chlorine and bromine. 
 
 When an excess of bromine water is added to an aqueous 
 solution f phenol, a precipitate of s-tribromo-phenol (colour- 
 less needles, melting at 92) is obtained. 
 
 Nitroso-phenol, OH'C 6 H 4 NO, prepared from phenol and 
 nitrous acid (Baeyer, B. 7, 964), by boiling nitroso-dimethyl- 
 aniline with caustic -soda solution (see p. 378), and by the 
 action of hydroxylamine upon quinone, is identical with qui- 
 none monoxime, 0:C 6 H 4 :NOH (p. 430). It crystallizes in 
 fine colourless needles which readily become brown, or in large 
 greenish-brown plates, and detonates when heated. 
 
 Nitro-phenols. A mixture of o- and p-nitio -phenols is ob- 
 tained when phenol is mixed with cold dilute nitric acid; the 
 ^-compound preponderates if the liquid is cold, and the ortho- 
 if it is warm. When distilled with steam, the 1:2 compound 
 volatilizes, while the 1:4 remains behind. m-Nitro-phenol is 
 obtained by diazotizing w-nitraniline. 
 
 The o- and jp-compounds can also be obtained by fusing o- 
 and ^-nitranilines with potash, and ^-nitro-phenol has been 
 synthesised from nitro-malonaldehyde, NO 2 CH(CHO) 2 , and 
 acetone (Hill and Torray, B. 1895, 28, 2598). 
 
 The o-compound crystallizes in yellow prisms, and melts at 
 45, the m- in yellow crystals, melting at 96, and the para- in 
 colourless needles, melting at 114. 
 
 The acid character of phenol is so strengthened by the 
 entrance of the nitro-group that its salts are not decomposed 
 by carbonic acid, but are formed from the nitro-phenols and 
 alkali carbonate. Sodium o-nitro-phenate, C 6 H 4 (N0 2 )ONa, 
 crystallizes in dark -red prisms, and potassium jo-nitro-phenate 
 in golden needles. (For constitution of the salts, see chapter 
 on Absorption Spectra.) Halogens and nitric acid readily 
 substitute further in these mono-nitro-compounds ; nitric acid 
 yields two isomeric dinitro-phenols, C 6 H 3 (N0 2 ) 2 OH, (OH: 
 NO 2 :N0 2 = 1:2:4 and 1:2:6, i.e. tt-e two N0 2 groups are 
 always in the m-position to one another). Further nitration 
 in the presence of sulphuric acid gives 
 
 Picric acid, s-Trinitro-phenol, C 6 H 2 (N0 2 ) 3 .OH, (OH:N0 2 : 
 N0 2 :N0 2 = 1:2:4:6). This compound was discovered in 
 1799. It may also be prepared by the direct oxidation of 
 s-trinitro-benzene with K 3 FeC 6 Ng, and is produced by the 
 action of concentrated nitric acid upon the most varied or- 
 ganic substances, e.g. silk, leather, wool, resins, and aniline. 
 
AMINO-PHENOLS 415 
 
 It is a strong acid and forms beautifully crystalline salts, which 
 explode violently when heated or struck. It crystallizes from 
 alcohol or water in yellow plates or prisms, melting at 122, is 
 only sparingly soluble in water, and the aqueous solutions have 
 a persistent deep-yellow colour. It is used for the preparation 
 of explosives, and is also a yellow dye. 
 
 Picryl chloride, CLH ? (N0 2 ) 3 C1 (from picric acid and PC1 5 ), 
 resembles the acid chlorides (p. 362) in behaviour. Picric acid 
 forms beautifully crystallizing additive compounds with many 
 aromatic hydrocarbons, and also with amines and phenols. 
 
 Ammo-phenols are obtained by the reduction of nitro- 
 phenols : 
 
 C 6 H 4 (OH)NH 2 C 6 H s (OH)(NH 2 ) a C 6 H 3 (OH)(N0 2 )(NH 2 ) C 6 H 2 (OH)(NH a ) 8 
 
 0-, m-, p- Diamino- Nitro-amino- Triamino- 
 
 Amino-phenols phenols phenols pheuoL 
 
 In the amino-phenols (Hofmann, 1857) the acid character of 
 the phenols is neutralized by the presence of the amino-group, 
 so that they only yield salts with acids. The amino-phenols 
 themselves are relatively unstable, and readily decompose on 
 exposure to moist air or sunlight, but the hydrochlorides are 
 much more stable. Derivatives of these compounds, as phenols 
 and as amines, are known. The amino-hydrogen is readily 
 replaceable by acyl groups. 
 
 ^-Ammo-phenol, m.-pt. 184, obtained by the electrolysis of 
 nitrobenzene in concentrated sulphuric acid (Gattermann), or 
 by molecular rearrangement from /3-phenyl-hydroxylamine, 
 is easily oxidized to quinone, C 6 H 4 2 , and is converted by 
 bleaching-powder into quinone chlor-imide, O:C 6 H 4 :NC1. It 
 is used as a photographic developer under the name of rodinal. 
 Amidol is a salt of 2:4-diamino-phenol. 
 
 m-Amino-phenol and diethyl-m- ammo-phenol, C 6 H 4 (OH) 
 [N(C 2 H ) 2 ], are formed when m-amino-benzene-sulphonic acid 
 or its diethyl-derivative is fused with alkali. 
 
 The anisidines, amino-anisoles, methoxy-anilines, CH 3 0C 6 H 4 
 NH 2 , and the phenetidines, C 2 H 5 O.C 6 H 4 -NH 2 , are bases 
 similar to aniline, and are used in the colour industry (azo- 
 dyes). The acetyl derivative, aceto-p-phenetidine, C 2 H 5 
 C 6 H 4 NH'CO'CH 3 , which forms colourless crystals, is used 
 as an anti-pyretic and as a remedy for neuralgia under the 
 name of "Phenacetine". Phenocoll is lactyl-phenetidine. 
 
 Numerous complex sulphur compounds derived from amino- 
 phenols are used as dyes (e.g. Primulines, Vidal-black, &c.). 
 
416 XXIV. PHENOLS 
 
 Phenol-sulphonic acids, OH- C 6 H 4 -S(V OH. The o- and 
 |?-acids are obtained from phenol and concentrated H S0 4 at 
 a moderate temperature, that is, with much greater ease than 
 the benzene-sulphonic acids; the ortho-acid changes into the 
 para- when its aqueous solution is heated. The two acids 
 may be separated by means of their potassium salts. The 
 m-compound can be prepared indirectly by fusing m-benzene- 
 disulphonic acid with potash. All three are crystalline. 
 
 The o- and m-acids yield o- and wi-dihydroxy-benzenes when 
 fused with KOH, but the ^?-acid does not react in this way, 
 being attacked only at temperatures over 320, when complex 
 products are formed. 0-Phenol-sulphonic acid is used as an 
 antiseptic under the name of "Aseptol" or "Sozolic acid"; simi- 
 larly, the salts of di-iodo-^-phenol-sulphonic acid, OHC 6 H 2 I 2 - 
 S0 3 H, "Sozo-iodol", form antiseptics resembling iodoform. 
 
 HOMOLOGUES OF PHENOL 
 
 The homologues of phenol resemble the latter very closely 
 in most of their properties, form perfectly analogous deriva- 
 tives, possess disinfecting properties, and also a peculiar odour 
 (the cresols an unpleasant faecal-like, and the higher homo- 
 logues only a faint odour). 
 
 They differ from phenol mainly by the presence of side 
 chains which, as in the case of toluene, &c., may undergo 
 certain transformations. Especially when they are used in 
 the form of alkyl or acyl derivatives or acid sulphates, they 
 can be oxidized in such a manner that the side chains (methyl 
 groups) are transformed into carboxyl, with the production of 
 hydroxy-carboxylic acids. The cresols themselves cannot be 
 oxidized in this way even by chromic acid mixture, and are 
 completely destroyed by potassic permanganate. Negative 
 substituents, especially if they are present in the 0-position, 
 render such oxidation more difficult in acid, but facilitate it 
 in alkaline solution. 
 
 All three cresols, CH 3 C 6 H 4 OH, are present in coal-tar, 
 and are also contained in the tar from pine and beech wood; 
 they are most readily prepared from the corresponding 
 toluidines. 0-Cresyl hydrogen sulphate (analogous to phenyl 
 hydrogen sulphate) is found in the urine of horses, and the 
 ^-compound in human urine. 
 
 m-Cresol is conveniently prepared by heating thymol with 
 phosphoric anhydride and then with potash. 
 
DIHYDRIO PHENOLS 417 
 
 ^-Cresol is produced during the putrefaction of albumen. 
 Its dinitro-compound is a golden-yellow dye which is used as 
 ammonium or potassium salt under the name of Victoria 
 orange. 
 
 Crude cresol is rendered soluble in water by the addition 
 of resin soap or of oil soap; the preparations so obtained are 
 termed creoline and lysol, and are employed as antiseptics. 
 
 Thymol, C^H^O, I -methyl- 4: -isopropyl- 3 -hydroxy -benzene, is 
 found together with cymene, C 10 H 14 , and thymene, 10 Hj 6 , in 
 oil of thyme, Thymus Serpyllum, and is used as an antiseptic. 
 
 The isomeric carvacrol, l-methyl-^-isopropyl-Z-hydroxy-benzene, 
 present in Origanum hirtum, is prepared either by heating 
 camphor with iodine or from its isomer, carvol, and glacial 
 phosphoric acid. 
 
 The constitutions of these two phenols have been established 
 as follows : (a) Both yield cymene (^-methyl-isopropyl-benzene) 
 when heated with phosphorus sulphide and similar compounds. 
 (b) Carvacrol, when heated with phosphorus pentoxide, yields 
 propylene and o-cresol. (c) Thymol, when similarly treated, 
 yields propylene and m-cresol. 
 
 C 3 H 7 .C 6 H 3 (CH 3 )(OH) = C 3 H fl + OH.C 6 H 4 .CH 3 (oorm). 
 
 B. Dihydrie Phenols 
 
 By the entrance of two hydroxyls into benzene and its 
 homologues, the dihydric phenols are produced. These are 
 analogous to the monohydric compounds in most of their 
 relations, but differ from them in the same way as the 
 dihydric alcohols from the monohydric. The methods of 
 formation are analogous to those used for the monohydric 
 phenols, especially by fusion of sulphonic acids and halogen 
 derivatives with potash; instead, however, of the compound 
 expected, an isomeride which is stable at that high tempera- 
 ture frequently results (see Resorcinol). The j?-dihydroxy- 
 compounds are characterized by their close connection with 
 the quinones. Many of the polyhydric phenols are strong 
 reducing agents. 
 
 Catechol, formerly called pyrocatechin, C 6 H 4 (OH) 2 (1:2), 
 which was first obtained by the distillation of catechin 
 (Mimosa Catechu), is present in raw beet-sugar, and is ob- 
 tained when many resins or 0-phenol-sulphonic acid are fused 
 with potash. It crystallizes in short, white, rhombic prisms, 
 
 (B480) 2D 
 
418 XXIV. PHENOLS 
 
 which can be sublimed, and dissolves readily in water, alcohol, 
 and ether. 
 
 It is usually prepared by heating its mono-methyl ether, 
 guaiacol, C 6 H 4 (OH)(OCH 3 ), a constituent of beech-wood tar, 
 with hydriodic acid (see Anisole, p. 410). Like most of the 
 polyhydric phenols, it is very unstable in alkaline solution, 
 which quickly becomes green and then black in the air. The 
 aqueous solution is coloured green by ferric chloride, and 
 then violet by ammonia (reactions of the o-dihydroxy-com- 
 pounds). It possesses reducing properties, and precipitates 
 silver even from a cold solution of silver nitrate. By the con- 
 tinued action of chlorine upon it, derivatives of pentamethy- 
 lene and finally of the fatty series result (Zincke and Kuster). 
 By boiling it with potash and potassic methyl-sulphate, it may 
 be reconverted into guaiacol, which likewise shows the ferric 
 chloride reaction and possesses reducing powers. 
 
 Resorcinol, or m-Dihydroxy-benzene (Hlasiwetz, Barth, 1864), 
 is obtained when many resins (Galbanum, Asafcetida), m-phenol- 
 sulphonic acid, all three bromo-benzene-sulphonic acids, or m- 
 and j?-benzene-disulphonic acids are fused with potash. The last- 
 mentioned compounds are employed for its preparation on the 
 technical scale. It crystallizes in rhombic prisms or plates, 
 which quickly become brown in the air, dissolves readily in 
 water, alcohol, and ether, and reduces an aqueous solution of 
 silver nitrate when warmed with it, and an alkaline solution 
 even in the cold. With ferric chloride it gives a dark-violet 
 coloration. It acts therapeutically like carbolic acid, only 
 more mildly. 
 
 When heated with phthalic anhydride, it is converted into 
 fluorescein (p. 493);. test for m-dihydroxy-benzenes), and it is 
 therefore manufactured on the large scale. Nitrous acid or dia- 
 zonium compounds transform it into azo-dyes ; with the latter 
 it can yield mono-azo-dyes or primary Bis-azo-dyes (cf. p. 402). 
 Its trinitro-derivative is styphnic acid, C 6 H(OH) 2 (N0 2 ) 3 , which 
 is formed by the action of nitric acid upon many gum resins. 
 
 Quinol, formerly called hydroquinone, p-dihydroxy -benzene 
 (Wohler, 1844), may be obtained by the oxidation of quinic 
 acid, C 7 H 12 6 , by means of Pb0 2 , by the hydrolysis of the 
 glucoside arbutin, and from succinylo-succinic ester (cf. p. 
 241), &c. It is usually prepared by the reduction of quinone 
 with sulphurous acid, and hence the name hydroquinone. 
 It crystallizes in monoclinic plates or hexagonal prisms, 
 of about the same solubility as its isomers, and may be 
 
TRIHYDRIC PHENOLS 419 
 
 sublimed. Ammonia colours it reddish-brown, while chromic 
 acid, ferric chloride, and other oxidizing agents convert it into 
 quinone or quinhydrone (p. 431). It melts at 169, and, being a 
 strong reducing agent, it is used as a developer in photography. 
 
 Lead acetate solution yields a white precipitate with a 
 solution of catechol, but none with resorcinol, while quinol is 
 only precipitated in presence of ammonia. From the observed 
 heats of neutralization, resorcinol and quinol behave towards 
 soda as dibasic acids, and catechol as a weak monobasic acid. 
 
 Orcinol, or m-Dihydrwy-toluene, (CH 3 :OH:OH = 1:3:5), is 
 found in many lichens (Rocella tindoria, Lecanora, &c.). It is 
 formed by the elimination of carbon dioxide from or-sellinic 
 acid, e.g. upon fusing extract of aloes with potash, and it can 
 also be prepared synthetically from toluene (B. 15, 2992). Of 
 especial interest is its synthesis from ethyl acetone-dicarboxylate 
 (p. 260) and sodium (B. 19, 1446). It does not yield a fluor- 
 escein with phthalic anhydride. 
 
 Homo-catechol, C 6 H 3 (CH 3 )(OH) 2 , (CH 3 :OH:OH = 1:3:4), 
 deserves mention on account of its mono-methyl ether creosol, 
 CH 3 - C 6 H 3 (OH)(0 CH 3 ), occurring in beech-wood tar. Creosol 
 is a liquid similar to guaiacol, boiling at 220, and, as a deri- 
 vative of catechol, gives a green coloration with ferric chloride. 
 
 Quinitol (Cydohexane -1:4- diol), p-dihydroxy - hexamethylene, 
 C 6 H 10 (OH) 2 , a dihydroxy -derivative of reduced benzene, is ob- 
 tained synthetically by the reduction of p-diketo-hexamethylene. 
 It crystallizes in crusts, and has a sweet taste with a bitter 
 after-taste; m.-pt. 144. It is the simplest representative of 
 the inosite sugar group (p. 421). 
 
 C. Trihydric Phenols 
 
 Pyrogallol, Pyrogallic add (Sclieele, 1786), l:2:3-trihydroxy- 
 benzene, is the most important of these three isomers.. It is 
 obtained, apart from synthetical reactions, by heating gallic 
 acid, when carbon dioxide is eliminated: 
 
 C 6 H 2 (OH) 3 .C0 2 H = C 6 H 3 (OH) 3 + C0 2 . 
 
 It crystallizes in white plates, melts at 132, is readily 
 soluble in water, and capable of subliming without decom- 
 position. It is an energetic reducing agent, e.g. for silver 
 salts, and is used as a developer in photography. Its alkaline 
 solution rapidly absorbs oxygen, hence its use in gas analysis. 
 
420 XXIV. PHENOLS 
 
 The aqueous solution is coloured bluish-black by a solution 
 of ferrous sulphate containing ferric salt, and purple-red by 
 iodine. It does not react with hydroxylamine (cf. Phloro- 
 glucinol). 
 
 Pyrogallol dimethyl ether, C 6 H S (OE)(OCH S ) 2 (Hofmann), 
 is contained in beech-wood tar, as are likewise the dimethyl 
 ethers of the compounds C 6 H 2 (CH 3 )(OH) 3 and C 6 H 2 (C 3 H 7 ) 
 (OH) 3 , homologous with pyrogallol. 
 
 Phloroglucinol, or l:3:5-Trihydroxy-benzene (Hlasiwetz, 1855), 
 is obtained by the fusion of various resins and of resorciriol 
 with potash or soda, by the action of alkali upon the gluco- 
 side phloretin, and by fusing its dicarboxylic ester (whose 
 synthetical formation is given on p. 439) with potash. It 
 forms large prisms which weather in the air, melts at 218, 
 and sublimes without decomposition. With ferric chloride it 
 gives a dark-violet coloration, its solutions in alkalis readily 
 absorb carbon dioxide, and it possesses reducing properties. 
 
 Phloroglucinol is a typical example of a tautomeric com- 
 pound. 
 
 In many reactions, e.g. (a) the formation of metallic deriva- 
 tives, C 6 H 3 (OK) 3 ; of a trimethyl ether, C 9 H 8 (OCH 8 ), which is 
 insoluble in alkali; and of a triacetyl derivative, C 6 H 3 (OAc) 3 ; 
 (b) its combination with phenyl-carbimide to form a tricarbani- 
 line derivative, C 6 H 3 (0CONHC 6 H 5 ) 3 , it reacts as a normal 
 phenol, i.e. as sym. trihydroxy-benzene. On the other hand, 
 however, in certain of its reactions it behaves as a ketone, i.e. 
 
 as triketo-hexamethylene, CO<^Qjj 2 ' < QQ^>CH 2 ; thus it yields 
 
 a trioxime, C 6 H 6 ( : N OH) 3 , and when alkylated in presence of 
 alcoholic potash yields tetra- and hexa-alkyl derivatives, e.g. 
 
 * Its ultra-violet absorption 
 
 rtrum (Hedley, J. C. S. 1906, 730) resembles that of other 
 lols. 
 
 Hydroxy-quinol, 1:2 -A- Trihydroxy-benzene, is obtained by 
 fusing quinol with potash. Like pyrogallol, it yields no 
 oxime with hydroxylamine. 
 
 Hexahydroxy-benzene, Cg(OH) 6 , forms as its potassium 
 salt potassium carboxide, C 6 6 K 6 , the explosive compound 
 sometimes obtained in the manufacture of metallic potassium. 
 It crystallizes in colourless prisms, has no definite melting- 
 point, but decomposes at about 200, and can be converted 
 into its quinone. 
 
AROMATIC ALCOHOLS 42 1 
 
 ftuercitol, CLH 7 (OH) 5 , found in the oak, and inosite or 
 iiiositol, C 6 H 6 (OH) 6 , found in the muscles of the heart, are 
 polyhydroxy-derivatives of hexamethylene. In many respects 
 they closely resemble the aliphatic polyhydric alcohols rham- 
 nitol and sorbitol. Quercitol melts at 235, is optically active, 
 and has [a] D = -j-24'16. Inositol or hexahydroxy-cyclohexane 
 exists in an inactive and in d-, /-, and r-modifications. 
 
 , XXV. AROMATIC ALCOHOLS, ALDEHYDES, AND 
 KETONES 
 
 A. Aromatic Alcohols 
 
 While the phenols remind us of the tertiary alcohols of the 
 fatty series, although they differ from these in many points, 
 we are acquainted with compounds which possess the alcoholic 
 character in its entirety; they are termed aromatic alcohols. 
 The most important of these is (primary) benzyl alcohol, 
 C 7 H 7 OH, which is isomeric with the cresols, this isomerism 
 being explained by the different position of the hydroxy-group 
 in the molecule; thus, while the cresols, like all phenols, con- 
 tain the hydroxyl linked to the benzene nucleus, in benzyl 
 alcohol it is present in the side chain: 
 
 CH 3 C 6 H 4 OH (cresols) C 6 H 6 CH 2 OH (benzyl alcohol). 
 
 * This follows from the formation of benzyl alcohol from 
 benzyl chloride, C 6 H 5 CH 2 C1 (and vice versa), and also from 
 the fact that it can be oxidized to an aldehyde and an acid 
 containing the same number of carbon atoms in the molecule 
 as itself, these being likewise mono-derivatives of benzene : 
 
 C 6 H 6 .CH 2 .OH C 6 H 5 .CHO C 6 H 5 .CO-OH 
 
 Benzyl alcohol (Benzene- Benzaldehyde (Benzene- Benzoic acid (Benzene- 
 methylol) methylal) carboxylic acid). 
 
 Benzyl alcohol may also be looked upon as methyl alcohol in 
 which one atom of hydrogen is replaced by the group C 6 H 5 : 
 
 H CH 2 OH (carbinol) C 6 H 6 CH 2 OH (phenyl-carbinol), 
 
 and is therefore the simplest aromatic alcohol. 
 
 In addition to primary alcohols, e.g. tolyl alcohols, CH- 
 C 6 H 4 .CH 2 OH, ^-phenyl-ethyl alcohol, C 6 H 6 CH 2 . CH 2 OH, 
 
422 XXV. AROMATIC ALCOHOLS, ALDEHYDES, ETC. 
 
 secondary, e.g. a-phenyl-ethyl alcohol, or l-pkenyl-hydroxy* 
 ethane, C 6 H 5 CH(OH) CH 3 , and even tertiary alcohols, e.g. 
 (C 6 H 5 ) 3 COH, triphenyl-carbinol, are known. Of the poly- 
 hydric alcohols, phenyl-glycerol (l-phenyl-l:2:3-trihydroxy- 
 propane) is the most important. All of these contain the 
 hydroxyl radicals attached to carbon atoms of the side chain 
 and not to those of the nucleus, and this is the fundamental 
 difference between an aromatic alcohol and a phenol. The alco- 
 hols are not of the same commercial importance as the phenols, 
 and hence have not been investigated to the same extent. 
 
 All these compounds are, as alcohols, perfectly analogous to 
 the alcohols of the fatty series, so far as regards the formation 
 of alcoholates, ethers, esters, mercaptans, amines, phosphines, 
 &c. They are, however, at the same time benzene derivatives, 
 and consequently yield chloro-, bromo-, nitro-, amino-, &c., 
 substitution products. Unsaturated aromatic alcohols are 
 also known, which resemble the unsaturated compounds of 
 the fatty series to the closest extent in their chemical be- 
 haviour, but are at the same time benzene derivatives. 
 
 These remarks also apply in full degree, mutatis mutandis, to 
 the aromatic aldehydes and ketones (see below). 
 
 Benzyl alcohol, C 6 H 5 'CHo'OH, is a colourless liquid of 
 faint aromatic odour, sparingly soluble in water, and boils at 
 204:. It occurs naturally in Peru and Tolu balsams as ben- 
 zoic and cinnamic esters, and is formed from benzyl chloride 
 just as alcohol is from ethyl chloride. It is usually prepared 
 by the action of concentrated aqueous potash on benzaldehyde, 
 whereby the one half of the aldehyde is oxidized and the re- 
 mainder reduced (B. 14, 2394): 
 
 2C 6 H 5 .CHO + KOH = C 6 H 5 .CH 2 OH + C 6 H 6 .COOK. 
 
 Benzyl alcohol is also formed when benzamide is reduced 
 with sodium amalgam. This is a reaction which has been 
 employed for the preparation of a number of substituted 
 benzyl alcohols (Hutchinson, B. 1891, 24, 173). 
 
 Phenyl-methyl-carbinol, C 6 H 5 . CH(OH) . CH 3 , b.-pt. 203, 
 can be prepared by reducing acetophenone, C 6 H 5 CO-CH 3 
 (p. 427), into which it is reconverted by gentle oxidation. 
 
 Numerous secondary and tertiary alcohols have been synthe- 
 sized within recent years by means of Grignard's compounds 
 (p. 356). 
 
 The simplest of the unsaturated alcohols is cinnamic alco- 
 hol, C 6 H 6 CH:CHCH 2 OH, which occurs as cinnamic ester 
 
AROMATIC ALDEHYDES 423 
 
 (" styracin ") in storax. It crystallizes in glistening needles 
 of hyacinth-like odour, yields cinnamic acid when gently oxi- 
 dized, and benzoic when the oxidation is more vigorous. 
 
 B. Aromatic Aldehydes 
 
 Benzaldehyde, Benzene-methylal, or oil of bitter almonds, 
 C 6 H 5 -CHO, was discovered in 1803 and investigated by Liebig 
 and W oliler (A. 22, 1). It is a colourless, strongly refracting 
 liquid of agreeable bitter almond-oil odour. It boils at 179, 
 has a sp. gr. 1*05 at 15, and is readily soluble in alcohol and 
 ether, but only sparingly in water (1 in 30). 
 
 The modes of formation are for the most part analogous to 
 those described under the aliphatic aldehydes (pp. 122 and 
 123): 
 
 (a) By the oxidation of the corresponding alcohol. This 
 method, although of considerable practical importance in the 
 aliphatic series, is of but theoretical interest in the aromatic, 
 as the alcohols themselves are usually prepared from the 
 aldehydes. 
 
 (b) By the distillation of the calcium salt of the correspond- 
 ing acid, benzoic acid, with calcium formate. 
 
 (c) By heating the corresponding dichloride, benzal chloride, 
 or benzylidene chloride, C 6 H 5 -CHC1 2 (from toluene), with 
 water or sulphuric acid, or, as is done on the technical scale, 
 with water and lime; also by heating benzyl chloride, C 6 H 5 
 CH 2 C1, with water and plumbous or cupric nitrate. 
 
 This last method involves a process of hydrolysis : 
 
 C 6 H 5 .CH 2 C1 C 6 H 6 .CH 2 .OH, 
 
 and also a process of oxidation: 
 
 C 6 H 5 .CH 2 .OH C 6 H 6 .C<^, 
 
 both of which are brought about by the copper nitrate solu- 
 tion. 
 
 (d) Together with dextrose and hydrocyanic acid by decom- 
 posing amygdalin, C 20 H 27 O n N, a glucoside (see Glucosides) 
 which occurs in bitter almonds and crystallizes in white plates, 
 either by means of sulphuric acid or by emulsin (an enzyme 
 likewise present in bitter almonds, cf. pp. 267 and 592): 
 
 C 20 H 27 U N + 2H 2 = C 6 H 5 .CHO + 2C 6 H 12 O 6 -f CNH. 
 
 (e) By the action of chromyl chloride, Cr0 2 Cl 2 , upon toluene, 
 
424 XXV. AKOMAT1C ALCOHOLS, ALDEHYDES, ETd. 
 
 This is Etard's reaction, and is of great value for the synthesis 
 of aldehydes and also of certain ketones from hydrocarbons. 
 An additive compound, C 6 H 5 CH 3 (Cr0 2 Cl 2 ) 2 , is first formed, 
 and yields the aldehyde on the addition of water (B. 17, 1462, 
 1700; 32, 1050. 
 
 (/) ^7 the action of Grigiiard's phenyl-magnesium bromide 
 on ethyl orthoformate (Bodroux, C. E. 1904, 138, 92 and 700), 
 e.g.: 
 
 C 6 H 6 .Mg.Br-f-CH(OEt) 3 = Mg-Br-OEt -f C 6 H 6 -CH(OEt) 2 . 
 C 6 H 6 -CH(OEt) 2 hydrolysed C 6 H 6 .CHO. 
 
 Gattermann and Maffezzoli (B. 1903, 36, 4152) have used Gri- 
 gnard's compound with a large excess of ethyl formate at low 
 temperatures.* 
 
 (g) Homologues of benzaldehyde are sometimes prepared 
 by the elimination of carbon dioxide from substituted phenyl- 
 glyoxylic acids : 
 
 C 6 H 4 X.CO-C0 2 H -* C 6 H 4 X.C^Q, 
 
 a reaction which usually takes place when the glyoxylic acid 
 is distilled. 
 
 Behaviour. 1. Its behaviour is that of an aldehyde, and in 
 many respects it closely resembles the aliphatic aldehydes. Thus 
 it is (a) easily oxidizable to the acid, and on this account 
 reduces an ammoniacal silver solution with the production of 
 a mirror; (b) reducible to the alcohol; (c) capable of forming 
 a crystalline additive compound with NaHS0 3 ; (d) capable of 
 combining with HCN (see Mandelic acid); (e) capable of 
 reacting with hydroxylamine and phenyl-hydrazine to benz- 
 aldoxime, GgHg-CHiN-OH, and benzaldehyde-phenyl-hydra- 
 zone, C 6 H 5 CH:N 2 H'CgH 5 , respectively; (/) converted into 
 benzylidene chloride, C 6 H 6 -CHC1 2 , by the action of phosphorus 
 pentachloride. 
 
 2. Benzaldehyde does not form an additive compound with 
 ammonia analogous to the aldehyde-ammonias of the aliphatic 
 series, but enters into a somewhat complex condensation, the 
 oxygen of the aldehyde being eliminated with the hydrogen 
 atoms of ammonia in the form of water, the complex conden- 
 sation product hydrobenzamide being formed : 
 
 3C 6 H 6 .CHO + 2NH 3 = (C 6 H 5 .CH) 3 N 2 + 3H 2 O. 
 
 3. Benzaldehyde and its homoiogues can undergo poly- 
 * For synthetical methods see Gattermann, A. 1906, 347, 347. 
 
REACTIONS OF ALDEHYDES 425 
 
 tnerization, e.g. when an alcoholic solution of benzaldehyde is 
 boiled with potassium cyanide, benzoin is formed : 
 
 C 6 H 6 .CH:0 + C 6 H 5 .CH:0 = C 6 H fi .CH(OH).CO.C 6 H 6 , 
 
 a compound which is both a secondary alcohol and a ketone. 
 
 4. A number of condensation products can be obtained 
 from the aromatic aldehydes, and many of these are of com- 
 mercial importance. The condensation usually takes place 
 in the presence of a condensing agent, e.g. acetic anhydride, 
 anhydrous zinc chloride, potassic hydroxide, sodic ethoxide, 
 &c. Among some of the simplest of these condensations are : 
 
 (a) With primary amines. The formation of benzylidene 
 anilines (Schifs Bases): 
 
 = H 2 O + C 6 H 5 .CH:N.C 6 H 6 . 
 
 It has been shown recently that this reaction is preceded by 
 the formation of an additive compound, C 6 H 5 CH(OH)NH 
 C 6 H 5 , which then passes into the benzylidene derivative. A 
 few such additive compounds have actually been isolated. 
 (Dimroth and Zoepritz, B. 1902, 35, 984.) 
 
 (b) With tertiary amines, e.g. : 
 
 2C 6 H 5 .NMe 2 + C 6 H 5 .CHO = H 2 O + C 6 H 6 .CH(C 6 H 4 .NMe 2 ) 2 , 
 
 when a substituted diamino-derivative of triphenyl-methane is 
 produced (p. 483). 
 
 (c) With the sodium salts of fatty acids, when unsaturated 
 acids are formed (Perkin's Synthesis, pp. 441 and 442): 
 
 C 6 H 6 CHO + CH 3 COONa = C 6 H 6 . CH : CH C0 2 Na + H 2 0. 
 
 (d) With fatty aldehydes, ketones, &c. : 
 
 C 6 H 6 .CH:0 + CHfc.CHiO = H 2 O + C 6 H 5 .CH:CH.CHO, 
 
 when unsaturated aldehydes (e.g. cinnamic aldehyde) or ketones 
 are formed. 
 
 5. Its reaction with alkalis (p. 422) is also different; in 
 the fatty series aldehyde resins are formed, and with benz- 
 aldehyde a mixture of primary alcohol and the corresponding 
 acid. This latter reaction is characteristic of aldehydes in 
 which the CHO group is directly attached to the benzene 
 nucleus. 
 
 6. As a benzene derivative, it can be substituted by halogens 
 (indirectly), and can be nitrated, sulphonated, &c. (directly). 
 
426 XXV. AROMATIC ALCOHOLS, ALDEHYDES, ETC. 
 
 As in the case of toluene, chlorine enters the side chain at 
 the boiling temperature, with formation of benzoyl chloride, 
 OJL.COC1. 
 
 Among its derivatives, the following deserve mention : 
 
 a-Benzaldoxime, Benz-anti-aldoxime, C 6 H B CH : N OH, is 
 formed from benzaldehyde and hydroxylamine; it melts at 
 35, and decomposes when boiled. It can be transformed by 
 means of acids into the isomeric /3-benzaldoxhne, benz-syn- 
 'aldoxime, which melts at 125 (for velocity, cf. Patterson, J. 
 . S. 1907, 504; 1908, 1041), and in contradistinction to the 
 isomer, readily reacts with acetic anhydride yielding benzo- 
 nitrile. The oximes are stereo-isomeric (Nitrogen-isomerism). 
 (Cf. pp. 138 and 428.) 
 
 Benzaldehyde - phenyl - hydrazone, C 6 H 5 CH : N NHC 6 H 5 , 
 forms colourless crystals, melting at 152. Benzylideneazine, 
 CHPh : N N : CHPh, from benzaldehyde and hydrazine sul- 
 phate, has m.-pt. 93. 
 
 Nitro-benzaldehydes, N0 2 .C 6 H 4 .CHO. The m-compound 
 is the chief product of nitration, but some 20 per cent of the 
 o-compound is formed at the same time. The latter is best 
 prepared by oxidizing o-nitro-cinnamic acid by KMn0 4 in pre- 
 sence of benzene; it forms long colourless needles, melting at 
 46, yields indigo (p. 527) with acetone and caustic soda, and 
 on exposure to sunlight forms o-nitroso-benzoic acid. It can 
 be reduced to o-amino-benzaldehyde, NH 2 'CJE 4 CHO, a com- 
 pound crystallizing in silvery glistening plates, m.-pt. 46, 
 which is of value for various synthetical reactions. (See 
 Quinoline; also B. 16, 1833.) m-Amino-benzaldehyde, which 
 is prepared from w-nitro-benzaldehyde, by the reduction of its 
 bisulphite compound, is used in the production of triphenyl- 
 methane dyes. 
 
 Cinnamic aldehyde, C 6 H 5 CH : CH CHO, is the chief con- 
 stituent of oil of cinnamon (Persea cinnamomum), from which 
 it may be isolated by means of its bisulphite-compound. It is 
 an oil of aromatic odour, boils at 246, and is readily volatile 
 with steam. In addition to its properties as an aldehyde, it 
 also possesses the properties of an unsaturated compound, e g. 
 forms a dibromide. Its reaction with potassium hydrogen sul- 
 phite is characteristic. It first forms an additive compound, 
 O 6 H 6 GH:CH.CH(OH)(S0 3 K), like an ordinary aldehyde, and 
 then, as an unsaturated compound, combines with a second 
 molecule of the sulphite, yielding C 6 H 5 CH(S0 3 K) CH 2 - 
 H(OH)(S0 3 K) + 2H 2 0. (B. 24, 1805; 31, 3301.) 
 
AROMATIC KETONES 42? 
 
 C. Aromatic Ketones 
 
 The aromatic ketones are usually divided into (1) mixed 
 aromatic ketones, viz. those which contain both an aryl and 
 an alphyl group, e.g. CgH 5 CO'CH 3 , and (2) true aromatic or 
 diaryl ketones, e.g. C 6 H 5 - CO C 6 H 5 . 
 
 Acetophenone, Phenyl-methyl ketone, C 6 H 5 'COCH 3 , is the 
 simplest representative of the mixed aromatic ketones. It 
 crystallizes in colourless plates, is readily soluble in water, 
 melts at 20, boils at 200, and is obtained by the normal 
 modes of preparation for ketones, e.g. by distilling a mixture 
 of acetate and benzoate of calcium, as also by the Friedel- Crafts' 
 synthesis (p. 346), viz. the conjoint action of acetyl chloride 
 and aluminium chloride upon benzene. When benzene and 
 its derivatives are converted into ketones by this method, 
 only one acyl group is introduced as a rule, and this into the 
 para-position with respect to any alkyl group already present. 
 With a sym. trialkylated benzene, e.g. mesitylene, it has been 
 found possible to introduce two acyl groups, e.g. diacetyl- 
 mesitylene, (CH 3 ) 3 6 H(COCH 3 ) 2 (V. Meyer, B. 1895, 28, 3212; 
 1896, 29, 846, 1413). When the temperature is kept low by 
 diluting the mixture with carbon disulphide, a good yield of 
 ketone may be obtained by the Friedel-Crafts' method. 
 
 Acetophenone unites in itself the properties of a ketone of 
 the fatty series and of a benzene derivative. It yields benzoic 
 acid and carbon dioxide when oxidized with ordinary oxidizing 
 agents, but with cold alkaline permanganate it yields C 6 H 5 - 
 CO'C0 2 H, phenyl-glyoxylic acid or benzoyl-formic acid. 
 When warmed with halogens, it is substituted in the side 
 chain (e.g. to "phenacyl bromide", C 6 H 5 CO CH 2 Br), and 
 with nitric acid it is nitrated. It is used as a soporific under 
 the name of "Hypnone". Its oxime melts at 59, and its 
 phenyl-hydrazone at 105. 
 
 Although it combines with hydrogen cyanide to form the 
 nitrile of a-phenyl-lactic acid, it cannot form an additive com 
 pound with sodic hydric sulphite. 
 
 Its homologues closely resemble it, but are liquid at the 
 ordinary temperature. Acetophenone and some of its homo- 
 logues can be prepared from hydrocarbons with long side 
 chains by Etard's reaction (see p. 424; B. 23, 1070; 24, 1356). 
 Aromatic poly ketones (cf. p. 221) have also been prepared, e.g.^ 
 benzoyl-acetone, C 6 H 5 CO CH 2 CO CH 3 , and acetophenone- 
 acetone, C 6 H 5 CO - CH 2 CH 2 CO CH 3 . The latter, like- 
 
428 XXV. AROMATIC ALCOHOLS, ALDEHYDES, ETC. 
 
 acetonyl-acetone, is readily converted into furane, pyrrole, and 
 thiophene derivatives (see p. 516). 
 
 Benzaldehyde condenses with acetone and acetophenone in the 
 presence of alkalis, yielding unsaturated ketones, e.g. Benzylid- 
 eneacetone, CHPh:CHCO-CH 3 , m.-pt. 41, and benzylidene- 
 acetophenone, chakone, CHPh CH : CH CO C 6 H 5 , m.-pt. 58. 
 
 Benzophenone, Diphenyl ketone, C 6 H 5 CO C 6 H 5 , may be 
 obtained (1) by distilling calcium benzoate, (2) by the Friedel- 
 Crafts' synthesis, (3) by the oxidation of diphenylmethane, 
 (C 6 H 5 ) 2 CH 2 , or of diphenyl-carbinol, (C 6 H 5 ) 2 CH OH. 
 
 Good yields of ketones are not usually obtained by the 
 action of Grignard's reagents on acid chlorides; as a rule the 
 reaction proceeds further, and a tertiary alcohol is obtained 
 (p. 356). An exception is found in the reaction between 
 a-naphthyl-magnesium bromide and benzoyl chloride. 
 
 Ketones have recently (Blaise, C. R 1901, 132, 38; 133, 299) 
 been synthesised from Gh'ignard's reagents and nitriles, e.g. : 
 
 R-CN + B/.Mg.I = RR'CiNMgl, 
 
 and this with water gives: 
 
 R.CO-R' + NH S + I-Mg-OH. 
 
 Acid amides react in a somewhat similar manner. 
 
 Benzophenone is dimorphous; the stable modification melts 
 at 49, and when boiled or distilled yields the unstable modi- 
 fication, melting at 26; but this gradually passes back again 
 into the stable modification. The reaction is, however, con- 
 siderably accelerated by the addition of a minute crystal of 
 the stable compound. It yields an oxime melting at 140 and 
 a phenyl-hydrazone melting at 105. 
 
 When reduced with zinc dust or hydriodic acid and red 
 phosphorus, it yields diphenylmethane. 
 
 Stereo-isomeric Oxirnes and Hydrazones. The isomerism 
 described on pp. 137 et seq. is more frequently met with in the 
 aromatic than in the aliphatic series. Benzaldehyde and most 
 of its substitution products yield two distinct oximes and most 
 of the unsymmetrical aromatic ketones, e.^..^?-chloro-benzo- 
 phenone, 6 H 4 C1 CO C 6 H 6 , and tolyl-phenyl-ketone, CH 3 
 C 6 H 4 COC 6 H 5 , also yield stereo-isomeric oximes of the syn- 
 and anti- types. The one isomeride is usually readily trans- 
 formed into the more stable by means of hydrochloric acid or 
 bromine, by rise of temperature, and by exposure to light. 
 
HYDROXY-ALCOHOLS, ETC. 429 
 
 The following relationships of the benzaldoximes are of 
 interest: 
 
 Benz-cwfo'-aldoxime * Benz-awft'-aldoxime hydrochloride 
 f heated J heated 
 
 Benz-syn-aldoxime * Benz-sytt-aldoxime hydrochloride. 
 HC1 
 
 The syn- or anti- configuration of the isomerides is determined 
 in the case of the aldoximes by a comparison of the readiness 
 with which water is eliminated and a nitrile formed, and in 
 the case of the ketoximes by an examination of the products 
 obtained by Beckmanris transformation (p. 139). Thus: 
 
 C 6 H 5 .C.C 6 H 4 .CH 3 gives C G H 6 .CO.NH.C 6 H 4 .CH 3 
 
 " Benz-#-toluidide 
 
 Phenyl-^-tolyl-antt-ketoxime 
 and 
 
 C 6 H 6 .C.C 6 H 4 .CH 3 gives CH 3 .C 6 H 4 .(X).NH.C 6 H 6 
 " Anilide of jp-toluic acid. 
 
 Phenyl-jj-tolyl-sj/n-ketojcime 
 
 Compare Henrich, B. 1911, 44, 1533. 
 
 D. Hydroxy or Phenolic Alcohols, Aldehydes, and 
 Ketones 
 
 Formula. Name. Constitution. 
 
 OH.C 6 H 4 .CH 2 OH Saligenin, 
 
 or o-hydroxy-benzyl alcohol. 
 
 OCH 3 .C 6 H 4 .CH 2 OH Anisyl alcohol, 
 
 or _p-methoxy-benzyl alcohol. 
 OH C 6 H 3 (OCH 8 ) . CH 2 OH .... Vanillic alcohol, 
 
 or 3-methoxy-4-hydroxy-benzyl 
 
 alcohol. 
 OH C 6 H 3 (OCH 3 ) (C 8 H 4 OH).. Coniferyl alcohol, 
 
 [OCH S :OH = 3:4]. 
 
 OH.C 6 H 4 .CHO :.... Salicyl-aldehyde, 
 
 or o-hydroxy-benzaldehyde. 
 
 OCH 8 .C 6 H 4 .CHO Anisaldehyde, 
 
 or >-methoxy-benzaldehyde. 
 
 (OH) 2 C 6 H 3 CHO Procatechuic aldehyde, 
 
 or 3 : 4-dihydroxy-benzaldehyde. 
 
 OH.C 6 H 3 (OCH 3 ).CHO Vanillin, 
 
 or 3 - methoxy - 4 - hydroxy - benz- 
 aldehyde. 
 
 CH 2 2 : C C H 3 CHO Piperonal, artificial heliotrope 
 
 or methylene-protocatechuic al- 
 dehyde. 
 
 A large number of compounds are known which possess 
 
430 XXV. AROMATIC ALCOHOLS, ALDEHYDES, ETC. 
 
 phenolic properties in addition to those of an alcohol, aldehyde 
 or ketone. They are derived from the simple alcohols, &c., 
 by the entrance of hydroxyl into the benzene nucleus. 
 
 Several of these compounds occur in nature, e.g. saligenin 
 is a constituent of salicin (see the Glucosides), while salicylic 
 aldehyde is found in Spiraea varieties and vanillin, in vanilla 
 capsules. Anisaldehyde is obtained from the oxidation of 
 anisole (methyl phenyl ether). 
 
 An extremely interesting synthesis of hydroxy-aldehydes is 
 by the Tiemann-Eeimer reaction. This consists of heating a 
 phenol with chloroform in the presence of concentrated potas- 
 sium hydroxide : 
 
 C 6 H 6 .OK + CHC1 3 = HC1 + CHC1 2 .C 6 H 4 .OK, 
 
 and the dichlor-derivative thus formed is hydrolyscd by the 
 alkali to CHO.C 6 H 4 .OK. The formyl-group -CH:0 always 
 takes up the o- or ^-position with respect to the hydroxy- 
 group, and, as a rule, the o- and jp-compounds are formed 
 together, and may often be separated by the difference in 
 volatility of the two compounds in steam. 
 
 Vanillin crystallizes in beautiful needles, and is prepared 
 on the large scale from coniferin, C 16 H2 2 8 -f- 2H 2 0, a com- 
 pound occurring in the sap of the cambium in the Coniferse. 
 This is hydrolysed by acids into glucose and coniferyl alcohol, 
 C 6 H 3 (OH)(pCH 3 )(C 3 H 4 .OH), and the latter yields vanillin 
 when oxidized (Tiemann and Haarmann) ', the CH 3 group is 
 removed by heating with hydrochloric acid at 200, with the 
 formation of protocatechuic aldehyde. Vanillin is also found 
 in asparagus, raw beet-sugar, and asafcetida, and it likewise 
 results from the oxidation of olive wood, &c. 
 
 Vanillin can also be obtained synthetically from m-chloro- 
 />-nitro-benzaldehyde (from m-chloro-^-nitro-toluene). 
 
 E. Quinones 
 
 Quinones are compounds derived from benzene and its 
 derivatives by the replacement of two atoms of hydrogen by 
 two of oxygen, e.g. C 6 H 4 2 . As a group they are characterized 
 by (a) their yellow colour, (b) being readily reduced to dihydric 
 phenols, and hence often acting as oxidizing agents. They are 
 often divided into para-quinones, in which the two oxygen 
 atoms are in the ^-position, and ortho-quinones, in which they 
 are in the 0-position. 
 
^-BENZOQUINONE 431 
 
 ^-Benzoquinoae or Quinone, C H 4 2 (1838), is produced 
 when chromic acid is added to a solution of quinol. It crys- 
 tallizes in yellow needles or prisms of a characteristic pungent 
 odour something like that of nut-shells, is sparingly soluble in 
 water but readily in alcohol and ether, and can be sublimed; 
 m.-pt. 116. Corresponding with it we have a large number 
 of higher homologues, &c. These also are solids, mostly of a 
 yellow colour, and are volatile with r steam; they are obtained 
 by the oxidation of the corresponding dihydroxy-phenols, or 
 of polyhydric pnenols, which contain two hydroxyls in the 
 para-position. 
 
 Quinone is also formed by the oxidation of many aniline 
 and phenol derivatives belonging to the para-series, e.g. 
 ^-amino-phenol, sulphanilic acid, and >-phenol-sulphonic acid; 
 it is usually prepared by the oxidation of aniline itself by 
 means of chromic acid (see B. 1887, 20, 2283). It was first 
 obtained by distilling quinic acid with manganese dioxide and 
 sulphuric acid. Exposure to light causes it to turn brown, 
 and it colours the skin yellow-brown. It is readily reduced 
 to quinol by S0 2 , HI, SnCl 2 and HC1, &c., and can therefore 
 act as an oxidizing agent. 
 
 In chloroform solution it takes up two or four atoms of 
 bromine to form a di- or tetra-bromide (C 6 H 4 2 Br 4 ). Under 
 other conditions chlorine and bromine act upon it as substi- 
 tuents, while hydrochloric acid forms chloroquinol : 
 
 C 6 H 4 2 + HC1 = C 6 H 3 C1(OH) 2 . 
 
 It yields sparingly soluble crystalline compounds with 
 primary amines, and also coloured compounds with phenols. 
 With quinol it forms an additive compound termed quin- 
 hydrone, C 6 H 4 2 + C 6 H 4 (OH) 2 ; this crystallizes in green 
 prisms with a metallic lustre, and is also formed as an inter- 
 mediate product in the oxidation of quinol or in the reduction 
 of quinone. Its constitution has not been definitely settled. 
 (Cf. Siegnunds, J. pr. 1911, 83, 553; also Knorr, B. 1911, 44, 
 1503.) 
 
 Constitution. Quinone is derived from benzene by the ex- 
 change of two atoms of hydrogen for two of oxygen, which, 
 from the close connection between quinone and quinol, must 
 be in the ^-position. The constitution of quinone may be 
 explained either by assuming that these two oxygen atoms 
 are linked together, as in peroxide of hydrogen, H0-0H, 
 so that the benzene nucleus remains unchanged, or that the 
 
432 XXV. AROMATIC ALCOHOLS, ALDEHYDES, ETC. 
 
 latter experiences a partial reduction, with the formation of a 
 derivative of C 6 H 8 , a " diketo-dihydro-benzene " : 
 
 C CO 
 
 CH .0 HC/NCH 
 
 According to the first of these two formulae, quinone would 
 be a peroxide ; according to the second, a ketone. In favour 
 of the latter view (which was brought forward by Fittig, and 
 is now almost universally accepted) are (1) the fact that qui- 
 
 none can be converted into an oxime, C 2 H ^ 
 
 22 
 
 (identical with nitroso-phenol, p. 414), and into a dioxime, 
 quinone dioxime, C 2 H 2 <^;oS>C 2 H 2 (B. 20, 613); (2) its 
 
 power of forming additive compounds with bromine; and (3) 
 its relations to the analogously constituted anthraquinone. 
 (Of. B. 18, 568; A. 223, 170; J. pr. Ch. 42, 161. Also chapter 
 on Physical Properties and Constitution.) 
 
 Tetrahydro-quinone, p-Diketo-hexamethylene (cyclo-hexane-l-A- 
 dione), 
 
 CH 2 .CO.CH 2 
 
 CH 2 .CO-CH 2 ' 
 
 can be prepared by hydrolysing and eliminating the carboxyl 
 groups from succinylo-succinic ester (p. 343). It crystallizes 
 in colourless prisms, melts at 78, and, on reduction, yields 
 quinitol (p. 419). (Cf. B. 22, 2168; 23, 1272.) 
 
 Chloranil, Tetrachloro-quinone, CgCl 4 2 , which crystallizes in 
 lustrous yellow plates, is obtained by chlorinating quinone and 
 also by oxidizing many organic compounds, e.g. phenol, with 
 HC1 and KC10 3 . A good yield may be obtained by chlorinat- 
 ing |?-nitraniline, reducing the 2 : 6-dichloro-4-nitraniline thus 
 obtained to 2 : 6-dichloro-^-phenylene-diamine, and then oxidiz- 
 ing and chlorinating by means of potassic chlorate and hydro- 
 chloric acid: 
 
 N 2 C 6 H 4 NH 2 -* N0 2 - C 6 H 2 C1 2 NH 2 C 6 H 2 C1 2 (NH 2 ) 2 -> C 6 C1 4 O 2 
 
 (Witt. Abstr. 1904, 1, 174.) When reduced, it yields the 
 colourless tetrachloro-quinol; it also acts as an oxidizing agent, 
 converting e.g. dimethylaniline into methyl-violet. A dilute 
 
QUINONES 433 
 
 solution of potassium hydroxide transforms it into potassium 
 chloranilate, C 6 C1 2 2 (OK) 2 + H 2 (dark-red needles), corre- 
 sponding with which there is also an analogous nitro-compound, 
 potassium nitranilate, C 6 (N0 2 ) 2 2 (OK) 2 . The latter salt is dis- 
 tinguished by its sparing solubility, hence its formation may 
 be made use of as a test for potassium compounds. (For its 
 constitution, see B. 19, 2398.) 
 
 Chlorine transforms chloranil and chloranilic acid into com- 
 plex chloro-products of the hexa- and pentamethylene series, 
 and finally into chlorinated fatty compounds. (For a tabular 
 summary, see Hantzsch, B. 22, 2841; cf. also B. 25, 827, 842.) 
 
 Toluquinone, C 6 H 3 (0 2 )(CH 3 ), xyloquinone, C 6 H 2 (O 2 )(CH 3 ) 2 , 
 thymoquinone, C 6 H 2 (0 2 )(CH 3 )(C 3 H T ), &c., are known. Several 
 of these can be prepared synthetically by the condensation 
 of 1:2 diketones; for instance, diacetyl yields xyloquinone 
 under the influence of alkali (cf. B. 21, 1411 and p. 342): 
 
 CHa-rCOj-CO-CHiHi: _ CH^C-CO-CH 
 
 " HC.CO-C.CH 3 4 2 ' 
 
 0-Benzoquinone, CO\IT ^ ^^' ^ some " c w ^ tne 
 
 j9-compound, has been recently prepared by Willstatter and 
 Pfannenstiel (B. 1904, 37, 4744) by the oxidation of an ethereal 
 solution of catechol (0-dihydroxy-benzene) with silver oxide. 
 It forms pale-red transparent plates, is relatively unstable, 
 and begins to decompose at 60-70. It is readily reduced 
 by sulphur dioxide to catechol, and dyes the skin brown. For 
 two isomeric forms, cf. B. 1908, 41, 2580; 1911, 44, 2632. 
 
 F. Quinone Chlorimides, Quinone Aniles, 
 and Anilino-quinones 
 
 A number of nitrogen derivatives closely related to the 
 quinones are known. As examples, we have C 6 H 4 ^Q ' , 
 quinone chlorimide; C fi H 4 Cxrni> quinone dichlorimide ; 
 
 NT OH 
 
 C 6 H 4 ^ , quinone oxime, and the corresponding dioxime; 
 
 < l uinone anile ; and C 6 H 4N.*C 6 H 5 ' ( l uinone 
 dianile. 
 
 The quinone chlorimides are obtained by the oxidation of 
 the ^-amino-phenols or ^>-phenylene-diamines with bleaching 
 
 (B480) 8l5 
 
434 XXV. AROMATIC ALCOHOLS, ALDEHYDES, ETC. 
 
 powder, e.g. quinone chlorimide, 0:CgH 4 :NCl, from ^-amino- 
 phenol hydrochloride, and quinone dicnlorimide, C1N:C 6 H 4 : 
 NC1, from ^-phenylene-diamine hydrochloride. The first- 
 named crystallizes in golden-yellow crystals, which are volatile 
 with steam; when reduced it yields amino-phenol, and when 
 boiled with water quinone; the dichorimide reacts similarly. 
 
 Quinone monoxime, obtained by the action of hydroxyl- 
 amine hydrochloride on quinone (H. Goldschmidt, B. 1884, 17, 
 213), is identical with the compound obtained by the action 
 of nitrous acid on phenol, or by the hydrolysis of ^-nitroso- 
 dimethyl-aniline, and previously termed ^-nitroso-phenol. It 
 would appear to have the oxime constitution 0:CgH 4 :N'OH, 
 as with hydroxylamine it yields the dioxime OHN:C 6 H 4 : 
 N'OH, and when alkylated yields ethers of the type 0:C 6 H 4 : 
 N-OK. (Cf. also Hartley, J. C. S. 1904, 1016.) 
 
 Quinone monanile is obtained by oxidizing j9-hydroxy-di- 
 phenylamine, OH C 6 H 4 NH CgH 5 , and forms fiery-red crys- 
 tals melting at 97; with aniline it yields dianilino-qumone 
 anile, : C 6 H 2 (NHPh) 2 : NPh. The dianile is obtained by- 
 oxidizing diphenyl - p - phenylene - diamine, C^H 4 (NHPh) 2 ; it 
 melts at 175-180, and its dianilide, viz. dianilino- quinone 
 dianile, NPh : C 6 Ho(NHPh) 2 : NPh, is most readily obtained by 
 heating p-nitroso-dimethyl-aniline with aniline and aniline hy- 
 drochloride. Such anilino-quinone aniles are usually termed 
 azophenines (Fischer and Hepp, A. 1889, 256, 257; 1890, 262, 
 247). The important groups of aniline dyes known as indo- 
 phenols and indamines are respectively hydroxy- and amino- 
 derivatives of these aniles, e.g. phenol blue is (CH 3 ) 2 NC 6 H 4 
 N : C 6 H 4 : 0, and is obtained by oxidizing a mixture of amino- 
 dimethyl-aniline and phenol; the corresponding a-naphthol de- 
 rivative, NMe 2 C 6 H 4 N:C 10 H 7 :0, is an important blue dye. 
 
 G. Pseudo-phenols. Methylene-quinones 
 
 Numerous phenolic alcohols react with halogen hydracids 
 yielding the corresponding esters of the alcohols, e.g. : 
 
 OH.C 6 H 3 Br.CH 2 .OH OH.C 6 H 3 Br.CH 2 Br, 
 OH.C 6 Br 2 Me 2 .CH 2 .OH - OH.C 6 Br 2 Me 2 -CH 2 .Br; 
 
 but the products thus obtained are insoluble in alkalis, and are 
 characterized by the reactivity of the bromine atom in the 
 CH 2 Br group. The compounds have been termed by Auwers 
 pseudo-phenols, and they are usually regarded as o- or ^-quinone 
 
AROMATIC ACIDS 435 
 
 derivatives, e.g. the two compounds mentioned above are repre- 
 sented as 
 
 Such compounds readily react with alkalis, losing hydrogen 
 bromide and yielding methylene - quinones of the type 
 0:C 6 H 3 Br:CHo; the majority of these are unstable, and im- 
 mediately yield condensation products which are insoluble in 
 alkalis (cf. Auwers, A. 301, 203; B. 32, 2978; 34, 4256; 36, 
 1878; 39, 435; Zincke, A. 320, 145; 322, 174; 329, 1; 353, 
 335, 357). 
 
 XXVI AROMATIC ACIDS 
 
 The aromatic acids are analogous to the fatty acids in most 
 respects. As acids they are capable of forming exactly the 
 same kinds of derivatives as the latter, e.g. metallic salts, 
 esters, chlorides, anhydrides, amides, &c.: 
 
 As benzene derivatives they yield chloro-, bromo-, iodo-, hy- 
 Iroxy-, nitro-, amino-, and sulphonic acid derivatives, &c., e.g.: 
 
 C 6 H 4 C1-CO 2 H (chloro-benzoic acids); 
 NH 2 'C 6 H 4 'CO 2 H (amino-benzoic acids); 
 OH-S0 2 -C 6 H 4 .CO 2 H (sulpho-benzoic acids); 
 OH'C 6 H 4 CO 2 H (hydroxy-benzoic acids); 
 C H 6 -CH(OH).CO 2 H (mandelic acid); &c. 
 
 Constitution. Corresponding with the aromatic acids there 
 are nitriles, e.g. with benzoic acid, benzo-nitrile, C 6 H 5 C:N, 
 which may also be regarded as cyanogen derivatives of the 
 lydrocarbons (in the above case, cyano-benzene), and which, 
 m hydrolysis, yield the i acids. From this, and from their 
 general properties, it follows that their constitution must 
 ;orrespond exactly with that of the fatty acids; like the 
 atter they are characterized by the presence of carboxyl, 
 CO* OH, in the molecule. There are monobasic, di-, tri-, 
 and up to hexabasic aromatic acids, according to the number 
 )f hydrogen atoms in the molecule which are readily re- 
 )laceable by metallic radicals, i.e. according to the number of 
 jarboxyl groups: 
 
 C 6 H 4 (C0 2 H) 2 C 6 H 3 (C0 2 H) 3 C 6 (CO 2 H) 6 
 
 Phthalic acids Benzene-tri-carboxylic acids Mellitic acid. 
 
436 XXVI. AROMATIC ACIDS 
 
 Numerous unsaturated aromatic acids are known. As un- 
 saturated compounds, they readily form additive compounds 
 with hydrogen, chlorine, hydrogen iodide, and are thereby 
 converted into saturated acids or their substitution products. 
 In most of these additions the benzene nucleus remains un- 
 altered. Their constitution is therefore entirely analogous tc 
 that of the acids of the acrylic or propiolic series; they contain 
 a side chain with a double or triple carbon bond : 
 
 C 6 H 6 CH : CH C0 2 H C 6 H 5 C : C - CO 2 H 
 
 Cinnamic acid Phenyl-propiolic acid. 
 
 In addition to the aromatic acids proper, which have just 
 been mentioned, other acids have been prepared recently, which 
 are derivatives either of a completely reduced or a partially reducea 
 benzene molecule. The acids of the former series, e.g. the hexa 
 hydro-benzoic acids, have properties very similar to those oJ 
 the saturated fatty acids; while those of the latter, e.g. the di- 
 and tetrahydro-benzoic acids, resemble the unsaturated fatty 
 acids. (Cf. p. 349.) 
 
 The aromatic hydroxy-acids, e.g. the hydroxy-benzoic acids, 
 which are both phenols and acids, manifestly contain phenolic 
 hydroxyl (i.e. hydroxyl which is linked directly to the ben 
 zene nucleus) in addition to the carboxyl group or groups 
 they are capable of yielding salts either as acids or as phenols, 
 but otherwise they correspond in many points with the ali 
 phatic hydroxy-acids. 
 
 The true aromatic hydroxy-acids, such as mandelic acic 
 (phenyl-gly collie acid), which correspond completely with the 
 aliphatic hydroxy-acids, manifestly contain their alcoholic hy 
 droxyl not in the benzene nucleus, but in the side chain, as is 
 also the case with the aromatic alcohols. 
 
 Nomenclature. One of the simplest systems of nomenclature 
 is the designation of the aromatic acids as carboxylic acidi 
 of the original hydrocarbons in question, e.g. phthalic acid it 
 benzene-1 : 2-dicarboxylic acid. Many names, such as xylic 
 acid, are taken from those of the hydrocarbons into whicl 
 the carboxyl has entered, while others, such as mesitylenic 
 acid, indicate the hydrocarbons from which the acids an 
 obtained by oxidation. An important principle as regards 
 nomenclature depends upon the fact that aromatic acids car 
 be derived from almost every fatty acid of any consequence 
 by the exchange of H for C 6 H 6 , e.g. : 
 
 CH 3 CO 2 H (acetic acid) C 6 Hg - CH 2 CO 2 H (phenyl-acetic acid). 
 
FORMATION OF AROMATIC ACIDS 437 
 
 There thus exist phenylated acids analogous to the acids of 
 the acetic, glycollic, succinic, malic, and tartaric series, &c. 
 For example, atropic acid, C 6 BL'C(C0 2 H):CH 2 , may be desig- 
 nated a-phenyl-acrylic acid, ana cinnamic acid, C 6 H 6 CH : CH 
 C0 2 H, /5-phenyl-acrylic acid. 
 
 Properties. Most of the aromatic acids are solid crystalline 
 substances, generally only sparingly soluble in water, and 
 therefore precipitated by acids from solutions of their salts, 
 but often readily soluble in alcohol and ether. The simpler 
 among them can be distilled or sublimed without decom- 
 position, while the more complicated, especially phenolic and 
 polycarboxylic acids, evolve carbon dioxide when heated; 
 e.g. salicylic acid, OH C 6 H 4 C0 2 H, breaks up into phenol and 
 C0 2 . The elimination of carbonic anhydride from those acids 
 which volatilize without decomposition may be effected by 
 heating with soda-lime; in poly basic acids the carboxyls may 
 be successively decomposed : 
 
 C 6 H 4 (C0 2 H) 2 = C 6 H 6 C0 2 H + C0 2 
 
 Occurrence. A large number of the aromatic acids are found 
 in nature, e.g. in many resins and balsams, and also in the 
 animal organism in the form of nitrogeneous derivatives such 
 as hippuric acid (benzoyl-glycocoll), C 6 H 5 CO NH CH 2 C0 2 H. 
 
 Modes of Formation. A. Of the saturated acids : 
 
 1. By the oxidation of the corresponding primary alcohols 
 or aldehydes, e.g. benzoic acid from benzyl alcohol, or from 
 benzaldehyde. 
 
 2. One of the commonest methods of obtaining aromatic 
 acids is by the oxidation of benzene homologues. Each alkyl 
 group present in the nucleus of the hydrocarbon can be oxi- 
 dized to a carboxylic group, whether it be long or short, e.g. 
 both C 6 H 5 .CH 3 and C 6 H 5 .CH 2 .CH 2 .CH 3 yield C 6 H 5 .C0 2 H. 
 
 All substituted benzene homologues which contain the sub- 
 stituent in the side chain are similarly oxidized to non-substi- 
 tuted aromatic acids, e.g. C 6 H 5 -CH 2 C], C 6 H 5 .CH 2 -NH 2 , and 
 C 6 H 5 .CH:CH.C0 2 H yield C 6 H 5 .C0 2 H. 
 
 A substituted benzene homologue which contains halogen, 
 nitro-, sulpho-, amino-, hydroxy-, &c., substituents attached to 
 the benzene nucleus, yields a similarly substituted aromatic 
 acid, e.g.-. C 6 H 4 C1.CH 3 C 6 ELC1.CO 2 H; 
 
 (OH) 2 C 6 H 3 .CH 3 (OH) 2 .C 6 H 3 .C0 2 H; 
 NO 2 .C 6 H 4 .CO 2 H. 
 
 N0 2 -C 6 ] 
 Should there be several side chains in the molecule, they 
 
438 XXVI. AROMATIC ACIDS 
 
 are usually all converted directly into carboxyl by chromic 
 acid; whereas by using dilute nitric acid, this transformation 
 can be effected step by step, e.g. : 
 
 C 6 H 4 (CH 3 ) 2 yield first C 6 H 4 (CH 3 )(CO 2 H) and then C 6 H 4 (CO 2 H) 2 
 The xylenes Toluic acids Phthalic acids. 
 
 Nevertheless, the three classes of isomeric benzene deriva 
 tives with two side chains comport themselves differently. 
 The para-compounds are the most readily oxidized to acids by 
 chromic acid mixture, and then the meta-; whereas the ortho 
 compounds are either completely destroyed by it (p. 348), or 
 not attacked at all. The last-named may, however, be oxi- 
 dized in the normal manner by nitric acid or potassic perman- 
 ganate. The entrance of a negative group or of hydroxyl into 
 the o-position with respect to the alkyl radical renders the oxi- 
 dation more difficult (cf. p. 416). 
 
 3. By the hydrolysis of the corresponding nitriles : 
 
 C 6 H 6 .CN-f-2H 2 = C 6 H 5 -CO 2 H-fNH 3 . 
 
 These nitriles, which can be prepared from the ammonium 
 salts of the acids in the same manner as those of the fatty 
 series, are often obtained by the following syntheses: 
 
 (a) By distilling the potassic salts of the sulphonic acids 
 with potassic cyanide or ferrocyanide (Merz\ just as the 
 nitriles of the fatty acids are formed from the potassium 
 alkyl-sulphates (p. 100): 
 
 C 6 H 6 .S0 3 K 
 
 Nitriles cannot, as a rule, be prepared from KCN and aro 
 matic halogen derivatives which contain the halogen attached 
 to the nucleus (cf. p. 355); the halogen is more readily re- 
 placed by cyanogen if sulphonic acid or nitro-groups are like- 
 wise present: 
 
 C 6 H 4 Br.N0 2 + KCN = CN.C 6 H 4 -N0 2 + KBr. 
 
 Benzyl chloride, C 6 H 5 'CH 2 C1, and all the haloid hydro- 
 carbons which are substituted in the side chain, on the other 
 hand, react with potassic cyanide in the manner characteristic 
 of the alphyl haloids : 
 
 C 6 H 6 .CH 2 C1 + KCN = KCl-f C 6 H 6 .CH 2 -CN 
 
 Benzyl cyanide. 
 
 (b) By diazotizing the primary amines and replacing the 
 diazo-group by cyanogen, according to Sandmeyer's reaction 
 
FORMATION OF ACIDS 439 
 
 (p. 388). This reaction is frequently made use of in the 
 preparation of substituted benzo-nitriles, e.g. 2 : 4-dibromo- 
 benzo-nitrile, CgH^FoCN, and the isomeric 2 : 6 -compound, 
 also of tolu-nitriles, CH 3 -C 6 H 4 .CN. 
 
 (c) By heating the mustard oils (phenyl-iso-thiocyanates, 
 p. 276), with copper or zinc dust (ffreitti): 
 
 
 C 6 H 5 .N:C:S + 2Cu = C 6 H 6 .C:N + Cu 2 S. 
 
 (d) By the molecular transformation of the isomeric iso- 
 nitriles at a somewhat high temperature: 
 
 C 6 H 6 .N:C C 6 H 6 .C:N. 
 
 (e) By eliminating the elements of water from the oximes of 
 the aldehydes by means of acetyl chloride (pp. 137 and 429): 
 
 Benzaldoxime, C 6 H 6 CH : N . OH = C 6 H 6 CN -f H 2 O. 
 
 4. By the reduction of unsaturated acids, thus hydrocinnamic 
 by the reduction of cinnamic acid with sodium amalgam find 
 water, or with hydrogen and finely divided Palladium : 
 
 C 6 H 6 .CH:CH.CO 2 H + 2H = C 6 H 5 .CH 2 .CH 2 -CO 2 H. 
 
 The acids obtained by this method always contain the C0 2 H 
 group attached to a side chain. Similar acids can also be ob- 
 tained by the reduction of hydroxy-, bromo-, or keto-acids, 
 where the OH, Br, CO, and C0 2 H are all in side chains, e.g. : 
 
 C 6 H 5 .CH(OH).CO 2 H C 6 H 5 .CH 2 .CO 2 H. 
 
 5. A number of syntheses of nucleus carboxylic acids can 
 be accomplished. These may be regarded as the more or less 
 direct introduction of the carboxylic group into the benzene 
 nucleus, and are usually effected by means of carbonic acid 
 derivatives. In many cases the yields are only small, and the 
 reactions are mainly of theoretical interest. 
 
 (a) Benzoic acid and its homologues are produced by the 
 action of carbon dioxide upon bromo-benzenes, &c., in presence 
 of sodium (Kehttt) : 
 
 C 6 H 6 Br + CO 2 + 2Na = C fl H 6 .CO 2 Na + NaBr. 
 
 (b) By the action of phosgene, COC1 2 , upon benzene and its 
 homologues in presence of A1C1 3 (Friedel and Crafts) : 
 
 COC1 2 = C 6 H 6 .COC1 
 
440 XXVL AROMATIC ACIDS 
 
 Acid chlorides are first formed, but can be readily decomposed 
 by water. By the further action of these chlorides upon benzene 
 in presence of A1C1 3 , ketones are formed (see Benzo-phenone). 
 Carbonyl chloride reacts most readily with tertiary amines: 
 
 = (CH 3 ) 2 N.C 6 H 4 .COC1 
 
 (c) By the action of carbamic chloride, C1-CO-NH 2 , upon 
 benzene (or phenol) in presence of A1C1 3 , amides of the aro- 
 matic acids are formed, and these can be hydrolysed (Gaiter- 
 man, B. 1899, 32, 1116): 
 
 C 6 H 6 -fCl.CO.NH 2 = C 6 H 6 .CO-NH 2 
 
 (d) By the action of sodium upon a mixture of a brominated 
 benzene and ethyl chloro-carbonate (Wurtz); in this case the 
 esters are first formed, but these are readily hydrolysed: 
 
 6 + NaBr -f NaCl. 
 
 (e) The phenolic acids are formed by passing carbon dioxide 
 over heated sodium phenates (Kolbe-, see Salicylic acid): 
 
 In the case of the polyhydroxy-phenols, e.g. resorcinol, an acid 
 is often formed by merely heating the phenol with a solution 
 of ammonium carbonate or potassium bicarbonate (B. 13, 930). 
 
 (/) jo-Hydroxy-acids are formed by the action of carbon 
 tetrachloride upon phenols in alkaline solution (B. 10, 2185; 
 Tiemann-Beimer reaction; cf. p. 430): 
 
 C 6 H 6 .ONa + CC1 4 = C 6 H 4 (OH).CC1 3 + NaCl. 
 
 C 6 H 4 (OH).C0 2 Na + SNaCl -f 2H 2 0. 
 
 (g) By heating the sulphonates with sodium formate (V. 
 Meyer) : 
 
 C 6 H 6 .S0 3 Na + HCO 2 Na = C 6 H 6 -C0 2 Na -j-HS0 3 Na. 
 
 (h) By the action of carbon dioxide on ethereal solutions of 
 organo-magnesium compounds (Grignard's reagents), and sub- 
 sequent treatment with acids: 
 
 C 6 H 6 .Mg.Br + C0 2 -> C 6 H 6 .CO 2 'MgBr C 6 H 6 .CO 2 H. 
 
 6. Syntheses by the aid of ethyl aceto-acetate and ethyl 
 malonate. 
 
 Ethyl aceto-acetate reacts with the halide derivatives which 
 are substituted in the side chain, e.g. benzyl chloride, exactly 
 
FORMATION OF ACIDS 
 
 as in the fatty series, with the formation of the more com- 
 plicated ketonic acids, which again are capable of undergoing 
 either the "acid hydrolysis" or the "ketone hydrolysis" 
 (p. 226), e.g.-. 
 
 C 8 H 6 CHoCl + CH, CO CHNa CO 2 Et 
 
 = CH 3 .CO.CH(CH 2 C 6 H 6 ).C0 2 Et + 
 
 Benzyl-aceto-acetic ester. 
 
 CH 3 .CO.CH(CH 2 .C 6 H 5 ).C0 2 Et -f 2H 2 O 
 
 = C 6 H 6 .CH 2 .CH 2 .C0 2 H + CH 3 .C0 2 
 
 /3-Phenyl-propionic acid. 
 
 Ethyl phloroglucinol dicarboxylate, (OH) 3 C H(C0 2 Et) 2 , 
 may be synthesised by heating ethyl sodio-malonate with 
 ethyl malonate at 145 (Movre, J. C. S. 1904, 165). 
 
 7. Hydroxy-acids and keto-acids are formed by exactly the 
 same methods as in the fatty series (pp. 205 and 206), e.g. 
 mandelic acid by the combination of hydrogen cyanide with 
 benzaldehyde, and hydrolysis of the nitrile thus formed (B. 14, 
 239,1965): 
 
 C 6 H 5 .CHO + HCN = C 6 H 5 .CH(OH).CN; 
 
 or from phenyl-chloro-acetic acid (B. 14, 239): 
 
 = C 6 H 5 .CH(OH).CO 2 H + KC1. 
 
 B. The following are some of the commoner methods em- 
 ployed for the preparation of unsaturated acids: 
 
 1. From the mono-haloid substitution products of the satu- 
 rated acids by the elimination of halogen hydracid (cf. p. 163); 
 also from the corresponding nitriles, primary alcohols, &c., as 
 in the case of the saturated compounds. 
 
 2. According to the so-called Perkin synthesis, by the action 
 of aromatic aldehydes upon the sodium salts of fatty acids in 
 the presence of a condensing agent, usually acetic anhydride. 
 Thus, when benzaldehyde is heated with acetic anhydride and 
 sodium acetate, cinnamic acid is formed : 
 
 The acetic anhydride probably acts as a dehydrating agent 
 in this instance, the reaction taking place between the sodium 
 acetate and the aldehyde (cf. A. 216, 101). Hydroxy-acids are 
 formed as intermediate products by a reaction similar to the 
 "aldol condensation" (p. 131); in the above case, for instance, 
 -phenyl-hydracrylic acid, C 6 H 5 . CH(OH) . CH 2 . C0 2 H. 
 
442 XXVI. AROMATIC ACIDS 
 
 When the sodium salt and the anhydride of two different 
 acids, e.g. sodic propionate and acetic anhydride, are used, the 
 product varies with the conditions (B. 1901, 34, 918), but 
 usually consists of a mixture of two unsaturated acids. 
 
 This reaction also takes place with the hydroxy-aldehydes, 
 with the homologues of acetic acid, and also with dibasic acids, 
 e.g. malonic; but all acids employed must contain a CH 2 group 
 in the a-position with respect to the C0 2 H, e.g. : 
 
 C 6 H 5 .CH:0 + CH 3 .CH 2 .C0 2 Na = H 2 O-f C 6 H 6 .CH:C(CH 3 ).C0 2 H 
 
 a-Methyl-cinnamic acid. 
 
 It is a very general mothod used for the preparation of 
 <x:/?-unsaturated acids; in certain cases, e.g. a-phenyl-cinnamic 
 acid, C 6 H 5 CH:C(C 6 H 5 )C0 2 H, and its nitro-derivatives, two 
 stereo-isomerides are produced corresponding with the two cro- 
 tonic acids or with fumaric and maleic acid. 
 
 Unsaturated monobasic acids are also formed when aromatic 
 aldehydes are heated with malonic acid in presence of ammonia, 
 aniline, or other amines (Knoevenagel) : 
 
 C 6 H 6 .CH:'O'+H2;C(CO 2 H) 2 = C 6 H 6 -CH:C(CX) 2 H) 2 
 = C fl H 5 - CH : CH C0 2 H + CO^ 
 
 The esters of these acids are formed when aromatic aldehydes 
 are condensed with the esters of fatty acids in the presence of 
 sodium ethoxide (Claisen, B. 23, 976; cf. Claisen condensation, 
 p. 224). 
 
 3. Uinnamic acid is also formed by the action of benzal 
 chloride upon sodium acetate (Caro): 
 
 = C 6 H 5 .CH:CH.C0 2 H + 2HC1. 
 
 4. By the action of aceto-acetic ester upon the phenols in 
 presence of concentrated H 2 S0 4 , unsaturated phenolic acids or 
 their anhydrides (B. 16, 2119; 17, 2191) are formed, e.g.: 
 
 (Pseudo-form) Methyl-cumarin. 
 
 A. Monobasic Aromatic Acids 
 
 Constitution and Isomers. The cases of isomerism in the 
 aromatic acids are easy to tabulate. An isomer of benzoic 
 acid is neither theoretically possible nor actually known. 
 Carboxylic acids of the formula C 8 H 8 2 may, however, be 
 
MONOBASIC AROMATIC ACIDS 
 
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444 XXVI. AROMATIC ACIDS 
 
 derived from toluene by the entrance of carboxyl either into 
 the benzene nucleus or into the side chain, thus : 
 
 o-m-p- 
 
 C 6 H 6 .CH 2 .C0 2 H 
 
 Phenyl-acetic acid. 
 
 The nature of their oxidation products yields proof of their 
 constitution, the former yielding the phthalic acids, and the latter 
 benzoic. 
 
 Of acids C 9 H 10 2 , a large number of isomers are already 
 known (see table). Hydrocinnamic acid and hydratropic acid 
 are phenyl-propionic acids, the former ft- and the latter a-, 
 corresponding with the lactic acids; the isomeric relations of 
 the fatty acids thus repeat themselves here. The tolyl-acetio 
 acids, CH 3 -CgH 4 -CH 2 -C0 2 H, and the ethyl-benzoic acids, 
 C 2 H 5 C 6 H 4 C0 2 H, stand in much the same relation to each 
 other as aceto-acetic acid, CH 3 CO CH 2 C0 2 H, to propionyl- 
 formic acid, CoH 6 CO C0 2 H, and they all yield phthalic acids 
 when oxidized. Lastly, mesitylenic acid and its isomers are 
 dimethyl-benzoic acids, and are oxidizable to benzene-tricarb- 
 oxylic acids. 
 
 As instances of isomers among the unsaturated acids, we may 
 take cinnamic and atropic acids (analogous to ft- and a-chlor- 
 acrylic acids, p. 168). 
 
 Further, the hydroxy-toluic acids, C 6 H 3 (CH 3 )(OH)(C0 2 H), 
 are isomeric with mandelic acid, C 6 H 5 'CH(OH)-COoH, the 
 former being oxidized to hydroxy-phthalic acids, C 6 H 3 (OH) 
 (C(XH) 2 , and the latter to benzoic acid; the hydrocoumaric acids, 
 CgIL 3 , are likewise isomeric with tropic acid. The first-named 
 yield hydroxy-benzoic acids on oxidation, and the last benzoic. 
 
 Differences are apparent, e.g. in respect to reducibility, 
 according as the carboxyl is linked directly to the nucleus or 
 to a side chain; the amides of the respective acids are in the 
 former case reduced to the corresponding alcohols, but not in 
 the latter. (Of. B. 24, 173.) 
 
 1. MONOBASIC SATURATED ACIDS 
 
 Benzoic acid, C 6 H 5 -C0 2 H, was discovered in gum benzoin 
 in 1608, and prepared from urine by Scheele in 1785. Its 
 composition was established by Liebig and Wohlei^s classical 
 researches in 1832. It occurs in nature in gum benzoin, 
 from which it may be obtained by sublimation ("acidum 
 benzoicum ex resina"); also in dragon's-blood (a resin), in 
 Peru and Tolu balsams, in castoreum, and in cranberries. I* 
 
BENZOIC ACIDS 445 
 
 is present in the urine of horses in combination with glycocoll 
 as hippuric acid, from which it may be obtained by hydrolysis 
 with hydrochloric acid ("acidum benzoicum ex urina"). It 
 is obtained on the large scale ("ac. benz. ex toluole") as a 
 by-product in the manufacture of oil of bitter almonds from 
 benzyl chloride or benzal chloride. The acid may also be 
 formed by heating benzo-trichloride with water to a some- 
 what high temperature: 
 
 C 6 H 6 .CC1 3 C 6 H 6 .qOH) 3 C 6 H 6 .CO.OH. 
 
 Benzoic acid is also present in coal-tar. It crystallizes in 
 colourless glistening plates or flat needles, sublimes readily, 
 and is volatile with steam; its vapour has a peculiar irritating 
 odour, and gives rise to coughing. It melts at 121, boils at 250, 
 and is readily soluble in hot water, but only sparingly in cold. 
 When heated with lime, it is decomposed into benzene and car- 
 bon dioxide. It is used in medicine and in the manufacture of 
 aniline blue. Some of its salts crystallize beautifully, e.g. cal- 
 cium benzoate, (C 6 H 5 C0 2 ) 2 Ca -f- 3 H 2 0, in glistening prisms. 
 
 From the partially or wholly reduced benzene molecule 
 there are derived (a) the dihydro-benzoic acids, C 6 H 7 'C0 2 H, 
 of which five are theoretically possible, according to the 
 position of the double linkings, viz. A-l:3-, A-l:4-, A-l:5-, 
 A-2:4-, and A-2 : 5-dihydro-benzoic acids, but only two known 
 (B. 1891, 24, 2623, and 1893, 26, 454); (b) the tetrahydro- 
 benzoic acids, C 6 H 9 C0 2 H, all three of which are actually 
 known, viz. A-1-, A-2-, and A-3-tetrahydro-benzoic acids (A. 
 271, 231); and a hexahydro-benzoic acid, C 6 H n C0 2 H (hexa- 
 Tnethylene-carboxylic acid), which is found in the petroleum from 
 Baku, and which can also be prepared from benzoic acid. 
 
 The Esters, e.g. methyl benzoate, C 6 H 5 .C0 2 CH 3 , b.-pt. 199, 
 and ethyl benzoate, C 6 H 5 .C0 2 C 2 H 5 , b.-pt. 213, are always 
 prepared by the catalytic method of esterification (p. 174), 
 namely, by boiling the acid for three to four hours with a 
 3-per-cent solution of dry hydrogen chloride or of concentrated 
 sulphuric acid in the requisite alcohol (E. Fischer and Speier, 
 B. 1895, 28, 3252). They may also be obtained by the other 
 general methods for the preparation of esters : (a) by the action 
 of an acid chloride on the alcohol alone, or in presence of alkali 
 (Schotten, Baumanri) or of pyridine (Emhorn and Hollandt, 
 Abstr. 1899, 1, 577); (b) by the action of an alkyl iodide on 
 the silver salt of the acid; and (c) by the action of alkyl 
 sulphates, more especially methyl sulphate, on aqueous solu- 
 
446 XXVI. AROMATIC ACIDS 
 
 tions of the alkali salts of the acids (Werner and Seybold, B. 
 1904, 37, 3658). These esters are liquids of pleasant aromatic 
 odour which boil for the most part without decomposition, 
 and frequently serve for the recognition and estimation of 
 alcohols. They may be hydrolysed in much the same mariner 
 as the aliphatic esters, although as a rule not so readily. 
 
 Benzyl benzoate, C 6 H 6 C0 2 -CH 2 'C 6 H 5 , is present in the 
 balsams of Peru and Tolu. 
 
 Benzoyl chloride, C 6 H 5 .CO-C1 (LieUg and jrtiMer), ob- 
 tained by the action of phosphorus pentachloride on the acid, 
 is the complete analogue of acetyl chloride, but more stable 
 than the latter, since it is only slowly hydrolysed by cold 
 water, although quickly by hot. It is a colourless liquid 
 boiling at 198, and has a most characteristic pungent* odour. 
 It is prepared technically by chlorinating benzaldehyde. 
 
 Benzole anhydride, (C 6 H 5 'CO) 2 (Gerhardt\ is exactly 
 analogous to acetic anhydride. It crystallizes in prisms in- 
 soluble in water, boils without decomposition, and becomes 
 hydrated on boiling with water. M.-pt. 39. 
 
 In addition to the ordinary anhydrides or oxides, peroxides 
 of the type benzoyl peroxide or benzo-peroxide, C 6 H 5 CO0- 
 CO C 6 H 5 , are known. They may be obtained by the action 
 of the acid chloride on a cooled solution of sodic peroxide 
 (B. 1900, 33, 1575, and C. C. 1899, 2, 396). Benzo-peroxide 
 crystallizes from alcohol in prisms, melts at 106-108, is 
 relatively stable, and is insoluble in water. When its ethereal 
 solution is mixed with sodic ethoxide, the products formed 
 are ethyl benzoate, and the sodic salt of perbenzoic acid, 
 C 6 H 6 .CO'O.OH, a hygroscopic acid melting at 41-43. It 
 has a strong odour resembling hypochlorous acid, is readily 
 volatile, but decomposes violently when heated, and is a 
 strong oxidizing agent Many aliphatic and aromatic acids 
 yield similar derivatives. 
 
 Benzamide, CgH^CO-NHg, corresponds with acetamide, and 
 is prepared from benzoyl chloride and ammonia or ammonium 
 carbonate. It forms lustrous, nacreous plates, melting at 130, 
 boils without decomposition, and is readily soluble in hot water. 
 
 The amido-hydrogen of benzamide may be substituted by 
 alkyl radicals such as phenyl, &c., with the formation, e.g. of 
 benzanilide, C ? H 5 CCKNHC 6 II 5 , the anilide of benzoic acid, 
 a compound which can be readily prepared from aniline and 
 benzoic acid, or aniline and benzoyl chloride. It crystallizes 
 in colourless plates, melts at 158, distils unchanged, and is in 
 
BENZOIC ACID DERIVATIVES 447 
 
 fact the complete analogue of acetanilide, but is much more 
 difficult to hydrolyse, fusion with potash being one of the best 
 methods. 
 
 Thio-benzamide, C 6 H 5 .CS-NH 2 , is obtained by the union 
 of benzo-nitrile with hydrogen sulphide, or by heating benzyl- 
 amine with sulphur. 
 
 Benzoyl-hydrazine, Benzhydrazide, C 6 H 5 -CO.NH.NH 2 , ob- 
 tained from ethyl benzoate and hydrazine hydrate, melts at 
 112, and with nitrous acid yields benzoyl-azimide, benzazide, 
 N 
 
 || , which yields benzoic and hydrazoic acids on 
 N" 
 hydrolysis. (Cf. Curtius, Abstr. 1895, 1, 32.) 
 
 Metallic derivatives of benzamide are also known, e.g. ben- 
 zamide silver. Titherley (J. C. S. 1897, 468; 1901, 407) has 
 shown that the silver derivative exists in two forms : a white 
 
 l^TTT 
 
 compound, which is stable and is probably C 6 H 5 *C<T;^ , and 
 
 UAg 
 
 an unstable orange compound, C 6 H 5 CO NH Ag. These two 
 metallic derivatives correspond with the pseudo and normal 
 
 formulae for benzamide, viz. C 6 H 5 -(X%vTT and CgHg-CO'NH^ 
 
 From the pseudo form are derived imino-ethers (cf. p. 185). 
 
 Hippuric acid, Benzamino-acetic acid, C 6 ILCO'NHCH 2 
 C0 2 H, is an amino-derivative of benzoic acia, being derived 
 from the latter and glycocoll (amino-acetic acid); it may be 
 prepared by heating benzoic anhydride with glycocoll (B. 17, 
 1663), and is present in the urine of horses and of other her- 
 bivora. When benzoic acid or toluene is taken internally, it 
 is eliminated from the system in the form of hippuric acid. 
 It crystallizes in rhombic prisms, sparingly soluble in cold 
 water but readily in hot, decomposes when heated, and forms 
 salts, esters, nitro-derivatives, &c. When hydrolysed with con- 
 centrated hydrochloric acid it yields glycocoll hydro'chloride 
 and benzoic acid. 
 
 Benzo-nitrile, C 6 H 5 CN (cf. p. 438), is an oil which smells 
 like oil of bitter almonds, and boils at 191*. It is prepared 
 either by the action of PC1 5 upon benzamide (p. 183), or by 
 distilling benzoic acid with ammonium thiocyanate. It pos- 
 sesses all the properties of a nitrile, combining slowly with 
 nascent hydrogen to benzylamine, readily with halogen hydride 
 to an imino-chloride, with amines to amidines (p. 1 87 ; cf . A. 
 192, 1), with hydroxylamine to amidoximes (p. 188). 
 
448 XXVI. AROMATIC ACIDS 
 
 Substituted Benzole Acids. The hydrogen atoms of ben- 
 zoic acid are replaceable by halogen with the formation e.g. 
 of chloro-benzoic acid, 6 H 4 C1C0 2 H. In such formation of 
 mono-substitution products the halogen takes up the meta- 
 position with respect to the carboxyl. Nitric acid (especially 
 a mixture of nitric and sulphuric acids) nitrates it readily, 
 w-nitro-benzoic acid being the chief product, together with a 
 smaller quantity of the ortho- and a very little of the para-acid. 
 
 The o- and ^-halogen and nitro-compounds are usually pre- 
 pared by indirect methods, e.g. : 
 
 o-CH 3 .C 6 H 4 .N0 2 C0 2 H.C 6 H 4 .NO 2 
 or 2:4-C 6 H 3 Br 2 .NH 2 -* C 6 H 3 Br 2 .CN - C 6 H 3 Br 2 .CO 2 H. 
 
 In the preceding pages attention has been drawn repeatedly 
 to the influence which a radical, already present in the benzene 
 molecule, exerts on the position taken up by a second radical 
 entering the molecule. As examples we have: 
 
 CeHjBr * ^-C 8 H3r 2 ; CeH 5 -OH * o-o-2>-C 6 H 2 Br 8 -OH. 
 
 C 6 H 5 .NO a - m-CoH^NOsk; C 6 H 5 .NH 2 -* o-o-p-C 6 H 2 Br 8 -NH 2 . 
 
 C,H 6 .S0 8 H m-C 8 H4(SO,H) 2 ; C 6 H 5 .CHO w-N0 2 -C 6 H 4 .CHO. 
 
 C 6 H 5 CH 8 * o- and p-CH 8 CeH* N0 2 . 
 
 The following broad generalizations will be found to apply 
 to most cases: 
 
 I. If the radical already present is Cl, Br, I, OH, NH 2 , 01 
 CH 3 , then, by the introduction of Cl, Br, I, N0 2 , or S0 3 H 
 radicals, para- and to a certain extent ortho-compounds are 
 formed, and only very exceptionally meta-compounds. 
 
 II. If the radical present is NO,, SOgH, OHO, or C0 2 H, 
 then, on chlorination, bromination, nitration, or sulphonation, 
 meta-compounds are formed. (See Crum Brown and Gibson, 
 J. C. S. 1892, 367. For details cf. Obermuller ; Hollemann, Die 
 Direkte Einfiihrung von Substituenten, 1910.) 
 
 In many reactions all three isomeric products have been 
 isolated, but in very different quantities; thus at benzoic 
 acid yields 80*2 per cent of m- t 18'5 of o-, and only 1*3 of 
 jp-nitro-benzoic acid; at 30 nitrobenzene yields 91 per cent of 
 m-, 8 of 0-, and 1 of p-dinitro-benzene. It is probable that 
 the three isomerides are also formed in other cases which have 
 not been examined so carefully. The temperature at which 
 the substitution occurs also appears to determine to a certain 
 extent the relative proportions of the isomers formed. 
 
INFLUENCE OF SUBSTITUENTS 
 
 449 
 
 The substituted benzole acids closely resemble benzoic acid, 
 and yield similar derivatives. The strengths of the different 
 acids largely depend upon the nature of the substituents and 
 their positions with respect to the carboxylic group. 
 
 Acid. M.-p. K. 
 
 Benzoiq 121 0*006 
 
 o-Methyl-benzoic 105 0*012 
 
 w-Methyl-benzoic 110 0*00514 
 
 p-Methyl-benzoic 180* 0'00515 
 
 o-Bromo-benzoic 150 0*145 
 
 wi-Bromo-benzoic 155 0*0137 
 
 jo-Bromo-benzoic 251 
 
 o-Nitro-benzoic 148 0*616 
 
 m-Nitro-benzoic 141 0*0345 
 
 jp-Nitro-benzoic 240 0*0396 
 
 o- Ammo-benzole 145 O'OOl 
 
 Ttt-Ammo-benzoic 176 0*003 
 
 ^- Ammo-benzole 186 0*001 
 
 Ethyl ester. 
 M.-p. B.-p. 
 
 211 
 220 
 225 
 228 
 254 
 259 
 
 30 
 47 
 57 
 13 
 
 89 
 
 267 
 294 
 
 The numbers for K given in the table indicate that the 
 introduction of negative radicals, e.g. N0 2 , Br, &c., more 
 especially into the ortho-position, markedly increases the 
 strength of the acid, whereas the introduction of positive 
 radicals, e.g. the amino-, more especially into ortho-positions, 
 tends to weaken the acid (cf. p. 168). 
 
 Chemical Retardation and Influence of Substituents (cf. 
 p. 175). Within recent years a number of examples of the 
 retardation or complete inhibition of chemical reactions by the 
 presence of ortho-substituents have been discovered. One of 
 the best known examples of this is met with in the esterifi- 
 cation of aromatic acids by the hydrogen chloride catalytic 
 method. Kellas (Zeit. Phys. Chem., 1897, 24, 221) has shown 
 that even one ortho-substituent, whether it be CH 3 , N0 2 , Br, 
 &c., retards the formation of ester; and V. Meyer and Sudborough 
 (B. 1894, 27, 510, 1580, and 3146) have shown that when two 
 such ortho-substituents are present an ester is not formed 
 at all.* The cause of this retardation and inhibition is now 
 generally supposed to be due to the fact that in the formation 
 of an ester an additive compound of the acid and alcohol, 
 
 + CH 3 .OH = 
 
 + H a O. 
 
 * Esters of such acids can be prepared by heating the acids with alcohol 
 to high temperatures. 
 
 (8480) 2? 
 
450 XXVI. AROMATIC ACIDS 
 
 is first formed, that this compound then decomposes into the 
 ester and water, and that the spatial arrangements are such 
 that ortho-substituents are so close to the carboxylic group 
 that they interfere with the formation of an additive com- 
 pound, and thus retard or inhibit esterification (Wegscheider). 
 In confirmation of this view we have the fact that 0-substituents 
 do not interfere to nearly the same extent when the carboxylic 
 group is removed some distance, e.g. by the interposition of a 
 chain of carbon atoms. The acid, 
 
 _ 
 Br/~ YCH 2 .CH 2 . 
 
 s-tribromo-hydrocinnamic acid, for example, is readily esterified 
 under the usual conditions. Other cases of chemical retarda- 
 tion due to o-substituents have been met with in the hydro- 
 lysis of substituted benzo-nitriles; compounds like 
 
 ON CN 
 
 cannot be hydrolysed to the corresponding acids by the usual 
 methods. Di-ortho-substituted benzoyl chlorides and benz- 
 amides and % benzoic esters are also remarkably stable and 
 difficult to hydrolyse to the acids (Sudborough, Ira Remsen). 
 Di-ortho-substituted ketones, 
 
 COE 
 
 CH 
 
 cannot be converted into oximes (F. Meyer), and di-ortho- 
 substituted tertiary amines, 
 
 N(CH 3 ) 2 
 
 
 cannot yield quaternary ammonium salts (p. 379) (E. Fischer). 
 That ortho-substituents do not retard or inhibit all chemical 
 actions is shown by the fact that esters of di-ortho-substituted 
 
INFLUENCE OF SUBSTITUENTS 451 
 
 benzoic acids may be obtained by other methods, viz. the 
 action of the alcohol on the acid chloride, and the action of 
 alkyl iodide on the silver salt of the acid, or of methyl sul- 
 phate on an alkali salt of the acid. 
 
 In certain reactions the presence of ortho-substituents ap- 
 pears to favour or accelerate a chemical reaction; examples of 
 this are to be met with in the diacetylation of arylamines 
 (Sudb&rough, J. C. S. 1901, 79, 533) and in the chemical re- 
 activity of picryl chloride, 
 
 2 
 
 and similar compounds. The reactivity of various substituents, 
 such as 01, NH 2 , &c., which are in the o- or ^-position with 
 respect to a nitro-group, has been noted previously (pp. 362, 
 374, 414). A simple explanation of this reactivity may be due 
 to the formation of an o- or jp-quinonoid additive product. 
 Thus in the action of alkalis on 0-nitraniline : 
 
 NH . 
 
 \/ NH > \/M>K 2 \/ K 
 
 where the NH 2 group is replaced by OK, an ortho-quinonoid 
 compound may be formed as indicated above, and this by the 
 loss of ammonia would yield the potassic derivative of 0-nitro- 
 phenol. 
 
 The amino-benzoic acids, NH 2 C 6 H 4 C0 2 H, which are ob- 
 tained by the reduction of the nitro-acids with tin and hydro- 
 chloric acid, &c., are interesting, as they are both bases and 
 acids, i.e. amphoteric, and therefore similar to glycocoll in 
 chemical character; they combine with hydrochloric acid, 
 chloro-platinic acid, &c., as well as reacting with mineral 
 bases to yield metallic salts. With regard to their consti- 
 tution, cf. Glycocoll, p. 212. 
 
 With nitrous acid they yield diazo- benzoic acids, 
 
 C 6 H 4 <^QQ /, which correspond with the diazo -benzene- 
 
 sulphonic acids. 
 0-Amino-benzoic acid is also obtained from phthalimide, 
 
 by the Hofmann reaction (cf. Amides, b 
 
452 XXVI. AROMATIC ACIDS 
 
 haviour of, par. 5), and by the oxidation of indigo with man- 
 ganese dioxide and caustic soda, and is often termed anthra- 
 nilic acid; it forms (in contradistinction to the m- and #-acids) 
 
 r-\r\ 
 
 an intramolecular anhydride, anthranil, C 6 H 4 <^jj^>, and is 
 
 an important intermediate product in the synthesis of indigo. 
 The methyl ester is an important constituent of the essential 
 oil of orange-blossom. 
 
 The sulpho-benzoic acids, OH . S0 2 . C 6 H 4 . CO . OH, are di- 
 basic acids. An ammonia derivative of o-sulpho-benzoic acid 
 
 QO 
 
 is the sweet substance "saccharine", C 6 H 4 <^Q 2 ^>NH, i.e. 
 
 0-sulpho-benzimide, or 0-benzoyl-sulphone-imide, an imide com- 
 parable with succinimide. It is a white crystalline powder, 
 almost three hundred times as sweet as cane-sugar, and is used 
 to some extent in place of the latter. 
 
 Acids, C 8 H 8 2 . 1. The three toluic acids, CH 3 .C 6 H 4 .C0 2 H, 
 can be prepared from the three xylenes. ^-Toluic acid is ob- 
 tained from ^-toluidine, by transforming it according to the 
 Sandmeyer reaction into ^-cyano-toluene and hydrolysing the 
 latter (A. 258, 9). Isomeric with them is 
 
 2. Phenyl - acetic acid, a -Toluic acid, C 6 H 5 CH 2 C0 2 H 
 (Cannizaro, 1855). This acid differs characteristically from its 
 isomers by its behaviour upon oxidation (see p. 444). It may 
 be obtained synthetically from benzyl chloride and potassium 
 cyanide, benzyl cyanide, C 6 H 5 CH 2 .CN (b.-pt. 232), being 
 formed as intermediate product; it crystallizes in lustrous 
 plates, melts at 76, and boils at 262. 
 
 It is capable of undergoing substitution either in the benzene 
 nucleus or in the side chain. In the latter case there are 
 formed compounds such as 
 
 Phenyl-chloracetic acid, CgH 5 CHCl-C0 2 H, and phenyl- 
 amino-acetic acid, C 6 H 5 CH(NH 2 ) C0 2 H, compounds which 
 possess precisely the same character as mono-chloracetic and 
 amino-acetic acids. Isomeric with phenyl-amino-acetic acid are 
 the three amino-phenyl-acetic acids, NH 2 C 6 H 4 CH 2 C0 2 H, 
 of which the 0-acid is interesting on account of its close relation 
 to the indigo group. It does not exist in the free state, but 
 forms an intramolecular anhydride, oxindole (p. 522): 
 
 Such formation of an intramolecular anhydride is of very 
 
HOMOLOGUES OF BENZOIO ACID 453 
 
 frequent occurrence in ortho-amino-compounds of this kind, 
 in contradistinction to the m- and ^-compounds (see Indole). 
 Theoretically, it may take place in the above instance in two 
 different ways, viz. either by the elimination of a hydrogen 
 atom of the ammo-group together with OH of the carboxyl, or 
 of both of the amino-hydrogen atoms with the oxygen atom 
 from the carbonyl group. These two cases are distinguished 
 by Baeyer as " Lactam formation " and " Lactim formation ". 
 Oxindole is the lactam of o-amino-phenylacetic acid, isatin, 
 
 C 6 H 4 <^>>CO (P- 523 )> tne lactam of o-amino-phenylgly- 
 oxylic acid, NH 2 .C 6 H 4 -CO.CO.OH, and carbostyril (p. 456), 
 
 /N=COH 
 
 C 6 HX , the lactim of o-amino-cinnamic acid. 
 
 x/H : CH 
 
 Both lactams and lactims contain hydrogen which is readily 
 replaceable; in the former case it is present in the amino- 
 group, and in the latter in the hydroxyl. 
 
 If the compounds which result from the replacement of 
 hydrogen by alkyl are very stable, the alkyl in them is 
 linked to the nitrogen, and they are derivatives ol the lac- 
 tams; if, on the contrary, they are easily saponifiable, the 
 alkyl is linked to oxygen, and they are ethers of the lactims. 
 Many lactams and lactims react as tautomeric substances (cf. 
 Isatin and chapter on Constitution and Physical Properties). 
 
 Acids, C 9 H 10 2 . 1. Dimethyl-benzole acids, Xylene-carloxylic 
 acids, C 6 IJ 3 Me 2 C0 2 H. Of these six are possible, and four 
 are known. Mesitylenic acid, (C0 2 H : CH 3 : CH 3 = 1:3:5), is 
 prepared by the oxidation of mesitylene. Isomeric with them 
 are 
 
 2. The Phenyl-propionic acids. 
 
 /3-Phenyl-propionic acid or hydrocinnamic acid, C G H 5 CH 2 
 CH 2 'C0 2 H, is prepared by reducing cinnamic acid with sodium 
 amalgam, or with hydrogen in presence of colloidal palladium, 
 and is also formed during the decay of albuminous matter. It 
 crystallizes in slender needles; m.-pt. 48, b.-pt. 280. 
 
 Many substitution products of this acid are known, among 
 which may be mentioned o-nitro- cinnamic acid dibromide, 
 N0 2 .C 6 H 4 .CHBr.CHBr.C0 2 H, a compound nearly related 
 to indigo (p. 523); further, phenyl-a-amino-propionic acid 
 (phenyl-alanine), C H 5 .CH 2 .CH(NH 2 ).C0 2 H, and phenyl-/?- 
 amino-propionic acid, C 6 H 5 .CH(NH 2 ).CH 2 .C0 2 H, both of 
 which can be prepared synthetically, the former being like- 
 
454 XXVT. AROMATIC ACIDS 
 
 wise produced during the decay of albumen and during the 
 germination of Lupinus luteus. 
 
 o-Amino-hydrociniiainic acid, C 6 H 4 <^ H 2 < QQ H , is not 
 
 stable, but is immediately transformed into its lactirn, hydro- 
 
 carbostyril, C 6 H 4 <^ - , a quinoline derivative. 
 
 ^CH 2 CH 2 
 
 Hydratropic acid, a-Phenyl-propionic acid, CH 3 CH(C 6 H 5 ) 
 C0 2 H, is obtained as its name implies by the addition of 
 hydrogen to atropic acid. It is liquid and volatile with steam. 
 
 2. MONOBASIC UNSATURATED ACIDS 
 
 1. Cinnamic acid, C 6 H 5 CH : CH . C0 2 H (Trommsdorf, 1780), 
 occurs in Peru and Tolu balsams and also in storax, and may 
 be prepared as given at p. 441. It crystallizes in needles or 
 prisms, dissolves readily in hot water, melts at 133, and boils 
 at 300. When fused with potash, it is split up into benzoic 
 and acetic acids; it also yields benzoic acid when oxidized. 
 It yields salts, esters, &c.j also additive compounds, with 
 chlorine, bromine, hydrogen chloride, bromide, iodide, and 
 also with hydrogen and hypochlorous acid, e.g. cinnamic acid 
 dibromide (/?-phenyl-a-/3-dibromo-propionic acid), C 6 H 5 'CHBr. 
 CHBr-C0 2 H. Further, the hydrogen in the benzene nucleus 
 may be replaced by Cl, Br, N0 2 , NH 2 , &c. 
 
 Cinnamic acids. According to the ordinary stereo-chemical 
 theory of unsaturated compounds, two cinnamic acids of the 
 formula C 6 H 5 CH : CH C0 2 H should exist (cf. Maleic and 
 Fumaric acids, p. 243). Two have been known for some 
 time, viz. storax-cinnamic acid, melting at 134, and a//o-cin- 
 namic acid, melting at 68, prepared by reducing /?-brom-allo- 
 cinnamic acid with zinc and alcohol. But, in addition to these, 
 several other cinnamic acids have been described (for summary 
 see Erhnmeyer, Biochem. Zeitsch. 1911, 34, 306): (a) Lieber- 
 mann's iso-cinnamic acid (B. 1890, 23, 141, 512), melting at 
 5S-59; this occurs naturally together with the allo acid in 
 cocaine alkaloids, and may also be obtained by fractionally 
 crystallizing the brucine salt of allo-cinnamic acid (B. 1905, 
 38, 2562), and decomposing with acid, or by the action of an 
 alcoholic solution of zinc bromide on allo-cinnamic acid (B. 
 1905, 38, 837). (b) Erlenmeyer's iso-cinnamic acid, melting at 
 37-38, and obtained by reducing a-brom-allo-cinriamic acid 
 with zinc and alcohol (A. 1895, 287, 1; B. 1904, 37, 3361) 
 
CINNAMIC ACIDS 455 
 
 (c) Triclinic cinnamic acid, melting at 80. (d) Hetero-cin- 
 namic acid, rn.-pt. 131. The synthetical acid prepared by 
 Perkin's method is, according to Erlenmeyer (Abs. 1911, i, 782), 
 a mixture of storax- and hetero-acids, and can be separated by 
 fractional precipitation of the sodium salt by hydrochloric 
 acid or by fractional distillation of the ethyl ester. It is 
 probable that the allo- and two eso-acids are trimorphous forms 
 of the same substance (Biilmann, B. 42, 182, 1443). They 
 appear to give the same melt as shown by examination of 
 refractive indices (Stobbe), and solubilities (Meyer), and also to 
 give the same solutions as shown by their electrical conduc- 
 tivities (Bjerum, B. 43, 571), and absorption spectra (Stobbe, 
 ibid., 504). Any one of the three acids can be obtained from 
 the melt by impregnating under suitable conditions with a 
 crystal of the desired form; and even the solids are mutu- 
 ally transformable (Stobbe, B. 44, 2735; Meyer, 2966). 
 
 According to Eiiber and Godschmidt (B. 43, 453) the hetero- 
 acid is an impure form of the storax-acid, but this is denied 
 by Erlenmeyer (Abs. 1911, i, 782), who also claims to have 
 prepared optically active cinnamic acids (ibid., 781), the mole- 
 cules of which must be asymmetric. No satisfactory explana- 
 tion of the existence of so many isomerides has been offered 
 so far. 
 
 Although some six cinnamic acids are known, only two 
 a-bromo-cinnamic acids and two /?-bromo-cinnamic acids have 
 been prepared. The a-bromo- and a-brom-allo-cinnamic acids 
 are obtained by the elimination of hydrogen bromide from 
 cinnamic acid dibromide: 
 
 C 6 H 6 CHBr CHBr C0 2 H - HBr = C 6 H 6 CH : CBr CO 2 H, 
 
 or its esters, and they melt respectively at 131 and 120. 
 The corresponding /3-acids can be prepared by the addition of 
 hydrogen bromide to phenyl-propiolic acid: 
 
 CfiHjj.C-C.COaH + HBr = C fl H 6 .CBr:CH.CO 2 H. 
 
 .They melt respectively at 135 and 159. (Compare Sudborough 
 and Thompson, J. C. S. 1903, 666, 1153; Sudborough and Lloyd, 
 ibid., 1898, 91; Sudborough and Roberts, ibid., 1905, 1841; Sud- 
 borough and James, ibid., 1906, 105; James, 1911, 1620. 
 o- and _p-Nitro-cinnamic acids, NOg-CgH^CHzCH 
 the first of which is of importance on account of its relation 
 to indigo, are obtained by the nitration of cinnamic acid. 
 
456 XXVI. AROMATIC ACIDS 
 
 On reduction the former yields o-amino-cinnamic acid, which 
 readily yields its lactim carbostyril (a-hydroxy-quinoline), 
 ")H:CH 
 
 =C.OH 
 
 The radical of cinnamic acid, i.e. (C 6 H 6 CH : CH CO ), 
 is termed " cinnamyl ", and the group (C 6 H 5 CH : CH ) 
 " cinnamenyl". 
 
 2. Atropic acid, CH 2 : C(C 6 H 5 ) C0 2 H, is a decomposition 
 product of atropine. It crystallizes in monoclinic plates, and 
 can be distilled with steam. It breaks up into formic and 
 a-toluic acids when fused with potash. 
 
 3. (y)-Phenyl-isocrotonic acid, C 6 H 5 . CH : CH . CH 2 . C0 2 H, is 
 formed when benzaldehyde is heated with sodium succinate and 
 acetic anhydride (W. H. Perkin, sen., also Jayne, A. 216, 100): 
 
 C 6 H 6 -CHO -f CH 2 (CO 2 H).CH 2 .CO 2 H - H 2 O 
 Oxi UJjL^vA^.tly ^-ti 2 
 
 6 co 
 
 = CO 2 + C 6 H 5 .CH:CH.CH 2 .CO 2 H. 
 
 It is of interest on account of its conversion into a-naphthol 
 (see this), C 10 H 7 OH, upon boiling. 
 
 4. Phenyl-propiolic acid, C 6 H 5 .C:C.C0 2 H (Glaser, 1870), 
 is prepared from cinnamic acid dibromide or its ethyl ester by 
 first converting into a-brom-cinnamic acid by elimination of 
 hydrogen bromide, and then into the acetylenic acid by 
 further elimination (just as ethylene is converted by bromine 
 into ethylene bromide, and the latter decomposed into acety- 
 lene by potash). It crystallizes in long needles, and melts at 
 136-137. When heated with water to 120, it breaks up 
 into C0 2 and phenyl-acetylene (p. 353). It can be reduced to 
 hydrocinnamic acid and transformed into benzoyl-acetic acid. 
 
 0-Nitro-phenyl-propiolic acid, N0 2 C 6 H 4 C C C0 2 H 
 (Baeyer), is prepared in a manner analogous to that just given, 
 viz. by the addition of bromine to ethyl 0-nitro-cinnamate and 
 treatment of the resulting bromide with alcoholic potash (A. 
 212, 240). It is of interest on account of its relation to indigo 
 (see p. 626). It breaks up into C0 2 and 0-nitro-phenyl-acety- 
 lene when heated. 
 
 3. SATURATED PHENOLIC ACIDS 
 
 (For modes of formation, see p. 440.) These acids may also 
 be obtained by the oxidation of the homologues of phenol 
 
PHENOLIC ACICS 467 
 
 and of the hydroxy-aldehydes, which is effected, among other 
 methods, by fusion with alkalis. 
 
 The phenolic acids form salts both as carboxylic acids and as 
 phenols, salicylic acid, for instance, the two following classes : 
 
 )H 
 
 and 
 
 Mono- and Di-sodium salicylate. 
 
 The first of these two salts is not decomposed by C0 2 , while 
 the second, as the salt of a phenol, is decomposed by it and 
 converted into the first. The phenolic acids behave, therefore, 
 like monobasic acids towards sodium carbonate. When both 
 of the hydrogen atoms are replaced by alkyl, there are formed 
 compounds such as C 2 H 5 CJH 4 C0 2 C 2 H 6 , which, as both 
 ethers and esters, are only half hydrolysed when boiled with 
 potash, e.g. to C 2 H 5 C 6 H 4 C0 2 H, ethyl salicylic acid. The 
 ether acids thus formed possess completely the character of 
 monobasic acids, their alphyl radical being only eliminated by 
 hydriodic acid at a rather high temperature. (Cf. p. 412.) 
 
 The 0-hydroxy-acids (C0 2 H:OH =1:2) are, in contradis- 
 tinction to their isomers, volatile with steam, give a violet or 
 bhie coloration with ferric chloride, and are readily soluble in 
 cold chloroform. 
 
 The m-hydroxy-acids are more stable than the o- and ^-com- 
 pounds; while most of the latter break up into carbon dioxide 
 and phenols when quickly heated, or when acted on by hydro- 
 T chloric acid at 220, the former remain unaltered. 
 
 The phenolic acids are much more easily converted into 
 halogen or nitro-substitution products than the monobasic 
 acids, just as the phenols are far more readily attacked than 
 \the benzene hydrocarbons. 
 
 v Salicylic acid, o-Hydroxy-lenzoic add (C0 2 H:OH = 1:2), 
 was discovered by Piria in 1839. It occurs in the blossom of 
 Spiraea Ulmaria, and as its methyl ester in oil of winter-green, 
 &c. It may be obtained by the oxidation of the glucoside 
 saligenin; by fusing coumarin, indigo, 0-cresol, &c., with potash; 
 by diazotizing o-amino-benzoic acid, &c. (see p. 387). 
 
 Preparation. Sodium phenoxide is heated in a stream of 
 carbon dioxide at 180-220 (Kolbe, A. 113, 125; 115, 201, &c.), 
 when half of the phenol distils over and basic salicylate of 
 sodium remains behind: 
 
 C 6 H 6 ONa + CO 2 = OH C 6 H 4 CO JSTa ; 
 
 2 Na + C 6 H 6 .ONa = ONa.C 6 H 4 .(X) 2 Na -f C 6 H 6 -OH. 
 
4:58 XXVI. AROMATIC ACIDS 
 
 Should potassic phenoxide be used instead of the sodic com- 
 pound, salicylic acid is likewise formed if the temperature be 
 kept low (150), but the isomeric para-hydroxy-benzoic acid 
 at a higher temperature (220). Mono-potassic salicylate, 
 C 6 H 4 (OH) C0 2 K, decomposes in an analogous manner at 220 
 into phenol and di-potassic ^-hydroxy-benzoate. 
 
 As Kolbe's original method of preparation converted only 
 50 per cent of the phenol into salicylic acid, Schmitt devised 
 the following modification: The sodic phenoxide is heated in 
 a closed vessel with carbon dioxide at 130, and the compound 
 
 first formed, C 6 H 5 '0C<^Q a , sodic phenyl-carbonate, is thus 
 
 transformed into mono-sodic salicylate by the exchange of the 
 CO ONa group with the ortho-hydrogen atom of the phenyl 
 radical. (Cf. B.I 905, 38, 1375; A. 1907,351,313;C.C.1907,ii,48.) 
 Salicylic acid crystallizes in colourless four-sided monoclinic 
 prisms, dissolves sparingly in cold water but readily in hot; 
 it melts at 155, can be sublimed, but is decomposed into 
 phenol and C0 2 when heated quickly; ferric chloride colours 
 the aqueous solution violet. It is an important antiseptic. 
 It forms two series of salts (the basic calcium salt being 
 insoluble in water), and two series of derivatives, viz.: (1) as 
 an acid it yields chlorides, esters, &c., and (2) as a phenol it 
 yields ethers, &c., e.g. ethyl-salicylic acid, C 6 H 4 (0 C 2 H 5 )C0 2 H. 
 
 Phenyl salicylate, CWKco-OC ^ , the ester derived from 
 
 phenol and salicylic acid, and generally termed "Salol", is 
 a good antiseptic, and is prepared by the action of an acid 
 chloride such as POC1 3 or COC1 2 upon a mixture of salicylic 
 acid and phenol, or by heating the acid itself at 220. It 
 forms colourless crystals. When its sodium salt is heated to 
 300, it undergoes molecular transformation into the sodium 
 salt of the isomeric phenyl-salicylic acid, C 6 H 5 O.C 6 H 4 -C0 2 Na 
 (B. 21, 501). Analogous "salols" are obtained from <;ther 
 phenols, e.g. j?-acetylaminophenol yields salophene. 
 
 m-Hydroxy-benzoic acid is prepared by diazotizing w-amino- 
 benzoic acid. It crystallizes in microscopic plates, dissolves 
 readily in hot water, and sublimes without decomposition; 
 ferric chloride does not colour its aqueous solution. 
 
 ^-Hydroxy-benzoic acid forms monoclinic prisms (-f- H 2 0), 
 and ferric chloride gives no coloration with the aqueous 
 solution. As a phenol it yields the methyl ether, anisic 
 
ttYDROXY-ACIDS 469 
 
 acid, C 6 H 4 (0 CH 3 ) C0 2 H, which can be prepared by treat- 
 ing ^-hydroxy-benzoic acid with methyl alcohol, potash and 
 methyl iodide, and saponifying the dimethyl derivative first 
 formed; it is also formed by the oxidation of anisole. In 
 consequence of the phenolic hydroxyl having been etherified, 
 it resembles the monobasic and not the phenolic acids, boiling 
 for example without decomposition; hydriodic and hydro- 
 chloric acids at high temperatures decompose it into j?-hy- 
 droxy-benzoic acid and methyl iodide or chloride. 
 
 Hydro-para-coumaric acid (1 : 4), OH C 6 H 4 CH 2 CH 2 C0. 2 H, 
 ^-p-hydroxy-plienyl-propionic add, is produced by the de 
 
 lecay of 
 
 tyrosine, fi-hydroxy-phenyl-alanine, OH C 6 H 4 CH 2 CH(NH 2 ) 
 C0 2 H, and also synthetically from jo-nitro-cinnamic acid : 
 
 NO 2 .C 6 H 4 .CH:CH.CO 2 H NH 2 .C 6 H 4 .CH 2 .CH 2 .CO 2 H 
 
 reduced 
 
 OH.C 6 H 4 .CH 2 .CH 2 .C0 2 H 
 
 diazotized 
 
 Tyrosine, which crystallizes in fine silky needles, is found in 
 old cheese (TU/>OS), in the pancreatic gland, in diseased liver, 
 in molasses, &c., and results from albumen, horn, &c., either 
 upon boiling these with sulphuric acid or from their pancreatic 
 digestion or their decay. 
 
 It has also been obtained synthetically, as indicated by the 
 following series of reactions: 
 
 C 6 H 6 .CH 2 .CHO 
 
 C 6 H 6 CH 2 CH(OH) . ON -f NH, 
 C 6 H 6 .CH 2 .CH(NH 9 ).CN 
 
 -* C 6 H 5 .CH 2 .CH(NH,)-CO 2 H 
 
 NO 2 -C 6 H 4 .CH 2 .CH(NH 2 ).CO 2 H 
 
 OH.C 6 H 4 .CH 2 .CH(NH 2 ).CO 2 H. 
 
 (Compare also B. 32, 3638.) 
 
 Of the numerous polyhydroxy-phenolic acids, the following 
 may be mentioned : 
 
 Protocatechuic acid, 3'A-Dihydroxy-benzoic acid, is obtained 
 by fusing various resins, such as catechu, benzoin, and kino, 
 with alkali. It may be prepared synthetically, together with 
 the 2 : 3-dihydroxy-acid, by heating catechol, C 6 H 4 (OH) 2 , with 
 ammonium carbonate. It crystallizes in glistening needles or 
 plates, and is readily soluble in water; the solution is coloured 
 green by ferric chloride, then after the addition of a very little 
 sodic carbonate blue, and finally red. Like catechol it pos- 
 sesses reducing properties. Its mono-methyl ether is vanillic 
 
460 X!XVi. AltOMATiC ACtt)S 
 
 acid, or p-hydroxy-nwnethoxy-benzoic acid, C 6 H 3 (C0 2 H)(0 CH 3 ) 
 (OH), which is obtained by the oxidation of vanillin (p. 430); 
 its dimethyl ether is the veratric acid of sabadilla seed (Ver- 
 atrum Sabadilla), and its methylene ether is piperonylic acid, 
 
 CH 2 <^Q^>C 6 H 3 C0 2 H, which can be prepared, among other 
 
 methods, by the oxidation of piperic acid (p. 464). 
 
 Gallic acid, 3 -A \5-Trihydroxy-benzoic acid, C 6 H 2 (OH) 3 C0 2 H, 
 occurs in nut-galls, in tea and many other plants, and as gluco- 
 sides in several tannins. It is prepared by boiling tannin with 
 dilute acids, or by allowing mould to form on its solution, and 
 has also been obtained synthetically by various reactions. It 
 crystallizes in fine silky needles (+ H 2 0), dissolves readily in 
 water, alcohol, and ether, and has a faintly acid and astringent 
 taste. It evolves carbon dioxide readily when heated, yield- 
 ing pyrogallol, reduces gold and silver salts, and yields a 
 bluish-black precipitate with ferric chloride. Like pyrogallol, 
 it is very readily oxidized in alkaline solution, with the pro- 
 duction of a brown colour. 
 
 Gallic acid is used in the manufacture of blue-black inks. 
 With ferrous sulphate it gives a pale -brown colour, which 
 rapidly turns black on exposure to the air; the presence of 
 a minute quantity of free sulphuric acid retards this oxida- 
 tion, but when the acidified solution is used with ordinary 
 paper the acid is neutralized by compounds present in the 
 paper, and the oxidation takes place. Indigo carmine is added 
 to the ink in order to give it a blue colour before oxidation 
 occurs. Dermatol and Airol are bismuth derivatives. 
 
 Tannin, Gallotanic add, is a colourless, amorphous, glistening 
 mass, readily soluble in water but only slightly in alcohol, 
 and almost insoluble in ether. It forms the chief constituent 
 of nut-galls, and is likewise present in sumach, tea, &c. It 
 yields gallic acid when boiled with dilute acids, and a product 
 similar to tannin may be obtained from gallic acid by the de- 
 hydrating action of phosphorus oxychloride. The constitution 
 is not known ; it is evidently a complex compound, and appears 
 to be optically active. 
 
 The aqueous solution is coloured dark-blue by ferric chloride. 
 The mercury salt is used in medicine. Tannin has an affinity 
 for the animal skin and for glue, and is abstracted from its 
 solution by these substances, the skin being thus tanned or 
 converted into leather. Numerous other tannic acids are 
 known, and are usually named according to the plant from 
 
ALCOHOL-ACIDS 461 
 
 which they are obtained, e.g. kino tannin, catechu tannin, 
 coffee tannin, &c. 
 
 Quinic acid, which is found in quinine bark, coffee beans, &c., 
 is a hexahydro-tetrahydroxy-benzoic acid, C 6 H 7 (OH) 4 C0 2 H. 
 It crystallizes in colourless prisms and is optically active, an 
 inactive modification being also known. 
 
 4. ALCOHOL- AND KETO-ACID3 
 
 The monobasic aromatic alcohol-acids, which possess at one 
 and the same time the characters of acids and of true alcohols 
 (p. 436), contain the alcoholic hydroxyl in the side chain; this 
 hydroxyl is consequently eliminated together with the side 
 chain when the compound is oxidized. 
 
 In behaviour they approximate very closely to the hydroxy- 
 acids of the fatty series, as the phenylated derivatives of which 
 they thus appear; at the same time they yield, as phenyl de- 
 rivatives, nitro-compounds, &c., although those compounds can 
 often not be prepared directly, on account of the readiness 
 with which the acids are oxidized. They differ from the 
 phenolic acids in being more soluble in water, less stable, and 
 non-volatile; as alcohols many of them give up water and 
 yield unsaturated acids (which the phenolic acids can never 
 do), and they can be esterified by hydrobromic acid, &c., with 
 the formation of haloid-substitution acids, &c. Further, they 
 are purely monobasic acids. 
 
 The hydroxy-acids may be either primary, secondary, or 
 tertiary alcohols, e.g. OH . CH 2 . C 6 H 4 . COOH, C 6 H 5 .CH(OH). 
 COOH, and C 6 H 5 . CH 2 . C(CH 3 )(OH) . COOH. The tertiary 
 can sometimes be prepared directly by the oxidation of such 
 acids C n H 2n _ 8 2 as contain a tertiary hydrogen atom (:CH), 
 by means of permanganate. 
 
 To the ketonic acids the corresponding reactions apply. As 
 ketones they may be reduced to secondary alcohol-acids, and 
 they further react with hydroxylamine, &c.; as acids they form 
 salts, esters, &c. 
 
 Mandelic acid, Phenyl-glycollic acid, C<.H 5 . CH(OH) . C0 2 H 
 (1835), is formed by hydrolysing amygdalin with hydrochloric 
 acid, and synthetically by the hydrolysis of benzaldehyde-cyan- 
 hydrin, C 6 H 5 . CH(OH) ON (see pp. 126 and 424). It forms 
 glistening crystals, dissolves somewhat readily in water, and 
 melts at 133. 
 
 Mandelic acid possesses an asymmetric carbon atom and 
 
462 XXVI. AROMATIC ACIDS 
 
 exists in two optically active modifications (cf. B. 16, 1565 and 
 2721), and these can form a racemic compound (para-mandelic 
 acid) in the same manner as d- and Z-tartaric acids. 
 
 The acid obtained synthetically is the racemic acid, but this 
 can be resolved (1) by the aid of chinchonine when the chin- 
 chonine salt of the d-acid crystallizes first; (2) by means of 
 green mould, " penicillium glaucum ", which when grown on a 
 solution of the ammonium salt of the acid destroys the Isevo 
 modification; (3) by partially esterifying the racemic acid with 
 an optically active alcohol, e.g. Z-menthol; the non-esterified 
 acid is then /-rotatory, as the d-acid is somewhat more readily 
 esterified by /-menthol than the Z-acid. The method is not 
 quantitative (Marckwald and Mackenzie, B. 1899, 32, 2130; 
 1901, 34, 469; also J. C. S. 1899, 964). The acid obtained 
 from amygdalin is the laevo compound. It is comparable with 
 lactic acid, CH 3 CH(OH) C0 2 H, yielding, like the latter, 
 formic acid (together with benzoic) when oxidized; hydriodic 
 acid reduces it to phenyl-acetic acid, just as it does lactic acid 
 to propionic. 
 
 o-Hydroxymethyl-benzoic acid, OH CH 2 CLH 4 CO OH, 
 which is isomeric with mandelic acid, is unstable in the free 
 state; as an ortho-compound, it readily yields the anhydride 
 
 or lactone, Phthalide, C 6 H 4 <\QQ 2 ^>0, which is obtained by 
 
 the reduction of phthalic anhydride or chloride. It crystallizes 
 in needles or plates, and can be sublimed unaltered. 
 
 Tropic acid, a- Phenyl-fi-hydroxy -propionic add, OHCH 2 
 CHPhC0 2 H (fine prisms), is obtained together with tropine 
 by boiling atropine with baryta water; it is reconverted into 
 atropine when warmed with tropine and hydrochloric acid. 
 It exists in several optically different (d- t J-, and r-) modifi- 
 cations. 
 
 Benzoyl-formic acid, Phenyl-glyoxylic acid, C 6 H 5 COC0 2 H, 
 is obtained synthetically by the hydrolysis of benzoyl cyanide, 
 CgHg-CO-CN, with cold fuming HC1 (Claisen, 1877), and also 
 by the cautious oxidation of mandelic acid or acetophenone. 
 It is an oil which only solidifies slowly, and when distilled 
 is largely decomposed into carbon monoxide and benzoic acid. 
 It reacts similarly to isatin with benzene containing thiophene 
 and sulphuric acid, and shows the normal reactions of the 
 ketonic acids with NaHS0 3 , HCN, NH 2 -OH, &c. 
 
 o-Nitro-benzoyl-fonnic acid, N0 2 C 6 H 4 .CO-C0 2 H, which 
 can be prepared from 0-nitro-benzoyl cyanide, yields o amino- 
 
UNSATURATED PHENOLIC ACIDS 463 
 
 benzoyl-formic acid, isatic acid, NH 2 'C 6 H 4 CO-C0 2 H (a white 
 powder), upon reduction; when a solution of the latter is 
 warmed, it yields its intramolecular anhydride (lactam), isatin, 
 
 > co < cf * 
 
 Benzoyl-acetic acid, C 6 H 5 .CO-CH 2 .C0 2 H (JBaeyer), is a 
 perfect analogue of acetoacetic acid, and, like the latter, can 
 be used for the most various syntheses. It is obtained as its 
 ethyl ester (which is soluble in cold sodic hydroxide solution) 
 by dissolving ethyl phenyl-propiolate in concentrated sulphuric 
 acid and pouring the solution into water (B. 16, 2128); or, 
 better, by the action of sodium ethoxide upon a mixture of 
 ethyl benzoate and acetate (Claisen's condensation, p. 225) 
 (B. 20, 651). It is crystalline, melts at 103, and readily splits 
 up into carbon dioxide and acetophenone, C 6 H 5 -CO'CH 3 ; the 
 aqueous solution is coloured a beautiful violet by ferric chloride. 
 
 5. UNSATURATED MONOBASIC PHENOLIC ACIDS 
 
 Hydroxy-cinnamic or Coumaric Acids, OHC 6 H 4 CH:CH 
 COoH. The ortho-acid is present in melilot (Melilotus offidnalis), 
 and can be prepared by diazotizing o-amino-cinnamic acid, or 
 from salicylic aldehyde by Perkiris synthesis. The alcoholic 
 solution is yellow with a green fluorescence. 
 
 yO CO 
 
 Coumarin, C 6 H 4 <^ , is the aromatic principle of wood- 
 
 M-/H i CH 
 
 ruff (Asperula odorata)^ and is also found in the Tonka bean 
 and other plants. It is obtained by the elimination of water 
 from 0-coumaric acid by means of acetic anhydride. It crys- 
 tallizes in prisms, dissolves readily in alcohol, ether, and hot 
 water; melts at 67, and boils at 290. It dissolves in sodium 
 hydroxide solution, yielding the sodium salt of couniarinic 
 acid. This salt is stereo-isomeric with that of 0-coumaric acid. 
 The free acid itself appears to be incapable of existence, as it 
 is immediately converted into coumarin (its anhydride), but 
 various derivatives are known. o-Coumarinic acid is regarded 
 as the cis-compound, as it yields an anhydride (cf. Maleic Acid). 
 The stereo-isomeric o-coumaric acid is the trans-&c,id (cf. Fu- 
 maric Acid): 
 
 H-C.C 6 H 4 .OH H.C.C 6 H 4 .:OH 
 
 H.OOC-C-H H c-co -6:H 
 
 o-Couinaric Coumarinic acid, 
 
464 XXVI. AROMATIC ACIDS 
 
 3 : 4-Dihydroxy-cinnamic acid, Cafeic add, (OH) 2 C 6 H 3 CH : 
 CHCO 2 H, crystallizes in yellow prisms, and is obtained from 
 caffetannic acid, whose mono-methyl ether is ferulic acid (from 
 asafoetida); the isomeric umhellic acid or^?-hydroxy-0-coumaric 
 acid readily changes into the anhydride corresponding to cou- 
 marin, viz. umbelliferone, C 9 H 6 C 3 ; this last-named compound 
 is present in varieties of Daphne. 
 
 Related to the above is piperic acid: 
 
 CH : CH CH : CH COaH, 
 
 a decomposition product of piperine (p. 540), which crystallizes 
 in long needles. 
 
 B. Dibasic Acids 
 
 The dibasic acids occupy exactly the same position in the 
 aromatic series as the dibasic acids C n H 2n _ 2 4 do in the fatty. 
 They contain two carboxyl groups; these may both be in the 
 nucleus or in the side chain or chains, or be divided between 
 them. They yield acid salts and normal salts, and similarly 
 two series of esters, amides, &c. Dibasic phenolic acids can 
 of course occur here also. 
 
 1. Phthalic acid, Benzene-o-dicarloxylic add, C 6 H 4 (C0 2 H) 2 
 (Laurent, 1836), is formed when any o-di-derivative of benzene, 
 which contains two carbon side chains, is oxidized by HN0 3 or 
 KMn0 4 , but not by Cr0 3 (cf. p. 438); it is generally formed by 
 the oxidation of naphthalene by nitric acid, and also of anthra- 
 cene derivatives. In preparing it on the large scale the naph- 
 thalene is first converted into its tetra-chlor-addition product, 
 CjpHgCl^ and then oxidized. At the present time phthalic 
 acid is prepared on the commercial scale by oxidizing naph- 
 thalene with concentrated sulphuric acid in the presence of 
 a small amount of mercury or mercuric sulphate at 220-300. 
 It crystallizes in short prisms or plates, melts at 213, and is 
 readily soluble in water, alcohol, and ether. When heated 
 above its melting-point, it yields the anhydride. When heated 
 with lime, it yields benzoic acid or benzene according to the 
 relative amounts of acid and lime used. Chromic acid dis- 
 integrates it completely, while sodium amalgam converts it 
 into dihydro-, tetrahydro-, and finally hexahydro-phthalic acid 
 (see below). Its barium salt, C 6 H 4 (C0 2 ) 2 Ba, is sparingly soluble 
 in water. K = 0-121. 
 
PHTHALIO ACIDS 465 
 
 Phthalic anhydride, C 6 H 4 <^pQ^>0, crystallizes in magnifi- 
 
 cent long prisms which can be sublimed; it melts at 128, boils 
 at 284, and is used in the preparation of eosin dyes (see 
 Fluorescein). 
 
 Phthalimide, C 6 H 4 <^QQ^>NH, corresponds with succinimide 
 
 in many respects. It is obtained by passing dry ammonia over 
 heated phthalic anhydride, and readily gives rise to metallic 
 derivatives. The potassium salt C 6 H 4 (CO) 2 NK, obtained by the 
 action of aqueous caustic potash on an alcoholic solution of the 
 imide, readily reacts with alkyl iodides, yielding alkylated 
 phthalimides, e.g. C 6 H 4 (CO) 2 NC 2 H 5 , and when these are hy- 
 drolysed, primary amines, free from secondary and tertiary, 
 are obtained, e.g. : 
 
 C 6 H 4 :(CO) 2 :NC 2 H 5 + 2H 2 = C 6 H 4 (CO 2 H) 2 + C 2 H 6 NH 2 
 
 (Gabriel, B. 1887-1897). Numerous primary amines, including 
 halogenated bases, which are difficult to prepare by other 
 methods, have been obtained in this way. E. Fischer (B. 1901, 
 34, 455) has also used the same method for the preparation of 
 the complex amine ornithine, 
 
 NH 2 .CH 2 .CH 2 .CH 2 .CH(NH 2 ).C0 2 H, 
 
 a5-diamino-?i- valeric acid. The various steps are: Potassium 
 phthalimide and trimethylene bromide yield 
 
 C 6 H 4 : (CO) 2 : N CH 2 CH 2 CH 2 Br, 
 
 and this on condensation with ethyl sodio-malonate gives 
 C 6 H 4 : (C0) 2 : N CH 2 CH 2 CH 2 CH(CO 2 Et) 2 ; 
 
 and on bromination and subsequent hydrolysis and loss of 
 carbon dioxide 
 
 C 6 H 4 :(CO) 2 :N.CH 2 .CH 2 .CH 2 .CHBr.C0 2 H 
 
 is obtained. Aqueous ammonia converts this into the corre- 
 sponding amino-compound, and subsequent hydrolysis gives 
 ornithine. 
 
 The chloride, phthalyl chloride, which is obtained by the 
 action of PCL upon the acid or the anhydride, appears not to 
 
 C^C^~\ 
 
 have the normal constitution C 6 H 4 (COC1) 2 , but C 6 H 4 
 
 as it yields phthalo-phenone, C 6 H 4 <>0, with benzene 
 
 (B480) 2G 
 
466 XXVI. AROMATIC ACIDS 
 
 and aluminium chloride, and on reduction with sodium amal- 
 
 PTT 
 gam it yields phthalide, C 6 H 4 <^pQ 2 ^>0, the constitution of 
 
 which is confirmed by its conversion on hydrolysis into 0-hy- 
 droxy-methyl-benzoic acid (p. 462), OH . CH 2 . C 6 H 4 CO OH. 
 
 2. Isophthalic acid (1:3), prepared from m-xylene, crystal- 
 lizes in slender needles from hot water, in which it is only 
 sparingly soluble; it sublimes without forming an anhydride. 
 The barium salt is readily soluble in water. K = 0'0287. 
 
 Tlvitic acid is 5-methyl-isophthalic acid, and may be obtained 
 by oxidizing mesitylene. 
 
 3. Terephthalic acid (1:4) is obtained by the oxidation of 
 jp-xylene, cymene, &c., and especially of oil of turpentine or oil 
 of cumin. It forms a powder almost insoluble in alcohol and 
 water, and sublimes unchanged. For its preparation jp-toluic 
 acid is oxidized by potassic permanganate (A. 258, 9). The 
 barium salt is only sparingly soluble. 
 
 A. Baeyer's researches (A. 245, 251, 258, 266, 269, and 276) 
 have introduced us to a whole series of reduction products of 
 phthalic acid, generally known as hydro-phthalic acids. The 
 isomers among them differ from one another either by the 
 position of the double bond in the ring (structural isomerism}, 
 or by the spatial arrangement of the carboxyl groups with 
 respect to the ring (stereo-isomerism). This latter isomerism 
 corresponds to a certain extent with that of fumaric and 
 maleic acids, but more closely with that of the poly-methylene 
 compounds (p. 325), and a distinction is therefore made here 
 also between a trans- and a as-form (cf. A. 245, 130). Exactly 
 the same applies to the hydro-terephthalic acids. 
 
 Of the hydro-phtlialic acids (A. 269, 147) there are now 
 known : Five dihydro-acids (two of which are stereo-isomeric), 
 four tetrahydro-acids (of which two again are stereo-isomeric), 
 and two hexahydro-adds (which are stereo-isomers). Of the 
 hydro-terephthalic acids (A. 258, 1), five dihydro-, three tetra- 
 hydro-, and two hexahydro-acids are known, two in each group 
 being stereo-isomeric. 
 
 The following principles have largely served for determin- 
 ing the position of the double bonds in these compounds: 
 (1) When bromine substitutes in a carboxylic acid it takes up 
 the a-position to the carboxyl (i.e. it is attached in the benzene 
 nucleus to the same carbon atom to which the carboxyl is 
 linked). (2) If two bromine atoms stand in the ortho-position 
 to one another in a reduced benzene nucleus, they are elimi- 
 
HYDRO-PHTHALIC ACIDS 467 
 
 nated, without replacement, by the action of zinc dust and 
 glacial acetic acid ; whereas, if they stand in the ^ra-positiori, 
 they are replaced by hydrogen. (3) As in the case of the ali- 
 phatic unsaturated acids, boiling with sodic hydroxide solution 
 often gives rise to an isomeric acid, due to the " wandering " 
 of a double bond in the direction of a carboxyl group (p. 162). 
 (4) The stereo-isomeric modifications are also easily transformed 
 one into the other. 
 
 The relations existing between the five known dihydro- 
 phthalic acids may be taken as an example. When phthalic 
 acid is reduced by sodium amalgam in presence of acetic acid, 
 tois-A-3 : 5-dihydro-phthalic acid is produced, and this changes 
 into the ces-A-3 : 5-acid when heated with acetic anhydride : 
 
 Both of these yield the A-2 : 6-dihydro-acid when warmed with 
 alkali. When the dihydrobromide of the latter acid is treated 
 with alcoholic potash, the A-2:4-dihydro-acid results, and, lastly, 
 the anhydride of this yields the anhydride of the A-l : 4-dihydro- 
 acid when heated: 
 
 H H H 
 
 A-2:6 A-2:4 A-l:4 
 
 All the dihydro-phthalic acids give anhydrides with the ex- 
 ception of the tois-A-3 : 5-acid, which in this respect comports 
 itself like fumaric acid. 
 
 The following relationships have been established between 
 the hydro-terephthalic acids: 
 
 Terephthalic acid reduced with pure sodium amalgam in 
 faintly alkaline solution gives a mixture of cis- and tois-A-2:5- 
 dihydro-acids, both of which on oxidation readily yield tere- 
 phthalic acid. When boiled with water both are converted 
 into the A-l:5-dihydro-acid, and when boiled with caustic soda 
 
 * In these formulae X = C0 2 H, A denotes the double bond, and the 
 numbers refer to the carbon atoms after which the double bonds are 
 placed. A-3:5 indicates two double bonds, one between carbons 3 and 4, 
 and a second between carbons 5 and 6. 
 
468 
 
 XXVI. AROMATIC ACIDS 
 
 solution into the A-l : 4-dihydro-acid. This acid is the most 
 stable of the dihydro-acids, and is always obtained by the 
 reduction of terephthalic acid unless great care is taken in the 
 reduction. 
 
 When reduced with sodium amalgam the A-l:5-acid is con 
 verted into a mixture of cis- and ^Yms-A-2-tetrahydro-acid. 
 Both acids readily combine with bromine, which can again 
 be removed by means of zinc dust; this dibromide, when 
 warmed with alcoholic potash, gives the A-l:3-dihydro-acid, 
 which cannot be obtained directly by the reduction of tere- 
 phthalic acid. 
 
 The A-1-tetrahydro-acid may be obtained by warming the 
 A-2-acid with sodium hydroxide solution. 
 
 The A-l -acid yields a mixture of two stereo-isomeric di- 
 bromides (cis and trans), and these when reduced with zinc 
 dust and acetic acid yield the cis- and /nws-hexahydro-tere- 
 phthalic acid: 
 
 X X 
 
 X I X X 
 
 II "I and I - 
 
 ^ 
 
 H A-l:5 
 
 Cis- and nms-A-2:5-dihydro 
 
 XH X XH 
 
 :H 
 
 Hexahydro 
 cis and trans 
 
 Hi 
 
 XH 
 
 A-2-tetrahydro 
 cis and trans 
 
 A-l: 3- 
 dihydro. 
 
 The completely hydrogenized acids show great differences 
 from the partially hydrogenized. Thus, hexahydro-terephthalic 
 acid is exactly similar to a saturated acid of the fatty series; 
 cold permanganate of potash has no effect upon it, while bro- 
 mine substitutes (upon warming). 
 
 On the other hand, the partially hydrogenized acids comport 
 themselves precisely like the unsaturated acids of the fatty 
 series with an open chain. They are very readily oxidized 
 by cold permanganate, and take up bromine or hydrobromic 
 
HYDROXY-PHTHALIC ACIDS 469 
 
 acid until the saturation stage of the hexa-methylene ring is 
 reached. All of the hydro-acids can be transformed back into 
 phthalic acid (A. 1894, 280, 94). 
 
 For hydro-ispphthalic acids, see W. H. Perkin, Jun., and S.S 
 Pickles, P. 1905, 75, and Baeyer and Filliger, A. 1893, 276, 255. 
 Two stereo-isomeric modifications of the hexahydro-acid are 
 also obtained synthetically from derivatives of the fatty series 
 (Perkin, J. C. S. 1891, 798). This constitutes a further proof 
 that the hexahydro-benzene-carboxylic acids are nothing more 
 than hexa-methylene derivatives. 
 
 A large number of substitution products of the phthalic acids 
 are known, e.g. chloro- and bromo-phthalic acids (which are 
 used in the eosin industry), nitro-, amino-, hydroxy- and sulpho- 
 phthalic acids, &c. 
 
 HYDROXY-PHTHALIC ACIDS 
 
 2^5-Dihydroxy-terephthalic acid, quinol-p-dicarloxyUc actd, 
 C 6 H 2 (OH) 2 (C0 2 H) 2 , in which both the hydroxyls and the car- 
 boxy Is are respectively in the ^-position to one another, is 
 obtained as its ethyl ester by the action of bromine upon 
 succinylo-succinic ester, or of sodium ethoxide upon dibromo- 
 acetoacetic ester. The free acid breaks up into quinol and 
 carbon dioxide when distilled, and is converted by nascent 
 hydrogen into succinylo-succinic acid. 
 
 Succinylo-succinic acid, p-dihydroxy-dihydro-tereplithalic acid, 
 C 6 H 4 (OH) 2 (C0 2 H) 2 , is obtained as its ethyl ester by the action 
 of sodium upon ethyl succinate (see p. 342). The ethyl ester 
 crystallizes in triclinic prisms which melt at 126, and dissolves 
 in alcohol to a bright-blue fluorescent liquid which is coloured 
 cherry-red by ferric chloride. It contains two replaceable hy- 
 drogen atoms, being analogous to acetoacetic ester. The free 
 acid, on losing carbon dioxide, changes into tetrahydro-quinone 
 or p-diketo-hexamethylene. 
 
 The ester may be represented as a dihydroxylic compound 
 or as a diketone: 
 
 C.C0 2 Et CH.C0 2 Et 
 
 OH 
 
 xx 
 
 CO 2 Et 
 
 ana reacts as a tautomeric substance (cf. Ethyl Acetoacetate). 
 
470. XXVI. AROMATIC ACIDS 
 
 C. Polybasie Acids 
 
 Benzene s-tricarboxylic acid or trimesic acid, CJH 3 (COOH; 3 , 
 can be obtained by the oxidation of mesitylene. The isomeric 
 unsym. acid or trimellitic acid is obtained by the oxidation of 
 colophonium, and the adjacent acid or heuiimellitic acid is 
 obtained by oxidizing naphthalene-l:8-dicarboxylic acid. 
 
 The benzene tetracarboxylic acids, C 6 H 2 (C0 2 H) 4 , prehnitic 
 acid [1:2:3:4], mellophanic acid [1:2:3:5], and pyromellitic 
 acid [1:2:4:5], are obtained by heating mellitic acid or its 
 hexahydro-derivatives. 
 
 Mellitic acid, Cg(CO 2 H) 6 , occurs in peat as aluminium salt 
 or honey-stone, C 12 A1 2 12 + 18H 2 0, which crystallizes in 
 octahedra, and is also formed by the oxidation of lignite or 
 graphite with KMn0 4 . It forms fine silky needles of great 
 stability, can neither be chlorinated, nitrated, nor sulphonated, 
 but is readily reduced by sodium amalgam to hydromellitic 
 acid, C 6 H 6 (C0 2 H) 6 , and yields benzene when distilled with 
 lime. 
 
 As regards the esterification of these polybasic acids, it has 
 been found that carboxylic groups which have other carboxylic 
 groups in two ortho-positions cannot be esterified by the usual 
 catalytic process, e.g. on esterification by the Fischer -Speyer 
 method, hemimellitic acid and prehnitic acid yield dimethyl 
 esters only, pyromellitic acid yields a tetramethyl ester, and 
 mellitic acid is not acted on (V. Meyer and Sudborouqh. B. 1894. 
 27, 3146). 
 
 XXVII. AROMATIC COMPOUNDS CONTAIN- 
 ING TWO OR MORE BENZENE NUCLEI. 
 DIPHENYL GROUP 
 
 The aromatic compounds hitherto considered, with the ex- 
 ception of azobenzene, benzophenone, &c., contain but one 
 benzene nucleus. In addition to these, however, a consider- 
 able number of compounds are known which contain two or 
 more such nuclei united in a variety of ways. Such com- 
 pounds are usually arranged in the following groups: 
 
 1. Diphenyl group; this comprises the compounds with two 
 benzene nuclei directly united together. The parent substance 
 of the group is diphenyl, C 6 H 6 .C 6 H 6 . 
 
Dli>HENYL 471 
 
 2. Diphenyl-methane group; this includes all compounds 
 with two benzene nuclei attached to a single carbon atom. 
 The parent substance is diphenyl-methane, C 6 H 5 CH 2 C 6 H 5 . 
 
 3. Dibenzyl or stilbene group, which comprises compounds 
 containing two benzene nuclei linked together by a chain of 
 two or more carbon atoms, e.g. dibenzyl, C fi !L CH 2 CH 2 CJEL, 
 and stilbene, C 6 H 5 . CH : CH . C 6 H 5 . 
 
 4. Triphenyl-methane group, which contains the compounds 
 with three benzene nuclei attached to a single carbon atom, 
 e.g. triphenyl-methane, CH(C 6 H 5 ) 3 . 
 
 5. In addition to the above groups several extremely im- 
 portant groups are known which contain two or more benzene 
 nuclei arranged in such a manner that they have two or more 
 carbon atoms in common, e.g.: 
 
 Naphthalene, ; anthracene, ; &c. 
 
 These are usually termed compounds with condensed benzene 
 nuclei. 
 
 DIPHENYL GEOUP 
 
 Diphenyl is related to benzene in much the same manner 
 as ethane to methane: 
 
 CH 4 and CH 3 - CH 3 C 6 H 6 and C 6 H 6 C 6 H 6 . 
 
 Its molecule consists of two benzene nuclei directly united 
 Its method of synthesis by Fittig, by the action of sodium on 
 an ethereal solution of monoiodo-benzene or of copper-bronze 
 at 230 (Ullmann, A. 332, 38), is analogous to the formation 
 of ethane by the action of zinc or sodium on methyl iodide: 
 2C 6 H 6 I + 2Cu = C 6 H 6 .C 6 H 5 + Cu 2 I 2 . 
 
 It is also formed by passing the vapour of benzene through a 
 red-hot tube. It is contained in coal-tar, crystallizes in large 
 colourless plates, melts at 71, boils at 254, and is readily 
 soluble in alcohol and ether. 
 
 Chromic acid oxidizes diphenyl to benzoic acid, one of the 
 two benzene nuclei being destroyed, thus leaving only one 
 carbon atom joined to the other benzene residue. From this 
 and from its synthesis, the constitutional formula of diphenyl 
 must be C 6 H 5 -C 6 H 6 . 
 
472 XXVII. DIPHENYL GROUP 
 
 Derivatives (Schulte, A. 207, 311). Like benzene, diphenyl 
 is the mother substance of an extended series of derivatives 
 which closely resemble the corresponding benzene derivatives 
 in most respects. With polysubstituted derivatives the sub- 
 stituents are usually denoted by the following numbers, accord- 
 ing to the position occupied : 
 
 Even the entrance of only one substituent produces isomers, 
 since the latter may stand either in the 0-, m-, or ^-position to 
 the point of union of the two benzene residues. The same 
 applies in still greater degree to isomeric di-derivatives, of 
 which o-o-, p-p-, o-p-, &c. compounds can exist. The consti- 
 tution of these is elucidated from their syntheses, from their 
 products of oxidation, or by conversion into compounds of 
 known constitution; thus a chloro-diphenyl, C 12 H 9 C1, which 
 yields ^>-chloro-benzoic acid when oxidized by chromic acid, is 
 obviously ^-chloro-diphenyl. Whether all the substituents are 
 attached to the one nucleus or are distributed between the 
 two, can also be proved by an examination of the products of 
 oxidation. 
 
 The substituents take up the ^-position for choice; in di- 
 derivatives the p-p- (and to a lesser extent the o-p-) position. 
 
 Di-p-diamino- diphenyl, benzidine, NH 2 C 6 H 4 C 6 H 4 NH 2 
 (Zinin, 1845), is obtained by the reduction of ^-j9-dinitro- 
 diphenyl (the direct nitration product of diphenyl); also, to- 
 gether with diphenyline, by the action of acids upon hydrazo- 
 benzene, the latter undergoing a molecular transformation 
 (p. 395): 
 
 C 6 H 6 .NH.NH.C 6 H 6 = NH 2 .C 6 H 4 .C 6 H 4 .NH 2 ; 
 
 it is consequently formed directly from azobenzene by treating 
 it with tin and hydrochloric acid. 
 
 Benzidine is a diacid base which crystallizes in colourless 
 silky plates, is readily soluble in hot water or alcohol, melts 
 at 122, and can readily be sublimed. Its sulphate, 
 C 12 H 10 (NH 2 ) 2 S0 4 H 2 , is sparingly soluble. Like its homo- 
 logues (tolidine, &c.), it is of special importance in the colour 
 industry, since, by coupling its diazonium-compound (tetra- 
 zonium-diphenyl chloride) with naphthol-sulphonic or naph- 
 thylamine-sulphonic acids, &c., colours are produced which 
 
CARBAZOLE. DIPHENYLENE OXIDE 473 
 
 dye unmordanted cotton directly, the so-called " substantive " 
 or cotton dyes. To this class belongs the dye congo, 
 
 (S0 3 Na)(NH 2 )C 10 H 6 N : N C 6 H 4 . C 6 H 4 . N : N C 10 H 6 (NH 2 )(S0 3 Na), 
 
 prepared by means of naphthionic acid (p. 499), and the dye 
 chrysamine G, prepared with salicylic acid. 
 
 The isomeric diphenyline, 2 : 4'-diamino-diphenyl, may be 
 obtained from 2 : 4'-dinitro-diphenyl, and also as a by-product 
 in the preparation of benzidine from azobenzene. It crystal- 
 lizes in needles, melting at 45, and yields a sulphate which is 
 readily soluble. 
 
 Carbazole, 
 
 NH 
 
 the imide of diphenyl, is contained in coal-tar and in crude 
 anthracene. It is formed by distilling o-amino-diphenyl over 
 lime at a low red heat, or by passing the vapour of diphenyl- 
 amine through red-hot tubes, just as diphenyl is obtained 
 from benzene: 
 
 (C 6 H 6 ) 2 NH = (C 6 H 4 ) 2 NH + H 2 . 
 
 It crystallizes in colourless plates sparingly soluble in cold 
 alcohol, melts at 238, distils unchanged, and is characterized 
 by the readiness with which it sublimes. Concentrated sul- 
 phuric acid dissolves it to a yellow solution, and it forms an 
 acetyl- and a nitro-compound, &c. The nitrogen in it occupies 
 the di-ortho-position ; it thus appears, like indole, to be a pyr- 
 role derivative, and it shows, in fact, most striking analogies 
 to the latter (B. 21, 3299). 
 
 Benzidine-mono-, di-, &c. sulphonic acids, e.g. C 12 H 6 (NH 2 ) 2 
 (S0 3 H) 2 , are of technical importance. The dihydroxy- 
 diphenyls, C 12 H 8 (OH) 2 , of which four isomers are known, are 
 formed (a) by diazotizing benzidine, (b) by fusing diphenyl- 
 disulphonic acid with potash, and (c) by fusing phenol with 
 potash or by oxidizing it with permanganate; in the last case 
 hydrogen is separated and two benzene residues join together. 
 
 p TT 
 
 Diphenylene oxide, 6 4 /0, is obtained by distilling phenol 
 C 6 H/ 
 
 with plumbous oxide; it crystallizes in plates which distil with- 
 out decomposition (cf. e.g. B. 25, 2745). 
 
 The carboxylic acids of diphenyl are obtained (1) from the 
 
474 XXVIII. DIPHENYL-METHANE GROUf 
 
 corresponding nitriles, which on their part are prepared by 
 distilling the sulphonic acids of diphenyl with KCN, e.g. di-p- 
 diphenyl-dicarboxylic acid, C 12 H 8 (C0 2 H) 2 , a white powder 
 insoluble in water, alcohol, and ether; (2) by the oxidation of 
 phenanthrene and similar compounds, e.g., diphenic acid, 
 C0 2 H-C 6 H 4 .C 6 H 4 .C0 2 H, the 2 : 2'-dicarboxylic acid, crystal- 
 lizing in needles or plates which are readily soluble in the 
 solvents just mentioned; rn.-pt. 229. Both of these are di- 
 basic acids, which yield diphenyl when heated with soda-lime. 
 
 The homologues of diphenyl are, like the latter, obtained by 
 means of Fittig's reaction. Analogous to benzidine is 0-tolidine, 
 Ci 2 H 6 (CH 3 ) 2 (NH 2 ) 2 , m.-pt. 128, whose diazo-compound unites 
 with naphthionic acid to the red substantive dye, benzo-pur- 
 purine 4B. Similarly di-anisidine or dimethoxy-benzidine, 
 C 12 H 6 (0 CH 3 ) 2 (NH 2 ) 2 , yields diazonium salts which combine 
 with a-naphthol-a-sulphonic acid to form a blue substantive 
 dye, benzazurine G. 
 
 Diphenyl may be regarded as monophenyl -benzene; the 
 corresponding di- and triphenyl-benzenes are also known. 
 
 ^-Diphenyl-benzene, C C H 4 (C 6 H 5 ) 2 , may be obtained by the 
 action of sodium upon a mixture of ^-dibromo-benzene and 
 bromo-benzene. It crystallizes in flat prisms, melts at 205, 
 and on oxidation yields diphenyl-monocarboxylic and tere- 
 phthalic acids. 
 
 When hydrochloric acid gas is led into acetophenone, C 6 H 5 
 CO CH 3 , a reaction analogous to the formation of mesitylene 
 from acetone (p. 342) ensues, and s-triphenyl-benzene, 
 C 6 H 3 (C 6 H 5 ) 3 (rhombic plates), is formed. 
 
 XXVIII. DIPHENYL-METHANE GROUP 
 
 Diphenyl-methane, C 6 H 5 CH 2 C 6 H 5 , is derived from methane 
 by the replacement of two hydrogen atoms by two phenyl 
 groups, and is thus closely related to phenyl-methane or toluene, 
 C 6 H 5 CH 3 . One important difference is that when oxidized it 
 cannot yield an acid containing the same number of carbon 
 atoms since it does not contain a methyl group. It can be 
 oxidized to the secondary alcohol benzhydrol, (C 6 H 5 ) 2 CHOH, 
 or the ketone benzophenone, (C 6 H 5 ) 2 CO. Compounds like 
 diphenyl-ethane, (C 6 H 5 ) 2 CH CH 3 , can yield acids. 
 
 The various derivatives are obtained by substituting one 
 
DIPHENYL-METHANE 475 
 
 or more of the twelve hydrogen atoms present in the diphenyl- 
 methane molecule. If the substituent replaces any of the ten 
 hydrogens directly attached to the benzene nuclei, a com- 
 pound is formed which closely resembles the corresponding 
 derivatives of benzene, e.g. C 6 H 5 CH 2 C 6 H 4 NH 2 closely re- 
 sembles aniline. If, on the other hand, the substituent replaces 
 a hydrogen atom of the methylene group, a compound with 
 aliphatic properties is obtained, e.g. (C 6 H 5 ) 2 CHOH closely 
 resembles a secondary aliphatic alcohol. 
 
 The method of numbering the carbon atoms in the diphenyl- 
 methane molecule is usually as follows : 
 
 Formation of diphenyl-methane and its derivatives. 
 
 1. Diphenyl-methane is produced by the action of benzyl 
 chloride upon benzene, in presence of zinc dust (Zincke, A. 159, 
 374), or of aluminium chloride (Friedel and Crafts): 
 
 = C 6 H 6 .CH 2 .C 6 H 5 + 
 
 The homologues of benzene, and also the phenols and 
 tertiary amines, may be used instead of benzene itself. 
 
 In an exactly analogous manner diphenyl-methane is ob- 
 tained by the action of methylene chloride, CH 2 C1 2 , upon 
 benzene in presence of aluminium chloride: 
 
 CH 2 C1 2 + 2C 6 H 6 = CH 2 (C 6 H 6 ) 2 
 
 2. Diphenyl-methane hydrocarbons are formed by the action 
 of the aliphatic aldehydes, e.g. acetaldehyde or formaldehyde, 
 upon benzene, &c., in the presence of concentrated sulphuric 
 acid (Baeyer, B. 6, 963). With formaldehyde diphenyl-methane, 
 or with acetaldehyde diphenyl-ethane, is formed: 
 
 CH 3 .CHO + 2C 6 H 6 = CH 3 .CH(C 6 H 6 ) 2 + 
 
 The acetaldehyde and formaldehyde are employed here in 
 the form of paraldehyde and methylal. Formaldehyde itself 
 condenses with aniline to diamino-, and with dimethyl-aniline 
 to tetramethyl- diamino -diphenyl-methane. When aromatic 
 aldehydes are used, triphenyl-methane derivatives are formed 
 (p. 480). 
 
 3. Aromatic alcohols react with benzene and sulphuric acid 
 in an analogous manner (V. Meyer): 
 C 6 H 6 .CH 2 -OH 
 
476 XXVIII. DIPHENYL-METHANB GROUP 
 
 Similar reactions have also been brought about by means of 
 ketones, aldehydo-acids, and keto-acids on the one hand, and 
 phenol and dialkylated anilines on the other. 
 
 The true aromatic ketones of the type of benzophenone may 
 be regarded as diphenyl-methane derivatives (see p. 428). 
 
 Diphenyl-methane, (CgH 5 ) 2 CH 2 , is most conveniently pre- 
 pared from benzyl chloride, benzene, and aluminic chloride. 
 It crystallizes in colourless needles of very low melting-point 
 (26), is readily soluble in alcohol and ether, has a pleasant 
 odour of oranges, and distils unaltered at 262. 
 
 It yields nitro-, amino-, and hydroxy-derivatives. ^-Diamino- 
 diphenyl-methane, CH 2 (C 6 H 4 NHA2, is obtained by heating 
 anhydro-formaldehyde-aniline, C 6 Hg N : CH 2 , prepared from 
 formaldehyde and aniline, with aniline and an aniline salt. 
 It crystallizes in lustrous silvery plates, melting at 87*, and 
 may be used for the preparation of fuchsine. Bromine at a 
 moderate temperature reacts with the hydrocarbon yielding 
 diphenyl-bromo- methane, (C 6 H 5 )oCHBr, and when this is 
 heated with water to 150, it yields benzhydrol, diphenyl-car- 
 binol, (C 6 H 6 ) 2 CHOH, which can also be obtained from benzo- 
 phenone and sodium amalgam, or by Grignard's synthesis. It 
 crystallizes in glistening silky needles, melts at 68, possesses 
 in every respect the character of a secondary alcohol (forming 
 esters, amines, &c.), and is readily oxidized to the correspond- 
 ing ketone, benzophenone, (C 6 IL) 2 CO (p. 428). 
 
 aa-Diphenyl-ethane, (C 6 H 5 ) 2 CH GEL (isomeric with dibenzyl, 
 see p. 477), is obtained by method of formation 2 (p. 475). It 
 is a liquid, boils at 286, and is oxidized to benzophenone by 
 chromic acid. From it is derived : 
 
 Benzilic acid, diphenyl-gly collie add, (C 6 H 5 ) 2 C(OH) C0 2 H, 
 which is formed by a molecular transformation when benzil, 
 C 6 H 5 .CO.CO-C 6 H 5 (p. 479), is fused with potash. It crystal- 
 lizes in needles or prisms, dissolves in concentrated sulphuric 
 acid to a blood-red solution, and is reduced by hydriodic acid 
 to diphenyl-acetic acid, (C 6 H 6 ) 2 CH C0 2 H (needles or plates), 
 which may also be obtained synthetically from phenyl-brom- 
 acetic acid, C 6 ILCHBr 'GOgH, benzene, and zinc dust, accord- 
 ing to mode of formation 1, p. 475. 
 
 Tolyl-phenyl-methanes, C 8 H 5 CH 2 C 6 H 4 CH 3 . The p- and o- 
 compounds are obtained from benzyl chloride and toluene. 
 
 Benzoyl-benzoic acids, benzophenone-carboxylic acids, C 6 H 5 
 CO.C 6 H 4 .C0 2 H (B. 6, 907). Of these the o-acid (m.-pt. 127) 
 has been prepared synthetically by heating phthalic anhydride 
 
DIBENZYL GROUP 477 
 
 with benzene and aluminic chloride. When heated with 
 phosphorus pentoxide at 180, it yields anthra-quinone, 
 
 H various transformations into the anthra- 
 
 cene series have been effected in a similar manner from o-tolyl- 
 phenyl-methane and the corresponding ketone. 
 
 C 6 H 4 \ 
 Fluorene, diphenylene-methane, /CH 2 , stands in the 
 
 CgH/ 
 
 same relation to diphenyl-methane as carbazole (p. 473) does 
 to diphenylamine; it is at the same time a diphenyl and a 
 methane derivative. It is contained in coal-tar, and is pro- 
 duced when diphenyl-methane is led through red-hot tubes 
 (like diphenyl from benzene), and also by passing the vapour 
 of diphenylene-ketone over red-hot zinc dust. It crystallizes 
 in colourless plates with a violet fluorescence, melts at 113, 
 and boils at 295. The corresponding ketone, diphenylene- 
 ketone, C 12 H 8 :CO, which crystallizes in yellow prisms melting 
 at 84, is obtained by heating phenanthra-quinone with lime, 
 and is converted into fluorenyl alcohol, (C 6 H 4 ) 2 : CH OH 
 (colourless plates, m.-pt. 153), by nascent hydrogen, and into 
 diphenyl-carboxylic acid, o-phenyl-benzoic acid, C 6 
 C0 2 H, by fusion with potash. 
 
 XXIX. DIBENZYL GROUP 
 
 This group comprises the compounds containing two ben- 
 zene nuclei connected by a chain of two carbon atoms. 
 Among the most important members are: Dibenzyl, 
 C 6 H 5 .CH 2 .CH 2 .C 6 H 5 ; stilbene, C 6 H 5 .CH:CH.C 6 H 5 ; tolane, 
 
 C 6 H 5 C : C C 6 EU; deoxybenzoin, C 6 H 5 CH 2 CO C 6 H 5 , 
 hydrobenzoin, C 6 H 5 CH(OH) CH(OH) C 6 H 5 ; benzoin, 
 C 6 H ff .CH(OH).CO.C 6 H,; benzil, C 6 H 5 .CO.CO.C 6 H 5 . 
 
 Dibenzyl is symmetrical diphenyl-ethane (for the unsym- 
 metrical compound, see p. 476), stilbene is s-diphenyl-ethylene, 
 and tolane diphenyl-acetylene. 
 
 All these compounds yield benzoic acid when oxidized. 
 
 Dibenzyl is formed when benzyl chloride is treated with 
 metallic sodium, or by the action of benzyl chloride on benzyl 
 magnesium chloride. It is often met with as a by-product in 
 Grignard's synthesis by means of benzyl magnesium chloride. 
 
478 XXIX. DIBENZYL GROUP 
 
 It is isoineric with ditolyl and with tolyl-plienyl-methane ; 
 it crystallizes in needles or small plates, melts at 52, and 
 sublimes unchanged. 
 
 Stilbene, s-diphenyl-ethylene, forms monoclinic plates or prisms, 
 melts at 125, and also boils without decomposition. It may 
 be prepared by the action of sodium upon benzal chloride, or 
 by heating deoxybenzoin with sodium ethoxide, or best by 
 the action of benzyl magnesium chloride on benzaldehyde, 
 and possesses the full character of an olefine, giving, for 
 instance, a dibromide, C 6 H 5 CHBr CHBr C 6 H 5 , with bro- 
 mine, and being converted into dibenzyl by hydriodic acid. 
 ^-Diamino- stilbene, C 14 H 10 (NH 2 ) 2 , and its disulphonic acid 
 (obtained by reducing ^-nitro-toluene or its sulphonic acid in 
 alkaline solution) are, like benzidine, mother substances of 
 "substantive dyes" (see p. 473). Stilbene should exist in two 
 stereo-isomeric modifications, the ordinary stilbene melting at 
 
 H .C-Ph 
 125 is usually regarded as the trans compound 
 
 Ph C H 
 
 An isomeride the cis compound has been described by Otto 
 and Sto/el (B. 1897, 30, 1799). Just as ethylene bromide 
 yields acetylene when boiled with alcoholic potash, so stilbene 
 dibromide yields tolane, which crystallizes in prisms or plates, 
 melting at 60. It may also be prepared by the following 
 series of reactions: 
 C 6 H 6 .CH 2 .CO.C 6 H 6 C 6 H 5 .CH:CC1.C 6 H 6 C 6 H 6 .C:C.C 6 H 6 . 
 
 Phosphorus pentachloride Alcoholic potash 
 
 Tolane corresponds with acetylene in its properties in so far 
 that it combines with chlorine to a dichloride and a tetra- 
 chloride; but it does not yield metallic derivatives, since it 
 contains no "acetylene hydrogen" (p. 51). 
 
 When stilbene dibromide is treated with silver acetate, two 
 di-acetates are formed; and when these are hydrolysed by 
 alcoholic ammonia, two isoineric substances of the composition, 
 C 6 H 5 .CH(OH).CH(OH).C 6 H 5 , hydrobenzoin and iso-hydro- 
 benzoin or s-diphenyl-glycol, are produced. Both compounds 
 are also formed by the action of sodium amalgam upon oil of 
 bitter almonds. The former crystallizes in rhombic plates, 
 melting at 138, and the latter in four-sided prisms, melting 
 at 119, and is the more soluble of the two. The two com- 
 pounds are stereo-isomeric in the same manner as meso-tartaric 
 and racemic acid, and JSrlenmeyer, Junr., has been able to re- 
 solve hydrobenzoin, which corresponds Mith racemic acid, into 
 
BENZIL. DEOXYBENZOIN 479 
 
 two optically active components, by separating two different 
 kinds of hemihedral crystals (A. 198, 115, 191; B. 30, 1531). 
 The compounds benzoin, benzil, and deoxy benzoin, which 
 have already been mentioned, are closely related to one an- 
 other, as their formulae show, and can also be prepared from 
 benzaldehyde. When the aldehyde is boiled with an alcoholic 
 solution of potassium cyanide it polymerises,* yielding benzoin, 
 2C 6 H 6 .CH:0 = C 6 H 6 .CH(OH).CO.C 6 H 6 , 
 
 which forms beautiful glistening prisms, m.-pt. 134; nascent 
 hydrogen reduces it to hydrobenzoin, from which it can also 
 be obtained by oxidation. It reduces Fehling's solution even 
 at the ordinary temperature, yielding benzil. 
 
 Benzil, C 6 H 5 CO CO C 6 H 5 , is obtained by oxidizing ben- 
 zoin with nitric acid. It crystallizes in large six-sided prisms, 
 melting at 95. It is oxidized to benzoic acid by chromic 
 anhydride, and reduced by nascent hydrogen according to 
 the conditions either to benzoin or to deoxybenzoin. It 
 reacts with hydroxylamine to produce: 
 
 Benzil-monoxime, C 6 H .CO^C(:N.OH).C 6 H 5 , and benzil- 
 dioxime, C 6 H 5 .C(:N.OH).C(:N.OH).C6H 5 , which exist in 
 the following sfeereo-isomeric modifications (Hantzsch and 
 Werner, B. 23, 11; 37, 4295; Dittrich, ibid., 24, 3267): 
 
 Monoximes : 
 
 C 6 H 6 .C.CO-C 6 H 6 C 6 H 6 .C.CO.C 6 H 6 
 
 N-OH Heated HO-N 
 
 eu M.-pt. 134* y. M.-pt. 113*. 
 
 Dioximes : 
 
 C 6 H 5 .C C.C 6 H 5 _^ C 6 H 6 .C C.C 6 H 5 ^_ C 6 H 5 .C C.C 6 H 6 
 
 N-OH HO-N " HO-N N-OH " " HO-N HO-N 
 
 ou M.-pt. 237 j3. M.-pt. 207 y. M.-pt. 163. 
 
 The configurations have been established as the result of an 
 examination of the products obtained by the Beckmann trans- 
 formation (A. 296, 279; 274, 1. Compare pp. 139 and 429). 
 
 Deoxybenzoin, C 6 H 5 CH 2 CO C 6 H 5 , forms large plates, 
 melting at 55, and may be sublimed or distilled unchanged. 
 It can be prepared by the action of benzene and aluminium 
 chloride upon phenyl-acetyl chloride, C 6 H 5 CHg CO Cl, and 
 hence its constitution, and yields di-benzyl with hydriodic 
 acid. Deoxybenzoin can also be prepared from benzil and 
 benzoin (B. 25, 1728). One of its methylene hydrogen atoms 
 
 * For mechanism, cf. Chalanay and Knoevenayd (B. 1892, 25, 295). 
 
480 XXX. TRIPHENYL-METHANE GROUI 
 
 is re t adilv replaceable by alkyl, just as in acetoacetic ester. 
 The radical, CH(C 6 H 5 ) . CO C 6 H 5 , is termed "desyl". 
 
 Benzilic acid, (C 6 H 5 ) 2 C(OH) C0 2 H (p. 476), is produced 
 when benzil is heated with alcoholic potash, by a peculiar 
 molecular transformation similar to that by which pinacoline 
 is formed (p. 193). 
 
 Compounds closely related to the dibenzyl group are those 
 which contain two benzene nuclei united by a chain of more 
 than two carbon atoms, e.g. ay-dipbenyl propane, and also 
 those compounds containing three or more benzene nuclei 
 united by a chain of carbon atoms, e.g. triphenyl-ethane, tetra- 
 phenyl-ethane, &c. 
 
 XXX. TRIPHENYL-METHANE GROUP 
 
 Triphenyl-methane, CH(C 6 H 5 ) 3 , is the compound obtained 
 as the result of the entrance of three phenyl groups into the 
 methane molecule; among its homologues are tolyl-diphenyl- 
 methane, (C 6 H.) 2 CH - C 6 H 4 CH, ditolyl - phenyl - methane, 
 C 6 H 5 .CH(0 6 H 4 .CH S ).,, &c. 
 
 These hydrocarbons are of especial interest as being the 
 mother substances of an extensive series of dyes; the amino-, 
 hydroxy-, and carboxy-derivatives of triphenyl- methane are 
 the leuco-bases obtained from such dyes as rosaniline, aurine, 
 malachite green, &c. 
 
 Their formation is effected in a manner analogous to that of 
 the diphenyl-methane derivatives, i.e. by the aid of zinc dust 
 or aluminic chloride when chlorine compounds are used, or 
 by the aid of phosphoric anhydride when oxygen compounds 
 are employed. 
 
 Thus, triphenyl-methane may be obtained (a) from benzal 
 chloride and benzene in the presence of aluminic chloride, 
 
 C 6 H 6 .CHC1 2 + 2C 6 H 6 = CH(C 6 H 6 ) 3 + 
 
 or from benzaldehyde, benzene, and zinc chloride; (b) from 
 chloroform and benzene in presence of aluminic chloride, 
 
 3C 6 H 6 + CHC1 3 = CH(C 6 H 6 ) 3 + 3HC1; 
 
 (c) from benzhydrol and benzene in the presence of phos- 
 phoric anhydride, 
 
 (C 6 H 6 ) 2 CH.OH-f C 6 H 6 = (C 6 H 6 ) 2 CH.(C 6 H 6 ) + H a O. 
 
I'RIPHENYL-METHANE 481 
 
 Derivatives of triphenyl - methane may be obtained by 
 similar methods, e.g. the leuco-base of bitter-almond-oil green, 
 tetramethyl-diamino-triphenyl-methane (cf. p. 483), may be 
 prepared by the condensation of benzaldehyde and dimethyl- 
 aniline : 
 
 C 6 H 6 .CHO + 2C 6 H 6 .N(CH3) 2 = C 6 H 6 .CH:[C 6 H 4 .N(CH s ) 2 ] 2 -f H 2 O. 
 
 When other amines or even phenols are used, a series of 
 allied compounds (which are often dyes) is obtained, the sepa- 
 ration of water being facilitated by the addition of zinc chlo- 
 ride, concentrated sulphuric acid, or anhydrous oxalic acid. 
 
 Triphenyl -methane, CH(C 6 H 5 ) 3 (KekuU and Franchimont, 
 B. 5, 906). This compound may be prepared from chloroform 
 and benzene by the Friedel-Cmfts reaction (cf. A. 194, 152), 
 diphenyl-methane being produced at the same time; also by 
 eliminating the amino-groups from ^-leucaniline, C 19 H 13 (NH 2 ) 3 , 
 and most readily by reducing triphenyl-carbinol with zinc dust 
 and acetic acid. It crystallizes in colourless prisms, m.-pt. 93, 
 b.-pt. 359, and dissolves readily in hot alcohol, ether, and 
 benzene. 
 
 It crystallizes from benzene with one molecule of " benzene 
 of crystallization", which is also the case with many triphenyl- 
 methane derivatives. When triphenyl-methane is treated with 
 bromine in a solution of carbon bisulphide, the methane hy- 
 drogen atom is exchanged for bromine with the formation of 
 triphenyl-methyl bromide, (C 6 H 5 ) 3 -CBr, which, when boiled 
 with water, yields triphenyl-carbinol, (C 6 H 5 ) 3 C-OH. This 
 crystallizes in glistening prisms, melts at 159, and can be 
 sublimed unchanged; it may also be prepared directly by 
 oxidizing a solution of triphenyl-methane in glacial acetic acid 
 with chromic acid, or synthetically by the action of Grignard's 
 phenyl magnesium bromide on benzophenone or ethyl benzoate : 
 
 (C 6 H 6 ) 2 CO (C 6 H 6 ) 3 C.OMgBr (C 6 H 6 ) 3 C.OH. 
 
 A number of homologues of triphenyl-methane have been- 
 prepared by this last method (Houben, B. 1903, 36, 3087). 
 
 Fuming nitric acid converts triphenyl-methane into trinitro- 
 triphenyl-methane, (C 6 H 4 N0 2 ) 3 *CH (yellow scales), which 
 can then be oxidized by chromic acid to trinitro-triphenyl- 
 carbinol, (C 6 H 4 N0 2 ) 3 C OH. The latter gives para-rosaniline, 
 (C 6 H 4 NH 2 ) 3 C OH, when reduced with zinc dust and glacial 
 acetic acid. 
 
 Homologous with triphenyl-methane are the tolyl-diphenyl- 
 
 (B480) 2H 
 
482 XXX. TRIPHENYL-METHANE GROUP 
 
 methanes, (C 6 H 5 ) 2 CH'C 6 H 4 CH 3 . From these also dyes are 
 derived, especially from m-tolyl-diphenyl-methane (in which 
 the CH 3 occupies the meta-position with regard to the methane 
 carbon atom), which can be prepared by diazotizing ordinary 
 leucaniline; it crystallizes in small prisms and melts at 59 -5 
 
 TRIPHENYL-METHANE DYES 
 
 Of the derivatives of triphenyl-me thane and of tolyl-di- 
 phenyl-methane, those are especially interesting which contain 
 amino-, hydroxy-, or carboxy-groups. The entrance of three 
 amino- or hydroxy-groups converts them into the leuco-com- 
 pounds of dyes, some of which latter are of great value. Two 
 amino -groups suffice for the full development of the dye 
 character only when the amino-hydrogen atoms are replaced 
 by alkyl radicals, one amino-group being insufficient for this 
 (see under ^-amino-triphenyl-methane). 
 
 The following are the chief groups of triphenyl-methane 
 dyes: 
 
 1. Those derived from diamino- triphenyl-methane. The 
 malachite-green group. 
 
 2. Those derived from triamino- triphenyl-methane. The 
 rosaniline group. 
 
 3. Those derived from trihydroxy-triphenyl-methane. The 
 aurine group. 
 
 4. Those derived from triphenyl-methane-carboxylic acid. 
 The eosin group. 
 
 Leuco-bases or leuco-compounds of dyes (p. 399) are the 
 colourless compounds formed by the reduction of the dyes, 
 usually by the addition of two atoms of hydrogen. When 
 oxidized they are converted back into the dyes. 
 
 All the dyes of the triphenyl-methane group, and also 
 indigo, methylene blue, safranine, &c., are capable of yielding 
 such leuco-compounds, generally on reduction with zinc and 
 hydrochloric acid, stannous chloride, or ammonium sulphide. 
 
 The oxidation of the leuco-compounds is often quickly 
 effected by the oxygen of the air (e.g. in the cases of indigo 
 white and of leuco-methylene blue) ; in the triphenyl-methane 
 group it is slower and frequently more complicated Leuco- 
 malachite green is readily oxidized to the corresponding 
 colour-base when treated with lead peroxide in acid solution, 
 and leucaniline when warmed with chloranil in alcoholic 
 solution, or when its hydrochloride is heated either alone or 
 
 
AMINO- AND DIAMINO-TRIPHENYL-METHANE DYES 483 
 
 with a concentrated solution of arsenic acM, or with metallic 
 hydroxides such as ferric hydroxide. 
 
 The leuco-bases of the triphenyl-methane dyes are deriva- 
 tives of triphenyl-methane or its homologues, the corresponding 
 dye-bases obtained by oxidizing the leuco-bases are derivatives 
 of triphenyl-carbinol or its homologues, and the dyes them- 
 selves are salts obtained by the elimination of water from the 
 dye-base and an acid. The relationships between the three 
 groups of compounds leuco-base, dye-base, and dyes are in- 
 dicated in the following scheme: 
 
 oxidized acid 
 
 Leuco-base ^ dye-base ^ dye. 
 reduced alkali 
 
 As an example: 
 CH(C H 4 .N H2 ) 3 - O 
 
 ' U T J^^ 1 
 
 -H 2 
 1. AMINO- AND DIAMINO- TRIPHENYL-METHANE GROUP 
 
 ^-Amino-triphenyl-methane can be synthesized either by 
 the condensation of jp-nitro-benzaldehyde with benzene and 
 subsequent reduction, or from benzhydrol and aniline. It 
 forms large prisms, and melts at 84. The corresponding car- 
 .binol is colourless and with acids yields red salts, but these 
 cannot dye animal fibres. 
 
 ^-Diamino- triphenyl-methane, C 6 H 5 CH(C 6 H 4 NH 2 ) 2 , is 
 prepared by the action of zinc chloride or of fuming hydro- 
 chloric acid upon a mixture of benzaldehyde and aniline 
 sulphate or chloride: 
 
 = C 6 H fi .CH(C 6 H 4 .NH 2 ) 2 + H 2 O. 
 
 It crystallizes in prisms, and the colourless salts yield an 
 unstable blue-violet dye, benzal violet, when oxidized. Me- 
 thylation converts the base into: 
 
 Tetramethyl - di-p-amino - triphenyl - methane, leuco-malachite 
 green, C 6 H 5 CH[C 6 H 4 -N(CH 3 ) 2 ] 2 , which is prepared on the 
 technical scale by heating benzaldehyde and dimethyl-aniline 
 with zinc chloride or concentrated sulphuric acid (0. Fischer, A. 
 206, 103). It forms colourless plates or prisms. As a diacid 
 base it yields colourless salts, which are slowly converted by 
 the air, but immediately by other oxidizing agents, such as 
 lead dioxide and sulphuric acid, into the salts of tetramethyl- 
 Oiamino - triphenyl - carbinol, C e tI 5 C (OH) [C 6 EyST(CH 3 ) 2 ] 2 . 
 
484 XXX. TRIPHENYL-METHANE GROUP 
 
 The free base is obtained by precipitating the salts with alkali. 
 It crystallizes in colourless needles and dissolves in cold acid 
 to a colourless solution; upon warming, however, the intense 
 green coloration of the salts is produced. (For an explana- 
 tion of this, see p. 486.) 
 
 The double salt with zinc chloride, ((X 3 H 25 N 2 C1) 3 , 2ZnCl 2 , 
 2 H 2 O, or the oxalate, (C 23 H 25 N 2 ) 2 , 3 H 2 C 2 O 4 , of this base is the 
 valuable dye bitter-almond-oil green, malachite green or Victoria 
 green, which forms green plates, readily soluble in water. This 
 can also be prepared directly by heating benzo-trichloride with 
 dimethyl-aniline and zinc chloride (Doebner). Brilliant green 
 is the corresponding tetraethyl compound. 
 
 The sulphonic acid of the diethyl-dibenzyl-diamino-triphenyl- 
 carbinol is acid green. 
 
 2. ROSANILINE GROUP 
 
 Fuchsine or magenta was first obtained in 1856 by Natanson, 
 who noticed the formation of a red substance, in addition to 
 that of aniline hydrochloride and ethylene-aniline, when ethy- 
 lene chloride was allowed to act upon aniline at a temperature 
 of 200 (A. 98, 297). It was prepared shortly afterwards by A. 
 W. Hofmann, by the action of carbon tetrachloride upon aniline, 
 and was first manufactured on the technical scale in 1859. Hof- 
 mann's scientific researches on this subject date from 1861. The 
 chemical constitution was made clear by Emit and Otto Fischer 
 in 1878 (A. 194, 242). (Of. also Caro and Grabs, B. 11, 1116.) 
 
 The rosaniline dyes are derived partly from triphenyl- 
 methane and partly from wi-tolyl-diphenyl-methane; in the 
 former case they are often designated para-compounds (e.g. 
 "para-rosaniline", because it is prepared from aniline and para- 
 toluidine ; " para-rosolic acid "). 
 
 Para-leucaniline, triamino-triphenyl-methane, CH(CLH 4 'NH 2 ) 3 , 
 andleucaniline, triamino-diplienyl-tolyl-'methane, CH 3 C 6 H 3 (NH 2 ) 
 CH(CgH 4 NH 2 ) 2 , are formed by the reduction of the corre- 
 sponding trinitro- compounds and also of the corresponding 
 dye-bases, para-rosaniline and rosaniline; the first named like- 
 wise by the reduction of ^-nitro-diamino-triphenyl-methane. 
 The free leuco-bases are precipitated by ammonia from solutions 
 of their salts as white or reddish flocculent masses, and crystal- 
 lize in colourless needles or plates; they melt at 203 and 100 
 respectively. As triacid bases they form colourless crystalline 
 salts. 
 
PARA-ROSANILINE AND ROSANILINE 485 
 
 Para-rosaniline, OH C(C 6 H 4 NH 2 ) 3 , and rosaniline, OH- 
 N xr 2 R are the bases of the fuchsine dyes. They 
 
 IN -0-2 
 
 are obtained by precipitating solutions of their salts with 
 alkalis, and crystallize from hot water or alcohol in colourless 
 needles or plates, which become red in the air. Both are tri- 
 acid bases, stronger than ammonia. As they yield tri-diazonium 
 salts on treatment with nitrous acid, they must contain three 
 primary amino- groups. The diazonium compounds readily 
 yield the corresponding hydroxylic dyes, aurine and rosolic 
 acid (p. 490), when boiled with water. 
 
 Constitution. The relations between the rosanilines and tri- 
 phenyl-methane were made clear by Emil and Otto Fischer, who 
 transformed leucaniline into diphenyl-tolyl-methane by diazo- 
 tizing and decomposing with alcohol. In a similar manner, 
 para-leucaniline was converted into triphenyl-methane. The 
 two leuco-bases are, therefore, undoubtedly triamino-derivatives 
 of diphenyl-^-tolyl-methane and of triphenyl-methane respec- 
 tively. The dye-bases, which differ from the leuco-bases by 
 one atom of oxygen, are the corresponding carbinol derivatives, 
 i.e. rosaniline is triamino-diphenyl-^-tolyl-carbinol, and para- 
 rosaniline triamino-triphenyl-carbinol. 
 
 That the three amino-groups are distributed equally among 
 the three benzene nuclei is clear from the synthesis of para- 
 leucaniline by means of ^-nitro-benzaldehyde. ^?-Nitro-ben- 
 zaldehyde, aniline, and sulphuric acid yield ^-nitro-diamino- 
 triphenyl-methane, N0 2 C 6 H 4 CH(C 6 H 4 NH 2 ) 2 , which, when 
 reduced, yields para-leucaniline. We have, therefore, the 
 following formulas : 
 
 5 H 4 .NH 2 yC 6 H 4 .NH 2 
 
 8 H 4 .NH 2 C(OH)^C 6 H 4 .NH 2 
 8 H 4 NH 2 \C 6 H 3 (CH 3 ) NH 2 
 
 Para-leucaniline. Rosaniline. 
 
 It can be shown that each amino -group occupies the p- 
 position with respect to the methane carbon atom. Diamino- 
 triphenyl-methane can be synthesized from benzaldehyde and 
 aniline in the presence of a dehydrating agent. When 
 diazotized and warmed with water, the corresponding dihy- 
 droxy-triphenyl-methane is formed, and this, when fused with 
 potash, yields ^-dihydroxy-benzophenone : 
 C 6 H 6 .CH(C 6 H 4 NH 2 ) 2 C 6 H 6 .CH(C 6 H 4 .OH) 2 CO(C 6 H 4 .OH) 2 
 
 in this last compound the ^-positions of the hydroxy-groupa 
 
486 XXX. TRIPHENYL-METHANE GROU? 
 
 have been established, and hence the original ammo-groups 
 must also have occupied the p-positions, unless intramolecular 
 rearrangement has occurred. 
 
 When^-nitro-benzaldehyde is condensed with aniline, ^-nitro- 
 diamino-triphenyl-methane is formed, and the nitro-group must 
 be in the ^-position, and by analogy with the previous reaction 
 the two amino-groups are also in ^-positions, and as this com- 
 pound on reduction yields para-leucaniline it follows that all 
 three amino-groups occupy ^-positions a conclusion which is 
 supported by the fact that para-leucaniline can also be trans- 
 formed into jp-dihydroxy-benzophenone. 
 
 The salts of rosaniline and para - rosaniline, fuchsine, 
 C 20 H 20 N 3 C1, rosaniline nitrate, C 20 H 20 N 3 (N0 3 ), rosaniline 
 acetate, C 20 H 2? N 3 (C 2 H 3 2 ), para-fuchsine, C 19 H 18 N 3 C1, &c., 
 are the actual dyes. While they possess a magnificent 
 fuchsine-red colour in solution, and have intense colouring 
 power (dyeing wool and silk without a mordant), their crys- 
 tals are of a brilliant metallic green with cantharides lustre, 
 i.e. of nearly the complementary colour. They are fairly 
 soluble in hot water and alcohol. 
 
 In the formation of the salts, water is eliminated: 
 qOH)(C 6 H 4 .NH 2 ) 3 + HCl = C 19 H 17 N 3 , HC1 + H 2 0. 
 
 In the dyes there is therefore present a peculiar nitrogen- 
 carbon linking (see formula I), which is reminiscent of the 
 older quinone formula; but the simpler constitution (formula 
 II), which corresponds with the newer quinone formula, is now 
 more generally accepted, and is usually termed the quinonoid 
 formula : 
 
 (I) (II) C(C 6 H 4 NH 2 ) 2 
 
 NH 2 /C 6 H 4 -NH 2 
 
 } H 4 .NH 2 C-C,H -NH 2 
 
 4 .NH,HC1 XVH 4 :NH,HC1 or 
 
 (Fischer) (Nietzki) 
 
 f<. Para-rosaniline chloride. NH 2 C1 
 
 An analogous separation of water is also observed in the 
 formation of salts of the malachite green base, but this only 
 takes place upon warming, as is proved by the fact that it 
 dissolves without colour in cold acids, and that the intense 
 coloration of the salts first becomes apparent after warming 
 the solution. 
 
 In addition to the above salts there also exist acid ones, 
 e.g. C 20 H 20 N 8 C1 + 3HC1 (which yields a yellow-brown solution, 
 
FUCHSINE AND PARA-FUCHSINE 487 
 
 not a fuchsine-coloured one); these dissociate into the neutral 
 salts and free acid upon the addition of much water. The 
 formation of such acid salts is readily accounted for by the 
 quinonoid formula. 
 
 Rosenstiel has suggested the constitution Cl C(C 6 H 4 NH 2 ) 3 
 for para-fuchsine, according to which the salt is the chloride 
 (ester) of a tertiary alcohol. Such a constitution, according 
 to Hantzsch and Osswald (B. 1900, 33, 278), is not in harmony 
 with known facts. 
 
 Assuming the quinonoid structure II for para-fuchsine, then 
 the conversion into para-rosaniline under the influence of 
 alkalis should be preceded by the formation of an unstable 
 quaternary ammonium hydroxide, which becomes transformed 
 into the carbinol compound, para-rosaniline: 
 
 C(C 6 H 4 NH 2 ) 2 C(C 6 H 4 NH 2 ) 2 
 
 NH 2 C1 NH 2 -OH 
 
 Para-fuchsine. Para-rosaniline. 
 
 Hantzsch and Osswald, by means of electrical conductivity 
 determinations (B. 1900, 33, 278), have been able to indicate 
 the presence of such an ammonium derivative in the solution 
 which is formed when the dye is brought into contact with an 
 equivalent of alkali. This compound is coloured in contra- 
 distinction to the carbinol base, is very strongly basic and 
 therefore strongly ionized, and is gradually transformed into 
 the insoluble carbinol base. Para-rosaniline and the dye-bases 
 generally are pseudo-bases corresponding in many respects with 
 the pseudo-acids (p. 363). 
 
 Formerly in the manufacture of magenta, a mixture of ani- 
 line with o- and ^?-toluidine was oxidized by syrupy arsenic 
 acid, stannic chloride or mercuric chloride or nitrate, &c.; in 
 the modern method, a mixture of nitro-benzene with aniline 
 and toluidine is heated with iron filings and hydrochloric 
 acid (Coupler). Nitro-toluene may also be employed instead 
 of nitro-benzene. If o-toluidine is present in the mixture of 
 aniline and ^?-toluidine to be oxidized, rosaniline is formed, 
 and if it is absent, para-rosaniline. When pure aniline is oxid- 
 ized alone, it yields no fuchsine at all, but products of the 
 nature of indulin. This is explained by the fact that for the 
 
488 XXX. TRIPHENYL-METHANE GROUP 
 
 formation of fuchsine a carbon atom is required which shall 
 serve to link the benzene nuclei together, a so-called " methane- 
 carbon"; in the action of carbon tetrachloride upon aniline, 
 this carbon originates from the tetrachloride, and in the oxi- 
 dation of a mixture of aniline and ^-toluidine, from the methyl 
 group of the latter, as is shown in the following scheme : 
 
 Para-rosaniline and rosaniline are also formed by heating p- 
 diamino-diphenyl-methane (p. 476) with aniline and o-toluidine 
 respectively, in presence of an oxidizing agent (B. 25, 302). 
 
 When rosaniline is heated with hydrochloric or hydriodic 
 acid to 200, it is split up into aniline and toluidines; when 
 superheated with water, para-rosaniline yields jp-dihydroxy-ben- 
 zophenone, ammonia, and phenol. When boiled with hydro- 
 chloric acid, rosaniline breaks up into ^>-diamino-benzophenone 
 and 0-toluidine (B. 16, 1928; 19, 107; 22, 988). A solution 
 of fuchsine is decolorized by sulphurous acid, an additive- 
 product, fuchsine-sulphurous acid, being formed. This solution, 
 Schiff's reagent, is a delicate reagent for aldehydes, which 
 colour it violet-red (see p. 127; B. 21, Kef. 149, &c.). 
 
 Derivatives of Rosaniline 
 
 1. Methylated rosanilines (Hofmann, Lauth). The red 
 colour of para-rosaniline and of rosaniline is changed into 
 violet by the entrance of methyl or ethyl groups, the intensity 
 of the latter colour increasing with an increasing number of 
 these groups. The salts of hexamethyl-para-rosaniline have 
 a magnificent bluish-violet shade. In the manufacture of these 
 "methyl-violets" one may either (1) methylate rosaniline (by 
 means of CH 3 C1 or CH 3 I); or (2) oxidize, instead of aniline, 
 a methylated aniline such as dimethyl-aniline by means of 
 cupric salts, whereby para-rosaniline derivatives result; or (3) 
 allow phosgene to act upon dimethyl-aniline (or the latter to 
 act upon the tetramethyl-diamino-benzophenone at first pro- 
 duced) (cf. B. 17, Kef. 339): 
 
 COC1 2 + 3C 6 H 6 .N(CH 3 ) 2 = C(OHXC 6 H 4 .N(CH 3 ) 2 ] 3 -f2HCl. 
 
 In the last case hexamethyl-violet, termed " crystal violet " 
 on account of the beauty of its crystals, is formed, while the 
 
HOSANILINE DERIVATIVES 489 
 
 hiethyl- violets prepared by methods (1) and (2) are mixtures of 
 hexa-, penta-, and tetramethyl-rosanilines and are amorphous. 
 
 The hydrochloride of the hexamethyl dye has the consti- 
 tution : 
 
 An interesting synthesis of this compound is by the action of 
 the magnesium derivative of ^-bromo-dimethyl-aniline on tetra- 
 methyl-diamino-benzophenone and subsequent treatment with 
 hydrochloric acid (cf. Synthesis of Tertiary Alcohols, p. 356). 
 
 The hexamethyl - carbinol no longer contains an amino- 
 hydrogen atom, in consequence of which any further methyl 
 chloride or iodide cannot effect an exchange of hydrogen for 
 alkyl, but can only form an additive compound, a quaternary 
 ammonium salt. Such addition causes a change of colour from 
 violet to green; thus the compound 
 
 is the dye methyl green or light green. Ethyl green (ethyl- 
 hexamethyl rosaniline) is formed by the action of ethyl bro- 
 mide on methyl violet. 
 
 Various ethyl violets are known corresponding with the 
 methyl violets. The hexa-substituted rosanilines, which con- 
 tain benzyl as well as methyl or ethyl groups, are similar to 
 crystal violet; their sulphonic acids form useful dyes, e.g. acid 
 violet. 
 
 2. Phenylated rosanilines. By the successive entrance of 
 phenyl-groups into rosaniline, there are formed in the first 
 instance violet dyes, which change to blue when three phenyl 
 groups have entered. Triphenyl-fuchsine or "aniline blue" 
 is a beautiful blue dye, insoluble in water but soluble in 
 alcohol. It is prepared by heating rosaniline with aniline in 
 presence of benzoic acid, when ammonia is eliminated; or by 
 the oxidation of phenylated aniline, i.e. diphenylamine, e.g. by 
 means of oxalic acid. The latter supplies the "methane carbon 
 atom", and the beautiful "diphenylamine blue" or spirit blue 
 which is formed is a para-rosaniline derivative. Formic alde- 
 hyde can also supply the methane carbon atom. 
 
 Dyes insoluble in water are converted into soluble sulphonic 
 acids. Such acids are Nicholson's blue, water blue, and light 
 blue. Patent blue, new patent blue, are disulphonic acids. 
 
490 XXX. TRIPHENYL-METHANE GROUP 
 
 i. TRIHYDROXY-TRIPHENYL-METHANE, 
 OR THE AURINE GROUP 
 
 The hydroxy-analogues of para-rosaniline and rosaniline are 
 aurine, C 19 H U 3 , and rosolic acid, C 20 H 16 3 : 
 
 (OH . C 6 H 4 ) 2 C C 6 H 4 O or (OH C 6 H 4 ) 2 . C : C 6 H 4 : 
 
 I I Aurine. 
 
 These likewise possess the dye character, but, instead of 
 being basic, they are acid dyes (phenol dyes); they are of far 
 less value than the basic dyes which have been already 
 described. 
 
 They are formed when the diazonium derivatives of para- 
 rosaniline or rosaniline are boiled with water (Caro and Wanlc- 
 lyn, 1866): 
 
 OH.C(C 6 H 4 N 2 S0 4 H) 8 + 3H 2 = OH.C(C 6 H 4 .OH) 3 + 3N 2 + 3H a S0 4 ; 
 OH.C(C 6 H,.OH) S = (OH.C 6 H 4 ) 2 C:C6H 4 :0 + H S 0. 
 
 The carbinol which must be produced here in the first instance 
 is incapable of existence, and loses water. The constitutional 
 formulae just given follow from this close relation to the rosani- 
 lines. 
 
 Aurine is also obtained by heating phenol with oxalic and 
 sulphuric acids to 130-150 (Kolbe and Schmitt, 1859), ,the 
 oxalic acid yielding the " methane carbon atom " ; rosolic acid 
 results in an analogous manner from a mixture of phenol and 
 cresol with arsenic and sulphuric acids. Phenol by itself yields 
 no rosolic acid upon oxidation. 
 
 Aurine and rosolic acid crystallize in beautiful green needles 
 or prisms with a metallic lustre, dissolve in alkalis with a 
 fuchsine-red colour, and are thrown down again from this 
 solution by acids. The alkaline salts are decidedly unstable, 
 aurine being but a weak phenol; at the same time it possesses 
 a slightly basic character. An ammonium salt is known 
 which crystallizes in dark-red needles with a blue lustre. 
 Upon reduction there are formed the leuco- compounds leu- 
 caurine, CH(C 6 H 4 -OH) 3 , and leuco-rosolic acid, OH-C 6 H 3 Me. 
 CH(C 6 H 4 OH) 2 , both of which crystallize in colourless needles 
 of phenolic character. Superheating with water transforms 
 aurine into ^-dihydroxy-benzophenone, CO(C 6 H 4 OH) 2 , and 
 phenol; superheating with ammonia, into para-rosaniline. 
 
1HTH ALOPHENONE 491 
 
 4. tmPHENYL-METHANE-CARBOXYLIC-ACID, OB THE 
 EOSIN GROUP 
 
 (Of. Eaeyer, A. 183, 1; 202, 36) 
 
 Triphenyl-methane-carboxylic acid, CH(C 6 H 5 ) 2 (C 6 H 4 .C0 2 H), 
 obtained by the reduction of phthalophenone (see below), crys- 
 tallizes in colourless needles melting at 162 and yields tri- 
 phenyl-methane by the elimination of carbon dioxide. 
 
 Triphenyl-carbinol-o-carboxylic acid, OH.C(C 6 H 5 ) 2 (C 6 H 4 . 
 C0 2 H). The anhydride of this acid, which is termed phtha- 
 lophenone, is obtained by heating phthalyl chloride with 
 benzene and aluminic chloride (A. 202, 50), and forms plates, 
 melting at 115. The acid itself is incapable of existence, but 
 its salts are obtained by dissolving the anhydride in alkalis. 
 Phthalophenone is on the one hand a triphenyl-methane de- 
 rivative and on the other a derivative of phthalic acid; in 
 accordance with the constitutional formula: 
 
 it is to be regarded as diphenyl-phthalide (Phthalide, p. 462). 
 Phthalophenone is the mother substance of a large series 
 of dyes, which are derived from it by the entrance either of 
 hydroxyl or of amino-groups. They are prepared by the action 
 of phenols upon phthalic anhydride, and are termed Phthaleins. 
 Phenol and resorcinol, for example, yield the compounds : 
 
 and 
 
 Phenol-phthalem Fluorescem. 
 
 Quinonoid formulae are also possible, e.g. for phenol-phthalein, 
 
 Free phenol-phthalein, which is colourless, probably has the 
 lactone formula, and its coloured salts the quinonoid structure. 
 Phenol-phthalein would then be a pseudo-acid (p. 364). 
 
 See also H. Meyer, M. 1899, 20, 337; R. Meyer and Spendkr, 
 
 B. 36, 2949; 38, 1318; Green and A. G. Perkin, 3. C. S. 1904, 
 398; Green and King, B. 39, 2365; 40, 3724; Stieglite, J. A. 
 
 C. S. 25, 1112; Acree, Am. C. J. 39, 528, 771; 42 5 115. 
 
492 XXX. TRIPHENYp-METHANE GROUP 
 
 In the case of fluorescein a molecule of water is split off 
 from two hydroxyls of the two resorcinol residues. Phthaleins 
 of this kind (being hydroxy-phthalophenones) are converted by 
 reduction into the hydroxy-derivatives of triphenyl-methane- 
 carboxylic acid, which are termed "Phthalines"; e.g. phenol- 
 phthalein into dihydroxy-triphenyl- methane -carboxy lie acid 
 
 (C H OH) 
 (i.e. phenol-phthaline), CH^n H t TO H' ^ e phthalines are 
 
 Vxg-L-*-^ V/Vyg-*-*- 
 
 colourless, and are to be looked upon as leuco-compounds of 
 the phthaleins. The phthaleins include among themselves 
 many dyes which are of technical value, e.g. the eosins (Caro, 
 Baeyer, 1871). 
 
 Phenol-phthalei'n is prepared by heating phthalic anhydride 
 with phenol and sulphuric acid, or better, stannic chloride (or 
 oxalic acid), to 115-120. It may also be obtained by nitrating 
 diphenyl-phthalide, reducing the two substituting nitro-groups, 
 and replacing the amino-groups thus formed by hydroxyl in 
 the usual manner (A. 202, 68). It crystallizes from alcohol in 
 colourless crusts; is nearly insoluble in water, but dissolves 
 in dilute alkalis with a beautiful red colour which vanishes 
 again on neutralization with acids; it is thus a valuable indi- 
 cator. With very concentrated alkalis (KOH) phenol-phthalein 
 yields colourless solutions probably containing metallic salts of 
 a non-quinonoid structure. The ^-positions of the two hydroxy- 
 groups have been proved by conversion into ^-dihydroxy- 
 benzophenone. It yields a di-acetyl derivative melting at 143 
 and an oxime melting at 212. It is reduced by potash and 
 zinc dust to phenol-phthaline (colourless needles), which dis- 
 solves in alkalfto a colourless solution, but is readily reoxidized 
 in this solution to phenol-phthalein. 
 
 Fluorane, C 20 H 12 3 , which was formerly regarded as phenol- 
 phthalein anhydride, is formed as a by-product in the phenol- 
 phthalein melt, and is the mother substance of fluorescein. 
 Both probably contain a pyrone ring (and hence the name 
 Pyronines for the whole group of dyes), and the constitution 
 of fluorane is represented as 
 
 Fluorane, ^ ^> C 
 CO-0 
 
 (Cf. R. Meyer, B. 1892, 25, 1385, 2118; 1893, 26, 1271.) 
 
FLUORESCEIN 493 
 
 Fluorescei'n, Dikydroxy-fluorane orresarcinol-phlhakw, C 20 H 12 5 
 f H 2 0, is prepared by heating phthalic anhydride and resor- 
 cinol at 200. It forms a dark-red crystalline powder, and dis- 
 solves in alcohol with a yellow-red colour, and in alkalis with 
 a red colour and splendid green fluorescence. It is reducible 
 to the phthaline " Fluorescin ", and with bromine yields red 
 crystals of tetrabromo-fluorescein, the potassium salt of which, 
 C 20 H(.Br 4 6 K 2 , is the magnificent dye eosin. Fluorescing dyes 
 are likewise formed in an analogous manner from all the de- 
 rivatives of 1 : 3-dihydroxy-benzene, in which position 5 is un- 
 occupied, and the reaction is often made use of on the one 
 hand for testing for ra-dihydroxy-derivatives, and on the other 
 for phthalic anhydride or succinic anhydride. 
 
 Instead of phthalic acid itself, chlorinated or brominated, 
 &c., phthalic acids may be employed, so that, by gradually 
 increasing the amount of halogen present, a whole series of 
 yellow-red to violet-red eosins can be prepared, e.g. tetrabromo- 
 di-iodo-eosin; these are known under the names of Erythrosin, 
 Eose de Bengale, Phloxin, &c. It is worthy of note that many 
 other dibasic acids (e.g. succinic) and also benzoic acid are 
 capable of yielding nuorescing compounds. 
 
 Gallein, C 20 H ] .,O 7 , is the dye obtained from pyrogallol and 
 phthalic anhydride. 
 
 The rhodamines are dyes closely allied to fluorescein. They 
 are obtained by the condensation of phthalic anhydride and 
 ^-alkylated-amino-phenols in presence of sulphuric acid. They 
 contain the pyrone ring, and may be regarded as fluorescein 
 in which the two hydroxyl groups have been replaced by 
 tertiary amino-groups. Tetra-ethyl rhodamine, 
 
 6 H 3 -NEt 2 - 
 
 is colourless, and has basic properties. The salts, e.g. sulphate, 
 are red dyes, and probably possess a quinonoid structure. 
 
 Tetraphenyl-methane, C(C 6 H 5 ) 4 . Many attempts to obtain 
 this compound were made, but without success, until Gomberg 
 (B. 1897, 30, 1897) succeeded in preparing it from triphenyl- 
 bromo- methane. With phenyl-hydrazine this yields CPh 3 
 NH.NHPh, triphenylmethane-hydrazobenzene, which gives 
 the corresponding azo-compound when oxidized, CPh 3 N:NPh, 
 
494 XXXI. NAPHTHALENE GROUP 
 
 and when this is heated nitrogen is evolved and tetraphenyl 
 methane is formed. It is more readily prepared by the action 
 of magnesium phenyl bromide on triphenyl-chloro- methane 
 (B. 1906, 39, 1462). It forms colourless crystals, m.-pt. 282. 
 
 XXXI. COMPOUNDS WITH CONDENSED BENZENE 
 NUCLEI. NAPHTHALENE GROUP 
 
 The higher fractions of coal tar contain hydrocarbons of 
 high molecular weight, especially naphthalene, C^Hg, an- 
 thracene, C 14 H 10 , and its isomeride phenanthrene. The first- 
 named is found in the fraction between 180-200, and the 
 two latter in that between 340-360. 
 
 These compounds are of more complex composition than 
 benzene, the molecule of naphthalene differing from that of 
 the latter by C 4 H 2 , and those of anthracene and phenanthrene 
 from that of naphthalene by the same increment. They 
 closely resemble benzene as regards behaviour, and give rise 
 to types of derivatives similar to those of benzene itself. 
 
 They undoubtedly contain benzene nuclei, as anthracene 
 yields benzoic acid upon oxidation, naphthalene phthalic acid, 
 and phenanthrene diphenic acid. From their modes of forma- 
 tion and behaviour it follows that in the building up of their 
 molecules the benzene residues combine together in such a 
 manner that 2 or (2 x 2) adjacent carbon atoms are common 
 to both (cf. pp. 496 and 506). 
 
 NAPHTHALENE GROUP 
 
 Naphthalene, C 10 H 8 , was discovered by Garden in 1820. 
 It is contained in coal-tar and crystallizes from the fraction 
 which distils over between 180-200. These crystals are 
 pressed to free them from oily impurities, and can then be 
 further purified by treatment with small amounts of con- 
 centrated sulphuric acid and subsequent sublimation. 
 
 It is also formed when various carbon compounds are sub- 
 jected to a red heat; thus, together with benzene, styrene, 
 &c., by passing the vapours of methane, ethylene, acetylene, 
 alcohol, acetic acid, &c., through red-hot tubes. Its presence 
 in coal-tar may be due to some similar cause. 
 
 The constitutional formula (p. 496) is largely based on the 
 following syntheses: 
 
NAPHTHALENE GROUP 495 
 
 1. By the action of 0-xylylene bromide upon the sodium 
 compound of the symmetrical ethane -tetracarboxy lie ester, 
 ethyl tetrahydronaphthalene-tetracarboxylate is formed: 
 r Na.C(C0 2 Et) 2 ,CH 2 .C(CO 2 Et) 2 
 
 and from this, naphthalene may be obtained by hydrolysis, 
 the elimination of the carboxyl groups and subsequent oxi- 
 dation (Baeyer and Perkin, B. 17, 448). 
 
 2. a-Naphthol, C^H^-OH, is produced by the elimination 
 of water from y-phenyl-isocrotonic acid (Fittig and Erdmann, 
 B. 16, 43; see p. 456), and yields naphthalene when heated 
 with zinc dust. 
 
 3. J. F. Thorpe (P. 1905, 21, 305) has succeeded in syn- 
 thesising a number of naphthalene derivatives by means of 
 ethyl sodio-cyano-acetate, e.g. ethyl 1 : 3-diamino-naphthalene-2- 
 carboxylate from ethyl sodio-cyano-acetate and benzyl cyanide. 
 
 C 6 H 6 CH 2 ON + CO 2 Et CH 2 - CN 
 
 C 6 H 5 .CH 2 .C(:NH).CH(C0 2 Et)CN, 
 
 and this with sulphuric acid yields the bicyclic compound I, 
 which is immediately transformed into the diamino-deriva- 
 tive II. 
 
 CH 2 
 
 CH-COoEt 
 :NH 
 
 The same compound may be synthesised from ethyl sodio- 
 cyano-acetate by the following stages (J. C. S. 1907, 91, 578). 
 Condensed with o-toluyl chloride, CH 3 C 6 H 4 ^CO'C1, it yields 
 ethyl cyano-0-toluyl-acetate, CH 3 - C 6 H 4 CO CH(CN)C0 2 Et, 
 and this when heated with ammonium acetate gives the corre- 
 sponding imino-derivative, CH 3 C^ C( : NH) CH(CN)C0 2 Et, 
 ethyl /3-imino-a-cyano-/3-o-tolyl-propionate, which reacts with 
 acids giving compound I. 
 
 l:4-Naphthalene-diamines have been prepared by similar 
 methods, using derivatives of phenyl-butyric acid (J. C. S. 
 1907, 91, 1004). 
 
 Constitution. That naphthalene contains a benzene nucleus, 
 in which two hydrogen atoms occupying the ortho- position 
 are replaced by the group (C 4 H 4 )", follows not only from its 
 oxidation to phthalic acid, but also from its formation from 
 
496 XXXI. NAPHTHALENE GROUP 
 
 0-xylylene bromide. And that the four carbon atoms of this 
 group are linked to one another without branching is shown 
 by the formation of a-naphthol. 
 
 CH 
 
 CO 
 
 ' TT a-Naphthol. 
 
 y-Phenyl-iso-crotonic acid 
 
 That there are actually two so-called " condensed " benzene 
 nuclei present in the naphthalene molecule is a necessary con- 
 sequence of the fact that phthalic acid or its derivatives ensue 
 on the breaking up of the compound, not only from one but 
 from both of the rings. 
 
 For instance, a-nitro-naphthalene (p. 499) on oxidation yields 
 nitro-phthalic acid, C 6 H 3 (NO 2 )(C0 2 H) 2 ; consequently the ben- 
 zene ring to which the nitro-group is linked remains intact. 
 But, on reducing the nitro-naphthalene to amino-naphthalene 
 and oxidizing the latter, no amino-phthalic acid nor any oxi- 
 dation product of it is obtained, but phthalic acid itself, a proof 
 that this time the benzene nucleus to which the amino-group is 
 attached has been destroyed, and that the other has remained 
 intact (Graebe, 1880; for an analogous proof by him, see 
 A. 149, 20). 
 
 Naphthalene therefore receives the constitutional formula 
 (Erlenmeyer, 1866): 
 
 H 
 
 //^ /^ 
 H 
 
 H 
 
 There is the same difficulty in deciding between the double 
 bond KekuU formula and the centric formula as in the case of 
 benzene. 
 
 The above constitutional formula is in complete harmony 
 with the number of isomeric forms in which naphthalene 
 derivatives occur, and also with the formation of additive 
 compounds with hydrogen or chlorine. (Cf. Bamberger^ A, 
 357, 1; B. 1891, 24, 2054.) 
 
NAPHTHALENE 497 
 
 This union of two benzene nuclei is accompanied by a 
 modification of their properties, so that naphthalene and its 
 derivatives differ characteristically from benzene in many 
 respects. Such differences show themselves, for instance, 
 between the naphthylamines and aniline, the naphthols and 
 phenol; and also especially in the greater readiness with 
 which the naphthalene derivatives are reduced, the latter 
 taking up as many as four atoms of hydrogen easily. 
 
 After such addition the reduced nucleus is found to have 
 entirely lost the characteristics of a benzene nucleus, and to 
 have become similar in properties to an alphyl radical, whereas 
 the non-reduced nucleus assumes the character of a benzene 
 nucleus in its entirety (Bamberger). (See the Tetrahydro-deriva- 
 tives of the Naphthylamines and Naphthols, pp. 500 and 502.) 
 
 Properties. Naphthalene crystallizes in glistening plates, is 
 insoluble in water, sparingly soluble in cold alcohol and ligroin, 
 but dissolves readily in hot alcohol and ether; it melts at 80 
 and boils at 218. It has a characteristic tarry smell, and is 
 distinguished by the ease with which it sublimes and volatilizes 
 with steam. 
 
 With picric acid it yields an additive compound, C 10 H 8 , 
 OH CgH 2 (N0 2 ) 3 , crystallizing in yellow needles and melting 
 at 149 . It takes up hydrogen far more readily than benzene 
 does, yielding di- and tetrahydronaphthalenes, C 10 Hp and 
 C 10 H 12 ; both of these are liquids of pungent odour which re- 
 generate naphthalene again when heated. By the powerful 
 action of hydriodic acid and phosphorus, the second benzene 
 nucleus can also be made to take up hydrogen, so that a hexa- 
 hydro-, Q, H 14 , and finally a dekahydronaphthalene, C 10 H 18 , are 
 formed. It also yields additive products with chlorine more 
 readily than benzene does, e.g. naphthalene dichloride, C 10 H 8 
 C1 2 , and -tetrachloride, C 10 H 8 -C1 4 (m.-pt. 182); the latter is oxi- 
 dized to phthalic acid more easily than naphthalene itself, hence 
 that acid is sometimes prepared from it on the large scale. 
 
 Naphthalene is principally used for the preparation of phthalic 
 acid (for eosin, indigo, &c.), and of naphthylamines and naph- 
 thols (for azo-dyes); also for the carburation of illuminating 
 gas. It is a powerful antiseptic, and is employed therapeuti- 
 cally. 
 
 NAPHTHALENE DERIVATIVES 
 
 The number of substitution products in the case of naph- 
 thalene is greater than with benzene. 
 
 (B480) 21 
 
498 XXXI. NAPHTHALENE GROUP 
 
 The mono-derivatives invariably exist in two isomeric forms, the 
 a- and ^-compounds, e.g.: 
 
 C 10 H 7 C1 (a- and /3-chloro-naphthalene). 
 C 10 H 7 NH 2 (a- and jS-naphthylamine). 
 C 10 H 7 OH (a- and /3-naphthol). 
 C 10 H 7 CH 3 (a- and /3-methyl-naphthalene). 
 
 As in the case of the benzene compounds, the existence of 
 two series of mono-derivatives has not only been established 
 empirically, but it has also been proved (in a manner similar 
 to that given on p. 329, et seq.) that in the naphthalene mole- 
 cule two sets of hydrogen atoms (the a and /?, a = 1, 4, 5, 8; 
 /3 = 2, 3, 6, 7) have an equal value as regards one another, 
 but the atoms of the one set differ from those of the other, so 
 that the a- and the /3-positions occur severally four times, i.e. 
 twice in each benzene nucleus (Atterberg). 
 
 The above constitutional formula for naphthalene satisfies 
 these conditions, since, according to it, the positions 1, 4, 5, 
 and 8 are severally equal and also the positions 2, 3, 6, and 7, 
 but not the positions 1 and 2. The conception that in the 
 a-compounds the position 1, 4, 5, or 8 is occupied is due to 
 Liebermann (A. 183, 225), Eeverdin and Noelting (B. 13, 36), 
 and Fittig and Erdmann (cf. the formation of a-naphthol given 
 above). 
 
 With regard to the di-derivatives of naphthalene, a consider- 
 able number of isomerides of a good many are known; accord- 
 ing to the naphthalene formula, ten are theoretically possible in 
 each case when the two substituents are the same, and fourteen 
 when they are different. The ten possible isomerides are 
 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 2:3, 2:6, and 2:7. All other 
 combinations are identical with one of these ten. According 
 to Armstrong and Wynne ten dichloro- and fourteen trichloro- 
 naphthalenes are actually known. (See also B. 1900, 33, 1910, 
 2131.) 
 
 The position 1:8 is termed the "peri-" position; it resembles 
 the ortho- position to some extent, e.g. >m-naphthalene-dicar- 
 boxylic acid like an o-dicarboxylic acid yields an anhydride. 
 
 The homologues of naphthalene are of comparatively small 
 importance, and are usually prepared by Fittig's or by Friedel 
 and Crafts' synthesis. Most of them are liquids, and on oxi- 
 dation yield acids resembling benzoic acid. 
 
 -Bromo-naphthalene can be prepared directly by brominat- 
 ing naphthalene, and is partially converted into the y&-compound 
 
NAPHTHYLAMINES 499 
 
 when heated with aluminium chloride. Its bromine atom is 
 somewhat more readily exchangeable than that of bromo- 
 benzene, but cannot be eliminated by boiling with alkalis. 
 Interesting methods of formation of the halogen derivatives 
 are by heating the hydroxy-, nitro-, or sulphonic acid deriva- 
 tives with phosphorus pentachloride. 
 
 a-Nitro-naphthalene, C 10 H 7 N0 2 (Laurent, 1835), is formed 
 by the direct nitration of naphthalene. It crystallizes in 
 yellow prisms, melts at 61, boils without decomposition, and 
 readily yields 1 : 5 and 1:8 di- and various tri- and tetra-nitro- 
 naphthalenes upon further nitration. On reduction it is con- 
 verted into a-naphthylamine. The position of the nitro-group 
 has been established by conversion of this compound into a- 
 naphthol. 
 
 The isomeric /?-nitro-naphthalene can be obtained indirectly 
 by diazotizing /3-naphthylamine, and acting on the product with 
 sodium nitrite in presence of cuprous oxide (B. 20, 1494; 36, 
 4157); it crystallizes in bright yellow needles melting at 79. 
 
 a-Naphthylamine, C 10 H 7 NH 2 (Zinin), forms colourless 
 needles or prisms, melts at 50, boils at 300, and is readily 
 soluble in alcohol. It can be obtained by reducing the a-nitro- 
 compound, and also readily by heating a-naphthol with the 
 double compound of calcium chloride arid ammonia, while 
 aniline can only be prepared from phenol in a similar manner 
 with difficulty: Ci H 7 .OH + NH 3 = C 10 H r NH 2 + H 2 0. 
 
 It possesses a disagreeable fsecal-like odour, sublimes readily, 
 and turns brown in the air. Certain oxidizing agents, such as 
 ferric chloride, produce a blue precipitate with solutions of its 
 salts, while others give rise to a red oxidation product; chromic 
 anhydride oxidizes it to a-naphthaquinone. In other respects 
 it resembles aniline; for differences, see B. 23, 1124. Its hy- 
 drochloride is only sparingly soluble in water. 
 
 The isomeric /3-naphthylamine, C 10 H r NH 2 (Liebermann, 
 1876), is most conveniently prepared by heating /?-naphthol 
 either in a stream of ammonia or with the double compound 
 of zinc chloride and ammonia. It is now generally prepared by 
 the action of ammonium hydroxide and sulphite on /2-naphthol 
 (C. C. 1901, 1, 349). Naphthyl ammonium sulphite is formed as 
 an intermediate product and reacts with the ammonia, yield- 
 ing naphthylamine and ammonium sulphite. This reaction is 
 frequently used for transforming derivatives of a and ft naph- 
 thol into corresponding amino-compounds. The reaction is 
 reversible and can be used for replacing NH 2 by OH. 
 
500 XXXI. NAPHTHALENE GROUP 
 
 /3-Naphthylamine crystallizes in nacreous plates, melts at 
 112, boils at 294, and has no odour. It is more stable than 
 a-naphthylamine, and is not coloured by oxidizing agents. 
 
 Both of these naphthylamines can be converted into tetra- 
 hydro-compounds by the action of sodium and amyl alcohol 
 (i.e. nascent hydrogen) upon them. The tetrahydro-a-naphthyl- 
 amine resembles its mother substance closely in most of its 
 properties, e.g. it can be diazotized and has entirely assumed 
 the character of aniline; the hydrogen atoms have entered the 
 nucleus which does not contain the amino-group. It is termed 
 aromatic or "ar"-tetrahydro-a-naphthylamine. (Formula I.) 
 Tetrahydro-^-naphthylamine, on the other hand, is not diazo- 
 tized by nitrous acid, but transformed into a very stable 
 nitrite. Here it is the benzene nucleus containing the 
 amino-group which has become reduced; the compound has 
 assumed the properties of an amine of the fatty series, and 
 is termed alicydic or "ac"-tetrahydro-/3-naphthylamine. 
 (Formula II.) The a-compound is oxidizable to adipic acid 
 (p. 231), and the ^-compound to o-hydrocinnamo-carboxylic 
 
 acid, C 6 H 4 <^2^ CH 2' C0 2 H . (Cf. Bamlerger and others, B. 
 21, 847, 1112, 1892; 22, 625, 767; 23, 876, 1124.) 
 H NH 2 
 
 II 
 \ 
 
 An ac-tetrahydro-o- and an ar-tetrahydro-^-naphthylamine 
 have also been prepared. 
 
 From both naphthylamines there are derived, as in the 
 benzene series, methyl- and dimethyl-naphthylamines, phenyl- 
 a- and -/3-naphthylamines (which are of technical importance), 
 nitro-naphthylamines, diamino-naphthalenes or naphthylene- 
 diamines, C 10 H 6 (NH 2 ) 2 , diazonium- compounds (which are in 
 every respect analogous to the diazonium salts of benzene, 
 especially in the formation of azo-dyes, many of which are of 
 great technical importance), diazo-amino-compounds, &c. 
 
 The diazo-amino-naphthalene, C 10 H r N : N NH C 10 H r , 
 which is formed by the action of nitrous acid upon a-naphthyl- 
 amine, readily undergoes a molecular transformation (like the 
 corresponding benzene compound) into amino-azo-naphthalene, 
 
NAPHTHALENE SULPHONIC ACIDS. NAPHTHOLS 501 
 
 C 10 H 7 N : N C 10 H 6 NH 2 . This latter compound crystallizes 
 in brownish-red needles with a green metallic lustre, and can 
 be diazotized, its diazo-compound yielding a-azo-naphthalene, 
 CjgHy.NiN'CjoHf (red to steel-blue glistening prisms), when 
 boiled with alcohol. This last can either not be prepared at 
 all or only with great difficulty by the methods which hold 
 good for azo-benzene. 
 
 A mixture of naphthalene a- and /3-sulphonic acids, C 10 H 7 
 S0 2 OH, is obtained by warming naphthalene to 80 with con- 
 centrated sulphuric acid. They may be separated by aid of 
 their calcic or baric salts, as the /3-sulphonates are less soluble 
 than the a-salts. The a-acid is transformed into the /?-acid 
 when heated with concentrated sulphuric acid, and hence the 
 chief product obtained by sulphonating naphthalene at 160 
 is the /3-acid. The sulphonic acid radicals in these compounds 
 may be readily replaced by hydroxyl or cyanogen by the usual 
 methods. 
 
 Naphthalene -disulphonic acids, C 10 H 6 (SO 3 H) 2 . Two iso- 
 meric /?-/?-acids (2:6 and 2:7) are formed when naphthalene is 
 heated with concentrated sulphuric acid at 160-200, while an 
 a-a-acid (1:5) is obtained with chloro-sulphonic acid, S0 3 HC1, 
 in the cold, and the a-/?-acid (1:6) from the /?-mono-sulphonic 
 acid in a similar manner. 
 
 Naphthylaxnine - mono - sulphonic acids, NH 2 C 10 H 6 S0 2 
 OH. Thirteen isomers of these are known (7 a- and 6 /?-). 
 Naphthionic acid (NH 2 : S0 3 H = 1 : 4) is obtained by the 
 sulphonation of a-naphthylamine ; it is employed in the pre- 
 paration of azo-dyes, as are also several of its isomers and 
 various naphthylamine - disulphonic acids. These last are 
 obtained (a) directly from a- or /3-naphthylamine, or (b) by 
 nitrating the naphthalene-sulphonic acids and then reducing 
 the nitro- to an amino-group. 
 
 a- and /?-Naphthols, 10 H 7 OH, which are present in coal-tar, 
 can be easily prepared, not only from the naphthalene-sulphonic 
 acids as above, but also by diazotizing the naphthylamines. 
 They crystallize in glistening plates, have a phenolic odour, 
 and dissolve readily in alcohol and ether but only sparingly in 
 hot water. a-Naphthol (Griess, 1866) melts at 95 and boils 
 at 282, while /3-naphthol (Scha/er, 1869) melts at 122 and 
 boils at 288; both of them are readily volatile at ordinary 
 temperatures. They possess a phenolic character but never- 
 theless resemble the alcohols of the benzene series more than 
 tho phenols, their hydroxy-groups being much more reactive 
 
502 XXXI. NAPBT&ALENE GROUP 
 
 than those of the latter, e.g. they can be readily replaced by 
 amino-groups (see above). /?-Naphthol is an antiseptic. 
 
 ar-Tetrahydro-a-naphthol, C 10 H 7 H 4 .(OH), obtained by 
 reducing a-naphthol, has the character of a pure phenol, and 
 not that of a-naphthol. A mixture of ar- and ac- tetrahydro- 
 /2-naphthols is obtained from /8-naphthol, the ar-compound 
 corresponds with phenol and the ac-compound with alcohol. 
 
 Ferric chloride oxidizes a- and /3-naphthols, with production 
 of violet and greenish colorations respectively, to di-naphthols, 
 C 20 H 12 (OH) 2 , which correspond with the dihydroxy-diphenyls 
 (p. 473), and are derivatives of di-naphthyls (p. 504). The 
 cautious oxidation of a-naphthol yields o-cinnamo-oarboxylic 
 acid, C0 2 H.C 6 H 4 .CH:CH.C0 2 H, and that of /3-naphthol, 
 o-carb'oxy-phenyl-glyoxylic acid, C0 2 H . C 6 H 4 CO C0 2 H. 
 
 The naphthols yield alkyl and acyl derivatives. The ethers 
 are formed by the action of an alcohol and hydrogen chloride 
 on the naphthols. /3-Naphthyl-methyl-ether, C 10 H r -0'CH 3 , 
 is the nerolin used as a perfume. 
 
 From the naphthols, as from the phenols, there are derived 
 nitro-, dinitro-, trinitro-, and amino-compounds, &c. The 
 calcium salt of dinitro-a-naphthol, C 10 H 5 (N0 2 ) 2 OH, is known 
 as Martins' yellow or naphthalene yellow, and its sulphonic 
 acid, naphthol yellow S or fast yellow, is a valuable dye. 
 
 Amino - naphthols, C 10 H 6 (NH 2 )(OH), are obtained by the 
 reduction of nitro-naphthols; like the amino-phenols they are 
 readily oxidized in the air. (NH 2 :OH in the a-compound 
 = 1:4, in the /^-compound = 1:2.) 
 
 A number of naphthol-mono-, -di-, &c., sulphonic acids are 
 known, also amino-naphthol-sulphonic acids, which are of great 
 technical value. Among these may be mentioned 1 : 4-naph- 
 thol- sulphonic acid (Nevile and JTinther), from naphthionic 
 acid, the 2:8-acid, the 2:6-acid, the /?-naphthol-disulphonic 
 acids E (2:3:6) or "It-salt", and G (2:6:8) or "G-salt". 
 l-Amino-8-naphthol-3:6-disulphonic acid = H acid. 
 
 Sodium l-amino-2-naphthol-6-sulphonate is used as a photo- 
 graphic developer under the name of Eikonogen. 
 
 Azo-dyes. A series of very important azo-dyes (see also 
 under Benzidine, p. 472) are produced by the action of dia- 
 zonium compounds, and of diazo-naphthalene-snlphonic acids 
 upon the naphthylamines and naphthols, and especially upon 
 the sulphonic acids of these, e.g.: 
 
 Benzene-azo-a-naphthylamine, C 6 EL N : N C-, H 6 NH 2 ; 
 
 Orange II, S0 8 Na.C 6 H 4 .N:N.C 10 H 6 .OH[/?]; 
 
NAIHTHAQUINONES 503 
 
 Ponceau 2R, from diazotized xylidine and "E-salt"; Fast 
 Red C ("EchMh"), S0 3 Na.C 10 H 6 .N:N.C 10 H 5 (pH)(S0 3 Na), 
 from naphthionic acid and l-naphthol-4-sulphonic acid; Bie- 
 brich Scarlet, S0 3 Na . C 6 H 4 - N : N . C 6 H 4 . N : N C 10 H 6 (OH), from 
 amino-azo-benzene-sulphonic acid and /3-naphthol; Brilliant 
 Black, (SOsNaJjC^.NiN.Cj^.NrN.O^OHJfSOsNaJa, 
 from naphthylamine-disulphonic acid, a-naphthylamine, and 
 "K-salt"; Palatin Black, S0 3 Na.C 6 H 4 .N 2 .C 10 H 3 (N 2 C 10 H 7 ) 
 (NH 2 )(OH)(S0 3 Na), from diazobenzenesulphonic acid, a-azo- 
 naphthalene, and l-amino-8-naphthol-4-sulphonic acid. 
 
 Quinones of the Naphthalene Series. Three isomeric quin- 
 ones, C 10 H 6 2 , are known; two correspond with para and 
 ortho benzoquinones. 
 
 a-Naphthaquinone may be obtained by the oxidation of 
 naphthalene, a-naphthylamine, l-amino-4-naphthol, l:4-di- 
 hydroxy-naphthalene, and of various derivatives of naphtha- 
 lene containing substituents in the a-positions, by chromic 
 acid. It crystallizes in yellow rhombic plates, melts at 125, 
 and is the complete analogue of ordinary quinone, having a 
 similar odour and being volatile with steam. It can be 
 reduced to 1 : 4-dihydroxy-naphthalene by sulphurous acid, 
 and can yield a dioxime, hence its constitution as a para- 
 or 1 : 4-quinone. (Formula I.) 
 
 /2-Naphthaquinone (II) has no odour and is not volatile, 
 being thus more like phenanthraquinone. It can be obtained 
 by the oxidation of l-amino-2-naphthol, and when reduced 
 with sulphurous acid yields 1 :2-dihydroxy-naphthalene; hence 
 its constitution as a 1 : 2 or orthoquinone. It decomposes at 
 115 without melting and crystallizes in red needles: 
 
 2 : 6-Naphthaquinone (III), isomeric with the a- and /?-com- 
 pounds, forms odourless, non- volatile, yellowish -red prisms, 
 and is a strong oxidizing agent. 
 
 Hydroxy-naphthaquinones are known; the common one is 
 2-hydroxy-a-naphthaquinone; juglone is the isomeric 5-hy- 
 droxy-compound, and occurs in nut shells; naphthazarine, 
 "alizarin black", is a valuable dye which is prepared by act- 
 ing upon a-dinitro-naphthalene with zinc and sulphuric acid, 
 
504 XXXII. ANTHRACENE AND PHENANTHRENE GROUPS 
 
 comports itself like the alizarin dyes; it is the "alizarin" of 
 the naphthalene series. 
 
 Carboxylic Acids. The naphthoic acids, C 10 H 7 C0 2 H, can 
 be obtained by saponifying the cyano-naphthalenes and also 
 by the other synthetical methods given for the acids of the 
 benzoic series. They crystallize in fine needles sparingly soluble 
 in hot water, and break up into naphthalene and carbon di- 
 oxide when distilled with lime. From them are derived the 
 hydroxy-naphthoic acids, C 10 H 6 (OH)(C0 2 H), which are re- 
 lated to salicylic acid or its isomers. Among the naphthalene- 
 dicarboxylic acids, C 10 Hg(C0 2 H) 2 , which are known may be 
 mentioned naphthalic acid, (1:8), which at a somewhat high 
 temperature yields an anhydride similar to phthalic anhydride. 
 
 Phenyl-naphthalene, C 10 H 7 (C 6 H 5 ), has also been prepared; 
 it is a compound built up of a naphthalene and of a benzene 
 nucleus, and is therefore analogous to diphenyl, G 6 H 5 C 6 H 5 . 
 The same applies to: 
 
 Di-naphthyl, C 10 H 7 C 10 H 7 , which yields derivatives (e.g. the 
 di-naphthols, see p. 502) analogous to those of diphenyl. The 
 three modifications which are theoretically possible, namely, 
 the a-a-, /?-/?-, and a-/?-compounds, are known. 
 
 Another derivative of naphthalene is acenaphthene, C 12 H 10 , 
 
 ^2 
 
 (1:8), which is found in coal-tar. It crystal- 
 )H 2 
 
 lizes in colourless prisms, melts at 95, boils at 277, and yields 
 naphthalic acid on oxidation. 
 
 XXXII. THE ANTHRACENE AND PHENAN- 
 THRENE GROUPS 
 
 A, Anthracene 
 
 Anthracene, C 14 H 10 (Dumas and Laurent, 1832; Fritzsche, 
 1857), is formed, together with benzene and naphthalene, by 
 the destructive distillation of coal and, generally, by the 
 pyrogenous reactions which give rise to these products, e.g. 
 by passing CH 4 , C 2 H 6 , C 2 H 2 , the vapour of alcohol, &c., 
 through red-hot tubes. 
 
 Although coal-tar contains only some 0'25-0'45 per cent of 
 anthracene, it is the chief source from which this hydrocarbon 
 
ANTHRACENE 505 
 
 is obtained. The fraction of coal-tar distilling above 270 and 
 known as anthracene oil yields, on further distillation and 
 digesting with solvent naphtha, a solid mass known as 50- 
 per-cent anthracene, which is then distilled with one-third of 
 of its weight of potassium carbonate. This serves to remove 
 carbazole (p. 473), which yields a non- volatile potassium de- 
 rivative - 6 yNK, and the distillate consists of anthracene 
 
 C 6 H/ 
 
 and phenanthrene. The phenanthrene is removed by extrac- 
 tion with carbon disulphide, and the anthracene crystallized 
 from benzene. 
 
 The following are some of the more important methods by 
 means of which the hydrocarbon has been synthesised, and 
 they throw considerable light upon its constitution: 
 
 1. By heating 0-tolyl phenyl ketone with zinc dust (B. 7, 17) : 
 
 2. Together with dibenzyl, by heating benzyl chloride with 
 water at 200 (B. 7, 276): 
 
 4C 6 H 5 .CH 2 C1 = C 14 H 10 + C 14 H I4 + 4HC1. 
 
 3. From o-bromo-benzyl bromide and sodium in ethereal 
 solution dihydro- anthracene is at first formed, and this is 
 converted by oxidation (which is partly spontaneous during 
 the above reaction) into anthracene (B. 12, 1965): 
 
 4. By heating benzene with symmetrical tetrabromo-ethane 
 and aluminic chloride (Anschutz, B. 16, 623) : 
 
 BrCHBr 
 
 I 
 BrCHBr 
 
 I + C 6 H 6 = C 6 H 4 
 rCH 
 
 5. When phthalic anhydride is heated with benzene and 
 aluminic chloride, o-benzoyl-benzoic acid is formed, and this 
 when heated with phosphoric anhydride yields anthraquinone 
 
506 XXXlI. ANTHRACENE AND FHENANTHRENE GROtJPS 
 
 (Behr and v. Dorp, B. 7, 578), which on reduction with zinc 
 dust gives anthracene: 
 
 -geH, = Co H 4 <gg>C e H 4 +H 2 0; 
 
 /ITT 
 
 C 6 H 4 <gg>C 6 H 4 + 6H = C 6 H 4 <^ >C 6 H 4 -f 2H 2 0. 
 
 6. When a mixture of wi-xylene and styrene is treated with 
 concentrated sulphuric acid, there is formed a-tolyl-fl-phenyl- 
 
 propane, CH 3 C 6 H 4 CH 2 CH<^Q|r 5 , which decomposes almost 
 
 quantitatively into methane, hydrogen, and methyl-anthracene 
 when strongly heated (B. 23, 3272). 
 
 Constitution. From mode of formation 5, the anthracene 
 molecule is seen to contain two benzene nuclei, C 6 H 4 , joined 
 together by a middle group, C 2 H 2 . The carbon atoms of this 
 middle group are likewise linked together, as is seen from 
 mode of formation 4, and take up the 0-position with regard 
 to each other on one or other of the benzene nuclei (on one 
 nucleus according to methods of formation 1 and 5, and on 
 the other according to method 3; for further proofs of this, 
 see e.g. v. Pechmann, B. 12, 2124). The constitution of an- 
 thracene is thus the following (Graebe and Liebermann, A. 
 Suppl. 7, 313): 
 
 CH CH CH 
 
 3H 
 
 or 
 
 The two carbon atoms of the middle group thus form a new 
 hexagon-ring with the carbon atoms of the benzene nuclei to 
 which they are linked, so that anthracene may also be looked 
 upon as being built up by the conjunction of three benzene 
 
 / CH \ 
 nuclei. Besides the formula C 6 H 4 <^ I yO 6 H 4 , the "quinoid" 
 
 QJT CH 
 
 formula CHTT>CH has also to be taken into consider- 
 
 ation (Armstrong, P. 1890, 101; Kehrmann, B. 1894, 21, 3348), 
 
 Properties and Behaviour. Anthracene crystallizes in colour 
 
 less plates which show a magnificent blue fluorescence. It is 
 
ANTHRACENE DERIVATIVES 507 
 
 insoluble in water and dissolves only sparingly in alcohol and 
 ether, but readily in hot benzene. It melts at 213, boils above 
 351, and with picric acid yields an additive compound which 
 crystallizes in beautiful red needles melting at 138. 
 
 Anthracene is transformed by sunlight into the polymeric 
 para-anthracene, (C 14 H 10 ) 2 . When reduced with hydriodic acid 
 and phosphorus it takes up, in the first instance, two atoms of 
 hydrogen, with the formation of 9:10-dihydro-anthracene, 
 
 (see p. 505, mode of formation 3). This crystallizes in colour- 
 less plates, melts at 107, and is readily soluble in alcohol. It 
 sublimes readily and distils without decomposition, but yields 
 anthracene at a red heat or when warmed with concentrated 
 sulphuric acid. 
 
 Further addition of hydrogen yields the hydrides C 14 H lfl 
 and, finally, C 14 H 24 . 
 
 DERIVATIVES OF ANTHRACENE 
 
 Theoretically three isomeric mono-derivatives are possible in 
 each case, viz., the a-, /?-, and -/-compounds : 
 
 since in the graphical formula given on the preceding page, 
 1 = 4 = 5 = 8 = a, 2 = 3 = 6 = 7 = ft and 9 = 10 = 7. 
 The observed facts are in complete accordance with this. 
 
 The position of the substituting group can usually be deter- 
 mined either by an examination of the oxidation products, e.g. 
 if it be in the y-position it will be eliminated and anthra- 
 quinone formed; or it is arrived at from the synthesis of the 
 compound, e.g. in the case of alizarin, the formation of which 
 from catechol and phthalic acid shows that its two hydroxyls 
 are contained in one and the same benzene nucleus. 
 
 The number of di-substituted derivatives is large, for example, 
 when both substituents are alike, 15 isomerides are theoretically 
 possible. 
 
508 XXXII. ANTHRACENE AND PHENANTHRENE GROUPS 
 
 Numerous derivatives of anthracene are known, e.g. halogen-, 
 nitro-, amino-, and sulphonic acid derivatives. 
 
 Hydroxy-anthracenes. The a- and /^-compounds are termed 
 a- and /3-anthrols; they are obtained by fusing the correspond- 
 ing sulphonic acids with alkali, and in their properties closely 
 resemble phenols and naphthols. 
 
 y-Hydroxy-anthracene or anthranol may be obtained by- 
 reducing anthraquinone with zinc and acetic acid, or syntheti- 
 cally, by the action of concentrated sulphuric acid on o- 
 benzyl-benzoic acid at 80 : 
 
 It is readily oxidized to anthraquinone, and with hydroxyl- 
 amine yields anthraquinone oxime. 
 
 Anthraquinone, C 14 H 8 O 2 (Laurent, 1834), is readily obtained 
 by oxidizing anthracene with chromic acid mixture (which is 
 the method followed on the large scale), or with chromic an- 
 hydride and glacial acetic acid, and is also produced when 
 calcium benzoate is distilled. 
 
 It crystallizes in yellow prisms or needles soluble in hot 
 benzene, melts at 285, sublimes with great readiness, and is 
 exceedingly stable as regards oxidizing agents. Hydriodic 
 acid at 150 reduces it either to anthracene or its dihydride, 
 while fusion with potash converts it into benzoic acid. It 
 possesses more of a ketonic than of a quinonic character 
 (Zincke, Fittig), as it is not reduced by sulphurous acid, and 
 gives an oxime with hydroxylamine. 
 
 It yields mono- and dibromo-, nitro- and sulphonic - acid 
 derivatives. Anthraquinone /3-mono-sulphonic acid crystal- 
 lizes in yellow plates, and is formed by the action of sul- 
 phuric acid under normal conditions, but in the presence of 
 mercury salts the isomeric a -acid is obtained; of the di- 
 sulphonic acids two are formed directly from anthraquinone, 
 and two may be prepared by the oxidation of the correspond- 
 ing anthracene-disulphonic acids. 
 
 Fusion of the sulphonic acids with potash does not generally 
 yield the analogous hydroxy-compounds in theoretical quantity, 
 oxygen being usually absorbed from the air at the same time ; 
 thus the mono-sulphonic acids yield mono- and dihydroxy-, 
 and the di-sulphonic acids di- and trihydroxy-anthraquinones. 
 In practical working the theoretical amount of chlorate of 
 
ALIZARIN 509 
 
 potash required is added to the "melt". Prolonged fusion 
 with potash tends to form hydroxy-benzoic acids. 
 
 Various hydrpxy-anthraquinones can also be prepared by 
 the synthetical mode of formation 5, p. 505, viz., from phthalic 
 anhydride and the mono- or dihydroxy-benzenes (Baeyer and 
 Caro, B. 7, 792; 8, 152), e.g.: 
 
 phenol yields by this method the two hydroxy-anthraquinones 
 (yellow needles), catechol yields alizarin, quinol yields quini- 
 zarin, and so on. The hydroxy-derivatives are further pro- 
 duced by fusing chloro- and bromo-anthraquinones with potash, 
 while m- hydroxy-benzoic acid can be converted directly by 
 sulphuric acid into anthraflavic acid, water being eliminated. 
 Cf. A. 240, 245. 
 
 Alizarin, 1 : 2-dihydroxy-anthraquinone, C U H 8 4 , is the most 
 important constituent of the beautiful red dye of the madder 
 root (Eubia tinctorum), which has been known for ages, being 
 present in the latter as the readily decomposable glucoside, 
 Euberythric acid, C^HggO^; in addition to alizarin, madder 
 also contains purpurin. It is manufactured on the large scale 
 by fusing anthraquinone-/3-sulphonic acid with potassic hy- 
 droxide and chlorate (Graebe and Liebermann, Caro, Perkin, B. 
 3, 359; A. 160, 130). 
 
 It crystallizes in magnificent red prisms or needles of a glassy 
 lustre, melts at 289, and can be sublimed; it dissolves readily 
 in alcohol and ether, only sparingly in hot water, but, as a 
 phenol, very readily in alkalis to a violet-red solution. It 
 yields insoluble coloured compounds the so-called "lakes" 
 with metallic oxides, the alumina and tin lakes being of a 
 magnificent red colour, iron lake violet-black, and lime lake 
 blue. In the Turkey Red manufacture, for instance, the 
 materials to be dyed are previously mordanted with acetate 
 of alumina or with " ricinoleic-sulphuric acid". 
 
 Its constitutional formula is based on the following con- 
 siderations: (a) Its conversion into anthracene when heated 
 with zinc dust (Graebe and Liebermann, B. 1868, 1, 49; A. Sup. 
 7, 297); (b) its formation by fusing dibromo-anthraquinone or 
 anthraquinone-sulphonic acid with potash; (c) its synthesis from 
 phthalic anhydride and catechol. 
 
 All these indicate that it is a dihydroxy-anthraquinone 
 
510 XXXII. ANTHRACENE AND PHENANTHRENE GROUPS 
 
 with the two hydroxy-groups in the 0-positions with respect 
 to one another: 
 
 CO OH 
 
 S\ yVAA,. /\ 
 
 H /Y Vl 011 
 
 2:3 or 1:2. 
 
 w/J 
 
 The fact that two isomeric mono-nitro-derivatives (with the 
 nitro-group in the same nucleus as the two hydroxy-groups) 
 have been prepared is a proof of the positions 1:2 for the 
 hydroxy-groups. 
 
 C(OH) 
 
 Anthrarobin, dihydroxy-anthranol, C 6 H 4 <( ^>C 6 H 2 (OH) 2 , 
 
 X CH / 
 
 obtained from alizarin, ammonia, and zinc dust, is a yellowish- 
 white powder which yields alizarin on oxidation; on account 
 of its reducing properties it is used in skin diseases. 
 
 Nitric peroxide converts alizarin into /2-nitro-alizarin or ali- 
 zarin orange, C 14 H 7 (N0 2 )0 4 , a yellowish-red dye; and this with 
 glycerol and sulphuric acid (the Skraup reaction, p. 542), yields 
 alizarin blue, C 17 H 9 N0 4 (see Quinoline), a valuable blue dye 
 which is converted by fuming sulphuric acid into alizarin green. 
 
 Purpurin, l:2-A-trihydroxy-, anthrapurpurin, 1:2:7 -trihydroxy-, 
 and flavopurpurin, l:2:Q-trihydroxy-anthraquinone, are also valu- 
 able dyes which are manufactured on a large scale; the same 
 applies to the isomeric compound anthragallol, l:2:3-trihydroxy- 
 anthraquinone, or "anthracene brown", which is prepared by 
 acting on a mixture of gallic and benzoic acids with concen- 
 trated sulphuric acid. 
 
 Tetra-, penta-, and hexa-hydroxyanthraquinones are also used 
 as dyes. (B. 1890, 23, 3739; J. pr. 43, 237, 246.) Alizarin 
 bordeaux is a l:2:5:8-tetrahydroxy- and alizarin- cyanine 
 1:2:4:5: 8-pentahydroxy anthraquinone. 
 
 According to v. Kostanecki the colouring power of these com- 
 pounds is connected with the presence of two hydroxyls in the 
 ortho-position to one another. 
 
 For Indanthrene dyes see B. 36, 3410. 
 
 B. Phenanthrene 
 
 Phenanthrene (Fittig and Ostermeyer, 1872, A. 166, 361) 
 which is isomeric with anthracene, accompanies this hydro- 
 carbon in coal-tar. It crystallizes in colourless glistening 
 
 
PHENANTHRENE 511 
 
 plates, dissolves in alcohol more readily than anthracene 
 (yielding a blue fluorescent solution), melts at 99, and boils 
 at 340. It may be separated from anthracene by partial 
 oxidation and subsequent distillation, as the latter is more 
 readily attacked. Oxidizing agents convert it into diphenic 
 acid (p. 474). Its picrate crystallizes in yellow needles melt- 
 ing at 145. 
 
 It may also be obtained: 1. By leading the vapour of tolu- 
 ene, stilbene, dibenzyl or 0-ditolyl through a red-hot tube, thus : 
 
 CH, OEL-CH 
 
 2. Together with anthracene from 0-bromo-benzyl bromide 
 and sodium. 
 
 3. A recent synthesis by Pschorr (B. 1896, 29, 496; 32, 162, 
 176; 33, 496) is from 0-nitro-benzaldehyde. This with sodic 
 phenyl-acetate and acetic anhydride (Perkiris synthesis, p. 441) 
 yields a-phenyl-o-nitro-cinnamic acid, N0 2 C 6 H 4 CH : CPh 
 C0 2 H. When this is reduced, diazotized, and treated with 
 copper powder, /3-phenanthrene-carboxylic acid is formed, 
 C 6 H 4 .CH 
 
 , and when carbon dioxide is eliminated this 
 ( C 6 H 4 CC0 2 H 
 
 yields phenanthrene. Numerous phenanthrene derivatives 
 have been synthesised in a similar manner. (See also Robe, 
 B. 1898, 31, 1896.) 
 
 The formation of phenanthrene from 0-ditolyl, and its oxi- 
 
 C 6 H 4 .C0 2 H 
 dation to diphenic acid, , show that it is a diphenyl 
 
 derivative, and that it contains a carbon atom linked to each 
 benzene nucleus; this carbon atom is joined to the corre- 
 sponding one by a double bond, as is shown, e.g., by its 
 
 C 6 H 5 .CH 
 formation from stilbene, , a reaction completely 
 
 analogous to the preparation of diphenyl from benzene. Since 
 diphenic acid is a di-ortho-diphenyl-dicarboxylic acid (Schultz, 
 A. 196, 1 ; 203, 95), phenanthrene is also a di-ortho-derivative 
 and possesses the following constitution: 
 
 CH CH 
 ^ C CH 
 
 CVH 4 .CH r 
 
512 XXXII. ANTHRACENE AND PHENANTHRENE GROUPS 
 
 According to the above formula, the two CH-groups form a 
 new hexagon ring with the carbon atoms of the two benzene 
 nuclei to which they are linked, so that phenanthrene like 
 anthracene may be looked upon as the product of the coali- 
 tion of three benzene nuclei, or of one naphthalene and one 
 benzene nucleus. 
 
 Additive and substitution products of phenantbrene are also 
 known, e.g. a tetrahydride, nitro-, amino-, cyano-, and hydroxy- 
 compounds, and sulphonic and carboxylic acids. Phenanthrol, 
 C 14 H 9 (OH), is a hydroxy- phenanthrene, and phenanthrene- 
 quinol, C 14 H 8 (OH) 2 , a dihydroxy-compound; when oxidized 
 
 C 6 H 4 -CO 
 the latter yields phenanthraquinone, , which may 
 
 C 6 H 4 CO 
 
 also be prepared directly from phenanthrene and chromic acid. 
 It crystallizes in odourless, orange needles, melts at 200, 
 distils unchanged, and is not volatile in steam. Phenanthra- 
 quinone possesses the character of a diketone, reacting with 
 hydroxylamine, sodium bisulphite, &c., but it can be reduced 
 to the corresponding quinol by sulphurous acid. It gives a 
 bluish-green coloration with toluene containing thio-tolene, 
 glacial acetic acid, and sulphuric acid, and when the mixture 
 is diluted and extracted with ether the latter becomes violet- 
 coloured; this is the Laubenheimer reaction (B. 17, 1338). 
 
 i C. Complex Hydrocarbons 
 
 Fluoranthene, C 15 H 10 , pyrene, C 16 H 10 , chrysene, C 18 H 12 , 
 retene, C 18 H 18 , and picene, C 22 H 14 , are hydrocarbons which 
 have been isolated from that portion of coal-tar which boils 
 above 360. Phenanthrene, pyrene, and fluoranthene are also 
 found in "Stupp" fat, i.e. the fat obtained as a by-product 
 from the working up of mercury ores in Idria. They all crys- 
 tallize in white plates, sublime without decomposition, and 
 when oxidized are converted into the corresponding ketones. 
 Their constitution is expressed by the following formulae: 
 
 C 6 H 4 .CH C 6 H 4 .CH C 10 H 6 .CH 
 
 r^TT v. 
 
 C 6 H 3 gCH C 10 H 6 .CH ^>C 6 H 2 .CH C 10 H 6 .CH 
 
 Fluoranthene Chrysene Retene or Methyl Picene. 
 
 iso-propyl phenanthrene 
 
 (Cf. A. 240, 147; 284, 52; 351, 218; B. 26, 1745; B. 36, 
 4200.) 
 
HETEROCYCLIC COMPOUNDS 513 
 
 HETEEOCYCLIC COMPOUNDS 
 
 XXXIII. INTRODUCTION 
 
 The third great division of carbon derivatives consists of 
 the Heterocydic Compounds. These, like the carbocyclic com- 
 pounds, contain a closed chain or ring, but differ from the 
 latter by the presence in the actual ring of atoms of elements 
 other than carbon (cf. formulae, p. 514). The number of such 
 compounds is enormous, although the number of elements 
 usually associated with carbon in rings is comparatively small. 
 The more common elements are oxygen and sulphur, but more 
 especially nitrogen. 
 
 A number of these compounds have been already mentioned; 
 among the oxygen compounds are ethylene oxide, glycolide, 
 phthalic anhydride, and among the nitrogen compounds suc- 
 cinimide, phthalimide, and lactams. 
 
 The compounds are divided into groups according to the 
 number of atoms constituting the ring, thus three-membered 
 rings, e.g. ethylene oxide; four-membered rings, e.g. betaine; 
 five-membered rings, e.g. thiophene; six-membered rings, e.g. 
 pyridine, &c. As in the carbocyclic series, the most important 
 and also the most stable are the five- and six-membered rings. 
 A further division of these groups can be made according to 
 the number of atoms other than carbon present. Thus in the 
 five-membered ring compounds we can have the following sub- 
 groups: 40 + IN; 30 + 2N; 20 + 3N; termed respectively 
 the monazole, di- and tri-azole sub-groups. 
 
 The stability of the compounds and their general chemical 
 characteristics depend to a large extent on the saturated or 
 unsaturated nature of the rings. Compounds like thiophene, 
 pyrrole and pyridine are stable and closely resemble ben- 
 zene they possess general aromatic properties. Like benzene 
 they can be reduced, the two former can each take up two or 
 four atoms of hydrogen, and pyridine two, four or six. These 
 reduction products no longer have aromatic properties. It is 
 interesting to note that although the five-membered hetero- 
 cyclic unsaturated compounds resemble benzene, the unsatu- 
 rated carbocyclic compound cyclopentadiene does not. 
 
 Some of the common heterocyclic compounds contain con- 
 densed nuclei, i.e. the two condensed rings have two carbon 
 atoms in common. A well-known example of condensed 
 
 (9480) 2K 
 
514 XXXIII. HETEROCYCLIC COMPOUNDS 
 
 heterocyclic rings is met with in purine and its derivatives 
 (p. 290). Examples of compounds containing a benzene 
 nucleus condensed with a heterocyclic ring are met with in 
 quinoline, coumarone and indole (see below). 
 
 Compounds with condensed nuclei behave very differently 
 on oxidation. Certain of them have the heterocyclic ring 
 ruptured, and thus yield ortho-derivatives of the carbon ring; 
 others, again, have the carbon ring ruptured, and yield ortho- 
 acids of the heterocyclic ring. The compounds dealt with in 
 the following sections will be grouped as follows: 
 
 1. Five-membered heterocyclic compounds containing 4C 
 -f 10, S or N atoms, or the furane group, e.g.: 
 
 CH:CH\ CH:CH 
 
 CH:CH/^ CHi 
 
 Furane Thiophene Pyrrole 
 
 :CH\ CEL:GR\ 
 
 iCH/ CH:CHX 
 
 2. Compounds formed by the condensation of these rings 
 with a benzene nucleus, e.g.: 
 
 Coumarone, Indole, j 
 
 3. Five-membered heterocyclic compounds containing three 
 carbon atoms, e.g. pyrazole and thiazole group. 
 
 4. Six-membered heterocyclic compounds or pyridine group, 
 e.g.: 
 
 CH CH 
 
 Pyridine, HC/ \N 
 
 5. The compounds formed by the condensation of a benzene 
 and pyridine ring, e.g. : 
 
 Quinoline, I I j and wo-Quinoline, 
 
 6. Six-membered heterocyclic compounds, with not more 
 than four carbon atoms in the ring. 
 
ffURANE GROUP 515 
 
 XXXIV. FURANE GROUP 
 CH:CH/ C CH:CH/ S CH:< 
 
 Furane Thiophene Pyrrole. 
 
 From these compounds a whole series of derivatives are 
 obtained by the substitution of hydrogen by halogen, and 
 also by the entrance of the groups 'CH 3 , CHgOH, CHO, 
 C0 2 H, &c. In their properties furane, thiophene, and pyrrole 
 remind one of benzene. Thiophene, in particular, is delusively 
 like the latter, e.g. in odour and boiling-point, and its various de- 
 rivatives often show a marvellous similarity in their chemical and 
 physical relations to the corresponding derivatives of benzene. 
 
 Furane, pyrrole, and thiophene also resemble one another in 
 many respects. All three boil at relatively low temperatures 
 ( -f- 32, 131, 84), are either insoluble or only sparingly soluble 
 in water, but readily in alcohol and ether, and show many an- 
 alogous colour reactions. Thus pyrrole and thiophene and their 
 derivatives give, for the most part, an intense violet to blue 
 coloration when mixed with isatin and concentrated sulphuric 
 acid, and a cherry-red or violet coloration with phenanthra- 
 quinone and glacial acetic or sulphuric acid. The vapour of 
 pyrrole colours a pine shaving which has been moistened with 
 hydrochloric acid carmine red (irvppos, fiery-red), while furalde- 
 hyde vapour colours it an emerald green; the latter likewise 
 colours a piece of paper moistened with xylidine- or aniline- 
 acetate red. Furane is converted by mineral acids, e.g. hydro- 
 chloric acid, into an insoluble amorphous powder, and pyrrole 
 into an insoluble amorphous brown-red powder, " pyrrole-red " 
 (with evolution of ammonia), while thiophene remains unal- 
 tered; the derivatives show a similar behaviour. Pyrrole is 
 distinguished from the two other compounds by having feebly 
 basic properties. 
 
 Derivatives of all three compounds may be obtained from 
 mucic acid, C0 2 H (CH OH) 4 C0 2 H (p. 259). When distilled, 
 mucic acid yields pyromucic acid or furane-a-carboxylic acid; 
 when its ammonium salt is distilled, pyrrole is formed; and 
 when free mucic acid is heated with barium sulphide, thiophene 
 a-carboxylic acid is obtained, e.g. : 
 
 CH.:(OH):.CiHi ;;(OH)I.:COO:H CH:CH . 
 
 = C0 2 +3H 2 0+ 1 >0. 
 
 3iIi;(0 : .H).i COOH CH:C(C0 2 H)/ 
 
516 XXXIV. FURANE GROUP 
 
 A very general method for the formation of derivatives of 
 this group is from y-diketones, e.g. acetonyl-acetone, CH 3 CO 
 CH 2 .CH 2 .CO.CH 3 (p. 221; also p. 230). When this com- 
 pound is heated with phosphorus pentoxide or zinc chloride, 
 dimethyl -furane is formed; with phosphorus pentasulphide, 
 dimethyl-thiophene; with alcoholic ammonia, dimethyl-pyrrole 
 (B. 18, 58, 367; 20, 1074). 
 
 This behaviour would indicate that the acetonyl- acetone 
 reacts as the tautomeric compound: 
 
 m,C(OH):CH.CH:C(OH).CH a or 
 
 upon this assumption the formation of dimethyl-furane appears 
 simply as that of an anhydride, that of dimethyl-pyrrole as an 
 exchange of 2 (OH) for NH (imide formation), and that of di- 
 methyl-thiophene as the formation of a sulphide, i.e. exchange 
 of 2(OH) for S, according to the following equations : 
 
 H CH:C(CH 3 K 
 H " CH:C(CH 3 )/ 
 CH:C(CH3>OH CH:C(CH 3 )\ 
 
 T " 
 
 H CH:C(CH 
 r H CH:C(CH 
 
 From the above reactions the constitutional formula for the 
 three compounds would be: 
 
 Furane Thiophene Pyrrole 
 
 CH:CHv CH:CHv ^ 
 
 CH:CBX CH:CH/ CH: 
 
 (ft) W 03) (a) 03) (a) 
 
 These formulae receive corroboration from the frequently ob- 
 served fact that the substances are capable of yielding additive 
 compounds with bromine or hydrogen (see Pyrroline). Ac- 
 cording to the above formulae, two isomeric mono-substituted 
 derivatives of furane and thiophene are possible: (1) one in 
 which the hydrogen atom (a) which stands nearest to the 
 oxygen, sulphur, or nitrogen atom, and (2) one in which a 
 quasi-middle hydrogen atom (ft) is substituted. AM a matter 
 
FtTRANE. FUROL 517 
 
 of fact, two such isomers have been observed in many cases, 
 e.g. two thiophenic acids. These form mixed crystals, the 
 crystals having a homogeneous appearance although they con- 
 tain both acids (V. Meyer, A. 236, 200). In the case of pyrrole, 
 on the other hand, three kinds of derivatives (a-, /?-, and n-) 
 are both possible and known. 
 
 An examination of the molecular refraction of thiophene 
 and also of its heat of combustion (B. 1885, 18, 1832) point to 
 the presence of only one double bond in the thiophene mole- 
 
 PTT PTT\ 
 cule. The formula J>S has been suggested, and this 
 
 CH CH/ 
 
 is quite in harmony with the production of substituted maleic 
 acids by the oxidation of thiophene derivatives. Probably the 
 simplest explanation is that the thiophene molecule contains 
 centric bonds, and should be represented as: 
 
 Furane or furfurane is a colourless mobile liquid, boiling at 
 32, and with an odour resembling that of chloroform. It is 
 present in pine-wood tar, in the first runnings from ordinary 
 wood tar, &c., and is obtained by the distillation of sugar with 
 lime, or by distilling barium pyromucate. a-Methyl-furane or 
 sylvane is likewise present in pine-wood tar, and in the pro- 
 ducts of distillation of sugar with lime. It boils at 65. aa- 
 Dimethyl-furane is obtained from sugar and lime, and also 
 from acetonyl-acetone (p. 516). It is a colourless mobile liquid 
 of a characteristic odour, and boils at 94. Concentrated acids 
 convert it into a resin; it can be transformed back into 
 acetonyl-acetone. 
 
 Furol, a-furaldehyde or furfuraldehyde, C 4 H 3 0CHO (Dobe- 
 reiner), is obtained when pentoses, e.g. arabinose and xylose, 
 are distilled with concentrated hydrochloric acid: 
 
 C 6 H 10 6 - 3H 2 = C 6 H 4 2 . 
 
 The yield is quantitative, and the method is made use of foi 
 determining the amounts of pentoses present in various sub- 
 stances. 
 
 It may also be obtained by distilling bran, wood, sugar, or 
 various carbohydrates with moderately concentrated sulphuric 
 
618 XXXIV. FURANE GROUP 
 
 acid. It is a colourless oil of agreeable odour, turns brown 
 in the air, and boils at 162. 
 
 It possesses all the properties of an aldehyde, and can yield 
 condensation products in much the same manner as benzalde- 
 hyde (p. 424): e.g. furom, C 4 H 3 O.CH(OH).(X).C 4 H 2 0, corre- 
 sponding with benzoin; furalmalonic acid, C 4 H 3 0-CH:C 
 (C0 2 H) 2 , corresponding with benzalmalonic acid; and furyl- 
 acrylic and aZfo-furylacrylic acid, C 4 H 3 CH : CH C0 2 H, 
 corresponding with cinnamic and a/fo-cinnamic acids. 
 
 Pyromucie acid, C 4 H 3 0-C0 2 H. Furane-a-carboxylic acid 
 crystallizes in needles or plates similar to those of benzoic 
 acid, and melts at 132; it sublimes easily, is readily soluble 
 in hot water and alcohol, and decolorizes alkaline permangan- 
 ate almost instantaneously. 
 
 Pyrrole is a constituent of coal-tar (Runge) and of bone-oi 1 
 (Anderson); it boils at 131, and possesses, like many of its 
 homologues, a chloroform odour. It is a secondary base, and 
 its imino-hydrogen is replaceable by metals and alkyl, or acyl 
 radicals. 
 
 In addition to the methods of formation mentioned on p. 516, 
 it may also be obtained v by heating succinimide (p. 239) with 
 zinc dust, or from acetylene and ammonia at a red heat. 
 
 When pyrrole is acted upon by hydroxylamine the ring is 
 
 CH 2 .CH:N.OH 
 
 broken, and the dioxime of succmic-aldehyde, , 
 
 CH 2 CH : N OH 
 
 is formed; this yields tetramethylene-diamine upon reduction 
 (R 22, 1968). Dimethyl-pyrrole in a similar manner yields 
 acetonyl-acetone-dioxime. 
 
 w-Potassium-pyrrole, C 4 H 4 NK, which is obtained from pyr- 
 role and potassium or solid potassic hydroxide, is a colourless 
 compound which is decomposed by water. A number of 
 w-alkyl and acyl derivatives may be prepared by the aid of 
 this potassium compound, but most of them are relatively 
 unstable, and when heated are transformed into the isomeric 
 a-alkyl or acyl compounds. A most interesting reaction is the 
 conversion of pyrrole into pyridine (p. 533) by means of sodium 
 methoxide and chloroform or methylene iodide. By the action 
 of iodine and alkali, substitution takes place with the forma- 
 tion of tetra-iodo-pyrrole or iodole, C 4 I 4 (NH), which crystal- 
 lizes in yellow plates, and is used as an antiseptic in place of 
 iodoform. 
 
 Zinc and glacial acetic acid convert pyrrole into pyrroline, 
 
tHIOPHENE 619 
 
 34, 3954), a colourless liquid boiling at 91 and also a strong 
 secondary base; when this latter is heated with hydriodic 
 
 r^TT OTT 
 
 acid, it is further reduced to pyrrolidine, 2 yNH, a 
 
 CH 2 CH 2 / 
 
 colourless, strongly alkaline base resembling piperidine, and 
 boiling at 86. It is also formed by the action of sodium on 
 an alcoholic solution of succinimide, and is obtained synthetic- 
 ally by heating S-chloro-butylamine with alkali, and by treating 
 ethylene cyanide with sodium and alcohol, thus : 
 
 CH 2 .CN CH 2 .CH 2 .NH 2 C 
 
 CH 2 .CN 4 CH 2 .CH 2 .NH 2 ' = CH 2 .CH/ N 
 
 it is consequently designated tetramethylene-imine (Ladenburg, 
 B. 19, 782; 20, 442). 
 
 The red colouring matter of blood yields pyrrole derivatives 
 as some of its products of decomposition, and pyrrolidine 
 derivatives, especially pyrrolidine -carboxy lie acid (proline), 
 are decomposition products of albumen. 
 
 Thiophene (V. Meyer, B. 16, 1465, &c.) is present in coal- 
 tar, being invariably found in benzene (up to 0*5 per cent); 
 the same applies to its homologues thiotolene (methyl-thio- 
 phene), and thioxene (dimethyl-thiophene), which accompany 
 toluene and xylene, &c. Its boiling-point (84) is almost the 
 same as that of benzene (80 - 4), from which it is extracted by 
 repeatedly shaking with small quantities of concentrated sul- 
 phuric acid, which transforms the thiophene into a soluble 
 sulphonic acid (B. 17, 2641, 2852). It is also attacked more 
 readily than benzene by other reagents, such as halogens. 
 
 Thiophene is also obtained synthetically by leading the 
 vapour of ethyl sulphide through a red-hot tube (Kekutt), and 
 in small quantity by heating crotonic acid, w-butyric acid, 
 paraldehyde, &c., with phosphorus pentasulphide. 
 
 Stilbene (p. 478) and sulphur yield tetraphenyltMophene, 
 thionessal, m.-pt. 183. 
 
 The preparation and properties of the thiophene derivatives 
 are almost identical with those of the corresponding benzene 
 compounds. Thus nitric acid acts on thiophene to produce 
 a nitro-thiophene, analogous to nitro-benzene, which can in 
 its turn be reduced to amino-thiophene; the latter is, how- 
 ever, much less stable than the corresponding ammo-benzene. 
 
620 XXXV. CONDENSED BENZENE, FURANE, ETC. RINGS 
 
 The boiling-points of thiophene compounds and their corre- 
 sponding benzene derivatives are almost identical. 
 
 The homologues can be obtained by Fittig's synthesis, the 
 a-compounds from 1 : 4-diketones, and the /^-derivatives from 
 mono- or di-substituted succinic acids and phosphorus penta- 
 sulphide. 
 
 Thiophene-sulphonic acid, OHS0 2 C 4 H 3 S, decomposes into 
 thiophene and sulphuric acid when superheated with water, 
 and does not yield a phenol on fusion with potash. 
 
 Hydroxythiotolene, C 4 H 2 S(CH 3 )(OH), the phenol of thiotol- 
 ene, is formed by heating Isevulic acid with P 2 S 5 (B. 19, 553). 
 
 A mixture of the a- and /3-monocarboxylic acids when 
 crystallized slowly from water yields mixed crystals, which 
 cannot be resolved into their components. 
 
 The blue coloration which is formed when benzene contain- 
 ing thiophene is shaken with isatin and concentrated sulphuric 
 acid, is due to the formation of the blue colouring matter 
 "Indophenin", C^ONS. 
 
 (Of. V. Meyer's "Die Thiophengruppe", Braunschweig, 1888.) 
 
 XXXV. COMPOUNDS FORMED BY THE CONDEN- 
 SATION OF A BENZENE NUCLEUS WITH A 
 FURANE, THIOPHENE, OR PYRROLE RING 
 
 NH 
 
 Coumarone Benzo-thiophene Indole. 
 
 Coumarone closely resembles pseudo-cumene. It occurs in 
 coal-tar, and may be isolated as its picrate. It is usually 
 obtained from bromocoumarin; this with alcoholic potash 
 yields coumarilic acid which gives coumarone when distilled 
 with lime: 
 
 It is a colourless liquid distilling at 170; yields a dibromide 
 and a dihydro-derivative, thus indicating the presence of a 
 double bond. Numerous derivatives are known. 
 
INDOLE 621 
 
 Benzo-tkiopkene, Thionaphthene, melts at 31, boils at 221, 
 and has an odour resembling naphthalene. 
 
 INDOLE GROUP 
 
 Indole (Baeyer, 1868) is the most important compound in 
 this group, as it is the parent substance of indigo. As a 
 derivative of pyrrole it possesses feebly basic properties. It 
 is obtained by distilling oxindole with zinc dust; by heating 
 o-nitro-cinnamic acid with potash and iron filings; by the 
 action of sodic ethoxide upon o-amino-/?-chloro-styrene (B. 17, 
 1067): 
 
 C6H4<^ : a CHC1 + NaO.C 2 H 5 = OJEL^^^CH. + NaCl + C 2 H S OH; 
 
 by the pancreatic fermentation of albumen; together with 
 skatole by fusing albumen with potash; and by passing the 
 vapours of various anilines, e.g. diethyl-o-toluidine, through 
 red-hot tubes, &c. It occurs in the essential oil of jasmine 
 flowers, crystallizes in plates, melts at 52, volatilizes readily 
 with steam, and usually has a peculiar faecal -like odour, 
 although in the pure state and diluted it is stated to have a 
 fragrant odour. It is feebly basic, colours a pine shaving 
 which has been moistened with hydrochloric acid cherry-red, 
 with nitrous acid gives a red precipitate, which consists partly 
 of the so-called nitroso-indole, [C 8 H 6 N(NO)] 2 (a delicate re- 
 action; see B. 22, 1976), and yields acetyl-indole when acety- 
 lated. These last reactions show that indole contains an imino- 
 group. When oxidized with ozone it yields indigo. 
 
 The system of numbering the substituents in the indole 
 molecule is as follows: 
 
 The 1 -substituted derivatives are sometimes termed w-de- 
 rivatives, e.g. %-methyl-indole, C 6 H 4 <^pTT_^CH. 
 
 Various derivatives may be obtained synthetically by the 
 condensation of the aromatic primary or secondary hydrazines 
 either with pyroracemic acid or with certain ketones or alde- 
 hydes, and treatment of the resulting hydrazones with dilute 
 hydrochloric acid or zinc chloride, when ammonia is eliminated 
 
622 XXXV. CONDENSED BENZENE, FURANE, ETC. RINGS 
 (E. Fischer, A. 236, 116: 242, 372); thus acetone -phenyl- 
 
 PIT 
 
 hydrazone, C 6 H 5 . NH . N : O^g 3 , yields a- methyl -indole, 
 CH 3 , propaldehyde - phenyl - bydrazone yields 
 
 skatole, and phenacyl bromide and aniline yield a-phenyl- 
 indole. See also B. 25, 2860. 
 
 Skatole, 3-methyl-indok, C 6 H 4 <^Q^ e ~^>CH, is found in faeces, 
 
 and is produced, together with indole, e.g., by the decay of 
 albumen, or by fusing it with potash. It crystallizes in colour- 
 less plates of a strong faecal odour and melts at 95. Nitrous 
 acid does not colour it red. It takes up two atoms of hydrogen 
 to form a hydro-compound. Acids, aldehydes, &c., are also 
 known. 
 
 Dioxindole, C fi H 4 <^ QH ^>CO, or the lactam of o-amino 
 
 mandelic acid, NH 2 .C 6 H 4 .CH(OH).C0 2 H, is obtained by the 
 reduction of isatin (into which it is again easily oxidized) with 
 zinc dust and hydrochloric acid, or by the oxidation of oxin- 
 dole. It crystallizes in colourless prisms, melts at 180, and 
 possesses both basic and acid properties (two hydrogen atoms 
 being replaceable); it also forms a nitroso- compound, an 
 N-acetyl derivative, &c. 
 
 Oxindole, C 6 H 4 <^QTT ^>CO, the lactam of o-amino-phenyl- 
 
 acetic acid, is formed by the reduction of 0-nitro-phenyl-acetic 
 acid (p. 452); also by that of dioxindole with tin and hydro- 
 chloric acid. It crystallizes in colourless needles, melts at 1 20, 
 is readily oxidized to dioxindole, and therefore possesses feebly 
 reducing properties. Oxindole is amphoteric, dissolving both 
 in alkalis and in hydrochloric acid. Baryta water at a some- 
 what high temperature transforms it into barium 0-amino- 
 phenyl-acetate. The imino-hydrogen is exchangeable for ethyl, 
 acetyl, the nitroso-group, &c. 
 
 Isomeric with oxindole is indoxyl, CgHi^Vr ^CH, which 
 
 is obtained by the elimination of carbon dioxide from indoxylic 
 acid, a product formed from phenyl-glycocoll (p. 452), also by 
 fusing indigo with potash. It is often present in the urine of 
 the carnivora as potassium indoxyl-sulphate or urine-indican, 
 C 8 H 6 N-0.(S0 3 K). It forms yellow crystals, melting at 85, 
 is moderately soluble in water with yellow fluorescence, and 
 
 
iSATiN 523 
 
 not volatile with steam. It is very unstable, quickly becoming 
 resinous, and is readily transformed into indigo when its alka- 
 line solution is exposed to the air, or when ferric chloride is 
 added to its solution in hydrochloric acid. 
 
 It yields a nitroso- compound, C 6 H 4 <Qy'QjTw>CH, of the 
 
 same character as the nitrosamines, and therefore it contains 
 an imino-group; further, its relation to indoxyl-sulphuric acid 
 shows that it contains an alcoholic hydroxy-group, and thus 
 its constitution follows. 
 
 Potassium indoxyl-sulphate is prepared synthetically by 
 warming indoxyl with potassium pyrosulphate; it crystallizes 
 in glistening plates and is hydrolysed when warmed with 
 
 acids. 
 
 Ethyl-indoxyl is obtained from indoxyl by the exchange of 
 the hydroxylic hydrogen for C 2 H 5 . Derivatives of the hypo- 
 
 thetical pseudo- indoxyl, C 6 H 4 <^QQj>CH 2 , are also known, 
 
 some of them being convertible into indigo derivatives (e.g. 
 diethyl-indigo). 
 
 Indoxylic acid, C6 H 4^^ C0 2 H, the carboxylic 
 
 acid of indoxyl, forms white crystals, is oxidized to indigo by 
 ferric chloride, and breaks up into indoxyl and carbon dioxide 
 when fused. It is obtained from its ester, ethyl indoxylate, by 
 fusing with soda. The latter compound crystallizes in stout 
 prisms, melts at 120, and may be obtained, among other 
 methods, by the reduction of ethyl o-nitro-phenyl-propiolate 
 with ammonium sulphide. 
 
 PO 
 Isatin, C 6 H 4 <^TT^>CO, the lactam of o-aminp-benzoyl-formic 
 
 acid (p. 463), is readily prepared by oxidizing indigo or in- 
 doxyl with nitric acid (Erdmann and Laurent, 1841 ; cf. also 
 B. 17, 976). It may also be obtained by the oxidation of 
 dioxindole or of oxindole (indirectly). 
 
 The following are among some of the most important 
 methods by means of which isatin has been synthesised: 
 
 (a) When o-nitro-phenyl-glyoxylic acid (o-nitro-benzoyl- 
 formic acid, p. 462) is reduced, the corresponding amino-acid 
 is obtained; but this immediately loses water, yielding a lactam 
 or lactim : 
 
 mi 
 
524 XXXV. CONDENSED BENZENE, FtTRANE, ETC. RINGS 
 
 (b) 0-Nitro-phenylacetic acid when reduced yields the 
 
 lactam, oxindole, C fi H 4 <^ XT T/^>CO, and this with nitrous acid 
 
 M.Mxi-^ P/"NT OT^ 
 
 gives the iso-nitroso-oxindole, 6 H 4 <i&T_ ; >CO, which 
 
 on reduction is converted into amino-oxindole, and this on 
 oxidation with ferric chloride yields isatin. 
 
 (c) Sandmeyer has worked out the following synthesis: 
 Aniline and carbon disulphide readily yield thio-carbanilide, 
 CS(NHC 6 H 5 } 2 , which, on boiling with potassium cyanide, 
 white-lead, and water, yields hydrocyano-carbo-diphenyl- 
 imide, C 6 H 5 N:C(CN).NHC 6 H 5 . With ammonium sulphide 
 
 this latter yields ^\ C |>C.NHC 6 H 5 , which is con- 
 verted by concentrated sulphuric acid into a-isatin-anilide, 
 C 6 H 4 <^jr ^C'NHC 6 H 5 , and this may be hydrolysed by dilute 
 
 acids to isatin and aniline (C.C. 1900, 2, 928). 
 
 (d) 0-Nitrophenyl-propiolic acid (p. 456) may be synthesised, 
 and when this is warmed with alkalis it undergoes molecular 
 rearrangement and yields isatogenic acid, which by elimi- 
 nation of carbon dioxide forms isatin: 
 
 Isatin crystallizes in reddish-yellow monoclinic prisms, which 
 are only sparingly soluble in cold water, but more readily in 
 hot water and in alcohol to a brownish-red solution. It dis- 
 solves in potassium hydroxide solution, yielding the potassium 
 
 derivative, C 6 H 4 <^ = ^>COK, which is readily hydrolysed to 
 potassium 0-amino-phenyl-glyoxylate when boiled with water. 
 
 /~^{~\ 
 
 Isatin chloride, C 6 H 4 <^;^C.C1, is obtained when isatin is 
 
 heated with phosphorus pentachloride, and on reduction with 
 zinc dust and acetic acid yields indigo. 
 Two isomeric methyl ethers are known : 
 
 and 
 
 O-methyl isatin N-methyl isatin or pseudo-methyl isatin. 
 
 The O-ether is obtained by converting the potassic-isatin 
 into the silver compound, and then heating this with methyl 
 
INDIGO 525 
 
 iodiae. It is a colourless solid melting at 102, and on 
 hydrolysis yields isatin or o-amino-phenyl-glyoxylic acid. 
 
 The N-ether may be obtained by the action of sodic hypo- 
 bromite on N-methyl-indole. Its constitution follows from 
 its method of formation, and also from the fact that on 
 hydrolysis it yields o - methyl amino - phenyl- glyoxy lie acid, 
 T /CO.CO 2 H 
 
 The constitution of isatin itself for some years was a matter 
 of dispute; from its method of formation it must be either the 
 lactam or lactim of o-amino-phenyl-glyoxylic acid. Certain 
 of its methods of formation and of its reactions, e.g. with 
 alkalis or phosphorus pentachloride, point to the lactim for- 
 mula, whereas others would indicate the lactam constitution 
 isatin is thus a typical tautomeric compound. Hartley and 
 Dobbie (J. C. S. 1899, 647) assign to it the lactam constitution. 
 The ultra-violet absorption of alcoholic solutions of isatin is 
 almost identical with that of the N-methyl ether, and quite 
 different from that of the 0-methyl ether, and hence the 
 N-methyl ether and the parent substance have similar formulae. 
 Isatin is thus a pseudo-acid, since the hydrogen compound 
 
 itself is the ketonic substance, C 6 H 4 <^p,Q^>COj but its sodic 
 
 derivative is the enolic compound, 
 
 INDIGO AND RELATED COMPOUNDS 
 Indole or benzo-pyrrole 
 
 Indoxyl or hydroxy-indole 
 
 Oxindole or o-amino-phenyl-aceticl n -rr /OH 
 acid lactam .......... . ..... ' .......... / C H 4\NB 
 
 Dioxindole or o - amino - mandelic 
 
 acid lactam 
 Isatin or o-amino-phenyl-glyoxylicl ~ ,-,. / CO \nr& 
 
 acid lactam ..... _...L:......:..../ C H *\NH/ 
 
 Indigo ..................................... C 6 H 4 <^>C:C<^>C 6 H 4 . 
 
 Indigo, which is obtained from the indigo plant (Indigofera 
 tinctoria), and from woad (Isatis tindoria), has been known 
 for thousands of years as a valuable blue dye, especially for 
 woollen fabrics. In addition to indigo -blue (indigotin), 
 
526 XXXV. CONDENSED BENZENE, FURANE, ETC. RINGS 
 
 commercial indigo contains indigo-gelatine, indigo-brown, and 
 indigo-red, all of which can be extracted from it by solvents. 
 The colouring matter is not present as such in the indigo plant, 
 but as the glucoside of indoxyl " Indican ", from which it can 
 be prepared either by dilute acids or certain enzymes and sub- 
 sequent oxidation with atmospheric oxygen. 
 
 It forms a dark-blue coppery and shimmering powder or, 
 after sublimation, copper-red prisms, insoluble in most solvents 
 (including the alkalis and dilute acids), but dissolving to a 
 blue solution in hot aniline and to a red one in paraffin, from 
 either of which it may be crystallized. Its vapour is dark-red. 
 The formula C 16 H 10 2 N 2 is confirmed by its vapour density. 
 It is converted by reducing agents, such as ferrous sulphate 
 and caustic soda solution or grape-sugar and soda, into the 
 leuco-compound, indigo-white, C 16 H 12 2 N 2 , a white crystalline 
 powder soluble in alcohol and ether, also in alkalis (as a 
 phenol); the alkaline solution quickly becomes oxidized by 
 the oxygen of the air, with the separation of a blue film of 
 indigo. It yields an acetyl compound which crystallizes in 
 colourless needles. 
 
 Warm concentrated or fuming sulphuric acid dissolves 
 indigo to indigo -monosulphonic and disulphonic acids, the 
 former of which (termed phoenicin-sulphonic acid) is sparingly 
 soluble in water, but the latter readily so; the sodium di- 
 sulphonate is the indigo-carmine of commerce. Nitric acid 
 oxidizes indigo to isatin, while distillation with potash yields 
 aniline, and heating with manganese dioxide and a solution of 
 potash, anthranilic acid. 
 
 Indigo has been prepared synthetically by numerous 
 methods. The following are among the most important: 
 
 1. By the reduction of isatin chloride with zinc dust and 
 acetic acid: 
 
 The syntheses of isatin already described (pp. 523 and 554) 
 are thus syntheses of indigo. 
 
 2. By warming o-nitro-phenyl-propiolic acid with grape-sugar 
 in alkaline solution (Baeyer, 1880): 
 
 2N0 2 .C 6 H 4 C:C.C0 2 H + 4H = C 1G H 10 N 2 O 2 + 2CO 2 + 2H 2 O. 
 
 3. Baeyer and Drewson (1882) started with toluene, and on 
 nitration obtained a mixture of o- and j?-mtro-toluenes, The 
 
INDIGO 527 
 
 0-compound was oxidized by manganese dioxide and sulphuric 
 acid to 0-nitro-benzaldehyde, and this was then condensed 
 with acetone, yielding o-nitro-phenyl-lactyl methyl ketone, 
 
 NO 2 C 6 H 4 CH(OH) CH 2 . CO CH 3 ; 
 
 which when warmed with alkalis gave indigo and water. The 
 yield was good, but the method was of no great practical 
 importance, as the amount of toluene is limited, and no use 
 could be found for the ^?-nitro-toluene obtained as a by-pro- 
 duct. 
 
 4. In 1890 Neumann obtained phenyl-glycocoll by the 
 condensation of aniline with chloracetic acid: 
 
 C 6 H 5 .NH.CH 2 .CO 2 H, 
 
 and when this was fused with alkali, indigo-white was obtained. 
 
 A modified form of Heumann's synthesis consists in con- 
 densing anthranilic acid (p. 452) with chloracetic acid, when 
 phenyl-glycocoll-o-carboxylic acid is obtained, and this on 
 fusion with alkali yields indoxyl, which oxidizes in the air 
 to indigo-blue. The yield is good, and this method is now 
 employed on a manufacturing scale by the "Badische Anilin 
 Fabrik" for the production of artificial indigo, as anthranilic 
 acid can be obtained cheaply; the general method being the 
 oxidation of naphthalene by mercury and sulphuric acid to 
 phthalic acid, the conversion of this into phthalic anhydride, 
 and then into phthalimide by the aid of ammonia. The 
 phthalimide with alkali and chlorine yields anthranilic acid 
 o-amino-benzoic acid (Hofmann reaction, p. 184). 
 
 Homologues of indigo are produced in an analogous manner, 
 and its sulpho-acids by the action of fuming sulphuric acid 
 upon phenyl-glycocoll. 
 
 Indigo-blue is one of the best of the blue dyes, on account 
 of its " fastness " to light, alkalis, acids, and soaps. As indigo- 
 blue itself is insoluble, its " leuco " compound indigo-white is 
 usually employed, the fabric being immersed in an alkaline 
 solution of this, and then exposed to the air, when oxidation 
 to indigo-blue takes place. Indigo-blue is usually reduced to 
 indigo-white by means of calcium hyposulphite. The indigo- 
 white is a colourless solid with phenolic properties, and probably 
 has the constitution represented by the formula 
 
528 XXXVI. PYRAZOLE GROUP 
 
 Iiidirubin, Indigo-purpurin, is an isomeride of indigo-blue, 
 and can be obtained synthetically by the condensation of 
 isatin and indoxyl in alkaline alcoholic solution: 
 
 It is also obtained, together with indigo-blue, by the reduc- 
 tion of isatin chloride. It crystallizes from aniline in chocolate- 
 brown needles, and on oxidation yields isatin. 
 
 (For history and manufacture of indigo, see /. Ind. 1901, 
 239, 332, 551, 802; J. C. S. 1905, 974.) 
 
 XXXVI. PYKAZOLE GROUP, ETC. 
 1. PYRAZOLE GROUP 
 
 This comprises compounds with a five-membered ring contain- 
 ing three carbon and two nitrogen, sulphur, or oxygen atoms. 
 Pyrazole, aCH-N-v 
 
 2 >NH, 
 
 *CH:< 
 
 5 
 
 is theoretically derivable from pyrrole in the same way aa 
 pyridine is from benzene, i.e. by the exchange of CH for N. 
 
 The positions three and five appear to be identical unless 
 the H of the NH is replaced by alkyl groups. 
 
 It is a weak base of great stability, crystallizing in colour- 
 less needles; it melts at 70, boils at 185, and possesses aro- 
 matic properties (B. 1895, 28, 714). Its simplest synthesis is 
 by the union of acetylene and diazo-methane: 
 
 HO CHf HC:CH 
 
 (Van, Pechmann, B. 1897, 31, 2950). (For other syntheses, 
 see B. 23, 1103; A. 273, 214.) 
 
 Pyrazoline, C 3 H 6 N 2 , and pyrazolidine, CgHgNg, are derived 
 theoretically from pyrazole by the addition of hydrogen. By 
 the exchange of two atoms of hydrogen for one. of oxygen, the 
 formula of pyrazole changes into that of pyrazolone, 
 
 CH : 
 
THIAZOLE 529 
 
 (an oil, b.-pt. 77; see B, 25, 3441), and by the entrance of 
 phenyl and methyl into this latter we get: 
 
 l-Phenyl-3-methyl-pyrazolone, which is obtained by the 
 action of phenylhydrazine on ethyl acetoacetate (p. 230): 
 
 CH,.CO H 2 N CH S .C:N 
 
 CH,COOEt + NHPh= 
 
 This crystallizes in compact prisms, melts at 127, and boils 
 without decomposition. As a weak base it dissolves in acids, 
 and is also soluble in alkalis; it further contains the chemi- 
 cally-active methylene group. When it is heated with methyl 
 iodide and methyl alcohol it yields : 
 
 l-Phenyl-2:3-dimethyl-pyrazolone or antipyrine, C n H 12 N 2 O, 
 which is also produced by the action of ethyl acetoacetate upon 
 methyl-phenyl-hydrazine, and which therefore possesses the 
 constitutional formula (L. Knorr, A. 238, 137), 
 
 CMe-NMex 
 
 L : ., cH_co> ph - (^ 
 
 It crystallizes in small colourless plates melting at 113. The 
 aqueous solution is coloured red by ferric chloride and blue- 
 green by nitrous acid. Antipyrine is an excellent febrifuge. 
 /3-Ketonic acids, /?-ketonic aldehydes, /3-diketones also yield 
 pyrazole derivatives with phenyl-hydrazine. 
 
 Isomeric with pyrazole is glyoxaline (p. 530), in which the 
 two atoms of N are separated by a C atom. 
 
 2. THIAZOLE GEOUP 
 Thiazole, 
 
 is derived from thiophene in the same way as pyridine is from 
 benzene, by the exchange of CH for N, and closely resembles 
 along with its derivatives the bases of the pyridine series 
 in properties. It is obtained from amino-thiazole (see below) 
 by the exchange of the amino-group for hydrogen, in a similar 
 manner to the conversion of aniline into benzene. It is a 
 colourless liquid, boiling at 117, hardly distinguishable from 
 pyridine; as a base it forms salts, but it is scarcely affected by 
 concentrated sulphuric acid, &c. (Hantzsch, Popp, A. 250, 273). 
 
 (B480) 2L 
 
530 XXXVI. PYRAZOLE GROUP 
 
 Amino-tMazole, 
 
 is formed by the action of mono-chloraldehyde upon thio-urea 
 (pseudo form), thus: 
 
 The constitution of the thiazoles follows from this and similar 
 modes of formation. Amino-thiazole is a base of perfect 
 " aromatic " character, like that of aniline. (Cf. Rantzsch and 
 his pupils, A. 249, 1, 7, 31; 250, 257; 265, 108.) 
 
 As further types of five-membered rings, may be cited : 
 
 CH.N 
 
 Imidazole or glyoxalin Oxazole, 
 
 which are related to thiazole as pyrrole and furane are tc 
 thiophene. 
 
 Triazole, NH, and tetrazole, 
 
 are examples of five-membered rings extremely rich in nitro- 
 gen. (Cf. B. 25, 225, 1411; 26, 2392.) 
 
 The foregoing constitutional formula with their double 
 linkings correspond with KekuU's benzene formula. But for- 
 mulse with diagonal (centric) linkings analogous to the centric 
 benzene formula (p. 334) have been introduced recently. (Cf. 
 Bamberger, B. 24, 1758; A. 273, 373; also A. 249, 1; 262, 265; 
 B. 21, Ref. 888; 24, 3485; 27, 3077; 28, 1501.) 
 
 XXXVII. SIX-MEMBERED HETEROCYCLIC RINGS 
 
 Ring compounds closely related to pyrrole, thiophene, and 
 furane, but containing six atoms in the ring (viz. five carbon 
 atoms + ne x yg en > sulphur, or nitrogen atom), are known. 
 
 The representatives of these are : 8 - valerolactone, 
 
 glutaric anhydride, 
 
y-PYRONE 531 
 
 (p. 240), and more especially the pyrones, e.t\ y-pyrone, 
 
 Of the nitrogen compounds, pyridine, 
 
 and piperidine, CH 2 <^QTT 2 "pTT 2 ^>NH, are of great importance. 
 The derivatives of the sulphur compound, penthiophene, 
 
 ^^CH'CHX^' are ^ ^ ut ^^ e i m P rtance - 
 Six-membered rings containing two nitrogen atoms are 
 the diazines, C 4 H 4 N 2 , the ortho compound is.pyjidazine, the 
 meta pyrimidine, and the para pyrazine. The compound, 
 
 is morpholin. Six-membered rings con- 
 
 fining three and four nitrogen atoms are termed respectively 
 triazines and tetrazines. (Of. triazole and tetrazole, p. 530.) 
 
 A. Pyrones 
 
 y-Pyrone, a solid, m.-pt. 32-5 and b.-pt. 315, is ob- 
 tained when its dicarboxylic acid, chelidonic acid (p. 533), is 
 
 heated, aa-dimethyl-y-pyrone, C0< ! ^' may be syn " 
 
 thesised from cupric ethyl aceto-acetate and carbonyl chloride. 
 
 (C0 2 Et).CO.CH 3 
 
 p 
 Uu CH(C0 2 Et).CO.CH 
 
 On hydrolysis with sulphuric acid the ester yields the free 
 acid, which loses carbon dioxide, yielding: 
 
 CO.CH S or xCH:C(OH)C 
 
 which immediately loses water, yielding dimethyl-y-pyrone : 
 
 (For a modified formula, see Collie, J. C. S. 1904, 971.) 
 Collie and Tidde (J. C. S. 1899, 710) have shown that this com- 
 pound can form definite salts with acids, e.g. the hydrochloride, 
 C 7 H 8 O 2 , HC1, and oxalate. The addition of the acid un- 
 doubtedly occurs at the oxygen atom, since the salts are 
 relatively unstable and are completely hydrolysed in dilute 
 aqueous solution. The oxygen atom in these salts, therefore, 
 
532 XXXVII. SIX-MEMBERED HETEROCYCLIC RINGS 
 
 probably functionates as a tetravalent atom, [oXKci 1 and 
 the salts are termed oxonium salts on account of their simi- 
 larity to ammonium salts. Numerous other compounds have 
 since been obtained, which tend to show that the oxygen 
 atom can frequently functionate in this manner, e.g. numerous 
 oxygen compounds, esters, ethers, ketones, acids, aldehydes 
 yield definite crystalline compounds with anhydrous metallic 
 salts, e.g. MgBr 2 or A1C1 8 (Walker, J. C. S. 1904, 1106; similar 
 oxygen compounds also form well-defined crystalline salts with 
 complex acids, e.g. ferrocyanic acid (Baeyer and Villiger, B. 
 1901, 34, 2679, 3612; 1902, 35, 1201); and lastly, the addi- 
 tive compound of organo-magnesium derivatives with ether 
 
 are probably of the type, c*ip>0<f gCHs . Solutions of the 
 
 oxonium salts have exactly the properties we should expect. 
 Since the salt is derived from a very feeble base (solutions 
 of dimethyl-pyrone are very feeble conductors) and a rela- 
 tively strong acid, the solution should be highly hydrolysed, 
 and should give a strongly acid reaction. That the hy- 
 drolysis is not complete in the case of a moderately con- 
 centrated solution of the picrate has been shown by WHlden 
 (B. 1901, 34, 4191), who compared the partition coefficient of 
 picric acid between water and benzene both with and without 
 the addition of dimethyl-pyrone, and found that the ratio 
 concentration of benzene solution ^ less when ^ is 
 
 concentration of aqueous solution 
 present. 
 
 Other methods which have also led to the conclusion that 
 a certain amount of salt exists in solution are (a) depression of 
 the freezing-point of aqueous solutions. If no compound exists 
 in an aqueous hydrochloric acid solution, then the depression 
 caused would be the sum of the depressions produced by the 
 known amounts of dimethyl-pyrone and hydrochloric acid 
 present. The actual value obtained is less than this sum 
 (Walderi). (b) A determination of the electrical conductivity. 
 If no compound is formed, the conductivity should be the same 
 as the conductivity of a solution of pure hydrochloric acid of 
 the same concentration; but if any appreciable amount of a salt 
 is formed in solution this will give rise to a certain number of 
 
 C r H 8 O 2 H and Cl, i.e. the number of hydrions will be less 
 than in a solution of pure hydrochloric acid of the same 
 
PYRIDINE 533 
 
 concentration, and hence the electrical conductivity will be 
 considerably reduced. It has actually been found that the 
 conductivity is less, and that it tends to decrease as the solution 
 becomes more concentrated. 
 
 y-Pyrone-dicarboxylic acid, or chelidonic acid, occurs in the 
 greater celandine (Chelidonium majvs), and may be synthesised 
 by Claisen's method (p. 224). Acetone and ethyl oxalate readily 
 condense, yielding the ester of acetone-dioxalic acid or xantho- 
 chelidonic acid : 
 
 XCH 3 , C0 2 Et-C0 2 Et _ m /CH:C(C0 2 Et)OH 
 C0 2 Et . C0 2 Et - CU \CH : C(CO 2 Et)OH 
 
 which immediately loses water, yielding ethyl chelidonate, and 
 this on careful hydrolysis yields chelidonic acid : 
 
 The salts of this acid are colourless, but when it is warmed 
 with an excess of alkali yellow salts of xantho-chelidonic acid 
 are formed, thus indicating the readiness with which the ring 
 is ruptured. 
 
 B. Pyridine 
 
 Pyridine, C 5 H 5 N, may be compared with benzene in many 
 points : 
 
 1. It is even more stable than benzene, and does not yield 
 substituted derivatives so readily with such reagents as sul- 
 phuric and nitric acids or the halogens. Sulphonic acids are 
 obtained at very high temperatures only; nitro-pyridines are 
 as yet unknown, as are also iodo-pyridines ; while chloro- and 
 bromo-pyridines have so far only been prepared in small num- 
 ber. Neither pyridine nor its carboxylic acids are affected by 
 nitric acid, chromic acid, or permanganate of potash. 
 
 2. The behaviour of its derivatives is on the whole very like 
 that of the derivatives of benzene. Thus its homologues (and 
 also quinoline, &c.) are transformed into pyridine-carboxylic 
 acids when oxidized, and these acids yield pyridine when dis- 
 tilled with lime, just as benzoic acid yields benzene. 
 
 3. The isomeric relations are also precisely analogous to those 
 of the benzene derivatives. Thus the number of the isomeric 
 mono-derivatives of pyridine is the same as that of the isomeric 
 bi-derivatives of benzene, viz., three; and the number of the 
 bi-derivatives of pyridine, containing the same substituents, the 
 same as that of the benzene derivatives C 6 H 3 XXX', viz., six. 
 
534 XXXVII. SIX-MEMBERED HETEROCYCLIC RINGS 
 
 4. Just as two benzene nuclei can form naphthalene, so can 
 a benzene and a pyridine form the compound quinoline : 
 
 N. 
 
 5. The products of reduction are likewise analogous. Pyri- 
 dine like benzene yields a hexahydro-derivative, C 5 H n N, only 
 somewhat more readily; this is known as piperidine. Quino- 
 line yields a tetrahydro-derivative, C 9 H n N, more readily than 
 naphthalene, and acridine readily yields a dihydro-derivative, 
 C 13 H n N", which is analogous to anthracene dihydride. In these 
 latter compounds further combination with hydrogen may take 
 place, but there is likewise a tendency to the reproduction of 
 the original bases. 
 
 We are therefore forced to the conclusion that pyridine has 
 a ring constitution similar to that of benzene, and is to be 
 represented as: 
 
 CH CH 
 
 HC 
 
 CH 
 
 HC 
 
 ^& 
 
 N N 
 
 In contradistinction to the neutral benzene hydrocarbons, 
 pyridine and its homologues are strong bases, most of them 
 having a pungent odour; pyridine is readily soluble in water, 
 but quinoline only slightly so. They distil or sublime with- 
 out decomposition, and form salts; those with hydrochloric 
 and sulphuric acids are for the most part readily soluble, 
 while those with chromic acid or hydro -ferrocyanic acid, 
 though often characteristic, are usually only sparingly soluble ; 
 they also form double salts with the chlorides of platinum, 
 gold, and mercury, most of which are sparingly soluble, e.g. 
 (C 5 H 5 N) 2 H 2 PtCl 6 . 
 
 The bases are tertiary, and hence cannot be acetylated; 
 they combine, however, with alkyl iodides, yielding quater- 
 nary ammonium salts, e.g. pyridine and methyl iodide yield 
 C 5 H 5 N, CH 3 I, methyl-pyridonium iodide. 
 
 Pyridine and some of its homologues are present in coal-tar, 
 and are therefore constituents of the lower boiling fractions. 
 They may be extracted from these by shaking with dilute 
 
SYNTHESES OF PYRIDINE DERIVATIVES 535 
 
 sulphuric acid, in which they dissolve. It is also present in 
 tobacco smoke. A number of pyridine bases are present in 
 bone-oil or Dippel's oil, a product obtained by fee dry distil- 
 lation of bones from which the fat has not been extracted. 
 
 Mixtures of pyridine bases can readily be obtained from 
 this source. Certain alkaloids 4Hfc^ 7) yield pyridine or its 
 derivatives when distilled alone^r with alkalis, e.g. chincho- 
 nine when distilled with potash yields a dimethyl-pyridine 
 or lutidine. Pure pyridine may be obtained by distilling its 
 carboxylic acid with lime. 
 
 Among the more interesting methods by means of which 
 pyridine and its derivatives have been synthesised are the 
 following : 
 
 1. When pentamethylene-diamine hydrochloride is strongly 
 heated it yields piperidine, and when this is oxidized with 
 concentrated sulphuric acid at 300 pyridine is formed (Laden- 
 burg): 
 
 CH 2 
 
 2 . |NH 2 
 
 A method very similar to this, which can be employed at 
 much lower temperatures, is the elimination of hydrogen 
 chloride from 5-chloroamylamine, CH 2 C1'(CH 2 ) 3 'CH 2 NH 2 . 
 This elimination occurs when an aqueous solution of the base 
 is heated on the water-bath; ring formation takes place, and 
 piperidine hydrochloride is formed (Gabriel). These two 
 methods are of great importance in deciding the constitution 
 of piperidine, and therefore indirectly that of pyridine. 
 
 2. The ammonia derivatives of various unsaturated aldehydes 
 yield pyridine homologues when distilled (p. 130), e.g. /3-methyl- 
 pyridine is obtained from acrolein ammonia, and collidine from 
 croton-aldehyde ammonia (Baeyer, A. 155, 283, 297). 
 
 3. When ethyl acetoacetate is warmed with aldehyde-am- 
 monia, the ester of " Dihydro-collidine-dicarboxylic acid", ie. 
 ethyl trimethyl-dihydro-pyridine-dicarboxylate is produced 
 (Hantzsch) (cf. p. 230): 
 
 CO 2 Et-CH 2 O-CHMe CH 2 .CO 2 Et 
 
 MeCO " NH 3 "^COMe 
 
 C0 2 Et - C CHMe C - CO 2 Et 
 
 ~~ 3H2 + CMe-NH.MeC 
 
636 XXXVII. SIX-MEMBEREt) IIETEfcOCYCLIC RINGS 
 
 This loses its two "hydro "-hydrogen atoms when acted 
 on by nitrous acid, and yields ethyl collidine-dicarboxylate, 
 C 5 N(CH 3 ) 3 (C0 2 Et) 2 , from which collidine may be obtained by 
 hydrolysis and elimination of carbon dioxide. 
 
 If, instead of aldehyde-ammonia, the ammonia compounds 
 of other aldehydes are uitf& homologous bases of the type 
 C 5 H 2 N(CH 3 ) 2 (C n H 2ntl ) are~rmed. 
 
 In the above reaction a molecule of the acetoacetic ester may 
 be replaced by one of an aldehyde, when the mono-carboxylic 
 esters of dialkylated pyridines are formed, thus : 
 
 C 6 H 10 O 3 + 2CH 3 .CHO + NH 3 = C 6 H 2 NH 2 (CH 3 ) 2 .C0 2 Et -f 3H 2 O. 
 
 This is a very important synthetical method (Hantzsch, 
 A. 215, 1, &c.). 
 
 Two methods of obtaining pyridine derivatives, which indi- 
 cate the relationship of pyridine to quinoline and pyrrole, are : 
 
 (a) The conversion of quinoline into quinolinic acid or pyri- 
 dine a/3-dicarboxylic acid (p. 544). 
 
 (b) The conversion of potassium-pyrrole into chloro-pyridine 
 when heated with chloroform, or into pyridine when heated 
 with methylene-chloride: 
 
 CH:CH\ CHiCH-N CH:CH.N 
 
 CH:CH/ CH-.CH-CCl r CH:CH.CH 
 
 Not merely is the ring constitutional formula (p. 534) in 
 perfect harmony with the characteristic properties of pyridine 
 and its derivatives, and also with certain of the synthetical 
 methods of formation, but this formula receives additional 
 support from a study of the number of isomeric forms in 
 which pyridine derivatives occur. 
 
 Three isomeric mono- substituted derivatives of pyridine 
 are known in each case. They are designated as a-, /?-, and 
 y-derivatives of pyridine, as is shown in the following graphic 
 formula : 
 
 or as 2-, 3-, or 4-derivatives according to the numbering 
 p. 534. 
 
 on 
 
PYRIDINE 537 
 
 In order to determine the position of any given group, it is 
 sought to exchange it for carboxyl; should picolinic acid result, 
 the group occupies the a-position, and should nicotinic or iso- 
 nicotinic, then it fills the fi- or y-position respectively, since 
 in these acids the a-, /?-, and y-positions of the carboxyl have 
 been determined by special means. (See M. 1, 800; 4, 436, 
 453, 595; B. 17, 1518; 18, 2967; 19, 2432.) 
 
 Di-derivatives of pyridine containing the same substituent 
 twice can exist theoretically in six isomeric forms. As a 
 matter of fact the six dicarboxylic acids are known (aa -, a/3-, 
 ay-, ap- t /?y-, and ftp- (see p. 538). 
 
 The isomerism of picoline, C 6 H^N, with aniline, C 6 H 5 NH 2 , 
 which repeats itself in their homologues, is also worthy of 
 notice. 
 
 Pyridine, C 5 H 5 N (Anderson, 1851), may be prepared from 
 bone-oil, and can be obtained pure by heating its carboxylic 
 acid with lime; the ferrocyanide is especially applicable for 
 its purification, on account of its sparing solubility in cold 
 water. It is also found in the ammonia of commerce. 
 Pyridine is a liquid of very characteristic odour, miscible 
 with water, and boiling at 115. It is used as a remedy for 
 asthma, and also in Germany for mixing with spirit of wine 
 in order to render the latter duty-free. When sodium is 
 added to its hot alcoholic solution, or when solutions of its 
 salts are electrolysed, hydrogen is taken up and piperidine, 
 CglLjN, formed (Ladenburg and Both, B. 17, 513). 
 
 When heated strongly with hydriodic acid, pyridine is 
 converted into normal pentane. 
 
 The ammonium iodides, e.g. C 5 H 5 N, CH 3 I, give a character- 
 istic pungent odour when heated with potash, a fact which 
 may be made use of as a test for pyridine bases; it depends 
 upon the formation of alkylated dihydro-pyridines, e.g. di- 
 hydro-methyl-pyridine, C 5 H 6 .N(CH 3 ) (Hofmann, B. 14, 1497). 
 
 Pyridine is polymerized by the action of metallic sodium 
 to dipyridine, C 10 H 10 N 2 (an oil, b.-pt. 286-290), with the 
 simultaneous production of ^-dipyridyl, C 5 H 4 N C 5 H 4 N (long 
 needles, m.-pt. 114), a compound corresponding to diphenyl 
 (p. 471); both of these yield iso-nicotinic acid when oxidized. 
 An isomeric m-dipyridyl has also been prepared, which gives 
 nicotinic acid when oxidized. 
 
 Pyridine can be brominated but not nitrated; it can also be 
 sulphonated with the formation of /2-pyridine-sulphonic acid, 
 C & H 4 N (S0 3 H), which with potassium cyanide yields /?-cyano- 
 
638 XXXVII. SIX-MEMBERED HETEROCYCLIC RINGS 
 
 pyridine, C 5 H 4 N-CN, or by fusion with potash, fthydroxy- 
 pyridine. 
 
 The three hydroxy-pyridines, C 5 H 4 N(OH) (a-, ft, y-), are 
 best prepared by the elimination of carbon dioxide from the 
 respective hydroxy-pyridine-carboxylic acids. The melting- 
 points are respectively: a, 107; ft 124; y, 148. They pos- 
 sess the character of phenols, and are coloured red or yellow by 
 ferric chloride. As in the case of phloroglucinol, so here also 
 there is a tertiary as well as a secondary form to be taken 
 into account, the former reminding one of the lactams and the 
 latter of the lactims; for instance, y-hydroxy-pyridine may 
 
 either have the "phenol" formula C 2 H 2 <C 2 H 2 or the 
 
 p*o 
 "pyridone" formula C 2 H 2 <^jj^>C 2 H 2 , the latter of the two 
 
 representing a keto-dihydro-pyridine. The two methyl ethers, 
 methoxy- pyridine and methyl -pyridone, which result from 
 these two forms by the exchange of H (of the OH or NH 
 respectively) for CH 3 , are both known, and differ considerably 
 in properties (M. 6, 307, 320; B. 24, 3144). 
 
 Homologues of Pyridine (cf. Ladenburg, A. 247, 1). 
 Methyl-pyridines or picolines, C 5 H 4 N(CH 3 ). All the three 
 picolines are contained in bone-oil, and probably also in coal- 
 tar. The ftcompound is obtained from acrolein-ammonia 
 (p. 130), and also when strychnine is heated with lime, or 
 when trimethylene-diamine hydrochloride is distilled. They 
 are liquids of unpleasant, piercing odour resembling that of 
 pyridine, and they yield a-, ft, or y-pyridine-carboxylic acid 
 when oxidized. The boiling-points are: a, 129; ft 142, 
 y, 142-144. 
 
 Ethyl-pyridines, C 5 H 4 N(C 2 H 5 ), are also known. 
 
 Propyl- and isopropyl pyridines, C 5 H 4 N(C 3 H 7 ), have been 
 carefully investigated on account of their relation to coniine. 
 They are prepared by heating pyridine with the alkyl iodides. 
 Conyrine, C 8 H n N (liquid, b.-pt. 166-168), which is formed 
 when coniine, CgH^N, is heated with zinc dust, and which 
 yields coniine again when treated with hydriodic acid, is 
 a-normal-propyl-pyridine. 
 
 a-Allyl-pyridine, C 5 H 4 N(C 3 H 5 ), is produced when a-picolino 
 is heated with aldehyde : 
 
 C 6 H 4 N.CH 3 4-OHC-CH 3 = C 6 H 4 N.CH:CH.CH 3 + H 2 O. 
 
 Reduction transforms it into inactive coniine (b.-pt. 189-190 ). 
 
PYRIDINE CARBOXYLIC ACIDS 539 
 
 Bimethyl-pyridines or Lutidines, C 5 H 3 N(CH 3 ) 2 . The pre- 
 sence of three lutidines has been proved in bone-oil and coal- 
 tar (B. 21, 1006; 29, 2996). ay-Lutidine boils at 157, the 
 aa'-compound at 142, and the /ty-compound at 164. 
 
 The trimethyl-pyridines or collidines, C 5 H 2 N(CH 3 ) 3 , are 
 isomeric with the propyl-pyridines. Some of them are pre- 
 sent in bone-oil, and can be prepared from cinchonine by dis- 
 tilling the latter with caustic potash (p. 560). The aa'y-colli- 
 dirie, which is obtained from the condensation product of 
 ethyl acetoacetate and aldehyde ammonia (p. 230), boils at 
 171-172. 
 
 Pyridine-carboxylic Acids (Weber, A. 1887, 241, 1). The 
 pyridine-mono-carboxylic acids, C 5 H 4 N(C0 2 H), are formed 
 by the oxidation of all mono-alkyl derivatives of pyridine, 
 i.e. from methyl-, propyl-, phenyl-, &c., pyridines; also from 
 the pyridine-dicarboxylic acids by the decomposition of one of 
 the carboxyl groups, just as benzoic may be got from phthalic 
 acid. The carboxyl which is in closest proximity to the nitro- 
 gen is the first to be eliminated. Nicotinic acid is also pro- 
 duced by the oxidation of nicotine. The acids unite in them- 
 selves the characters of the basic pyridine and of an acid, and 
 are therefore comparable with glycocoll. They yield salts with 
 HC1, &c., and double salts with HgCl 2 , PtCl 4 , &c.; on the other 
 hand, they form metallic salts as acids, those with copper being 
 frequently made use of for the separation of the acids. 
 
 (For constitution, see Skraup and Colenzl, M. 1883, 4, 436.) 
 
 The a-acid is picolinic acid, and forms needles melting at 
 135. 
 
 The /?-acid is nicotinic acid, and melts at 231. 
 
 The y-acid is iso-nicotinic acid, and melts at 309 in a sealed 
 tube. 
 
 It is noteworthy that all three acids (and also the /3y-dicar- 
 boxylic acid) readily yield up their nitrogen as ammonia when 
 acted upon by sodium amalgam, being thereby transformed 
 into unsaturated acids of the fatty series (Weidel, M. 1890, 
 11, 501). 
 
 The constitution of nicotinic acid follows from its relation- 
 ship to quinoline. Quinoline on oxidation yields pyridine 
 a/2-dicarboxylic acid, the constitution of which follows from 
 the constitution of quinoline. When heated, the dibasic acid 
 loses carbon dioxide, yielding a monobasic acid which is not 
 identical with picolinic acid (which can be shown to be the 
 a-acid), and therefore it must be pyridine /2-carboxylic acid. 
 
540 XXXVII. SIX-MEMBERED HETEROCYCLIC RINGS 
 
 Pyridine-dicarboxylic acids, C 5 H 3 N(C02H)2 
 
 a-j8- = Quinolinic acid M.-pt. 190. 
 
 0-7- = Lutidinic acid M.-pt. 235. 
 
 a-a'- = Dipicolinic acid M.-pt. 226. 
 
 a-j3'- = Iso-cinchomeronic acid M.-pt. 236. 
 
 /S-j8'- = Dinicotinic acid. . . . .* M. -pt. 323. 
 
 (3-y- = Cinchomeronic acid M.-pt. 266. 
 
 Quinolinic acid, which crystallizes in short glistening prisms, 
 is the analogue of phthalic acid, and is obtained by the oxi- 
 dation of quinoline, just as phthalic acid from naphthalene; 
 cinchomeronic and iso-cinchomeronic acids are obtained by the 
 oxidation of cinchonine and quinine. 
 
 Hydro-pyridines. According to theory, hexa-, tetra-, and 
 dihydro-pyridines may exist. The first of these receive the 
 generic name of " piperidines ", e.g. pipecoline, C 5 H 10 N(CH 3 ), 
 lupetidine, C 5 H 9 N(CH 3 ) 2 , and copellidine, C 5 H 8 N(CH 3 ) 3 ; while 
 the tetrahydro-compounds are termed " piperideins ". 
 
 Piperidine, CgH^N (Werftitim, Eochleder, 1850), is a colour- 
 less liquid of peculiar odour, slightly resembling that of pepper, 
 and of strongly basic properties yielding crystalline salts. It 
 dissolves readily in water and alcohol, and boils at 106. 
 
 It occurs in pepper in combination with piperic acid, 
 C 12 H 10 4 (p. 464), in the form of the alkaloid piperine, 
 C 18 H] 8 N0 8 = C H 10 N C 12 H 9 3 , i.e. piperyl-piperidine, which 
 crystallizes in prisms, melting at 129 e ; from this latter it may 
 be prepared by boiling with alkali. 
 
 (For its formation from pyridine and from pentamethylene- 
 diamine, see pp. 196, 535, 537.) 
 
 Piperidine is a secondary amine; its imino-hydrogen is 
 replaceable by alkyl and acyl radicals. When its vapour, 
 mixed with that of alcohol, is led over zinc dust, homologous 
 (ethylated) piperidines are formed. 
 
 When methylated, piperidine yields, as a secondary base, in 
 the first instance, tertiary n-methyl-piperidine, CgHj N(CH 3 ), 
 and then with a further quantity of methyl iodide an ammo- 
 nium iodide, dimethylpiperidonium iodide. The correspond- 
 ing hydroxide does not decompose in the usual manner when 
 distilled, but yields water and an aliphatic base, "dimethyl- 
 piperidine", 7 H 16 N or CH 2 :CH.CH 2 -CH 2 .CH 2 .NMe 2 . 
 
 The latter forms* a quaternary iodide, the hydroxide of 
 which, when distilled, gives trimethylamine and piperylene, 
 CHMe:CH-CN:CH 2 (exhaustive methylation. For further 
 examples, see Chap, on Alkaloids). 
 
QUINOLINE AND ACRIDINE GROUPS 
 
 541 
 
 XXXVIII. QUINOLINE AND ACKIDINE GROUPS 
 
 A. Quinoline Group 
 
 The quinoline group comprises the compounds formed by 
 the condensation of a benzene nucleus with a heterocyclic six- 
 membered ring. The best-known examples are: 
 
 O 
 
 Chromone (benzene + pyrone rings), 
 
 Quinoline (benzene + pyridine), 
 
 Iso-quinoline (benzene + pyridine), 
 
 1. CHROMONE GROUP 
 
 Chromone, Chromone itself melts at 59 (Buhemann and 
 Stapletwi, J. C. S. 1900, 1185), and the phenyl derivative, 
 
 /O C-C 6 H 5 
 
 flavone, C 6 HX , is the parent substance of a 
 \OO GH 
 
 number of yellow dyes which occur in the vegetable kingdom. 
 Most of these dyes are hydroxylic derivatives of flavone, and 
 occur in nature in the form of glucosides. 
 
 As examples we have Chrysin (dihydroxy-flavone), Luteolin 
 (5:7:3':4'-tetrahydroxy-flavone, Kostanedi, Abstr. 1901, 1, 92, 
 335), Quercitin (3:5:7:3':4'-pentahydroxy-flavone, Herzig, M. 
 1885, 6, 872), Rhamnetin (3:5:3':4'-tetrahydroxy-7-methoxy- 
 flavone), and Rhamnazm (3:5:4'-trihydroxy-7:3'-dimethoxy- 
 flavone, Perkin and Allison, J. C. S. 1902, 469). 
 
642 XXXVIII. QUINOLINE AND ACRIDINE GROUPS 
 
 The constitution of these compounds is often arrived at 
 by an examination of the products formed by the action of 
 alcoholic potash on the compound, or, more readily, by aspi- 
 rating air through the dilute alkaline solution; under these 
 conditions rhamnetin yields protocatechuic acid, 3:4-dihydroxy- 
 benzoic acid (p. 459), and phloroglucinol monomethyl ether. 
 
 2. QUINOLINE AND ITS DERIVATIVES 
 
 Quinoline, 
 
 bears the same relationship to naphthalene that pyridine does 
 to benzene, its molecule consisting of condensed benzene and 
 pyridine nuclei. It occurs, together with derivatives, in both 
 coal-tar and bone-oil, and may be obtained by heating certain 
 alkaloids with potash, e.g. cinchonine yields quinoline itself 
 (Gerhardtj 1842), and quinine gives methoxy-quinoline. 
 
 Among the various syntheses of quinoline and its deriva- 
 tives the following may be noted: 
 
 1. The first synthesis, which was accomplished by Koenigs, 
 was by the oxidation of allyl-aniline by passing its vapour 
 over heated lead oxide: 
 
 C 6 H 6 .NH.CH 2 .CH:CH a + 20 = C^ + 2H/X 
 
 2. One of the usual methods employed for the preparation 
 of pure quinoline is by Skraup's synthesis (B. 14, 1002). In 
 this process aniline is heated with glycerol and sulphuric acid 
 in presence of nitro-benzene or arsenic acid : 
 
 OH.CH 2 .CH -OH 
 + CH 8 .OH 
 
 The nitro-benzene simply acts as an oxidizing agent. The 
 formation of acrolein as an intermediate product is to be 
 assumed here, the latter combining in the first instance with 
 aniline to acrolein-anilme, C 6 H 5 N : CH CH : CH 2 . The homo- 
 logues and analogues of aniline yield homologues and ana- 
 logues of quinoline by corresponding reactions; when naph- 
 thylamine is used, the more complicated naphtho-quinolines 
 are formed. 
 
SYNTHESES OF QUINOLINE DERIVATIVES 543 
 
 3. Baeyer and Drewson (B. 16, 2207) obtained quinoline by 
 the elimination of the elements of water from 0-amino-cinnamic 
 aldehyde : 
 
 ::CH-CHO _ /CH:CH 
 
 If 0-amino-cinnamic acid is used, carbostyril (a-hydroxy- 
 quinoline, p. 546) is obtained (Baeyer): 
 
 TFT 
 
 + H 2 0. 
 
 4. When aniline is heated with aldehyde (paraldehyde) and 
 hydrochloric acid, a-methyl-quinoline (quinaldine) is obtained 
 (Doebner and v. Miller). 
 
 In this reaction ethylidene-aniline is formed as an inter- 
 mediate product (B. 24, 1720; 25, 2072): 
 
 OCH.CH 3 
 
 Aniline Quinaldine. 
 
 Here, again, various other primary arylamines may be used 
 instead of aniline, and other aldehydes (B. 18, 3361) or ketones 
 (e.g. B. 19, 1394) instead of paraldehyde. 
 
 5. Aniline and acetoacetic acid combine together at tem- 
 peratures above 110 to aceto-acetanilide, CH 3 -CO .CHACO- 
 NS 'CgR^ from which y-methyl-a-hydroxy-quinoline ("methyl- 
 carbostyril ") is formed by the elimination of water (Knorr, A. 
 1886,236,75): 
 
 CH 3 CO OH 2 yv/^OJEijj) : OH 
 
 C 6 H 6 .NH-CO 6 4 \N = C-0 
 
 Aniline can also react with acetoacetic ester below 100, 
 yielding ethyl /2-phenyl-amino-crotonate, C 6 H 5 .NH.C(CH 3 ): 
 CH COgCgH*, which yields y-hydroxy-quinaldine when heated 
 (Conrad and Limpach, B. 20, 944): 
 
 C 2 H 6 O.CO.CH /C(OH):CH 
 
 C 6 H 5 .NH.C.CH 3 4 \N=C.CH 3 T 
 
 /3-Diketones and other compounds closely related to aceto- 
 acetic ester also condense with aniline. In place of /5-di- 
 ketones, mixtures of ketones and aldehydes, or mixtures of 
 aldehydes which would yield /3-diketones or /3-ketonic alde- 
 hydes if condensed together (C. Beyer, B. 20, 1767), can be 
 
544 XXXVIII. QUINOLINE AND ACRIDINE GROUPS 
 
 employed. With acetyl-acetone we obtain ay-dimethyl-quino- 
 line (B. 1899, 32, 3228): 
 
 These reactions are nearly allied to those already spoken of 
 under 4. 
 
 6. 0-Amino-benzaldehyde condenses with aldehydes and 
 ketones under the influence of dilute caustic soda solution, 
 yielding quinoline derivatives (Friedldnder, B. 15, 2574; 16, 
 1833; 25, 1752). With aldehyde quinoline itself results, and 
 with acetone quinaldine : 
 
 /CHO CH 2 .E 
 C H <NH 2 +CO.B< ! 
 
 Acetophenone, acetoacetic ester, malonic ester, diketones, 
 &c., also react in a similar way. 
 
 Constitution. The above modes of formation (especially 3 
 and 6) show that quinoline is an ortho-di-substituted-derivative 
 of benzene, and that it contains its nitrogen linked directly to 
 the benzene nucleus; they also show that the three carbon 
 atoms, which enter the complex, form a new hexagon (pyri- 
 dine) ring with this nitrogen and with two carbon atoms of 
 the benzene ring. The latter point also follows from the 
 oxidation of quinoline to pyridine-dicarboxylic acid (Hoogewerff 
 and van Dorp] : 
 
 Quinoline Quiuolinic acid. 
 
 We have thus the following constitutional formula: 
 
 N o N 
 
 according to which quinoline is constituted in a manner per- 
 fectly analogous to naphthalene, and may be regarded as 
 derived from the latter by the exchange of CH for N, or as 
 formed by the "condensation" of a pyridine and a benzene 
 nucleus. 
 
QUINOLINE DERIVATIVES 545 
 
 When quinoline derivatives are oxidized, the benzene ring 
 is usually more readily ruptured than the pyridine one, e.g. 
 quinoline yields pyridine-dicarboxylic acid (p. 540). a-Methyl- 
 quinoline gives, on the other hand, 0-acetyl-amino-benzoic acid 
 when oxidized: 
 
 (For laws governing the oxidation of quinoline derivatives, 
 see W. v. Miller, B. 23, 2252; 24, 1900; M. 1891, 12, 304.) 
 
 The pyridine nucleus of quinoline takes up hydrogen more 
 readily than the benzene one; thus quinoline is easily con- 
 verted, even by tin and hydrochloric acid, into tetrahydro- 
 quinoline. It can be further reduced to the deca-hydride, but 
 only with difficulty. 
 
 The three hydrogen atoms of the pyridine nucleus, counting 
 from the N, are designated as a-, ft-, and 7-, and the four hy- 
 drogen atoms of the benzene nucleus as 0-, m-, p-, and a- (ana-) 
 hydrogen atoms, or more commonly the numbering shown 
 above is adopted, the nitrogen atom being numbered 1 and 
 the carbon atoms consecutively 2, 3, &c., up to 8. As no two 
 hydrogen atoms are symmetrically situated in the molecule, 
 seven mono-substituted derivatives of quinoline are in each 
 case theoretically possible. As a matter of fact, all seven 
 quinoline-monocarboxylic acids have been prepared. 
 
 The position of the substituents follows : (a) from the nature 
 of the oxidation products, e.g. B-quinoline-carboxylic acid (i.e. 
 an acid in which the carboxyl is attached to the benzene 
 nucleus) yields a pyridine-dicarboxylic acid, while a Py-quino- 
 line-carboxylic acid (in which the carboxyl is linked to the 
 pyridine nucleus) yields a pyridine-tricarboxylic acid; (b) from 
 the synthesis of the compound in question. The methyl- 
 quinoline, for instance, which is obtained from o-toluidine by 
 the Skraup synthesis must be the 8-methyl-quinoline : 
 
 /y\ 
 
 + C 3 H 6 (OH) 3 + = +4H 2 0, 
 
 NH 2 \/\/ 
 
 CH 3 CH 3 N 
 
 whilst m-toluidine must yield a 7- or 5-, and ^-toluidine a 
 6-methyl-quinoline. 
 
 Quinoline (Eunge, 1834) is a colourless strongly refracting 
 liquid of a peculiar and very characteristic odour. It boils at 
 
 (9480) 2M 
 
546 XXXVIII. QUINOLINE AND ACRIDINE GROUPS 
 
 239, is a mono-acid base, forms a sparingly soluble dichromate, 
 (C 9 H 7 N) 2 , H 2 O 2 7 , and is used as an antifebrile. As a tertiary 
 base it yields quinolonium salts (Boser, A. 1893, 272, 221). 
 
 Nascent hydrogen transforms it first into dihydro-quinoline, 
 C Q H Q N, which melts at 161, and then into tetrahydro-quinoline, 
 
 /CH CH 
 C 9 H U N, = C 6 H/ *' - * a liquid boiling at 245. Since 
 
 N JN 1 \ja-2 
 
 both of these yield nitrosamines and can be alkylated, they are 
 secondary bases. The tetrahydro-compound exerts a stronger 
 antifebrile action than the mother substance, especially in the 
 form of its ethyl derivative, cairolin (B. 16, 739). 
 
 Quinoline decahydride, CLK^N, is obtained when strong 
 reducing agents are employed. It forms crystals of a narcotic, 
 coniine-like odour, melts at 48, and boils at 204. 
 
 Halogen derivatives of quinoline and nitro-quinolines have 
 been prepared by the Skraup reaction, &c.; and, from the 
 reduction of the latter, amino-quinolines, C 9 H 6 N(NH 2 ). The 
 quinoline-sulphonic acids yield cyano-quinolines with potassium 
 cyanide, and hydroxy-quinolines when fused with potash. 
 
 l-Hydroxy-quinoline, carbostyril, is a quinoline hydroxylated 
 in the pyridine nucleus (see p. 543, mode of formation 3). It 
 crystallizes in colourless needles, melts at 198, and is soluble 
 in alkali, from which it is again thrown down by carbonic 
 acid. Its constitution follows from its formation from o-amino- 
 cinnamic acid (p. 456). 
 
 Quinaldine, 2-methyl-quinoline, C 10 H 9 N, is contained in coal- 
 tar. It is a colourless liquid of quinoline odour, and boils at 
 246. When oxidized with chromic acid it yields a quinoline 
 derivative, with permanganate a pyridine-tricarboxylic acid. 
 
 The hydrogen of the methyl group readily enters into re- 
 action; quinaldine reacts with phthalic anhydride to produce 
 a beautiful yellow dye, quinoline-yellow, C 1 QH 7 N(CO) 2 C 6 H 4 
 (B. 16, 2602). A mixture of quinoline and quinaldine is 
 transformed into the (unstable) blue dyes, the cyanines, when 
 alkylated and treated with caustic potash. These are used as 
 sensitizers for photographic plates. 
 
 ftuinoline-carboxylic Acids. All the seven quinoline mono- 
 carboxylic acids, which are possible according to theory, are 
 known. Quinoline-benz-carboxylic acids are those which con- 
 tain the carboxyl group in the benzene nucleus. 
 
 Cinchoninic acid, guinolineA-carloxylic acid, C 9 H 6 N(CO 2 H), 
 which is obtained by the oxidation of cinchonine with per- 
 
ISO-QUINOLINE 547 
 
 manganate of potash, crystallizes in needles or prisms and 
 melts at 254. From it is derived quinic acid, -methoxy- 
 quinoline-i-carloxylic acid, C 9 H 5 N(OCH 8 ) C0 2 H, which is ob- 
 tained by oxidizing quinine with chromic acid; it forms yellow 
 prisms, melting at 280. 
 
 Quinoline-2 : 3-dicarboxylic acid, or acridinic acid, is formed 
 by the oxidation of acridine. 
 
 3. ISO-QUINOLINE 
 
 Iso-quinoline, an isomer of quinoline, occurs along with the 
 latter in coal-tar (B. 18, Ref. 384). It is a solid, melts at 23, 
 and boils at 240. Since oxidation converts it into cincho- 
 meronic acid on the one hand and phthalic acid on the other, 
 it possesses the constitution : 
 
 Its constitution also follows from its synthesis* from homo- 
 
 PTT /~i/~\ TT 
 
 phthalic acid, C 6 H 4 <^ 2 A 2 , in which the substituents 
 
 are in the o-position. This may be converted into its imide. 
 
 PTT p/-w 
 
 C 6 H 4 <^ 2 , by heating the ammonium salt. This imide 
 
 M30 NH 
 with phosphorus oxychloride reacts as the tautomeride, 
 
 /CH=C(OH) 
 CgB^f , and yields the corresponding dichloro- 
 
 iso-quinoline, which is reduced by hydriodic acid and red 
 phosphorus to iso-quinoline. 
 
 B. The Acridine Group 
 
 Acridine, C 13 H 9 N (Graebe and Caro), is a basic constituent of 
 the crude anthracene of coal-tar, and also of crude diphenyl- 
 amine. It crystallizes in colourless needles, may be sublimed, 
 and is characterized by an intensely irritating action upon the 
 epidermis and the mucous membrane, and also by the greenish- 
 blue fluorescence shown by dilute solutions of its salts. 
 
 Acridine stands in the same relationship to anthracene that 
 pyridine does to benzene or quinoline to naphthalene. It may 
 
 *For synthesis from /3-naphthaquinone see B. 25, 1138, 1493; 27, 198; 
 and for synthesis from benzylaminoacetaldehyde hydro-chloride and sul- 
 phuric acid see E. Fischer, B. 26, 764. 
 
548 XXXVIII. QTJINOLINE AND ACRIDINE GROUPS 
 
 be regarded as anthracene in which one of the CH-groups of 
 the middle ring is replaced by N. This constitutional formula : 
 
 is based (a) upon the oxidation of acridine to qumoline- 
 2 : 3-dicarboxylic acid, and to pyridine tetracarboxylic acid 
 the ^-union between C and N becomes ruptured during the 
 oxidation; (b) upon its synthesis from diphenylamine and 
 formic acid, or formyl-diphenylamine, (C 6 H 5 ) 2 N CHO, with 
 zinc chloride (Bernthsen, A. 224, 1): 
 O 
 
 -T I'll 
 
 a 
 
 Formyl-diphenylamine Acridine. 
 
 It is also obtained when the vapour of 0-tolyl-aniline is passed 
 through a red-hot tube. 
 
 Acridine is a tertiary base, and as such combines with alkyl 
 iodides, yielding acridonium iodides. It is a much feebler 
 base than quinoline, and on reduction readily forms a dihydro- 
 derivative, which is not basic. 
 
 Methyl- and butyl-acridines, phenyl-acridine, 
 
 C 6 H 4 
 
 and naphtho-acridines (i.e. acridines which contain C 10 H 6 
 instead of C 6 H 4 ) have all been prepared synthetically in 
 an analogous manner. 
 
 Diamino - dimethyl - acridine, acridme yellow, C 13 H 5 (CH 3 ) 2 
 (NH 2 ) 2 N, a yellow basic dye, is formed by condensing formic 
 aldehyde with m-toluylene-diarnine, splitting off ammonia, and 
 oxidizing the leuco-base produced. 
 
 The chrysaniline orphosphin of commerce, a beautiful yellow 
 dye, is diamino-phenyl-acridine, C ]9 H n N(NH 2 ) 2 , since it yields 
 phenyl-acridine when its diazo - compound is boiled with 
 alcohol. 
 
 Acridine is therefore, like anthracene, a chromogene. 
 
 The oxygen analogue of dihydro-acridine, C 6 H 6 < 
 is diphenylene-methane oxide, C 6 H 4 <_o>C 6 H 4 , which can 
 
XXXIX. AZINE, ETC. GROUP 640 
 
 be prepared synthetically and also by distilling euxanthone 
 over zinc dust. It crystallizes in plates, and melts at 9 8 '5. 
 It is on the one hand the mother substance of xanthone, 
 
 4 , and its derivative euxanthone or dihydroxy- 
 xanthone, OH C 6 H 3 <^>C 6 H 3 OH, and on the other hand, 
 
 of the rhodamines and fluoresceins (p. 493). Its tetramethyl- 
 diamino- derivative results from the condensation of formic 
 aldehyde with dimethyl - m - amino - phenol to tetramethyl- 
 diamino-dihydroxy-diphenyl-methane and subsequent elimi- 
 nation of water (ring formation), and is the leuco-compound 
 of formo-rhodamine or pyronine, C 17 H 19 N 2 OC1, into which ifc 
 passes upon oxidation and production of quinoid linking, thus; 
 
 / C 6 H,.N(CH 3 ) 2 /} 
 
 H 2 C/ >0 HC/ >0 
 
 X C 6 H 3 .N(CH 3 ) 2 XH 3 :N( 
 
 Leuco-compound Formo-rhodamine hydrochloride. 
 
 XXXIX. SIX-MEMBERED HETEROCYCLIC COM- 
 POUNDS WITH NOT MORE THAN FOUR 
 CARBON ATOMS IN RING. AZINES, ETC, 
 
 A number of six-membered heterocyclic compounds, con- 
 taining four carbon and two other atoms, are known, e.g. par- 
 oxazine, with 4C, 10, and IN, the and N in the ^-position. 
 
 A derivative of this is morpholine, 0<g 2 *g 2 >NH. Simi- 
 
 larly, thiazines (4C, IS, IN) and diazines (4C, 2N) are 
 known; and these are the parent substances of numerous 
 important dyes. The majority of these dyes are not simple 
 derivatives of oxazines, thiazines, or diazines, but are derived 
 from condensed benzene and oxazine, or benzene and diazene 
 nuclei, and may be compared with anthracene. For example, 
 phenazine is anthracene in which two CH-groups have been 
 replaced by two N-radicals: 
 CH N 
 
 Anthracene Pheuazine 
 
650 XXXIX. SIX-MEMBERED AZINE GROUP 
 
 dihydro-phenazine corresponds with dihydro-anthracene, and 
 phenoxazine with dihydro-anthracerie in which one CH 2 has 
 been replaced by and another by NH, e.g. : 
 
 (I) C 6 H<^>C 6 H 4 (H) CeH^J^CeH, (III) CeH^g^CeH, 
 
 Dihydro-phenazine Phenoxazine Phentluazine 
 
 (thio-diphenyl amine). 
 
 Further, the benzene nuclei may be replaced by those of 
 naphthalene, with the formation of: 
 
 (IV) C 10 H 6 <C 10 H fl (Y) C 10 H 6 < ( >C 6 H 4 
 
 Naphthazine Naphtho-phenoxazine. 
 
 The compounds (I-III) of the type of dihydro-anthracene 
 are the leuco-compounds of dyes when they contain an amino- 
 (alkyl-amino-) or hydroxy-group in the ^ara-position to the 
 nitrogen. The dyes themselves are obtained from these by 
 oxidation (i.e. elimination of hydrogen), so that they are 
 derived from amino- or hydroxy-phenazines. In this way the 
 eurhodines (mon-amino-compounds) and the toluylene red dyes 
 (diamino-compounds) are derived from phenazine and hydro- 
 phenazine, and similarly the safranines and indulines; Nile 
 blue is derived from naphtho-phenoxazine; and the thionine 
 dyes from phenthiazine. 
 
 THE DIAZINES 
 
 The three simple diazines are : 
 
 :CH 
 
 Pyridazine. Pyrimidine. Pyrazine. 
 
 Pyridazine is a colourless liquid, b.-pt. 208, is miscible with 
 water, has an odour of pyridine, and forms soluble salts. 
 (Preparation, cf. B. 28, 451.) 
 
 Pyrimidine can be obtained from barbituric acid and from 
 methyluracil (p. 287); it forms colourless crystals, m.-pt. 22 
 and b.-pt. 124. The pyrimidme ring is met with in uric acid 
 and in most purine derivatives (cf. B. 34, 3248). 
 
 Pyrazine forms colourless prisms, m.-pt. 47, b.-pt. 118, and 
 is basic (J. pr. [ii], 51, 449). Dimethylpyrazine, Ketin, is 
 present in crude amyl alcohol, and can be obtained by the 
 reduction of isonitrosoacetone or by condensation of amino- 
 
fHENAZINES 51 
 
 acetone. Tetraphenylpyrazine is readily obtained from ben- 
 zoin. 
 
 Of the compounds formed by the union of a benzene 
 and a diazine nucleus the most important is quinoxaline, 
 
 C 6 H 4 ^ , which is obtained from 0-phenylene-diamine and 
 \N I C/rl 
 
 glyoxal. Substituted quinoxalines are formed by condensing 
 tt-dike tones, a-ketonic acids, &c., with 0-phenylene-diamines. 
 Of more importance is the group of compounds containing 
 two benzene nuclei condensed with one diazine ring, e.g. 
 phenazine. 
 
 Phenazine, or azo-phenylene (p. 549), is obtained by the dis- 
 tillation of barium azo-benzoate, or by leading the vapour of 
 aniline through red-hot tubes; also from nitrobenzene, aniline, 
 and sodium hydroxide at 140, or by the oxidation of its 
 hydro-compound (see below). It crystallizes in beautiful, 
 long, bright-yellow needles melting at 171, and can be readily 
 sublimed. It is only sparingly soluble in alcohol, but readily 
 in ether, and also dissolves in concentrated sulphuric acid to a 
 red solution; the alcoholic solution yields a green precipitate 
 on the addition of stannous chloride. When reduced with am- 
 monium sulphide it yields the colourless hydro-compound, di- 
 hydro-phenazine, C 12 H 10 2 , which may be obtained syntheti- 
 cally by heating catechol with 0-phenylene-diamine: 
 
 The entrance of hydroxy- or ammo-groups into these azines 
 converts them into dyes. In accordance with modern views of 
 the quinonoicl structure of dyes these derivatives are usually 
 given ortho or para quinonoid formulae : 
 
 Para, C 6 H 4 <*J=>C 6 H 3 :NH; ortho, C 6 H 4 <g>C 6 H 3 .NH 2 , 
 
 and similarly for hydroxy derivatives. 
 
 The amino-compounds are usually termed Eurhodines, and 
 may be obtained by condensing arylamines with o-amino-azo- 
 compounds. 
 
 Eurhodine, amino-naphtho-tolazine, 
 
 or CH 3 .C H 3 <N 2 H>C 10 H 6 :NH, 
 
 obtained from a-naphthylamine and 0-amino-azo-toluene, forms 
 lustrous golden crystals and yields scarlet salts (B. 19, 441 
 
552 XXXIX. SIX-MEMBERED PHENAZINE GROUP 
 
 21, 2418; 24, 1337). When heated with concentrated hydro- 
 chloric acid it is converted into the basic and at the same time 
 phenolic compound eurhodol, 
 
 HO.C 10 H 6 <N 2 >C H 3 .CH 3 or CH 3 .C 6 H 3 <N 2 H>C 10 H 6 :0 
 
 (cf. B. 24, 1337). 
 
 0-Diamino-phenazine, C 12 HgN 3 (NH 2 ) 2 , is obtained by the 
 oxidation of 0-phenylene-diamine with ferric chloride (B. 22, 
 355), and is the parent substance of the important dyes of the 
 toluylene red group. When a mixture of ^-phenylene-diamine 
 and m-toluylene-diamine is oxidized in the cold, the beautiful 
 blue compound, toluylene blue, an indamine (p. 434), is formed, 
 which is further oxidized to toluylene red, diamino-tolu-phen- 
 azine, when boiled : 
 
 NH 2 .C 6 H 4 .NH 2 + NH 2 .C 6 H 3 Me.NH 2 + 20 
 
 = NH 2 C 6 H 4 N : C 6 H 2 Me(NH 2 ) : NH + 2 H 2 O 
 NH 2 .C 6 H 4 .N:C 6 H 2 Me(NH 2 ):NH + O 
 
 = NH 2 C 6 H 3 <>C 6 H 2 Me NH 2 + H 2 0. 
 
 This diamino-tolu-phenazine is the simplest of the toluylene 
 reds, and its constitution follows from the fact that when 
 diazotized it yields methyl-phenazine. Analogous dyes are 
 neutral red, the hydrochloride of dimethyl-diamino-tolu-phen- 
 azine, NMe 2 .C 6 H 3 <N 2 ^C 6 H 2 MeNH 2 , HC1, and neutral violet, 
 dimethyl -diamino-pheriazine hydrochloride. The leuco- com- 
 pounds are the corresponding derivatives of dihydropheriazine. 
 
 The group of dyes known as the safranines are related to 
 toluylene red. They are amongst the oldest of the aniline 
 dyes, and include mauve, the first dye prepared by W. H. 
 Perkin, Senr., in 1856. The simplest member of this group 
 
 is pheno-safranine, NH:C 6 H 3 <^^>C 6 H 3 .NH 2 , which is of 
 
 historical interest only. The dye safranine is the hydro- 
 chloride of dimethyphenosafranine : 
 
 2 \/%NPhClX\/ 
 
SAFRANINES 553 
 
 I. represents the compound with a paraquinonoid, and II. 
 with an orthoquinonoid structure. 
 
 The commercial product is usually a mixture of this with a 
 homologue containing the 0-tolyl group in place of the Ph. 
 The method of manufacture consists in the oxidation of mole- 
 cular proportions of j?-toluylene-diamine and 0-toluidine to the 
 corresponding indamine, and then the condensation of this 
 with o-toluidine to give the tolu-safranine. It can be used for 
 cotton mordanted with tannin, and gives red colours. 
 
 The safranines are beautiful crystalline compounds of a 
 metallic green lustre, readily soluble in water, and dye yel- 
 lowish-red, red, and violet. The solution in concentrated sul- 
 phuric acid is green, becoming blue, violet, and finally red on 
 dilution with water. Reduction gives rise to leuco-compounds, 
 which are diamino-compounds of the as yet unknown substance 
 
 H 4 (B. 19, 2690, 3017, 3121; 29, 361, 
 
 1442, 1870, &c.); treatment with nitrous acid and alcohol 
 yields phenyl-phenazonium chloride. The safranines are there- 
 fore diamino-compounds of phenyl-phenazonium chloride: 
 
 Numerous other safranines are manufactured. Methylene 
 violet is asymmetric dimethyl - safranine chloride; sqfranine, 
 MN, is a dimethyl-tolyl-safranine chloride; and amethyst violet, 
 tetramethyl- safranine chloride. Parkin's mauve has the for- 
 mula: 
 
 Ph 
 
 The aposafranines are analogous to the safranines, but con- 
 tain only one amino- or substituted amino-group, and at least 
 one naphthalene residue in place of a benzene ring. They are 
 divided into Eosindulines and Isorosindulines. The former con- 
 tain the amino group attached to the naphthalene ring and 
 give red shades, the latter contain the amino group attached 
 to a benzene ring and give blue or green shades. 
 
 Safranines can be diazotized and coupled with alkaline 
 solutions of /?-naphthol. Indoin blue is the hydrochloride of 
 safranine-azo-naphthol, C 20 H 1G N 3 N : N C 10 H 6 OH, HC1. 
 
554 XL. ALKALOIDS 
 
 PHENOXAZINES AND PHENTHIAZINES 
 
 Phenoxazine (p. 550) is obtained by heating catechol with 
 o-aminophenol, and crystallizes in plates. The leuco-corapound 
 of nile blue is a diethyldiamino-naphthaphenoxazin. The dye 
 
 itself, NH:C 10 H 5 <Q>C 6 H 4 .NEt 2 , HC1, obtained by heating 
 
 the nitroso-derivative of diethyl-w-aminophenol with a-naph- 
 thylamine, is a brilliant green-blue basic dye. 
 
 Methylene blue, NMe 2 <C 6 H 8 <g>C 6 H 3 :NMe 2 Cl, a valuable 
 
 blue dye for wool, is formed by the action of ferric chloride 
 on amino-dimethylaniline and carbon disulphide. With nitrous 
 acid it yields methylene green. 
 
 For constitution cf. Kehrmann, B. 39, 914; Hantzsch, ibid. 
 1365. 
 
 XL. ALKALOIDS 
 
 The group of alkaloids at one time comprised the whole of 
 the nitrogenous basic compounds present in plants or derived 
 from the various plant tissues by distillation. Thus methyl- 
 amine, betaine, asparagine, caffeine, and the opium alkaloids 
 were all grouped together, but as their constitutional formulae 
 were established they were grouped with the compounds to 
 which they were closely related, e.g. methylamine with the 
 primary aliphatic amines, betaine with the alkyl derivatives of 
 
 flycocoll, and caffeine with the uric acid or purine derivatives, 
 'he name is now largely restricted to the nitrogenous basic 
 plant constituents which can be regarded as derived from pyri- 
 dine, quinoline, or iso-quinoline, and to those of unknown 
 constitution. 
 
 They form an extremely important group of compounds on 
 account of their physiological properties, and they constitute 
 the active principles of the common vegetable drugs and 
 poisons. 
 
 With a single exception they occur exclusively in dicotyle- 
 dons, and as a rule do not exist in the free state, but combined 
 with organic acids in the form of salts. Such acids are malic 
 (p. 247), citric (p. 261), and tannic (p. 460); quinic acid usually 
 accompanies the alkaloids of opium. 
 
 A few of the alkaloids are built up of carbon, hydrogen, and 
 
ALKALOIDS 555 
 
 nitrogen, e.g. coniine, nicotine. Such compounds as a rule are 
 liquids and are readily volatile; the majority, on the other 
 hand, contain in addition oxygen, and then are usually crystal- 
 line and non-volatile. All are optically active, and as a rule 
 laevo-rotatory. A few like coniine are secondary bases, but 
 the majority are tertiary, and a few quaternary ammonium 
 compounds. 
 
 The following reagents as a rule precipitate the alkaloids in 
 the form of complex derivatives from solutions of their salts, 
 viz. tannin, phosphomolybdic acid, a potassium iodide solution 
 of iodine, and also potassium mercuric iodide. They are 
 further characterized by their bitter astringent taste and by 
 their poisonous properties. Each individual alkaloid gives 
 characteristic colour reactions. 
 
 The alkaloids are usually extracted from plant tissues by 
 lixiviating the finely-divided tissue with acidified water. The 
 extract is then rendered alkaline with ammonia and the free 
 alkaloid separated by filtration, or, if it is at all readily soluble, 
 by extraction with chloroform. 
 
 For relationship between constitution and physiological 
 properties see P. May, " The Chemistry of Synthetic Drugs ", 
 London, 1911. 
 
 The structural formula for an alkaloid is usually determined 
 by a study of its more important chemical reactions and of its 
 degradation products. Among the reactions generally studied 
 are: 
 
 1. Determination of the number of free hydroxyl groups by 
 acetylation (cf. p. 201). Thus morphine can be shown to con- 
 tain two, codeine one, and papaverine none. 
 
 2. Determination of methoxy groups by Zeisel's method or 
 Perkin's modification. Papaverine contains four such groups, 
 narcotine three and codeine one. 
 
 3. Study of the action of hydrolysing agents. Esters are 
 hydrolysed, but most other types of linking are resistent to 
 such agents. Narcotine (p. 561) yields opianic acid and hydro- 
 cotarnine, and is presumably an ester derived from these two 
 compounds. Similarly, atropine (p. 565) on hydrolysis yields 
 tropic acid and tropine. As the products of hydrolysis are 
 simpler than the original alkaloid, the elucidation of their 
 constitutions is less difficult. 
 
 4. Examination of bhe products of oxidation. Thus codeine 
 contains a secondary alcoholic group, as on oxidation it yields 
 a ketone, codeinone, containing the same number of carbon 
 
556 XL. ALKALOIDS 
 
 atoms. Coniine when oxidized yields pieolinic acid, and must 
 thus be an a- substituted derivative of pyridine. Cinchonine 
 yields quinoline-y-carboxylic. acid. 
 
 5. Determination of the primary, secondary, tertiary, or 
 quaternary nature of the base. 
 
 6. Study of the degradation products obtained by exhaus- 
 tive methylation. As an example of this method the simple 
 secondary amine piperidine may be taken. When methylated 
 by means of methyl iodide it yields first the tertiary amine 
 methylpiperidine, and finally the quaternary ammonium iodide, 
 dimethylpiperidonium iodide. This with moist silver oxide 
 yields the quaternary base, which on distillation decomposes 
 into water and an unsaturated aliphatic tertiary amine: 
 
 = H 2 O f CH 2 :CH.CH 2 .CH 2 .CH 2 .NMe 2 . 
 
 When methylated and treated with silver oxide this un- 
 saturated base yields a quaternary hydroxide, which splits 
 up into water, trimethylamine, and A aS pentadiene when dis- 
 tilled: 
 
 7. An examination of the products obtained by fusing the 
 alkaloid with potash or by distilling it with zinc dust. Thus 
 morphine and zinc dust yield phenanthrene together with 
 other products, and hence the molecule of morphine probably 
 contains a phenanthrene ring. Papaverine, when fused with 
 potash, yields dimethoxy-iso-quinoline and 3:4-dimethoxy- 
 toluene, and hence papaverine is probably an iso-quinoline 
 derivative. The processes of fusion with potash and distilla- 
 tion with zinc dust require high temperatures, and as molecular 
 rearrangements occur much more readily at high than at low 
 temperatures, the conclusions drawn from a study of the 
 products formed during such processes shonld be accepted 
 with a certain amount of reserve unless supported by other 
 evidence. 
 
 The alkaloids can be grouped according to their origin, e.g. 
 the opium alkaloids, bases from solanine, &c., or according to 
 the heterocyclic ring which they contain. The latter method 
 is adopted here, and we thus have the pyridine, quinoline, iso- 
 auinoline, and phenanthrene groups. 
 
PYRIDINE ALKALOIDS 557 
 
 A. Alkaloids derived from Pyridine 
 
 Coniine, dextro-rotatory a-normal-pi'opyl-piperidine, C 5 H 10 N 
 (C 3 H 7 ), is the poisonous principle of hemlock (Conium macu- 
 latum). It is a colourless dextro-rotatory liquid of stupefying 
 odour, sparingly soluble in water, and boils at 167. Hy- 
 driodic acid at a high temperature reduces it to normal octane, 
 while nitric acid oxidizes it to butyric acid, and potassium 
 permanganate to picolinic acid (hence the a-position). 
 
 Ladenburg has prepared it synthetically by reducing a-allyl- 
 pyridine (p. 538) in alcoholic solution by means of sodium 
 (B. 19, 2578): 
 
 C 5 H 4 N(C 3 H 6 ) + 8H = C 6 H 10 N(C 3 H r ). 
 
 The pyridine ring is reduced to a piperidine ring, and at 
 the same' time the unsaturated allyl side-chain is reduced to a 
 %-propyl group. The a-carbon atom is an asymmetric carbon 
 atom, i.e. it is attached to four different monovalent radicals, 
 and the whole molecule is asymmetric. The synthetical pro- 
 duct is optically inactive, and thus differs from the natural 
 product, but it has been resolved by fractional crystallization 
 of the d-tartrate into dextro-coniine and a laevo-coniine. The 
 relations of these two bases to one another and to the inactive 
 modification are the same as that of dextro- to laevo-tartaric 
 acid and to racemic acid. 
 
 Nicotine, C 1 pH 14 N ? , is the poisonous constituent of the 
 tobacco plant, in which it exists in combination with malic 
 and citric acids. It is a colourless, oily liquid soluble in 
 water, and is Isevo-rotatory. It rapidly oxidizes in contact 
 with the air, and boils at 247. It is a di-tertiary base, and 
 therefore readily combines with methyl iodide. On oxidation 
 with permanganate it yields nicotinic acid, and hence must be 
 a ^-pyridine derivative. It has been synthesised recently by 
 Pictet (C. E. 1903, 137, 860), and been shown to be a-pyridyl- 
 N-methyl-pyrrolidine : 
 
 OH, -OH, 
 
 The method of synthesis is as follows: Nicotinic acid is 
 transformed first into its ethyl ester, and then into the amide; 
 
558 XL. ALKALOIDS 
 
 this with bromine and alkali (Hofmann's reaction, pp. 107, 183) 
 gives /?-amino-pyridine, and when the salt of this base with 
 mucic acid (p. 259) is distilled, N-pyridyl-pyrrole, 
 
 N< /CH:CH 
 
 is formed. When the vapour of this compound is passed 
 through a heated tube, it is transformed into the isomeric 
 a-pyridyl-pyrrole, CH-CH 
 
 This forms a potassic derivative which with methyl iodide 
 
 CH-CH 
 CH 
 
 N.CH 3 
 
 rCH 3 I 
 and this, when distilled with lime, gives 
 
 a-pyridyl-N-methyl-pyrrol, which can be converted into 
 a-pyridyl-N-methyl-pyrrolidine (z-nicotine) by the addition 
 of hydrogen. The racemic alkaloid thus obtained may be 
 resolved into its optically active components by the aid of 
 d-tartaric acid when J-nicotine-d-tartrate crystallizes out first. 
 
 B. Bases derived from Quinoline 
 
 Among tnese are the alkaloids contained in the barks of 
 certain species of Cinchona. 
 
 (a) Quinine, C 2 qH 24 2 N 2 -f 3H 2 0, a diacid base of intensely 
 bitter taste and alkaline reaction, of which the sulphate and 
 chloride are universally used as febrifuges. It crystallizes 
 in prisms or silky glistening needles, melts at 177 when 
 anhydrous, is sparingly soluble in water, and is laevo-rotatory. 
 
QUINOLINE BASES 559 
 
 The quinine salts in dilute solution are characterized by a 
 magnificent blue fluorescence. 
 
 As a base quinine is a tertiary diamine, but it contains in 
 addition as its reactions show one hydroxy-, one methoxy- 
 group and an ethylene linking, and seems to be built up of 
 two different ring systems, in accordance with the following 
 formula : 
 
 (CH 3 0) - C 9 H 5 N 
 
 The first of these represents the radical of a 6-methoxy- 
 quinoline, and this compound is obtained when quinine is 
 fused with potash. The second system probably possesses a 
 ring similar to that of tropine, since it yields as decomposition 
 products sometimes a pyridine derivative (e.g. jS-ethyl-pyridine 
 on fusion with alkali), and sometimes benzene derivatives 
 containing no nitrogen (e.g. a phenolic compound, Ci H 12 OH, 
 together with ammonia, on successive treatment with phos- 
 phorus pentachloride, potash, and hydrobromic acid). 
 
 It yields quinic acid, 6-methoxy-quinoline-4-carboxylic acid, 
 CgH 5 N(OCH 3 )C0 2 H (p. 547), and meroquinine when oxidized 
 with dichromate mixture. 
 
 Meroquinine appears to be either (a) 3-vinylpiperidyl-acetic 
 acid (B. .30, 1326), or (b) 3-vinyl-4-methylpiperidine-4-car- 
 boxylic acid (B. 28, 1060): 
 
 (a) 
 
 ,n-<cr,!r: (6) 
 
 as it yields loiponic acid, piperidine-3 : 4-dicarboxylic acid, when 
 oxidized with permanganate. 
 
 The formulae suggested for quinine are therefore either : 
 
 CH 2 - CH 2 
 
 CH 2 --- CH CH : CH 2 
 
 CH 2 - CH 2 
 
 or N C(OH)(CH2X) . CMe 
 
 CH 2 - CH . CH 
 
 where X represents the 6-methoxy-quinoline residue attached 
 to the CH 2 group in position 4. 
 Quinine is a valuable drug in cases of malaria; numerous 
 
560 XL. ALKALOIDS 
 
 substitutes are now employed, especially derivatives of quinine 
 which are free from bitter taste. 
 
 Various esters are used, e.g. aristoquinine is diquinine car- 
 bonate, euquinine is ethyl quinine carbonate, and saloquinine is 
 quinine salicylate. 
 
 (b) Cinchonine, C 19 H 22 ON 2 , is similar to quinine, but with- 
 out the methoxy group in the quinoline nucleus. It crystal- 
 lizes in colourless prisms, sublimes readily, and is not so active 
 a febrifuge as quinine. When oxidized with dichromate and 
 sulphuric acid it yields cinchoninic (quinoline- 4 -carboxylic) 
 acid and meroquinine; with permanganate it yields cincho- 
 tenine and carbonic acid. Cinchotenine no longer combines 
 with hydrogen chloride, and in the oxidation the double link- 
 ing present in cinchonine has been removed and a carboxylic 
 group introduced. When treated with PC1 5 and then with 
 alcoholic potash, cinchonine loses a molecule of water, yielding 
 cinchene, C 19 H 20 N 2 , which can be hydrolysed by 25 per cent 
 phosphoric acid to lepidine (4-methyl-quinoline) and mero- 
 quinine. 
 
 (c) Conchinine, C 2( )H 24 2 N 2 , and Cinchonidine, C 19 H 22 ON 2 , 
 are probably stereoisomeric with quinine and cinchonine 
 respectively, and are milder in their action. 
 
 These are but a few of the numerous alkaloids present in 
 these barks. In addition, organic acids (e.g. quinic and quino- 
 tannic) and neutral substances are also present. 
 
 C. Bases derived from /so-Quinoline 
 
 (a) Papaverine, C 20 H 21 4 N, is found (1 %) together with 
 narcotine, narceine, laudanosine, laudanine, and the morphine 
 alkaloids in opium, the solid obtained by drying the juices 
 extracted from the seed vessels of Papaver somniferum. In 
 addition to some twenty alkaloids, many of which are present 
 in only small quantities, opium also contains fats, resins, 
 sugars, albumins, &c. The alkaloid crystallizes in prisms, 
 m.-pt. 147, and is optically inactive. It has hypnotic pro- 
 perties, but not to the same extent as morphine. It is a ter- 
 tiary base, and all four oxygen atoms are present as methoxy 
 groups, and when hydrolysed with hydriodic acid the corre- 
 sponding tetrahydroxy-derivative, papaveroline, C 16 H 13 4 N, is 
 formed. When oxidized with permanganate it yields first 
 papareraldine, C 20 H 19 5 N, and finally dimethoxy-isoquinoline- 
 carboxylic acid and a-carbocinchomeronic acid (pyridine-1 : 2 : 3- 
 
/SO-QUINOLINE BASES 561 
 
 carboxylic acid). When fused with potash it takes up two 
 hydrogen atoms, and yields 4 : 5-dimethoxy-iso-quinoline and 
 3 : 4-dimethoxy toluene. 
 
 From these and other reactions G. Goldschmudt concluded 
 that the base is Si^-dimethoxybenzyl-^'ib'-dimethoxy-iso-qidnoline: 
 
 _OMe 
 /~ \OMe 
 
 and this formula has been confirmed by Pictet and Gan's syn- 
 thesis (B. 1909, 42, 2943) by the following steps: 
 
 1. C 6 H 4 (OMe) 2 C 6 H 3 (OMe) 2 .CO.CH 3 
 
 Veratrole or Friedel- Acetoveratrone 
 
 l:2-dimethoxybenzeue Crafts' 
 
 C 6 H 3 (OMe) 2 .CO.CH:N.OH 
 
 Amyl nitrite Isonitrosoacetoveratrone 
 
 C 6 H 3 (OMe). 2 . CO - CH 2 . NH 2 HC1 
 
 SnCl a Amino-acetoveratrone hydrochloride. 
 
 2. CHO.C 6 H 3 (OMe)OH CHO.C 6 H 3 (OMe) 2 
 
 Vanillin methylated MethylvaniUin 
 
 C 6 H 3 (OMe) 2 .CH(OH).CN C 6 H 3 (OMe) 2 .CH(OPI).C0 2 H 
 HCN hydrolysis 
 
 C 6 H 3 (OH) 2 .CH 2 .C0 2 H C 6 H 3 (OMe) 2 .CH 2 .C0 2 H 
 
 HI Homoprotocatechuic acid methylated Homoveratric acid 
 
 C 6 H 3 (OMe) 2 .CH 2 .COCl 
 
 Homoveratroyl chloride. 
 
 3. Amino-acetoveratrone hydrochloride and homoveratroyl 
 chloride condense in the presence of cold potassium hydroxide, 
 yielding (OMe) 2 C 6 H 3 CO - CH 2 . NH . CO . CH 2 . C 6 H 3 (OMe) 2 ; 
 this can be reduced to the corresponding secondary alcohol 
 vphich reacts with dehydrating agents, losing two molecules of 
 water and forming 3' :4'-dimethoxybenzyl- 4: 5-dimethoxy-iso- 
 quinoline, which is identical with papaverine. 
 
 (b) Laudanosine, C 21 H 27 4 N, crystallizes in needles, m.-pt. 
 89, and is dextro-rotatory. It has been shown by Pictet and 
 Athanescu (B. 33, 2346) to be an N-methyl-tetra-hydropapa- 
 verine, and has been synthesised by Pictet and Finkektein 
 (C. E. 1909, 148, 295). 
 
 (c) Narcotine, C 22 H 23 7 N, occurs in opium (6 per cent), 
 crystallizes in colourless needles, m.-pt. 176, and is Isevo- 
 rotatory. It is a feeble tertiary base, and its salts are readily 
 hydrolysed by water. It contains three methoxy groups, and 
 
 (B480) " 2N 
 
562 XL. ALKALOIDS 
 
 when hydrolysed by dilute acids or alkalis, yields opianic acid 
 and hydro-cotarnine. When reduced it yields meconine and 
 hydro-cotarnine, and when oxidized yields opianic acid and 
 cotarnirie, and when heated with alkalis at 220 yields methyl- 
 amines, thus indicating that the N-atom is methylated. 
 
 The racemic compound has been synthesised in small quan- 
 tities (PerUn and Robinson, J. C. S. 1911, 776) by boiling an 
 alcoholic solution of cotarnine and meconine, and has been 
 resolved by means of d-bromo-camphor-sul phonic acid. 
 
 CH 5 
 
 Narcotine, 
 
 OMe 
 OMe 
 
 Both opianic (2 : 3-dimethoxy-6-aldehydo-benzoic acid) acid 
 and cotarnine have been synthesised. " The former by Fritsch 
 (A. 301, 351) and the latter by Salway (J. C. S. 1910, 1208): 
 The structural formula: 
 
 was deduced by Eoser for cotarnine by a study of its degrada- 
 tion products. When methylated and decomposed by alkalis 
 it yields an aldehyde, cotarnone, which on further oxidation 
 gives a methoxy-dibasic acid, known as cotarnic acid, and this 
 with hydriodic acid and phosphorus at 160 yields gallic acid 
 (3:4:5-trihydroxybenzoic acid). Although cotarnine itself is 
 not an iso-quinoline derivative, its salts are. The salt forma- 
 tion is accompanied by a closing of the ring (cf. Debbie, Lauder, 
 and Tinkler, J. C. S. 1903, 598): 
 
/SO-QUINOLINE BASES 563 
 
 Hydro-cotarnine is also a reduced iso-quinoline derivative : 
 
 The steps in the synthesis of cotarnine are : Myristic aldehyde 
 (3-methoxy-4:5-methylenedioxy-benzaldehyde) 3-methoxy- 
 
 Perkin's synthesis. 
 
 4 : 5-methylenedioxy-cinnamic acid > corresponding dihydro 
 
 red. 
 
 acid acid amide /3- 3 -methoxy -4 : 5-methylenedioxy- 
 
 co. 
 
 phenylethylamine * phenacetyl-derivative of amine * 8-me- 
 thoxy-6 : 7-methylenedioxy-l-benzyl-3 : 4 -dihydro -iso-quino- 
 line - 1-benzylhydrocotarnine * cotarnine. 
 
 Methochloride H 2 S0 4 
 
 with tin and HC1. +Mn0 2 . e 
 
 (d) Hydrastine, C 21 H 21 6 N, occurs in the roots of Hydrastis 
 canadensis, and differs from narcotine by having no methoxy 
 group in the iso-quinoline ring. When oxidized it yields 
 opianic acid and hydrastinine, which is the analogue of cotar- 
 nine. (Synthesis, cf. Freund, B. 20, 2403.) 
 
 (e) Berberine, C 20 H llr 4 N, H 2 0, is the chief alkaloid present 
 in Hydrastis, but has not marked physiological properties. The 
 probable structural formula is I. (Perkin and Robinson, J. C. S. 
 1910, 305): 
 
 CH 2 
 
 I. CH 
 
 (/) Corydaline, C 22 H2 7 4 N, from Corydalis cava, crystallizes 
 in prisms, m.-pt. 134'5 , and contains four methoxy groups. 
 The structural formula suggested by DdbUe and Lander ( J. C. S. 
 1903, 605) is II: 
 
 CH 2 
 
 /Y Xc 
 
 ii. 1 1 
 
 OMeL IL, N CHMe 
 
 <T \__OMe 
 
 [ 2 / V)Me. 
 
 \. / 
 
564 XL. ALKALOIDS 
 
 D. The Morphine Group of Bases 
 
 The three alkaloids morphine, codeine, and thebaine are 
 characterized by containing a phenanthrene nucleus in addi- 
 tion to a nitrogen ring. They are all present in opium. 
 
 (a) Morphine, C 17 H 19 3 N, constitutes on the average 10 per 
 cent of opium. It crystallizes in small prisms (+H 2 0), melt- 
 ing and decomposing at 230, has a bitter taste, and is a valu- 
 able soporific. It is a mono-acid tertiary base, containing two 
 hydroxyl groups, one of which is phenolic and the second alco- 
 holic. When distilled with zinc dust it yields phenanthrene 
 together with pyrrole, pyridine, and trimethylamine. Further 
 proof of the presence of the phenanthrene nucleus has been 
 afforded by the process of exhaustive methylation. With 
 methyl iodide it yields codeine methiodide, formed by the 
 methylation of the phenolic hydroxyl group and addition of 
 methyl iodide to the tertiary N-atom. This product, with 
 potassium hydroxide, loses hydrogen iodide and yields a 
 tertiary base, methylmorphimethine, which with acetic anhydride 
 gives 3-methoxy-4-hydroxy-phenanthrene (methylmorphol) and 
 hydroxyethyldimethylamine, OH.CH 2 -CH 2 .NMe 2 . The for- 
 mula suggested by Pschorr is : 
 
 CH, NCH 3 
 
 (b) Codeine, C 18 H 21 3 N, is a methyl derivative of morphine, 
 and can be obtained from the latter by methylation of its 
 phenolic group. When oxidized it yields the ketone codeinone, 
 and this with acetic anhydride yields hydroxyethyl-methyl- 
 amine and 3-methoxy-4 : 6-dihydroxy-phenanthrene. 
 
 (c) Thebaine is morphine in which both phenolic and alco- 
 holic hydroxyls are methylated. 
 
 Numerous alkyl derivatives of morphine are manufactured 
 and used as drugs in place of codeine. Dionine is ethyl- 
 morphine hydrochloride, peronine is benzylmorphine hydro- 
 chloride, heroin is diacetylmorphine. 
 
 For synthetical products allied to morphine see Knorr, A 
 301, 1; 307, 171, 187; B. 32, 732. 
 
STRYCHNINE, SOLANINE, AND COCA BASES 565 
 
 E. Strychnine Bases 
 
 Strychnos nitx vomica and certain other beans contain : 
 
 (a) Strychnine, C 21 H 22 2 N 2 . This is excessively poisonous, 
 produces tetanic spasms, crystallizes in four-sided prisms, 
 and yields quinoline and indole when fused with potash, 
 /3-picoline when distilled with lime, and carbazole when 
 heated with zinc dust. It is a mono-acid tertiary base, and 
 melts at 284. (For suggested formula see Perkin and Robin- 
 son, J. C. S. 1910, 305.) 
 
 (b) Brucine, C 23 H 26 4 N 2 , 4H 2 0, which crystallizes in prisms, 
 and is converted into homologues of pyridine on fusion with 
 potash. 
 
 F. Solanine and Coca Bases 
 
 Atropine and hyoscyamine are isomeric bases of the for- 
 mula C 17 H 23 3 N, which can be respectively prepared from 
 Atropa Belladonna (Deadly Nightshade) and Datura Stramonium, 
 and which are remarkable for their mydriatic action (power 
 of dilating the pupil of the eye). 
 
 Atropine crystallizes in colourless prisms or needles melting 
 at 115, possesses an extremely bitter taste, is optically in- 
 active, and is hydrolysed by baryta water to (//-tropic acid 
 
 tropine. The alkaloid can be synthesised by evaporating 
 dilute hydrochloric acid solution of tropine and tropic acid. 
 A complete synthesis of atropine has been accomplished, as 
 both tropic acid and tropine have been synthesised. 
 
 When optically active (d- and I) tropic acids are used, a 
 dextro- and a laevo-rotatory atropine result (B. 22, 2590). 
 And if, instead of tropic acid itself, other organic acids are 
 employed, homologous bases, the "tropeines", are obtained; 
 thus mandelic acid yields homatropine, C 16 H 21 N0 8 , which exerts 
 like atropine a mydriatic action, although a less lasting one 
 (Ladenburg, A. 217, 82; Jowett and Pyman, J. C. S. 1909, 1090). 
 
 Tropine itself is a cycloheptanol with a nitrogen bridge : 
 
 CH 2 -CH CH 2 
 
 NCH 3 CH-OH 
 CH 2 .CH CH 2 
 
 (fTiUsWter, B. 1898, 31, 1538, 2498, 2655). For synthesis 
 cf. Willslatter, A. 1901, 317, 307. 
 
566 XL. ALKALOIDS 
 
 It is a tertiary base, crystallizes in plates, m.-pt. 62, and 
 b.-pt. 220. 
 
 On oxidation it yields the ketone tropinone, and then tro- 
 pinic acid, or N-methyl-pyrrolidine-a-carboxylic-a! '-acetic acid. 
 Concentrated hydrochloric acid converts it into tropidine, 
 
 CHjj-CH CH 2 
 NCH 3 CH 
 CH 2 -CH CH 2 
 
 an oily base distilling at 162, and also obtainable by the 
 elimination of carbon dioxide from anhydro-ecgonine. 
 Ecgonine, or tropine-carboxylic add, 
 
 CHjs-CH CH-CO 2 H 
 
 NCH S CH-OH 
 CH 2 .CH OK, 
 
 crystallizes with one molecule of water, and may be obtained 
 by the hydrolysis of products contained in coca leaves. It 
 melts at 198, and is laevo-rotatory; and on warming with 
 alkalis, gives iso-ecgonine, which is dextro-rotatory. As an 
 alcohol it forms a benzoyl derivative, and as an acid a methyl 
 ester. (See Cocaine.) 
 
 Cocaine, or benzoyl-l-ecgonine methyl ester, 
 
 CH 2 -CH CH.C0 2 CH S 
 
 NCH 3 CH.O-COC 6 H 6 
 CH 2 -CH CH 2 
 
 is the active constituent of the coca leaf (Erythroxylon coca); it 
 melts at 98, is Isevo-rotatory, and is used in surgery for deaden- 
 ing pain. It has been synthesised by the action of benzoic an- 
 hydride and methyl iodide on ecgonine (B. 1885, 18, 2953). 
 
 Hyoscyamine, which crystallizes in needles or plates, melt- 
 ing at 109, resembles atropine closely, and is readily trans- 
 formed into the latter under the influence of various alkalis 
 (Will, B. 21, 1725, 2777). In contact with water it is slowly 
 hydrolysed to /-tropic acid and inactive tropine. Atropine is 
 racemic hyoscyamine. 
 
 Various substitutes for cocaine have been recommended, as 
 its solutions do not keep well. Willstatter (B. 29, 1575, 2216) 
 obtained an isomeride of ecgonine by the addition of HCN to 
 tropinone (p. 566) and subsequent hydrolysis, and from this 
 
ETHEREAL OILS 567 
 
 a -cocaine was obtained by benzoylation and esterification. 
 a-Cocaine contains both C0 2 Me and COPh groups attached to 
 the same carbon atom. a-Eucaine is a cheap substitute for 
 
 cocaine prepared from triacetonamine, NH<^QJ^ 2 [Qg 2 ^>CO 
 
 (p. 134), by addition of HCN, hydrolysis, benzoylation of the 
 hydroxy-acid thus formed, and final methylation of the imino 
 and carboxylic groups. Its structure is: 
 
 /3-Eucaine has the formula: 
 
 .;;: : NH< 
 
 (Harries, B. 29, 2730). 
 
 XLI. TEEPENES AND CAMPHORS 
 
 For history of terpenes see Tilden, Science Progress, 1911, 
 6, 46. Cf. Wallaces "Terpene und Camphor", 1909. 
 
 Ethereal Oils. Many plants, especially varieties of Coniferse 
 and of Citrus, contain, in their blossoms and fruits, oily sub- 
 stances to which they owe their peculiar fragrance or odour, 
 and which can be obtained from them by distillation in steam 
 or by pressure. These oils, "ethereal oils", were formerly 
 grouped together in a special class, but now they are recog- 
 nized as being more or less heterogeneous; thus oil of bitter 
 almonds is benzoic aldehyde, and Roman oil of cumin is a 
 mixture of cymene and cumic aldehyde, &c. Many of these 
 ethereal oils contain unsaturated hydrocarbons, which are usu- 
 ally termed terpenes. The common hydrocarbons met with 
 have the general formula C 10 H 16 , and are spoken of as terpenes 
 proper; but, in addition to these, hydrocarbons, represented 
 by the formula C 5 H 8 and known as hemiterpenes, exist. The 
 commonest of these is isoprene, obtained by distilling caout- 
 chouc. Hydrocarbons represented by the formula C 15 H 24 are 
 termed sesquiterpenes, and the more complex hydrocarbons, 
 (C 5 Ho) n , polyterpenes. Certain ethereal oils consist chiefly of 
 such hydrocarbons, e.g. turpentine, oil of citron, orange oil, and 
 oil of thyme. Other oils contain appreciable amounts of oxy- 
 genated compounds, mainly of an alcoholic or ketonic character, 
 
668 XLI. TERPENES AND CAMPHORS 
 
 e.g. camphor and menthone, C 10 H 16 0, pulegone, &c. Many of 
 these terpenes and ketones are reduced benzene derivatives, 
 e.g. limonene, menthone; others again are more complex ring 
 compounds, e.g. pinene and camphor. In addition to these 
 two groups of compounds a third group has been discovered 
 within recent years, namely, open-chain olefinic alcohols, alde- 
 hydes, or ketones, e.g. citronellal, geraniol, linalool. 
 
 The terpenes are widely distributed in the vegetable king- 
 dom, especially in the Coniferse (Pinus, Picea, AUes, &c.), in 
 the varieties of Citrus, &c. The products which are isolated 
 in the first instance from the individual plants, and which 
 according to their source are designated terpene, citrene (from 
 oil of citron), hesperidene (from oil of orange), thymene (from 
 thyme, carvene (from oil of cumin), eucalyptene, olibene, &c., 
 have for the most part the formula C 10 H 16 , and approximately 
 jqual boiling-points (160- 190); they are not, however, 
 chemical individuals, but mixtures of isomeric compounds. 
 
 With the exception of camphene they are all liquid, but it 
 is hardly possible to separate them completely by fractional 
 distillation (see table, p. 578, for boiling-points). The terpenes 
 can, however, be obtained chemically pure from crystalline 
 derivatives. Quite recently, numerous compounds belonging 
 to this class have been synthesised. 
 
 For simplicity the terpenes and allied oxygen compounds 
 (camphors) may be divided into the following groups: 
 
 A. Open-chain olefinic compounds. 
 
 B. Monocyclic terpenes (mainly reduced benzene deriva- 
 tives). 
 
 C. Complex cyclic terpenes. 
 
 Practically all the compounds dealt with in these three 
 divisions could have been discussed under the aliphatic and 
 cyclic compounds. A clearer view, however, of their relation- 
 ships is obtained by bringing them together under the general 
 heading of terpenes and camphors. 
 
 A. Open-chain Olefinic Terpenes and Camphors 
 
 Isoprene, the best-known hemiterpene, is a diolefine repre- 
 sented by the constitutional formula, CH 2 : CMe CH : CH 2 , 
 2-methyl-A 1:3 -butadiene. It is a colourless liquid, b.-pt. 37, 
 is formed by the dry distillation of rubber, or by decompos- 
 ing turpentine at a dull red heat (cf. Staudinger, B. 44, 2212). 
 At 300 it undergoes polymerization to diisoprene (probably 
 
CITRONELLAL 569 
 
 dipentene), and is transformed into products analogous to 
 rubber when treated with concentrated hydrochloric acid, 
 when kept for some time or when exposed to sunlight in 
 fche presence of traces of acid. Two syntheses of isoprene 
 are of interest. 
 
 (a) From methyl -pyrrolidine by exhaustive methylation 
 (Euler, J. pr. [ii], 57, 132): 
 
 CH 2 CH 2 , H _ ^" 
 
 CHMe CH 2 ^ methylated CHMe 
 
 CH 2 :CH.CHMe.CH 2 .NMe 2 
 
 CH 2 : CH CHMe CH 2 NMe 3 I 
 methylated __ C H 2 :CH.CMe:CH 2 + NMe 3 + HL 
 
 KOH 
 
 (b) From dimethyl-allene by the addition of two molecules 
 of hydrogen bromide and subsequent elimination of the same 
 (Ipatieff, ibid. 55, 4): 
 
 CMe 2 :C:CH 2 CMe 2 Br.CH 2 .CH 2 Br CH 2 :CMe.CH:CH 2 . 
 
 It has been suggested that indiarubber should be syntb.esised 
 from isoprene, but the cost of the isoprene has so far interfered 
 with the adoption of this method on the commercial scale. 
 
 Practically all the natural products belonging to this group 
 contain oxygen and are either aldehydes or alcohols. 
 
 Citronellal, CH 2 : CMe . CH 2 . CH 2 . CH 2 - CHMe - CH 2 CHO, 
 is an example of an olefine aldehyde; it is present in citronella 
 oil and also in lemon-grass oil, together with citral and geraniol. 
 It has b.-pt. 205-208. Its aldehydic nature is proved by the 
 readiness with which it is reduced to a primary alcohol, citron- 
 ellol, and oxidized to a monobasic acid, citronellic acid, con- 
 taining the same number of carbon atoms. By oxidizing its 
 dimethyl-acetal, Harries and SchauwecJcer (B. 34, 1498, 2981) 
 obtained a dihydroxy-derivative, thus proving the presence 
 of an olefine linking; and on farther oxidation with chromic 
 anhydride they obtained the acetal of a keto-aldehyde contain- 
 ing nine carbon atoms, thus proving that the double bond is 
 between the last and last but one carbon atoms with respect 
 to the aldehyde group: 
 
 CH 2 :CMe(CH 2 ) 3 .CHMe.CH 2 .CHO -f 4O 
 
 = OO 2 -f- H 2 O + O:CMe(CH 2 ) 3 .CHMe.CH 2 .CHO. 
 
 The positions of the methyl groups are proved by the rela- 
 
670 XLI. TERPENES AND CAMPHORS 
 
 tionship of the aldehyde to isopulegol, into which it is trans- 
 formed when kept for some time, or more quickly when heated 
 with acetic anhydride at 180: 
 
 The constitution of pulegol follows from the fact that when 
 oxidized it yields isopulegone, and this with baryta is trans- 
 formed into pulegone by the wandering of an olefine linking. 
 
 Pulegone 
 
 An interesting reaction of citronellal is its oxidation in 
 alkaline solution with permanganate, when it yields acetone 
 and /?-methyladipic acid, a result which would lead to the con- 
 clusion that the double bond is in position 5:6 with respect 
 to the CHO group. 
 
 The only manner of reconciling this reaction with the 
 reactions already given is the assumption that in the oxida- 
 tion in alkaline solution a wandering of the double bond 
 occurs : 
 
 CH 2 : CMe (CH 2 ) 3 CHMe CH 2 CHO 
 
 CMe 2 :CH(CH 2 ) 2 . CHMe -CH 2 . CHO. 
 
 Citral or geranial, C 10 H 16 0, occurs in both oil of lemons 
 and of oranges, and may also be obtained by the oxidation of 
 geraniol. Lemon-grass oil contains 70-80 per cent. It is a 
 colourless oil, and distils at 110-112 under 12 mm. pressure. 
 Its constitution is represented as: 
 
 CMe 2 : CH CH 2 CH 2 CMe : CH CHO. 
 
 Its aldehydic nature follows from its reduction to geraniol, 
 and its oxidation to an acid containing the same number of 
 carbon atoms, namely, geranic acid. Its unsaturated character 
 and the positions of the double bonds within the molecule 
 follow from its general properties, but more especially (a) from 
 its products of oxidation, viz. acetone, laevulic acid, and carbon 
 dioxide : 
 
 CMe 2 : ! CH.CH 2 .CH 2 -CMe: j CH-CHO 
 
 MejjCO + CO 2 H-CH 2 .CH a .COMe -f 20O a ; 
 
GERANIOL 671 
 
 (b) from its conversion into methyl-heptenone and acetalde- 
 hyde by means of potassium carbonate: 
 
 CMe 2 :CH.GH 2 .CH 2 .CMe:CH.CHO=CMe 2 :CH.CH 2 .CH 2 .COMe 
 + H 2 +CH 3 .CHO. 
 
 When heated with potassium hydrogen sulphate, citral is con- 
 verted into ^Mjymene. 
 
 Both citral and geranic acid have been synthesised by 
 Earlier and Bouveault (C.E. 1896, 122, 393). 1-Methyl-A'- 
 heptenone reacts with metallic zinc and iodo -acetic acid 
 (Reformatsky reaction), yielding the compound: 
 
 H 2 .CO a H 
 
 L s 
 With dilute acid this yields the hydroxy-acid: 
 
 CMe 2 : CH CH 2 CH 2 CMe(OH) CHj CO 2 H, 
 
 and when this is distilled with acetic anhydride, water is 
 eliminated and geranic acid formed. 
 
 Geranic acid, when reduced in the form of its ethyl ester 
 with sodium and amyl alcohol, yields i-rhodinic acid: 
 
 CMe 2 : CH CH, CH 2 - CHMe CH 2 C0 2 H, 
 
 which is structurally isomeric with citronellic acid; and when 
 ethyl rhodinate is reduced with sodium and alcohol, the corre- 
 sponding primary alcohol, rhodinol, is formed. 
 
 Citral occurs in two stereoisomeric forms, termed a- and 
 6-citrals. They are both inactive, and the isomerism is of the 
 same type as that met with in the crotonic acids and fumaric 
 and maleic acids (p. 243). 
 
 Geraniol, C 10 H 18 0, is the alcohol corresponding with citral, 
 and is the chief constituent (90 per cent) of Indian geranium 
 oil, which is largely used for adulterating rose oil. Its con- 
 stitution follows from its relationship to citral and geranic 
 acid, into which it is readily oxidized. 
 
 By reducing citral with alcohol and sodium amalgam, two 
 stereoisomeric alcohols, geraniol and nerol, are obtained, and 
 both yield citral when reoxidized. Both alcohols yield ter- 
 pineol by the action of acetic acid containing 1 to 2 per cent 
 of sulphuric acid, but nerol reacts about nine times as readily 
 as geraniol. The formation of terpineol can be accounted for 
 by the addition and withdrawal of water. The two alcohols 
 
572 XLI. TERPENES AND CAMPHORS 
 
 are structurally identical, and are represented by the two 
 stereochemical formulae : 
 
 H.C.CH 2 .OH 01 
 
 I. 1| IL 
 
 CMe 2 :CH.(CH 2 ) 2 -C.CH 3 CMe 2 :CH.(CH 2 ).C.CH 3 
 
 Geraniol Nerol. 
 
 as No. II would lose water more readily than No. I to form 
 a six-membered ring. It is probable that citral a corresponds 
 with geraniol, and citral I with nerol. 
 
 Linalool or coriandrol is isomeric with geraniol, into which 
 it is readily transformed by the action of dilute organic acids. 
 It occurs as linalyl acetate in lavender, sage, and coriander 
 oils. It is optically active, reacts as a tertiary alcohol, and 
 hence is structurally- and not stereo-isomeric with geraniol. 
 Its reactions agree best with the formula: 
 
 CMe 2 : CH CH 2 . CH 2 CMe(OH) CH : CH^ 
 
 and its conversion into geraniol probably depends upon the 
 addition and subsequent removal of water, the glycol, 
 
 CMe 2 :CH.CH 2 .CH 2 .CMe(OH).CH 8 .CH 2 .OH, 
 
 being formed as the intermediate product. /-Linalool reacts 
 with acetic anhydride, yielding nerol, geraniol, and d-terpineol. 
 Compounds of this type with the carbon system : 
 
 7654321 
 
 are readily transformed into derivatives of j9-cymene by union 
 between carbon atoms numbers 1 and 6 (cf. p. 571), or into 
 tetrahydrobenzene derivatives by union of numbers 2 and 7 
 (cf. lonone, p. 589; also conversion of citral into a- and 
 /?-cyclo-citrals, cyclic /?y and a/3 unsaturated aldehydes). 
 
 B. Monoeyelie Terpenes and Camphors 
 
 I. Terpenes. These compounds are to be regarded as hydro- 
 derivatives of cymene (p. 352). Their close relationship to 
 cymene can be shown in very different ways: e.g. (a) the 
 hydrocarbon terpinene when heated with iodine is transformed 
 into ^-cymene, i.e. ^-methyl-isopropyl benzene; (b) the ketonc 
 
MONOCYCLIC TERPENES 573 
 
 carvone when heated with mineral acids yields carvacrol, i.e. 
 l-methyl-2-hydroxy-4-isopropyl benzene (p. 417); (c) on oxi- 
 dation many terpenes yield terephthalic acid; (d) when bro- 
 minated and then reduced many monocyclic terpenes yield 
 benzene hydrocarbons (B. 1898, 31, 2068). 
 
 The unsaturated nature of these compounds follows from 
 the readiness with which they form additive compounds; they 
 yield dihydrochlorides, C^H^Cl^ tetrabromides, C^H^Br^ 
 nitroso-chlorides, C 10 H ]6 (NOC1) 2 , nitrosites, C 10 H 16 (NO)(N0 2 ), 
 and nitrosates, C 10 H 16 N 2 4 . These compounds are of con- 
 siderable importance, as most of them are well-defined crystal- 
 line compounds with definite melting-points, and can therefore 
 be made use of in separating and identifying the various 
 liquid terpenes. The nitroso-chlorides were first prepared by 
 Tilden (J. C. S. 1877, 554), by the direct action of nitrosyl 
 chloride, but are now usually obtained by Wallaces method, 
 viz. by the action of a mixture of ethyl nitrite, acetic and 
 hydrochloric acids on the hydrocarbon. The nitrosites are 
 usually obtained by the action of sodium nitrite and acetic 
 acid on the hydrocarbon, and the nitrosates by the direct 
 addition of nitric peroxide or by the action of amyl nitrite 
 and concentrated nitric acid. 
 
 An interesting group of compounds are the nitrolamines, 
 obtained by the action of amines (piperidine or benzylamine) 
 on the nitroso-chlorides. They contain the NHE-group ID 
 place of the chlorine of the nitroso-chlorides. Such com- 
 pounds crystallize well, and can be used for identifying the 
 various terpenes. 
 
 All these reactions point to the presence (a) of a six- 
 membered carbon ring in the monocyclic terpenes; (b) to the 
 presence of two side chains, usually in ^-positions, one consist- 
 ing of the CHg-group, and the second containing the grouping 
 
 CX^o; (c) to the presence of two double bonds in the mole- 
 cule. These may be both in the carbon ring, or one in the 
 ring and one in a side chain, e.g.: 
 
 CH 3 
 
 H/V 
 
 II 
 
 qcH 8 ) a 
 
574 XLI. TERPENES AND CAMPHORS 
 
 Fourteen such isomerides are theoretically possible. The 
 carbon atoms are usually numbered as follows: 
 
 The saturated compound C 10 H 20 , viz. p -methyl -isopropyl- 
 hexamethylene, is called terpane*, and the compounds C 10 H 16 
 are terpadienes. I is A-l : 4-terpadiene, II is A-l : 4 (8)-ter- 
 padiene, and III A-l : 8 (9)-terpadiene. 
 
 The double linking in No. II between a carbon atom in the 
 ring and a carbon of a side chain is termed a semicyclic linking. 
 Such an unsaturated linking is quite stable under the influ- 
 ence of heat, but in the presence of acids it wanders into 
 the nucleus, e.g. A 4(8) ^-menthene is readily transformed into 
 A 3 j9-menthene. 
 
 A few of the terpenes contain the methyl- and isopropyl- 
 groups in the meta positions, e.g. sylvestrene; such com- 
 pounds are termed m-terpadienes. 
 
 The nitroso-chlorides are frequently colourless, and then ap- 
 pear to be bimolecular; some give blue solutions containing the 
 monomolecular form. Compounds with a semicyclic linking 
 ^>C:CR 2 yield unimolecular blue nitroso-chlorides volatile 
 with steam. The blue compounds are true nitroso-compounds. 
 When the NO-group becomes attached to ^>CH it usually 
 passes over into the isonitro-group ^>C:NOH, and the com- 
 pound becomes colourless. 
 
 The following hydrocarbons belong to this group : 
 
 Dipentene, A-l: 8 (9)-terpadiene or inactive limonene (see 
 formula III; for constitution cf. B. 1895, 28, 2145; 1898, 31, 
 1402; 1900, 33, 1457). It occurs together with cineol in Oleum 
 tince, and is prepared by heating pinene, camphene, sylvestrene, 
 or limonene to 250-270 for several hours, and also by the 
 abstraction of hydrogen chloride from its dihydrochloride. It 
 is further produced from pinene under the influence of dilute 
 alcoholic sulphuric acid, from terpin hydrate and terpineol by 
 the elimination of water, by the polymerization of isoprene, 
 and, together with the latter substance, on distilling caout- 
 chouc. Its formation from isoprene, CH 2 : C(CH 8 ) CH : CH 2 , by 
 heating at 300 is a synthesis, since isoprene has been synthe- 
 sised (p. 569). It is a liquid of pleasant odour like that of oil 
 
 * The name menthane is sometimes used for this hydrocarbon and 
 menthadienea for the terpadienes. 
 
LIMONENES 575 
 
 of citron, boils at 175-176, and is more stable than pinene, 
 although it can still be transformed into terpinene by acids. 
 It readily forms dipentene dihydrochloride with hydrochloric 
 acid, and with bromine a crystalline tetrabromide melting at 
 125. Its (inactive) nitroso-chloride yields, by the elimination 
 of hydrogen chloride, the so-called nitroso-dipentene (inactive 
 carvoxime), melting at 93. 
 
 c?-Limonene, hesperidene, dtrene, or carvene. The oil of the 
 orange rind consists almost entirely of dextro-limonene, which 
 is also the chief constituent of carvene, oil of dill, oil of eri- 
 geron, &c.; oil of citron consists mainly of d-limonene and 
 pinene. It boils at 175, and forms a dextro-rotatory tetra- 
 bromide, C 10 H 16 Br 4 , which melts at 104. The dextro- and 
 laBvo-tetrabromides are identical, except that their crystals are 
 the mirror images of one another. Dextro-limonene is very 
 readily racemized to dipentene. 
 
 /-Lunonene is present together with Isevo-pinene in the oil 
 of fir cones. 
 
 I- and d-limonenes yield nitroso-chlorides, C^H^NOCl, of 
 corresponding rotatory powers; and, on the elimination of 
 hydrogen chloride from these, /- and J-nitroso-limonenes, 
 C 10 H 15 NO, which are identical with the carvoximes. 
 
 The conversion of geraniol into dipentene is of considerable 
 interest (Tiemann and Schmidt, B. 1895, 28, 2137): 
 
 (CH 3 ) 2 C:CH.CH 2 .CH 2 .qCH 3 ):CH.CH 2 OH 
 
 Geraniol 
 
 -* (CH 3 ) 8 C(OH).CH 2 .CH 2 .CH 2 .C(CH 3 XOH).CH 2 .CH 2 OH 
 + 2H 2 O Terpin hydrate 
 
 Terpto 
 
 - 2H *p*2UT 
 
 Dipentene readily combines with hydrogen chloride, 
 a dihydrochloride, C ]0 H 18 C1 2 , which melts at 50. The same 
 compound is also formed by the action of hydrogen chloride on 
 limonene or on pinene, and when left in contact with aqueous 
 alcohol yields terpin hydrate, C 10 H 19 (OH) 3 (cf. formula above), 
 in the form of large rhombic crystals melting at 117. 
 
 Terpinene, probably &-l:3-terpadiene t is one of the most 
 stable of the terpenes. It may be obtained by the action of 
 alcoholic sulphuric acid on dipentene, or on other compounds 
 
576 XLI. TERPENES AND CAMPHORS 
 
 which yield dipentene as an intermediate product, e.g. by 
 shaking pinene with concentrated sulphuric acid, or by boiling 
 terpin hydrate with dilute sulphuric acid. It boils at 179- 
 181, is optically inactive, and most of its derivatives are oils, 
 with the exception of the nitrosite, which melts at 155. 
 
 Terpinolene, A-l:4 (8)-terpadiene, is formed when terpineol 
 is boiled for a short time with oxalic acid solution. It boils 
 at 183-185, and is readily transformed by acids into ter- 
 pinene. It forms a blue nitroso-chloride. 
 
 Sylvestrene, Carvestrene, A-l:8 (9)-mrterpadiene, b.-pt. 175, 
 is the chief dextro-rotatory constituent of Swedish and Eussian 
 oil of turpentine. It is one of the most stable of the terpenes, 
 and gives a magnificent blue coloration with acetic anhydride 
 and concentrated sulphuric acid. The CH 3 and C 3 H 5 substi- 
 tuents are in the m-positions, as treatment with bromine con- 
 verts it into T/Zrcymene. 
 
 It has been synthesised from m-hydroxybenzoic acid by 
 Perkin and Tattersall (J. C. S. 1907, 480) by reducing to its 
 hexahydro derivative, oxidizing to y-ketohexahydrobenzoic 
 acid, and proceeding as in the synthesis of terpineol. 
 
 The constitution of dipentene is derived from its relation- 
 ship to terpineol (p. 579), from which it is obtained by the 
 elimination of water. If molecular rearrangement does not 
 occur during this reaction, it is clear that dipentene must have 
 a constitutional formula corresponding with I or II: 
 
 Terpineol 
 
 Formula I is not asymmetric, and therefore cannot represent 
 the molecules of d- and Wimonenes and of dipentene; formula 
 II, on the other hand, contains an asymmetric carbon atom, 
 the one indicated by an asterisk, the molecule is asymmetric, 
 and can form d- t Z-, and r-modifications. 
 
 The correctness of formula II is confirmed by a study of 
 some of the reactions of dipentene. 
 
 Dipentene forms a nitroso- chloride (colourless), and this 
 with alkalis gives the oxime of carvone. The oxime when 
 hydrolysed yields carvone, and this on reduction yields dihy- 
 drocarveol, a secondary alcohol formed by the addition of two 
 
PHELLANDRENES 577 
 
 atoms of hydrogen to one of the ethylene linkings and two 
 atoms of hydrogen to the carbonyl group. Dihydrocarveol 
 when oxidized yields a ketonic alcohol, CH 3 .C 6 H 9 (OH).CO- 
 CH 3 , proving the presence of the C(CH 3 ) : CH 2 group in dihy- 
 drocarveol, carvone, and dipentene. 
 
 Terpinolene is also formed from terpineol by the elimina- 
 tion of water, and should therefore be represented by formula 
 No. I, a formula which is in harmony with the inactivity of 
 the hydrocarbon. The stable terpinene most probably con- 
 tains conjugate double bonds, and as it is formed from ter- 
 pinoline by the action of acids it is probably A-l:3-terpa- 
 diene. 
 
 Phellandrene. Three isomeric phellandrenes exist in nature : 
 d-a-phellandrene in oil of bitter fennel and in elemi oil, /-a-phel- 
 landrene in Australian eucalyptus oil (Eucalyptus amygdalina), 
 and d-/3-phellandrene in water dropwort (Phellandnum aqua- 
 ticum). The d- and /-a-phellandrenes are optical antipodes, 
 and are both &-l:5-terpadienes. The b.-pt. is 62/12 mm. It 
 is transformed into terpinene by the action of acids, and its 
 dibromide with alkalis yields cymene. This constitution fol- 
 lows from the fact that nitro-a-phellandrene, when carefully 
 reduced, yields active carvotanacetone, A-5-terpene-2-one, and 
 has been confirmed by the synthesis of a-phellandrene from 
 4-isopropyl-A2-hexenone (A. 359, 285): 
 
 Grignard 
 
 C 3 H 7 CH<2 ! 25>CMe, 
 
 dehydrated 
 
 and also by its synthesis from carvone (p. 579). 
 
 Carvone carvone hydrobromide * A6-terpen-2-one * 
 
 IIBr reduced PC1 S 
 
 6-chloro-A-l : 5-terpadiene * a-phellandrene. 
 
 reduced 
 
 /3-Phellandrene is A-2 : 1 (l)-terpadiene. It has boiling-point 
 57/ll mm., yields two nitrosites, melting-point 97 and 102. 
 Its constitution is based on the fact that it is oxidized by 
 atmospheric oxygen to 4-isopropyl-A-2-hexenone (A. 343, 29), 
 and on its synthesis from carvone (J. pr. [ii], 72, 193; 75, 141). 
 
 Carvone - carvomenthol (terpane-2-ol) * A-1-terpene * 
 
 reduced dehydrated bromine 
 
 terpenedibromide * /?-phellandrene. 
 
 ale. potash 
 (B480) ?0 
 
578 XLI. TERPENES AND CAMPHORS 
 
 Menthene, obtained from menthol by the elimination of 
 water, is A-3-terpene; when oxidized it yields a glycol, which 
 on further oxidation gives /2-methyladipic acid : 
 
 It has been synthesised by Wallach (B. 39, 2504) by con- 
 densing l-methylcyclohexan-4-one with ethyl a-bromoiso- 
 butyrate and zinc, hydrolysing and eliminating C0 2 and 
 water. 
 
 A synthetical terpene or dihydro-cymene boiling at 174 has 
 been prepared from succinylo-succinic ester (pp. 342, 469) 
 (B. 26, 233). It shows the complete terpene character, has a 
 turpentine odour, becomes resinous on exposure to the air, 
 decolorizes permanganate at once, and takes up bromine. 
 
 SUMMARY OF DERIVATIVES 
 
 nninn Tetra- Dihydro- xnt,it 
 
 Bo^ng- bromide, chloride. Nl jj * 
 
 point. M . p M _ p M.-p. 
 
 Limonene... 175 104 50 
 
 Dipentene 
 
 Terpinolene . . 
 
 Terpinene 
 
 Phellandrene. 
 Sylvestrene... 
 
 175 125 50 
 
 183-185 116 
 
 179-181 oil oil 153 
 
 171-172 oil oil 105 
 
 175 135 72 
 
 II. Camphor Compounds. Alcohols and Ketones. 
 Menthol, 3-terpanol, mint camphor, C 10 H 20 : 
 
 The /-modification is the chief constituent of oil of pepper- 
 mint. It melts at 43, has a strong odour of peppermint, and 
 is used as an antiseptic and anaesthetic. When heated with 
 copper sulphate it yields cymene, when reduced with hydriodic 
 acid, hexahydrocymene, and on oxidation with permanganate 
 it yields /3-methyladipic acid, and several fatty acids. As 
 the formula contains three asymmetric carbon atoms, several 
 stereo-isomerides are possible. 
 
 The corresponding ketone menthone, 3-lerpanone, 10 H 18 O, 
 is obtained when the alcohol is oxidized with dichromate 
 (Beckmann, A. 1891, 262, 31), and also occurs in oil of pepper- 
 mint. It boils at 207, and has the characteristic properties 
 
TERPINEOL 579 
 
 of a ketone; its semicarbazone melts at 184. It is readily 
 converted into thymol (l-methyl-3-hydroxy-4-isopropyl-ben- 
 zene) by bromination and elimination of hydrogen bromide, 
 and when oxidized yields /?-methyladipic acid. Hence follows 
 the constitution, which is supported by its synthesis by the 
 distillation of calcium /?-methyl-a'-isopropylpimelate (Kotz and 
 Schwarz, A. 357, 206): 
 
 CH a CHMe CH 2 CO(X CH 2 CHMe CH 2 
 
 CH 2 .CH(C 3 H r ).COO / * " CH 2 .CH(C 3 H 7 ).CO. 
 
 An unsaturated ketone pulegone, A-4 (&)-terpene-3-one, may 
 be obtained from oil of pennyroyal. It is isomerie with ordi- 
 nary camphor, and on reduction yields menthone. Its con- 
 stitution follows from the fact that when heated with water it 
 yields acetone and methylcyclohexanone. 
 
 Isomerie with menthol is carvomenthol or terpane-2-ol. 
 
 Carvone, A-6:8 (9)-terpadiene-2-one, is the chief constituent 
 of oil of carraway seeds, and is widely distributed in the 
 vegetable kingdom. It is a liquid, distils at 228, exists in 
 d-and /-modifications, and has the properties of an unsaturated 
 ketone (cf. A. 1897, 297, 122). With hydroxylamine it yields 
 carvoxime, which is identical with nitroso-limonene. When 
 heated with phosphoric acid carvone is isomerized to car- 
 vacrol. 
 
 Terpineol, &-l-terpen-8-ol, does not occur in large quantities 
 naturally, but is obtained readily from natural products, e.g. by 
 the action of dilute potash on limonene hydrochloride, or by 
 the hydration of pinene hydrate. It has m.-pt. 37, b.-pt. 218, 
 and [a] D 106. When treated with dilute acids it can give 
 dipentene, terpinolene, terpinene, terpin hydrate, cineol or 
 cymene, according to the conditions. Its constitution is of 
 importance, as those of several terpenes are deduced from that 
 of terpineol. The constitution is based on (1) examination of 
 its decomposition products, (2) its synthesis. 
 
 By means of dilute permanganate two hydroxyls are added 
 to the double bond, and l:2:8-trihydroxyterpane (trihydroxy- 
 hexahydro-jp-cymene) is formed, and this on further oxidation 
 yields a ketolactone, homoterpenylic methyl ketone, which can 
 be oxidized to acetic and terpenylic acids. The constitution 
 of the latter has been proved to be: 
 
 ,CH(CH 2 -CO 2 H).CH 2 
 CO 
 
 CMe 2 < Q 
 
580 XLI. TERPENES AND CAMPHORS 
 
 from its method of synthesis (Simonsen, J. C. S. 1907, 184). 
 This gives the formula,: 
 
 H(CH 2 - CH 2 . CO CH 3 ) . CH 2 
 
 for homoterpenylic methyl ketone, and proves the l:2:8-posi- 
 tions of the three hydroxyl groups in the first oxidation pro- 
 duct, and the A-1-position of the ethylene linking and position 
 8 of the hydroxyl group in terpineol. 
 
 Its synthesis (Perkin, J. C. S. 1904, 654) is from S-keto- 
 hexahydrobenzoic acid (S-keto-cyclohexarie-carboxylic acid). 
 The ester of this acid reacts with magnesium methyl iodide, 
 and then with water, yielding: 
 
 OH 
 
 By the action of fuming hydrobrornic acid the hydroxyl is 
 replaced by bromine, and then by the action of pyridine hy- 
 drogen bromide is eliminated and A-3-tetrahydro-p-toluic acid 
 is formed. The ethyl ester of this acid reacts with magnesium 
 methyl iodide, and then with water, in the normal manner, 
 yielding the tertiary alcohol, inactive terpineol: 
 
 and by the elimination of water from this alcohol dipentene 
 was obtained. 
 
 This method of synthesis has been extended by Perkin and 
 his students to a large number of cases, and they have obtained 
 alcohols and unsaturated hydrocarbons analogous to the natural 
 products, but which, so far, have not been obtained naturally. 
 From A-1-tetrahydro-^-toluic acid, A-3-j?-terpen-8-ol, and A-l : 8 
 (9) terpadiene. From hexahydro-o-toluic acid, compounds simi- 
 lar to terpineol and dipentene were obtained, but with the 
 substituents in o-positions. From hexahydrobenzoic acid a 
 compound was obtained analogous to dipentene, but without 
 the methyl substituent in position 1. By using optically 
 active A-1-tetrahydro-^-toluic acid, an active alcohol and ter- 
 pene were synthesisecL (Compare J. C. S. 1905, 639, 655, 661, 
 1067, 1083; 1906, 8*2, 839; 1908, 573, 1871, 1876; 1910, 
 2129, 2147; 1911, 111, 518, 526, 727, 741.) 
 
 Terpin, p-terpurl : 8-<*oJ, has been synthesised by the action 
 
COMPLEX CYCLIC TERPENES 581 
 
 of magnesium methyl iodide on both carbonyl groups of ethy 
 cyclohexanone-4-carboxylate (Kay and Perkin, J. C. S. 1907 
 372), and is also formed by boiling terpineol with dilute sul- 
 phuric acid. It exists in two stereoisomeric modifications, cis 
 and trans. The cis is the common form, and combines with 
 water to give terpin hydrate, C 10 H 22 3 , which forms well- 
 developed crystals, m.-pt. 116. When dehydrated the terpins 
 yield terpinene, terpinolene, terpineol, and cineol; the latter is 
 an inner anhydride (ether) formed by the elimination of water 
 from the two hydroxyl groups. 
 
 C. Complex Cyclic Terpenes and Camphors 
 
 The compounds belonging to this group are bicyclic, i.e. the 
 molecule is built up of two rings. Benzene or reduced ben- 
 zene derivatives containing a diagonal linking in the m- or 
 p-position (examples I and II) are bicyclic, also the com- 
 pounds which can be regarded as derived from a single ring 
 by the introduction of a bridge consisting of one or more 
 carbon atoms (examples III, IV, and V). 
 
 For systematic nomenclature cf. Baeyer, B. 33, 3771. 
 
 I. Terpenes. Pinene, C 10 H 16 , is the chief constituent of 
 German and American oil of turpentine, oil of jumper, euca- 
 lyptus, oil of sage, &c. It forms, together with sylvestrene 
 and dipentene, Russian and Swedish turpentine oil. 
 
 Oil of turpentine is obtained by distilling turpentine, the 
 resin of pines, with steam, colophonium (fiddle resin) remain 
 ing behind. It is a colourless, strongly refracting liquid of 
 characteristic odour, almost insoluble in water, but readily 
 soluble in alcohol and ether. It dissolves resins and caout- 
 chouc (being therefore used for the preparation of oil paints, 
 lakes), also sulphur, phosphorus, &c. Pinene absorbs oxygen 
 from the air with the formation of ozone arid production o* 
 resin, minute quantities of formic acid, cymene, &c., being 
 formed at the same time. Dilute nitric acid gives rise eithei 
 to terephthalic acid in addition to fatty acids, or under other 
 conditions to terpeuylic acid (p. 579), C 8 H 12 4 (which belongs 
 
582 XLI. TERPENES AND CAMPHORS 
 
 to the fatty series). Heating with iodine transforms it into 
 cymene, the action being violent. It acts as an antiseptic, 
 and arrests the secretions (e.g. that of the kidneys). 
 
 It exists in three stereoisomeric modifications: d-pinene or 
 australene occurs in large quantities in German, Eussian, and 
 Swedish oils; /-pinene or terebenthene in French turpentine 
 oil; tW-pinene is obtained by heating pinene nitroso-chloride 
 with aniline: 
 
 []" E.-pt. d 4 T 
 
 d +45 156 0-858 
 
 I 43-4 156 0-858 
 
 d-l 156 0-858 
 
 Pinene has all the characteristic properties of an unsaturated 
 compound. It forms a nitroso-chloride (C ]0 H 16 , NOC1) 2 , 
 colourless crystals melting at 103, which is used for isolating 
 pinene from mixtures; also a hydrochloride, C 10 H 17 C1, a 
 white crystalline solid melting at 131, with a camphor-like 
 odour, hence the name "artificial camphor". This is in- 
 soluble in water, but readily soluble in alcohol, and if hydro- 
 gen chloride is eliminated by weak alkali, e.g. by heating it 
 with soap or with silver acetate, camphene is obtained. It is 
 identical with bornyl chloride, and on oxidation yields cam- 
 phoric and apocamphoric acid. It is probable that by conver- 
 sion into the hydrochloride an intramolecular rearrangement 
 has taken place, as indicated by the following formulae: 
 
 CMeCl CMe 
 
 H 2 | ^XjHCl 
 CMe a I 
 
 H 2 C^ I CH 2 
 
 CH 
 
 Pinene Intermediate Pinene 
 
 Product hydrochloride 
 
 The presence of a double bond in the pinene molecule is 
 indicated by the formation of dibromides, an oil and a solid 
 melting at 169, and also by the formation of a glycol, pinene 
 glycol, C 10 Hi 6 (OH) 2 , by the action of dilute permanganate. 
 
 The constitution of pinene is based largely upon that of 
 pinole, CjoHjgO, a product obtained by the elimination of 
 water from soberol, Ci H 16 (OH) 2 , which is formed when pinene 
 is left exposed to sunlight in contact with air and water. With 
 
COMPLEX CYCLIC TERPENES * 
 
 583 
 
 dilute permanganate, pinole, which is an unsaturated ether, 
 yields pinoleglycol, 10 H ]6 0(OH) 2 , and this on further oxida- 
 tion yields a tetrahydric alcohol, sobrerythritol, C 10 H 16 (OH) 4 , 
 which can be oxidized to terpenylic acid. Pinole presumably 
 contains the same grouping of carbon atoms as terpenylic acid 
 (see p. 579), and should be either: 
 
 CH=CMe CH 
 
 cf 
 
 CH a dH 
 
 CH 2 CMe C 
 
 
 
 or 
 
 Sobrerol would then be : 
 
 CH= CMe CH OH 
 
 I I 6Me 2 .QH I 
 
 O tl-2 Oxi OJEL2 
 
 or 
 
 CH 2 CMe=C-OH 
 (*Me 2 .OH I 
 -CH CH, 
 
 but since sobrerol on further oxidation yields a tetrahydric 
 alcohol and not a dihydroxy-ketone, formula I is correct, and 
 the formula on p. 582 follows for pinene (Wagner). 
 
 When boiled with dilute acids pinene yields terpineol or its 
 esters; such a transformation is explicable if the assumption 
 is made that the four-membered ring is unstable, and that a 
 rupture between the CMe 2 and upper CH -group occurs. A 
 similar rupture, accompanied by the wandering of a chlorine 
 atom, occurs in the transformation of pinene nitroso-chloride 
 into hydrochlorocarvoxime under the influence of hydrochloric 
 acid. 
 
 When pinene is oxidized with permanganate the double link 
 ing is broken and a monobasic ketonic acid, pinonic acid, 
 
 is formed, and this on further oxidation yields the dibasic 
 acid pinic acid, 
 
 from which nor pinic acid, 1:1 -dimethyl- cyclobutane-2 : 4-dicar- 
 boxylic acid, can be obtained (Baeyer, B. 29, 1907), indicating 
 that the four-membered ring is stable in the presence of 
 
584 XLI. TERPENES AND CAMPHORS 
 
 oxidizing agents, although readily ruptured by hydrolysing 
 agents, e.g. pinonic acid yields when hydrolysed a lac tone, 
 homoterpenylic methyl ketone (cf. p. 580). 
 
 OH - CO C JI 2 CH>CH . CO CH 3 
 
 The only reactions of pinene difficult to account for by 
 means of Wagner's formula are its oxidation to isoketocam- 
 phoric acid, isocamphoronic acid, and terebic acid (Tiemann 
 and Semmler, B. 29, 529, 3027; Perkin, Proc. 1900, 214). 
 
 Bornylene is obtained by the action of alkalis on bornyl 
 iodide (from pinene and hydrogen iodide), and as it is readily 
 oxidized to camphoric acid it is represented by formula I. 
 
 The corresponding saturated hydrocarbon camphane, CjnHjg, 
 the parent substance of the camphor group, is obtained by 
 reducing bornyl iodide. It melts at 154, and is optically 
 inactive; its molecule should therefore be symmetrical. 
 
 CH 2 .CMe-CH CH 2 .CMe-CO CH 2 .CMe.CO 2 H 
 
 I I CMe 2 1! II I CMe 2 I III I CMe 2 
 
 CH 2 -CH CH CH 2 .CH CH 2 CH 2 .CH CO 2 H 
 
 Bornylene Camphor Camphoric acid. 
 
 Camphene, d and Z, is a solid, m.-pt. 50. It can be obtained 
 from pinene by combining with hydrogen chloride, forming 
 bornyl chloride, and then removing hydrogen chloride by 
 means of alkalis. For some years it was represented by 
 formula I, but it does not yield camphoric acid when oxidized. 
 Harries and Palmer (B. 1910, 43, 1432) have shown that it 
 forms an ozonide when its acetic -acid solution is saturated 
 with ozone, and that this when warmed yields a mixture of 
 camphenilone (30 per cent) (IV), 
 
 CMe 2 .CH-CH 2 CMe 2 .CH.CH 2 CMe 2 .CH-CH 2 
 
 IV I CH 2 I V 6 CH 2 I VI I CH 2 I 
 
 CO CH.CH 2 CO CH.CH 2 CH 2 :C - CH-CH 2 
 
 and rf-hydroxy-camphenilic acid lactone (50 per cent) (V), and 
 they therefore suggest formula VI for camphene. The for- 
 
CAMPHORS 585 
 
 tnation of camphene from bornyl chloride must thus involve 
 molecular rearrangements. 
 
 Sabinene occurs in marjoram oil; it has b.-pt. 163-165 
 and [a],, -f- 80. It forms a hydrochloride and a nitroso- 
 chloride; when oxidized it yields a ketone by the replacement 
 of CH 2 by 0, and therefore probably contains a methylene 
 group attached to the nucleus. It also probably contains 
 a three-membered ring and is represented as 
 
 The tri-ring is readily ruptured, as sabinene and its deriva- 
 tives can be transformed into terpinene and related hydroxy 
 compounds, a and /? Thujenes, C 10 H 16 (Tschugaeff, B. 34, 
 2279; 37, 1481), also contain a tri-ring and a double linking 
 in positions 1 and 3 respectively. 
 
 II. Camphors. The most important variety of -camphor 
 is: 
 
 Common or Japan camphor, C ]0 H 16 0, which is found in 
 the camphor tree (Laurus camphora), and can be obtained 
 from the latter by distillation in steam. It forms colourless, 
 transparent, glistening prisms of characteristic odour. It melts 
 at 175, boils at 204, has a sp. gr. 0-985, and can be sublimed 
 readily. It is dextro-rotatory in alcoholic solution, the amount 
 of rotation varying with the source of the camphor. When 
 distilled with phosphoric anhydride it yields cymene; zinc 
 chloride at high temperatures also transforms camphor into 
 cymene, though in the latter case the reaction is less simple: 
 
 C 10 H 16 = C ]0 H 14 + H 2 0. 
 
 When heated with iodine it yields carvacrol, i.e. hydroxy- 
 cymene (p. 417), just as oil of turpentine yields cymene. Nitric 
 acid oxidizes it to the dibasic camphoric acid, C 8 H U (C0 2 H) 2 , 
 which somewhat resembles phthalic acid (see R 23, 218), and 
 then to camphoronic acid, unsym. trim e thy 1-carbally lie acid, 
 &c. Camphor reacts with hydroxylamine to produce cam- 
 phor-oxime, C ]0 H 1 (NOH), and therefore contains a carbonyl 
 group, and with nitrous acid to produce isonitroso- camphor, 
 C 10 H 14 0:N-OH, and thus contains the group CH 2 CO. 
 The oxime by the loss of water is converted into the cyanide, 
 9 H 15 CN, which yields campholenic acid, C^I^COjH, on 
 
686 XLt TERPENES AND CAMPHO&S 
 
 saponification, and camphylamine, C 9 H 16 (CH 2 NH 2 ), on 
 reduction (B. 21, 1125). 
 
 A considerable amount of attention has been devoted by 
 various chemists to the question of the constitution of cam- 
 phor (Lapworth, B. A. Report, 1900, 299). At first, great im- 
 portance was attached to the readiness with which camphor 
 can be transformed into benzene derivatives, e.g. cymene and 
 carvacrol, and attempts were made to represent it as a simple 
 six-carbon ring compound, e.g. KekuU. 
 
 CO 
 
 whereas others represented it as a bridged six-carbon ring. 
 In 1893 Bredt suggested the formula II (p. 584), which is now 
 generally accepted, and which has been confirmed recently by 
 the synthesis of camphoric acid. Bredt drew especial atten- 
 tion to the oxidation products of camphor, namely camphoric, 
 camphoronic, and trimethyl-succinic acid previously obtained 
 by Koenigs. He showed that camphoronic acid when heated 
 gave trimethyl-succinic, isobutyric, and carbonic acids and 
 carbon, and suggested the formula C0 2 H'CH 2 -CMe(C0 2 H) 
 CMe 2 C0 2 H, viz. a-a-j8-trimethyl-carballylic acid, a consti- 
 tution which has since been confirmed by W. H. PerJcin and 
 Thorpe's synthesis (J. C. S. 1897, 1169). This consists in 
 condensing ethyl acetoacetate and ethyl a-bromo-isobuty- 
 rate by means of zinc to ethyl /?-hydroxy-a-a-/2-trimethyl 
 glutarate : 
 
 CBrMe 2 COJ&t CMe 2 CO 2 Et 
 
 CH s .CO.CH 2 .CO 2 Et ~* OH.CMe-CH 2 .CO 2 Et. 
 
 The OH group is replaced by Cl, and this by ON, and the 
 cyano-ester when hydrolysBd yields camphoronic acid : 
 
 CMe 2 .C0 2 Et 
 CN.CMe.CH 8 .C0 2 Et 
 
 The relationship between camphor and its oxidation products 
 is thus simple, as shown by the following scheme : 
 
 CH 2 .CMe.CO CH 2 .CMe.C0 2 H(/S) CH 2 CMe 2 .00 2 H 
 CMe 2 | -* CMe 2 -* I CMe 2 
 
 CH 2 .CH CH 2 CH 2 .CH CO 2 H(a) CO 2 H CO 2 H 
 
 Camphor Camphoric acid Camphoronic acid. 
 
CAMPHORS 587 
 
 Camphoric acid has been synthesised by Komppa (B. 1901, 
 34, 2472; 1903, 36, 4332). Ethyl oxalate and ethyl /3/?-di- 
 methyl-glutarate condense in the presence of sodic ethoxide, 
 yielding diketo-apocamphorate : 
 
 H CH CO 2 Et CO . CH C0 2 Et 
 
 C 
 CO-C 
 
 CMe 2 
 H-CH.C0 2 Et CO.CH.C0 2 Et. 
 
 This is methylated by means of sodium and methyl iodide, 
 and the ethyl ester of diketo-camphoric acid thus obtained, 
 
 >.CH.CO 2 Et 
 CMe 2 
 
 I 
 
 may be reduced with sodium amalgam to dihydroxy-camphoric 
 acid; and this, in its turn, with phosphorus and hydriodir 
 acid to dehydro-camphoric acid, 
 
 CH.CH.CO 2 Et 
 CMe 2 
 .CMe-CO,Et, 
 
 which combines with hydrogen bromide; and the /3-bromo- 
 camphoric acid thus obtained, when reduced with zinc and 
 acetic acid, yields the racemic modification of camphoric acid. 
 Camphor can be synthesised from camphoric acid by the 
 following series of reactions (Holler, C. R 1896, 122, 446): 
 
 I 
 
 Camphoric Campholide Homocamphoric 
 
 anhydride nitrile 
 
 /COOH 
 
 Homocamphoric acid distilled Camphor, 
 
 Considerable amounts of camphor are manufactured from 
 pinene by the following series of reactions: 
 
 Pinene * Bornyl chloride Isobornyl acetate 
 
 HCl Metallic 
 
 acetate 
 
 Isoborneol * Camphor. 
 hydrolysed oxidised 
 
 (Cf, Iloiisemann, Sci. Progress, No. 9.) 
 
588 XLI. TERPENES AND CAMPHORS 
 
 Camphoric acid is an unsymmetrical dibasic acid, as it gives 
 two isomeric monometbyl esters and two amic acids. One 
 carboxylic acid is probably attached to a tertiary and the 
 other to a secondary carbon atom, as the acid yields a single 
 monobromo substituted derivative when subjected to the Hell- 
 Volhard-Zelinsky method of bromination. The derivatives are 
 known respectively as a and fi (or ortho and allo), the a- 
 methyl ester, for example, contains the group ^>CH*C0 2 Me, 
 
 and the /?- methyl ester the group ^C C0 2 Me. As isonitroso- 
 camphor C(:NOH)CO when warmed with hydrochloric 
 acid yields a-camphoramic acid, \CH.CONH 2 , it follows 
 that the methylene group of camphor corresponds with the 
 a-carboxylic group in camphoric acid. 
 
 Camphoric acid exists in four optically active and two 
 racemic modifications, the latter known respectively as r-cam- 
 phoric and r-isocamphoric acids. This points to the presence 
 of two asymmetric carbon atoms in the molecule of the acid, 
 as indicated in the formula. Camphor, on the other hand, 
 exists in two active and one racemic form only. When d- 
 camphoric acid is racemized the product is not r-camphoric 
 acid, but a mixture of the original acid with Z-iso-camphoric 
 acid. This is due to the fact that only one asymmetric car- 
 bon atom is concerned in the racemization. In the oxidation 
 of camphoric acid to camphoronic acid, camphanic acid, the 
 lactone of a-hydroxy-camphoric acid is formed as an intei- 
 me/3iate product; its constitution follows from the fact that it 
 is formed by boiling bromo-camphoric anhydride with water. 
 
 .C^- CO 2 H 
 
 GMe 2 O Camphanic acid. 
 
 2-CMe-CO 
 
 Various chloro-, bromo-, nitro-, and ammo-camphors are 
 known. 
 
 Borneol or Borneo camphor, C 10 H ir .OH, occurs in nature 
 (in Dryobalanops camphora), and is produced by the action of 
 nascent hydrogen upon Japan camphor: 
 
 C 10 H 16 + 2H = C 10 H 18 0. 
 It resembles the latter, but has at the same time an odour 
 
IRONE. IONONES 589 
 
 of pepper. It crystallizes in hexagonal plates, melts at 208, 
 boils at 212, and when oxidized yields in the first instance 
 camphor. Borneol possesses the character of a secondary 
 alcohol, yielding esters, and with PC1 5 yields bornyl chloride, 
 C 10 Hi 7 Cl (m.-pt. 148), which is identical with pinene hydro- 
 chloride; bornyl chloride yields camphene when warmed with 
 alkalis. 
 
 D. Compounds related to Terpenes 
 
 Irone a methyl ketone, C 13 H 20 is the odoriferous prin- 
 ciple of the iris root, and also probably of the violet. When 
 boiled with hydriodic acid it yields the hydrocarbon irene, 
 
 GIS^IS- 
 The formulae suggested for these compounds are : 
 
 / * / CH 
 
 CH-CH:CH-COMe HC 
 
 CMe, ^C 
 C CH 
 
 CH 2 
 
 II -Me 
 
 CH 2 CH 
 
 Irone Irene 
 
 (cf. Tiemann and Kriiger, B. 26, 2675). These chemists have 
 synthesised two isomerides of irone, which they term a- and 
 /3-ionones. . s, 
 
 These also possess the odour of violets, and are employed 
 it the present time for the manufacture of violet essence. 
 
 The synthesis consists in the condensation of citral (p. 570) 
 with acetone to form the unsaturated ketone pseudo-ionone : 
 
 CMe 2 :CH.CH 2 .CH 2 .CMe:CH.CH;0 + H ? ;C 
 
 = CMe 2 : CH CH 2 CH 2 CMe : CH . CH : CH COMe, 
 
 which is transformed into the ring compounds a- and /2-ionones 
 when boiled with sulphuric acid : 
 
 CMe 2 CMe 2 
 
 H 2 CC.CH:CH.COMe 
 
 Cll CH 2 
 
 a-Ioaone 
 
590 XLI. TERPENES AND CAMPHORS 
 
 Carone, C 10 H 16 0, is one of the most important ring ketones 
 of the terpene series, and is formed when dihydrocarvone 
 hydrobromide, 8-bromoterpane-2-one, is treated with alcoholic 
 potash (Baeyer, B. 1896, 29, 5 and 2796). 
 
 CHMe CHMe 
 
 " nt T%I 
 
 CBrMe 2 CH 
 
 It is a colourless oil with an odour of camphor and pepper- 
 mint, and boils at 210, but is, at the same time, partially 
 transformed into the isomeric carvenone. The molecule, 
 according to Baeyer, contains a six-carbon ring with a bridge, 
 so that it is divided into a penta- and a tri-methylene ring. 
 One of the most characteristic properties is the readiness 
 with which the bridge is broken and derivatives of p- or 
 wi-terpane are produced. Thus when heated it yields car- 
 venone or A-3-^-terpene-2-one, 
 
 with hydrobromic acid it yields 8-bromoterpane-2-one, and 
 \vith sulphuric acid 8-hydroxy-terpane-2-one, 
 
 When oxidized, carone yields a dibasic acid, caronic acid 
 (cis and trans modifications), which Baeyer suggested was 
 dimethyl-trimethylene dicarboxylic acid, 
 
 CMe 2 < 
 
 X CH-C0 2 H, 
 
 a conclusion which has been confirmed by Perkin's synthesis 
 (J. C. S. 1899, 48). In this synthesis ethyl dimethylacrylate, 
 CMe 2 :CH.C0 2 Et, is condensed with ethyl sodio-malonate (or 
 ethyl sodio-cyanoacetate), and the product, ethyl dimethyl- 
 propane-tricarboxylate, (CO l2 Et) 2 CH.CMe 2 .CH 2 -C0 2 Et, when 
 hydrolysed and heated at 200, yields ft8-dimethyl glutaric 
 acid, C0 2 H-CH 2 .CMe 2 .CHo-C0 2 H. The a-bromo-derivative 
 of the ethyl ester of this"acid/C0 2 Et.CHBr.CMe 2 .CH 2 .C0 2 Et > 
 
RESINS 591 
 
 yields cis and trans caronic acids when heated with alcoholic 
 potash: 
 
 CMe 2 CMe 2 
 
 CO a Et.HCBr HCH.CO.jEt * COjH-HC CH.(X) a H. 
 
 XLII. RESINS; GLUCOSIDES 
 A. Resins 
 
 Many organic compounds, the terpenes in particular, possess 
 the property of becoming " resinified " by oxidation in the air 
 or under the influence of chemical reagents, i.e. of being con- 
 verted into substances very similar to the resins which occur 
 in nature. These natural resins are solid, amorphous, and 
 generally vitreous brittle masses of conchoidal fracture, in- 
 soluble in water and acids, but soluble in alcohol, ether, and 
 oil of turpentine. They are found naturally in abundance, 
 partly also as balsams, i.e. dissolved in terpenes or ethereal 
 oils, from which they can be separated by distilling in steam. 
 The resins dissolve in alkalis to form compounds of the nature 
 of soap (resin soaps), being again precipitated from the aqueous 
 solutions of these on the addition of acids; most resins must 
 therefore consist of a mixture of somewhat complicated acids 
 (the so-called resin-acids). 
 
 Abietic acid, C 19 H 28 O 2 , has been isolated from colophonium 
 (the residue from the distillation of turpentine); it crystallizes 
 in small plates, melts at 153, and is soluble in hot alcohol. 
 Pimaric acid, C 20 H S0 2 , has been prepared from galipot resin 
 (Pinus maritima) in a similar way. It melts at 144-146, 
 and closely resembles abiotic acid. 
 
 The resins show their relation to the aromatic compounds 
 by their conversion into hydrocarbons of the benzene or 
 naphthalene series when distilled with zinc dust, and by the 
 formation of di- and trihydroxy-benzenes when they are fused 
 with potash. 
 
 In addition to colophonium, there may be mentioned among 
 other resins shellac (from East Indian Ficus varieties), and 
 amber, a fossil resin which contains succinic acid in addition 
 to resin-acids and a volatile oil. 
 
 The resins are largely used for the manufacture of lacs, 
 varnishes, &c. 
 
592 XLII. RESINS; GLUCOSIDES 
 
 B. Glueosides 
 
 Glucoside is the name given to a number of complex organic 
 compounds which occur in vegetable tissues. They are all 
 characterized by the fact that on hydrolysis with acids, alkalis, 
 or enzymes, a sugar usually ^-glucose is formed. They are 
 therefore to be regarded as anhydro-compounds of d-glucose 
 or some other sugar with various organic compounds. 
 
 In addition to these natural glucosides, the constitutions ol 
 which are unknown, E. Fischer has prepared artificially simplei 
 glucosides, of the type of a- and /3-methyl-glueosides (p. 310) 
 by the action of methyl alcohol and hydrogen chloride on 
 glucose. These are probably stereoisomeric compounds: 
 
 OCH 3 - CH[CH OH] 2 . CH CH(OH) . CH 2 . OH. 
 
 The a-compound melts at 165 and the ft- at 107. They do 
 not reduce Fehling's solution, and on hydrolysis yield ^-glucose 
 and methyl alcohol. 
 
 Among the commoner natural glucosides are: 
 
 Amygdalin, C^H^C^N (p. 423), found in bitter almonds, 
 in the leaves of the cherry laurel, in the kernels of the peach, 
 cherry, and other Amygdalacese. It crystallizes in colourless 
 prisms, melts at 200, is readily soluble in water, and on hy- 
 drolysis with emulsin yields benzaldehyde, ^-glucose, and hy- 
 drogen cyanide. Emulsin is an enzyme which occurs in bitter 
 almonds. It is characteristic of most glucosides that in the 
 plant tissue they are accompanied by an enzyme, which is able 
 in the presence of water to hydrolyse them. Amygdalin may 
 also be hydrolysed by dilute mineral acids. 
 
 With concentrated hydrochloric acid it yields Z-mandelic 
 acid, and with an enzyme contained in yeast (amygdalase) 
 it yields glucose and /-mandelonitrile-glucoside. 
 
 Isoamygdalin, obtained by the action of alkalis on amyg- 
 dalin, is the racemic form of which ordinary amygdalin is 
 the /-modification. Amygdalin is the commonest of the cyano- 
 genetic glucosides, i.e. glucosides which give rise to hydrogen 
 cyanide in plant tissues or on hydrolysis. Some of the other 
 members are: dhurrin, p - hydroxy-mandelonitrile - glucoside 
 (Dunstan and Henry}, in the great millet; phaseolunatin, ace- 
 tone-cyanohydrine-a-glucoside, in beans of Phaseolus lunatus; 
 iotusin from Lotus arabicus. 
 
 Salicin, C 18 H 18 O 7 , found in varieties of Salix, is hydrolysed 
 
GLUOOSIDES 593 
 
 to saligenin (o-hydroxy-benzyl alcohol) and dextrose; populin 
 or benzoyl-salidn, C 10 H 22 8 (in varieties of Populus), can be pre- 
 pared artificially from benzoyl chloride and salicin. 
 
 Arbutin, C 12 H 16 7 , and methyl-arbutin, C 13 H 18 7 , present 
 in the leaves of the bear-berry, &c., yield glucose and quinol 
 or methyl-quinol respectively. Methyl-arbutin has been syn- 
 thesised by Michael (B. 1881, 14, 2097) from acetochloro- 
 glucose and quinol methyl ether. 
 
 Hesperidin, C 22 H 26 12 , which is contained in unripe oranges, 
 &c., can be decomposed into glucose, hesperetic acid (isomeric 
 with ferulic acid, p. 464), and phloroglucinol. 
 
 Phloridzin, C 21 H 24 O 10 , found in the bark of fruit-trees, 
 yields grape-sugar and phloretin, C 15 H 14 O 5 (B. 1895, 28, 1393), 
 and this latter, in its turn, phloretic acid and phloroglucinol 
 (p. 420). Both induce glycosuria (i.e. a functional derangement 
 of the liver, giving rise to temporary diabetes) in animals. 
 
 Aesculin, C 15 H 16 9 , present in the bark of the horse-chestnut, 
 is decomposed by acids into grape-sugar and Aesculetin (di- 
 hydroxy-coumarine), C 9 H 16 4 . 
 
 Digitonin, digitalin, and digitalei'n are three glucosides 
 which, together with digitoxin (the most important constituent 
 from a pharmacological point of view), are present in the digi- 
 talis of commerce (cf. B. 24, 339; 25, Ref. 680; 31, 2454). 
 
 Coniferin, C 16 H 22 8 + 2H 2 0, contained in the cambium sap 
 of the Coniferae, yields glucose and coniferyl alcohol on hy- 
 drolysis, and serves for the preparation of vanillin (p. 430). 
 
 Indican (p. 526) is indoxyl-glucoside. 
 
 Syringin, the glucoside of Syringa, is a methoxy-coniferin. 
 
 Myronic acid, C 10 Hi 7 9 NS 2 , is present as potassium salt 
 (Sinigrin), C^H^KOgNS* H 2 (glistening needles), in black 
 mustard seed. It is hydrolysed by baryta water, or by my- 
 rosin, an enzyme present in mustard seed, to grape-sugar, 
 potassium bisulphate, and allyl isothiocyanate (p. 277). 
 
 (For list of natural glucosides cf. Armstrong, " Simple Carbo- 
 hydrates and Glucosides ", p. 80.) 
 
 XLIII. ALBUMINS; PHYSIOLOGICAL CHEMISTRY 
 
 An extended description of the substances (other than those 
 already mentioned) which are found in the animal organism, and 
 which are therefore of importance for physiological chemistry, 
 
 (BttO) * 
 
594 XLIII. ALBUMINS; PHYSIOLOGICAL CHEMISTRY 
 
 will not be attempted here, since they are for the most part 
 better known from a physiological than from a chemical point 
 of view. Only the albumins and some of the substances which 
 are produced during metabolic processes will be dealt with. 
 
 Albumins 
 
 For an account of the modern views of the chemistry of 
 albumins see A. Kossel (B. 1901, 34, 3214; E. Fischer, B. 1906, 
 39, 530). 
 
 The albumins make up the chief part of the organism, being 
 present partly in the soluble and partly in the solid state; 
 they are found in protoplasm and in all the nutritive fluids of 
 the body. In the tissues of green plants the albumins are 
 synthesised in quite unknown ways from simple substances 
 like carbon dioxide, water, ammonium nitrate and sulphate. 
 (Cf. Meldola, J. C. S. 1906, 749.) The majority of albumins 
 are insoluble in water, but dissolve in dilute saline solutions. 
 Their presence in the juices of the animal organism is prob- 
 ably due to saline and other substances. In solution they 
 are opalescent, laevo-rotatory, and do not diffuse through parch- 
 ment paper, i.e. are colloids; but they are thrown down 
 when the solution is warmed, or upon the addition of strong 
 mineral acids, of many metallic salts [e.g. copper sulphate, 
 basic lead acetate, and mercuric chloride], of alcohol, tannic 
 acid, acetic acid together with a little potassium ferrocyanide, 
 picric acid, or phosphotungstic acid. They are insoluble in 
 alcohol or ether, and their solutions are usually precipitated 
 ("salted out") by the addition of ammonium sulphate, and 
 mixtures of different albumins can often be fractionally pre- 
 cipitated by gradually increasing the concentration of the 
 ammonium sulphate. This concentration is definite for each 
 albumin, as is also its temperature of coagulation. Proteins 
 can also be coagulated by treatment with absolute alcohol or 
 with boiling water. After coagulation all albumins become 
 insoluble in neutral solvents, but dissolve in alkalis or acids, 
 yielding metaproteins, which are also formed by boiling the 
 uncoagulated albumins with acetic acid or alkali. When 
 boiled: (a) with nitric acid, they are coloured yellow (the 
 xantho- protein reaction); (b) with a solution of mercuric 
 nitrate containing nitrous acid (Milloris reagent), red; (c) with 
 caustic soda solution and a very little cupric sulphate, violet. 
 
 Many of the albumins have been prepared pure, although 
 
ALBUMINS 595 
 
 this is a very difficult operation. With the exception of the 
 crystalline albumin which occurs in hemp, castor -oil, and 
 pumpkin seeds (B. 15, 953), and the recently isolated crystal- 
 line egg albumin and serum albumin (B. 24, Ref. 469; 25, 
 Ref. 173), they do not crystallize. 
 
 The different albumins vary only slightly among themselves 
 in percentage composition; they contain: 
 
 C = 52-7 to 54-5 p.c.; H = 6'9 to 7'3 p.c.; N = 16'4 to 17'6 p.c.; 
 O = 20*9 to 23'5 p.c. ; and S = 0'8 to 5'0 p.c. 
 
 It is impossible at present to construct a formula from these 
 numbers, and even approximate molecular weights have not 
 been determined. 
 
 The fact that albumin contains sulphur is worthy of note, 
 though the mode in which it is combined in the molecule is 
 unknown; warming with a dilute alkaline solution is sufficient 
 to eliminate it partially, e.g. when white of egg is boiled with 
 an alkaline solution of lead oxide, sulphide of lead is precipi- 
 tated (the test for sulphur in albumin). 
 
 Albumin preparations usually leave a very considerable 
 amount of ash, i.e. inorganic salts, on incineration. It is not 
 yet certain in how far this mineral matter forms an integral 
 constituent of these substances; but the properties of "egg 
 albumin free from ash " are materially different from those of 
 ordinary albumin (B. 25, 204). 
 
 Although the constitution of no single albumin has been 
 determined, a considerable amount of work has been done in 
 this direction, more especially by an examination of the 
 simpler products obtained when the albumins are (a) oxidized, 
 (b) hydrolysed, and (c) fermented by micro-organisms. 
 
 (a) The products obtained on oxidation consist largely of 
 volatile fatty acids, their aldehydes, ketones, and nitriles, 
 together with hydrogen cyanide and benzoic acid. 
 
 (b) The usual hydrolytic agents used are (1) baryta water, 
 (2) hydriodic acid, (3) concentrated hydrochloric acid, and 
 (4) sulphuric acid (25 per cent). The last of these appears to 
 be the best, as it produces less complex decomposition, e.g. 
 less ammonia and more amino- acids. The most marked 
 feature of the products thus obtained is the predominance 
 of amino-acids. 
 
 The list of compounds which have been isolated from the 
 hydrolytic products is as follows: (i) Ammonia; (ii) car- 
 bamide; (iii) diamino-acids; (iv) monamino-acids; (v) pyr- 
 
596 XUII. ALBUMINS; PHYSIOLOGICAL CHEMISTRY 
 
 rolidine - 2 - carboxylic acid (proline), HN< 2 , 
 
 M^ii(L'U 2 il) Url 2 
 
 and its hydroxy derivative (oxyproline) ; (vi) furaldehyde 
 (p. 517); (vii) histidine (iminazole-alanine), C G H 9 2 Ng; (viii) 
 arginine, or 8-guanino-a-amino valeric acid, NH 2 C( : NH) NH 
 CH 2 .CH 2 .CH 2 .CH(NH 2 ).C0 2 H, which has been synthesised 
 from ornithine (p. 465) and cyanamide (p. 277); (ix) trypto- 
 phan (indol-alanine); (x) tyrosine (p. 459). 
 
 Of the diamino-acids the following are the more important: 
 Diamino- acetic acid from casein, a8-diamino-valeric acid or 
 ornithine, ac-diamino-T^caproic acid or lysine. 
 
 Of the monamino-acids : Glycocoll, and derivatives such as 
 skatolglycocoll, a-amino-propionic acid or alanine, a-amino- 
 isobutylacetic acid or leucine, a-amino-isovaleric acid or valine, 
 a-amino-succinic or aspartic acid, a-amino-glutaric or glutamic 
 acid, phenylalanine or /?-phenyl-a-amino-propionic acid, CH 2 
 Ph CH(NH 2 ) C0 2 H, a-amino-a-hydroxy-propionic acid or 
 serine, a-amino-a-thiolactic acid or cystein, and the corre- 
 sponding disulphide or cystin, /?-hydroxy-phenyl-a-amino-pro- 
 pionic acid. 
 
 Certain albumins also yield carbohydrates, more especially 
 amino-sugars, e.g. glucosamine, C 6 H n 5 NH 2 (B. 1895, 28, 
 3082). 
 
 A simple method for the separation and isolation of many 
 of these amino-acids from the products of hydrolysis is due to 
 E. Fischer. He converts the acids into esters by the hydrogen- 
 chloride method, and then separates these by fractional dis- 
 tillation under reduced pressure. 
 
 A few simple proteins yield only a single ammo-derivative; 
 thus both salmine and clupeine, obtained respectively from the 
 testicles of the salmon and herring, yield very little besides 
 histidine. As a rule, the more complex proteins yield a 
 considerable number of amino-compounds, the number of such 
 compounds and also their relative proportions varying with 
 the protein. 
 
 A glance at the list of above products indicates that the 
 albumin molecule is largely built up of aliphatic groups. 
 The carboxylic groups present in the hydrolytic products 
 are probably not present in the original molecule, and it is 
 highly probable that most of the amino-groups are not present 
 as such, but are employed in uniting the various radicals 
 together, since only some 10 per cent of the total nitrogen in 
 
ALBUMINS 597 
 
 albumin is eliminated as such on treatment with nitrous acid ; 
 in other words, the amino-group of one molecule reacts with 
 the carboxylic group of another, yielding compounds with the 
 group, CO'NH', characteristic of acid amides. Emil Fischer 
 and others have synthesised complex compounds of this type 
 by the gradual condensation of amino-acids. Although none of 
 the proteins has been so far synthesised, the products the 
 polypeptides exhibit considerable analogy to the peptones. 
 
 The following general methods are used for the synthesis 
 of polypeptides : 
 
 1. The chloride of a halogenated fatty acid is condensed 
 with the ester of an amino-acid, the resulting ester hydrolysed, 
 and the halogen then replaced by an amino-group by means 
 of ammonia: 
 
 Cn 3 .CHBr.COCl 
 
 CH 8 -CHBr.CO.NH.CH 2 .C0 2 Et 
 CH 3 .CH(NH a ).CO. 
 
 Alanylglycine. 
 
 2. The dipeptide thus obtained can be converted into its 
 acid chloride, and this condensed with a molecule of an ester 
 of an amino-acid, e.g. glycine ester, yielding the compound 
 CH 3 .CH(NH 2 ).CO.NH.CH 2 .CO.NH.CH 2 .C0 2 C 2 H 5 , which 
 on careful hydrolysis yields the corresponding acid alanyl- 
 glycylglycine an example of a tripeptide. The operations 
 can be repeated, and in this way compounds containing 18 
 amino-acid residues have been synthesised, one of which has a 
 molecular weight 1213. 
 
 As the amino-acids obtained by hydrolysing natural pro- 
 teins are optically active, Fischer used optically active acids 
 and esters in his synthetical operations, the optically active 
 acid being obtained by resolving its racemic benzoyl derivative 
 by means of active bases and then removing the benzoyl group. 
 
 3. A modification of the above synthesis consists in con- 
 verting an amino-acid into its acid chloride by means of 
 acetyl chloride and phosphorus pentachloride, and then con- 
 densing this chloride with a molecule of an amino-acid. 
 
 4. Glycylglycine can be obtained by heating ethylglycine 
 
 when the anhydride diketopiperazine, NHQjj'^Q^NH, is 
 
 formed, and hydrolysing this with dilute alkali. 
 
 A few polypeptides, e.g. tetrapeptides, have been isolated 
 from the hydrolytic products of certain proteiiw. 
 
598 XLIII. ALBUMINS; PHYSIOLOGICAL CHEMISTRY 
 
 Kutscher has shown that many albumins can combine to- 
 gether to give complex substances, and it is probable that 
 many natural albumins are complexes formed by union of 
 simpler molecules. 
 
 (c) The putrefaction of albumins gives rise not only to amino- 
 acids, but also to other aromatic and fatty acids (e.g. butyric 
 acid, phenyl-acetic acid), indole, skatole, and cresol; further, 
 to the alkaloid-like ptomaines (the toxines or poisonous alka- 
 loids produced in dead bodies), of which tetramethylene- 
 diamine, or " putrescine ", and pentamethylene-diamine, or 
 " cadaverine ", B. 19, 2585, have been isolated (cf. p. 196). 
 For a compilation of the ptomaines, see Brieger, Archiv. f. 
 patholog. Anatomic, 115, 483. 
 
 Albuminous matters undergo change when acted upon by 
 the juices of the stomach at a temperature of 30-40, the 
 enzyme pepsin converting them in the first instance into anti- 
 and hemi-albumoses, both of which then pass into peptone; 
 trypsin, an enzyme of the pancreas, likewise gives rise to the 
 two above albumoses, but then transforms the anti-compound 
 into peptone and the hemi-compound into leucine, tyrosine, 
 aspartic acid and glutamic acid (the pancreatic digestion; for 
 details, see Kuhne, B. 17, Kef. 79). The peptones are readily 
 soluble in water, diffuse quickly through vegetable parchment, 
 and they are neither coagulated upon heating nor by most 
 of the reagents which coagulate albumin, e.g. ammonium 
 sulphate, whereas the albumoses are precipitated by this 
 reagent. These reactions indicate that the albumoses are 
 intermediate between the albumins proper and the simple 
 decomposition products already mentioned, and that the 
 peptones are intermediate between the same decomposition 
 products and the albumoses. Both albumoses and peptone 
 possess acidic and basic properties, and may be esterified by 
 means of alcohol and hydric chloride, hence they probably 
 contain carboxylic groups. 
 
 The different albumoses, e.g. hetero- and proto-albumoses, 
 must differ considerably as regards constitution, as the former 
 yields glycocoll, much arginine, but little histidine, and very 
 little tyrosine and indole on hydrolysis, whereas the latter 
 yields no glycocoll, equal amount of arginine and histidine, 
 and much tyrosine and indole. 
 
 Other methods adopted are to introduce chemical substances 
 into the animal system intravenously or per os, and then to 
 examine in what form the compound is excreted from the 
 
ALBUMINS 599 
 
 system; as examples, bromobenzene is excreted as bromo- 
 phenyl-mercapturic acid, and various terpene derivatives are 
 excreted in combination with glycuronic acid. 
 
 When soluble salts of iron are allowed to act upon white of 
 egg and upon peptone, iron albuminate and iron peptonate 
 are respectively produced, these being employed in medicine 
 as iron preparations for internal use under the names of liquor 
 ferri albuminati and peptonati. 
 
 The following scheme of nomenclature for proteins is ac- 
 cepted by most English-speaking chemical and physiological 
 societies : 
 
 1. Protamines. The simplest proteins, they include sal- 
 mine, sturine, &c., isolated from fish testicles. 
 
 2. Histones. These are somewhat more complex than the 
 protamines. They can be precipitated by ammonia. 
 
 3. Albumins, e.g. egg albumin, serum albumin from blood 
 and nutritive fluids, and lact- albumin from milk. These are 
 crystalline, dissolve in water, and are not precipitated by 
 common salt. They coagulate at 70-75. 
 
 4. Globulins are insoluble in water but dissolve in dilute salt 
 solution. They can be salted out by means of magnesium sul- 
 phate. Examples : Globulin from the crystalline lens of the eye, 
 nbrinogen from blood, fibrin from clotted blood, and myosin 
 from the plasma of living muscle, are globulin derivatives. 
 
 5. Gluteins are proteins of vegetable origin. They are 
 soluble in alkalis, and are closely allied to the globulins. 
 
 6. Gliadins. Vegetable proteins, soluble in alcohol. 
 
 7. Phospho-proteins, e.g. caseinogen, the principal protein 
 of milk; casein obtained from caseinogen by the action of 
 rennet. They are acidic and do not coagulate. 
 
 8. Sclero -proteins. Mainly insoluble proteins, which form 
 the skeletal parts of tissues, e.g. gelatin from cartilages, chon- 
 drin, elastin from ligaments, and keratin from hoofs, nails, 
 hair, &c. Sponge and coral contain similar substances. 
 
 9. Conjugated proteins consist of compounds containing a 
 protein molecule united to some other group. 
 
 (a) Nucleo -proteins are important constituents of the cell 
 nucleus, e.g. of pus cells, blood corpuscles, and yeast cells. 
 They are insoluble in water or acids, but dissolve in alkalis, 
 and contain combined phosphoric acid. On hydrolysis they 
 yield albumin and nucleic acid, and on further hydrolysis 
 the nuclein bases, viz. adenine, hypoxan thine, guanine, and 
 xanthine (p. 292). 
 
600 XLIII. ALBUMINS; PHYSIOLOGICAL CHEMISTRY 
 
 Certain varieties of nuclein are free from sulphur, while 
 others contain it; the latter group yield tyrosine when de- 
 composed. The product which is obtained when the albumin 
 of hens' eggs is coagulated by meta-phosphoric acid resembles 
 nuclein. 
 
 Nucleic acid may also be transformed into nuclein bases by 
 various enzymes present in the different organs of the animal 
 system. Recent work renders it highly probable that at least 
 three distinct enzymes take part in such transformations: 
 (a) an oxidase; (b) adenase, which transforms adenine into 
 hypoxanthine and xanthine; (c) guanase, which transforms 
 guanine into xanthine. 
 
 (b) Chroma-proteins or Haemoglobins. Haemoglobin is the 
 colouring matter of the red blood corpuscles. It can be de- 
 composed into globin and hsematin (see below). Haemoglobin 
 combines very readily with oxygen, e.g. in the lungs, to oxy- 
 haemoglobin, which yields up its oxygen again, not only in 
 the organism, but also in a vacuum and when exposed to the 
 action of reducing agents, e.g. ammonium sulphide. With car- 
 bon monoxide it combines to the compound, carbon monoxide- 
 hsemoglobin. All three compounds can be obtained crystal- 
 lize* in the cold, and they possess characteristic absorption 
 spectra. Hsemin, C 84 H3 2 4 N 4 FeCl, is obtained in the form of 
 characteristic microscopic, reddish-brown crystals by the action 
 of glacial acetic acid and some common salt upon oxy-hsemo- 
 globin; this is a delicate test for the presence of blood. 
 Hsematin, a dark-brown powder containing 8 per cent of iron, 
 is obtained by the spontaneous decomposition of haemoglobin, 
 or by the action of alkalis on hsemin, and contains' OH in 
 place of the Cl atom of hsemin (cf. Piloty and Eppinger, A. 
 377, 341). 
 
 (c) Gluco-proteins. The mucins yield albumin and carbo- 
 hydrate on hydrolysis; they are insoluble in water, but possess 
 acidic properties. The percentage of nitrogen is less than in 
 the ordinary albumins. 
 
 10. Protein derivatives, or the products of protein hy- 
 drolysis. 
 
 (a) Meta-proteins. This includes the substances previously 
 known as alkali-albumins and acid-albumins, (b) Froteoses, 
 including albumoses, globuloses, and gelatoses. (c) Peptones 
 (cf. p. 598). (d) Polypeptides (cf. p. 597). 
 
REDACTION WITH NASCENT HYDROGEN 601 
 
 XLIV. REDUCTION 
 
 Reduction is the name usually given to a reaction in which 
 oxygen is withdrawn from or hydrogen added to a compound; 
 in certain cases both of these processes occur. Numerous cases 
 of reduction have been mentioned in the preceding chapters, 
 as examples: 
 
 (C 6 H 6 ) 2 'N 2 0, azoxy -benzene, * (C 6 H 5 ) 2 N 2 , azo-benzene (p. 397); 
 (CH 3 ) 2 .CO, acetone, > (CH 3 ) 2 .CH.OH, iso-propyl alcohol 
 
 (P. 72); 
 nitre-benzene, - C 6 H 6 NH2, aniline (p. 372). 
 
 As the reaction is so general, a more detailed discussion of it 
 is given in this chapter. 
 
 In addition to the above reactions, viz. withdrawal of 
 oxygen or addition of hydrogen, the process previously 
 referred to as inverse substitution (p. 33) the replacement 
 of halogen by hydrogen, e.g. C 2 H 5 I - C 2 H 6 is usually re- 
 garded as a type of reduction. 
 
 A. Nascent Hydrogen. Of the numerous methods that can 
 be employed for reduction, one of the commonest is by means 
 of nascent hydrogen, i.e. hydrogen generated in the presence 
 of the substance to be reduced. The fact that the majority 
 of these reductions cannot be effected by means of ordinary 
 gaseous hydrogen, but can be readily attained by the use of 
 hydrogen at its moment of formation, is used as an argument 
 in favour of the view that nascent hydrogen consists of the 
 free atoms. As nascent hydrogen can be produced in a 
 variety of ways, it follows that reductions by this method 
 can be conducted under very varying conditions; and it is of 
 extreme importance to note that the conditions are a prime 
 factor in determining the nature of the product. It has 
 already been pointed out that the reduction of nitro-benzene 
 can give rise to azoxy-benzene, azo-benzene, phenyl-hydroxyl- 
 amine, or aniline, according to the conditions under which the 
 reaction occurs; and similar phenomena have been mentioned 
 in the case of the reduction of terephthalic acid (p. 468). 
 
 Reductions by means of nascent hydrogen may take place 
 in acid, alkaline, or neutral solution, and this affords a simple 
 method of classification for these reactions. 
 
 (a) Reduction in Acid Solution. Almost any combination 
 of acid and metal which gives rise to nascent hydrogen may 
 be employed for this purpose; but the usual combinations are 
 
XLIV. REDUCTION 
 
 tin and hydrochloric acid, zinc and hydrochloric acid, zinc and 
 acetic acid, zinc dust and acetic acid, iron and acetic acid. 
 
 The usual method employed in the laboratory for the 
 reduction of iiitro-compounds to the corresponding ammo- 
 compounds (see Aniline) is by means of tin and hydrochloric 
 acid. The metal is first converted into stannous, and then 
 into stannic chloride : 
 
 Sn + 2HCl = SnCl 2 + 2H; 
 SnCL + 2HCl = SnCl 4 + 2H; 
 C 6 H 5 N0 2 + 6H = C 6 H 5 .NH 2 + 2H 2 0; 
 or C 6 H 4 (N0 2 ) 2 + 12H = C 6 H 4 (NH 2 ) 2 + 4H 2 O. 
 
 The method has certain objectionable features which render 
 it unsuitable for use on the manufacturing scale. Among 
 these may be mentioned (a) need for large excess of concen- 
 trated acid, and the fact that this acid will subsequently have 
 to be neutralized, (b) The strong acid is liable to react with 
 the reduction product, yielding halogenated amines. The in- 
 troduction of the halogen into the benzene nucleus probably 
 occurs in the following manner: 
 
 C 6 H 6 .N0 2 C 6 H 6 .NH-OH C 6 H 6 .NHC1 -> C1.C 6 H 4 .NH 2 
 
 (Bamberger). Such chlorinated amines are always liable to be 
 formed when concentrated hydrochloric acid is used in com- 
 bination with a metal for the reduction of nitro-compounds. 
 (c) The reduced compound often combines with the stannic 
 chloride to form a double salt, e.g. C 6 H 5 NH 2 , HC1, SnCl 4 , 
 and certain of these are somewhat difficult to decompose. 
 
 Aliphatic nitro-derivatives may also be reduced to amines 
 by this method, except in cases where two nitro-groups are 
 attached to the same carbon atom, when a ketone is formed. 
 Other examples are the conversion of cyclic derivatives into 
 hydro-derivatives, e.g. jp-hydroxy-quinoline to tetrahydro-jp- 
 hydroxy-quinoline, and of sulphonic chlorides, R-S0 2 'C1, into 
 thio-phenols, R'SH. 
 
 In many cases tin-foil is stated to be preferable to granu- 
 lated tin, as it exposes a larger surface, and occasionally 
 alcoholic solutions of the hydrogen chloride are used in place 
 of aqueous. Stannous chloride and hydrochloric acid occa- 
 sionally give better yields than tin and acid; thus nitro- 
 methane is reduced to methyl-hydroxylamine, and the method 
 has been recommended for the estimation of nitro-groups. 
 An excess of standard stannous chloride solution is used, and 
 
REDUCTION WITH NASCENT HYDROGEN 603 
 
 the excess titrated after the reduction is complete, each nitro- 
 group requiring 3 gram molecules of stannous chloride. 
 
 Stannous chloride is sometimes used without the addition 
 of free acid; thus Witt, by reducing amino-azo-benzene with 
 alcoholic stannous chloride, obtained aniline and ^-phenylene- 
 diamine : 
 
 C c H 5 -N:N.C 6 H 4 .NH 2 -f 4H = C 6 H 5 -NH 2 + NH 2 .C 6 H 4 .NH 2 . 
 
 (Compare also Jacobson, A. 1895, 287, 100.) 
 
 Most of the objections referred to in connection with the 
 reduction of nitre-derivatives by means of tin and hydro- 
 chloric acid may be avoided by using iron and acetic acid or 
 dilute hydrochloric acid. This method is usually adopted on 
 the manufacturing scale, as only a small amount of acid, some 
 one-fortieth of that indicated by the equation, 
 
 C 6 H 5 N0 2 + 3Fe + 6HC1 = C 6 H 5 .NH 2 + 3FeCl 2 + 2H 2 O, 
 
 is required. The reason for this may be that the ferrous 
 chloride reacts with the aniline and water, yielding ferrous 
 hydroxide and aniline hydrochloride : 
 
 2C 6 H 6 NH 2 -f 2H 2 = Fe(OH) 2 + 2C 6 H 5 N 
 
 The hydrochloride then reacts with more iron, producing 
 ferrous chloride and nascent hydrogen, which can reduce 
 more of the nitro-compound. 
 
 The iron method possesses further advantages, as r the 
 reduction can be regulated much more readily than in the 
 case of tin and acid. Thus ^?-nitro-acetanilide reduced by 
 the iron method gives the corresponding ammo-compound, 
 NH 2 .C 6 H 4 .NH.CO-CH 3 , whereas with tin and hydrochloric 
 acid hydrolysis and reduction both occur, and the product is 
 jp-phenylene-diamine. 
 
 Iron and acid may also be employed for the reduction of 
 aromatic polynitro-compounds to amino-nitro-derivatives : 
 
 C 6 H 4 (N0 2 ) 2 
 
 but such a reduction is almost impossible with tin and acid. 
 
 Zinc, as granulated zinc, or more frequently as zinc dust, is 
 also used in conjunction with acids, usually hydrochloric or 
 acetic. When concentrated hydrochloric is employed, chlorine 
 is apt to enter the benzene ring (cf. p. 602); with glacial acetic 
 acid (Kra/ts, B. 1883, 16, 1715) acetyl derivatives are formed 
 occasionally instead of the simple reduction products. For 
 
604 3tLlV. REDACTION 
 
 example, when aldehydes are reduced, alkyl acetates and not 
 alcohols are formed: 
 
 K-CHO + 2H + CH 3 .C0 2 H = R-CH^O-CO-CH, 
 
 and when nitro-derivatives are reduced, acetylated amines are 
 obtained. Although aliphatic ketones cannot be reduced by 
 this method, all ketones containing one or two benzene nuclei 
 directly attached to the carbonyl group are readily reduced to 
 pinacones (p. 191). Hydroxy-derivatives of anthraquinone 
 may also be reduced in a similar manner, one or more of the 
 hydroxy- groups being replaced by hydrogen, and aliphatic 
 nitro-derivatives, such as nitro-guanidine, NH:C(NH 2 )NH- 
 N0 2 , may be reduced to the corresponding amino-compounds. 
 A transformation occasionally effected by means of zinc dust 
 and glacial acetic acid is the removal of two atoms of halogen 
 and the conversion of a saturated compound into an olefine, 
 e.g. tetramethyl-ethylene dibromide into tetramethyl-ethylene : 
 CMe 2 Br-CMe 2 Br + 2H = 2HBr -f CMe 2 :CMe 2 . 
 
 All peroxides (p. 181) are readily reduced by this method, 
 e.g. diethyl-peroxide, Et 2 2 , to ethyl alcohol (or ethyl acetate). 
 
 Dilute acetic acid is frequently used with zinc dust. This 
 is the usual method adopted for the reduction of osones to 
 ketoses (Fischer) (p. 304): 
 
 K.CO.CHO + 2H = B.CO.CH 2 .OH. 
 
 It is also extremely useful in the preparation of hydrazines 
 from nitrosamines and nitramines, e.g. Fischer (A. 1886, 236, 
 198) obtained methyl-phenyl-hydrazine, NPhMeNH 2 , by the 
 reduction of methyl-phenyl-nitrosamine, NPhMe-NO. Other 
 reducing agents, e.g. metal and concentrated hydrochloric 
 acid, stannous chloride, zinc dust and alkali, are all liable to 
 carry the reduction a stage further and yield a mixture of 
 ammonia and amine: 
 
 NPhMe.NH 2 + 2H = NHPhMe + NH 3 . 
 
 An extremely interesting example of the influence of the 
 reducing agent and the method of reduction on the nature 
 of the final product is met with in the case of nitro-benzyl- 
 phenyl-nitrosamine, N0 2 C 6 H 4 CH 2 NPh NO. With tin 
 and hydrochloric acid it yields phenyl-indazole, 
 
 M 
 
 >NPh; 
 
 c H <L> 
 
REDUCTION WITH NASCENT HYDROGEN 605 
 
 with sodium amalgam in alkaline solution, o-amino-benzyl- 
 aniline, NH 2 - C 6 H 4 CH 2 NHPh, and ammonia; and with zinc 
 dust and glacial acetic acid, o-amino-benzyl-phenyl-hydrazine, 
 NH 2 .C 6 H 4 .CH 2 .NPh.NH 2 . (Busch, B. 1894, 27, 2899.) 
 
 With zinc dust and dilute sulphuric acid the reaction is 
 somewhat slower than with acetic acid; with these reagents 
 sulphonic chlorides may be transformed into thio-phenols, or 
 the reaction may proceed a stage further and the sulphur be 
 completely removed. 
 
 Zinc dust and concentrated sulphuric acid are occasionally used 
 for the reduction of nitro-compounds, and in all cases the pro- 
 duct is an amino-hydroxy- and not a simple amino-derivative : 
 C 6 H 6 .N0 2 jE>-NH 2 .C 6 H 4 .OH; 
 
 -* NH 2 .C 6 H 3 (OH).C0 2 H. 
 
 Lassar-Cohn attributes this to the oxidizing action of the 
 concentrated sulphuric acid, whereas it is probable that 
 reduction to a phenyl-hydroxylamine first occurs; and this, 
 in the presence of the concentrated acid, undergoes intra- 
 molecular rearrangement, yielding the amino-phenol (cf.p.397): 
 C 6 H 5 .N0 2 C 6 H 6 .NH.OH OH.C 6 H 4 .NH 2 . 
 
 When zinc or zinc dust and any acid are added to the 
 nitrate of an aromatic amine, a diazonium salt is formed: 
 C 6 H a .NH2,HN0 3 -f Zn-f 3HC1 = ZnCl 2 -f C 6 H 5 N 2 C1 -f 3H 2 0. 
 
 Sodium amalgam is sometimes used as a reducing agent in 
 the presence of acid; thus with acetic acid it is used for the 
 reduction of hydrazones to primary amines : 
 
 Reductions by means of sodium amalgam and dilute sulphuric 
 acid have been largely used by E. Fischer in his synthetical 
 work on the sugars, since the lactones of hydroxy-acids when 
 reduced in this way at yield aldoses (pp. 304, 305) : 
 
 X.CH.CH(OH).CH(OH).CO-*X.CH(OH).CH(OH).CH(OH).CH:0. 
 
 I _ _ I 
 
 The same reducing agents convert phloroglucinol, s-C 6 H 3 (OH) 8 , 
 into its hexahydro-derivative. 
 
 A very common acid reducing agent is hydriodic acid, its 
 reducing action being attributed to the decomposition of the 
 hydrogen iodide into iodine and nascent hydrogen at moderate 
 temperatures. The method was first introduced by Berthelot, 
 
606 XLIV. REDUCTION 
 
 who, in his earlier experiments, used the acid alone; but when 
 he found that the liberated iodine interfered with the reduc- 
 tion by giving rise to iodo-derivatives or by oxidizing, he 
 added red phosphorus or sometimes phosphonium iodide. 
 The function of the phosphorus is to combine with the iodine 
 immediately it is liberated from the hydrogen iodide, and 
 thus form phosphorus tri-iodide, which is then decomposed by 
 the water present, yielding hydrogen iodide and phosphorous 
 acid. Phosphonium iodide is often formed as a by-product in 
 these reductions. It has been shown that with hydriodic acid 
 alone practically all oxygen compounds are reduced to satu- 
 rated hydrocarbons at a temperature of 275, the reduction 
 being conducted in sealed cubes, e.g. glycerol yields propane. 
 Amines are also transformed into paraffins, e.g. methylamine 
 yields methane. 
 
 When hydriodic acid and phosphorus are used, the reduction 
 can either take place in open vessels, e.g. a flask with reflux 
 condenser, or in sealed tubes if a higher temperature is required 
 As examples of the former we have the following : CHI 3 
 CHJL; anthraquinone * dihydro-anthracene ; benzilic acid, 
 OH.CPh 2 .G0 2 H diphenyl-acetic acid, CHPtyC0 2 H; tri- 
 hydroxy-glutaric acid, COJ! . [CH . OH] 3 . C0 2 H glutaric 
 acid; mixed ketones, e.g. C 6 H 5 CO CH 3 * hydrocarbons. 
 
 As examples of the latter we have the conversion of fatty 
 acids, from C 8 H ir C0 2 H upwards, into paraffin-hydrocarbons, 
 the reduction of anthracene to hydro-anthracenes, and of 
 hydroxy - hexamethylene carboxylic acid, OH C 6 H 10 C0 2 H, 
 to hexahydro-benzoic acid, C 6 H n C0 2 H. 
 
 It is interesting to note that hydriodic acid is not a good 
 reducing agent for nitre-compounds ; as a rule it leaves the 
 nitro- group intact, e.g. nitro - benzene - sulphonic chloride, 
 N0 2 .C 6 H 4 .S0 2 C1, yields first N0 2 .9 6 H 4 .SO.SO.C 6 H 4 .N0 2 , 
 and ultimately m-dinitro-diphenyl-disulphide, N0 2 -C 6 H 4 S 
 S.C 6 H 4 .N0 2 . 
 
 (b) Nascent Hydrogen in Alkaline Solution. There are 
 various methods of reducing with nascent hydrogen in al- 
 kaline solution; one of the commonest is the addition of 
 metallic sodium, in the form of wire or thin strips, to boiling 
 ethyl alcohol; as a rule it is necessary to use absolute alcohol* 
 as the presence of water diminishes the yields. As examples, 
 we have the reduction of nitriles to primary amines, RCN 
 *R.CH 2 -NH 2 (p. 106), of esters to alcohols (p. 72), of naph- 
 thalene to dihydro-naphthalene, of pyridine to piperidine (p. 537), 
 
REDUCTION WITH NASCENT HYDROGEN 607 
 
 although quinoline is not so readily converted by this process 
 into tetrahydro-quinoline, and lastly, of various benzene deriva- 
 tives, e.g. w-hydroxy- benzoic acids into corresponding hexa- 
 hydro-derivatives, i.e. derivatives of hexamethylene. When 
 a higher temperature is required than can be attained with 
 ethyl alcohol, boiling amyl alcohol is used (Bamberger). By 
 this method naphthalene and its derivatives may be converted 
 into their tetrahydro-compounds, e.g. the naphthols, C 10 H 7 'OH, 
 into tetrahydro-naphthols, C 10 H n OH. 
 
 It is interesting to note that the chief reduction product 
 obtained from a-naphthylamine is ar-tetrahydro-a-naphthyla- 
 mine (I), and from /3-naphthylamine a mixture of ar- and ac- 
 tetrahydro-derivatives (II and III): 
 
 H 2 NH 2 H 2 H 
 
 Similarly phenanthrene is reduced to its tetrahydro-deriva- 
 tive, anthracene to its dihydro-compound, and the benzene 
 carboxylic acids to di-, tetra-, or hexahydro-derivatives, accord- 
 ing to the temperature and other conditions of reduction 
 (cf. p. 467); with sodium and boiling amyl alcohol, benzoic 
 acid yields mainly C 6 H n C0 2 H. In a few cases, when sub- 
 stituted benzoic acids are reduced by this method, a rupture 
 of the ring occurs and an aliphatic acid is formed. One of the 
 best-known examples is the reduction of salicylic acid to pimelic 
 acid (p. 344); in this case it may be assumed that a tetra- 
 hydro-salicylic acid is first formed, and that by the addition 
 of the elements of water this is converted into pimelic acid : 
 
 < xCH 2 .C(C0 2 HK G O H 
 \CH 2 CH 2 - -/^ C 
 
 Although aniline cannot be converted into its hydro-deriva- 
 tives by this method, aniline-o-sulphonic acid yields a hexa- 
 hydro-derivative. In place of alcohol moist ether is sometimes 
 used in conjunction with sodium. This is generally accom- 
 plished by adding the metal to ether floating on water, or 
 better, on a solution of sodic bicarbonate. Dibenzyl ketone 
 can thus be reduced to dibenzyl-carbinol, mesityl oxide to 
 
608 XLIV. REDUCTION 
 
 methyl-isobutyl-carbinol, and acid chlorides, ECOC1, to the 
 corresponding alcohols, BCH 2 OH. 
 
 Sodium amalgam may be used in place of sodium itself, as 
 a rule in combination with water; the amalgam is added 
 gradually and the mixture kept agitated, and a small amount 
 of alcohol is added, if necessary, to prevent frothing. By this 
 method, benzene and its derivatives may be reduced to di- and 
 tetrahydro-compounds. Many olefine derivatives are reduced 
 to saturated compounds, e.g. cinnamic acid, CgH 5 CH:CH' 
 C0 2 H, to phenyl-propionic acid, C 6 H5.CH 2 .CH 2 .C0 2 H, and 
 ketones to secondary alcohols. Alcohol is occasionally a better 
 medium than water, and by this method azo- may be reduced 
 to hydrazo-compounds (p. 395), and benzaldehyde and its 
 substituted derivatives into benzyl alcohols. 
 
 In many instances the alkali formed by the action of the 
 metal on water or alcohol has a deleterious action on the pro- 
 ducts of reduction, and it becomes necessary to neutralize the 
 alkali as far as possible. This may be effected by the occasional 
 addition of mineral acid, but is most readily accomplished by 
 Aschan's method of leading carbon dioxide through the liquid 
 as the reduction proceeds, and in this way converting the 
 sodium hydroxide into bicarbonate as fast as formed. It is 
 the method often used in the reduction of phthalic acids, &c., 
 and may also be employed for converting naphthalene and 
 resorcinol into their dihydro-derivatives, and benzoic acid into 
 
 Zinc and alkali are often used to reduce aromatic ketones 
 to secondary alcohols, e.g. (CgH^CO -* (C 6 H 5 ) 2 CH.OH; 
 whereas when zinc and acetic acid are used, the corresponding 
 pinacpnes, (C 6 H 5 ) 2 C(OH) C(OH)(C 6 H 5 ) 2 , are formed. Alkali, 
 especially sodic hydroxide, may be used with zinc dust; the 
 usual method being to keep the alkali and substance well 
 stirred, and to add the zinc dust gradually. As examples we 
 have: Anthraquinone - anthranol ; fatty diazo-compounds * 
 hydrazo-compounds; o - nitraniline * o-phenylene-diamine. 
 Further examples are the dehalogenating of aromatic compounds 
 and the preparation of azoxy- and azo-compounds (p. 397). 
 
 (c) Nascent Hydrogen in Neutral Solution. Many reduc- 
 tions take place most readily in the absence of free acid or free 
 alkali, and may be effected by the following reagents : (i) Zinc 
 filings or granulated zinc and alcohol, e.g. /?-bromo-allo-cinnamic 
 acid * allo-cinnamic acid (p. 454); (ii) Gladstone-Tribe couple, 
 in the reduction of alkyl haloids to paraffins (p. 33); (iii) mix- 
 
REDUCTION WITH METALS 609 
 
 ture of zinc and iron, in the presence of certain metallic salts, 
 e.g. acetone * isopropyl alcohol; (iv) zinc dust and water (or 
 alcohol), which may be used for reducing azo-dyes to mixtures 
 of amines, e.g. chrysoidine, NPhiN'CgH^NHg)^ to aniline 
 and triamino-benzene, and also for reducing aromatic nitro- 
 compounds to the corresponding hydroxylamines, e.g. C 6 H 6 
 N0 2 C 6 H 5 -NH*OH, a reaction which proceeds extremely 
 readily in the presence of ammonic chloride solution. The 
 same reagents are extremely useful in converting sulphonic 
 chlorides into sulphinic acids, C 6 H 5 'S0 2 C1 * C 6 H 5 -S0 2 H. 
 (v) Aluminium amalgam (Cohen and Ormandy, B. A. Eeport, 1889, 
 550) is also a useful neutral reducing agent in the presence of 
 water; by this method nitro-derivatives are readily transformed 
 into hydroxylamines, and ketones to secondary alcohols. 
 
 B. Among other chemical methods we may mention heating 
 with metals. Thus azo-benzene is formed when azoxy-benzene 
 is heated with metallic iron, anthracene when alizarin is heated 
 with zinc dust, and pyrrole when succinimide is heated with 
 the same reagent. In all these cases the metal abstracts 
 oxygen and is converted into an oxide. It is a method fre- 
 quently adopted when dealing with unknown complex sub- 
 stances and it is desired to know from what simpler compounds 
 they are derived. 
 
 Alcohol alone, as in the conversion of diazonium salts into 
 hydrocarbons : 
 
 H = C 6 H 6 + N 2 + HC1 + CH 3 .CHO 
 
 (p. 387). 
 
 Sodium ethoxide, or often alcoholic potash, for the reduction 
 of nitro-compounds to azoxy- or azo-compounds (De Bruyn), 
 and also for reduction of deoxy-benzoin and other aromatic 
 ketones to secondary alcohols, e.g. hydroxy-dibenzyl : 
 C 6 H 6 .CO-CH 2 .C 6 H 5 -> C 6 H 6 .CH(OH).CH 2 .C 6 H 6 
 
 (J. C. S. 1895, 604). 
 
 Sodium stannite, obtained by adding an. excess of sodium 
 hydroxide to stannous chloride, is employed for preparing 
 azo-compounds from nitrated hydrocarbons, for the reduction 
 of diazonium salts to hydrocarbons, e.g. benzene from benzene 
 diazonium chloride. An interesting reduction is the conversion 
 of jMiitro-benzyl chloride into dinitro-dibenzyl : 
 
 2N0 2 .C 6 H 4 .CH 2 C1 -> N0 2 .C 6 H 4 .CH 2 .CH 2 .C 6 H 4 .N0 2) 
 as the nitro-groups are left intact. 
 
 (B480) 2Q 
 
610 XUV. REDUCTION 
 
 Hydrogen sulphide, or more frequently ammonium sulphide, 
 in alcoholic solution (Cohen and M'Candlish, J. C. S. 1905, 
 1257), is made use of for the reduction of nitro- and nitroso- 
 derivatives to amines, and is especially useful when several 
 nitro-groups are present and it is required to reduce only one, 
 e.g. 0^H 4 (N(X) a -> m-N0 2 .C 6 H 4 .NH 2 , C 6 H 2 Me(N0 2 ) 3 _* 
 NH 2 C 6 H 2 Me(N0 2 ) 2 , &c.; also 0-nitro-cinnamic acid * a- 
 hydroxy-quinoline or carbostyril (p. 546). In many cases 
 sulphur-derivatives are formed instead of simpler reduction 
 products, especially with ketones or aldehydes. 
 
 Sulphurous acid is used in reducing quinones to quinols, e.g. : 
 
 C 6 H 4 2 + H 2 S0 3 + H 2 = C 6 H 4 (OH) 2 + H 2 S0 4 ; 
 
 and sodium hyposulphite, Na 2 S 2 4 , is an extremely useful 
 reagent for preparing leuco-compounds from dyes. 
 
 C. Catalytic Reduction, or reduction by means of hydro- 
 gen in presence of finely-divided metals. The catalytic action 
 of finely-divided substances, especially platinum black, in the 
 combination of sulphur dioxide and oxygen, or hydrogen and 
 oxygen, or in the decomposition of hydrogen peroxide, is 
 well known. In a similar manner, numerous carbon com- 
 pounds, when mixed with excess of gaseous hydrogen and 
 passed over a layer of platinum black at a moderate tem- 
 perature, undergo complete reduction. 
 
 The action of other metals in a fine state of division has 
 been investigated in recent years (1897-1911) by Sabatier and 
 Senderens. They find that nickel, cobalt, copper, and iron can 
 act in somewhat the same manner as platinum black, and that 
 of these nickel is the most efficient. It is necessary that the 
 metal shall be in an extremely fine state of division, and this 
 is accomplished by reducing the metallic oxide in a current 
 of hydrogen at a temperature of about 300. The substance 
 to be reduced is usually vaporized, mixed with excess of 
 hydrogen, and passed over the metal heated to a temperature 
 which varies somewhat with the different substances, but 
 usually lies between 160 and 250. A few grams of the 
 metal are usually sufficient, and it retains its activity for a 
 long time. The finely -divided metal appears to transform 
 the hydrogen into an active condition comparable with what 
 is usually termed the nascent state. 
 
 Of the numerous reductions which have been accomplished 
 by this process, we may mention the following: Carbon ' 
 monoxide at 200 and carbon dioxide at 300 are reduced to 
 
CATALYTIC REDUCTION 611 
 
 methane and water. Ethylene, propylene, /?-hexene, a-octene, 
 &c., are quantitatively reduced to the corresponding paraffins. 
 Acetylene at 150 and o-heptine at 170 yield ethane and 
 heptane respectively. Aromatic hydrocarbons, e.g. benzene, 
 toluene, xylene, cymene, at 180 yield their hexahydro-deriva- 
 tives. Ethyl-benzene reacts in a somewhat curious manner; 
 it appears to be first reduced to its hexahydro-derivative, 
 CgHn'CgHg, but this is partially reduced to CJLj-CHg and 
 CH 4 . Similarly phenyl- acetylene, C 6 H 5 C:CH, yields a 
 mixture of ethyl - cyclohexane, methyl - cyclohexane, and 
 methane. The terpenes limonene, sylvestrene, terpinene, 
 menthene all yield ^-methyl-isopropyl-cyclohexane. Pinene 
 yields a dihydro-derivative and naphthalene a tetrahydro- 
 compound, and this with more hydrogen, dekahydro - naph- 
 thalene, C 10 H 18 (Leroux). 
 
 . Aliphatic nitriles at 180-200 yield primary amines, and 
 finally secondary and tertiary amines and ammonia: 
 
 E-ClSr -* K.CH 2 -NH 2 ; 2K-CH 2 .NH 2 * ( 
 
 Aromatic nitriles yield ammonia and an aromatic hydro 
 carbon : c 6 H 6 CN + 3H 2 = C 6 H 6 .CH 3 + NH 3 . 
 
 Aromatic chloro-derivatives are readily dehalogenized at 
 temperatures above 270 : 
 
 C 6 H 6 C1 C 6 H 6 , 
 
 and similarly for polychloro-derivatives. The presence of CHg, 
 OH, and NH 2 groups appear to facilitate reduction : 
 
 C1.C 6 H 4 .N0 2 C 6 H 6 .NH 2 ,HC1. 
 
 Aliphatic nitro-compounds at 150- 180 yield the corre- 
 sponding primary amines, but at higher temperatures paraffins 
 and ammonia. Aromatic nitro-compounds are best reduced 
 in presence of copper at 300-400; in this manner nitro- 
 benzene yields aniline and a-nitro- naphthalene a-naphthyl- 
 amine; whereas, when nickel is used, a-nitro -naphthalene 
 yields ammonia and tetrahydro-naphthalene. 
 
 Phenol, o-cresol, thymol, and carvacrol at 170- 180 are 
 reduced to their hexahydro-derivatives, as are also methyl- 
 and ethyl-anilines. Aniline at 190 also yields its hexahydro- 
 derivative, cyclohexylamine, C-H n NH 2 , but at the same 
 time dicyclohexylamine, (C 6 H n ) 2 NH, and cyclohexyl-aniline, 
 are produced. 
 
612 XLIV. REDUCTION 
 
 At moderate temperatures (130-160) polyhydric phenols 
 yield corresponding hexahydro-derivatives. 
 
 Alcohols are formed by the reduction of aldehydes and 
 ketones at temperatures slightly above their boiling-points, 
 e.g.: 
 
 (C 2 H 5 ) 2 CO -* (C 2 H 6 ) 2 CH.OH. 
 
 Olefine derivatives are readily transformed into the corre- 
 sponding saturated compounds at moderate temperatures, and 
 compounds of the aromatic series, e.g. cinnamic acid, can be 
 reduced to saturated compounds without the benzene nucleus 
 being affected. Unsaturated ketones, e.g. mesityl oxide and 
 phorone, can be reduced to the corresponding saturated 
 ketones. Diketones yield various products: thus diacetyl at 
 140-150 yields a mixture of hydroxyketone and glycol; 
 acetonylacetone yields the anhydride of the corresponding 
 glycol; benzil, benzoin, and benzoylacetone yield the corre- 
 sponding hydrocarbons. Lsevulic acid yields valerolactone, 
 quinones yield quinols, and carbylamines, alkyl isocyanates, 
 and oximes yield mixtures of amines, mainly secondary. 
 (Sabatier and Senderens, Annales, 1905 [viii], 4, 319; Sabatier 
 and Maihle, ibid. 1909, 16, 70; Sabatier, B. 1911, 44, 1984.) 
 
 Recent experiments have shown that finely divided palla- 
 dium or platinum can bring about the reduction of various 
 carbon compounds at moderately low temperatures. Paal and 
 Gerum (B. 1907, 40, 2209) show that when hydrogen is passed 
 through an alcoholic solution of nitrobenzene mixed with a 
 small amount of colloidal platinum, a 50-per-cent yield of 
 aniline can be obtained at temperatures between 65 and 85. 
 They also show (B. 1908, 41, 2273; 1909, 42, 1553, 2244, 
 3930) that unsaturated acids and esters, e.g. fumaric acid, 
 maleic acid, cinnamic acid, and methyl cinnamate can be 
 reduced to their saturated analogues by passing hydrogen 
 into their alcoholic solutions at the ordinary temperature, 
 provided small amounte of colloidal platinum or palladium, 
 or even of palladium black, are present. They have used the 
 method for converting unsaturated oils (oleic acid derivatives) 
 into saturated glycerides. (Cf. also Willstatter and Mayer, 
 ibid. 1475, 2199.) The most effective reagent appears to be 
 colloidal palladium. On this reaction FoJcin (Abs. 1908, ii, 637) 
 suggests a method for determining the " hydrogen value " of 
 unsaturated acids by ascertaining the volume hydrogen 
 absorbed by an alcoholic solution of a known weight of the 
 
CATALYTIC REDUCTION 613 
 
 unsaturated compound when well shaken with the gas in the 
 presence of molecular platinum. A. Skita prepares the col- 
 loidal palladium by the addition of gummi arabicum to a 
 slightly acidified solution of palladous chloride, and shows 
 that unsaturated ketones are converted into saturated, that 
 citral yields citronellal and citronellol, and that many alka- 
 loids take up hydrogen (B. 42, 1627; 44, 2862). 
 
 The reduction proceeds most rapidly when the hydrogen 
 is under an increased pressure of - 25 to 1 atmosphere. 
 (Skita and Hitter, B. 1910, 43, 3393.) By this method un- 
 saturated ketones are reduced to saturated without the 
 carbonyl group being affected: d-pulegone * e-menthone, 
 mesityl oxide methyl -isobutyl ketone. An exception is 
 met with in phorone (p. 137), which yields di-isobutyl car- 
 binol. If, however, a smaller pressure is used the reduction 
 stops at the formation of the saturated ketone, valerone. 
 Similarly in the other cases, if the pressure of the hydrogen 
 is increased, a saturated secondary alcohol is obtained. Cyclic 
 ketones and aromatic aldehydes can be reduced to alcohols, 
 using a pressure of 5 atmospheres. Skita (B. 44, 2862, and 
 Chem. Zeit., 1911, 35, 1098) shows that in many cases a solu- 
 tion of palladous chloride in hydrochloric acid can be used, 
 instead of the colloidal metal, with equally good results. 
 
 Ipatie/(B. 34, 596, 3579; 35, 1047, 1057; 36, 1990, 2003, 
 2014, 2016; 37, 2961, 2986; 40, 1270, 1281, 1827; 41, 991, 
 993, 996, 1001; 42, 2089, 2092, 2097) has studied the re- 
 duction by numerous carbon compounds with hydrogen under 
 pressures of 100-120 atmospheres in the presence of various 
 catalysers. 
 
 A special iron or gun-metal bomb has been constructed for 
 this purpose, and can be heated to the required temperature 
 in an electric furnace. Of the catalytic agents investigated, 
 namely, iron, nickel, copper, aluminium, nickelous and nickelic 
 oxide (Ni 2 3 ), the last named was found to be the most effec- 
 tive, and only 2-3 grm. were required for 20-30 grm, of the 
 substance to be reduced. The oxide may be used a second 
 time, but afterwards is less active; analysis of the recovered 
 oxide indicates that only a comparatively small amount of 
 reduction to metallic nickel has taken place. In most cases 
 the best temperature is 230-260. Under such conditions, 
 acetone yields pure isopropyl - alcohol ; phenol, hexahydro- 
 phenol; diphenyl, dicyclohexyl ; naphthalene, tetra- or deka- 
 hydronaphthalene; dibenzyl, dicyclohexylethane; a- and p- 
 
614 XLIV. REDUCTION 
 
 naphthols, o- and /2-dekahydronaphthols, and similarly for 
 sodium /3-naphthioate; benzophenone, diphenylmethane; so- 
 dium benzoate, sodium hexahydrobenzoate (60 per cent yield 
 of pure acid); aniline, hexahydroaniline (50 per cent yield); 
 diphenylamine, dicyclohexylamine (C 6 H n ) 2 NH; quinoline, de- 
 kahydroquinoline; anthracene, perhydroanthracene, C 14 H 24 ; 
 phenanthrene, perhydrophenanthrene, C 14 H 24 ; acenaphthene, 
 dekahydroacenaphthene. In the last-mentioned reactions it 
 is necessary to repeat the reduction three times in order to 
 obtain the perhydro - derivatives. Olefines are reduced to 
 paraffin derivatives. 
 
 It is claimed that this method is much better and yields 
 purer products than Sabatier and Seiiderens' method of reducing 
 with hydrogen at atmospheric pressure and in the presence of 
 finely divided nickel. 
 
 D. Electrolytic Reduction. Within recent years, numerous 
 reductions have been effected by electrolytic methods. The 
 basis of all these methods is the fact that when an electric 
 current is passed through an aqueous solution of an acid or 
 an alkali, using metal electrodes, hydrogen in the nascent 
 state is produced at the cathode or negative terminal. The 
 actual products formed are dependent not merely on the 
 substances reduced, but also upon the conditions, among the 
 most important of which we may mention: (a) nature and 
 concentration of solvent, e.g. dilute or concentrated acid, 
 alkaline or neutral solvent; (b) strength of current or the 
 current density, i.e. the intensity of the current per square 
 decimetre of electrode; (c) the materials of which the elec- 
 trodes are made, due to the difference of potential at which 
 the hydrogen ions are discharged (as a rule platinum, mercury 
 or lead electrodes are used); and (d) the temperature. 
 
 The method has been mainly used for the reduction of aro- 
 matic nitro-compounds, of ketones, and of unsaturated acids. 
 
 In many cases the reduction is carried out in a double cell pro- 
 vided with a diaphragm, (a) The cathode solution is placed in 
 an ordinary unglazed porous cell, and this is introduced into a 
 beaker which serves as the anode compartment; or (b) two 
 glazed pots with small perforations are used, and the small an- 
 nular space between these is packed with asbestos paper. If 
 necessary the liquid can be agitated by using a rotating cathode. 
 
 The reduction of nitro-benzene may be cited as one of the 
 best examples which show the effect of conditions on the 
 nature of the product: 
 
4LECTROLYTIO REDUCTION 
 
 615 
 
 .^- 
 
 3 
 
 
 Current 
 ensity in 
 imperes. 
 
 2 
 
 2 
 
 II 
 . 
 
 I! 
 
 s 
 
 
 
 P O 
 03 p, 
 
 S.s 
 
 S o^ 
 
 i|i 
 
 p fto 
 
 Cold satu 
 sodic ca 
 ate soluti 
 porous ce 
 
 8.2 
 
 Jfi 
 
 40 "73 
 
 ncentrated hy 
 drochloric acid 
 
616 XLV. OXIDATION 
 
 In the reduction of ketonic compounds, Tafel (B. 1900, 33, 
 2209) has shown that the best effects are obtained by using 
 pure lead electrodes, as the hydrogen ions are thus discharged 
 at a higher potential than when other metals are employed, 
 and by employing in the cathode compartment 30-60 per 
 cent sulphuric acid; with stronger acid, reduction of the acid 
 occurs and sulphur is deposited. It is also essential that the 
 current density shall be as low as possible. (For preparation 
 of cells, see Tafel.) Acetone when reduced under such con- 
 ditions, using mercury as cathode, yields isopropyl alcohol; 
 but under similar conditions with a lead cathode it yields a 
 mixture of isopropyl alcohol and pinacone. Camphor may be 
 reduced to borneol (p. 568), and caffeine to deoxy-caffeine : 
 
 NMe.CO NMe.CH 2 
 
 CO C-NMe\ CO C-NMex 
 
 .C-N=/ &Me-C.N=/ 
 
 Similarly uric acid may be reduced to purone : 
 NH-CO NH-CH 2 
 
 CO C-NHv CO CH.NH 
 
 NH 
 
 C-NHv CO CH.NHx 
 
 .C-NH/' NH.CH-NH/ 
 
 Further, acetanilide, CgH 5 NH CO CH 8 , may be reduced 
 to ethyl-aniline, C 6 H 5 NH'CH 2 CH 3 ; pyridine to piperidine, 
 using lead cathodes; aconitic acid to tricarballylic acid and 
 cinnamic to hydrocinnamic acid, by using mercury cathodes. 
 
 The esters of oxalic, malonic, acetoacetic, benzoic, and 
 phthalic acids, when reduced electrolytically, yield ethers, e.g.: 
 
 Ethyl benzoate *- benzyl-ethyl ether. 
 
 XLV. OXIDATION 
 
 Oxidation includes not only those processes in which oxygen 
 is added to a compound, e.g. conversion of an aldehyde, K CH : 0, 
 into an acid, R CO OH, but also processes in which hydrogen 
 is withdrawn from a compound, e.g. transformation of a primary 
 alcohol, R.CH 2 -OH, into an aldehyde, K-CH:0. In certain 
 cases both processes can occur, e.g. oxidation of aniline, 
 C e H 6 NH 2 , to nitroso-benzene, C 6 H 6 NO. 
 
OXIDATION 617 
 
 Moat of the oxidizing agents employed are substances rich 
 in oxygen, e.g. potassic dichromate or permanganate, nitric 
 acid, chromic anhydride, peroxides, &c. During the oxi- 
 dation, although the organic compound is oxidized, the Oxi- 
 dizing substance is reduced, e.g. nitric acid gives up part of 
 its oxygen to the substance to be oxidized, and itself becomes 
 reduced to nitrous acid or to various oxides of nitrogen. 
 
 Oxygen itself is sometimes made use of as an oxidizing 
 agent, but usually in the presence of a catalyser, e.g. finely- 
 divided metals such as platinum black or one of the enzymes 
 known as oxydases. Processes of oxidation, like those of 
 reduction, depend not merely upon the substances to be 
 oxidized, but also on the oxidizing agent selected, and on 
 such conditions as the acid, alkaline, or neutral nature of the 
 solvent, temperature, and concentration. Examples of this 
 have previously been cited among the aromatic hydrocarbons. 
 Thus w-xylene is not acted upon by dilute nitric acid, but 
 with chromic anhydride yields isophthalic acid. A very good 
 example is aniline: 
 
 'Manganese dioxide and) . -, -,.,., 
 
 sulphuric acid ) ** ammonia and little qumone ; 
 
 Dichromate mixture qumone: 
 
 Alkaline permanganate * azo-benzene and ammonia; 
 
 Acidified permanganate * aniline black; 
 
 Neutral permanganate * nitro-benzene and azo-benzene, 
 
 Bleaching-powder nitro-benzene; 
 
 .Hypochlorous acid * >-amino-phenol. 
 
 Compounds of similar constitution are not always oxidized 
 in the same manner; thus, to oxidize j9-nitro-toluene or p-nitTO- 
 cinnamic acid the best reagent is dichromate mixture, but for 
 the isomeric 0-compounds, dilute nitric acid or permanganate 
 are recommended. The inhibiting influence of halogen and 
 other negative radicals in the o-position with regard to the 
 alkyl group, on the oxidation of such hydrocarbons by means 
 of acid oxidizing agents, has already been referred to (p. 436), 
 and also the fact that the final product of oxidation of a 
 benzene homologue depends on the number and positions of 
 the side chains, and not on their length, each yielding ulti- 
 mately a C0 2 H group. 
 
 When a compound like cymene, CH 3 C 6 H 4 C 3 H 7 , is selec 
 tively oxidized, it is usually the longer side chain which is 
 first affected; and it has been found possible, in a few cases, 
 to carry the oxidation to a stage where a long side chain has 
 
618 XLV. OXIDATION 
 
 become only partially oxidized, e.g. aceto-mesitylene, CLH 2 Me 3 
 CO'CHg, to mesityl-glyoxylic acid, C 6 H 2 Me 3 -CO.C0 2 H; m- 
 butyl toluene, CH 3 'C 6 H 4 .C 4 H 9 , by nitric acid at 180, to m- 
 mejthyl-phenyl-propionic acid, CH 3 C 6 H 4 CH 2 CH 2 . C0 2 EL 
 
 Cohen and Miller (J. C. S. 1904, 174, 1622) find that com- 
 pounds containing chlorine or bromine in the meta-position 
 with regard to a methyl group are least readily oxidized by 
 nitric acid, those with similar substituents in the para-position 
 most readily, and those with 0-chloro- and bromo-substituents 
 are intermediate. 
 
 In certain cases of oxidation, labile groups are present 
 which have to be protected from the oxidizing agent; two 
 such groups are the amino- and aid ehydo - groups. An 
 amino- or imino-group can often be protected from under- 
 going oxidation by transformation into the acetylated group 
 NHAc or :NAc, or even better, into a nitroso-derivative, 
 :N*NO. The further oxidation of an aldehydo- to a car- 
 boxylic group can often be prevented by the addition of some 
 substance to the oxidizing mixture which will yield a spar- 
 ingly soluble compound with the aldehyde; such compounds 
 are a primary aryl-amine, which forms a compound of the 
 type of benzylidene-aniline, C 6 H 6 CH : NC 6 H 5 , sodic hydric 
 sulphite, or calcium naphthionate, the calcium salt of 1-amino- 
 naphthalene-4-sulphonic acid. From the additive compound 
 to which the last salt gives rise, the aldehyde may be ob- 
 tained by distillation in steam. 
 
 A. Potassium Permanganate, This is the commonest and 
 one of the most useful oxidizing agents, as it may be used 
 in 'neutral, alkaline, or acid solution. Other permanganates 
 are also employed, e.g. the calcium and barium salts, especially 
 for the oxidation of complex proteins. 
 
 (a) Alkaline Solution. Even when no alkali is added at the 
 beginning, the solution becomes alkaline during the reaction. 
 The permanganate, a derivative of Mn 2 r , becomes reduced 
 to hydrated Mn0 2 , and thus each molecule of permanganate, 
 K 2 Mn 2 8 , can yield three atoms of nascent oxygen: 
 
 K 2 Mn 2 O 8 4-H 2 O = 2MnO 2 -f 2KOH + 3O. 
 
 When the product formed is an acid, this remains dissolved 
 in the alkaline liquid, and may often be obtained by the 
 addition of mineral acid after the manganese dioxide has 
 been removed by filtration. In this manner, numerous ben 
 zene hydrocarbons and their derivatives can be oxidized to 
 
OXIDATION WITH PERMANGANATE 619 
 
 the corresponding acids, e.g. ^3-chloro- toluene to j9-chloro- 
 benzoic acid, naphthalene to phthalonic acid, 0-C0 2 HC 6 H 4 
 COC0 2 H. Other examples are the conversion of o-nitro- 
 
 Slienol into dinitro - dihydroxy - diphenyl, N0 2 (OH)C 6 H 3 
 6 H 3 (OH).N0 2 , and of uric acid into allantoin (p. 294). 
 
 The oxidation of olefine derivatives by two per cent perman- 
 ganate (Fittig) is of extreme interest. Two hydroxyl groups 
 are invariably added, and a glycol derivative formed; thus 
 cinnamic acid, C 6 H, CH : CH C0 2 H, yields phenyl-gly eerie 
 acid, C 6 H 5 .CH(OH).CH(OH).C0 2 H. When a stronger per- 
 manganate solution or a more powerful oxidizing agent is 
 used, the unsaturated compound is ruptured at the point of 
 the double bond, and a mixture of less complex acids or 
 ketones formed. 
 
 An excess of alkali is often added to the permanganate before 
 use. Under these conditions 0-toluic acid yields phthalic acid, 
 and the method is largely made use of for oxidizing 0-sub- 
 stituted derivatives of toluene, &c. When the solution is dilute 
 and the temperature is kept at 0, the oxidation is mild, and 
 can stop at the formation of a glyoxylic acid, e.g. : 
 
 C 6 H 2 Me 3 .(X).CH 3 C 6 H 2 Me 3 .CO.CO 2 H; 
 
 otherwise a substituted benzoic acid in this case C 6 H 2 Me 3 
 C0 2 H is always formed. Substituted cinnamic acids, by 
 this method, can be converted into corresponding benzoic 
 acids, e.g. : 
 
 N0 2 (OH)C 6 H 3 .CH:CH.C0 2 H to N0 2 (OH)C 6 H 3 .CO 2 H. 
 
 Similarly, hydrocarbons of the type of triphenyl-methane, 
 CHPhg, can be oxidized to carbinols, e.g. CPh 3 -OH, and 
 compounds of the type of diphenyl-methane, CH 2 Ph 2 , to 
 ketones, CPh 2 -CO. 
 
 (b) Neutral Solution, In a few cases it is necessary tc 
 keep the solution neutral from beginning to end, and this is 
 accomplished by the addition of an excess of magnesic sul- 
 phate, which yields insoluble magnesic hydroxide with the 
 caustic potash produced during the oxidation. When acet-o- 
 toluidide, CH 3 C 6 H 4 NH CO - CH 3 , is thus oxidized, an 
 80-per-cent yield of acetanthranilic acid, C0 2 H C 6 H 4 NH 
 CO'CH 3 , is formed, whereas in the presence of alkali the 
 yield is only some 30 per cent. 
 
 (c) Acid Solution. Acetic or sulphuric acid is used, and 
 the acid is added gradually with the permanganate. The 
 
620 XLV. OXIDATION 
 
 method is of use for the preparation of very stable compounds 
 only, as the majority are completely decomposed by these 
 reagents. The reaction is quite different from that in alka- 
 line solution, the permanganate (a derivative of Mn 2 r ) is 
 reduced to a manganous salt (derived from MnO), and thus 
 each molecule of permanganate gives rise to five atoms of 
 available oxygen: 
 
 K 2 Mn 2 O 8 + 3H 2 S0 4 = 2MnS0 4 + K 2 SO 4 + 3H 2 O -f 5O. 
 
 Sulphides or hydrosulphides in both the aliphatic and aro- 
 matic series may be oxidized to sulphonic acids, a reaction 
 which is useful for the preparation of certain naphthalene- 
 sulphonic acids which cannot be obtained by direct sulphona- 
 tion. o-Iodo-benzoic acid may be oxidized to o-iodoso-benzoic 
 acid, tetrabromo-p-xylene to tetrabromo-terephthalic acid, and 
 primary alcohols to aldehydes. 
 
 B. Chromic Acid Derivatives, Chromic anhydride, Cr0 3 , 
 is often used as an oxidizing agent when dissolved in glacial 
 acetic acid, two molecules of the anhydride yielding three atoms 
 of oxygen, 2 Cr0 3 = Cr 2 3 + 30. Usually only the theoretical 
 amount required for the oxidation is used, and this is gradually 
 run in from a dropping funnel. Quinoline homologues are 
 oxidized to quinoline carboxylic acids, and aromatic alcohols 
 to aldehydes, if a primary amine is present to form a Scki/'s 
 base (p. 425). Even benzene homologues may be oxidized to 
 aldehydes in the presence of acetic anhydride, as the acetyl 
 derivatives thus formed are stable. 
 
 Chromyl chloride, Cr0 2 Cl 2 , the chloride of chromic acid, is 
 used for oxidizing benzene hydrocarbons to aldehydes (Etard's 
 reaction, p. 424). The usual method is to dissolve the hydro- 
 carbon and chromyl chloride separately in carbon disulphide, 
 and to run in the chloride solution until the red colour per- 
 sists, and then to decompose with water. A precipitate of a 
 double compound, e.g. C 6 H 5 CH 3 , 2Cr0 2 Cl 9 , is first produced, 
 and this is decomposed by water according to the equation : 
 
 3[C 6 H 6 CH 3 ,2Cr0 2 Cl 2 ] = 3C C H 6 CHO -f 4OCl 3 -f 2H 2 CrO 4 + H 2 O. 
 
 The usual method of using chromic acid is in the form of 
 a mixture of a dichroinate and sulphuric acid, which react 
 according to the equation: 
 
 K 2 2 7 + 4H 2 S0 4 = K 2 S0 4 -f Cr 2 (SO 4 ) 3 -f 4H 2 O + 3O, 
 
 each molecule of dichromate yielding three atoms of available 
 
OXIDATION WITH NITRIC ACID 621 
 
 oxygen. Sometimes potassic dichromate is used, but more 
 frequently the sodic salt, as it is cheaper and more readily 
 soluble in water. As a rule, the dichromate mixture is added 
 gradually to the oxidizable substance. It is the common 
 method of preparing aldehydes from alcohols (see Acetalde- 
 hyde, p. 128), and also from aromatic hydrocarbons, as there 
 is not the same tendency for the -CHO group to be further 
 oxidized as when permanganate is employed. Complex alco- 
 hols may also be oxidized to ketones or aldehydes, e.g. menthol 
 to menthone (p. 578). Many compounds, such as hydroxy- 
 acids, ketones, ketonic acids, &c., are ruptured by chromic acid 
 mixture, and acids or ketones containing a smaller number of 
 carbon atoms are formed. 
 
 This is the oxidizing agent usually employed for the pre- 
 paration of quinones, e.g. from aniline, and as a rule the tem- 
 perature should be kept at about 0. According to Bamberger, 
 the following series of reactions occur: 
 
 6 H 6 .NH 2 -* C 6 H 6 .NH.OH -> p-OH.C c H 4 .NH 2 O:C 6 H 4 :O. 
 
 C. Nitric Acid. Examples of the complete oxidizing action 
 of fuming nitric acid are met with in the ordinary Carius 
 method for estimating halogens or sulphur. One of the chief 
 drawbacks of nitric acid is, that in addition to being an oxi- 
 dizing agent, it is also a nitrating agent, and the products of 
 oxidation, even when dilute acid is used, contain smaller or 
 larger amounts of nitro- derivatives. By means of dilute 
 nitric acid many benzene homologues are oxidized to car- 
 boxy lie acids, but the process is slow; thus pentamethyl 
 benzene dissolved in benzene requires sixty hours' boiling to 
 oxidize it to tetramethyl-benzoic acid, and slightly longer 
 time is required to oxidize 2 : 6-chloro-nitro-toluene to the 
 corresponding acid. An interesting oxidation is that of 
 m-butyl-toluene to w-methyl-phenyl-propionic acid, and a 
 somewhat complex oxidation is that of camphor to cam- 
 phoronic acid (p. 586). Kmffl (R 1889, 21, 2735) introduced 
 the use of concentrated nitric acid (sp. gr. 1-5) for oxidizing 
 purposes. The admixture was effected at 0-10, the tem- 
 perature gradually raised to 50, and the product poured into 
 water. This is a very good method for oxidizing compounds 
 which are already nitrated, as in other cases nitro-derivatives 
 are very liable to be formed. Dinitroxylene is oxidized in 
 this way to dinitrophthalic acid. Sulphoxides, e.g. Et 2 SO, 
 may be oxidized to sulphones, EtgSO^ iodo-benzoic acid to 
 
622 XLV. OXIDATION 
 
 iodoso-benzoic acid, cane-sugar to oxalic acid, &c. The 
 method adopted in oxidizing glycerol to glyceric acid is to 
 allow the aqueous solution of the glycerol to float on concen- 
 trated nitric acid. 
 
 A mixture of concentrated nitric and sulphuric acids, which 
 is an extremely good nitrating agent, may be used for oxidiz- 
 ing purposes, e.g. 0-nitro-benzyl alcohol to the corresponding 
 aldehyde, of ^-nitro-cinnamic acid to ^-nitro-benzaldehyde, and 
 of 5-trinitro-toluene to s-trinitro-benzoic acid. 
 
 D. Sulphuric Acid. One of the oldest examples of the 
 oxidizing action of concentrated sulphuric acid is the con- 
 version of ethyl mercaptan, C 2 H 6 SH, to ethyl disulphide, 
 (C 2 H 5 ) 2 S 2 , and another that of piperidine to pyridine. Schmidt 
 introduced the use of fuming sulphuric acid (60 or 70 per cent 
 S0 3 ) at low temperatures for converting alizarin and other 
 hydroxy- derivatives of anthraquinone into tri- to hexahy- 
 droxy-derivatives, many of which are important dyes. The 
 hydroxy-groups form an ester with the sulphuric acid, but this 
 is readily hydrolysed when boiled with dilute acid. Concen- 
 trated sulphuric acid may also be used for the preparation of 
 the same compounds, and the yields are largely increased by 
 the addition of boric acid, this being probably due to the fact 
 that boric esters are formed, which prevent the removal of the 
 hydroxy-groups when once introduced. 
 
 An oxidizing action of commercial importance is the con- 
 version of naphthalene into phthalic acid by means of con- 
 centrated sulphuric acid and a small amount of mercuric 
 sulphate at a temperature above 300. 
 
 E. Peroxides. The peroxides mainly employed are Mri0 2 , 
 Pb0 2 , and occasionally H 2 ? . Lead peroxide is frequently 
 used in the form of a paste with acetic acid, one of the earliest 
 oxidations with this reagent being that of uric acid to allan- 
 toin (p. 294). Characteristic oxidations are (i) that of a- 
 hydroxy-acids to aldehydo-acids, with one less carbon atom 
 (p. 305), e.g.: 
 
 C0 2 H.CH(OH).CH 2 .CO 2 H -* CO 2 + 0:CH.CH 2 .CO 2 H; 
 
 (ii) of alkyl acetates to aldehydes, e.g. : 
 
 o-N0 2 .C 6 H 4 .CH 2 .O.CO.CH 3 to o-N0 2 .C 6 H 4 .CH:O; 
 
 (iii) of triphenyl-methane-derivatives to the corresponding 
 carbinols, the salts of which are dyes, e.g.: 
 
OXIDATION WITH PEROXIDES 623 
 
 and (iv) of amino-hydroxy-derivatives of anthraquinone to the 
 corresponding polyhydroxy-derivatives, the NH 2 being replaced 
 by OH, a reaction which does not occur when the amino-group 
 is acetylated. Manganese dioxide alone, or in the presence 
 of sulphuric acid, may be used for converting CH 3 groups in 
 benzene homologues into aldehydo-groups. The mixture is 
 kept stirred, and an excess of hydrocarbon is always present. 
 Benzaldehyde, o-chloro-benzaldehyde, j?-nitro-benzaldehyde, 
 terephthalic aldehyde, &c., have been prepared by this method. 
 A remarkable oxidation is that of benzene to benzoic acid by 
 means of the peroxide and sulphuric acid. Hydroxy-acids 
 are often ruptured by these reagents, e.g. lactic acid, CH 3 - 
 CH(OH)-C0 2 H, yields aldehyde and carbonic acid. This is 
 the basis of a method for estimating the strength of solutions 
 of lactic acid by determining the amount of aldehyde formed. 
 The same reagents are also used for the oxidation of alkaloids, 
 and for the conversion of the leuco-bases of triphenyl-methane 
 dyes into the dye salts, e.g. jp-leucaniline into ^-rosaniline. 
 Hydrogen peroxide is often used in the presence of potassium 
 hydroxide for the preparation of organic peroxides, e.g. diethyl- 
 peroxide, Et 2 2 , benzoyl-peroxide, (C 6 H 5 CO) 2 2 . Piperidine, 
 when oxidized with three per cent peroxide solution, yields 
 glutaric acid owing to the rupture of the ring. Benzene, with 
 the peroxide, yields a certain amount of phenol. Azo-com- 
 pounds are converted into corresponding azoxy-derivatives, 
 and phenols into dihydric phenols or quinones. Fatty acids 
 are converted into ketones, E-CHg-CO-OH KCH 2 . CO- 
 CKLE, (DaMn, Am. C. J. 1910, 44, 41). 
 
 Fenton and others (J. C. S. 1894, 899; 1895, 48, 774; 1899, 
 1) have made use of hydrogen peroxide in the presence of 
 small amounts of ferrous salts; by this method the following 
 reactions have been effected: 
 
 Glycollic acid, OH-CH 2 .CO S H, > glyoxylic acid, CHO-C0 2 H; 
 
 Lactic acid, CH 3 .CH(OH).C0 2 H, pyruvic acid, CH 8 .CO-C0 2 H; 
 
 Tartronic acid, OH CH(C0 2 H) 2 , -* mesoxalic acid, CO(C0 2 H) 2 ; 
 
 Gly eerie acid, \ fhydroxy-ruvic acid 
 
 H OH.CH 2 .CH(OH).C0 2 H,j ' ' \ 
 
 Tartario acid, _^ 1 , /dUiydroxy^maleic : acid, 
 
 CO a H.CH(OH).CH(OH).C0 2 H,/ ' * I CO a H.C(OH):C(OH).C0 2 H; 
 Polyhydric alcohols, * aldoses. 
 
 F. Oxygen itself can often be used for oxidation, generally 
 in the presence of platinum black or platinized asbestos. Denn- 
 stedt's method for estimating carbon and hydrogen in organic 
 
624 XLV. OXIDATION 
 
 compounds is based on this. Many aldehydes, when exposed 
 to moist air, are transformed into acids; thus specimens of 
 benzaldehyde which have been kept for some time contain 
 appreciable amounts of benzoic acid. Cinnamic alcohol may 
 be oxidized to cirmam aldehyde, glycerol to glyceraldehyde, 
 and methyl alcohol to formaldehyde in presence of slightly 
 oxidized copper. Alkaline solutions of polyhydroxylic phenols 
 are readily oxidized (see Pyrogallol), and a similar solution of 
 gallic acid yields the yellow dye galloflavin. Glock has shown 
 that methane and air, when repeatedly passed over heated 
 metallic copper at 600, yield methyl alcohol and formalde- 
 hyde, and that ethane and air yield ethyl alcohol, acetalde- 
 hyde, and acetic acid. [Compare also Bone's experiments (pp. 
 36 and 37).] Ozone may also be used as an oxidizing agent; 
 it is employed commercially for refining oils, &c. (cf. J. Ind. 
 1898, 1101). G. Harries (A. 1905, 343, 311; 1910, 374, 288) 
 has examined the action of ozone on various types of carbon 
 compounds, mainly in glacial acetic acid solution. Methane, 
 ethyl alcohol, &c., are oxidized to aldehydes and acids, hydro- 
 gen peroxide also being formed. Saturated aldehydes and, 
 to a certain extent, ketones yield labile peroxides of the type, 
 R CH : : 0. Most unsaturated hydrocarbons and alcohols 
 combine with ozone, yielding ozonides, e.g. C 2 H 4 -J-0 3 , ethylene 
 ozonide. The structure of such compounds is usually repre- 
 sented as follows, e.g.: 
 
 CH 2 
 
 and for each ethylene linking one molecule of ozone is added. 
 Many compounds combine with more than this amount of 
 ozone, yielding oxozonides, e.g. propylene yields a product, 
 C 3 H 6 -}-0 4 , which are not readily transformed into normal 
 ozonides. They are regarded as derived from the hypothetical 
 4 . Unsaturated carbonyl derivatives, e.g. acids, aldehydes, 
 and ketones, also combine with ozone, yielding ozonides; they 
 can, however, combine with a fourth atom of oxygen, yielding 
 perozonides, which are decomposed by water, yielding the 
 ozonide and hydrogen peroxide. The three atoms of the 
 ozonide are regarded as attached to the two carbon atoms 
 of the ethylene linking, whilst the fourth atom is attached 
 to the carbonyl group. Oleic acid perozonide is represented 
 Mi 
 
OXIDATION WITH OZONE 625 
 
 CH 3 .[CH 2 ] r .CH . C 
 
 O-O-O OH 
 
 The ozonides are decomposed when gently heated, or when 
 the solutions in glacial acetic acid are warmed. Oleic acid 
 ozonide decomposes into the four products: 
 
 CH 3 .[CH 2 ] 7 .CH:0 + 
 
 I. Nonaldehyde. QS IL 
 
 and C 
 
 III. Nonaldehyde N U IV. Azelaic acid semi- 
 peroxide. aldehyde. 
 
 Some of these products are readily oxidized, e.g. nonalde- 
 hyde yields the corresponding acid, and the semialdehyde 
 yields azelaic. At the same time the aldehyde peroxides are 
 transformed into the isomeric carboxylic acids, so that appreci- 
 able amounts of nonylic and azelaic acids are always found in 
 the final decomposition products. The nonaldehyde peroxide 
 formed in this way is isomeric, and not identical with the per- 
 oxide obtained by the direct action of ozone on the aldehyde. 
 It is more stable, has m.-pt. 73, and is represented by for- 
 mula III. 
 
 Such decompositions of ozonides can be used for determin- 
 ing the position of the ethylene linking in the molecule of the 
 original compound, and also for the preparation of certain 
 aldehydes, aldehydic acids, and dialdehydes. 
 
 Benzene yields a highly explosive triozonide, (LHgOg. 
 
 G. Other Oxidizing Agents. Chlorine and bromine are 
 generally used in alkaline solution, i.e. in the form of hypo- 
 chlorite or hypobromite. As examples, we have the well- 
 known Hofmann reaction, the conversion of amides, and imides 
 such as succimmide and phthalimide, into amines or nitriles 
 (pp. 183 and 184); also the oxidation of reduced benzene 
 derivatives back to the original benzene compound. An in- 
 teresting oxidation is that of benzylidene-acetone to cinnamic 
 acid with four per cent sodium hypobromite : 
 
 C 6 H 6 . CH : CH - CO CH 3 -f 3 NaBrO 
 
 and of potassium cyanide to cyanate by hypochlorite. Bromine 
 water itself is frequently used for the oxidation of sugars, e.g. 
 
 (8480) 8& 
 
626 XLV. OXIDATION 
 
 of an aldose to the corresponding monobasic acid; thus gly- 
 cerose to gly eerie acid, glucose to gluconic acid. 
 
 Less common oxidizing agents are potassic ferricyanide, 
 which is reduced to the f errocyanide : 
 
 2K 3 FeC 6 N 6 + 2KOH = 2K 4 FeC 6 N 6 + H 2 O + 0. 
 
 s-Trinitro-benzene may be oxidized by this reagent to picric 
 acid, phenyl-acetylene to diphenyl-diacetylene, CPh:CC:CPh, 
 nitroso- to nitro- derivatives, quinone-dioxime to dinitroso- 
 benzene, benzene-diazo-oxides to salts of benzene-diazoic acid, 
 C 6 H 5 N : NO OH, and nitro-toluenes to nitro-benzoic acids. 
 Ferric chloride: 
 
 2FeCl 3 + H 2 = 2FeCl 2 + 2HCl + 0, 
 
 may be used for oxidizing hydroxylamine derivatives to 
 nitroso-compounds, e.g. : 
 
 C 6 H 4 Br.NH.OH - C 6 H 4 Br.NO; 
 
 quinols to quinones, and naphthols to dinaphthols: 
 OH.C 10 H 6 .C 10 H 6 .OH. 
 
 Silver oxide oxidizes glycerol to glycollic acid, and gener- 
 ally aldehydes to acids, and 0-dihydroxy-benzene to 0-benzo- 
 quinone. Mercuric oxide, usually with alkali, e.g. barium 
 hydroxide, is used for oxidizing fructose to trihydroxy-butyric 
 acid and glycollic acid, and glucose to gluconic acid. It also 
 oxidizes unsym. diethyl - hydrazine to tetraethyl - tetrazone, 
 NEt 2 N : N NEt 2 , and sym. diethyl -hydrazine to mercury- 
 diethyl, nitrogen, and water. Nitre-benzene is used as an 
 oxidizing agent in the manufacture of magenta (p. 487), and 
 also in the Skraup synthesis of quinoline (p. 542). Potassium 
 persulphate, mixed with concentrated sulphuric acid, is known 
 as Caro's reagent or sulphomono-per-acid, and can oxidize sali- 
 cylic acid to 2:5-dihydroxy-benzoic acid. It is also used for 
 oxidizing various terpene derivatives, and readily oxidizes aro- 
 matic primary amines to nitroso-derivatives, e.g. : 
 
 C fl H 5 NH 2 C 6 H 6 NO. 
 
 H. Electrolytic Oxidation. Organic compounds may be 
 oxidized by means of the oxygen formed at the anode of an 
 electrolytic cell. The method is not so general in application 
 as electrolytic reduction, as it is extremely difficult to stop 
 the reaction at the right point. Even when the theoretical 
 
ELECTROLYTIC OXIDATION 627 
 
 amount of oxygen has been formed, it is often found that 
 part of the compound is unacted on, and part has been com- 
 pletely oxidized. The following are fairly typical examples : 
 
 Purpuro-gallin is formed by the electrolysis of a solution 
 of pyrogallol in sodium sulphate solution, using a rotating 
 platinum anode of 2 sq. dm. The reaction is complete after 
 6-8 hours with a C.D. of 1-5-2 amperes and an E.M.F. of 
 4-3-4-5 volts. 
 
 Anthraquinone may be prepared by oxidizing an emulsion 
 of anthracene, water, and sulphuric acid, using a rotating lead 
 cathode, and a leaden vessel as anode. The best yields are 
 obtained when an oxygen carrier, e.g. manganese sulphate, is 
 employed with a temperature of 75-90, a C.D. of 1-2 am- 
 peres, and an E.M.F. of 2'8-3'5 volts. 
 
 Numerous azo-dyes have been obtained electrolytically; 
 thus, Orange II, or fi - naphthol - azo benzene - sulphonic acid, 
 OH.S0 2 .e 6 H 4 .N:N.C 10 H fl .OH (p. 502), is produced from 
 an aqueous solution containing sodic sulphanilate, /3-naphthol, 
 and sodic nitrite. The cathodes of nickel or platinum wire 
 are placed in two separate cathodic compartments consisting 
 of small porous cells and containing sodic hydroxide solution. 
 The rotating anode is of platinum; and a C.D. of 8-12 am- 
 peres, an E.M.F. of 15-18 volts, and as low a temperature as 
 possible, give the best results. The homologues of benzene, 
 when oxidized with platinum electrodes in the presence of 
 sulphuric acid and acetone, yield aldehydes, e.g. toluene * 
 benzaldehyde, o-xylene * o-toluic aldehyde, but the yields, 
 as a rule, are not good. Ortho-substituents of a negative char- 
 acter tend to inhibit such oxidations. Acetic acid solutions 
 of p- and o-nitro-toluenes yield the corresponding nitro-benzyl 
 alcohols, whereas the m-compound yields m-nitro-benzaldehyde. 
 Benzyl sulphide yiolds benzylsulphoxide, benzyldisulphoxide, 
 or tribenzylsulphonium sulphate according to conditions. 
 
 XLVI. STEREO-CHEMISTRY OF SULPHUR, 
 SELENION, TIN, AND NITROGEN COMPOUNDS 
 
 Attention has already (pp. 154 and 213) been drawn to the 
 fact that a compound containing an asymmetric carbon atom, 
 Ca, b, c, d, exists in two optically active isomerides which 
 can unite to form a racemic compound. The researches of 
 Pope and others within the past few years have proved that 
 compounds containing other quadravalent atoms, such as 
 
628 XLVI. STEREO-CHEMISTRY OF SULPHUR, ETC. 
 
 S, Se, and Sn, attached to four different univalent radicals, 
 also exist in optically active isomeric forms. 
 
 A. Sulphur Compounds (Pope and Peachey, J. C. S. 1900, 
 1072). The sulphur compounds selected were derivatives 
 of methylethylthetine bromide: 
 
 a product which can be prepared by the addition of bromo- 
 acetic acid to methylethyl sulphide. The bromide was mixed 
 with the theoretical amount of silver d-camphor-sulphonate in 
 aqueous solution, the silver bromide removed, the filtrate evap- 
 orated at 40, and the solid residue crystallized some 40-50 
 times from a mixture of absolute alcohol and dry ether. The 
 sparingly soluble ^-methylethylthetine d-camphor-sulphonate, 
 CHCH CO 
 
 melts at 118-120, and has a molecular rotation [M] D * = 
 + 68. The rotation for the camphor - sulphonate ion is 
 4-51-7, and this gives a rotation of +16-3 for the thetine 
 ion. A very similar value has been obtained by repeatedly 
 crystallizing the d- bromo- camphor -sulphonate. The corre- 
 sponding platinichloride, (SMeEtCl-CH 2 .C0 2 H) 2 , PtCl 4 , has 
 a molecular rotation + 30'2. 
 
 Smiles (J. C. S. 1900, 1174) has obtained methylethyl- 
 phenacylsulphine bromide: 
 
 (from methylethyl sulphide and bromo-acetophenone) in opti- 
 cally active modifications by a similar process. 
 
 B. Selenion Compounds have been resolved by Pope and 
 Neville (J. C. S. 1902, 1552). The compound used was 
 methylethylselenetine bromide, SeMeEtBr CH 2 C0 2 H, ob- 
 tained from methylethyl selenide and bromo-acetic acid; the 
 corresponding d- bromo -camphor- sulphonate was repeatedly 
 crystallized from alcohol, and the least soluble fraction melted 
 at 168, and had [M] D = +330-8, which gives a rotation of 
 + 60-8 for the methylethylselenetine ion. 
 
 The corresponding salt of the /-base -f d-acid was isolated; 
 it melted at 151, and had [M] D = +209 '6, which gives a 
 value of 60 '4 for the Z-selenetine ion. The platinichloride 
 
 * For meaning of this, see p. 627. 
 
OPTICALLY ACTIVE TIN COMPOUNDS 629 
 
 had a molecular rotation +55, but the mercuri - iodide, 
 SeMeEtI.CH 2 .C0 2 H, HgI 2 , was optically inactive. 
 
 C. Tin Compounds (Pope and Peachey, P. 1900, 42, and 
 116). A compound containing an asymmetric tin atom was 
 prepared by the following series of reactions: 
 
 2SnMe 3 I + ZnEt 2 = 2SnMe 3 Et + ZnI 2 ; 
 SnMegEt + 12 = SnMe 2 EtI + Mel; 
 2SnMe 2 EtI + ZnPr 2 = 2SnMe 2 EtPr + ZnI 2 ; 
 SnMe 2 EtPr + I 2 = SnMeEtPrI + Mel. 
 
 The methylethylpropyl-tin iodide (a liquid boiling at 270) 
 was converted into the ^-camphor -sulphonate by means of 
 silver d- camphor -sulphonate, and after the removal of the 
 silver iodide the solution was evaporated, when crystals of 
 d-methylethyl-7i-propyl-tin ^-camphor-sulphonate, SnMeEtPr- 
 O S0 2 C 1? H 15 0, melting at 125-126, were obtained. In 
 aqueous solution, [M] D = +95, which gives a value for the 
 univalent ion, SnMeEtPr, of about -f 45. When the mother 
 liquor from the above-mentioned crystals is evaporated, a 
 further quantity of the same compound is obtained, and the 
 operation can be continued until all the water has been 
 expelled. No trace of /-methylethylpropyl-tin d-camphor- 
 sulphonate can be isolated. Pope and Peachey attribute this 
 to the conversion of the /-base into the d-base by continued 
 racemization (p. 257), in the following manner: The solution 
 of the racemic base with the d-acid deposits a portion of its 
 d-base as the sparingly soluble salt d-base + d-acid; the excess 
 of I- over d-base remaining in the solution racemizes as eva- 
 poration proceeds, a further quantity of J-base separates as 
 salt, and racemization of the residue again proceeds. 
 
 A d-methylethyl-w-propyl-tin iodide with [a] D + 23 in 
 ethereal solution has been prepared from the camphor- 
 sulphonate. 
 
 The resolution of tin compounds has also been accomplished 
 by means of the d-bromo-camphor-sulphonate. If the aqueous 
 solution of rf-methylethyl-n-propyl-tin d-bromo-camphor-sul- 
 phonate is heated at 100 in a sealed tube for two hours, 
 racemization proceeds, and the rotation [M] D -f 272 is that 
 due to bromo-camphor-sulphonate ion only. 
 
 D. Silicon Compounds. Silicon is the element most closely 
 allied to carbon, and hence numerous attempts have been 
 made to prepare optically active silicon compounds containing 
 an asymmetric silicon atom. 
 
630 XLVI. STEREO-CHEMISTRY OF SULPHUR, Eta 
 
 It is only recently, however, that these experiments have 
 met with success. Kipping (J. C. S. 1907, 91, 209) has pre- 
 pared the compound 
 
 ethylpropylbenzylphenylsilicane, by the following series of re- 
 actions : 
 
 SiCl 4 + MgEtBr = SiEtCl 3 + MgClBr 
 
 SiEtCL -f- MgPhBr = SiEtPhCl 2 + MgClBr 
 
 SiEtPhCL + MgPrBr = SiEtPhPrCl -f MgClBr 
 
 SiEtPhPrCl -f MgBzCl = SiEtPhPrBz -f MgCl 2 . 
 
 This hydrocarbon when sulphonated gives rise to benzene 
 and a sulphonic acid: 
 
 S0 3 H C 6 H 4 CH 2 SiEtPr SiEtPr CH 2 C H 4 S0 3 H, 
 
 sulphobenzylethylpropylsilicyl oxide. As the formula indi- 
 cates, this compound contains two similar asymmetric silicon 
 atoms, and should presumably exist in the same number of 
 isomeric modifications as tartaric acid (p. 249). One of the 
 acids isolated by Kipping has been shown to be a ^-/-compound, 
 and its salt with the active base, d-methylhydrindamine can 
 be resolved into its optically active components when re- 
 peatedly crystallized from acetone or aqueous methyl alcohol. 
 The two acids have extremely low rotatory powers, e.g. [a] D 
 3 to 4. Similar active compounds containing an isobutyl 
 in place of the propyl group have been obtained; they have 
 [a] D 10'5. And still more recently compounds containing 
 a single asymmetric silicon atom have been isolated, e.g. 
 ethylpropyldibenzylsilicanemonosulphonic acid, 
 
 CH 2 Ph SiEtPr CH 2 C fl H 4 S0 3 H, 
 
 which can be resolved into active components by means of 
 brucine. Most of the active silicon derivatives are character- 
 ized by the close similarity between the active and racemic 
 forms and by the low rotatory powers, so that it is difficult 
 to say, in certain cases, whether resolution has been effected 
 or not. 
 
 Pope and PeacJiey conclude that all the elements of Group IV 
 of the Periodic Classification, namely C, Si, Ti, Ge, Zr, Sn, Ce, 
 Pb, Th, also probably O, S, Se, Te, should in a similar manner 
 give rise to optical activity in their asymmetric derivatives. 
 
OPTICALLY ACTIVE NITROGEN COMPOUNDS 631 
 
 E. Nitrogen Compounds (H. 0. Jones, B. A. Eep. 1904, 169). 
 (i) Terwlent Nitrogen Compounds. No optical activity has been 
 met with in compounds of the type N a, b, c, and all attempts 
 to resolve such compounds have proved fruitless. Jones and 
 Millington (C. C. 1904, 2, 952) have attempted to resolve 
 benzyl -phenyl-hydrazine by means of d- camphor -sulphonic 
 acid, and to resolve methylethylaniline - sulphonic acid by 
 means of brucine. Other chemists (Krafft, Behrend and Konig, 
 Ladenburg) have attempted to resolve benzyl - ethyl - amine, 
 p-tolyl-hydrazine, /?-benzyl-hydroxylamine, methyl-aniline, and 
 tetra-hydroquinoline by means of d-tartaric acid. 
 
 Kipping and Salway (J. 0. S. 1904, 438) have adopted the 
 method of treating a secondary amine with a racemic acid 
 chloride, namely 2-/-benzylmethylacetyl chloride, CHMeB 2 ^ 
 COC1, and examining the substituted acid amide formed. 
 With a true d-/-base, the following compounds should be 
 formed: dBdA, IB I A, dElA, ZBdA, of which 1 and 2 form 
 an enantiomorphously related pair, and 3 and 4 a similar pair. 
 Thus the complete product would be a mixture of two racemic 
 substituted acid amides. Experiments conducted with methyl- 
 aniline, ^?-toluidine, phenyl-hydrazine, and benzyl-aniline gave 
 a homogeneous product in each case. Similarly, when 
 p-toluidine and benzyl-aniline are condensed with d-methyl- 
 benzylacetyl chloride, no indication of the formation of iso- 
 merides is met with. 
 
 A pair of compounds, C 6 H 3 Me 2 NH . CHMe - CH 2 CHO, 
 containing tervalent nitrogen and stated to be stereoisomeric, 
 have been shown by Jones and White (J. C. S. 1910, 632) to 
 be structurally isomeric. 
 
 The general conclusion to be drawn is, that the centres of 
 gravity ]of the three radicals, and also of the nitrogen atom 
 itself, lie in a single plane, and the whole arrangement is the 
 most symmetrically possible one. (Cf. Oximes, pp. 138, 429.) 
 
 (ii) Quinquevalent Nitrogen Compounds. (For formation, see 
 pp. 105, 379.) The most interesting type of compound is 
 that in which all five radicals are different, e.g. N a, b, c, d, X. 
 These compounds are quaternary ammonium salts, in which 
 four of the radicals are alkyl groups, and the fifth an acid 
 group. No cases of inactive isomerides have been met with. 
 An example described by JFedekind, viz. methylallylphenyl- 
 benzylammonium iodide, has recently been shown by H. 0. 
 Jones (J. C. S. 1905, 1721) to be non-existent. 
 
 The only known examples of stereoisomerides are the 
 
632 XLVI. STEREO-CHEMISTRY 01* SULPHUR, ETC. 
 
 optically active modifications in which compounds of the 
 type methylethylpropylisobutylammonium chloride, N(CH 3 ) 
 (C 2 H 5 )(C 3 H 7 )(C 4 H 9 )C1, exist. This type of compound is 
 always obtained in an inactive form when synthesised in the 
 laboratory by the addition of an alkyl haloid to a tertiary 
 amine. In 1891 Le Bel claimed to have obtained a Icevo-modi- 
 fication by means of penicillium glaucum (green mould), and in 
 1899 he confirmed this result. In the same year Pope and 
 Peachey (J. C. S. 1899, 1127) obtained a resolution of Wede- 
 Jcind's benzylphenylallylmethylammonium iodide by the aid of 
 silver d-camphor-sulphonate. 
 
 When the mixture of benzylphenylallylmethylammonium 
 d-camphor-sulphonates is crystallized from acetone, a sparingly 
 soluble fraction is obtained, and this, when treated with 
 potassium iodide, yields an optically active iodide, N(C 7 H 7 ) 
 (C 6 H 5 )(C 3 H 5 )(CH 3 )I, with [M] D + 192. 
 
 H. 0. Jones (J. C. S. 1903, 1418; 1904, 223) has resolved 
 phenylbenzylmethylethylammonium iodide and phenylmethyl- 
 ethylallylammonium iodide by means of silver d-bromo-camphor- 
 sulphonate. Jones has observed that many of these salts show 
 a tendency to undergo racemization, and during the fractional 
 crystallization of the salts it is advisable to keep the tempera- 
 ture as low as possible. Auto-racemization (p. 257) occurs 
 when the cold chloroform solutions are kept in the dark, a 
 phenomenon also observed by Pope and Harvey (J. C. S. 1901, 
 828) with other optically active ammonium salts, and probably 
 due to a partial dissociation of the quaternary ammonium salt 
 into tertiary amine and alkyl iodide and subsequent recombina- 
 tion. (For other optically active ammonium salts, see Wedekind, 
 B. 1905, 38, 1838; Thomas and Jones, J. C. S. 1906, 280.) 
 
 Quinquevalent nitrogen derivatives of the type Na 2 bcX, 
 e.g. phenylallyldimethylammonium iodide, phenyldipropyl- 
 methylammonium iodide, &c., do not exist in isomeric modi- 
 fications, and attempts to resolve such compounds into optically 
 active components have given negative results (J. C. S. 1897, 
 522; 1903, 1141, 1406; 1904, 412). Aschan (Zeit. phys. 1903, 
 46, 304) has prepared isomeric cyclic nitrogen compounds 
 containing two quinquevalent nitrogen atoms, viz.: 
 
 Br Br 
 
 The one compound is formed by the union of ethylene-di- 
 
OPTICALLY ACTIVE NITROGEN COMPOUNDS 633 
 
 peridide with trimethylene bromide, and the other by the 
 combination of trimethylene-diperidide with ethylene bromide. 
 This isomerism can be accounted for if the bromine atoms and 
 the central ring lie in one plane and the other rings in a plane 
 at right angles to the first. 
 
 A similar compound containing one nitrogen atom, 
 
 has been shown by Scholz (B. 43, 2121) to exist in two opti- 
 cally active forms. 
 
 Methylethylaniline oxide, NMeEtO, has been resolved into 
 active modifications by means of bromocamphorsulphonic acid. 
 The base itself, probably NMeE^OH)^ has [a] D -25. The 
 compound 
 
 I NMeEtPh - CJJ 2 CH 2 CH 2 . NMeEtPhI, 
 
 containing two similar asymmetric nitrogen atoms, like tar- 
 taric acid, exists in two inactive forms, but so far neither has 
 been resolved into active components. When an asymmetric 
 nitrogen atom is introduced into a compound already con- 
 taining an asymmetric carbon atom, two stereoisomerides are 
 formed, just as two products are formed when a new asym- 
 metric carbon atom is introduced into an active compound. 
 
 One of the simplest spatial arrangements of the radicals 
 attached to a quinquevalent nitrogen atom is that suggested 
 by Bischoff and accepted by Jones. The nitrogen atom is 
 supposed to be situated at the centre of a pyramid on a rect- 
 angular base, and the five radicals at the five solid angles, the 
 four alkyl groups occupying the four angles of the base, and 
 the acid radical occupying the angle at the apex. Since the 
 three radicals in a tertiary amine all lie in one place, it follows 
 that in the conversion of a tertiary amine into a quaternary 
 ammonium salt a change of "valency direction" occurs. 
 
 The equilibrium positions of the radicals in the tervalent 
 nitrogen compound are disturbed, and new positions must be 
 found, which for any four alkyl groups must be determined 
 jointly by the forces between these radicals and the nitrogen 
 atom, and the mutual forces exerted by the groups on one 
 another; consequently there will be some definite spatial 
 arrangement around the nitrogen atom. The fifth group, 
 which is always different in character from the other four, 
 will always bear approximately the same relation to each of 
 
634 XLVI. STEREO-CHEMISTRY OF SULPHUR, ETC. 
 
 these four groups; in other words, it occupies the apex of the 
 pyramid, and it is improbable that it should ever take the place 
 of an alkyl group at the base of the pyramid. The relative 
 positions of the four alkyl radicals at the base of the pyramid 
 is fixed by the forces exerted by these radicals on one another. 
 
 F. Phosphorus Compounds. Meisenheimer and Lichtenstadt 
 (B. 1911, 44, 356) have obtained methylethylphenylphosphine 
 oxide, 0:PMeEtPh, in optically active forms. The base was 
 prepared by combining methyl iodide with ethyldiphenyl- 
 phosphine, liberating the base with moist silver oxide and 
 then distilling, and was resolved by means of d-bromocamphor- 
 sulphonic acid. The base has [a] D -f- 33 '8 in benzene solution. 
 Somewhat similar experiments of Caven (J. C. S. 1902, 1362) 
 and Ephraim (B. 1911, 44, 631) have given negative results. 
 
 G. Cobalt Compounds. Werner (B. 1911, 44, 1887, 2445, 
 3272, 3279) has obtained optically active derivatives of cobalt. 
 It is pointed out that compounds like CoA 3 BCD, CoABC 2 D 2 
 or CoABC 4 should exist in optically active isomerides, pro- 
 vided the cobalt atoms occupy the centre of an octahedron and 
 the six radicals are situated at the solid angles, e.g.: 
 
 Such active isomerides have been isolated in the case of 
 l-chloro(or bromo)-2-ammine-diethylenediamine-cobaltic salts, 
 [CoBrNHgenJBr 2 , where C 2 and D 2 are replaced by divalent 
 ethylenediamme radicals (NH 2 .CH 2 CH 2 -NH 2 :). The reso- 
 lution was effected by means of <2-bromocamphorsulphonic acid, 
 and the active salts obtained were quite stable. Similar cases 
 of isomerism have been met with in the case of chromium 
 derivatives (Werner, ibid., 3132, cf. also A. 386, 1). For stereo - 
 isomeric platinum-derivatives, see Kirmreuther, B. 44, 3115. 
 
 H. Carbon Compounds, with Semicyclic Double Linkings. 
 Many years ago van't Hoff predicted that compounds of the 
 
 allene type, ^>C:C:C<^f, should exist in optically active 
 
 modifications. Attempts by Lapworth and Wechsler (J. C. 8. 
 1910, 38) to obtain such compounds in optically active forms 
 have not met with success. Perkin and Pope (J. C. S. 1906, 
 
fcOILING-POINT 636 
 
 1075; 1909, 1789; 1911, 1510), however, have succeeded in 
 resolving l-methylcyclohexylidene-4-acetic acid, 
 
 into optically active components by means of its brucine salt. 
 The two forms have m.-pt. 52-5-53 and [a] D 81 in ethyl 
 alcohol. This resolution is of interest, as the formula does 
 not contain an asymmetric carbon atom, although the mole- 
 cule as a whole is asymmetric. By the addition of bromine 
 to the d- and Z-acids, it has been found possible to obtain 
 four optically active dibromides. 
 
 An example of somewhat the same type is met with in the 
 oxime of cyclohexan-l-one-4-carboxylic acid, 
 
 which has been resolved by Mills and Bain (J. C. S. 1910, 
 1866) into active forms by means of morphine or quinine. 
 Two active sodium salts were obtained, but when acidified 
 with hydrochloric acid an inactive acid was formed. 
 
 This resolution is used as a strong argument in favour of 
 Hantzsch and Werner's view (p. 138) that when a tervalent 
 nitrogen atom is attached by a double linking to carbon the 
 three valencies of the nitrogen do not lie in. a single plane. 
 If all three valencies were in the same plane the formula for 
 the oxime would contain a plane of symmetry and should 
 not be resolvable. 
 
 Azobenzene (p. 396) also appears to exist in two stereoiso- 
 meric forms (G&rntner, J. A. C. S. 1910, 32, 1294), viz. red 
 prisms, m.-pt. 68, and orange-red needles, m.-pt. 25, which 
 are represented by anti and syn configurations. 
 
 XLVII. RELATIONSHIPS BETWEEN PHYSICAL PRO- 
 PERTIES AND CHEMICAL CONSTITUTION 
 
 A. Boiling-point. Attention has been repeatedly drawn 
 to the fact that in any homologous series the boiling-point 
 tends to increase with the number of carbon atoms present 
 (see pp. 31, 66, HI). 
 
636 XLVII. PHYSICAL PROPERTIES AND CONSTITUTION 
 
 In the majority of cases the increase in boiling-point for 
 each additional CH 2 is not constant, but tends to decrease 
 with increasing molecular weight (e.g. fatty acids, and espe- 
 cially the paraffin hydrocarbons and alkyl haloids). 
 
 In the case of the ethyl esters of the normal fatty acids the 
 
 y ac 
 CH 2 
 
 increase is fairly constant, and is about 21 for a CH 2 group 
 (Kopp,W2),W> 
 
 Difference. 
 Ethyl formate ................ 54-5 
 
 Ethyl acetate ................. 77 _ 
 
 Ethyl propionate ............ 98 
 
 Ethyl butyrate ............... 120 
 
 Ethyl valerate ............... 144-5 " 
 
 Ethyl hexoate ................ 167 < 
 
 Ethyl heptoate ............... 188 *L 
 
 Ethyl octoate ................. 208 * 
 
 Ethyl nonoate ................ 228 
 
 With the alkyl chlorides the difference between methyl and 
 ethyl chlorides is 35, and this difference diminishes by 2 for 
 each subsequent homologue, so that the difference between 
 heptyl and octyl chlorides is only 23 (Schorlemmer). 
 
 Attempts have been made to find a general law for the 
 diminution of the difference in boiling-point with increase in 
 molecular complexity. Goldstein suggested the formula 
 
 p 380 + (n - 1) 19 - 340-9 
 
 for the boiling-points of the normal hydrocarbons, where n 
 the number of carbon atoms; this gives good results up to 
 C 12 H 26 , but not beyond. (Compare also Mills, Phil. Mag. [5], 
 17, 180.) 
 
 A comparison of isomeric substances shows that the boiling- 
 points can vary considerably, even when the isomerides belong 
 to the same series, e.g. the amyl alcohols : 
 
 CH 3 (CH 2 ) 3 .CH 2 .OH, 137; 
 (CH 3 ) 2 CH.CH 2 .CH 2 .OH, 131-6; 
 CH 3 .CH 2 .CH(CH 3 ).CH 2 .OH, 128*; 
 CH 3 (CH 2 ) 2 .CH(CH 3 )OH, 118-5; 
 CH 3 .CH 2 .CH(OH).CH 2 .CH 3 , 116'5; 
 (CH 3 ) 2 CH-(CH 3 ).OH, 112-5. 
 
 In all such cases the normal compound has the highest 
 boiling-point, and the more branched the carbon chain 
 
BOILING-POINT 637 
 
 becomes, the lower is the boiling-point. Generally there is a 
 difference of 7 between the boiling-points of a pair of isomeric 
 compounds of the type CH 3 CH 2 . CH 2 . X and (CH 3 ) 2 .CH.X. 
 According to Menschutkin> in a group of isomeric alcohols, 
 amines, or amides, the boiling-point falls as the side chain 
 approaches the hydroxy- or amino-substituent. 
 A comparison of isomeric esters, e.g. : 
 
 n-Butyl acetate, CH 3 .(X).OC 4 H 9 , 124; 
 n-Propyl propionate, CH 3 .CH 2 .CO-O-C 3 H r , 122'4; 
 Ethyl rc-butyrate, CH 3 .CH 2 .CH 2 .CO.O.C 2 H 5 , 121; 
 Methyl n-valerate, CH 3 .(CH 2 ) 3 .CO.OCH 3 , 127, 
 
 shows that the boiling-point is lower the nearer the oxygen 
 atoms are to the middle of the carbon chain. 
 
 A remarkable feature is the relatively high boiling-points of 
 hydroxylic compounds when compared with their isomerides 
 or with closely related compounds. As an example, the 
 n -acid isomeric with the last -mentioned group of esters, 
 namely w-hexoic acid, boils at 205. A similar relationship 
 can be shown by the comparison of an alcohol with the ethers 
 isomeric with it. Similarly, a comparison of the boiling- 
 points of the ethyl-derivatives, C 2 H 6 , C 2 H 5 .OH, C 2 H 5 C1, 
 C 2 H 5 Br, C 2 H 5 NH 2 , C 2 H 5 .QEt, C 2 H 5 .CN, indicates the enor- 
 mous effect of the hydroxyl group on the boiling-point, or, 
 again, a comparison of the boiling-point of an acid with those 
 of its chloride, esters, anhydride, or nitrile. 
 
 The effect of the introduction of halogen atoms has already 
 been referred to (p. 56). The introduction of an atom of 
 chlorine for hydrogen often raises the boiling-point some 60, 
 an atom of bromine about 84, and an atom of iodine 110; 
 and the introduction of a second or third chlorine atom 
 further raises the boiling-point, but not to the same extent. 
 
 Extremely interesting is the fact that a saturated compound 
 and its ethylene analogue have very nearly the same boiling- 
 points (cf. propyl and allyl alcohols, both 97; G^H 16 and 
 C r H 14 , both 99; propionic acid, 1407; and acrylic acid, 140), 
 although they differ considerably as regards most of their 
 other physical characteristics. Further, methyl ketones, 
 acetyl esters, and corresponding acid chlorides boil at very 
 nearly the same temperature, e.g. acetone, methyl acetate, and 
 acetyl chloride at 55-56; propyl methyl ketone, methyl 
 butyrate, and butyryl chloride at 101-105 (Schroder, B. 
 1883, 16, 1312). 
 
638 XLVII. PHYSICAL PROPERTIES AND CONSTITUTION 
 
 B. Melting-point Although, on the whole, in any homo- 
 logous series the melting-points of the solid members tend to 
 rise with increase in molecular complexity, in many series an 
 alternating rise and fall is met with, the members containing 
 an even number of carbon atoms melting at relatively higher 
 temperatures than those with an odd number. This is the 
 case with the higher fatty acids, as is readily seen when the 
 melting-points are plotted against the number of carbon atoms. 
 
 40- 
 
 
 
 
 
 1 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 30- 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 / 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 / 
 
 
 
 20 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 / 
 
 
 1 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 10H 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 / 
 
 
 
 
 
 
 
 
 
 
 r 
 
 
 
 
 I 
 
 
 
 / 
 
 
 ^ 
 
 
 
 
 
 
 
 
 a 
 
 o 
 
 
 
 
 ] 
 
 
 
 
 i 
 
 
 
 / 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 j\ 
 
 
 
 
 
 
 
 
 
 
 
 
 
 tt> 
 
 S -10 
 
 
 
 
 
 1 
 
 
 
 / 
 
 \ 
 
 / 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 / 
 
 \ 
 
 
 
 
 
 
 
 
 
 
 
 
 3-20. 
 
 
 
 
 
 
 I 
 
 
 / 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 1 
 
 
 n 
 
 
 
 
 
 
 
 
 
 
 
 
 
 -30 
 
 
 
 
 
 1 , 
 
 
 \ 
 
 / 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 \ / 
 
 
 
 | 
 
 
 
 
 
 
 
 
 
 
 
 
 
 -40. 
 
 
 
 
 
 
 
 
 
 fl 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 I 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 -50. 
 
 
 
 
 
 
 
 tir 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 Hn 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 T/t 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 1 
 
 
 1 1 
 
 
 
 
 
 
 
 
 
 
 
 
 
 ] 
 
 L 2 
 
 3 4 
 
 & 6 ; 
 
 ' i 
 
 } 
 
 1 
 
 1 
 
 1 1 
 
 2 
 
 No. of Carbon Atoms 
 
 Many other series show a similar relationship, e.g. succinic acid 
 and its homologues, where the melting-points are : 
 
 C 180; GO 97; C* 148; C r , 103; C & 140; C 9 , 106; C 10 , 127. 
 
 (Compare also Beach, Zeit. phys. 1904, 50, 43.) In the case 
 of a group of closely related isomeric compounds it is found 
 that the melting-point tends to rise with the number of side 
 chains or branches, e.g. CH 3 CH 2 CH 2 .CH 2 OH is a liquid, 
 and C(CH 3 ) 3 .OH melts at 25; or again, glutaric acid melts 
 at 97, methyl-succinic at 112, and dimethyl-malonic at 117. 
 The conversion of an acid into an ester always produces a 
 lowering of the melting-point, and the methyl ester always 
 has the highest melting-point of any of the esters derived 
 from a given acid; in fact, in many cases the methyl esters 
 
MOLECULAR VOLUME 639 
 
 are solids, and the ethyl and higher esters liquids at the 
 ordinary temperature. 
 
 In the aromatic series it is found that of the isomeric 0-, 
 ra-, and ^-compounds the para- has the highest melting-point. 
 G. Schultz (A. 1881, 207, 362) has also shown that in the 
 group of compounds, 
 
 Nitro * azoxy * azo hydrazo amine, 
 
 the melting-point increases up to the azo-compound, and then 
 falls again to the amine. According to Franchimont (Rec. 
 1897, 16, 126), the melting-point of an organic compound is 
 invariably raised when two hydrogen atoms attached to the 
 same carbon are replaced by oxygen, or when a hydrogen 
 atom is replaced by hydroxyl; cf. C 6 H 5 CH 2 OH and CJEL- 
 CO- OH, or C 6 H 6 and C 6 H 5 .QH. 
 
 C. Molecular Volume. The relationships between specific 
 gravity and chemical constitution are not so marked as in the 
 case of other physical properties. Attention has already been 
 drawn to the fact that in a homologous series the specific 
 gravity either decreases with an increase in the number of 
 carbon atoms, and tends to reach a minimum value (p. 141), 
 or increases with the number of carbon atoms and tends to 
 attain a maximum (p. 31). 
 
 More interesting results have been obtained by an exami- 
 
 nation of molecular volumes, i.e. the quantity mo e u ar wei g t 
 
 specific gravity 
 
 Kopp (1842) determined the molecular volumes of a number of 
 carbon compounds, and came to the conclusion that in the 
 case of closely related compounds the same difference in com- 
 position corresponds with a similar difference in molecular 
 volume, e.g. : 
 
 Mol. volume. Difference. 
 Alcohols, CHo-OH ............... 42'2 on 
 
 C 2 H 6 -OH ............... 62-2 20 
 
 C 3 H 7 .OH ............... 81-34 
 
 H ............... 101-58 ~ 
 
 Fatty acids, H.CO 2 H ............... 41'4 
 
 CH 3 .C0 2 H ............ 63-7 ^ *** 
 
 C 2 H 5 .C0 2 H ............ 85-4 |{4 
 
 C 3 H r .C0 2 H ............ 107-1 
 
 and further, that isomeric liquids have the same molecular 
 volumes, e.g. acetic acid 63 -7, and methyl formate 63 -4; pro- 
 pionic acid 85-4, ethyl formate 85 -3, and methyl acetate 84-8. 
 
640 XLVII. PHYSICAL PROPERTIES AND CONSTITUTION 
 
 The replacement of an atom of oxygen or an atom of carbon 
 by two atoms of hydrogen does not appear to alter the mole 
 cular volume to any considerable extent : 
 
 Methyl alcohol, CH 4 O.... 421 
 
 Formic acid, CH 2 O 2 41'4 
 
 Benzy 1 alcohol, C 7 H 8 O... 1237 
 
 Amyl alcohol, C 6 H 12 O .... 124'0 
 
 Ether, C 4 H 10 O 106-0 
 
 Butyric acid, C 4 H 8 O 2 107'1 
 
 The difference due to a CH 2 group is roughly 22, and since 
 the atomic volume of carbon is twice the atomic volume of 
 hydrogen, it follows that the atomic volume of carbon =11 
 and of hydrogen = 5*5. Kopp also indicated that the atomic 
 volume of a polyvalent element, e.g. oxygen, is not a constant 
 quantity, but varies according to the manner in which the 
 oxygen atom is united to the other atoms in the molecule. 
 
 Thus in the form of a carbonyl group, ^>C:0, the atomic 
 volume of oxygen is 12 '2 (carbonyl oxygen), but in the form 
 of ^C0'C^ or ^C0H (oxidic oxygen) it has the value 
 
 7 '8. Similarly, Schiff has shown that the carbon atom can 
 have different values according as it is united to another 
 carbon atom by a single, double, or triple bond. Thus each 
 double bond causes an increase of four units in the molecular 
 volume. By means of these atomic volumes it is possible to 
 calculate the molecular volume of any simple carbon com- 
 pound, e.g. ethyl formate, H-CO'O'CH^CHg, 
 
 30 = 33 ^ 
 6H = 33 I . n 
 10: = 12-2 f = 860 
 l.Q. = 7-8J 
 
 and the value actually obtained by experiment is 85-86. 
 Although such generalizations as those mentioned are of 
 considerable theoretical importance, the method is not one 
 which has been used to any great extent for determining 
 the constitution of chemical compounds (compare molecular 
 refraction and molecular magnetic rotation). This is partly 
 due to the fact that the specific gravity, and hence the mole- 
 cular volume, varies with the temperature. At first, Kopp 
 made all his determinations at 0, but obtained better results 
 by taking the specific gravity at the boiling-point of the 
 liquid. It is not necessary to actually make the determin- 
 ation at the boiling-point, but to determine the specific gravity 
 
MOLECULAR REFRACTION 641 
 
 at a lower temperature, and then to correct for the coefficient 
 of expansion as determined by the dilatometer. In reality, 
 the determinations should be made at temperatures when the 
 liquids are all in an exactly comparable condition, viz. at the 
 critical point (compare Zeit. phys. 1890, 6, 578). More recent 
 determinations of molecular volumes by T. E. Thorpe (J. C. S. 
 1880, 327) indicate that isomeric compounds have not always 
 the same molecular volumes, and that the differences amount 
 to several units per cent, but that elements such as chlorine 
 and bromine in the liquid state have the same atomic volumes 
 as in their organic compounds (compare also Lossen, A. 1883, 
 214, 138; Horstmann, B. 1885, 20, 766; Sehi/, A. 1884, 220, 71; 
 Zahnder, A. 1883, 214, 138). 
 
 D. Molecular Refraction. It has been shown that the 
 molecular refraction, like the molecular volume, is to a large 
 extent an additive property, i.e. the molecular refraction is 
 the sum of the atomic refractions of the atoms present in the 
 molecule, but, in addition, that it is to a certain extent consti- 
 tutive; thus the oxygen atom has distinct atomic refractions 
 according to whether it is in the carbonyl or oxidic state of 
 combination. 
 
 m, r ,. . j ., ir sine of angle of incidence 
 
 The refractive index itself, n = , ^ -. ? : , 
 
 sine of angle of refraction 
 
 does not lend itself to the study of generalizations, but, 
 according to Gladstone and Dale (1858), such generalizations 
 
 77 - T 
 
 are found when the specific refractory power, (where 
 
 d = specific gravity), is employed. This specific refraction 
 varies but little with the temperature; thus with water: 
 
 t o io" 20 90 100 
 
 Specific refraction... 0'3338 0'3338 0'3336 0'3321 0'3323 
 
 and is not largely affected by the presence of other substances. 
 A second formula for the specific refractive power has been 
 
 o i 
 
 introduced by Lorentz and Lorenz, viz. n ~ w ; this has the 
 
 (TI -f" 2)a 
 
 advantage that the value appears to be independent of the 
 physical state of the compound: 
 
 Lorentz- Lorenz Gladstone- Dale 
 
 t Gas. Liquid. Gas. Liquid. 
 
 Water 10 0*2068 0'2062 O'SlOl 0-3338 
 
 Carbon disulphide 10 0'2898 0-2805 0*4347 0-4977 
 
 Chloroform 10 0'1796 01790 0'2694 0-3000 
 
642 XLVII. PHYSICAL PROPERTIES AND CONSTITUTION 
 
 When the refractive powers of different substances are com- 
 pared, it is usual to employ the molecular refractive powers 
 rather than the specific refractions. The molecular refraction 
 is the product of the specific refraction into the molecular 
 
 weight; according to Gladstone ^ n ~" ', and according to 
 
 As the refractive index differs with light of different wave- 
 lengths, it is necessary to determine the value of n for mono- 
 chromatic light, and to indicate the special light employed; 
 generally determinations are made for the D line in the 
 sodium, or the a line in the hydrogen spectrum, and are 
 carried out in hollow prisms containing the liquid and pro- 
 vided with sides of plate glass. 
 
 Landolt examined the molecular refractions of the members 
 of several homologous series, and came to the conclusion that 
 the molecular refraction is an additive quantity, and that 
 similar changes in composition induce similar changes in the 
 molecular refractive power: 
 
 Alcohols 
 
 M(n-l) 
 
 d Diff. 
 
 CH,-OH 13-17 
 
 OH ........ 20-70 
 
 7-53 
 
 -> 7-60 
 
 Acids 
 
 Diff. 
 
 H-CO 2 H 13-91 
 
 CH 3 .C0 2 H 21-11 
 
 C 2 H 6 -C0 2 H 28-57 
 
 C 3 H 7 .C0 2 H 36-22 
 
 44-05 
 
 C 3 H r .OH 28-30 _ ,_ Q1 
 
 C 4 H 9 .OH 36-11 * Zji 
 
 C 6 H n .OH 43-38" 
 
 and similarly for various groups of esters, the mean value for 
 the CH 2 group being 7 '6 units. By methods similar to those 
 described under molecular volumes, values were obtained for 
 the atomic refractive powers of the elements for the a line, 
 e.g. C = 5, H = 1-3, = 3, Cl = 9-79, Br = 15-34, &c. The 
 values thus obtained for the halogens are practically identical 
 with those determined for the elements in the free state. 
 The molecular refraction of any simple carbon compound can 
 be calculated by adding together the atomic refractions of the 
 constituent elements. Thus, for ethyl alcohol, C 2 H 6 0, the 
 calculated molecular refraction is 2x5 + 6x1*3 + 3 = 2O8, 
 and that actually found experimentally is 20*7. 
 
 According to Landolt, the molecular refraction is purely 
 additive, and thus isomeric compounds should possess identical 
 molecular refractive powers. This is largely true in certain 
 
MOLECULAR REFRACTION 643 
 
 cases, e.g. the compounds C 3 H 6 3 propionic acid," 28-57: 
 methyl acetate, 29-36; and ethyl formate, 29-18. 
 
 In a series of investigations begun in 1878 (A. 1879, 200, 
 139; 1880, 203, 1 and 255) Bruhl has examined the influence 
 of atomic grouping on the molecular refraction, and has been 
 able to show that the property is not purely additive, but to a 
 certain extent constitutive. Thus a comparison of the experi- 
 mental and calculated values for unsaturated and the corre- 
 sponding saturated compounds at once exhibits anomalies : 
 
 . 
 
 for a-line. 
 
 Observed. Calculated. Difference. 
 Allyl alcohol, C 3 H 6 ............ 27'88 25'8 2'08 
 
 Propyl alcohol, C 3 H 8 .......... 28'60 28'4 0'2 
 
 Similarly in other unsaturated compounds it is found that a 
 double bond between two carbon atoms usually increases the 
 molecular refraction by about two units (mean value 2-15), 
 and a triple bond by T95 unit. 
 
 Other polyvalent elements have atomic refractions which 
 vary with their state of combination; thus oxygen in carbonyl 
 compounds has the value 3-4 in hydroxy-derivatives, and in 
 ethers the value 2-8. The following is a list of some of the 
 more important atomic refractions used by Gladstone and by 
 Bruhl: 
 
 Briihl 
 Gladstone. (L.-L. formula). 
 
 Carbon in saturated compounds ......... 5-0 2 -365 
 
 Hydrogen ..................................... 1-3 T103 
 
 Carbonyl oxygen in ^>C:O ............... 3'4 2*328 
 
 Ether oxygen in C-O-C ............. 2'8 1'655 
 
 Hydroxylic oxygen in ^C-O-H ........ 2*8 1-506 
 
 Chlorine ....................................... 9'9 6'014 
 
 Bromine ....................................... 15'3 8'863 
 
 Iodine ......................... ................. 24*5 13'808 
 
 Ethylenebond ............................... 2'1 1'836 
 
 Acetylene bond .............................. T95 2'22 
 
 Sulphur in C:S .............................. 16'0 
 
 Sulphur in C-S-H .......................... 141 
 
 Nitrogen in compounds -^C N<^ ...... ... 2'76 
 
 Briihl has employed the molecular refraction for the investi- 
 gation of certain tautomeric substances, e.g. ethyl acetoacetate, 
 
644 XLVII. PHYSICAL PROPERTIES AND CONSTITUTION 
 
 The observed value for the a line is 31*89, and the values 
 calculated for the ketonic and enolic formulae respectively, 
 31-53 and 32-55: 
 
 CH 3 CO CH 2 CO OC 2 H 5 
 60 = 14-190 
 
 10H = 11-03 
 
 2O (carbonyl) = 4'656 
 10 (ether) = 1'655 
 
 31-531 
 
 CH 3 C(OH) : CH CO OC 2 H 5 
 60 = 14-190 
 
 1 ethylene bond = 1'836 
 10H = 11-03 
 
 1O (carbonyl) = 2'328 
 1O (ether) = 1-655 
 
 lO(hydroxyl) = 1-506 
 
 32-545 
 
 The conclusion to be drawn from these numbers is that the 
 ethyl acetoacetate at the ordinary temperature consists mainly 
 of the ketonic form, but probably contains a small amount 
 of the enolic. Bruhl also tests the purity of numerous com- 
 pounds prepared by him, by means of molecular refraction and 
 dispersion determinations in place of ordinary combustions. 
 Perkin and Gladstone have examined the molecular refractive 
 powers of several di- and triketonic substances. Thus, for 
 
 acetylacetone at 11, using the formula ^ M for the a line, 
 
 the value 45-17 was obtained, and this decreased to 44*14 at 
 99*3. The ketonic formula requires 42*2, the mono-enolic 
 43*7, and the di-enolic 45-2. At 11 the diketone undoubtedly 
 consists mainly of the dihydroxylic compound CH 3 C(OH): 
 C:C(OH)-CH 3 , and at the higher temperature, probably of a 
 mixture of the mono- and dihydroxylic forms. 
 
 Schaum has also used the method to show that reagents like 
 sodic ethoxide or piperidine have no enolizing or ketonizing 
 actions on ethyl acetoacetate, as in presence of both these 
 compounds the molecular refraction is 32 for the sodium line 
 Compounds which have a strong dispersive power do not 
 appear to lend themselves to the calculation of molecular 
 rotation in the manner just described. 
 
 E. Molecular Magnetic Rotation, This is quite distinct 
 from the ordinary optical activity exhibited by substances 
 with asymmetric molecules, and is common to practically all 
 substances when they are examined by means of a polarimeter 
 in a strong magnetic field. The tube containing the liquid to 
 be examined is placed end on between the two poles of an 
 electro-magnet, these poles being pierced in order that the ob 
 
MOLECULAR MAGNETIC ROTATION 645 
 
 server may take readings, and the apparatus is often jacketed 
 in order that the temperature may be kept constant. (For 
 new form of apparatus, see J. C. S. 1906, 608.) When the 
 magnetic field is changed, it is found that the amount of 
 rotation remains the same but changes sign, and in each 
 determination several positive and several negative readings 
 are made. The rotations of all substances are compared with 
 water under the same conditions, and thus the molecular 
 
 magnetic rotation is LJ, where M is the molecular weight 
 Loa^d 
 
 of the substance, a its observed rotation using a column of 
 liquid I cm. long, and d the specific gravity of the liquid; 
 18 is the molecular weight of water, c^ its observed rotation, 
 d 1 its density, and / x the length of column used. As a rule 
 I = I-L and d-i = 1 (approx.). An examination of different 
 homologous series by W. H. Perkin, Sen., showed that for an 
 increase of CH 2 in the molecule there is usually an increase of 
 1-023 units in the molecular magnetic rotation. At first, 
 Perkin attempted to obtain atomic magnetic rotations for each 
 element in the same manner as already described for atomic 
 volumes and atomic refractions; the values so obtained gave 
 good results with several distinct series, but could not be 
 applied generally. The method of using series constants was 
 then adopted. The molecular magnetic rotation r of a com- 
 pound may be represented as: 
 
 r = C + 7i 1-023. 
 
 Where C is a constant which varies with different homolo- 
 gous series, n is the number of carbon atoms present. 
 A few of the constants are : 
 
 n-Parafnns 0'513 
 
 wo-Paraffins 0-631 
 
 n- Alcohols 0-699 
 
 iso- Alcohols 0-844 
 
 n- Fatty acids 0'391 
 
 Higher esters 0'337 
 
 Aldehydes 0'263 
 
 Alkyl chlorides 1'988 
 
 Alkyl bromides 3'816 
 
 Alkyl iodides 8-011 
 
 Alkyl acetates '370 
 
 If in any series it is required to calculate the molecular 
 magnetic rotation of a member, this is readily accomplished 
 by adding n x 1'023 to the series constant; thus for ?i-nononic 
 acid we have 
 
 0-391 + 9 X 1-023 = 9-598, 
 
 and the value actually found by experiment is 9-600. 
 
646 XLVII, PHYSICAL PROPERTIES AND CONSTITUTION 
 
 There is usually a definite relationship between the values 
 for an unsaturated compound and its saturated analogue, e.g.: 
 
 Diff. 
 
 Ethyl crotonate. . . 7 '589 , , , 9 
 Ethyl butyrate.... 6'477 J 
 
 Diff. 
 
 Ethyl oleate 21-909 -, ,, 9 
 
 Ethyl stearate... 20797 J 
 
 With allyl compounds the difference is not so great; thus 
 the difference between allyl alcohol, 4 -682, and propyl alcohol, 
 3 -768, is only 0-914, and similarly for other allyl compounds. 
 
 These facts have been used as arguments in the determina- 
 tion of the constitution of undecylenic acid (J. C. S. 1886, 205). 
 The difference in molecular magnetic rotation between unde- 
 cylenic acid, C 10 H 19 'C0 2 H, and undecylic acid, C^H^-COgH, 
 is 0*897, and similarly for the esters the difference is 0"890. It 
 is argued that this difference approximates to 0*91, the usual 
 difference between an allyl compound and the corresponding 
 saturated derivative, and hence undecylenic acid is presumably 
 an allyl derivative with the formula CH 2 : CH[CH 2 ] 8 - C0 2 H. 
 
 The molecular magnetic rotation of a complex compound can 
 be calculated by taking as the series constant the mean of the 
 series constants of the various groups of compounds which it 
 represents. Thus ethyl lactate, CH 3 .CH(OH)-C0 2 C 2 H 5 , pos- 
 sesses the groupings characteristic of an ethyl ester and also of 
 a secondary alcohol; the series constants for these are: 
 
 Ethyl ester = 0'337; secondary alcohol = 0'844. Mean = 0'590. 
 
 The series constant for ethyl lactate and homologues is thus 
 0-590, and the molecular magnetic rotation of the lactate 
 
 5 X 1-023 -f 0-590 = 5'705, 
 
 which agrees very well with the experimental value, 5-720. 
 The values of their molecular magnetic rotations have been 
 used by Perlcin in discussions on the constitutions of certain 
 tautomeric compounds, especially those of the keto-enolic type. 
 In the case of ethyl acetoacetate, the molecular magnetic 
 rotation for the ketonic form may be calculated as follows: 
 
 Series constant for alkyl acetate 0'370 
 
 Series constant for ketone 0'375 
 
 Mean 0'372 
 
 Molecular rotation = 6 X T023 + 0'372 = 6-510. 
 For the enolic form ethyl /3-hydroxy-crotonate, CH 3 C(OH): 
 
ABSORPTION SPECTRA 64? 
 
 CH'C0 2 C 2 H 5 the molecular rotation may be calculated by 
 the two following methods: 
 
 1. Molecular rotation of ethyl crotonate 7'589 
 
 OH replacing H as in alcohol 0'194 
 
 Molecular rotation of ethyl hydroxy-crotonate 7 '783 
 
 2. Mol ecular rotation for ethyl -hydroxy-butyrate 6 '737 
 
 Difference between unsaturated and corresponding satu-) 1.110 
 
 rated compound / 
 
 Molecular rotation for ethyl hydroxy-crotonate 7 '849 
 
 The experimental value actually found for ethyl acetoacetate 
 at the ordinary temperature is 6 '501, and this indicates that, 
 at this temperature, the ester consists essentially of the keto- 
 f orm. Some general conclusions drawn by Perkin. are : 
 
 (i) That monoketonic compounds and keto- esters, which 
 react as tautomeric substances, as a rule, have the ketonic and 
 not the enolic structure, except when a number of negative 
 groups, such as phenyl and car boxethyl, C0 2 C 2 H 5 , are present. 
 These have an enolizing tendency, as shown in ethyl benzoyl- 
 acetate, C 6 H 5 CO CH 2 C0 2 C 2 H 5 , which, according to Perkin, 
 is a mixture of some 75 per cent of the keto- and 25 per cent 
 enolic compound. 
 
 (ii) Acetylacetone at 17 consists of a mixture of some 
 80 per cent of the hydroxy-ketone, CH 3 -CO.CH:C(OH).CH 3 , 
 and some 20 per cent of the dienolic form, CH 3 C(OH):C: 
 C(OH)CH 3 . If alkyl radicals replace the hydrogen atoms 
 of the methylene group of acetylacetone, the tendency to form 
 the enolic form is less marked, whereas the introduction of 
 negative groups, 'COgEt, increases the tendency. 
 
 (iii) Rise of temperature favours ketonization. 
 
 (For full details, see J. C. S. 1884, 421; 1886, 205, 777; 
 1887, 362, 808; 1888, 561, 695; 1889, 680; 1891, 981; 1892, 
 800; 1893,488; 1894,402,815; 1895,255; 1896,1025; 1900, 
 267; 1902, 177, 292.) 
 
 F. Absorption Spectra. Ostwald (Zeit. phys. 1892, 9, 579) 
 has studied the absorption spectra of groups of closely related 
 coloured compounds, e.g. a series of soluble metallic perman- 
 ganates, various salts of fluorescein, eosin, and rosolic acid, and 
 has been able to show that, in dilute solutions, the absorption 
 spectrum of a salt is the sum of the spectra of the ions; thus 
 all the permanganates gave practically the same absorption 
 
 due to the Mn 2 8 ion. 
 
648 XLVIL PHYSICAL PROPERTIES AND CONSTITUTION 
 
 Hartley and others have carried out numerous investigations 
 on ultra-violet absorption spectra of carbon compounds, and 
 extremely important relationships have been established. 
 (For references, see B. A. Reports mentioned in Preface.) 
 Hartley photographed the spark spectrum of an alloy of tin, 
 lead, cadmium, and bismuth after it had passed through a 
 solution of the substance under examination. It was found 
 that practically all open-chain and even the closed-chain poly- 
 methylene compounds give no distinct selective absorption; 
 they are remarkably transparent to ultra-violet rays. 
 Numerous exceptions, e.g. ethyl acetoacetate derivatives, 
 ke tones, and practically all ketonic compounds, whether open- 
 chain or cyclic, have since been met with (Baly and Desch, 
 J. C. S. 1904, 1039). In any given series, e.g. the alcohols, it 
 is usually found that each increment of CH 2 produces a slight 
 increase in the absorption of the more refrangible rays. 
 
 Benzene derivatives, naphthalene, anthracene, phenanthrene, 
 and their derivatives, also pyridine, quinoline, dimethylpyrazin, 
 
 N^QjjfQ-jyj-^N, in alcoholic or aqueous solutions, exhibit, in 
 
 many cases, distinct absorption bands. Most of the terpenes, 
 furane, thiophene and pyrrole derivatives, piperidene and re- 
 duced benzene derivatives, resemble the aliphatic compounds. 
 
 In all cases Hartley examined the absorption for solutions of 
 very different concentrations, always increasing the dilution 
 until complete transmission was obtained. He also used layers 
 of the given solutions of different lengths, and then plotted the 
 results in the form of curves, putting the oscillation frequencies 
 (reciprocal of wave-lengths) as abscissae, and equivalent thick- 
 nesses of solution as ordinates. Thus with two solutions, one 
 01 N and the second -001 N, and using layers of each 30, 20, 
 15, 10, 5 mm. thick, the equivalent thicknesses are 300, 200, 
 150, 100, 50, 30, 20, 15, 10, and 5, and these numbers are used 
 in the plotting. Baly and Desch have used the iron arc spectrum 
 and a glass cell with quartz ends for containing the solution, 
 so arranged that the length of the column of liquid can easily 
 be varied. They also plot the oscillation frequencies against 
 the logarithms of the relative thicknesses of liquid. It is 
 claimed that from the absorption curves so plotted it is 
 very much easier to compare the relative persistence of the 
 absorption bands. 
 
 Hartley examined a number of isomeric benzene derivatives, 
 e.g. xylenes, cresols, and dihydroxy-benzenes, and found that 
 
ABSORPTION SPECTRA 649 
 
 the oscillation frequency of the extreme rays transmitted 
 follows the order ortho * meta > para, i.e. the para-com- 
 pounds exhibit the greatest absorption. The same generaliza- 
 tion does not hold for other groups of compounds, e.g. the 
 hydroxy-benzoic acids. 
 
 A most important fact is that the introduction of a methyl 
 group for a hydrogen atom affects the absorption spectrum 
 but little; as a rule, it slightly increases the general absorption, 
 but does not alter the general character of the spectrum, e.g. 
 benzene and toluene, benzoic acid and methyl benzoate. 
 
 This fact has been largely used by Hartley and Dobbie in 
 discussions on the constitution of certain tautomeric substances, 
 more especially those of the lactam-lactim type. A study of 
 the general chemical properties of isatin (p. 523) does not 
 render it possible to say whether this compound has the 
 lactam constitution I, or the lactim constitution II: 
 
 I C 6 H 4 <>00 II C 6 H 4 <*g>C.OH. 
 
 Isatin gives rise to the two distinct methyl ethers : (a) methyl- 
 isatin, III, a solid melting at 101, readily hydrolysed, and 
 obtained by the action of methyl iodide on silver isatin; 
 (b) pseudo- methyl -isatin, IV, a solid melting at 134, not 
 readily hydrolysed, and prepared by heating methyl-dibromo- 
 oxindole with water: 
 
 III CHC.OCH IV 
 
 
 An examination of the absorption curves of the three com- 
 pounds, isatin, methyl-isatin, and pseudo-methyl-isatin (J. C. S. 
 1899, 640), shows that the curves for isatin and the pseudo- 
 ether are practically identical, both possessing two bands of 
 similar intensity and differing considerably from that of 
 methyl-isatin, which consists of a single band. There can be 
 no question but that isatin itself has a constitution similar 
 to that of the pseudo-methyl ether; and since the reactions 
 of this prove beyond doubt that it is a nitrogen and not an 
 oxygen ether, isatin must have the lactam constitution repre- 
 sented by formula I. Similarly carbostyril (p. 541), by a com- 
 parison of its absorption curve with that of its two methyl 
 ethers, can be shown to possess the lactam constitution I and 
 not the lactim constitution II : 
 
650 XLVII. PHYSICAL PROPERTIES AND CONSTITUTION 
 
 and o-oxycarbanil, obtained by fusing o-amino-phenol hydro- 
 chloride with carbamide, has an absorption spectrum practi- 
 cally identical with that of its N-ethyl ether, and hence has 
 
 the lactam constitution C 6 H 4 <Q^>CO. 
 
 Hartley and DdbUe (J. C. S. 1900, 498) have also examined 
 the absorption spectra of the three dibenzoyl-succinates ob- 
 tained by Knorr. According to the latter, the a-compound has 
 the enolic constitution I, whereas the two solid /3- and y-com- 
 pounds are stereo-isomeric ketones with constitution II : 
 
 OH CPh : C CO 2 Et COPh - CH . CO 2 Et 
 
 1 OH.CPh:C-CO 2 Et l COPh CH 00 2 Et 
 
 In accord with this view is the fact that the /3- and y-com- 
 pounds give practically the same spectrum, which differs, how- 
 ever, considerably from that of the a-compound. The trans- 
 formation of the a- into a mixture of the /?- and y-compounds 
 can readily be followed by examining alcoholic solutions at 
 different intervals of time; at the end of three hours, consider- 
 able change has taken place, and at the end of three weeks the 
 ketonization is practically complete. 
 
 Baly and Descli have found that although ethyl aceto- 
 acetate in dilute solution, and its two ethyl derivatives, 
 CH 3 .CO.CHEt.C0 2 Et and CH 3 . C(OEt) : CH . C0 2 Et, give no 
 selective but only general absorption, the metallic derivatives, 
 e.g. ethyl sodio-acetoacetate, have distinct banded absorption 
 spectra, and that even the addition of a small amount of alkali 
 to ethyl acetoacetate produces a banded spectrum. Acetyl- 
 acetone itself and its aluminium, beryllium, and thorium deri- 
 vatives all give banded ultra-violet absorption spectra. Since 
 neither the C- nor the 0-ethyl derivative of ethyl acetoacetate 
 produces selective absorption, it would appear that the char- 
 acteristic band in open -chain compounds cannot be due to 
 either the ketonic or the enolic constitution, and Baly and 
 Desch draw the conclusion that these absorption bands are 
 only produced by compounds which are in an actual state of 
 change, for example, passing alternately from the ketonic to 
 the enolic form; in all cases valency changes (desmotropism), 
 and in particular cases, e.g. keto-enolic compounds, a wander- 
 ing of a labile atom (tautomerism) occur. Within certain 
 limits the same type of valency change produces an ultra- 
 violet absorption band in the same position, although the 
 
ABSORPTION SPECTRA 651 
 
 compounds undergoing change may contain elements of very 
 different atomic weights, e.g. hydrogen, sodium, aluminium, 
 thorium; the vibrations in the molecule which synchronize 
 with the oscillation frequency of the rays absorbed cannot, 
 therefore, be the vibration of the labile atoms themselves, but 
 may be due to the change of linking (J. C. S. 1905, 768), 
 i.e. according to the electronic theory to the vibrations of the 
 valency electrons. The persistence of the band over a definite 
 range of concentration is taken as a measure of the relative 
 number of molecules which are actually undergoing change. 
 
 The absorption bands characteristic of simple benzene deri- 
 vatives may be accounted for in a somewhat similar manner 
 (J. C. S. 1904, 1029; 1905, 1331). In the case of simple 
 benzene derivatives, especially hydrocarbons, seven distinct 
 bands are visible, due to seven distinct valency changes. 
 (Compare also J. C. S. 1906, 514, 983; 1907, 449, 1122; 1908, 
 1906; 1910, 571, 1337, 1494.) 
 
 Baly and Stewart (ibid. 1906, 489, 502, 618) have examined 
 the absorption curves of various ketones and quinones. Their 
 results with fairly concentrated solutions show that the ketones 
 which show the most persistent absorption bands are those 
 which are most reactive from a chemical point of view, e.g. 
 react most readily with sodium hydrogen sulphite or with 
 hydroxylamine. In these cases also, the bands are attributed 
 to actual valency changes (desmotropism) going on in the 
 molecules of the substances. With /3-diketones and mono- 
 ketones the change is between the keto- and enolic forms. 
 
 It is well known that the entrance of substituents into the 
 acetone molecule tends to diminish its reactivity, a pheno- 
 menon which for several years has been attributed to steric 
 hindrance (pp. 175, 449). Baly and Stewart object to this 
 view, since it does not account for the increased reactivity of 
 ethyl acetoacetate as compared with acetone, or more especially 
 with methylethyl ketone. The relative reactivities of the 
 three compounds are indicated by the following numbers: 
 Methylethyl ketone, 22*5; acetone, 39 '7; ethyl acetoacetate, 
 47 '0, which give the percentage amount of each compound 
 transformed into its bisulphite derivative after twenty minutes. 
 
 The ordinary theory of steric hindrance would lead us to 
 expect that ethyl acetoacetate would be less reactive than 
 acetone, since it contains the relatively large substituent 
 C0 2 Et. Since ketones, when arranged according to their 
 reactivities, and according to the persistence of their absorp- 
 
652 XLVII. PHYSICAL PROPERTIES AND CONSTITUTION 
 
 tion bands, follow the same order, there would appear to be 
 a simple relationship between the two properties; and accord- 
 ing to Baly and Stewart both are due to the same cause, 
 namely, the extent to which tautomeric or desmotropic change 
 occurs in the molecule. In the case of the keto-enolic com- 
 pounds, 
 
 R.CO.CH 2 R' z E.C(OH):CHK', 
 
 the carbonyl group is supposed to be in a specially reactive 
 state during the change in fact, to be in a condition com- 
 parable with what is usually termed the nascent state in the 
 case of the elements. The introduction of substituents, as a 
 rule, lessens the amount of tautomeric change occurring in the 
 molecule, and thus lessens its chemical reactivity. The intro- 
 duction of the carbethoxy-group, however, tends to increase 
 the desmotropism, as is shown by a comparison of the absorp- 
 tion curves of concentrated solutions of acetone and of ethyl 
 acetoacetate, and thus the chemical activity of the ketone is 
 increased and not diminished by the introduction of the 
 C0 2 Et group. 
 
 The enormous reactivity of ethyl pyruvate and its very 
 persistent absorption bands are accounted for by a dynamic 
 change of the type 
 
 CHg-C-C-OEt ^ CH 3 .C:C.OEt 
 
 oo 6-6 
 
 Quinones also give characteristic absorption bands which 
 are attributed to the change: 
 
 /CH : CH\ 
 (5.0 -- 0-C = 
 
 The introduction of substituents into the quinone molecule 
 renders the absorption bands less persistent, and also lessens 
 the chemical reactivity of the compound. 
 
 An examination of the absorption curves of the nitranilines, 
 where there are persistent bands in the visible part of the 
 spectrum closely resembling those of quinone, leads Baly, 
 Edwards, and Stewart (J. C. S. 1906, 513) to the conclusion 
 that the free amines have a quinonoid structure, 
 
ABSORPTION SPECTRA 653 
 
 and that tautomeric change of the same type as that de- 
 scribed under the quinones occurs. Their hydrochlorides, on 
 the other hand, have the ordinary benzenoid constitution, 
 N0 2 .C 6 H 4 .NH 2 , HC1. 
 
 The nitro-phenols give absorption spectra which closely 
 resemble those of their methyl ethers, and would appear to 
 have the benzenoid formula N0 2 C 6 H 4 .OH. The sodium 
 salts, on the other hand, give absorption curves which closely 
 resemble those for the nitranilines, and would thus be repre- 
 sented by the quinoid formula, 
 
 which would be capable of tautomeric change in much the 
 same manner as quinone. 
 
 According to Lomy and Desch (J. C. S. 1909, 807), intra- 
 molecular change is not always accompanied by selective 
 absorption. The conversion of normal nitrocamphor into the 
 pseudo-isomeride, a reaction which can be studied quanti- 
 tatively (p. 657), is not accompanied by any characteristic 
 absorption bands, but such bands make their appearance when 
 an alkali is added, and the addition of an excess of alkali does 
 not produce increased absorption. The absorption cannot be 
 due to tautomeric change, as in the presence of the alkali the 
 nitrocamphor exists as a stable sodium salt. The following 
 formulae are suggested (where X = C 8 H 14 ) : 
 
 ,Q 
 
 CH.N0 2 yO<- ^ 
 
 Normal, X- ; pseudo, X<. N-C'H. 
 
 y C:NO.ONa 
 sodium salt, X<^ 
 
 Hantzsch (B. 43, 1549), as the result of spectroscopic investi- 
 gations of ethyl acetoacetate and its derivatives, draws the 
 conclusion that the specific absorption observed in solutions 
 cannot be due to the enolic modification, nor yet to an oscil- 
 lation between the ketonic and enolic states, but to an iso- 
 meric aci-form in which the latent valencies of two oxygen 
 atoms are operative, e.g. : 
 
 CH 3 .C.OH 
 
 H-C-eb-OEt. 
 The fact that an increase in the amount of alkali produces an 
 
654 XLVII. PHYSICAL PROPERTIES AND CONSTITUTION 
 
 increase in the selective absorption is attributed to the fact 
 that an excess of alkali prevents the hydrolysis of the sodium 
 salt to the enol and sodium hydroxide. 
 
 The absorption bands of various vapours, e.g. benzene, py- 
 ridine, furane, and thiophene derivatives, have been studied by 
 Hartley (Phil. Trans. 1908, A. 208, 475) and Purvis (J. C. S. 
 1910, 692, 1035, 1546, 1648; 1911, 2318), who show that in 
 the form of vapour these compounds give absorption spectra 
 which are much more complex than those of their solutions. 
 
 The conclusion that ethyl acetoacetate is an equilibrium 
 mixture of the ketonic and enolic modifications a conclusion 
 based mainly on the study of physical properties has been 
 confirmed quite recently by other methods. Of these, the 
 following are the more important: 
 
 1. Kn&rr (B. 1911, 44, 1138) has shown that, by cooling to 
 
 78 a solution of the ordinary ester in alcohol and ether 
 in an apparatus specially designed to exclude moisture and to 
 maintain a high vacuum, the ketonic form separates as well- 
 defined needles or prisms, m.-pt. 39 and b.-pt. 39-40/ 2 mm. 
 It does not give a coloration with ferric chloride, and does not 
 react with bromine solution. Even at the ordinary tempera- 
 ture it takes several weeks before the equilibrium mixture is 
 again formed. The practically pure enol is obtained by sus- 
 pending the sodium derivative in light petroleum cooled to 
 
 78 in a special apparatus, and passing in hydrogen chloride 
 just insufficient for complete decomposition. The solution 
 when filtered and evaporated at 78 yields the enolic ester 
 as a colourless oil, which gives an intense coloration with ferric 
 chloride. At the ordinary temperature it requires ten to four- 
 teen days to again form the equilibrium mixture, but at 100 
 the change is completed in one minute. By comparing the 
 refractive index of the ordinary ester with the values for 
 mixtures of known concentration, it has been calculated that 
 the equilibrium mixture contains 2 per cent of the enol. 
 
 2. By means of experiments made with compounds which 
 exist in stable keto and enolic forms, K. H. Meyer (A. 380, 
 212; B. 44, 2718) shows that the unsaturated hydroxylic 
 modification reacts instantaneously with an alcoholic solution 
 of bromine, yielding an unstable dibromide, which immediately 
 gives off hydrogen bromide and forms the bromo - ketone. 
 The best method for estimating the amount of enol is to add 
 an excess of the alcoholic bromine solution, to remove the 
 excess by means of /3-naphthol, and then to determine the 
 
ANOMALOUS ELECTRIC ABSORPTION 655 
 
 amount of bromo-ketone by adding potassium iodide solution, 
 and titrating the liberated iodine by means of standard thio- 
 sulphate : 
 
 CO-CHBr * CI(OH).CHBr 
 
 CI(OH).CHI C(OH):CH + L, 
 
 In this way it has been shown that the ordinary ethyl aceto- 
 acetate contains about 7 per cent of the enol, and the same 
 results are obtained when freshly prepared solutions in various 
 solvents are examined; but such solutions when kept undergo 
 change, e.g. a hexane solution when kept for forty-eight hours 
 at 18 contains nearly equal amounts of keto and enolic modi- 
 fications. A rise in temperature also tends to favour the 
 formation of the ketonic form. In a similar manner acetyl- 
 acetone has been shown to contain 80 per cent of enol. 
 
 3. Knorr and Schubert (B. 1911, 44, 2772) use a colori- 
 metric method for estimating enols in allelotropic mixtures, 
 a method which is based on the reaction between the enol 
 and ferric chloride, 
 
 EH + FeCl 3 = FeRCl 2 + HC1, 
 
 where R is the enolic residue. The comparison is made with 
 standard solutions prepared by mixing solutions of the pure 
 enol with one of sublimed ferric chloride in molecular pro- 
 portions. 
 
 G. Anomalous Electric Absorption. P. Drude (B. 1897, 30, 
 941) has found that numerous organic compounds containing 
 hydroxyl groups are capable of absorbing electric waves of 
 high frequency (about 400 million per second), although they 
 are not good conductors; whereas ordinary non-conductors 
 show no such absorption. The phenomenon is termed by 
 Drude "anomalous electric absorption", and, with the ex- 
 ception of water, all liquid hydroxyl derivatives display this 
 anomalous absorption. The presence of hydroxyl groups 
 cannot always be inferred from the exhibition of anomalous 
 absorption, as a few compounds which contain no hydroxyl 
 groups possess the property to a slight extent. 
 
 Drude himself applied the method to the examination of 
 certain keto-enolic tautomeric substances. Ethyl acetoacetate 
 itself absorbs but slightly, and is thus presumably mainly the 
 keto-form. 
 
 Ethyl benzoylacetate and ethyl oxalacetate absorb strongly, 
 and should thus contain considerable percentages of the enols. 
 
656 XLVII. PHYSICAL PROPERTIES AND CONSTITUTION 
 
 H. Optical Activity. Attention has already been drawn t" 
 the fact that compounds, the molecules of which are asym- 
 metric, are, when in the liquid or dissolved state, optically 
 active, i.e. able to rotate the plane of polarization (p. 154) 
 either to the right (dextro-rotatory) or to the left (Isevo- 
 rotatory). The specific rotatory power [a] of a liquid is 
 obtained by dividing the observed rotation by the length of 
 the column of liquid used and by the specific gravity of the 
 
 liquid [a] = - -, and the molecular rotation is the product 
 
 of the specific rotatory power into the molecular weight (M). 
 For a solution : 
 
 r a ] = 1QQa IQOa _ IQOa X v 
 lXc ~ 
 
 where c = concentration or number of grams of the active 
 compound in 100 c.c. of solution, d = specific gravity of the 
 solution, p = per cent of active substance in the solution, and 
 g = number of grams of active substance in v c.c. of solution. 
 The specific rotatory power of a solution may often be in- 
 creased enormously by the introduction of an inorganic salt; 
 some of the most effective are boric acid and alkali molybdates 
 and tungstates. As a rule, the nature of the monochromatic 
 light, e.g. sodium light, is indicated, also the temperature and 
 the nature of the solvent, e.g. [a] 1 ^, where D indicates that the 
 number refers to sodium light and that the determination was 
 made at 15. Various attempts have been made to deduce 
 general conclusions bearing upon the amount of rotation and 
 the constitution of the compound. Guye (C. R. 110, 714) has 
 attempted to connect the degree of asymmetry of the molecule 
 of a compound C a, b, c, d with the masses of the four radicals 
 present and the distance of the centre of gravity of the mole- 
 cules from the centre of the tetrahedron (C. E. 1896, 1309; 
 1898, 181, 307). The researches of P. F.FranEand and others 
 (J. C. S. 1899, 337, 347, 493, &c.) have shown that Guye's 
 conclusions are not of general application. 
 
 Patterson (J. C. S. 1901, 167, 477; 1902, 1097, 1134; 1904, 
 765, 1116, 1153; 1905, 122, 313) has made a careful investi- 
 gation of the influence of solvent, temperature, &c., on the 
 optical activity of various substances. He finds that dilute 
 solutions of ethyl tartrate in water, or in methyl, ethyl, or 
 propyl alcohol, possess a higher specific rotation than the pure 
 ester itself, that the specific rotation increases with dilution 
 
OPTICAL ACTIVITY 657 
 
 until a concentration of 10 grams in 100 grams of solvent is 
 reached, and then the rotation remains practically constant. 
 The highest values are always obtained with aqueous solutions, 
 and the other solutions follow in the order methyl, ethyl, 
 Ti-propyl, isobutyl, and sec-octyl alcohol. 
 
 The effect of increase of temperature upon corresponding 
 solutions varies somewhat. In water the coefficient is nega- 
 tive for dilute solutions, but in the various alcoholic solutions 
 it is positive, as it is also for the pure ester. 
 
 According to Patterson the change in specific rotation with 
 solvent or temperature is not to be attributed to association, 
 but rather to the internal pressure of the solvents (compare 
 Abst. 1900, 2, 329). 
 
 Walden has also conducted numerous investigations on opti- 
 cally active compounds, and concludes that there is a relation- 
 ship of a qualitative nature only between the optical activity 
 of a substance in a given solution and its molecular weight in . 
 that solution. (For a summary of work on optical activity see 
 Walden, B. 1905, 38, 345-409). 
 
 The polarimetric method has been used by Lowry (J. C. S. 
 1899, 75, 211) for a quantitative study of the tautomerism or 
 dynamic isomerism of the nitro- and bromo-nitro-camphors. 
 
 Each of these compounds appears to exist in two distinct 
 
 forms, one of which contains the nitro-group, >CHN^Q, and 
 the other the isonitro-group, ^>C:NO'OH. Ordinary crystal- 
 
 line nitro-camphor, melting at 102, is regarded as consisting 
 of the normal form, its homogeneity being vouched for by the 
 constancy of its initial specific rotatory power ([a] D = 124 
 in 5-per-cent benzene solution), and by its well-defined crystal- 
 line form. When dissolved the nitro-compound at once begins 
 to change into the pseudo form, and this change is accompanied 
 by an alteration in the rotatory power; with the 5-per-cent 
 benzene solution the specific rotatory power has fallen to 
 104 at the end of four days, and then remains stationary. 
 This solution represents a mixture of the normal and pseudo- 
 compounds in dynamic equilibrium, and assuming that the 
 pseudo-compound, which so far has not been obtained in a 
 pure form, has a specific rotatory power +180 in benzene 
 solution, then the solution, with a rotation of 104, con- 
 tains some 93 per cent of the normal and 7 per cent of the 
 pseudo form, 
 
 (B4SO) 2T 
 
658 XLVII. PHYSICAL PROPERTIES AND CONSTITUTION 
 
 The velocity of the transformation, normal * pseudo, is 
 increased by rise of -temperature, by increase in concentration, 
 and by the addition of traces of alkalis. 
 
 Both the normal and pseudo forms of 7r-bromo-nitro-camphor 
 have been isolated (Lapworth and Kipping, J. C. S. 1896, 304). 
 The compound, melting at 142, when dissolved in benzene, 
 gives an initial specific rotatory power +1S8 , which changes 
 to 38 in a 3'33-per-cent benzene solution, and appears to 
 be the pseudo form. The compound melting at 108 3 shows 
 a change in rotatory power from 51 to 38, and appears 
 to be the normal compound. When either of the two pure 
 compounds is dissolved in benzene, tautomeric change occurs, 
 and a mixture of the two compounds in dynamic equilibrium 
 is obtained. From the specific rotatory power of this solution, 
 viz. 38, it follows that it contains some 5*5 per cent of 
 pseudo-compound for 94*5 of the normal. 
 
 XThe change in rotation of an optically active solution is 
 usually known as mutarotation (p. 309), and is a property 
 exhibited by various optically active compounds, especially 
 sugars, e.g. glucose, galactose, xylose, milk-sugar, and maltose, 
 and certain hydroxy-acids and their lactones, e.g. anhydrous 
 lactic acid. 
 
 In all cases the rotation changes when the solution is kept; 
 with glucose, for example, the value decreases to half, with 
 milk-sugar the values are as 1'6:1, with galactose 1*46:1, and 
 with xylose 4'67 : 1. The rotatory powers of maltose and lactic 
 acid solutions increase when kept. 
 
 All acids and alkalis appear to facilitate the conversion, and 
 in the order of their degree of ionization. Common salt, alco- 
 hol, and various organic compounds, on the other hand, tend 
 to retard the transformation. 
 
 Various theories have been brought forward in order to 
 account for the phenomenon. The first of these assumed the 
 presence of complex molecules, e.g. (C 6 H 12 6 ) X , in the freshly- 
 prepared solution, and the gradual decomposition of these into 
 the simpler molecules, C 6 H 12 6 , thus producing a lowering of 
 the rotatory power. The assumption of the presence of com- 
 plex molecules was rendered untenable as soon as it was shown 
 that the molecular weight, as determined by the cryoscopic 
 method, is the same in the freshly - prepared and the old 
 solution. The second explanation was that, after solution, 
 water is either withdrawn from or added on to the original 
 molecular aggregates. The latest theory is that the different 
 
MUTAROTATION 659 
 
 rotations are due to different isomeric substances present in 
 the two solutions, and that a gradual change in rotation 
 accompanies the conversion of the one isomeride into the 
 other. 
 
 Tanret (1895) claimed to have isolated three distinct modi- 
 fications of (/-glucose, which had the respective specific rotatory 
 powers a = +105, j3 = -f-52'5, and 7 = +22-5. More 
 recent work (E. F. Armstrong, J. C. S. 1903, 1305; 1904, 1043) 
 indicates that in the case of (/-glucose only two distinct iso- 
 merides actually exist in solution, viz. the a and 7, and that 
 the so-called /^-modification is merely a mixture of the a and 
 7 in chemical equilibrium. The a- and 7-modifications are 
 represented as stereo -isomeric, and correspond in structure 
 with the a- and /3-methyl-glucosides (p. 310), since these glu- 
 cosides, when hydrolysed with enzymes, have rotatory powers 
 of the order of those of the a- and 7-glucoses, and the addition 
 of an alkali to the products of hydrolysis produces the same 
 change as with the a- and 7-sugars. They are therefore now 
 termed a- and /^-glucoses, and may be represented by the 
 configurations : 
 
 OH.CH 2 .CH(OH).CH.CH(OH).CH(OH).C<o H (a) 
 
 and OH.CH 2 .CH(OH).CH.CH(OH).CH(OH).C<2 H O 8 ) 
 
 (Compare also Behrend and Both, A. 1904, 331, 359, and 
 Lowry, J. C. S. 1904, 1551). Lowry concludes that in an 
 ordinary solution of glucose, in addition to the a- and /?- 
 modifications, small amounts of the aldehyde or aldehyde- 
 hydrate are also present. This accounts for the aldehydic 
 properties of glucose solutions, and also affords an explanation 
 of the conversion of the a- into the /3-glucose: 
 
 H-C-OH CH(OH) 2 OH-CH 
 
 'CH-OH CH-OH X^CH-OH 
 
 XV H.OH ^ CH.OH X CH.OH 
 
 CH CH-OH CH 
 
 CH-OH CH-OH CH-OH 
 
 CH 2 -OH CH 2 -OH CH 2 -OH 
 
 a-Glucose Aldehyde-hydrate p-Glucoae. 
 
 (For rwimt, see Lowry, B. A. Kep. 1904, 193.) 
 
660 XLVII. PHYSICAL PROPERTIES AND CONSTITUTION 
 
 Asymmetric Synthesis. It has already been stated that the 
 product formed by the synthesis of a compound containing an 
 asymmetric carbon atom from symmetrical compounds is al- 
 ways a mixture or compound of the d- and /-modifications in 
 equal amounts, and a single active modification can only be ob- 
 tained by the resolution of this r^cemic compound or mixture. 
 Numerous attempts have been made to carry out an asym- 
 metric synthesis, i.e. according to Marckwald (B. 1904, 37, 1368), 
 to obtain artificially an optically active compound from a sym- 
 metrical substance by the employment of an active product 
 but without the use of an analytical process (such, for example, 
 as those involved in the usual separation of racemic mixtures). 
 A synthesis suggested by E. Fischer was as follows: By the 
 cyanhydrin reaction mentioned on p. 304 it is possible to trans- 
 form an optically active monose containing C n into a mixture 
 of two active sugars containing C n+1 . The amounts of the two 
 active compounds vary considerably in different cases, and with 
 d-mannose only one c/-mannoheptose can be isolated. Similarly 
 the d-mannoheptose yields only one mannooctose, and this 
 only one nonose. If it were possible by some method to de- 
 compose this d-manno-nonose so as to regenerate ctanannose 
 then the other product would be an active glyceric aldehyde : 
 
 Mannononose, CHO CH(OH) CH(OH)4-CH(OH) [CH OH] 4 CH 2 OH 
 
 -* glyceric aldehyde, CHO.CH(OH).CH 2 .OH and 
 CHO.LCH.OHJ4.CH2.0H. 
 
 Cohen and Whiteley (J. C. S. 1901, 1305), starting with cm 
 namic acid, prepared active amyl and menthyl esters, to which 
 they added bromine and then attempted to obtain an active 
 cinnamic acid dibromide, CgH^ CHBr - CHBr C0 2 H, by the 
 hydrolysis of the esters, but without success. The hydrolysis 
 of the products obtained by reducing the active amyl and 
 menthyl esters of mesaconic, a-methylcinnamic, and pyruvic 
 acids gave rise to inactive acids. Similar negative results were 
 obtained by Kipping (P. 1900, 226). A. M'Kenzie (J. C. S. 
 1904, 1250; 1905, 1373; 1906, 365) has succeeded in accom- 
 plishing several asymmetric syntheses. Thus when /-menthyl ( 
 pyruvate, CH 3 CO CO OC 10 H 19 , is reduced by aluminium 
 amalgam, a mixture of unequal amounts of /-menthyl d-lactate 
 and /-menthyl /-lactate is formed. When this mixture is hy- 
 drolysed by an excess of alcoholic potassic hydroxide and the 
 /-menthol removed, a dextro-rotatory potassic salt containing 
 
THE WALDKN INVERSION 661 
 
 an excess of Mactate over d-lactate is produced ; this mixture, 
 when acidified, becomes laevo-rotatory, and the asymmetric 
 synthesis of /-lactic acid is thus accomplished. If tmenthyl 
 benzoylformate, C 6 H 5 CO C0 2 C 10 H 19 , is treated in exactly 
 the same manner, the final product is r-mandelic acid, due, 
 probably, to the racemizing effect of the alkali. A second 
 asymmetric synthesis has been accomplished by M'Kenzie by 
 means of Grignard's reaction. Thus Z-menthyl benzoylformate 
 and magnesium methyl iodide yield the additive compound 
 CMePh(O.MgI)(C0 2 C lp H ]9 ), which is converted by dilute 
 acids into the Z-menthyl phenylmethylglycollate CMePh(OH) 
 (C0 2 C ]0 H 19 ), from which, on hydrolysis with alcoholic potas- 
 sium hydroxide, a laevo-rotatory potassium phenylmethylgly- 
 collate, CMePh(OH)(C0 2 K), was obtained. Thus 
 
 C 6 H 5 .CO-C0 2 H -* CeH 5 .CO.COAoH 19 C 6 H 6 .C(CH 8 )(OH)(C0 2 C 1 oH 19 ) 
 Inactive Active Active 
 
 -* C 6 H 5 .C(CH 3 )(OH)(C0 2 H) 
 Active. 
 
 Similar active acids have been obtained by using other Ghignard 
 reagents in conjunction with /-menthyl benzoylformate. 
 
 For a further asymmetric synthesis, see Marckwald, B. 1904, 
 37, 349. 
 
 The Walden Inversion. In a chemical reaction in which 
 one radical is displaced by another, it is usually assumed that 
 the group introduced takes the place of the radical removed, 
 unless reasons to the contrary can be adduced. When an 
 optically active compound is used we should expect the pro- 
 duct formed to correspond in configuration with the original 
 substance That this is not always true follows from the fact 
 that during certain reactions racemization occurs, and the pro- 
 duct obtained is optically inactive (cf. p. 257). Even more 
 remarkable than this is the phenomenon known as Walden's 
 inversion. An example of this is met with in the conversion 
 of J-chloro-succinic acid into the d-isomeride by the following 
 series of reactions : 
 
 J-Chloro-acid * -malic acid * c?-chloro-acid. 
 
 Moist Ag 2 PC1 5 
 
 It is not possible to say which of the two reactions is normal 
 and which abnormal, as although the malic acid may be laevo- 
 rotatory, its configuration may correspond with that of the 
 d-chloro-acid and not with that of the /-acid. 
 
 (B. 32, 1833) carried out a remarkable series of 
 
662 XLVII. PHYSICAL PROPERTIES AND CONSTITUtiOtf 
 
 experiments on the reaction between /-chloro- and /-bromo- 
 succinic acids and various alkalis. He found that the hydrox- 
 ides of potassium, rubidium, and ammonium gave practically 
 pure c/-malic acid, moist silver oxide gave the pure /-malic 
 acid; and the hydroxides of sodium, barium, lead, and lithium 
 gave mixtures in which the d-acid preponderated, whereas 
 oxides of mercury and palladium gave mixtures in which the 
 /-acid was in excess. The conclusion was drawn that the 
 reaction with potassium hydroxide is normal, and that inver- 
 sion occurs when silver oxide is used. 
 
 Interesting cases are those in which a complete cycle is 
 involved, e.g.: 
 
 1. /-Chloro-succinic acid * /-malic acid 
 
 I ifototAoO , 
 
 7 I * Moist Ag 2 * 
 
 a-mahc acid * a-chloro-succmic acid. 
 
 2. d- Alanine * /-bromo-propionic acid 
 
 t NH NOBr I NH 
 
 c?-bromo-propiomc acid * /-alanine. 
 
 3. d-C 6 H 5 .CH(OH).C0 2 H *- /-C 6 H 6 .CH(NH 2 ).C0 2 H 
 
 I T> HN 2 t xrrr 
 
 /-C 6 K 6 .CHC1.C0 2 H 
 
 d-C 6 H 5 .CHCl-CO 2 H 
 
 . CH(NH 2 ) C0 2 H 
 
 In some of these cases it is possible to determine in which 
 of the different reactions inversion occurs; thus in Example 
 No. 2 the reaction with nitrosyl bromide is abnormal and not 
 that with ammonia, as E. Fischer has shown that under very 
 varying conditions ammonia always gives the same product. 
 With NOBr c?-alanine gives /-bromo acid, but the ester of 
 r/-alanine reacts with NOBr, giving d-bromo-propionic acid. 
 /-Valin (amino-isovaleric acid), with NOBr gives the /-bromo 
 acid, and this with ammonia yields /-valin. 
 
 Practically all the inversions mentioned above occur wiien 
 the asymmetric carbon atom has a carboxyl group attached 
 to it. Experiments made by E. Fischer and Scheibler, with 
 compounds in which the asymmetric atom is in the /3-position 
 with respect to the carboxylic group, prove that inversion 
 does not take place: 
 
 PC1-, 
 
 -CH a .CH(OH).CH 2 .C0 2 H =r d-CH 3 .CH(OH).CH 2 .C0 2 II, 
 AftO 
 
WALDEN INVERSION 663 
 
 and similar results are obtained when the methyl esters are 
 used. The same holds good in the case of /3-hydroxy-/?-phenyl- 
 propionic acid (M'Kenzie and Humphreys). There are, how- 
 ever, several exceptions, e.g. : 
 
 1. Fischer: 
 
 c?-/3-Amino-butyric acid * Z-/3-hydroxy-butyric acid 
 NOCI 
 
 -j8-chloro-butyric acid c?-/3-hydroxy-butyric acid. 
 Water 
 
 2. M'Kemie and Barrow: 
 
 c?-/3-Hydroxy-)S-phenyl-propionic acid 
 
 * c?-j8-chloro-/3-phenyl-propionic acid 
 80C1 * J Water 
 
 J-j3-hydroxy-j8-phenyl-propionic acid. 
 
 Frequently phosphorus pentachloride and thionyl chloride 
 react differently, e.g.: 
 
 PC1 5 
 
 -Mandelic acid or ester * c?-chloro acid or ester 
 Z-mandelic acid or ester * Z-chloro acid or ester. 
 
 SOC1 2 
 
 In connection with this the following cycles are of interest. 
 
 Z-Mandelic acid * d-chloro acid 
 
 f NaOH rcl J NaOH 
 
 Z-chloro acid * c?-mandelic acid 
 
 PC1 6 
 
 MVIandelic acid ^-chloro acid 
 
 J Ag 2 C0 3 + water SOCI 2 J Ag 2 C0 3 + water 
 
 c?-chloro acid * c?-mandelic acid. 
 
 SOC1 2 
 
 of ^8-hydroxy-^-phenyl-propionic acid it has been 
 the reaction with thionyl chloride is normal, since 
 
 In the case 
 shown that the 
 
 the chloro ester derived from the Z-hydroxy ester is trans- 
 formed back into Z-hydroxy acid when warmed with water and 
 marble. 
 
 (For details see Walden, B. 28, 2772; 29, 133; 30, 3146 
 E. Fischer and students, B. 41, 889, 2891; 42, 1219; 43, 
 2020; A. 381, 123; 383, 337; 386, 374. Werner, A. 386, 65. 
 M l Kenzie and others, J. C. S. 1908, 811; 1909, 777; 1910, 
 121, 1016, 1355, 2564; 1911, 1910, 1912, 390. Bulmann, A. 
 1912, 388, 330.) 
 
664 XLVII. PHYSICAL PROPERTIES AND CONSTITUTION 
 
 I. Electrical Conductivity. Attention has previously (p, 
 161) been drawn to the fact that the degree of ionization, a, 
 of an acid in solutions of given concentration, v, may be deter- 
 mined by a comparison of the electrical conductivity, X (re- 
 ciprocal of resistance), at that dilution with the conductivity 
 at infinite dilution when ionization would be complete, i.e. 
 
 a = . From Ostwald's dilution law, based on the law of 
 aoc 2 
 
 mass action, it follows that - is a constant = &, where 
 
 v(l - a) 
 
 v = number of litres of solution containing one equivalent of 
 acid. This constant k (or 100& = K) is known as the dis- 
 sociation constant, and is used as a measure of the strength of 
 all feeble acids. The effect of the introduction of strongly 
 negative groups into the acid molecule on this constant has 
 been referred to (pp. 168, 447), and the influence of strongly 
 positive groups, e.g. NH 2 , is equally marked. Thus benzoic 
 acid == 0*006, 0-amino-benzoic = 0*0009, m-amino-benzoic = 
 O'OOIO, and jp-amino-benzoic = O'OOS. 
 
 Hantzsch has used the electrical conductivity method in the 
 diagnosis of pseudo-acids and bases. Thus with certain nitro- 
 compounds the ordinary compound R-CH 2 N0 2 is a pseudo- 
 acid and the isonitro-compound RCH:NOOH is a true acid, 
 and all the salts are derived from the latter. These salts, as a 
 rule, are but little hydrolysed, as the isonitro-compounds are 
 relatively strong acids. A solution of such a salt will thus 
 
 contain the metallic ions and the isonitro-ion KCH:NO0. 
 When this solution is mixed with an equivalent quantity of 
 
 hydrochloric acid the ions present are Na, Cl, E-CH:NO0', 
 
 + 
 
 and H. In the majority of cases there is a considerable ten- 
 dency for the strongly acidic and hence strongly ionized 
 isonitro-compound (true acid) to become transformed into the 
 ordinary nitro-compound (pseudo-acid). As this is practically 
 a non-electrolyte, it follows that as this transformation occurs 
 the conductivity of the solution will gradually diminish until 
 it attains the value of a sodium chloride solution of the given 
 concentration. Thus with sodium ^-bromophenylnitromethane, 
 C 6 H 4 Br.CH:NO.ONa, at 25, and 0= 256, after mixing with 
 an equivalent of hydrochloric acid, the conductivity, /* = 151 '4 
 after 1-5 minute, and after 45 minutes a constant value p = 129-5 
 was obtained. This approximates to the value /^ = 114'4 
 
ELECTRICAL CONDUCTIVITY 665 
 
 for sodic chloride, and the difference may be due to secondary 
 changes. 
 
 Similar results have been obtained with pseudo-bases. The 
 true base, methyl-phenyl-acridonium hydroxide (I), which is 
 first liberated when salts of the base are decomposed with 
 alkali, is readily transformed into the pseudo-base with the 
 carbinol formula (II): 
 
 II 
 
 which is practically a non-electrolyte. When a solution of the 
 chloride of the base is neutralized with an equivalent of sodic 
 hydroxide, the solution has a maximum conductivity which 
 gradually diminishes until the value for a solution of sodic 
 chloride of the given concentration is practically reached. 
 Similarly with the sulphate and an equivalent quantity of 
 barium hydroxide; at and v = 256, the initial conductivity 
 was /*= 119'2, but after 15 hours it had fallen to ft = 1-7 (due 
 to small amounts of dissolved baric sulphate). Phenomena 
 of this kind, which are termed by Hantzsch "slow neutrali- 
 zation ", are largely used to denote tautomeric change, i.e. the 
 change from a true acid to a pseudo-acid or from a true base 
 to a pseudo-base (cf. p. 485) during the conversion of the salt 
 into the acid or base. 
 
 The study of other physical properties such as Internal 
 Viscosity (Zeit. phys. 1887, 1, 285, 293; 1888, 2, 744; com- 
 pare also Dunstan, J. C. S. 1907, 1728; 1908, 1815, 1919; 
 1909, 1556; 1910, 1935), Heat of Combustion (Stohmann, 
 Zeit. phys. 1890, 6, 334; 1892, 10, 410), Capillary Constants 
 (Schiff, A. 1884, 223, 47), Magnetic Susceptibility (Pascal, 
 Bull. 1909, 1110; 1910, 17, 45; 1911, 6, 79, 134, 177, 336, 
 809. 868) indicate that here also there are similar relation- 
 ships between constitution and physical properties. 
 
666 XLVIIL FERMENTATION AND ENZYME ACTiOJi 
 
 XLVIII. FERMENTATION AND ENZYME ACTION 
 
 A. Alcoholic Fermentation. Lavoisier, 1789, was the first 
 to recognize that alcoholic fermentation consists essentially 
 in the ^decomposition of a sugar into alcohol and carbon 
 dioxide; and Gay-Lussac, 1810, drew attention to the fact that 
 the presence of air appeared to be essential for fermentation 
 and putrefaction to take place. The fact that brewers' yeast 
 is a low form of plant life was discovered independently by 
 Cagnaird-Latour, Theodor Schwann, and Kutzing, 1837. By 
 microscopical examination they observed the growth of the 
 organism, and showed that it could be destroyed by heat or 
 by certain poisons. These results were not accepted by 
 Berzelius, Liebig, and others, who still regarded yeast as a 
 chemical substance without life. According to Berzelius the 
 yeast acted as a contact substance which decomposes the 
 sugar without undergoing change itself; whereas Liebig re- 
 garded the ferment as an extremely susceptible substance, 
 which undergoes a change of the nature of decay, and sug- 
 gested that the decomposition of the sugar was a type of 
 sympathetic reaction induced by the change of the ferment. 
 In 1857 Pasteur began his researches on fermentations. He 
 was able to show that in other cases of fermentation, such as 
 the lactic fermentation of milk, micro-organisms are present. 
 He was further able to show that during alcoholic fermenta- 
 tion the yeast grows and multiplies, and was led to the 
 conclusion that fermentation is a physiological process ac- 
 companying the life of the yeast. 
 
 In his own words: "I am of opinion that alcoholic fer- 
 mentation never occurs without simultaneous organization, 
 development, multiplication of cells, or the continued life of 
 cells already formed". This conclusion harmonized with the 
 facts already known that boiled liquids could be kept from 
 fermenting by heating or filtering through cotton wool the 
 air admitted to the liquid. 
 
 It was Pasteur who proved that only 95 per cent of the glu- 
 cose is accounted for as carbon dioxide arid alcohol ; he was able 
 to isolate glycerol and succinic acid from the final products. 
 
 As early as 1858 M. Traube expressed the view that all 
 fermentations produced by living organisms are ultimately 
 due to ferments, which are definite chemical substances manu- 
 factured in the cells of the organism. These ferments he re- 
 
ALCOHOLIC FERMENTATION 667 
 
 garded as analogous to proteins. Traube's conclusions have 
 been verified in the case of alcoholic fermentation by Buchner's 
 isolation of " zymase " from yeast (see p. 77). Buchner's yeast 
 juice, when quite free from yeast cells, can ferment solutions 
 of glucose, fructose, sucrose, and maltose; and the fermenting 
 power is not destroyed by the addition of chloroform, benzene, 
 or sodium arsenite, antiseptics which inhibit the action of 
 living cells, by filtration through a Berkefeld filter, by eva- 
 poration to dryness at 30-35, or by precipitation with 
 alcohol. The fermenting power is, however, completely de- 
 stroyed by heating to 50, or by the addition of powerful anti- 
 septics. The activity of the juice diminishes in the course of 
 time, as a digestive enzyme is also present which gradually 
 decomposes the zymase. Both in rate of fermentation and in 
 the total fermentation produced, the extract or juice is much 
 less efficient than the equivalent amount of living yeast, and 
 
 g'ycerol is formed as a by-product when the extract is used, 
 uring fermentation a portion of the sugar is converted into 
 a compound of less reducing power which is not fermented, 
 but which yields sugar when hydrolysed with acids. Per- 
 manent preparations containing zymase can be obtained by 
 evaporating the juice to a syrup at 20-25, drying at 35, and 
 then exposing to sulphuric acid in a vacuum desiccator. Such 
 a powder when dry retains its activity for twelve months, and 
 can be heated at 85 for eight hours without any serious loss 
 of fermenting power. Another preparation can be obtained 
 by bringing the juice into 10 volumes of acetone, centrifuging, 
 washing the precipitate with acetone and then with ether, 
 and drying over sulphuric acid. An important medicinal 
 preparation known as zymin is manufactured by stirring 
 moist yeast with acetone, filtering and draining at the pump, 
 again mixing with acetone and draining. The product is 
 then roughly powdered, kneaded with ether, filtered, drained, 
 and spread on filter paper or porous plates, and finally dried 
 at 45 for twenty-four hours. This product is quite incapable 
 of growth or reproduction, but produces fermentation and 
 is much more active than yeast extract. 
 
 The researches of Harden and Young (Abs. 1905, ii. 109; 
 1906, i. 470) indicate that the activity of yeast juice or ex- 
 tract is due to an enzyme and a co-enzyme, which can be 
 separated by filtration or dialysis through a Martin gelatin 
 filter; the residue contains the enzyme, and the filtrate or 
 dialysate the co-enzyme. Neither by itself can induce fer- 
 
668 XLVIII. FERMENTATION AND ENZYME ACTION 
 
 mentation, but a mixture of the two is equal in activity to 
 the original juice. The co-enzyme is dialysable, and is not 
 destroyed by boiling, but disappears from yeast juice during 
 fermentation, or when the juice is allowed to undergo auto- 
 lysis. It cannot be a protein, and its nature has not yet been 
 determined. It is decomposed by acid or alkaline hydrolysing 
 agents, by repeatedly boiling the extract, and also by the 
 lipase of castor-oil seeds. In the case of other fermentations 
 brought about by enzymes, e.g. lipase, it has been clearly 
 demonstrated that both enzyme and co-enzyme are necessary, 
 and also that the co-enzyme is a metallic salt of the com- 
 plex taurochloric acid (p. 196). Harden and Young (Abs. 
 1908, i. 590) have also shown that phosphates added to a 
 mixture of glucose and yeast juice produce both an initial 
 acceleration and also an increased total fermentation. An 
 optimum concentration of phosphate exists which produces a 
 maximum initial rate of fermentation; an increase beyond this 
 optimum diminishes the rate. The reaction between the glu- 
 cose and phosphate is represented by the following equations : 
 2C 6 H 12 6 + 2Na 2 HP0 4 
 
 = 2C0 2 + 2C 2 H 6 + C 6 H 10 4 (P0 4 Na 2 ) 2 + 2H 2 
 and C 6 H 10 O 4 (P0 4 Na 2 ) 2 -f 2H 2 O = C 6 H 12 O 6 
 
 According to the second of these, the glucose phosphate is 
 hydrolysed by the water and yields sodium phosphate, which 
 can then react with a further quantity of glucose. These 
 conclusions are supported by the following facts. Careful 
 experiments have shown that during the period of increased 
 fermentation the amounts of alcohol and carbon dioxide pro- 
 duced exceed those which would have been formed in the 
 absence of added phosphate by a quantity exactly equivalent 
 to the phosphate added in the ratio C 2 H 6 : Na 2 HP0 4 . (Com- 
 pare also Iwanoff, Abs. 1909, 1, 752.) It has been proved that 
 the metallic phosphate is not the co-enzyme already mentioned, 
 as the filtered enzyme and phosphate are not capable of induc- 
 ing fermentation in the absence of the filtrate. Fermentation 
 does not proceed in the absence of phosphate although both 
 enzyme and co-enzyme are present, and although arsenates 
 and arsenites have accelerating actions on the rate of fer- 
 mentation they cannot be used in place of the phosphate. 
 The function of the arsenate or arsenite appears to be to act 
 as accelerators in the decomposition of the glucose phosphate. 
 Slator finds that phosphates have not an accelerating effect 
 
ALCOHOLIC FERMENTATION 669 
 
 when living yeast cells are employed. He has estimated 
 (J. C. S. 1906, 89, 128; 1908, 93, 217) the amounts of car- 
 bon dioxide evolved during given periods of time when yeast 
 itself is used, and finds that the rate of fermentation is exactly 
 proportional to the amounts of yeast present, and is almost 
 independent of the concentration of the glucose. A yeast 
 which can ferment glucose does not necessarily ferment iso- 
 meric sugar, e.g. galactose; it is probable that different 
 enzymes are required for the different sugars. 
 
 The fermentation of glucose undoubtedly consists of a whole 
 series of chemical reactions; at present we know the sub- 
 stances we start with and the final products obtained. Several 
 suggestions have been made with regard to the nature of some 
 of the intermediate products. Buchner and Meisenheimer (B. 
 1905, 38, 620) have suggested that lactic acid (p. 213) is first 
 formed by the action of zymase on glucose, and that a second 
 enzyme, lactacidase, then decomposes the lactic acid into ethyl 
 alcohol and carbon dioxide. A serious objection to this view 
 is that lactic acid itself is only very slowly fermented by 
 yeast (Slator). 
 
 Another suggestion is that dihydroxy-acetone, CO(CH 2 OH) 2 , 
 is an intermediate product, and it has been proved that this 
 compound can be fermented by yeast (Buchner and Meisen- 
 heimer, B. 43, 1773; Lebedew, 44, 2932); compare also Fmnzen 
 and Steppuhn, ibid., 2915. 
 
 Of the by-products mentioned on p. 76, glycerol is formed 
 from the sugar, as Buchner and Meisenheimer have shown that 
 it is also formed when yeast extract or zymin acts on sugar 
 solutions. The fusel oil and succinic acid, on the other hand, 
 do not owe their origin to the sugar, but to other products 
 present in the mixture undergoing alcoholic fermentation. 
 The researches of F. Ehrlich (1904-1910) prove that the 
 alcohols and also the aldehydes present in ordinary fusel oil 
 are derived from the amino-acids formed by the hydrolysis 
 of proteins. Thus isoamyl alcohol, one of the chief consti- 
 tuents of fusel oil, is closely related to leucine, a-amino 
 isohexoic acid, and active amyl alcohol to isoleucine, a-amino- 
 /J-methyl-valeric acid, both of which are formed by the hy- 
 drolysis of proteins, and according to Ehrlich both these acids 
 are transformed into the corresponding amyl alcohols under 
 the influence of pure yeast cultures, in the presence of sugar: 
 
 HO 
 
670 XLVIII. FERMENTATION AND ENZYME ACTION 
 
 These changes, although brought about by yeast, do not 
 occur when zymin or yeast extract is used. Other amino 
 acids undergo a similar decomposition : tyrosine (p. 459) yields 
 2?-hydroxy-phenyl-ethyl-alcohol, tyrosol, OH C 6 H 4 CH 2 CH 2 
 OH, and phenyl-alanine (p. 453) gives phenyl-ethyl alcohol. 
 
 The ammonia is not found at the end of the reaction, as it 
 is used up by the organism for the purpose of building up 
 new protein molecules. If appreciable amounts of simple 
 nitrogenous substances, such as ammonium salts, are originally 
 present in the fermenting liquor, the organism uses these in 
 preference to decomposing the amino-acids; and Ehrlich has 
 found it possible to increase or diminish the amounts of fusel 
 oil formed, by diminishing or increasing the amounts of am- 
 monium salts present at the beginning of the fermentation. 
 Practically all amino-acids formed by the hydrolysis of pro- 
 teins can undergo similar decomposition by yeast, but only 
 in the presence of sugar. The succinic acid found as a by- 
 product in alcoholic fermentation is probably formed in a 
 similar manner from glutamic acid. 
 
 According to Neuberg and Fromherz (1911), ketonic acids 
 are probably formed as intermediate products in the fermen- 
 tation of amino-acids to alcohols; and Neuberg has been able to 
 show that many a-ketonic acids, e.g. pyruvic, CH 3 -COC0 2 H, 
 and oxalacetic, C0 2 H CH 2 CO C0 2 H, are readily decom- 
 posed by yeast even in the absence of sugar, yielding carbon 
 dioxide and aldehyde : 
 
 CH 3 .CO.C0 2 H C 
 
 With a 1-per-cent solution of pyruvic acid the decomposition 
 is almost as rapid as with a sugar solution. The decomposi- 
 tion is probably due to an enzyme, termed " carboxylase " by 
 Neuberg. 
 
 For fermentations induced by organisms other than yeasts, 
 see pp. 150, 152, 214. According to Harden (J. C. S. 1901, 
 610), Badllus coli communis ferments glucose, fructose, or 
 mannitol, yielding lactic, succinic, and acetic acids, alcohol, 
 formic acid, carbon dioxide, and hydrogen. The main re- 
 action can be represented by the equation: 
 
 2C 6 H 12 6 + H 2 = 2C3Hs0 3 + C 2 H 4 O 2 + C 2 H 6 + 2C0 2 + 2H 2 . 
 
 With glucose the weight of lactic acid is practically 50 per 
 cent of the sugar, and the alcohol and acetic acid are formed 
 in equal amounts. The alcohol probably comes from the 
 
ENZYME ACTION 671 
 
 group CH 2 (OH) CH(OH), and as this group occurs twice in 
 the molecule of mannitol the yield of alcohol is much greater 
 when this compound is used. The lactic acid is probably 
 derived from the CH (OH) . CH (OH) . CH(OH) grouping. 
 B. typhosus yields similar products, except that it gives formic 
 acid instead of carbon dioxide and hydrogen (Abs. 1906, II, 
 380). 
 
 B. Enzyme Action. Attention has been drawn several 
 times (pp. 76, 77, 423) to the fact that chemical decomposi- 
 tions can be brought about by certain complex organic sub- 
 stances found in animal and plant tissues. Such substances 
 are termed unorganized ferments or enzymes. The great ma- 
 jority act as catalysts in processes of hydrolyses, e.g. invertase 
 which hydrolyses cane sugar, amylase which hydrolyses starch, 
 emulsin (p. 423), myrosin (p. 593), pepsin and trypsin (p. 598), 
 lipases which hydrolyse esters; but in addition there are 
 enzymes which bring about oxidation, viz. the oxidases, 
 enzymes which bring about complex reactions, e.g. zymases. 
 The enzymes are unstable nitrogenous compounds of colloidal 
 nature, but not necessarily proteins. They act as catalysts, 
 in the majority of cases as positive, but in a few as negative. 
 The catalytic nature is shown by the fact that the rate of 
 reaction is directly proportional to the concentration of the 
 enzyme, but that the total decomposition is independent of 
 the amount of enzyme, provided sufficient time is allowed, and 
 provided the enzyme does not undergo decomposition. They 
 are sensitive to high temperatures, e.g. when heated to below 
 100 their activity is completely destroyed; they are, how- 
 ever, resistant towards certain antiseptics which destroy pro- 
 toplasm and kill fermenting organisms. Strong antiseptics, 
 such as formaldehyde, tend to destroy enzymes. Enzymes 
 are often precipitated from their colloidal solutions by the 
 addition of alcohol or acetone, but such products are not pure; 
 in many cases they consist of a mixture of enzymes, and in 
 this way the study of their reactions is complicated. The 
 modern system of nomenclature is to name the enzymes ac- 
 cording to the compounds they hydrolyse, e.g. maltase, sucrase 
 ( = invertase), amylase ( = diastase), &c.^ The nature of 
 the products formed varies not merely with the substance 
 used, but also with the enzyme; thus the trisaccharose, raffi- 
 nose, if hydrolysed by acids, yields galactose, fructose, and 
 glucose; the same carbohydrate with diastase yields melibiose 
 and fructose, and with emulsin galactose and sucrose. The 
 
672 XLVIIL FERMENTATION AND ENZYME ACTION 
 
 action of enzymes is essentially selective, and in this respect 
 differs from the hydrolysing action of alkalis or acids. Thus 
 esters, amides, carbohydrates, glucosides, &c., are all hydro- 
 lysed by hydrochloric acid; whereas esters, but not carbo- 
 hydrates, can be hydrolysed by lipases, and maltose, but not 
 sucrose, can be hydrolysed by maltase. Even a slight differ- 
 ence in the configuration of two isomeric substances is suf- 
 ficient to affect their reactivity with a particular enzyme, e.g. 
 the two methyl-glucosides (p. 659), which are represented by 
 the spatial formulae: 
 
 C-OCHg 
 
 H.C-OH\ 
 
 HO.C.H HO.C.H 
 
 H-C-OH H-C-OH 
 
 CH 2 -OH CH 2 -OH, 
 
 the only difference being the arrangement of the H and OCH 3 
 attached to the upper carbon atom. Of these two compounds 
 the a can be hydrolysed by maltase but not by emulsin, and 
 the ft by emulsin but not by maltase, and hence the names 
 a and p glucase are sometimes used for the two enzymes 
 maltase and emulsin. Numerous other examples of the same 
 type have been met with, especially in the case of polypeptides 
 (Fischer and Bergell, B. 36, 2592; 37, 3103). As most of the 
 natural glucosides are hydrolysed by emulsin but not by mal- 
 tase, they are regarded as analogous to the /3-methyl-glucoside, 
 with complex radicals in place of the methyl group. Maltose 
 on the other hand is an a-glucoside resembling the a-methyl 
 compound in configuration. 
 
 It has been proved in many cases that a particular enzyme 
 can act not merely as a hydrolysing but also as a synthesizing 
 agent. The process of hydrolysis is frequently a balanced 
 reaction, although in the majority of cases the equilibrium is 
 mainly in the direction of analysis and not synthesis. The 
 synthesizing activity of an enzyme was first demonstrated by 
 Croft-Hill (J. C. S. 1898, 634; 1903, 578) in the case of maltase. 
 The greater portion of the maltose is hydrolysed to glucose, 
 but a certain proportion of disaccharose is always present, and 
 
ENZYME ACTION 673 
 
 in a solution of glucose maltase can produce a certain amount 
 of a disaccharose, which at first was thought to be maltose, 
 but has since been proved (E. F. Armstrong, 1905) to be a 
 mixture of maltose and isomaltose. Invertase, lactase, emulsin, 
 and lipases have all been shown to possess synthetical activity. 
 The formation of starch in plant and glycogen in animal 
 tissues is probably largely due to the activities of synthesizing 
 enzymes; and Potterin has succeeded in synthesizing atriolein, 
 one of the common constituents of natural fats, by means of a 
 lipase. 
 
 The rate of hydrolysis by means of enzymes has been 
 studied by different authorities. The investigations of O'Sul- 
 livan and Thompson (J. C. S. 1890, 834) and of Hudson (J. Am. 
 C. S. 1908, 1160, 1564; 1909, 655) prove that the inversion 
 of sucrose by invertase constant values for K can be obtained 
 by using the ordinary equation for a unimolecular reaction, 
 provided that the complications attending the mutarotation 
 of the glucose and fructose (p. 658) are avoided by adding a 
 small quantity of alkali before taking the polarimetric reading. 
 The alkali stops the inversion, and at the same time rapidly 
 brings about equilibrium between the a- and /3-glucoses and 
 the a- and /3-fructoses, so that the normal rotatory power of 
 invert sugar is given. Hudson's results clearly prove that the 
 a-modifications of glucose and fructose are first formed. 
 
 A view generally held with regard to the mechanism of 
 enzyme reaction is that combination (absorption compounds) 
 occurs between the enzyme and the substrate (the substance 
 decomposed), and that it is this compound which reacts with 
 water. The fact that a specific enzyme can hydrolyse only 
 particular substrates is in harmony with this view, as it is 
 known that chemical constitution plays an important part in 
 absorption. In living tissues a number of complex substances 
 are present which are capable of interfering with the action 
 of an enzyme. These are termed anti-enzymes. Some are 
 normally present in tissue, others appear to be formed when 
 an enzyme is injected into the tissue. 
 
674 XLIX. CATALYTIC ACTION 
 
 XLIX. CATALYTIC ACTION OF FINELY -DIVIDED 
 METALS AND METALLIC OXIDES 
 
 Attention has already been drawn to the reduction of 
 carbon compounds by hydrogen gas, using finely -divided 
 metals or metallic oxides as catalysts (p. 610). Within recent 
 years it has been shown that finely-divided solids can act as 
 catalysts in various other reactions. 
 
 Oxidations. One of the most interesting of these is the 
 decomposition of primary alcohols into aldehydes and hydrogen 
 when passed through a tube containing iron, zinc, brass, zinc 
 oxide, ferric oxide, or stannic oxide. At 660 in the presence 
 of zinc, ethyl alcohol gives an 80-per-cent yield of acetalde- 
 hyde, other primary alcohols behave in a similar manner, and 
 isopropyl alcohol gives an almost quantitative yield of acetone. 
 
 The reactions 
 
 Primary alcohol i aldehyde + H a 
 Secondary alcohol ^i ketone -{- H 2 
 
 are reversible in the presence of the catalyst, as an aldehyde 
 and hydrogen when heated in contact with zinc or iron yield 
 an alcohol. When alcohols are heated with hydrogen under 
 pressure, and in contact with zinc or iron, the final products 
 consist mainly of hydrocarbons if the temperature is fairly 
 high, e.g. isoamyl alcohol yields considerable amounts of pro- 
 pane and methane. The formation of these latter is probably 
 due to the following series of reactions : 
 
 (CH 3 ) 2 CH.CH 2 .CH 2 .OH (CH 3 ) 2 CH.CH 2 .CHO + HJJ. 
 (CH 3 ) 2 CH.CH 2 .CHO -* (CH^CH-CHg-f CO. 
 (CH 3 ) 2 CH.CH 3 + H 2 > CH 3 .CH 2 .CH 3 -f CH 4 . 
 
 Reduced benzene derivatives can be oxidized to benzene 
 compounds, but pentamethylene derivatives are not oxidized. 
 Zelinsky shows (B. 44, 3121) that palladium black can also 
 bring about oxidations at about 200-300 e.g. hexamethy- 
 lene benzene (ibid. p. 2302) and gives an example, viz. : 
 methyl-tetrahydro-terephthalate, which is both oxidized and 
 reduced by hydrogen in the presence of palladium black. 
 
 Dehydration. When alcohols are heated at 400-500 in 
 the presence of aluminic oxide (A1 2 8 ) a decomposition into 
 olefine and water occurs, no aldehyde being formed. This 
 appears to be a simple method for obtaining an olefine from 
 
DEHYDRATION 675 
 
 the corresponding alcohol. It has been shown that the alu- 
 minic oxide loses its activity when strongly heated and 
 rendered insoluble in acids or alkalis. Later experiments 
 have shown that when the alcohols are heated under pressure 
 with the oxide, the primary decomposition is into water and 
 an ether, and that at higher temperatures the ether yields an 
 olefine and water: 
 
 2CH 3 .CH 2 .OH (CH 3 -CH 2 ) 2 O + H 2 O (400) 
 (CH 3 .CH 2 ) 2 - 2CH 2 :CH 2 -fH 2 (530). 
 
 This reaction is characteristic of primary and secondary alco- 
 hols, and does not occur in the absence of the catalyst, even 
 when higher temperatures are used. The first reaction is 
 reversible, as ether, under similar conditions, yields a certain 
 amount of alcohol. 
 
 Unsaturated hydrocarbons can also be obtained by the action 
 of aluminic oxide on cyclic alcohols; thus menthol (p. 578) 
 yields menthene. The same catalyst at 200-300 is able to 
 transform ethylene oxide and its homologues into the isomeric 
 aldehydes : 
 
 - CH 3 .CH:a 
 
 A similar change occurs in the absence of the catalyst, but 
 at a higher temperature, viz. 500-600. Bouveault (Bull. Soc. 
 Chim. 1908 [4], 3, 119) finds that good yields of aldehydes 
 can be obtained by passing primary alcohols over copper coils 
 heated by an electric current. Secondary alcohols under 
 similar conditions ' yield ketones and hydrogen, and ketonic 
 alcohols, E.CH(OH).CO-E, yield kiketones, E-CO-CO-E, 
 and hydrogen. 
 
 Unsaturated alcohols undergo molecular transformation and 
 yield saturated aldehydes : 
 
 Numerous other substances, e.g. pumice, animal charcoal, sand, 
 red phosphorus, and aluminic phosphate, can decompose alco- 
 hols into olefines and water, but oxide of aluminium appears 
 to be the best (Senderens, C. E. 1907, 144, 381, 1109). ^ Bou- 
 veault has designed a special apparatus for the preparation of 
 olefines by this method. 
 
 The action of silica as a catalytic agent is extremely char- 
 acteristic. Pure precipitated silica, moderately calcined, decom- 
 
676 XLIX. CATALYTIC ACTION 
 
 poses ethyl alcohol at 280, yielding pure ethylene. After it 
 has been more strongly calcined, it induces decomposition only 
 at a higher temperature, and then yields ethylene and water 
 together with hydrogen and aldehyde. Pulverized quartz can 
 yield as much as 50 per cent of the theoretical amount of 
 hydrogen and 50 per cent of ethylene. Similarly, alumina 
 which has been strongly calcined decomposes part of the 
 alcohol into hydrogen and aldehyde. Experiments made with 
 gypsum (CaS0 4 , 2H 2 0) dehydrated below 400 and with an- 
 hydrite (CaS0 4 ) indicate that the catalytic dehydration of 
 alcohols is effected by substances which are capable of forming 
 temporary hydrates. Thoroughly calcined gypsum or natural 
 anhydrite decomposes alcohol at high temperatures only, and 
 then yields mainly hydrogen and acetaldehyde; on the other 
 hand, gypsum which has been dehydrated at a moderate tem- 
 perature is capable of combining with water, and decomposes 
 alcohol at about 400, yielding ethylene (Senderens, Bull. Soc. 
 Chim. 1908 [41, 3, 197, 633). 
 
 Sabatier and Maihle (Annales, 1910 [viii], 20, 289) have 
 studied the action of the following metallic oxides on primary 
 alcohols, more especially ethanol: Th0 2 , A1 2 3 , Cr 2 3 , Si0 2 , 
 Ti0 2 , BeO, Zr0 2 , U0 2 , Mo 2 5 , Fe.O^ V 2 3 , ZnO, MnO, CdO, 
 Mn 3 4 , MgO. The first four act almost entirely as dehy- 
 drating agents, and at 340-350 give 90-100 per cent yields 
 of olefine and little or no hydrogen. On the other hand, the 
 last five oxides bring about oxidations, and give practically 
 100 per cent of hydrogen and no olefine. BeO and Zr0 2 give 
 approximately equal volumes of hydrogen and olefine, i.e. they 
 are mixed catalysers, as are practically all the intermediate 
 oxides. According to these chemists the activity of finely- 
 divided metals or oxides is due to the formation of unstable 
 additive compounds; e.g. in catalytic oxidations of \mstable 
 hydrides : 
 
 Alcohol 4- metal * metallic hydride + aldehyde 
 Metallic hydride * metal -f- hydrogen, 
 
 such hydrides are readily decomposed, and yield the metal 
 which can react with a further quantity of alcohol. With the 
 readily reducible metals, SnO, CdO, &c., a small amount of 
 metal is formed, and this reacts as above. As the activity 
 does not increase with time, as might be expected as more 
 oxide becomes reduced, it is suggested that the metal gradu- 
 ally becomes less finely divided and hence less active. Oxides 
 
 
FORMATION OF AMINES 677 
 
 which are not readily reduced may form unstable compounds 
 with hydrogen or with the aldehyde. The mechanism of 
 catalytic dehydration does not consist in the formation of 
 unstable hydrates of the catalyst as at first supposed, but 
 in the formation of alkyl salts, formed by the union of the 
 alcohol with the acidic oxide used as catalyst: 
 
 ThO 2 + 2EtOH -* ThO(OEt) 2 + H 2 O 
 ThO(OEt) 2 -> 2C 2 H 4 -f ThO(OH) 2 
 
 ThO(OH) 2 Th0 2 + H 2 0. 
 
 Esterification. Sdbatier and Maihle (C. E. 1911, 152, 494) 
 have shown that Ti0 2 is a good catalyst for the conversion of 
 acids and alcohols into esters. The method is to allow a mix- 
 ture of molecular proportions of the vapour of the two com- 
 pounds to pass over a column of the diDxide kept at 290-300. 
 The yield of ester is about 70 per cent, and the process is 
 extremely rapid. A similar method may be used for hydro- 
 lysing esters, e.g. allowing a mixture of the ester vapour with 
 an excess of steam to pass over the dioxide at 280 -300. 
 Similar results are obtained with thorium oxide, provided 
 aromatic acids are used. 
 
 Formation of Amines, Thiols, Ketones. Amines are formed 
 when a mixture of an alcohol and ammonia is passed over 
 thorium dioxide at 350-370 (C. E. 1909, 148, 898); thiols 
 (mercaptans) are formed when a mixture of alcohol and hy- 
 drogen sulphide is passed over the dioxide at 300-360 (C. E. 
 1910, 150, 1217, 1569). The yields are especially good with 
 primary alcohols, and even phenol gives a 17-per-cent yield 
 of thiophenol at 430-480; and metallic sulphides, especially 
 CdS, at 320-330, decompose thiols into alkyl sulphides and 
 hydrogen sulphide. Ketones can be prepared by the action of 
 acid anhydrides or acids on thorium dioxide at 400 (Senderens, 
 C. E. 1909, 149, 213, 995; 1910, 150, 111, 702, 1136). Simple 
 and mixed aliphatic ketones and mixed aromatic aliphatic 
 ketones have been prepared, the mixed ketones by using mix- 
 tures of two acids. Aromatic acids containing the carboxylic 
 group attached to the benzene nucleus do not react unless 
 mixed with an aliphatic acid, but acids of the type of phenyl- 
 acetic do. The reaction probably consists in the formation 
 of a salt and its subsequent decomposition into ketone, cap 
 bon dioxide, and water. 
 
 Formic acid behaves somewhat differently from the other 
 fatty acids (Sdbatier and Maihle, C. E. 1911, 152, 1212). Finely 
 
67$ 1* tTNSATTTRATIOtf 
 
 divided Pd, Pt, Ni, Cu, Cd, and ZnO or SnO decompose it 
 into carbon dioxide and hydrogen. Ti(X and W 2 5 yield 
 water and carbon monoxide, and Si0 2 , Zr0 2 , AlgOg, &c., give 
 both reactions. 
 
 L. UNSATURATION 
 
 A. Types of Unsaturation. Unsaturated compounds are 
 usually defined as those which are capable of uniting with 
 another substance (element or compound) without disruption 
 of their original structure. Two main types of such com- 
 pounds have been dealt with in the previous chapters. 
 
 I. Cases in which the addenda unite with two different 
 atoms of the original compound. Such are the compounds 
 supposed to contain double or triple linkings between C and 
 C, C and 0, and S, C and N, N and N, as seen in the 
 groups of olefine and acetylene derivatives, carbonyl com- 
 pounds, thiocarbonyl derivatives, nitriles and Schiff's bases, 
 azo-com pounds. 
 
 II. Cases in which the addenda unite with one and the 
 same atom of the original compound, as in the conversion of 
 amines into salts and quaternary ammonium compounds, the 
 formation of oxonium salts from ethers, &c., and the formation 
 of sulphonium salts from alkyl sulphides. 
 
 The presence of such unsaturated groups as amino and 
 hydroxyl, and also the alkylated groups, -NHK, 'NK 2 , .OR, 
 produce marked effects on* the properties of the compounds 
 into which they are introduced. In the aromatic series they 
 render the compounds much more reactive towards reducing, 
 oxidizing, and substituting reagents (cf. p. 409). When fur- 
 ther substituents are introduced, e.g. Cl, Br, S0 3 H, N0 2 , &c., 
 these almost invariably take the ortho and para positions 
 with respect to the unsaturated group. These groups also 
 tend to make the compound luminesce under the influence 
 of electric discharges under small pressures. They are also 
 the most powerful auxochromes known; i.e. when introduced 
 into a compound containing chromophores, such as, 'N:N, 
 C:0, C:C, N0 2 , &c., they produce a deepening of the colour 
 of the compound. 
 
 In examples of the first type the question as to whether 
 addition or not takes place depends upon a variety of factors. 
 
PROPERTIES OF UNSATURATED ACIDS 679 
 
 (1) Whether the double linking is between C and C, C and 0, 
 C and N, or N and N. Thus although both olefines and 
 carbonyl derivatives combine with hydrogen, the first group 
 adds on bromine readily, whereas the second does not; and 
 the second combines with hydrogen cyanide or sodium bi- 
 sulphite more readily than the first group does. (2) The 
 nature of the groups already attached to the two atoms which 
 are united by the double linking. Thus although most olefine 
 derivatives combine with bromine, compounds in which there 
 are several negative groups, such as Ph, Br, CN, C0 2 H, 
 already attached to the two carbon atoms, do not form addi- 
 tive compounds with bromine (Hugo and Bauer, B. 37, 3317), 
 although they contain an olefine linking. (3) The nature of 
 the addenda. It has been pointed out already (p. 44) that 
 chlorine combines most readily and iodine least readily, but 
 that hydrogen iodide combines more readily than hydrogen 
 chloride or bromide. (4) Conditions of the experiment, e.g. 
 nature of solvent, sunlight, temperature, presence of a catalyst, 
 &c. Phenyl-propiolic acid does not combine with hydrogen 
 chloride when in aqueous solution below 80. 
 
 B. Properties of TTnsaturated Acids as affected by the 
 position of the Double Bond. Acids which contain a double 
 bond in the a/3 position differ in many respects from isomeric 
 acids in which this bond is further removed from the car- 
 boxylic group. 
 
 The (ip unsaturated acids are reduced much more readily 
 than their isomerides by sodium amalgam and water. This 
 is somewhat remarkable, since in the case of other additive 
 reactions, for example, the addition of bromine, the aj3 un- 
 saturated acids are less reactive, i.e. do not combine with 
 bromine so readily as /3y unsaturated acids or other acids 
 in which the double bond is far removed from the carboxyl 
 group (Sudborvugh and Thomas, J. C. S. 1910, 715, 2450). The 
 readiness with which aft unsaturated acids can be reduced 
 may perhaps be accounted for by the presence of the con- 
 jugated double bonds (cf. p. 681) 
 
 R.CH:CH.C:6 + 2H R.CH 2 .CH:C.OH -* R.CH 2 .CH 2 .C:O 
 OH OH OH 
 
 1:4 addition takes place, but the resulting unsaturated glycol 
 is unstable and, by a wandering of an atom of hydrogen, yields 
 the saturated acid. 
 
680 L. UNSATURATION 
 
 /. Bougault (C. E. 1905, i. 9) shows that /3y unsaturated 
 acids combine with the elements of hypoiodous acid (HIO), 
 yielding lactones, whereas the isomeric a/3 acids do not. This 
 provides the basis of a method for separating a mixture of an 
 a/3 and /3y unsaturated acid. 
 
 One of the best methods of separating a mixture of a/3 and 
 /3y unsaturated acids is due to Fittig (B. 1894, 27, 2667: A. 
 1894, 283, 51), and consists in heating the acids for a few 
 minutes at 140 with a mixture of equal volumes of concen- 
 trated sulphuric acid and water. The a/3 acid is unaffected 
 by this treatment, whereas the /3y acid is converted into a 
 y-lactone (p. 217) which is insoluble in sodium carbonate 
 solution. 
 
 (CH 3 ) 2 C:CH.CH 2 .CO.OH 
 
 When this method is used only the a/3 acid can be re- 
 covered. A method by means of which both acids can be 
 recovered is the separation by fractional esterification, as an 
 a/3 acid is esterified much less readily than isomeric unsatu- 
 rated acids (Sudborough and Thomas, J. C. S. 1911, 2307). 
 
 One of the best methods for determining the position of the 
 double bond in the case of an olefine acid is by an examination 
 of the oxidation products (p. 162). These consist, as a rule, 
 of a mixture of a monobasic and a dibasic acid, as the carbon 
 atoms between which the olefine bond functionated both yield 
 carboxylic groups; e.g. K'CH:CH.CH 2 .C0 2 H gives K-C0 2 H 
 and C0 2 H.CH 2 .C0 2 H. Cf. also Oleic acid, p. 165. 
 
 Dimethylacrylic acid, (CH 3 ) 2 C : CH C0 2 H, when oxidized 
 yields acetone, (CH 3 ) 2 CO, and oxalic acid or its oxidation 
 product carbonic acid. 
 
 The conversion into ozonides and the decomposition of these 
 (p. 624) is also used for the determination of the position of 
 the double linking. 
 
 Another method adopted for determining the position of an 
 olefine bond is by an examination of the hydrobromide. If 
 the bond is in the a/3 position the bromo-derivative of the 
 saturated acid loses hydrogen bromide when treated with 
 alkali and yields the original olefine acid. 
 
 CH 3 .CH:CH.C0 2 H * CH 3 .CHBr.CH 2 .C0 2 H 
 
 Crotonic acid /3-Bromobutyric acid 
 
 CH 3 .CH:CH.C0 2 H. 
 
 Crotonic acid. 
 
CONJUGATE DOUBLE BONDS 681 
 
 A /3y or 78 unsaturated acid also yields a hydrobromide, 
 but when this is treated with alkalis hydrogen bromide is 
 eliminated and a lactone formed. 
 
 CH S .CH:CH.CH 2 .CO 2 H 
 
 The presence of olefine linkings, as in maleic anhydride, in- 
 creases to an appreciable extent the readiness with which the 
 anhydride combines with water (Eweit and Sidgwick, J. C. S. 
 1910, 1677). 
 
 An extremely simple method of determining whether the 
 double bond is in the a/2 position or not, is by an examination 
 of the rate of esterification of the unsaturated acid and of 
 its saturated analogue by the catalytic method. If the un- 
 saturated acid has a much lower rate of esterification than its 
 reduction product the conclusion may be safely drawn that 
 the double bond is in the a/2 position, as /3y unsaturated 
 acids are esterified somewhat more quickly than their satu- 
 rated analogues, and acids in which the double bond is still 
 further removed from the carboxyl group have much the 
 same esterification constants as the corresponding saturated 
 acids (Sudborough and Gittins). 
 
 For the stereochemistry of compounds containing only one 
 ethylene linking, cf. p. 243. When two or more olefine bonds 
 are present in the molecule, the isomerism is more complex. 
 Not merely can we have structural isomerides, which differ in 
 the relative positions of the olefine linkings, but also the num- 
 ber of stereoisomerides increases. 
 
 For compounds of type, Cab:C:Cab, see p. 634. 
 
 C. Compounds with Conjugate Double Bonds. One of the 
 most interesting groups containing two double linkings are the 
 compounds with conjugate double bonds. Within recent years 
 numerous experiments have been made with compounds con- 
 taining two double bonds in the relative positions indicated by 
 the formula 
 
 E.CH:CH.CH:CH.E. 
 
 These have been termed conjugated double bonds by Thiele, 
 and extremely interesting results have been obtained by the 
 study of the additive reactions of such compounds. It is 
 
and 
 
 682 L tJNSATtJRATtotf 
 
 found that the atoms or radicals added on do not, as a rule, 
 become simply attached to the carbon atoms 1 and 2 or 3 and 
 4, but to numbers 1 and 4; so that a new ethylene linkage is 
 created in position 2 : 3. Thus cinnamylideneacetic and cinna- 
 mylidenemalonic acids when reduced yield l:4-dihydro-deriva- 
 tives (Ruber, B. 1904, 37, 3120) 
 
 C 8 H 6 .CH:CH.CH:CH.C0 2 H + 2H 
 
 -* C 6 H 6 .CH 2 .CH:CH.CH 2 .C0 2 H 
 
 C 6 H 6 .CH:CH.CH:C(C0 2 H) 2 + 2H 
 
 -* C 6 H 5 .CH 2 .CH:CH.CH(C0 2 H) 2 . 
 
 Sorbic acid (p. 166) yields CH 3 .CH 2 .CH:CH.CH 2 .C0 2 H: 
 similarly butadiene, CH 2 : CH CH : CH 2 , reacts with bromine, 
 yielding l:4-dibromo-A 2:3 -butene, CH 2 Br . CH : CH . CH 2 Br. 
 Similar results have been obtained when the double bonds 
 are between carbon and oxygen; thus benzil, 
 
 6:C(C 6 H 6 ).C(C 6 H 6 ):6, 
 
 when reduced under special conditions yields OHC(C 6 H 6 ): 
 C(C 6 H 5 )-OH a/3-dihydroxy-stilbene. 
 
 That additions do not always take place in the 1 : 4-positions 
 is shown by the following examples: Methyl cinnamylidene- 
 malonate adds on bromine in the 3: 4-positions and yields 
 C 6 H 5 CHBr CHBr . CH : C(C0 2 Me) 2 (Henrichsen and Triepel, 
 A. 1904, 336, 223). The addition of potassium hydrogen sul- 
 phite to cinnamylidenemalonic acid occurs in the 1 : 2-position, 
 and the product is 
 
 C 6 H 6 CH : CH CH(SO S K) . CH(C0 2 H) 2 
 
 (Kohler, Am. 1904, 31, 243); similarly with hydrogen cyanide. 
 Unsaturated aldoximes and ketoximes when reduced yield un- 
 saturated amines, indicating that the addition of hydrogen 
 
 K-CHiCH-CHiN-OH -f 4H 
 
 + R.CH:CH.CH 2 -NH 2 -f H 2 O 
 
 occurs in the 1: 2-position (Harries, A. 1903, 330, 193); a/3 
 unsaturated ketones also add on sulphinic acids in the 1:2 
 (carbonyl) position (Am. 1904, 31, 163). s-Diphenylbuta- 
 diene, CHPh:CHCH:CHPh, also adds on bromine in the 
 1 : 2-position. 
 
 Thick (A. 1889, 306, 87) has attempted to account for the 
 
DIVALENT CARBON 683 
 
 characteristic l:4-addition of most of the compounds with 
 conjugated double bonds by his theory of partial valencies. 
 
 It is supposed that when two atoms are united by a double 
 bond the whole of the energy of the atoms is not used up, but 
 that there is a slight residual affinity or partial valency which 
 Thiele denotes by dotted lines, e.g.\ 
 
 ECH:CHK. 
 
 He considers the power of forming additive compounds is due 
 to the presence of such partial valencies. 
 
 Now in a system with two double bonds in positions 1:2 
 and 3:4 there are four partial valencies, and according to 
 Thiele two of these, viz. 2 and 3, are supposed to have neu- 
 tralized one another and only 1 and 4 are active. This is 
 usually represented by the formula 
 
 K.CH:CH.CH:CH.K, 
 
 and hence the usual 1 : 4-addition with compounds containing 
 conjugated double bonds. Thiele's theory does not account for 
 the numerous exceptions mentioned above. 
 
 Probably it is simpler to regard the compound as containing 
 4 residual valencies in the 1, 2, 3, 4 positions, and to conclude 
 that the question as to which of these will be used up in the 
 formation of an additive compound depends largely on the 
 nature of the addenda and the nature of the groups already 
 attached to the atoms numbered 1, 2, 3, and 4. 
 
 The reaction between compounds with conjugated double 
 bonds and Grignard's reagents consists in many cases of 1:4- 
 addition. See Kohler (Am. 1904, 31, 642; 1905, 33, 21, 35, 
 153, 333; 34, 568; 1906, 35, 386; 36, 177, 529; 1907, 37, 
 369; 38, 511; 1910, 43, 412, 475). 
 
 D. Compounds of Di- and Trivalent Carbon. Carbon 
 monoxide may be written either as C:0 or CjO. In the 
 first formula both carbon and oxygen atoms are represented 
 as being divalent, and in the latter formula both are tetra- 
 valent. It has been argued that the formula, C:0, is prob- 
 ably the correct one, as when the monoxide forms additive 
 compounds the two addenda become attached to carbon 
 and not one to carbon and one to oxygen. Thus with 
 
 chlorine we get carbonyl chloride, 0:C<CQj, the constitution of 
 
684 L. tJNSATURATION 
 
 which is determined by the fact that it reacts with alcohol, 
 forming ethyl chloro-carbonate and finally ethyl carbonate, 
 0:C(OEt) 2 . With sodium hydroxide carbon monoxide gives 
 rise to sodium formate: 
 
 0:C-hNaOH = O:C 
 
 and with hydrogen chloride it yields the unstable formyl 
 chloride, OlCxpi. Although vapour-density determinations 
 
 indicate that in a mixture of the two gases very little com- 
 bination has taken place, yet Gattermann 's synthesis of acid 
 chlorides, by the action of a mixture of carbon monoxide and 
 hydrogen chloride on aromatic compounds in the presence 
 of aluminium chloride, proves that a small amount of an addi- 
 tive compound exists, and that its structural formula is the 
 one represented above. 
 
 Carbylamines. On p. 104 the conclusion has been drawn 
 that in the carbylamines (alkyl isocyanides) the alkjd group 
 must be attached* to nitrogen and not to carbon, and therefore 
 they are to be represented as R-N-C or RN:C. In the 
 latter formula the carbon atom is represented as being di- 
 valent, and the arguments used in support of this formula are 
 similar to those used in the case of carbon monoxide, viz. the 
 two addenda invariably unite with the carbon atom and not 
 one with carbon and one with nitrogen. The following ex- 
 amples can be given: (a) with chlorine: RN:CC1 9 ; (b) with 
 
 /COPh 
 acyl chlorides: RN:C<\ ; (c) with hydrogen sulphide: 
 
 R-NrCH.SH = R.NH-CH:S (an alkylated thioformamide) ; 
 (d) with oxygen: RN:C:0, alkyl isocyanates; (e) with sul- 
 phur: R-N:C:S, mustard oils; (/) with Grignard reagents: 
 
 T? ttf'C*/' . ~R "Nr-r*^ 
 N ' C \MgI n.,0 E N ' C \H' 
 
 an imino- derivative which is hydrolysed to an aldehyde, 
 0:CH.R; (g) with ethyl hypochlorite. Cf. Nef, A. 287, 273. 
 Metallic Cyanides. Both nitriles and carbylamines are 
 alkyl derivatives of hydrogen cyanide, and can be obtained 
 by the action of alkyl iodides or potassium alkyl sulphates on 
 different metallic cyanides, e.g. potassium cyanide and ethyl 
 iodide yield ethyl cyanide, whereas the same iodide with 
 silver cyanide yields mainly ethyl carbylamine. Although 
 two series of alkyl derivatives exist> only one hydrogen 
 
METALLIC CYANIDES 685 
 
 cyanide is known. Certain of its reactions point to the nitrile 
 structure H-C-N, and others to the carbylamine formula 
 HN:C; it is a typical tautomeric substance. The view gene- 
 rally held with regard to the metallic cyanides is that they 
 have a carbylamine structure. The arguments used are briefly 
 as follows: (1) The similarity between the additive reactions 
 of metallic cyanides and those of carbylamines (a) with 
 bromine potassium cyanide yields potassium bromide and 
 cyanogen bromide; although an additive compound cannot 
 be isolated, the reaction is in complete harmony with the view 
 that an unstable compound, 
 
 is formed which breaks up into KBr and N C Br; (b) po- 
 
 tassium cyanide and benzoyl chloride yield benzoyl cyanide, 
 N C CO CgH 5 , but here again an additive compound, 
 K N : CC1 COC 6 H 5 , is probably first formed; (c) potassium 
 cyanide combines with oxygen and sulphur in much the same 
 manner as the carbylamines; (d) with ethyl hypochlorite a 
 compound, HN : C(OEt) CN, ethyl cyano-imino- carbonate, is 
 formed. The reaction can be represented as follows: 
 
 K-NiC K-NiCCl-OEt K-N:C(OEt).CCl:NK 
 
 -* KCl + K.N:C(OEt).CN. 
 
 (2) Both alkyl carbylamines and alkali cyanides dissolve 
 silver cyanide yielding double salts, whereas alkyl cyanides 
 do not. (3) Tetramethylammonium cyanide, which probably 
 has a constitution similar to that of the metallic cyanides, 
 yields trimethylainine and methylcarbylamine when heated. 
 This last argument by itself is of but little value, as a com- 
 paratively high temperature is required and molecular rear- 
 rangements could occur. 
 
 Reactions of Metallic Cyanides. Formation of Nitriles 
 and Carbylamines. The following reactions occur: 
 
 HI 
 
 '->.':. . -, - alkyl cyanides, K-C:N 
 
 Potassium cyanide _ acyl cyanides, K- CO- C:N. 
 B-COCl 
 1 
 
 . , alkyl carbvlamines, E,N:G 
 
 Silver cyanide _ acy { 
 
 B.-COC1 
 
686 L. UNSATURATION 
 
 The reactions cannot be due to the tautomerism of silver 
 cyanide, as no cases are known where a heavy atom like 
 silver can wander. The view that carbylamines are first 
 formed by simple exchange in all cases, and then in three 
 of the four reactions the carbylamine becomes transformed 
 into a nitrile, is untenable, as carbylamines cannot be trans- 
 formed into nitriles. The reverse process is also improbable, 
 as carbylamines are formed from nitriles at high temperatures 
 only. 
 
 The views of Nef(A. 287, 274) as modified by Wade (J. C. S. 
 1902, 1596) are that in all four cases additive compounds are 
 first formed. When the metallic radical in the cyanide is 
 feebly positive, then feebly positive alkyl compounds combine 
 with N, but negative acyl derivatives combine with C. With 
 a strongly positive metallic atom in the cyanide, e.g. KCN, 
 both alkyl and acyl derivatives combine with N. Thus with 
 AgNC and EtI we have addition to N. Similarly with EtNC 
 and EtI; but with AgNC and AcCl, and EtNC and AcCl, 
 we have addition to C. With KNC and EtI and also with 
 KCN and AcCl the addition is to C. 
 
 K-NiC + Etl K.N:C< fc -> KI-fN:CEt 
 
 Ag.N: 
 
 Ag-N:C-fAcCl Ag-NiCK^ AgCl + N-C-Ac. 
 
 It may appear remarkable that in reaction 2 the alkyl 
 iodide adds on to the nitrogen atom and leaves the carbon 
 divalent. Nef assumed that the conversion of the silver salt 
 into carbylamine was an example of direct displacement, but 
 Wade proves that dry silver cyanide is able to absorb methyl 
 iodide at its boiling-point, yielding a viscid mass which evolves 
 methylcarbylamine when more strongly heated. The consti- 
 tution of this additive compound is based on a study of the 
 products from alkyl iodides and aikylcarbylamines ; when 
 hydrolysed these compounds yield small amounts of secondary 
 amines, and hence, according to Wade, must be represented as: 
 
 Me-N:C 
 
 and similar formulae are given to the products from silver 
 cyanide and alkyl iodides. 
 
METALLIO CYANIDES 687 
 
 Sidgivick (P. 1905, 120) concludes that in all cases addition 
 takes place at the carbon atom: 
 
 where M represents either K or Ag. Such a compound con- 
 tains the grouping: 
 
 characteristic of the oximes of aldehydes and of unsymmetri- 
 cal ketones (cf. pp. 137, 428), and can therefore exist in syn- 
 and anti- configurations. Potassium cyanide is supposed to 
 yield the sytt-compound : 
 
 E.C.I 
 
 which readily loses potassium iodide, as both metal and halo- 
 gen are on the same side of the molecule, and thus yields 
 a nitrile. Silver cyanide, on the other hand, yields the anti- 
 compound: 
 
 E-C-I 
 
 Ag-N. 
 
 Silver iodide is not readily split off, as the metal and halogen 
 are now on different sides of the molecule. It therefore 
 undergoes the Beckmann transformation (p. 429), yielding: 
 
 Ag-C.I 
 E.N ' 
 
 which loses silver iodide and forms C:NE, an alkyl carbyl- 
 amine. 
 
 Although the metallic cyanides are usually represented 
 by a carbylamine structure, it does not follow that hydrogen 
 cyanide is to be represented in a similar manner. Arguments 
 based on a study of its physical and chemical properties have 
 been brought forward; some point to the one, and others to 
 the alternative formula, but probably, on the whole, the pro- 
 perties are more in harmony with the nitrile structure, HC|N. 
 It is possible that it may be, like the tautomeric substance, 
 ethyl acetoacetate, a mixture of the two compounds but mainly 
 nitrile. (For summary see Sidgwick, " The Organic Chemistry 
 of Nitrogen", p. 209.) 
 
 J?ulminic acid, C ; N OH, is known chiefly in the form of its 
 
688 L. UNSATURATION 
 
 silver and mercury salts. The latter was first prepared in 
 1800 by Howard, by the action of alcohol and nitric acid on 
 mercuric nitrate. It crystallizes in lustrous prisms, explodes 
 with great violence when heated or struck, and is largely used 
 in the manufacture of percussion caps, dynamite cartridges, 
 &c. In 1824 Gay-Lussac and Liebig showed that the silver 
 salt had the same percentage composition as silver cyanate, 
 and thus afforded one of the first examples of isomerism. 
 They also showed that double salts, e.g. KAg(CNO) 2 , could 
 be obtained. Various formulae have been proposed. KekuU 
 suggested the formula N0 2 CH 2 .CN, riitroacetonitrile; Holle- 
 mann suggested a glyoxime peroxide formula, 
 
 CH CH 
 
 N.O-O-N ; 
 
 and Steiner in 1883 the formula OH.N:C:C:N.OH, di-iso- 
 nitroso ethylene. It will be noticed that all these formulae 
 represented the molecule as containing two carbon atoms. 
 The reasons for this were: (1) It is obtained from ethyl alcohol. 
 (2) With bromine or iodine it yields ethane derivatives. (3) As 
 it forms double salts the acid was thought to be dibasic. 
 Various arguments were brought forward in favour of and 
 against the first two formulae, but the question has been 
 definitely decided by the preparation of nitroacetonitrile 
 (Steinkopf and Jjohrmann, B. 41, 1044) and of glyoxime per- 
 oxide (Jomtschitsch, A. 347, 233), and showing that they 
 differ from fulminic acid. The main argument in favour of 
 Steiner's formula is that fulminates yield hydroxylamine when 
 treated with concentrated hydrochloric acid, just as V. Meyer 
 had previously shown that oximes do. Steiner was able to 
 prove that the whole of the nitrogen can be removed in this 
 way in the form of hydroxylamine, and also that formic acid 
 is the second product: 
 
 C 2 H 2 O 2 N 2 + 4H 2 O 2H 2 CO 2 + 2NH 2 OH. 
 
 Such a reaction proved that KekuU's formula could not be 
 correct. 
 
 In 1894 Nef (A. 280, 303) suggested the simple formula 
 C:NOH, now generally accepted, which represents the acid 
 as the oxime of carbon monoxide. The following arguments 
 were adduced: (1) By the action of one equivalent of hydrogen 
 chloride on one of the silver salt, no trace of silver chloride is 
 formed, but an additive product, which was shown to be the 
 
FULMINATES G89 
 
 chloride of formhydroxamic acid, or formyl- chloride oxime, 
 C1CH:N.OH. This forms colourless crystals volatile at the 
 ordinary temperature, and decomposes readily. With aniline 
 it yields formanilide oxime, NHPh.CHrN.QH or NPh:CH- 
 NH'OH. (2) It can be synthesized from a compound con 
 taining one carbon atom, namely nitromethane. The mercuric 
 salt of nitromethane, when heated with water, yields water 
 and mercury fulminate: 
 
 CH 2 :NO-OM H 2 O + C:N.OM. 
 
 (3) With nitrous acid it yields methylnitrolic acid (p. 96). 
 C:N.OH + H.N0 2 NO 2 -CH:N.OH. 
 
 (4) According to Schott (B. 32, 3492; 36, 10, 322, 648), when 
 benzene is treated with mercury fulminate and a mixture of 
 anhydrous and hydrated aluminium chloride, benzaldoxime is 
 formed (70 per cent). The water of the hydrated chloride 
 liberates hydrogen chloride, which combines with the fulmi- 
 nate, yielding the additive compound, OMN:CHC1, which 
 then condenses with the benzene in the manner of the Friedel- 
 Crafts reaction, yielding C 6 H 5 CH:N'OM, from which the 
 free oxime is liberated by means of mineral acid. 
 
 The hydrolysis of a fulminate to formic acid and hydroxyl- 
 amine by means of hydrochloric acid is almost undoubtedly 
 preceded by the formation of an additive compound: 
 
 OH.N:CH.C1 + H 2 O OH-NzCH-OH 
 OH.N:CH.OH + H 2 _* O:CH.QH + NH 2 OH. 
 
 Free fulminic acid can be obtained by the action of an ex- 
 cess of sulphuric acid on a solution of potassium fulminate and 
 extraction with ether. It volatilizes with the ether when this 
 is distilled, and readily polymerizes to meta-fulminic acid. Nef 
 has pointed out the remarkable analogy between hydrogen 
 cyanide and fulminic acid. No direct estimations of the mole- 
 cular weight of fulminic acid have been made, but an indirect 
 determination by L. Wohler (B. 1905, 38, 1351) points to the 
 simple formula HCNO. The method is based upon the deter- 
 mination of the value of van't Hofs dissociation factor i for the 
 sodium salt in 0'2 to O'l Absolution. The value was found to 
 be 1 -85, the usual value for the salt of a monobasic acid. Also 
 the increase in molecular conductivity in passing from N/32 to 
 JV/1024 solution was found to be 5 units, corresponding with 
 Ostwald's value 4-8 for the salt of a monobasic acid. 
 
 (B480) 2X 
 
690 L. UNSATURATION 
 
 The following has been suggested by Wieland as the prob- 
 able course of the reaction in the preparation of a fulminate 
 from ethyl alcohol: Oxidation to acetaldehyde, formation of 
 isonitroso - acetaldehyde, oxidation to isonitroso - acetic acid, 
 HO N : CH C0 2 H, nitration to nitro-isonitroso-acetic acid, de- 
 composition into carbon dioxide and methylnitrolic acid, con- 
 version of methylnitrolic acid into nitrous and fulminic acids. 
 
 A polymer of fulminic acid, known as fulminuric acid, has 
 been shown to be cyanonitroacetamide, 
 
 NO 2 CH(CN) CO . NHa. 
 
 Tervalent Carbon: Triphenyl- methyl. In attempting to 
 prepare hexaphenylethane by the action of finely divided silver 
 or zinc on triphenylchloromethane in benzene solution, Gom- 
 berg (J. Am. 1900, 22, 757) obtained a substance which con- 
 tained oxygen, but in the absence of air the product was free 
 from oxygen, and when the solution was carefully evaporated 
 a compound with pronounced unsaturated properties was iso- 
 lated. It combines vigorously with oxygen, yielding the 
 peroxide, CPhg-O-O-CPhg, m.-pt. 185-186, which is trans- 
 formed by sulphuric acid into triphenylcarbinol ; it also com- 
 bines with iodine, yielding triphenyliodomethane, and forms 
 additive compounds with ethers, ketones, esters, nitriles, &c. 
 It was suggested that these properties pointed to the formula, 
 CPh 3 , for the hydrocarbon, a formula which contains a ter- 
 
 valent carbon atom. The corresponding ion, CPh 3 , appears to 
 be formed when triphenylchloromethane is dissolved in liquid 
 sulphur dioxide, as such solutions are good conductors of the 
 electric current. Molecular weight determinations by the cryo- 
 scopic method point to the double formula, (CPh 3 ) 2 , for the 
 hydrocarbon. Tschitschabin (B. 37, 4709) has suggested that the 
 product is hexaphenylethane, and has supported this conclusion 
 by a study of the properties of pentaphenylethane, which is 
 somewhat unstable and readily attacked by oxygen, and is 
 completely ruptured by hydrochloric acid at 150. Quinonoid 
 formulae have also been suggested, the symmetrical formula I 
 by Heintschel (B. 36, 320, 579), and formula II by Jacobson 
 (B. 37, 196): 
 
 (I) CPh 2 :0<g|:>CH.CH<:gg>C:CPh 2 
 (II) 
 
KETENS 691 
 
 According to Schmidlin (B. 41, 2471) two forms of triphenyl- 
 methyl exist, a colourless and a yellow. When freshly dis- 
 solved in benzene the solution is colourless but changes 
 gradually to orange-yellow. The colour is destroyed by 
 shaking the solution with air, but returns again on standing, 
 and it is argued that the yellow form reacts with air more 
 readily than the colourless compound. In solution there is an 
 equilibrium between the colourless and coloured forms, and 
 the equilibrium is displaced in favour of the colourless by 
 lowering the temperature. The general view is that the 
 equilibrium may be represented by the equation: 
 
 CPh 3 .CPh s ^ 2CPh 3 ; 
 Colourless Yellow 
 
 and this view is supported by Wieland (B. 42, 3020), who 
 shows that in naphthalene solution, which contains more of 
 the yellow form than the benzene solution does, the molecular 
 weight is much less than that required by the formula (CPh 3 ) 2 , 
 indicating that the yellow compound presumably has the com- 
 position CPh 3 . Schlenk, Weickel, and Herzenstein (A. 372, 1) 
 have prepared a tri-diphenylmethyl, C(C 6 H 4 C 6 H 6 ) 3 , by the 
 action of finely divided copper on tri-diphenylchloromethane, 
 and have been able to show that in solution it is monomole- 
 cular. The corresponding bimolecular form is not known. 
 Its solutions have a deep-violet colour, and it reacts readily 
 with oxygen, giving a colourless peroxide. Corresponding 
 diphenyl-diphenylmethyl, CPh 2 C 6 H 4 Ph, and phenyl-di 
 diphenylmethyl, CPh(C 6 H 4 'Ph) 2 , have been prepared; they 
 exist in both coloured and colourless modifications. 
 
 Just as colourless hexaphenylethane tends to break up into 
 coloured triphenylmethyl, so pentaphenylethane when heated 
 in anisole solution in absence of air breaks up into CPh 3 
 (yellow) and CHPh 2 ; the formation of the latter is proved by 
 the formation of tetraphenylethane due to the union of two 
 CHPh 2 radicals. 
 
 E. Ketens. Wilsmore (J. C. S. 1907, 91, 1938; 1908, 93, 
 946) has isolated the simplest possible ketone, CH 2 :CO, which 
 he terms keten, and which may be regarded as a new [anhy- 
 dride of acetic acid. It is obtained by the action of a hot pla- 
 tinum wire on acetic anhydride; numerous other substances 
 are formed at the same time, but a 10-per-cent yield is obtained. 
 It is a colourless gas at the ordinary temperature, has a char- 
 acteristic odour, and reacts with hydrogen chloride, ammonia, 
 
692 L. UNSATURATION 
 
 and aniline, yielding acetyl chloride, acetamide, and acetanilide 
 respectively. When kept for some time it polymerizes, yield- 
 
 ing cyclohutane-l:3-dione, CH 2 <^Q>CH 2 , b.-pt. 126-127, 
 
 which combines with water to acetoacetic acid (p. 226), and 
 with aniline to acetoacetanilide (J. C. S. 1910, 1978). 
 
 Homologues of keten, e.g. dimethyl-keten, (CH 3 ) 2 C : CO, and 
 diphenyl-keten, (C 6 H 5 ) 2 C:CO (Staudinger, B. 1905, 38, 1735; 
 1906, 39, 968; 1907, 40, 1145, 1U9), have also been prepared. 
 The method consists in the action of zinc on a-bromoisobutyryl 
 bromide and diphenyl-chloroacetyl chloride respectively. The 
 compounds are unstable and readily polymerize. Dimethyl- 
 keten forms stable compounds with tertiary amines, and with 
 water, alcohol or amines give isobutyric acid, its ester or 
 amide : 
 
 CMe 2 C:CO + HX 
 
 The presence of a keten group, CHg'CO', is of great impor- 
 tance in the syntheses of numerous cyclic compounds (cf. Collie, 
 J. C. S. 1907, 91, 1806). 
 
 The homologues are frequently divided into (a) aldoketens, 
 (b) ketoketens. The aldo group comprises keten, its mono- 
 alkyl substituted derivatives, and carbon suboxide. They are 
 colourless, incapable of autoxidation, and are polymerized by 
 pyridine. The keto group consists of the dialkylated deriva- 
 tives. These are coloured, readily undergo autoxidation, and 
 form additive compounds with tertiary amines, such as pyri- 
 dine, quinoline, and acridine. These products from dialkyl 
 ketens and tertiary amines are stable and have basic pro- 
 perties; they contain two molecules of keten combined with 
 one of the base, and the compound with quinoline is repre- 
 sented as H 
 
 CH 
 
 CO.CMe 2 .CO-CMe 2 
 
 (A. 1910, 374, 1). They also form additive compounds with 
 substances containing the groupings C:N and C:0, for ex- 
 ample Schifs bases and quinones. Diphenyl keten and qui- 
 
 none yield the /3-lactone, : C 6 H 4 CO, which decom- 
 
 poses into C0 2 and : C 6 H 4 : CPhg, diphenyl-quinomethane, 
 when heated (Staudinger, B. 1908, 906, 1355, H93). 
 
tJNSATtJRATION AND PHYSICAL PROPERTIES 603 
 
 Ethyl ethylketene-carboxylate, C0 2 Et-CEt:CO, is colour- 
 less, and does not yield additive compounds, but readily poly- 
 merizes, yielding a cyclobutane derivative. 
 
 F. Unsaturation and Physical Properties. Unsaturation, 
 especially in the case of compounds with conjugate linkings, 
 produces a marked effect on numerous physical properties. 
 The phenomena which have been most closely studied are 
 those on the refraction and dispersion of light. The effect 
 of such a conjugate linking as in CHMe : CH CH : CHMe, is 
 to produce a considerable increase or exaltation in the specific 
 and molecular refraction and dispersions. In the case men- 
 tioned the molecular refraction is about one unit greater than 
 the value calculated from the atomic refractions -f- two olefine 
 linkings. The existence of such exaltation is frequently used 
 as an argument in favour of the presence of conjugate link- 
 ings (either two olefine or an olefine and carbonyl) in the com- 
 pound examined. In the case of hexatriene, CH 2 :CHCH: 
 CH '011:0112, the exaltation is 2*06 units. Exaltation is also 
 observed when an acetylene linking is in conjugation with a 
 carbonyl group. According to Moureau (Annales, 1906, [8], 
 7, 536), and Muller and Bauer (J. Chim. Phys. 1903, 1, 190), 
 the exaltation in certain series of compounds increases with 
 the negative character of the substituents. Little or no 
 exaltation is met with in the case of benzene, furane, diacetyl, 
 and similar compounds, although the formulae usually written 
 for these compounds contain conjugate bonds. This may be 
 due to special symmetrical ring structure or to mutual neutrali- 
 zation of residual affinities. Unsaturated groups such as amino, 
 vinyl and allyl, when present, in benzene compounds and 
 directly attached to the nucleus, produce exaltation, probably 
 owing to a readjustment of residual affinity. Exaltation is 
 extremely well marked in compounds containing conjugate 
 linkings, which, in their turn, are conjugate to the ethylene 
 bonds in phenyl groups: e.g. diphenyl-butadiene, CHPh:CH 
 CHiCHPh, has an exaltation of 15 units (Klages, B. 40, 1768); 
 cinnamylideneacetic acid, CHPh : CH CH : CH C(OH) : 0, of 
 10-5 units, and diphenyl-hexatriene, CHPh:CH.CH:CH.CH: 
 CHPh, of 24 units (Smedley, J. 0. S. 1908, 376). 
 
 Some of the most accurate work on unsaturated compounds 
 has been carried out by Auwers and Eisenlohr (J. pr. 82, 65; 
 84, 1, 37). They compare the specific refractions x 100, and 
 not molecular refractions, and make use of the following values 
 for atomic refractions n D as determined by Eisenlohr (Zeit. 
 
694 LI. ALIPHATIC DIAZO ANt> TRlAZO-COMPOtrfcDS 
 
 75, 585): CH 2 = 4-618, C = 2-418, H = 1, O (in car 
 myl) = 2-211, (in ethers) = 1-643, (in hydroxyl) = 
 1-525, Cl = 5-967, Br = 8-865, I = 13-900, define linking 
 = 1-733, and acetylene linking = 2*398. They find that a 
 single conjugation in a hydrocarbon produces an exaltation 
 of approximately 1*9 units, but that this value is reduced to 
 an appreciable extent by the introduction of substituents. 
 The amount of this interference depends upon the number 
 and position of the substiuients. In cinnamene and its /?-sub- 
 stituted derivatives the exaltation is about TO, and when 
 three substituents are present the exaltation is only 0-45. 
 They conclude that for a given type of compound the exalta- 
 tion is fairly constant, and within such limits the existence 
 of the exaltation may be made use of in discussions bearing 
 on constitution. 
 
 When several pairs of conjugate linkings are present, it is 
 found that the exaltation is much greater when these all form 
 a single chain (cf. hexatriene) than when they are " crossed " 
 
 as in 
 
 Semicyclic double bonds (p. 574) and rings formed of three 
 atoms, e.g. trimethylene, also produce optical exaltation. 
 
 For effects of unsaturation on heats of combustion, see 
 Auwers and Roth (A. 373, 239, 267). 
 
 For effects of unsaturation on optical activity, see Frank- 
 land and others, J. C. S. 1906, 1854, 1861; 1911, 2325; 
 Hildich, J. C. S. 1908, 1, 700, 1388, 1618; 1909, 331, 1570, 
 1578; 1910, 1091; 1911, 218, 224; Zeit. phys. 1911, 77, 482; 
 Rupe, A. 373, 121. 
 
 LI. ALIPHATIC DIAZO- AND TEIAZO-COM POUNDS 
 
 A. Diazo-compounds. By the action of nitrous acid on a 
 solution of a salt of a primary aromatic amine, the important 
 group of diazo or diazonium salts are formed. It is generally 
 stated that aliphatic amino-compounds differ from the aromatic 
 in this respect, and immediately yield the corresponding hy- 
 droxy-compounds. A few aliphatic amino-compounds do, how- 
 ever, yield diazo-derivatives with cold nitrous acid; one of the 
 
 N\ 
 best known of these compounds is ethyl diazo-acetate, - >CII- 
 
ALIPHATIC TRIAZO-COMPOUNDS 695 
 
 C0 2 Et (p. 212), a yellow oil, b.-pt. 141. It differs from the 
 aromatic diazonium salts in having both nitrogen atoms at- 
 tached to carbon, and may be regarded as the anhydride of a 
 diazo hydroxide, OH N : N CBL- C0 2 Et. It is extremely re- 
 active, and the N 2 group is readily replaced by I 2 , HC1, H^O, 
 &c. With concentrated alkalis it yields bis-diazo- acetic acid: 
 
 (Curtius, DurapsJcy, and E. Mutter, B. 1907). 
 
 The simplest aliphatic diazo-compound is cliazo-methane, 
 N 
 -., which may be regarded as the anhydride of CH 3 
 
 N:N'OH. Diazo-methane is most conveniently prepared by 
 decomposing nitroso-methyl-urethane, CH 3 N(NO) C0 2 Et, 
 with alkali, the compound, CH 3 N:NOK, being formed as 
 an intermediate product (Hantzsch and Lehmann, B. 1902. 35, 
 897). 
 
 It is a yellow, odourless gas at atmospheric temperature, 
 and is excessively poisonous. It is characterized by its re- 
 activity, and will readily convert acids into methyl esters, 
 alcohols and phenols into methyl ethers, aniline and its homo- 
 logues into secondary amines, and aldehydes into ketones. It 
 is also capable of uniting with unsaturated compounds, yielding 
 heterocyclic derivatives, e.g.: 
 
 CH N= CH.NH, 
 
 CH 2 N= CH 2 .NH 
 
 Cf. p. 528. 
 
 B. Triazo-compoimds. Forster (J. C. S. 1908, 93, 72, 669, 
 1070, 1174, 185$, 1865) has obtained a number of fairly 
 simple aliphatic triazo-derivatives containing the univalent 
 
 grouping, .. ;>N. Ethyl triazo-acetate, N 8 -CH 2 .C0 2 C 2 H 5 , ob- 
 
 N/ 
 
 tained by the action of sodium azide, NaN 8 , on an alcoholic 
 solution of ethyl chloro-acetate, is a colourless liquid, b.-pt. 
 44-46 under 2 mm. pressure, and has a sweet odour sugges- 
 tive of chloroform. From this ester triazo-acetic acid, m.-pt. 
 16, and almost as strong an acid as bromo-acetic, and triazo- 
 acetamide, m.-pt. 58, have been obtained by the ordinary 
 
696 LI. ALIPHATIC 1>IAZO- AND TRtAZO-COMPOUNDS 
 
 methods. Triazo-acetone, acetonyl-azoimide, N 3 CH 2 CO CH 3 , 
 obtained from chloro-acetone, is a colourless liquid, b.-pt. 54 
 under 2 mm. pressure. It has the properties of a ketone, e.g. 
 yields a semicarbazone, m.-pt. 152, and is instantly decom- 
 posed by alkalis. Ethyl a-triazo-propionate and the isomeric 
 /^-compound have been prepared, and also a-triazo-propionic 
 add, CH 3 CHN 3 C0 2 H, the last of which has been resolved 
 into optically active components. Ethyl f$-triazo-propionate is so 
 readily decomposed by alkalis that the corresponding acid and 
 amide have not been prepared. Allyt-azoimide, CH 2 :CHCH 2 
 Nj, b.-pt. 76-5; triazo-ethyl alcohol, N 3 - CH 2 . CH 2 - OH, b.-pt. 
 60/8 mm.; triazo-acetaldehyde, an oil, together with numerous 
 esters derived from triazo-ethyl alcohol, have been prepared. 
 Bis-triazo- compounds can be obtained, e.g. bis -triazo- ethane, 
 N 3 .CH 2 .CH 2 .N 3 , and ethyl bis-triazo-acetate, CH(N 3 ) 2 C0 2 Et, 
 but are extremely explosive. Triazo-malonic acid and ethyl 
 triazo-acetoacetate appear to be incapable of existence, but 
 substituted derivatives, e.g. CH 3 CO-CN 3 Me-C0 2 Et, and even 
 a bis -triazo -compound, CH 3 CO C(N 3 ) 2 (XXEt, are known. 
 Triazo-ethylene, N 3 CH:CH 2 , can be obtained by eliminating 
 hydrogen iodide from triazo-ethyl iodide. It is a pale-yellow 
 liquid, b.-pt. 26, and yields an oily dibromide. Numerous 
 aromatic triazo-compounds have also been prepared, mainly 
 from diazonium salts. (Cf. J. C. S. 1907, 855, 1350; 1909, 
 183; 1910, 126, 254, 1056, 1360, 2570.) 
 
 Staudinger and Kupfer (R 1911, 44, 2197) and /. Thide 
 (ibid. 2522) suggest that aliphatic diazo-compounds have an 
 open-chain structure, e.g. diazo-methane, CH 2 :N|N, and like 
 the aromatic diazonium salts contain a quinquevalent nitrogen 
 atom. The arguments brought forward are: (1) The fact that 
 the diazo-compounds can be obtained by the oxidation of 
 hydrazones of ketones: 
 
 H 2 0. 
 
 (2) The azo group is reactive, yet in the numerous reactions 
 of the aliphatic diazo-compound such a group does not take 
 part. 
 
 In a similar manner hydrazoic acid and its derivatives are 
 represented by open-chain formulae, e.g. HN:N|N. Such a 
 structure accounts for the fact that by the action of Grignard 
 reagents azides yield diazo-amino-compounds : 
 
 R-N:N:N > R-NiN-NHR'. 
 
INDEX 
 
 a= ana-position, 545. 
 
 ac=alicyclic, 500. 
 
 ar= aromatic, 500. 
 
 Abietic acid, 591. 
 
 Absorption spectra, 647. . 
 
 Acenaphthene, 504. 
 
 Acet-hydrazide, 185. 
 
 Acetal, 129. 
 
 Acetaldehyde, 128. 
 
 Acetaldehyde-semicarbazone, 136. 
 
 Acetaldoxime, 137. 
 
 Acetals, 125. 
 
 Acetamide, 185. 
 
 Acetamidine, 187. 
 
 Acetamido-chloride, 185. 
 
 Acetanilide, 382. 
 
 Acetates, 151. 
 
 Acetic acid, 18, 140, 149. 
 
 Acetic anhydride, 181. 
 
 Acetic fermentation, 150. 
 
 Acetimido-chloride, 186. 
 
 Acetimido-thio-methyl, 187. 
 
 Aceto-acetanilide, 543. 
 
 Aceto-acetic acid, 223, 226. 
 
 Aceto-acetic ester, 226. 
 
 Aceto-acetic ester syntheses, 228. 
 
 Aceto-bromamide, 183. 
 
 Aceto-chloroimide, 186. 
 
 Aceto-malpnic ester, 229. 
 
 Aceto-nitrile, 102. 
 
 Aceto-phenetidine, 415. 
 
 Aceto-phenone, 427. 
 
 Aceto-phenone-acetone, 427. 
 
 Aceto-phenone oxime, 427. 
 
 Aceto-phenone phenyl-hydrazone, 427. 
 
 Aceto-succinic ester, 229. 
 
 Aceto-tartaric acid, 253. 
 
 Acetone, 136. 
 
 Acetone-dicarboxylic acid, 261. 
 
 Acetone-dioxalic acid, 533. 
 
 Acetone peroxide, 181. 
 
 Acetone-phenyl-hydrazone, 135. 
 
 Acetone-semicarbazone, 136. 
 
 Acetonyl-acetone, 221. 
 
 Acetoxime, 137. 
 
 Acetoluidide, 382. 
 
 Aceturic acid, 212. 
 
 Acetyl, 147. 
 
 Acetyl-acetone, 221, 544, 655. 
 
 Acetyl-acetone, constitution of, 644, 647. 
 
 Acetyl chloride, 179. 
 
 Acetyl cyanide, 179. 
 
 Acetyl-diphenylamine, 377, 
 
 Acetyl glycollic acid, 209. 
 
 Acetyl hydride, 128. 
 
 Acetyl oxide, 180. 
 
 Acetyl peroxide, 181. 
 
 Acetyl-phenyl-hydrazide, 398, 
 
 Acetyl-urea, 285. 
 
 Acetylaminophenol, 458. 
 
 Acetylene, 52. 
 
 Acetylene-dicarboxylic acid, 247. 
 
 Acetylene series, 49. 
 
 Achroo-dextrine, 319. 
 
 Acid amides, 182. 
 
 Acid anhydrides, 180. 
 
 Acid azides, 185. 
 
 Acid bromides, 180. 
 
 Acid chlorides, 178, 684. 
 
 Acid derivatives, 171. 
 
 Acid esters, 91, 97. 
 
 Acid green, 484. 
 
 Acid hydrazides, 185. 
 
 Acid hydrolysis, 227. 
 
 Acid salts, 144. 
 
 Acid violet, 489. 
 
 Acids, aromatic, 435. 
 
 Acids, fatty, 140. 
 
 Aconitic acid, 262. 
 
 Acridine, 548. 
 
 Acridine yellow, 549. 
 
 Acridinic acid, 548. 
 
 Acridonium iodides, 549. 
 
 Acrolei'n, 130. 
 
 Acrolei'n-ammonia, 130. 
 
 Acrolei'n-aniline, 542. 
 
 a-Acrosazone, 312. 
 
 a-Acrose, 312. 
 
 a-Acrosone, 312. 
 
 Acrylic acid, 161, 164. 
 
 Active valeric acid, 154. 
 
 Acyl derivatives of ethyl aceto-acetate, 229. 
 
 Acyl oxides, 180. 
 
 Acyl ureas, 285 et seq. 
 
 Acyls, 147. 
 
 Additive compounds of aldehydes, 124-126, 
 
 Additive reactions of acetylenes, 50. 
 
 Additive reactions of nitriles, 101. 
 
 Additive reactions of olefines, 44. 
 
 Adenine, 293, 599. 
 
 Adipic acid, 231. 
 
 ^Esculetin, 593. 
 
 ^Esculin, 593. 
 
 Alanine, 211, 215, 596. 
 
 Alanylglycyl-glycine, 597. 
 
 Albumins, 594, 599. 
 
698 
 
 INDEX 
 
 Albumins, hydrolysis of, 595. 
 
 Albumins, oxidation of, 595. 
 
 Albumoses, 598. 
 
 Alcohol, 75. 
 
 Alcohol, constitution of, 17. 
 
 Alcohol of crystallization, 79. 
 
 Alcoholic fermentation, 76, 304, 666. 
 
 Alcohols, aliphatic, 65. 
 
 Alcohols, aromatic, 421. 
 
 Alcoholysis, 177. 
 
 Aldehyde, 128. 
 
 Aldehyde-acids, 204, 222. 
 
 Aldehyde-ammonia, 125. 
 
 Aldehyde "condensations", 126-127. 
 
 Aldehyde-phenyl-hydrazone, 127. 
 
 Aldehyde resin, 126. 
 
 Aldehydes, aliphatic, 1 22 et seq. 
 
 Aldehydes, aromatic, 423. 
 
 Aldehydes, the fuchsine test for, 127, 128. 
 
 Aldehydic acids, 222. 
 
 Aldohexoses, 307. 
 
 Aldoketens, 692. 
 
 Aldol, 131, 220. 
 
 Aldol "condensations", 131. 
 
 Aldoses, 300. 
 
 Aldoximes of the fatty series, 127, 137. 
 
 Aliphatic compounds, 24, 321. 
 
 Alizarin, 509. 
 
 Alizarin black, 503. 
 
 Alizarin blue, 510. 
 
 Alizarin bordeaux, 510. 
 
 Alizarin cyanine, 510. 
 
 Alizarin orange, 510. 
 
 Alkaloids, 554 et seq. 
 
 Alkaloids from dead bodies, 196, 598. 
 
 Alkarsin, 116. 
 
 Alkyl, 22, 366. 
 
 Alkyl cyanides, 100. 
 
 Alkyl hydrogen sulphates, 98. 
 
 Aikyl hydrosulphides, 88. 
 
 Alkyl-hydroxylamines, HI. 
 
 Alkyl-malonic acids, 237. 
 
 Alkyl nitrites, 94. 
 
 Alkyl salt, 74, 145. 
 
 Alkyl sulphates, 98. 
 
 Alkyl sulphides, 88. 
 
 Alkyl sulphites, 98. 
 
 Alkylated ureas, 284. 
 
 Alkylenes, 22, 42, 189. 
 
 Allantoin, 289. 
 
 Allene, 53. 
 
 Allo-cmnamic acid, 454. 
 
 Allophanic acid, 285. 
 
 Alloxan, 288. 
 
 Alloxanic acid, 288, 
 
 Alloxantin, 288. 
 
 Allyl alcohol, 82. 
 
 Allyl bromide, 56, 65. 
 
 Allyl chloride, 56, 65. 
 
 Allyl ether, 87. 
 
 Allyl iodide, 56, 65. 
 
 Allyl "mustard ou " = allyl Jsothiocyanate, 
 
 An 7 ?' 59 3> 
 
 A y -Py.'-'dine, 538, 557. 
 
 Allyl sulphide, 91. 
 Allyl thiocyanate, 276. 
 Allylene, 53. 
 Alphyl, 22, 366. 
 
 Aluminium amalgam as a reducing agent 
 
 609. 
 Aluminium chloride, action of; see Frie~ 
 
 del-Crafts' synthesis. 
 Aluminium methyl, 120. 
 A.malic acid, 289. 
 Amber, 591. 
 Amethyst violet, 53. 
 Amides of carbonic acid, 281. 
 Amides of malic acid, 248. 
 Amides of the fatty acids, 182. 
 Amidines, 187. 
 
 Amido, 182 ; see also Amino-group, 
 Amido chlorides, 185. 
 Amidoximes, 188. 
 Amines, aliphatic, 104, 677. 
 Amines, aromatic, 366. 
 Amino-acetic acid, 211. 
 Ammo-acetone, 136. 
 Amino-acids, 211. 
 Amino-azo-benzene, 397, 400. 
 Amino-azo-compounds, 393, 400. 
 Amino-azo-naphthalene, 500. 
 Amino-benzaldehydes, 426. 
 Amino-benzene, 372. 
 Amino-benzene-sulphonic acids, 405. 
 Amino-benzoic acids, 449, 451. 
 Amino-benzoyl-formic acid, 462, 522. 
 Amino-caproic acid = Leucine, 216, 596. 
 Amino-cinnamic acids, 456. 
 Amino-cinnamic aldehyde, 543. 
 Amino-derivatives, aromatic, 366. 
 Amino-dimethyl-aniline, 378. 
 Amino-ethane acid, 211. 
 Amino-ethyl-sulphonic acid, 197. 
 Amino-glutaric-acid, 249, 596. 
 Amino-group, 104. 
 Amino-guanidine, 297. 
 Amino-hexamethylene, 373. [596- 
 
 a-amino-/3-hydroxy-propionic acid, 218, 
 Amino-hypoxanthine, 293. 
 Amino-isobutyl-acetic acid, 596. 
 Amino-ketones, 136. 
 Amino-mandelic acid lactam, 522, 525. 
 Amino-mesitylene, 367. 
 Ammo-naphthalenes, 499. 
 Amino-naphthols, 502. 
 Amino-naphthol-sulphonic acid, 502. 
 Amino-naphthp-tolazine, 551. 
 Amino-oxypurine, 293. 
 Amino-phenols, 415. 
 Amino-phenyl-acetic acids, 452. 
 Amino-phenyl-glyoxylic acid, 462. 
 Amino-propionic acid; see Alanine, 596 
 Amino-purme = Adem'ne, 293. 
 Amino-pyridine, 558. 
 Amino-succinic acid, 249, 596. 
 Amino-sugars, 596. 
 Amino-thiazole, 530. 
 Amino-th jo-lactic SiC\A Cy stein, 596. 
 Amino^thiophene, 519. 
 Amino-trimethyl-benzenes, 367, 
 Amiiio-triphenyl-methane, 483. 
 Ammclide, 277. 
 Ammeline, 277. 
 Ammonium acetate, 151. 
 Ammonium cyanate, 273. 
 Ammonium ferri-thiocyanate, 276. 
 
INDEX 
 
 699 
 
 Ammonium formate, 148. 
 
 Ammonium thiocyanate, 275. 
 
 Amphoteric, 451. 
 
 Amygdalin, 267, 423, 592. 
 
 Amyl acetate, 178. 
 
 Amyl alcohols, 67, 80, 669. 
 
 Amyl nitrite, 94. 
 
 Amylase, 671. 
 
 Amylene glycols, 193. 
 
 Amylenes, 43, 49. 
 
 Amylo-dextrme, 319. 
 
 Amyloid, 317. 
 
 Amylum, 319. 
 
 Analysis, elementary, 4. 
 
 Analysis, qualitative, 2. 
 
 Analysis, quantitative, 4. 
 
 Ana-position, the, 545. 
 
 Angelic acid, 161, 165. 
 
 Anhydrides of the fatty acids, 180. 
 
 Anilic acids, 382. 
 
 Anilide of j^-toluic acid, 429. 
 
 Anilides, 370, 381. 
 
 Aniline, 367, 372. 
 
 Aniline, oxidation of, 617. 
 
 Aniline blue, 489. 
 
 Aniline yellow, 401. 
 
 Anilino-quinones, 433. 
 
 Anisaldehyde, 429. 
 
 Anisic acid, 459. 
 
 Anisidines, 415. 
 
 Anisole, 407, 412. 
 
 Anisyl alcohol, 429. 
 
 Anomalous electric absorption, 655. 
 
 Anthracene, 471, 504. 
 
 Anthracene brown, 510. 
 
 Anthragallol, 510. 
 
 Anthranil, 452. 
 
 Anthranilic acid, 452. 
 
 Anthranol, 508. 
 
 Anthrapurpurin, 510. 
 
 Anthraquinone, 477, 508. 
 
 Anthraquinone-sulphonic acids, 508. 
 
 Anthrarobin, 510. 
 
 Anthrols, 508. 
 
 Anti-albumoses, 598. 
 
 ^4w^'-aldoximes, 139, 428. 
 
 Anti-dia.z.0 compounds, 391. 
 
 Anti-febrine, 383. 
 
 Antimony pentamethyl, 117. 
 
 Antipyrine, 528. 
 
 Aposafranines, 553. 
 
 Arabinose, 219, 306. 
 
 Arabitol, 202. 
 
 Arabonic acid, 219. 
 
 Arachidic acid, 140, 157. 
 
 Arbutin, 593. 
 
 Arpfinine, 596. 
 
 Ansto-quimne, 560. 
 
 Aromatic acids, 435 ei seq. 
 
 Aromatic compounds, 321. 
 
 Aromatic nitriles, 438. 
 
 Aromatic properties, 328. 
 
 Arsenic compounds, 115. 
 
 Arsines, 115. 
 
 A rsonium compounds, 115. 
 
 Aryl, 366. 
 
 Arylamines, 366. 
 
 Asparagine, 248. 
 
 Aspartic acid, 249, 596. 
 
 Asphalt, 42. 
 
 Asymmetric carbon atoms, 154, 213, 250, 
 
 307, 461. ^ 
 
 Asymmetric synthesis, 660. 
 Atomic refractions; 643, 693. 
 Atomic volumes, 640. 
 Atropic acid, 443, 456. 
 Atropine, 565. 
 Aurichlorides, 107, 370= 
 Aurine, 500. 
 Australene, 582. 
 Auxochromes, 678. 
 Azealic acid, 165. 
 Azo-benzene, 394, 396. 
 Azo-compounds, aromatic, 396. 
 Azo-dyes, 389, 399. 
 
 Azo-dyes of the naphthalene series, 502 
 Azo-naphthalene, 501. 
 Azo-phenines, 434. 
 Azo-phenyl-ethyl, 397. 
 Azo-phenylene, 551. 
 Azoxy-benzene, 394, 395. 
 Azoxy-compounds, 394. 
 
 Bacillus butylicus, 152. 
 
 Baeyer s tension theory, 323. 
 
 Barbituric acid, 288. 
 
 Beckmann molecular transformation, the. 
 
 137. 139. 429. 479. 687- 
 Beer, 78. 
 
 Behemc acid, 140, 157. 
 Benzal chloride, 358. 
 Benzaldehyde, 4231,592. 
 Benzaldehyde-<rfanhydrin, 424. 
 Benzaldehyde-phenyl-hydrazone, 426. 
 Benzaldpximes, 426. 
 Benzamide, 446. 
 Benzamino-acetic acid, 447. 
 Benzanilide, 446. 
 Benz-a#-aldoxime, 429. 
 Benzazide, 447. 
 Benzazurine, 474. 
 Benzene, 341, 345, 350, 433. 
 Benzene, constitution of, 332. 
 Benzene, formation, 341, 350. 
 Benzene-azo-benzene, 396. 
 Benzene-azo-naphthylamine, 502. 
 Benzene-carboxylic acid = I}enzoic acid, 
 
 421, 444. 
 
 Benzene derivatives, 327. 
 Benzene derivatives, formation, 341, 344. 
 Benzene derivatives, isomerism, 332 et 
 
 seq. 
 
 Benzene derivatives, occurrence, 341. 
 Benzene-diazoic acid, 388. 
 Benzene-diazoimide, 389. 
 Benzene-diazonium perbromide, 389. 
 Benzene-dicarboxylic acids, 464. 
 Benzene-disulphonic acids, 406. 
 Benzene disulphoxide, 413. 
 Benzene formulae, 334 et seq. 
 Benzene hexabrormde, 354. 
 Benzene-hexacarboxylic acid, 470. 
 Benzene hexachloride, 354. 
 Benzene hydrocarbons, 344 et seq. 
 Benzene hydrocarbons, constitution of 
 
 347- 
 
700 
 
 INDEX 
 
 Benzene hydrocarbons, oxidation of, 348. 
 Benzene hydrocarbons, reduction of, 348. 
 Benzene-methylal, 421, 423. 
 Benzene-methylol, 421. 
 Benzene nucleus, 328. 
 Benzene of crystallization, 481. 
 Benzene-sulphinic acid, 405. 
 Benzene sulphonamide, 404. 
 Benzene-sulphonic acidi 403. 
 Benzene-sulphonic chloride, 404. 
 Benzene-tetracarboxylic acids, 470. 
 Benzene-tricarboxylic acids, 470. 
 Benzene-trisulphonic acids, 406. 
 Benzhydrazide, 447. 
 Benzhydrol, 474, 476. 
 Benzidam, 372. 
 Benzidine, 395, 472. 
 Benzidine-sulphonic acids, 473. 
 Benzil, 479. 
 Benzil-oximes, 479. 
 Benzilic acid, 476, 480. 
 Benzimido-azoles, 380. 
 Benzoic acid, 443, 444. 
 Benzoic anhydride, 446. 
 Benzoic esters, 445. 
 Benzoin, 425, 479. 
 Benzoline, 42. 
 Benzo-nitrile, 447. 
 Benzo-peroxide, 446. 
 Benzo-phenone, 428, 474. 
 Benzophenone-carboxylic acid, 476. 
 Benzo-purpurine 4 B, 474. 
 Benzoquinones, 431, 433. 
 Benzo-thiophene, 521. 
 Benzo-^-toluidide, 429. 
 Benzo-trichloride, 358. 
 Benzoyl-acetic acid, 463. 
 Benzoyl-acetone, 427. 
 Benzoyl-azimide, 447. 
 Benzoyl-benzoic acids, 476. 
 Benzoyl chloride, 446. 
 Benzoyl cyanide, 462. 
 Benzoyl-ecgonine methyl ester, 566. 
 Benzoyl-formic acid, 427, 462. 
 Benzoyl-glycocoll; see Hippuric acid, 447. 
 Benzoyl-nydrazine, 447. 
 Benzoyl peroxide, 446. 
 Benzoyl-salicin, 593. 
 Benz-syn-aldoxime, 429. 
 Benz^-toluidide, <pg. 
 Benzyl-aceto-acetic ester, 441. 
 Benzyl-alcohol, 421, 422. 
 Benzyl-benzene ; see Diphenyl-methane. 
 Benzyl-benzoate, 446. 
 Benzyl chloride, 358. 
 Benzyl cyanide, 452. 
 Benzylamine, 367, 383. 
 Benzylideneacetone, 428. 
 Benzylidene-aceto-phenone, 428. 
 Benzylidene-aniline, 371. 
 Benzylphenylallylmethyl-ammonium d- 
 
 camphor-sulphonate, 632. 
 Berberine, 563. 
 BetaYne, 212. 
 Biebrich scarlet, 402, 503. 
 Bilineurine, 196. 
 Birotation, 309. 
 Bis-azo-dyes, 402. 
 
 Bis-diazo-acetic acid, 695. 
 
 Bismarck brown, 401. 
 
 Bismuth compound, 118. 
 
 Bitter almond oil, 423. 
 
 Bitter-almond-oil green, 484. 
 
 Biuret, 289. 
 
 Blomstrand formula, 385. 
 
 Blood colouring- matter, 600. 
 
 Boiling-point, 26, 635. 
 
 Bonds, change in ; see Desmotropism, 
 
 227, 650, 651. 
 Bone glue, 579. 
 Bone oil, 518, 535. 
 Borneo camphor, 588. 
 Borneol, 588. 
 Bornyl chloride, 584, 589. 
 Bornyl iodide, 584. 
 Bornylene, 584. 
 Boron compounds, 118. 
 Brassidic acid, 166. 
 
 Brilliant black, 503. 
 Brilliant green, 484. 
 
 Brom-anilines, 374. 
 Brom-anthraqmnones, 509. 
 Bromacetic acid, 167. 
 Bromination, 55, 56, 169, 356. 
 Bromine as an oxidizing agent, 625. 
 Bromo-benzene, 3^4. 
 Bromo-benzoic acids, 449. 
 Bromo-benzyl bromide, 505. 
 Bromo-camphor, 588. 
 Bromo-camphoric acid, 588. 
 Bromo-cinnamic acids, 455. 
 Bromo-ethylene, 65. 
 Bromo-naphthalene, 498. 
 Bromo-nitro-benzenes, 362. 
 Bromo-nitro-camphors, 657, 658. 
 Bromo-phenols, 413. 
 Bromo-phenyl hydrazine, 399. 
 Bromo-phenyl-mtromethane, 664. 
 Bromo-propionic acids, 167. 
 Bromo-propyl-aldehyde, 130. 
 Bromo-succmic acids, 241. 
 Bromo-terpane-one, 590. 
 Bromoform, 56, 63. 
 Brucine, 565. 
 Butadiene, 682. 
 Butadiine, 53. 
 Butane acid, 152. 
 Butane di-acid, 238. 
 Butane-diamine, 195. 
 Butane-diol di-acid, 249. 
 Butane-dione, 221. 
 Butane-tetrol, 202. 
 Butanes, 30, 38. 
 Butanol, 73. 
 Butanol di-acid, 247. 
 Butanone, 137. 
 Butanone acid, 223. 
 Butanone di-acid, 260. 
 2-Butene-i-acid, 164. 
 i-Butene;4-acicl, 165. 
 Butene di-acids, 242. 
 Butenes^Butylenes, 43, 48. 
 Butine di-acid, 247. 
 Butyl-acridine, 548. 
 Butyl alcohols, 67, 80. 
 Butyl bromides, 56, 60. 
 
INDEX 
 
 701 
 
 Butyl chlorides, 56, 60. 
 Butyl iodides, 56, 60. 
 Butylamines, no. 
 Butylene glycols, 193. 
 -Butyric acid, 140, 152. 
 Butyric fermentation, 152. 
 Butyro-lactpne, 240. 
 Butyro-nitrile, 102. 
 Butyryl, 147. 
 
 Cacodyl, 116, 117. 
 Cacodyl chlorides, 116. 
 Cacodyl compounds, 116-117. 
 Cacodyl oxide, 116, 117. 
 Cacodylic acid, 117. 
 Cadayerine, 196, 598. 
 Cadet s liquid, 1 16. 
 Caffeic acid, 464. 
 Caffeine, 295. 
 Cairplin, 546. 
 Calcium carbide, 52. 
 Calcium cyanamide, 278. 
 Calcium glucosate, 302. 
 Camphane, 584. 
 Camphanic acid, 588. 
 Camphene, 584. 
 Camphenilone, 584. 
 Campholene cyanide, 586. 
 Campholenic acid, 586. 
 Camphor, 585. 
 Camphor, artificial, 582. 
 Camphor, synthesis of, 587. 
 Camphor-oxime, 585. 
 Camphoramic acid, 588. 
 Camphoric acid, 586, 588. 
 Camphoronic acid, 586. 
 Camphylamine, 586. 
 Cane sugar, 314. 
 Capillarity constants, 665. 
 Capric acid, 157. 
 Caprilic acid, 157. 
 Caproic acid, 140, 157. 
 Caramel, 315. 
 Carbamic acid, 281, 282. 
 Carbamic chloride, 282. 
 Carbamic compounds, 282. 
 Carbamic esters, 282. 
 Carbamide, 281, 282, 595. 
 Carbanilide, 383. 
 Carbazole, 473. 
 Carbinol, 73. 
 
 Carbocinchomeronic acid, 560, 
 Carbocyclic compounds, 322. 
 Carbohydrates, 298 et seq. 
 Carbolic acid, 411. 
 Carbon, detection of, 2. 
 Carbon, estimation of, 4. 
 Carbon monoxide, 683. 
 Carbon monoxide-haemoglobin, 600. 
 Carbon oxychloride, 280. 
 Carbon suboxide, 238. 
 Carbon tetrabromide, 56. 
 Carbon tetrachloride, <;6, 64, 281. 
 Carbonic acid, derivatives of, 279. 
 Carbonic acid, esters of, 279, 280. 
 Carbonyl chloride, 280, 683. 
 Carbostyril, 453, 456, 43, 546. 
 Carbostyril, constitution of, 649. 
 
 Carboxylic acids, aromatic, 435. 
 
 Carboxylic acids, fatty, 139. 
 
 Carboxylic group, 140. 
 
 Carbylamines, 102. 
 
 Carbylamines, constitution of, 103, 684, 
 
 Carone, 590. 
 
 Caronic acid, 590. 
 
 Carvacrol, 408, 417, 573. 
 
 Carvene, 568. 
 
 Carvenone, 590. 
 
 Carvestrene, 576. 
 
 Carvo-menthol, 579. 
 
 Carvone, 573, 577, 579. 
 
 Carvotanacetone, 577. 
 
 Carvoxime, 575, 576. 
 
 Casein, 599. 
 
 Caseinogen, 599. 
 
 Catalytic dehydration, 674. 
 
 Catalytic oxidation, 674. 
 
 Catalytic reduction, 610. 
 
 Catechol, 408, 4x7. 
 
 Cellulose, 317. 
 
 Centric formula of benzene, 335. 
 
 Cerotene, 43, 49. 
 
 Cerotic acid, 140, 157, 158. 
 
 Ceryl alcohol, 81. 
 
 Ceryl cerotate, 178. 
 
 Cetene, 43. 
 
 Cetyl alcohol, 81. 
 
 Cetvl palmitate, 178. 
 
 Chain isomerism, 87. 
 
 Chains, closed, 20, 24, 321. 
 
 Chains, open, 20, 321. 
 
 Chalcone, 428. 
 
 Chelidonic acid, 533. 
 
 Chemical retardation, 175, 449. 
 
 Chlor-acetanilide, 373. 
 
 Chlor-acetic acids, 167, 170, 210. 
 
 Chloracetyl chloride, 210. 
 
 Chloral, 129. 
 
 Chloral alcoholate, 130. 
 
 Chloral hydrate, 130. 
 
 Chloranil, 432. 
 
 Chloranilic acid, 433. 
 
 Chlorhydrins, 193, 199. 
 
 Chlorination, 56, 356. 
 
 Chlorine as an oxidizing agent, 625. 
 
 Chloro-aceto-acetic ester, 230. 
 
 Chloro-amylamine, 535. 
 
 Chloro-aniline, 373. 
 
 Chloro-benzene, 336. 
 
 Chloro-benzoic acid, 448, 449. 
 
 Chloro-bromo-benzenes, 358. 
 
 Chloro-butene acid, 171. 
 
 Chloro-camphor, 568- 
 
 Chloro-carbonic acid, 280. 
 
 Chloro-carbonic ester, 280. 
 
 Chloro-crotonic acids, 171. 
 
 Chloro-ethane acid, 170. 
 
 Chloro-formic acid, 170, 280. 
 
 Chloro-malonic ester, 238. 
 
 Chloro-methane-oxy-methanol, 128, 
 
 Chloro-methanol, 128. 
 
 Chloro-methyl alcohol, 128. 
 
 Chloro-naphthalenes, 498. 
 
 Chloro-nitro-benzenes, 362, 
 
 Chloro-phenols, 413. 
 
 Chloro-picrin, 97. 
 
 
702 
 
 INDEX 
 
 Chloro-propane-dfols, 200. 
 
 Chloro-propene, 65. 
 
 Chloro-propionic acids, 167, 171. 
 
 Chloro-propylene, 65. 
 
 Chloro-pyridine, 536. 
 
 Chloroform, 56, 63. 
 
 Cholestrophane, 287. 
 
 Choline, 196. 
 
 Chondrin, 599. 
 
 Chromic anhydride as an oxidizing 
 
 agent, 620. 
 Chromogene, 399. 
 Chromone, 541. 
 Chromophores, 399. 
 
 Chromo-proteins, 600. [620. 
 
 Chromyl chloride as an oxidizing agent, 
 Chrysamine, 473. 
 Chrysaniline, 548. 
 Chrysene, 512. 
 Chrysin, 541. 
 Chrysoidine, 401. 
 Chrysoidines, 400. 
 Cinchene, 560. 
 Cinchomeronio acid, 540. 
 Cinchona bases, 558. 
 Cinchonidine, 560. 
 Cinchonine, 560. 
 Cinchoninic acid, 560. 
 Cineol, 581. 
 Cinnamene, 353. 
 Cinnamenyl radical, 456. 
 Cinnamic acids, 443, 454. 
 Cinnamic alcohol, 422. 
 Cinnamic aldehyde, 426. 
 Cinnamo-carboxylic acid, 502. 
 Cinnamon, oil of, 426. 
 Cinnamyl radical, 456. 
 Cinnamylideneacetic acid, 682. 
 Cinnamylidenemalonic acid, 682. 
 "Cis-" form, 246, 326. 
 Citral, 570. 
 Citrazinic acid, 263. 
 Citrene, 368. 
 Citric acid, 262. 
 Citric esters, 262. 
 Citron, oil of, 568. 
 Citronellal, 569. 
 Classen reaction, 225. 
 Classification of organic compounds, 23, 
 
 321. 
 
 Closed chains (rings), 20, 24, 321 et seq. 
 Clupeine, 596. 
 Cocaine, 566. 
 Codeine, 564. 
 Co-enzymes, 667, 668. 
 Collidines, 539. 
 Collodion, 317. 
 Colophonium, 581, 591. 
 Combustion of hydrocarbons, 36. 
 Complex cyanides, 269. 
 Conchinine, 60. 
 " Condensation ", 126. 
 Condensed benzene nuclei, 471 et seq. 
 Configuration, spatial, 155. 
 "Congo "(dye), 473. 
 Coniferin, 430, 493. 
 Comferyl alcohol, 429, 430, 493. 
 Conune, 538, 557. 
 
 Conjugate double bonds, 681, 693. 
 Constitution of fructose, 311. 
 Constitution of glucose, 310. 
 Constitution of organic compounds, 16. 
 Constitutional formula, 17. 
 Continuous formation of ether, 84. 
 Conyrine, 538. 
 Copellidine, 540. 
 
 Copper powder and hydrogen as a re- 
 ducing agent, 611. 
 Copper-zinc couple, 35. 
 Coriandrol, 572. 
 Corydaline, 563. 
 Cotarnine, 562. 
 Coumaric acids, 443, 463. 
 Coumarilic acid, 520. 
 Coumarin, 463. 
 Coumarinic acid, 463. 
 Coumarone, 520. 
 Coumarone dibromide, 520. 
 Coumarone picrate, 520. 
 Creatine, 298. 
 Creatinine, 298. 
 Cremor tartari, 253. 
 Creosol, 419. 
 Cresols, 408, 416. 
 Crotonic acids, 161, 164. 
 Crotonic aldehyde, 130. 
 Cryoscopic method, 10. 
 Crystal violet, 488. 
 Crystalline, 372. 
 Cumene, 345, 352. 
 Cupric ferrocyanide, 269. 
 Cyamelide, 271. 
 Cyanamide, 277. 
 Cyanates, 271. 
 Cyanhydrins, 126, 135, 206. 
 Cyanic acid, 273. 
 Cyanic ester, 273. 
 Cyanides, metallic, 269 et seq. 
 Cyanines, 546. 
 Cyanmethine, 102. 
 Cyano-acetic acid, 167, 171. 
 Cyano-carbonic ester, 237. 
 Cyano-fatty acids, 170. 
 Cyano-nitroacetamide, 690. 
 Cyano-propipnic acids, 171. 
 Cyano-pyridine, 537-538. 
 Cyanogen, 237, 266. 
 Cyanogen bromide, 272. 
 Cyanogen chloride, 272. 
 Cyanogen compounds, 263 et seq. 
 Cyanogen iodide, 272. 
 Cyanogenetic glucosides, 592. 
 Cyanol, 372. 
 Cyanuramide, 277. 
 Cyanuric acid, 274. 
 Cyanuric chloride, 271. 
 Cyanuric esters, 273. 
 Cyclic ammonium salts, 197, 212. 
 Cyclic compounds, 24, 321. 
 Cyclic ureides, 286. 
 Cyclo-butane, 322. 
 Cyclo-butane-dione, 692. 
 Cyclo-hexane-diol, 419. 
 Cyclo-hexane-dione, 432. 
 Cyclo-propane, 322. 
 Cymene, 345, 352, 572. 
 
INDEX 
 
 703 
 
 Cystein, 596. 
 Cystin, 596. 
 
 d= dextro-rotatory, 154, 249. 
 
 Deca-tetrine di-acid, 247. 
 
 Decane, 30. 
 
 Decyl alcohol, 67. 
 
 Decylene, 43. 
 
 Dehydration, catalytic, 674-677. 
 
 Deka-hydronaphthalene, 497. 
 
 Deoxy-benzoi'n, 479. 
 
 Dephlegmators, 78. 
 
 Desmotropism, 227, 650, 651. 
 
 Determination of configuration of hex- 
 
 oses, 308. 
 Determination of configuration of olefine 
 
 compounds, 246. 
 Determination of configuration of oximes, 
 
 139, 429,479. 
 Dextrmes, 319. 
 Dextro-limonene, 575. 
 Dextro-tartaric acid, 252 et seg. 
 Dextrose, 309. 
 Dhurrin, 592. 
 Diacetamide, 185. 
 Diacetanilide, 383. 
 Diaceto-acetic ester, 229. 
 Diacetoglutaric acid, 261. 
 Diaceto-succinic acid, 261. 
 Diaceto-succinic ester, 229. 
 Diacetyl, 205, 221. 
 Diacetyl-dihydrazone, 222. 
 Diacetyl-osazone, 222. 
 Diacetylene, 33. 
 
 Diacetylene-dicarboxylic acid, 247. 
 Diagonal formula of benzene, 336. 
 Di-aldehydes, 97, 204, 221. 
 Di-allyl, 53. 
 Dialuric acid, 288. 
 Diamide ; see Hydrazine. 
 Diamines, 189, 194, 195. 
 Diamines, aromatic, 380. 
 Diamino-acetic acid, 596. 
 Diamino-azo-benzene, 401. 
 Diamino-azo-benzene hydrochloride, 401. 
 Diamino-caproic acid, 219, 596. 
 Diamino-dimethyl-acridine, 548. 
 Diamino-diphenyl, 472, 473. 
 Diamino-diphenyl-methane, 476. 
 Diamino-phenazine, 552. 
 Diamino-phenyl-acridme, 548. 
 Diamino-stilbene, 478. 
 Diamino-triphenyl-methane, 483. 
 Diamino-valeric acid = Ornithine, 219,596. 
 Dianilino-quinone-dianile, 434. 
 Di-anisidine, 474. 
 Diastase, 77, 671. 
 Diazines, 549. 
 Diazo-amino-benzene, 394. 
 Diazo-amino-compounds, 392 et seg. 
 Diazo-amino-naphthalene, 500. 
 Diazo-benzene-sulphonic acid, 406. 
 Diazo-benzoic acids, 451. 
 Diazo-compounds, 384, 390. 
 Diazo-compounds, fatty, 212, 694. 
 Diazo-compounds, isomerism of, 391. 
 Diazo-guanidine, 298. 
 Diazo-methane, 695. 
 
 Djazonium salts, 384. 
 Diazotizing, 386. 
 Dibasic acids, saturated, 231. 
 Dibenzyl, 471, 477. 
 Dibromo-acetic acid, 167. 
 Dibromo-benzeries, 357. 
 Dibromo-propionic acids, 167. 
 Dibromo-propyl aldehyde, 130. 
 Dibromo-succinic acids, 241. 
 Dicetyl ether, 87. 
 
 Dichlor-hydrins ; see Chlorhydrins. 
 Dichloro-acetic acid, 167, 170. 
 Dichloro-aceto-acetic ester, 230. 
 Dichloro-butyro-lactone, 240. 
 Dichloro-isoquinoline, 547. 
 Dichloro-maleic acid, 343. 
 Dichloro-propane-ols, 200. 
 Dichromates as oxidizing agents, 620 
 Diethyl ; see Normal butane, 38. 
 Diethyl-aniline, 367, 379. 
 Diethyl-butyro-lactone, 240. 
 Diethyl-cyanamide, 278. 
 Diethyl-disulphide, 89. 
 Diethyl ether, 85. 
 Diethyl-hydrazine, 112. 
 Diethyl ketone, 133. 
 Diethyl nitrosamme, 112. 
 Diethyl peroxide, 181. 
 Diethyl-semi-carbazide, ii2 
 Diethyl sulphide, 88. 
 Diethyl sulphone, 89. 
 Diethyl sulphoxide, 89. 
 Diethyl-thio-urea, 296. 
 Diethyl-urea, 112, 285. 
 Diethylamine, no, in. 
 Diethylamino-phenol, 415. 
 Dieth}dene-diamine, 195. 
 DigitaleYn, 593. 
 Digitalin, 593. 
 Digitomn, 593. 
 Digitoxin, 593. 
 Di-glycollic acid, 210. 
 Di-glycollic anhydride, 210. 
 Di-hydrazones, 221, 301. 
 Di-hydric alcohols, 188. 
 Di-hydric phenols, 417. 
 Dihydro-anthracene, 507. 
 Dihydro-benzenes, 349. 
 Dihydro-benzoic acids, 445. 
 Dihydro-carvone hydrobromide, 590. 
 Dihydro-cinnamylidene-acetic acid, 682= 
 Dihydro-collidine-dicarboxylic ester, 535 
 Dihydro-coumarone, 520. 
 Dihydro-cymene, 578. 
 Dihydro-methyl-pyridine, 537. 
 Dihydro-phenazine, 551. 
 Dihydro-phthalic acids, 466. 
 Dihydro-pyridines, 540. 
 Dihydro-quinoline, 546. 
 Dihydro-terephthalic acids, 467-468. 
 Dihydroxy-acetone, 669. 
 Dihydroxy-anthranol, 510. 
 Dihydroxy-anthraquinones, 509. 
 Dihydroxy-benzenes, 417. 
 Dihydroxy benzoic acids, 459. 
 Dihydroxy-benzo-phenone, 486, 492. 
 Dihydroxy-camphoric acid, 587. 
 Dihydroxy-cinnamic acids, 464, 
 
704 
 
 Dihydroxy-coumarine, 593. 
 Dihydroxy-dihydro-terephthalic acid, 469. 
 Dihydroxy-diphenyls, 473. 
 Dihydroxy-flavone, 541. 
 Dihydroxy-hexamethylene, 419. 
 Dihydroxy-naphthaquinones, 503. 
 Dihydroxy-purine, 292. 
 Dihydroxy-stilbene, 682. 
 Dihydroxy-tartaric acid, 261, 343. 
 Dihydroxy-terephthalic acid, 469. 
 Dihydroxy-toluene, 419. 
 Di-iodo-phenol-sulphonic acid, 416. 
 Diketo-butane, 221. 
 Diketo-camphoric ester, 587. 
 Diketo-hexamethylene, 419, 432, 469. 
 Diketo-hexane, 221. 
 Diketones, 221, 224. 
 Di-lactic acid, 215. 
 Dill, oil of, 575. 
 
 Dimethoxy-benzidine, 474. [$6i. 
 
 Dimethoxybenzyl-dimethoxyisoquinolme, 
 Dimethyl-acetic acid, 153. 
 Dimethyl-aceto-acetic ester, 228. 
 Dimethyl-acrylic acid, 680. 
 Dimethyl-allene, 669. 
 Dimethyl-allpxan, 288. 
 Dimethylamine, no. 
 Dimethyl-amino-azo-benzene, 400. 
 Dimethyl -amino-azo-benzene-sulphonic 
 
 acid, 401. 
 
 Dimethyl-aniline, 367, 378. 
 Dimethyl-arsine compounds, 115, 117. 
 Dimethyl-benzenes ; _see Xylene, 351. 
 Dimethyl-benzoic acids, 453. 
 Dimethyl-butane-diol, 193. 
 2-Dimethyl-3-butanone, 137. [583. 
 
 Dimethyl-cyclobutane-dicarboxylic acid, 
 Dimethyl-cyclohexenone, 342. 
 Dimethyl-diamino-tolu-phenazine, 551. 
 Dimethyl ether, 86. 
 Dimethyl-furane, 517. 
 Dimethyl-keten, 692. 
 Dimethyl-ketol, 205. 
 Dimethyl ketone, 136. 
 Dimethyl-naphthylamines, 500. 
 Dimethyl-nitrosamine, 108. 
 Dimethyl-oxamic ester, 106. 
 Dimethyl-oxamide, 106, 236. 
 Dimethyl-parabanic acid, 287. 
 Dimethyl-phenylamine oxide, 378. 
 Dimethyl-phosphinic acid, 114. 
 Dimethyl-piperidonium iodide, 540. 
 Dimethyl-pyrazine, 550. 
 Dimethyl-pyridines, 539. 
 Dimethyl-pyrone, 531. 
 Dimethyl-pyrrole, 518. 
 Dimethyl-quinoline, 544. 
 s-Dimethyl-succinic acids, 241. 
 Dimethyl-thiophene, 516. 
 Dimethyl - trimethylene - dicarboxylic acid 
 
 = Caronic acid, 590. 
 Dimethyl-uric acids, 292. 
 Dimethyl-xanthine, 293. 
 Dinaphthols, 502. 
 Dinaphthyls, ^04. 
 Dinicotinic acid, 540. 
 Dinitro-benzenes, 360, 361. 
 Dinitro-diphenyl, 472. 
 
 Dinitro-ethane, 97. 
 Dinitro-naphthalenes, 499. 
 Dinitro-phenols, 414. 
 Dinitro-toluenes, 360, 362. 
 Dionine, 564. 
 Dioximes, 479. 
 Dioxindole, 522, 525. 
 Dipalmitin, 201. 
 Dipentene, 374. 
 
 Dipentene dihydrochloride, 575, 578. 
 Dipentene tetrabromide, 578. 
 Diphenic acid, 474. 
 Diphenyl, 471. 
 Diphenyl-acetic acid, 476. 
 Diphenyl-acetylene ; see Tolane, 478, 
 Diphenyl-benzene, 474. 
 Diphenyl-bromo-methane, 476. 
 Diphenyl-butadiene, 628. 
 Diphenyl-butyro-lactone, 240. 
 Diphenyl-carbinol, 476. 
 Diphenyl-carbo-di-imide, 279. 
 Diphenyl-carboxylic acids, 473, 477. 
 Diphenyl-ethane, 474, 476. 
 Diphenyl-ethylene, 478. 
 Diphenyl-glycol, 478. 
 Diphenyl-glycollic acid, 476. 
 Diphenyl group, 470. 
 s-DiphenyT-hydrazme, 396. 
 unsym.-Diphenyl-hydrazine, 398. 
 Diphenyl-hydrazones, 221, 301. 
 Diphenyl-keten, 692. 
 Diphenyl ketone, 428. 
 Diphenyl-methane, 471, 474, 476. 
 Diphenyl-nitrosamine, 377. 
 Diphenyl-oxide, 412. 
 Diphenyl-quinp-methane, 692. 
 Diphenyl-succino-nitrile, 268. 
 Diphenyl-thio-urea, 383. 
 Diphenyl-urea ; see Thiocarbanilide, 
 Diphenylamine, 377. 
 Diphenylene ketone, 477. 
 Diphenylene-methane, 477. 
 Diphenylene-methane oxide, 548. 
 Diphenylene oxide, 473. 
 Diphenyline, 473. 
 Dipicohnic acid, 540. 
 Dippel's oil, 535. 
 Dipropareyl, 53. 
 Dipropyl ketone, 133. 
 Dipyndine, 537. 
 Dipyridyl, 537. 
 Disaccharoses, 299. 
 Dissociation constants of acids, 160, 167, 
 
 447, 664. 
 
 Distillation* fractional, 27. 
 Distillation, steam, 27. 
 Disulphides, 89. 
 Disulphoxides, 89. 
 Dithio-carbamic acid, 296. 
 Dithio-carbonic acid, 295. 
 Diurea, 284. 
 Divalent carbon, 683. 
 Dodecane, 30. 
 Dodecyl alcohol, 67. 
 Dodecylene, 43. 
 Double bond, 44, 643. 
 Dulcitol, 203, 307. 
 Durene, 345, 352. 
 
IND ^ 
 
 705 
 
 Dye, 400. 
 Dyeing, 399. 
 Dynamic isomensm, 657. 
 Dynamite, 201. 
 
 Earth-pitch, 42. 
 Ebulliscopic method, n. 
 Ecg-onine, 566. 
 Egg albumin, 599. 
 Eicosane, 30. 
 Eicosylene, 43. 
 Eikonogen, 502. 
 ElaVdic acid, 165. 
 Elastin, 599. 
 
 Electrical conductivity, 161, 663. 
 Electrolytic oxidation, 626. 
 Electrolytic reduction, 614. 
 Elementary analysis, 4. 
 Empirical Formulae, 7. 
 Emulsin, 267, 423, 592, 672. 
 Enzymes, 76, 77, 671. 
 Eosin, 493. 
 
 Eosin group, the, 491. 
 Epichlorhydrin, 200. 
 Erigeron, oil of, 575. 
 Erucic acid, 161, 166. 
 Erythrin, 202. 
 Erythritol, 202. 
 Erythro-dextrine, 319. 
 Erythrose, 306. 
 Erythrosin, 493. 
 Ester alcohols, 189. 
 Esterification, 172, 449, 677. ^ 
 Esters, 74, 91, 172, 445. 
 Etard reaction, the, 424, 620. 
 Ethanal, 128. 
 Ethanal acid, 222. 
 Ethane, 30, 37. 
 Ethane acid, 149. 
 Ethane-amide, 185. 
 Ethane-amidine, 187. 
 Ethane di-acid, 234. 
 Ethane-dial, 221. 
 s-Ethane-dicarboxylic acid, 238. 
 Ethane-nitrile, 102. 
 Ethane-oxy-ethane, 85. 
 Ethane-tetra-carboxylic ester (symmetr.), 
 Ethane-thio!, 88. [495. 
 
 Ethane-thiolic acid, 181. 
 Ethane-thion-amide, 186. 
 Ethanol, 75. 
 Ethanolic acid, 209. 
 Ethanoyl chloride, 179. 
 Ethene, 48. 
 
 Ethenyl-amidoxime, 188. 
 Ethenyl-diphenyl-amidine, 187. 
 Ether, 85. _ 
 Ethereal oils, 567. 
 Ethers, 83. 
 Ethers, mixed, 84. 
 Ethers, phenolic, 407. 
 Ethers, simple, ( 84. 
 Ethidene chloride, 62. 
 Ethine, 52. 
 Ethoxy-group, 177. 
 Ethyl acetate, 178. 
 Ethyl-acetchloroamide, 186. 
 Ethyl-acetchloroimide, 186. 
 (B480) 
 
 Ethyl-acetic acid, 152. 
 
 Ethyl aceto-acetate, 226. 
 
 Ethyl aceto-acetate, constitution of, 227,, 
 
 643, 646, 650, 653, 654. 
 Ethyl adipate, 232. 
 Ethyl alcohol, 67, 75. 
 Ethyl benzene, 345, 351. 
 Ethyl benzoate, 445. 
 Ethyl-benzoic acids, 443. 
 Ethyl benzoyl-acetate, 647, 655. 
 Ethyl bromide, 56. 
 Ethyl butyrate, 178. 
 Ethyl carbamate, 282. 
 Ethyl carbonate, 279. 
 Ethyl-cetyl-ether, 87. 
 Ethyl chloride, 56. 
 Ethyl chloro-carbonate, 280. 
 Ethyl chloro-formate, 280. 
 Ethyl collidine-dicarboxylate, 536. 
 Ethyl cyanamide, 278. 
 Ethyl cya.r\\Ae. = P-ropior>iiti'ile, 102. 
 Ethyl cyanurate, 274. 
 Ethyl diazoacetate, 212, 694. 
 Ethyl dibenzoyl-succinates, 649. 
 Ethyl dichloro-amine, in. 
 Ethyl dihydrocollidine-dicarboxylate, 230. 
 Ethyl diketo-apocamphorate, 587. 
 Ethyl diketo-camphorate, 587. 
 Ethyl dimethyl-aceto- acetate, 228. 
 Ethyl dimethylacrylate, 590. 
 Ethyl dimethyl-oxamate, 237. 
 Ethyl dimethyl - propanetricarboxylate, 
 Ethyl disulphide, 89. [590. 
 
 Ethyl disulphoxide, 89. 
 Ethyl ethanetricarboxylate, 239. 
 Ethyl ether, 85. 
 Ethyl ethyl-aceto-acetate, 228. 
 Ethyl ethyl-keten-carboxylate, 693. 
 Ethyl ethylsulphonate, 100. 
 Ethyl fluoride, 60. 
 Ethyl formate, 178. 
 Ethyl glycollate, 209. 
 Ethyl-glycollic acid, 209, 210. 
 Ethyl green, 489. 
 Ethyl hydrazine, 112. 
 Ethyl hydrogen carbonate, 280. 
 Ethyl hydrogen peroxide, 181. 
 Ethyl hydrogen sulphate, 98. 
 Ethyl hydrogen sulphite, 99. 
 Ethyl hydrosulphide, 88. 
 Ethyl ^-hydroxy-trimethylglutarate, 586, 
 Ethyl-indoxyl, 523. 
 Ethyl indoxylate, 523. 
 Ethyl iodide, 56. 
 Ethyl isocyanate, 273. 
 Ethyl isocyanide, 103. 
 Ethyl isocyanurate, 275. 
 Ethyl isothiocyanate, 277. 
 Ethyl lactate, 215. 
 Ethyl lactate, molecular magnetic rota 
 
 tion of, 646. 
 Ethyl-lactic acid, 215. 
 Ethyl malonate, 237. 
 Ethyl mercaptan, 88. 
 Ethyl-methyl-acetic acid, 154. 
 Ethyl methyl-aceto-acetate, aa6. 
 Ethyl nitrate, 93. 
 Ethyl nitrite, 94. 
 
706 
 
 INDEX 
 
 Ethyl-nitrogen chloride, in. 
 
 Ethyl-nitrolic acid, 96. 
 
 Ethyl orthocarbonate, 281. 
 
 Ethyl orthoformate, 142, 197. 
 
 Ethyl oxalacetate, 224, 260, 655. 
 
 Ethyl oxalate, 234, 236. 
 
 Ethyl oxalate, reactions of, with amines, 
 
 Ethyl oxalic acid, 234, 236. [106. 
 
 Ethyl-oxalyl chloride, 236. 
 
 Ethyl oxamate, 236. 
 
 Ethyl oxamic chloride, 237. 
 
 Ethyl phenylaminpcrotpnate, 543. 
 
 Ethyl phloroglucinoldicarboxylate, 343, 
 
 419, 441 
 th 
 
 , . 
 Ethyl propanetetracarboxylate, 240. 
 
 Ethyl propylbenzylphenylsilicane, 630. 
 Ethyl propyldibenzylsilicane monosul- 
 
 phonic acid, 630. 
 Ethyl-pyridines, 538. 
 Ethyl pyruvate, 654. 
 Ethyl succinylosuccinate, 241, 342, 578. 
 Ethyl sulphate, 98. 
 Ethyl sulphide, 88. 
 Ethyl-sulphinic acid, 100. 
 Ethyl sulphite, 99. 
 Ethyl sulphone, 89, 90. 
 Ethyl-sulphonic acid, 89, 90, 99. 
 Ethyl-sulphonic chloride, 100. 
 Ethyl sulphoxide, 89. 
 Ethyl tartrates, 253. 
 Ethyl tetrahydronaphthalene - tetra-car - 
 
 boxylate, 495. 
 Ethyl thiocyanate, 276. 
 Ethyl triazoacetate, 695. 
 Ethyl trimethyldihydropyridine - dicar - 
 
 boxylate, 535. 
 Ethyl-urea, 285. 
 Ethyl violets, 489. 
 Ethylamine, no, in. 
 Ethylamine ethyldithiocarbamate, 296. 
 Ethylaniline, 367. 
 Ethylene, 43, 48. 
 Ethylene bromide, 56, 62. 
 Ethylene-carbpxylic acid, 164. 
 Ethylene chloride, 56, 62. 
 
 .- 195- 
 
 Ethylene-dicarboxylic acids, 246. 
 Ethylene-glycol, 192. 
 Ethylene-lactic acid, 216. 
 Ethylene oxide, 191, 194. 
 Ethylene-succinic acid, 238. 
 Ethylidene-aniline, 543. 
 Ethylidene bromide, 56, 62. 
 Ethylidene chloride, 56, 62. 
 Ethylidene cyanhydrin, 126, 194. 
 Ethylidene-glycol, 192. 
 Ethylidene-lactic acids, 213 et seq. 
 Ethylidene-succinic acid, 241. 
 E thylol - trimethyl - ammonium hyd roxide, 
 Eucaine, 567. [196. 
 
 Eucalyptus oil, 581. 
 Euquinine, 560. 
 Eurhodine, 551. 
 Eurhodol, 552. 
 Euxanthone, 549. 
 Even numbers, law of, 21. 
 
 Exhaustive methylation, 540, 556, 564, 
 Extraction with ether, 28. [569, 
 
 Fast red, 503. 
 
 Fast yellow, 502. 
 
 Fats, 158, 198, 201. 
 
 Fatty acid series, 140. 
 
 Fatty compounds, 24.1 
 
 Fatty compounds from benzene deriva- 
 tives, 343. 
 
 Fehlings solution, 253. 
 
 Fermentation amyl-alcohol, 80. 
 
 Fermentation lactic acid, 214. 
 
 Fermentations, 76, 214, 666. 
 
 Ferments, 76. 
 
 Ferments, unorganized; see Enzymes, 
 76, 423, 671. 
 
 Ferric chloride as an oxidizing agent, 
 
 Ferropotassic oxalate, 236. [626. 
 
 Ferulic acid, 464. 
 
 Fibrin, 599. 
 
 Fibrinogen, 599. 
 
 Fire-<lamp, 34. 
 
 Fittigs synthesis, 344. 
 
 Flavone, 541. 
 
 Flavo-purpurin, 510. 
 
 Fluorane, 492. 
 
 Fluoranthene, 512. 
 
 Fluorene, 477. 
 
 Fluorenyl alcohol, 477. 
 
 Fluorescein, 493. 
 
 Formaldehyde, 128. 
 
 Formalin, 128. 
 
 Formamide, 185. 
 
 Formanilide, 382. 
 
 Formhydroxamic acid, 689. 
 
 Formic acid, 140, 147, 677. 
 
 Formo-rhodamine, 549. 
 
 Formose, 128, 312. 
 
 Formula, calculation of the empirical, 7. 
 
 Formulas, constitutional, 17 et seq. 
 
 Formyl chloride, 684. 
 
 Formyl chloride oxime, 689. 
 
 Formyl-diphenylamine, 548. 
 
 Fractional distillation, 27. 
 
 Freezing temperature of solutions, to. 
 
 Friedel-Crafts synthesis, 346, 427, 475, 
 
 Fructose, 311. [481. 
 
 Fruit sugar, 311. 
 
 Fuchsine, 484, 485. 
 
 Fuchsine-sulphurous acid, 488. 
 
 Fucose, 307. 
 
 Fulminic acid, 687. 
 
 Fulminuric acid, 690. 
 
 Fumaric acid, 242. 
 
 Furaldehyde, 306, 517, 596. 
 
 Furalmalonic acid, 518. 
 
 Furane or Furfurane, 322, 514, 517. 
 
 Furane-carboxylic acid, 518. 
 
 Furo'in, 518. 
 
 Furol, 517. 
 
 Furylacrylic acid, 518. 
 
 Fusel oil, 76, 669. 
 
 Galactonic acid, 307. 
 Galactoses, 307, 310. 
 Galipot resin, 591. 
 Gallein, 493. 
 
INDEX 
 
 707 
 
 Gallic acid, 460. 
 Gallo-tannic acid, 460. 
 Gelatin, 599. 
 Geranial, 570. 
 Geranic acid, 570. 
 Geraniol, 570, 571. 
 Gladstone- Tribe couple, 33. 
 Gliadins, 599. 
 Lrlobulms, 599. 
 Gluconic acid, 219, 307. 
 Gluco-proteins, 600. 
 Glucose-phenylhydrazone, 309. 
 Glucose phosphate, 668. 
 Glucosamines, 596. 
 Glucoses, 307, 309. 
 Glucosides, 303, 592, 672. 
 Glucosone, 309^"^-'-" 
 Glutamic acid, 249, 596, 670= 
 Glutamine, 249. 
 Glutaric acid, 231, 240, 241. 
 Glutaric anhydride, 530. 
 Gluteins, 599. 
 Glyceric acid, 218. 
 Glyceric aldehyde, 220. 
 Glycerides, 141, 201. 
 Glycerine, 198. 
 Glycerine nitrates, 200. 
 Glycerol, 76, 198, 669. 
 Glycerol chlorhydrins, 200. 
 Glycerose, 306. 
 Glyceryl-chloride, 64. 
 Glyceryl-phosphoric acid, 199. 
 Glyceryl-sulphuric acid, 199. 
 Glyceryl-trinitrate, 199, 201. 
 Glyceryl-tripalmitate, 158, 201. 
 Glycide alcohol, 199, 200. 
 Glycide compounds, 200. 
 Glycine, 211. 
 Glycocoll, 210, 211, 596. 
 Glycocoll, salts of, 211. 
 Glycocyamidine, 298. 
 Glycocyamine, 298. 
 Glycogen, 319. 
 Glycol, 192! 
 Glycol, ethers of, 193. 
 Glycol bromhydrins, 191. 
 Glycol chlorhydrins, 191, 193. 
 Glycol iodhydrin, 191. 
 Glycolide, 210. 
 Glycollamide, 209, 210. 
 Glycollic acetates, 189. 
 Glycollic acid, 204, 205, 209. 
 Glycollic aldehyde, 204, 220. 
 Glycollic anhydride, 210. 
 Glycollic di-nitrate, 193. 
 Glycollyl chloride, 209, 210. 
 Glycols, 188. 
 Glycoluric acid, 285. 
 Glycolyl-urea, 285. 
 Glycuronic acid, 222. 
 Glycylglycine, 597. 
 Glyoxal, 204, 221. 
 Glyoxalic acid, 204, 222. 
 Glyoxalin, 530. 
 Glyoxylic acid, 222. 
 Grape sugar, 309. 
 
 Grignarcts reagents, 72, 120 et seq., 126, 
 43 3S 6 . 422. 424. 4 28 - 44. 481. 
 
 Guaiacol, 418. 
 
 Guanidine, 278, 281, 297. 
 
 Guanine, 293, 599. 
 
 Guanino-amin^'ajeric acid, 596. 
 
 Guldberg and nonage's law, 160, 173. 
 
 Gulonic acid, 307. 
 
 Guloses, 307. 
 
 Gum benzoin, 444. 
 
 Gums, 319. 
 
 Gun cotton, 317. 
 
 Guye's hypothesis, 656. 
 
 Haematin, 600. 
 
 Haemin, 600. 
 
 Haemoglobin, 6op. 
 
 Halogen derivatives of the aromatic series, 
 
 Halogen derivatives of the fatty series, 
 
 Halogens, detection of, 3. [54. 
 
 Halogens, estimation of, 6. 
 
 Haloid fatty acids, 167. 
 
 Hatchett's brown, 269. 
 
 Heat of combustion, 665. 
 
 Helianthin, 401. 
 
 Heliotrope, 429. 
 
 Hemi-albumoses, 598. 
 
 Hemi-mellithene, 345. 
 
 Hemi-mellitic acid, 470. 
 
 Hemiterpenes, 567. 
 
 Heiieicosane, 30. 
 
 Hentria-contane, 30. 
 
 Heptane, 30. 
 
 Heptoic acid, 140. 
 
 Heptoses, 300. 
 
 Heptyl alcohol, 67. 
 
 Heptylene, 43. 
 
 Heptylic aldehyde, 129. 
 
 Heroin, 564. 
 
 Hesperidene, 568. 
 
 Hesperidin, 593. 
 
 Heterocyclic compounds, 24, 322, 513. 
 
 Hexabromo-benzene, 343, 357. 
 
 Hexachloro-benzene, 343, 357. 
 
 Hexachloro-ethane, 64. 
 
 Hexa-contane, 30. 
 
 Hexa-decane, 30. 
 
 Hexa-decylene, 43. 
 
 Hexa-diene, 53. 
 
 Hexa-diine, 53. 
 
 Hexahydric alcohols, 201, 203. 
 
 Hexahydro-benzene, 349. 
 
 Hexahydro-benzoic acid, 445. 
 
 Hexahydro-isophthalic acid, 342, 469. 
 
 Hexahydro-naphthalene, 497. 
 
 Hexahydro-phenol, 412. 
 
 Hexahydro-phthaJic acid, 466. 
 
 Hexahydro-pyridine = Pfyeridine, 534. 
 
 Hexahydro-terephthalic acid, 468. 
 
 Hexahydro - tetrahydroxy - benzoic acid, 
 
 Hexahydro-xylenes, 351. [461, 
 
 Hexahydroxy-benzene, 420. 
 
 Hexa-methyl-benzene, 353. 
 
 Hexamethyl-para-rosanihne, 488. 
 
 Hexa-methylene = Cyclo-hexane, 322. 
 
 Hexa-methylene-amme, 128. 
 
 Hexa-methylene carboxylic acid, 443. 
 
 Hexane, 30. 
 
 Hexane-pentolal, 309. 
 
708 
 
 INDEX 
 
 Hexa-phenyl-ethane, 690. 
 Hexoses, 300, 307 et seg. 
 Hexoses, synthesis of, 312, 319. 
 
 Hexoses, 300, 307 et seg. 
 
 , synthesis 
 Hexyl alcohol, 67. 
 
 Hexylene, 43. 
 Hippuric acid, 211, 447. 
 Histidine, 596, 599. 
 Histories, 599. 
 
 Hofmanris reaction, 107, 369. 
 Homatropine, 565. 
 Homocatechol, 419. 
 Homologous series, 20. 
 Homology, 20. 
 Homo-phthalic acid, 547. 
 Homoterpenylic methyl ketone, 579. 
 Honey-stone, 470. 
 Hydantoic acid, 285. 
 Hydantoi'n, 285. 
 Hydracryclic acid, 216. 
 Hydrastine, 563. 
 Hydratropic acid, 443, 454. 
 Hydrazides, 398. 
 Hydrazine, 212, 297. 
 Hydrazines, aromatic, 397. 
 Hydrazines, fatty, 109, in. 
 Hydrazo-benzene, 394, 396. 
 Hydrazo-compounds, 395. 
 Hydrazoic acid, 212, 298. 
 Hydrazones, aromatic, 424, 428. 
 Hydrazones, carbohydrate, 301. 
 Hydrazones, fatty, 127, 135. 
 Hydriodic acid as a reducing 1 agent, 605. 
 Hydro-benzoic acids, 445. 
 Hydro-benzoin, 478. 
 Hydro-carbostynl, 454. 
 Hydro-coumaric acids, 459. 
 Hydro-ferricyanic acid, 271. 
 Hydro-ferrocyanic acid, 270. 
 Hydro-isophthalic acids, 469. 
 Hydro-paracoumaric acid, 459. 
 Hydro-phthalic acids, 466-469. 
 Hydro-terephthalic acids, 466. 
 Hydrocarbons, benzene, 344. 
 Hydrocarbons, fatty, 30. 
 Hydrocinnamic acid, 443, 453. 
 Hydrocotarnine, 562, 563. 
 Hydrocyanic acid, 264, 266. 
 Hydrocyanic acid derivatives, 100. 
 Hydrocyano-carbpdiphenylimide, 524. 
 Hydrogen, detection of, 3. 
 Hydrogen, estimation of, 4. [623. 
 
 Hydrogen peroxide as an oxidizing agent, 
 Hydrolysis = Saponification, 70, 92, 159, 
 
 176, 183. 
 
 Hydrolysis of disaccharoses, 312. 
 Hydrolysis of esters, 176. 
 Hydrolysis of ethyl acetoacetate, 226- 
 Hydrolysis of nitriles, 101. [227. 
 
 Hydromellitic acid, 470. 
 Hydropyridines, 540. 
 Hydroquinolines, 546. 
 Hydroquinone = ?Mzw0/, 418. 
 Hydroxy-acetic acid, 209. 
 Hydroxy-acetone, 204. 
 Hydroxy-acids, 204 et seg., 247 et seq., 
 
 456 et seq. 
 
 Hydroxy aldehydes, 204. 
 Hydroxy-anthracenes, 508. 
 
 Hydroxy-anthraquinones, 509. 
 Hydroxy-azobenzene, 397. 
 Hydroxy-benzaldehydes, 429. 
 Ilydroxy-benzene, 411. 
 Hydroxy-benzoic acids, 443, 457 e 
 Hydroxy-benzyl alcohol, 429, 593. 
 Hydroxy-butyric acids, 207. 
 Hydroxy-camphenilic acid lactone, 584. 
 Hydroxy-caproic acids, 216. 
 Hydroxy-cmoromethyl ether, 
 Hydroxy-ethylamine, 189, 19 
 Hydroxy-ethyl-sulphonic aci 
 Hydroxy-isobutyric acid, 207. 
 Hydroxy-ketones, 204. 
 Hydroxy-malonic acid, 247. 
 Hydroxy-methyl-benzoic acid, 46 
 Hydroxy-phenyl-alanine, 459.' 
 
 28. 
 
 197. 
 
 Hydroxy - phenylamino - propiomc 
 Ilydroxy-pnenyl-ethyl alcohol, 670. 
 Hydroxy-phenyl-propionic acid, 459. 
 Hydroxy-propionic acids, 207, 213. 
 Hydroxy-pyndenes, 538. 
 Hydroxy-quinaldine, 543. 
 Hydroxy-quinol, 408, 420. 
 Hydroxy-quinoline, 543, 546. 
 Hydroxy-succinic acid, 247. 
 Hydroxy-terpane-one, 590. 
 Hydroxy-thiotolene, 20. 
 Hydroxy-tricarballylic acid, 262. 
 Hydroxy-uracyl, 287. 
 Hydroxyl groups, estimation of, 201., 
 Hydroxylamines, in, 397, 609. 
 Hydroxylenes, 351. 
 Hyoscyamine, 566. 
 Hypoxanthine, 293. 
 
 /= inactive, 249. 
 Iditol, 307. 
 Idonic acid, 307. 
 Idosaccharic acid, 307. 
 Idoses, 307. 
 Imid-azole, 530. 
 Imides, 239. 
 
 Imido-carbonic acid, 281. 
 Imido-chlorides, 186. 
 Imino-ethers, 185, 187, 447. 
 Imino-formyl chloride, 268. 
 Imino group, 104. 
 Imino-thio-ethers, 186. , T 
 
 Indamines, 434. 
 Indican, 526. 
 Indigo, 525. 
 Indigo-brown, 526. 
 Indigo-carmine, 526. 
 Indigo-purpurin, 528. 
 Indigo-red, 526. 
 Indigo-sulphonic acids, 526. 
 Indigo syntheses, 526-527. 
 Indigo-white, 526, 527. 
 Indirubin, 528. 
 Indol-alanine, 596. 
 Indole, 520, 521, 525. 
 Indophenin, 520. 
 Indophenols, 434. 
 Indoxyl, 522, 52^. 
 Indoxyl-sulphunc acid, 523, 
 Indoxylic acid, 523. 
 Inosite, 421. 
 
 [596. 
 acid, 
 
INDEX 
 
 709 
 
 internal viscosity, 665. 
 
 Inulin, 319. 
 
 Inversion, 315. 
 
 Invert sugar, 315. 
 
 Invertase, 77, 318. 
 
 lodoacetic acid, 167. 
 
 lodo-benzene, 354. 
 
 lodo-propionic acids, 167, 171 
 
 lodoform, 56, 63. 
 
 lodole, 518. 
 
 lodonium compounds, 360. 
 
 lodopropanes, 60. 
 
 lodoso-benzene, 359. 
 
 lodoxy-benzene, 359. 
 
 lonones, 589. 
 
 Irene, 589. 
 
 Iron albuminate, 599. 
 
 Iron and dilute acid as reducing agents, 
 
 Iron peptonate, 599. [603. 
 
 I rone, 589. 
 
 Isatic acid, 463. 
 
 I satin, 457, 463, 523, 525. 
 
 Isatin-anihde, 524. 
 
 Isatin chloride, 524. 
 
 Isatin, constitution of, 525, 649. 
 
 Isatin ethers, 524. 
 
 Isatogenic acid, 524. 
 
 Isethionic acid, 197. 
 
 Isoamygdalin, 592. 
 
 Iso-amyl-iso-valerate, 178. 
 
 Iso-barbituric acid, 287. 
 
 Iso-butane, 38. 
 
 Isobutyl alcohol, 67, 68. 
 
 Isobutyl carbinol, 80. 
 
 Isobutyric acid, 153. 
 
 Iso-cinchomeronic acid, 540. 
 
 Iso-cinnamic acids, 454. 
 
 Iso-crotonic acid, 164. 
 
 Isocyanic esters, 272. 
 
 Isocyanides, 102. 
 
 Isocyanuric esters, 275. 
 
 Isocyclic compounds, 322. 
 
 Iso-dialuric acid, 288. 
 
 Iso-durene, 345. 
 
 Isodynamic isomerism, 657. 
 
 Iso-hydrobenzo'in, 478. 
 
 Isomaltose, 316, 673. 
 
 Iso-melamines, 277. 
 
 Isomerism, 12, 87. 
 
 Isomerism, position, 133. 
 
 Isomerism, side-chain, 340. 
 
 Isomerism, stereo-chemical, 137, 154, 243, 
 
 2 5> 37. 3. 2 S' 34 1 - 39. 4 28 > 62 7- 
 Isomerism. in the cyanogen group, 100- 
 
 104, 273, 684. 
 Isomerism of fumaric and maleic acids, 
 Isomerism of paraffins, 38. [243. 
 
 Isomerism of polymethylene derivatives, 
 
 3 2 S- 
 Isomerism of the benzene derivatives, 329 
 
 et seq. 
 
 Isomers of the diazo-compounds, 389. 
 Iso-nicotinic acid, 539. 
 Iso-nitriles, 102, 371. 
 Iso-nitro-methane, 96. 
 Iso-nitroso-acetone, 136. 
 Iso-nitroso-camphor, 586. 
 Iso-nitroso-ketones, 136. 
 
 Iso-paraffins, 32. 
 Iso-phthalic acid, 466. 
 Isoprene, 567, 568. 
 Isopropyl, 39. 
 Isopropyl-acetic acid, 153. 
 Isopropyl alcohol, 67, 70. 
 Isopropyl-benzene, 353. 
 Isopropyl chloride, 60. 
 Isopropyl iodide, 60. 
 Isopropyl-methyl-benzene, 352. 
 Iso-quinoline, 541, 547. 
 Iso-rhamnose, 307. 
 Isorosindulines, 553. 
 Iso-saccharic acid, 260. 
 Iso-stilbene, 478. 
 Iso-succinic acid, 241. 
 Iso-thio acid amides, 186. 
 Iso-thiocyanates, 276, 371. 
 Iso-valeric acid, 153. 
 Isuret, 188. 
 
 Japan camphor, 585. 
 uglone, 503. 
 umper, oil of, 581. 
 
 Keratin, 599. 
 Ketens, 691. 
 Keto-butyric acid, 223. 
 Keto-enolic tautomensm, 227. 
 Keto-hexoses, 311. 
 Keto-ketens, 692. 
 Ketone-aldehydes, 204, 
 Ketones, aliphatic, 131 et seq., 677, 
 Ketones, aromatic, 427. 
 Ketones, constitution of, 132. 
 Ketones, mixed, 132. 
 Ketonic acids, aromatic, 461. 
 Ketonic acids, fatty, 204, 222, 259. 
 Ketonic acids, fermentation of, 670. 
 Ketonic hydrolysis, 226. 
 Ketoses, 300, 303. 
 Ketoximes, aliphatic, 135, 137. 
 
 /=lsevo-rotatory, 249. 
 
 Lactalbumin, 599. 
 
 Lactam formation, 453. 
 
 Lactamide, 215. 
 
 Lactates, 215. 
 
 /-Lactic acid, synthesis of, 661. 
 
 Lactic acids, 168, 205, 213 et seq,, 669. 
 
 Lactic acids, derivatives of, 215. 
 
 Lactic fermentation, 214, 
 
 Lactide, 215. 
 
 Lactim formation, 453. 
 
 Lacto-biose, 315. 
 
 Lactones, 217. 
 
 Lactose, 315. 
 
 Lactyl chloride, 215. 
 
 Lactyl-urea, 285. 
 
 Lactylic acid or Lactic anhydride, 215. 
 
 Laevo-coniine, 557. 
 
 Lffivo-limonene, 75. 
 
 Lasvo-tartaric acid, 249. 
 
 Laevulic acid, 223, 230. 
 
 Laevulose, 311. 
 
 Lakes, 400, 509. 
 
 Laudanosine, 561. 
 
 Laurie acid, 140, 157. 
 
710 
 
 INDEX 
 
 Lead, sugar of, 151. 
 
 Lead, tetraethyl, 120. 
 
 Lead, tetramethyl, 120. 
 
 Lead, trimethyl hydroxide, 120. 
 
 Lead acetates, 151. 
 
 Lead mercaptan, 89. 
 
 Lead peroxide as an oxidizing agent, 622, 
 
 Leather, 460. 
 
 Le Bel-van t ffoff hypothesis, 154. 
 
 Leucaniline, 484. 
 
 Leucaurine, 490. 
 
 Leucine, 216, 596, 669. 
 
 Leuco-bases, 482. 
 
 Leuco-compounds, 399, 482. 
 
 Leuco-malachite green, 483. 
 
 Leuco-rosolic acid, 490. 
 
 Lichenin, 319. 
 
 Ltebermanris reaction, 377, 409. 
 
 Light blue, 489. 
 
 Light green, 489. 
 
 Lignoceric acid, 140. 
 
 Ligroi'n, 42. 
 
 Limonene nitroso-chloride, 575, 578. 
 
 Limonene tetrabromide, 575, 578. 
 
 Limonenes, 574, 575. 
 
 Linalool, 572. 
 
 Lipase, 668, 672. 
 
 Liponic acid, 559. 
 
 Liver starch, 319. 
 
 Lotusin, 592. 
 
 Lupetidines, 540. 
 
 Luteolin, 541. 
 
 Lutidines, 539. 
 
 Lutidimc acid, 540. 
 
 Lysine, 219, 596. 
 
 Lyxose, 306. 
 
 Madder root, 509. 
 
 Magenta, 484, 487. 
 
 Magnetic susceptibility, 665. 
 
 Malachite green, 484. 
 
 Malamic acid, 248. 
 
 Malamide, 248. 
 
 Maleic acid, 242. 
 
 Malic acid, 247. 
 
 Malonic acid, 231, 237, 241. 
 
 Malonic anhydride, 238. 
 
 Malonic ester, 237. 
 
 Malonic ester synthesis, 237. 
 
 " Malonyl", 233. 
 
 Malonyl-urea, 288. 
 
 Malt sugar, 315. 
 
 Maltase, 78, 318, 671, 672. 
 
 Maltobiose, 315. 
 
 Maltose, 315, 673. 
 
 Mandelic acid, 443, 461. 
 
 Manganese dioxide as an oxidizing agent, 
 
 Mannide, 203. [623. 
 
 Mannitan, 203. 
 
 Mannitol, 203, 307. 
 
 Manno-heptose, 660. 
 
 Manno-nonose, 660. 
 
 Manno-octose, 660. 
 
 Manno-saccharic acid, 260, 307. 
 
 Mannonic acid, 220, 307. 
 
 Mannose-phenyl-hydrazone, 310. 
 
 Mannoses, 307, 310. 
 
 Margaric acid, 140. 
 
 Marsh -gas, 34. 
 Martins' yellow, 502. 
 Mauve, 552, 553. 
 Meconme, 562. 
 Melamine, 277. 
 Melene, 43, 49. 
 Melibiose, 316. 
 Melissic acid, 140. 
 Melissic alcohol, 81. 
 Melissic palmitate, 158, 178. 
 Melitriose, 316. 
 Mellitene, 353. 
 Mellitic acid, 34^, 470. 
 Mellophanic acid, 470. 
 Melting-point, 25, 638. 
 Melting-point curves, 638. 
 Melting-point curves of racemic com- 
 pounds, 258. 
 
 Mendius reaction, 106, 606. 
 Menthadienes, 574. 
 Menthane, 574. 
 Menthene, 578. 
 Menthol, 578. 
 Menthone, 578. 
 
 Menthone-semicarbazone, 579. 
 Menthyl benzoyl-formate, 661. 
 Menthyl lactates, 660. 
 Menthyl phenyl-methyl-glycollate, 661. 
 Menthyl pyruvate, 660. 
 Mercaptans, 88. 
 Mercaptides, 88. 
 Mercaptol, 136. 
 Mercurialin, no. 
 Mercuric cyanide, 269. 
 Mercuric 'formate, 149. 
 Mercuric mercaptide, 89. 
 Mercuric oxide as an oxidizing agent, 626. 
 Mercurous formate, 149. 
 Mercurous thiocyanate, 276. 
 Mercury ethyl, 120. 
 Mercury fulminate, 688. 
 Mercury methyl, 120. 
 Merpquinine, 559. 
 Mesidme, 367. 
 Mesityl oxide, 135, 137. 
 Mesitylene,-i3$. 339, 342, 345, 351. 
 Mesitylenic acid, 443, 453. 
 Meso-tartaric acid, 246, 249, 254. 
 Mesoxalic acid, 199, 260. 
 Mesoxalyl-urea, 288. 
 Meta-compounds, 333, 337. 
 Metacymene, 345. 
 Metaldehyde, 129. 
 Metallic cyanides, 268, 684-687. 
 Metamerism, 87. 
 Metanilic acid, 406. 
 Metaproteins, 600. 
 Meta-styrene, 353. 
 Methacrylic acid, 165. 
 Methanal, 128. 
 Methane, 30, 34. 
 Methane acid, 147. 
 Methane-amide, 185. 
 Methanol, 74. 
 Methene, 47. 
 
 Methoxy-benzaldehyde, 429. 
 Methoxy-benzyl alcohol, 429. 
 Methoxy-group, 177. 
 
INDEX 
 
 711 
 
 Methoxy-hydrqxy-benzaldehyde, 429. 
 Methoxy-pyridine, 538. 
 Methoxy-quinoline-carboxylic acid, 559. 
 Methyl-acetanilide, 382. 
 Methyl-acridine, 548. 
 Methyl alcohol, 67, 74. 
 Methyl-alloxan, 288. 
 Methyl -allyl - phenyl -benzyl -ammonium 
 
 iodide, 631. 
 Methyl-amine, no. 
 Methyl-aniline, 367, 377. 
 Methyl-arbutin, 593. 
 Methyl-arsenic compounds, 115 et seq. 
 Methyl-arsine chlorides, 115 et seq. 
 Methyl-benzene; see Toluene, 340, 345, 
 Methyl-benzimido-azole, 380. [350. 
 
 Methyl benzoate, 445. 
 Methyl-benzqic acids, 443, 449, 452. 
 Methyl bromide, 56. 
 2-Methyl-butane acid, 154. 
 3-Methyl-butane acid, 153. 
 Methyl carbonate, 280. 
 Methyl-carbqstyril, 543. 
 Methyl chloride, 56, 59. 
 Methyl-chloroform, 63. 
 Methyl-cyanamide, 278. 
 Methyl-cyanide, 102. 
 Methyl dimethyl-amino-acetate, 212. 
 Methyl ether, 86. 
 Methyl-ethyl-acetic acid, 154. 
 Methyl-ethyl-aceto-acetic ester, 228. 
 Methyl-ethyl-aniline oxide, 633. 
 Methyl-ethyl-benzenes, 345. 
 Methyl-ethyl-carbinol, 126. 
 Methyl-eth}'l ether, 84. 
 Methyl-ethyl ketone, i-;?. [628. 
 
 Methyl-cthyl-phenacyl-sulphine bromide, 
 Methyl-ethyl-propyl-iso-butyl-ammonium 
 
 chloride, 632. 
 Methyl-ethyi-w-propyl-tin ?-camphor sul- 
 
 phonate, 629. 
 
 Methyl-ethyl-propyl-tin iodide, 629. 
 Methyl-ethyl-selenetine bromide, 628. 
 Methyl-ethyl sulphide, 89. 
 Methyl-ethyl sulphone, 89. 
 Methyl-ethyl-thetine bromide, 628. 
 Methyl - ethyl - thetine d- camphor - sul - 
 
 phonate, 628. 
 Methyl-furane, 517. 
 Methyl galactoside, 311. 
 Methyl glucosides, 310, 592, 672. 
 Methyl-glycocoll, 212. 
 Methyl-glyoxal, 204. 
 Methyl-green, 480. 
 Methyl-heptenone, 571. 
 Methyl-hydantoin, 285. 
 Methyl-hydrazine, 112. 
 Methyl-indole, 521. 
 Methyl iodide, 56. 
 Methyl-isatin, 524, 649. 
 Methyl isocyanide, 103. 
 Methyl-isopropyl-benzene, 352. 
 Methyl-isoprqpyl-hydroxy-benzenes, 417. 
 Methyl-iso-thiacetanilide, 187. 
 Methyl isothiocyanate, 277. 
 Methyl-malonic acid, 233, 241. 
 Methyl-morphmethine, 564. 
 Methyl-morphol, 564. 
 
 Methyl-naphthylamines, 500. 
 
 Methyl-nitramine, 109. 
 
 Methyl nitrate, 93. 
 
 Methyl nitrite, 94. 
 
 Methyl-nitrolic acid, 96, 689. 
 
 Methyl-orange, 401. 
 
 Methyl oxalate, 236. 
 
 Methyl-oxamic ester, 106. 
 
 Methyl-parabanic acid, 287. 
 
 Methyl-phenyl-fr uctosazone, 311. 
 
 Methyl-phosphonic acid, 114. 
 
 Methyl-piperidines, 540. 
 
 Methyl-propane acid, 153. 
 
 Methyl-propane di-acid, 241. 
 
 2-Methyl-2-propene-i-acid, 165. 
 
 Methyl-propyl-benzenes, 352. 
 
 Methyl-pyridines, 538. 
 
 Methyl-pyridone, 538. 
 
 Methyl-pyridonium iodide, 534. 
 
 Methyl-pyrrolidine, 569. 
 
 Methyl-quinolines, 543, 546. 
 
 Methyl-succinic acid, "241. 
 
 Methyl sulphate, 98. 
 
 Methyl-sulphonic acid, 99. 
 
 Methyl-tertiary-butyl ketone, 137. 
 
 Methyl-uracyl, 230, 287. 
 
 Methyl-urea, 285. 
 
 Methyl-uric acids, 292. 
 
 Methyl violets, 488. 
 
 Methyladipic acid, 578. 
 
 Methylal, 128. 
 
 Methylamine platinichloride, 107. 
 
 Methylated rosanilines, 488. 
 
 Methylene, 47. 
 
 Methylene blue, 554. 
 
 Methylene bromide, 56, 61. 
 
 Methylene chloride, 56, 61. 
 
 Methylene-glycol, 192. 
 
 Methylene iodide, 56, 61. 
 
 Methylene-quinones, 434. 
 
 Methylene violet, 553. 
 
 Micro-organisms for resolving racemic 
 
 compounds, 256. 
 Milk sugar, 315. 
 Millon's reagent, 594. 
 Mineral lubricating oils, 42. 
 Mint camphor, 578. 
 Miricyl alcohol, 81. 
 Mixed amines, 106. 
 Mixed anhydrides, 181. 
 Mixed ethers, 84. 
 Mixed ketones, 132. 
 Mixed sulphides, 89. 
 Molasses, 314. 
 
 Molecular magnetic rotation, 644. 
 Molecular rearrangements, 108, 137, 163, 
 
 377. 393. 395- 39?. 4". 5<>i- 
 Molecular refraction, 641. 
 Molecular rotation, 656. 
 Molecular volume, 639. 
 Molecular weight, determination of, 8-ia 
 Monoformin, 148. 
 Monohydric alcohols, 65. 
 Monohydroxy fatty acids, 205. 
 Mononitrin, 200. 
 Monopalmitin, 201. 
 Monosaccharoses, 299. 
 Mordants, 400. 
 
712 
 
 INDEX 
 
 Morphine, 564. 
 Morpholine, 531. 
 Moss starch, 319. 
 Mucic acid, 259, 307. 
 Mucins, 600. 
 Multi-rotation, 309. 
 Murexide, 289. 
 Muscarine, 196. 
 Musk, artificial, 362. 
 Mustard oils, 275, 371". 
 Mutarotation, 309, 315, 658. 
 Myosin, 277, 599. 
 Mynstic acid, 140, 157. 
 Myronic acid, 593. 
 Myrosin, 275, 593. 
 
 Naphthalene, 471, 494. 
 Naphthalene-carboxylic acids, 504. 
 Naphthalene-dicarboxylic acids, 504. 
 Naphthalene dichloride, 497. 
 Naphthalene-sulphonic acids, 501. 
 Naphthalene tetrachloride, 497. 
 Naphthalic acid, 504. 
 Naphthaquinones, 503. 
 Naphthazarine, 503. 
 Naphthazines, 550. 
 Naphthenes, 41. 
 Naphthionic acid, 501. 
 Naphtho-acridines, 548. 
 Naphtho-phen-oxazine, 550. 
 Naphthoic acids, 503. 
 Naphthol dyes, 502. 
 Naphthol-sulphonic acids, 502. 
 Naphthol yellow, 502. 
 Naphthols, 495, 501. 
 Naphthylamine-sulphonic acids, 501. 
 Naphthylamines, 499. 
 Narcotine, 561. 
 Nerol, 572. 
 Nerolin, 502. 
 Neurine, 196. 
 Neutral esters, 91, 97. 
 Neutral red, 552. 
 Neutral violet, 552. 
 Nicholson's blue, 489. 
 Nickel powder and hydrogen as a reduc- 
 ing- agent, 610. 
 Nicotine, 557. 
 
 JJJf . nic acid ' 539. 557- 
 
 Nile blue, 554. 
 
 Nitracetanilides, 374. 
 
 Nitramines, 109. 
 
 Nitranilic acid,- 433. 
 
 Nitranilines, 375, 652. 
 
 Nitric acid, constitution, 95. 
 
 Nitric acid as an oxidizing agent, 621. 
 
 Nitriles, aliphatic, 101. 
 
 Nitriles, aromatic, 438. 
 
 Nitriles, constitution of, 103. 
 
 Nitro-alizarin, 510. 
 
 Nitro-benzaldehydes, 426, 521. 
 
 Nitro-benzene, 360, 361. 
 
 Nitro-benzene, electrolytic reduction of, 
 
 615. 
 
 Nitro-benzene as an oxidizing agent, 626. 
 Nitro-benzene-sulphonic acids, 405. 
 Nitro-benzoic acids, 446, 449. 
 Nitro-benzoyl-formic acid, 462, 523. 
 
 Nitro - benzyl - phenyl-nitrosamine, reduc 
 
 tion of, 604. 
 
 Nitro-camphors, 587, 657. 
 Nitro-cinnamenes, 362. 
 Nitro-cinnamic acid dibromide, 453. 
 Nitro-cinnamic acids, 455. 
 Nitro-decane, 95. 
 Nitro-derivatives, aliphatic, 94. 
 Nitro-derivatives, aromatic, 359. 
 Nitro-dimethyl-aniline, 378. 
 Nitro-diphenyl-amines, 377. 
 Nitro-ethane, 94. 
 Nitro-glycerine, 201. 
 Nitro-guanidine, 297. 
 Nitro-mesitylene, 360. 
 Nitro-methane, 94. 
 Nitro-naphthalenes, 499. 
 Nitro-naphthols, 502. 
 Nitro-naphthylamines, 500. 
 Nitro-phenols, 414, 653. 
 Nitro-phenols, salts of, 414, 653. 
 Nitro-phenyl-acetic acid, 524. 
 Nitro-phenyl-acetylene, 363. 
 Nitro-phenyl-glyoxylic acid, 523. 
 Nitro-phenyl-hydrazine, 399. 
 Nitro-phenyl-lactyl-methyl ketone, 527. 
 Nitro-phenyl-propiolic acid, 456, 524. 
 Nitro-prussic acid, 272. 
 Nitro-styrenes, 362. 
 Nitro- tartaric acid, 253. 
 Nitro-thiophene, 519. 
 Nitro-toluenes, 360, 362. 
 Nitro-uracyl, 287. 
 Nitro-uracyl-carboxylic acid ; 287. 
 Nitro-xylenes, 360. 
 Nitroform, 97. 
 Nitrogen, detection of, 3. 
 Nitrogen, estimation ofT 5. 
 Nitrogen, quinquevalent, 105, 379, 631. 
 Nitrogen bases of the alkyl radicals, 104. 
 Nitrogen isomerism, 138, 428, 631. 
 Nitrolamines, 573. 
 Nitrolic acids, 96. 
 Nitrosamines, 108, 376. 
 Nitrosamines of aromatic bases, 376.' 
 Nitrosates of terpenes, 573. 
 Nitrosites of terpenes, 573. 
 Nitroso-benzene, 365. 
 Nitroso-chlorides of terpenes, 573. 
 Nitroso-diethyl-aniline, 379. 
 Njtroso-dimethyl-aniline, 378. 
 Nitroso-indole, 521. 
 Nitroso-indoxyl, 523. 
 Nitroso-limonenes, 575. 
 Nitroso-phenol, 378, 414, 432. 
 Nitrous acid, constitution of, 95. 
 Nomenclature, international, 40. 
 Nomenclature of the alcohols, 73. 
 Nomenclature of the hydrocarbons, 39 
 Nonane, 30. \et seg. 
 
 Nondecyhc acid, 140. 
 Nonoses, 300. 
 Nonyl alcohol, 67. 
 Nonylene, 43. 
 Nonylic acid, 140. 
 Normal esters, 91, 97. 
 Normal salts, 144. 
 Norpinic acid, 583. 
 
INDEX 
 
 713 
 
 
 Nucleic acid, 599. 
 Nucleo-proteins, 599. 
 
 o = ortho; see Ortho-compounds. 
 
 Octa-acetyl derivatives of sugars, 314. 
 
 Octa-decyler.e, 43. 
 
 Octane, 30. 
 
 Octoses, 300. 
 
 Octyl alcohol, 67. 
 
 Octylamine, no, 
 
 Octylene, 43. 
 
 Octylic acid ; see Caprylic acid, 175. 
 
 CEnanthol, 129. 
 
 Oil of bitter almonds, 266, 423. 
 
 Oil of the Dutch chemists, 44. 
 
 Oils, ethereal, 567. 
 
 Oils and fats, 158. 
 
 Olefine bond, 44. 
 
 Olefines, 42. 
 
 Olefines, constitution of, 46. 
 
 Olefines, formation of, 45. 
 
 Oleic acid, 158, 161, 165. 
 
 Oleic series of acids, 162. 
 
 Olein, 158. 
 
 Olive oil, 158. 
 
 Open chains, 20, 321. 
 
 Opianic acid, 562. 
 
 Opium bases, 560, 564. 
 
 Optical activity, 154, 656, 694. 
 
 Optically active compounds, their pre- 
 paration by means of ferments, 256. 
 
 Orange, oil of, 568. 
 
 Orange II, 502. 
 
 Orcinol, 408, 419. 
 
 Organo-magnesium compounds, 121, 403. 
 
 Organp-metallic compounds, 1 18, 403. 
 
 Ornithine, 219, 596. 
 
 Ortho-acetic ester, 197. 
 
 Ortho-acids, 142. 
 
 Ortho-acids, derivatives of, 178. 
 
 Ortho-carbonic ester, 202, 281; 
 
 Ortho-compounds, 333; 337. 
 
 Ortho-formic acid, 197. 
 
 Ortho-quinones, 430. 
 
 Osazones, 222, 301. 
 
 Osones, 304. 
 
 Oxal-acetic acid, 260, 670. 
 
 Oxalic acid, 204, 231, 234, 241. 
 
 Oxalic ester; see Ethyl oxalate. 
 
 Oxaluric acid, 286, 287. 
 
 "Oxalyl", 233. 
 
 Oxalyl chloride, 234. 
 
 Oxalyl-urea ; see Parabanic acid, 286, 
 
 Oxamethane, 237. [287. 
 
 Oxamic acid, 234, 236. 
 
 Oxamide, 234, 236. 
 
 Oxanilic acid, 382. 
 
 Oxanilide, 382. 
 
 Oxazole, 530. 
 
 Oxidases, 671. 
 
 Oxidation, 616. 
 
 Oxidation, catalytic, 674. 
 
 Oxidation, effects of conditions on, 617. 
 
 Oxidation, electrolytic, 626. 
 
 Oxidation with acidified permanganate, 
 619. [618. 
 
 Oxidation with alkaline permanganate, 
 
 Oxidation with chromic anhydride, 620. 
 
 Oxidation with chromyl chloride, 620. 
 
 Oxidation with dichromate and acid, 620. 
 
 Oxidation with neutral permanganate, 
 
 Oxidation with nitric acid, 621. [619. 
 
 Oxidation with oxygen, 623. 
 
 Oxidation with ozone, 624. 
 
 Oxidation with peroxides, 622. 
 
 Oxidation with sulphuric acid, 622. 
 
 Oximes, 127, 135, 137/301, 428. 
 
 Oximide, 237. 
 
 Oxindole, 452, 522, 525. 
 
 Oxonium salts, 532. 
 
 Oxozonides, 624. 
 
 Oxy-carbanil, constitution of, 650. 
 
 Oxy-hasmoglobin, 600. 
 
 Oxy-methylene-camphor, 655. 
 
 Oxy-proline, 596. 
 
 Oxy-purine, 293. 
 
 Oxy-uvitic acid, 230. 
 
 Oxygen, estimation of, 6. 
 
 Ozokerite, 42. 
 
 Ozone as an oxidizing agent, 624. 
 
 Ozonides, 624. 
 
 /=para; see Para-compound& 
 
 Palatin black, 503. 
 
 Palmitic acid, 140, 157, 161. 
 
 Palmitin, 158. 
 
 Palmito-nitrile, 102. 
 
 Papaveraldine, 560. 
 
 Papaverine, 560. 
 
 Papaveroline, 560. 
 
 Para-aldehyde, 129. 
 
 Para-anthracene, 507. 
 
 Para-compounds, 333, 337. 
 
 Para-cyanogen, 265. 
 
 Para-formaldehyde, 128. 
 
 Para-fuchsine, 486. 
 
 Para-lactic acid, 2i.<;. 
 
 Para-leucaniline, 484, 485, 
 
 Para-quinones, 430. 
 
 Para-rosaniline, 485. 
 
 Para-tartaric acid; see Racemie acid, 24^,. 
 
 Parabanic -acid, 286, 287. 
 
 Paraffin, liquid, 42. 
 
 Paraffin wax, 42. 
 
 Paraffins, 31. 
 
 Paraffins, constitution of, 38. 
 
 Paraffins, formation of, 33. 
 
 Paraurazine, 284. 
 
 Paroxazine, 549. 
 
 Partial valencies, 683. 
 
 Partition coefficient, 28. ' 
 
 Patent blue, 480. 
 
 Pelargonic acid, 165. 
 
 Penta-chlor-aniline, 374. 
 
 Penta-decylene, 43. 
 
 Penta-decylic acid, 140. 
 
 Penta-hydric alcohols, 201, 202. 
 
 Penta-hydroxy-flavone, 541. 
 
 Penta-methylene, 322. 
 
 Penta-methylene-diamine, 196, 535, 598. 
 
 Penta-phenyl-ethane, 690. 
 
 Penta-triacontane, 30. 
 
 Pentacetyl-galactose, 311. 
 
 Pentacetyl-glucose, 303, 309. 
 
 Pentane acid, 153. . 
 
 Pentane di-acid, 240. 
 
714 
 
 Pentanes, 30, 38. 
 Pentanone di-acid, 260. 
 Pentoses, 300, 306. 
 Peppermint, oil or, 570. 
 Pepsin, 598. 
 Peptones, 598, 600 
 Per-acid salts, 144. 
 Perbenzoic acid, 440, 
 Perchlor-ether, 86. 
 
 Perchloro-ethane, 64. 
 
 " Peri "-position, 490- 
 
 Perkins synthesis, 425, 441- . . 
 
 Permanganate as an oxidizing ag_ent, 
 
 Peronine, 564. 
 
 INDEX 
 
 A _ oxidizing agents, 622. 
 
 Perozonides, 624. 
 Petroleum, 41. 
 Petroleum ether, 42. 
 Phaseolunatin, 592. 
 Phellandrene, 577- . Q 
 
 Phellandrene derivatives, 578. 
 "Phenacetine", 415- 
 Phenacyl bromide, 427. 
 Phenanthra-qumone, 512. 
 Phenanthrene, 510. 
 Phenanthrene-/3-carboxyhc acid, 5" 
 Phenanthrene picrate, 511. 
 Phenanthrene-qumol, 512 
 Phenanthrol, 512. 
 Phenates, 407. 
 Phenazine, 549, 55 1 - 
 Phenetedines, 415- 
 Phenetole, 412. 
 Pheno-safranine, 552. 
 Phenocoll, 415. 
 Phenol, 406. 4, 
 Phenol, esters of, 407. 
 Phenol, ethers of, 407. . 
 
 Phenol-methyl ether; vxAnisok, 407 
 Phenol-phthaleln, 492. 
 Phenol-phthaline, 40?. 
 Phenol-sulphonic acids, 416. 
 Phenolic acids, aromatic, 457. 
 Phenols, 407. 
 Phenoxazine, 554. 
 Phenoxides, 407. 
 Phenthiazine, 550. 
 Phenyl acetate, 413. 
 Phenyl-acetic acid, 443, 45^- 
 Phenyl-acetylene, 353. 
 Phenyl-acridine, 548. ., ~ 
 
 Phenyl-acridonium hydroxide, 665. 
 
 Phenyl-alanine, 453, S9&. 6 7- . .,., 
 Phenyl-allyLdimethyl-ammonium iodide, 
 
 Phenyl-amine, 372. 
 Phenyl-amino-acetic acid, 452. 
 Phenyl-amino-propionic acids, 453, 59- 
 
 Phenyl-benzoic acid, 477. 
 
 Phenyl -benzyl -methyl -ethyl -ammonium 
 
 iodide, 632. 
 
 Phenyl-carbimide, 383. 
 Phenyl-carbinol, 421. 
 Phenyl-chlpracetic acid, 452. 
 a-Phenyl-cinnamo-nitrile, 267. 
 Phenyl-cyanide ; see Bcnzomtrile, 447- 
 Phenyl-dibromo-propionic acid, 454. 
 Phenyl-dimethyl-pyrazolone, 230, 529. 
 
 Phenyl - dipropyl - methyl - ar ""-y:-"V 
 Phenyl-disulphide, 413. [iodide, 632. 
 
 Phenyl ether, 412. 
 Phenyl-ethyl-alcohols, 422, 670. 
 Phenyl-ethyl ether, 412. 
 Phenyl-ethylene, 353. 
 Phenyl-glucosazone, 309. 
 Phenyl-glycerol, 422. 
 Phenyl-glycine, 383. 
 Phenyl-glycocoll, 383, 527. 
 Phenyl-glycocoll-o-carboxyhc acid, 527. 
 Phenyl-glycollic acid, 460. 
 
 Phenyl-glyoxylic acid, 427, 462. 
 
 Phenyl-hydrazme, 398. 
 
 Phenyl-hydrazones, 127, 135, 424. 427.428. 
 
 Phenyl hydrogen sulphate, 412. 
 
 Phenyl-hydrosulphide, 413. 
 
 Phenyl-hydroxylamine, 394, 397- 
 
 Phenyl-hydroxy-propiomc acid, 462. 
 
 Phenyl-imi no-butyric acid, 383. 
 
 Phenyl-iodide'dichloride, 358. 
 Phenyl-isocrotonic acid, 456, 490. 
 Phenyl-isocyanate, 383. 
 Phenyl-isothiocyanate, 383. 
 Phenyl magnesium bromide, 403. 
 
 fnenyi-meLu>i-cu.v ^~ 
 Phenyl-methyl hydrazme, 398. 
 Phenyl-methyl ketone, 427. 
 Phenyl-methyl-pyrazolone, 230, 529- 
 Phenyl-naphthalene, 504. 
 Phenyl-naphthylammes, 500. 
 Phenyl-nitramine, 389. 
 Phenyl-nitro-methane, 363. 
 Phenyl-phenazomum chloride, 553. 
 Pheriyl-phosphine, 403- 
 Phenyl-phosphinic acid, 403. 
 Phenyl-propiolic acid, 443, 4S b - 
 
 Phenyl-propionic acids, 453. 
 
 Phenyl radical, 329. 
 
 Phenyl salicylate, 45- 
 
 Phenyl-salicylic acid, 458. 
 
 Phenyl sulphide, 413- 
 
 Phenyl-sulphonamic acid, 405. 
 
 Phenyl sulphone, 413- 
 
 Phenvl-^-tolyl-anti-ketoxime, 429. 
 
 Phenyl-J-tolyl-syn-ketoxime, 4 29. 
 
 Phenylene diammes, 380. 
 
 Phloretic acid, 593. 
 
 Phloretin, 593. 
 
 Phloridzin, 593- 
 
 Phloroglucinol, 343- ** 4 2 - 593- 
 
 Phloroglucinol-di-carboxyhc ester, 441- 
 
 PWorollucinol-hexa-methyl ether 42C 
 
 Phloroglucinol-mono-meth>-l ether, 542, 
 
 Phlorollucinol-trimethyl ether, 420. 
 
 Phloroglucinol-trioxime, 420. 
 
 Phloxin, 493. 
 
 Phorone, 135. i37 6l 3- 
 
 Phosgene, 280. < 
 
 Phosphenyl chloride, 403. 
 
 Phosphine, 548. 
 
 Phosphine-oxides, 113. 
 
 Phosphines, 113 et seq. 
 
 Phosphinic acids, 114. 
 
 Phosphino-benzene, 403. 
 
INDEX 
 
 715 
 
 Phospho-benzene, 403. 
 
 Phospho-proteins, 599. 
 
 Phosphonic acids, 1 14. 
 
 Phosphonium bases, 113, 114. 
 
 Phosphoric esters, too. 
 
 Phosphorous esters, 100. 
 
 Phosphorus, detection of, 4. 
 
 Phosphorus, estimation of, 6. 
 
 Phosphorus compounds, aromatic, 402. 
 
 Phthalei'ns, 491. 
 
 Phthalic acids, 464, 466. 
 
 Phthalic anhydride, 465. 
 
 Phthalide, 462, 466. 
 
 Phthalimide, 465. 
 
 Phthalines, 492. 
 
 Phthalo-phenone, 465, 491. 
 
 Phthalyl chloride, 465. 
 
 Physical properties of organic compounds, 
 
 Picene, 512. [24 et seq., 635 et seq. 
 
 Picolines, 538. 
 
 Picolinic acid, 539. 
 
 Picramide, 375. 
 
 Picric acid, 414. 
 
 Picryl chloride, 362, 415 
 
 Pimaric acid, 591. 
 
 Pimelic acid, 231, 344. 
 
 Pinacoline, 137, 193. 
 
 Pinacone, 193. 
 
 Pinene, 581. 
 
 Pinene dibromide, 582. 
 
 Pinene glycol, 582. 
 
 Pinene hydrochloride, 582. 
 
 Pinene nitroso-chloride, 582. 
 
 Pinic acid, 583. 
 
 Pinole, 582,. 
 
 Pinonic acid, 583. 
 
 Pipecplines, 540. 
 
 Piperic acid, 464, 540. 
 
 Piperidei'ns, 540. 
 
 Piperidine, 196, 531, 534, 535, 540. 
 
 Piperidme, constitution of, 535. 
 
 Piperine, 464, 540. 
 
 Piperonal, 429. 
 
 Piperpnylic acid, 460. 
 
 Pivalic acid, 157. 
 
 Platinichlorides, 107, 370. 
 
 Polyamines, aromatic, 380. 
 
 Polybasic acids, 261. 
 
 Polymerism, 12. 
 
 Polymerization of acetylenes, 51, 341. 
 
 Polymerization of aldehydes, 126. 
 
 Polymerization of nitriles, 102. 
 
 Polymerization of defines, 45. 
 
 Polymethylene derivatives, 322 et seq. 
 
 Polypeptides, 597, 600, 672. 
 
 Polysaccharoses, 299, 316. 
 
 Polyterpenes, 567. 
 
 Ponceau, 2 R, 503. 
 
 Populin, 593. 
 
 Position isomerism, 87. 
 
 Potassium acetates, 151. 
 
 Potassium antimonyl-tartrate, 253. 
 
 Potassium carboxide, 343. 
 
 Potassium cyanate, 273. 
 
 Potassium cyanide, 269. 
 
 Potassium diazobenzene oxide, 390. 
 
 Potassium ethide, 119. 
 
 Potassium ethyl-carbonate, 280. 
 
 Potassium ferricyanide, 271. 
 
 Potassium ferricyanide as an oxidizing 1 
 agent, 626. 
 
 Potassium ferri-ferrocyanide, 271. 
 
 Potassium ferrocyanide, 270. 
 
 Potassium ferro-ferrocyariide, 271. 
 
 Potassium formate, 148. 
 
 Potassium indoxyl-sulphate, 523. 
 
 Potassium methide, 119. 
 
 Potassium methoxide = potassium methy- 
 
 Potassium myronate, 277. [late, 75. 
 
 Potassium persulphate as an oxidizing 
 
 Potassium pyrrole, 518. [agent, 626. 
 
 Potassium thiocyanate, 275. 
 
 Potassium xanthate, 295. 
 
 Prehnitic acid, 470. [146. 
 
 Primary, secondary, and tertiary acids, 
 
 Primary, secondary, and tertiary alcohols, 
 68-70, 72, 97. [104 et seq. 
 
 Primary, secondary, and tertiary amines, 
 
 Primary, secondary, and tertiary di- 
 amines, 195. 
 
 Primary, secondary, and tertiary nitro- 
 compounds, 96. [phines, 113. 
 
 Primary, secondary, and tertiary phos- 
 
 Primary, secondary, tertiary, and qua- 
 ternary hydrazines, 112. 
 
 Prism formula of benzene, 336. 
 
 Proline, 596. 
 
 Propadiene, 53. 
 
 Propane, 30, 38. 
 
 Propane di-acid, 237. 
 
 Propane-diol acid, 218. 
 
 Propanc-diols, 192. 
 
 Propane-nitrile, 102. 
 
 Propane-2-pl-i-acid, 214. 
 
 Propane- tricarboxylic acid, 261. 
 
 Propane-triol, 198. 
 
 Propanol, 80. 
 
 Propanol di-acid, 247. 
 
 Propanone, 136. 
 
 Propargyl alcohol, 82. 
 
 Propargylic acid, 166. 
 
 Propenal, 130. 
 
 Propene, 48. 
 
 Propene acid, 164. 
 
 Propine, 53. 
 
 Propmol, 82. 
 
 Propio-nitrile, 102. 
 
 Propiolic acid, 166. 
 
 Propionic acid, 140, 152, 
 
 Propionyl, 14^7. 
 
 Propyl bromides, 56, Co. 
 
 Propyl carbonate, z''o. 
 
 Propyl chlorides, 56, Co. 
 
 Propyl iodides, 56, 60. 
 
 Propyl-acetic acid, 153. 
 
 Propyl-aceto-acetic ester, ziQ 
 
 Propyl-alcohols, 67, o. 
 
 Propyl- aldehyde, 129. 
 
 Propyl-amines, no. 
 
 Propyl-benzenes, 345, 352. 
 
 Propyl-methyl-benzenes, 352. 
 
 Propyl-piperidincs, 538. 
 
 Propyl-pseudo-nitrol, 96. 
 
 Propyl-pyridines, 538. 
 
 Propylene, 43, 48. 
 
 Propylene glycols, 192. 
 
716 
 
 INDEX 
 
 Protamines, 599. 
 
 Proteins, 599. 
 
 Proteoses, 600. 
 
 Protocatechuic acid, 459, 542. 
 
 Protocatechuic aldehyde, 429. 
 
 Prussian blues, 271. 
 
 Prussic acid, 266. 
 
 Pseudo-acids, 96, 364, 491, 665. 
 
 Pseudo-bases, 487. 
 
 Pseudo-cumene, 345, 352. 
 
 Pseudo-cumenol, 408. 
 
 Pseudo-cumidine, 367. 
 
 Pseudo-indoxyl. 523. 
 
 Pseudo-methylisatin, 524. 
 
 Pseudo-nitrols, 97. 
 
 Pseudo-phenols, 434. 
 
 Pseudo-uric acid, 291. 
 
 Ptoma'mes, 196, 598. 
 
 Pulegone, 570, 579. 
 
 Purine, 290. 
 
 Purine group, 290 et sea. 
 
 Purpuric acid, 289. . 
 
 Purpurin, 510. 
 
 Putrescine, 195, 598. 
 
 Pyrazine, 531, 550. 
 
 Pyrazole, 528, 695. 
 
 Pyrazolidine, 528. 
 
 Pyrazoline, 528, 695. 
 
 Pyrazolone, 528. 
 
 Pyrene, 512. 
 
 Pyridazine, 531, 550. 
 
 Pyridine, 322, 531, 533. 
 
 Pyndine-carboxylic acids, 539, 545, 560. 
 
 Pyridine derivatives, 536 et scq. 
 
 Pyridyl-methyl-pyrrole, 558. 
 
 Pyridyl-methyl-pyrrolidine, 557. 
 
 Pyridyl-pyrrole, 558. 
 
 Pyrimidine, 531, 550. 
 
 Pyro-mellitic acid, 470. 
 
 Pyro-mucic acid, 518. 
 
 Pyro-racemic acid, 223, 225. 
 
 Pyro-tartaric acid, 241. 
 
 Pyrocatechin = CafecAp/, 417. 
 
 Pyrogallol Pyrogallic acid, 408, 419. 
 
 Pyrogallol-carboxylic acid, 460. 
 
 Pyrogallol-dim,ethyl ether, 420. 
 
 Pyrohgneous acid, 150. 
 
 Pyrone, 531. 
 
 Pyrone-dicarboxylic acid, 533. 
 
 Pyronine, 492, 547. 
 
 Pyroxylme, 317. 
 
 Pyrrole, 322, 515, 518. 
 
 Pyrrolidine, 519. 
 
 Pyrrolidine-carboxylic acid, 596. 
 
 Pyrroline, 518. 
 
 Pyruvic acid, 204, 225, 670. 
 
 Pyruvic acid phenyl-hydrazone, 226. 
 
 Qualitative analysis, 2. 
 
 Quantitative analysis, 4. 
 
 Quaternary ammonium bases, 104, 379. 
 
 juercitin, 541. 
 
 Juercitol, 421. 
 
 Juinaldine, 543, 544, 546. 
 
 Jumhydrpne, 431. 
 
 )uinic acid, 461, 559. 
 
 nnine, 558. 
 
 linitol, 419. 
 
 >uinol, 408, 418. 
 )uinol-dicarboxylic acid, 469. 
 Juinoline, 541, 542. 
 )uinoline carboxylic acids, 546. 
 Juinoline decahydride, 546. 
 Juinoline yellow, 546. 
 )uinolinic acid, 536, 540. 
 >uinolinium salts, 546. 
 juinone chlorimide, 434. 
 Juinone dichlorimide, 434. 
 Juinone-aniles, 434. 
 Juinone-dioxime, 432. 
 Juinone-oxime, 434. 
 Juinones, 381, 430, 503, 508, 512, 652. 
 Juinonoid formulae, 486. 
 >uinovose, 307. 
 Quinoxaline, 551. 
 
 Racemic acid, 249, 253. 
 
 Racemic compounds, 253, 258. 
 
 "Racemic" modification, 156. 
 
 Racemisation, 257, 629. 
 
 Radicals, 22. 
 
 Raflfinose, 316, 671. 
 
 Red prussiate of potash, 271. 
 
 "Reduced" benzene derivatives, 348, 466 
 
 Reduction, 601. '[et seq. 
 
 Reduction, catalytic, 610. 
 
 Reduction, electrolytic, 614. 
 
 Reduction in acid solution, 601. 
 
 Reduction in alkaline solution, 606. 
 
 Reduction in neutral solution, 608. 
 
 Reduction with ethyl alcohol, 609. 
 
 Reduction with hydrogen sulphide, 610. 
 
 Reduction with metals, 609. , 
 
 Reduction with nascent hydrogen, 601. 
 
 Reduction with sodium ethoxide, 609. 
 
 Reduction with sodium hyposulphite, 610 
 
 Reduction with sodium stannite, 609. 
 
 Reduction with sulphurous acid, 610. 
 
 Reformatsky's reaction, 263. 
 
 Refraction, molecular, 641, 693. 
 
 Resin acids, 591. 
 
 Resin soaps, 591. 
 
 Resins, 591. 
 
 Resolution of ^-lactic acid, 215. 
 
 Resolution of f-mandelic acid, 462. 
 
 Resolution of racemic compounds, 253. 
 
 Resorcin yellow, 401. 
 
 Resorcinol, 408, 418. 
 
 Retene, 512. 
 
 Rhamnazin, 541. 
 
 Rhamnetin, 541. 
 
 Rhamnitol, 203. 
 
 Rhamnose, 306. 
 
 Rhodamines, 493. 
 
 Rhodeose, 307. 
 
 Ribose, 306. 
 
 Rochelle salt, 253. 
 
 Rosaniline, 485. 
 
 Rosaniline group, 484. 
 
 Rosaniline salts, 485. 
 
 Rosinaulines, 553. 
 
 Rosolic acid, 490. 
 
 Sabinene, 585. 
 Saccharate, strontium, 314. 
 Saccharic acid, 259, 307. 
 
INDEX 
 
 717 
 
 Saccharjmetry, 315. 
 
 Saccharine, 452. 
 
 Saccharo-biose, 314. 
 
 Saccharomyces, 76, 80. 
 
 Safranines, 552-553. 
 
 Sage, oil of, 581. 
 
 Salicin, 592. 
 
 Salicyl-aldehyde, 429. 
 
 Salicylic acid, 443, 457. 
 
 Saligenin, 429, 593. 
 
 Salmine, 596. 
 
 Salol, 458. 
 
 Salophene, 458. 
 
 Saloquinine, 560. 
 
 Salt out, 159, 594. 
 
 Salts or fatty acids, 144. 
 
 Salts of sorrel, 236. 
 
 Sandmeyer's reaction, 388. 
 
 Saponification, 70, 158. 
 
 Sarcine, 293. 
 
 Sarco-lactic acid, 215. 
 
 Sarcosine, 212. 
 
 Saturated hydrocarbons, 30. 
 
 Saturation isomerism, 133. 
 
 Scarlet, Biebrich, 503. 
 
 Schiff's bases, 371, 425. 
 
 Schijfs reagent, 488. 
 
 Scleroproteins, 599. 
 
 Secondary alcohols, 69 et seq., 126. 
 
 Secondary arsines, 1 16. 
 
 Secondary butyl iodide, 60. 
 
 Secondary nitro-compounds, 90. 
 
 Seignette salt, 253. 
 
 Selenium compounds, 91. 
 
 Semicarbazide, 136. 
 
 Semicarbazones, 136. 
 
 Semicylic bonds, 574, 694. 
 
 Serine, 218, 596. 
 
 Serum albumin, 599. 
 
 Sesqui-terpenes, 567. 
 
 Shellac, 591. 
 
 Side-chain isomerism, 340. 
 
 "Side chains", 347. 
 
 Silico-nonane, 1 18. 
 
 Silico-nonyl alcohol, 118. 
 
 Silicon compounds, 118, 629. 
 
 Silk, artificial, 318. 
 
 Silver formate, 149. 
 
 Silver fulminate, 688. 
 
 Silver oxide as an oxidizing agent, 626. 
 
 Simple ethers, 84. 
 
 Simple ketones, 132. 
 
 Sinigrin, 593. 
 
 Skatole, 522. 
 
 Skatolglycocoll, $96. 
 
 Skraup's synthesis, 542. 
 
 Slow neutralization, 665. 
 
 Soaps, 158 et seq. 
 
 Sobrerol, 582. 
 
 Sobrerythritol, 583. 
 
 Sodio-aceto-acetic ester, 228. 
 
 Sodio-malonic ester, 237. 
 
 Sodium acetate, 151. [608. 
 
 Sodium amalgam as reducing agent, 605, 
 
 Sodium as a reducing agent, 606. 
 
 Sodium ethide, 1 19. 
 
 Sodium ethoxide, 79. 
 
 Sodium formate, 147. 
 
 Sodium glycolls, 191. 
 
 Sodium methide, 119. 
 
 Sodium nitro-prusside, 270. 
 
 Solanine bases, 565. 
 
 Solubility, 24. 
 
 Soluble starch, 319. 
 
 Sorbic acid, 166, 682. 
 
 Sorbitols, 203, 307. 
 
 Sorbose, 312. 
 
 Sozo-iodol, 414. 
 
 Sozolic acid, 416. 
 
 Specific gravity, 25, 639. 
 
 Specific refractive power, 641. 
 
 Specific rotatory power, 656. 
 
 Specific volume, 25. 
 
 Spermaceti, 158. 
 
 Spirit blue, 489. 
 
 Spirits of wine, 75. [322. 
 
 Stability of polymethylene derivatives, 
 
 Stannous chloride as reducing agent, 603. 
 
 Starch, 319. 
 
 Starch, animal, 319. 
 
 Starch, soluble, 319. 
 
 Steam distillation, 27. 
 
 Stearic acid, 140, 157, 161, 198. 
 
 Stearin, 158. 
 
 Stearin candles, 158. 
 
 Stereochemistry of carbon, 154, 250, 307, 
 
 325, 340, 634. 
 
 Stereochemistry of cobalt, 634. 
 Stereochemistry of nitrogen, 138, 428, 631. 
 Stereochemistry of phosphorus, 634. 
 Stereochemistry of selenion, 628. 
 Stereochemistry of silicon, 629. 
 
 Stereochemistry of sulphur, 628. 
 
 Stereochemistry of tin, 629. 
 
 Stereoisomerism, 154. [340. 
 
 Stereoisomerism of benzene derivatives, 
 
 Stereoisomerism of glucoses, &c., 307. 
 
 Stereoisomerism of oximes, 138, 428, 635. 
 
 Stereoisomerism of polymethylene deriva- 
 tives, 325. 
 
 Stereoisomerism of tartaric acids, 250. 
 
 Stereoisomerism of valeric acids, &c., 154. 
 
 Steric retardation or hindrance, 175, 449, 
 
 Stilbene, 471, 478. [651. 
 
 Stilbene dibromide, 478. 
 
 Storax, 353, 423, 454. 
 
 Strychnine, 565. 
 
 Strychnine bases, 565. 
 
 Sturine, 599. 
 
 Styphnic acid, 418. 
 
 Styrene, 353. 
 
 Suberic acid, 231. 
 
 "Substantive dyes", 473, 478. 
 
 Substituted benzoic acids, 448. 
 
 Substitution, 31, 55. 
 
 Substitution, inverse, 45. 
 
 Substitution, laws governing, 448. 
 
 Succinamic acid, 239. 
 
 Succinamide, 239. 
 
 Succinic acid, 231, 238, 241, 669, 670, 
 
 Succinic anhydride, 240. 
 
 Succinimide, 234, 239. 
 
 Succinpnitrile, 194. 
 
 "Succinyl", 233. 
 
 Succinyl chloride, 240. 
 
 Succinylosuccinic acid, 469. 
 
718 
 
 INDEX 
 
 Sucrase, 671. 
 
 Sucrose, 314. 
 
 Sugars, the, 300 et seq. 
 
 Sulphanilic acid, 405. 
 
 Sulphides, 88, 90. 
 
 Sulphinic acids, aromatic, 405. 
 
 Sulphinic acids, fatty, 99. 
 
 Sulpho-acetic acid, 171. 
 
 Sulpho-benzimide, 452. 
 
 Sulpho-benzoic acids, 452. 
 
 Sulpho-urea, 296. 
 
 Sulphobenzylethylpropylsilicyl oxide, 630. 
 
 Sulphonal, 136. 
 
 Sulphones, 89, 90. 
 
 Sulphonic acids, aliphatic, 99. 
 
 Sulphonic acids, aromatic, 403. 
 
 Sulphonium salts, 90. 
 
 Sulphoxides, 89, 90. 
 
 Sulphur, detection of, 3. 
 
 Sulphur, estimation of7 6. 
 
 Sulphur, valency of, 90. 
 
 Sulphuric acid as an oxidizing- agent, 622. 
 
 " Sulphuric ether", 85. 
 
 Sylvane, 517. 
 
 Sylvestrene, 576. 
 
 Sylvestrene derivatives, 578. 
 
 5y?i-aldoximes, 139. 
 
 Syn-d'iazo compounds, 391. 
 
 Synthetic enzymes, 673. 
 
 Synthetical terpenes, 576, 578, 580. 
 
 Syringin, 593. 
 
 Tagatose, 312. 
 
 Talitols, 307. 
 
 Talo-mucic acid, 260, 307. 
 
 Talonic acid, 307. 
 
 Taloses, 307, 311. 
 
 Tannic acids, 460. 
 
 Tannin, 460. 
 
 Tar, coal, 340. 
 
 Tartar emetic, 253. 
 
 Tartaric acid, 249 et seq. 
 
 Tartaric acid, esters of, 253. 
 
 Tartaric acids, inactive, 246, 249, 343. 
 
 See also Dextro-, Lcevo-, and Parct- 
 
 tartaric acids. 
 
 Tartaric acids, stereoisomerism of the, 
 Tartrates, 233. [250. 
 
 Tartronic acid, 199, 247. 
 Tartronyl urea, 288. 
 Taurine, 196. 
 
 Taurochohc acid, 196, 668. 
 Tautomerism, 184, 227, 278, 420, 643, 649, 
 Tellurium compounds, 91. [650. 
 
 Terebenthene, 582. 
 Terephthalic acid, 466. 
 Terpadieneone, 579. 
 Terpadienes, 574. 
 Terpadiol, 580. 
 Terpane, 574. 
 Terpanol, 578, 579. 
 lerpanone, 578. 
 Terpeneone, 579. 
 Terpenes, 567 et seq. 
 Terpenylic acid, 579. 
 Terpin, 580. 
 Terpin hydrate, 581. 
 Terpinene, 572. 
 
 Terpinene derivatives, 578. 
 Terpineol, 576, 579, 583. 
 Terpmolene, 576. 
 Terpinolene tetrabromide, 578. 
 Tertiary alcohols, 70 et seq. 
 Tertiary-butyl iodide, 60. 
 Tertiary nitro-compounds, 96. 
 Tervalent carbon, 690. 
 Tetra-acet-hydrazide, 185. 
 Tetra-bromo-fluorescei'n, 493. 
 Tetra-bromo-methane, 56. 
 Tetra-chloro-aniline, 374. 
 Tetra-chloro-methane, 56, 64. 
 Tetra-chloro-quinone, 432. 
 Tetra-decane, 30. 
 Tetra-decylcne, 43. 
 Tetra-ethyl-rhpdamine, 493. 
 Tetra-ethyl-silicane, 118. 
 Tetra-ethyl-tetrazone, 112. 
 Tetra-hydro-benzene, 349. 
 Tetra-hydro-benzoic acids, 445. 
 Tetra-hydro-naphthalene, 497. 
 Tetra-hydro-naphthols, 502, 607. 
 Tetra-hydro-naphthylamines, 500, 607. 
 Tetra-hydro-phthalic acids, 466. 
 Tetra-hydro-pyridine, 540. 
 Tetra-hydro-quinoline, 534, 546. 
 Tetra-hydro-quinone, 432. 
 Tetra-hydro-terephthahc acids, 466, 468. 
 Tetra-hydro-xylenes, 351. 
 Tetra-hydroxy-anthra-quinone, 510. 
 Tetra-iodo-pyrrole, 518. 
 Tetra-methyl-ammonium compounds, 1 1 
 Tetra-methyl-benzenes, 345, 352. 
 Tetra-methyl-diamino-tnphenyl-c,arbino 
 
 483- [48; 
 
 Tetra-methyl-diammo-triphenyl-methani 
 Tetra-methyl-ethylene glycol, 193. 
 Tetra - methyl - phosphomum hydroxidi 
 Tetra-methyl-silicane, 118. [n, 
 
 Tctra-methyl-stibonium hydroxide, 118. 
 Tetra-methylene, 322. 
 Tetra-methylene-diamine, 195, 598. 
 Tetra-methylene-dicarboxylic acids, 325 
 Tetra-methylene-imine, 519. 
 Tetra-nitro-methane, 97. 
 Tetra-phenyl-methane, 493. 
 Tetra-phenyl-pyrazine, 551. 
 Tetra-phenyl thiopene, 519. 
 Tetracetylene-dicarboxylic acid, 247. 
 Tetraethyl-phosphonium hydroxide, 114 
 Tetrahydric alcohols, 201, 202. 
 Tetrazole, 530. 
 Tetrolic acid, 166. 
 Tetroses, 300. 
 Thebaine, 564. 
 Theine, 293. 
 Theobromme, 293. 
 Theophylline, .293. 
 Theory of valency, 13. 
 Thiacetamide, 186. 
 Thiacetic acid, 181. 
 Thiamides, 186. 
 Thiazines, 549. 
 Thiazole, 529. 
 Thio-acetamlide, 382. 
 Thio-acids, 181. 
 Thio-alcohols, 87. 
 
INDEX 
 
 719 
 
 Thio-benzamide, 447. 
 
 Thio-carbamic compounds, 296. 
 
 Thio-carbamide, 296. 
 
 Thio-carbanilide, 524. 
 
 Thio-carbonic acids, 295. 
 
 Thio-carbonic compounds, 295. 
 
 Thio-carbonyl chloride, 295. 
 
 Thio-cyanates, 275 et seq. 
 
 Thio-cyanic acid, 275. 
 
 Thio-cyanic ester, 275. 
 
 Thio-ethers, 87. 
 
 Thio-glycols, 191. 
 
 Thio-phenol, 413. 
 
 Thio-phosgene, 295. 
 
 Thio-urea, 278, 296. 
 
 Thiols, 88, 677. 
 
 Thionessal, 519. 
 
 Thiophene, 322, 350, 515, 519. 
 
 Thiophene-carboxylic acid, 520. 
 
 Thiophene-sulphonic acid, 520. 
 
 Thiotolene, 520. 
 
 Thujenes, 585. 
 
 Thyme, oil of, 568. 
 
 Thymo-quinone, 433. 
 
 Thymol, 408, 417, 579. 
 
 Tiemann-Reimer reaction, 409, 430, 440. 
 
 Tiglic acid, 161, 165. 
 
 Tin, alkyl compounds of, 120. 
 
 Tin and hydrochloric acid as reducing 
 
 agents, 602. 
 Tolane, 478. 
 Tolidine, 474. 
 Tolu-quinone, 433. 
 Toluene, 340, 345, 350. 
 Toluene-sulphonic acids, 406. 
 Toluic acids, 443, 452. 
 Toluidides, 382. 
 Toluidines, 367, 375. 
 Toluylene blue, 552. 
 Toluylene red, 552. 
 Tolyl alcohols, 422. 
 Tolyl-acetic acids, 443. 
 Tolyl-diphenyl-methanes, 482. 
 Tolyl-phenyl-methanes, 476. 
 Toxines, icJ6, 598. 
 "Trans" form, 246, 326. 
 Transition temperatures, 255. 
 Tri-acetone peroxide, 181. 
 Tri-amines, aromatic, 381. 
 Tri-amino-azobenzene nydrochloride, 401. 
 Tri-amino-diphenyl-tolyl-methane, 484. 
 Tri-amino-triphenyl-carbinol, 485. 
 Tri-amino-triphenyl-methane, 484. 
 Tri-azo compounds, 695. 
 Tri-azole, 530. 
 Tri-bromacetic acid, 167. 
 Tri-bromaniline, 374. 
 Tri-bromo-phenol, 414. 
 Tri-carballylic acid, 261. 
 Tri-chloraniline, 373. 
 Tri-chlorhydrin, 200. 
 Tri-chloro-acetal, 130. 
 Tri-chloro-acetic acid, 167, 170. 
 Tri-chloro-aldehyde = Chloral, 129. 
 Tri-chloro-benzenes, 357. 
 Tri-chloro-cyanogen, 272. 
 Tri chloro-ethanal, 129. 
 Tri-chloro-methane, 63. 
 
 Trj-chloro-phenomalic acid, 343. 
 
 Tri-chloro-propane, 200. 
 
 Tri-chloro-purine, 290. 
 
 Tri-cosane, 30. 
 
 Tri-decylene, 43. 
 
 Tri-decylic acid, 140. 
 
 Tri-diphenyl-methyl, 691. 
 
 Tri-ethylamine, in. 
 
 Tri-ethyl-arsine, 116. 
 
 Tri-ethyl-benzene, 342. 
 
 Tri-ethyl-phosphine, 114. 
 
 Tri-hydric alcohols, 197. 
 
 Tri-hydric phenols, 419. 
 
 Tri-hydrocyanic acid, 269. 
 
 Tri-hydroxy-anthraquinones, 510, 
 
 Tri-hydroxy-benzenes, 419. 
 
 Tri-hydroxy-benzoic acids, 460. 
 
 Tri-hydroxy-glutaric acids, 259. 
 
 Tri-hydroxy-purine, 290, 291. 
 
 Tri-hydroxy-terpane, 579. 
 
 Tri-keto-hexamethylene, 420. 
 
 Tri-mellitic acid, 470. 
 
 Tri-methyl-acetic acid, 157. 
 
 Tri-methyl-arsine, 116, 117. 
 
 Tri-methyl-arsine dichloride, 117. 
 
 Tri-methyl-arsine oxide, 117. 
 
 Tri-methyl-benzenes, 345, 351. 
 
 Tri - methyl - carballylic acid = Campho- 
 ronic acid, 586. 
 
 Tri-methyl-carbinol, 73. 
 
 Tri-methyl-glycocoll = Beta'ine, 212. 
 
 Tri-methyl-hydroxyethyl-ammonium hy- 
 droxide Choline, 196. [379. 
 
 Tri-methyl-phenyl-ammonium hydroxide, 
 
 Tri-methyl-phosphine oxide, 1 14. 
 
 Tri-methyl - pyndine - dicarboxylic ester, 
 
 Tri-methyl-pyridines= Collidines, 539. 
 Tri-methyl-stibine, 117. 
 Tri-methyl-succinic acid, 586. 
 Tri-m ethyl- sulphine hydroxide, 90. 
 Tri-methyl-sulphine iodide, 90. 
 Tri-methyl-sulphonium hydroxide, 90. 
 Tri-methyl-sulphonium iodide, 90. 
 Tri-methyl - vinyl - ammonium hydroxide, 
 Tri-methyl-xanthine, 293. [196. 
 
 Tri-methylamine, no. 
 Tri-methylamine oxide, in. 
 Tri-methylene, 322. 
 Tri-methylene bromide, 192. 
 Tri-methylene glycol, 192. 
 Tri*nitrin, 201. 
 
 Tri-nitro-benzene, 362. [ride, 362. 
 
 Tri-nitro-chloro-benzene = Picryl chlo- 
 Tri-nitro-naphthalene, 499. 
 Tri-nitro-phenol ; see Picric acid, 414. 
 Tri-nitro-tertiary-butyl-toluene, 362. 
 Tri-nitro-triphenyl-carbinol, 481. 
 Tri-nitro-triphenyl-methane, 481. 
 Tri-olei'n ; see Olein, 165. 
 Tri-oxy-methylene, 128. 
 Tri-palmitin, 201. 
 Tri-phenylamine, 379. 
 Tri-phenyl-benzene, 474. 
 Tri-phenyl-carbinol, 422, 481. 
 Tri-phenyl-carbinol-o-carboxylic acid, 491 
 Tri-phenyl-fuchsine, 489. 
 Tri-phenyl-methane, 471, 481. 
 
720 
 
 INDEX 
 
 Tri-phenyl-methanc-carboxylic acid, 491. 
 
 Tri-phenyl-methane dyes, 482. 
 
 Tri-phenyl-methyl, 690. 
 
 Tri-phenyl-methyl bromide, 481. 
 
 Tri-phenyl-methyl peroxide, 690. 
 
 Tri-saccharoses, 299. 
 
 Tri-stearin, 201. 
 
 Tri-thio-carbonic acid, 295. 
 
 Trimesic acid, 470. 
 
 Trimesic ester, 342. 
 
 Triple bond, 49. 
 
 Trisaccharoses, 299, 300, 305, 312. 
 
 Tropaeoline O, 402. 
 
 Tropaeolines, 401. 
 
 Tropei'nes, 565. 
 
 Tropic acid, 443, 462, 565. 
 
 Tropidine, 566. 
 
 Tropine, 565. 
 
 Tropine-carboxylic acid, 566. 
 
 Tropinic acid, 566. 
 
 Trypsin, 598. 
 
 Tryptophan, 596. 
 
 Turnbull's blue, 271. 
 
 Turpentine, oil of, 581. 
 
 Types, theory of, 13-15. 
 
 Tyrosine, 459, 596, 670. 
 
 Tyrosol, 670. 
 
 Umbellic acid, 464. 
 Umbelliferone, 464. 
 Undecane, 30. 
 Undecylene, 43. 
 Undecyljc acid, 140. 
 Unorganized ferments ; see Enzymes. 
 Unsaturated acids, 161, 434, 679. 
 Unsaturated alcohols, 81, 422. 
 Unsaturated dibasic acids, 241. 
 Unsaturated hydrocarbons, 42, 353. 
 Unsaturated monobasic acids, 161. 
 Unsaturation, types of, 678. 
 Unsaturation and physical properties, 
 
 Urea, acyl derivatives of, 285. 
 Urea, alkyl derivatives of, 284. 
 Urea, determination of, 283. 
 Urea, salts, &c., of, 283. 
 Urea = Carbamide, i, 281, 282. 
 Ureides, 285, 286 et seq. 
 Ureido-acids, 286 et seq. 
 Urethanes, 282. 
 Uric acid, 290, 291. 
 Uric acid, derivatives of, 294. 
 Uvitic acid, 466. 
 
 Valency, theory of, 13, 683. 
 Valency of sulphur, 90. 
 Valeric acids, 140, 153. 
 Valero-lactpne, 530. 
 Valero-nitrile, 102. 
 Valerone, i-i-j. 
 Valine, 596. 
 Vanillic acid, 459. 
 Vanillic alcohol, 429 
 Vanillin, 430, 593. 
 
 [693- 
 
 Vapour density, determination of, 9 
 
 Vapour pressure, lowering' of, 12. 
 
 Vaseline, 42. 
 
 Veratric acid, 460, 
 
 Victoria green, 484. 
 
 Victoria orange, 417. 
 
 Vinegar, 150. 
 
 Vinyl acetic acid, 165. 
 
 Vinyl alcohol, 81. 
 
 Vinyl bromide, 56, 65. 
 
 Vinyl chloride, 56. 
 
 Vinyl iodide, 56. 
 
 Vinyl-ethyl ether, 87. 
 
 Violuric acid, 288. 
 
 Viscoid, 318. 
 
 Viscose, 318. 
 
 Viscosity, 665. 
 
 Walden inversion, 661. 
 Wandering of groups, 395. 
 Water blue, 489. 
 Wax varieties, 158. 
 Williamson s blue, 271. 
 Wine, 78. 
 
 Wine, spirits of, 75. 
 Wintergreen, oil of, 74, 457. 
 Wood gum, 306. 
 Wood spirit, 74. 
 Wood sugar, 306. 
 Wood tar, 74. 
 
 Xanthjc acid, 296. 
 Xanthine, 292, 599. 
 Xantho-cheudonic acid, 533. 
 Xantho-protei'n reaction, the, 594. . 
 Xanthone, 549. 
 Xylene-carboxylic acids, 453. 
 Xylene-sulphonic acids, 406. 
 Xylenes, 345, 351. 
 Xylenols, 408. 
 Xylidides, 382. 
 Xylidines, 367. 
 Xylitol, 203. 
 Xylo-quinone, 342, 
 Xylose, 306. 
 
 Yeast, 76, 666. 
 
 Yeast juice, 667. 
 
 Yellow prussiate ot potash, 270. 
 
 Zinc and acid as reducing agents, 60^ 
 
 et seq. 
 
 Zinc and alcohol as reducing agents, 608. 
 Zinc and alkali as reducing agents, 608. 
 Zinc dust and acetic acid as reducing 
 
 Zinc dust and saline solutions as reducing 
 
 Zinc ethyl, 120. [agents, 609. 
 
 Zinc methide, 119. 
 
 Zinc methoxide, 120. 
 
 Zinc-methyl iodide, 120. 
 
 Zymase, 77, 304, 667, 
 
 Zymin, 667. 
 
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rB 16754 
 
 
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 UNIVERSITY OF CALIFORNIA LIBRARY