GIFT OF MICHAEL REESE A TREATISE ON CHEMISTRY TEEATISE ON CHEMISTRY BY SIB H. E. KOSCOE F.E.S. AND C. SCHOKLEMMEE F.K.S. VOLUME III THE CHEMISTRY OF THE HYDROCARBONS AND THEIR DERIVATIVES, OB ORGANIC CHEMISTRY PART IV " Chymia, alias Alchemia et Spagirica, est ars corpora vel mixta, vel composita, vel aggregata etiam in principia sua resolvendi, aut ex principiis in talia combinandi." STAHL, 1723. NEW YORK D. APPLETON AND COMPANY 1888 V. 3,' PREFACE TO VOL. III., PAKT IV. THE Fourth Part of the Treatise on Organic Chemistry now presented to the public includes a description of the Aromatic Compounds containing seven atoms of Carbon, and, like the preceding part, forms a chapter complete in itself. The first portion is concerned with the Toluene Group, then come the Benzyl, Benzoyl, and Hydrobenzyl Groups, and lastly the Xylene Group of Eight Carbon Compounds. CONTENTS. PAGE TOLUENE GROUP 3 Toluene or Methylbenzene 3 Addition Products of Toluene 6 Chlorine Substitution Products of Toluene 7 Monochlorotoluenes 8 Dichlorotoluenes . ........ . . . 9 Bromine Substitution Products of Toluene . . . . . . .10 Monobromotoluenes . . . .10 Dibromotoluenes 11 Tribromotoluenes . . .12 Tetrabromotoluenes . . . 12 Iodine Substitution Products of Toluene ....... 13 Fluorine Substitution Products of Toluene 13 Nitro-Substitution Products of Toluene . . . . . . .13 Mononitrotoluenes 13 Dinitrotoluenes 16 Trinitrotoluenes . . . . . .17 Chloronitrotoluenes 19 Bromonitrotoluenes . . . . 19 Toluenesulphonic Acids 20 Toluenemonosulphonic Acids . .... . . . .20 Toluenedisulphonic Acids . . . . . . . . . .22 Toluenetrisulphonic Acids . . - 22 Monohydroxy toluenes and Allied Bodies 23 The Cresols . 23 Dihydroxy toluenes and Allied Bodies 31 Homocatechol or Homopyrocatechin 31 Orcinol 37 Substitution Products of Orcinol 41 Chlorine Substitution Products 41 Bromine Substitution Products 41 Iodine Substitution Products . . 41 Nitro-Substitution Products 41 Cresorcinol 47 Toluquinol or Toluhydroquinone 48 Toluquinono 49 Substitution Products of Toluquinone 50 Toluquinonoxime Compounds . 50 Trihydroxytoluenes 53 CONTENTS. PAGE TOLUENE GROUP continued. Amido-Derivatives of Toluene 54 Amidotoluenes or Toluidines 54 Halogen Substitution Products of the Toluidines 67 Chlorotoluidines 68 Bromotoluidines 68 lodotoluidines 68 Nitrotoluidines 69 Dinitrotoluidines 71 Diamidotoluenes or Tolylenediamines 72 Diazo-Derivatives of Toluene 74 Hydrazine- Derivatives of Toluene 75 Azo-Derivatives of Toluene 75 Phosphorus Derivatives of Toluene . .83 Arsenic Derivatives of Toluene 84 Antimony Derivatives of Toluene 86 Boron and Silicon Derivatives of Toluene 87 Mercury Derivatives of Toluene 87 BENZYL GROUP 89 Benzyl Alcohol 89 Benzyl Ethers 94 Ethereal Salts of Benzyl 96 Substitution Products of Benzyl Alcohol and its Derivatives ... 98 Sulphur Compounds of Benzyl 105 Selenium Compounds of Benzyl 109 Nitrogen Bases of Benzyl . 110 The Benzylamines 110 Amido-Substituted Benzylamines 116 Substitution Products of the Benzylamines 118 Benzyl-Derivatives of the Acid-Amides and Allied Bodies . . . 121 Phosphorus Compounds of Benzyl 124 Arsenic Compounds of Benzyl . . . . ] 25 Silicon Compounds of Benzyl 127 BENZOYL GROUP 128 Benzaldehyde 129 Benzidene Compounds 136 Substitution Products cf Benzidene Compounds 143 Benzoic Acid 151 Salts and Ethers of Benzoic Acid ] 60 Oxides of Benzoyl 166 Halogen Compounds of Benzoyl 168 Sulphur Compounds of Benzoyl 170 Nitrogen Compounds of Benzoyl 172 Hippuric Acid 181 Benzenyl Compounds .194 Benzonitril and its Derivatives .197 Benzimido- Ethers 200 Benzenylamidines 202 Benzenyloxime Compounds 207 Halogen-Substittition Products of Benzoic Acid 216 Monochlorobenzoic Acids 217 Dichlorobenzoic Acids 221 Trichlorobenzoic Acids . CONTENTS. ix BENZOYL GROUP continued. Tetrachlorobenzoic Acid 222 Monobromobenzoic Acids 223 Dibromobenzoie Acids 224 Tribromobenzoic Acids 225 Mono-Iodobenzoic Acids 225 Monofluorbenzoic Acids 226 Nitre-Substitution Products of Benzoic Acid 227 Mononitrobenzoic Acids 229 Dinitrobenzoic Acids ... 234 Trinitrobenzoic Acid 235 Chloronitrobenzoic Acids 236 Bromonitrobenzoic Acids 236 lodonitrobenzoic Acids 237 Monamidobenzoic Acids 237 Chloramidobenzoic Acids 254 Bromamidobenzoic Acids 255 lodamidobenzoic Acids 255 Nitro-Amidobenzoic Acids 255 Dinitro-Amidobenzoic Acids . 257 Piamidobenzoic Acids 258 Triamidobenzoic Acid 260 Diazo-Derivatives of Benzoic Acid 260 Hydrazinebenzoic Acids 264 Azo-Derivatives of Benzoic Acid 265 Monosulphobenzoic Acids 268 Disulphobenzoic Acids 274 Chlorosulphobenzoic Acids 274 Bromosulphobenzoic Acids 274 Mtrosulphobenzoic Acids 275 Amidosulphobenzoic Acids 275 Benzophosphinic Acid 275 Benzarsenic Acids 277 HYDROXYBENZYL GROUP 279 Hydroxybenzyl Alcohols 279 Hydroxybenzaldehydes 285 Orthohydroxybenzaldebyde or Salicylaldehyde 285 Substitution Products of Salicylaldehyde 292 Metahydroxybenzaldehyde 293 Parahydroxybenzaldehyde 294 Hydroxybenzoic Acids 297 Orthohydroxybenzoic Acid or Salicylic Acid 297 Ethereal Salts of Salicylic Acid 306 Salicylic Ethers 306 ** Ethereal Salts of Salicylic Ethers . . 307 Substitution Products of Salicylic Acid 313 Metahydroxybenzoic Acid 320 Substitution Products of Metahydroxybenzoic Acid 323 Parahydroxybenzoic Acid 326 Substitution Products of Parahydroxybenzoic Acid 334 Substitution Products of Anisic Acid 336 Anisenyloxime Compounds 339 Dibenzanishydroxylamine 341 CONTENTS. PAGE HYDROXYBENZYL GROUP continued. Benzanisbenzhydroxylamine 341 Anisdibenzhydroxylamine 341 Anisbenzanishydroxylamine 342 Dianisbenzhydroxylamine 342 Benzdianishydroxylamine 342 Dihydroxybenzyl and Dihydroxybenzoyl Compounds . 343 Dihydroxybenzoic Acids 350 Protocatechuic Acid or Orthodihydroxybenzoic Acid . . . .350 Symmetric Metadihydroxybenzoic Acid or o-Resorcylic Acid . . . 358 Asymmetric Metadihydroxybenzoic Acid or j8-Resorcylic Acid . . 359 Adjacent Metadihydroxybenzoic Acid or 7-Resorcylic Acid . . . 360 Hydroxysalicylic Acid or Paradihydroxybenzoic Acid .... 361 Trihydroxybenzoic Acids 363 Gallic Acid 363 Pyrogallolcarboxylic Acid 378 Phloroglucinolcarboxylic Acid 380 Hydroxyquinolcarboxylic Acid 380 Constitution of the Trihydroxybenzoic Acids 381 Quinic Acid . 381 XYLENE GROUP 386 The Xylenes or Dimethylbenzenes 390 Substitution Products of the Xylenes 392 Halogen Substitution Products of the Xylenes 392 Nitro-Substitution Products of the Xylenes 395 Xylenesulphonic Acids 398 Hydroxy-Xylenes or Xylenols 399 Dihydroxy-Xylenes 402 Trihydroxy-Xylenes 403 The Xyloquinones 404 Amido-Derivatives of the Xylenes 405 The Amidoxylenes or Xylidines 405 Nitroxylidines . 408 Diamines and Triamines of the Xylenes 409 Xylyl-Compounds 410 Xylyl Alcohols r . 411 Xylylamines 412 The Tolualdehydes 413 The Toluic Acids 414 Hydroxytolualdehydes . 422 Hydroxytoluic Acids . . 423 Dihydroxytolualdehydes 427 Dihydroxytoluic Acids 428 Xylylene Alcohols 439 Hydroxymcthylbenzoic Acids 442 Aldehydes and Aldehydo-Acids . . . 447 The Phthalic Acids ' \ .450 Phthalic Acid < 452 Addition Products of Phthalic Acid ... . 469 Halogen Substitution Products of Phthalic Acid 471 Nitrophthalic Acids . 473 Amidophthalic Acids 475 Sulphophthalic Acids 476 CONTENTS. xi XYLENE GROUP continued. Isophthalic Acid or Metaphthalic Acid 479 Addition Products of Isophthalic Acid 481 Substitution Products of Isophthalic Acid 481 Terephthalic Acid 483 Addition Products of Terephthalic Acid 486 Substitution Products of Terephthalic Acid 488 Hydroxymethylhydroxybenzoic Acid 490 Aldehydohydroxybenzoic Acids 491 Hydroxyphthalic Acids 492 Hydroxymethyldihydroxybenzoic Acids 497 Aldehydodihydroxybenzoic Acids 502 Dihydroxyphthalic Acids . . . 510 Trihydroxyphthalic Acids 519 Tetrahydroxyphthalic Acids 519 ORGANIC CHEMISTRY. ORGANIC CHEMISTRY, OR THE CHEMISTRY OF THE HYDROCARBONS AND THEIR DERIVATIVES. PART IV. TOLUENE GROUP. TOLUENE OR METHYLBENZENE, C 6 H 5 .CH 3 . 2017 This hydrocarbon was discovered by Pelletier and Walter in the oil obtained as a by-product in the manufacture of illu- minating gas from the resin of Pinus maritima. They named it " retinaphtha " (rdtinnaphte) and determined its composition accurately. 1 Shortly afterwards, Couerbe examined the liquid obtained by compressing the resin gas, and isolated from it, among other hydrocarbons, his Heptacarbure quadrihydrique, C 7 H ((7=6), which, in spite of some differences, he believed to be identical with retinaphtha. 2 Deville next obtained a hydro- carbon of the same composition by distilling the resin contained in Tolu balsam. 3 He named it benzoene (benzo&ne), because, in the first place, the balsam 4 from which it had been obtained contains benzoic acid ; secondly, because, according to his for- mula, the hydrocarbon may be looked upon as the type of the 1 Ann. Chim. Phys. Ixvii. 269 ; Pogg. Ann. xliv. 8. 2 Ann. Chim. Phys. Ixix. 184 ; Journ. Prakt. Chem. xviii. 165. 3 Ann. Chim. Phys. [3] iii. 168 ; Journ. PraJct. Chem. xxv. 336. 4 Tolubalsam is obtained by incisions made in the bark of the Myroxylon toluifcra, as mentioned by the Spanish physician Monardes in his Historia de las cosas que se traen de nucstras Indias occidentals, which first appeared complete in Seville in 1574, and in which he says that the balsam was collected by the Indians, in the district Tolu, in the neighbourhood of Carthagena (Fliickiger and Hanbury, Phar?nacographia). AROMATIC COMPOUNDS. benzole series, and finally, because this name was similar to that of benzine (benzene), to which the substance bears the greatest resemblance. He considered, nevertheless, that benzoene, was not identical, but isomeric with retinaphtha; Glenard and Boudault also considered the dracyl, which they had obtained, by the dry distillation of dragon's blood (from Calamus draco), 1 to be an isomeride of the former. Hofmann and Muspratt then showed that it is identical with benzoene, for which somewhat unsuitable name Berzelius sub- stituted that of toluol, 2 - soon universally accepted, and still in use on the Continent, while in England it has been changed for the sake of consistency into toluene. A complete investigation of toluene has proved that not only as regards its empirical formula, but in all its properties, it is the next higher homologue of benzene. Deville, as well as Gldnard and Boudault, had already obtained from it nitrotoluene, C 7 H 7 NO 2 (nitrobenzoene, nitrodracyl), by the action of nitric acid, and Hofmann and Muspratt converted this by reduction into toluidine, C 7 H 7 NH 2 , which resembles aniline very closely. 3 Noad found that when cymene, C 10 H 14 , which is a constituent of Roman cumin-oil, is oxidized with nitric acid, toluic acid, C 8 H 8 2 , the homologue of benzoic acid, is formed, and on dis- tillation with caustic baryta decomposes into carbon dioxide and toluene, a reaction which corresponds exactly to the formation of benzene from benzoic acid. 4 The relation of toluene to the benzoic series, which had already been pointed out by the French chemists, was experi- mentally proved by Cannizzaro, who found that benzyl alcohol, C 7 H 7 O, which is converted by oxidation into benzoic acid, under- goes a simultaneous oxidation and reduction when heated with concentrated alcoholic potash, benzoic acid and toluene being formed. 5 Finally, Fittig and Tollens ascertained the constitution of toluene. These chemists obtained it synthetically by the action of sodium on a mixture of methyl iodide and bromobenzene, 6 by which reaction they not only proved that the product is methyl- benzene, but pointed out a general and simple method by which the higher homologues can be prepared, and their constitutions determined. 1 Journ Prakt. Chem. xxxi. Ill ; xxxiii. 466. 2 Jahrcsb. xxii. 354. 3 Chem. Soc. Mem. (1845) ii. 367. 4 jbid. iii. 421. 5 Ann. Chem. Fharm. xc. 252. Ibid, cxxxi. 303. TOLUENE. Mansfield, whose results were subsequently confirmed by Ritthausen, was the first to prove that light coal-tar oils contain toluene and higher homologues as well as benzene 1 (Part III. p. 66). Toluene also occurs, together with xylene, in wood-tar ; Cahours detected it in crude French pyroligneous acid, 2 and Volkel in the oil which comes over first in the distillation of beech-wood tar. 3 It is also found, together with its homologues, in several varieties of petroleum, such as that from Burmah (Rangoon tar), 4 as well as in the liquid obtained by the compression of the illuminating gas which is manufactured by heating the high boiling portions of petroleum, and has been used for lighting railway carriages. 5 It is obtained on the large scale from light coal-tar oil, and is chiefly employed in the colour industry. Properties. .Toluene is a strongly refractive liquid, possessing a smell similar to that of benzene; it boils at 11 0*3 and does not solidify at 20. Oxidizing agents convert it into benzoic acid. It combines with aluminium chloride forming the com- pound Al 2 Cl 6 +6 C 7 H 8 , a thickish, orange-coloured liquid, which is violently decomposed by water with separation of toluene. A similar compound is formed with aluminium bromide. 6 When toluene is heated with aluminium chloride to 200, a portion of it is converted into paradimethylbenzene, paramethyl- ethylbenzene, and metamethylethylbenzene, high boiling hydro- carbons being also formed, while benzene under the same con- ditions yields toluene, ethylbenzene and diphenyl. In order to explain this remarkable reaction, Friedel and Crafts 7 assume that the following first takes place : 2C 6 H 5 A1 2 C1 6 + 2HC1 = C 12 H 10 + 2A1 2 C1 6 + 2H 2 . The nascent hydrogen and the hydrochloric acid convert a. portion of the benzene into methyl chloride and ethyl chloride,, which then form toluene and ethyl benzene (Pt. III. p. 14.) : C 6 H 5 . A1 2 C1 5 + CH 3 C1 = C 6 H 6 .CH 3 + A1 2 C1 6 . When toluene is employed, a similar reaction takes place ;- methyl chloride is, however, probably formed simultaneously, according to the equation : C 6 H 5 .CH 3 + A1 2 C1 6 = C 6 H 5 A1 2 C1 6 + CH 3 C1. 1 Journ. PraU. Chem. Ixi. 74. 2 Ann. Chem. Pharm. Ixxvi. 286. 3 Ibid. Ixxxvi. 335. 4 Journ. Prakt. Chem. Ixx. 300. 8 Greville Williams, Chem. News, xlix. 197. 6 Guatavson, Ber. Deutsch. Chem. Ges. xi. 2152. 7 Compt. rend. c. 692.. 232 AROMATIC COMPOUNDS. When one part of chromium oxychloride is dissolved in ten parts of carbon disulphide, and the solution allowed to drop into a mixture of one part of toluene and ten parts of carbon' disul- phide, a chocolate-brown, crystalline precipitate of the empirical formula C 7 H 8 +2OO 2 C1 2 is formed; this is soluble in glacial acetic acid, rapidly absorbs moisture, and is decomposed by water with formation of benzaldehyde and chromous chromate, showing that it is benzidenedichlorochromic acid : OCrCl 2 .OH \OCrCl.OH C fl H 5 .CH< + H 2 = C 6 H 5 .CHO + 4HC1 + 2CrO 2 . Alcohol and ether exert a similar action, ethyl chloride being formed in these cases. On heating the compound to 240 245, the chloride, C 6 H 5 .CH (OOOC1) 2 , is obtained ; it has a darker colour and is more stable in moist air, but behaves towards water similarly to the acid. 1 ADDITION PRODUCTS OF TOLUENE. 2018 Dihydrotoluene, C 7 H 10 , is obtained by heating toluene with phosphonium iodide to 350, and is a liquid boiling at 105-108. 2 Tetrahydrotoluene, C 7 H 12 , occurs in the distillation products of pine resin and colophonium, which are obtained on the large scale, and employed in the manufacture of varnishes, &c. The fraction boiling below 300, which forms the smaller portion and is known as " resin spirit " or " essence of resin," is a mixture of fatty acids, aldehydes, paraffins, olefmes, aromatic hydrocarbons and their addition products, 3 among which is tetrahydrotoluene. This substance is a liquid boiling at 103 105, and is converted by bromine into a crystalline bromide, C 7 H 6 Br 6 . Tetrahydrotoluene combines with water to form a hydrate, C 7 H 12 -J-2H 2 O, which crystallizes in long, white crystals, and, according to Renard, is identical with Anderson's colophonin, C 7 H 14 O 2 , obtained by exposing resin spirit to the air for a long period ; 4 while accord- 1 fitard, Ann. Chim. Phys. [5] xxii. 223. - IJaoyer, Ann. Chem. Pfiarm. civ. 271. 3 Kelbe, ibid. ccx. 10 ; Kelbe and Bauer, Ber. Deutsch. Chem. Ges. xvi. 2559 ; Renard, Ann. Chim. Phys. [6], i. 223. 4 Chem. News, xx. 76. TOLUENE SUBSTITUTION PRODUCTS. ing to Tichborne, colophonin hydrate, C 10 H 22 O 3 -f H 2 O, is formed, and loses water on heating. 1 Hexhydrotoluene, C 7 H 14 , is prepared by heating toluene with a large excess of concentrated hydriodic acid to 280 , 2 and occurs in Baku petroleum 3 and in resin spirit (Renard). It is a liquid smelling like petroleum, boiling at 97, and having a specific gravity of 772 at 0. A mixture of concentrated sulphuric and nitric acids does not attack it in the cold, but when hot oxidizes it completely. CHLORINE SUBSTITUTION PRODUCTS OF TOLUENE. 2019 By the action of chlorine on toluene in the dark, Deville obtained Benzo&ne monochlord, C 7 H 7 C1, as a thin liquid boiling at 170 , 4 whilst Cannizzaro found that the monochlorinated toluene obtained by the repeated distillation of toluene in a stream of chlorine, and boiling at 175, is identical with benzyl chloride, as it can be readily converted into benzyl alcohol. 5 The same compound was also obtained by passing chlorine into toluene, but in this process an isomeric compound was frequently formed instead of the benzyl chloride, and this proved to be as stable as chlorobenzene. These enigmatical results were explained by Beil stein and Geitner, 6 who observed that the action of chlorine on toluene varies according to the temperature at which the chlorination is effected. Benzyl chloride alone is formed when the mixture is hot, while the stable chlorotoluene is formed when the process is conducted in the cold. As, however, heat is evolved by the action of the chlorine, the toluene, if used in large quantities and not carefully cooled, may become heated almost to the boiling point, benzyl chloride consequently being formed together with more or less chlorotoluene. The nature of this mixture can readily be exhibited by oxidizing it with chromic acid, the benzyl chloride being thus converted into benzoic acid, and the chlorotoluene into chlorodracylic acid 1 Chem. News, xx. 38. 2 Wreden and Znatowicz, Ann. Chem. Pharm. clxxxvii. 161. 3 Beilstein and Kurbatow, ibid. xiii. 1818 ; see also xiv. 1620. 4 Ann. Chim. Phijs. [3], iii. 178. 5 Ann. Chem. Pharm. xcvi. 246 ; ibid. cxli. 198. 6 Ibid, cxxxix. 331. AROMATIC COMPOUNDS. (parachlorobenzoic acid), the acids being readily separated by means of the very great difference in their solubilities in water. Beilstein and Geitner further found that chlorotoluene is more readily obtained by dissolving a little iodine in the toluene and then chlorinating, under which conditions no benzyl chloride is formed either in the cold or on heating. As already mentioned (Part III. p. 17) all the hydrogen atoms of the aromatic group can be thus replaced by chlorine, whilst at the boiling point, in absence of iodine, substitution can only take place in the methyl group. By working alternately according to these two methods no octochlorotoluene can be obtained, the final products being pentachlorobenzidene chloride, C 6 C1 6 .OHC1 2 and tetrachlorobenzal chloride, C 6 HC1 4 .CC1 3 . If these be heated with antimony pentachloride in order to effect a further chlorina- tion, they decompose with formation of hexchlorobenzene. 1 MONOCHLOROTOLUENES, C 6 H 4 C1.CH 3 . 2020 Orthochlorotoluene is formed only in small quantities by the chlorination of toluene in , the presence of iodine : it may, however, be readily obtained from orthotoluidine by means of the diazo-reaction. 2 It is a liquid boiling at 157, which is oxidized by potassium permanganate to orthochlorobenzoic acid, whilst chromic acid solution produces complete oxidation. 3 Mctachlorotoluene is not formed by the action of chlorine on toluene ; it has been prepared from metatoluidine, as well as from paratoluidine by converting this into acetoluide, C 6 H 4 (CH 3 ) NH(C 2 H 3 0), chlorinating and decomposing the product by heat- ing with caustic potash ; the monochloroparatoluidine thus ob- tained is converted into the diazo-compound, and then decom- posed with absolute alcohol ; 4 chloroparatoluidine has, therefore, the following constitution . CH 3 01 NH 2 . 1 Beilstein and Kuhlberg, Ann. Chem. Pharm. cl. 286. 2 Ibid. clvi. 79 ; Gascorowski and Wayss, Ber. Deutsch. Chem. Ges. xviii. 8 Emraerling, Ber. Deutsch. Chem. Ges. viii. 880. 4 Wroblevsky, Ann. Chem. Pharm. clxviii. 199. CHLOROTOLUENES. Hence we see that, on the chlorination of paratoluidine, the chlorine takes up the position adjacent to the basic group, and this also occurs in many other cases. Metachlorotoluene is a liquid which boils at 15(T and is con- verted by oxidation into metachlorobenzoic acid. Parachlorotoluene is the chief product of the action of chlorine on toluene in the presence of iodine. 1 It is advantageous to substitute molybdenum pentachloride for iodine, and to pass the chlorine through the mixture heated on the water-bath. 2 The product thus obtained does not solidify when cooled to a low temperature, since it contains various substances, such as the ortho-compound, &c., as impurities. If the parachlorotoluene be prepared from paratoluidine, it is obtained in a pure condi- tion, and then boils at 160'5 and solidifies at to a foliaceous mass, melting at 6'5. 3 On oxidation it is converted into para- chlorobenzoic acid. DlCHLOROTOLUENES, C 6 H 3 C1 2 .CH 3 . 2021 When toluene is treated with sufficient chlorine in presence of iodine or molybdenum pentachloride, and the pro- duct purified by fractional distillation, a liquid boiling at 196 is obtained, 4 which, in spite of its constant boiling point, is not a definite compound, but a mixture of three dichlorotoluenes. If chlorine be passed into the vapour of the boiling liquid until no further action takes place, the hydrogen of the methyl group is replaced by chlorine and the corresponding dichlorobenzenyl- trichlorides formed ; on heating with water to 200 these are converted into three dichlorobenzoic acids : C 6 H 3 C1 2 .CC1 3 + 2H 2 = C 6 H 3 C1 2 .C0 2 H + 3HC1. The formation of three dichlorotoluenes can readily be explained ; the monochlorotoluene, which is first formed, consists chiefly of the para-compound, which can yield two isomeric dichloro- toluenes, whilst the third is formed from the orthochlorotoluene which is also present, though in smaller quantity. The mixture appears to consist chiefly of asymmetric 1 Beilstein and Geitner, loc. tit. 2 Aronheim and Dietrich, Ber. Deutsch. Chcm. Gcs. viii. 1402. 3 Hiibner and Majert, ibid. vi. 794. 4 Beilstein and Geitner ; Beilstein and Euhlberg, Ann. Chem. Pharm. el. 313 ; Sclmltz, ibid, clxxxvii. 263. Aronheim and Dietrich. 10 AROMATIC COMPOUNDS. dichlorotoluene, (CH 3 :C1 :C1 1 :3 : 4), which yields the cor- responding dichlorobenzoic acid on oxidation. Dichlorotoluene hexchloride, C 6 H 3 C1 2 (CH 3 )C1 6 , is obtained by the continued action of chlorine on toluene in the cold, and crystallizes from carbon disulphide in large prisms melting at 150. When it is heated with alcoholic potash to 110, tetra- chlorotoluene, C 6 HC1 4 .CH 3 , is formed ; this compound is a liquid boiling at 280-290. 1 The following substitution products have been obtained by the continued action of chlorine, assisted finally by the addition of antimony chloride : Melting- Boiling- point, point. a-Trichlorotoluene 2 C 6 H 2 C1 3 .CH 3 (2 : 4 : 5) 82 230 /9-Trichlorotoluene 3 C 6 H 2 C1 3 .CH 3 (2 : 3 : 4) 41 232 Tetrachlorotoluene 4 C 6 HC1 4 .CH 3 96 276'5 Pentachlorotoluene 5 C 6 C1 5 .CH 3 218 301' BROMINE SUBSTITUTION PRODUCTS OF TOLUENE. 2022 All the theoretically possible compounds of this series are known. MONOBROMOTOLUENES, C 6 H 4 Br.CH 3 . Ortholromotoluene is formed, together with a larger amount of parabromotoluene, by the bromination of toluene in the cold. The para-compound, which crystallizes out, is removed by pressing, and the liquid cooled in a freezing mixture, in order to remove as much of the solid as possible ; the portion which remains liquid is then dissolved in alcohol and distilled, all the remaining parabromotoluene volatilizing in the vapour. 6 The para-compound may also be removed by means of sodium, which does not act upon the ortho-compound in the cold. 7 In order to effect this, the liquid is dissolved in benzene and allowed to stand over sodium for eight days ; it is then distilled, and the fraction boiling between 170 190 treated three or four times in the same way. 8 1 Pieper, Ann. C'hcm. Pharm. cxlii. 304. 2 Lirnpricht, ibid, cxxxix. 326 ; Schultz ; Aronheim and Dietrich ; Seelig, Ber. Dcutsch. Chem. Ges. xviii. 420. 3 Seelig. 4 Limpricht ; Beilstein and Kuhlberg. 8 Beilstein and Kuhlberg. 6 Hiibner and Jannasch, Ann. Chem. Pharm. clxx. 117. 7 Luginin, Bull. Soc. Chim. iv. 514. 8 Reymann, ibid. xxvi. 533. BROMOTOLUENES. 11 Orthobromotoluene has also been prepared from ortho- toluidine by means of the diazo-reaction. 1 It is a liquid, boiling at 182 183 and is oxidized by dilute nitric acid to orthobromo- benzoic acid, while chromic acid causes complete combustion. Mctabromotoluene has been obtained from metatoluidine and from parabromotoluidine (Wroblevsky). 2 It is a liquid which boils at 184-3 (Korner) and does not solidify at - 20. Parabromotoluene. The separation of this from orthobromo- toluene is described above. It may be more rapidly effected by agitating the rectified mixture with half its volume of fuming sulphuric acid ; the parabromotoluene separates out as a crystalline mass after some time. 3 It boils at 182'5, 4 and is deposited from an alcoholic solution in rhombic crystals melting at 28 '5. When given to a dog, it appears in the urine as parabromohippuric acid and parabromobenzoic acid. When it is treated with chromium oxychloride, bromobenzidenedichloro- chromyl chloride, C 6 H 4 Br.CH(OCrOCl) 2 is formed as a brown precipitate which is decomposed by water with formation of parabromobenzaldehyde (6tard). DlBROMOTOLUENES, C 6 H 3 Br 2 .CH 3 . 2023 These have been prepared from the monobromotoluidines by the replacement of the amido-group by bromine, and from the dibromotoluidines by the replacement of the amido-group by hydrogen. 5 The first compound in the following list has also been obtained by the direct bromination of toluene ; the process goes on much more rapidly in the presence of iodine and in the sunlight. 6 Melting- Boiling- CH 3 : Br : Br point. point. 134 liquid, does not solidify at -20 240 126 246 125,, 236 1^4,, 123 solid 28 135 long needles ...... 39 246 1 Wroblevsky, Ann. Chem. Pharm. clxviii. 171. 2 See also Grete, ibid, clxxvii. 231. 3 Hiibner and Wallaeh, Ann. Chem. Pharm. cliv. 293. 4 Hiibner and Post, ibid, clxix. 6. 5 Wroblevsky, ibid, clxviii. 161 ; Neville and Winther, Bcr. Deutsch. Chem. Ges. xiii. 962 ; xiv. 417. 6 Jannasch, Ann. Chem. Pharm. clxxvi. 286. 12 AROMATIC COMPOUNDS. On treatment with nitric acid they yield all the mononitro- compounds which are theoretically possible ; most of these com- pounds crystallize in needles. TRIBROMOTOLUENES, C 6 H 2 Br 3 .CH 3 These are obtained in a similar manner to the preceding compounds. 1 Melting- Boiling- CH 3 : Br : Br : Br : point. point. 1345 crystals .... 88 89 1234 crystals .... 46 1246 long needles . . 66 290 1235 flat needles . . 52'5 1245 long needles . . 112 1256 flat needles , 58 59 TETRABROMOTOLUENES, C G HBr 4 .CH 3 . 2 Melting- Boiling- CH 3 : Br : Br : Br : Br : point. point. 12345 thin needles . Ill 111 '5 12356 fine needles . 116 117 12346 crystals . . . 105 108 Pentabromotohiene, C 6 Br 5 .CH 3 , is formed when toluene is allowed to drop into bromine which is free from chlorine and to which some aluminium bromide has been added, as well as by replacing the amido-group of tetrabromotoluidine by bromine (Neville and Winther). It crystallizes from benzene in long needles, melting at 282 283. When toluene is treated with an excess of bromine containing iodine, and the temperature finally allowed to rise to 350 400, hexbromobenzene and tetrabromomethane are formed, the latter being, however, for the most part converted into the former. 3 1 Wroblevsky ; Neville and Winther, loc. cit. 2 Ibid. 3 Gessner, JSer. Deutsch. Chem. Gcs. ix. 1508. NITROTOLUENES. 13 IODINE SUBSTITUTION PRODUCTS OF TOLUENE. Only the mono-iodotoluenes, C 6 H 4 LCH 3 , which are obtained from the toluidines, are known. 1 Boiling- Melting- point, point. Ortho-iodotoluene liquid . . 204 Meta-iodotoluene . . 204 Para-iodotoluene plates . . 211'5 35 FLUORINE SUBSTITUTION PRODUCTS OF TOLUENE. Fluotoluene, C 6 H 4 F.CH 3 , is formed when the diazo-compound obtained from paramidotoluenesulphonic acid is decomposed with strong hydrofluoric acid. It is a liquid smelling of bitter almonds, and boiling at 114 . 2 NITRO-SUBSTITUTION PRODUCTS OF TOLUENE. MONONITKOTOLUENES, C ( .H 4 (N0. 2 )CH 3 . 2024 By dissolving toluene in fuming nitric acid and pre- cipitating with water, Deville obtained nitrotoluene (protonitro- benzo&ne) as a colourless liquid boiling at 225, and possessing a smell of bitter almonds and a very sweet, somewhat biting taste. This compound was then repeatedly prepared by many chemists, who confirmed Deville's statements. These circumstances served to render the following observations of Jaworsky the more remarkable ; this chemist found that when nitrotoluene is dissolved in fuming nitric acid, and water added to the solution, a precipitate is formed which separates from a hot, alcoholic solution in lustrous crystals melting at 54 1 Beilstein and Kuhlberg, Ann. Cliem. Pharm. clviii. 147 ; Korner, Zeitschr. Chcm. clxxxviii. 327. 2 Paterae and Oliveri, Gaz. Chim. Ital. xiii. 533. 14 AROMATIC COMPOUNDS. and which, boiling without decomposition at 238, has exactly the same composition as nitrotoluene. He obtained the same compound by continuing the distillation of the liquid nitrotoluene to 240 ; the residue, which solidified on cooling, was identical with the product obtained by the other method. He concluded from these experiments that pure nitrotoluene is a solid body, the crystallizing power of which is usually destroyed by liquid impurities, these also having the power of lowering the boiling point. 1 These observations were confirmed by other chemists and were even taken advantage of commercially, for well crystallized nitrotoluene was manufactured on the large scale in Paris in 1867. Alexejew confirmed Jaworsky's view by obtaining the same azotoluene from the solid as from the liquid nitrotoluene. 2 He also found that the solid compound is converted by reduction into a solid toluidine, 3 which could not be obtained from the liquid compound. Kekule, who also investigated these facts, confirmed the above observation, and showed in addition that the solid nitro- toluene is more readily oxidized to paranitrobenzoic acid and gives a better yield than the liquid ; the lower boiling portion of the latter yielded a liquid toluidine containing aniline, and he therefore considered it probable that the substance which had up to that time been looked upon as nitrotoluene was a mixture of nitrobenzene and nitrotoluene. 4 Rosenstiehl, however, made the discovery that the ordinary liquid toluidine is a mixture of the solid with the isomeric pseudo- toluidine, 5 and that, consequently, two nitrotoluenes are formed by the nitration of toluene. 6 In order to decide the question whether toluene itself is a mixture of two isomeric hydrocarbons, he investigated the behaviour of samples of toluene from various sources towards nitric acid. He took some which had been previously exposed to a red heat, and some which he had obtained by the decomposition of xylene, C 6 H 4 (CH 3 ) 2 , at a high temperature. He also investigated toluene synthetically prepared, and that obtained from Tolu balsam. In all cases he obtained the two toluidines. Finally, Berthelot reduced these by heating with hydriodic acid and obtained one and the same toluene. 7 1 Zcitschr. Ckem. 1865, 222. 2 Ibid. 1866, 269. 3 Bull SM. Chim. vii. 376. 4 Zcitschr. Chem. 1867, 225. 5 Ibid. 1868, 557. 6 Ibid. 1869, 190. 7 Ibid. XITROTOLUENES. 15 Hence the supposition appeared not improbable that the lower boiling portion of ordinary nitrotoluene would be an isomeride of the solid compound, which yields the pseudotoluidine ; Rosenstiehl, however, singularly enough, did not investigate this point, and it was reserved for Beilstein and Kuhlberg to answer the question. These chemists had already prepared the liquid /3-nitrotoluene from dinitrotoluene, by converting the latter into nitrotoluidine, C 6 H 3 (NH 2 )(N0 2 ).CH 3 , by partial reduction with ammonium sulphide, and then replacing the amido-group by hydrogen. They then found that this nitro- toluene, which they called metanitrotoluene, but which is now known as the ortho-compound, forms the more volatile portion of crude nitrotoluene and can be separated from the solid paranitro- toluene by repeated careful fractional distillation. 1 A small quantity of metanitrotoluene is formed, together with the ortho- and para-compounds, by the action of fuming nitric acid on toluene. 2 The relative quantities of the two chief pro- ducts which are formed depend upon the concentration of the acid, and the temperature at which the nitration is effected. When a very concentrated acid is employed and the temperature allowed to rise, paranitrotoluene is chiefly obtained, while the yield of the ortho-compound is greatly increased by employing a weaker acid and cooling the mixture well. The nitrotoluenes are manufactured on the large scale, by mixing 10 parts of toluene with 11 parts of nitric acid of specific gravity 1*22 and 1 part of sulphuric acid of specific gravity 1*33 with continual agitation, in the apparatus used for the manufacture of nitrobenzene ; the mixture is then either cooled or kept warm according to the product desired. The crude product is washed with water and caustic soda solution, freed from unattacked toluene by distillation with steam, and then distilled with super-heated steam. The distillate is then repeatedly fractionated ; the larger portion of the fraction distilling above 230 solidifies on cooling, and the crystals, after purification by draining and pressing, yield pure paranitrotoluene on distillation; the fraction boiling between 222 223 consists chiefly of orthonitrotoluene, while the inter- mediate fractions contain some of the meta-compound. Ortlionitrotoluene is obtained pure when the amido-group of the isomeric nitrotoluidines, which contain the nitroxyl in the 1 Ann. Chem. Pharni. civ. i. 2 Monnet, Reverdin and Nolting, Ber. Deutsch. Chem. Gcs. xii. 445. 16 AROMATIC COMPOUNDS. ortho-relation to the methyl group, is replaced by hydrogen: this is best effected by heating the compound with alcohol saturated with nitrogen trioxide. It is a liquid which boils at 223, does not solidify at 20, and has a specific gravity of T163 at 23-5. Metanitrctoluene is prepared by the same method from the corresponding nitrotoluidine. It solidifies in a freezing mixture to crystals which melt at 16; it boils at 230 231, and has a specific gravity of 1168 at 22 . 1 Paranitrotoluene boils at 238, and on the gradual evaporation of its alcoholic or ethereal solution separates in large, thick rhombic crystals melting at 54. DlNITROTOLUENES, C 6 H 3 (N0 2 ) 2 ,CH 3 . 2025 Ordinary Dinitrotoluene (CH 3 : NO 2 : N0 2 = l : 2 : 4) was obtained by Deville, and is formed by the further nitration of ortho- and para-nitrotoluene. In order to prepare it, toluene is run into fuming nitric acid, without any special cooling, until oily drops separate out ; the mixture is then allowed to cool, and an equal volume of sulphuric acid gradually added, the whole being then boiled for half an hour, poured into snow, and the precipi- tate recrystallized from hot carbon disulphide. 2 It crystallizes in long, monoclinic needles, which melt at 72, are only slightly soluble in cold alcohol, and still less so in cold carbon disulphide, but dissolve readily in boiling benzene. In the manufacture of dinitrotoluene on the large scale, a liquid by-product is obtained, which was formerly considered to be an isomeric dinitrotoluene. 3 According to Glaus and Becker it is a mixture of ordinary dinitrotoluene, orthodinitrotoluene, and orthomononitrotoluene. 4 Limpricht found that 1:2:5 dinitro- toluene is also contained in it ; he did not isolate this compound but converted it into the corresponding nitrotoluidine. 5 Nolting and Witt, who examined a larger quantity of the by-product, obtained from it by distillation in a rapid current of steam 40 per cent, of mononitrotoluenes, consisting of almost equal parts of the para- and meta-compounds, the ortho-compound being 1 Beilstein and Kuhlberg, Ann. Chem. Pharm. clviii. 348. 2 Ibid. clvi. 13. 3 Rosenstiehl, Ann. Chim. Phys. [4] xxvii. 407. Cunerth, Ann. Chem. Pharm. clxxii. 222. 4 Glaus and Becker, Ber. Deutsch. Chem. Ges. xvi. 1590. 5 Ibid, xviii. 1400. TRINITROTOLUENES. 17 present only in very small amount. Although metanitrotoluene is only formed to a small extent by the nitration of toluene, its presence in comparatively large quantities in the mixture can be readily understood, as it resists the further action of nitric acid much more strongly than its isomerides; it therefore accumulates in the by-product, while the more readily attacked ortho-compound almost disappears. 1 Orthodinitrotoluene (1:2:6) can best be obtained pure by con- verting a-trinitrotoluene into dinitroparatoluidine, and replacing the amido-group of this by hydrogen. It crystallizes in broad, golden needles, melting at 60 61. 2 Symmetric Dinitrotoluene (1 : 3 : 5) may be prepared from the dinitroparatoluidine which melts at 168, and from the dinitro- orthotoluidine melting at 208, by suspending these in concen- trated nitric acid and saturating the well-cooled liquid with nitrogen trioxide ; the product is then brought in small portions at a time into eight or ten parts of absolute alcohol, the solution cooled as soon as the evolution of nitrogen has ceased, and the dinitrotoluene then precipitated with water. On recrystallization from -hot water it is obtained in small needles, whilst it crystallizes from petroleum spirit in small prisms, which join to form chain-like masses. It melts at 92 and combines with benzene, forming a double compound, C 7 H 6 (N0 2 ) 2 -f- C 6 H 6 , crystallizing in large prisms which effloresce in the air. 3 ^-Dinitrotoluene. Beilstein and Kuhlberg obtained this com- pound by agitating metanitrotoluene with nitric acid of specific gravity 1'54 for a long time. It crystallizes from carbon disulphide in long needles melting at 60. TRINITROTOLUENES, C 6 H 2 (NO 2 ) 3 CH 3 . 2026 a- Trinitrotoluene (] : 2 : 4 : 6) is formed when toluene 4 or ordinary dinitrotoluene 5 is heated for some days with a mixture of nitric and sulphuric acids. It may be more rapidly prepared by dropping toluene into a mixture of pure nitric acid and sulphuric acid containing a large quantity of sulphur trioxide and warming on the water-bath. 6 It is very slightly soluble in 1 Claus and Becker, Ber. Deutsch. Chem. Ges. xviii. 1336. 2 Stiidel and Becker, Liebig's Ann. ccxvii. 205 ; Stadel, ibid, ccxxv. 384. 3 Stadel, Ber. Deutsch. Chew. Gcs. xiv. 901 ; Liebiy's Ann. ccxvii. 189 ; Hiibner, ibid, ccxxii. 74 ; Neville and Winther, Ber. Deutsch. Chem. Ges. xvi. 2985. 4 Wilbrandt, Ann. Chem. Pharm. cxxviii. 178. 5 Tiemann, Ber. Deut-sch. Chem. Ges. iii. 217. 6 H. Schmitt, private communication. 18 AROMATIC COMPOUNDS. cold, more readily in hot alcohol, from which it crystallizes in large, rhombic tablets or golden needles melting at 82. On heating with ten times its weight of fuming nitric acid to 180 it is con- verted into symmetric trinitrobenzene. 1 When aniline is added to its alcoholic solution, the compound C 7 H 5 (NO 2 ) 3 -f- C 6 H 7 N is obtained in long, red, lustrous needles melting at 83 84. 2 /3- Trinitrotoluene. Beilstein and Kuhlberg, by boiling meta- nitrotoluene with nitric and sulphuric acids, obtained a tri- nitrotoluene, the purity of which they doubted, adding that the small quantity of substance obtained by them was probably a mixture. Hepp then proved that at least two trinitrotoluenes are formed from metanitrotoluene, and that these can be separated by repeated crystallization from alcohol or carbon disulphide. /3-Trinitrotoluene, which is only formed in small quantity, is readily soluble in carbon disulphide, slightly in cold, more readily in hot alcohol, and freely in ether and acetone. It crystallizes on the gradual evaporation of its solution in the last-named solvent in transparent, asymmetric prisms melting at 112 ; whilst it separates from alcohol in dazzling white plates or flat needles. On heating with alcoholic ammonia, a dinitrotoluidine is formed which melts at 94 ; it is also readily attacked by aniline and caustic soda solution. 7- Trinitrotoluene is only very slightly soluble in carbon di- sulphide and cold alcohol, and separates from hot alcohol in hard, compact, yellowish white crystals, while it crystallizes from acetone in small, hexagonal tablets, melting at 104. Concentrated alcoholic ammonia converts it, even in the cold, into a dinitrotoluidine, melting at 192 193. On adding aniline to a hot, alcoholic solution of 7-trinitro- toluene, combination does not occur as in the case of the symmetric trinitrotoluene, but 7-dinitrotolylphenylamine is ob- tained, diazo-amidobenzene being probably simultaneously formed: CH 3 .C 6 H 2 (N0 2 ) 3 + 3C 6 H 5 .NH ? = CH 3 .C 6 H 2 (N0 2 ) 2 N(C 6 H 6 )H +C 6 H 6 N 2 .NH.C 6 H 6 + 2H 2 O. This compound forms orange-coloured needles melting at 142. 7-Trinitrotoluene is also readily attacked by caustic soda solu- tion, and it must, therefore, like /3-trinitrotoluene contain two nitroxyls in adjacent positions (Part III. p. 92). 1 Glaus and Becker, Ber. Deutsch. Chem. Ges. xvi. 1596. 2 Hepp, Licbigs Ann. ccxv. 344. CHLOKONITROTOLUENES. 19 CHLORONITROTOLUENES, C 6 H 3 C1(NO 2 )CH 3 . 2027 Parachlororthonilrotoluene (4 : 2) has been prepared from ordinary dinitrotoluene. It is slightly soluble in cold alcohol, readily volatilizes with steam, and crystallizes in needles melting at 38. It is not attacked by chromic acid solution. 1 Orthochloroparanitrotoluene (2:4). Wachendorff obtained this compound by heating paranitrotoluene with antimony chloride to 100. It is very readily volatile in steam, dissolves freely in alcohol, and forms long, pointed crystals melting at 64 65. Potassium permanganate oxidizes it to chloronitrobenzoic acid. 2 Lellmann has converted it into orthochlorotoluene'and ortho- chlorobenzoic acid. 3 WachendorfF found that metanitrotoluene could not be chlori- nated. Wroblevsky, by the action of nitric acid on crude liquid chlorotoluene obtained two liquid nitrochlorotoluenes ; 4 Engelbrecht, on the other hand, employing crystalline para- chloro toluene, obtained two solid compounds which he was unable to separate completely. 5 Parachlorometatoluene (4 : 3) has been prepared from meta- nitroparatoluidine by means of the diazo-reaction, and is identical with one of Wroblevsky's compounds. It is a strongly refractive, golden-yellow liquid, which boils at 260 261 and solidifies at a low temperature to yellow needles melting at 7. 6 BRO Br :1 2 MO *p, 5 NITROTOLUENES, C, ,H 3 Br(N0 2 ).CH 3 . 7 Melting-point. . . 76-3 2 : 4 needles . . 74 75 3 : 2 3 : 5 prisms 8 . . 86 5 2 rhombic crystals ^ . . 55 4 2 . . 45'5 4 : 3 crystals . . 31 32 1 Beilstein and Kuhlberg, Ann. Chem. Pharm. clviii. 336. 2 Ibid, clxxxv. 273. 3 Ber. Deutsch. Chem. Ges. xvii. 534. 4 Ann. Chem. Pkarm. clxviii. 203. 5 Bcr. Deutsch. Chem. Gcs. vii. 797. 6 Gattermaim and Kaiser, ibid, xviii. 2599. 7 Neville and Winther, ibid. xiv. 417. 8 Wroblevsky, Ann. Chem. Pharm. cxcii. 203. 9 Grete, ibid, clxxvii. 246. 10 Beilstein and Kuhlberg, Hiibner and Roos, Ber. Deutsch. Chem. Ges. vi. 799. 20 AROMATIC COMPOUNDS. TOLUENESULPHONIC ACIDS. TOLUENEMONOSULPHONIC ACIDS, C 6 H 4 (SO 3 H).CH 3 . 2028 By the action of fuming sulphuric acid on toluene, Deville obtained a monosulphonic acid (Acide sulfobenzotnique) in small, deliquescent crystalline plates, and prepared some of its salts. Later researches have shown that in this way toluene- parasulphonic acid is formed together with a little toluene-ortho- sulphonic acid. 1 If, however, concentrated sulphuric acid be allowed to run into boiling toluene, only the para-acid is formed, 2 while all the three isomeric sulphonic acids, together with their chlorides, are formed by the action of chlorosulphonic acid on toluene : 3 ,01 )H 3 /OH + S0,< +2HC1. \S0 3 H S0 2 C1 \OH The product is poured into ice-cold water, the chlorides separating as oily liquids. After some time the toluenepara- sulphonic chloride crystallizes out and is removed, an additional amount of this being obtained by repeatedly cooling the liquid. It is then purified by re-crystallization from pure ether and decom- posed by boiling with water. The liquid chlorides are converted into the amides by treatment with ammonia, and these are then separated by fractional distillation and converted into the acids by heating with hydrochloric acid to 140 150. The ammo- nium salts which are obtained by the evaporation of the solu- tions are converted into the barium salts, from which either the free acids or other salts can be prepared. The aqueous solution from which the chlorides have been separated is treated with milk of lime, the calcium salts of the acids being thus formed ; the potassium salts are prepared from these, converted into the sulphonic chlorides by the action of phosphorus pentachloride and these separated as just described. 1 Engelhardt and Latschinow, Zcitschr. Chcm. 1869, 67. 2 Chrustschow, Ber. Dcutsch. Chem. Ges. vii. 1167. 3 Claesson and Wallin, ibid. xii. 1848 ; Claesson, ibid. xvii. Ref. 283. TOLUENESULPHONIC ACIDS. 21 The meta- and ortho-sulphonic acids can also be obtained from the three toluidines, which are converted by fuming sulphuric acid into the following sulphonic acids : GH- 3 H i \ /S0 3 H \/NH 2 \/'S0 3 H. The toluenesulphonic acids are then obtained from these by replacing the amido-group by hydrogen ; they can also be pre- pared by the action of sulphur dioxide on the diazo-compounds of the toluidines : l C 6 H 4 < + S0. 2 + H 2 = C 6 H +HC1+N 2 . XN NCl \30 2 .OH. Tolueneparasulphonic acid, C 6 H 4 (CH 3 )S0 3 H+ H 2 0, crystallizes in thick deliquescent tablets or flat prisms. Tolueneparasulphonic chloride, C 6 H 4 (CH 3 )S0 2 C1, crystallizes from ether in rhombic tablets, and is only slowly decomposed by water. Tolueneparasulphonamide, C 6 H 4 (CH 3 )S0 2 .NH 2 , forms small crystalline plates melting at 136, which are slightly soluble in water, more readily in alcohol. A solution of this compound in the necessary amount' of caustic potash yields on evaporation a residue from which alcohol extracts the compound C 6 H 4 (CH 3 ) S0 2 .NHK+H 2 0, crystallizing in needles. 2 Toluenemetasulphonic acid, C 6 H 4 (CH 3 )S0 3 H + H 2 0, forms very deliquescent, thin crystalline crusts. Toluenemetasulphonic chloride, C 6 H 4 (CH 3 )S0 2 C1, is an oily liquid. Toluenemetasulphonamide, C 6 H 4 (CH 3 )S0 2 .NH 2 , crystallizes in long plates melting at 107-108. Toluene-orthosulphonic acid, C 6 H 4 (CH 3 )S0 3 H+2H 2 O, forms thin deliquescent plates ; the chloride is an oily liquid, and the amide crystallizes in quadratic pyramids or prisms, which are almost insoluble in cold water, and only slightly soluble in alcohol. The salts of the three acids as a rule crystallize well (Claesson and Wallin). 1 Miiller, Per. Deutsch. Chem. Gcs. xii. 1348. 2 Hakansson, ibid. v. 1084 ; Claesson and Berg, Hid. xiii. 1170. 233 22 AROMATIC COMPOUNDS. TOLUENEDISULPHONIC ACIDS, C 6 H 3 (CH 3 )(S0 3 H) 2 . 2029 a-Toluenedisulphonic acid (CH 3 : S0 3 H : S0 3 H=1 : 2 : 4), is a thick liquid which can be heated above 100 without de- composition ; it may be prepared by heating toluene, or its ortho- and para-sulphonic acids with fuming sulphuric acid, 1 as well as by passing toluene vapour into concentrated sulphuric acid heated to 240 . 2 Its amide, C 6 H 3 (CH 3 )(S0 2 .NH 2 ) 2 is tolerably soluble in warm water, and crystallizes in prisms melting at 185 -186. Senhofer and Forber, by heating toluene with a mixture of sulphuric acid and phosphorus pentoxide, obtained a 7-toluene- sulphonic acid, 3 which is, according to Claesson, identical with the a-acid. 4 j3-Toluenedisulphonic acid is obtained in small quantities in the preparation of the a-compound, and is also formed when toluenemetasulphonic acid is treated with fuming sulphuric acid (Hakansson). Its amide melts at 224 (Claesson). y-Toluenedisulphonic acid (1:3: 5). When orthotoluidine is heated with fuming sulphuric acid or with chlorosulphonic acid, toluidinedisulphonic acid (CH 3 : NH 2 : SO 3 H : SO 3 H = 1:2:3:5) is formed ; this yields a crystalline diazo-compound, CH 3 .C 6 H 2 (N 2 S0 3 )S0 3 H, which is, according to Neville and Winther, con- verted into the toluenedisulphonic acid by heating with absolute alcohol under pressure, 5 while Limpricht and Hasse observed that ethoxytoluenedisulphonic acid, CH 3 .C 6 H 2 (OC 2 H 5 )(S0 3 H) 2 is thus formed. In order to obtain the former, the diazo-com- pound is converted into iodotoluenedisulphonic acid, and this heated with concentrated hydriodic acid. 7-Toluenedisulphonic acid forms an amide which crystallizes in small lustrous plates melting above 240 . 6 TOLUENETRISULPHONIC ACIDS, C 6 H 2 (CH 3 )(S0 3 H) 3 . Only one of the six toluenetrisulphonic acids which are theo- retically possible is known ; it is obtained by gradually heating 1 Hakansson, Ber. DeiUsch. Chem. Ges. v. 1084 ; Claesson and Bey, ibid. xiii. 1170. 2 Gnehm, ibid. x. 542 ; see also Fahlberg, ibid. xii. 1052. 8 Ann. Chem. Pharm. clxiv. 226. 4 Ber. Deutsch. Chem. Ges. xvii. Ref. 284. 5 Ibid. xv. 2993. 6 Ibid, xviii. 2177. THE CRESOLS. 23 potassium a-toluenedisulphonate with three molecules of chloro- sulphonic acid to 24-0, until the product forms a clear solution in water. The barium salt is then prepared, and from this the potassium salt, which is converted by the action of phos- phorus pentachloride into toluenetrisulphonic chloride, C 6 H 2 (CH 3 )(SO 2 C1) 3 , which crystallizes from chloroform in rhombic tablets melting at 153. On heating with water to 130 -140 the free acid is obtained ; it crystallizes with six molecules of water in long, fine needles. 1 MONOHYDROXYTOLUENES AND ALLIED BODIES. CH 3 THE CRESOLS, C 6 H 2030 In 1851 Stadeler discovered in the urine of the cow, together with phenylic acid, a very similar body which he named Taurylic acid, and considered to be the next higher homologue of phenylic acid. 2 As the question was subsequently raised whether the creosote discovered by Reichenbach in wood-tar is identical with phenol or not, Fairlie, under Williamson's directions, con- ducted an investigation on the so-called coal-tar creosote (Part III. p. 70) and found in it " hydrate of cresyl" C 7 H 8 0, the homologue of phenyl hydrate ; he describes this compound as a strongly refractive liquid smelling like phenol and boiling at 203, and investigated its properties with some care. 3 Duclos discovered the same compound in tar from pine-wood 4 and Marasse in that from beech-wood. 5 Griess obtained cresol or cresyl alcohol artificially by boiling diazotoluene nitrate with water, 6 and Wurtz by fusing toluene- sulphonic acid with caustic potash. 7 Engelhardt and Latschinow were the first to prove that three isomeric cresols exist ; they obtained pure paracr"esol, or, as they called it, a-cresol, by fusing tolueneparasulphonic acid with caustic potash, and from ordinary toluidine by Griess' reaction. By the same reactions they prepared /3-cresol from the ortho- 1 Claesson, Ber. Deutsch. Chem. Ges. xiv. 307. 2 Ann. Chem. Pharm. Ixxvii. 188. 8 Chem. Soc. Journ. vii. 232. * Ann. Chem. Pharm. cix. 135. 6 Ibid. clii. 64. 6 Jahresber. 1866, 458. 7 Ann. Chem. Pharm. cxliv. 121. 24 AROMATIC COMPOUNDS. sulphonic acid and pseudotoluidine (orthotoluidine), but they did not obtain it in a pure state. They further found that thymol, C 6 H 3 (CH 3 )(C 3 H 7 )OH, on heating with phosphorus pent- oxide, decomposes into propylene and 7-cresol. 1 This metacresol was then obtained in larger quantities by Oppenheim and Pfaff by heating hydroxyuvitic acid with lime. 2 Kekul4 obtained pure orthoeresol by acting with nitrous acid on orthotoluidine and by heating carvacrol (cymophenol), an isomeride of thymol, with phosphorus pentoxide. 3 The constitution of the three cresols was determined with certainty by Barth, who showed that on fusion with caustic potash, orthoeresol is oxidized to salicylic acid, metacresol to hydroxybenzoic acid, and paracresol to parahydroxybenzoic acid (Part III. p. 45). 4 Further investigations have shown that the cresol contained in coal-tar is a mixture of the three isomerides. 5 It is obtained from the oily mother-liquor left after crystallization of the phenol by dissolving in caustic soda, removing all naphthalene by a current of steam, and then fractionally precipitating the solution with hydrochloric acid ; the cresol separates out first, the phenol, being a stronger, acid, remaining in solution. 6 Ac- cording to another method, the solution is neutralized with hydrochloric acid and the mixture agitated with sufficient baryta water to dissolve all the phenol. 7 The cresol obtained is purified by distillation until it boils at 198 203. Deriva- tives of all three cresols can be prepared from it, but only the para-compound can actually be extracted in the pure condition. This is effected by treating the mixture with benzoyl chloride, paracresyl benzoate, melting at 78, being formed ; this is sepa- rated by pressing from the liquid ethers of the two other cresols, purified by re-crystallization, and decomposed by caustic soda (Engelhard t and Latschinow). Baumann has pointed out that the cresol (taurylic acid) contained in the urine of graminivora occurs as the potassium salt of paracresylsulphuric acid. 8 This compound also occurs in human urine during scarlatina, ery- sipelas, &c. 9 The urine of horses also contains some orthocresyl Zeitschr. Chem. 1869, 618. Bcr. Dcutsch. Chem. Gcs. viii. 884. Ibid. vii. 1006. Ann. Chem. PJwtrm. cliv. 356. Schotten and Tiemann, ibid. xi. 783. Muller, Zeitschr. Chem. 1865," 27?. Ihle, Journ. PraJct. Chem. [2] xiv. 442. 8 Ber. Dcutsch. Chem. Ges. ix. 1389, 1716. 8 Brieger, Hoppe-Seyler's Zeitschr. iv. 204. ORTHOCRESOL. 2 5 sulphuric acid. 1 Para- and ortho-cresol are also formed when the liver of fche horse is caused to putrefy with the addition of river-mud. 2 2031 Orthocresol is best obtained by adding 12 parts of pure potassium nitrite to a solution of 15 parts of orthotoluidine and 15 parts of sulphuric acid in 500 parts of water ; the liquid is heated by a current of steam, and the cresol distilled off in the steam. 3 It forms colourless crystals, melts at 30 and boils at 188. Its aqueous solution is coloured blue by ferric chloride ; on fusion with caustic potash it is oxidized to salicylic acid. When administered to a dog it appears in the urine as ortho- cresylsulphuric acid and oxycresylsulphuric acid (hydrotolu- quinonesulphuric acid). By the action of potassium chlorate and hydrochloric acid it yields di- and tri-chlorotoluquinone. 4 Orthocresyl oxide, (CH 3 .C 6 H 4 ) 2 O. If a few grains of iodine and then some aluminium are added to boiling orthocresol, alu- minium orthocresylate, (CH 3 .C 6 H 4 0) G A1 2 , is formed, and this solidifies on cooling to a black vitreous mass. When subjected to dry distillation it yields, among other products, orthocresol and orthocresyl oxide, which is a colourless liquid smelling like the geranium, and boiling at 272- 278. 5 Dichlororthocresol, C 6 H 2 C1 2 (CH 3 ).OH, is obtained by the action of chlorine on boiling orthocresol ; it crystallizes from alcohol in needles with a silky lustre, melts at 55 and on oxidation under- goes partial combustion, at the same time yielding trichloro- toluquinone. 6 Bromorfkocresol, C 6 H 3 Br(CH 3 )OH, has been prepared from bromorthotoluidine, and crystallizes from alcohol in lustrous golden needles melting at 88' 5. 7 a-Nitro-orthocresol, C 6 H 3 (CH 3 ) (N0 2 ) OH (1:3: 2), is formed when a solution of 2 parts of orthocresol in 2 parts of glacial acetic acid is allowed to drop into a cold mixture of 3 parts of nitric acid, of specific gravity 1'4, and 6 parts of glacial acetic acid. It is insoluble in water and crystallizes from dilute alcohol in long, yellow prisms melting at 69 '5. Its potassium salt crystallizes in garnet-red, rhombic tablets. When the hydrochloride of the amidocresol obtained from Preusse, ibid. ii. 355 ; Bcr. Deutsch. Chem. Gcs. xi. 1911. Baumann and Brieger, Hoppe-Seyler's Zcitschr. iii. 149, 252. Schotten and Tiemann, loc. cit. Southworth, Ann. Chem. Pharm. clxviii. 273. Gladstone and Tribe, Journ. Chem. Soc. 1886, i. 25. Glaus and Riemann, Ber. Deutsch. Chem. Ges. xvi. 1598. 7 Wroblevsky, Ann. Chem. Pharm. clxviii. 165. AROMATIC COMPOUNDS. this compound is distilled with sodium formate, a methenyl compound is formed ; this reaction is characteristic of all the amidophenols in which the amido-group is in the ortho-relation to the hydroxyl. 1 Methenylamidorthocresol is formed according to the following equation : /NH 2 -N CH 3 .C 6 H 8 / + CHO.OH = CH 3 .C 6 H 3 < >CH+2H 2 0. It is a crystalline mass which melts- at 38 39, boils at 200 and has a peculiar smell, resembling that of acetamide, charac- teristic of these anhydro-bases. A liquid nitrocresol boiling at 226 230 is formed together with the solid compound. 2 fi-Nitro-ortJiocresol (1:5: 2) is prepared from the corresponding nitro-orthotoluidine by means of the diazo-reaction or by heating it with strong caustic soda. It crystallizes in fine, light yellow needles and melts at 95. 3 On reduction it yields fi-amido- orthocresol, the hydrochloride of which crystallizes readily. signifies to preserve, or save; the two may be etymologically united in the word creosote, which expresses meat-preserving or decay-saving." Very soon after this, Runge discovered carbolic acid, and Laurent phenyl hydrate, in coal-tar, the identity of these bodies being recognised somewhat later. No clear views, however, were held as to the relation existing between phenol and creosote, and a confusion arose which was maintained for many years with an obstinacy unparalleled in the annals of our science. Runge and Laurent showed that creosote, in spite of many similarities, is quite a different substance from the compound obtained by them. Phenol differs from creosote more especially in being an acid, in possessing a different boiling-point, in crystallizing when cooled, and in its different behaviour towards chlorine, bromine, and nitric acid. Runge moreover adds that it imparts to meat preserved by it an abominable taste. Reichenbach, nevertheless, considered carbolic acid to be identical with his creosote, the more so as he thought that he had also discovered it in coal-tar and bone-oil. Gmelin was also of this opinion ; according to him, carbolic acid, phenyl hydrate, and creosote, are chemically identical, dif- fering only in degree of purity. Gmelin's views found universal acceptance ; crystallized carbolic acid soon came into the market under the name of creosote and displaced the genuine substance obtained from wood -tar. Gorup-Besariez, who had some of the latter body, which had been prepared by Reichenbach at Blansko, in Moravia, at his disposal, compared it with " crystallized creosote," and, like Runge and Laurent, found them to be completely different ; the amount of substance in his possession, however, did not admit of a close investigation. Some years later, Batka supplied him with fresh samples of creosote from Blansko, and he found that when acted upon by nitric acid, no picric acid was formed, while potassium chlorate 34 AROMATIC COMPOUNDS. and hydrochloric acid, instead of giving chloranil, C 6 C1 4 O 2 , gave a similar substance, which, however, contained hydrogen. 1 These results, however, attracted but little attention ; Gmelin, indeed, mentions them in his hand-book, but only to add that Gorup-Besanez, to prove that creosote is a distinct substance, ought to have prepared it himself instead of investigating a commercial product. Two years later, Gorup-Besanez published a more extended treatise on creosote ; his determination of its composition agreed with that of Ettling, who had analysed a specimen sent by Reichenbach to Liebig. By the action of chlorine he obtained pentachloroxylone, C 13 H 7 C1 5 O 3 , and hexchloroxylone, C 13 H 6 C1 6 O 3 , substances which were very similar to the chlorinated quinones obtained by Stadeler. 2 About the same period Yolkel published a paper on the distillation products of wood, in which he relates his investi- gation of the creosote obtained from the tar in a pyroligneous acid works at Solothurn. He purified it by repeated solution in caustic potash, precipitation with sulphuric acid and distillation. The liquid, after purification in this manner, boiled at 202 208, and in its general properties resembled Reichenbach's compound, but had a different composition, as the following results of the analyses conducted by Ettling, Gorup-Besanez, and Volkel show : 8 Creosote from Blansko. Creosote from Solothurn. (Mean of 8 Analyses.) (Mean of 3 Analyses.) Carbon 75 '21 72-45 Hydrogen 7'90 7'10 Oxygen 16'89 2045 100-00 100-00 Deville had previously analysed creosote prepared by Pelletier, and obtained numbers only differing slightly from those of Volkel. Volkel considered that Gorup-Besanez had not purified his creosote sufficiently, whereupon the latter treated it repeatedly by Volkel's method, without, however, altering the results obtained by analysis to any appreciable extent. 4 In the same year, Williamson published the results of an 1 Ann. CJiem. Pharm. Ixxviii. 231. 2 Ibid. Ixxxvi. 233. 3 Ibid. Ixxxvi. 66, 93. 4 Ibid. xcvi. 39. HISTORY OF CREOSOTE. 35 investigation made by Fairlie towards the solution of the question whether coal-tar creosote consists chiefly of carbolic acid ; he thus discovered the homologue of phenol, cresyl hydrate or cresol, which boils at 203, or at nearly the same temperature as creosote, thus introducing a new source of confusion. The research had no direct bearing on the real issue. A new chapter in the history of creosote begins with Hlasi- wetz's investigation " On Beech- Wood Tar Creosote and the Products of Distillation of the Guaiacum Resin." He had already obtained the compound C 8 H 10 2 from the creosote from Blansko, and now found it in the distillation products of guaiacum resin, together with its lower homologue, guaiacol, C 7 H 8 2 , which Deville and Pelletier had already obtained from the same source; he therefore called his compound creosote- guaiacol or creosol. Hlasiwetz concluded that creosote is a kind of ether of the latter, and probably contains the radical C 9 H n , thus simply explaining the fact that it contains more carbon than creosol. In the following year Duclos published a paper on cresyl alcohol, which he had not only found in coal-tar, but also in the tar from the gas-works at Giessen where only wood, and for the most part fir-wood, was used. 1 In criticism of this paper, Gorup-Besanez observed that these results were in opposition to all the facts known concerning the distillation products of wood, in which no phenols had yet been found. If Duclos' results were to be accepted, it would be necessary to assume that fir-wood yields different products from beech-wood. In the meantime Gerhardt calculated the formulae of the chlorinated xylones as C 8 H 5 C1 3 O 2 and C 8 H 4 C1 4 2 , according to which they appear to be homologues of the chloroquinones, thus confirming Hlasiwetz's results ; Gorup-Besanez then undertook the reinvestigation of these compounds, but could not obtain any creosote from Blansko ; this source had failed. In the year 1864, Hugo Miiller made an important addition to the history of creosote ; he investigated a sample which had been prepared in London from Stockholm-tar and appeared to be identical with that from Blansko. By treating it with hydriodic acid be obtained methyl iodide and homocatechol (p. 31). These different researches afforded a complete proof that wood-tar creosote has nothing in common with coal-tar creosote. 1 Ann. Chcm. Pharm. cix. 135. AROMATIC COMPOUNDS. The only obstacles now remaining to a complete concordance of opinion on the subject were Reichenbach's statement, which he had never confirmed, that his creosote is contained in coal-tar, and that of Duclos that wood-tar contains phenols, which no one else had been able to detect. 2036 The creosote question seemed to have received a final answer, but it was nevertheless not yet settled. In the year 1865, A. E. Hofmann investigated several commercial products which he obtained from various firms as genuine beech-wood- tar creosote, and found that they consisted chiefly of phenol. Being unacquainted with the researches of Hlasiwetz and Muller, he called the existence of creosote in question and con- cluded that it was nothing but impure phenyl hydrate, the chlorinated xylones being mixtures of chloranil with chlorinated phenols. The name of creosote ought, therefore, to be removed from our list of chemical compounds, though this would not prevent its use as a commercial term. Gorup-Besanez replied to this by pointing out that Hofmann had only proved a fact which had long been known, that phenylic acid was often sold under the name of creosote. It was im- possible that the firms mentioned by him could have sent him genuine creosote, because this article had long disappeared from the German market. 1 This incident had a fortunate conclusion both for Gorup-Besanez and for tho facts. Fresenius corrected his statement, pointing out that the " Verein fur chemische Industrie " at Mayence worked up beech-wood-tar for creosote. The investigation of this showed that it differed from the Blansko samples, but was probably identical with those from Solothurn. Gorup-Besanez succeeded in extracting from it a considerable quantity of guaiacol together with a smaller amount of creosol ; by the action of potassium chlorate and hydrochloric acid on the crude creosote he ob- tained tetrachloroguaiacone, C 7 H 2 C1 4 2 , and tetrachlorocreosone, C 8 H 4 C1 4 2 , homologues of chloranil. When he treated creosote with hydriodic acid, he obtained methyl iodide and catechol, which were undoubtedly derived from the guaiacol. He assumed that catechol is the lower homologue of guaiacol and creosol, both of which yield chlorine products homologous with chloranil. He concluded from his analysis that Rhenish creosote contains the radical C 3 H 5 . 2 1 Journ. Prakt. Chem. xcvii. 63. 2 Ann. Chem. Pharm. cxliii. 129. ORCINOL. 37 Marasse opposed this view ; Gorup-Besanez had thought that the fraction boiling between 199 and 208 is the allyl ether of guaiacol, the latter being derived from it by the action of caustic potash. If this were the case, allyl alcohol or some similar com- pound must be simultaneously formed, whereas no one had hitherto observed this. Guaiacol, he continues, may be the methyl ether and not the homologue, of catechol, bearing the same relation to it as creosol to homocatechol. The difference between the composition of creosote and that of the two methyl ethers contained in it is easily accounted for on the supposition that it contains substances which boil at the same temperature as guaiacol and creosol but are richer in carbon and poorer in hydrogen. He also found that creosote contains, besides ordinary phenol, its homologues cresol and phlorol, which yield the chlorine pro- ducts now known as tetrachlorotoluquinone and tetrachloro- xyloquinone. 1 The composition of creosote is very variable. Brauniger found in one sample only traces of phenol and less than 2 per cent, of cresol, and in that investigated by Gorup-Besanez only a little cresol and still less phlorol, 2 while Tiemann and Mendelsohn found large quantities of the latter. 3 The relative amounts of guaiacol and creosol are also subject to great variations ; thus Biechle found scarcely any creosol in a second sample of Rhenish creosote obtained by Gorup-Besanez. 4 The higher boiling fractions contain, moreover, the dimethyl ethers of homocatechol, pyrogallol, dimethylpyrogallol, and propylpyrogallol, which have already been partially described. The presence of phenols in wood-tar-creosote shows that it is more closely related to the so-called coal-tar creosote than was previously supposed. The latter differs from the former by the- absence of guaiacol, creosol, and the dimethyl ethers just men- tioned. These must be derived from the characteristic aromatic compounds which various chemists have discovered in wood (Vol. III. Pt. II. p. 583). ORCINOL, C 6 H 3 (CH 3 )(OH) 2 (1:3: 5). 2037 Robiquet discovered this compound in 1829 in Vario- laria dealbata, and named it orcin, because this lichen had 1 Ann. Chcm. Pharm. clii. 59 2 Ibid, clxxxv. 339. 3 Ber. Deutsch. Chem. Ges. x. 59. 4 Ann. Chem. fliarm. cli. 104. 234 38 AROMATIC COMPOUNDS. formerly been called Lichen orcina, and because the name serves as a reminder that the lichen is used for the preparation of archil (or settle). 1 Orcinol was then further investigated by various other chemists, 2 from whose analyses Gerhardt first calculated its correct formula, 3 his result being confirmed by the researches of Stenhouse. 4 Orcinol occurs in the free state in all the lichens, the various species of Rocdla, Lecanora and Variolaria, which are em- ployed for the preparation of archil and litmus, and is a decomposition product of various acids and ether-like bodies prepared from these lichens. When these compounds are heated with an alkali or submitted to dry distillation, orcinol is formed, e.g : Erythrin. Orsellinic Acid. C 7 H 6 (OH) 2 C0 2X >C 4 H,(OH),+ 2H,0 = 2C 7 H 5 (OH) 2 C0 2 H C 7 H 6 (OH) 2 CO/ Erythrol. + C 4 H 6 (OH) 4 . Lecanoric Acid. Orsellinic Acid. C 7 H 5 (OH)O.C0 2 H + H 2 = 2C 7 H 5 (OH) 2 C0 2 H. C 7 H 5 (OH) 2 CO Orsellinic Acid. Orcinol. C 7 H 5 (OH) 2 C0 2 H = C 7 H 6 (OH) 2 + CO 2 . In order to prepare orcinol, 6 parts of Rocella fuciformis are -macerated for twenty minutes with 60 parts of milk of lime con- taining 1 part of lime, the mass filtered and the erythrin pre- cipitated from the filtrate by hydrochloric acid ; this is boiled for half an hour with a slight excess of milk of lime, the solu- tion filtered, treated with carbon dioxide to remove the excess of lime, and evaporated nearly to dryness. The orcinol is extracted from the residue by benzene, while erythrol is left behind. When the benzene solution is shaken with water, the orcinol is taken up by the latter and is obtained pure on evaporation. 5 The crude 1 Ann. Chim. Phys. xlii. 236. 2 Dumas, Ann. Chem. Pharm. xxvii. 140 ; Liebig and "Will, ibid, xxvii. 147 ; Sclmnk, ibid. xli. 159 ; liv. 269. 3 Compt. Rend. Chim. 1845, 287. 4 Phil. Trans. 1848, 63 ; 1349, 393. 5 Stenhouse. ORCINOL. . 39 orcinol can also be purified by distillation, 1 which is best carried on in vacuo. 2 Vogt and Henninger first prepared orcinol from toluene, by chlorinating toluene in presence of iodine, and warming the chlorotoluene with two to three times its weight of sulphuric acid on the water-bath ; two sulphonic acids are thus formed, which readily admit of separation, the barium salt of the one being much more soluble than that of the other, whith yields orcinol when fused with caustic potash. 3 The chlorotoluene obtained by the method described is a mixture of parachlorotoluene with a little orthochlorotoluene ; since, however, the side chains of orcinol are arranged symmetri- cally, an inter-molecular change must take place during its preparation just as in that of resorcinol from benzeneparadi- sulphonic acid. Neville and Winther obtained orcinol by fusing symmetric bromotoluenesulphonic acid, the toluenemetadisulphonic acid obtained from orthotoluidinedisulphonic acid, or bromometa- cresol with caustic potash ; they also prepared it by heating metadibromotoluene to 280 300 with caustic potash and a little water, and finally by replacing the amido-group of amido- metacresol by hydroxyl. 4 Orcinol is also formed, together with parahydroxybenzoic acid, when aloes are fused with caustic soda. 5 Properties. Orcinol is readily soluble in water, alcohol, and ether, and crystallizes with one molecule of water in six-sided monoclinic prisms, which effloresce gradually over sulphuric acid, and more rapidly when heated to 100. It is almost completely precipi- tated in fine needles when its concentrated solution is warmed with a saturated solution of common salt (Lamparter) ; it reduces ammoniacal silver solution, has an intensely sweet but unpleasant taste, and melts in the anhydrous state at 106'5 108 (Neville and Winther). When rapidly heated, it distils almost without decomposition between 287 and 290 (Dumas). Ferric chloride produces a violet-black colouration, and bleaching powder a dark red, soon changing to yellow. In the presence of ammonia and air it is converted into orcein, the colouring matter of archil, and becomes coloured a deep reddish violet (Robiquet). Its Lamparter, ibid, cxxxiv. 215. De Luynes, Ann. Chim. Phys. [4] vi. 184. Ann. Chem. Pharm. clxv. 366 ; Bull. Soc. Chim. xxi. 373. Ber. Deutsch. Chem. Gcs. xv. 2976. Barth and Hlasiwetz, Ann. Chem. Pharm. cxxxiv. 288. 40 AROMATIC COMPOUNDS. alkaline solution when heated with a little chloroform becomes coloured first purple-red and then bright red, and on dilution with water has an intense greenish yellow fluorescence, homo- fluorescein, C 23 H 18 O 5 , being formed. This reaction is so delicate that the compounds which yield orcinol can readily be detected in the lichens by its means. A few pieces are boiled with 5 per cent, caustic potash and a little chloroform added to the clear solution ; it is then warmed for ten minutes on the water-bath and diluted. 1 Orcinol may be quantitatively determined by adding standardized bromine water to the dilute solution until tribromorcinol is no longer precipitated and determining the excess of bromine by a solution of potassium iodide. 2 Orcinol monomethyl ether, C 6 H 3 (CH 3 )(OCH 3 )OH, is formed, together with the dimethyl ether, when orcinol is boiled with caustic potash, methyl iodide, and wood-spirit. It is a light yellow, oily liquid which boils at 273 and is soluble in alkalis. Orcinol dimethyl ether, C 6 H 3 (CH 3 )(OCH 3 ) 2 , is a yellowish, mobile fluid which boils at 244, is insoluble in alkalis, and is converted by oxidation into symmetric dimethoxybenzoic acid, or dimethyl a resorcylic acid, C 6 H 3 (OCH 3 ) 2 C0 2 H(5 : 3 : 1), thus establishing the constitution of orcinol. 3 Orcinol acetate, C 6 H 3 (CH 3 )(OC 2 H 3 O) 2 ,is obtained by the action of acetyl chloride on orcinol, and crystallizes from alcohol in needles melting at 25.* Orcinol dicthylcarbonate, C 6 H 3 (CH 3 )(O.COOC 2 H 5 ) 2 , is obtained by the action of chlorocarbonic ether on the potassium compound of orcinol, and is a thick, oily liquid boiling at 310 312 . 5 Orcinolazolenzene, C 6 H 5 N=NC 6 H 2 (CH 3 )(OH) 2 , is formed when orcinol and diazobenzene nitrate are brought together in aqueous solution. It crystallizes from a mixture of acetic acid and acetic ether in dark red needles melting at 183 . 6 1 Schwarz, Ber. Dcutsch. Chem. Ges. xiii. 543. 2 Reymann, ibid. viii. 790. 3 Streng and Tiemann, ibid. xiv. 1999. 4 Luynes and Lionet, Zeitschr. Chcm. 1867, 561. 5 Wallach, Licbig's Ann. ccxxvi. 86. 6 Typke, Ber. Deutsch. Chcm. Ges. x. 1579. SUBSTITUTION PRODUCTS OF ORCINOL. 41 SUBSTITUTION PRODUCTS OF ORCINOL. 2038 These are obtained by the same methods as the cor- responding resorcinol compounds, which they resemble very closely. CHLORINE SUBSTITUTION PRODUCTS. Melting- point. Trichlororcinol, 1 C 6 C1 3 (CH 3 )(OH) 2 , long needles 123 Pentachlororcinol, 2 C 6 C1 3 (CH 3 )(OC1) 2 , large prisms 120'5 BROMINE SUBSTITUTION PRODUCTS. Monobromorcinol, 3 C 6 H 2 Br(CH 3 )(OH) 2 , crystals 135 Dibromorcinol, 4 C 6 HBr 2 (CH 3 )(OH) 2 , needles ' 146 Tribromorcinol, 5 C 6 Br 3 (CH 3 )(OH) 2 , needles 98 Pentabromorcinol, 6 C 6 Br 3 (CH 3 )(OBr) 2 , triclinic crystals 126 IODINE SUBSTITUTION PRODUCTS. Mono-iodorcinol, 7 C 6 H 2 I(CH 3 )(OH) 2 , prisms 80'5 Tri-iodorcinol, 8 C 6 I 3 (CH 3 )(OH) 2 , brown tablets NlTRO-SUBSTITUTION PRODUCTS. ( golden ) -Nitro-orcinol, 9 C 6 H 2 NO 2 (CH 3 ) (OH) 2 , ^ lustrous V 120 (needles ) ( dark \ -Nitro-orcinol, C 6 H 2 NO 2 (CH 3 )(OH) 2 J yellow 115 (needles J f deep ^ -Dinitro-orcinol, 10 C 6 H(NO 2 ) 2 CH 3 (OH) 2 ,^ yellow 164'5 ( tablets J 1 Stenhouse, Proc. Roy. Soc. 1871. 2 Stenhouse, Dittler and Liebermann, Ann. Chem. Pharm. clxix. 265. 3 Lamparter, loc. cit. 4 Tiemann and Streng, loc. cit. Stenhouse and Groves, Journ. Chem. Soc. 1880, 402. 6 Stenhouse and Rammelsberg ; Dittler and Liebermann, loc. cit. 255. 7 Stenhouse, Proc. Roy. Soc. xxii. 53. 8 Stenhouse, Journ. Chem. Soc. 1864, 327. 9 Weselsky, Ber. Deutsch. Chem. Ges. vii. 441. 10 Stenhouse and Groves, Journ. Chem. Soc. 1877, i. 548. AROMATIC COMPOUNDS. ( golden i>\ Melting- point. ^-Dinitro-orcmol, 1 C 6 H(NO 2 ) 2 CH 3 (OH) 2 ,-| yellow V 109 110 (needles J C long ^ Trinitro-orcinol, 2 C 6 (NO 2 ) 3 CH 3 (OH) 2 , ] yellow 163'5 (needles J 2039 Archil. This name was formerly employed to designate both the colouring matter which is extracted from the lichens just mentioned, and the lichens themselves. Theophrastos and Dioscorides mention a plant (f>vicos 6a\daaiov or TTOVTIOV, called by Pliny Fucus marinus, which is not a sea-weed, as the name might be taken to imply, but a lichen which grows on the rocks of certain islands, especially Crete, and is capable of dyeing wool a beautiful violet or purple colour. Archil came into the European market as early as the four- teenth century; the following account of it is given by Beck- mann : 8 Among the oldest and principal Florentine families is that known under the name of Oricellarii or Rucellarii, Ruscellai or Rucellai, several of whom have distinguished themselves as statesmen and men of letters. This family are descended from a German nobleman named Ferro or Frederigo, who lived in the beginning of the twelfth century. One of his descendants in the year 1300 carried on a great trade in the Levant, by which he acquired considerable riches, and returning at length to Florence with his fortune, first made known in Europe the art of dyeing with archil. It is said that a little before his return from the Levant, happening to make water on a rock covered with this lichen, he observed that the plant, which was then called respio or respo, and in Spain orciglia, acquired by the urine a purple, or, as others say, a" red colour. He therefore tried several experiments, and when he had brought to perfection the art of dyeing wool with this plant, he made it known at Florence, where he alone practised it for a considerable time to the great benefit of the state. From this useful invention the family received the name Oricellarii, from which at last was formed Rucellai. 1 Leeds, Ber. Deuisch. Chem. Ges. xiv. 483. 2 Stenhouse, Proc. Hoy. Soc. xix. 41 ; Merz and Zeller, Ber. Deutsch. Chem. Ges. xii. 2038. 3 Beckmann's History of Inventions, vol. i. p. 37. ARCHIL. 43 As several documents, still preserved among the Florentine archives, confirm the above account of the origin of this family name, from the discovery of dyeing with oricello, 1 we may, in my opinion, consider it as certain that the Europeans, and first the Florentines, were made acquainted with this dye-stuff and its use in the beginning of the fourteenth century. At that time the Italians brought from the East the seeds of many arts and sciences, which, afterwards sown and nurtured in Europe, produced the richest harvests ; and nothing is more certain than that the art of dyeing was brought to us from the East by the Italians. I do not believe that the merit of having discovered this dye by the above-mentioned accident is due to that Floren- tine ; but I am of opinion that he learned the art in the Levant, and on his return taught it to his countrymen, which was doing them no small service. The archil lichens, the most valuable of which are Eocella tine- toria and It. fuciformis, occur in several varieties and in con- siderable quantity on the coasts of warm and tropical countries, such as the islands of the Mediterranean, the Canary and Cape Verde Islands, Madagascar, Zanzibar, Angola, Ceylon, Java, Peru, Chili, &c. The old method for the preparation of archil consisted in treating the lichens with stale urine and lime in large casks provided with moveable lids, a considerable quantity of alum and white arsenic being added to prevent the fermentation from passing to a further stage. The mixture is well agitated for a month and then stored in casks in which it is allowed to stand for a long time before use, the colour being found to improve on ceeping. A more modern process consists in treating the finely-chopped ichens with dilute ammonia, and keeping the mixture at the jmperature of the air or at a slightly higher one until a dark dolet paste has been formed ; this is diluted with ammonia and iltered through a press ; the solution thus obtained is known as )lue archil. Red archil is obtained from this by gentle heating, ammonia being thus removed. Stenhouse proposed first to extract the lichens with milk )f lime, precipitate the solution with hydrochloric acid and rork up the erythrin, &c., thus obtained as by-products, the 1 These documents from the Florentine records may be found in Dominici fariae Manni de Florentinis Inventis Commentarium. Ferrariae 1731. Beck- inn quotes the passage in question. 44 AROMATIC COMPOUNDS. colouring matter being thus left in a much purer condition. Marnas of Lyons found that the best results were obtained by extracting with dilute ammonia and warming the compounds precipitated from the solution with ammonia in a current of air to 70 for about three weeks. On addition of calcium chloride a precipitate, known as French purple (ponrpre franpaise), is thrown down, and the material thus obtained yields much finer and clearer shades than archil. Since the discovery of the aniline dyes, archil has lost much of its commercial importance ; it is now only used in combina- tion with other colouring matters in order to obtain certain shades of brown, and for the production of a cheap blue for wool dyeing ; the material is first grounded with indigo and then dyed with archil, the result being a dye which is similar to that of genuine indigo-blue. Cudbear or Persia. The inhabitants of Sweden, Scotland, Ireland, Wales, &c., have for centuries been in the habit of using various kinds of lichen, especially Lecanora tinctoria, for wool-dyeing, the colour being produced by treatment of the lichen with urine. During last century a patent was taken out by Dr. Cuthbert Gordon for the preparation of cudbear, 1 by drying and powdering the pasty mass obtained by the action of ammonia or urine on the lichens. Cudbear is prepared in the Auvergne from Variolaria orcina by a similar method. Orceln. Robiquet has given this name to the colouring matter of archil, which is formed, as he discovered, by the action of hydrogen and ammonia on orcinol. 2 Gerhardt calculated its formula from the analyses of Dumas and Kane, 3 and gave the following equation for its formation : C 7 H 8 2 + NH 3 + 30 = C 7 H 7 N0 3 + 2H 2 O. Kane prepared orcein from commercial archil ; he describes it as a carmine-red powder, containing carbon and nitrogen in a constant ratio, while the amount of oxygen is variable, being larger as the archil becomes older ; hence he assumed that it consists of two similar colouring-matters, a-orcein and /3-orcein. Liebermann, who obtained the colouring matter by the action of gaseous ammonia and air on pure orcinol, found that two 1 Bancroft, Philosophy of Permanent Colours, 1813, i. 300. 2 Ann. Chim. Phys. Iviii. 320. 8 Ann. Chem. Pharm. xxxix. 25. CUDBEAR AND LITMUS. 45 compounds are thus formed according to the following equations : 2C 7 H 8 2 + NH 3 + 30 = C 14 H n N0 8 + 3H 2 C U H 13 N0 4 + NH 3 + = C 14 H 12 N 2 3 + 2H 2 O. The latter is therefore formed in larger quantity when the a,ction of the ammonia is allowed to continue for some time ; it is less soluble in aqueous ammonia and alcohol than the former compound. Both occur as amorphous masses having a beetle- green lustre, and forming splendid purple solutions with alkalis ; but the solution of the second compound has a bluer shade than that of the first. 1 2040 Litmus (tournesolso Zac&mws) was discovered by the Dutch. 2 It is prepared from various species of Rocella, Variolaria and Lecanora, by allowing them to ferment in contact with ammonia and carbonate of potash, as in the manufacture of archil. When the mass has become violet, stale urine, lime and potashes are added, and the mass again allowed to ferment until it has as- sumed a blue colour ; it is then mixed with gypsum or chalk, and a little indigo, 3 and made up into small tablets. Kane was the first more accurately to investigate litmus, and he obtained several colouring matters and other substances from it. 4 Wartha, who also investigated the colouring matter of litmus, found indigo in it ; this, however, had probably been purposely added as just described, although it may possibly have been derived from the urine, which is known to contain appreciable quantities of a substance which yields indigo on decomposition. On extracting litmus with cold alcohol, Wartha obtained a red colouring matter which is indifferent towards acids, and yields litmus blue and another substance when treated with water. On evaporating the solution and treating the residue with absolute alcohol and a little acetic acid, a scarlet colouring matter is removed, and this is changed to a purple by ammonia, while the pure litmus blue remains behind as a brown powder, which forms a reddish brown aqueous solution turned blue by the slightest trace of an alkali. 5 According to De Luynes, the pure colouring matter is obtained by digesting 1 part of orcinol with 5 parts of ammonia and 25 1 Bcr. Deutsch. diem. Ges. viii. 1649. 2 The origin of this name is unknown ; it may perhaps be derived from Lacca musci, a lake prepared from moss. 3 Gottlieb, Chcm. Tech. p. 531. 4 Loc. cit. 5 Ber. Deutsch. Ghent. Ges. ix. 217. 46 AROMATIC COMPOUNDS. parts of crystallized carbonate of soda for four or five days at 60 80, and precipitating the solution with hydrochloric acid. It is only slightly soluble in water, and the wine-red colour of this solution is changed to bluish violet by alkalis, and to a reddish brown by acids. It yields a red solution with alcohol, and a yellow one with ether. De Luynes considers that the colouring matter is a weak acid which forms blue salts, the potassium salt existing in litmus. 1 Litmus is not only employed in the laboratory in the form of litmus paper and tincture, but is also used for colouring wine and vinegar. The colouring matter can readily be recognized by its absorption spectrum ; ether extracts it from an acid solution yielding a yellow liquid which absorbs the left end of the spec- trum up to E \ D. A drop of ammonia colours the solution blue, an absorption band being formed which begins at d, where it is very intense, gradually diminishing to E. On shaking with water the colouring matter is taken up, and the blue solution gives an absorption band at D ; the addition of acid now changes the colour to brick-red, and the solution gives an absorption spectrum similar to that of wine. 2 Ribbon Litmus (Tournesollappen, tournesol en drapeaux, Bezetta, Lackmus in Fleckchen) is obtained in southern France from the expressed sap of Croton tinctorium ; linen rags are soaked in the sap, dried in the sun, and then exposed on heaps of horse-dung covered with chopped straw, the ammonia evolved being sufficient to change the colour of the rags, which are fre- quently turned, to blue. They are then again dipped in the sap, to which urine has been added, the colour thus produced becoming dark green or purple-red on drying, and they are then brought into the market. It was formerly believed that the Dutch employed them for the manufacture of litmus, but this is not the case ; they are actually used to colour the exterior of cheeses red. The colouring matter contained in these ribbons has not been accurately investigated; acids change it to red, but the blue colour is not restored by alkalis. 1 Jahresber. 1864, 551. 2 Vogel, Spectralanalyse, p. 269. CRESORCINOL. 47 CRESORCINOL, C 6 H 3 (CH 3 )(OH) 2 (1 : 2 : 4). 2041 This dihydroxy toluene, which was called lute-rein by Vogt and Henninger, may be prepared from ft- and 7-amido- paracresol by the diazo-reaction l and by fusing bromoparacresol with caustic potash. 2 It is readily soluble in water, alcohol, ether and benzene, and crystallizes in monosymmetric prisms which form characteristic spherical aggregates and melt at 104 105. Ferric chloride produces an unstable, greenish blue colouration, and an alkaline solution becomes coloured red in the air. Like resorcinol it re- duces silver solution in the cold, is not precipitated by lead acetate, and gives a precipitate with bromine water which soon becomes crystalline. On heating with phthalic anhydride and dissolving the mass in dilute caustic soda, a solution is formed possessing as fine a green fluorescence as does that obtained by a similar process from resorcinol. It differs however from the latter in yielding no colouring matter* when heated with sul- phuric acid and nitrobenzene. In presence of ammonia and moist air it is converted into yellow cresorcein, which dissolves in dilute caustic soda, forming a blue solution turned red by acetic acid. Isorcinol. Senhofer obtained this compound by the fusion of 7-toluenedisulphonic acid, 3 and Hakansson prepared a-isorcinol in a similar manner from a-toluenedisulphonic acid. 4 Claesson subsequently showed that these two sulphonic acids are identical, and that, therefore, only one isorcinol can exist. It crystallizes *n needles melting at 87 88, but it resembles cresorcinol so closely that Neville and Winther look upon the two as identical, an opinion which is supported by the fact that the toluenedisulphonic acid has the side chains in the same relation as cresorciaol. 1 Knecht, Ber. Deutsch. Chem. Gcs. xv. 298 and 1069 ; Ann. Chem. Pharm. ccxv. 83 ; Wallach, ibid. xv. 2831 ; Neville and Winther, ibid. xv. 2980. 2 Vogt and Henninger, ibid. xv. 1081. 3 Ann. Chem. Pharm. clxiv. 131. 4 Ber. Deutsch. Chem. Ges. v. 1084. 48 AROMATIC COMPOUNDS. TOLUQUINOL, OR TOLUHYDROQUINONE. C 6 H 3 (CH 3 )(OH) 2 (1:2:5). 2042 This compound may be obtained from orthotoluidine just as is quinol from aniline, 1 and may also be prepared from /3-amido-orthocresol by means of the diazo-reaction. 2 It is readily soluble in water, alcohol and ether, and crystallizes from hot benzene or toluene in pointed, rhombic plates which have a nacreous lustre and melt at 124. Caustic soda produces a bluish green colouration which rapidly changes to dark brown ; bleaching powder solution gives the same reaction, but when very dilute produces a brownish red colour. Oxidizing agents readily convert it into toluquinone. Toluquinol monomethyl ether, C 6 H 3 (CH 3 )(OCH 3 )OH, is formed, together with the compound described below, by heating tolu- quinol with caustic soda, methyl iodide and wood-spirit to 190. It has a faint smell of creosote, crystallizes in plates melting at 72, boils at 240 245, and yields toluquinone on oxidation. Toluquinol dimethyl ether, C 6 H 3 (CH 3 )(OCH 3 ) 2 , can easily be separated from the monomethyl ether, since it is insoluble in alkalis and non-volatile in steam. It is a liquid which has a pleasant smell like fennel and boils at 214 218. When oxidized by chromic acid in acetic acid solution, it is converted into a compound, C 16 H 16 4 , which is precipitated by water in brick-red needles and crystallizes from its deep yellow alcoholic solution, in hair-like needles, which appear almost black when seen in masses and become silver-grey on drying. They melt at 153 and sublime when more strongly heated. Ammonium sul- phide reduces it to the compound C 18 H 18 O 4 , crystallizing from alcohol in small prisms, melting at 173, which are readily re-oxidized. Diacetotoluquinol, C 6 H 3 (CH 3 )(OCO.CH 3 ) 2 , is formed by the action of acetyl chloride on toluquinol ; it crystallizes from alcohol in large tablets melting at 72 (Nietzki). 1 Nietzki, Ber. Deutsch. Chem. Gcs. x. 834, 1935 ; Ann. Chem. Pharm. ccxv. 158. 2 Neville and Winther, Ber. Deutsch. Chem. Gcs. xv. 2979. TOLUQUINOL AND TOLUQUINONE. 49 TOLUQUINONE, C 6 H 3 (CH 3 )0 2 . 2043 This compound is formed when paradiamidotoluene, 1 crude cresol 2 or amidorthocresol 3 is oxidized with manganese dioxide and dilute sulphuric acid, or when orthotoluidine hydro- chloride is heated with ferric chloride. 4 It crystallizes in small golden-yellow plates which readily volatilize, have a penetrating smell resembling that of benzoquinone, and melt at 69. It dissolves slightly in cold, more readily in hot water, forming a golden-yellow solution which is coloured brownish red by alkalis. Sulphurous acid reduces it to toluquinol. Dianilidotoluquinone, C 6 H(CH 3 )0 2 (NH.C 6 H 5 ) 2 , is obtained by the action of aniline on toluquinone in alcoholic solution; it crystallizes from hot glacial acetic acid in brown, matted needles, which melt at 232 233 and form a blood -red solution in sulphuric acid. When boiled with alcohol and sulphuric acid, anilidoliydroxy toluquinone, C 6 H(CH 3 )0 2 (NH.C 6 H 5 )OH, is formed ; it crystallizes from alcohol or acetic acid in deep blue needles and forms salts with bases. Dianilidotoluquinone anilide, C 6 H(CH 3 )0(NC 6 H 5 )(NH.C 6 H 5 ) 2 , is formed when aniline and toluquinone are brought together in solution in a mixture of alcohol and acetic acid. It crystallizes in broad dark-brown plates which have a blue surface lustre, melt at 167 and combine with acids to form salts, which are only slightly soluble in water but crystallize well from alcohol. On heating with alcoholic sulphuric acid, anilido-ethoxytolu- quinone anilide, C 6 H(CH 3 )0(NC 6 H 5 )(NH.C6H 5 )OC 2 H 5 ,is formed ; this compound crystallizes from alcohol in silky, red needles melting at 115 116, is a tolerably strong base and forms blue salts. It dissolves in concentrated sulphuric acid with a green colour. On treatment with alcoholic potash it yields anilido- hydroxytoluquinone anilide, C 6 H(CH 3 )0(NC 6 H 5 )(NHC 6 H 5 )OH, crystallizing from hot, dilute acetic acid in brownish needles, which form a deep green solution in sulphuric acid. It forms insoluble or difficultly soluble salts with the metals. Dihydroxy toluquinone, C 6 H(CH 3 )0 2 (OHJ 2 , is obtained from 1 Nietzki, loc. cit. 2 Carstanjen, Journ. Prakt. Chem. [2] xxiii. 425. 3 Nolting and Kohn, Bcr. Deutsch. Chem. Ges. xvii. 370. 4 Ladenburg, ibid. x. 1125. 50 AROMATIC COMPOUNDS. the preceding compound by the action of very dilute caustic potash solution. It is readily soluble in most solvents and crystallizes from them badly ; it readily sublimes, however, in brownish yellow, lustrous plates, melting at 177. Its salts form insoluble or only slightly soluble precipitates which are not characteristic. 1 Toluquinhydrone, C ( .H 3 (CH 3 )O 2 -hC 6 H 3 (CH 3 )(OH) 2 , is obtained by mixing aqueous solutions of the two constituents, and crys- tallizes in fine, almost black needles which melt at 52 and are tolerably soluble in water forming a brownish yellow solution (Nietzki). SUBSTITUTION PRODUCTS OF TOLUQUINONE. The chlorine substitution products are obtained by treating orthocresol or metacresol, and therefore also crude cresol, with potassium chlorate and hydrochloric acid. 2 Trichloroquinone is likewise formed by this method from orthotoluidineparasulphonic acid. 3 Sulphurous acid converts them into the corresponding derivatives of toluquinol. Dichlorotoluquinone, C 7 H 4 C1 2 O 2 , yellow transparent tablets. Trichlorotoluquinone, C 7 H 3 C1 3 O 2 , yellow plates. Tetrachlorotoluquinone,C 7 H 2 Cl 4 2 , { ^^ Tribromotoluquinone, 4 C 7 H 3 Br 3 O 2 , yellow plates. TOLUQUINONOXIME COMPOUNDS. 2044 a-Toluquinonoxime, C 6 H 3 (CH 3 )0(NOH). This compound, which is generally known as nitroso-orthocresol, is formed in an analogous manner to quinonoxime (Part III. p. 171) by the action of nitrosyl sulphate on an aqueous solution of orthocresol, 5 or by adding hydroxylamine hydrochloride to a dilute solution of toluquinone. 6 It is only slightly soluble in cold, more readily in hot 1 Hagen and Zincke, Bcr. Deutsch. Chem. Ges. xvi. 1558. 2 Southworth, Ann. Chem. Pharm. clxviii. 274 ; Bergmann, ibid. clii. 248 ; Brauninger, ibid, clxxxv. 352 ; Knapp and Schultz, ibid. ccx. 176. 8 Hayduck, ibid, clxxii. 209. 4 Canzoneri and Spica, Bcr. Deutsch. Chem. Ges. xvi. 793. 8 Nolting and Kohn, ibid. xvii. 370. 6 Goldschmidt and Schmidt, ibid. xvii. 2063. TOLUQUINONOXIME COMPOUNDS. 51 water, from which it crystallizes in long, white needles, melting at 134 135, It forms a reddish brown solution in dilute alkalis, and is thrown down by acids as a white, flocculent precipitate. Potassium a-toluquinonoximate, C 6 H 3 (CH 3 )O(NOK), is ob- tained by the addition of an ethereal solution of toluquinone- oxime to a solution of potassium ethylate, as a yellowish green precipitate, which crystallizes from acetone in brown needles. Sodium a-toluquinonoximate, C 6 H 3 (CH 3 )0(NONa) + 3H 2 O, is a dark green precipitate which crystallizes from acetone in short, brown needles, and forms a reddish brown solution in water ; it detonates when heated. Toluquinonoxime gives Liebermann's reaction with phenol and sulphuric acid ; potassium ferricyanide oxidizes it to /3-nitro-orthocresol, and nitric acid to dinitro-orthocresol, while it is converted into #-amido-orthocresol by reduction. a-Toluquinone chlorimide, C 6 H 3 (CH 3 )O(NC1), is formed in an analogous manner to quinone chlorimide when a concentrated solution of bleaching powder is added to a dilute hydrochloric acid solution of ry-amido-orthocresol ; the liquid first becomes coloured cherry-red, changing to golden-yellow, the chlorimide then separating out. It crystallizes from benzene in yellow needles, which melt at 87 88 and detonate at higher temperatures. When boiled with water it volatilizes, a portion being simul- taneously decomposed into a-toluquinone and brown, amorphous bodies ; it also gives Liebermann's reaction. 1 ft- Toluquinonoxime, or Nitrosometacresol, C 6 H 3 (CH 3 )0(NOH), has been prepared by boiling nitrosodimethylmetatoluidine ; it is slightly soluble in hot water, from which it crystallizes in small, colourless needles, while it is deposited from solution in ether or acetic acid in thick needles or prisms, decomposing at 140 150. P-Toluquinonoxime acetate, C 6 H 3 (CH 3 )0(NO.C 2 H 3 O), is ob- tained by the action of acetic anhydride on the compound just described ; it crystallizes from alcohol in prisms melting at 92. /3-Toluquinonoxime gives Liebermann's reaction in a most characteristic manner; nitric acid oxidizes it to trinitrometa- cresol. 2 1 Hirsch, Bcr. Dcutsch. Chem. Gw. xviii. 1514. 2 Wursterand Riedel, ibid. xii. 1799. 52 AROMATIC COMPOUNDS. The following formulae explain the isomerism of the two toluquinonoximes : 13 CO CO HC C CH 3 HC CH II II II II HC CH HC C CH 3 v \/ C C II II NOH. NOH. Paracresol does not form a nitroso-compound or quinonoxime, since the methyl group is situated in the para-position. Hydroxytoluquinonoxime, C 6 H 2 (CH 3 )(OH)0(NOH). This compound, which is also called nitroso-orcinol, is obtained by evaporating a solution of 12 grammes of orcinol and 4 grammes of caustic soda to a syrup, and gradually adding 12 grammes of amyl nitrite to the cold mass with constant stirring; the mixture is then gently heated on the water-bath until a small portion dissolved in water gives a red precipitate with sulphuric acid. The fused mass is then dissolved in water and precipitated with dilute sulphuric acid. Nitroso-orcinol crystallizes from alcohol in small dark red prisms, which become coloured black at 110 without melting. 1 It has the following constitution : CO /\ HC CH II II OH C C CH 3 NOH. Azo-orcin, C 14 H U N0 3 . Weselsky obtained this compound by the action of his reagent on an ethereal solution of orcinol ; 2 it is also formed when orcinol is heated on the water-bath with nitroso- orcinol and sulphuric acid (Brunner and Kramer). It crystal- lizes in small, brownish red prisms which dissolve in alkalis forming a deep purple-coloured solution with a splendid orange- 1 Brunner and Kramer, Ber. Deutsch. Chem. Ges. xvii. 1879. 2 Ibid. vii. 439. METHYLPYROGALLOL. 5.3 red fluorescence; acids precipitate it from this as a scarlet powder. Its formation is quite analogous to that of azoresorcin, C 12 H 9 NO 4 (Part III. p. 176), but it is not homologous with this substance. The homologous compound is, however, first formed and is converted into azo-orcin with loss of water; the latter compound may probably possess the following constitution : O O CH 3 .C 6 H 3 < >NC 6 H 2 (CH 3 )< >C 6 H 2 (CH 3 )N< >C 6 H 3 CH 3 . O O O Liebermann obtained a similar colouring matter by gradually adding 40 grammes of his reagent to a solution of 10 grammes of orcinol in 10 grammes of sulphuric acid. 1 Another colouring matter is simultaneously formed but can easily be separated, as it forms a sodium salt which is insoluble in alcohol, while that of the former forms a purple-red solution with a cinnabar-red fluorescence. The colurring matter, C 22 H 21 N0 6 , separated from this solution by the addition of an acid, is an amorphous mass with a beetle-green fluorescence, the aqueous alkaline solution of which has a brownish red fluorescence. The formation of this compound corresponds exactly to that of Liebermann's phenol colouring-matter, and its constitution is therefore the following : OH H0 O.CH CH 362 HO/ \O.C 6 H 3 CH 3 OH. The second colouring matter, C 22 H 21 N0 7 , is an oxidation product of the former, which it resembles very closely ; its violet Ikaline solution, however, does not fluoresce (Brunner and ler). TRIHYDROXYTOLUENES, C 6 H 2 (CH 3 )(OH) 3 . 2045 Mcthylpyrogallol, or Methylpyro gallic acid, is the only mown compound of this group. Its dimethyl ether occurs, )gether with the same ethers of pyrogallol and propylpyrogallol 1 Ber. Deutsch. Chem. Gcs. vii. 1110. 235 54 AROMATIC COMPOUNDS. in the fraction of beech-wood-tar creosote which dissolves in alkalis and boils at between 255 and 270. In order to separate them, the mixture is heated with benzoyl chloride, the benzoic ethers separated by fractional crystallization and then decomposed by alcoholic potash. MetJiylpyrogallol dimethyl ether, C 6 H 2 (CH 3 )(OCH 3 ) 2 OH, is a crystalline substance, melts at 36, and boils at 265. On heating with concentrated hydrochloric acid, methylpyrogallol is obtained ; this closely resembles pyrogallol, and on heating sublimes in needles, which melt at 129. Its aqueous solution is coloured brown by ferrous sulphate, and its alkaline solution rapidly turns brown in the air. 1 AMIDO-DERIVATIVES OF TOLUENE. AMIDOTOLUENES, OR TOLUIDINES, C 6 H 4 (CH 3 )NH 2 . 2046 The history of these compounds goes hand in hand with that of the nitrotoluenes. Hofmann and Muspratt reduced crude nitrotoluene by repeated treatment with alcoholic am- monium sulphide and obtained the product free from unaltered nitrotoluene by washing well with water, treating with hydro- chloric acid and distilling the liquid, after the removal of all alcohol by evaporation, with caustic soda ; they thus obtained an oily liquid which solidified after some time to a crystalline mass, and to this new organic base they gave the name toluidine. The aqueous distillate obtained in the preparation contained some ammonia and a not inconsiderable amount of base in solution ; the whole distillate was therefore treated with an excess of ammonium oxalate, evaporated to dryness on the water-bath and the residue extracted with boiling absolute alcohol, ammonium oxalate being in this way left undissolved. On cooling, toluidine oxalate separated out in white crystals, which were washed, dissolved in hot water, and decomposed with concentrated caustic potash solution. The oil which separated out solidified on cooling to a radiating crystalline mass of pure toluidine, the properties of which were then accurately investigated. After the discovery of the aniline dyes, aniline and toluidine, 1 Hofmann, Ber. Deutsch. Chem. Ges. xii. 1371. TOLUIDINES. 55 or rather a mixture of the two called aniline oil, was manu- factured on the large scale; and Rosenstiehl found in this mixture a liquid base, isomeric with the ordinary toluidine, to which he gave the name of pseudotoluidine. We have already pointed out that the three nitrotoluenes are formed in varyino- quantities by the nitration of toluene. If concentrated acid be employed without cooling, paranitrotoluene is chiefly formed, and this yields on reduction the solid paratoluidine obtained by Hofmann and Muspratt. If, however, a weaker acid be employed, and the temperature be kept low, more of the ortho-compound is formed, and it is from this that the pseudotoluidine is derived ; a small quantity of metanitrotoluene being, however, invariably produced. The toluidines are manufactured on a large scale ; the para- compound is that which is most readily obtained in the pure state, as the purification of paranitrotoluene offers no difficulties, whilst it is very difficult, working on the large scale, to obtain an orthonitrotoluene free from paranitrotoluene, so that ordinary commercial orthotoluidine always contains some of the para-compound together with metatoluidine and generally a little aniline. The amount of paratoluidine in such a mixture can readily be determined by means of the different solubilities of the oxalates in ether; at 15 Acid paratoluidine oxalate requires 6660 parts of ether, Acid orthotoluidine oxalate 200 for solution. A small quantity, about 0'2 grms., of the mixture is dissolved in 80 grms. of ether and titrated with a solution of T062 grms. of oxalic acid in 250 c.c. of ether until no further precipitate is formed. Each cubic centimetre of the solution employed corresponds to 0'005 grms. of paratoluidine. 1 The end of the reaction can easily be recognised by the acid reaction of the solution towards litmus-paper as soon as the orthotoluidine oxalate commences to be formed. The deter- mination is rendered still more accurate by adding an excess of oxalic acid solution to the solution of the bases, filtering from the precipitate, evaporating the ether, dissolving the residue in a little water and determining the excess of oxalic acid by decinormal caustic soda solution. 2 1 Rosenstiehl, Ann. Chim. Phys. (1872), xxvi. 249. 2 Lorenz, Ann. Chcm. Pharm. clxxii. 190. 56 AROMATIC COMPOUNDS. In order to separate larger quantities of the base, an amount of oxalic or sulphuric acid equivalent to the paratoluidine present is added, and the whole distilled with steam; ortho- toluidine alone passes over, and the para-compound as the stronger base remains behind in /combination with the acid (Rosenstiehl). Ihle dissolves the bases in ether, precipitates with an ethereal solution of oxalic acid and from time to time treats a small portion of the solution with acetyl chloride. The product is re-crystallized from hot water and its melting-point observed. Since acetparatoluide melts at 145, and acetorthotoluide at 107, the point at which all the paratoluidine is removed can readily be recognised. 1 Binschedler gives the following process for the treatment of a mixture of 30 per cent, of paratoluidine and 70 per cent, of ortho- toluidine which comes into the market under the name of "aniline lourde spdciale" : 10 kilos, of the mixture of bases are gradually added to a solution of 2' 5 kilos, of oxalic acid in 25 litres of boiling water to which 6 litres of hydrochloric acid of specific gravity 1*15 have been added, the mixture being then heated to the boiling .point, and constantly stirred until it has cooled down again to 60. The crystalline precipitate which consists of pure paratoluidine oxalate, is rapidly filtered off, pressed, and washed with a little water ; 2 kilos, of oxalic acid are now added to the filtrate, a mixture of the oxalates being thus precipitated. When oxalic acid produces no further precipitate in the mother-liquor, it is distilled with caustic soda, orthotoluidine being obtained which contains a very small quantity of paratoluidine and only traces of aniline. 2 Another method of separation, which has been patented by Leo Levy, depends upon the behaviour of the hydrochlorides of the bases towards sodium phosphate. Aniline hydrochloride gives the following reaction : Na 2 HPO 4 + 2C 6 H 6 NH 3 C1 = 2NaCl + (C 6 H 5 .NH 3 ) 2 HP0 4 . Paratoluidine hydrochloride behaves in a similar manner, while the orthotoluidine salt yields 80 per cent, of the free base and 20 per cent, of the acid phosphate : 1) C 7 H 7 .NH 2 HC1 + Na 2 HP0 4 = C 7 H 7 .NH 2 + NaH 2 P0 4 + NaCl. 2) C 7 H 7 .NH 2 HC1 + NaH 2 P0 4 = (C 7 H 7 .NH 3 )H 2 PO 4 + NaCl. 1 Journ. PraTct. Chem. [2] xiv. 449. 2 Ber. Dcutsch. Chem Gcs. vi. 448. ORTHOTOLUIDINE. 57 The mixed hydrochlorides are therefore treated with a solution of sodium phosphate; the crystalline mass which is formed is then dissolved by warming, and the orthotoluidine removed from the surface. On cooling, the phosphates of aniline and paratoluidine separate out completely, while the phosphate of orthotoluidine remains in solution. The sodium phosphate can be recovered after separation of the bases ; sodium arsenate may also be employed. 1 Another process for the separation of orthotoluidine from aniline oil by means of the nitrate has been described by L. Schad.2 2047 Orthotoluidine, discovered by Rosenstiehl, 3 is formed by the reduction of orthonitrotoluene and by the distillation of paramidotoluic acid with lime. 4 It is a colourless liquid re- sembling aniline very closely ; it soon becomes brown in the air or on exposure to light, boils at 198' 5, has a specific gravity of 1-003 at 20'2, and does not solidify at - 20. A solution of this base in monohydrated sulphuric acid gives a blue colouration with a solution of chromium trioxide in sulphuric acid of the same strength ; the colour changes to a stable reddish violet on dilution. Nitric acid added to the sulphuric acid solution gives an orange to brown colouration, passing into yellow on the addi- tion of water. If the base be dissolved in ether and an equal volume of water added, the lower layer of the solution gives a yellow to brown colouration with dilute sulphuric acid. If the ethereal layer be now removed and shaken with dilute sulphuric acjd, it becomes coloured a stable reddish violet (Lorenz). Orthotoluidine further differs from its isomerides in giving a green colouration with ferric chloride and a little paradiamido- benzene. This reaction is so delicate that a solution containing 1 in 10,000 gives a tolerably deep colouration, and a solution only one-tenth as strong as this assumes a distinct shade of green. 6 All commercial aniline gives this reaction, as also does that obtained by the distillation of indigo with caustic potash, which was con- sidered to be chemically pure until Rosenstiehl proved that it contained orthotoluidine. The salts of orthotoluidine have been investigated by Beilstein and Kuhlberg. 1 Bcr. Dcutsch. Chem. Ges. xvi. 980. 2 Ibid. vi. 1361. 3 Zeitschr. Chem. [2] iv. 557. 1 Beilstein and Kuhlberg, Ann. Chem. Pharm. clvi. 75. 5 Monnet, Reverdin and Nblting, Ber. Deutsch. Chem. Ges. xi. 2278. See also Reinhardt and Stadel, ibid. xv. 29. 58 AROMATIC COMPOUNDS Orthotoluidine hydrochloride, C 7 H 9 NClH-f H 2 0, forms white crystalline crusts, 37'4 parts of which dissolve in 100 parts of water at 15'5 ; it is still more readily soluble in alcohol. Orthotoluidine hydrobromide, C 7 H 9 N.BrH, crystallizes very easily in large rhombic prisms ; the hydricdide resembles it, but is partially decomposed by water. 1 Orthotoluidine sulphate, (C 7 H 9 N) 2 H 2 S0 4 , forms small crystals which become coloured violet to green in the air; 100 parts of water at 22 dissolve 7*5 parts. It is only slightly soluble in alcohol. Orthotoluidine ni/rate, C 7 H 9 N.HNO 3 , crystallizes in small plates ; 100 parts of water at 19'2 dissolve lO'Ol parts. Orthotoluidine oxalate crystallizes in small colourless plates-, 100 parts of water at 21 dissolve 2'38 parts. Hethylorthotoluidine, C 6 H 4 (CH 3 )N(CH 3 )H, is formed when 750 grms. of Orthotoluidine are heated for a day to 200 220 with 400 grms. of methyl alcohol and 700 grins, of .hydrochloric acid. The product is distilled in steam, and every 100 grms. of distillate dissolved in 120 grms. of hydrochloric acid and 300 grms. of water, the solution being then treated with a con- centrated solution of 40 grms. of sodium nitrite, the mixture being cooled and well agitated. The methylorthotolylnitros- amine, C 6 H 4 (CH 3 )N(CH 3 )NO, formed, which is very similar to methylnitroso-aniline, is extracted with ether, reduced with tin and hydrochloric acid, decomposed with caustic soda, and distilled with steam. Methylorthotoluidine is a colourless liquid which rapidly becomes coloured violet-brown in the air, and boils at 207 208 . 2 Dimethylorthotoluidine, C 6 H 4 (CH 3 )N(CH 3 ) 2 . Thomsen ob- tained this compound by the distillation of trimethyltolyl- ammonium hydroxide ; it is also formed, together with other products, when trimethylphenylammonium iodide is heated to 220 23 0. 3 It can readily be prepared pure by heating 750 grms. of Orthotoluidine for two days with 670 grms. of methyl alcohol and 700 grms. of hydrochloric acid, the product being repeatedly rectified (Monnet, Reverdin and Nolting). It is a colourless liquid which has a characteristic aromatic odour and boils at 183. 1 Stadel, Ber. Deutsch. Chem. Ges. xvi. 28. 2 Monnet, Reverdin and Nolting, Bcr. Deutsch. Chem. Ges. xi. 2278. See also Reinhardt and Stadel, ibid. xv. 29. 3 Hofmann, ibid. x. 1585. DERIVATIVES OF ORTHOTOLUIDINE. 59 Trimethylorthotolylammonium iodide, C 6 H 4 (CH 3 )N(CH 3 ) 3 I, is formed by the continued action of methyl iodide on ortho- toluidine, 1 and crystallizes in large needles which assume a faint purple tint in the air. Boiling-point. Ethylorthotoluidine, C 7 H 9 N(C 2 H 5 )H, liquid 213 214 Diethylorthotoluidine, 2 C 7 H 9 N(C 2 H 5 ) 2 208 209. Phenylorthotolylamine, C 6 H 5 .NH(C 7 H 7 ), is formed, together with diphenylamine and di-orthotolylamine, when orthotoluidine is heated with aniline hydrochloride to 280. 3 It is a crystalline substance which melts at 41, boils at 297 299, and gives a violet-blue colouration with nitric acid. Di-orthotolylamine, (C 7 H 7 ) 2 NH, is a liquid boiling at 304 308. Acetorthotoluide, C 7 H 7 .N(C 2 H 3 O)H, forms long needles, melts at 107 and boils at 296; 100 parts of water at 19 dissolve 0*86 parts (Beilstein and Kuhlberg). Orthotolyl carbamide, (C 7 H 7 )NH.CO.NH 2 , is formed by the ion of potassium cyanate on orthotoluidine hydrochloride ; it is >luble in cold water, moderately soluble in hot water, and lily in alcohol, crystallizing in tablets which melt at 185 . 4 Di-orthotolyl carbamide, (C 7 H 7 ) 2 NCO.NH 2 , is formed by the action of carbonyl chloride on orthotoluidine, by heating the latter with urea, 5 or by heating its hydrochloride with cyanamide to 100. 6 It is insoluble in water, but slightly soluble in alcohol, rystallizing in fine needles which melt at 243. Orthotolyl carbamide, or Orthotolyl isocyanate, CON.C 6 H 4 .CH 3 . r hen orthotoluidine is acted upon by chlorocarbonic ether, rtolyl urethane, NH(C 7 H 7 )CO.OC 2 H 5 , is formed in crystals lelting at 46, 7 and on heating with phosphorus pentoxide is >n verted into the isocyanate, which is a liquid boiling at 186 and possessing a penetrating odour (Girard). Water decom- poses it with formation of ditolyl carbamide. Orthotolyl thiocarbamide, (C 7 H 7 )HN(CS)NH 2 , is obtained by the action of ammonia on orthotolyl mustard oil ; it melts at 155 and is readily soluble in boiling water. 8 1 Thomsen, Ber. Deutsch. Chcm. Ges. x. 1586. 2 Stadel and Reinhardt, loc. cit. ; Norton, Ann. Chcm. Journ. vii. 118. 3 Girard and Willm, Bull. Soc. CMm. xxv. 248. 4 Cosack, Ber. Deutsch. Chem. Ges. xiii. 1089. 6 Girard, ibid. vi. 444. Berger, ibid. xii. 1859. 7 Lachmann, ibid. xii. 1349 ; Neville and Winther, ibid. xii. 2324. 8 Staats, ibid. xiii. 135. 60 AROMATIC COMPOUNDS. Di-orthotolyl thiocarbamide, (C r H 7 .NH) 2 CS, is obtained by the action of carbon disulphide on an alcoholic solution of orthotolu- idine. 1 It crystallizes from hot alcohol in needles melting at 158. Orthotolyl thiocarbamide, or Orthotolyl mustard oil, CSN.C 6 H 4 . CH 3 , is formed when the compound just described is boiled with fuming hydrochloric acid. It is. a strongly refractive liquid, boiling at 239 and possessing a pungent odour (Girard). It combines with aniline forming phenylorthotolyl thiocarbamide, (C 6 H 5 )NH(CS)NH(C 7 H r ), which has also been prepared from orthotoluidine and phenyl mustard oil (Staats) ; it forms long needles melting at 139, and is decomposed by hydrochloric acid into aniline and tolyl mustard oil. 2048 Metatoluidine was obtained by Beilstein and Kuhlberg by the reduction of metanitrotoluene, 2 which is best effected by means of stannous chloride and hydrochloric acid (Cosack) According to Widmann, it is also formed when metanitrobenzyl- ene chloride, C 6 H 4 (NO 2 )CHC1 2 , obtained by the action of phos- phorus chloride on metanitrobenzaldehyde, is reduced with zinc dust and hydrochloric acid. 3 It is a colourless oily liquid which has a specific gravity of 0'998 at 25, and becomes converted into a brown resinous mass when exposed to the air (Lorenz) ; it boils at 197 and does not solidify even at 13. If it be dissolved in monohydrated sulphuric acid and treated with a sulphuric acid solution of chromium trioxide, a yellowish brown liquid is obtained which becomes brown on gentle heating, and is coloured greenish yellow by the addition of a little water, a larger quantity rendering it colour- less. Nitric acid added to the original solution produces a reddish colouration which rapidly becomes a deep blood-red, and then a dark dirty-red, and is converted into orange by the addition of water. When a solution of the base in equal volumes of ether and water is treated with bleaching powder solution, the aqueous layer is coloured brownish yellow and becomes turbid, while the ether exhibits a reddish fluorescence ; if the ether be poured off and shaken up with water and a drop of dilute sulphuric acid, the water becomes coloured a faint violet. The salts of metatoluidine have been investigated by Lorenz. 4 1 Girard, Ber. Deutsch. Chem. Ges. iv. 985 ; Berger, ibid. xii. 1854. 2 Ann. Chem. Pharm. clvi. 83. 3 Ber. Deutsch. Chem. Ges. xiii. 676 ; xiv. 2583. See also ibid. xiv. 1403. 4 Ann. Chem. Pharm. clxxii. 177. METATOLUIDINE. 61 Metatoluidine hydrochloride, C 7 H 9 N.C1H, crystallizes from a very concentrated aqueous solution in thin tablets, and from alcohol in thin, pale red crusts. Metatoluidine sulphate, (C 7 H 9 N) 2 S0 4 H 2 , crystallizes in long, transparent, light red, radiating needles, which are insoluble in ether, slightly soluble in alcohol, and more readily in water, 100 parts of which at 14 dissolve 6*25 parts. Metatoluidine nitrate, C 7 H 9 N.NO 3 H, crystallizes in large, pale red, rhombic plates, 16*42 parts of which dissolve in 100 parts of water at 15'5; it is still more soluble in alcohol, but only slightly soluble in ether. Acid mctatoluidine oxalate, C 7 H 9 N.C 2 O 4 H 2 , forms warty masses consisting of fine silky needles, which are only slightly soluble in ether, alcohol and water; 100 parts of the latter at 13 dissolve 2'65 parts. When its solution is warmed with meta- toluidine, the salt, (C 7 H 9 N) 3 (C 2 4 H 2 ) 2 , separates out in a mass of rhombic plates which are still less soluble than the mono- acid salt. If an excess of metatoluidine be added in warm Icoholic solution to oxalic acid, small rhombic plates separate nit on cooling in such quantity that the liquid solidifies to a }lly. These crystals appear to be the hydrated normal salt; washing with alcohol and drying, they possess the appear- ice of cholesterin; they are scarcely wetted by water and heated with it for a long time decompose into the acid It and the free base. Methylmetatoluidine, C 6 H 4 (CH 3 )N(CH 3 )H, is formed, together rith dimethylmetatoluidine, by the action of methyl iodide on ie primary base. The product is extracted with ether and jd from unattacked metatoluidine by the addition of sulphuric jid, an alkali is then added, the ether distilled off and the residual il dried and heated with acetic anhydride. On distillation, jetic acid and acetic anhydride first come over, followed by limethyltoluidine and finally by methylacetoluide, boiling above 550. This is purified by repeated distillation and decomposed by heating with dilute sulphuric acid, pure methylmetatoluidine being thus obtained ; it is a colourless liquid which boils at 206 207, and possesses a characteristic aromatic odour. Dimethylmetatoluidine, C 6 H 4 (CH 3 )N(CH 3 ) 2 , boils at 215 (Wurster and Eiedel), and has a characteristic odour differing from that of its isomerides, but resembling that of dimethyl- aniline. 1 1 Nolting, Ber. Deutsch. Ckcm. Gcs. xi. 2278. 62 AROMATIC COMPOUNDS. Nitrosodimcthylmdatoluidine, C 6 H 8 NO(CH 3 )N(CH 3 ) 2 , is formed on the addition of sodium nitrite to a cooled solution of di- methylmetatoluidine in hydrochloric acid. The hydrochloride thus prepared crystallizes from a hot, acidified solution in light yellow to greenish yellow needles which are only slightly soluble in cold water. Sodium carbonate liberates the free base, which crystallizes from ether in small, green plates or long needles, melting at 92. It is precipitated by petroleum ether from a solution in chloroform in moss-green needles, and separates from benzene in large, dark green crystals containing benzene of crystallization, which they lose in the air together with their colour and lustre. All its solutions are coloured deep green. It crystallizes from water in small, lustrous green plates. Like nitrosodimethylaniline, it forms deep steel-blue coloured compounds with aniline, orthotoluidine, &c., and does not give Liebermann's reaction in the cold. Boiling dilute caustic soda converts it into nitrosocresol ; potassium permanganate oxidizes it to nitrodimctJiylmetatoluidine, C 6 H 8 N0 2 (CH 3 )N(CH 3 ) 2 , which crystallizes in long yellow needles, melting at 84. It is re- duced by tin and hydrochloric acid to dimethyldiamidotoluene C 6 H 3 (CH 3 )(NH 2 )N(CH 3 ) 2 . Since the two isomerides of dimethyltoluidine give no nitroso-compounds, the presence of metatoluidine can readily be detected in orthotoluidine, and its amount approximately determined ; to effect this the hydrochlorides are prepared, the greater part of the orthotoluidine salt removed by crystallization, the mother-liquor evaporated to dryness, and the residue heated with methyl alcohol ; the almost insoluble nitrosodimethylmeta- toluidine is then prepared directly from the mixture of dimethyl- toluidines thus obtained. The two bases can also be separated by fractional distillation, since the ortho-compound boils at 183 C and the meta-compound at 215 . 1 Metaditolylamine, (C 6 H 4 .CH 3 ) 2 NH, is formed when meta- toluidine is heated with its hydrochloride. It is a thick, oily, light yellow liquid which becomes coloured brown in the air and boils at 319 320. 2 Acetmetatolmde, C 6 H 4 (CH 3 )N(C 2 H 3 0)H, crystallizes on the gradual evaporation of its aqueous solution in long needles united to form bushy aggregates ; it melts at 6 5 '5, and boils at 1 Wurster and Kiodel, Ber. Deutsch. Chem. Ges. xii. 1796. 2 Cosack, ibid. xiii. 1088. PARATOLUIDINE. 63 303. 100 parts of water at 13 dissolve 0'44 parts (Beilstein and Kuhlberg). Metatolyl carbamide, (C 6 H 4 .GH 3 )HN.CO.NH 2 , has been pre- pared from metatoluidine and potassium cyanate ; it crystallizes from water in small plates, and from alcohol in tablets or needles, melting at 142. Dimetatolyl carbamide, CO(NH.C 7 H 7 ) 2 . When metatoluidine acted upon by chlorocarbonic ether, metatolyl urethane, (C 7 H 7 )HKCO.OC 2 H 5 , is formed ; this is a liquid which on distillation in the moist state yields alcohol, carbon dioxide, and dimetatolyl carbamide. The latter crystallizes from hot alcohol in long needles melting at 217 (Cosack). 1 Metatolyl thiocarbamide, (C 7 H 7 )HN.CS.NH 2 , is obtained by the action of ammonia on metatolyl thiocarbimide. It is readily soluble in alcohol, slightly in cold, and more freely in hot water, and crystallizes in prisms which form star-shaped aggregates, and melt at 103 . 2 Dimetatolyl thiocarbamide, CS(NH.C 7 H 7 ) 2 , is formed when an alcoholic solution of metatoluidine is heated for a long time with carbon disulphide. It crystallizes in concentrically arranged needles, melting at 122, which are scarcely soluble in boiling water but dissolve readily in alcohol. Metatolyl thiocarbamide, or Metatolyl mustard o^/,CSN(C 6 H 4 .CH 3 ), is formed when the compound just described is heated with concentrated hydrochloric acid. It is a colourless liquid which boils at 244 and possesses the characteristic smell of the mustard oils in the highest degree (Weith and Landolt.) 2049 Paratoluidine is formed by the reduction of paranitro- )luene and by heating methylaniline hydrochloride for a day to 350 ; methylaniline hydriodide, on the other hand, gives a liquid toluidine, 3 which is probably the ortho-compound. It may also be obtained by heating paracresol with the compound of zinc chloride and ammonia to 300 . 4 It is slightly soluble in water, readily in alcohol and ether, and crystallizes from hot, dilute alcohol in large, colourless plates which melt at 45 and have a peculiar aromatic odour resembling that of aniline. According to Hofmann and Muspratt it boils at 198, while Stadeler found its boiling-point to be 204 206 . 5 When it is dissolved in monohydrated sulphuric acid and treated 1 Ber. Dcutsch. Chem. Gfes. ; see also xii. 1450. 2 Weith and Landolt, ibid. viii. 715. 3 Hofmann, ibid. v. 720. 4 Buch, ibid. xiv. 2345 ; xvii. 2637. 5 Jahresber. 1865, 409. 64 AROMATIC COMPOUNDS. with a solution of chromium trioxide in acid of the same strength, it is only coloured yellow. A drop of nitric acid added to the original solution produces a blue colouration, which soon passes through violet and red to brown (Lorenz) ; in presence of aniline or orthotoluidine no blue colouration is produced, but the liquid becomes coloured blood-red. Bleaching powder solution gives no colouration with solutions of pure paratoluidine ; in order therefore to detect the presence of aniline in paratoluidine, the mixture is dissolved in ether, and shaken up with an equal volume of water, a solution of bleaching powder then being added drop by drop. If aniline be present, the ether assumes a blue colour when the solution is agitated (Rosenstiehl). The salts of paratoluidine have been investigated by Hofmann and Muspratt and by Beilstein and Kuhlberg. 1 Paratoluidine hydrochloride, C 7 H 9 N,HC1, crystallizes in white crusts, which become coloured in the air. 100 parts of water at 11 dissolve 22'9 parts, while 100 parts of 89 per cent, alcohol dissolve 25 parts at 17. Paratoluidine hydrobromide, C 7 H 9 N, HBr, crystallizes in white plates ; the hydriodide is very similar (Reinhardt and Stiidel). Paratoluidine sulphate, (C 7 H 9 N) 2 H 2 SO 4 , forms lustrous, scaly crystals, 5*06 parts of which dissolve in 100 parts of water at 22 ; they are still less soluble in alcohol. Paratoluidine nitrate, C 7 H 9 N, HNO 3 , crystallizes, when its solu- tion is rapidly cooled, in large rhombic tablets ; when allowed to deposit more gradually, it forms long, transparent needles. 100 parts of water at 23'5 dissolve 17*7 parts; it is still more readily soluble in alcohol. Acid paratoluidine oxalate, C 7 H 9 N, C 2 4 H 2 , crystallizes in rhombic needles or prisms, 0'87 parts of which dissolve in 100 parts of water at 14 ; alcohol takes up even less. Paratoluidine phenate, C 7 H 9 N, C 6 H 6 O, crystallizes from petro- leum ether in long needles melting at 31 'I . 2 Methylparatoluidine, C 6 H 4 (CH 3 )N(CH 3 )H, is obtained by passing methyl chloride into heated paratoluidine. The pro- duct is extracted with ether, the paratoluidine hydrochloride formed being left undissolved. Any unaltered paratoluidine is precipitated by dilute sulphuric acid, and the ether evaporated, a mixture of methyltoluidine and dimethyltoluidine being thus obtained. The former is converted by the action of acetic 1 Ann. Chcm. Pharm. clvi. 73. 2 G. Dyson, Journ. Chcm. Soc. 1883, i. 468. METHYLTOLUIDINES. anhydride into acetmethylparatolnide, C 6 H 4 (CH 3 )N(C 2 H 3 O)CH 3 , which crystallizes from a mixture of ether and alcohol in large plates melting at 83. Pure methylparatoluidine is then ob- tained by boiling this compound with hydrochloric acid and decomposing the hydrochloride with caustic soda. 1 It can be even more simply separated by means of its nitrosamine, in the same way as its isomeride in the ortho-series. (Monnet, Reverdin and Nolting.) It is a liquid which boils at 208 and possesses an aromatic odour. Nitrosomethylparatoluidine, C 6 H 4 (CH 3 )N(CH 3 )NO, crystallizes from a mixture of ether and alcohol in large, well-formed prisms, melting at 54. Itimethylparatoluidine, C 6 H 4 (CH 3 )N(CH 3 ) 2 . By the action of lethyl iodide on paratoluidine, Thomsen obtained trimethyl- paratolylammonium iodide, C 7 H 7 N(CH 3 ) 3 I, which forms white crystals, and converted it by means of moist silver oxide into the hydroxide, which yielded the base on distillation ; 2 it is a liquid, which has a characteristic aromatic odour and boils at 208. Ethylparatoluidine, C 7 H 7 N(C 2 H 5 )H, Di-ethylparatoluidme, 3 C 7 H 7 N(C 2 H 5 ) 2 Boiling-point, liquid 217 229 Phenylparatoluidine, or Phenylparatolylamine, C 7 H 7 N(C 6 H 5 )H, obtained by Hofmann by the dry distillation of toluidine- lue or tritolylrosaniline, 4 while de Laire, Girard, and Chapoteau spared it by heating aniline with toluidine hydrochloride or >luidine with aniline hydrochloride. In both cases the product \ a mixture of diphenylamine, phenyltoluidine, and ditolylamine, cannot be readily separated by fractional distillation. 5 It is also formed when equal molecules of phenol and para- )luidine, or paracresol and aniline, are heated with an excess of inc chloride for twenty hours to 260 300 . 6 Phenylparatolui- line crystallizes readily from alcohol in long, silky needles, melts it 87 and boils at 334'5. Its salts, like those of diphenyl- ie, are decomposed by water, and it gives a fine blue colour- ion with concentrated nitric acid. When fused with mercuric ihloride or hexchlorethane, a splendid violet colouring matter formed. 1 Thomsen, Ber. Dcutsch. Chem. Ges. x. 1582. 2 See also Hiibner, Tolleand Athenstadt, Ann. Chem. Pharm. ccxxiv. 336. 3 Morley and Abel, ibid. 93, 313. 4 Ibid, cxxxii. 291. 6 Buch, Ber. Dcutsch. Chem. Ges. xvii. 2634. 6 Morley and Abel, Ann. Chem. Pharm. cxl. 347. 66 AROMATIC COMPOUNDS. Diparatolylamine, (C 6 H 4 .CH 3 ) 2 NH, is obtained by heating paratoluidine with its hydrochloride to 210 240. It forms long needles melting at 79 , 1 boils at 355 360, and is coloured yellow by nitric acid. Its salts are decomposed by water. Diparatolylnitrosamine, (C 6 H 4 .CH 3 ) 2 N(NO), is deposited from petroleum-ether in golden-yellow, hollow, rhombic crystals, melting at 100 101. When it is gradually added to well-cooled fuming nitric acid, hexnitrodiparatolylamine, (C 6 H(NO 2 ) 3 CH 3 ) 2 NH, is formed; this crystallizes in small yellow pyramids which melt at 258, and are slightly soluble in the usual solvents. 2 - Acetparatoluide, C 6 H 4 (CH 3 )N(C 2 H 3 0)H, was first observed by Riche and Berard in the preparation of aniline oil by means of iron and acetic acid, and then prepared by repeated distillation of paratoluidine with acetic acid. 3 Arndt and Stadeler obtained it in the same way from crude aniline, and separated it from the acetanilide formed by dissolving the mixture in acetic acid and precipitating the less soluble acet- toluide with water. 4 Acetparatoluide is dimorphous ; on the gradual evaporation of its alcoholic solution it separates in monoclinic crystals ; when a hot solution is allowed to cool, however, it crystallizes in rhombic needles. 5 It melts at 147 6 , and boils at 307 . 7 1,000 parts of water dissolve 0'56 parts at 65, and 0'886 parts at 22. Paratolyl carbamide, (C 7 H 7 )NH.CO.NH 2 . Sell prepared this compound by the action of potassium cyanate on toluidine sulphate, 8 and Steiner obtained it, together with ditolylguanidine, by treating fulminate of mercury with paratoluidine. 9 It is readily soluble in hot water, and crystallizes in thick needles melting at 172 . 10 Diparatolyl carbamide, (C 7 H 7 NH) 2 CO, is formed on the distillation of the compound just described (Sell), or when it is heated to 150 170 with paratoluidine. 11 It is also obtained when carbonyl chloride is passed into a solution of paratoluidine in chloroform. 12 It is insoluble in water, and crystallizes from 1 Ber. Deutsch. Chem. Ges. vi. 446. 2 Cosack, ibid. xiii. 1092 ; Lehne, ibid. xiii. 1544. 3 Ann. Chem. Pharm. cxxix. 77. * Chem. Centralbl. 1864, 707. 6 Panebianco, Jahrcsber. 1878, 678. 6 Hiibner, and Wallach, Ann. Chem. Pharm. cliv. 302. 7 Beilstein and Kuhlberg, ibid. clvi. 74. 8 Beilstein and Kuhlberg, ibid, cxxvi. 157. 9 Ber. Deutsch. Chem. Ges. viii. 519. 10 Cosack, ibid. xii. 1450. 11 Weith, ibid. ix. 821. 12 Michler, ibid. ix. 710 PARATOLYL URETHANE. 67 hot alcohol in flat needles, which resemble those of benzoic acid and melt at 256. Paratolyl urethane, or Ethyltolyl carbamate, (C 7 H 7 )NH(CO) (OC 2 H 5 ), is obtained by the action of chlorocarbonic ether on paratoluidine in ethereal solution. It is insoluble in water and crystallizes from alcohol in long prisms, melting at 52. Paratolyl carlimide, CO.N.C 7 H 7 , is obtained by the distillation >f the carbamic ether with phosphorus pentoxide, as a strongly ifractive liquid boiling at 185; its vapour possesses a penetrating odour and causes a flow of tears. 1 Paratolyl thiocarlamide, (C 7 H 7 )NH(CS)NH, is formed when paratoluidine hydrochloride is heated with ammonium thio- cyanate, 2 and by the combination of paratolyl mustard oil with ammonia. 3 It is slightly soluble in cold water and crystallizes from hot alcohol in small tablets or thick needles melting at 182. Diparatolyl thiocarbamide, (C 7 H 7 .NH) 2 CS, crystallizes from hot water in large, pointed prisms, melting at 176 . 4 Paratolyl thiocarbimide, or Paratolyl mustard oil, CS.N.C 7 H 7 . Hofmann obtained this compound by heating the substance just described with phosphorus pentoxide. 5 In order to prepare it, paratolyl thiocarbamide is heated to 160 with 30 per cent, sulphuric acid. 6 It crystallizes from ether in long, white needles, lelts at 26, and boils at 237. While both its isomerides iss the characteristic pungent odo.ur of the mustard oils, the lell of paratolyl thiocarbimide resembles that of oil of aniseed. Like other thiocarbimides it combines with ammonia, the imines, and the aromatic amido-bases to form compound LO- ureas. HALOGEN SUBSTITUTION PRODUCTS OF THE TOLUIDINES. 2050 A very large number of these has been prepared, but only the mono-substitution products will be here described. 1 Hofmann, Ber. Deutsch. Chem. Ges. iii. 656. 2 Clermont and Wehrlin, Bull. Soc. Chim. xxvi. 126. 8 Staats, Ber. Deutsch. Chem, Ges. xiii. 136. * Sell, loc. cit. ; Maly, Jahrcsber. 1869, 637. 6 Ber. Deutsch. Chem. Ges. i. 173. 6 Liebermann and Natanson, Li'Mg's Ann. ccvii. 160. 68 AROMATIC COMPOUNDS. CHLOROTOLUIDINES, C 6 H 3 C1(CH 3 )NH 2 . Melting- Boiling- CH 3 : NH 2 : Cl point. point. 1 2 4 small plates 1 29'5 241 134 thin plates 2 30 230 143 liquid 3 222 142 crystals 4 26 237 238'5 BROMOTOLUIDINES, C 6 H 3 Br(CH 3 )NH 2 . CH 3 : NH 3 : Br 123 liquid 5 1 24 plates 6 32 253 257 125 rhombohedra 7 58 240 134 prisms 8 ....... 32 1 3 5 9 36 255 260 1 3 6 10 78-5 240 1 4 2 " 26 1 4 3 12 8 240 Neville and Whither have also prepared dibromotoluidines together with higher substitution-products, by methods which giye a knowledge of their constitutions. 13 IODOTOLUIDINES, C 6 H 3 I(CH 3 )NH 2 . CH 3 : NH 2 : I 124 needles 14 . ..... 49 1 3 4 small plates 15 . .... 189 1 Beilstein and Kuhlberg, Ann. Chem. Pharm. clvi. 81 ; clviii. 337. 2 Gattermann and Kaiser, Ber. Deutsch. Chem. Ges. xviii. 2599. 3 Wroblevsky, Ann. Chem. Pharm. clxviii. 153 ; Ber. Deutsch. Chem. Ges. vii. 1062. 4 Lellmann, ibid. xvii. 534. 6 Neville and Winther, ibid. xiii. 1945. 6 Korner, Zeitschr. Chem. 1869, 636 ; Hiibner and Wallach, Ann. Chem. Pharm. cliv. 298 ; Heynemann, ibid, clviii. 340 ; Hiibner and Roos, Ber. Deutsch. Chem. Ges. vi. 799. 7 Wroblevsky ; Crete, Ann. Chem. Pharm. clxxvii 249. 8 Neville and Winther, Ber. Deutsch. Chem. Ges. xiii. 972. 9 Wroblevsky, Ann. Chem. Pharm. cxcii. 192, 203 ; Neville and Winther. 10 Wroblevsky ; Neville and Winther. 1 Neville and Winther, Ber. Deutsch. Chem. Ges. xiv. 418. 2 Wroblevsky, Ann. Chem. Pharm. clxviii. 153. 13 Ber. Deutsch. Chem. Ges. xiv. 419. 14 Heynemann, loc. cit. 15 Glassner, ibid. viii. 561. NITROTOLUIDINES. 69 NITROTOLUIDINES, C 6 H 3 (CH 3 )NH 2 (N0 2 ). 2051 The numbers subjoined refer to the positions of the side-chains in the order given in the formula. a-Orthonitro-orthotoluidine (1:2:6) is formed by the partial reduction of the orthodinitrotoluene melting at 60 61. It is slightly soluble in water, more readily in alcohol, and crystallizes in long, light yellow needles melting at 90 91; it may be converted into orthonitrotoluene by the elimination of tht amido-group. 1 /3-Orthonitro-orthotoluidine (1:2:3) is obtained as a by^ product in the preparation of the compound next described, and crystallizes from dilute alcohol in orange-yellow prisms, united in bushy aggregates, which melt at 97. It is converted into metanitrotoluene when heated with a solution of nitrogen trioxide. 2 Metanitro-orthotoluidine (1:2:5) is obtained by the nitration of acetorthotoluide and decomposition of the products with the calculated quantity of alcoholic potash. It is readily soluble in alcohol, but only very slightly in boiling water, from which it crystallizes in small, citron-yellow needles, melting at 127 128. On heating with an alcoholic solution of nitrogen trioxide, metanitrotoluene is obtained, while when the amido-group is replaced by bromine, orthobromometanitrotoluene is formed, and can be converted into orthobromotoluene by means of the diazo-reaction. Paranitro-ortJiotoluidine (1:2:4). When the phthalyl- toluide obtained by heating orthotoluidine with phthalic anhydride is nitrated, two mononitro-compounds are formed, one of which occurs only in small quantities and on decomposi- tion with ammonia yields the orthonitro-orthotoluidine just described, while the other gives paranitro-orthotoluidine, which melts at 109, and may be converted into paranitrotoluene by means of the diazo-reaction (Stadel). It is also formed when orthotoluidine is dissolved in 10 parts of sulphuric acid and the well-cooled solution treated with the calculated quantity of nitric acid, mixed with twice its weight of sulphuric acid. The 1 Cunerth, Ann. Chem. Pharm. clxxii. 223 ; Bernthsen, Ber. Deutsch. Chem. Ges. xv. 3016 ; Stadel, Ann. Chem. Pharm. ccxxv. 384. 2 Lellmann and Wiirthner, ibid, ccxxviii. 239. 8 Beilstein and Kuhlberg, ibid, clviii. 345. 236 70 AROMATIC COMPOUNDS. corresponding nitracet-toluide is obtained in a similar manner by dissolving acetorthotoluide in 20 parts of sulphuric acid ; if } however, only 4 parts be taken, the acetyl-compound of meta- nitro-orthotoluidine is also formed. 1 a-Orthonitrometatoluidine (1 : 3 : 2) is prepared by the nitra- tion of acetmetatoluide and decomposition of the product with alcoholic potash. It crystallizes in fine, saffron-yellow needles melting at 132 134. On heating with an alcoholic solution of nitrogen trioxide, it is converted into orthoiiitrotoluene (Beilstein and Kuhlberg). fi-Orthonitrometatoluidine (1:5:2) was obtained by Limpricht from the corresponding dinitrotoluene (p. 71). It is slightly, soluble in cold, more readily in hot water, and readily in alcohol ; crystallizes in reddish yellow needles, and may be converted into orthonitrotoluene by means of the diazo-reaction. 2 Orthonitroparatoluidine (1 : 4 : 2) was obtained by the partial reduction of ordinary dinitrotoluene. 3 This compound alone is formed when the reduction is effected with ammonium sulphide in the cold; if, however, the mixture be warmed, paranitro- orthotoluidine is also formed. 4 Orthonitroparatoluidine is best prepared by dissolving 100 grams, of paratoluidine in 2,000 grams, of concentrated sulphuric acid, and gradually adding a mixture of 75 grams, of concentrated nitric acid with 300 grams, of sulphuric acid to the solution cooled below 0. After standing for some time, the liquid is poured into ice-water. 5 It crystal- lizes from hot water in broad, yellow, monoclinic needles (Panebianco), melting at 77'5, and may be converted into orthonitrotoluene by means of the diazo-reaction. Metanitroparatoluidine (1:4: 3) was obtained by Beilstein and Euhlberg from acetnitroparatoluide ; the latter is best prepared by dissolving acetparatoluide in 4 parts of sulphuric acid, and adding the calculated amount of nitric acid mixed with 2 parts of sulphuric acid to the well-cooled solution. If the amount of sulphuric acid be increased, the acetyl-compound of Orthonitroparatoluidine is also formed, while metanitroparatolui- dine can be obtained by the direct nitration of paratoluidine if less sulphuric acid be used (Nolting and Collin). 1 Nolting and Collin, Ber. DeutscJi. Chem. Ges. xvii. 261. 2 Ibid, xviii. 1401. 3 Beilstein and Kuhlherg, Ann. Chem. Pharm. civ. 14. 4 Limpricht, Ber. Deutsch. Chcm. Ges. xviii. 1400 ; Graeff, Ann. Chem. Pharm. ccxxix. 340. 6 Nolting and Collin, loc. cit. DINITROTOLUIDINES. 71 It is readily soluble in alcohol, but only slightly in boiling water, and crystallizes in red needles or prisms, melting at 116 . 1 On heating with a solution of ethyl nitrite, metanitro- toiuene is formed. Metanitroparamethyltoluidine, C 6 H 3 (NO 2 )(GH 3 )NH(CH 3 ), is obtained by heating nitrotoluidine with methyl iodide and wood-spirit ; it crystallizes from alcohol in red needles, and from benzene in tablets melting at 84 85. Metanitropara-ethyltoluidine, C 6 H 3 (NO 2 )(CH 3 )NH(C 2 H 5 ), forms large, red needles melting at 58 59 (Gattermann). DINITROTOLUIDINES, C 6 H 2 (CH 3 )(NO 2 ) 2 NH 2 . 2052. a-Dinitro-orthotoluidine (1:3:5:2) is formed when linitro-orthocresyl ethyl ether is heated with alcoholic ammonia. It is scarcely soluble in boiling alcohol, slightly in toluene, and crystallizes in prisms or tablets which exhibit a blue iridescence and melt at 208 . 2 {3-Dinitrotoluidine is obtained by heating ft- trinitrotoluene with alcoholic ammonia ; it crystallizes from glacial acetic acid in short, golden-yellow needles, melting at 94. y-Dinitrotoluidine is formed, even in the cold, by the action of alcoholic ammonia on 7- trinitrotoluene; it is almost insoluble in the ordinary solvents with the exception of hot acetone and glacial acetic acid, and forms small, hard, golden-yellow crystals melting at 192 193. Adjacent Dinitroparatoluidine (1:3:5:4) is formed when acetparatoluide is brought into concentrated nitric acid and the product treated with alcoholic potash ; 3 it may also be obtained by the action of alcoholic potash on dinitroparacresyl ethyl ether. 4 It is slightly soluble in alcohol, and crystallizes from carbon disulphide in yellow needles, melting at 168 . 6 Chromic acid oxidizes it to chrysanisic acid, C 6 H 2 (CO 2 H)(NO 2 ) 2 NH 2 . Symmetric Dinitroparatoluidine (1:2:6:4) is obtained by the reduction of a- trinitrotoluene with ammonium sulphide ; it 1 Gattermann, Ber. Deutsch. Chem. Ges. xviii. 1482 2 Stadel, ibid. xiv. 900. 3 Beilstein and Kuhlberg, Ann. Chem. Pharm. clviii. 341 ; Kelbe, Ber. Deutsch. Chem Ges. viii. 877. 4 Stadel, loc. cit. 5 Hiibner, Ann. Chem. Pharm. ccxxii. 74. 72 AROMATIC COMPOUNDS. crystallizes from acetic acid in yellow, hair-like needles, melting at 166'5 168. It does not yield chrysanisic acid on oxidation, but a brown powder which is probably an azo-compound. 1 Thiotoluidine, (CH 3 .C 6 H 3 .NH 2 ) 2 S, is formed when paratolu- idine is heated with sulphur and litharge to 140. It crystallizes from alcohol in lustrous, odourless plates melting at 103, and is a di-acid base. Its salts crystallize well, but are decomposed by a large quantity of water. When the solution is heated with ferric chloride or any other oxidizing agent, it first becomes yellow, passing into brownish red, and then to dull red, a dark flocculent precipitate being finally formed. 2 DIAMIDOTOLUENES, or TOLYLENEDIAMINES, C 6 H 3 (CH 3 )(NH 2 ) 2 . 2053 a-Diamidotoluene, or ordinary Metatoluylenediamine (1:2:4) was discovered by Hofmann in the high boiling portions of crude aniline oil, 3 and was then obtained by him as a product of the reduction of ordinary dinitrotoluene with iron and acetic acid. It is best prepared by the reduction of dinitrotoluene with tin and hydrochloric acid. 4 It crystallizes from hot water in l needles, melts at 99, and boils at about 280. Its aqueous solution becomes dark -coloured in the air. a-Diamidotoluene monohydrochloride, C 7 H 10 N 2 .HC1, is obtained by dissolving the base in the calculated amount of hydrochloric acid, and is left as a radiating crystalline mass when the solution is evaporated. 5 a-Diamidotoluene dihydrochloride, 7 H 10 N 2 (C1H) 2 , crystallizes from warm hydrochloric acid in needles. a-Diamidotoluene sulphate, C 7 H JO N 2 .S0 4 H 2 + 2H 2 0, crystal- lizes from water in long prisms, with a vitreous lustre, and is precipitated in crystals by the addition of alcohol to its aqueous solution. fB-Diamidotoluene, or Orthotoluylenediamine (1 : 3 : 4) is formed by the reduction of metanitroparatoluidine with tin and hydro- 1 Beilstein, Bcr. Deutsch. Chem. Gcs. xiii. 243. 3 Merz and Weith, ibid. iv. 393. 3 Jahresb. Chem. 1861, 512 ; Hell and Schoop, Bcr. Deutsch. Chem. Ges. xii. 723. * Beilstein, Ann. Chem. Pharm. cxxx. 242. 5 Bernthsen, Bcr. Deutsch. Chem. Ges. xi. 1759. DIAMIDOTOLUENES. 73 chloric acid. It forms brilliant white scales, which are tolerably stable when dry ; its aqueous solution, on the contrary, rapidly becomes coloured black in the air. It melts at 88*5, and >ils at 265. When a crystal is thrown into water it takes up a rapid )tatory motion in dissolving, as do the other diamines (Pt. III. 238). f3-Diamidotoluene hydrochloride, C 7 H 10 N 2 (C1H) 2 , crystallizes in long, very soluble needles. /3-Diamidotoluene sulphate, 2(C 7 H 10 N 2 .S0 4 H 2 ) + 3H 2 0,is more jadily soluble in water than the a-compound, and is precipitated )y alcohol in brilliant white scales, with a nacreous lustre. 1 Methyl - (3 - diamidotoluene, or Metamidoparamethyltoluidine, C 6 H 3 (CH 3 ) (NH 2 ) NH (CH 3 ), is prepared in a similar manner to the following compound, and crystallizes in four-sided tablets, melting at 43 44. Ethyl-/3-diamidotoluene, C 6 H 3 (CH 3 )(NH 2 )NH(C 2 H 5 ), is ob- tined by the reduction of metanitropara-ethyltoluidine, and rstallizes from sulphuretted hydrogen water in large, colourless iblets, which melt at 54 55, and soon become dark-coloured the air. The peculiar rotatory motion assumed by the ies when dissolving in water was first observed with this >mpound. A crystal which is not too heavy acquires such a ipid motion that it appears to have a completely closed path, trace of fat on the water causes cessation of the motion (Gattermann). ^/-Diamidotoluene, or Paratoluylenediamine (1 : 3 : 5) was ob- dned by Beilstein and Kuhlberg from metanitro-orthotoluidine ; is also formed when ortho-amido-azotoluene or metamido- >toluene is reduced with tin and hydrochloric acid. 2 It is lily soluble in water, crystallizes from hot benzene in aggre- ttes of tablets, melts at 64, and boils at 273 274. On >xidation with manganese dioxide and sulphuric acid, it yields )luquinone. , is obtained by i the action of boron chloride on mercury paratolyl, and is a ' colourless crystalline mass, which melts at 27. Water converts it into tolylboric acid, CH 3 .C 6 H 4 B(OH) 2 , a violent reaction taking place ; this compound crystallizes from hot water in fine needles melting at 240 . 1 Paratolyhilicon chloride, CH 3 .C 6 H 4 SiCl 3 , is obtained by heating mercury tolyl with silicon tetrachloride to 300 320. It is a strongly refractive liquid which boils at 218 220, fumes in the air and is converted by dilute ammonia into paratolyl silicic acid, CH 3 .C 6 H 4 SiO(OH), which separates from ether as an oil which gradually changes into a thick, elastic mass. It commences to lose water at 100 and is completely converted at 200 into paratolylsilicon oxide, which is a solid mass. 2 Silicon paratolyl, Si(C 6 H 4 .CH 3 ) 4 , is readily obtained by the action of sodium on a mixture of silicon chloride and parabromo- toluene. It separates from benzene in transparent crystals melting at 228, and boils above 360 without decomposition. 3 Dichlorosilicon orthoditoluide, SiCl 2 (NH.C 7 H 7 ) 2 , is formed by the action of silicon tetrachloride on orthotoluidine. It forms a colourless, amorphous mass which readily absorbs moisture with formation of silica and toluidine hydrochloride. Hydrochloric acid gas decomposes it into toluidine hydrochloride and silicon tetrachloride. 4 MERCURY DERIVATIVES OF TOLUENE. 2063 Dreher and Otto obtained mercury paratolyl by the action of sodium amalgam on the bromotoluene obtained by the direct bromination of toluene. 5 Ladenburg then showed that the ortho-compound is also formed in this way and can readily be 1 Michaelis and Becker, ibid. xv. 185. 2 Ladenburg, Ann. Chem. Pharm. clxxiii. 162. 1 Polis, Ber. Deutsch. Chem. Ges. xviii. 1542. 4 Harden, Journ. Chem. Soc. 1887, 44. 6 Ann. Chem. Pharm. cliv. 171 88 AROMATIC COMPOUNDS. separated from the para-compound by re-crystallization from benzene. 1 In order to prepare it, bromotoluene to which a little acetic ether and petroleum have been added, is boiled with 1 '5 per cent, sodium amalgam for a longtime in an apparatus connected with an inverted condenser, and the products separated by re-crystallization from hot benzene. 2 Mercury orthotolyl, (CH 3 C 6 H 4 ) 2 Hg, is more readily soluble in benzene than the para-compound and crystallizes in large triclinic tablets melting at 107. Mercury paratolyl forms matted needles which melt at 238 and can be distilled without decomposition, if the heating be very carefully performed. It is only slightly soluble in cold water. Its derivatives resemble those of mercury phenyl. 1 Ann. Chem. Pharm. clxxiii. 162. 2 Ibid. cci. 246 BENZYL GROUP. 2064 The compounds obtained by the replacement of one atom of hydrogen in the methyl group of toluene by other elements or radicals are looked upon as derivatives of a mono- valent radical phenylmethyl or benzyl, C 6 H 5 .CH 2 . BENZYL ALCOHOL, C 6 H 5 .CH 2 .OH. Liebig and Wohler, in 1832, observed that when oil of bitter almonds, C 7 H 6 0, is treated with alcoholic potash in absence of air, benzoic acid, C 7 H 6 O 2 , is formed, together with an oily substance, which is different from the original oil ; they make the following remarks : " Although we have not investigated this new product more carefully, there can be no doubt, provided that the alcohol takes no essential part in the reaction, that it is formed either by separation of oxygen from the oil of bitter almonds or by some reaction involving the sharing of the elements of water. In the former case its composition will be expressed by the formula C 14 H 12 0, in the latter by C 14 H U 2 " * (C = 6, O = 8). Cannizzaro then found that this substance is " the alcohol corresponding to benzoic acid," and that although its composition does not correspond with that of the ordinary alcohols, it behaves towards reagents as an alcohol, the aldehyde of which would be oil of bitter almonds. He obtained the latter compound by oxidizing the alcohol with ordinary nitric acid, while chromic acid gave benzoic acid. He further showed that the action of hydrochloric acid produced an ethereal chlorine compound, C 7 H 7 C1, which is derived from the alcohol of benzoic acid and is reconverted into the alcohol by treatment with caustic potash ; when heated with alcoholic ammonia it yielded a base which differed essentially 1 Ann. Chem. Pharm. iii. 254, 261. 90 AROMATIC COMPOUNDS. from toluidine. He also prepared the acetate, which is decom- posed by warming with caustic potash into acetic acid and the alcohol of benzoic acid, and says : " This kind of alcohol appears to be the type of a whole class of new alcohols, the more complete investigation of which is now in progress." l In the course of this investigation he found that concentrated alcoholic potash produced a decomposition in which benzoic acid and toluene were formed from the alcohol, so that the latter stands in the same relation to toluene as wood-spirit to marsh gas: 2 C 7 H 8 + KOH = C 7 H 5 KO 2 + 2H 2 C 7 H 8 + H 2 = C 7 H 8 + H 2 0. He also succeeded in converting toluene into the alcohol ; by the action of chlorine on the boiling hydrocarbon he obtained chlorobenzyl, which was identical with that obtained by the action of hydrochloric acid on the alcohol. On heating with potassium acetate, both compounds gave benzyl acetate, which yielded the alcohol on saponification with caustic potash. 3 This compound had previously been in the hands of several chemists, who had not, however, recognised its nature. Fremy isolated from Peru balsam a compound which he named cinnamem, from which he obtained cinnamic acid and peruvin, C 9 H 12 O, by heating with caustic potash. 4 The latter compound, according to Plantamour, who prepared it the same way and also observed the formation of cinnamic acid, is ethyl cinnamate ; he was led to this conclusion by the fact that when he heated it with caustic potash and evaporated the whole to dryness, he obtained potassium cinnamate and a combustible vapour which he took for ethyl alcohol. He remarks that the origin of this substance, which was only recognised in this indirect and remarkable manner, still requires explanation. 5 Scharling first accurately determined the composition of cinnamein and looked upon it as a compound ether. The peruvin, C 7 H 8 O, obtained from it he considered as an alcohol, probably identical with Cannizzaro's compound. When he brought it into contact with platinum black, the smell of oil of bitter almonds was produced. 6 Strecker then expressed his conviction that cinnamein is the cinnamic ether of benzyl alcohol, 7 and was confirmed by Kraut, 1 Ann. Chem. Pharm. Ixxxviii. 129. 2 Ibid. xc. 252. 8 Ibid xcvi. 246. 4 Ibid. xxx. 324. 8 Ibid. xxx. 341. Ibid, xcvii. 168. 1 Lehrb. Org. Chem. 1856, 456. BENZYL COMPOUNDS. 91 . according to whom Fremy's peruvin was a mixture of this alcohol and toluene, Plantamour's compound being, however, the pure alcohol. The acid taken for cinnamic acid was obviously benzoic acid and the combustible vapour consisted of toluene. 1 The liquid portion of Peru balsam 2 consists chiefly of the benzoate and cinnamate of benzyl, but also contains some free benzyl alcohol. 3 Both ethereal salts occur in Tolu balsam, 4 and the latter in liquid styrax. 5 Benzyl alcohol also seems to be contained in the oil of the cherry-laurel, which consists chiefly of benzaldehyde and its cyanhydrin (Tilden). 6 The action of alcoholic potash on oil of bitter almonds, which was observed by Cannizzaro, is characteristic of the aromatic aldehydes, oxidation and reduction taking place simultaneously : C 6 H 5 .CHO + KOH = C 6 H 5 .CO.OK + H 2 C 6 H 5 .CHO + H 2 = C 6 H 5 .CH 2 .OH. Benzyl alcohol is also formed by the action of sodium amalgam and water on benzaldehyde 7 and on benzoic acid, 8 while the fatty acids are not changed by nascent hydrogen. Benzoyl chloride, C 6 H 5 .COC1, is also reduced to benzyl alcohol by the action of sodium amalgam and hydrochloric acid, 9 while a better yield may be obtained by adding sodium amalgam to an ethereal solution of benzamide, C 6 H 5 .CONH 2 , which contains water and has been rendered faintly acid with hydrochloric acid. 10 1 Ann. Chem. Pharm. cvii. 208. 2 Peru balsam, like Tolu balsam, was first described by the Spanish physician Monardes (p. 3) ; the latter is derived from Myroxylon toluifera, the former from Myroxylon pareirae, a native of Central America in the district of Costa del Balsamo. Peru balsam contains the same substances as that from Tolu, together with several of a different nature, this being due to the difference in the methods of extraction employed in the two cases. While the latter is obtained by the simple process of making incisions, it is necessary to remove the bark before extracting the Peru balsam. In order to accomplish this, it is first loosened by blows of a hammer or the back of an axe, and is then superficially charred by burning torches or bundles of twigs, the effect of this treatment being either to detach it or to render its removal a matter of no difficulty. The stem is next wrapped round with rags, which become saturated with the balsam, and are then removed and heated with water ; the balsam is thus separated from the cloth and sinks to the bottom of the vessel (Fliickiger and Hanbury, Pharmacographia, 2 Ed. p. 205). 3 Kraut, Ann. Chem. Pharm. clii. 131. 4 Ber. Deutsch. Chem. Ges. ix. 830. 8 Laubenheimer, Ann. Chem. Pharm. clxiv. 289. 6 Pharm. Journ. Trans. [3] v. 761. 7 Friedel, Ann. Chem. Pharm. cxxiv. 324. 8 Herrmann, ibid, cxxxii. 75. 9 Lippmann, ibid, cxxxvii. 252. 10 Guareschi, Gazz. Chim. Ital. iv. 465 ; Ber. Deutsch. Chem. Ges. vii. 1462. 92 AROMATIC COMPOUNDS. It is best obtained from benzyl chloride, which can readily be prepared from toluene, by boiling it for two hours with water and lead hydroxide, 1 or by simply boiling it for two days with 25 30 parts of water, 76 per cent, of the theoretical yield being thus obtained. 2 According to Mennier, it may be advantageously prepared by boiling equal parts of benzyl chloride and potassium carbonate with 10 parts of water for several hours. 3 Cannizzaro's process does not serve for the preparation of the alcohol from benzaldehyde, as the action of the alcoholic potash is only gradual, even on long continued heating, and a consi- derable loss is experienced through the formation of resinous products. If, however, 10 parts of the aldehyde be shaken up with a solution of 9 parts of caustic potash in 6 parts of water until a permanent emulsion is obtained, and sufficient water to form a clear solution be then added to the semi-solid mass of crystals formed on standing by the separation of potas- sium benzoate, the benzyl alcohol can readily be extracted from the liquid with ether. The ether is then distilled off and the residue purified by rectification without being dried. In this way 92 per cent, of the theoretical yield can be obtained, while the application of alcoholic potash only gives a yield of 43 per cent. Since only one half of the benzaldehyde is converted into the alcohol, benzyl chloride is a more economical source ; it is, however, more difficult to obtain in a state of purity than benzaldehyde and therefore does not yield a pure product so readily. As mentioned above, it is impossible to dry the alcohol before distillation; it combines with calcium chloride slowly in the cold, more rapidly on heating, and is attacked by solid caustic potash. 4 If two molecules of benzaldehyde be added to a solution of one atom of sodium in 12 parts of methyl alcohol and the mixture heated in an apparatus connected with inverted condenser, a white substance soon separates out, which seems to be a compound of methyl benzoate and sodium methylate, since it is formed when these are heated together. If the heating be continued for about two days and the mass neutralized with glacial acetic acid, and then heated with water, an oil separates out which can 1 Grimaux and Lauth, Ann. Chem. Pharm. cxliii. 80. 2 Niederist, ibid, cxcvi. 353. 3 Bull. Soc. Chim. xxxviii. 159. 4 B. Meyer, Ber. Deutsch. Chem. Ges. xix. 2394. BENZYL ALCOHOL. 93 be separated into two portions by distillation. About two-thirds of the whole boil between 198 210, and consist of a mix- ture of equal molecules of methyl benzoate, boiling at 199, and benzyl alcohol, boiling at 206. These cannot be separated, but if the benzoate be saponified, pure benzyl alcohol can readily be obtained. The smaller portion of the product, about 20 30 per cent, on the benzaldehyde employed, boils at 320 324, and consists of benzyl benzoate. This is polymeric with the aldehyde and is formed directly from it : C 6 ^5- CHO C 6 H 5 .CH 2 x C 6 H 5 -CHO C 6 H 5 .CO > The chief reaction, however, consists in the conversion of the benzaldehyde in the presence of sodium methylate into methyl benzoate and benzyl alcohol : 2C 6 H 5 .CHO + CH 3 .OH = C 6 H 5 .CO.OCH 3 + C 6 H 5 .CH 2 .OH. The two latter appear to be then partially converted into benzyl benzoate and methyl alcohol. 1 If this reaction be employed for the preparation of benzyl alcohol, the original product is simply saponified. In order to prepare it from Peru balsam, the latter is thoroughly agitated with 2 volumes of caustic potash of sp. gr. 1*2, the emulsion exhausted with ether, the extract separated and eva- >rated, and the residual oil heated with 4 volumes of caustic )tash of sp. gr. 1*3 until a homogeneous liquid is obtained. The >ulpy mass of crystals formed on cooling is pressed in linen, md the liquid diluted with water and distilled until the dis- illate ceases to appear milky. The alcohol is then separated >m the aqueous distillate and the portion which remains dis- )lved in the latter extracted by ether. 2 Properties. Benzyl alcohol is a liquid which possesses a faint aromatic odour, boils at 206, and has a sp. gr. of T063 at 0. It is not insoluble in water, as was at one time thought, for 100 parts of water at 17 dissolve 4 parts (E. Meyer). When heated with hydriodic acid and a little phosphorus to 170 180, it is almost completely reduced to toluene, only a small 1 L. Claisen, private communication. 2 Kachler, Ber. Deutach. Chem. Ges. ii. 512. 94 AROMATIC COMPOUNDS. amount of higher boiling substances being formed. 1 Its other characteristic properties which were ascertained by Cannizzaro have been already mentioned. BENZYL ETHERS. 2065 Benzyl methyl ether, C 6 H 5 .CH 2 .O.CH 3 , was obtained by Sintenis by heating benzyl chloride with methyl alcohol and caustic potash. 2 It is a pleasant smelling liquid, which boils at 167 168 and is decomposed by chlorine in the cold with formation of benzaldehyde and methyl chloride : C 6 H 5 .CH 2 .O.CH 3 + C1 2 = C 6 H 5 .COH + CH 3 C1 + HC1. Benzyl ethyl ether, C 6 H 5 .CH 2 .O.C 2 H 5 , is formed when benzyl .chloride is boiled with alcoholic potash, and is a mobile liquid, possessing a pleasant odour and boiling at 182 184 . 3 Chlorine acts upon it in the cold just as on the methyl ether ; at the boiling point, however, benzoyl chloride is formed : C 6 H 5 .CH 2 .O.C 2 H 5 + 2C1 2 = C 6 H 5 .COC1 + C 2 H 5 C1 + 2HC1. In the presence of iodine, ethyl iodide and parachlorobenz- aldehyde, C 6 H 4 C1.COH, are obtained (Sintenis). Bromine produces a similar decomposition, benzaldehyde, ethyl bromide and hydrobromic acid being first formed ; the latter then decomposes another portion of the ether into benzyl bromide and ethyl bromide, and the benzaldehyde is converted into benzoyl bromide by the excess of bromine. 4 Dibenzyl ether or Benzyl oxide, (C 6 H 5 .CH 2 ) 2 O. Cannizzaro obtained this compound by heating benzyl alcohol to 120 125 with boron trioxide and treating the product with water and potassium carbonate. When the dried oil is distilled, unaltered benzyl alcohol comes over first, and then the ether, a resinous hydrocarbon remaining behind in the retort. Dibenzyl ether is a colourless, oily liquid, which boils at 310 315 and has a faint indigo-blue fluorescence. It decomposes into toluene and 1 Grabe, Per. Deutsch. Chem. Ges. viii. 1054. 2 Ann. Chem. Pharm. clxi. 334. 8 Cannizzaro, Jahresb. 1856, 582. * Paterno, Gaz. Chim. Ital. i. 586. BENZYL ETHERS. 95 benzaldehyde when heated to a few degrees above 315 in a sealed tube ; a very small quantity of the resinous hydrocarbon is also formed in this way. Dibenzyl ether is also formed in small quantity, together with various hydrocarbons, when benzyl chloride is heated with water to 190 . 1 C. W. Lowe prepared dibenzyl ether in the following way : Sodium was added to benzyl alcohol diluted with ether. Towards the end of the reaction heat was applied in order to convert all the alcohol into sodium benzylate. The product was mixed with benzyl chloride and gently heated, when a rather violent reaction set in. Dibenzyl ether is a perfectly colourless liquid, having a slight but persistent odour of hawthorn blossom. Its sp. gr. at 16 is r0359. It boils at 295 298, at the same time being partially resolved into toluene and benzaldehyde. This decomposition goes on more rapidly at 315 as Cannizzaro found, a very small quantity of a resinous body being formed at the same time. Benzyl phenyl ether, C 6 H 5 .CH 2 .O.C 6 H 5 , is obtained by heating benzyl chloride with potassium phenate and alcohol to 100 . 2 It forms scaly crystals with a nacreous lustre, melts at 38 39 and boils at 286 287 (Sintenis). On heating with con- centrated hydrochloric acid to 100, it decomposes into benzyl chloride and phenol ; hydrobromic acid produces a similar decomposition. Chlorine attacks it in the cold with formation of benzyl chloride and substitution products of phenol, the action of bromine being quite analogous. In the presence of mercuric oxide, on the other hand, substitution products of the ether are formed (Sintenis). Melting- Boiling- point, point. Benzyl chloro- ) C r H..CH., ) ~ , phenyl ether j 6 C 6 H 4 C1 \ lon S needles 70 ~ 71 Benzyl bromo- j C 6 H 5 X!H 2 j fe 59-59'5 - phenyl ether j C 6 H 4 Br j Benzyl ortho-tC fi HCH 2 j d _ 285 o_ 29() o cresyl ether 3 y CH 3 .C 6 H 4 j Benzyl para- | C 6 H 5 .CH 2 [Q hexagonal ) ,. cresyl ether j CH 3 .C 6 H 4 ) prisms } Ethers of benzyl ivith the dihydroxylenzenes are formed when 1 Limpricht, Ann. Chem. Phartn. cxxxix. 307. 2 Lauth and Grimaux, ibid, cxliii. 81. 3 Stadel, Bcr. Deutsch. Chem. Ges. xiv. 898. 96 AROMATIC COMPOUNDS. the latter are heated with benzyl bromide and alcoholic potash. 1 Melting- point. Benzylquinol, C 6 H 4 { ^ j large lustrous j 4 ( O.CH 2 .C 6 H 5 j scales j Dibenzylquinol, C 6 H 4 (O.CH 2 .C 6 H 5 ) 2 , lustrous tablets 130 Dibenzylresor- 1 p TT / n prr n TT N J small lustrous } ,.,,0 cinol, j C 6 H 4 (O.CH 2 .C 6 H 5 ) 2 , j ^^ j 76 Dibenzylcate- | C 6 H,(O.CH 2 .C 6 H 6 ) 2 , yellow needles 61 CI1O1, J ETHEREAL SALTS OF BENZYL. 2066 Benzyl chloride, C 6 H 5 .CH 2 C1. Cannizzaro obtained this compound by the action of hydrochloric acid on benzyl alcohol and it is also formed by that of chlorine on boiling toluene. 2 It is prepared on the large scale by the latter method, the toluene being contained in large glass balloons heated by a bath of calcium chloride, and the chlorine passed through in such a manner that it chiefly comes in contact with the vapour of the toluene. This is effected by only allowing the leaden conducting tube, which terminates in a short piece of glass tubing, to dip a small distance below the surface of the boiling liquid. The vapours of toluene are condensed by a cooling arrangement and the hydrochloric acid evolved is led into water. The product is washed with water containing a little caustic soda, and the benzyl chloride freed from unaltered toluene and higher substitution products by distillation. It is a colourless liquid, the vapour of which has a penetrating aromatic smell, rapidly produces a flow of tears and attacks the mucous membrane most violently. It boils at 176 and has a sp. gr. of 1*107 at 14. As it undergoes double decom- position very readily, it is employed for the preparation of the other benzyl compounds, and it is also used to a considerable extent in the synthesis of the higher members of the aromatic series. It is also technically employed in the manufacture of benzaldehyde and in the colour industry. 1 Schiff and Pellizzari, Ann. Ghem. Pharm. ccxxi. 365. 2 Beilstein and Geitner, ibid, cxxxix. 337. BENZYL IODIDE. 97 Benzyl Iromide, C 6 H 5 .CH 2 Br, is formed by the action of hydrobromic acid on benzyl alcohol, and by that of bromine on boiling toluene. 1 It is a liquid which first smells like cress and then like mustard oil ; its vapour, like that of the chloride, pro- duces a flow of tears. It boils at 198 199, and has a sp. gr. of 1-438 at 22. Benzyl iodide, C 6 H 5 .CH 2 I, was obtained by Cannizzaro in the impure state by the action of iodine and phosphorus on benzyl alcohol. Lieben prepared the pure compound by allowing benzyl chloride to stand in the dark for three weeks with five times its weight of hydriodic acid. 2 It is also formed by the action of potassium iodide on benzyl chloride, 3 and is a colourless, crystal- line body, the vapour of which produces a most copious flow of tears; it is only slightly soluble in alcohol, but readily in ether and carbon disulphide. It fuses at 24 to a liquid which has a sp. gr. of 17335, and on further heating becomes coloured red, decomposing at about 240, at which temperature it com- mences to boil, into iodine, hydriodic acid, and a hydrocarbon which smells like toluene. Benzyl nitrate, C 6 H 5 .CH 2 .N0 3 . appears to be formed by the action of silver nitrate on benzylt chloride : the product of the reaction decomposes on distillation with an energetic evolution of red fumes, the distillate consisting of benzaldehyde and benzoic acid. 4 The same products are obtained by treating benzyl iodide with silver nitrite. 5 2067 Benzyl acetate, C 6 H 5 .CH 2 C 2 H 3 O 2 . Cannizzaro obtained this compound by distilling benzyl alcohol with acetic and sulphuric acids, as well as by heating benzyl chloride with potassium acetate, and alcohol. It is a liquid which possesses an aromatic odour, boils at 206, and has a sp. gr. of T057 at 16'5. 6 It is converted into the benzyl ether of hydrocinnamic acid or benzylacetic acid by the action of sodium : 4C 6 H 5 .CH 2 .O.CO.CH 3 + 2Na = 2C 6 H 5 .CH 2 .O.CO.CH 2 .CH 2 .C 6 H 5 + 2NaO.CO.CH 3 + H 2 . Boiling-point. Benzyl propionate, C 7 H 7 .O.C 3 H 5 O 219 220. Benzyl butyrate, C 7 H 7 .OC 4 H 7 O 238 240. 1 Kekule, Ann. Chem. Pharm. cxxxvii. 139 ; Cannizzaro, ibid. cxli. 198 ; Beilstein, ibid, cxliii. 369 ; Lauth and Grimaux, ibid. cxlv. 113. 2 Zeitschr. Chem. [2] vi. 736. 3 V. Meyer, Ber. Deutsch. Chem. Oes. x. 311. Brunner, Ber. Deutsch. Chem. Ges. ix. 1744. 5 van Renesse, ibid. ix. 1454. 6 Conrad and Hodgkinson, Licbig's Ann. cxciii. 298. VOL. III. PART IV. 98 AROMATIC COMPOUNDS. These ethers are acted upon by sodium in the same way as the acetate (Conrad and Hodgkinson). The compounds thus formed will be subsequently described. Benzyl oxalate, (C 6 H 5 .CH 2 ) 2 C 2 4 , is formed by the action of benzyl chloride on silver oxalate, 1 and by heating benzyl alcohol with oxalic acid. 2 It crystallizes from hot alcohol in lustrous white, scaly crystals, melting at 80'5. Isonitrosobenzyl ether, C 6 H 5 .CH 2 .O.Nz=CH.CO.CH 3 , is prepared by heating benzyl chloride with a solution of sodium and isonitroso-acetone (Part I. p. 572, and Part III. p. 170, note) in absolute alcohol. It crystallizes from petroleum ether in colourless tablets, which have a pleasant smell of flowers and melt at 45 46. 3 Acetoxime benzyl ether, C 6 H 5 .CH 2 .ON=:C(CH 3 ) 2 , is obtained in a similar manner from acetoxime, and is a pleasant smelling liquid which decomposes into acetone and benzylhydroxylamine when boiled with concentrated hydrochloric acid : C 6 H 5 .CH 2 .O.N=C(CH 3 ) 2 + H 2 O^C 6 H 5 .CH 2 .O.NII? | CO(CH 3 ) 2 . The compound actually obtained in this way is lenzylhydroxy- ammonium chloride, which crystallizes in silvery scales, and is converted into benzyl iodide by heating with hydriodic acid : 4 C 6 H 5 . CH 2 .O.NH 3 C1 + 3HI = C 6 H 5 .CH 2 I + NH 4 C1 + H 2 + 1 2 . SUBSTITUTION PRODUCTS OF BENZYL ALCOHOL AND ITS DERIVATIVES. 2068 Substitution-products are not formed by the direct action of chlorine, bromine, or nitric acid on benzyl alcohol, since all these reagents produce oxidation. Its ethers, how- ever, can undergo direct substitution, and if an atom of hydrogen in one of them be replaced, para-compounds are formed, from which the corresponding alcohols may readily 1 Beilstein and Kuhlberg, Liebig's Ann. cxlvii. 341. 2 Dumas and Dema^ay, Compt. Rend. Ixxxiii. 688. 3 Meyer and Ceresole, Ber. Deutsch. Chcm. Gcs. xv. 3071. 4 Janny, ibid, xvi 170. SUBSTITUTION PRODUCTS OF BENZYL ALCOHOL. 99 be obtained. Thus, parachlorobenzyl alcohol, C 6 H 4 C1.CH 2 .OH, is prepared by boiling its chloride or bromide with water : C 6 H 4 CLCH 2 Br + H 2 O = C 6 H 4 CLCH 2 OH + HBr. The haloid ethers can also be converted into the acetate by boil- ing with alcohol and potassium acetate, and this saponified by heating with ammonia : C 6 H 4 C1.CH 2 .0. C 2 H 3 + NH 3 = C 6 H 4 CLCH 2 .OH + C 2 H 3 O.NH 2 . The higher chlorinated benzyl chlorides have been converted ito their alcohols by means of this reaction. Paranitrobenzyl alcohol can readily be prepared by nitrating jnzyl acetate or oxalate and heating the product with am- lonia. Chlorine substitution-products of benzyl chloride can be )btained, as already mentioned, by treating it with chlorine in cold or in presence of iodine, as well as by allowing chlorine act upon the vapour of boiling, chlorinated toluene. Accord- to Beilstein and Kuhlberg, the latter is the better method, id is now generally adopted. The bromine substitution-products are prepared in a similar lanner; the use of this method has shown that substitution loes not readily take place in the methyl group when bromine allowed to act on boiling orthobromotoluene. Paranitrotoluene is converted by bromine at high temperatures ito paranitrobenzyl bromide ; paranitrobenzyl chloride and letanitrobenzyl bromide can also be readily obtained, but not le ortho-compound. If orthonitrotoluene be heated with >mine, no orthonitrobenzyl bromide is found, but the product, wording to Wachendorff, consists of dibromorthonitrotoluene, " 6 H 2 Br 2 (N0 2 )CH 3 , which is not attacked by potassium acetate silver acetate even at 160 . 1 It possesses the exceptional >roperty of dissolving in aqueous alkalis and being reprecipitated >y mineral acids, and Greiff was therefore induced to examine it more carefully. He found that it is not dibromonitrotoluene, but the isomeric dibromortho-amidobenzoic acid,C 6 H 2 Br 2 (NH 2 )C0 2 H. Since the isomerides of orthonitrotoluene behave quite differently towards bromine, it follows that the ortho-position facilitates a mutual exchange between the oxygen of the nitroxyl and the 1 Ann. Chem. Pharm. clxxxv. 259. 100 AROMATIC COMPOUNDS. hydrogen of the methyl. How this intermolecular change takes place has not yet been explained, but it seems probable that orthonitrobenzyl bromide is first formed and is then con- verted by the nitroxyl group into ortho-amidobenzoic acid, just as benzyl chloride is oxidized to benzoic acid by nitric acid. 2069 Parachlorobenzyl alcohol, C 6 H 4 C1.CH 2 .OH, is formed by boiling the corresponding bromide or chloride with water, 1 or by heating parachlorobenzyl acetate to 100 with aqueous ammonia. 2 It is readily soluble in alcohol, scarcely in cold, but somewhat more readily in warm water, from which it crystallizes in long needles melting at 70*5 (Jackson and Field). Oxidizing agents convert it into parachlorobenzoic acid. Melting-point. Dichlorobenzyl alcohol, 3 C 6 H 3 C1 2 .CH 2 OH, needles 77 Trichlorobenzyl alcohol, 4 C^ClglCHgOH, crystals Tetrachlorobenzyl alcohol, 5 C 6 HC1 4 .CH 2 OH, Pentachlorobenzylalcohol, 6 C 6 Cl 5 .CH 2 .OH, short needles 193 Parachlorobenzyl ethyl ether, C 6 H 4 C1.CH 2 .O.C 2 H 5 , is formed by heating parachlorobenzyl chloride 7 or parachlorobenzyl acetate 8 with alcoholic potash ; it is a liquid which boils at 218, 9 and is split up by chlorine in the cold into ethyl chloride and parachlorobenzaldehyde. Phenylchlorocarlylethyl ether, or Benzylethoxyl chloride, C 6 H 5 . CHC1.0.C 2 H 5 , is prepared by boiling benzylidene chloride, C 6 H 5 .CHC1 2 , for a long time with alcoholic ammonia. It is a liquid which boils at 210 212 and is converted into ethyl metanitrobenzoate, C 6 H 4 (N0 2 )CO.OC 2 H 5 , by nitric acid. 10 Parachlorobenzyl chloride, C 6 H 4 C1.CH 2 C1, is obtained together with a little of the ortho-compound, by the chlorination of benzyl chloride in presence of iodine, and by the action of chlorine on boiling monochlorotoluene, as a liquid which boils at 213 214 . 11 It is prepared pure from parachlorotoluene ; 12 it crystallizes from alcohol in lustrous needles or prisms which 1 Jackson and Field, Ber. Deutsch. Chem. Ges. xi. 905 ; Amer. Chem. Journ. ii. 88. * Beilstein and Kuhlberg, Ann. Chem. Pharm. cxlvii. 344. 8 Ibid. 350. * Ibid. clii. 241. 6 Ibid. 245. 6 Ibid. 246 7 Naquet, ibid. Suppl. [2] 250. 8 Neuhof, ibid, cxlvii. 345 9 Sintenis, ibid. clxi. 335. 10 Hiibner and Bente, Ber. Deutsch. Chem. Ges. vi. 805. 11 Neuhof, Ann. Chem. Pharm. cxlvi. 320. 12 Jackson and Field, Ber. Deutsch. Chem. Ges. xi. 904. (PARABROMOBENZYL ALCOHOL. 101 3lt at 29, readily sublime, and possess an aromatic vapour lich attacks the mucous membrane very violently. Melting- Boiling- chloro- ^ point. point. benzyl- V C 6 H 3 C1 2 .CH 2 C1, liquid . . 241 hloride, 1 j ichloro- ^ benzyl- VC 6 H 2 C1 3 .CH 2 C1, . . 273 chloride, 2 j Tetrachloro- ) benzyl- V C 6 HC1 4 .CH 2 C1, 296 chloride, 3 j 'entachloro- \ benzyl- I C 6 C1 5 .CH 2 C1, fine needles 103 325 327 chloride, 4 j Parachlorobenzyl bromide, C 6 H 4 Cl.CH 2 Br, resembles the iloride very closely ; it melts at 48'5. 5 Parachlorobenzyl acetate, C 6 H 4 C1.CH 2 O.C 2 H 3 O, is obtained >y boiling the chloride with potassium acetate and absolute Icohol ; it is a liquid which boils at 240 and has an aromatic lour. 6 Parabromobenzyl alcohol, C 6 H 4 Br.CH 2 .OH, is formed when the bromide is boiled with water for several days ; it crystallizes from a hot solution in flat, elastic, pearly needles which have an romatic odour, melt at 69, and only volatilize slowly with steam. 7 Parabromobenzyl bromide, C 6 H 4 Br.CH 2 Br. This compound is prepared by passing bromine vapour into a boiling mixture of parabromotoluene and orthobromotoluene, which is obtained by direct bromination of toluene. After the calculated quantity been added, the liquid is allowed to cool, a portion of the )romide crystallizing out in large, rhombic prisms. The mother- liquor is then distilled with steam in which the ortho- is more lily volatile than the para-compound. The latter can also ?adily be obtained in long, thick, transparent prisms by allowing >romine to act upon the mixture of bromotoluenes in the sun- light. 8 Parabromobenzyl bromide crystallizes from alcohol in needles which melt at 61 and are volatile with steam ; its vapour 1 Beilstein and Kuhlberg, Ann. Chem. Pharm. cxlvi. 146, 326. 2 Ibid. cl. 290. 3 Ibid. 299. 4 Ibid. 302. 8 Field and Jackson, loc. cit. B Neuhof, Ann. Chem. Pharm. cxlvii. 345. 7 Jackson and Lowry, Ber. Dcutsch. Chem. Ges. x. 1209. 8 Schramm, ibid. xvii. 2922 ; xviii. 350. 238 102 AKOMATIC COMPOUNDS. has a pleasant, aromatic odour, .but attacks the eyes, nose, and throat very violently. 1 Pardbromobenzyl acetate, C 6 H 4 Br.CH 2 .O.C 2 H 3 O, is a liquid which has a pleasant smell resembling that of acetic ether, and decomposes on distillation. 2 Metabromobenzyl bromide, C 6 H 4 Br.CH 2 Br, is obtained in a similar manner to the para-compound ; the yield is, however, very poor. It crystallizes in plates or needles which melt at 41, and its vapour attacks the mucous membrane violently, but has a somewhat different smell from that of the para-compound. It only volatilizes slowly in a current of steam, but with remark- able rapidity in ether and tolerably readily in alcohol. It is not attacked by chromic acid solution, but the corresponding alcohol, which has not been further investigated, is oxidized by it to metabromobenzoic acid. 3 Orthdbromobenzyl alcohol, C 6 H 4 Br.CH 2 .OH, crystallizes from hot water in flat needles, which melt at 80, and readily volatilize with steam. 4 Ortholromolenzyl bromide, C 6 H 4 Br.CH 2 Br, is only formed with difficulty, and has not been obtained pure, since it decomposes on distillation. It is an oily liquid, which does not solidify at 15, volatilizes with steam, possesses an aromatic odour, and rapidly attacks the mucous membrane ; a drop placed on the tongue causes severe pain. 5 Sodium acts upon its ethereal solution with formation of various products, among them being anthracene : GH Para-iodolenzyl alcohol, C 6 H 4 I.CH 2 .OH, crystallizes from carbon disulphide in scales and from boiling water in long needles, which have an aromatic odour and melt at 71 '7. 6 Para-iodolenzyl bromide, C 6 H 4 I.CH 2 Br, is formed by the action of bromine vapour on heated para-iodotoluene, and crystallizes from alcohol in flat, white needles, which melt at 78'7, possess an aromatic odour, and attack the mucous membrane less violently than the bromobenzyl bromides. Boiling water con- verts it into the alcohol. 7 1 Schramm, Ber. Deutsch. Chem. Gcs. viii. 1672 ; ix. 931. 2 Jackson and Lowry, ibid. x. 1209. 3 Jackson and White, Amcr. Chem. Journ. ii. 315. 4 Jackson, ibid. viii. 932. 8 Jackson, Ber. Dcutsch. CJiem. Ges. ix. 932. 6 Jackson and Mabery, ibid. xi. 56 ; Amer. Chem. Journ. ii. 251. 7 Jackson and Mabery, loc. cit. PARANITROBENZYL ALCOHOL. 103 2070 Paranitrobenzyl a/c0M,-C 6 H 4 (NO 2 )CH 2 .OH, is prepared by heating its acetate or oxalate with ammonia to 100 , 1 and by the action of caustic soda on paranitrobenzaldehyde. 2 It crystal- lizes from boiling water in fine, lustrous, colourless needles, which become coloured in the air and melt at 93. On oxidation it yields paranitrobenzoic acid. Paranitrobenzyl chloride, C 6 H 4 (NO 2 ).CH 2 C1, is obtained, to- gether with the ortho- and meta-compounds, by the action of concentrated nitric acid on benzyl chloride, 3 the chloride being gradually added to the acid which has been previously cooled to 15. 4 It is also formed by treating paranitrotoluene with chlorine at 185 190 . 5 It crystallizes from boiling alcohol in fine, white needles, or small, nacreous plates, which melt at 76. An alkaline solution of pyrogallol reduces it to paranitro- toluene. 6 Paranitrobenzyl bromide, C 6 H 4 (N0 2 )CH 2 Br, is formed when paranitrotoluene is heated to 120 130 with bromine ; the reaction takes place at 70 80 in the presence of ferrous bromide, which acts as a bromine carrier. 7 On the gradual evaporation of its solution in a mixture of ether and alcohol, it crystallizes in thin tablets, which melt at 99 100. It destroys the skin, producing a burning pain, and the vapour given off by its hot alcoholic solution attacks the mucous membrane most violently (Wachendorff). Paranitrobenzyl iodide, C 6 H 4 (NO 2 )CH 2 I, is obtained by heat- ing the chloride with potassium iodide and alcohol; it crystallizes in four-sided tablets, melting at 127, and its vapour produces a flow of tears. 8 Paranitrobenzyl nitrate, C 6 H 4 (NO 2 )CH 2 NO 3 . Beilstein and Kuhlberg prepared this compound by the action of concentrated nitric acid on the alcohol, and believed that it was dinitrobenzyl alcohol. Stadel found, however, that it loses nitric acid when heated with water to 100, and that it yields paranitrobenzoic acid on oxidation, 9 and Orth prepared it by heating the chloride 1 Beilstein and Kuhlberg, Ann. Chcm. Pharm. cxlvii. 343. Easier, Bcr. Dcutsch, Chcm. Gcs. xvi. 2715. 3 Beilstein and Geitner, Ann. Chcm. Pharm. exxxix. 327 ; Grimaux, ibid. cxlv. 146 ; Abelli, Gaz. Chim. Ital. xiii. 97. * Strakosch, Bcr. Dcutsch. Chcm. Gcs. vi. 1056. B Wacheudorff, Ann. Chcm. Phann. clxxxv. 271. 6 Pellizzari, Bcr. Dcutsch. Chcm. Gcs. xviii. Ref. 150. 7 Scheufeln, Ann. Chcm. Pharm. ccxxxi. 177. 8 Kumpf, ibid. xvii. 1074. '> Ibid. xiv. 903. 104 AROMATIC COMPOUNDS. 4 with alcohol and silver nitrate. 1 It crystallizes from hot water in fine, white needles, and from alcohol in long, flat needles, melting at 71. Paranitrolenzyl acetate, C 6 H 4 (NO. 2 )CH 2 .C 2 H 3 O 2 , is obtained by dissolving benzyl acetate in well-cooled concentrated nitric acid (Beilstein and Kuhlberg) or by heating the chloride with potassium acetate and alcohol (Grimaux). It crystallizes from hot alcohol in long, pale yellow needles, melting at 78. Paranitrobenzyl oxalate, (C 6 H 4 (N0 2 )CH 2 ) 2 C 2 O 4 , was obtained by Beilstein and Kuhlberg by dissolving benzyl oxalate in concentrated nitric aeid ; on heating with aqueous ammonia it is converted into the alcohol. 2071 Metanitrobenzyl alcohol, C 6 H 4 (N0 2 )CH 2 . OH, was prepared by Grimaux, together with metanitrobenzoic acid, by the action of alcoholic potash on metanitrobenzaldehyde as a thick, oily liquid, which decomposes on heating, but boils at 178 180 under a pressure of 3 mm. 2 Metanitrobenzyl chloride, C 6 H 4 (N0 2 )CH 2 C1, is formed by the action of phosphorus pentachloride on the alcohol ; it crystallizes from hot petroleum ether in long, light yellow needles, which melt at 45 47, and produces painful irritation and burning on the skin. 3 Orthonitrobenzyl alcohol, C 6 H 4 (N0 2 )CH 2 .OH. When ortho- nitrotoluene is given to a dog, it appears in the urine as ortho- nitrobenzoic acid, and as the urea salt of uronitrotoluic acid t 2C p H 15 N0 9 .CO(NH 2 ) 2 + 5H 2 O, crystallizing in long needles! which are very readily soluble in water, slightly in cold alcohol, and insoluble in ether. On boiling this with baryta water and decomposing the barium salt formed with sulphuric acid, uro- nitrotoluic acid, C 13 H 15 N0 9 , is obtained as a crystalline mass resembling asbestos, which is extremely soluble in water and alcohol and has a strongly acid reaction. On boiling with dilute sulphuric acid it decomposes into a syrupy acid and orthonitro- benzyl alcohol ; 4 this compound can also be prepared by the action of caustic soda on orthonitrobenzaldehyde. 5 It is slightly soluble in water, readily in alcohol and ether, and crystallizes in long, fine needles, which melt at 74, and can be sublimed, but detonate when rapidly heated. 1 Kumpf, xv. 1136. 2 Zeitschr. CJicm. 1867, 562. 3 Gabriel and Borgraann, Bf>r. Deut*cli. Chem. Gcs. xvi. 2064. 4 Jaffe, Hoppe-Seyler's Zcfachr. ii. 47. 5 Friedlander and Henriques, Btr. Deutsch. Chcm. Ges. xiv. 2801. SULPHUR COMPOUNDS OF BENZYL. 105 OrtTwnitrobenzyl chloride, C 6 H 4 (NO 2 )CH 2 C1, is formed, as already mentioned, together with its isomerides, by the nitration of benzyl chloride, and was first isolated from the product by Kumpf. 1 It is also obtained by the action of phosphorus penta- chloride on the alcohol. 2 It crystallizes from petroleum ether in large rhombohedra melting at 48 49. Orthonitrdbenzyl iodide, C 6 H 4 (N0 2 )CH 2 I, is prepared by heat- ing the chloride with potassium iodide and alcohol; it forms rhombohedral plates melting at 75, and its vapour causes a flow tears. Orthamidoibenzyl alcohol, C 6 H 4 (NH 2 )CH 2 .OH, is obtained by the action of hydrochloric acid and zinc-dust on orthonitrobenzyl Icohol in alcoholic solution. It crystallizes from benzene in rhite needles, which melt at 82, become coloured brown in the jht or in the air, and have a faint smell resembling that of liline. It combines with acids forming soluble, crystallizable salts. 3 SULPHUR COMPOUNDS OF BENZYL. 2072 Benzyl Jiydrosulphide, or Benzyl mercaptan, C 6 H 5 .CH 2 .SH. [arcker obtained this compound by heating benzyl chloride or mzyl bromide with an alcoholic solution of potassium hydro- ilphide. 4 Otto prepared it by the action of benzyl chloride on >tassium thiosulphate, 5 and Bottinger by fusing thiobenzalde- lyde, C 6 H 5 .CSH, with caustic potash, benzyl disulphide and a Little benzoic acid being simultaneously formed. 6 It is a colourless, powerfully refractive liquid which has an unpleasant smell of leeks, boils at 195, and has a sp. gr. of 1'058 at 20 ; its vapour produces a flow of tears. It gradually >xidizes in the air, more rapidly in the presence of ammonia to benzyl disulphide ; an ethereal solution of bromine produces the same effect. Mercury benzyl mercaptide, (C 6 H 5 .CH 2 S) 2 Hg, is formed by heating the hydrosulphide with mercuric oxide ; it crystallizes from alcohol in long, silky needles. Mercuric chloride, in 1 Friedlander and Henrique*, xvii. 1073. J Gabriel and Borgmann, Ber. Deutech. Chem. Ges. xvi. 2064. Friedlander and Henriques, ibid. xv. 2109. | Ann. Chcm. Phann. cxxxvi. 75. 5 Zeitschr. Chem. [2] vi. 23. 6 Bcr. Deutsch. Chem. Ges. xii. 1055. 106 AROMATIC COMPOUNDS. alcoholic solution, gives with the mercaptan a white precipitate of 6 H 5 .CH 2 .S.HgCl. Lead benzyl mercaptide, (C 6 H 5 .CH 2 S) 2 Pb, is obtained in small yellow plates by mixing hot, alcoholic solutions of lead acetate and benzyl mercaptan. Parachlorobenzyl hydrosulphide, C 6 II 4 C1.CH 2 .SH, is formed when parachlorobenzyl chloride is boiled with an alcoholic solu- tion of potassium hydrosulphide. According to Beilstein, it is obtained in lustrous crystals, melting at 84 85 , 1 while accord- ing to Jackson and White, it is an oily liquid which possesses a most repulsive and penetrating odour, and solidifies on cooling in crystals which melt at 19 20. 2 Paranitrobenzyl hydrosulphide, C 6 H 4 (NO 2 )CH 2 .SH, crystallizes from alcohol in small, colourless, lustrous plates, melting at 140 . 3 Benzyl ethyl sulphide, C 6 H 5 .CH 2 .S.C 2 H 5 , is prepared by the action of ethyl iodide on a solution of sodium in benzyl hydro- sulphide, and is a transparent liquid, which boils at 214 216 , 4 and possesses a penetrating odour resembling that of ordinary mercaptan. Orthobenzyl thioformate, (C 6 H 5 .CH 2 .S) 3 CH, is formed when an aqueous solution of sodium benzyl mercaptide is heated with chloroform ; it separates from hot alcohol in colourless crystals, melting at 98. When heated with fuming nitric acid to 250, it is decomposed into benzyl mercaptan and formic acid. 5 Benzyl sulphide, (C 6 H 5 .CH 2 ) 2 S. Marcker obtained this com- pound by heating benzyl chloride with an alcoholic solution of potassium sulphide. It crystallizes from hot alcohol in large, dazzling white plates, and from ether or chloroform in large, thick, rhombic tablets, 6 melting at 49. On distillation it yields stilbene, C 14 H 10 , and sulphuretted hydrogen ; dibenzyl, C 14 H 14 , tolallyl sulphide, C 14 H 10 S, and thio- nessal, C 28 H 20 S, are simultaneously formed. Methyl iodide and benzyl sulphide react even in the cold, more rapidly on warming, with formation of bcnzyldimethyl- sulphine iodide, C 6 H 5 .CH 2 (CH 3 ) 2 SI, and trimethylsulphine iodide, 1 Beilstein, Ann. Chem. Pharm. cxvi. 347 ; cxlvii. 346. 2 Amer. Chem, Journ. ii. 167. 3 Strakosch, Ber. Dcutsch. Chem. Ges. v. 598. 4 Marcker, Ann. Chem. Pharm. cxl. 88. 5 Dennstedt, Ber. Deutsch. Chem. Ges. xi. 2265. 6 Forst, Ann. Chem. Pharm. clxxviii. 671. SULPHUR COMPOUNDS OF BENZYL. 107 (CH g ) 3 SI. The first stage of the reaction is represented by the following equation : 2CH 3 I + (C 6 H 6 .CEg 2 S = (CH 3 ) 2 S + 2C 6 H 6 .CH 2 I. The methyl sulphide then combines with the iodides forming the compounds mentioned. If the product be extracted with water, shaken up with silver chloride and the filtrate then fractionally precipitated with platinum chloride, benzyl dimethyl- sulphine platinichloride, (C 6 H 5 .CH 2 (CH 3 ) 2 S) a PtCl 6 , separates out first ; it crystallizes from water in long, orange-red needles. 1 Cahours, 2 who has also investigated the action of methyl iodide on benzyl sulphide, gives the following equation : 3CH 3 I + (C 6 H 5 .CH 2 ) 2 S = (CH 3 ) 3 SI + 2C 6 H 5 .CH 2 I. Benzyl bromide and methyl sulphide, on the other hand, react the following way : C 6 H 5 .CH 2 Br+2(CH 3 ) 2 S = (CH 3 ) 3 SBr+C 6 H 5 .CH 2 .S.CH 3 . If methyl alcohol be also present, benzyl methyl ether is formed instead of benzyl methyl sulphide : C 6 H 5 .CH 2 Br + (CHg^S + 2CH 3 .OH - (CH 3 ) 3 SBr + C 6 H 5 .CH 2 .O.CH 3 + H 2 0. Benzyl oxy sulphide, (C 6 H 5 .CH 2 ) 2 SO, is formed by the action of oncentrated nitric acid on the sulphide ; it crystallizes from cohol in small plates which have a satin lustre, melt at 133 , 3 d are converted into sulphuric acid and benzoic acid by e further action of nitric acid (Marcker). Benzyl disulphide, (C 6 H 5 .CH 2 ) 2 S 2 , is best obtained by the tion of bromine in ethereal solution on benzyl mercaptan, and s also formed when benzyl chloride is treated in alcoholic lution with potassium disulphide ; it crystallizes from alcohol small, lustrous plates, melting at 66 67. Nascent hydrogen nverts it into benzyl mercaptan (Marcker). It is decomposed on heating, yielding the same products as benzyl sulphide. Benzyl dioxy sulphide, or Dibenzyl sulphone, (C 6 H 5 .CH 2 ) 2 S0 2 , is formed in small quantity in the preparation of potassium benzyl 1 Scholler, Ber. Dcutsch. Chem. Ges. vii. 1274. 2 Compt. Rend. Ixxx. 1319. 3 Otto and Liiders, Ber. Deutsch. Chcm. Ges. xiii. 1284. 108 AROMATIC COMPOUNDS. sulphonate. 1 It may readily be obtained, however, by oxidizing benzyl oxysulphide with potassium permanganate and glacial acetic acid (Otto and Lliders) ; it is insoluble in water, and crystallizes from hot alcohol in flat needles, which melt at 150. 2073 Benzylsulphonic acid, C 6 H 5 .CH 2 .S0 2 .OH. Bohler pre- pared this compound by boiling benzyl chloride for several hours with a concentrated solution of normal potassium sulphite, the potassium salt obtained being converted into the lead salt, and this decomposed with sulphuretted hydrogen. 2 It is a deliquescent crystalline mass, and is also formed by the oxidation of benzyl disulphide with nitric acid. 3 When it is fused with caustic potash, it yields benzoic acid (Vogt), together with some benzene and a larger quantity of toluene. 4 Potassium lenzylsulphonate, C 6 H 5 .CH 2 .S0 3 K + H 2 O, crystal- lizes from hot water in well-developed rhombic prisms. Barium lenzylsulphonate, (C 6 H 5 .CH 2 .S0 3 ) 2 Ba + 2H 2 O, is obtained by the addition of barium chloride to the solution of the potassium salt; it forms plates, which are only slightly soluble in water. Lead lenzylsulphonate, (C H 5 .CH 2 .SO 3 ) 2 Pb. If the barium salt be decomposed with dilute sulphuric acid, and the hot nitrate saturated with lead hydroxide, the basic salt C 6 H 5 .CH 2 . S0 3 .PbOH, is obtained as a lustrous, crystalline precipitate, which is converted into the normal salt by carbon dioxide ; this crystallizes from hot water in lustrous plates. Potassium chlorolenzylsulphonate, C 6 H 4 C1.CH 2 .SO 3 K + H 2 0, is prepared from chlorobenzyl chloride and potassium sulphite, and crystallizes in needles; barium chloride added to the potassium salt yields barium chlorolenzylsulphonate, (C 6 H 4 C1. CH 2 .SO 3 ) 2 Ba + H 2 O, which forms colourless lustrous crystals. When the potassium salt is fused with caustic potash, sali- cylic acid and parahydroxybenzoic acid are formed (Vogt and Henniuger). Benzylsulphonic chloride, C 6 H 5 .CH 2 .S0 2 C1. Barbaglia endea- voured to prepare this compound by the distillation of potassium benzylsulphonate with phosphorus pentachloride, but only ob- tained benzyl chloride, together with phosphorus oxychloride and some thionyl chloride. 5 In order to prepare it, the potas- sium salt is treated with an equal weight of phosphorus chloride 1 Vogt and Henninger, Ann. Chem. Pharm. clxv. 375. 2 Ibid. cliv. 50. 8 Barbaglia, Ber. Deutsch. Chem. Ges. v. 687. 4 Otto, ibid. xiii. 1288. 5 Ibid. v. 270. SELENIUM COMPOUNDS OF BENZYL. 109 and the mixture gently warmed until the reaction is complete. The product is then washed with water and the residue crystal- lized from ether. Benzenesulphonic chloride forms colourless prisms, which melt at 92 and are decomposed when more strongly heated into benzyl chloride and sulphur dioxide ; it is con- verted by ammonia into benzylsulphonamide, C 6 H 5 .CH 2 .SO 2 .NH 2 , rhich crystallizes from water in prisms melting at 105 . 1 Nttrdbenzylsulphonic acid, C 6 H 4 (NO 2 )CH 2 .S0 3 H, is formed )y the action of fuming nitric acid on barium benzyl sulphate, mixture is thus obtained which contains, together with the L-compound, a little of the orthonitro-acid and the dinitro- ;id, which cannot be completely separated. On boiling with a ixture of nitric and sulphuric acids, dinitrobenzylsulphonic nd, C 6 H 3 (N0 2 ) 2 CH 2 .S0 3 H, is obtained; it forms salts, which rystallize well. On reduction it is converted into diamido- lenzylsulphonic acid, C 6 H 3 (NH 2 ) 2 CH 2 .SO 3 H, which crystallizes from hot water in silky needles. 2 SELENIUM COMPOUNDS OF BENZYL. 2074 Benzyl selenide, (C 6 H 5 .CH 2 ) 2 Se, is prepared by treating phosphorus pentaselenide with alcoholic soda solution in absence of air, and heating the sodium selenide thus formed with benzyl hloride to the boiling point of the latter. When the solution Is, benzyl selenide separates out first and then some benzyl elenide, which is separated by recrystallization from hot hoi. Benzyl selenide crystallizes in long, white needles transparent prisms, which have a faint aromatic odour and melt at 45 '5. Like methyl selenide, it combines with acids forming unstable salts. Benzyl diselenide, (C 6 H 5 .CH 2 ) 2 Se 2 , is obtained by boiling crude sodium selenide, prepared by igniting sodium selenite with char- coal, with alcohol and benzyl chloride. It crystallizes from hot alcohol in straw-yellow, fatty scales, which melt at 90 and become coloured red in the sunlight. Nitric acid oxidizes it to benzylselenic acid, C^H^.CHg Se0 2 H, crystallizing from hot water in needles which when impure possess a most unpleasant smell, which is not nearly so strong in the pure compound. It is a strong acid. 1 v. Pechmann, Ber. Deutsck. Chem. Ges. vi. 534. 2 Mohr, Ann. Chcm. Pharm. ccxxi. 215. 110 AEOMATIC COMPOUNDS. When benzyldiselenide is digested for some days with methyl iodide, a black mass is obtained which is a mixture of benzyl iodide, trimethylselenine iodide and lenzyldimethylselenine tri- iodide : (C 6 H 5 .CH 2 ) 2 Se 2 +5CH 3 I = C 6 H 5 .CH 2 I + (CBy.Se! + C 6 H 5 .CH 2 (CH 3 ) 2 SeI 3 . The latter crystallizes from hot alcohol in black, heavy needles which have a metallic lustre, melt at 65 and possess a repulsive odour. They commence to sublime below 100, and their vapour attacks the eyes violently. If the alcoholic solution be treated with silver nitrate, the excess of silver removed by hydrochloric acid and the filtrate then treated with platinum chloride, a precipitate of (C 6 H 5 .CH 2 .(CH 3 ) 2 Se) 2 PtCl 6 is obtained consisting of microscopic, yellow, quadratic plates. 1 NITROGEN BASES OF BENZYL. THE BENZYLAMINES. 2075 Cannizzaro states in his first paper on the alcohol of benzoic acid, that when the ethereal chloride prepared from it by the action of hydrochloric acid is treated with alcoholic ammonia, a base which differs from toluidine is formed (p. 89). Three years later he found that this is tribenzylamine, (C 7 H 7 ) 3 N. 2 In the year 1862, Mendius made the important discovery that the nitrils of the fatty acids combine with hydrogen to form amines, and that those of the aromatic series behave in a similar manner, inasmuch as benzonitril, C 7 H 5 N, yields a powerful base, C 7 H 9 N, which, however, is not identical with toluidine, " as might have been expected from the hitherto accepted views as to the re- lations of the bases homologous with aniline to the corresponding members of the benzoic acid series," but differs both from it and the isomeric methylaniline in its properties. It also appeared to him improbable that it was identical with the lutidine con- tained in coal-tar oil ; he, therefore, decided, in the absence of a careful comparison between the two substances, "to introduce 1 Loring Jackson, Ann. Chcm. Phann. clxxix. 8. 2 Jahresb. 1856, 582. NITROGEN BASES OF BENZYL. ill the base prepared from benzonitril into scientific literature as a new compound and to denote it by a new name." x Two years later, Cannizzaro published a paper on " The Amines of Benzyl Alcohol " in which he says " Toluidine, C 7 H 9 N, is generally looked upon as the primary benzylamine. I have obtained results which do not agree with this supposition." He found that the primary benzylamine, which he had prepared from benzyl cyanate (benzyl isocyanurate), is a strong base resembling ethylamine and amyla- mine in its properties. He also obtained it, together with dibenzyl- amine and triberizylamine, by heating benzyl chloride with alcoholic ammonia, 2 and described the separation of these bases and the properties of benzylamine. 3 In order to prepare the latter, a mixture of benzyl chloride and alcoholic ammonia is allowed to stand for some days ; a portion of the tribenzylamine separates out in crystals, and a further quantity is left behind when the alcohol is removed from the filtrate by distillation and the residue treated with hot water. The solution is then evaporated to dryness, and the most soluble portion of the residue, consisting chiefly of benzylamine hydrochloride is separated by fractional crystallization. This is then decomposed by caustic potash and the base allowed to remain in contact with some solid potash in order to dry it, and at the same time avoid exposure to carbon dioxide. It is then purified as much as possible by fractional distillation and treated with dry carbon dioxide ; a solid compound is formed which is washed with anhydrous ether to remove the last adhering traces of dibenzylamine. The residue is then converted into the crystal- lized hydrochloride and the pure base finally liberated by caustic potash. According to Limpricht, the base is prepared by heating benzyl chloride with a solution of ammonia in commercial absolute alcohol for twenty-four hours in a steam bath and re- moving free ammonia and the largest portion of the alcohol by distillation. The residue is treated with water to precipitate the mixed bases, which are then dissolved in alcohol and treated with hydrochloric acid, the acid solution being allowed to cool gradually. Tribenzylamine hydrochloride separates out in prisms or needles, and a mixture of this salt with plates of dibenzyl- amine hydrochloride is obtained by the concentration of the mother-liquor ; the residual liquid after repeated evaporation 1 Ann. Chcm. Pharm. cxxi. 144. 2 Ibid, cxxxiv. 128. 3 Ibid. Suppl. iv. 24. 112 AROMATIC COMPOUNDS. to a syrup, solution in hot water and reconcentration, yields benzylamine hydrochloride. The water employed for the precipitation of the hases contains some benzylamine, which may be extracted by saturating the liquid with hydrochloric acid, evaporating to dryness and extracting with hot absolute alcohol, which leaves ammonium chloride undissolved. The hydrochlorides of di- and tri-benzylamine are purified by re-crystallization from water or alcohol. The primary base is always present in the smallest quantity, while the relative amounts of the other two are very variable ; sometimes a large quantity of tribenzylamine is formed with only traces of dibenzylamine, while in other cases the relation is the inverse of this. x 2076 Benzylamine, C 6 H 5 .CH 9 .NH 2 . Mendius obtained this compound by treating benzonitril in alcoholic solution with zinc and hydrochloric acid, freeing the solution from alcohol and unattacked nitril by distillation, saturating the residue with caustic potash and extracting the benzylamine with ether. The ethereal solution is then treated with hydrochloric acid, the benzylamine hydrochlorid.e, which is obtained on evaporating the solution, re-crystallized from absolute alcohol and the pure base then set free by caustic potash. Hofmann obtained benzylamine by the action of zinc and hydrochloric acid on thiobenzamide, C 6 H 5 .CS.NH 2 , 2 which is formed by the direct combination of sulphuretted hydrogen with benzonitril : C 6 H 5 .CS. NH 2 + 4H = C 6 H 5 .CH 2 .NH 2 + H 2 S. Both these methods are tedious, and, like the preparation from benzyl chloride and ammonia, only give a small yield. Benzyl- amine can, however, be readily prepared in large quantities by heating benzyl chloride with an equivalent amount of silver cyanate, until the violent reaction has ceased; a mixture of benzyl isocyanate and benzyl isocyanurate is formed and after distillation is re-distilled over caustic potash. The product thus obtained contains some di- and tri-benzylamine, since the mix- ture of isocyanates always contains some benzyl chloride. These can be removed by converting the whole into the hydrochlorides or by extracting the benzylamine by shaking out witlrwater. 1 Ann. Chem. Pharm. cxliv. 304. 2 Ber. DeiOsch. Chem. Ges. i. 102. BENZYLAMINE. 113 . . . It is then converted into the hydrochloride which is decomposed by caustic potash, and the base dried over solid potash and redistilled. l It can also be readily obtained by decomposing benzylacet- amide, C 6 H 5 .CH 2 .NH.(C 2 H 3 0), which is prepared by the action of benzyl chloride on acetamide, with alcoholic potash. 2 Another simple method of preparation has been found by Hofmann. On heating benzyl chloride with potassium cyanide, phenylacetonitril, C 6 H 5 .CH 2 .CN, is obtained ; when water is added to a solution of this compound in concentrated sulphuric acid, phenylacetamide, C 6 H 5 .CH 2 .CO.NH 2 is precipitated. This is then treated with a molecule of bromine, a 5 per cent, solution of four molecules of caustic potash added with continual agita- tion and the liquid heated by a current of steam : a mixture of benzylamine and brominated benzylamine distils over, which is converted into pure benzylamine when allowed to stand for some time over sodium amalgam, all the bromine being replaced by hydrogen. 3 Hofmann has shown that the amides of other monobasic acids can readily be converted by this reaction into amines containing one atom of carbon less in the molecule. He has carefully investigated the course of the reaction in the case of acetamide, and finds that acetbromamide, CH 3 .CO.NHBr, is first formed, and that this loses hydrobromic acid with formation of methyl isocyanate, which assumes the elements of water and splits up into carbon dioxide and methylamine. Benzaldehyde, which is now a cheap commercial product, can also be readily converted into benzylamine. It combines with hydrocyanic acid to form phenylhydroxyacetonitril, C 6 H 5 .CH (OH 2 )CN, which is converted by treatment with alcoholic ammonia into phenylamido-acetonitril, C 6 H 5 .CH(NH 2 )CN. On boiling this with dilute sulphuric acid, phenylamido- acetic acid is formed and decomposes into benzylamine and carbon dioxide on distillation. These products of decom- position recombine to some extent forming benzylammonium benzylcarbamate (p. 114), which is, however, readily decomposed by alkalis. Pure benzylamine hydrochloride may also be obtained by treating the distillate with hydrochloric acid. 4 Properties. Benzylamine is a colourless liquid which has a 1 Strakosch, Bcr. Deutsch. Chem. Ges. v. 692. 2 Rudolph, ibid. xii. 1297. 3 Ibid, xviii. 2734. 4 Friedlander and Tiemann, ibid. xiv. 1969. 114 AROMATIC COMPOUNDS. characteristic, faint, aromatic odour, does not become coloured in the light, boils at 185 and has a sp. gr. of O990 at 14. It is soluble in water in every proportion, but is insoluble in strong alkalis, and is therefore precipitated by caustic potach from its aqueous solution. It has a strong alkaline reaction, fumes with hydrochloric acid and rapidly absorbs carbon dioxide, so that a drop exposed to the air is soon converted into small, silky needles of the carbonate. It combines with benzyl chloride to form dibenzylamine hydro- chloride. Benzylamine hydrochloride, C 7 H 7 NH 3 C1, forms quadratic tablets, very soluble in water and alcohol ; its platinichloride is a granular, crystalline precipitate. Benzylamine nitrite, C 7 H 7 NH 3 .N0 2 , is obtained by shaking the hydrochloride with silver nitrite and ether. It is extracted from the silver chloride, which is simultaneously formed, by cold absolute alcohol, and is deposited on the evaporation of this solution in well-formed crystals, which decompose with evolution of nitrogen when gently warmed. 1 Benzylammonium benzylcarbamate is formed by the com- bination of benzylamine with carbon dioxide : / ONH 3 (CH 2 .C 6 H 6 ) C0 2 + 2NH. 2 .CH 2 .C 6 H 5 = CO< \NH(CH 2 .C 6 H 5 ). It is readily soluble in water, volatilizes when the solution is boiled, and crystallizes from alcohol in small, lustrous plates which melt at .99. 2077 Dibenzylamine, (C 6 H 5 .CH 2 ) 2 NH, is a thick liquid, which has a sp. gr. of T033 at 14 and is insoluble in water, but readily soluble in alcohol. When a small quantity is rapidly heated it distils unaltered at above 300, but on gradual distilla- tion it is decomposed with formation of ammonia, toluene, dibenzyl, C 14 H 14 , stilbene, C 14 H 12 , lophine, C 21 H 16 N 2 , and other bodies. 2 When heated to 260 in a stream of hydrochloric acid, it gradually and incompletely decomposes into benzyl chloride and benzylamine hydrochloride, while at 100 it combines with benzyl chloride forming tribenzylamine. On treatment with 1 Curtius, Bcr. Dcutsch. Chem. Got. xvii. 958. 2 Bruuner, Ann. C'fiem. Pfiarm. cli. 131. DIBENZYLAMINE. bromine and a large quantity of water, it decomposes into benzylamine and benzaldehyde : (C 6 H 5 .CH 2 ) 2 NH + H.,0+Br 2 = C 6 H 5 .COH+C 6 H 5 .CH 2 .NH 2 +2HBr. Iodine has a similar action but requires a temperature of 140 (Limpricht). Dibenzylamine hydrochloride, (C 7 H 7 ) 2 NH 2 C1, is readily soluble in hot water and alcohol, but much less freely in the cold, and crystallizes in large, flat, prisms, or, when its alcoholic solution is rapidly cooled, in thin plates. The hydrobromide and hydriodide are very similar. Dibenzylamine nitrate, (C 7 H 7 ) 2 NH 2 .N0 3 , is less soluble than the other salts and crystallizes in flat needles or prisms. Tribenzylamine, (C 6 H 5 .CH 2 ) 3 N, is also formed, together with other bodies, when benzaldehyde is gradually heated to 180 with ammonium formate. Formamide is the first product and decomposes into carbonic oxide and ammonia, which then act upon the benzaldehyde : 3C 6 H 5 .COH + SCO + NH 3 = (C 6 H 5 .CH 2 ) 3 N + 3CO 2 . This is the most convenient method for the preparation of tribenzylamine, 100 grms. of benzaldehyde yielding 40 grms. of the pure product. 1 It is slightly soluble in cold alcohol and crystallizes from a hot solution in needles, plates, or monoclinic tablets (Panebianco) melting at 91. Small quantities can be distilled without decomposition, but larger quantities split up, yielding the same products as the secondary base. It also resembles the latter in its behaviour towards bromine and iodine, benzaldehyde and dibenzylamine being formed. When its hydrochloride is heated to 250 in a stream of hydrochloric acid, it decomposes into benzyl chloride and dibenzylamine hydrochloride, while Lauth obtained benzyl chloride and ammonium chloride by treating the free base in a similar manner at 180 2 . It does not combine with benzyl chloride, and hence no tetrabenzylammonium chloride is formed in its preparation from benzyl chloride and ammonia ; it com- bines with ethyl iodide, however, on heating to form a crystal- lized compound, which does not yield a hydroxide on treatment with silver oxide, but decomposes into its constituents. 3 It 1 Leuckart, Ber. Deutsch. Chcm. Ges. xviii. 2341. 2 Ibid. vi. 678. 3 Vasca-Lanza, ibid. vii. 82. 1 16 AROMATIC COMPOUNDS. also forms a crystallized compound when heated with methyl sulphate to 100 . 1 The salts of tribenzylamine have been crystallographically investigated by Panebianco. 2 Tribenzylamine hydrochloride, (C 7 H 7 ) 3 NHC1, is slightly soluble in cold alcohol and water, and crystallizes from its hot solution in quadratic prisms. It decomposes above 270, a large quantity of toluene being formed (Rohde). The platinichloride crystal- lizes in orange-coloured, monoclinic needles. Tribenzylamine nitrate, (C 7 H 7 ) 3 NHNO 3 , forms rhombic crystals which are insoluble in water and slightly soluble in alcohol. Tribenzylamine sulphate, (C 7 H 7 ) 3 NH). 2 SO 4 , forms monoclinic crystals, is insoluble in water, slightly soluble in alcohol, and combines with aluminium sulphate forming tribenzylammonium alum, (C 21 H 22 N) 2 A1 2 (SO 4 ) 4 + 24H 2 0, which is deposited in regular crystals and is soluble in water but not in alcohol. Nitrosodibenzylamine, (C 7 H 7 ) 2 N(NO). Rohde obtained this compound, together with benzaldehyde, by distilling a con- centrated alcoholic solution, of tribenzylamine with nitric acid : CH 2 .C 6 H 5 /CH 2 .C 6 H 5 -CH 2 .C 6 tT 5 + NO 2 .OH = N-NO + COH.C 6 H 5 +H 9 O. \GBLOH. \CH*CLH. It is readily soluble in alcohol and ether, and crystallizes in quadratic tablets, melting at 52; it does not combine with acids, and is converted into dibenzylamine by the action of nascent hydrogen or hydrochloric acid. AMIDO-SUBSTITUTED BENZYLAMINES. 2078 I>iethylbenzylamine, C 6 H 5 .CH 2 .N(C 2 H 5 ) 2 , is obtained by heating benzylamine with ethyl iodide, or benzyl chloride with diethylamirie. It is a transparent, oily liquid, which boils at 211 212, and combines with ethyl iodide on heating with formation of triethylbenzylammonium iodide, N(C 6 H 5 .CH 2 ) (C 2 H 5 ) 3 I, which can also be prepared from benzyl iodide and 1 Claessou and Lundvall, Eer. Dcutseh. Chem. Gcs. xiii. 1703. 2 Jahresb. 1878, 476. ETHYLBENZYLAMINE. 117 triethylamine, and forms large, colourless crystals, which are readily soluble in water ; on dry distillation it is decomposed into triethylamine and benzyl iodide, while it is not attacked when heated with concentrated hydriodic acid. 1 When iodine is added to it in alcoholic solution, the periodide, N(C 6 H 5 .CH 2 ) (C 2 H 5 ) 3 I 3 , separates out in black-blue monoclinic prisms, which have a metallic lustre. Ethyldibenzylamine, (C 6 H 5 .CH 2 ) 2 NC 2 H 5 , was obtained by Limpricht from ethyl iodide and dibenzylamifie ; it is an oily liquid. Dietliyldibenzylammonium iodide, (C 6 H 5 .CH 2 ) 2 (C 2 H 5 ) 2 NI, is formed by the combination of diethylbenzylamine with benzyl iodide. It crystallizes from hot water in needles possessing a diamond lustre ; when it is distilled with hydriodic acid, benzyl iodide is liberated (V. Meyer). Benzylphenylamine, or Benzylaniline, C 6 H 5 .CH 2 .N(C 6 H 5 )H, is formed when benzyl chloride is heated with aniline to 160. The free base crystallizes from hot alcohol in four-sided prisms, melting at 32. 2 It may also be obtained by the action of hydrochloric acid and zinc-dust on thiobenzanilide, 3 C 6 H 5 .CS.N (C 6 H 5 )H. Benzylphenyldimethylammonium chloride, (C 6 H 5 .CH 2 ) C 6 H 5 (CH 3 ) 2 NC1, is readily formed by the direct combination of benzyl chloride with dimethylaniline. It crystallizes from water or alcohol in tablets, which melt at 110, and is split up into its constituents by distillation. It is not decomposed by boiling with water and silver oxide, but its decomposition may be effected by employing silver sulphate. If the sulphuric acid be removed by baryta water from the solution thus formed, and the filtrate concentrated, the hydroxide is obtained as a strongly alkaline, syrupy mass, which is converted into the carbonate in the air. On distillation it decomposes smoothly into dimethyl- aniline and benzyl alcohol, 4 while tetra-ethylammonium hydroxide under similar conditions yields triethylamine. ethylene and water. Eenzyldiphenylamine, C 6 H 5 .CH 2 .N(C 6 H 5 ) 2 , is formed when diphenylbenzothiamide, C 6 H 5 .CS.N(C 6 H 5 ) 2 , is treated with hydrochloric acid and zinc-dust. It crystallizes from hot alcohol - a \ *f denbur S and Struve, Her. Deutsch. Cham. Gcs. x. 43 ; Ladenburg, ibid. x. 561, 1153, 1634 ; V. Meyer, ibid. x. 309, 964, 1291. Fleischer, Ann. Chcm. Pharm. cxxxviii. 22. Bern thsen and Trompetter, Bcr. Deutsch. Chcm. GM. xi. 1760. * Michler arid Gradmaun, ibid. x. 2079. 239 118 AROMATIC COMPOUNDS. in long white needles which melt at 87, and does not combine with acids (Bernthsen and Trompetter). Dibenzyltolylamine, (C 6 H 5 .CH 2 ) 2 NC 6 H 4 .CH 3 . This base, which is also known as dibenzyltoluidine, was prepared by Cannizzaro by heating paratoluidine with alcohol and benzyl chloride. It crystallizes from hot alcohol in very fine needles, melting at 54*5 55, and is a weak base ; it differs from the isomeric tribenzylamine in forming salts which are decomposed by water. 1 SUBSTITUTION PRODUCTS OF THE BENZYLAMINES. 2079 These are formed by the action of ammonia on the corresponding haloid ethers. Halogen substitution products. These compounds are strong bases and form crystalline salts ; the primary compounds absorb carbon dioxide from the air. Melting-point. Paratrichloro- benzylamine,* Paratribromo- benzylamine - ) M CAC1.CH, N H 2 , liquid . crstals . ( rhombic ) j prisms j- prisms J^AICH^NH, needles . . 20 78-5 78 79 C 76 114-5 Paratri-iodo- | (C H 4 I.CH 2 ) 3 N, needles . benzylamiue, 8 J v 6 4 Orthobromo- I c H Br CH NH u id . benzylamme, 9 j 1 Ann. Chem. Pharm. Suppl. iv. 80. 2 Bei-lin, Ann. Chem. Pharm. Suppl. cli. 137 ; Jackson and Field, Amer. Chem. Jr. nw *\ ATTT / rhombic | <> i T r (L/ A -tl x j3r.Uxl )nJN 1 < x i r oo benzylamme, 1 j ^ ( crystals j Orthotribromo- | /p TT Br CH ^ N crvstals 1 21'5 1 22 1 ' 9 L \ V^cAl^-Dl. v^-LJ-oyoi-N , ClyotcHQ . . JL^i. c> J.*< benzylamme, 2 j v e Paranitrobenzylamines have been prepared by Strakosch by heating paranitrobenzyl chloride with aqueous ammonia to 100. The primary base could not be isolated ; the secondary base combines with acids, while the tertiary does not, thus rendering the separation of these two a matter of no difficulty. 3 Paradinitrobenzylamine, (C 6 H 4 (NO 2 )CH 2 ) 2 NH, crystallizes from hot alcohol in large, yellowish, lustrous plates, melting at 93; its hydrochloride forms lustrous, yellow prisms, which are only slightly soluble in water and alcohol, while its platini- chloride, which crystallizes in yellow needles, is almost insoluble. Paratrinitrobenzylamine, (C 6 H 4 (NO 2 )CH 2 ) 3 N, is slightly soluble in hot alcohol, readily in glacial acetic acid and nitro- benzene, and crystallizes in lustrous, white needles, which melt at 163, and possess a pleasant odour. Paranitrobenzylphenylamine, C 6 H 4 (N 2 )CH 2 .N(C 6 H 5 )H, is formed by heating paranitrobenzyl chloride with aniline ; it crystallizes from hot alcohol in pointed, lustrous, yellow needles. Its hydrochloride crystallizes from hot hydrochloric acid in small lustrous plates which are decomposed by water with separation of the base (Strakosch). Metanitrobenzylamines. Aqueous ammonia converts meta- nitrobenzyl chloride into the secondary and tertiary amines, while in the presence of alcohol only the former, together with a small quantity of the primary base, is formed. 4 Metanitrolenzylamine, C 6 H 4 (N0 2 )CH 2 .NH 2 , is a yellow, oily liquid, which becomes solid in the air from absorption of carbon dioxide. Its oxalate crystallizes in needles, which are only slightly soluble in water. Metadinitrobenzylamine crystallizes from alcohol in small yellow, rhombic plates, melting at 87. Its hydrochloride and platinichloride are only slightly soluble in water. Mctatrinitrobenzylamine is slightly soluble in alcohol, more readily in benzene, and forms monoclmic prisms, melting at 162. It does not combine with hydrochloric acid. Metanitrobenzylplienylamine is formed by the action of aniline 1 Jackson and White, Amer. Chcm. Journ. ii. 317. 2 Ibid. 3 Ber. Dcutsch. Chem. Ges. vi. 1056. 4 Borgruaim, Chcm. Centralb. 1885, 456. 120 AROMATIC COMPOUNDS. on metanitrobenzyl chloride. The hydrochloride, which is thus obtained, forms small white, lustrous plates. It is decomposed by water with formation of the base, which crystallizes in long, orange-red needles, melting at 86. Amiddbenzylamines are obtained by the reduction of the iiitro-compounds with tin and hydrochloric acid. Paradiamidobenzylamine, (C 6 H 4 (NH 2 )CH 2 ) 2 NH, is readily soluble in hot water and alcohol ; it crystallizes in needles with a satin lustre, or in plates which melt at 106, and volatilize without decomposition when more strongly heated. The hydrochloride, (C 6 H 4 (NH 3 C1)CH 2 ) 2 NH 2 C1, is readily soluble in water, slightly in hydrochloric acid, and crystallizes in small white, lustrous plates ; the platinichloride, C 14 H 18 N 3 Cl.PtCl 6 , forms large pointed reddish-yellow needles which are readily soluble in water. Paratriamidobenzylamine, (C 6 H 4 (NH 2 )CH 2 ) 3 N, is insoluble in water, and crystallizes from hot alcohol in octahedra, possessing a diamond lustre and melting at * 136. Its hydrochloride crystallizes in yellow needles, and is so readily soluble in water, alcohol, and hydrochloric acid, that it cannot be obtained pure. In the preparation of the base, the action of the tin and hydrochloric acid must not be allowed to continue too long, as under these circumstances it is split up into paradiamido- benzylamine and paratoluidine : /CH 2 .C 6 H 4 .NH 2 CH 2 .C 6 H 4 .NH 2 Nf-CH .C 6 H 4 .NH 2 +2H = HN< +CH 3 .C r H 4 .NH 2 . \CH;C 6 H 4 .NH 2 X CH 2 .C 6 H 4 .NH 2 Paramidobenzylphenylamine, C 6 H 4 (NH 2 )CH 2 .N(C 6 H 5 )H, can- not be obtained by the action of tin and hydrochloric acid on the mtro-compoimd, since a more deeply seated decomposition takes place; the reduction may, however, be effected by employing ammonium sulphide. The base is soluble in water and alcohol, and crystallizes in silky scales, which melt at 88 and become coloured red in the light. Metadiamidobenzylamine forms prismatic needles, melting at 86; its hydrochloride, (C 6 H 4 (NH 3 C1)CH 2 ) 2 NH 2 C1, crystallizes from concentrated hydrochloric acid in long, pinkish needles, and forms a readily soluble platinichloride. Metatriamidobenzylamine forms needles melting at 142; its platinichloride is only slightly soluble. Metamidobenzylphenylamine melts at 67. BENZYLACETAMIDE. 121 BENZYL-DERIVATIVES OF THE ACID-AMIDES AND ALLIED BODIES. 2080 Benzylacetamide, C 6 H 5 .CH. 2 .N(C. 2 H 3 0)H > was prepared by Strakosch by heating benzylamine with glacial acetic acid for several hours ; 1 it is more readily formed by the action of benzyl chloride on acetamide, 2 and* is very soluble in alcohol and ether, slightly in petroleum naphtha, from which it crystallizes in small plates, which have a pleasant smell of flowers and melt at 57. It boils at 300 and is not attacked by acids or aqueous alkalis ; alcoholic potash, however, converts it into acetic acid and benzylamine. Dibenzyloxamide, (C 6 H 5 .CH 2 .NH 2 ) 2 C 2 O 2 , is obtained by boiling benzylamine with ethyl oxalate ; it is insoluble in water, slightly soluble in hot alcohol, from which it crystallizes in scales, which possess a satin lustre and melt at 216. Cyanobenzylamine, C 18 H 16 N 4 , is obtained by passing cyanogen into a cold solution of benzylamine : C 6 H 5 .CH 2 .NH 2 C=N C 6 H 5 .CH 2 .NH.C=NH + I I C 6 H 5 .CH 2 .NH 2 C=N C 6 H 5 .CH 2 .NH.C=NH. It forms lustrous crystals, which are soluble in alcohol and melt at 140. If hydrochloric acid be added to the alcoholic solution, the salt, C 18 H 16 N 4 (C1H) 2 , is obtained in white, silky needles. When it is allowed to stand in contact with hydro- chleric acid for some time, it is converted into dibenzyloxamide (Strakosch). Benzykyanamide, C 6 H 5 .CH 2 .NH(CN), is formed when cyan- ogen chloride is passed into an ethereal solution of benzyl- amine, and crystallizes in tablets melting at 33. It changes spontaneously into ~benzy Icy anur amide or lenzylmelamine, (C 6 H 5 . CH 2 .NH) 3 C 3 N 3 , which has a much higher melting-point and crystallizes from alcohol in plates ; the change takes place more readily at 100. When an alcoholic solution of benzylcyanamide is boiled with benzylamine hydrochloride, dibenzyl guanidine (C 6 H 5 .CH 2 .NH) 2 C.NH, is formed ; this compound crystallizes from alcohol in 1 Ber. Deutsch. Chem. Ges. v. 697. 2 Rudolph, ibid. xii. 1297. 122 AROMATIC COMPOUNDS. plates or tablets, melting at 100. The hydrochloride, (C 7 H 7 . NH) 2 C.NH.C1H, is slightly soluble in water, more readily in alcohol (Strakosch). Dibenzylcyanamide, (C 6 H 5 .CH 2 ) 2 N.CN, was obtained by Lim- pricht from dibenzylamine and cyanogen chloride ; it crystallizes from alcohol in plates, melting at 53 54. Benzyl isocyanate, or Benzyl carbimide, C 6 H 5 .CH N : CO, was prepared by Letts in the impure state and in small quantity, by distilling benzyl chloride with silver cyanate ; l the isocyanurate is always formed at the same time. It is a liquid which gives all the characteristic reactions of the isocyanates and possesses an extremely penetrating odour, its vapour attacking the eyes violently. Benzyl isocyanurate, (C 6 H 5 .CH 2 ) 3 N 3 (CO) 3 , crystallizes from hot alcohol in silky needles, melting at 157. It boils above 320, and when fused with caustic potash yields benzylamine. Cannizzaro seems to have obtained the same substance in small quantity and together with other products by the action of cyanuric chloride on benzyl alcohol. 2 Benzyl isothiocyanate, or Benzyl mustard oil, C 6 H 5 .CH 2 .N:CS. Hofmann obtained this compound by dissolving benzylamine in carbon disulphide, and distilling the white, crystalline compound formed with an alcoholic solution of mercuric chloride 3 It is a liquid which boils at about 243 and possesses the smell of water-cress (Nasturtium officinale) in such a remarkable degree that Hofmann was induced to search for it in the oil of this plant ; it is not, however, present, the odoriferous constituent in water-cress being phenylpropionitril, C 6 H 5 .C 2 H 4 .CN, 4 w,hile benzonitril, C 6 H 5 CN, is that of the nasturtium (Tropaeolum majuslf Benzyl tkiocyanate, C 6 H 5 .CH 2 .S.CN, is formed by heating benzyl chloride with an alcoholic solution of potassium thio- cyanate. It is insoluble in water, and crystallizes from alcohol in long, transparent prisms, which have a sharp, burning taste, and a penetrating smell resembling that of cress. According to Henry, 6 it melts at 36 38 and boils with partial decomposition at 256, while Barbaglia found its melting-point to be 41 and its boiling-point 230 235 . 7 1 J3er. Deutsch. Chem. Ges. v. 90 ; see also Strakosch, ibid, v, 692 ; Ladenburg, ibid. x. 46. 2 Ber. Deutsch. Chcm. Ges. iii. 517. 3 Ibid. i. 201. 4 Ibid. vii. 520. 6 Ibid. vii. 518. 6 Ibid. ii. 638. 7 Ibid. v. 688. BENZYL UREAS. 123 Concentrated nitric acid converts it into paranitrobenzyl thio- cyanate, C 6 H 4 (N0 2 )CH 2 .S.CN, which can also be obtained by the action of paranitrobenzyl chloride on potassium thiocyanate. It crystallizes from alcoholic solution in small, brittle crystals. Various halogen substitution-products of this compound are also known. 1 Benzyl selenocyanate^^^.GYL^Q. ON, crystallizes from alcohol in white needles or prisms, which have an extremely repulsive smell and melt at 7l'5. 2 Benzyl carbamate, or Benzyl urethane, C 6 H 5 .CH 2 .O.CO.NH 2 , was obtained by Cannizzaro, together with a little benzyl isocyanurate and dibenzyl urea, by the action of cyanogen chloride and cyanuric chloride on benzyl alcohol. 3 It is also formed when urea nitrate is heated to 130 140 4 with benzyl alcohol; it crystallizes from hot water in large plates, which melt at 86 and decompose into benzyl alcohol and cyanuric acid at 220. Benzyl urea, (C 6 H 5 .CH 2 )NH CO.NH 2 , is formed, together with symmetric dibenzyl urea, by the action of benzyl chloride on an alcoholic solution of potassium cyanate, 5 as well as by that of alcoholic ammonia on benzyl isocyanate (Letts). It is also obtained when a solution of benzylamine hydrochloride is boiled with potassium cyanate. 6 It is tolerably soluble in hot, readily in boiling alcohol, and crystallizes in long, white needles, melting at 147 147-5. Symmetric dibenzyl urea, CO(NH.CH 2 .C 6 H 5 ) 2 , is formed when the compound just described is heated to 200 (Cannizzaro), as well as when benzyl isocyanate is heated with water in a sealed tube to 100, and also when benzyl alcohol is heated to 100 with urea nitrate (Letts), benzylaldehyde being simultaneously formed (Campisi and Amato). It is insoluble in water and crystallizes from alcohol in needles melting at 167. It does not combine with hydrochloric acid or nitric acid, but gives a plantinichloride. Asymmetric dibenzyl urea, (C 6 H 5 .CH 2 ) 2 N.CO.NH 2 , has been obtained by Paterno and Spica from dibenzylamine hydrochloride and potassium cyanate ; it is slightly soluble in cold, readily in hot water, and crystallizes in thick prisms, melting at 124 125. 1 Jackson, Field, Mabery, Lowry, loc. cit. 2 Jackson, Ann. Chem. Pharm. clxxix. 15. 3 Ber. Dcutsch. CJiem. Ges. iii. 517 ; iv. 412. 4 Campisi and Amato, ibid. iv. 412. 6 Patemo and Spica, ibid. ix. 81. 8 Ibid. 124 AROMATIC COMPOUNDS. Benzyl tJiiocarbamide , C 6 H 5 .CH 2 .NH.CS.NH 2 ,has been prepared in an analogous manner from benzylamine hydrochloride and potassium thiocyanate ; it is very soluble in water and melts at 101. Symmetric dibenzyl thiocarbamide, (C 6 H 5 .CH 2 .NH) 9 CS, is formed when an alcoholic solution of benzylamine is heated with carbon disulphide until the evolution of sulphuretted hydrogen ceases. It crystallizes in large, four-sided, lustrous tablets, melt- ing at 114 ; it is converted into dibenzyl urea when its alcoholic solution is treated with mercuric oxide (Strakosch). Asymmetric dibenzyl thiocarbamide, (C 6 H 5 .CH 9 N) 2 CS.NH , is prepared from dibenzylamine hydrochloride and potassium thiocyanate ; it is slightly soluble in water, readily in alcohol, and crystallizes in long needles melting at 156 157 (Paterno and Spica). PHOSPHORUS COMPOUNDS OF BENZYL. 2081 Primary and secondary benzylphosphine are formed when benzyl chloride is heated with phosphonium iodide and zinc oxide. The product of the reaction is distilled with water, an oily liquid coming over, which possesses a very characteristic, persistent odour, and is a mixture of toluene and benzylphos- phine. The residue contains dibenzylphosphine and other substances, which, however, remain in solution, while the dibenzylphosphine crystallizes out on standing, more rapidly in the presence of caustic potash ; it is then removed from the liquid and recryst alii zed from boiling alcohol. 1 Benzylphosphine, C 6 H 5 .CH 2 .PH 2 , is a strongly refractive liquid, boiling at 180 ; it is oxidized on exposure to the air with such rapidity that its temperature rises to above 100, thick, white needles being deposited. Benzyl phosplionium iodide, C 6 H 5 .CH 2 .PH 3 I, is obtained by the addition of fuming hydriodic acid to benzylphosphine, as a white precipitate which crystallizes from the hot acid in long, white needles. When these are washed with ether and dried in a stream of hydrogen, they are converted into large, well-formed tablets. Water decomposes the compound into its constituents. 1 Hofmann, Bcr. Dcutsch. Chem. Gc\ v. 100. ARSENIC COMPOUNDS OF BENZYL. 125 1 ' * - " - Dibenzylphosphine, (C 6 H 5 CH 2 ) 2 PH, crystallizes in needles rhich form star-like aggregates, are colourless and tasteless, do >t combine with acids, and melt at 205. While dimethyl- losphine and ethylphosphine are spontaneously inflammable in air, dibenzylphosphine is not acted upon by oxygen, even a higher temperature. Triphenylbenzylphosphonium chloride, P(C 6 H 5 ) 3 (CH 2 .C 6 H 5 ) Cl, readily formed by the combination of benzylchloride with iphenylphosphine. It is readily soluble in alcohol and water, id separates from the latter in rhombic crystals which contain molecule of water and are efflorescent. Other salts, which characterized by their power of crystallization, have been spared from this compound by double decomposition ; they are lecomposed by boiling caustic soda, with formation of triphenyl- losphine oxide and toluene : l ARSENIC COMPOUNDS OF BENZYL. 2082 When benzyl chloride, diluted with absolute ether, is ited with arsenic trichloride and sodium, a reaction commences ir some time, which in the course of a few days may raise the jmperature to the boiling-point of ether, the following com- mnds being formed : Dibenzylarsine trichloride. 2C 7 H 7 C1 + AsCl 3 + 2Na = (C 7 H 7 ) 2 AsCl 3 + 2N aCl. Tribenzylarsine di chloride. 3C 7 H 7 C1 + AsCl 3 + 4Na= (C 7 H 7 ) 3 AsCl 2 + 4NaCl. If the sodium chloride be now removed, the ether distilled off id the residue treated with ordinary ether containing water, le chlorides are converted into oxychlorides, which separate out a powder, while resinous by-products containing arsenic go ito solution. The powder is washed with ether and then treated ith boiling dilute caustic soda solution ; dibenzylarsenic acid into solution, while the residue consists of tribenzylarsine >xide, which is very slightly soluble in the cold solution, and is, therefore, removed by cooling and filtering. 1 Michaelis and V. Soden, Ann. Chcm. Pharm. ccxxix. 319. 126 AKOMATIC COMPOUNDS, Dibenzylarsenic acid, (C 6 H 5 .CH 2 ) 2 AsO.OH, is precipitated from its alkaline solution by acids ; it is only very slightly soluble in cold, more readily in boiling water, and crystallizes from hot dilute alcohol in fine, white plates, melting at 210'5. It dissolves in hot dilute hydrochloric acid and the solution on cooling deposits the compound (C 7 H 7 ) 2 As(OH) 2 Cl, in fine needles, which melt at 128 and are reconverted into the acid by water. It forms similar compounds with hydrobromic, hydriodic and nitric acids. It is decomposed on heating with concentrated hydro- chloric acid : 2(C 7 H 7 ) 2 As0 2 H + 2HC1 = 2C 7 H 7 C1 + 2C 7 H 8 + As 2 O 3 + H 2 0. It behaves in this reaction similarly to cacodylic or di- methylarsenic acid. Its alkaline salts are soluble in water and alcohol; those of the calcium group separate from alcohol in crystals ; the silver salt is a white precipitate, insoluble in water. Tribenzylarsine oxide, (C 6 H 5 .CH 2 ) 3 AsO, crystallizes from dilute alcohol in lustrous needles, melting at 219'5. On heating with hydrochloric acid it is converted into the oxychloride, (C 7 H 7 ) 3 As(OH)Cl, which melts at 162 163 and is reconverted into the oxide by alkalis. Tribenzylarsine, (C 6 H 5 CH 2 ) 3 As. When a little acetic ether is added to the mixture employed in the preparation of the compounds just described, the reaction becomes so violent that it has to be moderated by cooling : 3C 7 H 7 C1 + AsCl 3 + 6Na = (C 7 H 7 ) 3 As + GNaCl. If the treatment described above be then proceeded with, the oxychlorides are obtained as before, but the solution contains tribenzylarsine and no resinous by-products ; it crystallizes from alcohol in large colourless needles, melting at 104. On heating with ethyl iodide, tribenzylarsonium iodide, (C 6 H 5 .CH 2 ) 3 C 2 H 5 Asl, is formed, and crystallizes in small white plates, which are slightly soluble in water, readily in alcohol. 1 Tribenzylarsine is isomeric with tritolylarsine, (C 6 H 4 .CH 3 ) 3 As, which, like triphenylarsine, forms no compounds with the alcoholic iodides. 1 Michaelis and Paetow, Ber. Deutsch. Chem. Ges. xviii. 41. SILICON TETKABENZYL. 127 SILICON COMPOUNDS OF BENZYL. 2083 Silicon tetrabenzyl, or Silieotetrdbenzylmethane, Si(CH 2 . ; C H 5 ) 4 , is formed by the action of sodium on a mixture of jnzylchloride and silicon chloride, to which a little acetic ether been added, and which has been diluted with ether. It ?parates fiom warm ether in crystals melting at 1 Polls, Ber. Deutsch. Chem. Ges. xviii. 1543. 128 AROMATIC COMPOUNDS. THE BENZOYL GROUP. 2084 It has been already mentioned in the introductory sketch of the development of organic chemistry (Part I. p. 11), that Wohler and Liebig showed in their classical research, Investiga- tions on the Radical of Benzoic Acid, that oil of bitter almonds, benzoic acid, and a number of substances prepared from these, all contain a "compound basis " of the formula C 7 H 5 O, to which they gave the name of benzoyl (the latter portion of the word being derived from v\7j, matter). 1 They communicated their results to Berzelius, who makes the following remarks in his reply : " The results which you have obtained by the investigation of oil of bitter almonds, are certainly the most important which have hitherto been attained in the field of vegetable chemistry, and promise to throw an unexpected light upon that department of science. The fact that a substance which is composed of carbon, hydrogen and oxygen, combines with other substances, but especially with those which form salts and bases, in precisely the same manner as do simple substances, proves that there are ternary compound atoms (of the first order), and the radical of benzoic acid is the first well-established instance of a ternary substance which possesses the properties of an element. " The facts brought forward by you give rise to such wide considerations that they may be looked upon as marking the commencement of a new era in vegetable chemistry. From this standpoint I should propose to name the first discovered radical composed of more than two elements, proin (from the word commencement of the day, in the sense, CLTTO Trpwl eo>? Acts xxviii. 23), or orthrin (from 6p(p>p6?, dawn.)" In view, however, of the circumstance that the long familiar name benzoic acid would have also been altered, and that it is customary to respect terms in general use, provided only that 1 Ann. Chem. Pharm. iii. 249. BEXZALDEHYDE. they do not admit of a double interpretation, it seemed to him most suitable to accept the name benzoyl. 1 In the next year, nevertheless, he opposed the idea of the existence of oxygenated radicals and looked upon oil of bitter almonds as an oxide of picramyl, C 7 H 6 (in/epos, bitter, and , almond), a name which was never generally adopted. BENZALDEHYDE, C 6 H 5 .CHO. 2085 The poisonous qualities of bitter almonds were known to the ancients, and they were employed in medicine in the middle ages : Valerius Cordus, who has been already mentioned under the history of ether, described them as constituents of lozenges. At the commencement of this century, Bohm, an apothecary's assistant in Berlin, discovered that the aqueous distillate of bitter almonds contains prussic acid, 2 and this dis- covery led to the assumption that the latter is poisonous, a property which its discoverer, Scheele, had, somewhat strangely, overlooked. Schaub, Schrader, Ittner and other chemists 3 confirmed the dangerous nature of this substance, and Schrader, 4 and Matres, 5 an apothecary in Montauban, observed that a liquid oil is also obtained by the distillation of bitter almonds with water. This oil was more closely examined by Vogel and Robiquet, the former of whom found that the most remarkable and striking property of oil of bitter almonds is that it is converted into a crystalline body by exposure to the air or by treat- ment with pure oxygen or oxy muriatic acid (chlorine), while Robiquet showed that the leaves of the cherry-laurel yield an oil which resembles oil of bitter almonds in every respect, and that the substance obtained from it by oxidation has acid pro- perties. 7 Stange, an apothecary of Basel, who also obtained this solid substance from the cherry-laurel, recognized it as benzoic acid, 8 an 1 Ann. Chem. Pharm. iii. 282. - Scherer's Journ. x. 126 ; Gilbert, Ann. Phys. xiii. 503. 3 Ittner, Bcitrdge zur Geschichte dcr Blamaure, Freiburg and Constanz, 1809 ; Preyer, Die Blausaure, Bonn, 1870, 154. 4 Schrader, Berlin. Jahrb. Pharm. ii. 43. 5 Journ. Pharm. v. 289. 6 Schweigger, Journ. Chem. Phy*. xx. 59 ; xxxii. 119. r Ann. Chim. Phys. xv. 29 ; xxi. 250. 8 Buclmer'.s Rcpert. Pharm. xiv. 329, 361 ; xvi. 80. 130 AKOMATIC COMPOUNDS. observation which was confirmed by Wohler and Liebig. These chemists determined its composition, and that of the oil of bitter almonds, and ascertained the relations of the two com- pounds. To oil of bitter almonds they gave the name of benzoyl hydride, which was later changed to benzoic aldehyde and benzaldehyde. Shortly before this, Robiquet and Boutron-Charlard had found that when bitter almonds are freed from fatty matters by pressure, an odourless residue is left which yields the characteristic smell of oil of bitter almonds on the addition of water. The oil in question, or its elements, had there- fore been left behind in the pressed mass and had not been removed by the process. They, therefore, concluded that oil of bitter almonds is a compound of water with a peculiar principle, which they endeavoured to isolate. The use of water being impossible, they extracted the pressed almonds with boiling alcohol, and obtained, together with resin and a liquid sugar, a crystalline compound containing nitrogen, to which they gave the name of amygdalin. This compound, to which the taste of bitter almonds is due, gave .no smell of bitter almonds when treated with water, nor did either of the two other compounds, nor the residue, nor even of a mixture of them all. The prussic acid and oil of bitter almonds had vanished from their hands. 1 They found further, that sweet almonds contain no amygdalin and that the latter yields benzoic acid when oxidized by nitric acid, while Peligot observed the formation of oil of bitter almonds as an intermediate product in this reaction. Wohler and Liebig, who also accurately determined the composition of amygdalin, succeeded in finding the solution of the problem. They showed that both sweet and bitter almonds contain a peculiar nitrogenous substance, emulsin, which con- verts amygdalin in presence of water into benzaldehyde, prussic acid, and grape sugar C 20 H 27 NO U + 2H 2 = C 7 H 6 * CNH + 2C 6 H 12 6 . The action of the ferment is destroyed by boiling water and by heating with alcohol, so that when dried and powdered bitter almonds are shaken up with boiling water and distilled, none of the liquid oil is obtained, and the same result occurs when, as in 1 Ann. Chim. Phys. xliv. 352. OCCURRENCE OF BENZALDEHYDE. 131 Robiquet and Boutron-Charlard's process, they are treated with boiling alcohol. 1 Amygdalin, which is the first example of a glucoside, a large number of which bodies is now known, occurs in many plants, chiefly the Amygdalacece, Drupacece and Pomacece, which all yield benzaldehyde and prussic acid when distilled with water. The kernel of the peach also yields an oil resembling oil of bitter almonds in every respect, 2 while that obtained from the leaves, flowers, seeds and bark of the cherry, contains both oil of bitter almonds and another oil which has a penetrating, repul- sive odour. 3 This subject will be further discussed under Amygdalin. According to Winkler, the fresh leaves of the cherry-laurel (Prunus laurocerams), the cherry (Prunus padus) and the peach, contain a small quantity of free oil of bitter almonds varying in amount with the water present, 4 which can be extracted by ether. Ittner looked upon oil of bitter almonds as a compound of hydrocyanic acid and an ethereal oil, but \ T ogel opposed this view, for he had found that it could be easily freed from hydro- cyanic acid by treatment with caustic potash or baryta water, or by distillation with mercuric oxide. 5 Since, however, the oil containing hydrocyanic acid is readily converted into the polymeric benzoin, C 14 H 12 O 2 , by caustic potash, Wohler and Liebig proposed to remove the acid by shaking up with milk of lime and ferrous sulphate, calcium ferrocyanide being formed ; a loss of about 1 per cent, is experienced in the process. According to Bertagnini it is better to shake the oil with three or four volumes of acid sodium sulphite, remove the crystals which separate out and wash with alcohol. 6 All the hydrocyanic acid is not removed by this process, and the double sulphite is therefore recrystal- lized from hot alcohol before being distilled with caustic soda. 7 The oil containing hydrocyanic acid is not simply a mixture of benzaldehyde and hydrocyanic acid, but contains phenylhydroxy- acetonitril, C 6 H 5 .CH(OH)CN, which, like other cyanhydrins or nitrils of hydroxyacids, readily decomposes into its constituents. Winkler had noticed some time previously that crude oil of bitter almonds is converted by hydrochloric acid into mandelic acid 1 Ann. Chem. Pharm. xxii. 1 ; Robiquet and Boutron, ibid. xxv. 175 ; Liebig, ibid. xxv. 190. 2 Righini, ibid. x. 359 ; Geissler, ibid, xxxvi. 331. 3 Winkler, Repcrt. Pharm. Ixvii. 1, 56. 4 Jahresb. Chem. iv. 519. 6 Loc. cit. ; Ittner, ibid. xxiv. 395. 6 Ann. Chem. Pharm. Ixxxv. 183. 7 Muller and Limpricht, ibid. cxi. 136. 132 AKOMATIC COMPOUNDS. or plienylhydroxy 'acetic acid, C C H 5 .CH(OH)C0 2 H, the formation of which, however, cannot be taken as a proof of the presence of the nitril, for this acid is also formed when a mixture of hydrochloric acid, hydrocyanic acid and benzaldehyde, is heated to boiling. Fileti, however, supplied the proof by showing that phenyl- ethylamine, C 6 H 5 .CH 2 .CH 2 .NH 2 , is formed by the action of zinc and hydrochloric acid on an alcoholic solution of crude oil of bitter almonds or of the cherry-laurel, while a mixture of benz- aldehyde and hydrocyanic acid subjected to the same treatment yielded methylamine. 1 2086 Oil of bitter almonds is prepared on the large scale by distilling the pressed residue of bitter almonds with water. In order to get all the amygdalin into solution and obtain the best yield of oil, Pettenhofer brings 12 parts of the roughly powdered mass into 100 120 parts of boiling water, keeps it at the boiling-point for 15 30 minutes, and after cooling adds 1 part of the powder stirred up with 6 7 parts of water, and then rapidly distils. 2 The aqueous distillate contains some oil in solution, which is removed by a subsequent distillation. Pettenhofer obtains a yield of 0*9 per cent, of oil of bitter almonds on the pressed residue, while on the large scale the yield is in this way 074 1'67 per cent, or 0*42 0'95 parts in 100 of bitter almonds. The great variation in these numbers is partly accounted for by the varying amounts of amygdalin present, but is also due to the admixture of sweet almonds. 3 Some manufacturers free the oil from hydrocyanic acid ; the purified oil, however, oxidizes much more readily than when in the crude state, so that others add hydrocyanic acid and warm gently 4 in order to make it keep better, the nitril, which will be described under Phenylhydroxyacetic acid, being formed. Oil of bitter almonds is chiefly employed in perfumery, and as a flavouring, for which, however, it must be used with care. Extracts of bitter almonds and of cherry-laurel are used in medicine. Benzaldehyde can be obtained in many other ways, some of which have been already mentioned under the benzyl com- pounds. Dumas and Peligot obtained it by oxidation of cinnamic acid, C G H 5 .CH=CH.C0 2 H; 5 Muller prepared it in a similar 1 (7az. Chim. Itnl. viii. 446. 2 Ann. Chem.. Pharm. cxxii. 77. 3 Fliickiger and Hanbury, Pharmncographia, 2nd ed. 250. 4 'Dustat, Bull, fine. Chim. [2] viii. 459. 5 Ann. Chem. Pharm. xiv. 385. PREPARATION OF BENZALDEHYDE. 133 manner from oil of cinnamon, which contains cinnyl alde- hyde, 1 arid Toel from styrone or cinnyl alcohol, C 6 H 5 .CH= CH.CH 2 .OH. 2 Various other allied aromatic compounds yield benzaldehyde on oxidation. Cannizzaro showed that it is the first product of the oxidation of benzyl alcohol (p. 91), while Guckelberger and Keller found it among the products which are formed by the action of potassium permanganate and sulphuric acid on the albuminoids. 3 It is readily obtained from benzoic acid by reduction carried on in -aqueous solution by means of sodium amalgam, 4 or by heating with stannous oxide. 5 Baeyer obtained it by passing the vapour of benzoic acid or of phthalic acid, C 6 H 4 (C0 2 H) 2 , over heated zinc-dust 6 and Chiozza by the action of copper hydride on benzoyl chloride. 7 Piria found that it is formed by distilling a mixture of calcium benzoate and formate. 8 When the vapour of benzene or toluene, mixed with air, is brought into contact with a glowing spiral of platinum or palla- dium, benzoic acid is formed together with some benzaldehyde, which is formed in larger quantity from xylene (dimethylbenzene) or cymene (methylpropylbenzene.) 9 Toluene, as already men- tioned (p. 6), forms a compound with chromium oxychloride, which is decomposed by water with formation of benzaldehyde. This is also formed when benzyl chloride is boiled with dilute nitric acid or water and lead nitrate, 10 as well as by heating benzidene chloride, C 6 H 5 .CHC1 2 , with silver oxide, mercuric oxide, 11 or alcoholic potash, 12 or with water to 140 160 . 13 When this compound is heated with two molecules of sulphuric acid to 30, hydrochloric acid is evolved and a syrupy liquid formed, which is decomposed by water into sulphuric acid and benz- aldehyde. 14 On the small scale benzaldehyde is best prepared by gradually heating benzidene chloride to 130 with the necessary amount of anhydrous oxalic acid : C 6 H 5 .CHC1 2 + C 2 H 2 O 4 = C 6 H 5 .CHO + CO + CO 2 + 2HC1. 1 Journ. Prakt. Chem. xviii. 385. 2 Ann. Chem. Pharm. Ixx. 5. 3 Ibid. Ixiv. 60 ; Ixxii. 86. * Kolbe, ibid, cxviii. 122. 5 Dusart, Compt. Rend. Iv. 448. 6 Ann. Chem. Pharm. crl. 296. 7 ibid. Ixxxv. 232. 8 Ibid. c. 105. 9 Coquillon, Compt. Rend. Ixxvii. 444 ; Ixxx. 1089. 10 Grimaux and Lauth, Bull. Soc. Chim. [2] vii. 106. ^ Gerhardt, Traite Chim. iv. 721. 12 Cahours, Ann. Chem. Pharm. Suppl. ii. 253. 13 Limpricht, ibid, cxxxix. 319. 14 Oppenheim, Ber. Dcutsch. Chem. Ges. ii. 213. 240 134 AROMATIC COMPOUNDS. The residue is distilled under diminished pressure, and the aldehyde purified by a single rectification. 1 2087 Benzaldehyde is manufactured by boiling 2 parts of benzyl chloride with 3 parts of lead nitrate, or better, copper nitrate, and 10 parts of water for several hours in an apparatus connected with an inverted condenser, the operation being conducted in a current of carbon dioxide ; half the liquid is then distilled off, and the oil separated from the water. It is obtained from benzidene chloride by heating it under pressure in an iron vessel with caustic soda. According to Espenschied it is possible to heat without pressure in an apparatus connected with an inverted condenser if milk of lime be used, or if whitening, or some other finely-divided insoluble substance, be added and the whole stirred into an emulsion, which boils at a higher temperature and thus facilitates the decomposition of the chloride. Jacobsen recommends a process in which benzidene chloride is heated with glacial acetic acid and zinc chloride, benzaldehyde and acetyl chloride being formed ; the necessary amount of water is then allowed to flow in, and the acetic acid which is formed, recovered. 2 The benzaldehyde thus obtained, which always contains chlorine compounds, is used in the colour industry. The pure compound may be obtained from it by preparing the double sulphite, which has already been mentioned, and decomposing this with caustic soda solution. Properties. Benzaldehyde is a colourless, strongly refractive liquid which has a well known characteristic smell and a burn- ing aromatic taste. It dissolves in more than 300 parts of water ; 3 boils at 179, and has a specific gravity of T0636 at and of 1'0504 at 15. In the pure state it rapidly oxidizes in the air and is also oxidized by boiling with chromic acid solution, manganese dioxide and sulphuric acid, or freshly precipitated ferric oxide. 4 It is, however, only slowly attacked by strong, boiling nitric acid ; the red, fuming acid only yields benzoic acid, but when mixed with sulphuric 'acid gives substitution products. 5 It differs from the aldehydes of the fatty series in not reducing an alkaline copper solution. 6 1 Anschiitz, Liebig's Ann. ccxxvi. 18. 2 Ber. Dcutsch. Chem. Ges. xiii. 2013 ; xiv. 1425. 3 Fliickiger, Jahresb. Chem. 1875, 182. 4 Grager, Ann. Chem. Pharm. cxi. 124. 8 Lippmann and Hawliczek, Ber. Dcutsch. Chem. Ges. ix. 1463. 6 Tollens, ibid. xiv. 1950. BENZALDEHYDE. 135 It is converted into benzyl alcohol by treatment with sodium amalgam and water; hydrobenzoin is simultaneously formed, together with the isomeric isohydrobenzoin C 14 H 12 (OH) 2 , which compounds, together with benzoin, C 6 H 5 .CH(OH)CO.C 6 H 5 , obtained by heating benzaldehyde with alcoholic potassium cyanide solution, will be subsequently described. Benzaldehyde is not poisonous ; when taken internally it appears in the urine as hippuric acid ; l it is not decomposed when heated to dull redness, but is decomposed, chiefly into benzene and carbon monoxide, when passed through a tube filled with pumice stone and heated to bright redness. 2 Benzaldehyde readily combines with other carbon compounds with elimination of water and is therefore largely employed, both on the small and large scale, for the synthesis of con- densation products, which will be subsequently described. Only a few of the most important reactions will be mentioned here. (1.) When benzaldehyde is heated with sodium acetate and acetic anhydride, cinnamic acid, C 6 H 5 .CHz=OH.CO 2 H, is formed. The homologues of this acid are prepared in an analogous manner from the other fatty acids. (2.) Aromatic ke tones are easily obtained by the con-- densation of a fatty ketone with benzaldehyde; thus ordinary acetone yields methylcinnyl ketone, CH 3 .CO.CH=CH.C 6 H 5 , which is converted by the further action of benzaldehyde into dicinnyl ketone or cinnamone, CO(CHz=CH.C 6 H 5 ) 2 . (3.) When benzaldehyde is heated with aniline and zinc chloride, diamidotriphenylmethane, C 6 H 5 .CH(C 6 H 4 .NH 2 ) 2 , is obtained ; if dimethylaniline be employed, the base, G 6 H 5 .CH (C 6 H 4 .N.(CH 3 ) 2 ) 2 , is formed, and this yields on oxidation the colouring matter known as benzaldehyde-green or malachite- green. (4.) Benzaldehyde combines with the nitroparaffins to form aromatic nitro-olefines, such as phenylnitro-ethylene, C 6 H,. CH=CHN0 2 , etc. 1 Frerichs and Wohler, Ann. Chcm. Pharm.Ixv. 337. 2 Barreswill and BouJault, ibid. lii. 360. 136 AROMATIC COMPOUNDS. BENZIDENE COMPOUNDS. 2088 Benzaldehyde, like other aldehydes, behaves as the oxide of a dyad radical, which is called benzylene, benzylidene or benzidene. As in all analogous cases, the corresponding alcohol cannot be prepared, but ethers, ethereal salts, and other derivatives are known. Benzidene diethyl ether, C 6 H 5 .CH(OC 2 H 5 ) 2 , was obtained by Wicke by the action of benzidene chloride on sodium othylate. It is a liquid which possesses a pleasant smell resembling that of the geranium, and boils at 222. Wicke has also prepared various other ethers. 1 Benzidene dichloride, C 6 H 5 .CHC1 2 . Cahours prepared this compound by the action of phosphorus pentachloride on oil of bitter almonds 2 and named it chlorobenzol, a name which was subsequently changed into chloride of oil of bitter almonds and finally into benzal chloride (benzaldehyde chloride), which is still employed. It is also obtained by treating benzaldehyde with carbonyl chloride or succinyl chloride : 3 x cci 2X x co x C 6 H 5 .CHO + G 2 H 4 < > = C 6 H 5 .CHC1 2 + C.H/ )o. XX) / X CCK It is, however, most readily prepared by passing chlorine into boiling toluene until it has gained 75 per cent, in weight and then purifying the product by fractional distillation. 4 It is a colourless liquid which boils at 206 207 and has a specific gravity of T295 at 16. 5 In the cold it has only a feeble smell, but when heated it gives off a penetrating vapour which produces a flow of tears. It is manufactured and employed for the preparation of benzaldehyde. Benzidene, dibromide, C 6 H 5 .CHBr 2 , is formed by the action of phosphorus pentabromide on benzaldehyde ; it is a powerfully 1 Wicke, Ann. Chem. Pharm. cii. 363. 2 Ann. Chim. Phys. [3] xxiii. 329. 3 Rembold, Ann. Chem. Pharm. cxxxviii. 189. 4 Beilstein and Kuhlberg, ibid, cxlvi. 322. 5 Hiibner and Bente, Ber. Deutich. Chem. Ges. vi. 804. BENZIDENE COMPOUNDS. 137 refractive liquid, which can only be distilled without decomposi- tion under considerably reduced pressure. 1 Bcnzidcne di-iodide, C 6 H 5 .CHI 2 . Geuther and Cartmell, by the action of hydriodic acid gas on benzaldehyde, obtained a peculiar compound, which they named benzaldehyde oxy iodide, C 21 H 18 I 4 ; it forms colourless, rhombic tablets, which melt at 28 and rapidly become coloured dark in the light. It smells exactly like cress, and can be volatilized with steam, yielding a vapour which attacks the eyes and nose most violently, the dn caused being greater and more enduring than that pro- luced by acrolein. When it is heated with silver nitrate solution, smell of benzaldehyde is produced. 2 The constitution of this body, the formula of which can be [pressed as C 6 H 5 .CHO + 2C 6 H 5 .CHI 2 , is unknown. Benzidene diacetate, C 6 H 5 .CH(C 2 H 3 2 ) 2 . Wicke obtained this nnpound by the action of silver acetate on benzidene chloride ; 3 is also formed when benzaldehyde is heated with acetic ihydride, 4 and crystallizes from ether in small, monoclinic iblets or in twins, which have the swallow-tail form of crystals )f gypsum. It melts at 45 46, 5 and boils at 220 . 6 Wicke has also prepared some other ethereal salts of mzidene. Potassium benzidene sulphite, C 6 H 5 .CH(OH)S0 3 K. This )mpouiid, which was earlier called the bisulphite of benz- ildehyde-potash, was obtained by Bertagnini in crystals by ^itating benzaldehyde with a concentrated solution of acid )tassium sulphite. 7 It crystallizes from hot, dilute alcohol in mg plates, which are slightly soluble in cold alcohol, readily in rater, but are almost insoluble in a concentrated solution of acid )tassium .sulphite. It is decomposed by simply boiling with iter, more readily by acids or alkalis, with separation of benz- ildehyde, which can thus be obtained pure (p. 134). Sodium benzidene sulphite, C 6 H 5 .CH(OH)SO 3 Na + H 2 O, forms tall crystals, and behaves like the potassium salt. Ammonium benzidene sulphite, C 6 H 5 .CH(OH)S0 3 NH 4 + H 2 O. irtagnini, on shaking benzaldehyde with a concentrated solu- tion of acid ammonium sulphite, observed an evolution of heat id obtained a clear solution from which no crystals separated out. 1 Michaelson and Lippmann, Ber. Dcutsch. Chem. Ges. Suppl. iv. 113. 2 Ann. Chem. Pharm. cxii. 20. 3 Ibid. cii. 368. 4 Geuther, ibid. cvi. 251 ; Hiibner, Zcitschr. Chem. 1867, 277. s Perkin, ibid. 1868, 172. 6 Neuhof, Ann. Chem. Pharm. cxlvi. 323. 1 Ibid. Ixxxv. 183. 138 AROMATIC COMPOUNDS. Otto, however, obtained the compound in crystals by mixing alcoholic solutions of sulphur dioxide and hydrobenzamide ; a precipitate is formed consisting of microscopic needles which are slightly soluble in alcohol, readily in water, and separate from the latter in transparent crystals containing three molecules of water. 1 Benzaldehyde does not form an analogous compound with acid aniline sulphite, but a very stable substance of the empirical formula, 2C 7 H 6 O + 2C 6 H 7 N + S0 2 , is produced, and crystallizes from water in long, flat needles. 2 Benzidene sulphide, C H 5 .CHS. Cahours prepared this com- pound by heating benzidene chloride with an alcoholic solution of potassium hydrosulphide and named it sulphobenzene. 3 It was then further investigated by Fleischer 4 and Bottinger. 5 It crystallizes from hot alcohol in nacreous plates and from ether in transparent, four-sided prisms, melting at 70 71. On heating with caustic potash it yields benzyl hydrosulphide, benzyl disulphide and some benzoic acid, and on dry distillation gives stilbene, C 14 H 12 , tolallyl sulphide, C U H 10 S, arid thionessal, C 23 H 20 S - Pardbenzidene sulphide, (C 6 H 5 .CHS) n . By the action of am- monium sulphide on an alcoholic solution of benzaldehyde, Laurent obtained a compound of this composition, which he called sulphobenzoyl hydride (hydrure de sulfobenzo'ile), and de- scribed as a powder consisting of microscopic granules, which became soft at 90 95, and, after careful fusion, solidified to a transparent mass. It is odourless, but imparts to the hands a very repulsive, adhering alliaceous odour. 6 On dry distillation it yields the same products as benzidene sulphide. The compound which Klinger obtained by passing sulphuretted hydrogen into a solution of benzaldehyde in absolute alcohol and named a-benzothio-aldehyde, is probably identical with this body. It is amorphous, softens at 80 85, and is converted by acid chlorides into P~~benzothio-aldehyde, which is slightly soluble in alcohol, readily in hot glacial acetic acid, and crystallizes in lustrous white needles, melting at 225 226 . 7 This compound is most readily obtained by dissolving 1 Neuhof, Ann. Chem. Pharm. cxii. 308. 2 Schiff, ibid. cxl. 130 ; ccx. 128. 3 Ann. Chim. Phys. [3] xxiii. 333 ; Ann. Chem. Pharm. Ixx. 40. 4 Ibid. cxl. 234. 5 Ber. Deutsch. Chem. Gcs. xii. 1053. 6 Ann. Chim. Phys. [3] i. 292 ; Ann. Chem. Pharm. xxxviii. 320 ; see also Roehleder, ibid, xxxvii. 346. 7 Ber. Deutsch. Chem. Ges. ix. 1893. BENZALDOXIME. 139 amorphous benzothio-aldehyde in hot benzene and adding a small quantity of iodine also dissolved in benzene ; lustrous needles of the formula C 6 H 5 .CHS + C 6 H 6 soon separate out, which lose benzene and become opaque at 125 130 . 1 a-Benzothio-aldehyde is also formed, together with ammonia, when an alkaline solution of benzothiamide, C 6 H 5 .CS.NH 2 , is treated with sodium amalgam. 2 Both thio-aldehydes, when heated with copper dust, yield stilbene, C 14 H 10 , as the chief product, and the amorphous com- pound on fusion with caustic potash yields the same products as benzidene sulphide (Bottinger). Klinger was unable to convert the latter, which he considered to be y-lenzotJiio-aldehyde, into the /3-compound by the action of acetyl chloride or iodine ; the ^-compound is probably a polymeric modification, and is best called parabenzidene sulphide. 2089 Benzidenoxime, or Benzaldoxime, C 6 H 5 .CH.NOH, is formed when benzaldehyde and sufficient alcohol to form a clear solution are added to an aqueous solution of hydroxylamine hydrochloride containing an excess of sodium carbonate : C 6 H 5 .CHO + H 2 N.OH = C 6 H 5 .CH=N.OH + H. 2 O. After twenty-four hours the mixture is extracted with ether id the residue, after the evaporation of the ether, rectified. Benzaldoxime is an oily liquid, which boils above 220 with :ial decomposition, and is decomposed by hydrochloric acid ito the substances from which it is formed. On treatment with )holic caustic soda it gives the compound C 6 H 5 .CH.NONa, which crystallizes from water in small, lustrous plates. By the action of methyl iodide on this, the methyl ether, C 6 H 5 .CH, NOCH 3 , is obtained as a light, oily liquid, which has a very pleasant, fruity odour, and boils at 190 192; other ethers have been prepared in a similar manner. 3 Hydrobcnzamide, or Tribenzidenediamine, N 2 (CH.C 6 H 6 ) 8 . Acet- aldehyde combines directly with ammonia to form aldehyde ammonia, CH 3 .CH(OH)NH 2 , but benzaldehyde behaves in a completely different manner ; three molecules of the latter lose all their oxygen, which combines with the hydrogen of two molecules of ammonia, the place of this being taken by the benzidene groups. 1 Ber. Deutsch. Chem. Ges. x. 1877. 2 Berathsen, ibid, x . 36. 3 Petraczek, ibid. xv. 2783 ; xvi. 823. 140 AROMATIC COMPOUNDS. Hydrobenzamide is slowly formed when benzaldehyde is allowed to stand in contact with aqueous ammonia ; l more rapidly when the two are heated together. 2 Benzaldehyde absorbs dry ammonia, and if the product of this absorption be allowed to stand in a vacuum, water is lost and hydrobenzamide remains ; 3 it is also formed when benzidene- dichloride is allowed to stand for some months with aqueous ammonia. 4 It is readily soluble in alcohol and ether, and crystallizes in lustrous, rhombic pyramids, melting at 110; very fine crystals may be obtained by pouring an excess of aqueous ammonia on to a mixture of equal volumes of benzaldehyde and ether, and allowing the whole to stand. 5 It is tasteless, but its alcoholic solution has, according to Laurent, a faint taste of burnt almonds. On boiling with alcohol it slowly decomposes into ammonia and benzaldehyde ; acids rapidly produce this decom- position. On oxidation with aqueous chromic acid, a large quantity of benzoic acid is formed (Fownes). When it is boiled with caustic potash or heated to 120 130, it is converted into the isomeric amarine, which will be sub- sequently described ; the relation between the two compounds is shown by the following formulae : Hydrobenzamide. Amarine. C 6 H 5 .CH=N X C 6 H 5 .C.NH >CH.C 6 H 5 . | >CN.C 6 H 5 . C 6 H 5 .CH=N/ C 6 H 5 .C.NH Thiobenzaldine, (0 6 H 5 .CH) 3 S 2 NH. Laurent obtained this compound, the analogue of thialdine (Pt. II. p. 75), by allowing a mixture of crude oil of bitter almonds, ammonium sulphide and ether, to stand for several weeks. It crystallizes in nacreous plates or monoclinic prisms which melt at 125, and impart an unpleasant smell to the skin. When it is boiled with alcohol, sulphuretted hydrogen is given off, while alcoholic potash decomposes it with evolution of ammonia. 6 Benzidcne-aniline, C 6 H 5 .CH=:N.C 6 H 5 . Gerhardt and Laurent obtained this compound by heating benzaldehyde with aniline, 1 Laurent (1836), Ann. Chim. Phys. Ixii. 23 ; Ixvi. 18 ; Ann. Chem. Phann. xxi. 130. 2 Rochleder, ibid. xli. 89. 3 Herzfeld, Ber. Dcutsch. Chem. Ges. x. 1271. 4 Engelhardt, Ann. Chcm. Pharm. ex. 77. 5 Eckmann, ibid. cxii. 175. 9 Ann. Chem. Pharm. xxxviii. 323. CONDENSATION PRODUCTS OF BENZALDEHYDE. 141 and named it benzoylanilide. 1 The same compound is formed, as shown by Schiff, when benzaldehyde is heated with thio- carbanilide : 2 3CS(NHC 6 H 5 ) 2 + 6C 6 H 5 .CHO = 6C 6 H 5 .CH N. C 6 H 5 + CS 2 + 2CO 2 4- H 2 S + 2H 2 O. It is very soluble in alcohol and ether, separating from the latter in warty crystals, and crystallizing from carbon disulphide in yellow needles, which melt at 42, 3 and are volatile with steam. It does not combine with acids, and is partially decomposed on heating into benzaldehyde and aniline. 2090 Benzidene-aniline cyanhydrate, C 6 H 5 .CH^N.C 6 H 5 .CNH. Cech obtained this compound by the action of potassium cyanide on an alcoholic solution of benzaldehyde and aniline or aniline hydrochloride ; it is also formed when hydrocyanic acid is passed into fused benzidene-aniline, and is decomposed into its com- ponents by heat. It crystallizes from carbon disulphide in silky needles, which melt at 82, sublime readily, and are volatile with steam. Benzidenephenylhydrazine, C 6 H 5 .CH:=N.NH.C 6 H 5 , is formed by a violent reaction when benzaldehyde and phenylhydrazine are brought together. It crystallizes from dilute alcohol in monoclinic prisms, which melt at 152*5 and can be volatilized without decomposition. Benzidenediphenylhydrazine, C 6 H 5 .CH = NC.(C 6 H 5 ) 2 , forms small yellow crystals, melting at 122 . 4 Phenylbenzaldehydine, or Benzidene-orthodiamidolenzene, (C 6 H 5 . CH=N) 2 6 H 4 , is formed when a dilute aqueous solution of orthodiamidobenzene hydrochloride is shaken up with benz- aldehyde, the hydrochloride thus obtained being purified by re-crystallization, and the base precipitated with caustic potash. Phenylbenzaldehydine is insoluble in water and crystallizes from alcohol in six-sided prisms, melting at 133 134. Phenylbenzaldehydine hydrochloride, C 20 H 16 N 2 .HC1, crystallizes in colourless prisms which are only slightly soluble in water, and lose hydrochloric acid when their solution is boiled. When the base is heated with ethyl iodide to 100 120, the compound C 20 H 16 N 2 .C 2 H 5 I is formed ; it crystallizes from hot water in colourless, thick prisms, melting at 211 213 . 5 1 Jahresb. Chem. 1850, 488. 2 Ann. Chem. Pharm. cxlviii. 336. 3 Cech, Bcr. Deutsch. Chem. Gfes. xi. 246. 4 E. Fischer, Ann. Chem. Pharm. cxc. 134, 179. 5 Engelbrecht and Ladenburg, Ber. Deutsch. Chem. Ges. xi. 1653, 142 AROMATIC COMPOUNDS. Benzideneparadiamidobenzene, (C 6 H 5 .CHi=:N) 2 C 6 H 4 , is formed by the action of paradiamidobenzene on benzaldehyde ; it crystallizes from alcohol in plates which have a silver lustre, and melt at 140 ; it is decomposed by acids into its components, since only the ortho-diamines form stable basic aldehydines l (Part III. p. 62). Benzidenedimethylparadiamid.obenzene, C C H 5 .CH N.C 6 H 4 .N (CH 3 ) 2 , is readily formed by heating benzaldehyde with di- methylparadiamidobenzene, and crystallizes from hot alcohol in lustrous plates or needles, melting at 93. It is a feeble, di-acid base. 2 Dibenzidene-orthodiamidotoluene, or Tohibenzaldehydine, (C 6 H 5 . CH=N) 2 C 6 H 3 .CH 3 , has been obtained by Ladenburg from orthodiamidotoluene ; it crystallizes in lustrous, monoclinic prisms, melting at 195 '5 ; on oxidation with potassium perman- ganate, it yields dibenzidenediamidobenzoic acid, (C 6 H 5 .CHi=:N) 2 . C 6 H 3 CO 2 H. The hydrochloride, C 21 H 18 N 2 .C1H, crystallizes from hot dilute hydrochloric acid in long needles. When it is heated with ethyl iodide, it is converted into the iodide, C 21 H 18 N 2 .C 2 H 5 I, which crystallizes in thick prisms, and, on treatment with silver oxide, yields the corresponding hydroxide, which remains behind after evaporation of the solution as a strongly alkaline, oily liquid. 3 Dibenzidenemetadiamidotoluene crystallizes from a mixture of ether and alcohol in small lustrous tablets, melting at 122 128. It does not combine with acids, but when heated to 140 150 for a considerable time, it is converted into a base, which Schiff considers to be amarine. 4 Benzidenephenyldiamine, C 6 H 5 .CH(NH 2 )NH(C 6 H 5 ). When benzonitril, C 6 H 5 .CN, is heated with aniline hydrochloride to 220 240, phenylbenzenylamidine 5 is formed, and this is con- verted into the diamine by the action of zinc and dilute acetic acid : NH X NH 2 C 6 H 5 .C^ +2H = C 6 H 5 .CH( \NH.C 6 H 5 X NH.C 6 H 5 . It is very soluble in all solvents, with the exception of water and separates from dilute alcohol in indistinct crystals, melting at Ladenburg, Ber. Deutsch. CJiem. Ges. xi. 599. Calm, ibid. xvii. 2938. Ibid. x. 1126 ; xi. 591, 1648. Ann. Chcm. Pharm. cxl. 98. Bernthsen, Liebig's Ann. clxxxiv. 348. BENZIDENE UREIDES. 143 114"5 115. At a higher temperature it distils without decom- position, and on heating with chloroform and alcoholic potash yields the smell of the carbamines. Benzidenephenylamine hydrochloride, C 13 H 14 N 2 .C1H, crystallizes from water in thick prisms, melting at 223 224'5. 1 Benzidene-acetamide, C 6 H 5 .CH(NH.C 2 H 3 0) 2 , is formed by heating benzaldehyde with acetamide, and crystallizes from hot water in fine silky needles. 2 Benzidene urethane, C 6 H 5 .CH(NH.CO.OC 2 H 5 ) 2 , is formed when hydrochloric acid is added to a mixture of benzaldehyde and ethyl carbamate. It separates from alcohol as a silky crystalline mass, which melts at 171, and can be sublimed. 3 Benzidene ure'ides are formed by heating benzaldehyde with urea, and are split up again into these substances by boiling with water. 4 ,NH.CO.NH 2 Benzidenedi-ure'ide, C 6 H,.CH\ , fine needles. >enzidenetri-ureide, C 6 H 5 .CH< C 6 H 5 .CH ,NH.CO.NH 2 >N CO.NH 2 ' , white powder. NH.CO.NH 2 . NH.CO.NH C 6 H 5 .CH<; \N CO.NH 2 mzidenetetra-ureide, C 6 H 5 .CH<^ , white powder. N_CO.NH 2 ^TH.CO.NH 2 . lUBSTITUTION PRODUCTS OF BENZIDENE COMPOUNDS. 2091 Orthochlordbenzaldehyde, C 6 H 4 C1.CHO. By the action of phosphorus pentachloride on salicylaldehyde, C 6 H 4 (OH)CHO, orthochlorobenzidene chloride, C 6 H 4 G1.CHC1 2 , is obtained as an 1 Bernthsen and Soymanski, Ber. Deutsch. Chem. Gcs. xiii. 917. 2 Roth, Ann. Chem. Pharm. cliv. 72. 3 Bisclioff, Ber. Deutsch. Chem. Ges. vii. 634, 1082. 4 Schiff, Ann. Chem. Pharm. cxl. 115 ; cxlviii. 330 ; cli. 892. 144 AROMATIC COMPOUNDS. oily liquid, which boils at 227 230, and possesses a penetrating smell and a sharp burning taste. When this compound is heated with water to 170, the aldehyde is formed ; it is a liquid which boils at 210, has a sharp smell and taste, and readily oxidizes in the air to orthochlorobenzoic acid. It combines with acid sodium sulphite. 1 Metachlorolwnzaldeliyde is formed when benzaldehyde is chlorinated in presence of a dehydrating agent, such as sul- phuric acid, zinc chloride, aluminium chloride, etc., and is a liquid boiling at 210 213 . 2 It may also be obtained by heating a hydrochloric acid solution of metamidobenzaldehyde and cuprous chloride to the boiling-point and then gradually adding a solution of sodium nitrite. 3 Parachlorobenzaldeliydc is obtained by boiling parachlorobenzyl bromide with water and lead nitrate in an atmosphere of carbon dioxide. It crystallizes in white tablets, melting at 47'5, which are slightly soluble in cold, more readily in hot water, and readily in alcohol ; it smells like benzaldehyde, readily oxidizes in the air and unites with acid sodium sulphite to form a compound which is only slightly soluble. 4 The product of the action of chlorine on benzidene chloride in presence of iodine is a mixture of ortho- and para-chloro- benzidene chlorides, which boils at 230 237 , 5 and was formerly thought to be the pure para-compound. 6 When it is heated with anhydrous oxalic acid, boiled with lead nitrate, or heated to 170 with water, a mixture of the aldehydes is obtained, boiling at 210 214 ; in the cold it smells like benzaldehyde, but when heated has a very sharp, penetrating odour arid causes a flow of tears. The same mixture is formed, together with ethyl iodide, when benzyl ethyl ether is treated with chlorine in presence of iodine : 7 C 6 H 5 .CH 2 .O.C 2 H 5 + IC1 3 :=C 6 H 4 C1.CHO + C 2 H 5 I + 2HC1. DicUorolenzaldchyde, C 6 H 3 C1,.CHO(C1 : Cl = 3 : 4). Beilstein and Kuhlberg, by the action of chlorine on boiling dichloro- Henry, Bcr. Dculsch. Chcm. Gc.s. ii. 135. Miiller, ibid, xviii. Ref. viii. 660. Jbid. xviii. Ref. '695. Jackson and White, ibid. xi. 1042. Anschiitz, Ann. Chcm. Pharm. ccxxvi. 19. 6 Beilstein and Kuhlberg, ibid, cxlvi. 327. 7 Sintenis, Ber. Deutsch. Chcm. Ges. iv. 699. CHLORINE DERIVATIONS OF BENZALDEHYDE. 145 toluene, obtained a dichlorobenzidene chloride, C 6 H 3 C1. 2 .CHC1. 2 , 1 which boils at 257, and is converted into the aldehyde by heating with water to 200. It is soluble in boiling water, more readily in alcohol, and crystallizes in fine needles, which melt at 68, volatilize in steam, and combine with acid sodium sulphite. 2 A compound, which is probably identical with this, is ob- tained by the further chlorination of metachlorobenzaldehyde in presence of a dehydrating agent, and is described as a liquid, iling at 240 243 . 3 a-Trichlorolenzaldehyde, C 6 H 2 C1 3 .CHO. The further chlori- ion of a-trichlorotoluene yields a-trichlorobenzidene chloride, jCl 3 .CHCl 2 , which boils at 280 281, and solidifies be-' >w in fine needles. 4 The aldehyde obtained by heating it with water to 260 is insoluble in water, crystallizes in very fine needles, which melt at 112 113, and is volatile with steam. 5 ft-Trichlorobenzaldehyde. The /3-trichlorobenzidene chloride ined from /3-trichlorotoluene, melts at 84, boils at 280, and Ids the /3-trichlorobenzaldehyde which melts at 90 (Seelig). Tetrachlorobenzidene chloride, C 6 HC1 4 .CHC1 2 , has been prepared >m tetrachlorotoluene ; it is a liquid, which boils at 305 306, and is decomposed by water at 250. The aldehyde thus formed not been further investigated. 6 Pentachlorobenzidene chloride, C 6 C1 5 .CHC1 2 , is formed by the ntinued action of chlorine on benzidene chloride in presence iodine and finally of antimony chloride. It crystallizes from ohol in long flat plates, melts at 109, boils at 334, and is not ttacked 'by water even at 300 . 7 Orthobromobenzaldehyde, C 6 H 4 Br.CHO, has been prepared by boiling orthobromobenzyl bromide with water and lead nitrate ; it is a heavy, oily liquid, which oxidizes very rapidly in the air. 8 Mctabromobenzaldehyde, C 6 H 4 Br.CHO, is a liquid which does not solidify in a freezing mixture (Jackson and White), boils at 233 236, and may be prepared by the bromination of benzaldehyde in presence of a dehydrating agent (Muller). Parabromobenzaldehyde, C 6 H 4 Br.GHO, crystallizes in long white needles, melting at 57. Ann. Chem. Pharm. cl. 291. 2 Ibid. clii. 228. Ber. Dcutsch. Chem. Gcs. Kef. xviii. 25. Ann. Chem. Pharm. cl. 299 ; Seelig, Ber. Dcutsch. Chem. Ges. xviii. 420. Ibid. ; Ann. Chem. Pharm. clii. 238. Ibid. cl. 303. 7 1Ud . cl. 306. Jackson and White, Amer. Chem. Journ. iii. 32. 146 AROMATIC COMPOUNDS. Para-iodobenzaldehyde, C 6 H 4 I.CHO, also forms needles, melting at 73 (Jackson and White). 2092 Orthonitrobenzaldehyde, C 6 H 4 (N0 2 )CHO, is formed in small quantity, together with the m eta-compound, by the action of a mixture of nitric and sulphuric acids on benzaldehyde. 1 It may, however, be more readily prepared from orthonitrocinnamic acid, C 6 H 4 (NO 2 )CH=CH.C0 2 H. When the ethyl ether of this acid is dissolved in concentrated nitric acid and treated with sodium nitrite, the temperature of the mixture not being allowed to rise more than a few degrees, a compound is formed which contains a nitric acid residue in the side chain. The mixture is poured, after having stood for some hours, into water, and the oil which separates out distilled in steam, sodium carbonate being added from time to time ; the distillate consists of water and pure orthonitrobenzaldehyde. 2 It can be still more conveniently prepared by oxidizing orthonitrocinnamic acid with potassium permanganate in alkaline solution (Friedlander and Henriques). The solution must be cooled with ice and shaken up with benzene at short intervals in order to remove the aldehyde from the further action of the oxidizing agent. The benzene solution is then evaporated, the aldehyde remaining behind. 3 It is readily soluble in alcohol, slightly in water, and crystal- lizes in long, light yellow needles, melting at 46, which smell like benzaldehyde in the cold, but give off a penetrating vapour when heated. It forms a readily soluble compound with acid sodium sulphite, which crystallizes in small, lustrous plates ; concentrated caustic soda solution decomposes it completely into orthonitrobenzyl alcohol and orthonitrobenzoic acid. When a little water and caustic soda are added to its solution in acetone, indigotin, C 16 H 10 N 2 O 2 , the colouring matter of indigo, separates out after a short time. 4 Orthonitrobenzaldoxime, C 6 H 4 (NO 2 )CH.NOH. Gabriel and Meyer, by the action of hydrochloric acid and amyl nitrite on amidorthonitrophenylacetic acid, obtained a diazo-compound : NH 2 .C 6 H 3 (N0 2 )CH 2 .C0 2 H + 2NO 2 H + HC1 = C1N = NC 6 H 3 (NO 2 )CH 2 NO + CO 2 + 3H 2 O. 1 Rudolph, Ser. De,utsch. Chem. Gcs. xiii. 310. . 2 Friedlander and Henriques, ibid. xiv. 2801. 3 Einhorn, ibid. xvii. 119. 4 Baeyer and Drewsen, ibid. xv. 2857. METANITROBENZ ALDEHYDE. 147 On heating with alcohol, this is converted into nitroso- methylnitrolenzene, C 6 H 4 (NO 2 )CH 2 NO, this being decomposed by oxidation with formation of nitrogen monoxide and orthonitro- benzaldehyde, which was first prepared pure by this method. 1 This substance was subsequently recognised as orthonitrobenzal- doxime and prepared from the aldehyde and hydroxylamine. 2 crystallizes from hot water in hair-like needles, which melt 95, have a sweet taste, and form a yellow solution in alkalis, methyl ether, C^H/NCgCH.NOCHg, is formed by heating to 100 with caustic potash, methyl alcohol and methyl iodide ; is only slightly soluble in water, readily in alcohol, and stallizes in silky needles, melting at 58. Metanitrobcnzaldehyde, C 6 H 4 (NO 2 )CHO, was first obtained by jrtagnini by the action of a mixture of nitric and sulphuric ;ids on benzaldehyde. 3 In order to prepare it, 1 part of the ir is dissolved in a mixture of 5 volumes of fuming nitric with 10 volumes of sulphuric acid, the temperature being :ept below 15. The nitro-compound is precipitated by water, shed and re-crystallized from dilute alcohol. 4 It forms lustrous rhite needles, melting at 58, 5 smells like benzaldehyde when )ld, but gives off a penetrating vapour when heated, and combines with the acid sulphites of the alkalis (Bertagnini), as fell as with acid aniline sulphite 6 to form crystalline compounds. Metanitrobenzidene chloride, C 6 H 4 (NO 2 )CHC1 2 , is obtained by action of phosphorus pentachloride on the aldehyde ; it stallizes from alcohol in needles or small thin plates, melting 65. 7 Metanitrobenzidene bromide, C 6 H 4 (NO 2 )CHBr 9 , is formed by heating the aldehyde with bromine to 140, and crystallizes in microscopic tablets, melting at 101 102 . 8 Metanitrobenzaldoxime, CgH/NO^CH.NOH, was first obtained from metanitro-amidophenylacetic acid and was called nitroso- methylmetanitrobenzene? It is readily formed by the combination of hydroxylamine 1 Ber. Deutsch. Chem. Ges. xiv. 832, 2332. 2 Gabriel, ibid. xv. 3057. 3 Ann. Chem. Pharm. Ixxix. 260. 4 Widmann, Ber. Deutech. Chem. Ges. xili. 678 Henriques, ibid. xiv. 2801. 5 Lippmann and Hawliczek, ibid. ix. 1463. 8 Sctnff, Ann. Chem. Pharm. cxcv. 301. 7 Widmann, Ber. Deutsch. Chem. Ges. xiii. 676. 8 Wachendorff, Ann. Chem. Pharm. clxxxv. 266. 9 Gabriel, Ber. Deutsch. Chem. Ges. xv. 834. see also Friedlander and 148 AROMATIC COMPOUNDS. with metanitrobenzaldehyde, 1 and crystallizes from water in long, flat needles, melting at 118 119. Its methyl ether also forms flat needles and melts at 63 63'5. Trinitrohydrobenzamide, N 2 (CH.C 6 H 4 .NO. 2 ) 3 , is formed by the action of ammonia on metanitrobenzaldehyde ; it is insoluble in water and ether, and only slightly soluble in boiling alcohol, from which it separates out in flocks consisting of very thin needles. When it is heated to 125 or boiled with dilute caustic potash solution, it is converted into the isomeric trinitro-amarine, which forms warty crystals and has a feeble alkaline reaction. Its salts are difficultly soluble and have a very bitter taste (Bertagnini). Paranitrobenzaldehyde, C 6 H 4 (N0 2 )CHO, is prepared by boiling 10 parts of paranitrobenzyl chloride with 60 parts of water, 14 parts of lead nitrate, and 10 parts of nitric acid of sp. gr. T3, for several hours. If the solution be more dilute, nitrobenzyl alcohol is formed instead of the aldehyde. The product is shaken out with ether and the aldehyde separated by means of acid sodium sulphite. 2 Paranitrobenzaldehyde may also be readily obtained by the oxidation of paranitrocinnamic acid. 3 It crystallizes from hot water in thin prisms, often an inch in length, which melt at 106, have a characteristic smell, and do not volatilize readily in steam. Its compound with acid sodium sulphite is readily soluble in water and crystallizes in small iridescent plates. It is not attacked to an appreciable extent by boiling nitric acid, which must not, however, be too concentrated, but is quantitatively converted into parahydroxybenzoic acid by chromic acid. 4 When it is heated with aniline hydrochloride and zinc chloride, paranitrodiamidotriphenylmethane, CH(C 6 H 4 .NH 2 ) 2 C 6 H 4 .N0 2 , is formed, which on reduction yields paraleucaniline, CH(C 6 H 4 .NH 2 ) 3 . It is oxidized by mercuric oxide to pararosani- line, C(OH)(C 6 H 4 .NH 2 ) 3 (Fischer and Greiff). Paranitrobenzidene chloride, C 6 H 4 (NO 2 )CHC1 2; is formed by the action of phosphorus pentachloride on paranitrobenzalde- hyde ; it crystallizes from alcohol in short, well-formed prisms, melting at 46. 5 Paranitrobenzidene bromide, C 6 H 4 (NO 2 )CHBr 2 , is formed by 1 Gabriel, Ber. Dcutscli. Chem. Gcs. xv. 3061. 2 O. Fischer and Greiff, ibid. xiii. 669. 8 Baeyer, ibid. xiv. 2317 ; Friedlander, ibid. xiv. 2577 ; Easier, ibid. xvi. 2714. 4 0. Fischer, ibid. xiv. 2525. 5 Zimmermann and Miiller, ibid, xviii. 996. ORTHAMIDOBENZALDEHYDE. 149 heating paranitrotoluene with bromine to 140, and crystallizes from alcohol in needles or small rectangular plates, melting at 82-5 . 1 Both compounds are converted into pararosaniline when ted with aniline. 2 Paranitrdbenzaldoxime, C 6 H 4 (N0 2 )CH=iN.OH, crystallizes m hot water in long needles, melting at 128'5. 3 2093 Orthamidobenzaldehyde, C 6 H 4 (NH 2 )CHO, was first ob- ined by Gabriel in small quantities by oxidizing orthamido- nzaldoxime with an acid solution of ferric chloride. 4 Fried- lander and Henriques found that orthonitrobenzaldehyde is converted by the action of tin and acetic acid into anthranil, 5 C 7 H 5 NO, a compound which stands to anthranilic acid or orthamidobenzoic acid in the same relation as lactimide to a-amidopropionic acid (Part II. p. 142). This is converted into orthamidobenzaldehyde by heating with ferrous sulphate .d ammonia : 6 C 6 H 4 | + 2H = 6 H \CO CHO. The latter can also be obtained directly in the same way from thonitrobenzaldehyde. 7 It is very soluble in alcohol, less lily in water, forming a yellow solution, and crystallizes in strous plates, which are volatile with steam, their vapour sessing a penetrating smell resembling that of an indigo vat. [t melts at 39 40, and solidifies on cooling in a crystalline lass; at a higher temperature a portion distils without de- >mposition, while the remainder is converted into a dark jllow, resinous mass. It can be heated with caustic soda )lution or ammonia without undergoing any change ; dilute tineral acids, however, readily convert it into an amorphous mdensation product. When it is heated with acetic anhydride, acdylorthamidolenzaldehyde, C 6 H 4 (NH.C 2 H 3 O)CHO, is formed; it crystallizes from hot water in long white needles, melting at 70 71. Orthamidobenzaldoxime, C 6 H 4 (NH 2 )CH=N.OH, is formed by 1 Wachendorft', Ann. Chem. Pharm. clxxxv. 268. 2 Zimmermarm and Miiller, Ber. Deutsch. 'Chem. Ges. xvii. 2936. 3 Gabriel and Herzberg, ibid. xvi. 2000. 4 Ber. Deutsch. Chem. Ges. xv. 2004. 5 Ibid. xv. 2105. 6 Friedlander, ibid. xv. 2572. 7 Friedlander and Coining, ibid. xvii. 456. 241 150 AROMATIC COMPOUNDS. the reduction of the corresponding nitro-compound with am- monium sulphide, and crystallizes from hot water in long, flat, lustrous needles, melting at 132 133 . 1 Metamidobenzaldeliyde, C 6 H 4 (NH 2 )CHO, is obtained hy re- ducing metanitrobenzaldehyde with ammonia and ferrous sulphate, and distilling the product with steam ; it is a yellow, oily liquid, which solidifies at low temperatures and yields amorphous condensation products with even greater readiness than the ortho-compound (Friedlander and Gohring). Metamidobenzaldoxime, C 6 H 4 (NH 2 )CH:=N.OH, is formed when a solution of metanitrobenzaldoxime in caustic soda is added to a hot solution of ferrous sulphate saturated with ammonia, the blue-black ferrous hydroxide being converted into brown ferric hydroxide. The filtrate is rendered faintly acid with hydrochloric acid, treated with ammonia and then extracted with ether; the residue left on evaporation of the ethereal extract consists of metamidobenzaldoxime, which crystallizes from hot benzene in fine, snow-white needles, melt- ing at 88. Oxidation with an acid solution of ferric chloride yields an amorphous, yellow oxidation product of metamido- benzaldehyde. 2 Paramidobenzaldehyde, C 6 H 4 (NH 2 )CHO, has been obtained as a decomposition product of its aldoxime ; it crystallizes from water in small, indented plates, which melt at 69'5 71 '5, but soon change into a modification insoluble in water and melting at a higher temperature. When heated with acetic anhydride and sodium acetate, it is converted into acetylparamidobenzalde- hyde, C 6 H 4 (NH.C 2 H 3 O)CHO, which crystallizes from hot water in long, lustrous needles, melting at 155. Paramidobenzaldoxime, C 6 H 4 (NH 2 )CHi=N.OH, is formed by the action of ammonium sulphide on paranitrobenzaldoxime, and crystallizes from hot water in yellow tablets, melting at 124. It dissolves in an excess of hydrochloric acid, forming a solution which soon deposits dark red needles with a blue re- flection, while hydroxylamine remains in solution. Caustic soda decomposes the red compound, paramidobenzaldehyde or its con- densation products being set free. 3 Dimethylparamidobenzaldehydc, C 6 H 4 .N(CH 3 ) 2 CHO. When zinc chloride is allowed to act on a mixture of chloral hydrate 1 Gabriel and Mayer, Ber. Deutsch. Chcm. Ges. xiv. 2338. 2 Gabriel, ibid. xvi. 1997. 3 Gabriel and Herzberg, ibid. xvi. 2000, BENZOIC ACID. 151 dimethylaniline, dimethylamidophenylhydroxytrichlorethane is formed, and is decomposed by caustic potash with formation of lethylparamidobenzaldehyde and chloroform or decomposition iucts of these : /CHO C 6 H/ +CHC1 3 . \N(CH 3 ) 2 X N(CH 3 ) 2 The new compound crystallizes in small plates, which melt at 73, readily dissolve in alcohol and hot water, and are volatile with steam. 1 BENZOIC ACID, C 6 H 5 .COOH. 94 The products formed by the dry distillation of gum ben- in 2 are mentioned in writings which date back as far as the sixteenth century. Hieronymus Rosello, who, under the name of Alexius Pedemontanus, published a work, De Secretis, in the year 1557, mentions in it the butter of benzoin, and Libavius in his Alchymia, written in 1595, says that when laser* vel in is distilled, water comes over first, followed by a thick ., " ultima exit instar mannae, gummi." Blaise de Vigenere, whose TraiU de feu et du sel, appeared after his death in 1608, ys that with a strong fire " infinies petitcs aiguilles et fila- appear, which must be soon removed because they would otherwise melt like marrow (moelle). About the same period, Turquet de Mayerne in his Pharmacopoea teaches how to obtain flowers of benzoin from the residue by subliming it in an says 1 ments Tir/-\-n 1 r\ 1 Rocssneck, Ber. Deutsch. Chem. Ges. xviii. 1516 ; xix. 365. 2 This resin is obtained by means of incisions in the bark of Styrax Benzoin, a tree indigenous to Java and Sumatra. It is sent into the European market from the latter island, and this was formerly the only source from which it could be obtained. A highly valued variety is now sent from Siam, but nothing further is known as to its origin. It was formerly counted as one of the costly spices. It is first mentioned by Ibn Batuta, who travelled in the East about the years 1325 1349, and describes it under the name of Luban Javvi (incense of Java). The latter word was then the name of Sumatra, and the \rnbs designated by it the whole archipelago, as well as the products obtained from it. The Arabic name gradually became corrupted into banjawi, benjui, benzui, benzoe, benzoin, and in English also benjamin or gum benjamin, which is now the name in general commercial use (Fliickiger and Hanbury, Pharmacographia, 2nd ed. p. 403). 3 Laser is the name of a Persian and Indian product on which a tax was imposed at the Roman customs-house in Alexandria during the second century of our era. Some suppose that it was asa foetida, while benzoe was also called asa dulcis. 152 AROMATIC COMPOUNDS. earthen vessel to which a cap of paper has been adapted, or by heating it mixed with sand in a retort, and since that time flores benzoes have been an ordinary pharmaceutical prepara- tion. A solution of the resin in alcohol was also in use ; mixed with lead acetate it was employed as a choice cosmetic under the names of magisterium lenzoes or lac virginis. Ehrenfried Hagendorn, a physician of Gorlitz, in 1671 found in this a salt which was identical with flowers of benzoin, both in smell and taste. Lemery in 1675 also remarked on the acid nature of this substance, saying, " les fleurs de lenjoin ont une addiU fort agrdable" a fact which was further proved by the researches of Scheele, who showed, in 1775, that the flowers of benzoin could be more economically obtained by digesting the resin with slaked lime and water for some hours, boiling and adding hydrochloric acid to the filtrate; finally, Lichtenstein in 1782 conclusively proved that they are an acid. The correct composition of benzoic acid was determined in 1832 by Liebig and Wohler, 1 who showed that it is a compound of the radical benzoyl, C 7 H 6 O (p. 89). Mitscherlich, on the other hand, showed in 1834 that it is decomposed into carbon dioxide and benzol on heating with milk of lime, and looked upon it as a carbonic acid derivative of benzol ; Liebig opposed this view, as he considered the benzol to be merely a product of the destruction of the benzoic acid ; the latter compound can, however, as was shown somewhat later, be readily prepared synthetically from carbon dioxide and benzol, and we can therefore look upon it as carbonic acid, CO(OH) 2 , in which one hydroxyl has been replaced by phenyl, or as a compound of phenyl with carboxyl. The latter supposition corresponds to that of Berzelius, according to which, benzoic acid is oxalic acid copulated with phenyl, oxalic acid being dicarboxyl. Many varieties of benzoin contain cinnamic acid 2 in addition to benzoic acid and frequently only the former. 3 Both these acids occur, either free or in the form of ethereal salts, together with other aromatic compounds, in Tolu balsam (p. 1), Peru balsam (concerning which Lehmann had already stated in his Dissertation de balsamo peruviano (1709), that on decomposition it yields flowers resembling flowers of benzoin), Mecca balsam (Balsamodendron Opobalsamum et gileadensis), myrrh (B. Myrrlia), 1 Ann. Ohem. Pharm. iii. 249. 2 Kolbe and Lautemann, ibid. cxix. 136 ; Fliickiger, Pharmacographia. 3 Aschoff, Jahrcsb. 1861, 400. OCCURRENCE OF BENZOIC ACID. 153 liquid styrax, acaroid resin (Xantlwrrheo hastilis), dragon's blood and other resins. Benzoic acid has also been found in the per- fume known as hilan-hilan or ilang-ilang, which is prepared from the flowers of Unona odoratissima} as well as in plums (Prunus domestica clilorocarpaf and the cranberry. 3 It also occurs in vanilla, the fruit of the clove-tree, the seeds of the spindle-tree (Eiwnymus europaeus) and the root of the sweet flag (Acorus calamus), &c. The coumarin which occurs in Holcus odoratus, Anthoxanthum odoratum (sweet-scented vernal grass), and woodruff was at one time mistaken for benzoic acid. In the year 1776, Rouelle stated that the urine of the cow and the camel contains a salt similar to flowers of benzoin, and Scheele, in 1785, obtained a substance, the properties of which agreed with those of benzoic acid, by extracting with alcohol the solid residue left on the evaporation of urine and treating the " soapy extract " with nitric acid. Fourcroy and Vauque- lin found, in 1797, that the urine of gramimvora contains benzoic acid, but Liebig, in 1829, showed that this substance is a new nitrogenous acid, which he named hippuric acid, and which splits up when the urine is allowed to stand, yielding benzoic acid. According to some observers, however, benzoic acid frequently occurs along with hippuric acid in the urine, and it has also been found in a gland in the beaver, 4 and in the kidneys of the ox. 5 It is probable that in all these cases the acid is formed by the decomposition of hippuric acid. It has also been observed as a decomposition product of various alkaloids, such as atropine, cotoine, &c., and is formed in small quantity by the oxidation of albuminoids. It may be obtained in large quantities by the oxidation of those aromatic compounds which possess a side chain containing carbon (Part III. p. 12). It also occurs in coal-tar. 6 The various synthetical methods by which it has been pro- duced have already been given (Part III. p. 30). 2095 It was formerly prepared exclusively from gum benzoin, and the acid used in medicine is still obtained from it by sublima- tion ; it always contains a small amount of an ethereal oil, which 1 Gal, Ber. Deutsch. Chem. Ges. vi. 824. 2 Ducheek, Gmelin's Org. Chem. v. 332. 3 Loew, Journ. Prakt. Chem. [2] xix. 312. 4 Wohler, Ann. Chem. Pharm. Ixvii. 360. 5 Seligsohn, Chem. Centralbl. 1861, 241. 6 Schuke, Ber. Deutsch. Chem. Ges. xviii. 615. 154 AROMATIC COMPOUNDS. gives it its peculiar smell. 1 In order to obtain it in this way, the coarsely powdered resin is heated to about 170 in a flat iron vessel ; this is covered with filter-paper and fitted with a conical cap of strong paper, in which the acid collects. 2 Accord- ing to Wohler, the gum benzoin is dissolved in an equal volume of absolute alcohol and fuming hydrochloric acid added to the hot solution until the resin commences to separate out ; it is then distilled, water being added at intervals, and the distillate, which contains ethyl benzoate, warmed with caustic potash and then heated to boiling and saturated with hydrochloric acid. Benzoic acid separates out on cooling and is found to possess precisely the same smell as the sublimed acid. 3 In order to extract the acid from the resin by Scheele's method, it is well mixed with an equal weight of slaked lime, repeatedly boiled out with water, the filtrate evaporated to one -sixth of its original bulk, treated with bleaching-powder solution, and then boiled with hydrochloric acid until all the chlorine has been removed. The acid separates out on cooling and is re -crystallized from hot water. 4 It is prepared from the urine of cows or horses by allowing it to stand for several days, clarifying with milk of lime, evaporating the liquid to one-fourth of its bulk and precipitating the benzoic acid with hydrochloric acid. Since the evaporation produces a very unpleasant smell, it is better to precipitate the excess of lime by carbonic acid and add ferric chloride, to precipitate ferric benzoate, which is then decomposed by hydrochloric acid. The acid thus obtained is purified by being redissolved in milk of lime with the addition of a little bleaching-powder solution, separated by hydrochloric acid and re-crystallized from hot water. The final product (acidum benzoicum ex urina) still smells of urine, and is not employed for pharmaceutical purposes. The smell may, however, be disguised by the addition of some of the sublimed acid. About two kilos, of acid are obtained from 1,000 kilos, of urine. 5 P. and E. Depouilly have proposed to obtain 'benzoic acid from phthalic acid, 6 which is obtained by the oxidation of 1 Jacobsen found in it methyl benzoate, benzyl benzoate, vanillin, guiacol, catechol and other aromatic compounds (Ber. Deutsch. Chcm. Ges. xvii. Kef. 354). 2 Mohr, Ann. Chem. Pharm. xxix. 117 ; Lowe, Journ. Prakt. Chcm. cviii. 257. 3 Ann. Chem. Pharm. xlix. 245. 4 Stenhouse. 5 Hofmann, Ber. Enlw. Chem. 2nd. ii. 431. 6 Jahrcsb. Chcm. 1865, 323. PREPARATION OF BENZOIC ACID. 155 naphthalene and is now manufactured on the large scale. When its calcium salt is heated to 330 350 with slaked lime in absence of air, calcium benzoate and calcium carbonate are )rmed : 2C 6 H 4 (C0 2 ) 2 Ca + Ca(OH) 2 = (C 6 H 5 .CO 2 ) 2 Ca + 2CO 3 Ca. . According to the method of Laurent and Castelhaz, 1 acid ammonium phthalate is converted into phthalimide by heating, and this is then distilled with lime, benzonitril being formed : C=NH " = C 6 H 5 CN + CaC0 3 + H 2 O. ; The benzonitril is then converted into benzoic acid by boiling with caustic soda solution. Benzoic acid is now generally prepared from toluene ; this may simply oxidized by boiling with dilute nitric acid, but it is ore advantageous to first convert it into benzyl chloride, 2 and en boil 100 parts of this with 300 parts of nitric acid of . gr. 1*313 and 200 parts of water for about ten hours in an paratus connected with an inverted condenser, until the smell of benzyl chloride and benzaldehyde has disappeared, and the liquid solidifies on cooling to a crystalline mass, no oily rops being formed. 3 This method, according to A. von Rad, is not adapted for the preparation of the acid on the large scale ; it can, however, be readily obtained by heating benzotrichloride or benzenyl chloride with water under pressure : 4 C 6 H 5 .CC1 3 + 2H 2 = C 6 H 5 .C0 2 H + 3HC1. Since it is difficult to prepare pure benzenyl chloride, the acid obtained always contains chlorine substitution products, which adhere to it very obstinately. Espenschied proposes to boil benzenyl chloride with milk of lime or caustic soda and whitening, and then to proceed as in the preparation of benzaldehyde from benzal chloride (p. 136). 1 Jahresb. Chem. 1868, 459. 2 Grimaux and Lauth, Bull. Soc. Chim. vii. 100. 3 Lunge and Petri, Bcr. Deutsch. Chem. Ges. x. 1275. 4 Dingier 's Polyt. Journ. ccxxxi. 538. 156 AROMATIC COMPOUNDS. Jacobsen obtains benzole acid, together with acetyl chloride, by heating benzenyl chloride with glacial acetic acid and some zinc chloride : C 6 H 5 .CC1 3 + 2CH 3 .CO.OH = C 6 H 5 .CO.OH + 2CH 3 .COCl + HC1. In order to avoid the evolution of hydrochloric acid, which carries off acetyl chloride with it, half of the acetic acid is replaced by zinc acetate. Benzoic acid can also be prepared without the formation of acetyl chloride, by heating benzenyl chloride with a little acetic acid and zinc acetate, and gradually adding the amount of water necessary for the formation of the acid. 1 Since benzaldehyde is now manufactured, it can readily be employed as a source of benzoic acid. 2096 Properties. It crystallizes in lustrous, flat, monoclinic plates or needles ; by the gradual evaporation of its solution it is obtained in larger tablets, which however are always thin, while when Guichard allowed a mixture of benzoin resin and carbon disulphide to stand for a long time, tolerably large crystals were formed, which had exactly the appearance of crystals of gypsum. 2 Benzoic acid has a sharp acid taste and produces a peculiar irritation in the throat ; it melts at 121 '4, and boils at 249 (Kopp), but volatilizes at 100, and sublimes rapidly at 140. It also volatilizes with steam, one gramme passing over with two litres of water (Nolting). Its vapour has an aromatic, pene- trating odour, produces coughing and attacks the eyes violently, more mildly when it is mixed with steam. The specific gravity of its vapour is, according to Mitscherlich, 4'27 ; according to C. and V. Meyer, who determined it in diphenylamine vapour, it is 4'24, 3 the calculated number being 4*229. 1,000 parts of water dissolve : 4 at 10 20 30 40 50 60 70 80 90 100 170 2-10 2-90 410 5*55 775 11'55 1775 27'15 4075 5875 parts of the acid. 100 parts of absolute ether at 15 dissolve 31 '35 parts ; 100 parts of 40 per cent, alcohol, 41'62 parts ; and 100 parts of 1 Ser. Deutsch. Chem. Ges. xiii. 2013. 2 Ibid. vi. 453. 3 Ibid. xi. 2258. 4 Bourgoin, Ann. Chim. Phys. [5] xv. 168. SALYLIC ACID. 157 absolute alcohol, 4G'68 parts of benzole acid ; l boiling alcohol dissolves about twice this quantity. It also readily dissolves in chloroform, carbon disulphide, volatile and fatty oils and con- centrated sulphuric acid. It is characteristic of benzoic acid that certain impurities, even when they are present in extremely small quantities, alter its physical properties to a very considerable extent ; so largely in fact, that the impure acid has been mistaken for an isomeride. Thus, E. Kopp, by the oxidation of gum benzoin with dilute nitric acid, obtained the amorphous parabenzoic acid as a white powder, which melts at 113; it is converted into ordinary benzoic acid by distillation. 2 Another so-called isomeric acid named salylic acid by Lautemann and Kolbe, because they d obtained it from salicylic acid, C 6 H 4 (OH)COOH. 3 The itter was converted into a chlorine compound by phosphorus >ntachloride and this was decomposed by water into hydro- iloric acid and chlorosalylic acid or orthochlorobenzoic acid, C 6 H 4 C1.CO 2 H. Salylic acid was obtained from this by the action of water and sodium amalgam. This compound crystal- lizes from hot water in indistinct needles or small plates, which, on drying, form an odourless sandy powder, while the soft, light ttes of benzoic acid have a faint but distinct aromatic odour. r hen its aqueous solution is boiled, however, the characteristic lell becomes perceptible. It melts at a lower temperature lan benzoic acid, from which it also differs in fusing when leated with a quantity of water insufficient to dissolve it, and in fact that its hot, saturated solution becomes milky on )ling and then again clear, crystalline flocks being deposited, salts also differ from the benzoates in crystalline form and solubility. Kekule confirmed these results, 4 and Griess obtained a substance which he found to be identical with salylic acid, by decomposing azo-amidobenzoic acid suspended in boiling alcohol with nitrogen trioxide. 5 Kolbe and Lautemann put forward the suggestion that the isomerism of these acids was due to a difference be- tween their radicals, 6 but Cannizzaro showed that on distillation with caustic baryta they both yield the same substance, viz., benzene. 7 The two acids were then assumed to be physical isomerides, 1 Bourgoin ; Bull. Soc. Chim. xxix. 242. 2 Compt. Rend. CMm. 1849, 154. Ann. Cfam. Pharm. cxv. 187. 4 Ibid, cxvii. 158. 6 Ibid, cxvii. 34. 6 Ibid. cxv. 169. * Ibid. Suppl. i. 247. 158 AROMATIC COMPOUNDS. until Reichenbach and Beilstein showed that salylic acid is nothing but a more or less impure benzoic acid. 1 If the acid ob- tained from salicylic acid be subjected to distillation with steam, a perfectly pure benzoic acid passes over which possesses the correct melting-point and all the characteristic properties. Kolbe has confirmed this result, and finds that his salylic acid contains a small quantity of a yellow, resinous substance, which is not volatile in steam. When some of this is added to a hot, satu- rated solution of pure benzoic acid, the liquid on cooling deposits crystals of salylic acid. The admixed substance can be destroyed by the addition of potassium permanganate to the hot solution. 2 The salylic acid obtained from azo-amidobenzoic acid con- tains a little nitrobenzoic acid, as does the benzoic acid which is prepared by the oxidation of toluene with dilute nitric acid. 3 When this acid is distilled, a trace of the nitro-compound vola- tilizes with it and prevents it from crystallizing well, while when a little of the nitro-compound is added to a hot saturated solution of pure benzoic acid, it becomes milky on cooling and deposits flocks, which are much more soluble than the pure acid and melt at a' lower temperature. Pure benzoic acid cannot be prepared from this either by sublimation or re-crystallization, but the impurity can readily be removed by dissolving in concentrated ammonia, saturating with sulphuretted hydrogen, heating to boil- ing, and then evaporating off the ammonium sulphide on the water-bath. Hydrochloric acid now precipitates pure benzoic acid, while amidobenzoic acid remains in solution (Reichenbach and Beilstein). An admixture of cinnamic acid, which melts at 133'3, also lowers the melting-point of benzoic acid considerably, 4 so that a mixture of equal parts of the two acids melts at 84'3, an excess of either acid raising the melting-point. 5 Benzoic acid is employed in the manufacture of colouring matters and in medicine. It has antiseptic properties, but exerts a more feeble action than salicylic acid. 6 The observation that cranberries withstand fermentation and putrefaction better than most other fruits, gave the clue to the discovery of benzoic acid in them. 1 Ann. Chem. Pharm. cxxxi. 309. 2 Journ. PraU. Chem. [2] xii. 151. 8 Fittig, Ann. Chem. Pharm. cxx. 214. 4 Kolbe. and Lautermanu, Ann. Chem. Pharm. cxix. 136. 5 Kachlar, Ber. Deutsch. Chem. Ges. ii. 515. 6 Kolbe and v. Meyer, Journ. Prakt. Chem. [2] xxii. 133, 178. DECOMPOSITIONS OF BENZOIC ACID. 159 2097 When benzole acid is distilled with slaked lime or caustic baryta, it is decomposed into benzene and carbon dioxide (Mitscherlich). It also undergoes this decomposition when heated with caustic soda, 1 and when its vapour is passed over heated pumice stone 2 or iron. 3 Some diphenyl is always formed in this way, and at a very high temperature the acid is decomposed with separation of graphite and formation of carbonic oxide, carbon dioxide, hydrogen and diphenyl, C 19 H 10 . 4 When its vapour is passed over heated zinc-dust, it is reduced to benz- aldehyde. 5 Sodium amalgam reduces its boiling solution with formation of benzaldehyde, benzyl alcohol, a crystalline com- pound, C 14 H U O 2 , and benzoleic acid, C 7 H 10 O 2 , 6 which is further described below. On heating with concentrated hydriodic acid to 275 280, it is first reduced to toluene, but heptane and hexane are formed on further heating, the latter being derived from the benzene, which is formed by the decomposition of the acid. 7 It is not attacked by chromic acid solution ; ozone converts it in alkaline solution into carbon dioxide and water. 8 It is con- verted in the animal organism into hippuric acid and appears in this form in the urine ; 9 a portion is simultaneously oxidized to succinic acid, which is also formed when an aqueous solution of benzoic acid is treated with lead dioxide and sulphuric acid. 10 On oxidation with manganese dioxide and sulphuric acid, Carius obtained carbon dioxide, formic acid, and some phthalic acid, 11 while Oudemans also detected a small quantity of the isomeric terephthalic acid. 12 When the solution of its calcium salt is electrolyzed, the acid is not decomposed in a similar manner to the fatty acids, but the nascent oxygen exerts an oxidizing action, with formation of carbon dioxide, carbonic oxide, and some acetylene. 13 Benzoleic acid, or Hydrobenzoic acid, C 7 H 10 2 , is formed when sodium amalgam is allowed to act on a boiling solution of benzoic I Barth and Schreder, Ber. Deutsch. Chem. fte.s. xii. 2555. . - Barreswill and Boudault, Journ. Pharm. Chim. v. 265. 3 F. d'Arcet, Journ. Prakt. Cham. xiii. 427. 4 Schulz, Ann. Chem. Pharm. clxxiv. 202. 5 Baeyer, ibid. cxl. 295. 6 Kolbe, ibid, cxviii. 122 ; Herrmann, ibid, cxxxii. 75. 7 Berthelot, Jahresb. Chem. 1867, 364. 8 Gorup-Besanez, Ann. Chem. Pharm. cxxv. 207. 9 "Wohler, BcrzeUus 1 Lehrb. Ed. 4, iv. 376 ; see also hippuric acid. 10 Meissner and Shepard, Jahresb. Chem. 1866, 397. II Ann. Chem. Pharm. cxlviii. 72. 12 Zcitschr. Chem. 1869, 84. 13 Berthelot, Bull. Soc. Chim. [2] ix. 103 ; Bourgoin, ibid. 431. 160 AROMATIC COMPOUNDS. acid, hydrochloric acid being added at intervals benzyl alcohol and a crystalline substance, C 14 H 14 O 2 , 1 are simultaneously formed. Otto obtained the same acid from hydrobenzuric acid, 2 and, together with other compounds, by the action of sodium amalgam on benzoyl glycollic acid (p. 165). 3 It is an oily liquid, which has a repulsive odour resembling that of valerianic acid, and is rapidly altered in the air. When hydrochloric acid is passed into its alcoholic solution, the ethyl ether is formed and resembles ethyl valerate, but has a sharper smell ; in the air the smell becomes exceedingly disagreeable, and, since it clings persistently to the clothes, increases the difficulty of the investigation of the compound and the free acid. SALTS AND ETHERS OF BENZOIC ACID. 2098 Benzoic acid decomposes carbonates in aqueous solution, but when a current of carbon dioxide is passed into an alcoholic solution of potassium benzpate, potassium carbonate separates out. Most of the benzoates are soluble in water and alcohol ; some, such as the sodium and barium salts, are withdrawn from their solutions by animal charcoal, and calcium benzoate is decomposed by it, so that free benzoic acid can be extracted by ether. 4 Potassium benzoate, C 7 H 5 K0 2 -f 3H 2 0, crystallizes with diffi- culty in small plates which effloresce in the air and are very soluble in water and alcohol. Sodium benzoate, C 7 H 5 NaO 2 + H 2 0, crystallizes in needles, which also effloresce in the air and are very soluble in alcohol It is used in medicine. Ammonium benzoate, C 7 H 5 (NH 4 )O 2 , separates from a solution containing an excess of ammonia in deliquescent rhombic crystals ; it is also employed medicinally. Large crystals of the less soluble acid salt, C 7 H 5 (NH 4 )O 2 + C 7 H 6 O 2 , are obtained by the gradual evaporation of its aqueous solution (Berzelius). Calcium benzoate, (C 7 H 5 O 2 ) 2 Ca + 2H 2 O, crystallizes from hot water in long lustrous needles which form fascicular aggregates ; they dissolve in 29 parts of cold water and effloresce in the air. 1 Herrmann, Ann. Chem. P7utrm. cxxxii. 75, 2 Ibid, cxxxiv. 115. 3 Ibid. cxlv. 350. * L. Liebermann, Ber. Wien. Akad. 1877, 331. ETHYL BENZOATE. ir,l Barium lenzoate, (C 7 H 5 O 2 ) 2 Ba ~h 3H 2 O, is only slightly soluble in water, and crystallizes in needles or hard, lustrous tablets. Lead lenzoate, (C 7 H 6 O 2 ) 2 Pb + H 2 O, is obtained by the addi- tion of lead acetate to a solution of the potassium salt ; it is a crystalline, difficultly soluble precipitate. Copper lenzoate, (C 7 H 5 O 2 ) 2 Cu+ 2H 2 0, crystallizes in light blue plates united in spherical masses or in needles. Silver lenzoate, C 7 H 5 Ag0 2 , is a curdy precipitate, which is soluble in alcohol and crystallizes from hot water in flat needles. Mercuric lenzoate, (C 7 H 5 O 2 ) 2 Hg + H 2 0, crystallizes from hot rater in needles which are almost insoluble in cold water. Ferric lenzoate, (C 7 H 5 O 2 ) 6 Fe 2 . Berzelius obtained this salt in yellow needles by dissolving ferric hydroxide in aqueous benzoic nd ; it is decomposed by water and alcohol with formation an insoluble basic salt. Sestini was unable to prepare this mipound. 1 When a soluble benzoate is added to neutral ferric chloride, a reddish yellow precipitate is thrown down, which is decomposed by washing with water into a soluble acid salt and an insoluble basic salt. If the iron solution has been previously treated with sufficient ammonia to produce a dark red coloura- tion, soluble benzoates give a voluminous, hydrated, flesh-coloured precipitate of (C 7 H 5 O 2 ) 3 Fe 2 (OH) 3 , which is not altered by cold water. These reactions are employed for the separation of iron from iganese and for the detection of benzoic acid and its separa- tion from other acids. Methyl lenzoate, C 6 H 5 .CO.OCH 3 , is best prepared by passing lydrochloric acid into a solution of benzoic acid in methyl alcohol, distilling, and then precipitating the ether with water. 2 It is a liquid which possesses an aromatic odour and boils at 199. Ethyl lenzoate was prepared by Scheele as long ago as 1*785, by the distillation of a mixture of alcohol, benzoic acid and hydro- chloric acid. It is not formed when an alcoholic solution of the acid is allowed to stand in the cold, but the ether is gradually formed if a little hydrochloric acid be added, or if the liquid be heated to 100. In order to prepare it, the method adopted for the preparation of the methyl ether may be followed, or the alcoholic solution of the acid may be heated with sulphuric or 1 Zeitschr. Chem iv. 668. 2 Carius, Ann. Chem. Pharm. ex. 210. 162 AROMATIC COMPOUNDS. hydrochloric acid. It is a liquid which has a pleasant aromatic smell,, and boils at 213. Ethyl benzoate is also readily formed by the action of benzoyl chloride on alcohol (Wohler and Liebig), which is more readily attacked by it than water. The presence of alcohol even in very dilute aqueous solution can therefore be detected by warming it with a little benzoyl chloride and removing the excess of this by caustic soda; even when only 01 per cent, of alcohol is present, the characteristic smell of ethyl benzoate can be distinctly recognized (Berthelot ; see Part I. p. 318). Boiling-point. Isopropyl benzoate, 1 C 6 H 5 .CO.OCH(CH 3 ) 2 . 218 Propyl benzoate, 2 C 6 H 5 .CO.OC 3 H 7 . . 229'5 Butyl benzoate, 3 C 6 H 5 .CO.OC 4 H 9 . . . 247-3 Amyl benzoate, 4 C 6 H 5 .CO.OC 5 H n . . . 260 7 Octyl benzoate, 5 C 6 H 5 .CO.OC 8 H 17 . . . 306 Allyl benzoate, 6 C 6 H 5 .CO.OC 3 H 5 . . . 228 Benzyl benzoate, C 6 H 5 .CO.OCH 2 .C 6 H 5 . Cannizzaro obtained this compound by the distillation of benzyl alcohol with benzoyl chloride or benzoic anhydride. 7 It boils at 323 324, has the sp. gr. of 1'1227 at 19, and solidifies in a freezing mixture to lustrous, compact crystals, melting at 21 . 8 As already mentioned, it is also formed by the action of sodium methylate on benz- aldehyde (p. 93) and is a constituent of Peru balsam 9 and of Tblu balsam, 10 but has not yet been obtained from them in the pure state. If the ether be submitted to distillation while it still contains water, it is decomposed with formation of benzoic acid, benzyl alcohol and toluene. Ethylene benzoate, (C 6 H 5 .CO 2 ) 2 C 2 H 4 . Wurtz prepared this compound by the action of silver benzoate on ethylene bromide ; n it crystallizes from ether in lustrous, rhombic prisms, 12 melting at 67. 1 Silva, Ann. Chem. Pharm. cliv. 255. 2 Linnemann, ibid. clxi. 28. 3 Ibid. clxi. 92. * Rieckher, ibid. Ixiv. 336. 5 Zincke, ibid. clii. 7. 6 Hofmann and Cahours, ibid. c. 358 ; cii. 297. 7 Ibid. xc. 254. 8 L Claisen, private communication. 9 Kraut, Ann. Ghcm. Pharm. clii. 129 ; Ber. Deutsch. Chem. Ges. ii. 18. 10 Busse, ibid. ix. 830. 11 Jahresb. Chem. 1859, 676. 12 Bodewig, ibid. 1879, 676. PHENYL BENZOATE. 163 The following propylene ethers have been prepared in a similar manner : Melting-point. Propylene benzoate : 1 C 6 H 5 .CO.OCH 2 , viscous fluid ..... C 6 H 5 .CO.OCH.CH 3 Trimethylene benzoate : 2 scal ? cr y stals ---- 53 Dimethylmethylene benzoate : 3 , monoclinic pyramids . 6971 The last of these yields acetone on saponification. Benzidcne lenzoate, (C 6 H 5 .CO.O) 2 CH.C 6 H 5 , is formed by the action of benzidene chloride on silver benzoate, and crystallizes in transparent prisms, melting at 50. 4 The benzoic ethers of glycerol, erythrol, mannitol, the glucoses, etc., have also been prepared. 5 2099 Phenyl -lenzoate, C 6 H 5 .CO.OC 6 H 5 . Ettling and Sten- house observed a compound among the distillation products of copper benzoate which they named benzoic oxide, C 7 H 5 0, 6 while Gerhardt considered it to be the radical benzoyl. 7 List and Limpricht then found that it has the formula C 13 H 10 2 , and is decomposed by alcoholic potash into benzoic and carbolic acids, so that it is a compound of benzoic acid and phenyl oxide. 8 They further showed that it is identical with the benzophenide, which Laurent and Gerhardt obtained by the action of benzoyl chloride on phenol. 9 Phenyl benzoate is readily formed when benzoyl chloride is heated with phenol until hydrochloric acid ceases to be evolved, and also when phenol is heated with benzamide. 10 It is readily soluble in alcohol and ether, and crystallizes from a mixture of these in lustrous, monoclinic prisms, 11 which melt at 71 and sublime at a higher temperature. Its smell resembles that of 1 Friedel and Crafts, Zcitschr. Chcm. 1871, 489 ; Mayer, Ann. Chcm. Pharm. cxxxiii. 255. 2 Reboul, Ann. Chim. Phys. [5] xiv. 500. 3 Oppenheim, Ann. Chcm. Pharm. Suppl. vi. 360 ; Friedel and Ladenburg, ibid. cxlv. 195. 4 Engelhardt, Jahresber. Chem. 1857, 471 ; Wicke, Ann. Chcm. Pharm. cii. 356. 5 Berthelot, ibid. Ixxxviii. 311 ; xcii. 302 ; Jahresber. 1855, 677 ; 1856, 660 ; 1860, 509. 6 Ann. Chcm. Pharm. liii. 77, 94. 7 Ibid. Ixxxvii. 162. 8 Ibid. xc. 190. 9 Ibid. Ixxv. 75 ; Ixxxvii. 161. 10 Guareschi, ibid, clxxi. 141. " Bodewig, Jahresber. 1879, 675. 1G4 AROMATIC COMPOUNDS. the geranium. Chlorine and bromine effect substitution in the phenyl and not in the benzoyl group. Trinitrophenyl bcnzoate, C 6 H 5 .CO.OC 6 H 2 (NO 2 ) 3 , Gerhardt and Laurent prepared this compound by heating picric acid with benzoyl chloride. It is insoluble in water, slightly soluble in cold, more readily in hot alcohol, and crystallizes in lustrous, golden-yellow, rhombic plates, which detonate when heated. 1 Cresyl benzoate, C 6 H 5 .CO.OC 6 H 4 .CH 3 . The three isomeric ethers have been prepared by Engelhardt and Latschinow. 2 Melting- Boiling- point, point. Orthocresyl benzoate, oily liquid ... Metacresyl benzoate, crystals .... 38 290 300 Paracresyl benzoate, six-sided tablets . 70 Phenylene benzoate, (C 6 H 5 .CO.O) 2 C 6 H 4 , is also known in three isomeric forms, which are obtained from the dihydroxybenzenes. Melting-point. Dibenzoylcatechol, rhombic crystals 3 . . . Dibenzoylresorcinol, scales 4 117 Dibenzoylquinol, silky needles 5 199 Tribenzoylphloroglucinol, (C 6 H 5 .CO.O) 3 C 6 H 3 , forms small, lus- trous scales, which are almost insoluble in alcohol. 6 The benzoic ether of pyrogallol, according to Malin, does not crystallize, but its dimethyl ether, and two homologues of the latter which occur in the higher boiling portions of beech-wood-tar oil, give very characteristic ethereal salts of benzoyl. 7 Since these three ethereal salts, which are very similar in their properties, can be separated by means of their different solubilities, they will be mentioned here : Melting-point. Benzoylpyrogallol dimethyl ether : C 6 H 5 .CO.OC 6 H 3 (OCH 3 ) :! 118 Benzoylmethylpyrogallol dimethyl ether : C 6 H 5 .CO.OC 6 H 2 (CH 3 )(OCH 3 ) 2 . . . . 118 119 Benzoylpropylpyrogallol dimethyl ether : C 6 H 5 .CO.OC 6 H 2 (C 3 H 7 )(OCH 3 ) 2 ... 91 1 Ann. Chem. Pharm. Ixxv. 77. - Zcitschr. Chem. 1869, 615 ; see also Kekule, Ber. Dcutsch. Chem. Ges. vii. 1007 ; Guareschi, Ann. Chem. Pharm. clxxi. 142. 3 Nachbauer, ibid. cvii. 243. * Malin, ibid, cxxxviii. 76 ; Dobner, Bcr. Dcutsch. Chem. Gcs. xi. 2269. 5 Dbbner and Wolft', ibid. xii. 661. 6 Hlasiwetz and Pfuundler, Ann. Chem. Pharm. cxix. 199. 7 Hofmann, Ber. Lcutsch. Chem. Ges. xii. 1373. BENZOYL-LACTIC ACID. 165 Quinonoxime benzoate, C 6 H 4 O(NO.CO.C 6 H 5 ), is formed when benzoyl chloride is added to sodium quinonoximate (Part III. p. 172), which is covered with pure ether or chloroform. It crystallizes in yellowish needles, which melt with decomposition at 168 175, and give Lieberrnann's reaction with phenol and sulphuric acid. 1 2100 Benzoyl- gly collie acid, C 6 H 5 .CO.OCH 2 .C0 2 H, has hitherto only been prepared from hippuric acid or benzoylamido-acetic acid, by treating it with nitrous acid, 2 or by passing chlorine into its dilute alkaline solution. 3 It crystallizes from hot water in thin tablets or large prisms, and decomposes on boiling with water, or more rapidly with dilute mineral acids, into benzoic and glycollic acids. Otto, by the action of sodium amalgam on its aqueous solution, obtained benzoleic acid (p. 159) and two other isomeric acids which have not yet been thoroughly investigated. Ethyl lenzoyl-glycollate, C 6 H 5 .CO.OCH 2 .C0 2 C 2 H 5 . Andrejew obtained this substance by heating ethyl chloracetate with sodium benzoate ; it is a liquid which boils at 277 279, and decomposes into alcohol, benzoic acid and glycollic acid, when boiled with alcoholic potash. 4 Benzoyl-lactic acid, CH 3 (CH.O.CO.C 6 H 5 )C0 2 H, is formed when lactic acid is heated to 180 with benzoic acid, 5 as well as by the action of benzoyl chloride on lactic acid or calcium lac- tate. 6 It separates from a hot, aqueous solution in tablets or needles, melting at 112. On boiling with water or a dilute id it is decomposed into lactic and benzoic acids. Ethyl lenzoyl-lactate, C 10 H 9 O 4 .C 2 H 5 , is formed by the action of oyl chloride on ethyl lactate, and by heating silver benzoyl- lactate with ethyl iodide. It is a liquid which boils at 288, and is decomposed into lactic acid and ethyl benzoate by heating with water to 150. Benzoyl compounds of tartaric and racemic acids have also been prepared. 7 1 Walker, Per. Deutsch. Chem. Ges. xvii. 399. 2 Strecker, Ann. Chem. Pharm. Ixviii. 54 ; Strecker and Sokolow, ibid. Ixxx. 3 Gbssmann, ibid. xcix. 181. * Ibid, cxxxiii. 284. Strecker and Sokolow, loc. cit. ; Strecker, ibid. xci. 359. 6 Wislicenus, ibid, cxxxiii. 264. 7 Dessaignes, Jahresber. 1857, 307 ; Perkin, Ann. Chem. Pharm. Suppl. v. 2/4 ; Anschiitzand Pictet, Ber. Deutsch. Chem. Ges. xiii. 1178. 242 166 AROMATIC COMPOUNDS. OXIDES OF BENZOYL. 2101 Benzoyl oxide, or Benzoic anhydride, (C 6 H 5 .CO) 2 0, was discovered by Gerhardt in 1853. He first prepared it by heating benzoyl chloride with sodium benzoate, and named it anhydrous benzoic acid or benzoyl benzoate ; l he subsequently found that it can be more simply obtained by the action of phosphorus oxy- chloride on an excess of sodium benzoate, a portion of this being simultaneously converted into benzoyl chloride. 2 Phos- phorus pentachloride 3 or chloride of sulphur 4 may be employed instead of phosphorus oxychloride. It is also formed in small quantity when benzoic acid is heated with phosphorus pent- oxide, 6 and in larger amount by heating benzoyl chloride to 140 150 with barium oxide, 6 or to 160 220 with benzoic acid. 7 Gerhardt had already found that it may easily be ob- tained by the action of benzoyl chloride on potassium oxalate : K 2 C 2 4 + 2C 6 H 5 .COC1 = (C 6 H 5 .CO) 2 + 2KC1 + CO + C0 2 , Anhydrous oxalic acid may be advantageously employed instead of the potassium salt ; the reaction takes place at 50 60 ac- companied by a regular evolution of gas, and 80 per cent, of the theoretical yield is obtained, together with some unattacked chloride and benzoic acid. 8 Finally, it can also be obtained by heating benzenyl trichloride with silver oxide, or with concen- trated sulphuric acid containing 4'6 per cent, of water : 9 C 6 H 6 .CO X 2C.H..CCL + 3H = >O + 6HC1. C 6 H 6 .CO/ Anhydrous oxalic acid may be substituted for the sulphuric acid : 10 2C 6 H 5 .CC1 3 + 3C 2 4 H 2 = (C 6 H 5 .CO) 2 + 3HC1 + SCO + 3CO,. Ann. Chem. Pharm. Ixxxii. 127. 2 Ibid. Ixxxvii. 73. Wunder, Journ. Prakt. Chem. Ixi. 280. Heintz, Pogg. Ann. xcviii. 458. Etard and Gal, Bull. Soc. Chim. xxv. 342. Gal, Ann. Chem. Pharm. cxxviii. 127. Anschiitz, Ber. Deutsch. Chem. Ges. x. 1882. Ibid. Janssen, ibid. xii. 1495, Patent 30 Oct. 1878 (No. 6689). 10 Anschiitz, ibid, ccxxvi. 20. BENZOIC ANHYDRIDE. 167 Benzoic anhydride crystallizes in rhombic prisms (Bodewig), melting at 42 ; it boils at 360 (Anschutz), and is tolerably soluble in alcohol and ether. It is scarcely attacked by cold water, but when heated with water it gradually forms benzoic acid, and with alcohol, ethyl benzoate. When heated in a stream of hydrochloric acid, it decomposes into benzoyl chloride and benzoic acid. 1 Chlorine and bromine exert a similar action, substitution products being simultaneously formed. Benzoyl acctyl oxide, CH 3 .CO.O.CO.C 6 H 5 . Gerhardt prepared this compound by the action of acetyl chloride on sodium benzoate, and named it anhydrous benzoic acetic acid. 2 It is a heavy, oily liquid, which has a pleasant smell like that of Spanish wine, is gradually attacked by water, more rapidly by alkalis, and is completely decomposed by distillation into benzoic anhydride and acetic anhydride. 3 It is also formed when ben- zoic acid is heated to 220 with acetic anhydride. 4 According to Loir, an anhydride is obtained by the action of benzoyl chloride on sodium acetate, which differs from that prepared by Gerhardt's method in yielding acetyl chloride when heated with hydro- chloric acid to 130, while Gerhardt's compound is first attacked at 160, with formation of benzoyl chloride. 5 This, however, is inaccurate, and Greene has shown that the compound, in what- ever way it is prepared, behaves in exactly the same manner towards hydrochloric acid, the same products acetyl chloride and acetic acid, benzoyl chloride and benzoic acid being formed as in the case of the anhydrides themselves. 6 A number of other mixed anhydrides are now known, which, like the foregoing, decompose on distillation into benzoic an- hydride and another simple anhydride, 7 and must therefore be looked upon rather as mixtures than definite compounds. Benzoyl dioxide, or Benzoyl peroxide, (C 6 H 5 .CO) 2 O 2 , was prepared by Brodie by the action of benzoyl chloride on barium dioxide ; it separates from ether or carbon disulphide in rhombic crystals, which melt at 103-5, detonate when more strongly heated, and when boiled with caustic potash are converted into benzoic acid with evolution of oxygen. 8 1 Mosling, Ann. Chcm. Pharm. cxviii. 303. 2 Ibid. Ixxxvii. 81. 3 Anschiitz, ibid, ccxxvi. 12. * Ibid. 8 Ann. Chim. Phys. [5] xviii. 132. 6 Bull. Soc. Chim. xxxiii. 424. 7 Gerhardt, Ann. Chcm. Pharm. Ixxxii. 127 ; Ixxxvii. 163 ; Chiozza, ibid. Ixxxiv. 106 ; Ixxxvi. 259 ; Chiozza and Malerba, ibid. xci. 102. 8 Ann. Chcm. Pharm. cviii. 80 ; Lippmann, Monatsh. Chem. v. 560. 1G8 AROMATIC COMPOUNDS. HALOGEN COMPOUNDS OF BENZOYL. 2102 Benzoyl chloride, C 6 H 5 .COC1, was discovered in 1832 by Wohler and Liebig ; they obtained it by the action of dry chlorine on pure oil of bitter almonds, and describe it as a trans- parent liquid the vapour of which violently attacks the eyes, and has a peculiar, very penetrating odour resembling the sharp smell of horse-radish. 1 Cahours then prepared it by the action of phosphorus pentachloride on benzoic acid, 2 Gerhardt by that of phosphorus oxychloride on sodium benzoate, 3 and Bechamp by heating benzoic acid with phosphorus trichloride. 4 Friedel sub- sequently observed its formation when hydrochloric acid is passed over a mixture of benzoic acid and phosphorus pentoxide heated to 200 , 5 this being an important general method for the forma- tion of acid chlorides. Harnitz-Harnitzky stated that it might also be obtained by exposing a mixture of carbonyl chloride and benzene vapour to the action of sunlight, 6 but Berthelot was unable to confirm this statement, 7 although it is undoubtedly formed in this way when aluminium chloride is present, ( P . soy It also may be obtained by heating benzenyl trichloride with anhydrous oxalic acid : C 6 H 5 .CC1 3 + C 2 0,H 2 = C 6 H 5 .COC1 + 2HC1+C0 2 +CO. Benzoic anhydride is also formed in this reaction. In order to prepare the chloride, a mixture of two molecules of phosphorus trichloride with three molecules of benzoic acid is heated until hydrochloric acid ceases to be evolved, water is then added and the oily liquid which separates purified by distillation ; accord- ing to another method, benzoic acid is heated with one molecule of phosphorus pentachloride, and the mixture distilled, the dis- tillate consisting at first of phosphorus oxychloride mixed with a little benzoyl chloride, followed by pure benzoyl chloride. The phosphorus oxychloride is then employed for a further prepara- tion by being heated with sodium benzoate, an excess of which 1 Monatsh. Chcm. iii. 262. 2 Ibid. Ix. 251. 3 Ibid i xxxv ii. 63 . 4 Journ. Prakt. Chcm. Ixviii. 489. 6 Bull. Soc. Chim. ii. 80. 6 Ann. Chcm. Pharm. cxxxii. 72. 7 Bull. Soc. Chim. xiii. 9, 392. 8 Ador, Crafts and Friedel, Ber. Dcutsch. Chem. Gcs. x. 1854. BENZOYL CHLORIDE. 169 must be avoided, as, otherwise, some benzoic anhydride would be formed. The crude chloride, prepared by either of these methods, is freed from adhering chlorides of phosphorus by treatment with cold water, and is then purified by distillation. Properties. It is a strongly refractive liquid, which fumes in the air, has a sp. gr. of 1'2324 at and solidifies when cooled in crystals melting at 1. It boils at 198 ; its vapour attacks the lungs and mucous membrane very violently. It is gradually decomposed by cold, more rapidly by hot water, with formation of benzoic and hydrochloric acids ; it is rapidly converted into ethyl benzoate by alcohol, and the other alcohols produce a similar reaction. Since it undergoes double decomposition so readily, it is largely employed for the preparation of other benzoyl derivatives ; many examples of this have been already given and others will be met with in the sequel. It is also employed to a considerable extent in the same way as acetyl chloride, for determining the number of hydroxyl groups con- tained in carbon compounds. Gerhardt and Laurent found that the compound C 6 H 5 .CHO -f C 6 H 5 .COC1 is formed by the action of chlorine on benzaldehyde ; this substance is insoluble in cold alcohol, crystallizes in lustrous plates, is decomposed by distillation into its components, and by boiling with water into hydrochloric acid and benzaldehydo- benzoic acid ; 1 the latter compound corresponds to the ethidene- chloracetin (Part II. p. 72) obtained in a similar manner from acetaldehyde, and is, therefore, lenzidene lenzochlorohydrin : C 6 H 6 .CHc Benzoyl 'bromide, C 6 H 5 .COBr. Wohler and Liebig, by the action of bromine on oil of bitter almonds, obtained a crystalline compound which they looked upon as beiizoyl bromide. This substance was subsequently shown by Claisen to be benzidene- benzobromohydrin ; this chemist then prepared benzoyl bromide by heating three molecules of benzoic acid with two molecules of phosphorus tribromide ; it is a transparent, colourless liquid, has an odour resembling that of the chloride, but fumes more strongly in the air, is more readily attacked by water and boils at 218 219 . 2 It combines with benzaldehyde to form the corn- 1 Jahresber. Chcm. 1850, 489. 2 Ber. Dcutsch. Chem. Gcs. xiv. 2473. 170 AROMATIC COMPOUNDS. pound just mentioned, benzidcne benzobromohydrin or bromo- bcnzylbenzoatc, C 6 H 5 .CHBr.O.CO.C 6 H 5 , which crystallizes from boiling petroleum ether in short prisms or thick tablets, which melt at 69 70 and are decomposed by distillation into their components. Paterno obtained the same compound, together with ethyl bromide, benzyl bromide and benzaldehyde, by the action of bromine on ethyl benzoate, but considered it to be benzoyl bromide. 1 Benzoyl iodide, C 6 H 5 .COI. Wohler and Liebig obtained this compound by heating the chloride with potassium iodide as a colourless, foliated, crystalline mass, which readily melts, a little iodine being set free, has a penetrating odour and is decom- posed by water and alcohol. It has not been analyzed. Benzoyl fluoride, C 6 H 5 .COF. Borodin prepared this compound by the distillation of the chloride with acid potassium fluoride, F 2 HK, in a platinum retort. It is a heavy, oily and colourless liquid, which boils at 161 '5, has a still more powerful odour than the chloride, and is decomposed by water into benzoic and hydrofluoric acids. 2 SULPHUR COMPOUNDS OF BENZOYL. 2103 Thiobenzoic acid, C 6 H 5 .CO.SH. Cloez obtained salts of this acid by the action of benzoyl chloride on .potassium sulphide and double decomposition of the potassium thiobenzoate thus formed with other metallic salts. 3 The compound which he separated from the potassium salt and looked upon as thio- benzoic acid proved to be benzoyl disulphide. The free acid is obtained by decomposing the potassium salt with dilute hydro- chloric acid ; a yellow liquid, smelling of sulphur compounds, separates out and soon solidifies to a crystalline mass, melting at 24, which decomposes on distillation but is volatile with steam. It is readily oxidized to benzoyl disulphide, this action taking place even when its alcoholic solution is evaporated in the air. 4 Potassium thiobenzoate, C 6 H 5 .CO.SK, crystallizes from alcohol in yellowish tablets or prisms, and is very readily soluble in water. The silver salt is a yellowish white, and the lead salt a 1 Gaz. Chim. Ital. i. 586. 3 Ann Chcm. Pharm. cxxvi. 60. 3 Ibid. cxv. 27. 4 Engelhardt, Latschinow and Malyschew, ZcUsclir. Chcm. 1868, 353. THIOBENZOIC ACID. ite precipitate ; both of these readily blacken and decompose. )pper sulphate gives a greenish yellow precipitate which after time becomes red and then contains benzoyl disulphide : ic chloride yields a violet-brown precipitate which becomes low on warming. Ethyl thiobenzoate, C 6 H 5 .CO.SC 2 H 5 , is formed by the action of benzoyl chloride on lead mercaptide, Pb(SC 2 H 5 ) 2 , 1 and of ethyl iodide on silver thiobenzoate. It is a yellow, repulsive smell- ing liquid, which boils at 242 243 and is decomposed by saponification with caustic potash into ben zoic acid and ethyl hydrosulphide, while potassium hydrosulphide yields the latter compound and thiobenzoic acid. It is oxidized by potassium permanganate and dilute sulphuric acid to benzoic acid and ethylsulphonic acid. 2 Phenyl thiobenzoate, C 6 H 5 .CO.SC 6 H 5 , is obtained by heating benzoyl chloride with phenyl hydrosulphide. 3 It crystallizes from alcohol or benzene in long lustrous needles, melting at 56. Benzyl thiobenzoate, C 6 H 5 .CO.S.CH 2 .C 6 H 5 , is readily soluble in alcohol and benzene, and forms lustrous, asymmetric crystals, melting at 39'5. Its behaviour towards reagents resembles that of the ethyl ether. 4 Benzoyl sulphide, or Thiobenzoic anhydride, (C 6 H 5 .CO) 2 S, was obtained by Wohler and Liebig in an impure condition by the distillation of benzoyl chloride with lead sulphide. It is pre- pared by treating potassium thiobenzoate with benzoyl chloride (Engelhardt, Latschinow and Malyschew). It crystallizes from ether in large prisms, which melt at 48 and decompose on distillation. When heated with ammonia it yields benzamide and thiobenzoic acid ; the latter is also formed by the action of potassium hydrosulphide, while benzoic acid is obtained in addition when caustic potash is employed. Benzoyl disulphide, (C 6 H 5 .CO) 2 S 2 , is formed by the oxidation of thiobenzoic acid and by heating benzoic anhydride in a stream of dry sulphuretted hydrogen. 5 It is prepared by adding a solution of iodine in potassium iodide to an aqueous solution of potassium thiobenzoate. It is only slightly soluble in alcohol and ether, and crystallizes from hot carbon disulphide in large 1 Tiitschew, Jahresbcr. Chcm. 1863, 483. 2 Beckmann, Journ. Prakt. Chcm. [2] xvii. 463. 3 Schiller and Otto, Ber. Deutsch. Chcm. Gcs. ix. 1635. 4 Liiders and Otto, ibid. xiii. 1285. 5 Mosliug; Ann. Chcm. Pharm. cxviii. 304. 172 AROMATIC COMPOUNDS. prisms or six-sided tablets which melt at 128, and become coloured violet-red at a slightly higher temperature. Dithidbcnzoic acid, C 6 H 5 .CS.SH, is formed in small quantity when benzoyl chloride is heated with lead sulphide. It is more easily obtained by treating benzenyl trichloride with a very dilute alcoholic solution of potassium sulphide : : C 6 H 5 .CC1 3 + 2K 2 S = C 6 H 6 .CS.SK + 3KC1. Acetate of lead first precipitates lead sulphide from the solution obtained, and then the lead salt of the acid, which is finally decomposed by hydrochloric acid. It is a dark violet-red, heavy, oily liquid, which gives a carmine-coloured solution in ether-, and rapidly forms a resinous mass when exposed to the air. Lead dithiolenzoate, (C 6 H 5 .CS 2 ) 2 Pb, is a vermilion-coloured precipitate, which crystallizes from boiling xylene in fine, red needles. Benzoyl thiocyanate, C 6 H 5 .CO.S.CN, is obtained by the action of benzoyl chloride on lead thiocyanate in the cold. It is a yellow liquid which has a penetrating odour resembling that of bitter almonds, and can only be distilled without 'decomposition in a vacuum. 2 It combines with ammonia, forming benzoyl thiocarbamide, (C 6 H 6 .CO)HN.CS.NH 2 , and is, therefore, probably benzoyl mustard oil, C 6 H 5 .CO.N.CS. NITROGEN COMPOUNDS OF BENZOYL. 2104 Benzamide, C 6 H & .CO.NH 2 . Wohler and Liebig obtained this compound by the action of benzoyl chloride on ammonia, and Fehling subsequently prepared it by boiling hippuric acid with water and lead dioxide. 3 Dumas found that it is also formed when ethyl benzoate is brought into contact with aqueous ammonia, the reaction taking place more rapidly when the mixture is heated to 100.* It is also formed by a similar reaction from benzoic anhydride. 5 1 Engelhardt and Latsehinow, Zeitschr. Chcm. 1868, 456 ; see also Fleischer, Ann. Chem. Pharm. cxl. 240. 2 Miquel, Ann. Chim. Phys. [5] xi. 300. 3 Fehling, Ann. Chem. Pharm. xxv. 48 ; Schwarz, ibid. Ixxv. 195. * Compt. Rend. xxv. 734. 5 Scheitz, Marsh and Geuther, Zeitschr. Chem. 1868, 302. BENZAMIDE. 173 In order to prepare it, benzoyl chloride is triturated with solid ammonium chloride, the product washed with cold water, and crystallized from hot water or alcohol ; 1 or equal molecules of benzoic acid and ammonium thiocyanate may be heated to 150 170, carbonyl sulphide, ammonia, sulphuretted hydrogen and carbon dioxide being evolved, while benzamide remains behind and only requires to be freed from benzoic acid by washing with imonia. 2 It is slightly soluble in cold, more readily in hot water, illy when it contains ammonia, and dissolves readily in >th alcohol and ether. When its aqueous solution is rapidly cooled, it separates out in small plates, while on more gradual cooling it is deposited in fine needles, which gradually change into larger crystals. The latter are also obtained by allowing a mixture of ethyl benzoate and ammonia to stand, or by gradually cooling the fused compound ; they consist of well-formed, mono- clinic tablets, 3 melting at 128 . 4 It boils at 286 290, a small portion being decomposed into water and benzonitril, C 6 H 5 .CN. The latter compound may be readily prepared from it by simply heating with a dehydrating agent ; Wdhler and Liebig had observed that when heated with caustic baryta, an oily, aromatic liquid having a sweet taste, was formed, and that it might also be obtained by passing the vapour of the compound through a red-hot tube. This substance was afterwards recognized as the izonitril discovered by Fehling in the year 1844. 5 Benzamide is not decomposed by heating with dilute alkalis : len it is boiled with strong caustic potash or hydrochloric acid decomposes into ammonia and benzoic acid, and on boiling rith phenol, ammonia and phenyl benzoate are formed. 6 When ited with ethyl nitrite to 120, the following reaction takes )lace ; 7 6 H 5 .CO.NH 2 + NO.OC 2 H 5 = C 6 H 6 .CO.OC 2 H 6 + H 2 O + N 2 . If its solution in aqueous ether be treated with sodium amalgam and kept neutral by the addition of hydrochloric acid, benzyl alcohol is formed. 8 1 Gorhardt, Chim. Org. iii. 268. 2 Keknle, Bcr. Deutsch. Chem. Ges. vi. 113. 3 Klein, Ann. Chem. Pharm. clxvi. 184. 4 Schiff and Tassinari, Ber. Deutsch. Chem. Ges. x. 1785. 5 Wohler, Ann. Chem. Pharm. cxcii. 362. 6 Guareschi, ibid, clxxi. 141. 7 Meyer and Stiiber, ibid clxv. 186. 8 Guareschi, Bcr. Deutsch, Chem. Ges. vii. 1462. 174 AROMATIC COMPOUNDS. It is converted into aniline by the action of bromine in alkaline solution, just as acetamide in similar circumstances yields methylamine (p. 113). Benzamide hydrochloride, C 6 H 5 .CO.NH 2 .C1H, is formed by dissolving benzamide in hot concentrated hydrochloric acid, 1 or by passing hydrochloric acid into a mixture of equal mole- cules of benzonitril and water. 2 It crystallizes in long prisms, which rapidly lose acid in the air. Mercuric lenzamide, (C 6 H 5 .CO.NH) 2 Hg, is prepared by dis- solving mercuric oxide in a hot, aqueous solution of benzamide ; 3 on cooling the liquid, a semi-solid crystalline mass is formed, which is obtained by re-crystallization from alcohol in plates melting at 222 224.* 2105 Benzoyl derivatives of amines and amido-bases are formed by the action of benzoyl chloride on the latter : Melting- Boiling- point, point. Dimethylbenzamide : 5 C 6 H 5 .CO.N(CH 3 ) 2 , large crystals . 41 42 255 257 Diethylbenzamide : 6 C 6 H 5 .CO.N(C 2 H 5 ) 2 , liquid . ... 280 282 Ethylenebenzamide : 7 (C 6 H 5 .CO.NH) 2 C 2 H 4 , needles . . 249 Benzanilide, or Benzoylaniline, C 6 H 5 .N(CO.C 6 H 5 )H. Gerhardt obtained this compound by the action of benzoyl chloride on aniline, 8 and Leuckart found that it is also formed when phenyl isocyanate is treated with benzene in presence of aluminium chloride. 9 It is insoluble in water and crystallizes from alcohol in nacreous plates, which melt at 160 161 , 10 and volatilize without decomposition at a higher temperature. It is not attacked by boiling aqueous acids or alkalis, but yields aniline and benzoic acid when it is fused with caustic potash. Concen- 1 Dessaignes, Ann. Chem. Pharm. Ixxxii. 234. - Pinner and Klein, Ber. Deutsch. Chem. Gcs. x. 1896 ; xi. 10. 3 Dessaignes, loc. tit. * Oppenheim, Bcr. Deutsch. Chem. Gcs. vi. 1392, 5 Hallmann, ibid. ix. 846. 6 Ibid. 7 Hofmann, ibid. v. 246 ; Kraut and Schwartz, Ann. Chem. Pharm. ccxxiii. 43. 8 Ibid. Ix. 311 ; Ixxxvii. 164. 9 Bcr. Deutsch. Chem. Gcs. xviii. 873. 10 Wallach and Hofmann, Ann. Chem. Pharm. clxxxiv. 80. BENZANILIDE. 175 trated nitric acid converts it into the three isomeric lenzoyl- nitmnilines, C 6 H 4 (N0 2 )N(CO.C 6 H 5 )H : Melting-point. Ortho, 1 long, light yellow needles . . 94 95 Meta, 2 plates 155'5 Para, 3 small prisms ....... 199 The two latter are converted by reduction into the corre- sponding benzoyldiamidobenzenes, C 6 H 4 (NH 2 )N(OO.C 6 H 5 )H, while the ortho-compound forms phenylenebenzamidine, X NH \ C 6 H 5 .C-,v yC 6 H 4 , a substance which will be subsequently ^ N ' described. Melting point. Benzoylmethylaniline : 5 C 6 H ft N(CO.C 6 H 5 )CH 3 , small monoclinic crystals 59 Benzoyldiphenylamine : 6 ( C 6 H 5)2 N ( CO -C' 6 H 5 ), rhombic needles . . . 176 177 Benzoylorthotoluide : 7 (C 6 H 4 .CH 3 )N(CO.C 6 H 5 )H, needles .... 142 143 Benzoylparatoluide : 8 (C 6 H 4 .CH 3 )N(CO.C 6 H 5 )H, long needles . . 155 2106 Methylenedibenzamide,CK 2 (N~H..CQ.CQR 5 ) 2 . By heating hippuric acid, C 9 H 9 N0 3 (p. 181), with lead peroxide and dilute sulphuric or nitric acid, Schwarz obtained a crystalline substance, which he extracted from the product by alcohol. This dissolves in concentrated sulphuric or nitric acid without change, and is only attacked by oxidizing agents with difficulty and he therefore called it hipparaffin (ITTTTO?, parum affinis). Its analysis led to the formula C 16 H 16 N 2 O 2 . 9 Maier, who also prepared it, assigned to it the composition C 8 H 7 NO, and found that another crystal- line substance, hipparin, C 8 H 9 NO 2 , is obtained in its prepara- tion. 10 Schwarz subsequently resumed his investigation, and showed that the latter compound is ethyl hippurate ; by heating 1 Mears, Bcr. Dcutsch. Chem. Ges. ix. 774 ; Schwarz, ibid. x. 1709. 2 Bell, ibid. vii. 498 ; Hiibner, ibid. x. 1716. 3 Stover, ibid. vii. 463 and 1314. 4 C. A. Bell, ibid. vii. 497 arid 1504 ; Sennewald, ibid. ix. 775 ; Stover, loe. cit. Hepp, ibid. x. 237. 6 Hofmann, Ann. Chem. Pharm. cxxxii. 166 ; Bernthsen, ibid, cxcii. 13. 7 Bruckner, ibid. ccv. 230. 8 Kelbe, Bcr. Dcutsch. Chem. Gcs. viii. 875. 9 Ann. Chem. Pharm. Ixxv. 201. 10 Ibid, cxxvii. 162. 176 AROMATIC COMPOUNDS. hipparaffin with water to 170 180, he obtained benzamide and a substance which gave the reactions of an aldehyde, and which he identified, in spite of some differences in its properties, with the ethylenedibenzimide which he had obtained by the action of phosphorus pentoxide on a mixture of aldehyde and benzamide. 1 Kraut and Schwarz, however, found that it is actually identical with methylenedibenzamide, 2 which had been obtained by Hepp and Spiess by the action of concentrated sulphuric acid on a mixture of methylal, CH 2 (OCH 3 ) 2 , and benzonitril. 3 It is insoluble in cold, slightly soluble in hot water, and crystallizes from alcohol in bushy aggregates of needles, melting at 223. It is decomposed on boiling with 32 per cent, sulphuric acid, with formation of ammonia, benzoic acid and formaldehyde. Ethidenedibenzamide, CH 3 .CH(NH.COC 6 H 5 ) 2 . Limpricht obtained this compound by the action of benzoyl chloride on aldehyde-ammonia, 4 and Nencki by that of benzamide on alde- hyde containing a few drops of hydrochloric acid. 5 It is prepared by adding first paraldehyde and then benzonitril to well-cooled sulphuric acid, and diluting with water after some hours (Hepp and Spiess). It crystallizes from alcohol in long, white needles, which melt at 204 and sublime without decomposition. It is decomposed by fuming nitric acid into aldehyde and benzamide. Dibenzamide, N(CO.C 6 H 5 ) 2 H, was prepared by Baumert and Landolt, together with benzamide, by the action of benzoyl chloride on potassium amide. 6 Barth and Senhofer found that it is readily formed when benzonitril is treated with a mixture of sulphuric acid and phosphorus pentoxide ; the solution is allowed to stand for some hours and then diluted with water, which slowly precipitates the compound in crystals : 7 2C 6 H 5 .CN + 2H 2 = (C 6 H 5 .CO) 2 NH + NH 3 . It is also formed when lophine, which is obtained by the dry distillation of hydrobenzamide, is treated with a solution of chromium trioxide in acetic acid, it being thus smoothly converted into benzamide and dibenzamide : 8 C 21 H 16 N 2 + 20 + H 2 = C 7 H 5 O.NH 2 + (C 7 H 5 O) 2 NH. 1 Wicn. Akad. Ber. Ixxvii. 762. 2 Ann. Chtm. Pharm. ccxxiii. 40. 3 Ber. Dcutsch. Chem. Ges. ix. 1424. 4 Ann. Chcm. Pharm. xcix. 119. 6 Ber. Dcutsch. Chem. Ges. vii. 159. 6 Ann. Chem. Pharm. exi. 5. 7 Ber. Dcutsch. Chem. Ges. ix. 975, 1073. 8 E. Fischer and Proschke, ibid. xiii. 708. THIOBENZAMIDE. separates from dilute alcohol in long, thin needles, which It at 148, and decompose at a higher temperature, giving ofi odour of benzaldehyde. It is almost insoluble in cold and :ely soluble in hot water, but dissolves readily in ether, chloroform and benzene, from the last two of which it separates in rhombic crystals. On boiling with caustic potash it decom- poses into benzoic acid and ammonia. It dissolves readily in dilute caustic soda, the solution when centrated depositing small glittering needles of the com- pound (C 7 H 5 O) 2 NNa ; it also occurs in short, distorted prisms containing half a molecule of water, which is lost at 120. The solution gives a precipitate with silver nitrate, consisting of (C 7 H 5 O) 2 NAg, and is also precipitated by other metallic salts. Schafer, by heating benzamide in a stream of hydrochloric acid, obtained a compound which he considered to be dibenz- amide hydrate (C 7 H 5 0) 2 NH + 2H 2 0; it crystallizes in small plates, which melt at 99, and do not lose water at a higher temperature, but decompose into benzoic acid and benz- amide. 1 This substance is evidently acid ammonium benzoate, C 7 H 5 (NH 4 )0. 2 +C 7 H 6 2 . 2 Dibenzanilide, (C 6 H 5 .CO) ? NC 6 H 5 . Gerhardt and Chiozza ob- tained this compound by the action of benzoyl chloride on benz- anilide. It crystallizes from alcohol in fine, lustrous needles, which melt at 137 and sublime when more strongly heated. 3 By heating benzoic acid with phenyl mustard oil, Losanitsch obtained a crystalline, foliaceous mass of a dibenzanilide, melt- ing at 155 . 4 Steiner, on the other hand, who prepared it by Gerhardt's method and also by heating tribenzhydroxylamine, N(OC 7 H 5 0)(C 7 H 5 O) 2 , found the melting-point of both prepara- tions to be 161 . 5 Thiobenzamide, C 6 H 5 .CS.NH 2 , was prepared by Cahours by passing sulphuretted hydrogen into an alcoholic, ammoniacal solution of benzonitril : C 6 H 5 .CN + SH 2 = C 6 H 5 .CS.NH 2 . It crystallizes from hot water in long, yellow needles, melting at 117 ; when heated with water and mercuric oxide, it is recon- verted into benzonitril, while it is reduced to benzylamine by 1 Ann. Chem. Pharm. clxix. 111. 2 Beilstein, Org. Chem. 1101. 8 Ann. Chcm. Pharm. Ixxxvii. 302. 4 Bcr. Deutftch. Chem. Gcs. vi. 176. 5 Ann. Chcm. Pharm. clxxviii. 235. 178 AROMATIC COMPOUNDS. zinc and hydrochloric acid. 1 Iodine acts upon its alcoholic solution in the following manner : 2C 7 H 7 SN + 2I 2 = C U H 10 SN 2 + 4HI + S. The compound obtained in this way crystallizes from hot alcohol in lustrous, snow-white needles, which melt at 90 and distil without decomposition at a higher temperature. It is a very stable compound, and is not altered by being heated to 150 with hydrochloric acid, sulphuric acid or tolerably concentrated nitric acid. On boiling with caustic potash it is gradually con- verted into benzoic acid, ammonia being evolved. Zinc and hydrochloric acid reduce it in alcoholic solution to the base, C U H M N 2 , 2 which is isomeric with ethenyldiphenylamidine (Part III. p. 217) ; benzene and benzonitril are simultaneously formed. 3 It crystallizes in small plates, melting at 71, is a monacid base and forms an alkaline solution in alcohol. Thiolenzanilide, or Phenylthiobenzamide, C 6 H 5 .CS.N(C 6 H 5 )H, is formed when benzanilide is heated with phosphorus penta- sulphide, 4 and crystallizes from alcohol in thin, yellow tablets or prisms, melting at 97*5 98'5. DiphenyltMobenzamide, C 6 H 5 .CS.N(C 6 H 5 ) 2 , is formed when asymmetric diphenylbenzenylamidine is heated to 130 140 with carbon disulphide : C 6 H 5 .C(NH)N(C 6 H 6 ) 2 + CS 2 = C 6 H 5 .CS.N(C 6 H 5 ) 2 + CNSH. It crystallizes from solution in benzene or alcohol in dark yellow, asymmetric prisms, melting at 150 151 . 5 2107 Benzoyl urea, C 6 H 5 .CO.NH.CO.NH 2 . Zinin obtained this compound by heating urea to 150 155 with benzoyl chloride ; 6 the anhydride may be substituted for the chloride in this reaction. 7 The monobenzoyl urea crystallizes, from alcohol in long, thin plates, which melt at about 200 and decompose into benz- amide and cyanuric acid when carefully heated beyond this point. {N H \ NH GO H ' neec ^ es - Asymmetric ethyl- ) /-,/-i f NH 9 , i -, , Q J > OC < TVT//~< TT \nr\ ri TT , rhombonedra. benzoyl urea, 9 J \ N(C 2 H 5 )CO.C 6 H 5 ' 1 Hofmann, Ber. Deutsch. Chem. Ges. i. 102. 2 Ibid. ii. 644. 3 Wanstrat, ibid. vi. 335. 4 Bernthsen, ibid. xi. 503. 5 Bernthsen, Ann. Chem. Pharm. .cxcii. 37. 6 Ibid. xcii. 404. 7 Geuther, Scheitz and Marsh, Zeitschr. Chrm. 1868, 305. 8 Leuckart, Journ. Prakt. Chem. [2] xxi. 33 ; Miquel, Ann. Chim. Phys. [5] xi. 318. 9 Lossner, Journ. Prakt. Chem. [2] x. 251. DIBENZOYL UREA. Dibenzoyl urea, CO(NH.CO.C 6 H 5 ) 2 , is formed, together with ijdrochloric acid, carbon dioxide, ammonium chloride, benzoic ;id and benzonitril, when benzamide is heated to 160 170 carbonyl chloride, 1 and also from guanidine and benzoic lydrideat 100 : 2 C=NH 2 =NH + 0< ,CO.C 6 H 5 NH.CO.C 6 H 5 = NH,+CO NI NH.CO.C 6 H 5 . It crystallizes from alcohol in needles melting at 210, and is decomposed by boiling with strong acids into carbon dioxide, ammonia and benzoic acid, while dilute caustic potash solution converts it into benzamide and carbon dioxide. Benzoyl thio-urea, C 6 H 5 .CO.NH.CS.NH 2 , is formed when thio- urea is heated with benzoyl chloride 3 and by the action of dilute ammonia on benzoyl thiocyanate. 4 It crystallizes from dilute alcohol in small prisms which have a very bitter taste and melt at 171. Miquel has prepared the following compounds by the action of benzoyl thiocyanate on amines and amido-bases : Ethylbenzoyl thio-urea : , & needles. 'henylbenzoyl thio-urea : / NH.CO.C 6 H 5 1 NH.C 6 H 5 ' >enzylbenzoyl thio-urea : NH.CO.C 6 H, NH.CH 2 .C 6 H 5 ' sma11 P nsms ' Paratolylbenzoyl thio-urea : NH.CO.C 6 H 5 Melting-point. 134 . 148 149 145 165 Benzoylphenylhydrazine, C 6 H 5 .NH - NH(CO.C 6 H 5 ). In order to obtain this compound, two molecules of phenylhydrazine are dissolved in five times their amount of ether, the solution cooled 1 Schmidt, Journ. PrakL Chem. [2] v. 58. 2 Creath, Ber. Dcutsch. Chem. Ges. vii. 1739. 3 Pike, ibid. vi. 755. 4 Miquel, Ann. Chim. Phijs. [5] xi. 313. AROMATIC COMPOUNDS. and then treated with a molecule of benzoyl chloride. The mixture is filtered, the hydrochloride of phenylhydrazine removed by boiling with water, and the residual benzoylphenylhydrazine crystallized from boiling alcohol. It forms fine prisms, melting at 168, dissolves readily in warm, dilute caustic potash, and is precipitated from this solution by acids. Yellow mercuric oxide converts it in alcoholic solution into benzoylazobenzene, C 6 H 5 .N=N.CO.C 6 H 5 , a dark red, oily liquid, which is reconverted into the original compound by reduction. 1 Methylbenzoylphenylhydrazine, C 6 H 5 N(CH 3 ).NH(CO.C 6 H 5 ). This compound is prepared by adding sodium and then methyl iodide to a solution of benzoylhydrazine in wood-spirit; the mixture becomes warm, and after standing for several hours is heated to 100 for a short time in order to complete the reaction. Methylbenzoylphenylhydrazine crystallizes from hot alcohol in fine, white needles, melting at 153. When its solution in hydrochloric acid is treated with a trace of nitrous acid, an intense red colouration is produced, which becomes dark brown with large quantities. When methylbenzoylphenylhydrazine is heated with concentrated hydrochloric acid, it is decomposed into benzoic acid and methylphenylhydrazine ; the latter compound may be detected by conversion into its characteristic tetrazone, which melts at 137, and not, as was formerly stated, at 133 (Part III. p. 270). 2 Dibenzoylphenylhydrazine, C 6 H 5 N(CO.C 6 H 5 )N(CO.C 6 H 5 )H, is obtained by the action of benzoyl chloride on benzoylphenyl- hydrazine or on potassium phenylhydrazinesulphonate. It crystal- lizes from hot alcohol in fine prisms, which melt at 177 178, and dissolve slowly in aqueous alkalis. If the alkaline solution be treated with the calculated quantity of sodium and heated, the sodium dissolves and on cooling, a salt, C 20 H 15 N 2 O 2 Na, separates out in lustrous plates, which are readily soluble in water. M^hj^ibm^lph^ CH 3 , is formed when the solution of the sodium salt is heated with methyl iodide. It forms well-developed, soft, white crystals which melt at 145, and are insoluble in water or alkalis, but dissolve readily in hot alcohol. On distillation with caustic potash it is decomposed into benzoic acid and hydrazophenyl- mcthyl, C 6 H 5 .NH NH(CH 3 ). This substance is a colourless oil which rapidly oxidizes in the air, but forms stable salts. When 1 E. Fischer, Ann. Chcm. Pharni. cxc. 125. 3 Tafel, Ber. Dcutsch. Chem. Ges. xviii. 1739. HIPPUR1C ACID. 181 mercuric oxide is added to its ethereal solution, it is converted into azophenylmethyl, C^NizzNCHg, a yellow oil, which pos- sesses a characteristic smell, volatilizes with ether vapour, more rapidly with steam, and distils at about 150 with considerable decomposition (Tafel). Benzoyldiphenylhydrazine^CfiH.^^! NH(CO.C 6 H 5 ), was ob- tained by Fischer from benzoyl chloride and diphenylhydrazine ; it is slightly soluble in alcohol and ether, and crystallizes from hot acetone in fine needles, melting at 192 . 1 HIPPURIC ACID, C 9 H 9 NO 3 . 2108 Rouelle, in the year 1776, as has been already mentioned under benzoic acid, found a salt in the urine of the cow and the camel, which is analogous to flowers of benzoin, and Fourcroy and Vauquelin observed a peculiar acid, which they took to be benzoic acid, in the urine of graminivora. Liebig, however, showed in 1829, that this acid contains nitrogen and differs completely from benzoic acid in its properties ; he says, ' Since I have more especially investigated the acid obtained from the urine of the horse, I will designate it, for want of a more suit- able term, as " hippuric acid " (tWo?, horse, ovpov, urine). On heating it decomposes with formation of various products, among them being benzoic acid, the experience of Fourcroy and Vauquelin, " that benzoic acid can be obtained from horse's urine, but is not contained in it as such " being thus confirmed/ 2 Liebig first obtained for it the formula C 10 H 10 NO 3 , which he subsequently corrected, 3 his later analyses being confirmed by those of Dumas and Peligot. 4 Pelouze then found that on boiling hippuric acid with manganese dioxide and very dilute sulphuric acid, benzoic acid, ammonia and carbon dioxide are formed, 5 while Fehling obtained benzamide and carbon dioxide by boiling it with water arid lead dioxide. 6 Dessaignes then made the important observation that it is decomposed into .benzoic acid and glycocoll (amido-acetic acid) when treated with boiling alkalis or acids, 7 and he, with the majority of chemists, 1 Ann. Chcm. Pharm. cxc. 78. 2 Pogg. Ann. xvii. 389. 3 Ibid, xxxii. 573. 4 Ann. Chcm. Pharm. xiv. 69. 6 Ibid, xx vi. 60. 6 Ibid, xxviii. 40. 7 Journ. Prald. Chcm. xxxvii. 244. 243 182 AROMATIC COMPOUNDS. assumed that hippuric acid is a copulated compound of benzoic acid and glycocoll, although, as was pointed out by Berzelius, this assumption does not in the least account for the action of lead dioxide. An important advance towards the determination of the consti- tution of hippuric acid was made by Strecker, 1 who found that it is converted by the action of nitrous acid into benzoylglycollic acid (p. 165), which was more closely investigated by him in conjunc- tion with Sokolow. This compound assumes the elements of water and splits up into benzoic acid and glycollic acid, and must, therefore, be considered as a copulated compound of these, its amido-derivative being hippuric acid. 2 Dessaignes now endeavoured to prepare hippuric acid arti- ficially by heating glycocoll with benzoyl chloride, but without success ; he attributed his failure to the evolution of hydrochloric acid and therefore substituted the zinc salt of glycocoll, zinc amido- acetate, and found that hippuric acid is slowly formed when benzoyl chloride is allowed to act upon this in the cold, more rapidly at 120 . 3 He also obtained it subsequently by heat- ing benzoic acid with glycocoll to 160 , 4 and Jazukowitzsch pre- pared it by heating chloracetic acid with benzamide ; 5 the yield was, however, small, owing to the formation of free hydrochloric acid. These syntheses finally proved that hippuric acid is benzoylamido-acetic acid : CH 2 .NH 2 CH 2 .NH.CO.C 6 H 5 + HO.CO.C 6 H 5 = | +H 2 0. COOH CO.OH CH,C1 CH 2 .NH.CO.C 6 H 5 | +NH 2 CO.C 6 H 6 = | + HC1. CO.OH CO.OH It is also formed, together with other products which will be subsequently mentioned, from benzoyl chloride and silver amido- ^acetate, 6 and very readily when glycocoll is heated with benzoic anhydride 7 or when benzoyl chloride is added to a concentrated aqueous solution of the former. 8 Liebig detected it in human urine, about 1 grm. being excreted 1 Ann. Chcm. Pkarm. Ixviii. 54. 2 Ibid. Ixxx. 17. 3 Ibid. Ixxxvii. 325. * Jahresber. Ohem. 1857, 367. 6 Zeitschr. Chcm. 1867, 466. 6 Journ. PraJct. Chem. [2] xxiv. 239 ; xxvi. 145. 7 Curtius, Be,r. Deutsch. Chcm. Ges. xvii. 1662. 8 Baum, Zeitschr. Physiolog. Chem. ix. 465. HIPPURIC ACID. ]83 per diem. 1 According to Weismann it is formed more freely during a vegetable than an animal diet, 2 and according to Ducheck it is not invariably present. 3 Pettenkofer found 1'3 per cent, of it in the urine of a girl suffering from St. Vitus's dance, whose diet consisted exclusively of apples and bread ; the amount decreased as soon as meat was again taken. 4 Lehmann observed its occurrence during diabetes, even before Liebig had detected its presence in normal human urine, 5 and since that time it has frequently been observed in large quantities in diabetic urine. It also occurs largely in the acid urine of persons suffering from fevers of every kind. 6 Liebig, 7 and Dumas 8 assumed that fresh horses' urine contains hippuric acid which is converted into benzoic acid on standing. The former subsequently stated that horses and bullocks excrete hippuric aciol when they are allowed to remain idle for some time, and benzoic acid when they are working to the full extent of their powers, 9 and Erdmann and Marchand found 10 that the urine of carriage horses usually contains the former and that of plough horses the latter. Lehmann, however, who investigated the urine of a large number of horses, both sound and diseased, well and badly fed, found only hippuric acid without exception, provided that the urine had not been allowed to stand too long in the air. After standing for a considerable time, and especially after the formation of ammonia, only benzoic acid is present, being formed by a special ferment. When such urine was added to a sample of the fresh material, containing hippuric acid alone, the latter decomposed on evaporation and only benzoic acid could then be detected. 11 Roussin found a large quantity of urea but no hippuric acid in the urine of Arab stallions, which did not work but were kept for breeding ; that of others, which were used by the Spahis for riding, contained little urea, but 0'5 1 per cent, of hippuric acid ; in one sample of urine which was passed after a long journey the amount rose to 1*4 per cent., and 0'78 per cent, was found in that of omnibus horses. 12 Stiideler found about 1*5 per cent, of hippuric acid in cows' 1 Baum, Zcitschr. Physiolog. Chein. cvi. 164. 2 Jahresber. Chcm. 1858, 572. 3 Gmelin, Org, Chem. v. 332. , 4 Ann. Chem. Fharm. Hi. 86. 5 Journ. Prdkt. Chem. vi. 113. 6 Gmelin's Org. Chem. v. 334. 7 Ann. Chem. Pharm. xxx. 280. 8 Ann. Chim. Phys. Ivii. 331. * Ann. Chem. Pharm. xli. 272 ; Organ. Chem. in Anwendung auf Phys. und Pathol. Ixxxiv. 10 Journ. PraJct. Chem. xxvi. 491. u Gmelin, Organ. Chem. v. 332. 12 Compt. rend. xlii. 583. 184 AROMATIC COMPOUNDS. urine, 1 and, according to Hallwachs, a cow passes more than 50 grms. of the acid during twenty-four hours. 2 Kraut observed that cows which are allowed to graze give more hippuric acid than those which are stall fed, 3 while only traces are formed when they are fed on spent grain from a distillery. 4 In the urine of cows fed on oat-straw and wheat-straw, with the addition of some beans, 2'1 2*7 per cent, was found, while that of cattle fed on bean-straw and clover contained only 0'4 ]>LT cent., and when ordinary meadow hay was given, 1*4 per cent. 5 The urine of sucking calves contains uric acid but no hippuric acid (Wohler). The latter occurs in the urine of sheep, goats, hares, rabbits, and elephants (Schwarz). Schwarz found it in very considerable quantity in the urine of a camel, the sample being very concentrated, as only four ounces were passed during the day, and Lehmann detected it in the urine of the tortoise (Testudo graeca). Pettenkofer observed its occurrence in the scurf which is formed on the skin during the rare disease known as ichthiosis, 6 and J. Davy found it in butterflies, moths, and their chrysalides and excrements. 7 The urine of dogs also contains a small quantity of the acid even during an exclusively meat diet or after long fasting, 8 while it has never been found in the urine of pigs. 9 2109 Ure was the first to make the important observation that the urine of a patient who has taken benzoic acid contains a large amount of hippuric acid. 10 Wohler had previously suggested that benzoic acid is changed to hippuric acid in the organism, for he had found in the urine of a dog to which half a drachm of benzoic acid had been given an acid which he mistook for benzoic acid, but which he subsequently found to be identical with the hippuric acid discovered by Liebig. 11 Under his direc- tions Keller conducted a research on the subject, taking 2 grains of benzoic acid in the evening and repeating the dose three times daily during the following days. His urine, which now possessed a strongly acid reaction, contained a considerable amount of hippuric acid, and, as Wohler says, " since benzoic acid seems 1 Ann. Chem. Pharm. Ixxvii. 17. 2 Ibid. cv. 209 3 Chem. Centralbl. 1858, 831. 4 Schwarz, Ann. Chem. Pharm. liv. 31. 6 Henneberg, Stohmann and Rautenberg, ibid, cxxiv. 201. 6 Ibid. xc. 378. 7 New Edinb. Phil Journ. xlv. 17. 8 Salkowski, Ber. Deutsch. Chem. Ges. xi. 500. 9 Boussingault, Ann. Chim. Phys. [3] xv. 97 ; von Bibra, Ann. Chem. Pharm. liii. 98. 10 Repert. Pharm. xxvii. 642. 11 Berzelius, Lehrb. Chem. 1831, iv. 376. HIPPURIC ACID. 185 not to affect the health, large quantities of hippuric acid might readily be prepared in this manner, the only requisite being a man who would continue the manufacture for weeks. 1 These observations were confirmed by Garrod, 2 Schwarz and others; Marchand found 39 2 grains of hippuric acid in his urine after eating 30 grains of benzoic acid. 3 Many other compounds, which are converted into benzoic acid by oxidation, are changed into hippuric acid by their passage through the organism ; such are benzaldehyde, 4 cinnamic acid, 5 C 6 H 5 .CH=CH.CO 2 H, hydrocinnamic acid or phenylpro- pionic acid, 6 C 6 H 5 .C 2 H 4 .CO 2 H, phenylglycollic acid, 7 C 6 H 5 .CH (OH)CO 2 H, quinic acid, 8 C 6 H 7 (OH) 4 CO 2 H, and even toluene. 9 The substitution products of benzoic acid appear in the urine as the corresponding derivatives of hippuric acid ; thus phenylacetic acid, C 6 H 5 .CH 2 .CO 2 H, gives phenylaceturic acid 10 ; salicylic acid, C 6 H 4 (OH)C0 2 H, is converted into salicyluric acid, 11 and toluic acid, C 6 H 4 (CH 3 )C0 2 H, into toluyluric acid; 12 phthalic acid, however, remains unchanged. 13 It follows from this, that the monobasic aromatic acids, and hydroxy-acids, combine with glycocoll with elimination of water in their passage through the organism. After Liebig had discovered hippuric acid, he raised the ques- tion whether it must be considered as a compound of benzoic acid with an unknown compound body, or as a peculiar acid by the decomposition of which benzoic acid is formed, just as oxalic and formic acids are formed when sugar or starch is treated with nitric acid. He decided for the latter view, and says: "The first view is rendered improbable by the fact that I have been unable to prepare even the slightest trace of benzoic acid from horses' fodder, which is the source of their urine, even if this acid be contained in Anthoxanthum odoratum and Holcus odoratus, as found by Vogel, its identity being rendered doubtful by its 1 Ann. Chcm. Pharm. xliii. 108. 2 Phil. Mag. xx. 501. 3 Journ. Prakt. Chcm. xxxv. 309. 4 Frerichs and Wohler, Ann. Chcm. Pharm. Ixviii. 336. 6 Erdmannand Marchand, Journ. Prakt. Chem. xxvi. 491. 6 E. and H. Salkowski, Ber. Deutsch. Chem. Ges. xii. 653. 7 Grabe and Schultzen, Ann. Chcm. Pharm. cxlii. 349. 8 Lautetnann, ibid. cxxv. 12. 9 Nauyen and Schultzen, Zeitschr. Chem. 1868, 29. E. and H. Salkowski, loc. cit. 1 Bertagnini, Ann. Chem. Pharm. xcvii. 249. 12 Kraut, ibid, xcviii. 360. 13 Grabe and Schultzen, loc. cit. 186 AROMATIC COMPOUNDS. different crystalline form." These fragrant grasses were after- wards found to contain not benzoic acid but coumarin, C 9 H 6 2 , which is the anhydride of orthohydroxyphenylacrylic acid, C 6 H 4 (OH)C 2 H 2 .C0 2 H. After it had been proved that benzoic acid and allied sub- stances are converted into hippuric acid in the organism, it seemed probable that that occurring in the urine of graminivora would be derived from benzoic acid or other benzoyl compounds occurring in the fodder. Hallwachs, therefore, investigated the chief grasses and plants in question, but was unable to detect the slightest trace of benzoic acid or any other compound which could yield hippuric acid ; he also showed that coumarin and chlorophyll, which might be looked upon as allies of the benzoyl series, pass through the organism unchanged. 1 O. Loew found, however, that quinic acid, which occurs in many plants, is also present in hay, and considered it to be the source of the hippuric acid. 2 Although the latter acid can be obtained from quinic acid, it passes through the organism almost unchanged, only a very small portion being converted into hippuric acid. 3 The amount of hippuric acid in the urine is naturally greater when such fruits as plums and cranberries, which contain benzoic acid, have been eaten; 4 but Ducheck found a much larger quantity than would correspond to the amount of benzoic acid contained in the plums. As already mentioned, hippuric acid occurs largely in the urine of diabetic patients who subsist on a meat diet, and in that of others who have passed several days without taking food, as well as in small quantity in the urine of dogs after a meat diet or long fasting. It follows from these facts with tolerable certainty that the hippuric acid, or rather the aromatic group contained in it, is derived from the albuminoids, which are known to yield benz- aldehyde and benzoic acid on oxidation, while phenylpropionic acid is formed from them by the pancreatic fermentation (E. and H. Salkowski). E. Salkowski has adduced a further proof for this in the fact that phenylaceturic acid, (C 6 H 5 .CH 2 .CO)NH.CH 2 .CO 2 H, which is the homologue of hippuric acid, occurs in horses' urine and ^ Ann. Chcm. Pharm. cv. 207. " Journ. Prakt. Chem. [2] xix. 309. 3 Stadelmann, Jahresber. Chem. 1879, 982. 4 Ducheck, Gmeliris Org. Chem. v. 332 ; Thudichum, Jahresber. Chem. 1863, 656. PREPARATION OF HIPPURIC ACID. 187 can readily be split up into glycocoll and phenylacetic acid, C 6 H 5 .CH 2 .C0 2 H. The latter acid is also formed, together with phenylpropioriic acid, by the putrefraction of albumen. 1 The source of the hippuric acid is therefore identical with that of the uric acid, which is especially formed in the organism of the carnivora. 21 10 The acid is best prepared from the urine of cows or oxen, which often contains such a large quantity that it is preci- pitated by the addition of hydrochloric acid. If this be not the case, the urine is boiled up with milk of lime, filtered, and the filtrate neutralized with hydrochloric acid, evaporated, and then treated with an excess of hydrochloric acid. 2 Putz proposes to precipitate the neutral solution with ferric chloride and decom- pose the washed precipitate with hydrochloric acid. 3 The acid obtained by these methods is always discoloured, but the im- purity may be removed by dissolving it in warm chlorine water, 4 or treating its aqueous solution with bleaching powder. 5 It is more convenient to effect the purification by allowing 3 parts of the acid to stand in contact with 1 part of nitric acid, of sp. gr. To, and filtering off the mother-liquor after twenty- four hours. 6 It can also be dissolved in hot, dilute caustic soda solution and treated with potassium permanganate until yellow crystals separate out on the addition of hydrochloric acid. 7 These are boiled with water and animal charcoal and then finally re-crystallized from hot water. Hippuric acid is also readily obtained when finely powdered, dry amido-acetic acid is gradually added to an excess of heated benzoic anhydride, and the mixture heated on an oil-bath until it becomes coloured red. It is then allowed to cool, dissolved in water and neutralized with caustic soda, the solution being subsequently acidified with hydrochloric acid and allowed to stand for several days. The precipitated hippuric acid is boiled with water and animal charcoal, the filtrate concentrated on the water-bath and then allowed to cool slowly. The large crystals which are formed are then washed with petroleum spirit to remove any adhering benzoic acid. 8 1 Ber. Dcutsch. Chem. Ges. xvii. 3010. 2 Gregory, Ann. Chem. Pharm. Ixiii. 125. 3 Jahrcsber. Chem. 1877, 795. 4 Dauber, Ann. Chem. Pharm. Ixxiv. 202. 5 Conrad, Journ. PraJct. Chem. [2] xv. 244. 6 Hutstein, Jahrcsb. 1854, 453 7 Gossmann, Ann. Chem. Pharm. xcix. 374 ; Conrad, loc. cit. 8 Curtius, Ber. Dcutsch. Chem. Ges. xvii. 1662. 188 AROMATIC COMPOUNDS. Properties. It forms long, lustrous, rhombic prisms or needles (Fig. 1), which are sometimes opaque, and which dissolve in 600 parts of water at ; it is only slightly soluble in cold alcohol and ether, but dissolves readily in warm water and alcohol. It is in- soluble in petroleum spirit, and can be separated from benzoic acid by means of this property. It reddens litmus, but has not a sour taste, melts at 187'5 (Conrad) and decomposes at tem- peratures above 240, with formation of hydrocyanic acid, benzoic acid, benzonitril, and a black, resinous substance. 1 When it is heated with caustic potash to 260, ammonia and benzonitril are given off, while calcium carbonate, calcium benzoate and carbon remain behind. Caustic baryta effects a similar decomposition, FIG. i. barium cyanate being formed in addition, while when an excess of baryta is employed, benzene, ammonia and methylamine are given off and barium carbonate and benzoate formed, but no cyanide. 2 It has been already mentioned that on heating with strong acids or alkalis it decomposes into benzoic acid and glycocoll ; these products are also formed when it is heated to 120 with a concentrated solution of zinc chloride ; when, how- ever, it is distilled with anhydrous zinc chloride, benzonitril and carbon dioxide are formed. 3 On oxidation with lead dioxide and sulphuric acid or with 1 Limpricht and Uslar, Ann. Chem. Pharm. Ixxxviii. 133. 2 Kraut, Jahresber, 1863, 348 ; Conrad, loc. cit. 3 Gossmann, Ann. Chem. Pharm. c. 69. the THE HIPPURATES. ... . *ic acid, it is converted into hipparaffin or methylenedibenz- amide (p. 175) : CH 2 .NH(CO.C 6 H 5 ) C0 2 H The substitution products of hippuric acid will be described among the corresponding derivatives of benzoic acid. 21 1 1 The Hippurates. Hippuric acid decomposes carbonates dissolves zinc with evolution of hydrogen. Its salts are for e most part soluble in water and crystallize well ; they have been investigated by Schwarz. 1 Potassium hippurate, C 9 H 8 KNO 3 + H 2 0, forms vermicular crusts consisting of pointed rhombic prisms ; on heating it forms a vapour which possesses a smell resembling that of Satureja hortensis. It combines with hippuric acid forming the acid salt, C 9 H 8 KN0 3 + C 9 H 9 NO 3 + H 2 O, which crystallizes in quadratic tablets possessing a satin lustre. Sodium hippurate, 4C 9 H 8 NaNO 3 -f- H 2 O, is a crystalline mass which readily dissolves in water and hot alcohol. Acid ammonium hippurate, C 9 H 8 (NH 4 )N0 3 +C 9 H 9 NO 3 -fH 2 O, crystallizes in small, quadratic prisms ; the normal salt has not n prepared. Calcium hippurate, (C 9 H 8 N0 3 ) 2 Ca 4- 3H 2 O, forms rhombic prisms, 2 which are soluble in 18 parts of cold and 6 parts of boiling water (Liebig). Strontium hippurate, (C 9 H 8 NO 3 ) 2 Sr + 5H 2 0, crystallizes in fascicular aggregates, composed of four-sided prisms ; it is only slightly soluble in cold water and alcohol, but dissolves readily in them when hot. Barium hippurate, (C 9 H 8 N0 3 ) 2 Ba-hH 2 0, crystallizes in crusts made up of quadratic prisms. Schwarz, in endeavouring to separate a mixture of hippuric and benzoic acids by means of their barium salts, obtained, first, barium benzoate, then barium hippurate, and, finally, from the mother-liquor, the double salt, C 7 H 5 2 .Ba.C 9 H 8 N0 3 4- 5H 2 O, in characteristic warty masses. 3 Magnesium hippurate, (C 9 H 8 NO 3 ) 2 Mg + 5H 2 O, forms warty crystals. Zinc hippurate, (C 9 H 8 N0 3 ) 2 Zn + 5H 2 O, crystallizes in small 1 Ann. Chem. Pharm. liv. 33. 2 Schabus, Jahresber. Chem. 1850, 411. 8 Ann. Chem. Pharm. Ixxv. 192. "V 1 190 AROMATIC COMPOUNDS. plates, which after dehydration dissolve in 5 3' 2 parts of water at 17 '5, and in 4 parts at 100 . 1 Lead hippurate, (C 9 H 8 NO 3 ) 2 Pb + 2H 2 0, is a curdy precipitate crystallizing from a large quantity of hot water in fine, silky needles, which often suddenly take up a molecule of water arid change into lustrous, four- sided tablets. Copper hippurate, (C 9 H 8 N0 3 ) 2 Cu + 3H 2 O, is slightly soluble in cold water, more readily in hot alcohol, and crystallizes in small, pointed, rhombic prisms of a blue colour. Silver hippurate, 2C 9 H 8 AgN0 3 + H 2 O, is a curdy precipitate, which crystallizes from hot water in aggregates of lustrous needles. When ferric chloride is added to a solution of a normal hippurate, a -cream-coloured precipitate of ferric hippurate is thrown down, which contains more or less basic salt according to the greater or less dilution of the solution ; this fact was dis- covered by Putz, who employed the compound for the prepara- tion of hippuric acid from urine. It is almost insoluble in pure water, but dissolves in presence of free hippuric acid, an excess of ferric chloride and in alcohol. Wreden has proposed to employ this reaction for the determination of hippuric acid in urine. Henneberg, Stohmann, and Rautenberg, found that it is most convenient for this purpose to make use of a solution of ferric nitrate which has been standardized with pure hippuric acid. The urine is acidified with nitric acid, heated to boiling to remove carbon dioxide, neutralized with calcium carbonate, treated with an excess of lead nitrate, and then diluted to a known volume and filtered. An aliquot portion of the filtrate is heated and titrated with the ferric nitrate solution until a drop of the clear liquid gives a blue colouration with potassium ferrocyanide, the distinction between this and the white of the lead ferrocyanide which is formed at first, being very sharp. 2 Methyl hippurate, C 9 H 8 (CH 3 )NO 3 , is obtained by the action of hydrochloric acid on a hot solution of hippuric acid in methyl alcohol. 3 It is slightly soluble in cold, more readily in hot water and in alcohol, and crystallizes in long, white prisms, which melt at 80'5, and decompose at 250 with formation of ammonia and benzonitril. Ethyl hippurate, C 9 H 8 (C 2 H 5 )NO 3 , is formed in a similar 1 Lowe, Jahrcsber. 1855, 536. 2 Ann. Chem. Pharm. cxxiv. 182. 3 Jaqucmin and Schlagdenhauffen, Compt. Rend. xlv. 1011 ; Conrad, Journ. Prakt. Chem. [2] xv. 247. THE HIPPURATES. 191 manner to the methyl ether, 1 and also by allowing a saturated, warm alcoholic solution of hippuric acid to stand for a month in a warm place. 2 It may also be readily prepared by heating ethyl amido-acetate with benzoic anhydride to 100. 3 It crystallizes from hot water in long, white, silky needles, which melt at 60'5, have no odour, but a sharp taste resembling that of oil of turpentine, and de- compose on heating. On distillation with steam, it decomposes into alcohol and the free acid. The following ethers have also been prepared : 4 Melting- point. Butyl hippurate, C 9 H 8 (C 4 H 9 )N0 3 , prisms 40 41 Isobutyl hippurate, C 9 H 8 (C 4 H 9 )N0 3 small, rhombic prisms 45 46 Amyl hippurate, C 9 H 8 (C 6 H U )N0 8> small needles . . 27 28 When hippuric acid is distilled with phosphorus pentachloricle, hydrochloric acid is evolved and the distillate consists, first, of phosphorus oxychloride, then of benzoyl chloride and finally of the compound C 9 H 6 C1NO, which crystallizes from ether in flat, four-sided, monoclinic prisms, melting at 40 50. It boils at 220, is not attacked by alcoholic potash, and on fusion with potash yields benzoic acid and ammonia. 5 The formation of this substance may be explained by the following equations : CH .NH.CO.C 6 H 5 CH 2 .NH.CO.C 6 H 5 +2PC1 5 = | + 2POC1 3 +HC1. CO.OH CC1 3 CH 9 .NH.CO.C 6 H 5 I =|| >N.CO.C 6 H 5 + 2HC1. CC1 3 CC1/ Hippuramide, (C 6 H 5 .CO)NH.C 2 H 2 O.NH 2 , is formed by the action of aqueous ammonia on the ethyl ether; it separates from hot water in short, thick crystals, melting at 183 (Jaque- min and Schlagdenhauffen ; Conrad). Hippuramido-acetic acid, C U H 12 N 2 O 4 , is formed, together with hippuric acid, by the action of benzoyl chloride on silver 1 Stenhouse, Ann. Chem. Pharm. xxi 148 ; Conrad, loc. cit. 2 Liebig, Ann. Chem. Pharm. Ixv. 351. 3 Curtius, Ber. Dcutsch. Chem. Gcs. xvii. 1662. 4 Campani and Bizzarri, Bull. Soc. Chim. xxxv. 427 ; Carapani, Ber Dcutsch. Chem. Gcs. xi. 1247. 5 Schwanert, Ann. Chem. Pharm. cxii. 59. 192 AKOMATIC COMPOUNDS. amido-acetate, and is probably derived from the hippuric acid which is first formed : CH 2 ,NH.CO.C 6 H 5 CH 2 .NH.CO.C 6 H, | + NH 2 .CH 2 .CO.OH = | CO.OH CO.NH.CH.,.CO.OH + H 2 It crystallizes from hot water in rhombic tablets or needles, melting at 206'5. On boiling with hydrochloric acid, it decom- poses into amido-acetic acid and benzoic acid ; on heating with dilute acids, on the other hand, both hippuric acid and amido- acetic acid are formed. Its salts crystallize well; the ethyl ether, which melts at 117, combines with ammonia forming hippurglycollamide, which crystallizes in large, transparent plates, melting at 202. An acid, C 10 H 12 N 3 4 , is also formed by the reaction just men- tioned, and crystallizes from hot water in microscopic needles which melt at 240, and are decomposed by hot hydrochloric acid into amido-acetic acid, benzoic acid, and a non-crystallizable, nitrogenous compound. 1 Hydrobenzuric acid, C 18 H 24 N 2 O 6 , is obtained by the action of sodium amalgam on a concentrated solution of hippuric acid in caustic soda solution ; it forms a mass resembling turpentine, and becomes crystalline after standing for months. When it is treated with an excess of sodium amalgam and water, it decom- poses into hydrobenzyluric acid, C 16 H 21 NO 4 , and amido-acetic acid. The former is an oily liquid, which gradually solidifies ; on boiling with alkalis it decomposes into hydrobenzoic acid, benzyl alcohol and amido-acetic acid. Its alkaline solution oxidizes in the air with formation of hydroxybenzyluric acid, C 16 H 2] NO 5 , which is a crystalline mass melting at 60 70. 2 2 1 12 Ornithuric acid, C 19 H 20 N 2 O 4 . Shepard found that ben- zoic acid is not converted into hippuric acid in the organism of birds, but into another nitrogenous compound, which was more closely examined by JafFe. 3 He obtained it from the excre- ments of hens which were fed with benzoic acid; it is very slightly soluble in water and crystallizes from hot alcohol in minute needles, melting at 182. Its solution reddens litmus. The following salts are characteristic : 1 Curtius, Journ. Prakt. Chem. [2] xxvi. 145. 2 Otto, Ann. Chem. Pharm. cxxxiv. 303. 8 Jaffe, Ber. Deutsch. Chem. Ges. x. 1925 ; xi. 406. ORNITHINE. 193 Calcium ornithurate, (C 19 H 19 ~N" 2 O 4 ) 2 Ca, is obtained by adding the ammonium salt to a solution of calcium chloride and heating the mixture ; it is a crystalline precipitate, which is only very slightly soluble in water. Barium ornithurate, (C 19 H 19 N 2 O 4 ) 2 Ba, is exceptionally soluble in water and alcohol, and is deposited from its alcoholic solution in opaque, crystalline flocks, which after drying form a snow- white powder. On boiling the acid with hydrochloric acid, it decomposes almost immediately into benzoic acid and lenzoylornithine, C^HjgN^Og, which is almost insoluble in alcohol and crystallizes from water in very brittle needles, melting at 225 230. It forms readily soluble salts with the mineral acids. If the boiling with hydrochloric acid be continued for some time, the acid decomposes into benzoic acid and ornithine, C 5 H 12 N 2 2 , which is very deliquescent, has a strongly alkaline reaction and a somewhat caustic taste. It combines with acids to form salts which crystallize well. Ornithine has the composition of a diamidovalerianic acid, and the constitution of these compounds can therefore be expressed by the following formulae : Ornithine. NH 2 C 4 H 7 .C9 2 H NH Benzoylornithine. NH 2 C 4 H 7 .C0 2 H NH.CO.C 6 H 5 Ornithuric acid. NH.CO.C 6 H 5 C 4 H 7 .C0 2 H I NH.CO.C 6 H 5 . Free ornithine, which has an alkaline reaction, will, of course, ive the following formula : NH 2 C 4 H 7 .CO I I NH 3 .0 194 AROMATIC COMPOUNDS. BENZENYL COMPOUNDS. 2113 These compounds are closely allied to the benzoyl deriva- tives. Phosphorus chloride converts benzoic acid, C 6 H 5 .CO.OH, first into benzoyl chloride, C 6 H 5 .COC1, and then by further action into benzenyl chloride, C 6 H 5 .CC1 3 . The latter is also formed by the continued action of chlorine on boiling toluene ; on heating with caustic potash it is reconverted into benzoic acid, which therefore bears the same relation to it as formic acid to chloroform. The action of the potash is probably to form benzenyl alcohol or orthobenzoic acid in the first instance : C 6 H 5 .CC1 3 +3KOH^:C 6 H 5 .C(OH) 3 + 3KC1. This is, however, as unstable as orthoformic acid and immedi- ately decomposes into water and benzoic acid ; ethers are, how- ever, known, such as ethyl orthobenzoate, C 6 H 5 .C(OC 2 H 5 ) 3 , obtained by the action of sodium ethylate on benzenyl tri- chloride. Benzoic acid itself may, therefore, be looked upon as a benzenyl compound, and this view was actually taken by Berzelius (Part I., p. 12). A large number of compounds which are formed by the action of hydroxylamine on benzoyl chloride may also be in- cluded among the benzenyl derivatives. The simplest of these is benzyhydroxamic acid : ^N.OH \OH. Benzonitril, C 6 H 5 .CN, and its compounds with alcohols, such as benzimido-ethyl ether : ^H X OC 2 H 5 . also belong to this class. The latter compound is converted by ammonia into benzenylamidine or benzimido- amide : ^H \NH 2 . BENZENYL TRICHLORIDE. 195 Benzenyl amidines which contain the radical phenyl, &c., are obtained by heating benzonitril with the hydrochlorides of ido-bases ; thus aniline yields phenylbenzenylamidine : C 6 H 6 .C; N(C 6 H 6 )H. Another series of amidines (Part III., p. 216) consists of the anhydro-bases, which are formed from the orthoamido-compounds by the elimination of water; benzoylorthodiamidobenzene in this way yields phenylenebenzenylamidine : Benzenyl trichloride or Benzo-trichloride, C 6 H 5 .CC1 3 . Liebig d Wohler found during their researches on the radical of zoic acid, that benzoyl chloride is converted by phosphorus tachloride into a strongly-smelling, oily substance, which they did not investigate more closely. 1 It was made the subject of research by Schischkow and Rosing 2 and also by Limpricht, 3 who found that it is also formed when benziderie dichloride, C 6 H 5 .CHC1 2 , is treated with chlorine, and named it benzoic trichloride. Benzenyl trichloride is most readily obtained by passing chlorine into boiling toluene until no further increase in weight takes place. 4 The product is then washed with caustic soda solution, dried over ignited potassium carbonate and recti- fied ; it is employed in the colour industry and is manufactured on the large scale, being purified by distillation in a vacuum. Benzenyl trichloride, which is also known as phenylchloroform, is a powerfully refractive liquid, which has a characteristic penetrating odour, boils at 213 214, and has a sp. gr. of 1'380 at 14. On heating with water to 150, it is converted into benzoic acid, while benzoic anhydride is formed when it is heated with sulphuric acid which contains 4'6 per cent, of water ij). 166). It is decomposed by fuming nitric acid with formation of metanitrobenzoic acid (Beilstein and Kuhlberg). 1 Ann. Chem. Pkarm. iii. 265. 2 Jahrcsbcr. Chem. 1858, 279. 1 Ann. Chem. Pharm. cxxxiv. 55 ; cxxxv. 80 ; cxxxix. 323. 4 Beilstein and Kuhlberg, ibid, cxlvi. 330. 198 AROMATIC COMPOUNDS. Benzenyl tribromide, C 6 H 5 .CBr 3 , is formed by the action of bromine on boiling toluene, and is a colourless liquid which has an exceedingly violent action on the eyes and mucous mem- brane. It cannot be distilled, since it decomposes at about 150 ; on heating with water it is readily converted into benzoic acid, while it is only very slowly attacked by boiling alcohol. 1 Benzcnyl ethyl ether, C 6 H 5 .C(OC 2 H 5 ) 3 . This compound, which j is also called ethyl orthobenzoate, was obtained by Limpricht, j who heated the chloride to 100 with a solution of sodium in absolute alcohol. It is a transparent, colourless liquid, which smells like ethyl benzoate and boils at 220 225. Benzenyl triacetate, C 6 H 5 .C(OC 2 H 3 O) 3 , is formed by the action of silver acetate on the chloride, and is a liquid which decom- poses on distillation into acetic anhydride and benzoic an- hydride. If it be allowed to stand in the air or over sulphuric acid in a vacuum, white needles separate out, which melt at 70, and have the composition of acetobenzoic anhydride (Limpricht). Monochlorobenzenyl trichloride, C 6 H 4 C1.CC1 3 . The ortho- compound has been obtained by the action of phosphorus penta- chloride on salicylic acid, C 6 H 4 (OH)C0 2 H ; it is crystalline, melts at 30 and boils at 260 . 2 The meta-compound has been prepared in a similar manner from metasulphobenzoic acid, C 6 H 4 (SO 3 H)CO. 2 H, and boils at 235 ; 3 the para-compound is formed by the chlorination of benzenyl trichloride in presence of iodine ; it boils at 245 and yields parachlorobenzoic acid when heated with water to 200 (Beilstein and Kuhlberg). Dichlorobcnzenyl trichloride, C 6 H 3 C1 2 .CC1 3 , has been prepared by the action of chlorine on a boiling mixture of the dichloro- toluenes obtained by chlorinating toluene. The product boils at 273 280 and yields three dichlorobenzoic acids on heating with water. 4 Trichlorobenzenyl trichloride, C 6 H 2 C1 3 .CC1 3 , is formed by pass- ing chlorine into boiling trichlorotoluene ; it crystallizes from alcohol in very fine needles, melts at 82 and boils at 307 308. Tctrachlorobenzcnyl trichloride, C 6 HC1 4 .CC1 3 , forms fine, short needles, melts at 104 and boils at 316 . 5 1 Tnce, Abst. Proc. Chem. Soc. 1885-6, 131. 2 Kolbe and Lautemann, Ann. Chem. Pharm. cxv. 195. 3 Carius and Kammerer, ibid, cxxxviii. 58. 4 Schulz, ibid, clxxxvii. 260 ; Aronheim and Dietrich, Bcr. Deutsch. Chem. Ges. viii. 1401. 8 Beilstein and Kuhlberg, Ann. Chem. Pharm. cl. 286. BENZONITRIL. BENZONITRIL AND ITS DERIVATIVES. 2114 Benzonitril, C 6 H 5 .CN. This substance was prepared by Liebig and Wohler by heating benzamide with baryta, 1 but was not investigated by them, and its identity with the benzonitril discovered by Fehling was established at a much later period. The latter chemist obtained it by the dry distillation of ammo- nium benzoate, 2 from which it is formed by loss of water. It can be prepared by a similar reaction from benzamide, C 6 H 5 .CO.NH 2 , by heating it with phosphorus pentoxide, 3 phos- phorus pentachloride, 4 phosphorus pentasulphide, 5 benzoyl chlo- ride, 6 potassium benzoate, 7 or caustic lime. 8 Among many other methods of preparation, some of which have been already mentioned (Part III., p. 31), the following are the most important. It can readily be obtained by distilling two molecules of benzoic acid with one molecule of potassium thiocyanate : C 6 H 6 .C0 2 H + HSCN = C 6 H 5 .CN + CO 2 + H 2 S. One half of the benzoic acid is converted into the potassium salt, from which it can readily be recovered. 9 Lead thiocyanate may be substituted for the potassium salt : 10 2C C H 5 .C0 2 H + Pb(SCN) 2 = 2C 6 H 5 .CN + PbS + H 2 S + 2C0 2 . Benzonitril is synthetically prepared by the distillation of sodium benzenesulphonate with potassium cyanide, 11 as well as by heating iodobenzene to 350 with silver cyanide, 12 or by the action of cyanogen chloride on benzene in presence of aluminium chloride. 13 It is obtained from aniline by converting the latter into diazobenzene chloride and heating this with a solution of Wohler, Ann. Chem. Pharm. cxcii. 362. 2 Ibid. xlix. 91. Hofmann and Buckton, ibid. c. 155. Gerhardt, Chim Org. iv. 762 ; Henke, Ann. Chem. Pharm, cvi. 276. Henry, Bcr. Deutsch. Chem. Ges. ii. 307. ( Sokolow, Gerhardt' s Org. Chim. i. 386. Kekule, Bcr. Deutsch. Chem. Ges. vi. 113. Anschiitz and Schulz, Ann. Chem. Pharm. cxcvi. 48. Letts, Bcr. Deutsch. Chem. Ges. v. 673. 10 Kriiss, ibid. xvii. 1766 1 Merz, Zeitschr. Chem. 1868, 33 ; Ber. Deutsch. Chem. Ges. iii. 710. 2 Merz and Weith, ibid. x. 746. 13 Friedel and Crafts, Bull. Soc. Chim. xxix. 2. 244 198 AROMATIC COMPOUNDS. the double cyanide of potassium and copper. 1 It can easily be prepared in the pure state by distilling benzamide with phos- phorus pentoxide and rectifying the product over the latter. A good yield is obtained by Letts's process, according to which the mixture of benzoic acid and potassium thiocyanate is heated in an apparatus connected with an inverted condenser until a white, solid mass has been formed. The product is then dis- tilled, the distillate freed from benzoic acid by means of ammonia, and the benzonitril finally distilled in steam ; he thus obtains 80 per cent, of the theoretical yield. Merz, by the distillation of 500 grms. of sodium benzenesulphonate with 330 grins, of potassium cyanide, obtained in one case 130 and in another 140 grms. of the crude 80 per cent, nitril, while Henry, employing his own method, obtained half the theoretical yield. Properties. Benzonitril is a mobile liquid, which smells like oil of bitter almonds, has a sp. gr. of T023 at 0, boils at 191 and solidifies in a mixture of ether and solid carbon dioxide to a crystal- line mass, melting at 1 7. 2 It is miscible with alcohol and ether, and dissolves in about 100 parts of water (Fehling). On boiling with caustic potash it is converted into benzoic acid, and it is re- duced in alcoholic solution by zinc and hydrochloric acid to benzyl- amine (Mendius) ; fuming sulphuric acid in the cold polymerizes it to cyanphenin, but on heating, forms metasulphobenzoic and benzenedisulphonic acids (Hofmann and Buckton). When it is mixed with benzene and concentrated sulphuric acid, dibenz- imido-oxide, C 14 H 12 N 2 O, is obtained; it crystallizes in thick vitre- ous prisms and has basic properties. 3 On heating it with dilute hydrochloric acid, dibenzamide is formed. 4 Both substances are obtained when well-cooled, fuming sulphuric acid is allowed to drop into benzonitril, and the mixture treated with water after standing for some time. 5 Their formation is explained by the following equations : C 6 H 5 .CN C 6 H 5 .CO X + H 2 >NH C 6 H 5 .CN C 6 H 5 .C4NH. C 6 H 5 .CO X C 6 H 5 CO >NH-f-H 2 = >NH+NH r C 6 H 5 .CdNH C 6 H 5 CO/ 1 Sandmeyer, Bcr. Deutsch. Ckem. Ges. xvii. 2653. 2 Hofmann, Jahrcsber. 1862, 335. 3 Klein and Pinner, Her. Dcutsch. Chem. Ges. xi. 764. 4 Pinner, ibid. xvii. 2006. 6 Gumpert, Journ. Prakt. Chem. [2] xxx. 87 ; Pinner, ibid. xxx. 125. BENZONITRIL. 199 When benzonitril is shaken up with a warm mixture of caustic potash solution and hydrogen peroxide, it is rapidly converted into benzamide, pure oxygen being evolved : x V> liiv tt C 6 H 5 .CN + 2H 2 O 2 =C 6 H 5 .CO.NH 2 + H 2 O + 2 . If benzonitril be taken internally, it appears in the urine in the form of oxybenzonitrilsulphuric acid, C 6 H 4 (O.S0 3 H)CN, which readily decomposes into sulphuric acid and the nitrils of icylic acid and parahydroxybenzoic acid ; the meta-compound, ever, is not formed. 2 Benzonitril combines with hydrobromic acid to form the crystalline compound, C 6 H 5 .CN + 2HBr, which is converted by water into benzamide : 3 C 6 H 5 .CBr 2 .NH 2 + H 2 O = C 6 H 5 .CO.NH 2 + 2HBr. According to Henry, a similar compound is formed with hydriodic, 4 but not with hydrochloric acid ; when, however, a current of the latter gas is passed into an ethereal solution of platinum chloride and benzonitril, long needles separate out, which decompose in dry air into their three components. 5 When benzonitril is heated with bromine, the monobromide, (C 7 H 5 NBr) 2 , is formed ; it crystallizes from ether in small needles, which partially sublime when heated and are partially decomposed into bromine, benzonitril and cyanphenin ; while on heating with lime, some carbon dioxide and ammonia are evolved in addition to the compounds mentioned. A dibromide also appears to exist, but it is very unstable. 6 It combines with some metallic chlorides to form the following solid compounds, C 7 H 5 N,AuCl 3 , (C 7 H 5 N) 2 PtCl 4 , (C 7 H 5 N) 2 SnCl 4 and (C 7 H 5 N) 2 TiCl 4 , the last of which forms bright crystals which may be sublimed. 7 2115 Cyanphenin, C 21 H 15 N 3 . This compound, which corre- sponds to cyanethin (Part I., p. 562), was obtained by Cloez by heating benzoyl chloride with potassium cyanate, 8 and i Engler prepared it, as already mentioned, from benzonitril 1 Radziszewski, Ber. Deutsch. Chem. Gfcs. xviii. 355. 2 Baumann, ibid. xvii. Ref 256. 3 Engler, Ann. Chem. Pharm. cxlix. 307. 4 Bull. Soc. Chim. vii. 85. 5 Klein and Pinner, Ber. Deuisch. Chem. Ges. x. 1891. 6 Engler, Ann. Chem. Pharm. cxxxiii. 144. 7 Henke, ibid. cvi. 284. 8 Ibid. cxv. 27. 200 AROMATIC COMPOUNDS. bromide. Hofmann found that it is formed when benzonitril is heated with sodium, 1 and Klein and Pinner when it is treated with fuming sulphuric acid. 2 It is also obtained in tolerable quantity, according to Henry, together with benzonitril, by the action of phosphorus pentasulphide on benzamide, and, together with an oily base, C 16 H 18 N 2 , the hydrochloride of which, C 1G H 1( , N 2 C1, crystallizes in six-sided tablets, when benzonitril is heated with zinc ethyl. 3 Cyanphenin is a hard, crystalline substance, which melts at 231, sublimes in needles, and boils above 350. It is insoluble in water, slightly soluble in alcohol and ether, more readily in carbon disulphide and ethyl iodide. It is not attacked when heated with aqueous or alcoholic potash, but is converted into benzoic acid by heating to 220 4 with fuming hydriodic acid, or to 250 with concentrated hydrochloric acid (Frankland and Evans). BENZIMIDO-ETHERS. 2116 The Benzimido-ethers include the compounds which are formed by the action of hydrochloric acid on a mixture of benzonitril with an alcohol. Of these compounds the isobutyl ether has been more fully described ; 5 its formation is preceded by that of a compound which forms large, lustrous crystals, which fume in moist air and decompose into hydrochloric acid, ammonium chloride and isobutyl benzoate : /NH 3 C1 C 6 H 6 .C^OC 4 H 9 -|-H 2 O = HC1+NH 4 C1+C 6 H 5 .CO.OC 4 H 9 . M-tt If, however, the compound be freed from benzonitril and isobutyl alcohol by washing with ether and allowed to stand over caustic soda, a molecule of hydrochloric acid is given off and the hydrochloride of benzimido-isobutyl ether remains 1 Ber. Deutsch. Chem. Ges. i. 198. 2 Ibid. xi. 764 ; Pinner, Journ. Prakt. Chem. [2] xxx. 125. 8 Frankland and Evans, Journ. Chem. Soc. 1880, i. 563. 4 Engler, Ann. Chem. Pharm. cxlix. 310. 8 Pinner and Klein, Ber. Deutsch. Chem. Ges. x. 1889 ; xi. 4. BENZIMIDO-ETHERS. it decomposes on heating into benzamide and isobutyl chloride : ,NH 2 C1 C 6 H 5 .C^ = C 6 H 5 .CO.NH 2 +C,H 9 CL OC 4 H 9 It is decomposed by a solution of ammonia in absolute alcohol, with formation of the free isobutyl ether, ammonium chloride and benzenylamidine hydrochloride. Benzimido-isobutyl ether, C 6 H 5 .C(NH)OC 4 H 9 , is a thick, oily liquid, which partially decomposes on distillation ; it readily recombines with hydrochloric acid ; cold, concentrated sulphuric acid converts the hydrochloride into the acid sulphate, C 6 H 5 C (OC 4 H 9 )NH 2 .SO 4 H, which crystallizes in long, pliant needles. Benzimido-acetic ether, C 6 H 5 .C(NH)OC 2 H 3 O, is formed by boiling the isobutyl ether with acetic anhydride ; it is insoluble in water and acids, dissolves in alcohol and crystallizes in needles, melting at 116. Berizimido-ethyl ether, C 6 H 5 .C(NH)OC 2 H 5 . The hydrochloride of this compound forms large, lustrous, transparent prisms, which decompose at 118 120 with formation of benzamide. In other respects the compound resembles its isobutyl analogue. 1 Benzimido-thio-ethyl ether, C 6 H 5 .C(NH)SC 2 H 5 . The hydro- chloride of this compound is formed when hydrochloric acid is passed into a mixture of ethyl mercaptan and benzonitril : NH 2 C1 C 6 H 5 .CN4 HS.C 2 H 5 +HC1 = C 6 H 5 X SC 2 H 5 . It crystallizes in thick prisms, which melt at 188 and are readily soluble in water and alcohol. The hydriodide is obtained by heating thiobenzamide to 100 with ethyl iodide : NHI It forms long, monosymmetric prisms, melting at 142. Alkalis separate the ether from these salts as a strongly-smelling, oily liquid, which is soluble in water and readily decomposes into benzonitril and mercaptan. 2 1 Pinner, Ber. Deutsch. Chem. Ges. xvi. 1654. 2 Bernthsen, Ann. Chem Pharm. cxcvii. 348. 202 AROMATIC COMPOUNDS. Benzimido-tUobenzyl ether, C 6 H 5 .C(NH)S.CH 2 .C 6 H 5 . The hydrochloride is obtained by the action of benzyl chloride on thiobenzamide, or of hydrochloric acid on a mixture of benzyl hydrosulphide and benzomtril. It is soluble in water and alcohol, and crystallizes in white tablets melting at 181. The free base is very unstable (Bernthsen). BENZENYLAMIDINES. 2117 Benzenylamidine or Benzimido-amide, C 6 H 5 .C(NH)NH 2 , is formed, as already mentioned, by the action of alcoholic ammonia on the hydrochloride of benzimido-isobutyl ether : HO.C 4 H 9 . Free benzimido-isobutyl ether is simultaneously formed, but the quantity of this product diminishes when the temperature at which the reaction is carried out is raised. 1 The product is evaporated in a vacuum, the residue washed with ether and crystallized from alcohol, yielding benzenylamidine hydrochloride in flat needles, which are decomposed by caustic potash but not by ammonia ; by shaking out with ether and evaporating, the free base is obtained as a crystalline mass, which is slightly soluble in water, readily in alcohol and has an alkaline taste and reaction. It decomposes spontaneously after some time with evolution of ammonia, which is also given off on heating, benzomtril and cyanphenin being formed. If it be heated to 100 with ethyl iodide, the product decomposed with caustic soda and extracted with ether, ethyl- lenzenylamidine, C 6 H 5 C(NC 2 H 5 )NH 2 , is obtained as a strongly alkaline, thick, oily liquid. Dibenzenyltriamine, C 14 H 13 N 3 , is formed, together with acet- amide, when benzenylamidine is boiled with acetic anhydride : NH .NH C 6 H 5 .C^ 2C 6 H 5 .cf >NH + NH 3 . ^NH 1 Pinner and Klein, Ber. Dcutsch. Chem. Ges. x. 1889. PHENYLBENZENYLAMIDINE. 203 It crystallizes in long, flat needles, which melt at 108 109 and are not decomposed even at 240 . 1 Phenylbenzenylamidine, C 6 H 5 .C(NH)N(C 6 H 5 )H, is obtained, together with diphenylbenzenylamidine, by heating benzouitril 1220 240 with aniline hydrochloride : NH e. The product is extracted with cold water and the solution precipitated with ammonia ; the base thus obtained is very readily soluble in alcohol, and crystallizes badly in small crusts or warts composed of plates, which melt at 111 112, and, on further heating, partially sublime and are partially decomposed into aniline and benzonitril. Phenylbenzenylamidine hydrochloride is a syrup, miscible with water and alcohol in all proportions. 2 It is converted by the action of sodium amalgam on its alcoholic solution into benzidenephenyldiamine, C 6 H 5 .CH(NH 2 )N(C 6 H 5 )H. 3 When phenylbenzenylamidine is heated with carbon disul- phide, its thiocyanate is obtained together with thiobenzanilide ; an. intermediate product is probably first formed and then decomposed at the higher temperature : 4 / NH \ ^-S^CS = C 6 H 5 .CS.N(C 6 H 6 )H + KCSH. \N(C 6 H 6 )H Symmetric diphenylbenzenylamidine, C 6 H 5 .C(NC 6 H 5 )N(C 6 H 5 )H. This compound was first prepared by Gerhardt, who obtained it by warming benzanilide with phosphorus pentachloride and then heating the product with aniline. 5 The compound C 6 H 5 .CC1 2 .N(C 6 H 5 )H is first formed, and is converted, with loss of hydrochloric acid, into 'benzanilidimidocliloride, which acts upon the aniline in the following manner : +N(C 6 H 6 )H 2 = C 6 H 5 .C + HC1. NCI , X N(C 6 H 6 )H 1 Bcr. Deutsch. Chem. Ges. xi. 4. 2 Bernthseu, Ann. Chem. Pharm. clxxxiv. 348. 3 Bornthsen and Szymanski, Ber.- Deutsch. Chem. Ges. xiii. 917. 4 Bernthsen, Ann. Chem. Pharm. cxcii. 31. 5 Ann. Chem. Pharm. cviii. 217. 204 AROMATIC COMPOUNDS. Benzanilidimidochloride crystallizes from petroleum ether in large, transparent, lustrous plates, melts at 39 40, and boils without decomposition at about 310; water decomposes it rapidly, benzanilide being reproduced. 1 Diphenylbenzenylamidine is also formed by the action of aniline on benzenyl trichloride, 2 and by heating benzanilide with aniline hydrochloride and phosphorus trichloride. 3 It is slightly soluble in water, readily in alcohol, and crystallizes in needles, melting at 144 (Wallach and Hoffmann). On heating with hydrochloric acid to 150, it decomposes into benzoic acid and aniline, while, on heating with sulphuric acid, thiobenzanilide and phenyl mustard oil are formed (Bernthsen). Its hydro- chloride, C 19 H 16 N 2 .C1H, is only very slightly soluble in cold water and crystallizes from alcohol in needles. Asymmetric diphenylbenzenylamidine, C 6 H 5 C(NH)N(C 6 H 5 ) 2 , is prepared by heating benzonitril with diphenylamine hydro- chloride to 180 190. It is exceptionally soluble in alcohol and tolerably in ether, from which it crystallizes in thin, yellowish, alkaline, rhombic tablets, melting at 112. It decomposes on boiling into diphenylamine and benzonitril ; when it is heated with carbon disulphide, its thiocyanate is formed together with diphenylthiobenzanilide, C 6 H 5 .CS.N(C 6 H 5 ) 2 . Its hydrochloride crystallizes in needles or monoclinic prisms, which are readily soluble in water (Bernthsen). Diphenylparamidobcnzenylamidine or Carbotriphenyltriamine, C 19 H 17 N 3 , was first prepared by Hofmann by heating aniline with tetrachloromethane ; 4 it is more readily formed, however, from tetrabromomethane. 5 Weith obtained it by heating para- nitrobenzoic acid with aniline and phosphorus trichloride, and reducing the diphenylparanitrobenzenylamidine thus formed with tin and hydrochloric acid, 6 while Michler and Walder prepared it by the action of aniline on trichloromethylsulphonyl chloride, CC1 3 .SO 2 C1. 7 It is insoluble in water, slightly soluble in ether, and crystallizes in long tablets, melting at 198. On distillation it decomposes into hydrocyanic acid, benzonitril, ammonia, aniline, and diphenylamine, while on heating with 1 "Wallach and Hoffmann, Ann. Chem. Pharm. clxxxiv. 79. 2 Limpricht, ibid, cxxxv. 82 ; Dobner, Ber. Deutsch. Chem. Ges. xv. 233. 3 Hofmann, Zeitschr. Chem. 1866, 165 4 Hofmann, Jahresbcr. Chem. 1858. 351. 5 Bolas and Groves, Ann. Chem. Pharm. clx. 173. 6 Her. Deutsch. Chem. Ges. xii. 101. 7 Ibid. xiv. 2174. PHENYLENEBENZENYLAMIDINE. 205 hydrochloric acid to 160, aniline and paramidobenzoic acid are formed : H,N.C 6 H 4 .C + 2F 2 = H 2 N.C 6 H,.C0 2 H + \N(C 6 H 5 )H 2N(C 6 H 5 )H 2 . Plienyknebenzenylamidine, C 13 H 10 N 2 , was termed arihydro- lenzodiamidolenzene by Hiibner, and is obtained by heating benzoylorthodiamidobenzene : /NH 2 KK. C 6 H 4 < CO.C 2 H 5 = C fl H / >C.C 6 H 5 + H 2 0. X NH/ \ N ^ It may also be easily prepared by reducing benzoylorthonitro- anilide with tin and hydrochloric acid, the rise of temperature caused by the reaction being sufficient to bring about the forma- tion of the anhydro-base. It is slightly soluble in water, readily in alcohol, and crystallizes from glacial acetic acid in lustrous tablets, melting at about 280 ; the hydrochloride, C 13 H 10 N 2 .C1H, forms long needles, which are readily soluble in water. The base is not attacked by benzoyl chloride even at 260 on heating with iodine and alcohol, however, the periodide, C 13 H 10 N 2 .IH.I 2 , is formed, and crystallizes in small plates which resemble iodine, but have a green surface lustre and are con- verted by boiling with water into the hydriodide, C 13 H 10 N 2 .IH + H 2 O, crystallizing in long, light yellow needles. Dimethylphenylenebenzenylam.ide ammonium iodide, C 13 H 10 N 2 (CH 3 ) 2 I. When the anhydro-base is heated with methyl iodide to 180, the periodide, C 13 H 10 N 2 (CH 3 ) 2 I 3 , is formed ; this sub- stance crystallizes in long, brownish red needles, and is con- verted into the mono-iodide by boiling in alcoholic solution with freshly precipitated lead hydroxide. This compound crystallizes from hot water in long needles ; caustic potash precipitates from its solution the hydroxide, C 13 H 10 N 2 (CH 3 ) 2 OH, in white flocks, which melt at 152 and are insoluble in water, but dissolve readily in hot alcohol. Its solution has a bitter taste, and its salts crystallize well ; it has the following constitution : OH 4\ ^- 206 AROMATIC COMPOUNDS. Phenylencnitrobenzcnylwnidine, C 13 H 9 (NO 9 )N 9 , is obtained by dissolving the anhydro-base in fuming nitric acid ; it crystallizes from alcohol in yellowish, microscopic needles, melting at 196. It is reduced by tin and hydrochloric acid to amidobenzenyl- phtwylcne-amidine, C 13 H 9 (NH )N 2 , which crystallizes from alcohol in small needles, melting at 240. The hydrochloride, C 13 H 9 (NH 2 )N 2 (C1H) 2 , forms small plates, which are very soluble in water; the sulphate, C 13 H 9 (NH 2 )N 2 .S0 4 H 2 + 2H 9 0, is only slightly soluble in hot water, and crystallizes in broad needles. A large number of other similar anhydro-bases is also known. 1 The following compounds belong to the same class. BenzenylamidopJienate, C 13 H 9 NO. Ladenburg prepared this compound by heating ortho-amidophenol with benzoyl chloride, and by the distillation of the former with phthalic anhydride : /C( C 6 H 4 / It crystallizes from dilute alcohol in lustrous plates, melts at 103, and boils at 314 317 ; it combines with acids to form unstable salts ; the platinichloride, (C 13 H 10 NO) 2 PtCl 6 , crystal- lizes from alcohol which contains hydrochloric acid in yellow prisms. On heating the base with concentrated hydrochloric acid to 150, it decomposes into benzoic acid and orthamido- phenol. 2 Benzenylamidothiophenate, C 13 H 9 NS, is formed by boiling benzanilide with sulphur : 3 C 6 H 5 .CO.NH(C 6 H 5 ) + S = C 6 H 5 .C^ \C 6 H 4 + H 2 0. It is also obtained by the action of benzoyl chloride on ortho- amidothiophenol, as well as by heating the latter with benz- aldehyde, or benzonitril. 4 It is formed in smaller quantity, together with other products, when phenyl mustard oil is heated with benzoyl chloride. 5 It crystallizes from alcohol in needles, which, especially when heated, smell like tea-roses and geraniums, melt at 115, and boil at about 360. Like the preceding compound, it is a base and forms a platinichloride 1 Hiibner, Ann. Chem. Pharm. ccviii. 278 ; ccix. 339 ; ccx. 328. 2 Ber. Deutsch. Chem. Ges. ix. 1526. 3 Hofmann, ibid. xii. 2359. 4 Ibid. xiii. 1223. 5 Ibid. xiii. 17. BENZHYDROXAMIC ACID. 207 which crystallizes in long needles. It is not attacked when heated with concentrated hydrochloric acid to 200; on fusion with caustic potash it is resolved into amidothiophenol and benzoic acid. BENZENYLOXIME COMPOUNDS. 2118 The three hydrogen atoms of hydroxylamine can, as was pointed out by Lossen, be successively replaced by benzoyl : Benzhydroxylamine, NOH 2 (CO.C 6 H 5 ), Dibenzhydroxylamine, NOH(CO.C 6 H 5 ) 2 , Tribenzhydroxylamine, NO(CO.C 6 H 5 ) 3 . The last of these compounds is an indifferent substance ; the two others are acids, and have therefore been called by Lossen benzhydroxamic acid and dibenzhydroxamic acid. 1 Certain cases of physical isomerism and of metamerism are characteristic of them and their derivatives. Lossen showed somewhat later that these peculiarities as well as numerous decompositions of the compounds in question can readily be explained if benzhydrox- amic acid be looked upon as an oximido-compound of benzenyl ; 2 its formation is then expressed by the following equations: N.OH C 6 H 5 .COC1 + H 2 N.OH = C 6 H 5 .C + HO. /N.OH /N.OH C,H 6 .CC + H 2 = C 6 H 5 .Cf 4- HC1. \C1 \OH It is, however, also possible that the hydroxylamine forms an additive compound with the benzoyl chloride, and that hydro- chloric acid is then given off : 3 -OH /OH V NH.OH - C 6 H 5 .C/ \ci C 6 H 5 .CNH.OH = CH.C< + HC1. 1 Ann. Chem. Pharm. clxi. 347. 2 Ber. Deutsch. Chem. Ges. xvi. 873. 3 Ibid, xviii. 1189. 208 AROMATIC -COMPOUNDS. The other compounds are then formed by the replacement of the hydrogen of the hydroxyls. Hydroxylamine hydrochloride is dissolved in 8 10 parts of water, together with an equivalent amount of sodium car- bonate, and 3 parts of benzoyl chloride gradually added, the whole being then well shaken up and cooled; the dibenz- hydroxamic acid separates out together with a portion of the benzhydroxamic acid, which is removed by recrystallization from hot alcohol. The benzhydroxamic acid remaining in the solution is precipitated by barium chloride, and then liberated from the well-washed precipitate by dilute sulphuric acid. A further quantity of it can be obtained, since dibenzhydroxamic acid splits up into benzoic acid and benzhydroxamic acid when heated with baryta water. Benzhydroxamic acid or Benzenyloximic acid, C 6 H 5 .C(OH)NOH, crystallizes in rhombic plates or tablets, and dissolves in 44*5 parts of water at 6, much more readily in tolerably warm water, very readily in alcohol and slightly in ether. It has an acid reaction, melts at 124 125, and undergoes a sudden, violent decomposition at a higher temperature. When heated with dilute hydrochloric acid, it decomposes into hydroxylamine and benzoic acid. It is monobasic, but forms acid salts with the alkali metals. Acid potassium benzhydroxamate, C 6 H 5 .C(OH)NOK-f C 6 H 3 .C (OH)NOH, is tolerably soluble in cold water, scarcely in alcohol, and crystallizes in small rhombic plates or flat, pointed prisms, which deflagrate sometimes with the production of flame, when heated. The normal salt is readily soluble in alcohol ; on evaporation of the solution, however, the acid salt and potassium carbonate separate out. Acid sodium benzhydroxamate, C 6 H 5 .C(OH)NOjSTa-f-C 6 H 5 .C (OH)NOH + 3H 2 0, is somewhat more readily soluble in water, slightly in alcohol, and crystallizes in long, thin plates, or large elongated tablets, which rapidly deliquesce in the air. Acid barium hydroxamate, (C 7 H 6 NO 2 ) 2 Ba + C 7 H 7 NO 2 , forms small prisms scarcely soluble in water and alcohol. Normal barium hydroxamate, (C 7 H 6 NO 2 ) 2 Ba, is obtained by the addition of barium chloride to a solution of the acid potassium salt which has been treated with ammonia ; it forms microscopic needles. The calcium salt is a precipitate resembling alumina ; the benzhydroxamates of most of the other metals are also insoluble. The behaviour of the acid and its acid salts towards ferric DIBENZHYDROXAMIC ACID. 209 chloride is very characteristic ; a dark red precipitate is formed which dissolves in an excess of the precipitant with a deep cherry-red colour, which is not altered by the addition of dilute hydrochloric or sulphuric acid, but is destroyed by concentrated hydrochloric acid ; the addition of water causes the reappearance of the colour. If the original solution contains hydrochloric acid, ferric chloride only produces a colouration. When the barium salt is distilled with a little water aniline is formed : l 2(C H 6 C(OH)NO) 2 Ba + H 2 = 2C 6 H 5 .NH 2 + C0 2 +BaC0 3 . Ethyl benzhydroxam-ate, C 6 H 5 .C(OH)OC 2 H 5 , is obtained by the action of ethyl iodide and caustic potash on a solution of the acid in alcohol, 2 as well as by that of benzoyl chloride on ethyl hydroxylamine, H 2 N(OC 2 H 5 ). 3 It is very slightly soluble in water, readily in alcohol, and crystallizes in thick tablets, which melt at 64 65 and are resolved at 190 into alcohol, aldehyde, benzamide and phenyl isocyanate. It is readily soluble in alkalis, being re-precipitated from solution by acids and even by carbon dioxide ; on heating with concentrated hydrochloric acid, it decomposes into benzoic acid and ethyl hydroxylamine. If equal molecules of the ether and caustic potash be dissolved in alcohol and treated with silver nitrate, a white precipitate of C 6 H 5 .C(OAg)NOC 2 H 5 , is obtained, which blackens only on heating, while silver benzhydroxamate blackens and decomposes immediately on precipitation. Benzoyl ethylbenzhydroxamate, or Benzethylbenzhydroxylamine, C 6 H 5 .C(O.CO.C 6 H 5 )NOC 2 H 5 , is obtained by the action of benzoyl chloride on an alkaline solution of the ether ; it is readily soluble in alcohol and ether and forms transparent rhombic crystals, melting at 48 49. 4 2119 Dibenzhydroxamic acid, or Benzoylbenzoximic acid, C 6 H 5 .C (OH)NO.CO.C 6 H 5 , which is produced by the action of benzoyl chloride on benzhydroxamic acid, crystallizes from hot alcohol in needles, and on the spontaneous evaporation of the solution in large, lustrous, rhombic prisms ; it has an acid reaction, melts at 153 , 5 and decomposes violently at a higher temperature with formation of carbon dioxide, benzoic acid, benzanilide and phenyl isocyanate. 6 On heating with hydrochloric acid it splits up into 1 Ann. Chem. Pharm. clxxv. 323. 2 Waldstein, ibid, clxxxi. 384. 8 Giirke, ibid. ccv. 278. 4 Pieper, ibid, ccxvii. 8. 5 Steinor, ibid, clxxviii. 226. 6 Pieschel, ibid, clxxv. 305. 210 AROMATIC COMPOUNDS. benzole acid and hydroxylamine, while alkalis decompose it into benzhydroxamic acid and benzoic acid, so that the former acid can be prepared from it by means of baryta water. Its alkali salts on the other hand are decomposed by water even in the cold, more rapidly on heating, with formation of benzoic acid, carbon dioxide and diphenyl urea : NO.CO.C 6 H 6 2C 6 H 5 .Cf + H 2 = 2C 6 H 6 .CO.OK \OK /N(C 6 H 5 )H C0( + CO,. \N(C 6 H 5 )H As already mentioned, benzhydroxamic acid can be directly converted into aniline, while dibenzhydroxamic acid yields derivatives of this phenyl isocyanate, benzanilide and diphenyl urea f rom which aniline can easily be obtained. Since the homologues of benzoic acid also yield oximes, a general method is established by which the carboxyl of a monobasic aromatic acid can be replaced by an amido-group (Lossen). Inversely, the amido-group of amido-compounds can be re- placed by carboxyl, and aniline thus converted into benzoic acid (Part III. p. 31). Potassium dibenzhydroxamate, C 6 H 5 .C(OK)NO.CO.C 6 H 5 , is precipitated in thin plates when alcoholic solutions of the acid and caustic potash are mixed. If silver nitrate be added to its freshly prepared aqueous solution, a white precipitate of the silver salt is obtained ; if this be dried, covered with ether and treated with ethyl iodide, the ethyl ether is obtained in two isomeric forms, one of which is an oily substance, 1 while the other is dimorphous. a-Ethyl dibemhydroxamate, C 6 H 5 .C(OC 2 H 5 )NO.CO.C 6 H 5 , is the chief product of the reaction ; it is readily soluble in ether and alcohol, and crystallizes In four- or eight-sided rhombic prisms, melting at 58. ft-Ethyl dibcnzhydroxamate, which is only formed in very small quantity, is more readily soluble than the a-compound and forms triclinic crystals, melting at 63. These modifications cannot be directly converted into each 1 Eiseler, Ann. Chcm. Pharm. clxxv. 326 ; Giirke, ibid. ccv. 279. TiUBENZHYDROXYLAMINE. 211 other; on heating they 'decompose into benzonitril, aldehyde and ben zoic acid : C 6 H 5 .C(OC 2 H 5 )NO.CO.C 6 H 5 = C 6 H 5 .CN + C 2 H 4 O+ C 6 H 5 CO.OH. Concentrated hydrochloric acid decomposes them into benzoic acid, ethyl benzoate and hydroxylamine, while on heating with caustic potash, benzoic acid and two isomeric ethylhydroxamic acids are formed. The oily ether is also readily soluble in alcohol and ether, and behaves chemically like the two others ; it is only formed in small quantity and has not been closely investigated. a-Ethylbenzhydroxamic acid, C 6 H 5 .C(OC 2 H 5 )NOH, is readily soluble in alcohol and ether ; it crystallizes from a mixture of ether and benzene in monoclinic tablets or prisms, melting at 53'5. The ethyl ether, C 6 H 5 .C(OC 2 H 5 )NOC 2 H 5 , is formed by the action of ethyl iodide on a solution of the acid in alcoholic potash. 1 It is a powerfully refractive liquid which has a pleasant aromatic odour, and boils at 244 with slight decom- position ; its vapour has a sp. gr. of 6 '5 6 (Giirke). On heating with alcohol and hydrochloric acid, it forms ethyl benzoate and ethyl hydroxylamine. fB-Ethylhydroxamic acid is isomorphous with the a-compound, but it melts at 67'5 68, is more soluble in petroleum spirit, less so in caustic potash, and is more readily extracted from this by ether. Its ethyl ether is so similar to that of the a-compound that it is doubtful whether they are distinct substances. Both acids are formed simultaneously by the action of hydroxylamine on benzimido-ethyl ether. 2 It is almost completely converted into ethyl /3-dibenzhydroxa- mate by the action of benzoyl chloride. 3 '2 1 20 Tribenzhydro&ylamine, or Dibcnzobenzoximate, C 6 H 5 .C (O.CO.C 6 H 5 )NO.CO.C 6 H 5 , is obtained in three modifications by treating dry hydroxylamine hydrochloride with a solution of benzoyl chloride in toluene, or by heating potassium dibenz- hydroxamate with benzoyl chloride. 4 It is, however, best 1 Lessen and Zarmi, Ann. Chem. Pharm. clxxxii. 220. 2 Lessen, Bcr. Deutsch. Chem. Ges. xvii. 1587. 3 Giirke, Ann. Chem. Pharm. ccv. 281. 4 Lessen, Ann. Chem. Pharm. clxi. 360 ; clxxv. 282 ; clxxxvi. 34 ; Steiner, ibid, clxxviii. 225. 212 AROMATIC COMPOUNDS. prepared by acting upon silver dibenzhydroxamate with a solution of benzoyl chloride in petroleum ether, and allowing the whole to stand until the silver chloride has separated as a dense precipitate (Lossen). a-Tribenzhydroxylamine is slightly soluble in cold, more readily in hot alcohol and ether, and forms monoclinic crystals, elongated in the direction of the ortho-diagonal, 1 which melt at 100. It is completely split up into benzoic acid and dibenz- hydroxamic acid by heating for an hour with hydrochloric acid of sp. gr. 1*05. p-Tribcnzhydroxylamine is insoluble in ether, slightly soluble in cold, more readily in hot alcohol, and forms small, lustrous, monoclinic crystals, melting at 141 142 (Klein and Trech- mann). It is decomposed by concentrated hydrochloric acid at 150 into benzoic acid, dibenzhydroxamic acid and hydroxyl- amine. NOC 2 H 5 c 6 H 5 .c<; + HOI = c 6 H 5 .c r + N 2 -h H 2 o. \C1 The chloride is also readily produced by the action of phosphorus mtachloride on ethyl benzhydroxamate, C 6 H 5 .C(NOC 2 H 5 )OH. 3 It is an oily, aromatic liquid, which boils at 239, is not decom- posed by water or alcohol, and is not even attacked when heated for a short time with acids and alkalis. When heated with Icoholic ammonia to 160 180, however, the amidoxime ethyl jther is re-formed, and it is converted by the action of a 1 Kriiger and Ticmann, Ber Deutsch. Chem. Ges. xviii. 184. 2 Ber. Deutsch. Chem. Ges. xviii. 1193. 3 Ibid. 245 214 AROMATIC COMPOUNDS. solution of sodium in absolute alcohol into ethyl ethylbenz- hydroxamate. Benzoylbenzenylamidoxime, C 6 H 5 .C(NO.CO.C 6 H 5 )NH 2 , is formed by the action of benzoyl chloride on benzenylamidoxime. It crystallizes in fine, white needles, which melt at 140, and are soluble in alcohol, ether, and acids, but not in alkalis. 2 121 Dibcnzenylazoxime, (C 7 H 5 ) 2 N 2 O, is obtained by heating the compound just described beyond its melting-point, or by treating it with dehydrating agents, such as benzoic anhydride or benzoyl chloride : NO.CO.C 6 H 5 NO, C 6 H,C^ = C 6 H,C^ \C.C,H, + H/>. \NH 2 X -N-^ It is scarcely soluble in water, but readily in alcohol, and crystallizes in long, fine needles, which, after drying, resemble asbestos and melt at 108, but sublime at a much lower temperature. Ethenylbenzenylazoxime is formed by the action of acetic anhy- dride on benzenylamidoxime, and is very similar to the preceding compound, crystallizing in needles which readily sublime, have a characteristic odour and melt at 41. It is isomeric with benz- enylethenylazoxime, which is obtained by the action of benzoyl chloride on ethenylamidoxime, CH 3 .C(NOH)~NH 2 , and forms aromatic needles, which melt at 57 and sublime very easily. 1 The isomerism of these two compounds is shown by the follow- ing formulae : Ethenylbenzenylazoxime. Benzenylethenylazoxime. C.CH 3 3 . . Acetylbenzenylamidoxime, C 6 H 5 .C(NO.CO.CH 3 )NH 2 , is formed by the action of acetyl chloride on an ethereal solution of benz- enylamidoxime. It crystallizes from alcohol in small plates or flat prisms, which melt at 96, and are easily converted into ethenylbenzenylazoxime, the change being brought about even by boiling with water. 2 Ethyl benzenylamidoximecarboxylate, C 6 H 5 .C(NH 2 )NO.CO.OC 2 H 6 , 1 Nordmann, Ber. Deutsch. Chem. Ges. xv. 2754. 2 Schultz, ibid, xviii. 1080. BENZENYLAZOXIME CARBINOL. 215 is obtained by adding ethyl chlorocarbonate to a solution of benzenylamidoxime in chloroform. It crystallizes in long, lustrous needles, which melt at 127 and are decomposed at a higher temperature, or on heating with water, into the following compound, alcohol being removed : Benzenylazoxime carbinol, C 8 H 6 N 2 O 2 , is most simply prepared by heating benzenylamidoxime with ethyl chlorocarbonate. It crystallizes from hot water in long needles/melting at 197. It readily dissolves in alkalis ; its aqueous solution has an acid reaction and decomposes the carbonates of the alkaline earth metals. Silver nitrate precipitates the white crystalline silver salt from a solution neutralized with ammonia, and copper sul- phate, the green copper salt, (C 8 H 5 N 2 2 ) 2 Cu. According to the method by which it is prepared, benzenyl-, azoxime carbinol should have the first of the following formulse ; its whole behaviour, however, corresponds with the second, and an intramolecular change must therefore be assumed : Carbonyldibenzenylamidoxime, (C 6 H 5 .C (NH 2 )NO) 2 CO, is formed when benzenylamidoxime is brought into contact with carbonyl chloride dissolved in benzene. It is almost insoluble in the latter and is precipitated by water from its alcoholic solution in small plates, melting at 128 129. On heating with caustic soda solution, the preceding compound is formed. 1 Benzenylazoxime propenylcarloxylic acid, C 11 H IO N 2 O 3 , is ob- tained by heating benzenylamidoxime with succinic andydride : CH 2 -CO V + | \0 = . CH 2 CCK N (X C 6 H 5- C \ J)C CH 2 CH 2 CO.OH -f H 2 O. It crystallizes from hot water in small, lustrous, white, rhombic plates or prisms, melting at 1 20. The anhydrides of other dibasic acids give similar compounds. 2 1 Falck, Ber. Deutsch. Chem. Oes. xviii. 2467. 2 Schultz, ibid, xviii. 2458. 216 AROMATIC COMPOUNDS. Metanitrobenzcnylamidoximc, C 6 H 4 (NO 2 )C(NH 2 )NOH. Meta- nitrobenzonitril readily combines with hydroxylamine to form this compound. It crystallizes in orange -coloured prisms, melt- ing at 174. A series of compounds has been prepared from it, corresponding to those described above. 1 Mctamidobenzenylamidoxime, C 6 H 4 (NH 2 )C(NH 2 )NOH, is formed by the reduction of the preceding compound, and separates from ether as a yellow oil which gradually solidifies. Its hydrochloride, C 6 H 4 (NH 3 C1)C(NH 3 C1)NOH, crystallizes from hot water in prisms. Metahydroxylenzenylamidoxime, C 6 H 4 (OH)C(NH 2 )NOH, has been prepared from the amido-compound by the diazo-reaction, and crystallizes from dilute alcohol in light yellow needles, melt- ing at 163 . 2 HALOGEN-SUBSTITUTION PRODUCTS OF BENZOIC ACID. 2122 When an atom of hydrogen in benzoic acid is replaced by an element of the chlorine group, a meta-compound is formed, and not, as in the case of toluene and the benzyl compounds, a para-compound, accompanied by a small amount of an ortho- compound. Substituted benzoic acids are obtained by the oxidation of the corresponding alcohols and aldehydes, as well as of the substitu- tion products of toluene and such other compounds as are them- selves readily oxidized to benzoic acid. They may also be obtained from the amidobenzoic acids by means of the diazo-reaction. The old method, proposed by Griess, consisted in heating a diazo- amidobenzoic acid with hydrochloric, hydrobromic, or hydrofluoric acid : N.NH.C 6 H 4 .C(XH 1 1 - + HC1 = NH 2 .C 6 H 4 .CO 2 H + C 6 H 4 C1.CO H + N 2 . NC 6 H 4 .C0 2 H He subsequently found that the sulphates of the diazobenzoic acids are more suitable for the purpose ; one part is boiled with 3 to 5 parts of the hydracid, the substituted benzoic acid 1 Schopff, Ber. Dcutsch. Chem. Ges. xviii. 1063. 2 lUd. xviii. 2472. ORTHOCHLOROBENZOIC ACID. 217 separating out on cooling as a mass of crystals. Hydriodic acid acts in this way even in the cold : * NC 6 H 4 .C0 2 H + HI = C 6 H 4 LC0 2 H + S0 4 H 2 + N 2 . H NS0 4 ] A reaction which possesses considerable theoretical interest has been employed for the preparation of these compounds by v. Richter. When paranitrochlorobenzeneorparanitrobromobenzene is heated with alcohol and potassium cyanide, the nitroxyl group is replaced by hydrogen, and the cyanogen group takes the meta-position, the nitnl of metachloro- or metabromobenzoic acid being formed, while metanitrochlorobenzene is converted into orthochlorobenzoyl chloride. Orthonitrochlorobenzene and orthonitrobromobenzene, on the other hand, are not attacked by potassium cyanide. 2 The halogen-substitution products are readily converted into benzoic acid by the action of sodium amalgam and water. MONOCHLOROBENZOIC ACIDS, C 6 H 4 C1.CO 2 H. 2122 Orthochlorobenzoic acid was obtained by Chiozzain 1852, by heating salicylic acid (orthohydroxybenzoic acid) with phos- phorus pentachloride, and decomposing the fraction of the dis- tillate boiling between 200 250 with water. 3 It was believed to be identical with the chlorobenzoic acid which is formed by the direct chlorination of benzoic acid, until Limpricht and Uslar, as well as Kolbe and Lautemann, showed that the latter compound is a distinct substance, and gave it a distinctive name, chloro- salylic acid. 4 Kekule obtained the same acid in a similar manner from wintergreen oil, which consists chiefly of methyl salicylate. 5 Its formation will be discussed under salicylic acid. In order to prepare it, an intimate mixture of one molecule of sodium salicylate with two molecules of phosphorus pentachloride is distilled, the portion boiling above 240 separated, and de- composed by boiling caustic soda solution, the acid being then precipitated by hydrochloric acid (Kolbe and Lautemann). The precipitate is dissolved in the smallest possible quantity of 1 Bcr. Deutsch. Chem. Gen. xviii. 960. 3 Ibid. iv. 459. 3 Ann. Chem. Pharm Ixxxiii. 317. * Ibid. cxv. 183. 9 Ibid, cxvii. 145. 21-8 AROMATIC COMPOUNDS. boiling water arid treated with a slight excess of weak milk of lime ; calcium salicylate is thus formed and separates completely when the solution is well stirred and heated on the water-bath for some hours. The filtrate is precipitated with hydrochloric acid, and the orthoehlorobenzoic acid purified by re-crystallization from boiling water. 1 The mixture of acids can also be separated .by distillation with steam, with which salicylic acid alone vola- tilizes. 2 Pure salicylic acid may be substituted for the sodium salicylate. 3 According to Glutz, it is better to employ wintergreen oil, to which the phosphorus pentachloride must be gradually added, the mixture heated for a considerable time until hydrochloric jacid ceases to be evolved, and then distilled and treated as .above. 4 Orthoehlorobenzoic acid is also formed when orthochloro- toluene is boiled with a dilute solution of potassium perman- ganate. 5 It dissolves in 881 parts of water at 0, is readily soluble in hot water and alcohol, and crystallizes in long, silky needles, which melt at 137, and sublime in lustrous crystals. It melts when heated with a little water, in the same manner as benzoic acid. ,WJien heated to 200 with caustic potash, it yields 10 per cent, of salicylic acid and 20 per cent, of meta- hydroxybenzoie acid, equal quantities being formed when caustic soda is employed (Ost). Calcium wthocblorobenzoate, (C 7 H 4 C10 2 ) 2 Ca + 2H 2 O, crystallizes in prisms, which are Very slightly soluble in alcohol, but very readily in water. The solution of the acid in ammonia is there- fore not precipitated by calcium chloride, and it may thus be distinguished from its isomerides. Orthochlorobenzoyl chloride, C 6 H 4 C1.COC1, is obtained in the pure state by the action of phosphorus chloride on the acid. It is a heavy, powerfully refractive liquid which fumes in the air and boils at 235 238 (Emmerling). OrtJiochlorobenzonitril, C 6 H 4 C1.CN, is formed by the action of phosphorus pentachloride on salicylamide, C 6 H 4 (OH)CO.NH 2 , It crystallizes from hot water or ether in white needles, which -smell like benzonitril and melt at 42 43. It sublimes readily, , * Beilstein and Reiqhenbach, Ann. Chem. Pharm. cxxxii. 311. * Hiibner and Upmann, Zcitschr. Ckcm. 1870, 293. ' 3 Hiibner and Biedermann, Ann. Chcm. Pharm. cxlii. 263 ; Wilkens and Rack, ibid, ccxxii. 192. 4 Glutz, ibid, exliii. 194 ; Ost, Journ. Pratt.' Chcm. [2] ad. 386, 5 Emmerling, Ber. Deutsch. Chcm. Ges. viii.,880. METACHLOROBENZOIC ACID. 219 boils at 232, and is converted into orthochlorobenzoic acid when heated to 150 with dilute hydrochloric acid. 1 2124 Metaclilorobenzoic acid. Herzog, in 1840, found that the action of chlorine upon benzoic acid produces, among other pro- ducts, a chlorinated acid resembling benzoic acid, but he did not analyze the substance. 2 Scharling subsequently obtained an acid by the distillation of urine with hydrochloric acid, which had the composition of chlorobenzoic acid, and which he named chloro- michmic acid (o/jLt^a, urine), 3 but, as Gmelin pointed out, it was not to be distinguished from chlorobenzoic acid. 4 Stenhouse prepared the latter by treating benzoic or cinnamic acid with chlorine, bleaching powder or potassium chlorate and hydro- chloric acid, but was unable to free it from higher chlorine substitution products. 5 Field, however, found that it can be obtained pure by boiling benzoic acid with potassium chlorate and hydrochloric acid, and this was confirmed by Otto. 6 As already mentioned, this acid was believed to be identical with the chlorobenzoic acid prepared from salicylic acid, until Lim- pricht and Uslar showed that the acid obtained in this way is different from that obtained by treating sulphobenzoic acid with phosphorus pentachloride, and decomposing the resulting chloro- benzoyl chloride with water. 7 The chlorobenzoic acids formed by these different reactions were made the subject of a close investigation by Beilstein and Schlun, which resulted in their proving the existence of three isomerides, the third of which had been obtained by Beilstein and Wilbrand from iiitrodracylic acid (Part III. p. 34). 8 Metachlorobenzoic acid was also obtained by Saint-Evre 9 by the action of chlorine on a solution of benzoic acid in caustic potash, and was named chloronicelnic acid, C 6 H 5 C10 2 . It. is also formed when benzoic acid is heated with antimony chloride and the product treated with water, 10 as well as by the oxidation of metachlorotoluene with chromic acid. 11 In order to prepare it, potassium chlorate is gradually add^d to benzoic acid suspended in hydrochloric acid ; the reaction, 1 Henry, Ber. Dcutsch. Chem. Ges. vi. 492. 2 Brandes, Arch. Pharm. xxiii. 15. 3 Ann. Chem. Pharm. xli. 48 ; xlii. 265. 4 Handb. Org. Chem. iii. 92. 5 Phil. Mag. xxvii. 129 ; Ann. Chem. Pharm. Ixv. 55. 6 Ibid, cxxii. 142. 7 Ibid. cii. 259. 8 Ibid, cxxxiii. 293. Ibid. Ixx. 257. 10 Gerhardt, Traitt Chim. Org. iii. 214. -, ' 11 Wroblewsky, Ann. Chem. Pharm. clxviii. 200. 220 AROMATIC COMPOUNDS. which proceeds quietly, must be occasionally aided by gentle warming. When 26 parts of chlorate have been added to 10 parts of the acid and about 90 parts of hydrochloric acid, the mixture is heated to boiling, and the acid which separates on cooling converted into the barium salt, which is then purified by re-crystallization. According to Hiibner and Weiss, it can readily be obtained and in a very pure condition by heating 7 grms. of benzoic acid to 150 with 4 grms. of manganese dioxide which has been washed with hydrochloric acid, and 40 grms. of fuming hydrochloric acid, and re-crystalling the product two or three times. 1 Properties. It dissolves at in 2840 parts of water (Kolbe and Lautemann), more readily in hot water and alcohol, and crystallizes in concentrically grouped needles, which melt at 153 and readily sublime. On fusion with caustic potash it yields only metahydroxybenzoic acid 2 ; it does not melt under water. Calcium metachlorobenzoate, (C 7 H 4 C10 2 ) 2 Ca + 3H 2 O, forms scaly crystals, which dissolve in 82*6 parts of water at 12. Metachlorobenzoyl chloride, C 6 H 4 C1.COC1, is a strongly refrac- tive liquid, boiling at 225 . 3 MetacUoroUppuric acid, C 6 H 4 C1.CO.NHCH 2 .CO 2 H, is formed together with dichlorohippuric acid by the action of potassium chlorate and hydrochloric acid on hippuric acid, 4 and is found in the urine after metachlorobenzoic acid has been administered. 5 It is a tough, amorphous mass, which is scarcely soluble in cold, more readily in boiling water; it forms crystalline salts. It decomposes into amido-acetic acid and metachlorobenzoic acid when boiled with concentrated hydrochloric acid. Dichlorohippuric acid, C 6 H 3 C1 2 .CO.NH.CH 2 .CO 2 H, is less soluble in hot water than the preceding compound, and is con- verted by long contact with water into a granular crystalline mass; on boiling with hydrochloric acid it decomposes into a-dichlorobenzoic acid and amido-acetic acid. Metachlorolenzonitril, C 6 H 4 C1.CN, was prepared by Lim- pricht and Uslar by the distillation of metasulphobenzamide, C 6 H 4 (CO.NH 2 )SO 2 .]NH 2 , and metasulphamidobenzoic acid, C 6 H 4 (CO 2 H)SO 2 .NH 2 , with phosphorus chloride. It crystallizes 3 Her. Deutsch. CJwm. Gcs. vi. 175. 3 Dembey, Ann. Chem. Pharm. cxlviii. 221. 1 Limpricht and Uslar, ibid. cii. 262 ; Graebe ; ibid, cxxxviii. 197. 4 Otto, ibid, cxxii. 129. 8 Ibid, cxlii. 346. PARACHLOROBENZOIC ACID. 221 from alcohol in prisms, which smell like benzaldehyde, melt at 40, and readily volatilize with steam. 1 Parachlorobenzoic acid, or CJilorodracylic acid, was first obtained by Beilstein and Wilbrand from paramidobenzoic acid by the diazo-reaction. 2 Beilstein and Geitner then prepared it by the oxidation of parachloro toluene with chromic acid solution, 3 while Emmerling found that it is better to employ crude chlorotoluene and a dilute solution of potassium permanganate for this pur- pose, the orthochlorobenzoic acid formed being easily removed by boiling water. 4 Mliller found that it is also formed when chlorobenzene is oxidized with manganese dioxide and sulphuric acid, 5 a formation corresponding to that of benzoic acid from benzene. Parachlorobenzoic acid dissolves in 5288 parts of water at 10, crystallizes from alcohol in long, lustrous needles, melts at 236 and sublimes in plates at a higher temperature. Calcium parachlordbenzoate, (C 7 H 4 ClO 2 ). 2 Ca + 3H 2 O, crystal- lizes in small plates or needles, and is even less soluble in water than the corresponding salt of the meta-acid. Paraclilorobcnzoyl chloride, C 6 H 4 C1.COC1, is a heavy liquid, which fumes in the air, is strongly refractive, and boils at 220 222 (Emmerling). DICHLOROBENZOIC ACIDS, C 6 H 3 C1. 2 .C0 2 H. 2125 a-Dichlorobenzoic acid, (3 : 4). Otto first prepared this compound by boiling dichlorohippuric acid with hydrochloric acid ; 6 it is also obtained by the oxidation of dichlorotoluene and dichlorobenzyl chloride, 7 as well as when parachlorobenzoic acid is heated to 200 with antimony pentachloride. 8 It is formed, together with the following compound, by heating benzoic acid with bleaching powder solution, 9 or by the action of potassium chlorate and hydrochloric acid, 10 metachloro- benzoic acid being, of course, the first product. It is slightly soluble in cold, more readily in hot water, and crystallizes in fine, lustrous needles, melting at 201 202. 1 Ann. Cham. Pharm. cvi. 32. 2 Ibid, cxxviii. 270. 3 Ibid, cxxxix. 336. 4 Ber. Deutsch. Chem. Ges. viii. 880. 6 Zeitschr. Chem. 1869, 137. 6 Ann. Chcm. Pharm. cxxii. 147. 7 Beilstein and Kuhlberg, ibid. clii. 225 ; Lellmann and Klotz, ib id. ccxxxi. 308. 8 Beilstein, ibid, clxxix. 284. 9 Claus and Thiel, Bcr. Deutsch. Chem. Gcs. viii. 948. 10 Claus and Pfeifer, ibid. v. 658 ; vi. 721. 222 AROMATIC COMPOUNDS. fi-Dicklorobenzoic acid, (3:6), is formed by heating ortho- chlorobenzoic acid with hydrochloric acid and potassium chlorate or potassium dichromate, 1 and by replacing the amido-group of a-chloramidobenzoic acid by chlorine. 2 It crystallizes in needles, which melt at 153'5(Lellmann and Klotz) and dissolve in about 1200 parts of cold water. enzoate ) C 6 H.4(7$0^)C0 2 .C 2 H. 5 , forms assymetric plates, which melt at 57, and are converted by heating with ammonia into paranitrobenzamide, C 6 H 4 (N0 2 )CO.NH 2 , which crystallizes in needles melting at 197 198. Paranitrobenzoyl chloride, C 6 H 4 (NO 2 )COC1, boils at 202 205 under a pressure of 105 mm., and crystallizes from petro- leum spirit in fine needles, melting at 75. 6 1 Ann. Chem. Pharm. Ixxviii. 100 ; Schwanert, ibid. cxii. 69 ; Conrad. Journ. Prakt. Chem. [2] xv. 254. 2 Beilstein, Ann. Chem. Pharm. cxlvi. 336 ; Engler, ibid, cxlix. 297 ; Schoppf, Ber. Deutseh. Chem. Ges. xviii. 1063. 3 Beilstein and Geitner, Ann. Chem. Pharm. cxxxix. 335 ; Kbrner, Zeitschr. Chem. 1869, 635 ; Rosenstiehl, ibid. 1869, 701. 4 Michael and Norton, Bcr. Deutseh. Chem. Ges. x. 580. 5 Salkowsky, ibid. ix. 24 ; x. 1257. 6 Gevekoht, Ann. Chem. Pharm. ccxxi. 335. PARANITROHIPPURIC ACID. 233 Paranitrobenzonitril, C 6 H 4 (NO 2 )CN, is obtained by heating the amide with phosphorus pentoxide, 1 as well as by diazotizing paranitraniline and pouring the solution into a well agitated solution of potassium cuprous cyanide in potassium cyanide, heated to 90. 2 It crystallizes from alcohol in plates, and sublimes on heating in long, feathery crystals, melting at 147. ParanitroUppuric acid, C 6 H 4 (NO 2 )CO.NH.CH 2 .C0 2 H, is formed, together with paranitrobenzoic acid, by the passage of paranitro toluene through the system in the dog, and is found in the urine combined with urea. It crystallizes from hot water in orange-red prisms, melting at 129 . 3 So-called isomerides of the three nitrobenzoic acids. It was early stated by Mills that four mononitrobenzoic acids exist, and Fittica thought that he had prepared five new isomerides, differing from the three already mentioned in their melting points, three of them being also distinguished by their citron- yellow colour. He obtained these substances " by peculiar methods, which chiefly consisted in avoiding with the greatest care all trustworthy modes of purification," 4 but the researches of others have shown that his compounds do not exist. 5 The melting points and physical properties of the nitrobenzoic acids, like those of benzoic acid itself, are greatly altered by very small quantities of admixed impurities ; when benzoic acid is nitrated, small amounts of the dinitrobenzoic acids are always formed in addition to the three mononitrobenzoic acids, and the product also contains benzoic acid and styphnic acid (trini- troresorcinol), the latter of which gives it its yellow colour. Bodewig found that three of Fittica's new acids are simply impure forms of metanitrobenzoic acid, which he obtained from them by crystallization ; the two others gave no measurable crystals ; he also observed that this acid, besides its stable form, exists in two unstable modifications, which also crystallize in the monoclinic system, but differ from the stable form in their crystallographic constants. Their crystals soon become opaque, from the formation of the stable form, a change which takes place in one of the unstable modifications even when its crystals are allowed to remain in the mother liquor. He further 1 Fricke, Ber. Deutsch. Chem. Ges. vii. 1322. Sandmeyer, ibid, xviii. 1492. 3 Jaffe. ibid. vii. 1673. 4 Kekule, Lehrb. Org. Ckem. iii. 554. 5 Erlenmeyer and Widnmann, Ber. Deutsch. Chem. Ges. viii. 392 ; Griess, ibid. viii. 526 ; Ladenburg, ibid. viii. 535 and 853 ; Salkowsky, ibid. viii. 636 ; Liebermaun, ibid. x. 1036 ; Glaus, ibid. xiii. 891 ; Fittica, ibid. xiii. 1537. 234 AROMATIC COMPOUNDS. proved their identity by converting them into the ethyl ether. 1 Fittica's acids, therefore, have no more real existence than salylic acid (p. 158). DINITROBENZOIC ACIDS, C 6 H 3 (NO 2 ) 3 CO 2 H. 2134 The appended numbers indicate the position of the nitroxyls when that of the carboxyls is 1. a-Dinitrobenzoic acid, (2 : 5), was obtained by Griess, together with the two following and styphnic acid, by heating one part of orthonitrobenzoic acid with ten parts of a mixture of equal amounts of fuming sulphuric and nitric acids. 2 It is slightly soluble in cold water, and on evaporation separates out in prisms ; it is deposited from the hot saturated solution as a yellowish oil, which solidifies in needles, melting at 177. It is reduced to a-diamidobenzoic acid by tin and hydrochloric acid. Barium a-dinitrobenzoate, (C 6 H 3 (NO 2 ) 2 C0 2 )<>Ba + 4H 2 O, forms long, six-sided plates, which are slightly soluble in cold, more readily in hot water. ft-Dinitrobenzoic acid, (2 : 4), 'is also formed by the oxidation of ordinary dinitrotoluene with fuming nitric acid, 3 and by the nitration of paranitrobenzoic acid. 4 It melts in hot water and crystallizes from it in long, lustrous, brittle needles, or on spon- taneous evaporation in large, rhombic tablets or prisms, which melt at 179 and have a bitter taste. Tin and hydrochloric acid convert it into metadiamidobenzene, carbon dioxide being eliminated. Barium (3-dinitrobenzoate, (C 6 H 3 (N0 2 ) 2 C0 2 ) 2 Ba + 3H 2 0, is tolerably soluble in cold water and crystallizes" in white, rhombic, or six-sided tablets. C CO.OH CO - NH It crystallizes in nacreous plates, which are only slightly soluble in water and alcohol. Benzoylguanidine nitrate, CgHgNgO.NOg, is a very characteristic salt ; it crystallizes in small plates, which are almost insoluble in water and alcohol. 2139 a-MethylortJiobenzoglycocyamidine, or a-OrtJidbenzocreatin- ine, G 8 H 6 (CH 3 )N 3 O, is formed when a strongly alkaline solution of the preceding compound is treated with methyl iodide and allowed to stand for some days. It is almost insoluble in cold, slightly soluble in hot water, more readily in boiling alcohol, and 1 Griess, Journ. PraJct. Chem. [2] v. 371. 2 Griess, Ber. Deutsch. Chem. Ges. xiii. 977. 244 AROMATIC COMPOUNDS. crystallizes in lustrous needles, which have a slightly bitter taste and a neutral reaction. The hydrochloride, C 9 H 9 N 3 O.C1H, crystallizes in narrow plates, which readily dissolve in water without decomposition. /3-Orthobenzocreatinine is obtained by heating ethoxycyan- amidobenzoyl with aqueous methylamine. It resembles the a-compound in forming lustrous needles, which have a very faintly bitter taste, but differs from it in being soluble in baryta water and caustic potash solution, and in forming salts which are decomposed by water. The constitution of these compounds is shown by the following. formulae : C 6 H 4 N.CH 3 C 6 H 4 NH >C=NH >C=NH. CO NH CO NCH 3 Oxalanthranilic acid, or Orthobenzamoxalic acid, C 9 H 7 NO 6 -j-H 2 0. Friedlander and Ostermaier first obtained this compound by the oxidation of carbostyril, C 9 H 7 lNi O, with potassium permanganate ? and named it carbostyrilic acid. They then found that on heating with dilute hydrochloric acid or caustic soda solution it decomposes into anthranilic acid and oxalio acid. 1 Kretschy recognized it by this property as identical with the cynuric acid which is formed by the oxidation of cynurenic acid, C 9 H 6 NO (CO 2 H), a substance occurring in the urine of the dog. He also prepared it by gradually heating oxalic acid to 150 with anthranilic acid : 2 ,NH 2 /NH.CO.OH C 6 H 4 < + HO.CO.CO.OH=C 6 H 4 < +H 2 O. \CO.OH \CO.OH It has also been obtained by the oxidation of other substances, which, like those just mentioned, are derivatives of quinoline, a compound which has the following constitution : HC N HC C CH II I C CH CH CH 1 Griess, Ber. Deutsch. Chem. Ges. xv. 332. 2 Monatshcft Chem. v. 16. DINITRODIPHENYLAMINE-ORTHOCARBOXYLIC ACID. 245 Oxalanthramlic acid is slightly soluble in cold water, readily in alcohol and ether, and crystallizes from the latter in hard needles united to form druses. It is a powerful dibasic acid. Normal calcium benzamoxalale, 2C 9 H 5 NO 5 Ca-f 5H 2 O, is the most characteristic salt of this acid. It separates out in glittering prisms when calcium chloride is added to a solution of the ammonium salt. 2140 Dinitrudiplienylamine-ortJiocarboxylic acid, C 6 H 4 (NH. C 6 H 3 (NO 2 ) 2 )C0 2 H, is formed when anthranilic acid is heated with chlorodinitrobenzene, (Cl : NO 2 : N0 2 = 1 : 2 : 4), and an excess of ammonia : C 6 H 4 + C 6 H 3 C1(N0 2 ) 2 + 2NH 3 = \CO.OH C 6 H 4 +NH 4 C1. \CO.ONH 4 The ammonium salt produced in this way forms lustrous, ruby- red plates ; the free acid is obtained by the addition of strong hydrochloric acid to this salt, and is almost insoluble in water, only very slightly soluble in cold alcohol and glacial acetic acid, crystallizing from a hot mixture of these in small, orange-yellow, matted needles, which fuse at 262 264 to a brownish red liquid, which appears almost black when seen in thick layers ; when it is carefully heated a portion distils without decomposi- tion, but it detonates when rapidly heated on platinum foil. Its alkaline salts are slightly soluble in cold* more readily in hot water, and crystallize in reddish yellow to ruby-red plates, which detonate on heating. All the other salts are almost insoluble. The barium salt is a dark cinnabar-red precipitate. This compound does not yield the corresponding amido-acid on reduction with tin and hydrochloric acid, but this is converted into diamidohydro-acridine Jcetone with elimination of water ; this substance, which will be subsequently described, has the follow- ing constitution : CH NH CNH HC C C CH I II I! I HC C C CNH 2 CH CO CH 247 246 AROMATIC COMPOUNDS. Other amido-acids, in which the carboxyl does not stand in the ortho-position to the amido-group, also yield dinitro- diphenylaminecarboxylic acids with chlorodinitrobenzene, but these are converted by reduction into the corresponding diamido- acids. This reaction, therefore, may be employed as a ready method for ascertaining whether or not an aromatic arnido-acid belongs to the ortho-series. The compound to be tested is heated to boiling with chlorodinitrobenzene, alcohol and some ammonia for some time. If an ortho-compound be present, the product yields on reduction a base insoluble in alkalis ; in other cases an acid is obtained. 1 2141 Metamiddbenzoic acid. Zinin obtained this compound in 1845 by the action of ammonium sulphide on nitrobenzinic acid (metanitrobenzoic acid) and named it benzamic acid. 2 Chancel, in 1849, converted nitrobenzamide into amidobenzamide by the same method, but he looked upon the substance obtained as aniline urea and named it carbanilamide. By boiling it with caustic potash solution he obtained carbanilidic acid, which Gerland subsequently proved to- be identical with benzamic acid. 3 Voit, who investigated its salts, remarked that the latter name is unsuitable, since only the radicals of dibasic acids form amic- acids, and he therefore proposed the name amidobenzoic acid. 4 In order to prepare it, a solution of metanitrobenzoic acid in strong ammonia is saturated with sulphuretted hydrogen in absence of air, concentrated and treated with acetic acid. Meta- nitrobenzoic acid may also be reduced with tin and hydrochloric acid and the double tin salt of the amido-acid decomposed with sulphuretted hydrogen. The amidobenzoic acid is then pre- cipitated from the nitrate, previously neutralized with ammonia, by acetic acid. It is slightly soluble in cold, more readily in hot water and alcohol, and crystallizes in warty masses of needles, which melt at 174 and partially volatilize at a higher temperature without decomposition ; when it is heated with spongy platinum (Chancel) or baryta, it decomposes into carbon dioxide and aniline. Its solu- tion has an acid reaction but a sweet taste, and decomposes in the air with separation of a brown powder, its alkaline solution 1 Jourdan, Ber. Deutsch. Chem. Ges. xviii. 1444. 2 Journ. Prakt. Chem. xxxvi. 93. 3 Ann. Chem. Pharm. Ixxxvi. 142. * Ibid. xcix. 100. METAMIDOBENZOIC ACID. 247 behaving in a similar manner. Its metallic salts crystallize well. Metamidobenzoic acid hydrochloride, C 7 H 7 NO 2 .C1H, crystallizes in prisms, which are readily soluble in water, slightly in hydro- chloric acid; the platinichloride forms golden-yellow needles, and the double tin salt, C 7 H 7 NO 2 .ClH + SnCl 2 , crystallizes in plates (Beilstein and Wilbrand). Its other compounds with acids also crystallize well. Metamidobenzamide, C 6 H 4 (NH 2 )CO.NH 2 , is obtained, accord- ing to Chancel, when ammonium sulphide is added to a boiling aqueous solution of metanitrobenzamide. It is readily soluble in water, and forms large, yellow crystals, melting at 75 . 1 Like amidobenzoic acid it is a monacid base. Metamidobenzonitril, C 6 H 4 (NH 2 )CN, is formed when meta- nitrobenzonitril is reduced with zinc and hydrochloric acid 2 or tin and acetic acid, 3 as well as by heating meta-uramidobenzoic acid with phosphoric acid : 4 CO O x /ON C 6 H / NH 3 = C 6 H 4 +C0 2 H 2 0. It crystallizes from dilute alcohol in long, white needles, melts at 53 54, boils at 288 290, and is decomposed by powerful reducing agents into ammonia and benzonitril, the latter being partially converted into benzylamine. When it is treated with alcoholic potash and chloroform, the carbamine, C C) H 4 (NC)CN, is formed ; it has an overpowering odour and has not been further investigated. Metamidobenzonitril is a monacid base and forms salts which crystallize well. Methylmetamidobenzoic acid, or Metabenzosar cosine, C 6 H 4 (NH. CH 3 )C0 2 H, was obtained by Griess as a decomposition product of a-benzocreatine ; it is slightly soluble in cold, more readily in hot water, and crystallizes in small plates. Dimethylmetamidobenzoic acid, C 6 H 4 .N(CH 3 ) 2 CO 2 H. The methyl ether of this acid is formed by a molecular change from the following compound, and is a liquid which has a faint aromatic odour, and boils at 270. The acid is obtained from it by decomposition with alcoholic potash, and is also only slightly 1 Beilstein and Reichenbach, Ann. Chem. Pharm. cxxxii. 142. 2 Hofmann, Ber. Deutsch. Chem. Ges. i. 196. 3 Fricke, ibid. vii. 1321. 4 Griess, ibid. viii. 861. 24fl AROMATIC COMPOUNDS. soluble in hot water ; it crystallizes in dull needles, melting at 151. Trimethylamidobenzoic acid, or Metabenzoleta'ine, C 7 H 4 N(CH 3 ) 3 O 9 + H 2 O. The iodide of this compound is formed when a solu- tion of amidobenzoic acid in methyl alcohol is allowed to stand in contact with an excess of caustic potash and methyl iodide ; it forms short prisms of the formula C 7 H 5 2 N(CH 3 ) 3 I + H 2 O. The free base, which is obtained by the action of lead hydroxide, crystallizes in deliquescent needles, which lose one molecule of water at 105, and have a neutral reaction and bitter taste. The anhydrous compound is converted on fusion into the methyl ether of the preceding compound. 1 /C 6 H 4X C 6 H 4 N(CH 3 ) 2 C0< >N(CH 3 ) 3 = CO \ O / / N(C 2 H 3 0)H Acetmetamidobenzoic acid, C 6 H 4 <( , is metameric \C0 2 H with hippuric acid and is formed when metamidobenzoic acid is heated to 160 with glacial acetic acid. It crystallizes in fine, white needles, is almost insoluble in cold water, has a bitter taste, at the same time resembling that of saltpetre, and melts at 245; it sublimes, however, at a lower temperature. 2 2142 Amidobenzoic acid percyanide> (C 6 H 4 (NH 2 )C0 2 H) 2 C 2 N 2 , is the name given by Griess to a compound to which he had previously assigned the formula C 6 H 4 (NH 2 )C0 2 HC 2 N 2> and which is obtained by passing cyanogen into an aqueous solution of metamidobenzoic acid. It is a yellow, crystalline substance, which is insoluble in water, scarcely soluble in alcohol and ether, and has acid properties. On distillation it decomposes into water, carbon dioxide, ammonia, ammonium cyanide and met- amidobenzonitril. When heated to 130 with alcohol, it decom- poses into metamidobenzoic acid and metabenzamoxalic acid. C 6 H 4 .NH.C(NH)C(NH)NH.C 6 H 4 I I + 3H 2 = C0 9 H C0 9 H CLH 4 .NH 2 * OJL.NH.CO.CO.OH | ' + | +2NH 3 . C0 2 H C0 2 H 1 Griess, Bcr. Deutsch. Chcm. Gcs. vi. 586. 2 Forster, Ann. Chem. Pharm. cxvii. 165 ; Kaiser, Ber. Deutsch. Chem. Ges. xviii. 2946. CYANOCARBOXAMIDOBENZOIC ACID. 249 Metalenzamoxalic acid, or Oxalamidobenzoic acid, is also formed by heating metamidobenzoic acid with oxalic acid, and crystal- lizes from hot water in narrow white plates. 1 Cyanocarbimidobenzoic acid, 3C 9 H 7 N 3 O 2 -f H 2 O, is formed together with the percyanide according to the equation : .NH 2 ON /NH C=NH C 6 H/ + | = C 6 H 4 <; I \C0 2 H CN \C0 2 H CN It is only very slightly soluble in cold water, readily in hot alcohol, and crystallizes in elliptical plates, which have an acid reaction and combine with bases and acids. Cyanocarloxamidobenzoic acid, C 9 H 6 NO 3 , is obtained by the action of nitrous acid on a cold solution of the preceding com- pound in hydrochloric acid : C=NH C 6 H 4 < | + HN0 2 = \C0 9 H CN /NH CO I +N CN It crystallizes in lustrous, white plates, which have a sweet taste, and are almost insoluble in cold water, but are decomposed by boiling water with formation of carbon dioxide, hydrocyanic acid and carboxamidobenzoic acid. When it is dissolved in ammonia, uramidobenzoic acid is formed : ,NH - CO X NH - CO C 6 H 4 | +NH 3 = C 6 H 4 <; | +HCK CN \C0H NH Methylamine, ethylamine, &c., act in a similar manner, and a large number of substituted uramidobenzoic -acids can, therefore, be prepared in this way. 2 If cyanogen be passed into an alcoholic solution of metamido- benzoic acid, the percyanide, which has been already mentioned, 1 Griess, Ber. Deutsch. Chem. Ges. i. 191 ; xi. 1985 ; xvi. 336 ; xviii. 2412 ; Schiff, ibid. xix. 252. 2 Griess, ibid, xviii. 2415. 250 AROMATIC COMPOUNDS. is deposited, and the two following compounds crystallize out on allowing the mother liquor to stand : Carbimidamidobenzoic acid. XJ0 2 H X2 V 2C 6 H 4 < + C 2 N 2 = >C=NH + HON. \C0 2 H /NH/ C 6 H 4 < \C0 2 H Ethoxycarbimidamidobenzoic acid . X NH 2 H/ + C 2 N 2 4HO.C 2 H 6 = X C0H h=NH C 6 H/ | +HCN. \rTk TI rr TT N L-Uojl UL-oJLJL 25 Carbimidamidobenzoic acid, or Guanidodibenzoic acid, C 15 H 13 N 3 4 , is obtained from the crude product by extraction with boiling water; it separates out on cooling in needles, which are purified by being dissolved in hydrochloric acid, the solution neutralized with ammonia and then precipitated by acetic acid. The precipitate is at first amorphous, but soon changes into needles. It forms salts with both acids and bases. 1 Ethoxycarbimidamido'benzoic acid, 2C 10 H 12 N 2 O 3 + 3H 2 0, is slightly soluble in water, more readily in alcohol, and crystallizes in needles. 2 Meta-uramidolenzoic acid, C 8 H 8 N 2 3 + H 2 O, is formed when the preceding compound is boiled with hydrochloric acid : NH CnzNH X NH CO C 6 H 4 < | +H 2 = C 6 H 4 < | +HO.C 2 H 5 . \C0 2 H OCH 3 \C0 2 H NH 2 Menschutkin obtained it from potassium cyanate and met- amidobenzoic acid hydrochloride, and named it oxybenzuramic acid. 3 Griess then showed that it is also formed by bringing metamidobenzoic acid into fused urea. 4 It is slightly soluble in water, more readily in alcohol, and crystallizes in needles or 1 Griess, Zcitschr. Chem. 1867, 534. 2 Journ. Prakt. Chem. [2] iv. 296. 8 Ann. Chem. Pharm. cliii. 84. 4 er. Deutsch. Chem. Ges. ii. 47. METABENZOGLYCOCYAMINE. 251 fine prisms. Its salts have been investigated by Menschutkin. On treatment with concentrated nitric acid it yields three di- nitro-compounds (p. 255). Meta-urethanebenzoic acid, C 10 H 11 NO 4 , is formed by the action of nitrous acid on ethoxycarbimidamidobenzoic acid 1 and by treating metamidobenzoic acid with ethyl chlorocarbonate : /NH 2 COC1 /NH - CO C 6 H 4 < + | = C 6 H 4 < | + HCL \C0 2 H OC 2 H 5 \C0 2 H OC 2 H 5 It crystallizes in plates, which are slightly soluble in water, dissolve in alcohol in every proportion, and melt at 189. Carboxamidobenzoic acid, or Metacarbamidobenzoic acid, C 15 H l2 N 2 O 5 , is obtained by heating uramidobenzoic acid to 200, or by repeatedly evaporating the solution of its barium salt : 2 /NH 9 /NH.C 6 H 4 .C0 2 H 2CO< = C0< + CO(NH 2 ) 2 . \NH.C 6 H 4 .C0 2 H \NH.C fl H 4 .C0 2 H It is also formed when meta-urethanebenzoic acid is heated above its melting-point, 3 and crystallizes in microscopic needles, which are insoluble in water, alcohol and ether. 2143 Metabcnzoglycocyamine, or Metaguanidobenzoic acid, C 8 H 9 N 3 O 2 + H 2 O, was first obtained by Griess by boiling amido- benzoic acid percyanide with caustic potash solution ; it is also formed by the action of ammonia on ethoxycarbimidamido- benzoic acid, as well as, similarly to glycocyamine (Part II. p. 97), by allowing an alcoholic and ammoniacal solution of cyanamide and metamidobenzoic acid to stand : 4 C 6 H 4 .NH 2 C=N C 6 H 4 .NH C=NH I +1=1 I C0 2 H NH 2 C0 2 H NH 2 It is slightly soluble in alcohol, and crystallizes from hot water in thin, four-sided tablets which dissolve in caustic potash, but are reprecipitated by carbon dioxide. It forms salts with the 1 Griess, Her. Deutsch. Chem. Ges. ix. 796. Griess, Zcitschr. Chem. 1868, 650; Ann. Chem. Pharm. clxxii. 170. 3 Wacbendorff, Ber. Deutsch. Chem. Ges. xi. 701. * Griess, ibid. vii. 575 ; viii. 323. 252 AROMATIC COMPOUNDS. mineral acids, but does not combine with acetic acid. On boil ing with baryta water, uramidobenzoic acid is first formed : /NH.C(NH)NH 2 /NH.CO.NH On continued boiling, metamidobenzoic acid and urea or de- composition products of these are produced. a-Metcibenzocreatine, 2C 8 H 8 (CH 3 )N 3 O 2 + 3H 2 0, is formed by the action of methyl iodide and caustic potash on a solution of the preceding compound. It is slightly soluble in water and alcohol, crystallizes in pointed plates, and decomposes into urea and benzosarcosine when boiled with baryta water. ft-Metabenzocreatine is prepared from ethoxycarbimidamido- benzoic acid and methylamine, and crystallizes from hot water in small plates. On heating with baryta water it yields meta- amidobenzoic acid, methylamine, and carbon dioxide (Griess). The metabenzocreatines, like benzoglycocyamine, exist in the free state as salts, and have the following constitution : C 6 H 4 .N (CH 3 ) C=N H C 6 H 4 .NH.C=NH CO - O -- NH 3 CO O N(CH 3 )H 2 ' If these compounds be compared with those of the ortho-series, it is found that the latter contain a molecule of water less or are anhydro-compounds, this class of bodies being very readily formed by and characteristic of the ortho-series. PJienylmetabenzoglycocyamine, C 8 H 8 (C 6 H 5 )N 3 O 2 + H 2 0,is formed when cyanocarbimidamidobenzoic acid is heated with aniline : /NH - C=NH C 6 H 4 < | + H 2 N.C 6 H 5 = \CO 2 H CN /NH - C=NH C 6 H 4 < | +HON. \CO 2 H. N.C 6 H 5 H It is insoluble in alcohol, but slightly soluble in hot water, readily in hydrochloric acid and caustic potash, and crystallizes in needles or plates, which have a bitter taste followed by a sweet after-taste. PARAMIDOBENZOIC ACID. 253 Amidophenylmetabenzoglycocyamine, G 8 H 8 (C 6 H 4 .NH 2 )N 8 O 2 , is prepared in a similar manner from paradiamidobenzene ; it crystallizes in small prisms, and is a diacid base. 1 2144 Paramidobenzoic acid is obtained by the reduction of paranitrobenzoic acid with ammonium sulphide, 2 or better with tin and hydrochloric acid. 3 It is tolerably soluble in water, very readily in alcohol, and crystallizes in long needles forming fascicular aggregates ; it melts at 186 187, and decomposes at a higher temperature into carbon dioxide and aniline, a decomposition which may also be effected by heating it to 160 180 with hydrochloric acid. It is characteristic of paramidobenzoic acid that lead acetate gives with its aqueous solution a crystalline precipitate of the double salt, C 7 H 4 (NH 2 )0 2 PbC 2 H 3 2 . 4 Paramidobenzoic acid hydrochloride, C 7 H 7 NO 2 .HC1, crystallizes in small plates or prisms. Paramidobenzamide, C 6 H 4 (NH 2 )CO.NH 2 , is formed by the reduction of paranitrobenzamide with ammonium sulphide, and forms large, light yellow crystals, which melt at 178 179, and are much less soluble in water than those of the meta-compound. 5 Paramidobenzonitril, C 6 H 4 (NH 2 )CN, may be prepared from paranitrobenzonitril, 6 and by the distillation of para-uramido- benzoic acid with phosphorus pentoxide. 7 It is readily soluble in alcohol and boiling water, and crystallizes in needles, melting at 100 (Fricke). It forms crystalline salts with acids. Dimethylparamidobenzoic acid, C 6 H 4 N~(CH 3 ) 2 C0 2 H, is obtained by heating the amido-acid with caustic potash, methyl iodide and wood spirit. It crystallizes in short, broad needles, melt- ing at 235, and combines with acids and bases, but is insoluble in acetic acid. 8 Acetparamidobenzoic acid, C 6 H 4 (NH.C 2 H 3 0)CO 9 H. Hofmann obtained this compound by the oxidation of acetparatoluide with potassium permanganate. It is slightly soluble in water, readily in alcohol, and crystallizes in needles, which melt with decomposition at 250 . 9 On boiling with hydrochloric acid it is converted into paramidobenzoic acid. 10 1 Griess, Ber. Deutsch. Chem. Ges. xvi. 336. 2 Fischer, Ann. Chem. Pharm. cxxvii. 142. Beilstein and Wilbrand, ibid, cxxviii. 264. Ladenburg, Ber. Dcutsch. Chem. Ges. vi. 130. Beilstein and Eeichenbach. Ann. Chem. Pharm. cxxxii. 144. Engler, ibid, cxlix. 302 ; Fricke, Ber. Deutsch. Chem. Ges. vii. 1322. Griess, ibid. viii. 861. 8 Michler, ibid. ix. 401. Ibid. ix. 401. 10 Kaiser, ibid, xviii. 2942. 254 AROMATIC COMPOUNDS. Para-uramidobenzoic acid, C Q H B N Oo, is formed at the same * o o d time as paracarbamidobenzoic acid by fusing paramidobenzoic acid with urea, or potassium cyanate with paramidobenzoic acid hydrochloride. It forms elongated plates, is scarcely soluble in cold, only very slightly in boiling water, more readily in hot alcohol. Concentrated nitric acid only forms one dinitro-cpm- pound. Paracarbamidobenzoic acid, C 15 H 12 N 2 O 5 , is obtained by heating the preceding compound, and forms small needles which are insoluble in the ordinary solvents. CHLORAMIDOBENZOIC ACIDS, C 6 H 3 C1(NH 2 )C0 2 H. Cl : NH 2 Melting-point. a) 2:5 small, readily soluble needles, 1 . . 212 /3) 3:6 long, almost insoluble needles, 2 . . 148 8) 3:5 needles, 3 . 216 e) 4:3 small needles, 4 212 2145 The chloramidobenzoic acids corresponding to 7- and f- chloronitrobenzoic acids are unknown. Two others have, how- ever, been prepared, one of which has been obtained from chlorisatin, and should be identical with the /3-acid, but melts at 204 ; 5 it will subsequently be mentioned. The second has been prepared by Griess together with the e-acid by decomposing metadiazobenzoic acid imide, C 6 H 4 N 3 .C0 2 H, with hydrochloric acid ; it crystallizes in small prisms and has the constitution C1:NH 2 =2:3. 6 1 Hiibnerand Biedermann, Ann. Chem. Pharm. cxlvii. 258 ; Eack and Wilken, ibid, ccxxii. 198. 2 Cunze and Hubner, ibid, cxxxv. Ill ; Hiibner and Weiss, Ber. Dcutsch. Chem. Ges. vi. 175. 3 Grube, ibid. x. 1703. 4 Hubner and Biedermann ; Raveill, Ann. Chem. Pharm. ccxxii. 177. 5 Dorsch, Journ. Prakt. Chem. [2] xxxiii. 50. 6 Griess, Ber. Deutsch. Chem. Ges. xix. 313. NITRO-AMIDOBENZOIC ACIDS. 255 BROMAMIDOBENZOIC ACIDS, C 6 H 3 Br(NH 2 )C0 2 H. 'O Br : NH 2 Melting-point. a) 2:5 broad needles l 180 {) 3:6 long, slightly soluble needles 2 . . 208 y) 3:2 needles 3 172 8) 4:3 light yellow needles 4 . ..... 225 C e) 3:5 colourless, tough needles 5 .... 215' IODAMIDOBENZOIC ACIDS, C 6 H 3 I(NH 2 )C0 2 H. Melting-point. a) 3:2 brown needles 137 /3) 3:6 needles melting with decomposition 209 These have been prepared from the iodonitrobenzoic acids and are converted by reduction into orthamidobenzoic acid. NITRO-AMIDOBENZOIC ACIDS, C 6 H 3 N0 2 (NH 2 )C0 2 H. 2146 Seven of the ten acids possessing this composition which are possible according to theory are known, and their constitution is shown on the next page. The first three have been obtained from meta-uramidobenzoic acid, which, as already mentioned, yields three dinitro-compounds. These cannot be directly separ- ated, but on boiling with dilute ammonia are converted into the mononitro-uramidobenzoic acids, which can be separated by means of their barium salts : C A(N0 2 ) 2 N 2 3 + H 2 = C 8 H 7 (N0 2 )N 2 3 + NO 2 .OH. They are re-converted by concentrated nitric acid into the 1 Burghard, Ber. Dcutsch. Chem. Gcs. viii. 560. 2 Hiibner and Meeker, Zeitschr. Chem. 1867, 564 ; Hiibner, Only and Philipp, Ann. Chem. Pharm. cxliii. 241 ; Hiibner and Petermann, ibid, cxlix. 133. 8 Ibid. 4 Burghard ; Raveill. 5 Hesemann and Kohler, Ann. Chem. Pharm. ccxxii. 169. 256 AROMATIC COMPOUNDS. dinitro-compounds, which, on boiling with water yield the nitro- amidobenzoic acids : l NH.CO.NH, NH 9 - NO, C H 2 (N0 2 ) 2 <^ = C 6 H 3 (N0 2 )<^ +N 2 0+C!0 2 . C0 2 H CO,H C0 2 H ,/^ X- NO 2 CO 2 H C0 2 H C0 2 H CO H NH _.KO V ^o, a-Nitro-amidobenzoic acid is slightly soluble in water, readily in alcohol, and crystallizes in yellow needles or prisms. 2 Nitrous acid converts it into orthonitrobenzoic acid, and on reduction with tin and hydrochloric acid it yields a-diamidobenzoic acid. fS-Nitro-amidobenzoic acid forms lustrous, yellowish red needles or plates, which are readily soluble in alcohol and slightly in water, and when gently heated sublime in rhombic plates with- out melting. Heated in a capillary tube it melts at 298 with complete decomposition. 3 It is converted by nitrous acid into paranitrobenzoic acid, and by tin and hydrochloric acid into /3-diamidobenzoic acid. y-Nitro-amidobenzoic acid crystallizes in thick, golden yellow needles or prisms, which melt at 156 157, 4 and dissolve readily in alcohol and hot water. Nitrous acid converts it into orthonitrobenzoic acid, and reducing agents into 7-diamido- benzoic acid. ^-Nitro-amidobenzoic acid was obtained by Griess from dinitro- para-uramidobenzoic acid, 5 and by Salkowski by heating nitro- anisic acid, C 6 H 3 NO 2 (OCH 3 )CO 2 H, with ammonia to 140- 170 . 6 It crystallizes in small, yellow needles, which are scarcely soluble in water, only slightly in boiling alcohol, and melt at Griess, Per. Deutsch. Chem. Gcs. ii. 434 ; v. 192 ; xi. 1733. Journ. Prakt. Chem. [2] v. 235. Kaiser, Ber. Deutsch. Chem. Ges. xviii. 2947. Ibid, xviii. 2951. Loc. cit. Ann. Chem. Pharm. clxxiii. 52. DINITBO-AMIDOBENZOIC ACIDS. 257 284. It is converted by the diazo-reaction into metanitrobenzoic acid, and by reduction into /S-diamidobenzoic acid. e-Nitro-amidobenzoic acid was prepared by Griess from dinitro- ortho-uramidobenzoic acid, and by Hiibner from the nitrosalicylic acid which melts at 228 by heating the ethyl ether with alcoholic ammonia; e-nitro-amidobenzamide, C 6 H 3 N0 2 (NH 2 )CO. NH 2 , is thus obtained, and crystallizes in small, yellow needles, melting at 140 ; it is converted into the acid by boiling with baryta water. 1 Khalis obtained it, together with paranitraniline, by heating the nitrobromobenzoic acid which melts at 179 180 with ammonia. 2 It crystallizes from hot water in long, lustrous, yellow needles, melting at 270. Ethyl nitrite con- verts it into metanitrobenzoic acid, and on reduction it yields a-diamidobenzoic acid. %-Nitro-amidobenzoic acid. Hiibner obtained the amide of this acid from the nitrosalicylic acid which melts at 144; it crystallizes in yellow plates, melting at 109, and on boiling with baryta water yields the acid, which is readily soluble in alcohol and crystallizes from hot water in long, yellow, silky needles, melting at 204. Nitrous acid converts it into metanitrobenzoic acid. rj-Nitro-amidobenzoic acid is formed by the reduction of S-dinitrobenzoic acid with ammonium sulphide, 3 and crystallizes from water in long, golden yellow needles, or small, compact prisms, melting at 208. It is converted into metanitrobenzoic acid by ethyl nitrite, while metachlorobenzoic acid may be obtained from it by replacing the amido-group by chlorine and the nitroxyl by hydrogen ; its constitution is thus established. DINITRO-AMIDOBENZOIC ACIDS, 2147 Dinitro-orthamidobenzoic acid or Dinitro-anthranilic acid (NO 2 :NO 2 = 3 :.5) is prepared by the action of ammonia on the ether of dinitrosalicylic acid. It is slightly soluble in alcohol, and crystallizes from it in lustrous, golden scales, melting at 256 . 4 1 Ann. Chem. Pharm. xix. 21. 2 Ibid, cxcviii. 112. 3 Bocker, Grube and Kollwage, Bcr. Deutsch. Chem. Ges. x. 1703 ; Ann. Chem. Pharm. ccxxii. 81. 4 Salkowski, Ann. Chem. Pharm. clxxiii. 40. 258 AROMATIC COMPOUNDS. Dinitroparamidobenzoic acid, (NO 2 : NO 2 = 2 : G). Cahours, in 1 849, found that an acid soluble in ammonia is formed by the action of fuming nitric acid on nitranisic acid, in addition to dinitro-anisol and trinitro-anisol (Part III., p. 125). This sub- stance being of a splendid golden yellow colour, he named it chrysanisic acid, C 7 H 5 N 3 7 , looking upon it as a homologue of picric acid. 1 After trinitrocresol had been prepared, Kolbe suggested that it is identical with chrysanisic acid, 2 but Beilstein and Kellner showed that this is not the case, since the latter has the formula C 7 H 5 N 3 6 , and differs from the isomeric trinitro- toluene, which was prepared and described by Wilbrand. 3 The actual constitution of chrysanisic acid was determined by Salkowski, who found that it is not contained in the product of the action of nitric acid on nitranisic acid, but is formed by the action of ammonia on dinitro-anisic acid : 4 C 6 H 2 (OCH 3 )(N O^COjH + NH 3 = C 6 H 2 (NH 2 )(NO 2 ) 2 CO 2 H + HO.CH 3 . It may also be obtained by the oxidation of dinitropara- toluidine, 5 and crystallizes froni hot water, in which it is only very slightly soluble, in fine needles, and from alcohol in lustrous, golden, rhombic plates, melting at 259. On heating to 200 210 with fuming hydrochloric acid, /3-trichlorobenzoic acid is formed, and with nitric acid it yields picric acid, while the dinitro-anisic acid from which it is prepared is converted into /3-dinitrophenol when heated with water to 170 . 6 DIAMIDOBENZOIC ACIDS, C 6 H 3 (NH 2 ) 2 C0 2 H. 2148 The formation of these has been already mentioned under the dinitro- and nitro-amido-benzoic acids. The numbers signify the position of the amido groups. a-Diamidobenzoic acid (2 : 5) is slightly soluble in alcohol and hot water, and crystallizes in very small prisms, which decompose on heating with formation of paradiamidobenzene. Ann. Chim. Phys. [3] xxvii. 454. Lehrb. Org. Chcm. ii. 145. Ann. Chcm. Pharm. cxxviii. 164. Ibid, clxiii. 1. Friederici, Bcr. Deutsch. Chem. Ges. xi. 1975. Salkowski and Paidolph, ibid. x. 1254. DIAMIDOBENZOIC ACIDS. 259 (S-Diamidobenzoic acid (3 : 4) crystallizes from hot water in small plates, which melt at 211, and decompose at a higher temperature, more easily when mixed with powdered glass or lime, into carbon dioxide and orthodiamidobenzene. y-Diamidobenzoic acid (2:3) forms long, yellowish white needles, and also yields orthodiamidobenzene on heating. S-Diamidobenzoic acid (3 : 5) is slightly soluble in water, more readily in alcohol, and crystallizes in long needles which melt at 228 when gradually heated, but at 236 when rapidly heated, 1 and are carbonized at a higher temperature with evolution of ammonia. On heating with caustic baryta, it decomposes into carbon dioxide and metadiamidobenzene. It decomposes car- bonates and forms salts which crystallize well. Its dilute aqueous solution is coloured deep yellow by nitrous acid (p. 263). Barium diamidobenzoate, 2(C 6 H 3 (NH 2 ) 2 CO 2 ) 2 Ba {- 3H 2 O, cry- stallizes in yellowish prisms, which are readily soluble in water. Like its isomerides, it also combines with acids. S-Diamidobenzoic acid hydrochloride, C 6 H 3 (CO 2 H)(NH 2 ) 2 (C1H) 2 , is readily soluble in water, but only slightly in hydro- chloric acid, and crystallizes in needles. S-Diamidobenzoic acid sulphate, (C 6 H 3 (CO 2 H)(NH 2 ) 2 )SO 4 H 2 , forms white needles or prisms, which are slightly soluble in water and still less so in alcohol. 2 Hexmethyl--diamidobenzoic acid, or, as Griess called it, six- fold methylated diamidobenzoic acid, is not an acid in its properties but a strongly alkaline ammonium hydroxide and, at the same time, a salt. The iodide is formed by the action of methyl iodide and caustic potash on a solution of 3-diamido- benzoic acid in methyl alcohol. It crystallizes in six-sided tablets or plates, and when treated in concentrated aqueous solution with silver oxide yields the free base : N(CH 3 ) 3 /N(CH 3 ) 3 I C 6 H / CO.OH + Ag 2 = C 6 H 3 f CO.O + 2AgI. \N(CH 3 ) 3 I \N(CH 3 ) 3 OH It is obtained on evaporation as a crystalline mass, which consists of small plates, is very hygroscopic and behaves like 1 Hiibner, Ann. Chem. Pharm. ccxxii. 85. 2 Griess, ibid. cliv. 328. 260 AROMATIC COMPOUNDS. caustic potash. The carbonate crystallizes from alcohol in small plates, is readily soluble in water and has an alkaline reaction. 1 TRI-AMIDOBENZOIC ACID, C 6 H 2 (NH 2 ) 3 CO 2 H. Salkovvski obtained this compound by the reduction of chrysanisic acid with tin and hydrochloric acid. It crystal- lizes from boiling water in fine, lustrous needles, and decom- poses on heating into carbon dioxide and triamidobenzene. Its solution has an acid reaction, and it is at once a monobasic acid and a diacid base. DIAZO-DERIVATIVES OF BENZOIC ACID. 2149 The amidobenzoic acids behave in some respects like amido-acetic acid and its homologues, and in others like aniline, since they can be easily converted into diazobenzoic acids. For this purpose, a magma of amidobenzoic acid and nitric acid is well cooled by ice and saturated with nitrogen trioxide, the nitrate formed being then precipitated with alcohol and ether. Other salts are obtained in a similar manner. The sulphates are best prepared by dissolving the nitrate in a cold mixture of equal parts of water and sulphuric acid, and precipitat- ing in crystals by the addition of strong alcohol and then ether. 2 The diazobenzoic acids, which, like the diazophenols, only exist as anhydrides, are obtained from these salts by the action of caustic potash. They also form double salts, which Griess looks upon as basic salts : Diazobenzoic acid. Diazobenzoic acid nitrate. Nz=N /N=N.NO 3 | C 6 H 4 < CO-O \CO.OH. Diazobenzoic acid seminitrate. x NzzN.O.CO.C 6 H 4 C 6 H/ | NJO.OH N=N.NO 3 . 1 Griess, Ber. Deutsch. Chem. Ges. vii. 39 ; Briihl, ibid. viii. 485. 2 Griess, ibid, xviii. 960. DIAZO-DERIVATIVES. 261 The substituted amidobenzoic acids, as well as their amides, uitrils, &c., also form diazo-compounds. Orthodiazdbenzoic acid nitrate, NO 3 .N 2 .C 6 H 4 .CO 2 H, is readily soluble in water, and crystallizes in rhombic or six-sided tablets, or prisms, which explode violently on heating. When it is re- peatedly dissolved in water and precipitated with alcohol and ether, or when an alcoholic solution of anthranilic acid is treated with nitrogen trioxide, orthodiazobenzoic acid seminitrate, NO 3 .N 2 . C 6 H 4 .CO 2 .N 2 .C 6 H 4 .CO 2 H, is formed ; it crystallizes in long, white needles, and detonates violently when heated. 1 Metadiazobenzoic acid nitrate crystallizes in prisms, which are slightly soluble in cold water. 2 On adding an alkali to its solution, ,N = N a precipitate of metadiazobenzoic acid, C 6 H 4 y . | , is thrown \CO-0 down. This forms a yellow mass which is very unstable. Metadiazobenzoic acid sulphate, HSO 4 .N 2 .C 6 H 4 .CO 2 H, forms long, narrow plates, which are readily soluble in water. When it is repeatedly precipitated from aqueous solution by the addition of alcohol and ether, it becomes converted into the basic salt, to which Griess has given the formula 5C 7 H 4 N 2 O 2 , 2SO 4 H 2 . 3 According to Beilstein it is probably 2(C 7 H 5 N 2 O 2 ) 2 SO 4 + C 7 H 5 N 2 O 2 (OH). 4 It crystallizes in small needles. When the normal sulphate is heated, it decomposes with a violent evolution of gas and formation of free sulphuric acid, sulphoxybenzoic acid, and a very stable compound, C U H 10 SO 8 , 5 which probably has the following constitution : S0 2 (C 6 H 3 (OH) C0 2 H) 2 . Metadiazobenzoic acid platinichloride, (C 7 H 5 N 2 O 2 ) 2 PtCl 6 , is obtained by the addition of platinum chloride to a solution of the nitrate ; it crystallizes in yellow prisms. Metadiazobenzoic acid perbromide, Br 2 N BrN.C 6 H 4 .CO 2 H, is precipitated as an oil by the addition of a solution of bromine in hydrobromic acid to a solution of the nitrate ; it soon solidifies to a mass of yellow prisms, and is converted by ammonia into diazobenzoic acid imide. Metadiazobenzamide nitrate, NO 3 .N 2 .C 6 H 4 .CO.NH 2 , crystallizes in white, explosive needles. 1 Griess, Ann. Chem. Pharm. cxvii. 39, cxxxv. 121 ; Bcr. Deutsch. Chem. Gcs. ix. 1653. a Griess, Ann. Chem. Pharm. cxx. 126. 3 Ber. Deutsch. Chem. Ges. ix. 1655. 4 Haiulb. Org. Chem. 1139. 5 Jahresb. Chem. 1864, 351. 248 21)2 AROMATIC COMPOUNDS. Metadiazobenzonitril nitrate, NO 3 .N 2 .C 6 H 4 .CN, forms explosive needles or prisms which are only slightly soluble in cold water. 1 Paradiazobenzoic acid nitrate also crystallizes in white, explosive prisms. 2 / N *\ Nitrodiazobenzoic acid, C 6 H 3 (NO 2 )<^ V), is formed when S-nitro-amidobenzoic acid is brought into absolute alcohol nearly saturated with nitrogen trioxide ; it forms light yellow, explosive plates. 3 Diazobenzene-amidobenzoic acid, C 6 H 5 .N=N.NH.C 6 H 4 .CO 2 H, is obtained by mixing aqueous solutions of diazobenzene nitrate and metamidobenzoic acid. 4 According to Griess, this compound is identical with that obtained by the action of aniline on metadiazobenzoic acid, and which was therefore considered to have the constitution C 6 H 6 .NH.N=N.C 6 H 4 .CO 2 H. Griess, however, expresses the constitution of both compounds by the same formula, C 6 H 5 .NH=NH=NH.C 6 H 4 .CO 2 H (Part III, p. 269). 5 By either process, a yellow, crystalline substance is obtained, which separates from ether in small plates, and is decomposed by hydrochloric acid with formation of metamidobenzoic acid, metachlorobenzoic acid, metahydroxybenzoic acid, aniline, phenol and nitrogen. The acid forms a yellow solution in alkalis ; on the addition of barium chloride to its ammoniacal solution, which must not be too dilute, the barium salt separates out in small, light yellow crystals. is formed by the action of metamidobenzoic acid on metadiazo- benzoic acid, 6 and therefore as an intermediate product when nitrogen trioxide is passed into an alcoholic solution of metamido- benzoic acid. 7 It forms orange-yellow, crystalline granules, which are almost insoluble in water, alcohol, ether, &c., and detonate at 180. It is soluble in alkalis, and is reprecipitated by acids, even acetic acid. On boiling with hydrochloric acid, it decomposes with evolution of nitrogen into metamidobenzoic acid and metachlorobenzoic acid. It is a tolerably strong dibasic acid and decomposes carbonates. 1 Griess, Bcr. Deuisch. Chem. Ges. ii. 370. 2 Jahresb. Chem. 1864, 353. 3 Salkowski, Ann. Chem. Pliarm. clxxiii. 63. 4 Griess, ibid, cxxxvii. 63. 5 Bcr. Deutsch. Chem. Ges. vii. 1619. 6 Jahreab. Chem. 1864, 353. 7 Ann. Chem. Pharm. cxvii. 1. DIAMIDOBENZOIC ACIDS. 263 Paradiazo-amidobenzoic acid was obtained by Beilstein and Wilbrand by treating a saturated alcoholic solution of paramido- benzoic acid with a solution of nitrogen trioxide in alcohol. It is an orange-yellow, crystalline powder, which is only slightly soluble in boiling alcohol. 1 Isomeric compounds are formed from metadiazobenzoic acid and paramidobenzoic acid, and from paradiazobenzoic acid and metamidobenzoic acid (Griess). 2150 The Action of Nitrous Acid on the Diamidobenzoic Acids. When sodium nitrite is added to a neutral solution of a-diamido- benzoic acid, which contains the amido-group in the para-position, paramidodiazobenzoic acid is formed : /NH + NO.H-QA .OH NO 2 H = C 6 H 3 N=N + 2H 2 O. CO O It is insoluble in ether, slightly soluble in hot alcohol, readily in hot water, and crystallizes in fine needles or four-sided plates, which are brass coloured, have a very bitter taste, and detonate on heating. It does not combine with bases, but forms crystal- line salts with acids ; it also combines with amido-bases and phenols to form azo-compounds. 2 Nitrous acid acts upon the two orthodiamidobenzoic acids (/5 and 7) in the following manner : /NH\ , 2 + N0 2 H = C 6 H 3 f-N = N + 2H 2 0. '\COOH \CO.OH The diazo-imidobenzoic acids obtained in this manner crystal- lize in needles and are powerful acids, the barium salts of which are only slightly soluble in cold water. 3 Metadiamidobenzoic acid corresponds exactly with metadi- amidobenzene in its behaviour towards nitrous acid. In a very dilute solution a yellow colouration, is produced, and this reaction is so delicate that one part of nitrous acid can be detected in five million parts of water. In concentrated 1 Ann. Chem. Pharm. cxxviii. 269. 2 Griess, Ber. Deutsch. Chem. Ges. v. 200, xvii. 603. 3 Griess, ibid. ii. 436. 264 AROMATIC COMPOUNDS. solutions a reddish-brown precipitate of triamido-azobenzoic acid is formed : /NH 2 /NH 2 /NH 2 2C 6 H 3 ^-NH 2 +N0 2 H=C 6 H 3 f-N=N-C 6 H 2 ^NH 2 +2KLO. \CO.OH \CO.OH \CO.OH This substance is soluble in alkalis, and is reprecipitated by acids. 1 /NILNH, HYDRAZINEBENZOIC ACIDS, C 6 H 4 < \OO.OH. 2151 These compounds are obtained from the amidobenzoic acids by the methods which are employed in the preparation of phenylhydrazine from aniline (Part III., p. 275). Orthohydrazinebenzoic acid is slightly soluble in alcohol and ether, and crystallizes from hot water in fine needles. It reduces Fehling's solution and salts of silver and mercury in the cold, and combines with bases and acids. When it is gently heated with concentrated hydrochloric acid or heated rapidly to 220 230 in a stream of carbon dioxide, the anhydride is formed. / NH \ Orthobenzoylhydrazide, C 6 H 4 <^ />NH, forms crystals which MXK are slightly soluble in alcohol, ether, and hot water, have an acid reaction, and are readily dissolved by alkalis. It does not com- bine with acids, and does not reduce salts of mercury or Fehling's solution, but causes a precipitation of silver from an ammoniacal solution. 2 Metahydrazinebenzoic acid is insoluble in ether, slightly soluble in alcohol and hot water, and crystallizes in small, yellowish plates, which melt with decomposition at 186. It has an acid reaction, combines with acids and bases, and reduces Fehling's solution. Nitrous acid converts it into the imide of metadiazo- benzoic acid : /C0 2 H /CO 2 H 1 Voit, Ann. Chem. Pharm. xcix. 100 ; Griess, ibid. cliv. 334 ; Ber. Deutsch. Chem. Qes. xvii. 606. 2 Fischer, Ber. Deutsch. Chem. Qes. xiii. 679. AZO-DERIVATIVES OF BENZOIC ACID. 265 This is a monobasic acid, which is scarcely soluble in cold, slightly in hot water, and readily in alcohol ; it crystallizes in thin plates, melting at 160. Metahydrazinebenzoic acid is decom- posed in presence of diazobeuzene nitrate with formation of diazobenzoic acid imide, metamidobenzoic acid, diazobenzene- imide and aniline. 1 AZO-DERIVATIVES OF BENZOIC ACID. 2152 These are formed, like other azo-compounds, by the reduction of the corresponding nitro-derivatives, the following substances being obtained : Azoxybenzoic acids. Azobenzoic acids. Hydrazobenzoic acids. .N.CeH^COjjH N.C 6 H 4 .C0 2 H HN.C 6 H 4 .C0 2 H X N.C 6 H 4 .C0 2 H N.C 6 H 4 .C0 2 H HN.C 6 H 4 .CO 2 H. Ortho-azoxylenzoic add. Griess prepared this body by heating equal parts of orthonitrobenzoic acid and caustic potash with alcohol. 2 It may also be obtained, together with orthonitro- toluene, by boiling orthonitrobenzyl alcohol with caustic potash. 3 It is only slightly soluble in water, and crystallizes from hot alcohol in small, white, rhombic prisms, which decompose on fusion. The barium salt is readily soluble in water and forms pointed crystals. Ortho-azobenzoic acid is formed by the action of sodium amalgam on a solution of sodium orthonitrobenzoate. It is almost insoluble in water and crystallizes from hot alcohol in fine, dark-yellow needles, which melt at 237 with partial decomposition. Its yellow barium salt crystallizes with seven molecules of water in prisms, or with nine molecules in needles. 4 Orthohydrazobenzoic acid is obtained by treating a concentrated alkaline solution of azoxybenzoic acid with sodium amalgam. 5 It crystallizes from alcohol in colourless, elliptical plates or Griess, Ann. Chem. Pharm. ix. 1657 ; Fischer, ibid. xvi. 1335. Ibid. vii. 1611. Jaffe, Hoppe-Seyler's Zeitschr. ii. 57. Griess, Ber. Deutsch. Chem. Ges. x. 1869. Griess, ibid. vii. 1612. 266 AROMATIC COMPOUNDS. microscopic prisms, and is readily oxidized to the preceding compound. Metazoxylenzoic acid is insoluble in water, slightly soluble in alcohol and ether, and forms microscopic needles or plates. Its barium salt is an almost insoluble precipitate. 1 Metazobenzoic acid was first prepared by Neubauer by the oxidation of metamidobenzoic acid with potassium perman- ganate, bat was not further investigated. 2 Beilstein and Wil- brand then found that an acid is formed by the action of zinc on an alkaline solution of metanitrobenzoic acid, which, according to its composition, lies between nitro- and amido-benzoic acids. 3 Strecker, who prepared it by means of sodium amalgam, named it azobenzoic acid. 4 It is also formed by the action of zinc on ammonium metanitrobenzoate. 5 Acids separate it from its salts as a light-yellow, viscid precipitate, which becomes granular when heated with alcohol, and is only slightly soluble in water, alcohol, and ether. Its almost insoluble barium salt crystallizes in microscopic, rhombic plates containing five mole- cules of water. On distillation with lime, azophenylene, C 12 H 8 ~N" 2 , is formed, while its copper salt yields azobenzene on dry distillation. 6 Metahydrazdbenzoic acid was obtained by Strecker by adding ferrous sulphate and then hydrochloric acid to an alkaline solution of the azo-acid. It is also formed by the continued action of sodium amalgam and other reducing agents. It is amorphous, insoluble in water, and only slightly soluble in alcohol. It is readily oxidized in alkaline solution to the preceding compound and, like hydrazobenzene, undergoes an intermolecular change (Part III., p. 295), when it is boiled with concentrated hydrochloric acid, diamidodiphenic acid, C 12 H 6 (NH 2 ) 2 (C0 2 H) 2 , being formed. 7 Parazobenzoic acid is almost insoluble in alcohol, water and ether, and forms a yellow or reddish precipitate, which becomes granular on boiling and melts at about 240. 8 The barium salt is a flesh-coloured precipitate ; azophenylene is formed when the calcium salt is distilled (Glaus). Parahydrazobenzoic acid is insoluble in water and crystallizes 1 Griess, Jahrcsber. 1864, 352. 2 Ann. Chem. Pharm. cvi. 70. 8 Ibid, cxxviii. 267. * Ibid, cxxix. 129. 6 Sokolow, Journ. Prakt. Chem. xciii. 425 ; Liebert, ibid, xciii. 429. 6 Claus, Ber. Deutsch. Chem. Ges. viii. 41. 7 Griess, ibid. vii. 1609 ; Schultz, Ann. Chem. Pharm. cxcvi. 18. 8 Reichenbach and Beilstein, Ann. Chem. Pharm. cxxix. 144 ; Bilfinger, ibid. cxxxv. 154. DIAZOXYBENZOIC ACID. 267 from alcohol in needles; its alkaline solution absorbs oxygen with formation of the azo-acid. / N \ Diazoxylcnzoic acid, 0< | )C 6 H 3 .CO 2 H. When 8-dinitro- oenzoic acid is dissolved in caustic soda and treated with sodium amalgam, the liquid becomes coloured black but remains perfectly clear, appearing brown when diluted. Acids added to this solu- tion precipitate diazoxybenzoic acid as an amorphous, black powder, which is insoluble in water, alcohol, ether, &c., and detonates feebly on heating. The alkali salts form black solu- tions in water ; the salts of other metals are black precipitates. The barium salt, when dried at 70, becomes so strongly electrified that the particles continue in motion for hours; it loses this property at a higher temperature. Tin and hydrochloric acid reduce the acid to S-diamidobenzoic acid. Isodiazoxybcnzoic acid is obtained from /3-dinitrobenzoic acid and resembles the preceding compound, but is not attacked by tin and hydrochloric acid. 1 Azonitromethanebenzoic acid, N0 2 .CH 2 N:=NC 6 H 4 .CO 2 H, is formed when an aqueous solution of pure metadiazobenzoic acid nitrate is mixed with a dilute solution of nitromethane in caustic potash, and the whole treated with an excess of hydrochloric acid after standing for some time. It is readily soluble in hot alcohol and ether, slightly in boiling water, and crystallizes in stellate groups of yellowish-red plates, which are almost tasteless and detonate on heating. Silver nitrate added to its ammoniacal solution produces a deep red precipitate. 2 N.C 6 H 4 .C0 2 H Azo-aceto-acetic lenzoic acid, \\ , is obtained N.CH(CO.CH 3 )C0 2 H by the action of metadiazobenzoic acid sulphate on aceto-acetic ether, the method described for the preparation of the preceding compound being followed. It is thrown down by hydrochloric acid as a light yellow precipitate consisting of microscopic spheres, and is insoluble in boiling water, crystallizing from hot alcohol in narrow plates or small needles, which have a bitter taste. On careful heating it fuses to an oil, which solidifies on cooling to a waxy mass, but at a higher temperature it detonates 1 Meyer and Michler, Ann. Chem. Pharm. clxxv. 152 ; Ber. Deutsch. Chem. Ges. vi. 746, vii. 422. 2 Griess, ibid, xviii. 961. 268 AEOMATIC COMPOUNDS. feebly, a large quantity of carbon separating out. Its silver salt is a light yellow, amorphous precipitate. NC 6 H 4 .C0 2 H Azomalonic-benzoic acid, \ . Griess obtained this NCH(C0 2 H) 2 compound in a similar manner from malonic ether. Hydrochloric acid separates it from the product as an amorphous, fiery yellowish red precipitate, which crystallizes from hot alcohol in microscopic plates. On heating it froths up and chars. X S0 3 H MONOSULPHOBENZOIC ACIDS, C 6 H 4 < \COOH. 2153 OrthosulpJiobenzoic acid is formed, together with ortho- sulphamidobenzoic acid, when orthotoluenesulphamide is oxidized with potassium permanganate. On the addition of hydrochloric acid to the nitrate, the anhydride of the sulphamide separates out, while acid potassium orthosulphobenzoate remains in solu- tion and is deposited in large monoclinic tablets. 1 It may also be obtained by heating the diazo-compound of anthranilic acid with an alcoholic solution of sulphur dioxide. 2 It crystallizes from water in large, monoclinic tablets, which do not deliquesce in the air and melt at 240 with decomposition. On fusion with caustic potash salicylic acid is formed. 3 Acid barium orthosulpholenzoate, (C 7 H 5 S0 3 ) 2 Ba -f 2H 2 O, crystallizes in needles, and is less soluble in water than the normal salt. OrthosulpTiamidobenzoic acid is not known in the free state, as when it is liberated from its salts by the addition of an acid it is immediately converted into the anhydride : SO,NH 2 C 6 H 4 = C 6 H 4 < >NH + H,0. \CO.OH ^ GQ/ This body is slightly soluble in cold, more readily in hot water and alcohol, and forms crystals which melt at 220 and are 1 Remsen, Ann. Chcm. Pharm. clxxviii. 293 ; Fahlberg and Remsen, Bcr. Deutsch. Chem. Ges. xii. 471. 2 Wiesinger, ibid. xii. 1349. 3 Bottinger, ibid. viii. 374. SACCHARIN. 269 sweeter than sugar. The salts, which are readily soluble in water, have also a sweet taste. When the anhydride, which is called lenzoylsulphimide, is heated to 150 with hydrochloric acid, it is converted into orthosulphobenzoic acid. It is not attacked by phosphorus pentachloride. According to Fahlberg and List x it is a powerful antiseptic, and, since a very dilute solution of it is as sweet as a concen- trated solution of cane sugar, they believe that it may find an extended application. It could thus be used as a sweetening agent in the diet of patients suffering from diabetes and in many other cases as a cheap substitute for sugar. They propose for it the unsuitable name of saccharin, which has also been given (Part II., p. 547) to the lactone of saccharic acid. 2154 Metasulphobenzoic acid. In 1834 Mitscherlich found that benzoic acid combines with anhydrous sulphuric acid, SO 3 , to form an acid which can be heated to above 150, and boiled with water without decomposition. Its barium salt can also be boiled with caustic potash without losing sulphuric acid. He says, " I propose to name it provisionally benzoylsulphuric acid, since the complexity of its composition necessitates a name which gives a clue to its constitution without indicating it fully." 2 Fehling, who investigated its salts more closely, observed that when heated with an excess of caustic potash until complete decomposition has taken place, it yields a residue containing both sulphite and sulphate of potassium, a behaviour which is characteristic of the salts of hyposulphuric acid. " This acid, therefore, contains hyposulphuric and not sulphuric acid," and he therefore called it benzoylhyposulphuric acid. 3 It was then investigated with great care by Limpricht and v. Uslar, who recognised it as a sulphonic acid. 4 It is also formed by the action of sulphuric acid on benzonitril 5 and benzoyl chloride, 6 as well as by heating the latter with silver sulphate ; 7 and by treating metadiazo-amidobenzoic acid with an alcoholic solution of sulphur dioxide. 8 1 Journ. Soc. Chem. Ind. iv. 608 ; Ber. Deutsch. Chem. Ges. xix. Ref. 374. 2 Ann. Chem. Pharm. xii. 314. 3 Ibid, xxvii. 322. 4 Ibid. cii. 239 ; cvi. 27. 5 Buckton and Hofraann, ibid. c. 155. 6 Oppenheim, Ber. Deutsch. Chem. Ges. iii. 735. 7 Carius and Kammerer, Ann. Chem. Pharm. cxxxi. 155 ; Ador and Oppenheim, Ber. Deutsch. Chem. Ges. iii. 738 ; Kammerer, ibid. iv. 219. 8 Vollbrecht and Wiesinger, ibid. x. 715. 270 AROMATIC COMPOUNDS. In order to prepare metasulphobenzoic acid, the vapour of sulphur trioxide is passed over benzoic acid, which has been previously fused and powdered, until a transparent mass is formed ; or two parts of benzoic acid are heated with one part of fuming sulphuric acid for some time. The product then contains some parasulphobenzoic acid in addition to metasulpho- benzoic acid and free sulphuric acid. 1 It is diluted with water, neutralized with barium carbonate and filtered, the nitrate being then heated and treated with hydrochloric acid. The acid salt of the para-acid crystallizes out first on cooling, and then that of the meta-acid, which is purified by recrystallization. The product of the reaction may also be saturated with milk of lime, the filtrate treated with potassium carbonate, and the potassium salt which is thus obtained, recrystallized. 2 Metasulphobenzoic acid is a colourless, crystalline mass, which deliquesces in moist air, but solidifies again in dry air. It is not altered by boiling nitric acid. On fusion with potash, metahydroxybenzoic acid is formed (Barth), while with sodium formate it yields isophthalic acid (v. Meyer). The Mctasnlphobenzoates. Metasulphobenzoic acid is a power- ful dibasic acid, which decomposes even barium chloride and barium nitrate. Its normal salts are usually readily soluble, while the acid salts dissolve much less easily. Normal potassium metasulpholenzoate, C 7 H 4 S0 5 K 2 , forms de- liquescent crystals ; the acid salt, C 7 H 5 S0 5 K, crystallizes in long needles, which contain two and half or five molecules of water and are readily soluble in water and alcohol. 3 Normal barium metasulpholenzoate, C 7 H 4 SO 5 Ba + 3H 2 O, is very soluble, and can with difficulty be obtained in well- developed crystals ; it is usually deposited in crusts. The acid salt, (C 7 H 5 Sb 5 ) 2 Ba + 3H 2 O, dissolves in 20 parts of cold water, readily in hot water and alcohol, and crystallizes in monoclinic prisms. Normal lead metasulpholenzoate, C 7 H 4 S0 5 Pb + 2H 2 O, is much more readily soluble in hot water than in cold, and forms fine, radiating crystals, resembling those of wavellite. Silver metasulpholenzoate, C 7 H 4 SO 5 Ag 2 4- H 2 O, crystallizes in yellow prisms which readily dissolve. Normal ethyl metasulpholenzoate , C 7 H 4 SO 5 (C 2 H 5 ) 2 . is prepared from the chloride of the acid and absolute alcohol, and forms a 1 Ann. Che?n. Pharm. clxxviii. 275. 2 Barth, ibid, cxlviii. 33. 3 Otto, ibid, cxxii. 155. MONOSULPHOBENZOIC ACIDS. 271 thick liquid which has a faint ethereal odour, and decomposes on heating. It is soluble in water, and its solution decomposes when heated into alcohol and the acid. Acid ethyl metasulphobenzoate or Ethyl metasulphobenzoic acid, C 7 H 5 S0 6 .C 2 H 5 . The ammonium salt of this acid, C 7 H 4 SO 5 (NH 4 ).C 2 H 5 , is obtained by passing ammonia into an alcoholic solution of the normal ether or by the action of alcoholic ammonia on the chloride. It crystallizes in large, four-sided, transparent tablets. If the ammonia be precipitated with platinum chloride, and the excess of platinum removed by sulphuretted hydrogen, a solution of the free acid is obtained ; its salts crystallize well and are readily soluble. Its constitution is probably represented by the former of the two following formulas : /S0 3 H /S0 3 .C 2 H 5 CTJ / C\ TT / 6 M 4\ U * 1 4\ \C0 2 .C 2 H 5 \C0 2 H Metasulphdbenzoyl chloride, C 7 H 4 S0 3 C1 2 , is obtained by heating the dry acid with phosphorus pentachloride; the phosphorus oxychloride is then distilled off and the residue washed with water. It is a thick, oily liquid, which has a faint but unpleasant odour, and decomposes on distillation into sulphur dioxide and metachlorobenzoyl chloride. The latter is also formed when the compound is heated to 140 150 with phosphorus pentachloride. When it is allowed to stand for some time in contact with water or when the acid is acted upon by one molecule of phosphorus pentachloride, the monochloride is formed : Cj f\ /~\TJ~ O /~\ /^11 xDL/ 2 .V>>JLjL ,/k5VJ 9 v^l C 6 H 4 x or C 6 H 4 v \COC1 \CO.OH This separates from ether in warty masses, and is decomposed by boiling water, &c., with formation of metasulphobenzoic acid. Metasulpholcnzamide, C 7 H 4 SO 3 (NH 2 ) 2 , is formed by the action of concentrated aqueous ammonia on the chloride. It is almost insoluble in cold water and crystallizes from hot water or ordinary alcohol in needles containing a molecule of water, while it separates from absolute alcohol in small, vitreous, anhydrous crystals. 272 AROMATIC COMPOUNDS. When it is heated with phosphorus pentachloride the following reaction takes place : /S0 2 NH 2 X SO 9 .NH 2 C 6 H/ + PCL = C 6 H 4 < + POOL + HC1. \CO.NH 2 \CC1=NH The imido-chloride which is thus formed has not been obtained pure ; * it decomposes on distillation with formation of meta- chlorobenzonitril, while ammonia or water converts it into sulpliamidobenzonitril, CN.C 6 H 4 .SO 2 .NH 2 , which separates from alcohol in crystals, melting at 152 153. Metasulphamidobenzoic acid, C 7 H 7 NS0 4 , is formed when the nitril or amide is heated with caustic potash solution : /S0 2 .NH 2 /S0 2 .NH 2 C 6 H 4 < + KOH = C 6 H 4 < + NH 3 . \CO.NH 2 \CO.OK It is slightly soluble in cold water, and crystallizes from a hot solution in scales resembling those of potassium chlorate, and melting above 200. It is a monobasic acid, and forms crystallizable salts. Ethyl metasulphamidobenzoate, C 7 H 6 (C 2 H 5 )NSO 4 , is obtained by heating the silver salt with ethyl iodide, or by passing hydro- chloric acid into an alcoholic solution of the acid. It is also formed when ammonia is passed into a solution of sulphobenzoyl chloride in a mixture of alcohol and ether. It crystallizes from alcohol in monoclinic prisms. 2 Metathiohydrobenzoic acid, C 6 H 4 < , is prepared by the action of tin and hydrochloric acid on metasulphobenzoyl chloride. It is tolerably soluble in water, more readily in alcohol, and sublimes, when heated in a current of carbon dioxide, in flat needles, melting at 146 147. It oxidizes when exposed to the air in a moist state, or more rapidly when acted upon by bromine water, to metadithiobenzoic acid, S 2 (C 6 H 4 .CO 2 H) 2 , which is scarcely soluble in water, and only slightly in alcohol, crystallizing from the latter in short needles which melt at 24G -247 . 3 1 Huth and Wallach, Ber. Deutsch. Chem. Ges. ix. 427. 2 Hart, Amer. Chem. Journ. i. 342. 3 Frehrichs, Ber. Deutsch. Chem. Ges. vii. 792. PARASULPHOBENZOIC ACID. 273 2155 Parasulphobenzoic acid is obtained by the oxidation of paratoluenesulphonic acid ; it is not necessary to employ pure material for its preparation, and the mixture of the three isomeric acids which is obtained by dissolving toluene in sulphuric acid may be conveniently made use of. The para-compound is the chief constituent of the mixture, and, together with the meta- acid, is readily oxidized, while the ortho-acid remains unaltered (Remsen). One hundred grammes of toluene are dissolved in the smallest possible quantity of fuming sulphuric acid, the solution made up to five litres with water, and heated until it becomes colourless. Hydrochloric acid and barium chloride are then added to the filtrate and the precipitated acid barium salt purified by re- crystallization ; 200 grammes of it are obtained in this way. 1 It is also formed by the action of alcoholic sulphurous acid on paradiazobenzoic acid (Vollbrecht and Wiesinger). Parasulphobenzoic acid is readily soluble in water, and crystallizes in needles, which are not deliquescent and melt with decomposition at about 200. On fusion with caustic potash, parahydroxybenzoic acid is formed, while with potas- sium formate it yields terephthalic acid. The potassium salt forms transparent needles which easily dissolve. Normal "barium parasulpfiolenzoate, C 7 H 4 S0 5 Ba-f-2H 2 O, crystallizes in small, tolerably soluble needles. The acid salt, (C 7 H 5 SO 5 ) 2 Ba + 3H 2 O, is slightly soluble in hot water, and forms long, flat, lustrous needles. ,S0 2 .NH 2 Parasulphamidobenzoic acid, C fl H-\ , is formed by \CO.OH the oxidation of paratoluenesulphamide with chromic acid solution. It is almost insoluble in cold, slightly soluble in hot water, and readily in alcohol, crystallizing in long, flat, lustrous prisms. 1 Hart, loc. cit. 274 AROMATIC COMPOUNDS. /SO,H DISULPHOBENZOIC ACIDS, C 6 H/-CO 2 H. \SO 3 H 2156 a-Disulphobenzoic acid (2 : 4) is obtained by the oxida- tion of a-toluenedisulphonic acid. 1 It is readily soluble in water, insoluble in alcohol, and is deposited from solution in concentrated hydrochloric acid in large crystals, melting above 285. On heating to 250 with caustic potash, the asymmetric dihydroxybenzoic acid melting at 204 is formed ; at a higher temperature resorcinol is obtained. ft-Disulphobenzoic acid (3 : 5) is formed when benzoic acid is heated to 250 Avith fuming sulphuric acid and phosphorus pentoxide. It is a white, hygroscopic, crystalline mass, which on fusion with potash yields the asymmetric dihydroxybenzoic acid, which melts at 232 233, while resorcinol is formed when it is heated to 350 with caustic soda. 2 Both compounds are strong tribasic acids. /SO 3 H CHLOROSULPHOBENZOIC ACIDS, C r H,Cl< \C0 2 H 2157 Four of these compounds are known. The first is obtained by the oxidation of orthochlorotoluenesulphuric acid, 3 the second by the action of sulphur trioxide on metachlorobenzoic acid, 4 and the last two, one of which only has been examined, from parachlorobenzoic acid. 5 BROMOSULPHOBENZOIC ACIDS, C fi H,Br< \C0 2 H One of these derivatives has been prepared by the oxidation of orthobromotoluene, 6 a second from metabromobenzoic acid and sulphur trioxide, 7 and two others by the oxidation of the isomeric parabromotoluenesulphonic acids, 8 one of them having been also obtained from parabromobenzoic acid. 9 1 Blomstrand, Bcr. Deutsch. Chem. Gcs. v. 1084 ; Fahlber^, Amcr. Chem. Journ. ii. 181. 2 Earth and Senhofer, Ann. Chem. Pharm. clix. 271. 3 Hiibner and Majert, Ber. Deutsch. Chem. Ges. vi. 792. 4 Otto, Ann. Chem. Pharm. cxxiii. 216. 5 Bbttinger and Coll en, ibid. cxci. 29. 6 Hiibner and Retschy, ibid, clxix. 45. 7 Hiibner and Upmann, Zeitsch. Chem. 1870, 295 ; Hiibner and Lennep, ibid. 1871, 67. 8 Hiibner and Post, Ann. Chem. Pharm. clxix. 6. 9 Bb'ttinger, ibid. cxci. 13. NITROSULPHOBENZOIC ACIDS. 275 /S0 3 H. NITROSULPHOBENZOIC ACIDS, C 6 H 3 (N0 2 ) 2158 Mulder, as early as the year 1840, prepared a nitro- sulpho'benzoic acid by the action of fuming sulphuric acid on metanitrobenzoic acid, but did not investigate it. Limpricht and v. Uslar then obtained one by the nitration of meta- sulphobenzoic acid. 1 Remsen prepared another from parasulph- amidobenzoic acid 2 in the same way, and Hart obtained the same compound by nitrating parasulphobenzoic acid. He also prepared another^ isomeride from orthosulphobenzoic acid and two additional ones by the oxidation of the corresponding nitro- toluenesulphonic acids. AMIDOSULPHOBENZOIC ACIDS. Two of these compounds have been obtained by the action of sulphuric acid on metamidobenzoic acid. 3 One of these and three others are formed when the corresponding nitrosulpho- benzoic acids are reduced. 4 X PO(OH) 2 BENZOPHOSPHINIC ACID, C 6 H 4 ( X CO.DH 2159 This body may be readily obtained by dissolving 10 grams, of paratolylphosphinic acid in a litre of water, adding an excess of caustic potash, heating to 50, and then running in a solution of 18'4 grams, of potassium permanganate. The latter is completely reduced after about a week, and the solution is then filtered, acidified with acetic acid and evaporated. The potassium acetate is extracted from the residue by alcohol, and the residual acid potassium benzophosphinite dissolved in hot, concentrated hydrochloric acid, the benzophosphinic acid being 1 Bbttinger, Ann. Chem. Pharm. cvi. 27. 2 Ibid, clxxviii. 288 ; Hart, Amer. Chem. Journ. i. 342. 3 Griess, Journ. Prakt. Chem. [2] v. 244. 4 Limpricht and v. Uslar ; Hart, 276 AROMATIC COMPOUNDS. deposited from this solution on cooling in transparent, lustrous, striated tablets, which are readily soluble in water, and crystal- lize from it in matted needles with a satin lustre. It melts above 300, and decomposes when more strongly heated, one portion becoming carbonized while the remainder decomposes into benzoic and metaphosphoric acids. It is not attacked by bromine and water at 130, while tolylphosphinic acid is decomposed by these at the ordinary temperature into phosphoric acid and bromotoluene. It is a tribasic acid, but readily forms acid salts. Acid potassium benzophosphinate, C 6 H 4 (P0 3 H 2 )CO 2 K-f H O, crystallizes in fine needles, which are readily soluble in water, slightly in alcohol. When hydrochloric acid is added to its solution, the double salt, C 6 H 4 (PO 3 H 2 )C0 2 K+C 6 H 4 (PO 3 H 2 )C0 2 H, separates out ; it crystallizes from hot water in small prisms. It may also be obtained as a precipitate resembling cream of tartar, by adding the free acid to a tolerably concentrated solution of a potassium salt. Silver benzophosphinate, C 6 H 4 (P0 3 Ag 2 )CO 2 Ag, is obtained as an amorphous precipitate by adding silver nitrate to a solution of the acid neutralized with ammonia. Oil heating with methyl iodide, the methyl ether is formed as a thick liquid, which decomposes on boiling. Benzophosphine chloride, C 6 H 4 (POC1 2 )COC1, is formed by the action of phosphorus chloride on the acid ; it is a crystalline mass, melts at 83, boils at 315, and is attacked by cold water, but is readily decomposed by boiling water. 1 Trimethylphosphobenzobetame, C 6 H 4 (CO.O)P(CH 3 ) 3 + 3H 2 0- The chloride of this compound is formed by the oxidation of trimethylparatolylphosphonium chloride with potassium per- manganate : /CH 3 /CO.OH C 6 H 4 < +30 = C 6 H 4 <; +H 2 0. . X P(CH 3 ) 3 C1 X P(CH 3 ) 3 C1 It crystallizes in short, lustrous prisms, which are readily soluble in water, less so in alcohol. The base, which is liberated by alkalis, crystallizes from hot alcohol in rhombohedra, which deliquesce in the air. When the chloride is heated with an excess of caustic potash solution it decomposes with formation of benzoic acid and trimethylphosphine oxide. 1 Michaelis and Panek, Bcr. Dcutsch. Chem. Gcs. xiv. 405. BENZAESENIC ACIDS. 277 Dimethylphospliinc-oxide benzoic add, C 6 H 4 .PO(CH 3 ) 2 .C0 2 H, is formed by the oxidation of dimethyltolylphosphine oxide, and crystallizes in prisms which have a feebly acid taste, melt at 243, sublime almost without decomposition, and are not easily attacked by caustic potash solution. 1 BENZARSENIC ACIDS. 2160 Benzarsenic acid, C 6 H 4 (As0 3 H 2 )C0 2 H, is obtained by oxidizing paratolylarsenic acid in alkaline solution. It is only slightly soluble in water, and crystallizes in large, transparent tablets or nacreous plates. On heating the anhydride, arseno- benzoic acid, C 6 H 4 (AsO 2 )C0 2 H, is formed ; this compound, which corresponds to paranitrobenzoic acid, is a yellowish powder, soluble in hot alcohol. Acid potassium benzar senate, C 6 H 4 (As0 3 H 2 )C0 2 K + C 6 H 4 (As0 3 H 2 )CO 2 H, crystallizes from hot water in transparent, triclinic tablets. Acid calcium benzar senate, C 6 H C forms nacreous plates, slightly soluble in water. Silver benzarsenate, C 6 H 4 (AsO 3 Ag 2 )CO 2 Ag, is an amorphous precipitate, which yields the crystalline methyl ether on heating with methyl iodide. Benzarsene chloride, C 6 H 4 (AsCl. 2 )C0 2 H, is obtained by the action of phosphorus trichloride on the acid : C 6 H 4 (As0 3 H 2 )C0 2 H + 2PC1 3 = C 6 H 4 (AsCl 2 )COCl + POC1 3 + P(OH) 3 . The product of the reaction is carefully treated with water, and yields the chloride, crystallizing in needles, which melt at 157 158, and are decomposed by boiling water. Benzarsene iodide, C 6 H 4 (AsI 2 )C0 2 H, is formed by the action of hydriodic acid and phosphorus on the acid, and crystallizes from chloroform in yellow needles, melting at 153. Benzarsenious acid, C 6 H 4 As(OH) 2 CO 2 H, is prepared by dis- solving the iodide in carbonate of soda and precipitating with hydrochloric acid ; it is thrown down in crystals, and crystallizes 1 Michaelis and Czimatis, Bcr. Dcutsch. Chem. Ges. xv. 2018. 249 278 AROMATIC COMPOUNDS. from hot water in fine needles, which are converted into the anhydride, C 6 H 4 (AsO)CO 2 H, at 160. Calcium benzarsenite, (C 6 H 4 (AsO 2 H 2 )C0 2 ) 2 Ca, crystallizes in nacreous plates, which lose a molecule of water on heating. Silver nitrate added to its solution produces a white precipitate of silver benzarsenite, C 6 H 4 (AsO)CO 2 Ag. Dibenzarsenic acid, (C 6 H 4 .C0 2 H) 2 AsO.OH, is formed by the oxidation of paraditolylarsenic acid with potassium permanganate and forms fine, lustrous plates, which are scarcely soluble in water, and only slightly in alcohol and hydrochloric acid. Its salts do not crystallize well. Dibenzarsene iodide, (C 6 H 4 .CO 2 H) 2 AsI, is obtained by heating the acid with hydriodic acid and amorphous phosphorus. It is a crystalline mass which dissolves in alcohol and ether, and melts above 280. Dibenzarsenious acid, (C 6 H 4 .C0 2 H) 2 AsOH, is prepared by de- composing the iodide with sodium carbonate ; on the addition of hydrochloric acid, it is obtained as a crystalline precipitate, which is slightly soluble in water, more readily in alcohol. Calcium dibenzarsenite, HOAs(C 6 H 4 .C0 2 ) 2 Ca + 2H 2 O, is pre- cipitated by alcohol from its aqueous solution as a white powder. Tribenzarsenic acid, (HO) 2 As(C 6 H 4 .C0 2 H) 3 , is formed when tritolylarsine is oxidized ; it is tolerably soluble in water and separates from alcohol in crusts, from ether in granular crystals. Potassium tribenzar senate, AsO(C 6 H 4 .C0 2 K) 3 , separates from alcohol in crystalline crusts, which are readily soluble in water. Tribenzarsenious acid, or Arsenetribenzoic acid, As(C 6 H 4 .CO 2 H) 3 , is obtained by the reduction of tribenzarsenic acid with hydriodic acid and phosphorus ; it crystallizes from ether, in small, colourless needles. Sodium arsenetribenzoate,As(C 6 H. 4: .CO 2 ^8i) s + 2H 2 0, crystallizes from hot water in short, fine needles. The silver salt is a yellowish precipitate. 1 1 La Coste, Ann. Chcm. Pharm. ccviii. 1. HYDROXYBENZYL GROUP. 279 HYDROXYBENZYL GROUP. /OH HYDROXYBENZYL ALCOHOLS, C 6 H 4 < 2161 Orthohydroxybenzyl alcohol. Piria, in 1845, found that salicin, which is contained in willow bark, is split up by the action of dilute acids or of emulsin (p. 130) into grape sugar and a new compound which he therefore named .1 C 13 H 18 7 + H 2 = C 6 H 12 6 + C 7 H 8 2 . This substance, which was subsequently also called salicyl alcohol, because it was found to stand to salicylic acid in the same relation as benzyl alcohol to benzoic acid, was obtained by Beilstein and Reineke by the action of sodium amalgam and water on salicyl aldehyde, 2 and Greene found that it is also formed when phenol is heated with methylene chloride and caustic soda solution : 3 /OH C 6 H 5 .ONa + CH 2 C1 2 + NaOH=C 6 H 4 < + 2NaCl. The decomposition of salicin by dilute acids cannot be employed for its preparation, since a portion of the alcohol is converted into saliretin (p. 280), and the following method, devised by Piria, is therefore made use of. Fifty parts of salicin are brought into 200 parts of water, and 3 parts of emulsin added, this substance being obtained by macerating pressed almonds with 3 parts of water for two hours, and precipitating the solution with alcohol. After twelve hours the greater portion of the saligenin has crystallized out, and the remainder is extracted from the 1 Ann. Chem. Pharm. Ivi. 37. 2 Beilstein and Reineke, ibid, cxxviii. 179. 3 Amer. Chem. Journ. ii. 19. 280 AROMATIC COMPOUNDS. solution with ether. The crude product is then re-crystallized from hot benzene. 1 Orthohydroxybenzyl alcohol dissolves in 15 parts of water at 22, and in almost all proportions in boiling water, readily in alcohol and ether. It crystallizes in small rhombohedra, or tablets, which melt at 82 and sublime at 100. It forms a bluish red solution in sulphuric acid, and its aqueous solution is coloured deep blue by ferric chloride. Saliretin, C 14 H U O 3 = C 6 H 4 (OH)CH 2 O.C 6 H 4 ,CH 2 OH. Bracon- not found that concentrated sulphuric acid converts salicin into a resinous substance, and Piria, who observed that dilute acids have the same effect, gave the product its name, which is intended to suggest both its nature and source. 2 Saliretin is formed from salicin by elimination of the elements of water ; in order to prepare it, salicin is heated to 80 with 10 parts of fuming hydrochloric acid, the product precipitated by water, dissolved in dilute alcohol and again precipitated by a solution of salt. 3 It is a yellowish powder, which dissolves in alkalis and does not yield either salicylaldehyde or salicylic acid on oxidation. Concentrated nitric acid converts it into picric acid. The saliretin obtained by the action of concentrated sulphuric acid has the formula C 28 H 26 5 , 4 while a compound, C 56 H 50 9 , is formed by heating saligenin with acetic anhydride (Beilstein and Seelheim). Salireton, C 14 H 12 3 , is formed in small quantity, together with other resinous products, when saligenin is heated with glycerol. It crystallizes from hot water in plates or needles, which melt at 121 '5, are coloured red by strong sulphuric acid, and are not affected by ferric chloride. 5 Orthohydroxybenzyl methyl ether, or Orthomethoxybenzyl alcohol, C 6 H 4 (OCH 3 )CH 2 OH, is formed when saligenin is heated with methyl iodide, caustic potash and wood spirit ; it is a liquid, which boils at 247'5 and solidifies in a mixture of ether and solid carbonic acid to a glassy mass. 6 Orthohydroxylenzyl ethyl ether, C 6 H 4 (OC 2 H 5 )CH 2 .OH, is pleasant smelling liquid, which boils at 265 and solidifies at O c 1 Beilstein and Seelheim, Amer. Chem. Journ. cxvii. 84. 2 Ann. Chem. Pharm. xxx. 179. 3 Kraut, ibid. clvi. 124. * Gerhardt, Ann. Chim. Phys. [3] vii. 215. 6 Giacosa, Journ. Prakt. Chem. [2] xxi. 221. 6 Cannizzaro and Korner, Ber. Deutsch. Chem Ges. v. 436. SALICIN. 281 to a crystalline mass. It gives no colouration with ferric chloride, and is oxidized by dilute nitric acid to ethoxybenzoic acid or ethyl salicylic acid, C^OC^CO.OH. 1 Caffeol, C 8 H 10 O 2 . When coffee beans are roasted, the follow- ing substances are given off from 100 parts: 0*05 of caffeol, 0'18 of caffeine, 0'48 of fatty acids, chiefly palmitic and acetic, carbon dioxide and small quantities of pyrrol, methylamine and quinol, derived probably from the quinic acid which is contained in the beans. Caffeol is a liquid which boils at 195 197, and possesses the fine aroma of coffee in a very marked degree. Its alcoholic solution gives with ferric chloride a red colouration which is not destroyed by sodium carbonate. It only dissolves with difficulty in concentrated caustic potash solution, and on fusion with caustic potash yields salicylic acid ; it is probably therefore a methyl ether of saligenin, and has the constitution C 6 H 4 (OH)CH 2 .OCH 3 . 2 The fact that it gives a red colouration with ferric chloride which shows it to be a phenol, is in accordance with this sup- position. Rotsch has also found that hydroxybenzyl methyl ether, already mentioned, which is isomeric with caffeol, smells strongly of burnt coffee, but loses the smell completely on purification. This behaviour may be explained by the formation of small quantities of caffeol as a by-product, to which the crude product owes its smell. 2162 Salicin, or Orthohydroxylenzyl glucoside, C 6 H 4 (CH 2 .OH) OC 6 H 11 O 5 . After several chemists had unsuccessfully endeavoured to obtain the bitter principle of willow-bark, which was recom- mended in cases of intermittent fever as a substitute for quinine, in the pure state, Leroux succeeded in purifying it to such an extent that it could be readily crystallized. 3 It was at first thought to be an alkaloid, although this was afterwards shown not to be the case, and the difficulty experienced in obtaining compounds of it with other substances prevented chemists from examining it more closely until Piria subjected it to a careful investigation, which resulted in a complete explanation of its nature. 4 It occurs in the bark, leaves, and female flowers of many trees which do not all belong to the willow tribe, and to the extent of 4 per cent, in Salix helix, pentandra, and prcecox\ it 1 Rotsch, Monarch. Chem. i. 621. 2 Bernheimer, ibid. i. 456. 8 ^TtTi. Chim. Phys. xliii. 440. . 4 Ann. Cham. Pharm. xxx. 151 and 189 ; Ivi. 49 ; Liebig, ibid. xxx. 185. AROMATIC COMPOUNDS. has also been found in the bark and leaves of the poplar, 1 in the flower buds of Spirwa Ulmaria (p. 286) and in castoreum 2 (Wohler). In order to prepare it, 3 parts of willow-bark are extracted three times with boiling water, the extract evaporated down to 9 parts, digested for twenty-four hours with 1 part of litharge, filtered and evaporated to a syrup. The salicin separates out and is purified by re-crystallization. 3 It forms needles, plates, or rhombic prisms, which dissolve in 30 parts of water at the ordinary temperature, and freely in hot water and alcohol, but are insoluble in ether ; it has a very bitter taste, and forms a purple-red solution in sulphuric acid. Dilute nitric acid oxidizes it to helicin, C 6 H 4 (CHO)OC 6 H U O 5 (p. 288), which may be re- converted into salicin by sodium amalgam and water. As helicin can be artificially prepared by the action of acetochloro- hydrose on salicyl aldehyde, it is also possible, as Michael has shown, to prepare salicin artificially ; this is the first instance of the synthesis of a glucoside occurring in nature. 4 Salicin melts at 201, and solidifies on cooling to a crystalline mass ; when it is heated, however, for some time to 230 240, it partially decomposes into saliretin and glucosane 5 (Part II. p. 540). Its aqueous solution rotates the plane of polarization to the left. 6 When taken internally a portion of it appears in the urine as saligenin, salicylaldehyde and salicylic acid, the remainder being excreted unchanged ; 7 its occurrence in castoreum is thus explained. It is used in medicine in cases of intermittent fever, acute rheumatism, &c., and is also employed for adulterating quinine. Populin, or Benzoylsalicin, C 13 H 17 (C 6 H 5 .CO)0 7 -f 2H 2 0, was discovered by Braconnot in the bark and leaves of the aspen poplar, Popidus tremula* and carefully investigated by Piria. 9 Piccard also observed it, along with salicin and other substances, in the buds of Populus pyramidalis, nigra et balsamifera, 10 and SchifF obtained it artificially by fusing salicin with benzoic anhydride. 11 1 Braconnot, Ann. Chim. Phys. xliv. 296 ; Tischhausen, Ann. Chem. Pharm. vii. 280. 2 Ibid. Ixvii. 360. 3 Duflos, ibid. viii. 200. 4 Amer. Chem. Journ. v. 171. 5 Schiff, Ber. Deutsch. Chem. Gcs. xiv. 304. 6 Hesse, Ann. Chem. Pharm. clxxvi. 116. 7 Laveran and Millon, ibid. lii. 435 ; Ranke, Jahresb. Chem. 1852, 711. 8 Ann. Chim. Phys. xliv. 296. 9 Ann. Chem. Pharm. Ixxxi. 245 ; xcvi. 375. 10 Ber. Deutsch. Chem. Ges. vi. 890. n Ann. Chem. Pharm. cliv. 5. BENZOYLSALICIN. 283 It crystallizes in extremely thin needles, which dissolve in 2,420 parts of water at 15 and in 42 parts at 100; it loses its water of crystallization at 100 and melts at 180. Its taste resembles that of liquorice ; it is coloured amaranthine red by sulphuric acid. Boiling baryta water decomposes it into saliciu and benzoic acid ; emulsin has no action upon it, but on boiling with a dilute acid it yields saliretin, benzoic acid and dextrose, 1 while salicin, benzamide, and ethyl benzoate are obtained by heating it with alcoholic ammonia. Nitric acid oxidizes it to benzoyl-helicin, which is the corresponding aldehyde. It has, therefore, the following constitution : /CH 2 .OH c 6 n / \OC 6 H 10 (CO.C 6 H 5 )0 5 2163 Metahydroxybenzyl alcohol is obtained by the action of sodium amalgam on an aqueous solution of metahydroxybenzoic acid which is kept acid by the repeated addition of small quantities of hydrochloric acid. It is readily soluble in alcohol and hot water, crystallizes in tough needles, melts at 63, and boils with partial decomposition at about 300 ; its aqueous solution is coloured violet-blue by ferric chloride. Hydrochloric acid converts it into a viscid resin, and on fusion with caustic potash it is oxidized to metahydroxybenzoic acid. Metahydroxybenzyl acetate, C 6 H 4 (OH)CH 2 .O.C 2 H 3 O, is formed by the action of a mixture of acetic and sulphuric acids on the alcohol, and forms crystals which melt at 55 and only very slightly soluble in water ; the solution is coloured violet-blue by ferric chloride. It boils with decom- position at 295 302. Metahydroxybenzyl diacetate, or Meta-acetobenzyl acetate, C 6 H 4 (OC 2 H 3 O)CH 2 .OC 2 H 3 O, is formed by heating the alcohol to 160 with acetic anhydride, and is a liquid which boils at 290, and does not give a colouration with ferric chloride. 2 Pardhydroxybenzyl alcohol is obtained by the action of sodium amalgam on a solution of parabenzaldehyde in dilute alcohol acidified with sulphuric acid. It is readily soluble in water, alcohol and ether, and crystallizes in needles, melting at 110. It forms a splendid reddish violet solution in concentrated sulphuric acid. 3 1 Schmidt, Ann. Chem. Pharm. xix. 92. 2 Velden, Journ. Pralet Chem. [2] xv. 165. 3 Biedermann, Ber. Deutsch. Chem. Ges. xix. 2373. 284 AROMATIC COMPOUNDS. Parahydroxyl>enzyl methyl ether, or Anise alcohol, C 6 H 4 (OCH 3 ) CH 2 .OH, is formed by the action of alcoholic potash on anis- aldehyde (paramethoxybenzaldehyde). 1 It is also formed when parahydroxybenzyl alcohol is heated with methyl iodide and caustic potash, and crystallizes in hard, lustrous needles, which have a faint spirituous odour and a burning taste ; it melts at 25, and boils at 258'8. 2 Paramethoxylenzyl chloride, C 6 H 4 (OCH 3 )CH 2 C1, is prepared by saturating the alcohol with hydrochloric acid ; it is a liquid with a fruity odour and burning taste. On treatment with sodium methylate it yields the dimethyl ether C 6 H 4 (OCH 3 )CH 2 .OCH 3 , a liquid boiling at 225'5. 3 Parahydroxylenzyl acetate, C 6 H 4 (OH)CH 2 .O.C 2 H 3 0, is formed in a similar manner to the meta-compound, and crystallizes in yellowish needles melting at 84. Para-acetobenzyl acetate, C 6 H 4 (OC 2 H 3 O)CH 2 .OC 2 H 3 O, also forms yellow needles, melting at 75 (Biedermann). Paramethoxylenzylamine, C 6 H 4 (OCH 3 )CH 2 .NH 2 , is obtained by the action of ammonia on the chloride, and crystallizes from hob water in small needles which have a strongly alkaline reaction and melt above 100. The secondary base, (C 8 H 9 0) 2 NH, is formed simultaneously ; it is less soluble in water, and crystal- lizes in plates melting at 32 33. 4 Parahydroxybenzyl thiocarbimide, C 6 H 4 (OH)CH 2 N zn CS, has been already mentioned as sinalbin mustard oil (Part II. p. 392). It is a product of the decomposition of sinalbin, C 30 H 44 N 2 S 2 16 , which crystallizes in small, lustrous needles and is readily soluble in water, slightly in alcohol ; it is converted by myrosin in presence of water into sinalbin mustard oil, acid sinapin sulphate, and grape sugar: ,. = C 8 H 7 NOS + C^NO^SO, + C 6 H 12 6 - Sinalbin mustard oil is a non-volatile, oily liquid, which has a very sharp taste and blisters the skin. When the sulphur is removed it is converted into parahydroxyphenylacetonitril, C 6 H 4 (OH)CH 2 .CN, which was considered to be the ortho- compound by Laubenheimer and Will. 5 1 Bertagnini and Cannizzaro, Ann. Chem. Pharm. xcviii. 189. 2 Cannizzaro and Korner, Ber. Deutsch. Chem. Ges. v. 436. Cannizzaro, Ann. Chem. Pharm. cxxxvii. 246. * Ibid, cxvii. 240. 5 Ann. Chem. Pharm. cxcix. 150. SALICYLALDEHYDE. 285 /OH HYDROXYBENZALDEHYDES, C 6 H 4 < ORTHOHYDROXYBENZ ALDEHYDE, OR SALICYLALDEHYDE. 2164 The volatile oil of the flowers of Spircea Ulmaria was first examined by Pagenstecher, an apothecary of Berne, who discovered in it an acid, the aqueous solution of which is coloured violet by ferric chloride, 1 and which was called " spiroylwasser- sloffsdure" C 12 H 6 0(C = 6,O = 8) by Lowig, to whom Pagenstecher intrusted its further investigation. 2 He and Weidmann sub- sequently found that when the ethereal solution is shaken with caustic potash, this is coloured yellow, and on evaporation of the ether an indifferent oil remains behind, which possesses the smell of the flowers in a very marked degree, while if the alkaline solution be distilled with phosphoric acid, an acid oil passes over first, followed by an acid crystallizing in long needles. They now called the former of these spirccic acid, or spiroyl hydride, C 13 H 10 4 . 3 About the same time, Piria, working in Dumas' laboratory, found that salicin on oxidation with potassium dichromate and dilute sulphuric acid yields a volatile, oily, aromatic liquid, which he called salicyl hydride, C 7 H 6 O 2 . This is isomeric with benzoic acid, and is to be looked upon as a hydracid, which, on heating with caustic potash, yields salicylic acid, C 7 H 6 3 , just as benzoyl hydride under similar circumstances yields benzoic acid. The radicals lenzoyl, C 7 H 5 O, and salicyl, C 7 H 5 2 , are different oxidation products of the hydrocarbon, C 7 H 5 . 4 Dumas, to whom Pagenstecher showed his preparations from Spiraea, noticed the great similarity of the oil to salicyl hydride and suggested that spira3ic acid is identical with the latter ; 5 this had already been proved by Ettling, who named the compound salicylous or spiroylous acid. 6 The compound was mistaken for an acid because it is at once an aldehyde and a phenol, and therefore forms salts. Salicylaldehyde also occurs in the juice of various plants 1 Buchner's Rcpert. Pharm. xlix. 337 ; li. 364. 2 Pogg. Ann. xxxvi. 383. 3 Ibid. xlvi. 57. 4 Ann. Chem. Pharm. xxix. 300, xxx. 151. 5 Ibid. xxix. 306. 8 Ibid. xxix. 309 ; xxxv. 241. 280 AROMATIC COMPOUNDS. belonging to the genus Spiraea, 1 in the stem and root of Crepis fcetida, 2 and in the larvae of Chrysomela populi, which live on willows and poplars, and possess small openings along the body from which salicyl aldehyde may be pressed out in oily drops. 3 Enz also obtained it by distilling the beetle with water. 4 In order to prepare it, a mixture of 3 parts of salicin and 3 parts of potassium dichromate is treated with 24 parts of water, to which 4*5 parts of sulphuric acid diluted with 12 parts of water are added. When the reaction is complete, the mixture is distilled until the distillate passes over clear, and the oily portion then separated from the water ; some of the aldehyde remains dissolved in the water and is extracted by ether. 5 If the distillation be continued too long, furfurol passes over, and all preparations made from the aldehyde then become intensely red-coloured on standing. 6 The flower-buds of Spircea Ulmaria omy give a very small yield of salicyl aldehyde on distillation with water, but a larger quantity is obtained when sulphuric acid and potassium di- chromate are added, thus showing that the buds contain salicin. 7 Salicyl aldehyde is obtained synthetically, along with the isomeric parahydroxybenzaldehyde, by the action of chloroform on a solution of phenol in caustic soda (Part III. p. 32). They are separated by distillation in steam, with which the latter is not volatile. 8 Properties. Salicylaldehyde is a liquid with a pleasant aromatic smell and a burning spice-like taste ; it boils at 196'5, solidifies at 20 to large crystals, and has a specific gravity of 1*1731 at 13'5. Its aqueous solution, even when very dilute, is coloured violet by ferric chloride, and yellow by alkalis ; it does not reduce Fehling's solution, 9 and forms difficultly soluble com- pounds with the acid sulphites of the alkali metals, 10 this property being made use of in its purification (Reimer and Tiemann). It produces a fine reddish violet colouration in a solution of rosaniline which has been decolourized by sulphurous acid. 11 The aldehydes, of the fatty acids, benzaldehyde, &c., also give this reaction (Part II. p. 495). 1 "Wicke, Ann. Chem. Pharm. Ixxxiii. 175. 2 Ibid. xci. 374. 3 Jahresbcr. Chem. 1850, 583. 4 Ibid. 1859, 312. 6 Sehiff, .47m. Chem. Pharm. cl. 193. 6 Ibid. ccx. 115. 7 Buchner, ibid. Ixxxviii. 284. 8 Reimer and Tiemann, Bcr. DeuUch. Chem. Ges. ix. 824. 9 Tollens, ibid. xiv. 1959. 10 Bertagnini, Ann. Chem, Pharm. Ixxxv. 93. 11 Schmidt, Ber. Deutsch. Chem. Ges. xiv. 1848. SALICYLALDEHYDE COMPOUNDS. 287 As a phenol it forms salts, ethers, and ethereal salts. Potassium salicylaldehyde, C 6 H 4 (OK)CHO + H 2 O, is obtained by adding caustic potash to a solution of the aldehyde in dilute alcohol ; it crystallizes in light yellow, nacreous, quadratic tablets, which are readily soluble in water. The compound C 6 H 4 (OK) CHO + C 6 H 4 (OH)CHO is obtained in fine, fascicular groups of needles by adding the aldehyde to an alcoholic solution of the potassium salt. Barium salicylaldehyde, (C 6 H 4 (CHO)0) 2 Ba+ 2H 2 0, crystallizes in yellow needles, which are slightly soluble in cold water. Copper salicylaldehyde, (C 6 H 4 (CHO)0) 2 Cu > is a very character- istic salt ; when an aqueous solution of copper acetate is added to a dilute alcoholic solution of the aldehyde, the liquid becomes coloured emerald green, and after a few minutes deposits spark- ling crystals; the liquid then presents a most beautiful appearance when placecj in the sunlight. The crystals become brownish- green on drying, and are only slightly soluble in water and alcohol (Ettling). Lead salicylaldehyde, C 6 H 4 (CHO)OPb.OH, is formed when basic lead acetate is added to an alcoholic solution of the alde- hyde ; it is a yellow precipitate which dissolves on heating, and separates out on cooling in heavy, light-yellow granules. Methyl salicylaldehyde, C 6 H 4 (OCH 3 )CHO, is obtained by heating the sodium salt with methyl alcohol and methyl iodide. 1 It is an oily liquid which possesses a faint odour, boils at 238, and, when perfectly free from salicylaldehyde, solidifies after some time to tough prisms melting at 35. It forms a compound with acid ammonium sulphite, which crystallizes in lustrous prisms and is readily soluble in water and alcohol. The potassium sulphite compound also crystallizes well, but is only slightly soluble in cold alcohol. Ethyl salicylaldehyde, C 6 H 4 (OC 2 H 5 )CHO, was obtained by Perkin in a similar manner, as a strongly refractive liquid boiling at 247 249. It is also formed when a mixture of calcium formate and calcium ethyl salicylate is distilled, while, when calcium salicylate is substituted for the ethyl compound, only phenol is formed. 2 Benzyl salicylaldehyde, C 6 H 4 (OCH 2 .C 6 H 5 )CHO, crystallizes from boiling alcohol in flat, rhombic prisms, which melt at 46, 1 Perkin, Journ. Chem. Soc. xx. 418 ; Yoswinkel, Ber. Deutsch. Chem. Ges. xv. 2024. 2 Gottig, ibid. x. 8. 288 AROMATIC COMPOUNDS. and have a faint odour resembling that of cloves. It boils above 360, and forms an irritating vapour. 1 Acetyl salicylaldehyde, C 6 H 4 (OC 2 H 3 O)CHO, is formed when the sodium salt is suspended in ether and treated with acetic anhydride. It is extremely soluble in alcohol, crystallizes in fine, silky needles, melts at 37, and then solidifies to a mass possessing a satin lustre. Its boiling-point lies at about 253; it combines with the acid sulphites of the alkali metals. 2 Benzoyl salicylaldehyde, C 6 H 4 (O.CO.C 6 H 5 )CHO, was obtained by Perkin by the action of benzoyl chloride on the sodium compound. It is a thick oily liquid, which boils above 360, and forms the usual compounds with the acid sulphites of the alkali metals. 3 2165 Eelicin, 4C 6 H/OC 6 H n 5 )CHO + 3H 2 0, is formed by the action of dilute nitric acid on salicin. 4 In order to prepare it, salicin is treated in flat basins or plates with eight times its weight of nitric acid of sp. gr. 1/15, containing lower oxides of nitrogen, which may be introduced by the addition of a few drops of the red, fuming acid. The helicin is filtered off after some hours and washed two or three times with cold water. 5 It is readily soluble in hot water and alcohol, but not in ether, and crystallizes in small, very fine needles, which have a faint, bitter taste, lose their water of crystallization at 100 and melt at 175. It is not coloured by ferric chloride; if a blood- red colouration be produced, it contains nitrosalicylic acid. It is resolved into dextrose and salicylaldehyde by the action of acids, alkalis and emulsin. It can be synthetically prepared by acting upon potassium salicylaldehyde with an alcoholic solution of acetochlorohydrose : 6 CHO + C 6 H 7 C1(C 2 H 3 0) 4 5 + 4C 2 H 5 .OH = C 6 H 4 < + 4C 2 H 5 OC 2 H 3 O + KC1. \OC 6 H n 5 It is reduced to salicin by the action of sodium amalgam and water. 7 It forms a compound with acid sodium sulphite, 1 Perkin, Journ. Chem. Soc. xxi. 122. 2 Ibid. xxi. 181. 3 Ibid. cxlv. 295. 4 Piria, ibid. Ivi. 64. 5 Schiff, ibid. cliv. 14. 8 Michael, Amcr. Ohcm. Journ. i. 309. 7 Liseuko, Jahresber. Chem. 1864, 588. DERIVATIVES OF HELICIN. 289 which has the formula C 13 H 16 7 .S0 3 HNa, and forms a dazzling white, hygroscopic, crystalline mass. 1 When it is moistened with one per cent, nitric acid, dried and heated to 110 115, it is converted into parahelicin, which is without doubt a polymeride; this substance is an amorphous, starchy, tasteless powder, which is scarcely soluble in water and alcohol, and has no action upon a solution of rosaniline reduced by sulphurous acid, whereas helicin forms a reddish violet crystalline compound with it. It dissolves in very dilute hydrochloric acid which has been slightly warmed, and is thus reconverted into helicin. 2 Tetracetylhelicin, C 13 H 12 (C 2 H 3 0) 4 , was obtained by Schiff by heating helicin with acetyl chloride or acetic anhydride ; it crystallizes from hot alcohol in long, silky needles or prisms. Benzoylhelicin, C 13 H 15 (CO.C 6 H 5 )O 7 . Piria prepared this com- pound by the action of nitric acid on populin (p. 282), 3 and Schiff by heating helicin with benzoyl chloride. 4 It crystallizes in silky needles, which are slightly soluble in water, more readily in alcohol. Sodium amalgam and water reduce it again to populin ; on boiling with water and magnesia it is decomposed into helicin and benzoic acid. Helico'idin, C 26 H 34 O 14 , is formed by dissolving salicin in nitric acid of sp. gr. TOS5 : 2C 13 H 18 7 + = CaftA* + H 2 0. It crystallizes from hot water in needles, and is very similar to helicin, from which it differs in being resolved by acids, &c., into dextrose, salicylaldehyde, and saligenin (Piria). Odacetylhelico'idin, C 26 H 26 (C 2 H 3 O) 8 O 14 , is obtained by heating helicoidin to 100 with acetic anhydride; it is insoluble in water, and crystallizes from alcohol in druse-like aggregates, melting at 80 (Schiff). Ortho-aldehydophenoxyacetic acid, C 6 H 4 (COH)OCH 2 .C0 2 H, is formed when equal molecules of salicylaldehyde and chloracetic acid are heated together and the fused mass treated with an excess of caustic soda solution of sp. gr. 1'2 1'3; the mixture is then heated on the water-bath until it has become almost solid, the acid precipitated by hydrochloric acid and 1 Schiff, Ann. Chcm. Pharm. ccx. 126. 2 Ibid. Ber. Deutsch. Chcm. Ges. xiv. 317. 3 Ann. Chem. Pharm. xcvi. 379. 4 Ibid. cliv. 23. 290 AROMATIC COMPOUNDS. re-crystallized from hot water. It forms large, yellow plates, which melt at 132, and sublime when gradually heated. Like other aldehydes it reduces Fehling's solution and am- moniacal silver solution, and combines with phenylhydra- zine and acid sodium sulphite. Its salts are readily soluble and crystallize well; its ethyl ether forms needles melting at 114 . 1 2166 Orthohydroxybenzidene compounds. These are obtained in a similar manner to the benzidene compounds. OrtTiohydroxyltenzidene acetate, C 6 H 4 CH.CC1 3 , is formed when >COo salicylic acid is heated to 130 150 for a long time with an excess of chloral. It is insoluble in water, slightly soluble in alcohol and ether, and crystallizes from the latter in prisms, melting at 124 125 . 1 Disalicylic acid, (C 6 H 4 .C0 2 H) 2 0. This compound, which is also called salicylic anhydride, or sal icylo salicylic acid, was ob- tained b} r Gerhardt by the action of phosphorus oxychloride on sodium salicylate. 2 It is also formed when acetylsalicylic acid is heated, or when salicylic acid is heated for a long time to 130 140 with acetyl chloride. 3 It is an amorphous mass, which dissolves in the alkaline carbonates and is reprecipitated by acids. It gives no colouration with ferric chloride ; aqueous ammonia converts it into salicylamide and ammonium salicylate, while potassium salicylate is formed by the action of caustic potash. Salicylide, C 7 H 4 O 2 , is formed by heating salicylic acid with phosphorus oxychloride : = c 6 H 4 < + H 2 o. It crystallizes from absolute alcohol in spherical aggregates of lustrous plates, which melt at 195 200; it gives no colour- ation with ferric chloride, and is converted into salicylic acid by the action of caustic potash. 4 Tetrasalicylide, C. 28 H 18 9 , is formed at the same time as the preceding compound, and is a resinous mass insoluble in alcohol. 1 Wallach, Ann. Chem. Pharm. cxcvii. 41. 2 Ibid. Ixxxvii. 159. 8 Kraut, ibid. cl. 13. 4 Schiff, ibid, clxiii. 220. SALICYLHYDROXYACETIC ACID. 309 Salicylhydroxyacetic acid, C 6 H 4 (OCH 2 CO 2 H)CO 2 H, is obtained by oxidizing ortho-aldehydophenoxyacetic acid (p. 289) with potassium permanganate. It crystallizes from hot water in white needles, melting at 186 187. It forms readily soluble salts which crystallize well. 1 2175 The Action of Phosphorus Pentachloride upon Salicylic Acid. As already mentioned, Chiozza found, in 1852, that when salicylic acid is treated with phosphorus pentachloride and the product distilled, the distillate yields orthochlorobenzoic acid when treated with water (p. 217). Gerhardt repeated this experiment, and found that the liquid before distillation is salicyl chloride, C 7 H 5 O 2 C1, as it is converted by water into sali- cylic acid, and by alcohol into an ethereal salt of this ; he also obtained it together with methyl alcohol by treating winter-green oil with phosphorus pentachloride. 2 Drion made the further observations that only a trace of phosphorus oxychloride is formed in this reaction, and that a portion of the product is converted into chlorobenzoyl chloride by distillation. 3 Couper, however, obtained different results. He acted upon one molecule of methyl salicylate with two molecules of phos- phorus chloride, and distilled the resulting liquid ; the excess of the chloride came over first, followed by a liquid distilling between 285 295, to which he gave the name of salicyl trichlorophos- phate, explaining its formation by the following equation : C 8 H 8 3 f PC1 5 = HC1 + CH 3 C1 + C 7 H 4 C1 3 P0 3 . This compound, which he also obtained from salicylic acid, is decomposed by water into hydrochloric acid, phosphoric acid and salicylic acid : C 7 H 4 C1 3 P0 3 + 4H 2 = 3HC1 + H 3 P0 4 + C 7 H 6 3 . When he submitted it to rapid distillation, a considerable quantity of hydrochloric acid was evolved, and the distillate consisted of a liquid boiling above 300, which deposited large crystals of salicyl monochlorophosphate, C 7 H 4 C1P0 4 , when pre- served in a sealed tube ; this substance, like the trichlorophos- phate, is converted into phosphosalicylic acid, C 7 H 7 PO 6 , in moist air. He therefore considered that the existence of salicyl 1 Rossing, Ber. Deutsch. Chem. Ges. xvii. 2988. 3 Ann. Chem. Pharm. Ixxxix. 363. 8 Ibid. xcii. 312. 251 310 AROMATIC COMPOUNDS. chloride, no analyses of which had been published, was very doubtful. 1 Drion replied to this, that although the latter compound had not been obtained in a state of purity, its existence was proved by the fact that ethers of salicylic acid are formed by the action of alcohol upon it. 2 Kolbe and Lautemann came to the same conclusion. Accord- ing to them, a mixture of chlorobenzoyl chloride, salicyl chloride and chlorosalicyl trichloride is obtained by distilling salicylic acid with phosphorus pentachloride. 3 Kekule", who investigated this reaction at about the same period, found that when the product is heated to 180 200 to remove phosphorus chloride and oxychloride, a liquid remained which yielded salicylic acid and traces of chlorobenzoic acid when decomposed by water. It also contained 3 per cent, of phosphorus, and considerably more chlorine than corresponds with the composition of salicyl chloride ; on dis- tillation he obtained considerable quantities of phosphorus oxychloride and chlorobenzoyl chloride, but not Couper's com- pound. 4 It therefore became the generally accepted view, that the following compounds are formed by the action of phosphorus pentachloride on salicylic acid : Salicyl chloride. Chlorobenzoyl chloride. Chlorobenzenyl trichloride. /OH /Cl /Cl C 6 H 4 < C 6 H 4 <( C 6 H 4 <( \COC1 XJOC1 \CCl r The salicyl chloride could not be obtained pure because it decomposed on distillation, and could not therefore be freed from chlorobenzoyl chloride and phosphorus oxychloride ; according to Miquel, it adheres most obstinately to the latter. 5 The solution of the problem was found by Anschiitz, who, by bringing together equal molecules of salicylic acid and phos- phorus pentachloride, obtained an evolution of hydrochloric acid and a yellow liquid, which distilled under a pressure of 11 mm. as a colourless, refractive liquid, only a small quantity of residue being left. This has the composition of Couper's salicyl tri- 1 Ann. Chem. Pharm. cix. 369. 2 Ibid. cix. 373. 3 Ibid. cxv. 183. 4 Ibid, cxvii. 148. 5 Ann. Chim. Phys. [5] xi. 304. ORTHOCHLOROCARBONYLPHENYL METAPHOSPHATE. 311 chlorophosphate and is orthocarbonylphenylphosphoryl chloride, formed according to the following equations : /OH /OH C 6 H 4 < + PC1 5 = C 6 H 4 < + POC1 3 + H 2 0. \CO.OH \COC1 The phosphorus oxychloride then acts upon the salicyl chloride just as it does upon phenol : /OH /O.POC1 2 C 6 H 4 < + POC1 3 = C 6 H 4 < 4 HC1. \COC1 \COC1 2 The pure chloride distils at 285 295 under the ordinary pressure. If it be submitted to slow distillation, a mixture of phosphorus oxychloride, orthochlorobenzoyl chloride and ortho- chlorotribenzenyl chloride is obtained, boiling at 270 290. If the distillation be now continued under diminished pressure, Couper's salicyl monochlorophosphate, or orthochlorocarbonyl- phcnyl metaphosphate passes over; it is formed, together with orthochlorobenzoyl chloride, according to the following equation : O.POCL /Cl /OP0 9 2C 6 H 4 =C 6 H 4 + C fl H POC1 3 . \COC1 \COC1 \COC1 It boils at 187 under a pressure of 11 mm., and solidifies on cooling to crystals, which melt at 30. The chloride is decomposed by a small quantity of water into hydrochloric acid, phosphoric acid and salicylic acid ; in moist air, on the other hand, or on distillation with anhydrous oxalic acid, it is converted into orthochlorocarbonylphenyl meta- phosphate : OPOC1 2 /OP0 It dissolves, however, in a large quantity of cold water, with formation of orthocarboxylphenylphosphoric acid, C 6 H 4 (CO.OH) OPO(OH) 2 , which on evaporation in a vacuum over soda lime gives a crystalline mass, which melts at 147 and is readily soluble in water. If the chloride be heated to 165 170 with phosphorus pentachloride, benzenyltrichlorophosphoryl chloride, Cg 312 AROMATIC COMPOUNDS. CC1 3 , is formed ; it is a powerfully refractive liquid, which boils at 178 179 under a pressure of 11 12 mm., and is not con- verted by water into hydroxybenzenyl trichloride, as might have been expected, but into phosphosalicylic acid. When it is heated with phosphorus chloride to 180, ortho- chlorobenzenyl trichloride is formed : l /OPOC1 2 ,01 ' C H 0. This com- \N(CH 3 ) 3 pound, which may also be called hydroxybenzobetaine, is formed by the action of methyl iodide and caustic potash on amidosalicylic acid, and crystallizes from water in large, snow-white needles, often an inch in length, which contain four molecules of water, have a very bitter taste and are coloured reddish violet by ferric chloride. It combines with the mineral acids to form salts which crystallize well. Methyl dimethylamidosalicylate, C 6 H 3 (OH)N(CH 3 ) 2 C0 2 CH 3 , is prepared by heating the preceding compound, after previously removing its water of crystallization. It forms rhombic prisms, and is decomposed on boiling with hydrochloric acid into methyl alcohol and dimethylamidosalicylic acid, which crystallizes in small, almost insoluble needles. 2 (3- Amidosalicylic acid is not known in the free state; its hydrochloride crystallizes in needles which readily decompose (Hubner). Nitro-amidosalicylic acid, C 6 H 2 (NO 2 )NH 2 (OH)C0 2 H, is formed by the partial reduction of dinitrosalicylic acid ; it forms crystals, melting at 220 ; a-nitrosalicylic is obtained 3 when the amido- group is replaced by hydrogen. Diamidosalicylic acid, C 6 H 2 (NH 2 )(OH)CO 2 H, was prepared by Saytzew by the action of hydriodic acid on the methyl ether of dinitrosalicylic acid. 4 It is very slightly soluble in cold, more readily in hot water, and crystallizes in small needles. It combines with acids to form salts which crystallize well ; ferric chloride produces a brownish red colouration, followed by a black precipitate. Sulphosalicylic acid, C 6 H 3 (S0 3 H)(OH)C0 2 H, was obtained by Mendius by the action of sulphur trioxide on salicylic acid, 5 and 1 Schmitt, Jahresber. 1864, 423. 2 Griess, Ber. Dcutsch. Ctwm. Ges. xii. 2307. 3 Babcock, ibid. xii. 1345. * Ann. Chcm. Pharm. cxxxiii. 321. 5 Ibid. ciii. DIAZOSALICYLIC ACID. 319 may also be prepared by heating salicylic acid with sulphuric acid. 1 It crystallizes in long, thin, very soluble needles, which melt at 120, and are coloured an intense reddish violet by ferric chloride. Its salts crystallize well ; on fusion with caustic potash, no dihydroxybenzene is formed, the product consisting entirely of phenol and salicylic acid. Salieylsulphuric acid, C 6 H 4 (SO 4 H)C0 2 H. The potassium salt may be obtained by heating salicylic acid with caustic potash and potassium disulphate ; it crystallizes in colourless, pointed prisms and is readily soluble in water, but insoluble in absolute alcohol. It gives no colouration with ferric chloride and is decomposed by dilute acids, including even acetic acid, into potassium sulphate and salicylic acid. 2 ,!$=$ Diazosalicylic acid, C 6 H 3 (OH)<; | , is formed by passing ; | \co.o nitrogen trioxide into an alcoholic solution of the hydrochloride of amidosalicylic acid. It crystallizes in fine needles and combines with acids to form salts which crystallize well ; 3 iodosalicylic acid is formed on heating with hydriodic acid. Azobenzenesalicylic acid, C 6 H 5 .N 2 .C 6 H 3 (OH)C0 2 H, is obtained by the action of diazobenzene nitrate on an alkaline solution of salicylic acid ; it crystallizes in orange -red needles, which are insoluble in water, but dissolve readily in alcohol. Sulphuric acid converts it into a sulphonic acid, which is probably identical with the following compound. 4 Salicylparazobenzenesulphonic acid, C 6 H 4 (SO 3 H)N 2 .C 6 H 3 (OH) C0 2 H, is formed by bringing salicylic acid into a solution of paradiazobenzenesulphonic acid in caustic potash. It crystallizes in golden-yellow needles, which are only slightly soluble in hot water ; barium chloride produces a yellow precipitate of (C 13 H 9 N 2 S0 6 ) 2 Ba, which is converted on boiling into irregular, six-sided, lustrous plates. 5 1 Remsen, Ann. Chem. Pharm. clxxix. 107. 2 Baumann, Ber. Dcutsch. Chem. Ges. xi. 1914. 3 Schmitt, Jahresber. Chem. 1864, 384 ; Schmidt and Mittenzwey, Journ. Prakt. Chem. [2] xviii. 193 ; Goldberg, ibid. x'ix. 362. 4 Stebbins, Ber. Deutsch. Chem. Ges. xiii. 716. 6 Griess, ibid. xi. 2196. 320 AROMATIC COMPOUNDS. METAHYDROXYBENZOIC ACID. 2180 Gerland obtained this isomeride of salicylic acid by the action of nitrous acid on a hot solution of ordinary amidobenzoic acid, and gave it the name of oxybenzoic acid, 1 by which it is still generally designated. It is also formed by fusing sulpho- benzoic acid, 2 metachlorobenzoic acid, 3 or metachlorocresol 4 with caustic potash. In order to prepare it, 2 parts of potassium sulphobenzoate are fused with 5 parts of caustic potash and a little water, the melt acidified with sulphuric acid and the whole extracted with ether. The metahydroxybenzoic acid is left on evaporation in thick, white crusts which are purified by re-crystallization from hot water. Any adhering benzoic acid is finally removed by washing with carbon disulphide (Barth). Metahydroxybenzoic acid crystallizes in small prisms or needles, melting at 200, which usually form warty aggregates. It dissolves at in 265, and at 18 in 108'2 parts of water, has a sweet taste, is not coloured by feme chloride and can be distilled without undergoing decomposition. It differs from its isomerides in being reduced by sodium amalgam in an acid solution to metahydroxybenzyl alcohol, and in blackening at 300 without a trace of phenol being formed ; decomposition, accom- panied by the formation of small quantities of the latter, only occurs at higher temperatures. 5 The Metahydroxybenzoates. The salts of the alkali metals are readily soluble and do not crystallize well ; they are very stable and only decompose at a high temperature, very little phenol and no isomeric acid being formed. The basic salts do not combine with carbon dioxide at a high temperature (Kupferberg) ; when the acid is fused with an excess of sodium carbonate, decomposition sets in above 300, the greater portion of the acid being completely burnt, and only a small quantity of phenol being therefore formed. 6 If two molecules of the acid are heated 1 Ann. Chem. Pharm. Ixxxvi. 143 ; xci. 189 ; Fischer, ibid, cxxvii. 138. 2 Barth, ibid, cxlviii. 30. 3 Dembey, ibid, cxlviii. 222. 4 Barth, ibid. cliv. 361. 6 Klepl, Journ. Prakt, Chem. [2] xxv. 464 ; xxvii. 159. 6 Barth and Schreder, Ber. Deutsch. Chem. Ges. xii. 1254. THE METAHYDROXYBENZOATES. 321 to 350 with three molecules of caustic baryta, no change takes place, but if seven molecules of the latter be employed, a complete decomposition into carbon dioxide and phenol occurs (Klepl). Ammonium metahydroxybenzoate, C 6 H 4 (OH)C0 2 NH 4 , crystal- lizes in needles which form fascicular aggregates. Calcium metahydroxybenzoate, (C 6 H 4 .OH.CO 2 ) 2 Ca + 3H 2 O, forms readily soluble crystals. Barium metahydroxybenzoate, (C 6 H 4 .OH.C0 2 ) Ba, is an amor- phous, gummy mass ; it has been found impossible to prepare a basic salt. Copper metahydroxybenzoate, (C 6 H. i .O'H..CO^) 2 C\i +H 2 0, crystal- lizes from hot water in greenish needles. Thallium metahydroxybenzoate, C 6 H 4 (OH)CO 2 T1, is prepared by neutralizing a hot solution of the acid with thallium carbonate ; it crystallizes on cooling in lustrous, colourless prisms. When a solution of the hydroxide is neutralized with the acid and an equal quantity of the hydroxide added to the neutral solution, the basic salt, C 6 H 4 (OT1)CO 2 T1, crystallizes on evaporation in yellowish prisms ; it is more readily soluble than the normal salt and has an alkaline reaction (Kupferberg). The methylamine salt decomposes into its constituents when heated, and the aniline salt behaves in a similar manner, a little hydroxybenzanilide being also formed, while tetra-ethylammonium metahydroxybenzoate splits up into tri-ethylamine and ethyl metahydroxybenzoate. Ethyl metahydroxybenzoate, C 6 H 4 (OH)CO 2 .C 2 H 5 , is formed by the action of hydrochloric acid gas on an alcoholic solution of the acid, 1 or by heating the normal potassium salt with ethyl iodide. 2 It crystallizes from ether in tablets, melts at 72, boils at 282, and is converted by caustic soda into a crystalline mass of C 6 H 4 (ONa)C0 2 .C 2 H 5 , which is readily soluble in water and alcohol. Metamethoxybenzoic acid, C 6 H 4 (OCH 3 )CO 2 H, is obtained by heating metahydroxybenzoic acid with the calculated quantity of caustic potash and methyl iodide, and decomposing the ethereal salt thus formed with a solution of caustic potash in wood-spirit (Grabe and Schultzen). It is also formed by the oxidation of metacresyl methyl ether with potassium permanganate, 3 and by 1 Grabe and Schultzen, Ann. Chem. Pharm. cxlii. 351. 2 Heiutz, ibid, cliii. 337. 3 Oppenheim and Pfaff, Ber. Deutsch. Chem. Ges. viii. 887. 322 AROMATIC COMPOUNDS. the action of carbon dioxide on a mixture of metabromophenyl methyl ether and sodium. 1 It crystallizes from hot water in long needles, which melt at 106 107, and sublime without decomposition. Meta-ethoxylenzoic acid, C 6 H 4 (OC 2 H 5 )C0 2 H, was prepared by Heintz from the ethyl ether ; it is also formed by the decom- position of the sulphate of metadiazobenzoic acid with alcohol 2 It crystallizes in small needles, melting at 137, which are scarcely soluble in cold, slightly in hot water, but readily in alcohol, and sublime undecomposed. Ethyl meta-ethoxylenzoate, C 6 H 4 (OC 2 H 5 )C0 2 .C 2 H 5 , is obtained by heating metahydroxybenzoic acid with two molecules of caustic potash and ethyl iodide ; it is a liquid, boiling at 263. Meta-acetoxybenzoic acid, C 6 H 4 (OCO.CH 3 )C0 2 H, is produced by the action of acetyl chloride on the acid (Heintz) ; it forms granular crystals melting at 127, and gives amorphous salts. 2181 Metahydroxybenzoic acid behaves towards phosphorus pentachloride in a very similar manner to salicylic acid. Metacarbonylphenylphosphoryl chloride, C 6 H 4 (OPOC1 2 )COC1, is a colourless liquid, which boils at 168 170 under a pressure of 11 12 mm. A yield of 57'5 per cent, of the theoretical quantity is obtained, and the unattacked acid may be extracted from the residue in the retort by boiling water or alkalis. Metacarboxyorthophosphoric acid, C 6 H 4 (CO 2 H)PO(OH) 2 , is formed when the chloride is treated with water, a considerable evolution of heat taking place, but no metahydroxybenzoic acid being reformed. It crystallizes in fine, white scales, which melt at 200 201, and are only decomposed by water at a tem- perature of 150 160, phosphoric and metahydroxybenzoic acids being formed. When the chloride is submitted to slow distillation, a portion passes over unchanged, together with phosphorus oxychloride, no metachlorobenzoyl chloride, C 6 H 4 C1(COC1), or metachloro- benzenyl trichloride, C 6 H 4 C1(CC1 3 ), being produced, and a black syrupy residue is left, which yields metahydroxybenzoic acid on boiling with water or alkalis, and therefore probably contains the compounds (C 6 H 4 (COC1)0) 2 POC1 and (C 6 H 4 (COC1)0) 3 PO. Metabenzenyltrichlorophosphoryl chloride, C 6 H 4 (OPOC1 2 )CC1 3 , is obtained in a similar manner to the corresponding salicylic acid derivative. It boils at 178 under a pressure of 11 mm., and is 1 Korner, Jahresber. Chem. 1867, 414. 2 Griess, Zeitschr. Chem. 1866, 1. IODOMETAHYDROXYBENZOIC ACID. 323 converted by water into metacarboxyphenylphosphoric acid, while on heating with phosphorus pentachloride to 180, a portion is converted into metachlorobenzenyl trichloride. 1 Metahydroxylenzamide, C 6 H 4 (OH)CO.NH 2 , is formed when diazobenzamide nitrate is boiled with water 2 as well as by the action of ammonia on ethyl metahydroxybenzoate. It crystallizes from water in thin plates, which have a bitter taste and melt at 167. MetaJiydroxylenzanilid.c, C 6 H 4 (OH)CO.NH(C 6 H 5 ), is obtained in the same way as salicylanilide ; it crystallizes from dilute alcohol in needles, melting at 154 155, and combines with alkalis to form salts which crystallize well. It is not attacked by boiling alkalis, but is decomposed by them on fusion (Kupferberg). Metahydroxylenzuric acid, C 6 H 4 (OH)CO.NH.CH 2 .CO 2 H, occurs in the urine of the dog after metahydroxybenzoic acid has been administered ; it crystallizes in needles. 3 Metahydroxylenzonitril, C 6 H 4 (OH)CN, is formed by boiling diazobenzonitril sulphate with water 4 and by heating meta- hydroxybenzoic acid in a current of ammonia, first to 220 230 and then to 300 320 ; the isomeric compounds are decomposed by this treatment into phenol and carbon dioxide, but yield no nitril. 5 Metahydroxybenzonitril crystallizes from hot water in small plates and from alcohol in small, rhombic prisms ; it has an intensely sweet and at the same time sharp taste, melts at 82, and decomposes on heating with hydrochloric acid into ammonia and metahydroxybenzoic acid. SUBSTITUTION PRODUCTS OF METAHYDROXY- BENZOIC ACID. 2182 Iodometahydroxy'benzoicacid ) C Q H. 3 l(01I)CO.fi. Weselsky obtained this substance by the action of iodine and mercuric oxide on an alcoholic solution of metahydroxybenzoic acid. It cry- stallizes in needles, which are only slightly soluble in cold water. Nitrometahydroxybenzoic aWs,C 6 H 3 (NO 2 )(OH)CO 2 H. Gerland found that the direct nitration of metahydroxybenzoic acid yields 1 Anschiitz, private communication. 2 Griess, Zeitschr. Chem. 1866, 1. 3 Baumann arid Heiter, Hoppe-Seyler's Zeitschrift, i. 260. 4 Griess, Ber. Deutsch. Chem. Ges. viii. 859. 5 Smith, Journ. Prakt. Chem. [2] xvi. 218. 324 AROMATIC COMPOUNDS. a nitrohydroxybenzoic acid, -which forms yellow, rhombic crystals, and has a repulsive, bitter taste ; it must be identical with one of those described below, since metahydroxybenzoic acid can only yield four mononitro-derivatives. The first three were prepared by Griess by boiling the corresponding nitro-amido- benzoic acids with caustic potash. 1 a-Nitrometahydroxylenzoic acid, (CO 2 H : OH : NO 2 = 1:3:6), is readily soluble in water, and crystallizes in thick, honey-yellow prisms or in needles containing one molecule of water, which is given off at a few degrees above 100. It melts at 169, has a slightly acid taste, and is coloured a faint reddish brown by ferric chloride. The barium salt, C 7 H 3 NO 5 Ba + 6H 2 O, forms yellowish red prisms, which are readily soluble in water. (S-Nitrometahydroxylenzoic acid (1 : 3 : 4), is slightly soluble in hot water, and crystallizes in long, yellow, four- or six-sided plates, melting at 230. The barium salt, C 7 H 3 NO 5 Ba + H 2 O, is almost insoluble and crystallizes in yellowish red plates. ry-Nitrometahydroxybenzoic acid (1:3: 2),is less soluble in water than the a-acid, has an intensely sweet taste, and crystallizes with one molecule of water in long, four-sided plates or large tablets, which melt at 178 and give a faint reddish brown colouration with ferric chloride. The barium salt, 2C 7 H 3 NO 5 Ba + 3H 2 O, also has a very sweet taste, and forms tolerably soluble reddish brown plates. ri-Nitrometahydroxylenzoic acid (1:3: 5), was prepared by Grube from the corresponding nitro-amidobenzoic acid, 2 and is a yellowish brown, crystalline precipitate. Its salts crystallize badly. Trinitrometahydroxy'benzoic acid, C 6 H(NO 2 ) 3 (OH)CO 2 H, is formed by heating diazo-amidobenzoic acid with ordinary strong nitric acid, 3 and by the action of fuming nitric acid on metamido- benzoic acid. 4 It crystallizes in large, almost colourless, rhombic prisms, which have a vitreous lustre, and are best obtained from solution in concentrated nitric acid ; it is readily dissolved by water, alcohol, and ether, forming intensely yellow solutions, which dye animal fabrics in the same way as picric acid. It melts when heated and then explodes. The barium salt, C 7 HN 3 O 9 Ba + 3H 2 O, is tolerably soluble in water, but insoluble in alcohol, and crystallizes in thick, light yellow needles, which are very explosive. 1 Bcr. Deutsch. Chem. Ges. xi. 1729. 2 Ibid. x. 1704. 8 Griess, Ann. Chem. Pharm. cxvii. 28. 4 Beilstein and Geitner, ibid, cxxxix. 11 THIOMETAHYDROXYBENZOIC ACID. 325 When metahydroxybenzoic acid is heated with sulphuric acid, three compounds isomeric with alizarin, C 14 H 8 O 4 , are formed. 1 If the product be .boiled with strong nitric acid, a trinitrometahy- droxybenzoic acid is produced among other products, which is readily soluble in water, and crystallizes in tablets or prisms con- taining one molecule of water, which is lost at 100. It melts at 105 and then commences to sublime ; when rapidly heated it detonates. The barium salt, C 7 HN 3 9 Ba + 2H 2 0, is readily soluble in water, and crystallizes in yellow needles, which explode at 29 9. 2 Thiometahydroxybenzoic acid, C 6 H 4 (SH)CO 2 H, is formed by the action of tin and hydrochloric acid on sulphobenzoyl chloride, C 6 H 4 (SO 2 C1)COC1. It is tolerably soluble in water, more readily in alcohol, and sublimes very easily in small plates, melting at 146 147. Dithiometahydroxybenzoic acid, S 2 (C 6 H 4 .C0 2 H) 2 , is obtained by exposing the monothio-compound to the air in the moist state, or more rapidly by adding bromine water to its aqueous solution. 3 Griess prepared it by decomposing diazobenzoic acid aurichloride with sulphuretted hydrogen : 4 3C1N 2 C 6 H 4 .C0 2 H + 2H 2 S = S.C 6 H 4 .C0 9 H J + C 6 H 5 .C0 2 H43HC1 + 3N 9 . SC 6 H 4 .C0 2 H It crystallizes in microscopic needles, which are scarcely soluble in water, more readily in alcohol, and melt at 242 244. Sulplwmetahydroxybenzoic acid, C 6 H 3 (S0 3 H)(OH)C0 2 H, is formed by the action of sulphur trioxide on metahydroxybenzoic acid ; it crystallizes in green, deliquescent needles, melting at 208, is almost insoluble in ether and is coloured wine-red by ferric chloride. 5 Isosulplwmetahydroxylenzoic acid is obtained by dissolving the sulphate of diazobenzoic acid in warm sulphuric acid ; it crystal- lizes in plates, which are readily soluble in water and alcohol. It is decomposed by strong nitric acid into trinitrometahydroxy- benzoic acid and sulphuric acid. 6 1 Schunck and Romer, Ber. Deutsch. Chem. Ges. xi. 1167. 2 Schardinger, ibid: viii. 1490. 3 Hiibner and Upmann, Zeitschr. Chem. 1870, 294 ; Frerichs, Ber. Deutsch. Chem. Ges. vii. 793. 4 Journ. Prakt. Chem. [2] i. 102. 5 Earth, Ann. Chem. Pharm. cxlviii. 38 ; Senhofer, ibid. clii. 102. 6 Griess, Jahresber. Chem. 1864, 351. 252 AROMATIC COMPOUNDS. DisulpJiometahydroxy'benzoic acid, C 6 H 2 (S0 3 H) 2 (OH)C0 2 H, seems to be formed when metahydroxybenzonitril is heated with fuming sulphuric acid ; l its barium salt is obtained by boiling the following compound with baryta water. 2 Trisulphometahydroxylenzoic acid, C 6 H(SO 3 H) 3 (OH)C0 2 H, is obtained by heating metahydroxybenzoic acid to 250 with a mix- ture of fuming sulphuric acid and phosphorus pentoxide. The free acid is a honey-yellow syrup ; it is coloured an intense carmine-red by ferric chloride, and on fusion with caustic potash undergoes complete oxidation. Metahydroxylcnzoylsulphuric acid, C 6 H 4 (S0 4 H)C0 2 H, is found in the urine of men and dogs after the administration of meta- hydroxybenzoic acid (Baumann and Heiter). Its potassium salt is obtained in a similar manner to that of salicylsulphuric acid ; it forms deliquescent needles, and decomposes on boiling with hydrochloric acid or alcoholic potash into metahydroxy- benzoic acid and sulphuric acid. 3 PARAHYDROXYBENZOIC ACID. 2183 Fischer obtained this acid by the action of nitrous acid on an aqueous solution of paramidobenzoic acid, 4 and Saytzew by heating anisic acid (methylparahydroxybenzoic acid) with hydriodic acid. 5 It is also formed when para-compounds such as anisic acid, 6 paracresol, 7 parasulphobenzoic acid, 8 &c., are fused with caustic potash ; it may be obtained by the same method from various resins, as gum benzoin, dragon's blood, aloes and acaroid resin. 9 Kolbe prepared it synthetically by adding potassium to boiling phenol and at the same time passing in carbon dioxide ; para- hydroxybenzoic acid alone is formed, while if the temperature be not allowed to rise above 130 150, salicylic acid is obtained. Parahydroxybenzoic acid may also be prepared by the action 1 Smith, Joum. Prakt. Chem. [2] xvi. 229. 2 Kretschy, Ber. Deutsch. Chem. Ges. xi. 858. Baumann, ibid. xi. 1915. Ann. Chem. Pharm. cxxvii. 129. Ibid, cxxvii. 145. Earth, Zeitschrift. Chem. 1866, 650. Earth, Ann. Chem. Pharm. cliv. 359. 8 Remsen, ibid clxxviii. 281. 9 Earth and Hlasiwetz, ibid, cxxxiv. 274 ; cxxxix. 78. PARAHYDROXYBENZOIC ACID. 327 of carbon dioxide on potassium phenate at 170 21 ; 1 it is formed in sma-11 quantities, together with salicylic acid, when sodium phenate is treated in a similar manner at a lower temperature. 2 The fact that normal potassium salicylate de- composes at 220 into carbon dioxide, phenol and basic potassium parahydroxybenzoate, has been already mentioned. Parahydroxy- benzoic acid is further obtained, together with a smaller quantity of salicylic acid, 3 by heating tetrachloromethane to 100 with phenol and alcoholic soda. 4 It is formed in theoretical amount when the potassium salt of paracresylsulphuric acid is oxidized with potassium per- manganate in alkaline solution. 5 Paracresol is also converted into parahydroxybenzoic acid in passing through the animal organism, while metacresol is found in the urine as metacresyl- sulphuric acid, and orthocresol is partly converted into ortho- cresylsulphuric acid and partly into hydrotoluquinone. 6 In order to prepare parahydroxybenzoic acid, a mixture of equal molecules of caustic potash and phenol is heated in a current of hydrogen, the temperature being finally raised to 180 ; carbon dioxide is then passed in until the theoretical quantity of phenol has distilled over, and the residue is then dissolved in water and decomposed by hydrochloric acid. The parahydroxybenzoic acid is boiled with animal charcoal and crystallized from hot water. It is thus obtained in small, monoclinic prisms, while it is deposited from dilute alcohol in larger crystals, 7 containing one molecule of water, which is lost at 100; it dissolves in 580 parts of water at 0, and in 126 parts at 15, and is readily soluble in hot water, alcohol and ether, but only slightly in chloroform, which is therefore employed to free it from salicylic acid. Its slight solubility in carbon disulphide is made use of in separating it from benzoic acid. It melts at 200 and when rapidly heated decomposes partly into carbon dioxide and phenol, and partly into other products, which will be described below. It decom- poses completely and readily into phenol and carbon dioxide on heating with dilute sulphuric acid in a sealed tube. 8 Its aqueous solution gives an amorphous, yellow precipitate with ferric 1 Kolbe, Joum. PraJct. Chem. [2] x. 100. 2 Ost, ibid. [2] xx. 208. 3 Hasse, Her. Deutsch. Chem. Gfes. ix. 2186. 4 Reimer and Tiemann, ibid. ix. 1285. 5 Heymann and Kbnigs, ibid. xix. 704. 6 Baumann and Preusse, ibid. xix. 706. 7 Hartmann, Joum. Prakt. Chem. [2] xvi. 35. 8 Klepl, ibid. [2] xxv. 464. 328 AROMATIC COMPOUNDS. chloride. Phosphorus pentachloride converts it into parachloro- benzoyl chloride. The Parahydroxylenzoates. The normal sodium salt decom- poses completely at 240 250 into carbon dioxide, phenol and the basic salt ; when, however, it is heated to 280 295 in a, current of carbon dioxide, salicylic acid is obtained, while both hydroxyisophthalic acid and hydroxytrimesic acid are formed at temperatures above 340 (Kupferberg). When, on the other hand, the acid is heated with eight to ten parts of caustic soda, a partial decomposition into phenol and carbon dioxide sets in at 355 (Barth and Schreder), The salts of methylamine and aniline decompose at a higher temperature into phenol, carbon dioxide and the base, while that of tetra-ethylammonium decomposes on distillation into tri-ethylamine and ethyl para- hydroxybenzoate, the latter of which is then partially resolved into carbon dioxide and phenetol. Sodium parahydroxylenzoate, C 6 H 4 (OH/CO 2 Na + 5H 2 O, crys- tallizes from concentrated solutions in transparent tablets, which effloresce in the air. Potassium parahydroxybenzoate, C 6 H 4 (OH)C0 2 K + 3H 9 0, is similar to the sodium salt, but is stable in the air. Ammonium parahydroxylienzoate, C 6 H 4 (OH)CO 2 NH 4 -f H 2 0, crystallizes in long prisms. Calcium parahydroxylenzoate, (C 7 H 5 O 3 ) 2 Ca + 4H 2 0, forms fine needtes grouped in stellate forms, and is very soluble. Barium parahydroxylenzoate, (C 7 H 5 O 3 ) 2 Ba + H 2 0, crystallizes in flat, lustrous needles or with two molecules of water in pointed rhombohedra ; baryta water added to its solution pro- duces a precipitate of the basic salt, C 7 H 4 O 3 Ba, as a sandy, crystalline powder, which is scarcely soluble in cold water. Lead parahydroxylenzoate, (C 7 H 5 O 3 ) 2 Pb -f 2H 2 0, is a very characteristic salt, and is obtained by neutralizing the boiling aqueous solution of the acid with lead carbonate. It separates out on cooling in thin, iridescent plates which take a silver lustre on drying, and resemble those of benzoic acid. Copper parahydroxybenzoate, (C 7 H 5 O 3 ) 2 Cu + 6H 2 0, crystal- lizes in small, bluish green needles, which become dull and insoluble on boiling with water. Silver parahydroxylenzoate, C 7 H 5 3 Ag + 2H 2 0, crystallizes from hot water in small, lustrous plates. Methyl parahydroxylenzoate, C 6 H 4 (OH)C0 2 CH 3 , is formed by heating together equal molecules of parahydroxybenzoic acid, ANISIC ACID. 329 caustic potash and methyl iodide ; it crystallizes from ether in large tablets, melts at 17 and boils at 283 . 1 2 184 Paramethoxylenzoic acid, or Anisic acid, C 6 H 4 (OCH 3 )C0 2 H. Cahours obtained this compound in 1839 by the oxidation of oil of anise-seed, and showed at the same time that it is formed from the " camphor " (anethol or allylphenol, C 6 H 4 (OH)C 3 H 5 ), contained in this substance. 2 Laurent, in 1841, prepared from tarragon oil (from Artemisia dracunculus), the so-called dragonic acid (acide draconique), which, according to Gerhardt, is identical with anisic acid. This view was subsequently confirmed by Laurent, who also accurately determined its composition. 3 At about the same time Persoz submitted oil of anise -seed, fennel oil, and star-anise oil (Jiuile de badiane, from Illicium anisatuni) to oxidation, and obtained two acids, which he named umbellic acid (acide ombellique) and badianic acid (acide ladianique)* Hempel showed, however, that these are both anisic acid, 5 the formation of which might have been expected, since the oils employed contain anethol. 6 Anisic acid was at first looked upon as the homologue of salicylic acid ; Kolbe, however, considered it to be methoxy- benzoic acid, since it behaves very similarly to benzoic acid, and decomposes into anisol (phenyl methyl ether) and carbon dioxide when distilled with caustic baryta. 7 In order to determine from which of the hydroxybenzoic acids it is derived, Saytzew heated it with hydriodic acid, and found that the product consists of parahydroxybenzoic acid. It was then thought probable that anisic acid and winter-green oil would have similar constitutions, but Grabe showed that the latter is the methyl ether of salicylic acid, while Ladenburg proved that in anisic acid the methyl group replaces the hydrogen of the phenol hydroxyl ; by heating equal molecules of potassium parahydroxybenzoate and caustic potash with two molecules of methyl iodide, he obtained the methyl ether of paramethoxybenzoic acid (anisic acid) and prepared the free acid by saponifying with potash and decomposing the product with hydrochloric acid. 8 Anisic acid may also be obtained by oxidizing orthocresyl methyl ether with chromic acid solution. 9 1 Ladenburg and Fitz, Ann. Chem. Pharm. cxli. 247. 2 Ibid. xli. 66. 3 Ibid. xliv. 313. 4 Ibid. xliv. 311. 8 Ibid. lix. 104. 6 Cahours, ibid. xxxv. 312. 7 Lehrb. d. Organ. Chem. ii. 135. 8 Ann. Chem. Pharm. cxli. 241. 9 Korner, Zeitschr. Chem. 1868, 326. 320 AROMATIC COMPOUNDS. In order to prepare it, 1 part of oil of anise seed is poured into a solution of 5 parts of potassium dichromate in 10 parts of sulphuric acid and 20 parts of water, which is heated to 50. The reaction is completed in a few minutes and the solution is then allowed to cool, the anisic acid filtered off and purified by precipitation with hydrochloric acid from solution in ammonia (Ladenburg and Fitz). It crystallizes in long monoclinic prisms or needles, melting at 184% which dissolve in 2500 parts of water at 18. It is tolerably soluble in boiling water and very readily in alcohol. On heating with hydriodic or concentrated hydrochloric acid, or on fusion with potash, it is converted into parahydroxybenzoic acid. Its salts, which crystallize well, have been chiefly investigated by Engelhardt and by Borella. 1 Melting-point. Boiling-point. Methyl paramethoxybenzoate, 2 C 6 H 4 (OCH 3 )C0 2 .CH 3 , scales . . 45 46 255 Ethyl paramethoxybenzoate, 3 C 6 H 4 (OCH 3 )C0 2 .C 2 H 5 , liquid ,. . 250 255 C Ethyl parahydroxybenzoate, 4 C 6 H 4 (OH)CO 2 .C 2 H 5 , crystals . . 116 297 298 Para-ethoxybenzoic acid, 5 C 6 H 4 (OC 2 H 5 )C0 2 H, needles . . 195 Ethyl para-ethoxybenzoate, 6 C 6 H 4 (OC 2 H 5 )C0 2 .C 2 H 5 , liquid . 275 f Para-acetoxybenzoic acid, C 6 H 4 (OCO.CH 3 )CO 2 H, is formed when parahydroxybenzoic acid is heated with acetic anhy- dride. It is slightly soluble in water, and crystallizes from chloroform in large plates, which have a silver lustre and melt at 185 (Klepl). Phenyl parahydroxybenzoate, C 6 H 4 (OH)CO 2 .C 6 H 5 , occurs in the products which are formed by the dry distillation of the acid. It is insoluble in water, but readily soluble in alcohol and chloro- form, from which it crystallizes in compact, rhombic tablets, which melt at 176, dissolve readily in caustic soda, and are decom- 1 Gaz. Chim. Ital. xv. 304 ; Ann. Chem. Pharm. cviii. 240. 2 Ladenburg and Fitz, ibid. cxli. 252. 3 Cahours, ibid. Ivi. 310. 4 Grabe, ibid, cxxxix. 146 ; Hartmann, Journ. PraU. Chem. [2] xvi. 50. 5 Ladenburg and Fitz ; Fuchs, Ber. Deutsch. Chem. Ges. ii. 624. 6 Ladenburg and Fitz. METHYL PARAMETHOXYBENZOATE. 331 posed by it even in the cold with formation of phenol and parahydroxybenzoic acid (Klepl). Paraphcnoxylenzoic acid, C 6 H 4 (OC 6 H 5 )CO 2 H, is obtained by boiling the following compound with alcoholic potash, or by heat- ing it to 200 with concentrated hydrochloric acid. It is readily soluble in alcohol and ether, and crystallizes from chloroform in long prisms melting at 159'5. When heated with caustic baryta it decomposes into carbon dioxide and diphenyl ether. Phenyl paraphcnoxylenzoate, C 6 H 4 (OC 6 H 5 )C0 2 .C 6 H 5 , is formed when parahydroxybenzide, which is described below, is heated to about 400, preferably in a current of carbon dioxide. It crystallizes from dilute alcohol in fatty scales, which melt at 73 78, and sublime at a higher temperature, forming a vapour which smells like the geranium. 2185 Anhydrides of parahydroxybenzoic acid. When para- hydroxybenzoic acid is submitted to dry distillation, only half of it is decomposed into carbon dioxide and phenol, which distils over accompanied by water, and phenyl parahydroxybenzoate ; as the distillation is continued, the boiling acid suddenly becomes turbid, and a milky liquid settles in the retort, until at 350 the residue solidifies to a white amorphous mass. 1 Parahydroxybcnzoylparahydroxyltenzoic acid, X OCO.C 6 H 4 .OH C 6 H 4 is prepared by the action of phosphorus pentachloride on de- hydrated parahydroxybenzoic acid, the reaction being more violent than in the case of salicylic or metahydroxybenzoic acids. It boils at 176 under a pressure of 13 14 mm., and is a powerfully refractive liquid. Water converts it into paracarbonyl- orthophosphoric acid, C 6 H 4 (C0 2 H)PO(OH) 2 , which crystallizes in fine, white plates, melting at 200 ; it is only decomposed by water at 150 160, parahydroxybenzoic and phosphoric acids being formed. When the chloride is distilled slowly under the ordinary pressure, it passes over almost unaltered, only a small 1 Pisani, Ann. Chem. Pkarm. cii. 284. 2 Cahours, ibid. Ixx. 47- 3 Lessen, ibid, clxxv. 284. ANISIC ANHYDRIDE. 333 portion decomposing into phosphorus oxychloride and para- chlorobenzoyl chloride. The behaviour of this chloride towards a second molecule of phosphorus pentachloride is of considerable interest, since it differs from that of its isomerides inasmuch as no parabenzenyl- trichlorophosphoryl chloride is formed, but the compound decomposes into phosphorus oxychloride and parachlorobenzoyl chloride, the latter being then partially converted into para- chlorobenzenyl trichloride. The phenol-oxygen is therefore more readily replaced by chlorine when it occupies the para- position than when it is present in either an ortho- or meta-disubstituted compound. 1 Parahydroxylenzamide, C 6 H 4 (OH)CO.NH 2 + H 2 O, is obtained by heating the ethyl ether with ammonia under pressure. It crystallizes from hot water in strongly lustrous, rhombic needles, which lose their water of crystallization at 100 and then melt at 162. Anisamide, C 6 H 4 (OCH 3 )CO.NH 2 , was prepared by Cahours from the chloride by the action of ammonia ; it crystallizes in prisms, melts at 137 138, sublimes in broad plates and boils at 295 (Henry). Parahydroxylenzanilide, C 6 H 4 (OH)CO.NH(C 6 H 5 ), is formed when the acid is heated with aniline and the product treated with phosphorus trichloride. It crystallizes from hot water in yellowish, lustrous plates, melting at 196 197. It forms salts of potassium and sodium, which are readily soluble and crystallize well (Kupferberg). Anisanilide, C 6 H 4 (OCH 3 )CO.NH(C 6 H 5 ), was obtained by ssen as a product of the distillation of benzanishydroxamic acid (p. 340). It is slightly soluble in cold alcohol, and crystallizes in rhombic plates, melting at 168 169. Parahydroxylenzuric acid, C 6 H 4 (OH)CO.NH.CH 2 .CO 2 H, ap- pears, together with parahydroxybenzoylsulphuric acid, in the urine of the dog after the administration of parahydroxybenzoic acid ; it crystallizes in short prisms, which are tolerably soluble in water (Baumann and Heiter). Anisuric acid, C 6 H 4 (OCH 3 )CO.NH.CH 2 .CO 2 H, was obtained by Cahours from silver amido-acetate and anisyl chloride, 2 and is also found in the urine after anisic acid has been taken ; 3 it 1 Anschiitz, private communication. 2 Ann. Chem: Pharm. cix. 32. 3 Griibe and Schultzen, ibid, cxlii. 348. 334 AROMATIC COMPOUNDS. forms foliaceous crystals, which are readily soluble in hot water. Parahydroxylenzonitril, C 6 H 4 (OH)CN, is formed when am- monium parahydroxybenzoate mixed with phosphorus pentoxide is distilled in a current of carbon dioxide (Hartmann), and by the action of ammonia on parahydroxybenzide mixed with pumice-stone and heated to 250 (Klepl). It crystallizes from hot water in rhombic tablets, which melt at 113, and have a sweet but pungent taste ; it forms a series of salts in which the phenol-hydrogen is replaced by the metal. Anisonitril, C 6 H 4 (OCH 3 )CN. Henry obtained this substance by distilling the amide with phosphorus pentachloride. It crystallizes from hot water in small needles, and from ether in long, white, lustrous prisms, has a penetrating, characteristic rank odour, melts at 56 57, and boils at 253 254 . 1 SUBSTITUTION PRODUCTS OF PARAHYDROXY- BENZOIC ACID. 2186 ChloroparaJiydroxylenzoic acid, C 6 H 3 C1(OH)C0 2 H, (3:4: 1), is formed by heating parahydroxybenzoic acid with antimony pentachloride, 2 and by the action of alcoholic potash on orthochlorophenol at 125 136. 3 It is slightly soluble in cold, more readily in hot water, and crystallizes in small needles, which melt at 169 170, and sublime without decomposition. Ferric chloride produces a brown precipitate in a concentrated solution ; phosphorus pentachloride converts it into the chloride of a-dichlorobenzoic acid (Lossner). Dichloroparahydroxylenzoic acid, C 6 H 2 C1 2 (OH)C0 2 H, has also been prepared by Lossner ; it crystallizes in fine needles, which melt at 255 256. Dibromoparahydroxybenzoic acid, C 6 H 2 Br 2 (OH)C0 2 H, (3:5: 4:1), has been obtained from dibromanisic acid. It is scarcely soluble in water, and crystallizes from alcohol in needles, which melt with decomposition at 266 268, but sublime at a lower temperature. A monobromoparahydroxybenzoic acid is not known; when bromine water is added to a solution of para- 1 Bcr. Deutsch. Chem. Gcs. ii. 666. 2 Lossner, Journ. Prakt. Chem. [2] xiii. 432. 3 Hasse, Ber. Deutsch. Chem. Ges. x. 2192. CHLOROPARAHYDROXYBENZOIC ACID. 335 hydroxybenzoic acid,- a precipitate of tribromophenol is produced (Bar th and Hlasiwetz). lodoparahydroxylenzoic acid, 2C 6 H 3 I(OH)CO 2 H 4- H 2 O, is formed when parahydroxybenzoic acid is boiled with water;, iodine and iodic acid ; it crystallizes from hot water in small needles, which become anhydrous at 100 and then melt at 192 . 1 Di-iodoparaliydroxybenzoic acid, C 6 H 2 T 2 (OH)C0 2 H, is formed together with the preceding compound, and crystallizes in small needles, which are scarcely soluble in water, but readily in alcohol. Nitroparahydroxylenzoic acid, C 6 H 3 (NO 2 )(OH)CO 2 H, (3:4: 1). Griess obtained this compound by the action of boiling potash on 3-nitro-amidobenzoic acid. 2 It is also formed in small quantity, together with /3-nitro-salicylic acid, by heating orthonitrophenol with alcoholic potash and tetrachloromethane (Hasse). It crystal- lizes from boiling water in yellowish needles, melting at 185. Its solution is not coloured by ferric chloride. Basic barium nitroparaTiydroxybenzoate, C 7 H 3 N0 5 Ba + H 2 O, is obtained by adding barium chloride to a hot, ammoniacal solu- tion of the acid. It forms yellowish red, lustrous plates. Dinitroparaliydroxybcnzoic acid, C 6 H 2 (NO 2 ) 9 (OH)CO.,H, (3:5: 1:4) is formed when a boiling solution of dinitroparamidobenzoic acid is treated with nitrous acid or with caustic potash. It is slightly soluble in cold, more readily in hot water, and crystallizes in large, thin tablets, which are coloured light yellow to bronze, and melt at 235 237 . 3 Its salts are coloured yellow or orange- red, and crystallize well. Earth has prepared a mono- and a di- nitro-acid by the action of nitric acid on parahydroxybenzoic acid, both of which seem to be different from the preceding compounds. Amidoparafiydroxybenzoic acid, C 6 H 3 (NH 2 )(OH)C0 2 H. Barth obtained this substance by the reduction of hisnitroparahydroxy- benzoic acid. It crystallizes in needles and forms a sulphate which also crystallizes in needles, and gives a dark cherry-red colouration with concentrated nitric acid. Sulphoparahydroxybenzoic acid, C 6 H 3 (SO 3 H)(OH)CO 2 H, was prepared by Kolle by the action of sulphur trioxide on para- 1 Pelzer, Ann. Chem. Pharm. cxlvi. 288. * Ber. Deutsch. Chem. Gcs. v. 856. 3 Salkowski, Ann. Chem. Pharm. clxiii. 36. 336 AROMATIC COMPOUNDS. hydroxybenzoic acid. 1 It is also obtained when the latter, or parahydroxybenzide, is heated with concentrated sulphuric acid (Klepl), and forms deliquescent needles, which are insoluble in ether. Its solution is coloured blood-red by ferric chloride ; on fusion with potash, it yields protocatechuic acid. Acid potassium sulphoparahydroxylenzoate, C 7 H 5 SO 6 K + H 2 0, is a very characteristic salt, since it is even less soluble in water than acid potassium tartrate. It crystallizes from a hot solution in quadratic tablets or prisms, and from a less concentrated solution in rectangular plates which are obliquely striated (Klepl). Parahydroxylenzoyl sulphuric acid, C 6 H 4 (S0 4 H)CO 2 H, occurs as an alkali salt in the urine of the dog after administration of parahydroxybenzoic acid. The potassium salt, C 6 H 4 (SO 4 K)C0 2 K, is obtained by heating an alkaline solution of parahydroxybenzoic acid with potassium disulphate, and crystallizes in lustrous plates or .tablets, which decompose at 250 with formation of potassium sulphate and anhydrides of parahydroxybenzoic acid. 2 SUBSTITUTION PRODUCTS OF ANISIC ACID. 2187 Chloranisic acid, C 6 H 3 C1(OCH 3 )CO 2 H, is formed by the action of chlorine on fused anisic acid, and crystallizes from dilute alcohol in needles or rhombic prisms, which melt at 176 and volatilize without decomposition. 3 Dichlor anisic acid, C 6 H 2 C1 2 (OCH 3 )C0 2 H, is obtained, together with chloranil, by heating anisic acid with hydrochloric acid and potassium chlorate ; it crystallizes from alcohol in large needles melting at 196 . 4 Bromanisic acid, C 6 H 3 Br(OCH 3 )C0 2 H, is formed by the action of bromine on anisic acid (Cahours), the latter being kept covered with hot water. 5 It crystallizes from alcohol in needles which melt at 213 214 and sublime in small plates. Dibromanisic acid, C 6 H 2 Br 2 (OCH 3 )CO 2 H. Reinecke pre- pared this substance by heating anisic acid to 120 with bromine and water ; it crystallizes in long needles melting at 207. On 1 Ann. Chem. Pharm. clxiv. 150. 2 Baumann, Ber. Dcutsch. Chem. Ges. xi. 1916. 8 Cahours, Ann. Chem. Pharm. Ivi. 312. 4 Reinecke, Zcitschr. Chem. 1866, 366. 6 Salkow&ki, Ber. Dcutsch. Chem. Ges. vii. 1013. IODANISIC ACID. 337 further treatment with bromine, tribromanisol and tetrabromo- quinone are formed, while fuming nitric acid converts it into dibromonitro-anisol, C 6 H 2 Br 2 (N0 2 )OH, (3:5:4: 1), which was previously obtained by Korner in a different manner, the con- stitution of the acid being thus shown. 1 When its sodium salt is distilled with lime, the methyl ether is formed, together with the basic sodium salt of dibromoparahydroxybenzoic acid : 2 /C0 2 Na /C0 2 .OCH 3 /CO 2 Na, 2C 6 H 2 Br 2 < = C 6 H 2 Br/ + C 6 H 2 Br 2 <( \OCH 3 \OCH 3 X ONa This ether crystallizes from alcohol in lustrous needles melting at 91-5 92. The dibromoparahydroxybenzoic acid is also obtained by heating dibromanisic acid with hydriodic acid. 3 lodanisic acid, C 6 H 3 I(OCH 3 )CO 2 H, was prepared by Griess from diazo-amido-anisic acid, 4 while Peltzer obtained it by heating anisic acid to 145 150 with iodine and iodic acid. 5 It crystallizes from alcohol in needles, which melt at 234*5, and sublime in small plates. Nitro-anisic acid, C 6 H 3 (NO 2 )(OCH 3 )C0 2 H, was obtained by Cahours as a product of the action of nitric acid on anisic acid and anisol. 6 In order to prepare it, anisol is allowed to drop into ten times its weight of warm nitric acid, of specific gravity 1'4, the mixture boiled for a short time, and the acid then precipitated by water ; it is well washed and finally freed >m an admixed oil by solution in ammonia and reprecipitation by hydrochloric acid. 7 Nitro-anisic acid is slightly soluble in water, and crystallizes from alcohol in compact prisms melting at 189. On heating with water to 220, it decomposes into ortho- nitrophenol, methyl alcohol and carbon dioxide, 8 while aqueous ammonia at 140 170 converts it into S-nitro-amidobenzoic acid. 9 Its salts have been investigated by Engelhardt. 10 Dinitro-anisic acid, C 6 H 2 (NO 2 ) 2 (OCH 3 )C0 2 H. Salkowski and Rudolph prepared this substance by dissolving anisic acid in 1 Balbiano, Gaz. Chim. Ital. xiv. 9. 2 Ibid. xiii. 65. 8 Alessi, ibid. xv. 242. 4 Ann. Chem. Pharm. cxvii. 54. 5 Ibid, cxlvi. 302. 6 Cahours, ibid. xh. 71. 7 Salkowski, ibid, clxiii. 6. 8 Salkowski and Rudolph, Ber. Deutsch. Chem. Ges. x. 1254. 9 Salkowski, Ann. Chem. Pharm. clxxiii. 35. 10 Zinin, ibid. xcii. 327 ; Cahours, ibid. cix. 21. 338 AROMATIC COMPOUNDS. portions of 40 grammes at a time in a well-cooled mixture of sulphuric and nitric acids, 160 grammes of the former and 140 of the latter being required for each portion of anisic acid ; notwithstanding the low temperature, carbon dioxide is evolved and di- and tri-nitro-anisol are formed. The dinitro-anisic acid separates from the acid solution on standing, and is then dissolved in a cold, dilute solution of sodium bicarbonate, re-precipitated by alcohol and finally purified by re-crystallization from dilute alcohol. It forms yellowish needles melting at 181 182, and on boiling with caustic soda decomposes into methyl alcohol and dinitroparahydroxybenzoic acid, while it is immediately converted into chrysanisic acid by boiling, concentrated ammonia (p. 258). Amido-anisic acid, C 6 H 3 (NH 2 )(OCH 3 )CO 2 H, is obtained by reducing nitre-anisic acid with alcoholic ammonium sulphide. 1 It is slightly soluble in water, readily in alcohol, and crystal- lizes in long, thin, four-sided prisms, which melt at 180 and are decomposed into carbon dioxide and anisidine when heated with caustic baryta (Part III. p. 249). Methyl amido-anisate, C 6 H 3 (NH 2 )(OCH 3 )C0 2 .CH 3 , was pre- pared by Cahours from the methyl ether of nitro-anisic acid by re- duction ; it crystallizes in prisms which readily dissolve in alcohol. Methylamido-anisic acid, C 6 H 3 (NH.CH 3 )(OCH 3 )CO 2 H. Griess obtained this substance by heating potassium amido-anisate with methyl iodide. It is slightly soluble in hot water and cold alcohol, but more readily in hot alcohol, and melts above 20 0. 2 Trimethylamido-anisic acid, or Trim,ethylanise-betaine,C ll H. l5 NQ 3 + 5H 2 0, is formed by the action of methyl iodide and caustic potash on anisic acid, and crystallizes from water in well- formed, vitreous prisms, which have a bitter taste and are neutral to litmus paper. It is completely converted by distillation into the metameric methyl ether of dimethylamido-anisic acid : /OCH 3 /OCH 3 C 6 H 3 CO-0 = C 6 H / CO.OCH 3 . \ / \N(CH 3 ) 2 N (CH 3 ) 3 The latter substance is a yellowish liquid, which has a faint aromatic odour and boils at 288 . 3 1 Zinin, Ann. Chem. Pkarm. xcii. 327 ; Cahours, ibid. cix. 21. 2 Bcr. Deutsch. Chem. Ges. v. 1042. 8 Griess, ibid, vi. 587. ANISENYLOXIME COMPOUNDS. 339 ANISENYLOXIME COMPOUNDS. 2188 These bodies, which correspond to the benzenyloxime compounds (p. 207), are prepared in an exactly similar manner, anisyl chloride being gradually added to a solution of hydroxyl- amine hydrochloride, which is kept faintly alkaline by the addition of dilute carbonate of soda solution. A mixture of anishydrox- amic acid, di-anishydroxamic acid and anisic acid is thus obtained. Boiling water extracts from this a portion of the anisic acid and all the anishydroxamic acid, these being sub- sequently separated by means of their barium salts, that of the former being soluble while that of the latter is insoluble in water. The dry mixture of the two acids may also be extracted with warm absolute ether, in which anishydroxamic acid is almost insoluble. The di-anishydroxamic and anisic acids are separated by treatment with a cold solution of sodium carbonate, which lissolves the latter completely, while only a small portion of the former enters into solution. The liquid is filtered rapidly, tuse di-anishydroxamic acid is easily decomposed by carbon - ite of soda, the filtrate almost neutralized with hydrochloric nd, and then saturated with carbon dioxide, all the di-anis- hydroxamic acid present being thus precipitated. 1 Anishydroxamic acid, . CH 3 O.C 6 H 4 .C(OH)NOH, is slightly )luble in cold, readily in hot water and alcohol, but is almost insoluble in ether ; it crystallizes in small plates, melting at 156 157, and is coloured deep violet by ferric chloride. The acid potassium salt, C 8 H 8 KNO 3 + C 8 H 9 N0 3 , forms long, flat needles, which are tolerably soluble in cold water. Lead acetate produces a thick, white precipitate 2 of C 2 H 3 O 2 PbC 8 H 8 NO 3 . Ethyl anishydroxamate, CH 3 O.C 6 H 4 .C(OH)NOC 2 H 5 , is formed by the action of anisyl chloride on ethylhydroxylamine ; it is insoluble in water, readily soluble in alcohol, less easily in ether, from which it crystallizes in tablets, which melt at 84 and have feeble acid properties. On heating with concentrated hydrochloric acid, it is split up into anisic acid and ethyl- hydroxylamine. 3 Ethylanishydroxamic acid, CH 3 O.C 6 H 4 .C(OC 2 H 6 )NOH, is 1 Lessen, Ann. Chem. Pharm. clxxv. 234. 2 Hodges, ibid, clxxxii. 218. 3 Pieper, ibid, ccxvii. 16. 340 AROMATIC COMPOUNDS. obtained by heating the ethyl ether of anisbenzhydroxamic acid with caustic potash. It is precipitated by carbon dioxide as an oily liquid, which solidifies to a crystalline mass, melting at 32. It is readily soluble in alcohol and ether, and decomposes on heating with hydrochloric acid into ethyl anisate and hydroxylamine. 1 Dianishydroxamic acid, CH 3 O.C 6 H 4 .C(NO.CO.C 6 H 4 .OCH 3 )OH, is scarcely soluble in water and ether, slightly in alcohol, and crystallizes in needles, melting at 142 143. It is de- composed by baryta water into anisic acid and anishydroxamic acid. Benzaniskydroxamic acid, C 6 H 5 .C(NO.CO.C 6 H 4 .OCH 3 )OH, is formed by heating benzhydroxamic acid to 100 with anisyl chloride. It crystallizes from alcohol in needles or prisms, which melt at 131 132. On heating with baryta water, it decom- poses into anisic acid and benzhydroxamic acid, while boiling water splits it up into carbon dioxide, anisic acid and diphenyl urea. When heated alone, it yields carbon dioxide, phenyl isocyanate, anisic acid and anisanilide,C 6 H 5 .NH(CO.C 6 H 4 .OCH 3 ). a-Ethylbenzanishydroxamate^ or Benzanisethylhydroxylamine, C 6 H 5 .C(NO.CO.C 6 H 4 .OCH 3 )OC 2 H 5 , is obtained by the action of ethyl iodide on silver benzanishydroxamate. It crystallizes from a mixture of ether and benzene in thick, monoclinic tablets, melting at 74 (Pieper). It is decomposed by caustic potash into anisic and a-ethylbenzhydroxamic acids, and by hydrochloric acid into anisic acid, ethyl benzoate and hydroxylamine. ft-Ethylbenzanishydroxamate is formed by the action of anisyl chloride on a- or /3-ethylbenzhydroxamic acid, and separates from ether in monoclinic crystals, melting at 89. On heating with concentrated caustic potash solution, it decomposes into anisic acid and /3-ethylbenzhydroxamic acid, while on dry distillation it decomposes into benzonitril, anisic acid and aldehyde. Anisbenzhydroxamic acid, CH 3 O.C 6 H 4 C(NO.CO.C 6 H 5 )OH, is obtained from anishydroxamic acid and benzoyl chloride; it crystallizes in needles or prisms, which melt at 147 148, and decompose at a higher temperature into carbon dioxide, benzoic acid, anisol isocyanate, CON.C 6 H 4 .OCH 3 , and benzoylanisidine, NH(CO.C 6 H 5 )C 6 H 4 .OCH 3 . Ethyl anisbenzhydroxamate, or Anisoenzethylhydroxylamine, CH 3 O.C 6 H 4 C(NO.CO.C 6 H 5 )OC 3 H 5 , crystallizes in short, four- sided, asymmetric pyramids, melts at 79 and is decomposed 1 Eisler, Ann. Chem. Pharm. clxxv. 338. DIBENZANISHYDROXYLAMINE. 341 by caustic potash into benzole acid and ethylanishydroxamic acid. Benzethylanishydroxylamine, C 6 H 5 C(N O C 2 H 5 )O. C O.C 6 H 4 . OCH 3 , is obtained by the action of anisyl chloride on the silver salt of ethylbenzhydroxamate, and separates from ether in asymmetric crystals, melting at 64. It is decomposed by highly concentrated caustic potash into anisic acid and ethylbenzhydroxamate. is formed when a solution of ethylanishydroxamate in caustic potash is treated with benzoyl chloride, and forms monosymmetric crystals, melting at 93 94. It is split up into benzoic acid and ethyl anishydroxamate on heating with caustic potash. 1 2189 Hydroxylamine Derivatives containing three Acid Radicals are formed by the action of anisyl or benzoyl chloride on the silver salts of the dihydroxamic acids. They are insoluble in water and sodium carbonate solution, and only very slightly soluble in cold alcohol. On heating with hydrochloric acid, the radical which was last introduced is split off. 2 ^NO.CO.C 6 H 5 DlBEXZANISHYDROXYLAMINE, C 6 H 5 C\ X O.CO.C 6 H 4 .OCH 3 Melting-point. a) Long, monosymmetric needles or prisms . 110 110'5 /S) Small crystals 109 110 4 OCH 3 BENZANISBENZHYDROXYLAMINE, C 6 H 5 .C \O.CO.C 6 H 5 Melting-point. a) Short, asymmetric prisms 113 114 /?) Long, rhombic prisms 124 125 7) Monosymmetric tablets ; decompose on fusion jsro.co.c 6 H 5 ANISDIBENZHYDROXYLAMINE, CH 3 O.C 6 H 4 C\ \OCO.C 6 H 6 Melting-point. a) Lustrous monoclinic tablets 137 137'5 ) Very small crystals, usually opaque . . . 109'5 110'5 1 Pieper, Ann. Chcm. Pharm. ccxvii. 1. 2 Lessen, ibid, clxxxvi. 1. 253 342 AROMATIC COMPOUNDS. ANISBENZANISHYDROXYLAMINE, NO.CO.C 6 H 6 CH 3 O.C 6 H 4 .Cf \OCO.C 6 H 4 .OCH 3 Melting-point. a) Very small, monosymmetric tablets .... 152 153 ft) Monosymmetric tablets 148 149 DlANISBENZHYDROXYLAMINE, /NO.CO.C 6 H 4 .OCH 3 CH 3 O.C 6 H 4 .Cy-resorcylic acid, C 6 H 3 (OCH 3 ) 2 C0 2 H. When meta- dinitrobenzene is treated with methyl alcohol and potassium cyanide, methoxynitro^enzonitril ) C Q H. 3 (l^O 2 )(OCH 3 )C^, is formed; it crystallizes from chloroform in pliant needles, which melt at 171, and are converted on heating with methyl alcohol and caustic potash into dimethoxylenzonitril, C 6 H 3 (OCH 3 ) 2 CN, which crystallizes from alcohol in needles or rectangular tablets, melting at 118. It boils at about 310, and when heated with baryta water yields dimethyl-7-resorcylic acid, which forms crystals melting at 179, and is converted into 7-resorcylic acid by heating with caustic potash. If methoxynitrobenzonitril is heated with caustic potash and ethyl alcohol, ethoxymetlioxylienzonitril, C 6 H 3 (OCH 3 )(OC 2 H 5 ) ON, is formed, and crystallizes from alcohol in prisms or tablets, melting at 66. This compound is also formed when meta- dinitrobenzene is treated with ethyl alcohol and potassium cyanide, and the ethoxynitrobenzwiitril, C 6 H 3 (NO<,)(OC 2 H 5 )CN, thus formed, which melts at 137, is heated with methyl alcohol and caustic potash. A new and simple proof is thus afforded of the identity of the positions 1 and 6 in the benzene nucleus. 1 ' HYDROXYSALICYLIC ACID OR PARADIHY- DROXYBENZOIC ACID (1:2: 5). 22 oo This isomeride has been prepared by fusing iodosalicylic acid with caustic potash ; 2 it is more readily obtained, however, by fusing bromosalicylic acid with caustic soda, 3 and is also 1 Lobry de Bruyn, Ber. Deutsch. Chem. Ges. xviii. Kef. 148 ; Chem. CentralU. 1884, 119; 1885, 357. 2 Lautemann, Ann. Chcm. Pharm. cxx. 311 ; Liechti, ibid. Suppl. vii. 144; Demole, Ber, Deutsch. Chem. Ges. vii. 1438 ; Goldberg, Jvurn. Prakt. Chem. [2] xix. 371. 3 Leppert and Rakowski, Ber. Deutsch. Chem. Ges. viii. 788. AROMATIC COMPOUNDS. formed by the action of nitrous acid on a-amidosalicylic acid, 1 and when quinol is heated with potassium bicarbonate, water and a little potassium sulphite. 2 Hlasiwetz and Habermann, by fusing gentisin, C 14 H 10 5 , from Gentidna lutea, with caustic potash, obtained a dihydroxybenzoic acid, which they named gentisic acid, since they believed that it was different from those previously known; 3 they subsequently found, however, that it is identical with hydroxysalicylic acid. 4 It is readily soluble in water, alcohol and ether, crystallizes in needles or prisms, which melt at 196 197, and gives a deep blue coloura- tion with ferric chloride. It reduces Fehling's solution and ammoniacal silver solution on heating. On dry distillation it is resolved into carbon dioxide and quinol. Ethyl hydroxysalicylate, C 6 H S (OH) 2 C0 2 .C 2 H 5 , crystallizes from hot water in needles, which have a pleasant fruity odour and melt at 75 (Goldberg). Methylhydroxysalicylic acid, C 6 H 3 (OCH 3 )(OH)CO 2 H.(C0 2 H : OH : OCH 3 =1 : 3 : 5), was prepared by Korner and Bertoni by the action of carbon dioxide on sodium methylquinol at 220 225 , 5 and named a-methylhydroquinoneformic acid. Tiemann and Miiller then obtained it by oxidizing the acetyl- derivative of the corresponding aldehyde with potassium per- manganate and saponifying the product with caustic soda. 6 It crystallizes from hot water in long needles, melting at 142, and gives a light blue colouration with ferric chloride. Dimethylhydroxysalicylic acid, C 6 H 3 (OCH 3 ) 2 C0 2 H, is formed by the oxidation of its aldehyde ; it crystallizes from hot water in silky needles, melting at 76. 7 When the reactions of the bodies just described are compared, it is found that protocatechuic acid, its aldehyde, and also catechol, which contain the hydroxyls in the ortho-position, give a green colouration with ferric chloride. Those cofa- pounds, on the other hand, in which a hydroxyl is situated in the ortho-position with regard to a carboxyl, and which can therefore be considered as derivatives of salicylic acid, give a blue to dark red colouration, while those in which the hydroxyls are in the meta-position, give as little colouration as meta- hydroxybenzoic acid. 1 Goldberg, loc. cit. " Senhofer and Sarlay, Monatsh. Chem. ii. 448. 3 Ann. GJiem. Pharm. clxxv. 66. 4 Ibid, clxxx. 343. 6 Ber. Deutsch. Chem. Ges. xiv. 848. 6 Ibid. xiv. 1997. 7 Ibid. 1993. GALLIC ACID. According to theory, six dihydroxybenzoic acids can exist. In addition to the five just mentioned, two others have been shortly described. One of these was obtained by Leeds by allowing toluene saturated with nitrogen peroxide to stand in a loosely covered vessel for a whole summer. It crystallizes from alcohol in small plates, which sublime at 170 without fusing and give no colouration with ferric chloride. 1 Aescioxalic acid, C 7 H 6 O 4 , is the name given by Rochleder to a compound which he obtained, together with formic acid, oxalic acid and frequently protocatechuic acid, by boiling aesculetin, C 9 H 6 4 , with concentrated caustic potash or baryta water. It forms an extremely fine crystalline mass and gives a reddish brown colouration with ferric chloride, which is changed by sodium carbonate to purple-violet, while ferrous sulphate and a little carbonate of soda produce an intense blue colouration. 2 TRIHYDROXYBENZOIC ACIDS, C 6 H 2 (OH) 3 C0 2 H. GALLIC ACID. 2201 The history of this substance goes hand in hand with that of tannic acid. In the introduction to organic chemistry it has already been mentioned how Pliny states that paper dipped in an extract of nut-galls was used to ascertain whether verdigris was adulterated with green vitriol. He also informs us that the juice of nut-galls was used to recognize a kind of alumen, employed for dyeing wool black, which was either natural green vitriol or a mineral containing this salt. It was also known in very early times that certain parts of plants, which have an astringent taste, give a black colouration with bodies containing iron. In addition to nut-galls, Paracelsus enumerates the sap of oaks, alders, &c., which colour solutions of iron and copper black, and Libavius used this reaction in the analysis of mineral waters, which were coloured black in the presence of iron, but only darkened when containing copper ; he thus discovered the presence of copper vitriol in the " Wein- brunnen " at Schwalbach. Tachenius states in Hippocrates chymicus, 1766, that tinc- ture of nut-galls produces various coloured precipitates with 1 Ber. Deutsch. Chcm. Ges. xiv. 482. 2 Jahresb. CJiem. 1867, 752. AROMATIC COMPOUNDS. solutions of iron, copper, lead and mercury, and separates metallic gold from solutions of its salts. Other astringent plants have a similar action, which he compares with that of the volatile alkalis, since these remove acids from vitriols in a similar manner. Lemery takes the same view in his paper on the kinds of vitriol and the formation of ink, which is published in the Memoirs of the Paris Academy for 1707 ; nut-galls, according to him, are of an absorbent or alkaline nature, and therefore act like salt of tartar, lime-water, ammonia, &c. That the latter do not produce a black precipitate with iron is accounted for by the fact that the sulphurous particles present in nut-galls are absent in the alkalis. As a proof of this he mentions that when these absorbent substances are made to combine with sulphur, they do give a black precipitate with solutions containing iron. Bergman, on the other hand, suggested in 1775, that a vegetable acid is contained in astringent substances, and in his Elemens de Chymie 1777, published by Morveau, Maret, and Durande, it is stated that on the dry distillation of nut-galls a substance sublimes which blackens solutions of iron and behaves as a true acid. In order to obtain it in a purer condition, Retzius, in 1783, treated the dried extract of nut-galls with cold water, and in this way obtained a substance which had the properties of an acid and effervesced with alkaline carbonates. In 1786, Scheele prepared gallic acid by exposing extract of nut- galls to the air in a warm place and frequently removing the film of mould which was formed. The crystalline precipitate which gradually separated out was purified by recrystallization. He observed that when gallic acid is heated a body sublimes which also precipitates iron salts, but which he considered to be different from gallic acid, a view which was also taken by Berthollet in his Statique chimique, 1803, while Fourcroy and Berzelius believed that the sublimate is the pure gallic acid, this being denied by Braconnot and also by Pelouze (Part III., p. 181). The astringent constituent of nut-galls, subsequently called tannic acid, was first recognized as a distinct substance by Deyeux in 1793, and more definitely by Seguin in 1795, after which Berzelius obtained it in a pure or almost pure con- dition. It had already been noticed that it is readily converted into gallic acid, but the relations of the two substances had not been explained, although many chemists had investigated the question. GALLIC AND TANNIC ACIDS. 365 Pelouze and Berzelius gave to tannic acid the formula C 18 H 18 O 12 , which was altered by Liebig to C 18 H 16 O 12 , since the latter explains in a simple manner its conversion into gallic acid in presence of water and oxygen : " From one atom of tannic acid and four atoms of oxygen, exactly two atoms of gallic acid and two atoms of carbonic acid are formed, while according to the formula C 18 H 18 O 12 , two atoms of hydrogen remain over, and no one knows what becomes of them." l At a later period he proposed the formula C 18 H 10 O 9 4- 3aq, which can be expressed as the sum of the formulas of anhydrous acetic acid and gallic acid ; he had found that tannic acid can be converted into gallic acid without the intervention of oxygen by simply boiling for a few minutes with caustic potash, or better, dilute sulphuric acid. 2 He could not, however, detect any acetic acid and suggested that an isomeride of this is formed, which, however, from the behaviour of tannic acid towards sulphuric acid, could not be a sugar 3 as had been suggested by Stas. 4 Wetherill, on the other hand, assumed that tannic and gallic acids were isomeric, 5 while Mulder gave to the former the formula C 14 H 10 O 9 , according to which it forms two molecules of gallic acid by the assumption of the elements of water ; 6 subsequently, however, he altered his formula to C 14 H 12 O 9 , and looked upon gallic acid as an oxidation product. 7 Tannic acid was then carefully investigated in Liebig's laboratory by Strecker, who succeeded in resolving it into grape sugar and gallic acid, expressing the reaction by the following equation : 8 C^Ar + 4H 2 = 3C 7 H 6 5 + C 6 H 12 O 6 . This view was almost universally accepted, the .more so as other tannic matters had proved to be glucosides, and as the formation of gallic acid by fermentation received a simple explanation. According to Strecker's equation, 29 '1 per cent, of grape sugar should be formed, while he only obtained 15 22 per cent., and Rochleder found that by proper purification the amount can be reduced to 4 per cent, without altering the chemical and physical properties of the tannic acid to any 1 Ann. Chem. Pharm. x. 172. 2 Ibid. xxvi. 128. 3 Handb. Chem. 854. * Ann. Chem. Pharm. xxx. 205. 3 Journ. PraJct. Chem. xlii. 247. 6 Jahrcsb. Chem. 1848, 524. 7 Ibid. 1858, 261. 8 Ann. Chem. Pharm. xc. 328. 366 AROMATIC COMPOUNDS. important extent. 1 His results confirmed those of Knop, who succeeded in converting 95 per cent, of the tannic acid into gallic acid, ellagic acid, C 14 H 6 O 8 , and a carbohydrate being also formed. 2 Stenhouse had previously arrived at similar results, having found that by the . use of sufficiently dilute sulphuric or hydrochloric acid almost the whole of the tannic acid can be converted into gallic acid. 3 Rochleder then assumed that the sugar is formed from some admixture, and that tannic acid stands in the same relation to gallic acid as dextrin to grape sugar. Hlasiwetz remarks on this question : " If tannin is not a glucoside, it may perhaps be a digallic acid, which corresponds to gallic acid in the same way as diethylene alcohol to ordinary glycol, and it would then have the formula which was first proposed for it by Mulder : 2C 7 H 6 6 -H 2 = C 14 H 10 9 . " The analyses of tannin and its salts agree with this com- position as well as can be expected in the case of a substance which is so difficult to purify." 4 Lowe, however, came to a different conclusion ; he found that silver nitrate and arsenic acid are reduced by gallic acid with formation of ellagic acid and a substance which has all the pro- perties of tannic acid, so that he considered the latter to be an oxidation product of gallic acid. 5 He subsequently found that the correct formula of tannic acid is C 14 H 10 O 9 , but assumed that gallic acid is not formed from it only by assumption of water, but that a molecular change takes place. 6 Schiff, on the contrary, showed conclusively that arsenic acid and also phosphorus oxychloride simply exert a dehydrating action, and that the digallic acid thus formed is identical with tannic acid. This question will be more fully considered under the latter. 2202 Gallic acid occurs ready formed in nut-galls, sumach and divi-divi, the fruit of Caesalpinia coriaria. 7 It is also found in the leaves of the red bear-berry (ArctostapTiylos Uva ursi), 8 in China tea, 9 and in red Bundner wine. 10 Etti obtained it by heating 1 Chem. Centralbl. 1858, 579. 2 Pkarm. Centralbl. 1855, 658. 3 Chem. Soc. Mem. i. p. 147. 4 Ann. Chem. Pharm. cxliii. 295. 5 Journ. PraJct. Chem. cii. Ill j ciii. 446. 6 Freseniits' Zeitschr. xi. 365. 7 Stenhouse, Chem. Soc. Mem. i. 137. 8 Kawalier, Jahresb. Chem. 1852, 683. 9 Hlasiwetz and Malin, Zeitschr. Chem. 1867, 271. 10 Simler, Jahresb. Chem. 1861. 923. GALLIC ACID. 367 kinoin, C 14 H 12 O 6 , with hydrochloric acid ; l it is also formed when di-iodoparahydroxybenzoic acid, 2 bromoprotocatechuic acid, 3 bromoveratric acid, 4 and a-bromoresorcylic acid, 5 are fused with caustic potash. According to Lautemann it is also formed in this way from di-iodosalicylic acid, 6 but Demole failed to obtain it by this method, 7 and it is probable that Lautemann's com- pound, which was only obtained in small quantity, is the isomeric pyrogallolcarboxylic acid. In order / HO/ \CO.OH. This explains in a simple manner its conversion into gallic acid by the assumption of water, its decomposition into gallamide and gallic acid by the action of ammonia and the formation of a penta-acetyl-derivative. The fact that when monobromocatechuic acid is heated with potassium gallate and alcohol, a substance is formed 1 Biedermann, Bcr. Entw. Chem. Ind. ; 2 Halfte, p. 456. 2 Schiff, Ann. Chem. Plwrm. clxx. 75. 8 Ber. Deutsch. Chem. Ges. xii. 1576. 4 Ibid. xiii. 454. PROPERTIES OF TANNIN. 373 which gives all the reactions of tannin, is also in favour of this formula : 1 C 6 H 9 (OH) 3 CO.OK + BrC 6 H 2 (OH) 2 CO.OH = CX(OH) 3 CO.O.C 6 H 2 (OH) 2 CO.OH + KBr. Properties. Tannin is a colourless, amorphous mass, which is left on the evaporation of its solution in brittle, vitreous masses, which become coloured yellow in the light, even when exposed in closed vessels. It reddens litmus and has a very strong astringent taste, is readily soluble in water, less so in absolute alcohol, and almost insoluble in absolute ether. Finely-powdered tannin coagulates in ether which contains water, and then de- liquesces, so that it can be employed to detect the presence of water in ether. If water be slowly dropped into the vessel containing the thick solution covered by ether, a point is attained at which three layers are formed. 2 This occurs when 100 ccms. of water and 150 ccms. of ether are present to 100 grms. of tannin ; the lowest layer contains most tannic acid, the middle layer some tannic acid and a large amount of water while the upper layer consists almost entirely of ether, but contains a little tannic acid. 3 Tannin is insoluble in carbon disulphide, chloroform, petroleum ether, benzene, &c. Its aqueous solution gives a black-blue colouration and precipitate with ferric salts, a partial reduction taking place (Wackenroder) ; ferrous sulphate produces in a concentrated solution a white, gelatinous precipitate which becomes coloured blue in the air. When tannin is heated it darkens at 150 160, and at 215 decomposes into water, carbon dioxide and pyrogallol, which volatilize, while metagallic acid or melangallic acid is left behind; this substance alone is formed when tannic acid is rapidly heated to 250, and is a black, amorphous, tasteless mass. Tannin very readily undergoes oxidation; strongly ozonized air produces complete combustion, oxalic acid being formed as an intermediate product (Schonbein) ; it reduces the salts of copper, silver, mercury, gold, &c. In alkaline solution it rapidly absorbs oxygen, the liquid becoming coloured dark. Tannin is precipitated from aqueous solution by dilute hydro- chloric acid, sulphuric acid, common salt, potassium chloride, 1 Hunt, Chem. News, lii. 49. 2 Bolley, Ann. Chem. Pharm. cxv. 63. 3 Luboldt, Jahresb. Chem. 1859, 296. 255 374 AROMATIC COMPOUNDS. potassium acetate and other salts, but not by nitric acid or sodium sulphate. Animal skin removes it from solution com- - pletely ; it precipitates gelatine solution, egg albumen, alkaloids and other substances. The Tannates. Tannin decomposes carbonates and is a mono- basic acid, the salts of which are amorphous and difficult to prepare pure. Many of them are insoluble precipitates, such as the tannates of lead, copper, tin, and antimony, and these may be used for the quantitative estimation of the acid. Tannin, or rather the material containing it, is employed in medicine, dyeing, the manufacture of inks, the clarification of beer and wine, &c. It is not adapted for use as a tanning agent. Penta-acetyltannin, C 14 H 5 (C 2 H 3 O) 5 O 9 , is obtained by boiling- tannin with acetic anhydride for one hour ; it is insoluble in water and separates from boiling alcohol in white spherical or warty aggregates of crystals, which melt at 137. Its solution is precipitated by lead acetate, but is not coloured by ferric chloride (Schiff). Kino'in, C U H 12 O 6 , was discovered by Etti in Malabar kino, the dried sap of Pterocarpus Marsupium (p. 351). It crystallizes in prisms, which are slightly soluble in cold, readily in hot water and alcohol ; its solution is coloured red by ferric chloride. On heating to 120 with hydrochloric acid, it decomposes into methyl chloride, catechol and gallic acid : C 14 H 12 6 + H 2 + HC1 = CH 3 C1 + C 6 H 6 O 2 4- C 7 H 6 O 5 . It is therefore gallylcatechol methyl ether, and probably has the following constitution : HO V /OH >C 6 H 2 < EKK \CO.OC 6 H 4 .OCH 3 . Kino-red, C 28 H 22 O n , is an astringent substance which also occurs in kino, and is formed by heating kinoin to 120 130. It is a red, resinous substance, which is slightly soluble in water, readily in alcohol and alkalis, gives a dirty-green colouration with ferric chloride, and precipitates gelatine solution. On heating to 160 170, it melts with loss of water and is converted into an amorphous red compound, C 28 rI 20 O l0 , which may also be obtained by heating kino-red with dilute hydro- chloric or sulphuric acids. On dry distillation, the larger SLNAPIN. 375 portion becomes carbonized, phenol, catechol and a small amount of anisol or guaiacol being formed. 1 2205 Sinapin, C IQ H.J$O 5 . Henry and Garot discovered in the seeds of the white mustard, a crystalline compound, con- taining both sulphur and nitrogen, to which they gave the name of sulphosinapin, 2 and which was subsequently recognized by Babo and Hirschbrunn as sinapin thiocyanate. 3 Robiquet and Boutron Charlard, repeating the research of Henry and Garot, obtained another substance, 4 which Will and Lauben- heimer named sinalbin, and which is resolved into acid sinapin sulphate, sinalbin mustard oil, and grape sugar, by the action of myrosin in aqueous solution (Vol. III., Part II., p. 393). Sinapin, which is generally classed among the alkaloids, is extremely deliquescent, but forms stable salts. Sinapin thiocyanate, C 16 H 23 N0 5 .HSCN, is obtained from the powdered seeds by first extracting them with ether and cold alcohol, and then boiling up with 90 per cent, alcohol. A very voluminous crystalline mass, which bears a strong resemblance to quinine sulphate, separates out on cooling. It crystallizes from a dilute, hot, aqueous solution in large, fascicular groups of needles, which melt at 176 , 5 and are only slightly soluble in cold alcohol and water. Acid sinapin sulphate, C 16 H 23 N0 5 ,H 2 SO 4 + 2H 2 O, is obtained by adding sulphuric acid to a concentrated, hot solution of the thiocyanate ; it crystallizes in rectangular plates, has an acid reaction and is readily soluble in water. The normal sulphate may be prepared from the acid by neutralizing with baryta water and evaporating the filtrate; it forms an extremely soluble crystalline mass. The nitrate and hydrochloride of sinapin can be prepared from it by means of barium nitrate or chloride, and crystallizes in fine, very soluble needles. The hydrochloride combines with mercuric chloride to form the compound C 16 H 23 NO 5 ,HC1 + HgCl 2 , which crystallizes from water in thin, lustrous prisms (Will and Laubenheimer). When the sulphuric acid is completely removed by baryta water from a solution of the sulphate, a solution of free sinapin is obtained which has a deep yellow colour, is alkaline to litmus, 1 Ber. Deutsch. Chem. Ges. xi. 1879. 2 Berzelius, Jahresber. vi. 242 ; xii. 263. 3 Ann. Chem. Pharm. Ixxxiv. 10. 4 Ibid. xii. 266. 6 Remsen and Coale, Amer. Chem. Journ. vi. 50. 376 AROMATIC COMPOUNDS. and precipitates the salts of the heavy metals. It decomposes on evaporation, the colour changing through green and red into brown and a noncrystalline residue being left. If sinapin thiocyanate be boiled with baryta water or caustic potash solution, it decomposes into thiocyanic acid, sinapic acid and a base, which was named sinkalin by Babo and Hirsch- brunn, but has since been identified as choline (Vol. III., Part II, p. 64). C^H^NO^HSCN + 2H 2 = HSCN + C U H I2 O 6 + C 16 H 15 NO 2 . Sinapic acid, C n H 12 O 5 , is best prepared, according to Remsen and Coale, by boiling sinapin with baryta water and decom- posing the precipitate, which is formed, with hydrochloric acid. It is only slightly soluble in cold water and alcohol, and crystal- lizes from a hot solution in small, yellowish, transparent prisms, melting at 192. Its alkaline solution rapidly turns green, red, and brown in the air. The addition of alcohol to the freshly prepared solution of the potassium salt precipitates it in iridescent plates, which rapidly change after the removal of the alcohol. Calcium chloride and barium chloride produce white precipitates, and ferric chloride gives a rose-red or fine purple- red precipitate, a partial reduction being also effected. Lead salts added to a neutral solution of the acid produce a white precipitate, which soon becomes green and then brown, while the colourless precipitates yielded by the salts of silver and mercury, are rapidly reduced ; the metal is immediately separated from gold solutions. The barium salt alone has been obtained in a condition suitable for analysis by precipitating a solution of the acid, neutralized by potash or ammonia, with barium chloride, or more readily by boiling the acid with baryta water in absence of air ; it has the composition C n H 10 Ba0 5 . Babo says : " Since it is a matter of some difficulty to obtain another salt of the acid in a state fitted for analysis, and I could not spare too much material for this research, the question whether the acid is mono- or dibasic must remain for the present undecided." This point was settled by Remsen and Coale, who heated weighed amounts of the acid with calcium or barium carbonate and determined the amount of metal which had entered into solution ; they found that sinapic acid is monobasic, and that the normal barium salt has the formula (C n H n O 5 ) 2 Ba. SINAPIC ACID. 377 The insoluble barium salt is therefore a basic compound, corresponding to the basic salicylates, and sinapic acid should therefore be a hydroxy-acid, as is proved to be the case by the existence of the following compound. Acetylsinapic acid, C 11 H 11 (C 2 H 3 0)0 5 , is obtained by boiling the acid with acetic anhydride, and forms crystals, which are soluble in hot water and melt at 281. When sinapic acid is heated on platinum foil, vapours are given off which smell like incense, and are also formed when the acid is fused with caustic potash, pyrogallol being among the products. According to Remsen and Coale, sinapic acid is probably butylenegallic acid : C 6 H 2 \CO.OH. If this view be correct, the following formulae will represent the constitution of sinapin and its thiocyanate : 6 XX \CO.OC 2 H 4 N(CH 3 ) 3 OH. X\ X OH C 4 H 8 < >C 6 H / XX \CO.OC 2 H 4 N(CH 3 ) 3 S.CN. If it be further assumed that sinalbin contains two molecules of water of crystallization, its constitution may be represented as follows : XX X OC 6 H U 6 C H ' ^C H ' N)/ \CO.O.C 2 H 4 (CH 3 ) 3 NO.S0 2 .OC 6 H 4 .CH 2 .NCS. Grallocyanin. This dye, which was discovered by Kochlin, and which is also known as solid-violet (violet solide), is manu- factured by heating nitrosodimethylaniline hydrochloride with gallic acid or tannin in alcoholic solution. It is a crystalline substance with a green metallic lustre, readily dissolves in alkalis, and yields salts which crystallize well, that with aniline forming small, green crystals. Gallocyanin forms a blue solution in concentrated sulphuric acid. It is used for dyeing cotton and in calico printing, since it forms a beautiful violet- black 378 AROMATIC COMPOUNDS. lake with chromium oxide, with which the material is mordanted. The shades produced are as bright as those of aniline violet, but much more stable towards light, alkalis and acids. In the presence of quercitron or similar yellow dyes, dark blue shades resembling indigo are produced and can be varied to the greenest shades of blue. It dyes silk and wool directly violet-blue, and is also used as an acid blue on azo-colours ; the goods are dyed in ponceau or some other shade, and the pattern is then printed on in the shape of a mixture of solid-violet, indophenol and an alkaline reducing agent, which effects the usual decomposition of the azo-coiour, while the blue colours are reduced to leuco-compounds, which penetrate the fibre and on exposure to air produce a fast blue on a red ground. 1 Gallocyanin belongs to the class of the indophenols, but its analysis has not yet been published. Its method of formation leads to the following constitution or some similar one (Part III., p. 331). H x X C0 2 H \Q Q/ 0C( '\C=N.C 6 H 4 .N(CH 3 ) 2 . >C=C< OH/ X)H PYROGALLOLCARBOXYLIC ACID. 2206 This compound is formed, together with gallocarboxylic acid, C 6 H(OH) 3 (C0 2 H) 2 , 2 by heating pyrogallol to 130 with ammonium carbonate, or more simply by heating pyrogallol in an open flask with a concentrated solution of acid potassium carbonate. 8 It crystallizes from hot water in silky needles of the composition 3C 6 H 2 (OH) 3 CO 2 H -f H 2 O, which become anhydrous at 110 and have a markedly acid taste. One part dissolves at 12'5 in 767 parts of water ; it is readily soluble in alcohol, but less so in ether. On heating in a current of hydrogen, a gradual evolution of carbon dioxide accompanied by fusion sets in at 195 200, while it sublimes slowly, but without decomposition, in a current of carbon dioxide. Its aqueous solution is coloured 1 Kochlin, Chem. News, xlvii. 170 ; Pabst, Bull. Soc. Chim. xxxviii. 162 ; ChemiTcerzeit, ix. 1444. 2 Senhofer and Branner, Monatsh. Chcm. . i. 468. 3 Kostanecki, Ber. Deutsch. Chem. Ges. xviii. 3202. PYROGALLOL CARBOXYLIC ACID. 379 violet by very dilute ferric chloride, while a strong solution pro- duces a greenish brown colouration ; ferrous sulphate produces no immediate colouration, but the liquid becomes violet on stand- ing. The same colouration is produced by concentrated sulphuric acid which contains a trace of nitric acid. Baryta water and lime water produce blue precipitates which are at first so finely divided that the liquid appears clear. The acid is coloured dark brown by strong potash solution, especially on boiling. It reduces ammoniacal silver solution in the cold and imparts a green colour to Fehling's solution, reduction taking place on warming. It differs sharply from gallic acid in remaining unacted on by sulphuric acid at 140, no rufigallic acid being formed ; de- composition, accompanied by a violent evolution of gas, sets in, however, at a higher temperature. The Pyrogallokarboxylates. The following salts are charac- teristic : Calcium pyrogallolcarboxylate, (G 7 H 5 O 5 ) 2 Ca + 4H 2 0, separates from a hot solution in hard, granular crystalline masses. Barium pyrogallolcarboxylate, (C 7 H 5 O 5 ) 2 Ba + 5H 2 O, crystallizes from a hot solution in hard, yellow prisms. Basic lead pyrogallolcarboxylate, C 7 H 2 Pb 2 O 5 + H 2 O, is a white, flocculent precipitate, which becomes anhydrous at 100. Ethyl pyrogallolcarboxylate, 2C 6 H 2 (OH) 3 CO 2 .C 2 H 5 + 3H 2 O, is insoluble in cold water, but readily in alcohol and ether, and separates from a hot aqueous solution in crystals, which become anhydrous over sulphuric acid or at 100, at which temperature they commence to sublime, and then melt at 102. Ferric chloride colours the aqueous solution greenish brown. Triethylpyrogallolcarloxylic acid, C 6 H 2 (OC 2 H 5 ) 3 C0 2 H. The ethyl ether of this substance is prepared by heating the preceding compound with caustic potash, ethyl iodide and alcohol. It is an odourless, volatile liquid, which is readily decomposed by alcoholic potash. 1 The free acid is slightly soluble in cold, more readily in hot water and alcohol, and crystallizes in long, silky needles, melting at 100*5. It was first obtained from triethyl- daphnetic acid, C 6 H 2 (OC 2 H 5 ) 3 C 2 H 2 .C0 2 H, by oxidation with potassium permanganate, its aldehyde C 6 H 2 (OC 2 H 5 ) 3 CHO, being simultaneously formed as an oily liquid which gradually solidifies to a crystalline mass melting at 70. 2 1 Will and Albrecht, Ber. Deutsch. Chem. Ges. xvii. 2100. 2 Ber. Deutsch. Chem. Ges. xvii. 1087. 380 AROMATIC COMPOUNDS. PHLOROGLUCINOLCARBOXYLIC ACID. This acid is obtained by heating phloroglucinol with acid potas- sium carbonate and water to 130 . 1 It crystallizes in needles, which contain a molecule of water and are only slightly soluble in water, more readily in alcohol, very readily in ether and have an acid taste. The water is lost at 100, carbon dioxide being also slowly evolved. On boiling with water it is decomposed smoothly into phloroglucinol and carbon dioxide. Its aqueous solution is coloured an intense blue by ferric chloride, which soon changes to dirty brown, and its alkaline solution turns brown in the air. When its alcoholic solution is saturated with hydrochloric acid, carbon dioxide is evolved and phloroglucinol diethyl ether is formed (Part III., p. 187). HYDROXYQUINOLCARBOXYLIC ACID. The following derivatives of this acid are alone known : Triethylhydroxyquinolcarboxylic acid, C 6 H 2 (OC 2 H 5 ) 3 C0 2 H, is formed by the oxidation of the two isomeric triethylaesculetic acids, C 6 H 2 (OC 2 H 5 ) 3 C 2 H 2 .CO 2 H, with potassium permanganate, and crystallizes from hot water in fine needles, melting at 134. Its aldehyde, C 6 H 2 (OC 2 H 5 ) 3 COH, is also formed and crystallizes from alcohol in splendid pointed prisms, melting at 95. Trimethylhydroxyguinolcarboxylic acid, C 6 H 2 (OCH 3 ) 3 C0 2 H, resembles the ethyl compound and melts at 108 109 . 2 These compounds were at first considered as derivatives of phloroglucinolcarboxylic acid. When the triethylcompound is distilled with lime, however, a triethoxybenzene is obtained, which melts at 34, and is therefore different from the triethyl ether of pyrogallol or phloroglucinol, so that it must be that of hydroxyquinol. 3 1 Bcr. Deutsch. Chem. Ges. xvii. 2103. 2 Will, ibid. xvi. 2112. 3 Will and Albrecht, ibid. xvii. 2108. QUINIC ACID. 381 CONSTITUTION OF THE TRIHYDROXY- BENZOIC ACIDS. According to theory, six of these compounds can exist, but only four are known : Pyrogallolcarboxylic Phloroglucinolcarboxylic Gallic acid. acid. acid. C0 2 H C0 2 H CQ 2 H ( i ( r T r OH\ /OH \/OH \/ OH OH OH Hydroxyquinolcarboxylic acids. CO 2 H OH/\OH '\/OH C0 2 H /\OH OH\/OH CO 2 H M H OH The constitution of gallic acid is determined by its formation from bromoprotocatechuic acid and a-bromoresorcylic acid, whence it also follows that pyrogallol is an adjacent trihydroxy- benzene, and that in phloroglucinol the hydroxyls are symmetri- cally arranged (Part III., p. 181). The latter can only yield one carboxylic acid, so that the constitution of phloroglucinol- carboxylic acid is determined ; this is confirmed by its formation from daphnetic acid, in which a hydroxyl is known to be in the ortho-position to the carboxyl. The constitution of the hydroxyquinolcarboxylic acid from aesculetic acid has not yet been determined. QUINIC ACID, C H 7 (OH) 4 C0 2 H. 2207 Count Claude de la Garaye, in 1746, obtained a crystal- line deposit l from the extract of Peruvian bark, which became known as Sel essentiel de la Garaye. Hermbstiidt of Berlin showed in 1785 that this " Chinasalz " is a salt of lime, 2 and Hofmann, an apothecary of Leer, in 1790 detected in it a 1 Chimie hydraulique, Paris, 1746, 114. 2 Crell's Ann. ii. 115. 382 AROMATIC COMPOUNDS. characteristic acid, which he named " Chinasiiure," J and which was carefully investigated by Vauquelin in 1806, who called it acide quinique? Its correct formula was determined by Liebig 3 and Woskresensky. 4 It occurs to the amount of 5 8 per cent, in true Peruvian bark, combined with alkaloids and lime. Stenhouse 5 was unable to obtain the slightest trace from the false China nova s. surina- mensis (Biwna magnifolia) ; but Hlasiwetz subsequently showed that it is present, although only in small amount. 6 Zwenger and Siebert have also detected it in bilberry leaves (Vac- cinium Myrtilhis), 7 and in coffee beans. 8 They obtained an ounce of the acid from some baskets of bilberry leaves gathered in May, and one variety of Java coffee yielded 0*3 per cent. Loew discovered it in meadow hay, 9 which contains about 0*6 per cent. Calcium quinate was formerly a by-product of the manufacture of quinine, but is not obtained by the method now in use. 10 It is prepared by treating the powdered bark for two or three days with cold water, adding a little milk of lime to the extract, in order to precipitate tanning matters and the small quantity of alkaloids present, and evaporating the nitrate until it has the consistency of syrup. The calcium quinate which separates out after some weeks is purified by re -crystallization and decom- posed by sulphuric or oxalic acid. Quinic acid crystallizes in hard, transparent, monoclinic prisms or tablets, has a very sour taste, and dissolves at 9 in 2 - 5 parts of water, more readily in alcohol, and scarcely at all in ether. It is optically active and its aqueous solution is laevorotatory. When it is heated it melts at 161'6, n and loses water at a higher temperature, forming quinide, C 7 H 10 O 5 , which separates from water in crystals resembling those of salammoniac, which have an acid reaction and combine with bases to form salts of quinic acid. 12 It probably has the following constitution, C 6 H 7 (OH) 4 CO.OC 6 H 7 (OH) 3 C0 2 H. Quinic acid decomposes on dry distillation with formation of phenol, quinol, catechol, ben zoic acid and other products. 13 I CrelVs Ann. ii. 314. 2 Ann. Chim. lix. 162. 3 Ann. Chcm. Pharm. vi. 14. 4 Ibid. xxiv. 257. 5 Ibid. liv. 100. Ibid. Ixxix. 144. 7 Ibid. cxv. 108. 8 Ibid. Suppl. i. 77. 9 Journ. Prakt. Chcm. [2] xix. 309. 10 Neues Uandwdrtcrb. ii. 532. II Hesse, Ann. Chem. Pharm. cxiv. 292. 12 Hesse, ibid. ex. 335. 13 Wohler, ibid. Ii. 146. QUINIC ACID. When lead dioxide is added to its aqueous solution, carbon dioxide is evolved and the reaction may be carried on by heating the mixture, lead quinate and quinol being formed : 1 C 7 H 12 O e When it is heated with manganese dioxide and sulphuric acid, quinone is formed, while protocatechuic acid may be obtained by evaporating a solution of the acid to which bro- mine has been added, 2 or by fusing the acid with caustic potash, 3 or caustic soda, 4 as well as, together with a large amount of benzoic acid, by heating quinic acid to 150 with fuming hydrochloric acid. 5 Fuming hydriodic acid reduces it at 120 to benzoic acid : 6 C 7 H 12 6 +2HI = C 7 H 6 2 +4H 2 + I 2 . On heating with concentrated hydrochloric acid to 140 150, parahydroxybenzoic acid and quinol are formed ; it dissolves when heated with sulphuric acid with evolution of carbon dioxide and formation of quinoldisulphonic acid (Hesse). Phosphorus chloride converts it into metachlorobenzoyl chloride (Grabe) : C 7 H 12 6 + 5PC1 5 = C 7 H 4 C1 2 + 5POC1 3 + 8HC1. It is converted by the animal organism into hippuric acid (Lautemann). The whole behaviour of quinic acid points to the fact that it belongs to the aromatic addition-products. 7 It is tetrahydroxy- hexhydrobenzoic acid, and, since it is optically active, must contain an asymmetric carbon atom, so that it has the following constitution : C0 2 H CH H 2 Q iCH.OH HO.HC, X CH.OH ;H 1 Hesse, Ann. Chcm. Pharni. cxiv. 292. 2 Hesse, ibid. cc. 239. 8 Grabe, ibid, cxxxviii. 203. 4 Hesse, loc. cit. 6 Fittig and Hillebrand, ibid, cxciii. 197. 6 Ibid. cxxv. 9. 7 Grabe, Ann. Chem. Pharm. cxlvi. 66. 384 AROMATIC COMPOUNDS. It differs from quercitol (Part III. p. 194) in containing a carboxyl in the place of one hydroxyl. A different formula has been proposed by Lieben, who found that quinic acid yields iodoform when treated with iodine and caustic potash ; he therefore assumes that its constitution must be expressed by the following or some similar formula : l HO.CH CH 3 HO.C CH.OH HO.CH CH.CO 2 H. The Quinates. The salts of quinic acid are for the most part readily soluble in water, slightly in alcohol, and crystallize well. They have been investigated by Baup, 2 Woskrensky, Hesse, and Clemm. 3 Sodium quinate, C 7 H n 6 Na -f 2H 2 O, crystallizes in large, nacreous, rhombic prisms. Clemm was unable to obtain the potassium and ammonium salts in crystals ; their solutions only gave syrupy residues on evaporation over sulphuric acid. Calcium quinate, (C 7 H n 6 ) 2 Ca + 10H 2 O, forms silky, rhombic plates, or long, concentrically-grouped prisms, which dissolve at 10 in 6 parts of water and are insoluble in absolute alcohol. Barium quinate, (C 7 H n O 6 ) 2 Ba+6H 2 O, crystallizes, according to Henry and Plisson, in acute octohedral pyramids, while Baup always obtained it in dodecahedra formed by the combination of two pointed pyramids, and Clemm only as a partially crystalline mass. Lead quinate, (C 7 H n O 6 ) 2 Pb, crystallizes in readily soluble needles ; ammonia added to its solution produces a voluminous, hydrated precipitate which has the formula C 7 H 8 O 6 Pb 2 , after drying at 200. Silver quinate, C 7 H n O 6 Ag, forms warty crystals, which readily dissolve in water and blacken in the light. Copper quinate, (C 7 H n O 6 ) 2 Cu + 5H 2 O, crystallizes in light blue plates. Basic copper quinate, C 7 Tl 1() Q 6 Cu + 2R 2 O, is obtained by boiling the aqueous solution of the acid with an excess of copper oxide : 1 Ann. Chcm. Pharm. Suppl. vii. 232. 2 Ibid. vi. 1 ; Ann. Chim. Phys. [2] li. 56. 3 Ann. Chem. Pharm. ex. 345. ETHYL QUINATE. 385 it forms small, green crystals, which are only slightly soluble in cold water. Ethyl quinate, C 6 H 7 (OH) 4 C0 2 .C 2 H 5 , was obtained by Hesse by the action of ethyl iodide on the silver salt ; it is a viscid mass, which is readily soluble in water and alcohol, and has a very bitter taste. Ethyl tetracetylquinate, C 6 H 7 (OCO.CH 3 ) 4 CO.OC 2 H 5 , is formed by boiling the ethyl ether with acetic anhydride, and crystallizes from boiling water in plates ; it separates from ether in large, rhombic crystals which melt at 135, and sublime without decomposition (Fittig and Hilldebrand). 386 AROMATIC COMPOUNDS. THE XYLENE GROUP. 2208 It has been already mentioned under benzene (Part III. p. 66) that Mansfield in 1848 discovered that coal-tar naphtha contains, besides benzene, its homologues; of these he isolated the following (C = 6) : Boiling-point. Toluol, C U H 8 about 113. Cumol, C 18 H 12 143 145. Cymol, C 20 H 14 170 172. He adds, it is interesting to note, "that tar-oil contains among its constituents the only four known members of the series C 6 -f-n(C 2 H 9 ). It seems, therefore, not improbable that the gap which still exists in this series (n = 5), corresponding to a substance whose boiling-point lies between those of toluol and cumol, will be filled by a compound to be obtained from tar-oil. 1 Soon after this, Cahours discovered xylol (icy&ne),C 8 H 10 (C = 12), boiling at 128 130, along with toluol in crude wood-spirit (v\ov, wood), 2 and Volkel found the same hydrocarbons in wood-tar. 3 Church then stated that xylol is also contained in coal-tar oil, and boils at 126'2, 4 whereas Ritthausen 5 and Hiltenkamp 6 could only detect in it the hydrocarbons already discovered by Mansfield. Warren de la Itue and H. Miiller then showed that Rangoon tar contains benzol and its homologues, which they were unable to isolate, but recognised by conversion into their characteristic nitro-compounds. 7 Shortly before this time, Bussenius and Eisenstuck had investigated the rock oil from 1 Ann. Chem. Pharm. Ixix. 162. 2 Ibid. Ixxiv. 168 ; Ixxvi. 286. 8 Ibid. Ixxxvi. 331. 4 Phil. Mag. [4] ix. 256. 8 Journ. Prakt. Chem. Ixi. 74. Ann. Chem. Pharm. xcv. 89. 7 Journ. Prakt. Chem. Ixx. 300. THE XYLENE GROUP. 387 Sehnde in Hanover, and discovered in it a new hydrocarbon, which they called petrol, C 8 H 10 , its existence being proved by its characteristic trinitro-derivative; 1 and Hugo Miiller then showed that the hydrocarbon obtained from coal-tar and boiling at 140 is not cumol, but xylol, which also occurs in the oils from Burmah and Sehnde, trinitropetrol being identical with trinitro- xylol. 2 In spite of this Bechamp repeated the statement that xylol boils at 126 130, adding that coal-tar also contains a "new" hydrocarbon boiling at 139 140. 3 Mansfield's cumol was subsequently proved to be a mixture of trimethylbenzenes. After Fittig and Tollens had made the important discovery that the synthetic methylphenyl or methylbenzol is identical with toluol, 4 it was supposed that ethylphenyl or ethylbenzol would be identical with xylol. This, however, was found not to be the case, since it boils as much as 7 lower than the latter, and does not yield a crystallized trinitro-derivative. Beilstein then investigated xylol more carefully ; he fully con- firmed Mliller's observations and found that on oxidation with chromic acid it yields dibasic terephthalic acid, C 8 H 6 O 4 . 5 About this time Fittig prepared methylbenzyl, which he considered to be identical with xylol, by the action of sodium on a mixture of bromotoluol and methyl iodide. 6 He also found that ethyl- phenyl is easily oxidized to benzoic acid and that its derivatives are completely different from those of xylol. 7 Glinzer and Fittig then undertook a careful examination of methylbenzyl, or, as they now termed jt, methyltoluol ; like xylol it yielded terephthalic acid on oxidation, but the trinitro- derivatives proved to have different properties. 8 A further investigation of the oxidation products of xylol showed that toluic acid, the next homologue of benzoic acid, 9 is first formed, and this was also obtained from methyltoluol. In spite of this, however, the hydrocarbons were shown to be different, as the properties of their substitution products did not agree. 10 Fittig and Velguth then obtained a third isomeric hydrocarbon, which they named isoxylol, by heating monobasic mesitylenic acid, C 6 H 3 (CH 3 ) 2 CO 2 H, prepared by the oxidation of mesitylene, 1 Ann. Chem. Pharm. cxiii. 151. 2 Zeitschr. Chcm. 1864, 161. 3 Compt. Rend. lix. 47. 4 Ann. Chem. Pharm. cxxxi. 303. 5 Ibid, cxxxiii. 32. 6 Ibid, cxxxiii. 47. 7 Ibid, cxxxiii. 222. 8 Ibid, cxxxvi. 303. 9 Yssel de Schepper and Beilstein, ibid, cxxxvii. 301. 10 Fittig, Ahreus and Mattheides, ibid, cxlvii. 15. AROMATIC COMPOUNDS. C 6 H 3 (CH 3 ) 3 , with lime. The substitution products of this body agreed so exactly with those of xylol, that the two hydro- carbons would have been considered identical had not their oxidation products been completely different. Isoxylol was not attacked by dilute nitric acid, while chromic acid oxidized it to isophthalic acid, the isomeride of terephthalic acid. 1 Fittig soon found a very simple explanation of this exceptional and almost incredible fact. Xylol proved to be a mixture of methyltoluol or paraxylol with isoxylol, or, as it is now termed, metaxylol. Beilstein, who had looked upon it as a chemical individual, had only obtained in a pure state the difficultly soluble substitution products of metaxylol and the oxidation pro- ducts of paraxylol, which are most readily formed. 2 The third isomeric dimethylbenzene, orthoxylol was then prepared syn- thetically and subsequently discovered in coal-tar by Jacobsen. 3 According to Fittig, coal-tar naphtha contains a preponde- rating amount of metaxylene, while Jacobsen found 20 25 per cent, of orthoxylene, and 1015 per cent, of paraxylene in a series of samples of xylene. In order to separate these, the coal-tar xylene, boiling at about 140, is repeatedly shaken up with ordinary concentrated sulphuric acid, the ortho- and meta-compounds alone being dissolved. The solution is diluted with water and neutralized with chalk, the filtrate being then treated with a slight excess of sodium carbonate and concentrated by evaporation. The sodium orthoxylenesulphonate separates out on cooling in large prisms, which can readily be purified by re-crystallization. An additional crop of this salt can be obtained by further eva- poration, while the meta-salt remains in solution. The pure hydrocarbons are then obtained by heating the salts with concentrated hydrochloric acid. The portion of the crude xylene which does not dissolve in ordinary sulphuric is agitated with the slightly fuming acid, the mixture being gently heated ; the paraffins are thus left undissolved, while paraxylenesulphonic acid is formed, which is only slightly soluble in dilute sulphuric acid, and is purified by re-crystallization (Jacobsen), the hydrocarbon being then obtained, as before, by the action of hydrochloric acid. The meta-compourid alone may be extracted from crude xylene by boiling it for a considerable time with a mixture of 1 Ann. Chem. Pharm. cxlviii. 1. 2 Ibid. clui. 265. 3 Ber. Deutsch. Clwrn. Ges. x. 1010. THE XYLENES. - 389 one volume of concentrated nitric acid and two or three volumes of water, the ortho- and para-compounds being thus oxidized to the corresponding toluic acids, C 6 H 4 (CH 3 )CO 2 H, or their nitro- derivatives, while the meta- compound is scarcely attacked. When the evolution of red fumes ceases, the liquid is distilled with steam and the distillate agitated with caustic soda, washed with water, dried and distilled. 1 In order to estimate the amounts of the three isomerides quantitatively, 100 c.c. of the crude xylene are boiled for half an hour to an hour with a mixture of 40 c.c. of nitric acid of sp. gr. 1'4 and 60 c.c. of water, the whole being repeatedly agitated. The unattacked portion is then washed with caustic soda and distilled with steam, the distillate is measured and shaken up with 1*5 vols. of concentrated sulphuric acid, the metaxylene being thus dissolved, while the paraffins remain behind and are measured in a graduated cylinder. The amount of paraxylene is found by thoroughly agitating 100 c.c. of the crude xylene with- 120 c.c. of concentrated sul- phuric acid for half an hour, a mixture of paraffins and para- xylene being left undissolved ; this is then treated with an equal volume of fuming sulphuric acid, containing 20 per cent, of trioxide, which dissolves out the paraxylene. The amounts of paraxylene, metaxylene and paraffins are thus directly measured, the difference from 100 c.c. being that of the orthoxylene. In this way Levinstein has found in various samples of crude English and Scotch xylene : 2 Paraxylene . 3 10 percent. Metaxylene 7087 Orthoxylene 215 Paraffins 310 According to Reuter these methods of separation are not accurate, since nitric acid of the concentration employed also attacks metaxylene, and paraxylene dissolves in ordinary sulphuric acid^ although to a much smaller extent than its isomerides. The resistance of the xylenes to the action of acids is, however, considerably increased by the presence of paraffins. 3 1 Fittig and Velguth, Ann. Chem. Pharm. cxlviii. 10 ; Tawildarow, Zcitschr. Chem. 1870, 418 ; Bruckner, Ber. Deutsch. Chem. Ges. ix. 405. 2 Ibid. xvii. 444. 3 Ibid. xvii. 2028. 256 390 - AROMATIC COMPOUNDS. When a mixture of the three xylenes is treated with bromine containing 1 per cent, of iodine, they are converted into the tetra- bromoxylenes, C 6 Br 4 (CH 3 ) 2 , which yield the tetrabromophthalic acids quantitatively when heated with bromine and water to 160 170: C 6 Br 4 (CH 3 ) 2 + 6Br 2 + 4H 2 = C 6 Br 4 (C0 2 H) 2 + 1 2HBr. Since these can readily be separated, the composition of the original mixture can be determined in this way. 1 THE XYLENES, OR DIMETHYLBENZENES, 2209 Orthoxylene, (1 : 2), was first prepared pure by the dis- tillation of paraxylic acid, C 6 H 3 (CH 3 ) 2 CO 2 H, with lime ; 2 it is also formed by the action of sodium on a mixture of ortho- bromotoluene and methyl iodide, 3 and when a hot mixture of toluene and aluminium chloride is treated with methyl chloride. A small quantity of paraxylene is always formed in this reaction, together with still less metaxylene and a larger amount of the isomeric trimethylbenzenes. 4 It has also been prepared from cantharidin, C 10 H 12 O 4 , which is the characteristic con- stituent of Spanish flies, and yields pure orthoxylene when heated with phosphorus pentasulphide. 5 It is a liquid which boils at 142 143, solidifies in a freezing mixture to crystals, melting at 28, 6 and is oxidized to ortho- toluic acid by heating with dilute nitric acid, while chromic acid produces complete combustion. When agitated with a boiling solution of potassium permanganate, however, it yields phthalic acid. 7 A cold mixture of nitric and sulphuric acids converts it into liquid nitro-derivatives, and a single drop of orthoxylene can thus be distinguished from the para- and meta-compounds. 8 1 Friedel and Crafts, Compt. rend. ci. 1218. 2 Bieber and Fittig, Ann. Chem. Pharm. clvi. 238. 3 HiibnerandJannasch, ibid. clxx. 117 ; Reymann, Bull. Soc. Chim. xxvi. 582. 4 Jacobsen, Bcr. Dcutsch. Chcm. Ges. xiv. 2624. 5 Piccard, ibid. xii. 580. 6 Colson, Ann. Chim. Phys. [6] vi. 128. 7 Clans and Pieszcek, Be.r. Deutsch. Chem. Ges. xix. 3083. 8 Jacobsen, ibid. xix. 2518. ORTHOXYLENE. 391 Dihydro-orthoxyhne, or Cantharcne, C 6 H 6 (CH 3 ) 2 . The com- pound C 10 H 13 I 9j O 3 is formed by the action of hydriodic acid on cantharidin, and is converted into cantharene by heating with concentrated caustic potash; the latter boils at 134, smells like camphor and oil of turpentine, rapidly absorbs oxygen from the air and is oxidized to orthotoluic acid by dilute nitric acid. 1 Metaxylene (1 : 3) may be obtained pure by heating xylic acid C 6 H 3 (CH 3 ) 2 C0 2 H (Bieber and Fittig), or the isomeric mesity- lenic acid (Fittig and Velguth) with lime, and by the action of sodium on a mixture of methyl iodide and meta-iodotoluene. 2 It boils at 139'8 and has a specific gravity of 0*8780 at 0, and of 0'8660 at 15; it solidifies when strongly cooled and then melts at 54 to 53. 3 It is only attacked with difficulty by dilute nitric acid, even on boiling ; when, however, it is boiled for several hours with nitric acid of specific gravity 1'4, diluted with one and a half times its volume of water, metatoluic acid is obtained (Reuter), while chromic acid solution oxidizes it to isophthalic acid, which is also formed, together with metatoluic acid, by the action of potassium permanganate. 4 Metaxylene, as already mentioned, occurs in various tars and petroleums, and it has also been found in that from the Caucasus. 5 It forms a characteristic trinitro-derivative, which is only slightly soluble in alcohol and yields nitrodiamidometaxy- lene (p. 409) on partial reduction. These reactions serve to detect small quantities of metaxylene in petroleum, &c. Tetrahydrometaxylene, C 6 H 8 (CH 3 ) 2 , is formed when camphoric acid, C 8 H 14 (C0 2 H) 2 , is heated to 200 with concentrated hydriodic acid, 6 and has also been prepared from oxycamphoric acid, under which it will be mentioned. It is a liquid which boils at 119, and is converted into trinitrometaxylene by a mixture of nitric and sulphuric acids. Hexhydrometaxylene, C 6 H 10 (CH 3 ) 2 , is obtained by heating camphoric acid or metaxylene with hydriodic acid to 280. It occurs in Baku petroleum (Beilstein and Kurbatow) and in essence of resin (Renard) ; it boils at 116 120, and also yields trinitrometaxylene with nitric and sulphuric acids. 7 ParaxyUne (1 : 4) is formed by the action of sodium on a 1 Piccard, Ber. Deutsch. Chem. Ges. xix. 1406. 2 Wroblewsky, Ann. Chem. Pharm. cxcii. 200. 3 Colson, loc. cit. 4 Glaus and Burstert, JBcr. Deutsch. Chem. Ges. xix. 3084. 5 Doroschenko, xviii. Ref. 662 : Markownikow, Ann. Chem. Pharm. ccxxxiv. 89. 6 Wreden, Ann. Chem. Pharm. clxxxvii. 171. 7 Ibid, clxxxvii. 151. AROMATIC COMPOUNDS. mixture of methyl iodide and parabromotoluene l or paradi- bromobenzene. 2 It boils at 136 137, and has a specific gravity of 0'8621 at!9'5; when strongly cooled it solidifies to rhombic prisms resembling heavy spar, 3 which melt at + 15. Dilute nitric acid oxidizes it to paratoluic acid, while chromic acid or potassium permanganate give terephthalic acid. Paraxylene occurs in the petroleum from Galicia along with metaxylene. 4 Hcxhydroparaxylene, C 6 H 10 (CH 3 ) 2 , is obtained by heating mono- bromocamphor, C 10 H 15 BrO, with zinc chloride to 150 160, and is a liquid boiling at 157 '6, which is converted into trinitropara- xylene by nitric and sulphuric acids. 5 SUBSTITUTION PRODUCTS OF THE XYLENES. 22 10 When one atom of hydrogen is replaced in the aromatic nucleus, six isomeric compounds may be formed. Metaxylene yields three, which are distinguished as symmetric = s, asym- metric = a, and adjacent (vicinus) v. Two, asymmetric = a, and adjacent = v, are derived from orthoxylene, while paraxylene only yields one, which has therefore received no more particular designation. HALOGEN SUBSTITUTION PRODUCTS OF THE XYLENES. v-CUor orthoxylene, C 6 H 3 (CH 3 ) 2 C1(1 : 2 : 3), is formed, together with the following compound, when orthoxylene, to which 5 per cent, of iodine has been added, is treated with chlorine at 0. In order to separate the two isomerides, they are converted into the sulphonic acids, the pure sodium salts of which are then decomposed by heating with concentrated hydrochloric acid. Adjacent chlor orthoxylene is a liquid boiling at 189'5. a-Chlororthoxylene (1:2:4) boils at 191'5 and, like its isomeride, remains liquid at 20. 6 1 Fittig and Glinzer, Ann. Chcm. Pharm. cxxxvi. 303. 2 V. Meyer, Ber. Dcutsch. Chem. Ges. iii. 753 ; Jannasch, ibid. x. 1356. 3 Jacobsen, ibid. xvii. 2379. 4 Palewski, ibid, xviii. 1915. 6 R. Schiff, ibid. xiii. 1408. 6 Kriiger, ibid, xviii. 1755. XYLENE SUBSTITUTION-PRODUCTS. 393 The chlororthoxylenes are converted by oxidation into the corresponding chlorotoluic and chlorophthalic acids. According to Glaus and Kautz, only one chlororthoxylene is formed, which boils at 205 and yields the following compounds on further chlorination : x Melting- Boiling- Dichlororthoxylene, C 6 H 2 C1 2 (CH 3 ) 2 , point. point. crystalline mass . . . + 3 227 Trichlororthoxylene, C 6 HC1 3 (CH 3 ) 2 , lustrous needles .... 93 265 Tetrachlororthoxylene, C 6 C1 4 (CH 3 ) 2 , long needles 215 a- Chlorometaxylene, C 6 H 3 (CH 3 ) 2 C1(1 : 3 : 4), is formed when letaxylene is chlorinated at in presence of iodine ; the crude luct, which distils between 185 188, is purified by con- certing it into the sulphonic acid and then preparing the sodium salt or chlorometaxylenesulphamide, C 6 H 2 (SO 2 .NH 2 )C1(CH 3 ) 2 , from this. The latter crystallizes from hot alcohol in hard, com- pact, lustrous prisms melting at 195. Both of these compounds yield pure chlorometaxylene when heated with hydrochloric acid. It boils at 186*5 and does not solidify at - 20 ; it is oxidized to chlorometatoluic acid by chromic acid, while it is converted into ortho-horn oparahydroxybenzoic acid by fusion with caustic potash. 2 Chloroparaxylene, C 6 H 3 (CH 3 ) 2 C1(1 : 4 : 2), is obtained in a precisely similar manner to chlorometaxylene ; it boils at 186 and solidifies in a freezing mixture to a crystalline mass, which melts at + 2. Dichloroparaxylene, C 6 H 2 (CH 3 ) 2 C1 2 , is only slightly soluble in cold, readily in hot alcohol, and crystallizes in flat needles or plates ; it melts at 71 and boils at 221 . 3 a-Bromorthoxylene, C 6 H 3 (CH 3 ) 2 Br(l : 2 : 4), is formed by the direct bromination of orthoxylene in the cold in the presence of iodine, no isomeride being produced, 4 and more slowly when bromine alone is allowed to act in the dark, orthoxylyl bromide being obtained in the sunlight 5 It boils at 214'5 and solidifies below to a fibrous, crystalline mass, melting at 0'2. When heated with ethyl chloroformate and sodium amalgam, paraxylic acid, C 6 H 3 (CH 3 ) 2 CO 2 H, is formed. 1 Jacobsen, Ber. Dcutsch. Chem. Ges. xviii. 1367. 2 Ibid, xviii. 1760. 3 Kluge, ibid, xviii. 2098. 4 Jacobsen, ibid. xvii. 2372. 5 Schramra, ibid, xviii. 1278. AROMATIC COMPOUNDS. The following compounds are formed by the further action of bromine (Jacobsen) : Solid dilromorthoxylene,C 6 R 2 (CH 3 ) 2 Br 2 (l : 2 : 4 : 5), crystallizes from hot alcohol in large, rhombic plates, which melt at 88 ; it readily sublimes in very large, thin plates, boils at 278 and yields symmetric tetramethylbenzene, C 6 H 2 (CH 3 ) 4 , on treatment with sodium and methyl iodide. Liquid dibromorihoxylene boils at 277 and solidifies in the cold to a hard crystalline mass, melting at + 6'8. Tctrdbromorthoxylene, C 6 (CH 3 ) 2 Br 4 , is formed when orthoxylene is allowed to drop into bromine containing 1 per cent, of alumi- nium bromide, the whole being kept at O . 1 It is very slightly soluble in alcohol, readily in benzene, and crystallizes in long, lustrous needles, which melt at 262, or according to Bliimlein at 254 255, and boil at 374 375. Jacobsen was unable to prepare tribromorthoxylene pure. a-Bromometaxylene, C 6 H 3 (CH 3 ) 2 Br (1:3:4), is prepared like the ortho-compound ; it is a liquid, which boils at 203 204, and is converted into the corresponding bromotoluic acid by oxi- dation, 2 while xylic acid is formed by the action of carbon dioxide and sodium. 3 s-Bromometaxylene, (1:3: 5), has been prepared from bromi- nated metaxylidine by the diazo-reaction. It boils at 204, remains liquid at 20, and is converted into symmetric dimethylethylbenzene by sodium and ethyl bromide. 4 a-Dilromometaxylene, C 6 H 2 (CH 3 ) 2 Br 2 , is formed when meta- xylene is allpwed to stand in contact with an excess of bromine for twenty-four hours, the liquid being kept cool. 5 It crystallizes from alcohol in colourless, nacreous plates, boils at 255 256, and melts at 72. 6 f3-Dibromometaxylene was obtained by Wroblewsky, together with his monobromoxylene, as a liquid which boils at 252 and does not solidify at 20. Tetrabromometaxylene, C 6 (CH 3 ) 2 Br 4 , is formed when meta- xylene is allowed to stand for a long time in contact with a large excess of bromine. It is scarcely soluble in cold, slightly in boiling alcohol, but dissolves readily in benzene, 1 Bliimlein, Ber. Deutsch. Chcm. Gcs. xvii. 2492. 2 Fittig, Ann. Chcm. Pharm. cxlvii. 31. 3 Kekule, ibid, cxxxvii. 186. 4 Wroblewsky, ibid, cxcii. 115. 5 Fittig, Ahrens and Mattheides, ibid, cxlvii. 24, 6 Fittig and Bieber, ibid. clvi. 236. NITRO-ORTHOXYLENES. 395 and crystallizes in fine needles which melt at 241 (Fittig and Bieber). Bromoparaxyhne, C 6 H 3 (CH 3 ) 2 Br (1:4: 2), is prepared by the action of bromine on cooled paraxylene in the presence of iodine, and is also formed when bromine is allowed to act alone in the dark (Schramm). It is a liquid, which boils at 205'5, and some- times solidifies when strongly cooled, but frequently remains liquid until a crystal of the solid compound has been added, when it forms plates or tablets, melting at + 9. 1 Dibromoparaxylene, C 6 H 2 (CH 3 ) 2 Br 2 (1:4:2: 5), boils at 261, and crystallizes from alcohol in large plates or flat needles, melting at 75*5. When these are allowed to remain in the mother liquor they are converted into transparent, asymmetric crystals, which closely resemble regular octohedra (Jacobsen). It is converted into symmetric tetramethylbenzene by the action of sodium and methyl iodide. 2 In addition to this compound, a liquid dibromoparaxylene, which boils at 260 264 and solidifies in a freezing mixture, is formed in small quantity. A tribromoparaxylene was not formed when the necessary quantity of bromine was added, the following substance being obtained together with the preceding compounds : Tetrabromoparaxylene, C 6 (CH 3 ) 2 Br 4 , is very slightly soluble in alcohol, and crystallizes from hot toluene in long, fine needles, melting at 253. NITRO-SUBSTITUTION PRODUCTS OF THE XYLENES. 2211 v-Nitro-ortJwxylene, C 6 H 3 (CH 3 ) 2 N0 2 (1:2: 3), is formed, together with the following compound, when orthoxylene is treated in a freezing mixture with concentrated nitric and sulphuric acids ; it is a liquid, which boils at 245 247 . 3 a-Nitro-orthoxylene (1:2: 4) is almost the sole product when pure nitric acid is employed ; it crystallizes from alcohol in long, brittle, light yellow, lustrous prisms, melts at 290 and boils at 280 . 4 1 Jannasch, Ann. Chcm. Pharm. clxxi. 82 ; Jacobsen, Ber. Dcutsch. Chem. Ges. xviii. 356. 2 Jannasch, ibid. x. 1357. 3 Nolting and Forel, ibid, xviii. 2669. 4 Ibid. xvii. 159. 396 AROMATIC COMPOUNDS. Zkrtitro-orthoxylene, C 6 H 2 (CH 3 ) 2 (N0 2 ) 2 , is formed, together with the following compound when orthoxylene is heated for a considerable time to 100 with a mixture of -nitric and sul- phuric acids. It crystallizes from boiling alcohol in long, lustrous needles, melting at 71. Trinitro-orthoxylene, C 6 H(CH 3 ) 2 (NO 2 ) 3 , forms white, lustrous scales, which melt at 178, and are almost insoluble in alcohol. 1 v-Nitrometaxylene (1 : 3 : 2) is obtained by the action of nitric and sulphuric acids on metaxylene in the cold. 2 It has been prepared pure from the corresponding nitrometaxylidine by the diazo-reaction. 3 It is a liquid boiling at 225. a-Nitrometaxylene (1:3: 4) is formed in the preparation of the preceding compound, and in preponderating amount when pure, well-cooled nitric acid is employed. It is a light yellow liquid, which boils at 238 and does not solidify at - 20. 4 s-Nitrometaxylene (1:3:5) is obtained from nitro-a-metaxy- lidine by dissolving it in absolute alcohol, adding two molecules of sulphuric acid, and then treating the well-cooled liquid with twice the theoretical quantity of ethyl nitrite in order to prevent the formation of the diazo-amido-compound. The liquid is heated to boiling after standing for some time, the alcohol driven off and the remainder distilled with steam. s-Nitrometaxylene boils at 263, and crystallizes from alcohol in large, flat needles, melting at 74 75. 5 s-Dinitrometaxylene, C 6 H 2 (CH 3 ) 2 (NO 2 ) 2 (1 : 3 : 4 : 6), is readily prepared by heating metaxylene with fuming nitric acid; it crystallizes from hot alcohol in large, flat, colourless needles or lustrous prisms, melting at 93. 6 v-Dinitrometaxylene (1 : 3 : 4 : 2) is formed together with . its isomerides when xylene is nitrated at a low temperature with a mixture of nitric and sulphuric acids ; it is readily soluble in alcohol, and crystallizes in scale-like plates, melting at 83. 7 Trinitrometaxylene, C 6 H(CH 3 ) 2 (NO 2 ) 3 (1:3:2:4:6). This characteristic compound, which has been previously mentioned 1 Drossbach, Ber. Deutsch. Chem. Gcs. xix. 2156. 2 Noltiug and Forel, Ber. Deutsch. Chem. Gcs. xviii. 2668. 3 Grevingk, ibid. xvii. 2430. 4 Tawildarow, Zeitschr. Chem. 1870, 418 ; Harmsen, Ber, Deutsch. Chem. Ges. xiii. 1558. 5 Wroblewsky, Ann. Chem. Pharm. ccvii. 91 ; Thb'l, Ber. Deutsch. Chem. Ges. xviii. 359 ; Nblting and Forel. Fittig, Ann. Chem. Pharm. cxlvii. 16 ; cxlviii. 5. 7 Grevingk, Ber. Deuttsch. Chem. Gcs. xvii. 2422. NITROXYLENES. 397 (p. 387), is formed when metaxylene or the preceding compounds are heated with a mixture of nitric and sulphuric acids. It is scarcely soluble in cold, very slightly in boiling alcohol, and crystallizes in fine, flat, colourless needles, melting at 176 . 1 ^ Nitroparaxylcne, C 6 H 3 (CH 3 ) 2 N0 2 , is obtained by allowing the calculated quantity of fuming nitric acid to drop into well-cooled paraxylene. It is a yellow liquid, which boils at 239 and does not solidfy at - 20. 2 a-Dinitroparaxylene, C 6 H 2 (CH 3 ) 2 (N0 2 ) 2 (1 : 4 : 2 : 6), is formed, together with its isomerides, when paraxylene is dissolved in cold, fuming nitric acid. It crystallizes from alcohol in very thin, lustrous needles, melting at 124, and is deposited from glacial acetic acid in long, broad needles. P-JDinitroparaxylenc (1:4:2:3) is more readily soluble in alcohol, and crystallizes on gradual evaporation in monoclinic tablets, which resemble crystals of calcspar, and melt at 93. 3 It is a characteristic property of these two nitroxylenes that equal molecules of them combine to form a double compound, which can be crystallized from glacial acetic acid, but is de- composed by alcohol into its constituents. 4 It forms transparent monoclinic prisms with sphenoid faces, and melts at 99'5. needles j a-Tribromometaxylenol, C 8 H 6 Br 3 .OH, long, colourless ) needles j v-Metaxyknol (1:3:2) crystallizes in silky plates or long, flat needles, melts at 74'5, boils at 211 212, and gives no colouration with ferric chloride. v- Tribromometaxylenol crystallizes from hot alcohol in long, light yellow needles, melting at 175. s-Metaxylenol (1:3:5) is deposited from solution in hot water or from sublimation in splendid white needles, melting at 68. It boils at 219'5, and gives no colouration with ferric chloride. s- Tribromometaxylenol crystallizes from alcohol or benzene in fine, white needles, melting at 166. Paraxylenol (1 : 4 : 2) has been prepared from paraxylidine ; 1 it melts at 74' 5, sublimes in needles at a slightly higher temperature, boils at 21 1*5 and crystallizes from hot water or very dilute alcohol in large, flat needles. It gives no colouration with ferric chloride. The solid compound prepared by Wurtz was almost pure paraxylenol. Melting-point. Monobromoparaxylenol, CLILBr.OH, colourless, flex- ( Qh7 o ible needles f 87 Tribromoparaxylenol, C 8 H 6 Br 3 .OH, deep golden \ .. ,_-<> yellow needles J The great similarity existing between para- and v-meta- xylenol is somewhat remarkable (Jacobsen). A xylenol occurs in crude creosote, which boils at 220, does not crystallize, and on heating with potash and methyl iodide yields a methyl ether, boiling at 200 . 2 This substance is pro- bably a mixture, and, from its high boiling-point, would seem to consist chiefly of a-orthoxylenol. s 1 Nolting, Witt and Forel, Bor. Deittach. Chem. Ges. xviii. 2664. 2 Marasse, Ann. Chem. Pharm. clii. 75 ; Tiemann and Mendelsohn, Ber. D&utseh. Chem. Gcs. x. 57. 8 N citing, Witt and Forel, ibid, xviii. 2664. 402 AROMATIC COMPOUNDS. Robiquet, by the distillation of aloes with lime, obtained a liquid which he called alo'isol. This substance has been shown by Rembold to be a mixture, the portion soluble in alkalis having the composition of a xylenol. 1 DIHYDROXY-XYLENES, C 6 H 2 (CH 3 ) 2 (OH) 2 . 2214 Homorcinol, or Paraxylorcinol (1:4:2:6), was obtained by Stenhouse from Usnea larbata and Cladonia rangiferina, and named by him /3-orcin, 2 a name which was subsequently changed by him and Groves into beta-orcinol. It is a decom- position product of the barbatic acid, C 19 H 20 O 7 , which occurs in these lichens. 3 Lamparter has succeeded in obtaining it, together with orcinol, from Eocella fuciformis* Its constitution was determined by Kostanecki, who prepared it from a-nitroparaxylidine, by first converting it into nitroxylenol, reducing this to amidoxylenol, and finally passing from this to paraxylorcinol by means of the diazo-reaction. 5 It is less soluble in water than orcinol, and is deposited in quadratic crystals, melting at 163. It possesses a slightly sweet taste, boils at 277 280, and is coloured red by ammonia in presence of air more rapidly than orcinol. Its aqueous solution gives with ferric chloride a light carmine-red colouration, quite distinct from the purple-red produced with orcinol. Like the latter it yields a red solution with a beautiful green fluorescence when heated with chloroform and caustic soda (Kostanecki). Nitrosoparaxylortinol, C 6 H(CH 3 ) 2 (OH)0(NOH), is formed by the action of nitrosyl sulphate (Part III. p. 171) on an aqueous solution of paraxylorcinol, as a lustrous, orange-red precipitate, which crystallizes from glacial acetic acid in small, lustrous, red prisms. Metaxyloroinol (1:3:4:6) is obtained from s-nitro-a-meta- xylidine. It is readily soluble in water, has an acid taste, melts at 125 and boils at 276 279. It crystallizes from chloroform in brilliant white, monosymmetric plates, which can also be obtained by sublimation. No red colouration is produced by exposure to ammonia and air. 6 1 Ann. Chcm. PJiarm. cxxxviii. 186. 2 Phil. Traits. 1848, 63. 3 Ibid, cciii. 285. * Ibid, cxxxiv. 243. 5 Bcr. Deutsch. Chem. Gfcs. xix. 2318. tf Pfaff, ibid. xvi. 611 and 1135 ; Kostanecki, loc. cit. TRIHYDROXY-XYLENES. 403 Gundelach, by heating chlorometaxylenesulphoiiic acid to 230 250 with caustic potash, obtained a dihydroxy-xylene which should be identical with metaxylorcinol, since, according to Jacobsen, the side chains of the sulphonic acid have the following arrangement : CH 3 : CH 3 : Cl : SO 3 H = 1 : 3 : 4 : 6.1 It crystallizes in microscopic prisms, which are tolerably soluble in water, melt at 120 and are coloured deep red by ammoniacal air. 2 This compound is probably impure metaxylorcinol. The following dihydroxy-xylenes have been prepared by the reduction of the xyloquinones : Paraxyloquinol, QT Hydrophlorone (1 : 4 : 2 : 5), is readily soluble in alcohol, slightly in boiling water and benzene, and crystallizes in nacreous plates or tablets, which melt at 210 and sublime in long needles. It reduces silver solution and is re-oxidized to the quinone by ferric chloride. The diethyl ether, C 8 H 8 (OC 2 H 5 ) 2 , is formed by heating it with ethyl bromide and caustic potash ; it forms lustrous plates, which melt at 105 106, and have an odour resembling that of peppermint (Stiidel and Holz). Metaxyloyuinol (1:3:2:5) sublimes in needles and melts at 149. Ortlwxyloquinol (1:2:3:6) crystallizes from water in crusts, which melt at 221 with decomposition. TRIHYDROXY-XYLENES. 2215 Trihydroxymetaxylene,C^(fll^^ z (Q'S)^i^ formed by the reduction of hydroxymetaxyloquinone (p. 404) with sulphurous acid. It is tolerably soluble in cold, readily in hot water, and crystallizes in colourless or yellowish transparent tablets, con- taining a molecule of water, which is lost at 80, the anhydrous compound melting at 121 122. It is reduced to metaxylene when heated with zinc-dust. Oxidizing agents readily convert it into the quinone ; if the aqueous solution be merely allowed to evaporate in the air, the quinhydrone crystallizes out in long needles resembling those of potassium permanganate. Triacetoxy metaxylene, C 6 H(CH 3 ) 2 (O.CO.CH 3 ) 3 , is obtained by the action of acetyl chloride, and crystallizes from alcohol in colourless, lustrous prisms, which melt at 99, and sublime without decomposition when carefully heated. 1 Ber. Deutsch. Chcm. Gcs. xviii. 1762. 2 Bull. Soc. Chim. xxviii. 343. 404 AROMATIC COMPOUNDS. THE XYLOQUINONES, C 6 H 2 (CH 3 ) 2 O 2 . 2216 Paraxyloquinone (1:4:2:5). Rommier and Bouilhon, by oxidizing the fraction of crude cresol boiling between 195- 220 with sulphuric acid and manganese dioxide, obtained two isomeric quinones, C 8 H 8 2 , and gave to the one, which is formed in larger quantity and melts at 60 62, the name of phlorone, and to the other, melting at 125, that of metaphlorone. 1 Accord- ing to Gorup-Besanez and v. Rad, phlorone is also formed by the oxidation of wood-tar creosote. 2 Nietzki then obtained para- xyloquinone by the oxidation of crude xylidine and of paradi- amidoxylene with potassium dichromate and sulphuric acid, and found that its properties agree with those of metaphlorone ; 3 Carstanjen then showed that phlorone is a mixture of toluquinone with paraxyloquinone, and that the latter yields paraxylene on heating with zinc-dust. 4 It is best prepared from paraxylidine in the same way as benzoquinone from aniline. 5 Paraxyloquinone is only slightly soluble in water and cold alcohol ; it crystallizes from hot alcohol in splendid golden- yellow needles, which melt at 123'5 and readily sublime. Ortboxyloquinone (1:2:3:6) has been prepared from v-ortho- xylidine by oxidation ; it is slightly soluble in water, more readily in alcohol, and sublimes in yellow needles, which melt at 55. Metaxyloquinone (1:3:2:5) is formed by the oxidation of v- and s-metaxylidine, and crystallizes in splendid yellow needles, melting at 73. Hydroxymetaxyloquinone, C 6 H(CH 3 ) 2 (OH)0 2 , is formed when diamidomesitylene, C 6 H(CH 3 ) 3 (NH 2 ) 2 , is distilled with potassium dichromate and dilute sulphuric acid. It crystallizes from hot water or ether in orange-red needles, has a characteristic smell resembling that of benzoquinone, melts at 103, and sublimes very readily in splendid, lustrous, deep golden-yellow needles. Its aqueous solution is instantly coloured a splendid reddish violet by the addition of any alkaline substance, and' this reaction is so delicate that the slightest traces of the quinone 1 Compt, Rend. Iv. 214. 2 Zeitschr. Chem. [2] iv. 560 ; Ann. Chem. Pharm. cli. 158. 3 Bcr. Deutsch. Chem. Gcs. xiii. 470. 4 Journ. Prakt. Chem. [2] xxiii. 421. 6 bolting and Forel, Ber. Deutsdi. Chem. Gcs. xviii. 2668. AMIDOXYLENES. 405 can be detected by it. Insoluble carbonates also produce this colouration ; thus, if a O'l per cent, solution of the quinone be shaken up with calcium carbonate, the colouration produced is so deep that even a thin layer of the liquid appears quite opaque. The presence of calcium carbonate can thus be shown in very small quantities of mineral waters ; free carbonic acid does not affect the colouration, so that the quinone forms a valuable indicator for alkalimetry. It forms salts, which readily decompose on warming or on exposure to the air in presence of an excess of the base. The potassium salt, C 8 H 7 (OK)O 2 , crystallizes from hot alcohol in small, black needles, 1 mgrm. of which is sufficient to impart a deep red colour to a litre of water. 1 AMIDO-DERIVATIVES OF THE XYLENES. THE AMIDOXYLENES, OR XYLIDINES, C 6 H 3 (CH 3 ) 2 NH 2 . 2217 Cahours gave the name of xylidine to the homologue of toluidine and aniline which he obtained from his xylene (p. 386), >y nitrating it and submitting the nitroxylene formed to reduc- tion. This substance and the xylidine obtained by Church in the same manner was obviously a mixture of toluidines and xylidines, while that prepared by Deumelandt from xylene boiling at 140 consisted chiefly of a-metaxylidine, as was also the case with that prepared by Hofmann and Martius by heating paratoluidine hydrochloride to 300 with methyl alcohol. It only became possible to obtain the six xylidines after the three xylenes had been obtained in the pure condition and the six nitroxylenes prepared from these. A mixture of them is manu- factured on the large scale from tar-xylene, and the purity and composition of commercial xylidine is therefore dependent on that of the latter. Specimens now come into the market containing as much as 25 per cent, of paraxylidine in addition to ordinary metaxylidine. 2 The commercial product is employed in the manufacture of azo-colours and of the cumidines, C 6 H 2 (CH 3 ) 3 NH 2 , which are obtained by heating the hydrochlorides with wood-spirit. 1 Fittig and Siepermann, Ann. Chem. Pharm. clxxx. 27. 2 Nblting, Witt and Forel, Ber. Deutsch. Chem, Ges. xviii. 2664 ; Stadel and Holz, ibid, xviii. 2919. 257 406 AROMATIC COMPOUNDS. v-Ortlioxylidine (1:2:3) is formed when solid dibromortho- xylene is nitrated, the nitrodibromorthoxylene reduced to dibromo- xylidine, and the bromine removed by treatment with sodium amalgam and water. 1 It is a liquid which boils at 223; its hydrochloride is tolerably soluble in water, and crystallizes in white needles, containing a molecule of water. The sulphate is only slightly soluble. v-Acetorthoxylide, C 6 H 3 (CH 3 ) 2 NH(CO.CH 3 ), crystallizes from hot benzene in white needles, melting at 134 . 3 a-Orthoxylidine (1:2:4) melts at 49 and boils at 226. It is tolerably soluble in hot water, readily in alcohol, and crystal- lizes when caused to solidify quickly or when rapidly deposited from solution, in transparent, vitreous tablets, while it may be obtained by the gradual evaporation of its petroleum-ether solution in thick, monoclinic crystals. Its aqueous solution is not coloured by bleaching powder; the solutions of its salts colour pine-wood an intense yellow. The hydrochloride is readily soluble in water, but only slightly in hydrochloric acid, and crystallizes with one molecule of water in long, very thin prisms. a-Acetorthoxylide crystallizes from hot water containing a little alcohol in long, thin, vitreous prisms, which melt at 99. The base is converted by the diazo-reaction into a-ortho- xylenol. 3 v-Metaxylidine (1:3:2) was first obtained by Schmitz by heating /3-amidomesitylenic acid, C 6 H 2 (CH 3 ) 2 (NH 2 )CO 2 H, with lime. 4 Grevingk, 5 and Nolting and Forel, 6 then prepared it from v-nitrometaxylene. It is a liquid boiling at 214. Its hydrochloride crystallizes in thin, anhydrous, monoclinic plates, which are readily soluble in water. v-Acetmetaxylide crystallizes from benzene in white needles, which melt at 176 8. It is not attacked by caustic potash solution, sulphuric acid, or hydrochloric acid, on heating in an open vessel, but is decomposed by the last of these at 150. a-Metaxylidine (1:3:4) has been known for a longer period than any of its isomerides and is therefore also called ordinary metaxylidine. It is formed by the distillation of a-amidomesity- lenic acid with lime (Schmitz) and by the reduction of a-nitro- 1 Thol, Ber. Deutsch. Chem. Gas. xviii. 2561 ; Wroblewsky, ibid, xviii. 2904, xix. 235 ; Jacobsen, ibid, xviii. 3166. 2 Nolting and Forel, ibid, xviii. 2668. 8 Jacobsen, ibid. xvii. 159. 4 Ann. Chem. Pharm. cxciii. 377. 6 Ber. Deutsch. Chem. Ges. xvii. 2422. 6 Ibid xviii. 2676. XYLIDINES. 407 metaxylene. 1 It may also be readily obtained from commercial xylidine by converting this into the hydrochloride and purifying by re-crystallization. In order to obtain it perfectly pure, the acet- xylide is prepared, purified by re-crystallization, and decomposed with sulphuric acid. The other xylidine can also be- easily obtained pure in this way. It is a liquid boiling at 212. The hydrochloride is only slightly soluble in cold water, and crystallizes in anhydrous, rhombic tablets; the hydrobromide crystallizes even better, forming splendid prisms (Stadel andHolz). a-Acetmetaxylide crystallizes from benzene in white needles melting at 129 ; impurities cause a considerable lowering of the melting-point. s-Mttaxylidine (1:3:5) is obtained by the reduction of the corresponding nitroxylene ; 2 it is a liquid boiling at 220. Its hydrochloride and nitrate crystallize in large, anhydrous needles ; 4 '66 parts of the latter dissolve in 100 parts of water at 13. s-Acetmetaxylide crystallizes from alcohol in large, flat needles, melting at 140'5. Paraxylidine (1:4:2) may be prepared in the usual way by the reduction of nitroparaxylene, 3 and also from commercial xylidine ; the latter is run into fuming sulphuric acid containing sufficient trioxide to convert the bases into sulphonic acids, the mixture being well stirred and then heated on the water-bath. The solution is allowed to cool and the solid mass pressed under water to separate the metaxylidinesulphonic acid in the crystalline state. The sodium salt of paraxylidinesulphonic acid is then prepared from the mother-liquor by neutralizing it with lime, filtering, removing the calcium with carbonate of soda, and concentrating the filtrate. It separates in splendid, nacreous plates, which are freed from any adhering traces of the readily soluble salt of the metaxylidinesulphonic acid by washing with a little cold water. P.ure paraxylidine is then obtained by the dry distillation of the salt. 4 It is a liquid boiling at 215; its hydrochloride and nitrate crystallize in flat needles or large tablets, and the sulphate, which is only slightly soluble, forms small plates. Acetparaxylide crystallizes from hot water or toluene in long lustrous needles, melting at 139. 1 Tawildarow, Zeitschr. Chem. 1870, 418 ; Nolting and Forel, loc. cit. 2 Wroblewsky, Ann. Chem. Pharm. ccvii. 95 ; Thol, Ber. Deutsch. Chem. Ges. xviii. 359 ; Nolting and Forel, loc. cit. 3 Schaumann, Ber. Deutsch. Chcm. Ges. xi. 1537 ; Nolting and Forel. ibid. viii. 2680. 4 Nolting, Witt and Forel, xviii. 2664. 408 AROMATIC COMPOUNDS. NITROXYLIDINES, C 6 H 2 (CH 3 ) 2 (NH 2 ) 2 N0 2 . 2218 $-Nitro-a-metaxylidine (1:3:4:6) is formed by the reduction of s-dinitrometaxylene with ammonium sulphide, and crystallizes from hot water or alcohol in orange-red needles, while it separates on the gradual evaporation of its alcoholic solution in thick, deep red crystals, which melt at 123 . 1 v-Nitro-a-metaxylidine (1:3:4:2) has also been prepared from v-dinitrometaxylene, and forms golden-yellow needles, which melt at 78. 2 a-Nitro-a-metaxylidine (1:3:4:5). In order to prepare this compound, a-acetmetaxylide is treated with concentrated nitric acid in the cold, and the product decomposed by heating with sulphuric acid, diluted with half its volume of water. It crystallizes from alcohol in long, red needles, which melt at 76. 3 A small quantity of s-nitro-a-metaxylidine is formed at the same time (Nblting and Forel); a-Nitro-s-metaxylidine (1 : 3 : 5 : 4) is obtained by the nitration of s-metaxylidine with a mixture of nitric and sulphuric acids ; it crystallizes in yellow needles, which melt at 54, and readily volatilize with steam (Nolting and Forel). a-Nitroparaxylidine (1:4:2:6) has been prepared by the reduction of a-dinitroparaxylene with ammonium sulphide, and crystallizes from alcohol in long, golden-yellow needles, melting at 96. 4 fS-Nitroparaxylidine has not yet been obtained, as the cor- responding dinitroparaxylene is immediately reduced to the diamine by ammonium sulphide. y-Nilroparaxylidine (1:4:2:5) is formed by the nitration of paraxylidine with a mixture of sulphuric and nitric acids, and forms brownish yellow, lustrous crystals, which are readily soluble in alcohol and melt at 142 . 5 Dinitroparaxylidine, C 6 H(CH 3 ) 2 (N0 2 ) 2 NH 2 (5:2: 3), is ob- tained by the long-continued heating of trinitroparaxylene with 1 Fittig, Ahrens and Mattheides, Ann. Chcm. Pharm. cxlvii. 18. 2 Grevingk, Ber. DeuLsch. Chcm. Ges. xvii. 2425. 3 Hofmann, ibid. ix. 1295 ; Wroblewsky, Ann. Chem. Phwrn. ccvii. 91 ; Thbl, Ber. Dcutsch. Chcm. Ges. xviii. 359 ; Nolting and Forel, ibid, xviii. 2677. 4 Fittig, Ahrens and Mattheides, Ann. Chcm. Pharm. cxlvii. 22. 5 Nolting, Witt and Forel, Ber. Deutsch. Chcm. Ges. xviii. 2664. DIAMIDO XYLENES. 409 alcoholic ammonia. It crystallizes from glacial acetic acid in yellow needles, which melt at 202 203, and are converted by the diazo-reaction into a-dinitroparaxylene. 1 DIAMINES AND TRIAMINES OF THE XYLENES, C 2219 a-Diamidometaxylene, C 6 H a (CH 3 ) 2 (NH 2 ) 2 (1 : 3 : 4 : 5), is formed by the reduction of a-nitro-a-metaxylidine, 2 and amido- azo-a-metaxylene. 3 It crystallizes from hot benzene in small, white plates, which melt at 77 78, and are readily soluble in alcohol. s-Diamidometaxylene (1:3:4:6) has been prepared from s-dinitrometaxylene and the corresponding nitroxylidene ; it sublimes in white crystals, melting at 104. v-Diamidometaxylene (1 : 3 : 4 : 2) sublimes in white needles and melts at 64. Nitrodiamidometaxylene, C 6 H(CH 3 ) 2 (NH 2 ) 2 N0 2 , is formed by the reduction of trinitrometaxylene with ammonium sulphide and was first described by Bussenius and Eisenstuck as nitro- petroldiamine (p. 387). It is slightly soluble in cold, more readily in boiling water and readily in alcohol, from which it crystallizes in lustrous, ruby-red prisms, an inch in length, which melt at 212 213. 4 Triamidometaxylene, C 6 H(CH 3 ) 2 (NH 2 ) 3 (1:3:2:4:6), has been obtained by reducing trinitrometaxylene with hydrochloric acid and stannous chloride ; it crystallizes in white needles, which decompose at about 140 without melting. Diamidometaxylene contains the amido-groups in the ortho- position, and gives all the characteristic reactions of the ortho- diamines (Nolting and Forel) ; the two other diamidometa- xylenes are metadiamines, and therefore yield azo-dyes when their hydrochlorides are treated with sodium nitrite, as does also triamidometaxylene. The colour prepared from v-diamido- metaxylene dyes silk reddish brown, that from s-diamidometa- xylene, yellowish brown, while the derivative of the triamine 1 Nolting and Geissmann, Ber. Deutsch. Cfwm. Ges. xix. 144. 2 Hofmann, ibid. ix. 1298. 3 Nolting and Forel, ibid, xviii. 2683. 4 Fittig and Velguth, Ann. Chcm. Pharm. cxlviii. 6. 410 AROMATIC COMPOUNDS. produces a grey shade of olive. With diazobenzenesulphonic acid, on the other hand, the v-diamine gives a light yellowish red colouring matter, while that from the s-diamine is darker and that from the triamine a dark, red-black. The shades produced on silk, however, are in the inverse relation ; the lightest coloured dye gives the darkest shade, then follows that of the s-diamine, while the substance prepared from the triamine dyes an almost pure golden yellow. 1 a-Diamidoparaxylene, C fl H 2 (CH 8 ) 2 (NH 2 ) 2 (1:4:2:6), sublimes in white needles, melting at 101*5 102'5; its hydrochloride gives a brown colouring matter with sodium nitrite; it forms chrysoidines with diazo-salts and a dye analogous to toluylene- blue (p. 82) with nitrosodimethylaniline. fB-Diamidoparaxylene (1:4:2:3) sublimes in small needles, melting at 75; sodium nitrite, added to the solution of its hydrochloride, precipitates an azimido-compound (Part III. p. 270), 2 while ferric chloride produces a deep red colouration. ry-Diamidoparaxylene (1:4:2: 5). Nietzki prepared this com- pound by the action of zinc and hydrochloric acid on the amido- azoxylene, C 6 H 3 (CH 3 ) 2 .N 2 .C 6 H 2 (CH 3 ) 2 NH 2 , prepared from com- mercial xylidine. 3 Nolting and Forel then obtained it from amido-azoparaxylene, and showed that Nietzki's compound consists of amido-azometaparaxylene. 4 It is also formed by the reduction of 7-nitroparaxylidine. It is slightly soluble in cold, readily in hot water and alcohol, but less readily in benzene, from which it crystallizes in white needles, melting at 146'5 147. It yields paraxyloquinone on oxidation. XYLYL COMPOUNDS. 2220 When an atom of hydrogen in the methyl group of one of the xylenes is replaced by another element or radical, com- pounds of the monovalent radical xylyl, CH 3 .C 6 H 4 .CH 2 , are ob- tained ; this radical has also been called tolyl, because the monobasic acids, CH 3 .C 6 H 4 .C0 2 H, which correspond to the xylyl alcohols, CH 3 .C 6 H 4 .CH 2 .OH, and which decompose into toluene and carbon dioxide when heated with lime, have received 1 Grevingk, Ber. Deutsch. Ckem. Ges. xvii. 2442. 2 Nolting and Geissmann, ibid. xix. 144. 3 Ibid. xiii. 470. 4 Ibid, xviii. 2685. XYLYL COMPOUNDS. 411 the name of toluic acids. The term tolyl has, however, been also applied to the group C 7 H 7 , and it is therefore preferable to designate the derivatives of the xylenes as xylyl compounds. 1 The use of this term is open to the objection that the acids, |(CH 3 ) 2 C 6 H 3 .CO 2 H, are called xyiic acids, because they stand to xylene in the same relation as the toluic acids to toluene and benzoic acid to benzene. 2 In order to avoid this confusion of terms, it has been proposed to give the name of tolyl to the group CH 3 .C 6 H 4 and to desig- nate the xylyl alcohols according to Kolbe's nomenclature as tolyl carbinols, 3 the toluic acids being called tolylformic acids. In the sequel, however, the names which are in general use will be retained. Chlorine acts upon boiling xylene in the same way as on toluene, substitution taking place in the methyl group. The first xylyl-compounds were obtained from tar-xylene, but they have now been prepared from the pure hydrocarbons. 4 Bromine acts on the xylenes at the boiling-point in a similar manner ; 5 an energetic reaction also takes places in the sunlight, the first product consisting of a mixture of xylyl bromides. 6 XYLYL ALCOHOLS, CH 3 .C 6 H 4 .CH 2 .OH. Orihoxylyl alcohol was prepared by Raymann by the action of sodium amalgam and water on orthotolualdehyde, which he had prepared from the chloride. It is slightly soluble in water, iadily in alcohol, and crystallizes in needles, melting at 54. Lccording to Colson, who prepared it by heating the bromide with water, it melts at 34'2 and boils at 217 . 7 Metaxylyl alcohol has been obtained both from the acetate and bromide ; it is a liquid, which boils at 215 and has a faint odour. Metaxylyl ethyl ether, CH 3 .C 6 H 4 .CH 2 .O.C 2 H 6 , is a liquid and boils at 202. 1 Jahresb. Chem. 1866, 605. 2 Kekule, Ann. Chem. Pharm. cxxxvii. 186. 1 Beilstein, Org. Chem. 1084. Raymann, Bull. Soc. Chim. xxvi. 532 ; xxvii. 498 ; Gundelach, ibid. xxvi. 43. Radziszewski and Wispek, Ber. Deutsch.Chem. Ges. xv. 1743 ; xviii. 1279. 6 Schramm, ibid, xviii. 1272. 7 Colson, Bull. Soc. Chim. xliii. 6 ; Ann. Chim. Phys. [6] vi 115. 412 AROMATIC COMPOUNDS. Metaxylyl acetate, CH 3 .C 6 H 4 .CH 2 O.CO.CH 3 , was prepared by Volrath by heating the chloride obtained from tar-xylene with silver acetate. 1 Radziszewski and Wispek then prepared it from the pure bromide. It is a liquid which boils at 226 and possesses an aromatic odour resembling that of apples. Paraxylyl alcohol was obtained by Cannizzaro from paratolu- aldehyde by the action of alcoholic potash, and was named toluenyl alcohol. It crystallizes in white needles, and is slightly soluble in cold, more readily in hot water, from which it sepa- rates in oily drops which solidify to fine needles, melting at 58 '5 59'5 and boiling at 217. Hydrochloric acid converts it into the liquid chloride. 2 Paraxylyl ethyl ether is a liquid which has a similar smell to benzyl alcohol and boils at 203 (Radziszewski and Wispek). Xylyl chlorides, CH 3 .C 6 H 4 .CH 2 C1. These compounds are colour- less liquids. Melting- Boiling- point, point. Orthoxylyl chloride 197 199 Metaxylyl chloride . 195 196 Xylyl bromides, CH 3 .C 6 H 4 .CH 2 Br. Orthoxylyl bromide, rhombic prisms 21 216 217 Metaxylyl bromide, liquid .... 212 215 Paraxylyl bromide, long needles . . 35'5 218 220 XYLYLAMINES. These have been prepared by heating the xylyl chloride from tar-xylene with ammonia, 3 and are therefore more or less pure meta-compounds. Monoxylylamine, CH 3 .C 6 H 4 .CH 2 .NH 2 , is an oily, alkaline liquid which boils at 196 and smells strongly of herring brine ; its hydrochloride is readily soluble in water and alcohol, and crystallizes in needles. Dixylylamine, (CH 3 .C 6 H 4 .CH 2 ) 2 NH, is a similar liquid, which decomposes above 210; its hydrochloride forms white needles, which are only slightly soluble in cold, readily in hot water and alcohol. 1 Ann. Chem. Pharm. cxliv. 261. 2 Ibid, cxxiv. 252. 8 Jannasch, ibid, cxlii. 303 ; Pieper, ibid. cli. 129. THE TOLUALDEHYDES. 413 Trixylylamine, (CH 3 .C 6 H 4 .CH 2 ) 3 N, is a thick, colourless oil, which has a characteristic odour and a faint alkaline reaction. The hydrochloride crystallizes in loose groups of needles, which are insoluble in water, but slightly soluble in cold and readily in hot alcohol. It decomposes into xylyl chloride and dixylyl- amine hydrochloride when heated in a current of hydrochloric acid gas. THE TOLUALDEHYDES. 2221 Chromyl chloride combines with the xylenes, as with benzene and toluene, to form compounds which are decomposed by water with formation of the tolualdehydes. 1 3CH 3 .C 6 H 4 CH(OCrCl 2 .OH) 3CH 3 .C 6 H 4 .CHO + 2Cr0 3 + Cr 2 (OH) 6 + 6HC1. Orthotolualdehyde was first prepared by boiling orthoxylyl chloride with water and lead nitrate ; it is a yellowish, strongly refractive liquid, which smells like benzaldehyde and boils at 200 . 2 MetatolualdeJiyde has been obtained in a similar manner from metaxylyl chloride ; 3 it possesses a similar smell and boils at 199. It combines with phenylhydrazine to form metaxyli- denekydrazine, CH 3 .C 6 H 4 .CH.N 2 H.C 6 H 5 , which crystallizes from alcohol in thick, yellow prisms, melting at 91. Orthonitrometatolualdekyde, CH 3 .C 6 H 3 (N0 2 )CHO, is formed when the aldehyde is allowed to drop into a cold mixture of nitric and sulphuric acids. It is a yellowish liquid, volatile with steam, and is converted into methylindigo when warmed with caustic soda and acetone. 4 Paratolualdehyde was prepared by Cannizzaro by the distilla- tion of a mixture of calcium formate and calcium paratoluate, and is a liquid which boils at 204 and possesses a smell re- sembling that of peppermint. 5 1 Etard, Ann. Chim. Phys. [5] xxii. 218, 1881 ; Bornemann, Per. Deutsch. Chcm. Ges. xvii. 1462. 2 Raymann, Bull. Soc. Chim. xxvii. 498. 3 Lauth and Grimaux, ibid. vii. 234 ; Gundelach, ibid. xxvi. 44. 4 Meister, Lucius and Briining, Ber. Deutsch. Chem. Ges. xvi. 817 ; Bornemann, loc. cit. 5 Ann. Chem. Pharm. cxxiv. 254. 414 AKOMATIC COMPOUNDS. THE TOLUIC ACIDS, C 6 H / CH 3 C(XH 2222 Orthotoluic acid was first obtained by Bieber and Fittig by oxidizing orthox}dene with dilute nitric acid. 1 It may also be easily prepared from its nitril, and its ethyl ether is formed by the action of ethyl chlorocarbonate on a mixture of ortho- iodotoluene and sodium amalgam. 2 It is best prepared by heating phthalide with phosphorus and hydriodic acid : 3 C 6 H 4 < +1, 'CO XXXOH It crystallizes in long, lustrous needles, which melt at 102, and are slightly soluble in cold, more readily in hot water and very readily in alcohol. It is completely burnt by chromic acid solution, while dilute nitric acid 4 and alkaline permanganate 5 convert it into phthalic acid. Calcium orthotoluate, (C 8 H 7 2 ) 2 Ca + 2H 2 0, crystallizes in small needles, which are readily soluble in water but only slightly in alcohol. Ethyl orthololuate, C 8 H 7 2 .C 2 H 5 , is a liquid which boils at 219*5, and has an aromatic odour. 6 Orthotoluyl chloride, CH 3 .C 6 H 4 .COC1, is a liquid which boils at 211 (Ador and Rilliet). Ortlwtoluamide, CH 3 .C 6 H 4 .CONH 2 , crystallizes from boiling water in fine, silky needles, melting at 138. Orthotolunitril, CH 3 .C 6 H 4 .CN, is formed by the distillation of potassium orthoxylenesulphonate with potassium cyanide, 7 and also when orthotolyl mustard oil is heated for an hour with copper filings. 8 It is a colourless, strongly refractive liquid boiling at 203 204, which is converted into the amide by heating with alcoholic potash, and into the acid by concentrated hydrochloric acid at 180 200. 1 Ann. Chem. Phann. clvi. 242. 2 Kekule, Bcr. Dcutsch. Chem. Ges. vii. 1007. 3 Grabe,#ta. xix. 778. 4 Weith, ibid. vii. 1057. 8 Piccard, ibid. xii. 579. 6 Ador and Rilliet, ibid. xii. 2298. 7 Fittig and Ramsay, Ann. Chem. Pharm. clxviii. 246. 8 Weith, Bcr. Dcutsch. Chem. Ges. vi. 418. THE TOLCJIC ACIDS. 415 Chlororthotoluic acids, C 6 H 3 C1(CH 3 )CO 2 H, are obtained by oxidizing the chloroxylenes with dilute nitric acid : x Cl CH 3 C0 2 H Melting-point. 4:2:1 compact prisms 130 4:1:2 compact prisms 166 3:2:1 needles 154 a-Bromorthotoluic acid, C 6 H 3 Br(CH 3 )C0 2 H (4:1: 2), is formed by the oxidation of bromorthoxylene, and crystallizes from hot alcohol in stellate aggregates of flat needles, which melt at 174 176- 2 /3-Bromorthotoluic acid (3:1:2) is obtained by the action of bromine on orthotoluic acid. It is scarcely soluble in cold, slightly in boiling water, but readily in alcohol, and crystallizes in long needles, melting at 167. 3 Nitro-orthotohdc acids, C 6 H 3 (NO 2 )(CH 3 )C0 2 H. The first of these is formed, together with the second, by the nitration of orthotoluic acid, 4 and, together with the third, when nitro- orthoxylene is oxidized. 5 The last also occurs, according to Racine, in the products of the nitration of orthotoluic acid. 6 NO 2 CH S CO 2 H Melting-point, a) 4 : 1 : 2 needles or microscopic prisms . 179 ) 6 : 1 : 2 needles 145 7) 4 : 2 : 1 long, lustrous needles . . . . 152 Amido-orthotoluic acids, C 6 H 3 (NH 2 )(CH 3 )CO 2 H : NH 2 CH 3 C0 2 H a) 4 : 1 : 2 small prisms 196 /3) 6 : 1 : 2 small, lustrous needles . . . 191 7) 4 : 2 : 1 long, flat needles ..... 153 The last of these acids decomposes into carbon dioxide and metatoluidine when it is heated with lime (Jacobsen). Sulphorthotoluic acid, C 6 H 3 (SO 3 H)(CH 3 )CO 2 H (1:2: 3), is obtained by heating orthotoluic acid to 160 with sulphuric 1 Kriiger, Ber. Dcutsch. Chem. Ges. xviii. 1755. 2 Jacobsen, ibid, xvii. 2372. 3 Jacobsen and Wierss, ibid. xvi. 1956. 4 Fittig and Bieber, Ann. Chem. Pharm. cxlvi. 245 ; Fittig and Ramsay, ibid. clxviii. 250 ; Jacobsen and Wierss, Ber. Deutsch. Chem. Gfes. xvi. 1956. 5 Jacobsen, ibid. xvii. 162. 6 Ibid, xviii. 3450. 416 AROMATIC COMPOUNDS. acid ; it forms a fibrous crystalline mass, which dissolves readily in water, but only slightly in dilute sulphuric acid. Disulphorthotoluic acid, C 6 H 2 (SO 3 H) 2 (CH 3 )CO a H, is formed when orthotoluic acid is heated to 170 with disulphuric acid; it forms microscopic needles, which are extremely soluble in water (Jacobsen and Wierss). Parasulphamido-orthotoluic acid, C 6 H 3 (S0 2 .NH 2 )(CH 3 )C0 2 H (4:2:1), is formed, together with the following compound, when orthoxylenesulphamide is oxidized with an alkaline solution of potassium permanganate. It is slightly soluble in cold, readily in hot water, and crystallizes in long needles, which melt at 217. Its potassium salt crystallizes in large, compact rhombohedra. Metasulphamido-orthotoluic acid (4 : 1 : 2) is less soluble in hot water than the isomeric acid, and forms long, brittle needles, melting at 243. Its potassium salt is extremely soluble, and can only be obtained in a crystalline state by exposing its concentrated solution over sulphuric acid for a long time. 1 2223 Metatoluic acid is obtained by the oxidation of metaxy- lene with nitric acid 2 or potassium permanganate. 3 Richter prepared it from orthonitrotoluene by converting this into bromometatolunitril by heating with alcohol and potassium cyanide (p. 217), and treating the acid obtained from this with sodium amalgam and water. 4 It has also been obtained from mesitylene, or symmetric trimethylbenzene, by oxidizing this to uvitic acid, C 6 H 3 (CH 3 )(CO 2 H) 2 , and heating the calcium salt of the latter with half its weight of slaked lime to above the melting-point of lead. 5 In order to prepare it, metaxylene is heated to 130 150 for one or two days with a mixture of one volume of nitric acid and two volumes of water, and the product distilled with steam, isoph- thalic acid and nitro-compounds being left behind (Bruckner). Metatoluic acid is more readily soluble in water than its isomerides, and crystallizes, when its solution is rapidly cooled, in long, fine needles, while it is deposited on gradual evaporation in clear, well-formed prisms. It melts at 108 109, and readily sublimes. Calcium metatoluate, (C 8 H 7 O 2 ) 2 Ca + 3H 2 O, crystallizes in aggre- gates of lustrous needles, similar to those of calcium benzoate. 1 Jacobsen, Ber. Deutsch. Chcm. Gcs. xiv. 38. 2 Ahrens, Zcitschr. Chcm. 1869 ; 106 ; Tawildarow, Ber. Deutsch. Chein. Ges. iv. 410 ; Bruckner, ibid. ix. 405. 3 Schrbtter, KekuUs Org. Chcm. iii. 701. 4 Ber. Deutsch. Chem. Gcs. v. 424. 6 Bottinger and Ramsay, ibid. ix. 405. NITROMETATOLUIC ACIDS. 417 Ethyl mctatoluatc, C 8 H 7 O 2 .C 2 H 5 , is a liquid, which boils at 224-5 226-5 . 1 Metatoluyl chloride boils at 218 (Ador and Rilliet). Mctatolunitril, C 6 H 4 (CH 3 )CN, has been obtained by heating metatolyl mustard oil with copper dust as a liquid which smells like benzonitril, and is converted into metatoluic acid by heating with concentrated hydrochloric acid to 180 200 . 2 Chlorometatoluicacid, C 6 H 3 C1(CH 3 )CO 2 H (4:3: 1), is formed by boiling a-chlorometaxylene with chromic acid, 3 as well as by replacing the amido-group of amidometatoluic acid by chlorine. 4 It is only very slightly soluble in water, and sublimes in dazzling white needles, which melt at 209 210. a-Bromometatoluic acid, C 6 H 3 Br(CH 3 )C0 2 H (4:3: 1), is obtained by the oxidation of bromometaxylene 5 and of a-bromo- isocymene, 6 as well as, together with the /3-acid, by the bromina- tion of metatoluic acid. 7 It separates from hot alcohol as a crystalline powder or in small thick prisms, which melt at 209 210. ft-Bromometatoluic acid (4:1:3) is formed by the oxidation of /3-bromo-isocymene, and separates from hot glacial acetic acid as a faintly lustrous, crystalline powder, melting at 152 153 . 8 Nitrometatoluic acids, C 6 H 3 (N0 2 )(CH 3 )C0 2 H. Two of these are formed by the nitration of metatoluic acid, 9 and both the others by the oxidation of the corresponding nitrometaxylene, 10 while the third has also been obtained by the oxidation of nitro- isocymene : n NO 2 CH 3 CO 2 H Melting-point. a) 4 : 1 : 3 compact prisms ...... 219 /?) 2 : 1 : 3 compact prisms 182 7) 6 : 1 : 3 lustrous needles or crystalline powder . . 214 8) 5 : 1 : 3 silky needles 167 1 Ador and Rilliet, Bcr. Deutsch. Chem. Gcs. xii. 2300. 2 Weith and Landolt, ibid, viii. 719. 3 Volrath, Ann. Chem. Pharm. cxliv. 266 ; Jacobsen, Ber, Deutsch. Chem. Ges. xviii. 1760. 4 Beilstein and Kriisler, Ann. Chem. Pharm. cxliv. 181. 5 Fittig, Ahrens and Mattheides, ibid, cxlvii. 32. 6 Kelbe, Ber. Deutsch. Chem. Ges. xv. 39. 7 Jacobsen, ibid. xiv. 2351. 8 Kelbe and Czarnomski, Ann. Chem. Pharm. ccxxxv. 291. 9 Jacobsen, Ber. Deutsch. Chem. Ges. xiv. 2353. 10 Kreusler and Beilstein, loc. cit. ; Remsen and Kuhara, Amer. Chem. Journ. iii. 424 ; Thol, Ber. Deutsch. Chem. Ges. xviii. 359. 11 Kelbe and A\ r arth, Ann. Chem. Pharm. ccxxi.,161. 418 AROMATIC COMPOUNDS. Amidometatoluic acids, C 6 H./NH 2 )(CH 3 )CO 2 H, have been prepared by the reduction of the first three nitro-acids with tin and hydrochloric acid : Melting-point. NH 2 CH 3 C0 2 H a) 4 : 1 : 3 long, thin, colourless plates . 172 /3) 2 : 1 : 3 small, flat prisms 132 7) 6 : 1 : 3 long needles 167 a-Sulphamidomctatoluic acid, C 6 H 3 (SO 2 .NH 2 )(CH 3 )C0 2 H (4:3: 1), is formed when a-metaxylenesulphamide is oxidized with chromic acid or potassium permanganate ; it crystallizes from hot water in long needles, melting at 254 . 1 v-Sulphamidometatoluic acid (2:3:1) has been obtained by the oxidation of v-metaxylenesulphamide, and forms crystals which melt at 202 203 (Jacobsen). 2224 Paratoluic acid was prepared by Noad in 1847 by the oxidation of cyrnene, CH 3 .C 6 H 4 .C 3 H 7 , with nitric acid ; 2 it is formed in this way from many other hydrocarbons which con- tain two side-chains in the para-position, such as paramethyl- ethylbenzene, 3 paraxylene, 4 &c. The latter is also converted into the acid by the action of potassium permanganate 5 and of chromyl chloride. 6 Oil of turpentine and its isomerides, which must be looked upon as dihydroxycymenes, and various deriva- tives of these are also oxidized to paratoluic acid by dilute nitric acid. 7 Kekule obtained it synthetically by the action of carbon dioxide on a mixture of sodium and parabromotoluene, 8 while Wurtz obtained the ethyl ether by employing ethyl chloro-car- bonate. 9 It has also been synthetically prepared by many of the reactions previously mentioned (Part III., p. 30). The cymene which is contained in Roman cumin oil and which can easily be obtained from camphor, is employed as the starting point in the preparation of the acid. It is heated for a con- siderable time in an apparatus connected with an inverted con- denser with a mixture of 1 vol. of nitric acid of spec. gr. T38 1 lies and Remsen, Ber. Deutsch. Chem. Ges. x. 1044 ; xi. 229 and 88 ; Jacobsen, ibid. xi. 895 ; Coale and Remsen, Amer. Chem. Journ. iii. 205. 2 Chem. Soc. Mem. iii. 425. 3 Jannasch and Dieckmann, Ber. Deutsch. Chem. Ges. vii. 1514. * Yssel de Schepper and Beilstein, Ann. Chem. Pharm. oxxxvii. 306. s Berthelot, Bull. Soc. Chim. vii. 134. 6 Carstanjen, Ber. Deutsch. Chem. Ges. ii. 635. 7 Hirzel, Zeitschr. Chew. 1866, 205 ; Miclk, Ann. Clicm. Pharm. clxxx. 49 J Hempel, ibid, clxxx. 74 ; Kcibig, ibid. cxcv. 106. 8 Ibid, cxxxvii. 184. Ibid. Suppl. vii. 127. PARATOLUIC ACID. 419 and 4 vols. of water, then neutralized with caustic soda and boiled in order to remove unattacked cymene and nitro-products. It is then precipitated with hydrochloric acid and the precipitate freed from nitroparatoluic acid, &c., by boiling with tin and hydrochloric acid. The product always contains terephthalic acid, which remains behind on treatment with water. The paratoluic acid is finally purified by distillation with steam. 1 It crystallizes in needles, which are slightly soluble in cold, more readily in hot water, and very readily in alcohol and ether; it melts at 180, boils at 274 275 , 2 and is readily volatile with steam. It is converted into terephthalic acid by oxidation. All its salts are soluble in water. Calcium paratoluate, (C 8 H 7 O 2 ) 2 Ca + 3H 2 O, crystallizes from hot water in dazzling white needles, which resemble those of calcium benzoate. Methyl paratoluate, C 8 H 7 2 .CH 3 , forms crystals which have a very pleasant, penetrating odour; it melts at 32 and boils at 217 (Fischli). Ethyl paratoluate, C 8 H 7 O. 2 .C 2 H 5 , is a liquid, which boils at 228, has a bitter taste and a smell resembling that of ethyl benzoate (Noad). Phenyl paratoluate, C 8 H 7 O 2 .C 6 H 5 . When paratoluyl chloride is heated with sodium salicylate, a viscid mass of paratoluyl- salicylic acid, CH 3 .C 6 H 4 CO.OC 6 H 4 .C0 2 H, resembling turpentine, is formed and decomposes into phenyl paratoluate and carbon dioxide on distillation with lime. It forms white plates, which have a nacreous lustre, smell like the geranium and melt at 71 72. 3 Paratoluyl chloride, CH 3 .C 6 H 4 .COC1, is a strongly refractive liquid, boiling at 218. 4 Paratoluamide, CH 3 C 6 H 4 .CO.NH 2 , crystallizes from hot water in needles or plates, which melt at 151 (Fischli). Paratoluylamido-acetic acid, CH 3 .C 6 H 4 .CO.NH.CH 2 .C0 2 H, which is also called toluric acid, occurs in the urine after the administration of paratoluic acid. It is slightly soluble in cold, readily in hot water and alcohol, and crystallizes in nacreous plates or rhombic tablets, which melt at 1GO 165, and are 1 Dittmar and Kekule, Ann. Chcm. Pharm. clxii. 339 ; Bruckner, ibid. ccv. 113. 2 Fischli, Bcr. Deutsch. Chcm. Ges. xii. 615. 3 Kraut, Chem. Centralbl. 1859, 84. * Cahours, Ann. Chem. Pharm. cviii. 316 ; Bruckner, ibid. ccv. 114 ; Ador and Rilliet, Ber. Dcutsch. Chcm. Ges. xii. 2298. 420 AROMATIC COMPOUNDS. decomposed into paratoluic acid and amido-acetic acid by con- tinued boiling with hydrochloric acid. 1 Schultzen and Naunyn, after taking coal-tar xylene, found in the urine a toluric acid, which did not crystallize but was only obtained as a colourless liquid ; 2 this substance probably con- sists entirely or chiefly of the meta-compound. Paratolunitril, CH 3 .C 6 H 4 .CN, is best prepared by distilling paratoluic acid with potassium thiocyanate (Part III., p. 197). It is a powerfully refractive liquid, smelling like benzonitril, boils at 217'8 and solidifies at a low temperature to a mass, which melts at 28'5. 3 Chloroparatoluic acid, C 6 H 3 C1(CH 3 )CO 2 H (3:4: 1), is formed by the oxidation of chlorocymene, C 6 H 3 C1(CH 3 )C 3 H 7 , with dilute nitric acid. 4 It is slightly soluble in hot water, readily in alcohol, and crystallizes in large plates melting at 194 196. a- Bromoparatoluic acid, C 6 H 3 Br(CH 3 )CO 2 H (3:4: 1), has been obtained by the oxidation of orthobromocymene, 5 bromethyl- methylbenzene, 6 and bromoparaxylene, 7 and is also formed when paratoluic acid is allowed to stand in contact with dry bromine. 8 It is almost insoluble in cold, slightly soluble in hot water and readily in alcohol, crystallizing in needles, which melt at 204. (3 -Bromoparatoluic acid, which is formed by the oxidation of metabromocymene, crystallizes from alcohol in plates melting at 196 , 9 Dibromoparatoluic acid, C 6 H 2 Br 2 (CH 3 )C0 2 H (3:6:4:1), is obtained by oxidizing solid dibromoparaxylene with a solution of chromium trioxide in acetic acid. It is only very slightly soluble in water, and crystallizes from alcohol in stellate aggregates of needles, which melt at 195 . 10 lodoparatoluic acid, C 6 H 3 I(CH 3 )C0 2 H, was obtained by Griess together with amidoparatoluic acid, by the action of hydriodic acid on diazo-amidotoluic acid, it is slightly soluble in water, readily in alcohol, and crystallizes in white, plates or needles. 1 Kraut, Ann. Chem. Phrt.rm. xcviii. 360. 2 Zeitschr. Chem. 1868, 29. 3 Paterno and Pisati, JSor. Deutsch. Chem. Ges. viii. 441 ; see also Volrath, ZeUschr. Chem. 1866, 489 ; Hofmann, Ann. Chem. Pharm. oxlii. 126 ; Merz, Zeitschr. Chem. 1868, 33 ; Weith, Ber. Deutsch. Chem. Ges. vi. 421. 4 Kekule and Fleischer, ibid. vi. 1090 ; v. Gerichten, ibid. x. 1250 ; xi. 368. 6 Landolph, Bcr. Deutsch Chem. Ges. v. 268. e Fittica, Ann. Chem. Fharm. clxxii. 312. 7 Morse and Remsen, Ber. Deutsch. Chem. Ges xi. 225. 8 Jannasch and Dieckmann, Ann. Chem. Pharm. clxxi. 83. 9 Kelhe and Koschnitzky, ibid. xix. 1730. i0 Schultz, ibid, xviii. 1762. NITROPARATOLUIC ACIDS. 421 a-Nitroparatoluic acid, C 6 H 3 (NO 2 )(CH 3 )CO 2 H (3:4:1), is formed by the action of fuming nitric acid on cymene 1 or paratoluic acid. 2 It is slightly soluble in cold, more readily in hot water and readily in alcohol, from which it crystallizes in light yellow, monoclinic prisms, which melt at 189 190. (S-Nitroparatoluic acid (2 : 4 : 1) is obtained by the oxidation of liquid nitrocymene with chromic acid solution (Landolph, Fittica). It is scarcely soluble in cold, slightly in hot water, and only with difficulty in alcohol, crystallizing in small plates or needles, which sublime without melting when heated. Accord- ing to Widmaii and Bladin, the so-called liquid nitrocymene consists chiefly of paratolylmethylketone, 3 and the acid prepared from it is therefore probably not a nitrotoluic acid. ft-Nitroparatolunitril, C 6 H 3 (NO 2 )(CH 3 )CN, is obtained by heating the diazo-compound of metanitroparatoluidine with potassium cuprocyanide ; it melts at 99 100. 4 a-Amidoparatoluic acid, C 6 H 3 (NH 2 )(CH 3 )CO 2 H (3:4:1), is tolerably soluble in water and crystallizes in hair-like needles, which melt at 164 165 (Ahrens). C0 2 H, is formed by the action of nitrogen trioxide on an alcoholic solution of the amido-acid. It forms yellow microscopic prisms, which are insoluble in water and alcohol, and is decomposed by the haloid acids with formation of substituted toluic acids. 5 Sulphoparatoluic acid, C 6 H 3 (SO 3 H)(CH 3 )CO 2 H (2:1: 4), has been prepared by the action of sulphur trioxide on paratoluic acid, 6 and by the oxidation of thiocymene, C 6 H 3 (SH)(CH 3 )C 3 H 7 7 and cymene-orthosulphonic acid. 8 It crystallizes in small plates which contain two molecules of water and are stable in the air. Sulphamidoparatoluic acid, C 6 H 3 (S0 2 .NH 2 )(CH 2 )CO 2 H, is formed by the oxidation of paraxylenesulphamide 9 or cymene- sulphamide, 10 and crystallizes from hot water in long needles which melt at 167 . 11 1 Noad, Chem. Soc. Mem. iii. 431 ; Ahrens, Zeitschr. Cham. 1869, 102 ; Landolph, Ber. Deutsch. Chem. Ges. vi. 936 ; Fittica, ibid. vi. 938. 2 Ann. Chem. Pharm. clxviii. 250. 3 Ber. Deutsch. Chem. Ges. xix. 584. 4 Leukart, ibid. xix. 417. 5 Griess, Ann. Chem. Pharm. cxvii. 58. 6 Fischli, Ber. Deuttch. Chem. Ges. xii. 615. 7 Flesch, ibid. vi. 478 ; Bechler, Journ. PraU. Chem. [2] viii. 170. 8 Remsen and Burney, Amer. Chem. Journ. ii. 405 ; Baur and Meyer, Ann. Chem. Pharm. ccxx. 18. 9 Ahrens, Zeitschr. Chem. 1869, 102 ; Landolph, Ber. Deutsch. Chem. Ges. vi. 936 ; Fittica, ibid. vi. 938. 10 Ann. Chem. Pharm. clxviii. 250. 11 lies and Remsen, Ber. Deutsch. Chem. Ges. xi. 230 ; Hall and Remsen, ibid. xii. 1433. 258 422 AROMATIC COMPOUNDS. HYDROXYTOLUALDEHYDES, C 6 H 4 (OH)(CH 3 )COH. 2225 These compounds are formed when the cresols are heated with caustic soda solution and chloroform, homosalicyl- aldehydes being formed, which are volatile with steam. Ortho- and meta-cresol also yield homologues of parahydroxybenz- aldehyde, which are not volatile with steam, but this is not the case with paracresol, since in the chloroform reaction the alde- hyde-group always takes up either the ortho- or para-position with respect to the hydroxyl. 1 Parahomosalicylaldehyde or Orthohydroxymetatohialdehyde (COH : OH : CH 3 = 1 : 2 : 5) is slightly soluble in water, readily in alcohol, and crystallizes from dilute alcohol in six-sided plates which have a nacreous lustre, and melt at 56. It boils at 217 218, has a powerful, almost repulsive aromatic odour, and gives a deep blue colouration with ferric chloride. It is converted by the action of water and sodium amalgam into homosaligenin or ortlwhydroxymetaxylyl alcohol, C 6 H 3 (OH) (CH 3 )CH 2 .OH, which crystallizes from hot water in lustrous plates, melts at 105 and, like saligenin, gives a deep blue colouration with ferric chloride. OrtJiohomosalicylaldehyde or Orthohydroxymetatolualdehyde (1 : 2 : 3) is an oily liquid, which has a smell resembling both salicyl- aldehyde and oil of bitter almonds, solidifies on cooling to crystals which melt at 17, and gives a bluish colouration with ferric chloride. Metahomosalicylaldehyde or Orthohydroxyparatolnaldehyde (1 : 2 : 4) forms crystals, which melt at 54 and have a pleasant aromatic odour. It boils at 222 223 and gives a violet colouration with ferric chloride, Orthohomoparahydroxylenzaldeliyde or Parahydroxymetatolu- aldehyde (1:4:3) crystallizes from hot water in pointed prisms, which occur chiefly in twinned forms, resembling gypsum. It melts at 115 and gives a bluish violet colouration with ferric chloride. Metahomopardhydroxybenzaldehyde or ParahydroxyortTiotolu- aldehyde (1:4:2) crystallizes in lustrous plates, melts at 110 and gives a light rose-red colouration with ferric chloride. 1 Tiemann and Schotten, Bcr. Dcutsch. Chem. Ges. xi. 770. HYDROXYTOLUIC ACIDS. 423 Menyanthol, G 8 H 8 O. An amorphous substance, called meny- anthin, C 30 H 46 O 14 , which has an intensely bitter taste, occurs in the common buckbean (Menyanthes trifoliata) and is decom- posed by heating with dilute sulphuric acid into grape sugar and menyanthol. This substance is a liquid which smells like benzaldehyde, reduces ammoniacal silver solution, and is con- verted into a crystalline acid on exposure to the air or on fusion with caustic potash. 1 It is probably identical with orthohomo- salicylaldehyde. HYDROXYTOLUIC ACIDS, C 6 H 3 (OH)(CH 3 )C0 2 H. 2226 Kolbe and Lautemann, after finding that salicylic acid is formed by the action of carbon dioxide on a mixture of phenol and sodium, prepared its homologue, cresotic acid, from the cresol which boils at 120 . 2 The three cresotic acids were then pre- pared from the isomeric cresols, 3 and, on account of their similarity to salicylic acid, were also called homosalicylw acids. Ihle has shown that, like their lower homologue, they may be obtained by passing carbon dioxide over the heated sodium cresols. 4 These compounds and the other hydroxytoluic acids, the ten of which are all known, are also formed by reactions similar to those employed for the preparation of the hydroxybenzoic acids and other hydroxy-acids (Part III., p. 32). The dimethyl ethers, C 6 H 3 (CH 3 )(OCH 3 )CO 2 .CH 3 , are formed by heating the acids with caustic potash and methyl iodide, and these are converted by saponification into the methoxytoluic acids, C 6 H 3 (CH 3 )(OCH 3 )CO 2 H. 5 The numbers appended in brackets give the position of the side chains in the order C0 2 H : OH : CH 3 . Parahomosalicylic acid, a-Cresotic acid or a-OrtJiohydroxymeta- toluic add (1:2:5), may be obtained, in addition to the methods just described, by fusing ^-metaxylenol 6 or /3-bromometatoluic acid 7 with caustic potash, by the action of nitrous acid on the Kromayer, Jahresb. Chem. 1861, 749. Ann. Chem. Pharm,. cxv. 203. Engelhardt and Latschinow, Zeitschr. Chem. 1869, 622 ; Biedermann, Ber. Deutsch. Chem. Ges. vi. 325 ; Kekule, ibid. vii. 1006. Journ. Prakt. Chem. [2] xiv. 454. Schall, Ber. Deutsch. Chem. Ges. xii. 822. Jacobsen, ibid. xi. 374. 7 Ibid. xiv. 2347. 424 AROMATIC COMPOUNDS. amidometatoluic acid which melts at 172 , 1 and by heating para- cresol with caustic soda and tetrachloromethane. 2 It crystallizes from hot water in very long needles or rhombic prisms, melting at 151, and is readily volatile with steam. Its aqueous solution is coloured an intense violet-blue by ferric chloride ; it decom- poses into paracresol and carbon dioxide when heated to 180 with hydrochloric acid, while a remarkable reaction occurs when its calcium salt is heated with lime, orthocresol being formed (Jacobsen). Methylparahomosalicylic acid forms long, thin needles, melting at 67. Orthohomosalicylic acid, j3-Cresotic acid, or v-OrtTioTiydroxymeta- toluic acid (1 : 2 : 3) is also formed by fusing v-sulphamidometa- toluic acid with caustic potash 3 and by the action of nitrous acid on the amidometatoluic acid melting at 132 (Jacobsen). It crystallizes from hot water in long, flat needles, which melt at 163 164. It decomposes into orthocresol and carbon dioxide when heated with hydrochloric acid to 210 ; ferric chloride colours its aqueous solution deep violet. Methylorthoh&niosalicylic acid crystallizes in feathery needles and melts at 81. a-Metaliomosalicylic acid, y-Oresotic acid, or Orthohydroxypara- tduic acid (1 : 2 : 4) is also obtained by fusing paraxylenol with caustic potash (Jacobsen), and, together with metahomopara- hydroxybenzoic acid, when metacresol is heated with tetrachloro- methane and caustic soda (Schall). It crystallizes from water in needles and from alcohol in monoclinic prisms, which melt at 177 , 4 and are volatile with steam. On heating with hydro- chloric acid to 170, it decomposes into metacresol and carbon dioxide ; ferric chloride produces a deep violet colouration in its aqueous solution. a-Methylmeiahomosalicylic acid crystallizes in plates, which melt at 103 104. /3-Metahomosalicylic acid (1:2:6) has been obtained from /3-bromorthotoluic acid. It is slightly soluble in cold, readily in hot water, very freely in alcohol, crystallizes in long needles, melting at 1(58, and is tolerably volatile with steam. Its solution is coloured a deep blue-violet by ferric chloride; 1 Ber. Deutsch. Chcm. Ges. xiv. 2352. ; Panaotovi6, Journ. PraU. Cliem. [2] xxxiii. 63. 2 Schall, ibid. xii. 821. 3 Ber. Deutsch. Chcm Ges. xi. 902. 4 Oppenheimer and Pfiiff, ibid. viii. 889. PARAHOMOMETAHYDROXYBENZOIC ACID. 425 on heating to 200 with concentrated hydrochloric acid, it decomposes into metacresol and carbon dioxide. 1 2227 Parahomometahydroxy~benzoic acid or Metahydroxyortho- toluic acid (1:5: 2) is formed by fusing metasulphamido-ortho- toluic acid, 2 a-bromorthotoluic acid, 3 or the chlororthotoluic acid melting at 166 , 4 with caustic potash, and from /3-amidortho- toluic acid by means of the diazo-reaction. 5 It is slightly soluble in cold, readily in hot water, crystallizes in transparent prisms, which melt at 172 and sublime in needles, and is also volatile with steam. Ferric chloride, added to its cold saturated solution or to that of its ammonium salt, produces a light brown precipitate soluble in a large quantity of hot water. It is not attacked by concentrated hydrochloric acid even at 220. Metahomometahydroxybenzoic acid or s-Hydroxytoluic acid (1:3: 5). Fuming sulphuric acid converts metatoluic acid into two isomeric sulphonic acids, which yield a mixture of symmetric hydroxymetatoluic acid and parahomosalicylic acid on fusion with caustic potash ; the latter may be removed by distillation with steam, while the former differs from all its isomerides in not being volatile. Symmetric hydroxytoluic acid is tolerably soluble in cold, readily in hot water, and crystallizes in fascicular aggregates of needles, which melt at 208; it solidifies to hard, transparent prisms and sublimes in stellate groups of needles. Solutions of the acid and of its salts give a fawn-coloured precipitate with ferric chloride, which dissolves in a large excess of the reagent, forming a dark brown solution. It is not attacked by concentrated hydrochloric acid at 230, and yields metacresol when distilled with lime. 6 s-Trinitrohydroxytoluicacid, C 6 (N0 2 ) 3 (OH)(CH 3 )C0 2 H + H 2 O Warren de la Rue, by heating the colouring matter of cochineal with nitric acid, obtained nitrococcusic acid, which possesses the same composition as the trinitro-anisic acid prepared by Cahours, but is obviously not identical with it. 7 Gmelin states that it is isomeric with the latter and also with methyltrinitrosalicylic acid. 8 It differs from both of these by being dibasic, and Strecker on this account suggested that it might be trinitrocresotic acid. 9 1 Jacobsen, Per. Deutsch. Chem. Ges. xvi. 1962. 2 Ibid. xiv. 38. 3 Ibid. xvii. 2375. 4 Kriiger, ibid, xviii. 1758. 5 Jacobsen and Wierss, ibid. xvi. 1959. 6 Jacobsen, ibid. xiv. 235.7. 7 Ann. Chem. Pharm. Ixiv. 23. 8 Handb. Org. Chem. iii. 398. 9 Lehrb. Org. Chem. v. Aufl. 727. 426 AROMATIC COMPOUNDS. Liebermann and Dorp found that it decomposes into carbon dioxide and trinitrometacresol when heated with water to ISO , 1 and therefore considered it to be a trinitro-derivative of the then unknown symmetric hydroxytoluic acid. After the dis- covery of the latter, Kostanecki and Niementowski showed that on solution in warm nitric acid it is converted into nitrococcusic acid. 2 It crystallizes from hot water in colourless, rhombic plates, which are yellow when not perfectly pure, and form a yellow solution in water which dyes animal fabrics and the skin an intense yellow. It melts with decomposition between 170 and 180, and detonates at a higher temperature. Its salts are soluble in water and detonate violently on heating. a-Orthohomometahydroxylenzoic acid or Metakydroxyparatoluic acid (1:3:4) is formed by fusing paratolulylsulphonic acid, 3 chloroparatoluic acid, bromoparatoluic acid 4 or sulphamidopara- toluic acid 5 with caustic potash, as well as by the action of nitrous acid on amidoparatoluic acid. 6 It crystallizes in long needles, melting at 206 207, is slightly soluble in cold, readily in hot water, and volatilizes with steam. Ferric chloride gives no colouration, and hydrochloric acid has no action upon it at 270. On distillation with lime it decomposes into orthocresol and carbon dioxide. j3-0rthohomometahydroxybenzoic acid (1:3:2) was obtained by Jacobsen from sulphorthotoluic acid. It crystallizes from hot water in long needles with a vitreous lustre, which melt at 183. are volatile with steam, and are not attacked by hydro- chloric acid at 200 210. It yields orthocresol on distillation with lime. Ferric chloride, added to an aqueous solution of the acid or one of its salts, produces a heavy, bulky, light brown precipitate. j3-Methylorthohomometahydroxybenzoic acid crystallizes in long, fine needles, and melts at 146 . 7 2228 Metahomoparahydroxybenzoic acid or ParahydroxyortTio- toluic acid (1:4:2) is obtained by fusing the aldehyde with caustic potash. 8 It is also formed, together with a small quantity of metahomosalicylic acid, when metacresol is heated 1 Ann. Chem. Pharm. clxiii. 99. 2 Ber. Deutsch. Chem. Gcs. xviii. 250. 3 Flesch, ibid. vi. 481. 4 v. Gerichten, ibid. xi. 368. 5 Hall and Remsen, ibid. xii. 1433. 6 Fittica, ibid. vii. 927 ; v. Gerichten and Rossler, ibid. xi. 705. 7 Jacobsen, ibid. xvi. 1962. 8 Schrotten and Tiemann, ibid. xi. 778. DIHYDROXYTOLUALDEHYDES. 427 with tetrachloromethane and concentrated caustic soda solution, 1 and when parasulphamido-orthotoluic acid 2 or the chlorortho- toluic acid which melts at 130 3 is fused with caustic potash. It crystallizes from hot water in small needles which contain half a molecule of water of crystallization ; this is lost at 100 and the anhydrous residue then melts at 177 178. Ferric chloride produces no colouration, but gives a reddish brown precipitate with its salts, which dissolves in an excess of the reagent forming a dark -brown solution. On heating to 200 with hydrochloric acid it decomposes into carbon dioxide and metacresol. Methylmetahomoparahydroxybenzoic acid crystallizes in long needles and melts at 176. Orthohomoparahydroxybenzoic acid or Parahydroxymetatoluic acid (1 : 4 : 3) is formed by fusing the aldehyde, 4 a-sulphamido- toluic acid 5 a-bromometatoluic acid, 6 or chlorometatoluic acid 7 with caustic potash, and together with a small quantity of *orthohomosalicylic acid by heating orthocresol with tetrachloro- methane and caustic soda (Schall). It crystallizes from hot water in small needles, containing half a molecule of water, which is lost at 100; the anhydrous acid melts at 171 173, and is volatile with steam. Ferric chloride produces no coloura- tion; on heating with hydrochloric acid to 180 185 it decomposes into carbon dioxide and orthocresol. MetJiyltyrthohomoparahydroxybenzoic acid forms microscopic silky needles, melting at 192 193. DIHYDROXYTOLUALDEHYDES, C 6 H 2 (CH 3 )(OH) 2 CHO. 2229 Para-orsellinaldeJiyde,(CTLO : OH : OH : CH 3 = 1:2:4:6). This compound, which is also known as orcylaldehydc, is formed together with two orcendialdehydes, C 6 H(CH 3 )(OH) 2 (CHO) 2 , by heating orcinol with caustic potash and chloroform ; it crystallizes from hot water in fascicular or stellate aggregates of needles, which melt at 177 178. Its aqueous solution is coloured reddish brown by ferric chloride. 8 The constitution of this body 1 Schall, Bcr. Deutsch. Chem. Ges. xii. 819. - Jacobsen, ibid. xiv. 40. 3 Kriiger, loc. cit. 4 Schotten and Tiemann. 5 Jacobsen, ibid. xi. 897. 6 Jacobsen, ibid. xiv. 2351. 7 Ibid, xviii. 1760. 8 Tiemann and Helkenberg, ibid. xii. 999. 428 AROMATIC COMPOUNDS. has not been determined, but since resorcinol is converted by the above reaction into /2-resorcylaldehyde, in which the alde- hyde group takes the para-position with regard to one hydroxyl and the ortho-position to the other, this is probably also the case with orcylaldehyde. Metdhomomethoxysalicylaldehyde (1:2:3:5) has been obtained from creosol and chloroform, and forms an oily liquid, which possesses a smell resembling that of salicylaldehyde, and, like the latter, forms a deep yellow coloured solution in alkalis. Ferric chloride produces a deep green colouration. 1 DIHYDROXYTOLUIC ACIDS, CH 3 .C 6 H 2 (OH) 2 C0 2 H. 2230 In the year 1830, Heeren investigated the lichens Eocella tinctoria and Lecanora tartarea, which are employed in Holland for the manufacture of litmus and archil, and found in them a characteristic, colourless, crystalline substance, which is converted into a red dye by the united action of air and ammonia, and which he therefore named erythrin (e'pvS/oo?, red). On boiling with a solution of ammonium carbonate, it was con- verted into the amorphous erythrinbitter. In order to obtain erythrin in larger quantities, he extracted the lichens with alcohol, but found that the erythrin was thus converted into a similar substance, which was, however, unsuitable for the pre- paration of the dye, and which he named pscudoerythrin? He also found rocellic acid in the lichens which he examined (Pt. II. p. 289). Kane, however, obtained different results ; in extracting the lichens with hot alcohol he obtained erythrylin, insoluble in water, and a soluble crystalline compound, which is identical with pseudoerythrin and is not an accidental product, but one of the most important of the whole series. He therefore transferred the name erythrin to this substance and assumed that Heeren's erythrin was a mixture of erythrylin with other bodies. When its solution is exposed to the air, erythrinbitter or amarythrin is formed, and this converted after several months' exposure into crystalline tclerythrin, to which he gave this name in contradis- tinction to erythrylin, since the word reXo? denotes the end, and v\rj the beginning of the series. 3 1 Tiemann and Koppe, Ber. Deutsch. Chem. Gcs. xiv. 2026. 2 Schweigycr's Journ. lix. 313. 3 Phil. Trans. 1840, 273. DIHYDROXYTOLUIC ACIDS. 429 Schunck then investigated many varieties of Lccanora and Variolaria from the Vogelsberg, and found in them a crystalline compound, which, like Heeren's erythrin, is converted into a red dye by exposure to the air, but has a different composition, and which he therefore named lecanorin. 1 On boiling with baryta water, it decomposed into carbon dioxide and orcinol, which had already been prepared from these species of lichens by Robiquet, while on boiling with alcohol it was converted into Heeren's pseudoerythrin. 2 Eochleder and Heldt, who detected lecanorin in Everma Prunastri, showed that it is also converted into pseudo- erythrin by the action of hydrochloric acid and alcohol; the latter substance must therefore be looked upon as the ethyl ether of lecanorin, or as it is more suitably called, lecanoric acid. 31 This compound was then carefully examined by Schunck, 4 who also submitted the substances contained in Rocella tinctoria var. fuciformis from Madagascar and Angola to a new investiga- tion. The most important of these is erythric acid, which yields the colouring matter. This is so readily converted into the ethyl ether or pseudoerythrin by boiling with alcohol, that the latter is always obtained when the lichens are extracted with boiling alcohol. This compound has the same composition as ethyl-lecanoric acid, and appears to be identical with it a fact which admits of the simple explanation that erythric acid is a copulated compound of lecanoric acid and orcinol. On boiling with alcohol, orcinol is set free and the lecanoric acid combines with the ethoxyl residue. 5 Erythric acid is converted by boiling with water into picro- erythrin, the properties of which are not identical either with those of Heeren's erythrinbitter or of Kane's amarythrin ; they approach most closely to those of telerythrin. Stenhouse, who investigated a South American sample of Rocella tinctoria, found in it a-orsellic acid, which is decomposed by boiling with milk of lime or baryta into orcinol and a-orsellinic acid, while Schunck's lichen, which is E. Montagnei, contains erythric acid, which yields picroerythrin and erythrelinic acid, which is very similar to a-orsellinic acid. According to Schunck, picroerythrin is decomposed by boiling with an excess of lime or 1 Ann. Chem. PJiarm. xli, 157. 2 Ibid. xlv. 250. 3 Ibid, xlviii. 1. 4 Ibid. liv. 261. 6 Ibid. Ixi. 64. 430 AROMATIC COMPOUNDS. baryta into carbon dioxide and orcinol, but Stenhouse lias shown that crythroglucin is also formed. 1 Stenhouse also discovered a {3-orscllic acid in Eocella tinctoria from the Cape of Good Hope, but this was shown by Gerhardt, who was subsequently confirmed by Stenhouse himself, to be identical with the a -acid. In "Remarks on the Preceding Communication," Strecker observes : Stenhouse has made us acquainted with a series of acids which are of special interest, both on account of their similar properties and analogous reactions, and from the fact of their occurrence in the same plants. It is for this reason desirable that the changes undergone by these compounds should be represented by formulae, and for this purpose it is necessary to sub- stitute new expressions for some of the empirical formulae given by Stenhouse, since the former agree equally well with the experimental results and are also capable of representing the decompositions and reactions of the substances in question. a-Orsellic acid, then, is converted into two molecules of orsellinic acid, the elements of water being taken up : C 16 H 14 7 +H 2 = 2C 8 H 8 4 . The former can also form orcinol with loss of carbon dioxide : C 16 H 14 7 + H 2 = 2C 7 H 8 4 + 2C0 2 . The conversion of orsellinic acid into orcinol takes place with the separation of carbon dioxide : C 8 H 8 4 =C 7 H 8 2 +C0 2 . Erythric acid is resolved into picroerythrin and erythrelic acid, which is undoubtedly orsellinic acid : = C 12 H 16 7 + C 8 H 8 O 4 . Finally, picroerythrin decomposes into carbon dioxide, orcinol and erythroglucin : C 12 H 16 7 + H 2 = C0 2 + C 7 H 8 2 + C 4 H 10 4 . He adds that erythric acid can yield twice as much orsellinic acid as given by the equation, but Stenhouse considers this as improbable. In this case the formula of the former would be C 14 H 15 7 : 2 2C 8 H 8 4 + C 12 H 8 7 = 2C 14 H 15 7 + H 2 0. 1 Stenhouse, Phil Trans. 1848, 63. 2 Ann. Chem. Phann. Ixviii. 108. ERYTHRIN AND PICROERYTHRIN. 431 Gerhardt came to the conclusion that orsellic acid has the formula C 16 O U O 7 , and is identical with lecanoric acid, 1 while Schunck expressed the opinion that the ethyl' ether of orsellinic acid is identical with that of lecanoric acid, just as is the case with erythrin and pseudoerythrin. 2 Hesse then undertook a new investigation of these lichen substances. He ascertained that the Angola lichen, which comes into the market under many names, is Rocella fuciformis, and retained Heeren's name of erythrin for the chroniogen con- tained in it, since it scarcely possesses the properties of an acid. His analysis gave him results in accordance with Strecker's second formula, which, however, he doubled and wrote C 28 H 30 14 . The acid obtained from it by decomposition proved as Strecker had correctly foreseen, to be identical with orsellinic acid. 3 Stenhouse confirmed these observations, and adopted the same formula for erythrin, giving equations to explain its changes and decompositions, 4 but, in spite of this, Strecker's first formula has been shown to be correct. After it had been recognized that erythroglucin or erythrol as it is now called, is an alcohol, Berthelot suggested that erythrin is the orsellinic ether of this, and de Luynes has observed that it is in fact the di-acid ether of this alcohol, picro- ery thriii being the mono-acid derivative. 5 Orsellinic acid has proved to be a dihydroxytoluic acid, and the compounds in question have, therefore, the following constitution : Erythrin : CH 3 .C 6 H 2 (OH) 2 CO.(\ > 4 H 6 (OH) 2 . CH 3 .C 6 H 2 (OH) 2 CO.(X Picroerythrin : CH 3 .C 6 H 2 (OH) 2 CO.OC 4 H 6 (OH) S . Further investigations conducted by Hesse have finally decided that the archil lichens which occur in commerce consist chiefly of two species. Rocella fuciformis (Acharius) comprises those from Lima, Angola, Mozambique, Zanzibar and Ceylon; this contains erythrin alone, while Hocella tinctoria (De Candolle), 1 Compt. Rend. Chim. 1849, 127. 2 Phil. Mag. xxxiii. 249, 3 Ann. Chem. Pharm. cxvii. 297. 4 Proc. Roy. Soc. xii. 263. 5 Ann. Chem. Pharm. cxxxii. 355. 432 AROMATIC COMPOUNDS. which comes from Cape Verde and the neighbouring islands, contains a chromogen, lecanoric acid, 1 which is identical with orsellic acid. Stenhouse remarks on this point that the South American lichens examined by him are also Rocella tinctoria. They are sent into the market under the name of Valparaiso lichens, but are seldom exported to England, while the Lima lichens (Rocella fuciforniis) are sent there in large quantities. 2 Lecanor;c acid is monobasic and stands in the same relation to orsellic acid as glycollic acid to glycoglycollic acid : /OH CH 3 .C 6 H 2 (-OH \CO\ /O / CH 3 .C 6 H 2 ^-OH \C0 2 H. 2231 Orsellinic acid, CH 3 .C 6 H 2 (OH) 2 C0 2 H + H 2 O, is readily prepared from erythrin by heating it on the water bath with baryta water until barium carbonate commences to separate. A few drops of the solution are then tested with hydrochloric acid at short intervals, and as soon as a gelatinous precipitate is no longer formed, hydrochloric acid is added to the solution, the orsellinic acid being thus soon precipitated. It crystal- lizes from acetic acid in stellate aggregates of needles, and separates from dilute alcohol as a crystalline mass, which is readily soluble in water, becomes anhydrous at 100, and melts at 176, a gradual decomposition into carbon dioxide and orcinol accompanied by violent frothing, taking place. The same decomposition occurs on boiling with water or alkalis. Its aqueous solution is coloured purple-violet by ferric chloride, and gives an amorphous precipitate with an ammoniacal solution of lead acetate. Barium orsellinate, (C 8 H 7 4 ) 2 Ba, is extremely soluble in water, and crystallizes from dilute alcohol in hydrated prisms, which decompose even at 100 with formation of barium carbonate. Methyl orsellinate, C 8 H 7 4 (CH 3 ), is formed by boiling lecanoric acid (Schunck) or erythrin (Stenhouse) with methyl alcohol, and crystallizes in lustrous needles, or flat, pointed prisms, which 1 Ann. Chem. PJiarm cxxxix. 22. 2 Journ. Chem. Soc. v. 221. LECANORIC ACID. 433 are readily soluble in water. It dissolves in alkalis and is reprecipitated by acids. Ethyl orsellinate, C 8 H 7 4 (C 2 H 5 ). The formation of this ether, which was described by Heeren as pseudoerythrin, has been frequently referred to in the preceding pages. It is slightly soluble in cold, readily in hot water and alcohol, and crystallizes in needles or small plates, which melt at 132. Its aqueous solution is precipitated by lead acetate. Amyl orsellinate, CgHyO^CgHj,), is prepared by boiling erythrin with amyl alcohol. It is scarcely soluble in water, readily in alcohol and ether, from which it crystallizes in vitreous prisms, melting at 76 . 1 Orsellinic acid is decomposed by the action of bromine into carbon dioxide and tribromorcinol ; if, however, the substances are mixed in ethereal solution, substitution products are formed. Dibromorsellinic acid, C 8 H 6 Br 2 4 , is slightly soluble in hot water, readily in alcohol and ether, and crystallizes in small, white prisms ; its alcoholic solution is coloured a splendid dark blue by ferric chloride, and blood-red by bleaching powder (Hesse). Phosphorsellinic acid, C 40 H 36 P 4 O 24 . When orsellinic acid is gradually heated with phosphorus oxychloride to 90 100, the liquid becomes coloured brown, violet-green, and, finally, indigo- blue. If it be now allowed to drop into ice water, phosphorsellinic acid separates out, and may be purified by repeated solution in water and precipitation with hydrochloric acid or common salt. It is an amorphous, indigo-blue powder, which takes a cupreous lustre under strong pressure and readily forms deep blue solutions in water and alcohol. The solution in 20,000 parts of water has the colour of a concentrated solution of copper sulphate and a distinct violet colouration is visible when 50,000 parts of water are employed. It dissolves in alkalis, lime water and baryta water with a violet-red colour ; the salts of the heavy metals produce bluish violet, flocculent precipitates. Phosphor sellinanilide, C 40 H 34 (C 6 H 5 .NH) 2 P 4 O 22 , is formed by boiling the acid with aniline and alcohol ; it is a dark violet powder, which is insoluble in water, but forms a splendid violet solution in alcohol. 2 2232 Lecanoric acid or Diorsellinic acid, C 16 H 14 O 7 -f H 2 0, is, according to Hese, best prepared from the JR. tinctoria from Cape Verde. The lichens are extracted with ether, and the greenish 1 Hesse, Ann. Chem. Pharm. cxxxix. 22. 2 Schiff, ibid, ccxxviii. 56. 434 AKOMATIC COMPOUNDS. white, crystalline residue left after the evaporation of the ether dissolved in milk of lime, filtered, precipitated with sulphuric acid and crystallized from alcohol. It is scarcely soluble in cold water, but dissolves in 2,500 parts of boiling water, more readily in alcohol and ether, and crystallizes in needles or prisms, which become anhydrous at 100, melt at 153, and simultaneously decompose with evolution of carbon dioxide. The alcoholic solution is coloured dark purple-red by ferric chloride and is not precipitated by lead acetate ; copper acetate, however, produces a pale, apple-green precipitate on standing (Schunck). It reduces ammoniacal silver solution on heating, and is converted on boiling with water into orsellinic acid, and with alcohol into its ether. Barium lecanorate, (C 16 H 13 O 7 ) 2 Ba, separates from hot alcohol in small, star-shaped aggregates of needles. Substitution products are formed by the action of bromine on an ethereal solution : Melting- point. Dibromolecanoric acid, C 16 H 12 Br 2 7 , small white prisms . 179 Tetrabromolecanoric acid, C 16 H 10 Br 4 O 7 , pale yellow prisms 157 Both these bodies evolve carbon dioxide on fusion ; their alcoholic solutions are coloured purple-red by ferric chloride and blood-red by bleaching powder (Hesse). Erythrin, 2C 20 H 22 O 10 + 3H 2 O. In order to prepare this sub- stance, 1 part QtR.fuciformis is macerated for twenty minutes with 10 parts of milk of lime containing T6 per cent, of lime, filtered and precipitated immediately with hydrochloric acid. The re- sidue is treated a second time with milk of lime, which is then employed for the extraction of a new quantity of lichen. The precipitate is redissolved in milk of lime, the filtrate treated with carbon dioxide and the precipitated mixture of calcium carbonate and erythrin gently warmed with alcohol; hot water is then added to the solution until a permanent turbidity is produced. The erythrin separates on cooling in spherical crystalline masses, which become anhydrous at 100 and melt at 137. It is slightly soluble in cold water, with difficulty in ether, but readily in alcohol ; ferric chloride added to the alcoholic solution produces a purple-violet colouration, which changes on further addition to a brownish red precipitate. Picroerythrin, C 12 H 16 O 7 + 3H 2 O, is the first product of the decomposition of erythrin by boiling water, alcohols or alkalis, EVERNIC ACID. 435 When erythrin is dissolved in milk of lime it decomposes in the course of a day or two with formation of picroerythrin, which is also obtained pure when erythrin is boiled for some hours with amyl alcohol. It crystallizes in silky prisms, which readily effloresce, melt at 158 and have a slightly sweet and intensely bitter taste. It is exceptionally soluble in hot water and under- goes no change when boiled with absolute alcohol. Ferric chloride produces a purple-violet colouration. 2233 In connection with these compounds, the following, which are to some extent homologous with them, may be mentioned here. Evernic acid, C 17 H 16 7 . According to Rochleder and Heldt, lecanoric acid occurs in Evernia Prunastri ; Stenhouse, how- ever, could not detect it in lichens grown in Scotland, but found in them evernic acid, together with usnic acid, C 18 H 18 7 , thus proving either that the German and Scotch lichens contain different compounds, or, what is much more probable, that the German chemists had not investigated the true Evernia Pru- nastri, 1 a view which is supported by the fact that Hesse, who examined this lichen collected in various parts of Germany, always found evernic acid in it. 2 It is almost insoluble in water, but dissolves easily in alcohol, and crystallizes in spherical aggregates of needles, which melt at 164. Everninic acid, C 9 H 10 4 , is formed, together with carbon dioxide and orcinol, when evernic acid is boiled with lime water or baryta water. It is tolerably soluble in hot water, readily in alcohol, and crystallizes in flat, lustrous needles, resembling those of benzoic acid. It melts at 159, and on further heating emits a penetrating odour and yields a colourless sublimate. Ferric chloride colours the aqueous solution violet. Barlalic acid, C 19 H 20 O 7 . This substance, which stands in the same relation to homorcinol (p. 402) as evernic acid to orcinol, occurs with usnic acid in Usnea larbata. It crystallizes from benzene in long plates, needles, or short prisms, which melt at 168, and decompose at a higher temperature with evolution of carbon dioxide and formation of homorcinol. 3 ^Erythrin or Homo-ery C 4 H 6 (OH) 2 . N . o / Picrorocellin, C 27 H 29 N 3 O 5 , was found along with erythrin by Stenhouse and Groves in a variety of R. tinctoria which pro- bably came from western Africa. It is insoluble in water, tolerably soluble in hot alcohol, and crystallizes in long, lus- trous prisms, which melt at 192 194, and have an intensely bitter taste. On oxidation with chromic acid, benzoic acid is obtained together with a liquid smelling like benzaldehyde. On dry distillation it yields water, ammonia, and xanthorocellin, C 21 H 17 N 2 O 2 , which is also obtained by heating picrorocellin with dilute acids, and crystallizes from alcohol in long, yellow needles, melting at 183 . 1 2234 Para-orsellinic acid, C 6 H 2 (CH 3 )(OH) 2 C0 2 H + H 2 0, is prepared by heating orcinol with 4 parts of ammonium car- bonate and 4 parts of water for 10 15 hours to the boiling- point of amyl alcohol, 2 or by passing carbon dioxide over the potassium compound of orcinol at 250 260 . 3 It crystallizes from dilute alcohol in fine, hard needles, which dissolve in about 660 parts of cold water ; the solution is coloured blue by ferric chloride. On heating the acid it loses water at 100 and commenees to melt at about 150 with evolution of carbon dioxide, which is also given off when the acid is simply boiled with water ; on dry distillation it decomposes completely with formation of orcinol. Barium para-orsellinate, (C 8 H 7 O 4 ) 2 Ba + 6H 2 O, crystallizes in four-sided tablets, which are readily soluble in water. Paraphosphorsellinic acid is formed as a chromegreen powder by heating para-orsellinic acid with phosphorus oxychloride (p. 433). 1 Ann. Chem. Pharm. clxxxv. 14. * Brunner and Senhofer, Monatsh. xiii. 1643. 8 Schwarz, Ber. Deutsch. Chem. Oes. xiii. 1643. CRESORSELLINIC ACID. 437 Cresordnolcarloxylic acid, C 6 H 2 (CH 3 )(OH) 2 C0 2 H + H 2 O, is formed when cresorcinol is heated in a small flask with 4 parts of potassium 01 sodium bicarbonate for half an hour. It is slightly soluble in cold, readily in hot water and alcohol, and crystallizes in very long, thin, lustrous prisms, which lose their water at 100 and melt at 208 with decomposition. Its solution is coloured bluish violet by ferric chloride and is not precipitated by lead acetate. 1 Cresorsellinic acid, C 6 H 2 (CH 3 )(OH) 2 C0 2 H (1 :2:4:6), is pre- pared by fusing disulphorthotoluic acid with caustic potash. It is slightly soluble in cold, readily in hot water, and crystallizes in long, hard, vitreous needles, which melt at 245. It reduces ammoniacal silver solution on heating and Fehling's solution on boiling; its aqueous solution is coloured dark brown by ferric salts, a ferrous compound being formed. On heating with sulphuric acid the liquid assumes a splendid stable magenta colour ; water precipitates from it yellow flocks, which form an intense golden- yellow solution in alkalis. It therefore gives a similar reaction to that which is characteristic of the analogous a-resorcylic acid (p. 358). When it is heated to 220 225 with hydrochloric acid, dark flocks separate out, which form a reddish brown solution in alcohol ; on the addition of a little alkali, the liquid takes a splendid dark green fluorescence, which disappears when an excess of alkali is added, a deep purple-red solution being formed. Cresorcinol is formed when the acid is distilled with slaked lime. 2 Three carboxylic acids are derived from cresorcinol : C0 2 H C0 2 H C0 2 H OH/\OH OH The last of these expresses the constitution of cresorsellinic acid, which is a derivative of orthotoluic acid. The second probably represents that of cresorcinolcarboxylic acid, since the readiness with which it is formed supports the conclusion that the carboxyl takes up the same position in the nucleus in the case of cresorcinol as it does in the analogous formation of /8-resorcylic acid from resorcinol (p. 359). 1 Kostanccki, Ber. DeutscTi. CJiem. Gcs. xviii. 3202. 2 Jacobsen and Wierss, ibid. xvi. 1956. 259 438 AROMATIC COMPOUNDS. The constitution of para-orsellinic acid, and therefore that of orsellinic acid, follows from these considerations (Kostanecki) : Orsellinic acid. Para-orsellinic acid. CO 2 H CO 2 H OH 1 CH 3 OH. 2235 Homohydroxysalicylic acid, C 6 H 2 (CH 3 )(OH) 2 C0 2 H, is prepared by heating 40 grms. of toluquinol for thirty-six hours in a bath of oil of turpentine with 130 grms. of potassium bicarbonate, 110 ccs. of water, and 40 ccs. of a saturated solution of potassium sulphite. It dissolves in 1,366 parts of water at 8, more readily in hot water, and crystallizes from dilute alcohol in microscopic, acute rhombic plates, while, when prepared from the ammoniacal salt by precipitation with hydro- chloric acid, it separates as a crystalline powder containing half a molecule of water. Ferric chloride produces an azure-blue colouration, which passes into a beautiful green on standing or on the addition of an excess of the chloride ; it reduces Fehling's solution on warming, but a neutral silver solution in the cold. It is decomposed at 210 220 into carbon dioxide and toluquinol. 1 Barium homohydroxysalicylate, (C 8 H 7 4 ) 2 Ba + 2H 2 O, forms fine prismatic needles, readily soluble in water. Creosolcarboxylicacid, C 6 H 2 (CH 3 )(OCH 3 )(OH)CO 2 H (1:3:4:5). According to the researches of Kostanecki, only those phenols which contain hydroxyl groups in the meta-position are con- verted into carboxylic acids by boiling with the alkali bicar- bonates, and as creosol does not belong to this class of bodies, the corresponding acid is prepared by adding sodium, warming gently and passing in a current of carbon dioxide. Creosolcarboxylic acid crystallizes from a mixture of chloroform and benzene in concentrically arranged needles, which melt at 180 182 and sublime when carefully heated. It is readily soluble in alcohol, ether and chloroform, but only slightly in water and scarcely at all in benzene and petroleum ether ; its solution is coloured deep blue by ferric chloride. The barium salt crystallizes in small, anhydrous needles, which are only slightly soluble in water. 1 Brunner, Monatsh. Chem. ii. 458. XYLYLENE ALCOHOLS. 439 Methyl creosolcarloxylate, C 6 H 4 (CH 3 )(OCH 3 )(OH)C0 2 .CH 3 , forms small, rhombic prisms, melts at 92 and gives a bluish green colouration with ferric chloride. 1 ,CH 2 .OH XYLYLENE ALCOHOLS, C 6 H 4 < 2236 Orthoxylylene alcohol was first prepared by the action of sodium amalgam on a boiling solution of phthalyl chloride, C 6 H 4 .C 2 O 2 C1 2 (p. 458), in glacial acetic acid, and named phthal- alcohol. 2 It is also obtained by boiling its bromide with a solution of sodium carbonate 3 or potassium carbonate. 4 It is tolerably soluble in water, readily in alcohol, and crystallizes in rhombic tablets, which have a bitter taste and melt at 64*5. Concentrated sulphuric acid imparts to them a red colour and then converts them into a resinous mass. Potassium permanganate or chromic acid oxidize it to phthalic acid, while it is reduced to orthoxylene by heating with hydriodic acid and amorphous phosphorus. Orthoxylylene ethyl ether, C 6 H 4 (CH 2 OC 2 H 5 ) 2 , is obtained by boiling the bromide with alcoholic potash, and is a very pleasant- smelling, oily liquid, which boils at 247 249 (Leser). Orthoxylylene chloride, C 6 H 4 (CH 2 C1) 2 , is formed when ten ccs. of orthoxylene are heated to 190 with 35 grms. of phos- phorus pentachloride, 5 as well as by heating the alcohol with hydrochloric acid, and separates from ether in crystals, which melt at 54*8 and readily sublime. Its vapour attacks the eyes with great violence. Raymann, by the action of chlorine on boiling orthoxylene, obtained an isomeric substance, which crystallizes in tablets and melts at 103 . 6 These properties correspond with those of paraxylylene chloride, and the hydrocarbon employed by Ray- mann must have contained paraxylene, which is much more readily attacked by chlorine and bromine than its isomerides. This property can be made use of to detect even traces of paraxylene in the presence of the ortho- and meta- compounds ; the 1 Wende, Ber. Deutsch. Chem. Ges. xix. 2324. 2 Hessert, ibid. xii. 642. 3 Baeyer and Perkin, xvii. 122. 4 Colson, Ann. Chim. Phys. [6] vi. 104. 6 Colson and Gautier, Bull. Soc. Chim. xlv, 6 : Colson, Ann. Chim. Phys. [6] vi. 108. 6 Bull. Soc. Chim. xxvi. 553. 440 AROMATIC COMPOUNDS. mixture is treated at the boiling point with sufficient bromine to form the monobromo-derivatives ; any paraxylene present is converted into paraxylylene bromide, which separates out on cooling. 1 Orthoxylylene bromide, C 6 H 4 (CH 2 Br) 2 is obtained when or- thoxylene is heated with the calculated quantity of bromine to 150 155, or when the latter is allowed to drop into the boil- ing hydrocarbon, the temperature being gradually raised to 180. It is also formed when orthoxylene is treated with bromine in the sunlight, 2 and crystallizes from chloroform in splendid, rhombic pyramids, which melt at 94'9, and dissolve in 5 parts of ether. Orthoxylylene iodide, C 6 H 4 (CH 2 I) 2 , is prepared by heating the alcohol with phosphorus and hydriodic acid, and crystallizes from ether in splendid, well-formed yellowish prisms, melting at 109 110. 3 Orthoxylylene acetate, C 6 H 4 (CH 2 O.CO.CH 3 ) 2 , is formed by the action of acetyl chloride on the alcohol ; it is a crystalline mass, which melts at 37 and boils without decomposition. Orthoxylylene sulphide, C 6 H 4 \ ")S, is obtained by heating X / the bromide with an alcoholic solution of potassium sulphide, and is a colourless liquid which smells like mercaptan and solidifies in large crystals at about (Leser). Diphenylorthoxylylenediamine, C 6 H 4 (CH 2 .NH.C 6 H 5 ) 2 , is pre- pared by the action of aniline on the bromide. It crystallizes from alcohol in small plates, melting at 172, and dissolves in concentrated hydrochloric acid, but is reprecipitated by water. Metaxylylene alcohol, C 6 H 4 (CH 2 .OH) 2 . This compound, which is also known as isophthalalcohol, is prepared by heating the bromide with a solution of carbonate of potassium. It is readily soluble in water and separates from ether as an oily liquid, which solidifies to microscopic, twinned crystals, melting at 46 47.* ' Metaxylylene ethyl ether is obtained by heating the bromide with alcoholic potash, and is an oily liquid, which boils at 247 249, and is oxidized by chromic acid to isophthalic acid. 5 1 Radziszewski and Wispek, Ber. Dcutsch. Chem. Ges. xviii. 1279. 2 Schramm, ibid, xviii. 1272. 3 Leser, ibid. xvii. 1824. 4 Colson, Ann. Chim. Phys. [6] vi. 109. 5 W. H. Perkin, jun., Private communication. METAXYLYLENE CHLORIDE. 441 Metaxylykne chloride, C 6 H 4 (CH 2 C1) 2 , is prepared by heating the alcohol with hydrochloric acid (Colson); it is also formed when metaxylene is heated with phosphorus pentachloride, the yield being, however, very poor (Colson and Gautier). It crystallizes in pointed prisms, melts at 34 and boils at 250 255 . 1 Metaxylylene bromide, C 6 H 4 (CH 2 Br) 2 , forms long, prismatic needles, melting at 77, and is obtained by heating metaxylene with bromine (Colson, Radziszewski and Wispek), as well as by bringing these two substances together in the sunlight (Schramm). Paraxylylene alcohol, C 6 H 4 (CH 2 .OH) 2 , was prepared by Gri- maux by heating the chloride or bromide with 30 parts of water to 170 180, and was named tolly lene glycol. 2 It crystallizes in lustrous needles, which melt at 112 113, are readily soluble in water, alcohol and ether, and are converted by oxidation into terephthalic acid. Paraxylylene mono-ethyl ether, C 6 H 4 (CH 2 .OH)CH 2 .O.C 2 H 5 , is formed when the chloride is heated with alcoholic potash ; it is a pleasant-smelling liquid which boils at 250 252 . 3 Paraxylylene chloride, C 6 H 4 (CH 2 C1) 2 , is prepared by the action of chlorine on boiling paraxylene, 4 or by heating the alcohol with hydrochloric acid. It may also be obtained in a similar manner to the ortho-compound by heating paraxylene with phosphorus pentachloride (Colson and Gautier). It crystallizes )m alcohol in pointed, rhombic tablets, melts at 100 and >ils with decomposition at 240 250. Paraxylylene bromide, C 6 H 4 (CH 2 Br) 2 , is obtained by passing bromine vapour into paraxylene or by heating the alcohol with hydrobromic acid ; it boils at 240 250, and crystallizes from chloroform in plates, which melt at 143'5, 5 and dissolve in about >0 parts of ether. Paraxylylene iodide, C 6 H 4 (CH 2 I) 2 , is prepared by heating the ilcohol with hydriodic acid ; it forms fine needles, which melt it 170, and rapidly become coloured yellow in the air. Paraxylylene acetate, C 6 H 4 (CH 2 .O.CO.CH 3 ) 2 , is formed when the chloride is heated to 150 with an alcoholic solution of sodium acetate. It is readily soluble in alcohol and ether, and 1 Bull. Soc. Chim. xliii. 6. 2 Ann. Chem. Pharm. civ. 338. 3 Grimaux, Butt. Soc. Chim. xvi. 193. 4 Grimaux, Zcitschr. Chem. 1867, 381. 6 Radziszewski and Wispek, Ber. Dcutsch. Chem. Oes. xviii. 1280 ; Low, ibid, xviii. 2072. 442 AROMATIC COMPOUNDS. crystallizes from the latter in hard, lustrous plates, which have a pungent, camphor-like taste, and melt at 47. Paraxylylene monobenzoate, C 6 H 4 .(CH 2 .OCO.C 6 H 5 )CH 2 .OH, is obtained by heating the chloride with an alcoholic solution of sodium benzoate, and crystallizes in long, thin needles, melting at 73 74. HYDROXYMETHYLBENZOIC ACIDS, C0H 2237 These compounds are isomeric with the hydroxytoluic acids, from which they differ in being alcohols while the latter are phenols. Parahydroxymeihylbenzoic acid was prepared by Dittmar and Kekule, who named it oxymethylphenylformic acid, by heating paratoluic acid with bromine at 160 170, and boiling the product with baryta water. It crystallizes in white plates or flat needles, which are more readily soluble in water than para- toluic acid, melt a few degrees higher and sublime in feathery needles. 1 Orthohydroxymethylbenzoic acid was first prepared by Hessert, who named it " Benzolorthoalcoholsaure" by the action of alkalis on phthalide, which is its anhydride. Acids precipitate it as a fine powder, which is slightly soluble in cold water, readily in alcohol, has a strongly acid reaction, and melts at 118, being thus converted into the anhydride, which is also formed when the acid is simply boiled with water. Silver orthohydroxymethylbenzoate, C 8 H 7 O 3 Ag, crystallizes from water in small octohedra. Phthalide, C 8 H 6 O 2 , was obtained by Kolbe and Wischin, who prepared it by the action of zinc and hydrochloric acid on phthalyl chloride, C 8 H 4 2 C1 2 , and named it pJithalaldehyde, C 6 H 4 (COH) 2 . 2 It is also formed by the action of phosphorus and hydriodic acid on the chloride, 3 and when orthoxylidene chloride is boiled with water and lead nitrate. 4 Hessert has proved 1 Ann. Chem. Pharm. clxii. 337. 2 Zeitschr. Chem. 1866, 315. 3 Baeyer, Ber. Deutsch. Chem. Ges. x. 123. 4 Raymann, Bull. Soc. Chim. x. 1180. PHTHALIDE. 443 that it is not the aldehyde of phthalic acid but the anhydride or lactone of the preceding compound. 1 Its formation was explained by the following reactions : /COC1 /CH 2 .OH C 6 H 4 < + 4H = C 6 H 4 < + HC1. \COC1 \COC1 /CH 2 .OH X CH 2X C 6 H 4 < = C 6 H/ \0 + HCL \COC1 \CO/ It has since been shown that phthalyl chloride has not the constitution assumed above (p. 460), and the formation of phthalide is now represented much more simply : C 6 H 4 < + 4H = C 6 H >0 + 2HC1. \CO/ \CO/ This is confirmed by the observation of Hjelt,who found that it is also obtained when bromine is passed into orthotoluic acid heate'd to 140 ; the brominated acid which is first formed being decom- posed as follows : 2 C 6 H 4 =C 6 H 4 + HBr. \CO.OH \CO X It crystallizes from boiling water in needles which smell like cinnamon, melts at 73 and boils at 290 (Grabe). It does not combine with hydroxylamine, 3 gives no compounds with the acid sulphites of the alkalis and does not reduce ammoniacal silver solution (Hessert). It is oxidized to phthalic acid by alkaline permanganate, while it is reduced to orthotoluic acid on heating with phosphorus and hydriodic acid, and to orthoxylene together with a little toluene by heated zinc dust. Monobromoplithalide is formed by the action of bromine vapour on heated phthalide ; it crystallizes in plates, melting at 86, and is converted into phthalaldehydic acid (p. 447) when heated with water ; it has, therefore, the following constitution : 4 /CHBr C 6 H 4 < > O. \GO 1 Ber. Deutsch. Chem. Ges. x. 1445 ; xi. 237. 2 Ibid. xix. 412. 3 Lach, ibid. xvi. 1782. 4 Racine, ibid. xix. 778, 444 AROMATIC COMPOUNDS. Dibromoplitlialide, C 8 H 4 Br 2 O 2 , is obtained, together with dibromonaphthoquinone, by the oxidation of a-dibromo- naphthalene with chromic acid, and crystallizes from boiling alcohol in hard, white prisms, which sublime in needles and melt at 187'5 ; it does not reduce ammoniacai silver solution and only dissolves slowly in boiling caustic soda solution. 1 It has the following constitution : CBr HC C CH 2 I II >0. HC C CO CBr Guareschi obtained dichlorophthalide in a similar manner from dichloronaphthalene ; it resembles the bromine compound, and melts at 163 . 2 Hydrophthalide, C 8 H 8 O 2 , is formed together with phthalyl- pinacone, C 1C H 18 O 4 , by the action of sodium amalgam on an acid solution of phthalide, and is a syrupy mass, extremely soluble in all solvents ; it probably has the following constitution (Hessert) : X CH 2 C 6 H 4 < > O. X CH.OH Phthalimidine, C 8 H 7 NO, is obtained by heating phthalide with zinc ammonium chloride, or by treating it at its boiling- point with ammonia : /C O /C=:NH O + NH 3 = C 6 H 4 < > O + H 2 0. \CH It may be more simply prepared by the action of tin and hydrochloric acid on phthalimide, C 6 H 4 (C 2 O 2 )NH. It is readily soluble in alcohol and hot water, crystallizes in prisms or needles, melts at 150 and boils at 337. When sodium nitrite is added to its solution in hydrochloric acid, yellow needles of nitrosophthalimidine separate out; they melt at 156, 1 Guareschi, Ann. Chem. Pharm. ccxxii. 282. 2 Ber. Deutsch. Chem. Ges. xix. 1155. METHYLPHTHALIMIDINE. 445 and are rapidly converted into orthohydroxymethylbenzoic acid by the action of aqueous caustic soda : /C0 2 Na >0 + NaOH = C 6 H 4 <( + N 2 . \CH 2 .OH Hydrochloric acid precipitates either the free acid or phthalide from this solution according to the temperature, and the latter substance is in fact most conveniently prepared in this way from phthalimide, which can itself be readily obtained from phthalic acid. 1 Methylphthcdimidine, C 8 H 6 O(NCH 3 ), is formed by the action of tin and hydrochloric acid on methylphthalimide, and is readily soluble in water, alcohol and ether, from which it crystallizes in large tablets, melting at 120; it boils without decomposition at about 300 . 2 PhenylphtJialimidine or Phthalide-anil is prepared by heating phthalide to 200 220 with aniline : CO ' / C=N.C fl H 6 6 H 5 = C 6 H 4 >0 +H 2 O. It crystallizes from alcohol in silvery plates, melting at 160 (Hessert). Phthalidehydrazide, C 14 H 12 lSr 2 O, is formed by heating phthalide with phenylhydrazine for some time : CH 2 >O + H 2 0. CO C=N 2 H.C 6 H 5 It crystallizes from hot water or alcohol in needles, which possess a silver lustre, and melt at 165 . 3 Paranitropkthalide, C 8 H 5 (N0 2 )0 2 , is prepared by dissolving 20 grms. of phthalide in 200 grms. of sulphuric acid, and running in a solution of rather more than the calculated quantity of potassium nitrate in 80 grms. of sulphuric acid, the solution being well cooled during the operation. It forms long, colourless needles, which melt at 141, and are almost insoluble in cold water, but dissolve slightly on boiling, more readily in alcohol, 1 Grabe, Bcr. Deutsch. Chem. Ges. xvii. 2598 ; xviii. 1408. 2 Grabe and Pictet, ibid, xviii. 1173. 3 V. Meyer and Miinchmeyer, ibid. xix. 1706 and 2132. 446 AROMATIC COMPOUNDS. and readily in benzene. Alcoholic potash produces a charac- teristic violet colouration, while aqueous potash forms a yellow solution. Dilute sulphuric acid precipitates paranitrohydroxy- methylbenzoic acid, C 6 H 3 (NO2)(CH 2 .OH)C0 2 H, from the cool solution. This body crystallizes in microscopic needles united in stellate forms, and is extremely soluble in ether, readily in alcohol and hot water. It melts at 129, and decomposes at a higher temperature into water and nitrophthalide. Paramidophthalide, C 8 H 5 (NH 2 )O 2 , is obtained by the reduc- tion of the preceding compound, and is almost insoluble in water, but dissolves slightly in alcohol, and more readily in chloroform, from which it crystallizes in short prisms, melting at 178. Its hydrochloride forms needles which are readily soluble in water. It also dissolves in alkalis, salts of para- amidohydroxymethylbenzoic acid being formed. The free acid has not yet been prepared. When paranitrophthalide is heated with hydriodic acid and phosphorus, 7-amido-orthotoluic acid is formed. 1 Orthonitrophthalide was prepared by Beilstein and Kurbatow, together with the corresponding nitrophthalic acid, by oxidizing a-nitronaphthalene with a solution of chromium trioxide in acetic acid. They mention that the substance obtained has the formula of nitrophthalaldehyde, but must possess a different constitution, because it is only attacked with difficulty by the oxidizing mixture just named. 2 Its properties prove that it is actually Orthonitrophthalide. 3 It crystallizes in small plates, melting at 136, is much more readily soluble in alcohol and chloroform than the para-com- pound, and forms a yellow solution in alkalis. On heating in a sealed tube with dilute hydrochloric acid, it is smoothly con- verted into v-nitrophthalic acid (Honig). 1 Honig, Bcr. Deutsch. Chem. Ges. xviii. 3447. 2 Ann. Chem. Pharm. ccii. 217. 3 Guareschi, ibid, ccxxii. 283 ; Honig, loc. cit. PHTHALALDEHYDE. 447 ALDEHYDES, C 6 H 4 (CHO) 2 , AND ALDEHYDO- ACIDS, C 6 H 4 (COH)(COOH). 2238 Phthalaldehyde. When orthoxylejie is submitted at the boiling-point to the continued action of chlorine, or is heated to 195 with eight parts of phosphorus pentachloride, orthoxylidene tetrachloride, C 6 H 4 (CHC1 2 ) 2 , is formed ; it crystallizes from ether in large asymmetric prisms, melts at 89 and boils at 273 274. On heating with water it is converted into phthalaldehyde, which is also formed by the oxidation of phthal alcohol, and is an oily liquid, which has not yet been prepared pure since it so readily passes into the isomeric phthalide (Hjelt). According to Colson and Gautier, phthalaldehyde is a yellow crystalline substance melting at 52. Ammonia produces a deep blue or yellow colouration, followed by a brown precipitate. 1 Phthalaldehydic acid is prepared by heating monobromo- phthalide with water : 2 X CHO = C 6 H 4 < H-HBr. - CO < \CO.OH It may also be obtained by heating orthoxylene to 200 with 12* 5 parts of phosphorus pentachloride and boiling the product, xylidenyl pentachloride, C 6 H 4 (CHC1 2 )CC1 3 , with water (Colson and Gautier). It forms lemon-yellow crystals, which melt at 98 to 100, and are readily soluble in water. Its phenylhydrazine compound crystallizes in fine, yellow needles. Isophthalaldehyde is prepared in a similar manner from meta- xylidene tetrachloride, C 6 H 4 (CHC1 2 ) 2 , which is a liquid boiling at 273. It is an oily liquid which, as well as its solution in water, gives a green colouration with ammonia, f llowed by a brown precipitate (Colson and Gautier). Terephthalaldehyde, C 6 H 4 (CHO) 2 , was obtained by Grimaux from paraxylylene chloride, C 6 H 4 (CH 2 C1) 2 , by boiling with lead nitrate and water, 3 while Low prepared it by the same method from paraxylylene bromide. 4 1 Hjelt, Bcr. Dcutsch. Chcm. Ges. xviii. 2879 ; xix. 411 ; Colson and Gautier, Bull. Soc. Chim. xlv. 6 and 506. 2 Racine, Bcr. Dcutsch. Chcm. Ges. xix. 778. 3 Jahrsber. Chcm. 1876, 490 ; Colson and Gautier, loc. cit. 4 Ann. Chcm. Pharm. ccxxxi. 361. 448 AROMATIC COMPOUNDS. It is also formed when paraxylene is heated to 190 with eight parts of phosphorus pentachloride, and the paraxylidene tctrachloride which is thus formed boiled with water for some time. The latter forms well-developed crystals, melting at 93. Terephthalaldehyde is only very slightly soluble in cold ether, but readily in alcohol and tolerably freely in hot water, from which it crystallizes in fine needles, melting at 116. It forms a readily soluble compound with acid sodium sulphite. Con- centrated caustic soda solution decomposes it with formation of parahydroxymethylbenzoic acid, paraxylylene alcohol and tere- phthalic acid : /CHO /CH 2 .OH C 6 H 4 <; +H 2 = C 6 H 4 < \CHO \CO.OH. /CH 2 .OH X CH 2 .OH CO.OH 2C 6 H 4 < = \CO.OH 4 6 \CH.OH \CO.OH. Terephthalaldehyde is also obtained when paraxylylene bro- mide is dissolved in cold, concentrated nitric acid. The com- pound C 24 H 20 Br 2 4 is simultaneously formed ; it is insoluble in water, but dissolves readily in -ether, from which it crystallizes in stunted needles, which melt at 80 and are converted into tere- phthalaldehyde, paraxylylene alcohol and hydrobromic acid, by heating with water : /CHO C 6 H 4 < \CHBr.O.CH 2X >C 6 H 4 + 2H 2 = /CHBr.O.CH/ C 6 H 4 < \CHO /CHO HO.CH 2X C 6 H 4 + 2HBr. \CHO HO.CH It is noteworthy that concentrated nitric acid exerts an oxidizing action upon paraxylylene bromide, and does not effect nitration as in the case of benzyl chloride. 1 Xylylidenediamine, C 8 H 8 N 2 , is deposited in very brittle, 1 Low, Ber. Deutsch. Chem. Ges. xviii. 20/2. HYDROBENZAMIDE TRIALDEHYDE. 449 vitreous crystals when an alcoholic solution of terephthalaldehyde is saturated with ammonia and allowed to stand : /CHO /CH=NH C 6 H 4 < + 2NH 3 = C 6 H 4 < _ + 2H 2 0. It is also formed when dry ammonia is passed over the aldehyde, but is decomposed again by acids, or even on boiling with water, into ammonia and the aldehyde. Hydrobenzamide trialdehyde, N 2 (CH.C 6 H 4 .CHO) 3$ is formed by the action of aqueous ammonia on terephthalaldehyde, as a white powder consisting of matted microscopic needles, which is insoluble in water and alcohol and is dissolved by acids, the aldehyde being set free. 1 Nitroterephthalaldehyde, C 6 H 3 (N0 2 )(CHO) 2 . In order to pre- pare this substance, a solution of the aldehyde heated to 150 is treated with an equal quantity of potassium nitrate dissolved in sulphuric acid, kept at a temperature of 110 115 for 10 15 minutes, poured into water and then extracted with ether. It is very readily soluble in alcohol, with greater difficulty in hot water and ether, crystallizing from the latter in rhombohedra, which melt at 86 and sublime in large needles. A blue indigo derivative is formed when it is heated with caustic soda and acetone (p. 146) (Low). Terephthalaldehydic acid, C 6 H 4 (CHO)C0 2 H, is formed, together with terephthalic acid, by the oxidation of the aldehyde with chromic acid solution. It is only slightly soluble in ether and chloroform, and still less readily in hot water, from which it crystallizes in needles, which melt at 246 .and sublime in well- formed needles. It forms a barium salt which is readily soluble in water, as well as a scarcely soluble silver salt, and only reduces ammoniacal silver solution after continued boiling. The ethyl ether, C 6 H 4 (CHO)CO 2 .C 2 H 5 , forms groups of pointed needles, easily reduces ammoniacal silver solution on heating, and gives all the reactions of benzaldehyde (Low). Hydrdbenzamidctricarloxylic acid, N 2 (CH.C 6 H 4 .CO 2 H) 3 is not formed by the action of ammonia on the aldehydo-acid, but by the oxidation of the trialdehyde with potassium permanganate. It crystallizes in nacreous, rhombohedral tablets (Oppenheimer). NitrotcrcpUhalaldehydic acid, C 6 H 3 (NO 2 )(CHO)C0 2 H(2 : 1 : 4, 1 Oppenheimer, Bcr. Dcutsch. Chem. Ges. xix. 574. 450 AROMATIC COMPOUNDS. is prepared in a similar manner to nitrophthal aldehyde. It is readily soluble in hot water, and crystallizes from it in large, four-sided needles, which melt at 160. On heating with caustic soda solution and acetone it is converted into indigocarboxylic acid, C 16 H 8 N 2 2 (CO 2 H) 2 , a reaction which proves that the nitroxylyl-group stands in the ortho-position with respect to the aldehyde group. In its preparation a small quantity of the isomeric acid (NO 2 :COH:C0 2 H=:3:1:4), which melts at 184, is also formed (Low). /C0 2 H THE PHTHALIC ACIDS, C 6 H 4 < X C0 2 H. 2239 In the year 1836, Laurent prepared naphthalic acid (acide naphtalique), C 10 H 6 O 5 , by boiling naphthalene tetrachloride, C 10 H 8 C1 4 , with nitric acid, 1 and Marignac, who was subsequently confirmed by Laurent, proposed for it the formula C 8 H 6 O 4 . The latter chemist found that it is also obtained, together with other products, by boiling naphthalene with nitric acid, oxalic acid being always simultaneously formed. 2 Since it no longer belongs to the naphthalene series, he named it phthalic acid (acide phtalique)? It decomposes on distillation with lime, as was shown by Marignac, into carbon dioxide and benzene. 4 During his investigation of the colouring matter of madder root, Schunck found that alizarin is converted by oxidation into alizaric acid, C U H 10 O 7 , 5 which, according to Gerhardt, 6 con- firmed by Strecker and Wolff, 7 is identical with phthalic acid. The naphthesic acid (acide naphtesique), C 10 H C O 4 , which Laurent had obtained by the action of potassium dichromate and sulphuric acid on naphthalene, 8 was also recognized as phthalic acid by Scheibler 9 and F. Lossen, the latter of whom found that it is also formed by the action of potassium permanganate on naphthalene. 10 An isomeric substance was prepared by Cailletet 1 Ann. CMm. Phys. Ixi. 114 ; Ann. Chem. Pharm. xix. 38. 2 Ibid, xxxviii. 13. 3 Ibid. xli. 107. 4 Ibid. xlii. 215. 8 Ibid. Ixvi. 197. 6 Compt. Rend. Trav. Chim. 1849, 222. 7 Ann. Chem. Pharm. Ixxv. 12. 8 Revue Scient. xiv. 560 ; Compt. Rend. xxi. 36. 9 Ber. Deutsch. Chem. Oes. i. 125. 10 Zeitschr. Chem. x. 419 ; Ann, Chem. Pharm. cxliv. 71. THE PHTHALIO ACIDS. 451 in 1847, by heating oil of turpentine (essence de te're'benthine) with dilute nitric acid, and named on this account terephthalic acid (acide terephtahque). 1 Five years previously, Persoz had obtained cumino-cyminic acid (acide cumino-cyminique) by the oxidation of the ethereal oil contained in the seeds of Roman cumin (Cuminum Cyminum}, but had not analysed it. 2 Hofmann, in attempting to purify cumic acid, C 10 H 12 O 2 , by treatment with dilute sulphuric acid and potassium dichromate, found that it is thus oxidized to insolinic acid, C 9 H 8 4 , which he also obtained from Roman cumin oil, and which, as he pointed out, is very similar to terephthalic acid, 3 these being afterwards shown by H. Miiller and Warren de la Rue to be identical. 4 Fittig then prepared a third acid by the oxidation of isoxylene and named it isophthalic acid. 5 The methods employed in the determination of the position of the carboxyl groups in these three acids have already been described in detail (Part III., p. 38). Quite recently, however, Nolting has added a very simple proof of their constitution. The three acids can be quantitatively obtained by the oxidation of the three dimethylbenzenes with an alkaline solution of potassium permanganate. Paraxylene yields terephthalic acid and on nitration gives only one mononitroxylene, while ortho- xylene is oxidized to phthalic acid and yields two nitre-deriva- tives. Finally, three nitroxylenes can be obtained from isoxylene, which corresponds to isophthalic acid. The position of the carboxyls is, therefore, in : Phthalic acid 1:2 Isophthalic acid 1:3 Terephthalic acid 1:4 This proof is exactly analogous to that employed by Korner to determine the positions of the bromine atoms in the three dibromobenzenes, and by Griess in ascertaining the constitution of the diamidobenzenes (Part III., pp. 47, 48). 6 1 Ann. Chim. Phys. [3] xxi. 28. 2 Journ. PraU. Chem. xxiv. 55 ; Compt. Rend, xxxiii. 433. 3 Ann. Chem. Pharm. xcvii. 197. 4 Ibid. cxxi. 86. 5 Ibid, cxlviii. 11. c Ber. Deutsch. Chem. Ges. xviii. 2687. 452 AROMATIC COMPOUNDS. PHTHALIC ACID. 2240 This acid is most simply formed by the oxidation of orthoxylene or orthotoluic acid 1 with potassium permanganate or dilute nitric acid. 2 Carius found that it is also obtained in small quantity when benzene or benzoic acid is treated with manganese dioxide and concentrated sulphuric acid in the cold, 3 diphenylbenzene, C 6 H 4 (C 6 H 5 ) 2 , being probably the intermediate product (Part III., p. 76). According to Guyard, it is also formed when a mixture of salicylic, formic and sulphuric acids is heated. 4 Phthalic acid is manufactured from naphthalene, C 10 H 8 , which is first converted into the tetrachloride, C 10 H 8 C1 4 , by passing chlorine through the fused hydrocarbon, the plant shown in section and elevation in Figs. 2 and 3 being employed. The mass becomes heated to such an extent that the iron vessel containing it has to be cooled by water, the temperature being kept below 160 170, above which carbonization takes place. The tetrachloride is also manufactured by grinding naphthalene with water and potassium chlorate, making up the paste into balls, and bringing these, after drying, into concentrated hydro- chloric acid. The chlorate may be replaced by bleaching powder which is mixed with naphthalene and pressed into cakes. One part of the chloride is then heated with 5 6 parts of nitric acid of sp. gr. 1*35 in flat stoneware retorts placed in an air-bath (Figs. 4 and 5). The vapours which are evolved are condensed and employed in a subsequent operation. The acid may be finally purified by crystallization, but the product is usually distilled and thus immediately converted into the anhydride. The yield amounts to 30 per cent, on the naphthalene. 5 Phthalic acid is also formed when naphthalene is heated to 130 with 20 parts of nitric acid of sp. gr. I'lo, 40 percent of the theoretical yield being obtained. 6 1 Weith, Ber. Deutsch. Ckcm. Ges. vii. 1057. 2 Piocard, ibid. xii. 579. 3 Ann. Chem. Pharm. cxlviii. 60. 4 Bull. Soc. Chim. xxix. 248. e Schultz, Stcinkohlentkecr, S. 540 ; s. E. Fischer, Ber. Deutsch. Chem. Ges. xi. 735 ; Depouilly, Ann. Chem. Pharm. cxxxvii. 373. 6 Beilstein and Kurbatow, Ann. Chem. Pharm. ccii. 215. PHTHAL1C ACID. 453 i 260 454 AROMATIC COMPOUNDS. PHTHALIC ACID. 455 Properties. It crystallizes from hot water in thin plates or lustrous, rhombic prisms, 1 which dissolve in 130 parts of water at 11-5. 100 parts of dissolve at 15 ether absolute alcohol 90 per cent, alcohol, 10-08 11-70 parts. 2 FTG. 4. Varying statements have been made as to the melting-point of the acid, the discrepancies being due to the fact that it loses water on heating, the anhydride being formed. According to 1 Scheibler, Ser. Deutsch. Chem. Ges. i. 125; Groth, Jahresber. Chem. 1870, 5. 2 Bourgoin, Bull. Soc. Chim. xxix. 247. 456 AROMATIC COMPOUNDS. Lessen, this takes place at 184, while Ador states that the unbroken crystals melt at 213, but the powder at 203 . 1 It is completely burned by chromic acid solution on heating,2 and on this account cannot be prepared by means of this reagent from orthoxylene or other ortho-compounds which possess two side chains. On distillation with lime it decomposes into carbon FIG. 5. dioxide and benzene, but if the temperature be not allowed to rise above 330 350, it is converted into benzoic acid, which was formerly manufactured in this way (p. 155). 2241 The normal phthalates of the alkali metals are readily soluble in water and crystallize in small plates or scales. Acid ammonium phthalate, C 8 H 5 4 (NH 4 ), separates on the spontaneous evaporation of a solution of the normal salt in six- 1 Ann. Chem. Pharm. clxiii. 230. 2 Fittig and Bieber, ibid. clvi. 242. SALTS OF PHTHALIC ACID. 457 sided, rhombic tablets, prisms or pyramids, which dissolve very readily in water but only slightly in alcohol. Calcium phthalate C 8 H 4 O 4 Ca-f-H 2 O, is tolerably soluble in water and crystallizes in lustrous, rhombic prisms. 1 Acid barium phthalate, (C 8 H 5 O 4 ) 2 Ba, is readily soluble in hot water and crystallizes in small, rhombic prisms. Normal barium phthalate, C 8 H 4 O 4 Ba, is obtained by preci- pitating the normal ammonium salt with barium chloride, or by mixing hot solutions of the acid and caustic baryta ; it forms small, white scales or silky needles, which are only slightly soluble in hot water. On evaporating the solution, a basic salt separates out in crystalline crusts (Carius, Hermann). Lead phthalate, C 8 H 4 O 4 Pb, is a precipitate, consisting of scaly crystals. Copper phthalate, C 8 H 4 O 4 Cu + H 2 O, crystallizes in lustrous blue, rhombic prisms, which dissolve readily in hot water (Hermann). Silver phthalate, C 8 H 4 O 4 Ag 2 , forms a light, crystalline powder, which is tolerably soluble in water and detonates when rapidly heated. JZthers ofphthalic acid are formed by the action of hydrochloric acid on the alcoholic solution of the acid and by that of an alco- holic iodide upon the silver salt. The two following have been prepared, and are both odourless liquids : 2 Boiling-point. Methyl phthalate, C 6 H 4 (C0 2 .CH 3 ) 2 ..... 280 Ethyl phthalate, C 6 H 4 (C0 2 .C 2 H 5 ) 2 . . . 294 Phthalyl oxide or Phthalic anhydride, (C 6 H 4 .C0 2 ) 2 O, is formed when the acid is heated alone or with acetyl chloride : CO.OH + CH 8 .COC1 = C0 C 6 H 4 < + CH 8 .COC1 = \CO.OH .OH + HC1. The anhydride remains behind in splendid prisms after the acetic acid and excess of acetyl chloride have been removed. 3 It is manufactured by subliming phthalic acid in a current of 1 Hermann, Ann. Chetn. Pharm. cli. 77. 2 Grabe and Born, ibid, cxlii. 344 ; Grabe, Bcr. Deutsch. Chcm. Ges. xvi. 860. 3 Anschiitz, ibid. x. 235 ; Ann. Chem. Pharm. ccxxvi. 1. 458 AROMATIC COMPOUNDS. air, or better, of carbon dioxide, the apparatus shown in Fig. 6 being employed. 1 It is thus obtained in long, white, pliant, rhombic needles, while on rapid heating it distils as a liquid and then solidifies to a hard, crystalline mass. It melts at 128 and boils at 284'5 (Schultz, Griibe), is only very slightly soluble in cold, more readily in hot water, and is reconverted into phthalic acid when boiled with water for a long time, more rapidly in presence of alkalis. It is reduced by zinc dust and acetic acid to phthalide, di- phthalyl (v. post) and zinc phthalate being also formed. 2 It is employed in the manufacture of dyes and of many other com- pounds, as it very readily enters into chemical reactions. Thus it combines with the acid anhydrides, forming with acetic X C=CH.C0. 2 H anhydride, phthalylacetic acid, C 6 H 4 <^ >O It also combines with the aromatic hydrocarbons in presence of aluminium chloride, forming acids ; thus benzene yields benzoyl- benzoic acid : /CO V /CO.OH C 6 H 4 < >0 + C 6 H 6 = C 6 H 4 <; \C(K \CO.C 6 H 5 . A specially characteristic property is that of combining with phenols on heating to form pkthale'ins, water being eliminated. As already mentioned, resorcinol yields fluorescent in this way, the formation of this substance, which is employed as a test for the presence of the phenol in question, taking place in the following manner : CO C \CH I ^e n 4 I e4 + 2C 6 H 4 W fcc -M H 5 S O S.*3 CO Eo'd S >2 3 g" EH 43 j3 N'ff B III SS1 3 *>a ft 1 1' e5 &: -f g l Bit 460 AROMATIC COMPOUNDS. chloride. 1 From analogy with other acid chlorides it would be formed according to the following equation : /CO.OH /COC1 C 6 H 4 < + 2PC1 5 = C 6 H 4 < +2POC1 3 + 2HC1. \CO.OH \COC1 Careful investigation, however, has shown that it does not possess this constitution. It is formed in two stages : /CO.OH /CO V C H 4 < + PC1 5 = C 6 H 4 < >0 + POC1 3 + 2HC1. \CO.OH Nxx^ /c<\ C 6 H 4 < >0 + PC1 5 = C 6 H 4 < >0 + POOL, \CCK \ CO / It is also obtained, therefore, when equal molecules of phthalic anhydride and phosphorus pentachloride are heated together for 12 hours at 170 . 2 In order to prepare it, phthalic acid is boiled with rather more than two molecules of phosphorus chloride for 5-6 hours and then distilled. 3 It is an oily liquid, which boils at 268 arid solidifies at about 0. It is only slowly decomposed by boiling water and even boiling caustic soda solution. On heating with finely-divided silver, diphthalyl, which will be subsequently described, is obtained, its formation taking place according to the following equation : / co \ / co \ C ' H C ' H + 4Ag= || +4AgCL s C v C 6 H 4 C 6 H 4 The proof that it possesses this constitution, rests not only on the whole behaviour of the substance, which shows it to be a dilac- 1 Zeitschr. Chem. 1863, 257. 2 Claus and Hoch, Bcr. Dcutach. Chem. Ges. xix. 1187. 3 Wischin, Ann. Chem. Pharm. cxliii. 259. PHTHALYL CHLORIDE. 461 tone, but also on the fact that it is formed when phthalide is heated with phthalic anhydride : 1 ,00 /\ C 6 H/ >0 H 2 O. The following compounds have been prepared by the action of sodium methylate and ethylate on phthalyl chloride : /C(OCH 3 ) 2 />0 Boiling-point. 280 294' co These are liquids which boil at the same temperature as the isomeric phthalic ethers, from which they differ only in possess- ing a slightly lower specific gravity. That they are actually distinct bodies is shown by the fact that tetrachlorophthalic acid yields compounds which differ both in crystalline form and melt- ing point from those derived from its chloride. 2 The corresponding phenyl ether, C 6 H 4 (CO)C(OC 6 H 5 ) 2 O, is prepared by heating the chloride with phenol, and crystallizes from alcohol in small prisms, melting at 70. 3 When phthalyl chloride is heated in a sealed tube with phosphorus pentachloride to 210 220, two isomeric chlorides, C 8 H 4 C1 4 O, are formed, both of which crystallize in monosyrn- metric forms ; the one melts at 47, and the other, which is also a product of the action of phosphorus pentachloride on phthalide, at 88. Theory, indeed, allows the formation of two isomeric tetrachlorides : /cci 2 ; /coci r, H ' \o r TT / 6 4 \cci / A \cci 8 . The compounds in question, however, exhibit an identical chemical behaviour. On heating with concentrated sulphuric acid, or on boiling with alcoholic potash, they are converted into 1 Grabe and Guye, Ber. Deutsch. Chcm. Ges. xvii. 2851. 2 Grabe, Ber. Deutsch. Chem. Ges. xvi. 860. 3 Schreder, ibid. vii. 705 ; v. Gerichten, ibid. xiii. 419. 462 AROMATIC COMPOUNDS. phthalic acid, and phenol combines with them to form the phenyl ether mentioned above. These facts seem to indicate a case of physical isomerism, but all endeavours to convert either of the compounds into the other have proved unsuccessful (v. Gerichten). According to Glaus and Hoch, the tetrachloride, which melts at 88 and boils at about 274, is alone obtained and is best prepared by heating for 15 hours at 245. Carbonyl chloride and orthochlorobenzoyl chloride are also formed in the reaction. 1 A compound is formed by the action of zinc ethyl on phthalyl chloride, which is looked upon by Wischin as phenylenediethyl- acetone, C 6 H 4 (CO.C 2 H 5 ) 2 . It separates from ethereal solution in splendid crystals, which possess a pleasant, fruity smell, and melt at 52. Wischin was, however, unable to obtain a com- pound of it with acid sodium sulphite, and V. Meyer has shown that it is not a ketone, since it does not form a hydroxylamine compound. 2 The constitution of this compound can readily be explained in accordance with the present views in regard to phtbalyl chloride, and is as follows : / C H Succinyl chloride (Part II., p. 191) has obviously an analogous constitution to phthalyl chloride, and its reduction to the anhydride or lactone of 7-hydroxybutyric acid (Part. II., p. 169) thus receives a simple explanation : / 2\ /^-*-*-2\ C A0 + 4H = C 2 H 4 < ' >0 -t 2HC1. X CO ' \CO ' Phthalyl sulphide or Thiophthalic anhydride, C 8 H 4 2 S, is formed by the action of potassium hydrosulphide on phthalyl chloride 3 or its phenyl ether : 4 CC1 C*S C 6 H 4 C=NH C 6 H/ =C 6 H 4 <( >0+H,0. \CO.OH \CO It is also formed by the action of ammonia on the anhydride, chloride, 2 or sulphide, 3 as well as by heating phthalic acid with ammonium or potassium thiocyanates. 4 It is insoluble in cold water, slightly soluble on boiling, and crystallizes from ether in six-sided prisms, which melt at 228 5 and sublime in small plates. It is decomposed on heating with slaked lime into carbon dioxide and benzonitril, 6 and is reduced to phthalimidine (p. 444) >y tin and hydrochloric acid. When phthalimide is heated with aniline or one of its homologues, ammonia is evolved and the corresponding substi- tuted phthalimide formed. If a phenol be substituted for the amine, ammonia is also evolved, and a substance belonging to the class of phthaleins is produced. These bodies are identical with those prepared from phthalic anhydride. 7 Potassium phthalimide, C 8 H 4 (NK), is obtained in white plates by adding alcoholic potash to an alcoholic solution of phthal- imide (Cohn). Silver phthalimide, C 8 H 4 2 (NAg), is formed as a heavy, white precipitate when silver nitrate is added to an aqueous solution of the potassium salt, or when an alcoholic solution of phthalimide is treated with an ammoniacal silver solution (Laurent). Phthalamic acid, C 6 H 4 (CO.NH 2 )CO 2 H. Marignac prepared the ammonium salt of this acid by dissolving anhydrous naph- thalic acid (phthalic acid) in ammonia, and named it naphthal- amide. 8 It was also obtained by Laurent, who added ammonia to a hot, alcoholic solution of the anhydride . 9 /CO. /CO.NH 2 C 6 H 4 < >0 + 2NH 3 = C 6 H 4 < \CO/ \CO.ONH 4 1 Laurent, Ann. Chem. Pharm. xli. 110. 2 Kuhara, Amer. Chem. Journ. iii. 26. 3 Grabe and Zschokke, loc. cit. 4 Ossian Aschan, Ber. Deutsch. Chem. Gcs. xix. 1398. 6 Cohn, Ann. Chem. Pharm. ccv. 301. 6 Laurent, Jahrcsb, Chem. 1868, 549. 7 Hall, Private Communication. 8 Ann. Chem. Pharm. xlii. 219. Ann. Chim. Phys. [3] xxiii. 117. 464 AROMATIC COMPOUNDS. The barium salt is formed when phthalimide is boiled with baryta water (Kuhara), and the potassium salt by the continued boiling of potassium phthalimide with water. 1 It may be more simply prepared by the action of 25 per cent, caustic potash solution on phthalimide. 2 When concentrated hydrochloric acid is added to the solution, the phthalamic acid is gradually deposited in short, well developed, transparent prisms, which melt at 148 149 and decompose at a slightly higher temperature into water and phthalimide. It has an acid taste, is tolerably soluble in cold water and is gradually converted by it into acid ammonium phthalate, the change taking place rapidly on boiling (Aschan). Ethyl phthalimide, C 6 H 4 O 2 (NC 2 H 5 ), is prepared by the distilla- tion of phthalic anhydride with aqueous ethylamine; it crystal- lizes in needles or prisms, melts at 78'5 and boils at 276 278 . 4 Acetphthalimide, C 8 H 4 O 2 (NCO.CH 3 ), is formed by heating phthalimide with acetic anhydride for some time. It crystallizes in large octohedra and is decomposed by boiling water or by alkalis in the cold into acetic acid and phthalimide. 5 Phthaluric acid is obtained by heating phthalic anhydride with amido-acetic acid : / C0 \ C 6 H 4 < )0 + NH 2 .CH 2 .C0. 7 H = XXX X C=N.CH 2 .C0 2 H >0 +H 2 0. It crystallizes from hot water in long, thin needles, which melt at 191 192, and are decomposed on boiling with con- centrated hydrochloric acid into phthalic and amido-acetic acids. 6 Phenylphtlialimide or Phthalanil, C 8 H 4 2 (NC 6 H 5 ), is prepared by distilling phthalic acid with aniline; it crystallizes from alcohol in needles, which melt at 205, but sublime at a lower temperature. 7 On boiling with ammonia and alcohol, it is con- verted into phtlialanilic acid, or phenylphthalamic acid : /C=NC 6 H 5 /CO. NH. C 6 H 5 C 6 H 4 < >0 + H 2 0=C 6 H/ \CO NCO.OH. 1 Landsberg, Ann. Chem. Pharm. ccxv. 198. 2 Ossian Aschan, Ber. Deutsch. Chem. Gcs. xix. 1401. 3 Michael, ibid. x. 1646. 4 Wallach and Kamenski, ibid. xiv. 171. 6 Ossian Aschan, ibid. xix. 1400. 6 Drechsel, Journ. Prakt. Chem. [2] ccxxvii. 418. 7 Gerhardt and Laurent, Ann. Chem. Phys. [2] xxiv. 189 ; Dbbner, Ann. Chem. Pharm. ccx. 267. DIPHENYLPHTHALEIN. 465 This substance crystallizes from hot water or alcohol in small plates, which melt at 192 and decompose into water and phthalanil at a higher temperature. Analogous compounds are obtained from the substitution products of aniline 1 and its homologues, 2 from the amido- phenols, 3 and from the amidobenzoic acids. 4 Diphenylphthalamic acid is formed when equal molecules of phthalic anhydride and diphenylamine are heated together : It is insoluble in water and' crystallizes from alcohol in warty masses of small, lustrous prisms, which melt at 147 148 . 5 If two molecules of diphenylamine are employed, the so-called diphenylphthale'in is formed; it is also obtained by the action of the base on phthalyl chloride, 6 and is tolerably soluble in alcohol, more readily in benzene, from which it crystallizes in large prisms, melting at 238. It has the following constitu- tion : The aromatic diamines form two series of compounds with phthalic anhydride : 7 X C=N.C 6 H 4 . NH 2 X C=H. C 6 H 4 .N=C X C 6 H 4 < >0 -C 6 H 4 <( >0 0< ^C 6 H 4 . \CO \CO CO/ When orthamidothiophenol is heated with phthalic anhydride or phthalyl chloride, the compound C 20 H 12 N 2 S 2 is formed, and probably has the following constitution : N. K. 1 Gabriel, Bcr. Dcutsch. Chcm. Gcs. xi. 2260 ; Frohlich, ibid. xvii. 1801 and 2679. 2 Michael, ibid. x. 579. 3 Ladenburg, ibid. ix. 1528. 4 Gabriel loc. cit. Piutti, Gaz. Chim. Ital. xiii. 542 ; xiv. 470. 6 Lellmann, Bcr. Deutsch. Chem. Ges. xv. 830. 7 Biedermann, ibid. x. 1160. 466 AROMATIC COMPOUNDS. It crystallizes from alcohol in thin needles or thick prisms, which melt at 112; it is a weak base and forms a hydrochloride which is only slightly soluble and crystallizes well, but is readily decomposed by water. 1 2244 PhtJialyldiamide. Phthalylmalonic ether is formed by the action of phthalyl chloride on sodmalonic ether, and reacts with ammonia to form malonamide, alcohol and phthalyldi- amide : 2 X C=C(CO.OC 2 H 5 ) 2 C 6 H 4 >0 +4NH 3 = / C - CH 2 (CO.NH 2 ) 2 + 2HO.C 2 H 5 + C 6 H 4 < This body may also be obtained in a similar manner from phthalylaceto-acetic ether, 3 and by allowing phthalimide to stand for some hours in contact with concentrated ammonia/ It forms a glittering powder, consisting of microscopic, very refractive rhombohedra, only slightly soluble in water and alcohol, and is decomposed into ammonia and phthalimide when heated with either of these. It fuses at 219 220, when carefully heated, forming a clear liquid, but ammonia is given off and the residue finally consists of phthalimide. Phthalylliydroxylamine, N(C 8 H 4 O 9 )OH,is formed when phthalyl chloride and sodium carbonate are alternately added to a con- centrated solution of hydroxylamine hydrochloride, so that the liquid is always kept alkaline : /CC1 2 C=N.OH C 6 H 4 < >0 + H 2 N.OH = C 6 H 4 < >O + 2HC1. \CO/ \CO It is insoluble in ether, but dissolves slightly in water, more readily in boiling alcohol, from which it crystallizes in small plates or needles, which, after drying, form a yellow powder, melting at 230 with decomposition. It is an acid, decomposes carbonates and forms a red solution in alkalis. Alcoholic potash 1 Hofmann, Ber. Deutsch. Chem. Ges. 13, 1233. 2 Wislicenus, ibid. xvii. Eef. 529. 3 Billow, Ann. Chem. Pharm.. ccxxxvi. 188. 4 Ossian Oschan, Bcr. Deutsch. Chem. Ges. xix. 1398. ETHYLPHTHALYLHYDROXYLAMINE. 467 added to its solution in alcohol precipitates the potassium salt, N(C 8 H 4 O 2 )OK, which consists, as does the sodium compound, of an amorphous red powder. The silver compound is obtained by double decomposition as a dark-red precipitate, the barium and lead salts being light red and yellowish red precipitates, while the copper salt, which is only thrown down from a concentrated solu- tion, is green, and the aluminium and mercury salts are yellow. Ethylphthalylhydroxylamine, N(C 8 H 4 O 2 )OC 2 H 5 , is obtained by treating the silver salt with ethyl iodide. It forms large crystals which melt at 103 104 and boil at 270. Phthalylhydroxylamine decomposes on dry distillation into phthalic anhydride, ammonia and nitrogen; a boiling solution of caustic potash resolves it into phthalic acid and hydroxylamine, while orthamidobenzoic acid is formed when it is heated in alcoholic solution with one molecule of potash : /C=N.OH /NH 2 C 6 H 4 < >0 + KOH = C 6 H 4 < +C0 2 . \CO \CO.OK Hydroxyphthalamic acid is formed when an alcoholic solution of phthalylhydroxylamine is heated with potash for a short time : /C=N.OH /CH=N.OH C 6 H 4 < >0 +KOH=C 6 HX X)0 XXXOK Potassium hydroxypkthalamate separates out on cooling ; it is readily soluble in water, and is deposited on evaporation in hard, yellow crystals. The lead salt is thrown down when lead acetate is added to a solution of the potassium salt ; it has the following constitution : /CH=N.(\ P TT / \PV <^ 6 -ti 4 \ /rb. \00 O/ When this is suspended in water and treated with sulphuretted hydrogen, a solution of the free acid is formed, which reddens lit- mus and, like that of the potassium salt, is coloured violet by ferric chloride. The solution of the acid decomposes gradually on standing, more rapidly when heated, with separation of phthalyl- hydroxylamine. Phthalylhydroxylamine shows great similarity to the nitrolic 468 AROMATIC COMPOUNDS. acids, which, like the former, are colourless but are coloured red by the slightest trace of an alkali, and have a similar constitu- tion : L . Phthalylhydroxylamine Ethylnitrolic acid. cy3- 4 \ >o x co Benzenylazoximebenzenylcarboxylic acid, C 15 H 10 N 2 O 3 , is formed when phthalic anhydride is fused with benzenylamidoxime : ^N.OH C 6 H 6 ,< C 6 H 6 .C^ ^C.C 6 H 4 .C0 2 H+H 2 0. It crystallizes from hot alcohol in lustrous needles melting at 151 . 2 OrtTiocyanobenzoic acid, C 6 H 4 (CN)CO 2 H, is obtained by adding orthodiazobenzoyl chloride to a hot solution of copper sulphate and cuprous cyanide ; it is a thick, viscous liquid, which has not hitherto been prepared pure, since it readily changes into the isomeric phthalimide, phthalamic acid being probably formed as an intermediate product : 0 . \CO-OH \CO Ethyl orthocyanobenzoate, C 6 H 4 (CN)CO 2 .C 2 H 5 , is prepared by diazotizing the ethyl ether of orthamidobenzoic acid and treating the product in the manner just described; it crystallizes in thick needles, melting at 70. 5 It is gradually attacked when 1 Cohn, Ann. Chem. Pharm. ccv. 295. 2 Schulz, Ber. Deutscli. Chem. Ges. xviii. 2463. 3 Sandmeyer, ibid, xviii. 1496. 4 Liebermann, ibid. xix. 2283. 5 Muller, ibid. xix. 1491. DIHYDROPHTHALIC ACID. 469 heated with hydroxylamine in alcoholic solution, phthalimide- oxime being formed : C=N / C 6 H 4 < + H 2 N.OH = C 6 H >0 + HO.C 2 H 5 . \CO.OC 2 H 5 The latter crystallizes from dilute alcohol in needles, which melt at 250 and are converted into phthalimide by boiling with ferric chloride and hydrochloric acid. ADDITION PRODUCTS OF PHTHALIC ACID. 2245 Dihydrophthalic acid, C 6 H 6 (C0 2 H) 2 , is formed when a cold alkaline solution of phthalic acid is treated with sodium amalgam, 1 or better when the operation is carried on at the boiling point. 2 It crystallizes in hard, rhombic tablets, which are only slightly soluble in cold, more readily in hot water, and readily in alcohol. It is a strong dibasic acid ; on heating with soda lime it decomposes into carbon dioxide, hydrogen and benzene, while the action of phosphorus pentachloride upon it yields hydrochloric acid, carbon dioxide, phosphorus oxychloride and benzoyl chloride. Bromine acts upon its aqueous solution in the following manner (Grabe and Born) : C 6 H 6 (C0 2 H) 2 + Br 2 = C 6 H 5 .C0 2 H + CO 2 + HBr. On heating with sulphuric or nitric acids, ben zoic acid is also formed, together with phthalic acid, while ethyl benzoate, pro- bably accompanied by ethyl formate, is produced when hydro- chloric acid is passed into its alcoholic solution. Hydrophthalic acid can be heated to 200 without undergoing any alteration ; at a higher temperature, however, it decomposes with formation of phthalic anhydride. All these reactions may be simply explained if we ascribe the following constitution to the acid : CH HC HC s\ CH CO 2 H CH C0 2 H V CH 1 Grabe and Born, Ann. Chem* Pharm. cxlii. 330. 8 Baeyer, Ber. Deulsch. Chem. Ges. xix. 1807. 261 470 AROMATIC COMPOUNDS. Tetrahydrophthalic acid, C 6 H 8 (C0 2 H) 2 . The anhydride of this acid, C 8 H 8 O 3 , is formed by the distillation of hydropyromellitic acid, C 6 H 6 (C0 2 H) 4 , and crystallizes from ether in hard, lustrous plates, which melt at 68 and sublime readily. It is insoluble in cold water, but dissolves in hot water with formation of the acid, which crystallizes in large plates, and is readily soluble in water, being, however, converted into the anhydride when the solution is heated to about 100 . 1 Dibromotetrahydrophthalic acid, C 6 H 6 Br 2 (CO 2 H) 2 , is obtained by the combination of dry bromine with dihydrophthalic acid, and crystallizes in rhombohedra (Baeyer). HexhydropTithalic acid, C 6 H 10 (C0 2 H) 2 , is formed when tetra- hydrophthalic acid or dihydrophthalic acid 2 is heated to 230 with hydriodic acid, or when the former is treated with sodium amalgam and water, while dihydrophthalic acid is not attacked by these re-agents (Baeyer). It is slightly soluble in cold, somewhat more readily in hot water, and crystallizes in small prisms or plates, which melt at 203 205 without forming an anhydride. Bromomaloplithalic acid, C 6 H 8 Br(OH)(C0 2 H) 2 , is prepared by adding bromine to an aqueous solution of tetrahydrophthalic acid, a dibromide being first formed, which is then decomposed by water : C 6 H 8 Br 2 (C0 2 H) 2 + H 2 O = C 6 H 8 Br(OH)(C0 2 H) 2 + HBr. It is readily soluble in water and crystallizes in small rhombic prisms or tablets. On heating with baryta water it is converted into the following compound. 3 Tartrophthalic acid, C 6 H 8 (OH) 2 (C0 2 H) 2 is best obtained by dissolving the anhydride of tetrahydrophthalic acid in boiling water, and adding to one part of the anhydride rather more than an equal amount of bromine, the mixture being then heated on the water bath and treated with baryta water until the liquid has a permanent alkaline reaction. The barium salt is obtained on concentration in plates, from which the tartrophthalic acid is prepared by means of sulphuric acid. It crystallizes from a con- centrated solution in colourless prisms containing two molecules of water, which are lost in a vacuum. On heating with hydri- odic acid it is converted into hexhydrophthalic acid, the 1 Baeyer, Ann. Chem. Pharm. clxvi. 344. 2 Mierski, Ber. Deutsch. Chem. Ges. iv. 558. 3 Baeyer, Ann. Chem. Pharm. clxvl 354. CHLOROPHTHALIC ACIDS. 471 relation existing between these two bodies being similar to that between succinic and tartaric acids, while tetrahydrophthalic acid corresponds to fumaric acid. HALOGEN SUBSTITUTION PRODUCTS OF PHTHALIC ACID. 2246 Chlorine does not act upon free phthalic acid, even in the presence of iodine ; substitution takes place, however, when the gas is passed into an alkaline solution of the acid. Auerbach obtained in this way a monochlorophthalic acid, which crystal- lized from -benzene in needles, melted at 149 150, was readily soluble in alcohol and remained on the evaporation of this solu- tion as a syrup which gradually solidified. On heating, it yielded an anhydride boiling at 140 143 . 1 Kriiger obtained different results by oxidizing the two chloro-orthotoluic acids with potas- sium permanganate in faintly alkaline solution. 2 v-Chlorophtkalic acid, C 6 H 3 C1(C0 2 H) 2 (3 : 1 : 2), is also formed by the oxidation of the dichloronaphthalene melting at 107, and crystallizes from hot water in stellate groups of silky needles, which melt at 184 and yield an anhydride which sublimes in long needles and melts at 1*22 123 . 3 a-Chlorophthalic acid (4:1:2) has also been prepared by the oxidation of e-dichloronaphthalene 4 and by the action of phos- phorus pentachloride on the corresponding sulphonic acid. 5 It is more readily soluble in water and alcohol than the v-acid, and crystallizes in silky needles, which melt at 130 134 (Kriiger) but according to Olaus and Ree at 148. It decom- poses on distillation into water and the anhydride, which crystallizes in lustrous, asymmetric tablets, and melts at 96 97. Dichlorophthalic acid. C 6 H 2 C1 2 (CO 2 H) 2 , is obtained by heating dichloronaphthalene tetrachloride, C 10 C1 2 H 6 C1 4 , 6 and ^-dichloro- naphthalene 7 with nitric acid. It is readily soluble in alcohol and hot water, and crystallizes in compact prisms, which melt at 1 Jahrcsb. Chem. 1880, 862. 2 Ber. Deutsch. Chem. Ges. xviii. 1758. 3 Gnareschi, ibid. xix. 134. 4 Alen, Bull. Soc. Chem. xxxvi. 434 ; Clans and Delme, Ber. Deutsch. Chem. Ges. xv. 319 ; Claus and Miiller, ibid, xviii. 3073. 5 Re, ibid, xviii. 3359 ; Inaugurate. Bern. 1886. 6 Faust, Ann. Chem. Pharm. clx. 64. 7 Atterberg, Ber. Deutsch. Chem. Ges. x. 574. 472 AROMATIC COMPOUNDS. 183 185. Its anhydride melts at 187 and forms crystals which are very similar to those of benzoic acid. Trichlorophthalic acid, C 6 HC1 3 (CO 2 H) 2 , which has been pre- pared by the oxidation of /?-pentachloronaphthalene with nitric acid, forms a yellowish, crystalline mass, and is converted on heating into the anhydride which melts at 157 and sublimes in long needles. 1 Tetrachlorophthalic acid, CC1 4 (CO 2 H) 2 . was -obtained from a-pentachloronaphthalene. It is also formed by the action of chlorine on phthalic acid in presence of antimony chloride, 2 and crystallizes from water in small plates or hard, thick prisms, which melt at 250 and form an anhydride, which crystallizes in long needles, melting at 245; these are insoluble in cold water but gradually dissolve in hot water, the acid being re- formed. 3 Ethyl tetrachlorophthalate, C 6 C1 4 (C0 2 C 2 H 6 ) 2 , is prepared by heating the silver salt with ethyl iodide ; it forms large prisms which melt at 60. An isomeric compound is obtained when the acid is treated with phosphorus chloride and the tetrachloro- phthalyl chloride formed submitted to the action, of sodium ethylate (p. 461) ; it crystallizes in tablets and melts at 124 . 4 v-BromopUhalic acid, C 6 H 3 Br(C0 2 H) 2 (3:1: 2), is formed when phthalic acid is heated with bromine and water to 180; it is an indistinctly crystalline powder which melts at 138 140 and yields an anhydride melting at 60 65. 5 a-Bromophthalic acid (4 : 1 : 2) is obtained by the oxidation of bromonitronaphthalene, C 10 H 6 Br(NO 2 ), 6 tetrabromo-/3-naphthol 7 and dibromamidonaphthalene 8 with potassium permanganate. It crystallizes in white, prismatic needles, which melt at 175- 176 and are converted into an anhydride melting at 131 132. a-Dibromophthalic acid, C 6 H 2 Br 2 (C0 2 H) 2 (3:6:1: 2), was pre- pared by Guareschi by the oxidation of a-dibromonaphthalene with nitric acid. It separates from hot water as a crystalline powder, which melts at about 135 with decomposition; on further heating the anhydride sublimes in light, nacreous needles melting at 207'5 208. 1 Atterberg and Widmann, Ber. Deutsch. Chem. Ges. x. 1843. " Ibid, xviii. Kef. 676. 3 Grabe, Ann. Chem. Pharm. cxlix. 18. Grabe, Ber. Deutsch. Chem. Ges. xvi. 860. Faust, Ann. Chem. Pharm. clx. 62 ; Pechmann, Ber. Deutsch. Chem. Ges. xii. 2126. Guareschi, Ann. Chem. Pharm. ccxxii. 262. A. J. Smith. Journ. Chem. Soc. 1879, i. 792. Meldola, ibid. 1885, i. 511 ; see also Stallard, ibid. 1886, i. 187. NITROPHTHALIC ACIDS. 473 (S-Dibromophthalic acid is formed by the oxidation of penta- bromo-a-naphthol, and crystallizes from hot water in needles which melt at 206 and are thus converted into the anhydride, which sublimes in long needles and melts at 208. The salts of this acid are, with the exception of those of the alkali metals, only slightly soluble in water. 1 Tribromophthalic acid, C 6 HBr 3 (CO 2 H) 2 , is prepared from penta- bromo-/3-naphthol ; it is almost insoluble in cold water and crystallizes from hot water in lustrous plates which melt at 190 191 and are converted at a higher temperature into the anhydride, which sublimes in white plates and melts at 157 . 2 Tetrdbromophthalic acid, C 6 Br 4 (CO 2 H) 2 , was obtained by Blum- lein as a product of the oxidation of tetrabromorthoxylene ; it is almost insoluble in the ordinary solvents, and crystallizes from boiling water in lustrous needles, and on the evaporation of its solution in benzene in prisms, which melt at 266 and are thus converted into the anhydride, which sublimes in small, lustrous needles, melting at 258 259. Its salts are for the most part insoluble, or only slightly soluble, in water. NITROPHTHALIC ACIDS. 2247 v-NitropUhalic acid, C 6 H 3 (N0 2 )(CO 2 H) 2 (3:2: 1), is formed by the continued boiling of naphthalene with nitric acid, 3 by the action of a mixture of nitric and sulphuric acids on phthalic acid 4 and by the oxidation a-nitronaphthalene with potassium permanganate 5 or of a-dinitronaphthalene with nitric acid. 6 In order to prepare it, one part of nitronaphthalene is dissolved in 7 parts of 90 per cent, acetic acid, and to this are gradually added 5 parts of chromium trioxide ; water is then added and the solu- tion extracted with chloroform to remove the orthonitrophthalide which is always formed. The acid liquid is then treated with barium carbonate, and the insoluble barium nitrophthalate de- composed by carbonate of soda. The solution of the sodium salt is then acidified and the nitrophthalic acid extracted with 1 Bliimlein, Ber. Deutsch. Chem.Ges. xvii. 2485. 2 Flessa, ibid. xvii. 1479. 3 Laureut, Ann. Chcm. Pharm. xli. 110 ; Marignac, ibid. xlii. 7. 4 Faust, ibid. clx. 57. 5 Guareschi, Ber. Deutsch. Chem. Ges. x. 294. 6 Aguiar, ibid. v. 899. 474 AROMATIC COMPOUNDS. ether. 1 It crystallizes from this in light yellow, monoclinic prisms, which are slightly soluble in cold, more freely in hot water, and readily in alcohol. It decomposes on heating into water and the anhydride ; in a small sealed tube it melts at 218 (Miller). Acid ethyl v-nitrophthalate, C 6 H 3 (NO 2 )(C0 2 C 2 H 5 )CO 2 H, is ob- tained by passing hydrochloric acid into an alcoholic solution of the acid ; it crystallizes from hot water in long needles, melting at 110-5. Normal ethyl v-nitrophthalate, C 6 H 3 (N0 2 )(CO 2 C 2 H 5 ) 2 , is pre- pared from the silver salt by the action of ethyl iodide, and crystallizes from alcohol in long, rhombic prisms, melting at 45 (Miller). a-Nitrophthalic acid, C 6 H 3 (NO 2 )(CO 2 H) 2 + H 2 O (4:2:1), is formed, together with the preceding compound, by the nitration of phthalic acid. 2 In order to prepare it, 50 grms. of phthalic acid are heated with 75 grms of sulphuric acid and the same amount of fuming nitric acid for two hours on the water bath ; 120 grms. of water are then added, and the whole allowed to stand for twelve hours in the cold. The precipitate is washed and extracted with ether, the residue after the evaporation of this consisting of a mixture of the two acids accompanied by a little picric acid. It is re-crystallized from water, to remove the greater portion of the v-acid, the mother liquor evaporated to dryness, and the residue dissolved in alcohol and treated with hydrochloric acid gas, which converts the v-acid into the acid and the a-acid into the normal ether. These are separated by car- bonate of soda solution, and the normal ether then converted into the potassium salt by the action of alcoholic potash ; this is then acidified with hydrochloric acid and the free acid ex- tracted with ether. It may be still more easily obtained by heating paranitrophthalide with dilute nitric acid to 140 . 3 It crystallizes in small needles, which are readily soluble in water and alcohol, effloresce in the air, lose their water at 100, and then melt at 161. Acid ethyl a-nitrophthalate, C 6 H 3 (NO 2 )(C0 2 .C 2 H 5 )CO 2 H, is formed in small quantity when an alcoholic solution of the acid is treated for a short time with hydrochloric acid, and crystallizes from water, in long, thin needles, which melt at 127 128. 1 Beilstein and Kurbatow, Ann. Chem. Pharm. ccii. 217. 2 Miller, ibid, ccviii. 223. 8 Honig, Ber. Deutsch. Chem. Ges. xvii. 3447. AMIDOPHTHAL1C ACIDS. 475 is in- Normal ethyl a-nitrophthalate, C 6 H 3 (NO 2 )(C0 2 .C 2 H soluble in water and crystallizes from alcohol in lustrous tablets, which melt at 34. a-Nitrophthalic anhydride, C 8 H 3 (NO 2 )O 3 , is obtained by heat- ing the acid to 170 and subliming the residue in a current of air at 210, in the form of fascicular crystals, which melt at 114 and are readily soluble in ether and hot water. If the aqueous solution be evaporated, a-nitrophthalic acid is deposited. Dinitrophthalic acid, C 6 H 2 (NO 2 ) 2 (C0 2 H) 2 (5:3:2:1), is formed when /8-dinitrophthalene is heated to 150 with nitric acid of sp. gr. I'lo in a sealed tube, small quantities of nitro- phthalic acid, s-dinitrobenzoic acid, and picric acid being also formed. It crystallizes in large prisms, which are readily soluble in water and alcohol, and melt at 226 . 1 X C0 2 H AMIDOPHTHALIC ACIDS, C 6 H 3 ^-NH 2 . \C0 2 H 2248 v-Amidophthalic acid. When the v-nitro-acid is treated with tin and hydrochloric acid in the cold, needles of the com- pound C 6 H 3 (NH 2 .ClH)(C0 2 H) 2 -f-SnCl 2 +2H 2 O are formed. If the hydrochloric acid solution of this be treated with sulphuretted hydrogen and evaporated, carbon dioxide is given off and meta- amidobenzoic acid formed. Ethyl v-amidophthalate, C 6 H 3 (NH 2 )(C0 2 .C 2 H 5 ) 2 , is prepared by treating a well -cooled alcoholic solution of the ether of the nitro-acid with hydrochloric acid and zinc dust. It is a yellow liquid, which decomposes on heating and forms a splendid blue, fluorescent solution in ether (Miller). a-Amidophthalic acid. When the a-nitro-acid is reduced, no carbon dioxide is evolved, but no double tin salt is formed. On removing the tin and evaporating, however, carbon dioxide is evolved just as in the case of the v-acid, and metamidobenzoic acid formed. If the reduction be carried on by means of zinc dust and acetic acid, a double compound of zinc acetate and zinc amido- phenate is formed, which has probably the constitution C 6 H 3 (NH 2 )(C0 2 H)CO 2 .Zn.O.CO.CH 3 , and crystallizes in fine, white 1 Beilstein and Kurbatow, Ann. Chem. Pharm. ccii. 224. 476 AROMATIC COMPOUNDS. needles, which form an almost colourless solution in hot water, while its solution in acetic acid is coloured yellow and has a green fluorescence. It dissolves in caustic soda, but the solution decomposes on heating, zinc carbonate is deposited and the amidophthalic acid decomposed. 1 Ethyl a-amidophthalate was first prepared by Baeyer but mistaken for the v-compound 2 until Miller showed that it is derived from the a-acid. 3 This substance is obtained in a similar manner to the isomeric compound; it is insoluble in water, slightly soluble in dilute acid, readily in alcohol, from which it crystallizes in monoclinic prisms, which melt at 95 ; the dilute ethereal solution shows a faint blue fluorescence. H SULPHOPHTHALIC ACIDS aELSOJH. \C0 3 2 H 2249 a-Sulphophthalic acid (1:4:2) is obtained by heating phthalic acid or phthalic anhydride with strong, fuming sul- phuric acid, 4 and by the oxidation of /3-naphthalenesulphamide, C 10 H 7 S0 2 .NH 2 , and dinitronaphtholsulphonic acid, C 10 H 4 (NO 2 ) 2 (OH)S0 3 H. 5 It remains as a syrup when its solution is evaporated on the water bath, but solidifies after heating for some time to a mass consisting of stellate groups of sharply pointed prisms ; these contain a molecule of water, which is lost at 140, a brownish syrup being formed, which often solidifies on standing. On heating to 180, the anhydride, C 6 H 3 (C 2 3 ) SO 3 H, is formed as a hard, brown, very hygroscopic mass. The normal barium salt crystallizes in plates or silky needles, slightly soluble in water ; when it is dissolved in the necessary amount of hydrochloric acid, the monacid salt, C 6 H 3 (C0 2 BaSO 3 ) CO 2 H+2H 2 0, is formed, and crystallizes from hot water in large needles ; it is converted by solution in an excess of hydrochloric acid into the diacid salt, (C 6 H 3 (CO 2 H) 2 SO 3 ) 2 Ba+5H 2 O, which also crystallizes in lustrous needles. 1 Bernthsen and Semper, Bcr. Deutsch. Chem. Ges. xix. 164. 2 Ibid. x. 124 and 1079. 8 Ibid. xi. 1191. 4 Low, Ann. Chem. Pharm. cxliii. 249 ; Ree, Bcr. Deutsch. Chem. Ges. xviii. 1629 ; Inaugurald. Bern. 1886 ; Ann. Chem. Pharm. ccxxxiii. 216. 8 Grabe, Ber. Deutsch. Chem. Ges. xviii. 1126. SULPHAMICPHTHALIC ACIDS. 477 When the monacid ammonium salt is heated, the ammonium salt of a-sulphophthalimide is formed ; it crystallizes in mono- symmetric prisms, and is decomposed on heating with formation of phthalimide : >0 X C = C 6 H 4 < >0 + S0 2 + NH 2 + H 2 0. S0 3 NH 4 XX) a-Sulphamidophthalic acid, C 6 H 3 (S0 3 .NH 2 )(CO 2 H) 2 . When a-sulphophthalic anhydride is treated with phosphorus penta- chloride, the monochloride, C 6 H 3 (SO 2 C1)(CO 2 H) 2 , is formed, and is converted by ammonia into the amide, which crystallizes from water in small, transparent prisms (Ree). v-Sulphophthalic acid (1:3: 2) is formed when a-naphthalene- sulphamide is oxidized with potassium permanganate. The first product is the anhydride of sulphamidophthalic acid, which yields the sulphonic acid on heating with hydrochloric acid : V^gXi 3 E5vJ 2 -|- ^ J.J- 2 VX -^ VygJUJ- 4 K_/V^ 3 JL_I. \C0 2 H \CO 2 H It is readily soluble in water, and forms salts which crystallize well. 1 The normal barium salt, (C 6 H 3 (CO 2 ) 2 Ba.SO 3 ) 2 Ba+8H 2 O, crystallizes in transparent tablets. Sulphamidophthalic anhydride or Sulphinidephthalic acid, C 8 H 5 NS0 3 + 2H 2 0, crystallizes from hot water in needles, which become anhydrous at 155. Alkalis do not convert it into sul- phamicphthalic acid ; it is a dibasic acid, the hydrogen of the imide-group being easily replaced by metals. Normal potassium sidphinidephthalate, C 8 H 3 K 2 NSO 3 , is very readily soluble in water and dries to an elastic mass, from which semi-crystalline, spherical masses separate on standing. Acid potassium sulphinidephthalate, C 8 H 4 KNS0 3 + H 2 O, is only slightly soluble in cold, readily in hot water, and crystallizes in long acute prisms, which rapidly lose their water at 100. Normal silver sulphinidephthalate, C 8 H 3 Ag 2 NSO 3 -f H 2 O, is a white precipitate, which is scarcely soluble in boiling water, but dissolves in a hot solution of potassium nitrate and separates out again on cooling. 1 Remsen and Comstock, Amer. Chem. Journ. v. 106 ; Stokes, ibid. \\. 262. 478 AROMATIC COMPOUNDS. Acid silver sulphinidephthalatc, C 8 H 4 AgNSO 3 -I- H 2 0, is formed when the normal salt is heated with nitric acid, or when silver nitrate is added to a dilute boiling solution of the acid potassium salt. It crystallizes on cooling in long, pliant needles, which become anhydrous below 135. The silver salt is converted into the methyl ether by treat- ment with methyl iodide. Normal methyl sulphinidcphthalate, C 8 H 3 (CH 3 ) 2 NS0 3 , crys- tallizes from alcohol in colourless needles, which melt at 180 and readily sublime in iridescent plates. Acid methyl sulphinidephthalate, C 8 H 4 (CH 3 )NSO 3 , separates from an alcoholic or hot aqueous solution in long, striated prisms, or long, narrow tablets, which melt at 1907 191*7 and readily volatilize. When it is successively treated with phosphorus trichloride and methyl alcohol the dimethyl ether is formed. In order to determine the constitution of the acid sulphinide- phthalates, the acid potassium salt was heated with phosphorus pentachloride, the compound C 8 H 3 C1 3 S0 2 NPOC1 2 being formed ; it crystallizes in small prisms, and is converted by methyl alcohol into the trimethyl ether, C 8 H 4 (CH 3 ) 3 NSO 6 , which separates from hot water in needles or long narrow prisms, which melt at 140'5- 141'5. The constitution of these compounds is expressed by the following formulae : 2 632 \COC1 \CO.OCH Since the monomethyl ether is converted into the diethyl ether by the action of phosphorus chloride for a short time, followed by the treatment described above, it follows that in the first of these, and therefore in the acid sulphinidephthalates, it is the hydrogen of the imido-group which is replaced (Stokes) : 3X Z + PC1 5 \CO.OH >r ^^o -}~ JbLOl-l-POC/Jq. \COC1 -r HO.CH 3 =C 6 H 3 ^S0 2 >NCH a +HCL \COC1 \CO:OCH, ISOPHTHALIC ACID. 479 ISOPHTHALIC ACID OR METAPHTHALIC ACID. 2250 This compound is formed by the oxidation of meta- xylene, 1 metatoluic acid, 2 and other meta-compounds with two side-chains containing carbon. It has also been obtained by fusing potassium metasulphobenzoate 3 and potassium meta- bromobenzoate * with sodium formate (Part III. p. 31), and has been found among the products of the oxidation of colophony with nitric acid. 5 In order to prepare it, metaxylene is converted into metaxylylene diethyl ether, and this is then oxidized with chromic acid solution, the reaction proceeding very smoothly. 6 It dissolves in 7,800 parts of water at 25 and in 460 parts at 100, crystallizing in hair-like needles, which usually extend through the whole liquid, and are readily soluble in alcohol. 7 It melts at above 300 and sublimes without decomposition. Potassium isophthalate, C 8 H 4 O 4 K 2 , is readily soluble in water, less readily in alcohol, from which it crystallizes in fascicular groups of needles. Calcium isophthalate, 2C 8 H 4 4 Ca + 5H 2 O, is scarcely more soluble in hot than in cold water and forms fine needles. Barium isophthalate, 2C 8 H 4 O 4 Ba + 7H 2 O, is readily soluble in water and crystallizes from a concentrated solution in lustrous needles, which effloresce in the air. 8 Silver isophthalate, C 8 H 4 4 Ag 2 , is an amorphous precipitate, which, like mercury thiocyanate, forms a voluminous vermiform mass on heating. Methyl isophthalate, C 8 H 4 (CO 2 .CH 3 ) 2 , has been prepared from the silver salt by means of methyl iodide. It crystallizes from dilute alcohol in long fine needles, melts at 64 65, and distils without decomposition. 9 Ethyl isophthalate, C 6 H 4 (C0 2 .C 2 H 5 ) 2 , has been obtained by the action of hydrochloric acid on an alcoholic solution of the acid. 1 Fittig and Yelguth, Ann. Chem. Pharm. cxlviii. 11. 2 Weith and Landolt, Ber. Deutsch. Chem. Ges. viii. 721. 3 V. Meyer, Ann. Chem. Pharm. clvi. 275. 4 Ador and Meyer, ibid. clix. 16. 6 Fittig and Storss, ibid, cliii. 284. 6 W. H. Perkin, jun. Private communication. 7 Fittig and Storss, Ann. Chem. Pharm. cliii. 284. 8 Kelbe, ibid. ccx. 20. 9 V. Meyer, Ber. Deutsch. Chem. Ges. iv. 262 ; Baeyer, Ann. Chem. Pharm. clxvi. 340. 480 AROMATIC COMPOUNDS. It is a liquid which possesses a faint but pleasant odour, boils at about 285, and solidifies at to a dazzling white, radiating mass (Fittig and Storss). Phenyl isophthalate, C 6 H 4 (C0 2 .C 6 H 5 ) 2 , is formed when phenol is heated with the chloride ; it crystallizes in long, fine needles which melt at 120 and are only slightly soluble in alcohol. 1 Isophthalyl chloride, C 6 H 4 (COC1) 2 , is obtained by the distilla- tion of the acid with phosphorus chloride as an oily liquid, which boils at 276 and solidifies to a radiating, crystalline mass, melting at 41 (Schreder). Isophtkalamidc, C 6 H 4 (CO.NH 2 ) 2 , is formed by the action of ammonia on the chloride and is a light, white powder, which melts at 265, is slightly soluble in alcohol, but scarcely dissolves in any other of the ordinary solvents. On heating with phosphorus pentoxide it is converted into isophthalonitril. 2 Metacyanobenzoic acid, C 6 H 4 (CN)CO 2 H, is obtained by allow- ing a hydrochloric acid solution of metadiazobenzoic acid to run into a solution of copper sulphate and cuprous cyanide : CN X COH XX)H 2C 6 H 4 < + Cu 2 (CN) 2 = 2C 6 H 4 + Cu 2 Cl 2 + 2N 2 . 2 It is readily soluble in alcohol and hot water, and crystallizes from the latter in microscopic, arborescent needles, which after drying form a dull white powder and melt at 217. Boiling caustic soda solution readily converts it into iso- phthalic acid. 3 Ethyl mctacyanobenzoate, C 6 H 4 (CN)CO.C 2 H 5 , crystallizes in fine, matted needles, which melt at 48. Benzenylamidoximemetacarboxylic acid, is prepared by heating metacyanobenzoic acid for a long time with an alcoholic solution of hydroxylamine, and forms crystals which are readily soluble in alcohol and hot water, and melt at 200. It is formed according to the equation : /ON C 6 H 4 < 2 . 64 \C0 2 H \C0 2 H 1 Schreder, Bcr. Deutsch. Chem. Gcs. vii. 708. 2 Beyer, Journ. Prakt. Chem. [2] xxii. 351. 8 Sandmeyer, Ber. Deutsch. Chem. Gcs. xviii. 1496. CHLORO-ISOPHTHALIC ACID. 481 The ethyl ether is prepared in a similar manner from the corresponding ether of metacyanobenzoic acid and crystallizes from hot water in needles, which melt at 118 . 1 Isophthalonitril, C 6 H 4 (CN) 2 , is formed by the distillation of potassium benzenemetadisulphonate with potassium cyanide, 2 or of potassium metabromosulphonate with dehydrated potassium ferrocyanide ; 3 it forms fine needles, which melt at 160 161, are only very slightly soluble in water, somewhat more readily in alcohol, and are converted into isophthalic acid by heating with alkalis. ADDITION PRODUCTS OF ISOPHTHALIC ACID. Tetrahydro-isophthalic acid, C 6 H 8 (G0 2 H) 2 , is prepared by boil- ing an alkaline solution of isophthalic acid with sodium amalgam for some time, and crystallizes from hot water in needles, which melt at 199. Its dimethyl ether is an oily liquid. 4 SUBSTITUTION PRODUCTS OF ISOPHTHALIC ACID. 2251 CUoro-isopUhalic acid, 2C 6 H 3 C1(CO 2 H) 2 + H 2 0, has been obtained from the amido-acid by means of the diazo- reaction, and crystallizes from hot water in long, very fine needles, which become anhydrous at 120, and melt at 278 (Beyer). lodo-isopUhalic acid, C 6 H 3 I(C0 2 H) 2 (4:3: 1), is formed by the oxidation of acetyliodotoluene, CH 3 .CO.C 6 H 3 I.CH 3 , which will be subsequently described. It is scarcely soluble in cold, only very slightly in boiling water, and crystallizes from hot acetic acid in small, white needles, which melt at 203 204, but sublime in white, lustrous flocks, without previously melting, when carefully heated. On fusion with caustic potash, para- 1 Miiller, Bcr. Deutsch. Chem. Ges. xix. 1491. 2 Earth and Senhofer, ibid. viii. 1481 ; Ann. Chem. Pharm. clxxiv. 235. 3 Limpricht, ibid, clxxx. 92. 4 Baeyer, Bcr. Devtsch. Chem. Ges. xix. 1806. 482 AKOMATIC COMPOUNDS. hydroxybenzoic acid is formed, while it yields benzoic acid when reduced in alcoholic solution by sodium amalgam. 1 Nitro-isophthalic acid, 2C 6 H 3 (NO 2 )(CO 2 H) 2 + 3H 2 O, is pre- pared by heating isophthalic acid with fuming nitric acid for some time ; 2 it is slightly soluble in cold, very readily in boiling water and alcohol, and crystallizes in thin, lustrous plates, re- sembling those of benzoic acid, which readily lose their water and melt with slight decomposition at 248 249. Its salts, some of which crystallize well, have been fully examined by Beyer. Methyl nitro-isophthalate, C 6 H 3 (N0 2 )(CO 2 .CH 3 ) 2 , is formed when hydrochloric acid is passed into an alcoholic solution of the acid, and crystallizes in fine, lustrous needles, which melt at 121 '5, and yield a vapour which smells like aniseed. Ethyl nitro-isophthalate, C 6 H 3 (N0 2 )(CO 2 .C 2 H 5 ) 2 , forms fine needles or transparent prisms, which melt at 83" 5. Amido-isophthalic acid, C 6 H 3 (NH 2 )(CO 2 H) 2 , is readily obtained from the nitro-acid by reduction with tin and hydrochloric acid. It is only slightly soluble in cold water and alcohol, crystallizing from hot water in lustrous plates and from alcohol in prisms. It combines with acids and bases forming compounds which have been investigated by Beyer. Its ethers are obtained by the reduction of the corresponding nitro-compounds. Methyl amido-isophthalate, C 6 H 3 (NH 2 )(CO 2 .CH 3 ) 2 , crystallizes from wood-spirit in thin, yellowish plates or tablets, which melt at 176> Ethyl amido-isophthalate, C 6 H 3 (NH 2 )(C0 2 .C 2 H 5 ) 2 , forms thin plates or fascicular needles, melting at 118. Its ethereal solution has a splendid violet fluorescence. s-Sulpho-isophthalic acid, CH 3 (C0 2 H) 2 SO 3 H + 2H 2 (1:3: 5), is prepared by the action of sulphur trioxide on isophthalic acid, 3 and by heating the latter to 200 with fuming sulphuric acid. 4 It is very readily soluble in water, but only slightly in dilute sulphuric acid, and crystallizes in long needles or transparent, four-sided, pointed, rhombic columns, which effloresce in dry air, but deliquesce in very damp air. The anhydrous acid melts at 257 258, a slight discolouration taking place. a-Sulpho-isophthalicacid, C 6 H 3 (CO 2 H) 2 SO 3 H + 2H 2 O (1:3: 4), is obtained by the oxidation of an alkaline solution of a-meta- 1 Klingel, Ber. Deutsch. Chem. Ges. xviii. 2701. 2 Fittig and Storss, ibid, cliii. 285 ; Beyer, Journ. Prakt. Chcm. [2] xxv. 465. 8 Heine, Ber. Deutsch. Chem. Ges. xiii. 491. 4 *Lonnies, ibid. xiii. 703. TEREPHTHALIC ACID. 483 xylenesulphonic acid, 1 or metatoluylsulphamic acid 2 with potas- sium permanganate. It is readily soluble in water, and crystallizes from dilute sulphuric acid in flat, very hygroscopic needles melting at 235 240. TEREPHTHALIC ACID. 2252 Paraphthalic acid is readily formed by the oxidation of those para- compounds which possess two side-chains containing carbon, such as paraxylene, 3 cymene, or methylpropylbenzene, CH 3 .C 6 H 4 .C 3 H 7 , cuminol or cuminaldehyde, COH.C 6 H 4 .C 3 H 7 , 4 paratoluic acid, 5 &c. Caillot, as already mentioned, obtained it from oil of turpentine, C 10 H 16 , which is closely related to cymene. The isomerides of this, oil of cajeput, oil of citron, and the thymene contained in thymian, all yield terephthalic acid on oxidation, 6 and it is also formed when potassium parasulpho- benzoate is fused with sodium formate. 7 In order to prepare it, a mixture of 100 grms. of paraxylene, which need not be pure, 400 grms. of potassium dichromate and 550 grms. of sulphuric acid, diluted with two volumes of water, is heated for several days in a flask connected with a reflux condenser until the solution has become coloured a pure green ; the unattacked xylene is then distilled off, and the solution filtered from the precipitated acid, which is dissolved in dilute carbonate of soda and precipitated by hydrochloric acid. The acid is obtained pure by repeating this process two or three times. Cymene, which is easily prepared by distilling camphor with phosphorus pentoxide, may be employed instead of paraxylene, or Roman cumin oil, a mixture of cymene and cuminol, may be used. Terephthalic acid is a tasteless powder, which appears crystal- line under the microscope, is insoluble in ether and chloroform, and scarcely soluble in water and alcohol ; the hot, saturated, aqueous solution has an acid reaction, and deposits the acid on 1 Jacobsen and Lonnies, Ber. Deutsch. CUem.Ges. xiii. 1556. - Coale and Remsen, Amer. Chem. Journ. iii. 214. 3 Bcilstein, Ann. Chem. Pharm. cxxxiii. 40. 4 Miiller and Warren de la Rue, ibid. cxxi. 87. 5 Beilstcin and Yssel de Schepper, ibid, cxxxvii. 308. 6 Schwanert, ibid, cxxxii. 260. 7 Remsen, Ber. Deutsch. Chem. Ges. v. 379. 484 AROMATIC COMPOUNDS. cooling as an indistinctly crystalline powder. It sublimes when heated without previously melting. Ammonium terephthalate, C 8 H 4 O 4 (NH 4 ) 2 , is deposited on the evaporation of its solution in small, lustrous crystals. Calcium terephthalate, C 8 H 4 O 4 Ca + 3H 2 0, separates from hot water in small crystals, which dissolve in 1,214 parts of water at 6. Barium terephthalate, C 8 H 4 O 4 Ba + 4H 2 0, is deposited from a rapidly cooled solution as a white, granular powder ; by gradual evaporation it is obtained in small, concentrically arranged tablets, which dissolve in 355 parts of water at 5. Silver terephthalate, C 8 H 4 4 Ag 2 , is an amorphous precipitate, which blackens in the light. Methyl terephthalate, C 8 H 4 O 4 (CH 3 ) 2 , 4s formed by the action of the chloride on methyl alcohol, 1 and crystallizes from hot alcohol in large flat prisms, which melt at 140 and are volatile without decomposition. By means of this compound the smallest quantity of terephthalic acid can be detected. The substance is treated with phosphorus chloride and then with methyl alcohol, water being finally added and the methyl compound extracted with ether. On the evaporation of the latter characteristic crystals of the compound are obtained. Ethyl terephthalate, C 6 H 4 (C0 2 .C 2 H 5 ) 2 , forms white odourless prisms, which resemble those of urea and melt at 44. The following ethereal salts have been prepared by Beyer, some by means of the chloride, the remainder from the silver salt: 2 Melting- point. Propyl terephthalate, C 6 H 4 (C0 2 .C 3 H 7 ) 2 , long needles .... 31'0 Isopropyl terephthalate, C 6 H 4 (CO 2 .C 3 H 7 ) 2 , lustrous plates . 55'5 Isobutyl terephthalate, C 6 H 4 (C0 2 .C 4 H 9 ) 2 ~ needles 52'5 The normal butyl ether is liquid, while the tertiary butyl ether is only formed with great difficulty, and has not yet been obtained in considerable amount. Miiller and Warren de la Rue have prepared the amyl ether; it crystallizes in scales, which are melted even by the warmth of the hand. Phenyl terephthalate, C 6 H 4 (CO 2 .C 6 H 5 ) 2 , crystallizes from alcohol in fine needles, melting at 19 1 . 3 1 Warren de la Rue and Muller ; Schwanert, loc. cit. 2 Ber. Deutsch. Chem. Ges. x. 1742. 3 Schreder, ibid. vii. 707. TEREPHTHALAMIC ACID. 485 TerepUhalyl chloride, C 6 H 4 (COC1.) 2 , is formed by the distilla- tion of the acid with phosphorus pentachloride and is a crys- talline mass, which has a somewhat sharp odour resembling cinnamon, melts at 78 (Schreder) and boils at 259 (Beyer). Terephthalamide, C 6 H 4 (CO.NH 2 ) 2 , is obtained by the action of ammonia on the chloride, as a white amorphous powder, which is insoluble in all solvents (Warren de la Rue and Muller). Terephthalamic acid, C 6 H 4 (CO.NH 2 )C0 2 H, is obtained as the product of all reactions by which paracyanobenzoic acid might be prepared, as the elements of water are taken up by the latter according to the following equation : ,CN = C 6 H 4 < Terephthalamic acid crystallizes in indistinct, microscopic plates, which are slightly soluble in cold, readily in hot water and alcohol, melt at 214, and are converted into terephthalic acid by boiling with caustic soda (Sandmeyer). Ethyl paracyanobenzoate, C 6 H 4 (CN)CO 2 .C 2 H 5 , is prepared from ethyl paramidobenzoate and crystallizes in needles, melting at 54. On heating with an alcoholic solution of hydroxylamine, the ethyl ether of benzenylamidoximeparacarboxylic acid, C 6 H 4 (CO 2 H)C(NH 2 )NOH, is formed ; it melts at 135 and yields the free acid which melts above 330. l The meta- and para-cyano- benzoic acids and their ethers, therefore, behave towards hydro- xylamine like other nitrils, while the ortho-compounds differ from these. Terephthalonitril, C 6 H 4 (CN) 2 , is prepared by heating terephtha- lamide with phosphorus pentoxide (Warren de la Rue and Muller) or by distilling potassium benzeneparadisulphonate, 2 potassium parachlorobenzenesulphonate, 3 or potassium para- bromobenzenesulphonate 4 with potassium cyanide or dehydrated potassium ferrocyanide. 5 It is insoluble in water, slightly soluble in cold, readily in hot alcohol, and crystallizes in needles or lustrous prisms, which melt at 215 and readily sublime. It is 1 Miiller, Bcr. Deutsch. Chem. Gcs. xviii. 2485 ; xix. 1491. 2 Garrick, Zcitschr. Chem. IS 69, 551. 3 Nolting, Bcr. Deutech. Chan,. Gcs. viii. 1110. * Irelan, Zcitschr. Chem. 1869, 164 ; Earth and Senliofer, Ann. Chem. PJiarm. 174, 242. 3 Limpriclit, ibid, clxxx. 88. 262 486 AROMATIC COMPOUNDS. converted into terephthalic acid by boiling with an aqueous, or more rapidly with an alcoholic, solution of potash. It is, how- ever, better to decompose it by heating to 160 with hydrochloric acid (Limpricht). ADDITION PRODUCTS OF TEREPHTHALIC ACID.i 2253 Tetrahydroterephthalic acid, C 6 H 8 (CO 2 H) 2 . In order to prepare this substance, 5 grins, of terephthalic acid are dissolved in a little caustic soda solution and boiled for twenty hours, 500 grms. of 4 per cent, sodium amalgam being gradually added. It is scarcely soluble in cold water and requires 120 parts of boiling water for solution, from which it crystallizes on cooling in small, arborescent prisms, which melt above 300 and sublime. Its silver salt is a white amorphous precipitate which blackens in the light. Methyl tetrahydroterephthalate,. C 6 H 8 (CO 2 .CH 3 ) 2 , is formed by the action of methyl iodide on the silver salt, as well as by passing hydrochloric acid into a solution of the acid in wood- spirit. It is thus obtained as an oily liquid, which smells of fennel and soon solidifies in large prisms, melting at 39. It crystallizes from ether, in which it forms a blue fluorescent solution, in long needles. Hexhydroterephthalic acid, C 6 H 10 (CO 2 H) 2 ,is obtained by heating the tetrahydro-acid to 240 for six hours with concentrated hydriodic acid. It is even less soluble in water than the tetra- hydro-compound and crystallizes from hot water in small prisms, melting at about 295. It is very stable towards alkaline per- manganate solution, while the tetrahydro-derivative is oxidized to oxalic acid by this even in the cold. Its methyl ether melts at 58 and resembles the preceding compound, but does not give a fluorescent solution. Dibromohexhydroterephthalic acid, C 6 H 8 Br 2 (C0 2 H) 2 -f H 2 0, is best prepared by treating finely divided tetrahydroterephthalic acid for several hours with an ethereal solution of bromine, the mixture being agitated at intervals, and repeating this operation until the acid is almost completely dissolved. The solution is J Baeyer, Bcr. Deutsch. Chcm. Ges. xix. 1805. TETRAHYDROTEREPHTHALIC ACID. 487 then decolourized with sulphur dioxide and the acid extracted by carbonate of soda solution. It is precipitated from the latter by hydrochloric acid in granular, cubic crystals. Its methyl ether is formed by the combination of bromine with the ether of tetrahydroterephthalic acid, and crystallizes in large prisms melting at 73. Tetrahydrophthalic acid behaves towards bromine in the same manner as cinnamic and fumaric acids. When the brominated acid is heated with caustic soda solution, a dihydroterephthalic acid is formed, which resembles terephthalic acid very closely. A syrupy acid is however formed by the action of freshly pre- cipitated silver oxide, which is probably a dihydroxyhexhydro- terephthalic acid, and is converted by the action of bromine into tetrabromocatechol : C 6 H 8 (OH) 2 (C0 2 H) 2 + 7Br 2 = C 6 Br,(OH) 2 + 2C0 2 + 1 OHBr. The constitution of tetrahydrophthalic acid is proved by the formation of this substance, and may also be deduced from the following considerations. Phthalic acid only assumes two atoms of hydrogen when acted upon by sodium amalgam and water, while isophthalic and tere- phthalic acids combine with four. The simplest explanation of this fact is that the double linking of two carbon atoms is con- verted into a single one, if at least one of these be combined with a carboxyl group. The following formulae are thus arrived at : Dihydrophthalic acid. Tetrahydro-isophthalic acid. CH CH C0 2 H HC^ \CH C0 2 H H 2 Cj/\CH 2 Hc'\/CH CO 9 H HC\/CH C0 2 H CH CH Tetrahydroterephthalic acid. Dihydroxyhexhydroterephthalic acid. CH CO 2 H CH C0 2 H H 2 C\/CH H 2 C\/CH.OH CH CO 2 H CH C0 2 H 488 AROMATIC COMPOUNDS. SUBSTITUTION PRODUCTS OF TERE- PHTHALIC ACID. 2254 Chloroterephthalic acid, C 6 H 3 C1(CO 2 H), is prepared from amidoterephthalic acid, and is slightly soluble in hot water, more readily in alcohol. It is crystalline, and melts above 300. The chloride, C 6 H 3 C1(COC1) 2 , obtained by the action of phosphorus chloride, is also crystalline and boils at about 300. By treating this with ammonium carbonate, the arnide, C 6 H 3 C1(CO.NH 2 ) 2 , is formed, and crystallizes from alcohol in crusts, melting above 300. Methyl chloroterephthalate, C 6 H 3 C1(C0 2 .CH 3 ) 2 , forms silky plates, melting at 60. 1 Bromoterephthalic acid, C 6 H 3 Br(CO 2 H) 2 + H 2 O, is formed by the action of potassium permanganate on an alkaline solution of bromoparatoluic acid. , It is almost insoluble in cold water, and crystallizes from hot water in dazzling white, microscopic needles, which melt at 304 305. Phosphorus pentachloride converts it into the chloride, C 6 H 3 Br(COCl) 2 , an oily liquid, which boils at 3 04' 5 305 '5, is only gradually decomposed by water, and combines with aqueous ammonia to form the amide, C 6 H 3 Br(CO.NH 2 ) 2 , which crystallizes from hot water in small needles, melting at 270. Methyl lrow,oterephthalate, C 6 H 3 Br(C0 2 .CH 3 ) 2 , crystallizes in concentrically arranged groups of needles, melts at 42 and boils at above 300 . 2 Dibromoterephthalic acid, C 6 H 2 Br 2 (C0 2 H) 2 , is prepared by heat- ing dibromocymene, C 6 H 2 Br 2 (CH 3 )C 3 H 7 , for some time with nitric acid, 3 and by the oxidation of dibromotoluic acid with potassium permanganate. 4 It crystallizes from hot, dilute alcohol in small plates, which have a satin lustre, do not melt even at 320, and sublime at a higher temperature with decomposition. Ethyl dibromoterephthalate crystallizes from alcohol in nacreous plates, melts at 121 and boils at about 335. Nitroterephthalic acid, C 6 H 3 (NO 2 )(C0 2 H) 2 , is formed by treat- ing terephthalic acid with a mixture of fuming sulphuric and 1 Ahrens, Ber. Deutsch. Chem. Ges. xix. 1634. 2 Fischli, ibid. xii. 619. 3 Claus and Wimmel, ibid. xiii. 902. 4 Schultz, ibid, xviii. 1762. CHLOROTEREPHTHALIC ACID. 489 nitric acids, and crystallizes in prisms ; it separates from hot water in cauliflower-like masses, which melt at 270 . 1 Methyl nitrotcrcphthalate, C 6 H^NO 2 )(CO 2 .CH 3 ) 2 , crystallizes from ether in splendid prisms, which melt at 70. 2 Nitroterephthalamide, C 6 H 3 (NO 2 )(CO.NH 2 ) 2 , was obtained by Warren de la Rue and Miiller in well formed prisms by the nitration of terephthalamide. Amidoterephthalic acid, C 6 H 3 (NH 2 )(CO 2 H) 2 , is formed by the reduction of the nitro-acid with tin and hydrochloric acid, and crystallizes in thin, lemon-yellow prisms or moss-like forms, which are only slightly soluble in cold water and alcohol, and decompose on heating without melting. Their aqueous or alkaline solutions, and those of their salts and ethers, which latter are crystalline bodies but have not been described in detail, show a remarkable blue fluorescence, while acidified solutions of the acid do not possess this property. Methyl am^o^r^A^a/a^,C 6 H 3 (NH 2 )(CO 2 CH 3 ) 2 , forms crystals, melting at 126; its alcoholic and ethereal solutions also show a strong blue fluorescence (Ahrens). Diamidoterephthalic acid, C 6 H 2 (NH 2 ) 2 (CO 2 H) 2 , is not known in the free state; its ethyl ether has been prepared from succinosuccinic ether (Pt. III., p. 146). When the latter is heated with ammonium acetate, a di-imide is formed, which crystallizes in shining, yellow needles, melting at 181. Diethyl- diamidoterephthalate is obtained by the action of bromine on its solution in sulphuric acid : CO.CH 5 CO 2 .C 2 H 6 CH + Br 2 = xl 2^ H 2 C\/C=NH CH C0 2 C 2 H 5 C0 2 C 2 H 6 It crystallizes from hot alcohol in lustrous golden needles of the colour of potassium dichromate, which melt at 168. Its brown alcoholic or ethereal solution shows a golden-yellow fluorescence. It forms slightly soluble salts with hydrochloric and sulphuric acids. 1 Warren de la Rue and M filler, Ann. Chem. Pharm. cxxi. 90 ; Burckhardt, Ber. Deutsch. Chem. Gcs. x. 144. 2 Ahrens, ibid. xix. 1634. 490 AROMATIC COMPOUNDS. When a solution of its diazo-compound in hydrochloric acid is heated with an acid solution of cuprous chloride, an acid is formed which is probably dichloroterephthalic acid, since it is converted into terephthalic acid by the action of sodium amalgam and water. 1 Sulphoterephtlialic acid, C 6 H 3 (S0 3 H)(CO 2 H) 2 , is obtained by heating terephthalic acid with fuming sulphuric acid, 2 and by the oxidation of sulphoparatoluic acid, paratoluylsulphamic acid, or paraxylenesulphonic acid with potassium permanganate. 3 It forms a hygroscopic mass, and yields salts which are soluble in water, but insoluble in alcohol. HYDROXYMETHYLHYDROXYBENZOIC ACID, /OH C 6 H 3 fCG 2 H \CH 2 .OH. 2255 These compounds, which are simultaneously alcohols and phenols, are formed by the action of sodium amalgam on the aldehydo-acids, which are described below. 4 Orthohydroxymelhylsalicylic acid (1:2: 6) is precipitated by acids from its alkaline solution as an oil, which solidifies after some time to hard, white crystals ; it is readily soluble in hot water, alcohol and ether, and crystallizes from the latter in transparent prisms, which melt at 142. Its aqueous solution is coloured an intense bluish-violet by ferric chloride. Parahydroxymethylsalicylic acid (1:2:4) is slightly soluble in alcohol and ether, and crystallizes from the latter in long prisms, which melt at 160 with decomposition. Ferric chloride colours the solution violet. Orthohydroxymelhylparaliydroxybenzoic acid (1:4:2) is a white powder, which does not melt below 270, and gives no colouration with ferric chloride. 1 Baeyer, Ber. Deutsch. Chem. Gcs. xix. 428. 2 Ascher, Ann. Chem. Pharm. clxi. 2 ; Schoop, Ber. Deutsch. Chem. Ges. xiv. 223. 3 Hall and Remsen, ibid. xii. 1434 ; Burney and Remsen, Amer. Chem. Journ. ii. 405 and 413. 4 Reimer, Ber. Deutsch. Chem. Ges. xi. 790. ALDEHYDOHYDKOXYBENZOIC ACIDS. 491 ALDEHYDOHYDROXYBENZOIC ACIDS, /OH C 6 H/C0 2 H \COH 2256 These are prepared by heating the hydroxybenzoic acids with caustic soda and chloroform : C 6 H 4 < 4 SNaOH 4 CHC1 3 = Ta /ONa w + 3NaCl42H 2 0. \C0 2 Na They are converted by reduction into the preceding alcohol- acids, and by fusion with caustic potash into the hydroxyphthalic acids. They combine, like other aldehydes, with the sulphites of the alkali metals. Ortho-aldchydosalicylic acid (1 : 2 : 6) is obtained, together with the following compound, from salicylic acid. It crystallizes in fine, matted needles, which dissolve at 23 25 in 1,500 1,600 parts, or at 100 in 1516 parts of water. The aqueous solution is coloured deep yellow by caustic soda, and red by ferric chloride, and the alcoholic solution shows a faint, bluish violet fluorescence. It melts at 179 and sublimes without decomposition when carefully heated. On distillation with slaked lime it decomposes into salicylaldehyde and carbon dioxide. The copper salt is a gelatinous precipitate, which is soluble in ammonia; on boiling the solution a light blue precipitate of C 8 H 4 O 4 Cu is thrown down. Para-aldehydosalicylic acid (1:2:4) forms long, fine needles, which melt at 248 249, and dissolve in 2,6002,700 parts of water at 25, and in 145 150 parts at 100. Its aqueous solution is not coloured by caustic soda, while ferric chloride produces a deep cherry-red colouration. On distillation with lime, parahydroxybenzaldehyde is formed; its copper salt is also soluble in ammonia, but is not precipitated on boiling. 1 Ortho-aldehydoparahydroxylenzoic acid (1:4:2), was obtained by Reimer and Tiemann from parahydroxybenzoic acid; it 1 Reimer and Tiemann, Bcr. Deutsch. Chem. Ges. ix. 1268, x. 1562. 492 AROMATIC COMPOUNDS. crystallizes from hot water in thin, arborescent prisms, which melt at 243 244, and sublime in splendid, white needles. Its aqueous solution is coloured deep yellow by caustic soda and brownish red by ferric chloride. Salicylaldehyde is formed when it is distilled with caustic lime. Ortho-aldehydometahydroxybenzoic acid (1:3:6) is obtained, together with the following compound, from metahydroxybenzoic acid. It crystallizes in needles, which melt at 234, and are slightly soluble in hot water and readily in alcohol. Its aqueous solution is coloured violet by ferric chloride and deep yellow by caustic soda. On boiling with caustic soda it is only decomposed at a high temperature, phenol being formed. Para-aldehydometahydroxylenzoic acid (1:3:4) has only been obtained as a syrup ; it is very unstable and reduces Fehling's solution readily. On fusion with caustic potash it is converted into a-hydroxyisophthalic acid. 1 >H HYDROXYPHTHALIC ACIDS, C B H-f-< 2 H 2257 a-Hydroxyphthalic acid (4:1: 2). When the ethyl ether of a-amidophthalic acid is dissolved in dilute sulphuric acid, treated with sodium nitrite and then heated to 100, the ether of a-hydroxyphthalic acid separates out as a yellowish oil, which yields the free acid on saponifying with potash ; it is purified by precipitating the neutral solution with basic lead acetate and removing the lead by sulphuretted hydrogen. 2 It is also obtained by oxidizing the sulphamido-orthotoluic acids with potassium permanganate and fusing the residue with potash, 3 and is formed when para-aldehydometahydroxybenzoic acid, 4 a-chlorophthalic acid, 5 and a-sulphophthalic acid 6 are fused with caustic potash or soda. It is tolerably soluble in cold, very readily in hot water and alcohol, and crystallizes in large stellate groups of pointed prisms which melt at about 185, the anhydride being formed ; on heating with dilute hydrochloric acid to 180, it decomposes 1 Landshoff and Tiemann, Bcr. Deutsch. Chem. Ges. xii. 1334. - Baeyer, ibid. x. 1079. 3 Jacobsen, ibid. xiv. 42. 4 Tiemann and Lamlshoff, ibid. xii. 1337. 5 Kriiger, ibid, xviii. 1759. 6 Griibe, ibid, xviii. 1130 ; Ree, Inaugurate. Bern. 1886. HYDKOXYPHTHALIC ACIDS. 493 into carbon dioxide and metahydroxybenzoic acid (Ree). Its aqueous solution is coloured reddish yellow by feme chloride. When the acid is heated with resorcinol, hydroxyfluoresce'in is obtained, which forms a dark, yellowish red solution in caustic potash, and is slightly soluble in water with a yellowish green fluorescence; acids separate it from its alkaline solution as a yellow precipitate. a-Hydroxyphthalic anhydride, C 8 H 4 4 , sublimes in feathery needles, when the acid is heated and melts at 165 166. a-Methylhydroxyphthalic acid, C 6 H 3 (OCH 3 )(C0 2 H) 2 , is formed by the oxidation of methylparahydroxyorthotoluic acid with potassium permanganate, and crystallizes from water in stellate groups of needles, which lose water on heating, forming the anhydride, which sublimes in long needles and melts at 93 . 1 v-Hydroxyorthophthalic acid (3:1:2) is prepared by gently fusing v-methylhy.droxyphthalic acid with potash, and by means of the diazo-reaction from the product of reduction of a-nitro- phthalic acid, which contains amidophthalic acid. It separates from hot water as a compact, crystalline mass, consisting of short, hard prisms, which are partly converted by heating into the anhydride, melting at 145 148, and are partly de- composed into phenol and carbon dioxide. Its aqueous solution is coloured a deep cherry-red by ferric chloride. When it is heated to 200 with resorcinol, hydroxyfluorescem is formed. Dinitro-v-liydroxyphthalic acid, C 6 H(NO^) 2 (OH)(CO 2 H) 2 , was first obtained by the action of nitric acid on juglon, a hydroxy- naphthoquinone, C 10 H 5 (OH)O 2 , which occurs in green walnut shells (Juglans regia), and was c&lled juglonic acid. It may also be prepared by the nitration of v-hydroxyphthalic acid ; it is exceptionally soluble in water, alcohol and ether, and separates from petroleum ether in small crystals. Its acid potassium salt, C 8 H 3 KN 2 O 9 , crystallizes in yellow, rhombic plates, which detonate violently on heating. It can be recrystallized from nitric acid or dilute sulphuric acid without undergoing decomposition. 2 v-Mcthylhydroxyphthalic acid has been prepared by the oxidation of v-methylorthohomometahydroxybenzoic acid ; it is tolerably soluble in water, and crystallizes in microscopic prisms, which melt at 160, and are thus converted into the anhydride, which sublimes in needles and melts at 87. 3 1 Schall, Ber. Dcutsch. Chem. Ges. xii. 829. 2 Bernthsen and Semper, ibid, xviii. 210 ; xix. 164. 3 Jacobsen, ibid. xvi. 1962. 494 AROMATIC COMPOUNDS. 2258 a-Hydroxyisophthalic acid (4:1:3) is formed, together with a large quantity of hydroxytrimesic acid, C 6 H 2 (OH)(C0 2 H) 3 , when carbon dioxide is passed over disodium salicylate heated to 370 380 . 1 It may be obtained in a similar manner from parahydroxybenzoic acid, which first changes into salicylic acid. 2 It is also formed by the oxidation of para-aldehydosalicylic acid or ortho-aldehydoparahydroxybenzoic acid with potassium per- manganate, and when this acid, 3 a-metaxylenol, 4 or a-metaxylene- sulphonic acid, 5 is fused with potash. When an alkaline solution of salicylic acid is heated to 120 130 with tetrachloromethane, a-hydroxyisophthalic acid is obtained, together with a little v-hydroxyisophthalic acid. 6 In order to prepare it, phenol is dissolved in an alkaline solu- tion which contains one molecule of potash to three of soda, the mass evaporated and carbon dioxide passed over the dry residue for some time at 120 160, the temperature, being finally raised to 300 320. The chief product of the reaction is a-hydroxy- isophthalic acid accompanied by parahydroxybenzoic acid and hydroxytrimesic acid, almost two-thirds of the phenol coming over unchanged. The residue is decomposed with hydrochloric acid, and the a-hydroxyisophthalic acid repeatedly recrystallized from water. 7 It forms long needles, which cross each other at an angle of 60, melt at 305 306, and dissolve at 10 in 5,000, at 24 in 3,000, and at 100 in 160 parts of water. It is readily soluble in alcohol and ether, but not in chloroform, by means of which it can be separated from hydroxytrimesic acid. Its aqueous solution is coloured a deep cherry-red by ferric chloride. On heat- ing to 200 with hydrochloric acid, it decomposes into phenol and carbon dioxide, while on dry distillation it yields salicylic acid, phenol and carbon dioxide. When its disodium salt, C 6 H 3 (OH)(CO 2 Na) 2 , is heated to 250, the trisodium salt, C 6 H 3 (ONa) (CO 2 Na) 2 , is obtained, together with phenol and carbon dioxide, while the potassium salt yields a large amount of parahydroxy- benzoic acid when heated to 280 300 (Ost). a-Methoxyisophthalic acid, C 6 H 3 (OCH 3 )(CO 2 H) 2 , is formed by 1 Ost, Journ. Pralcl. Chem. [2] xiv. 99. 2 Kupferberg, ibid. [2] xvi. 423. 3 Tiemann and Keimer, Ber. Deutsch. Chem. Ges. x. 1571. 4 Jacobsen, ibid. xi. 377. 5 Jacobseu and Remsen, ibid. xi. 377. 6 Hasse, ibid. x. 2195. 7 Ost, Journ. Prakt. Chem. [2] xv. 301. HYDROXYTEREPHTHALIC ACID. 495 the oxidation of a-metaxylenyl monomethyl ether, 1 or methyl- parahomosalicylic acid 2 with potassium permanganate, and crystallizes from hot water in microscopic needles, melting at 261 (Schall). Dimethyl a-hydroxyisophthalate, C 6 H 3 (OH)(CO 2 .CH 3 ) 2 , forms large, flat needles which melt at 96 (Jacobsen). Diethyl a-Jiydroxyisophtlialate, C 6 H 3 (OH)(CO 2 .C 2 H 5 ) 2 , crystal- lizes in fine needles, which melt at 52 and are soluble in caustic soda (Ost). v-HydroxyisopTithalic acid (2:1:3) is formed when ortho- aldehydosalicylic acid 3 or sulphamido-isophthalic acid 4 is fused with potash. It crystallizes in hair-like needles, which melt at 243 244, dissolve in 700 parts of water at 24, and in 35-40 parts at 100. Ferric chloride produces a cherry-red colouration ; the aqueous and alcoholic solutions show a bluish violet fluorescence, which is destroyed by alkalis. The acid de- composes on heating, the chief portion being resolved into salicylic acid and carbon dioxide. v-Methoxyisoplithalic acid, C 6 H 3 (OCH 3 )(C0 2 H) 2 , is prepared by the oxidation of methylorthohomosalicylic acid and crystallizes from water in prisms, which melt at 216 218, turning brown and subliming at the same time (Schall). s-Hydroxyisophthalic acid (5 : 1 : 3) is obtained by fusing s-sul- pho-isophthalic acid with potash, and by means of the diazo- reaction from amido-isophthalic acid. It crystallizes from hot water, in which it readily dissolves, in fascicular groups of needles with two molecules of water, which are lost at 100. It melts at 288 and sublimes in broad, lustrous needles, which dissolve in 3280 parts of water at 5 and are coloured a faint yellow by ferric chloride. It decomposes into phenol and carbon dioxide on distillation with lime : 5 Melting- point. Dimethyl s-hydroxyisophthalate, C 6 H 3 (OH)(CO 2 .CH 3 ) 2 , fine needles " 160 Diethyl s-hydroxyisophthalate, C 6 H 3 (OH)(CO 2 .C 2 H 5 ) 2 mono- clinic prisms 103 2259 Hydroxyterephthalic acid (2:1:4) was prepared by Warren de la Rue and Muller from amidoterephthalic acid by 1 Jacobsen, Ber. Deutsch. Chem. Ges. xi. 898. 2 Schall, ibid. xii. 828. 3 Tiemann and Riemer, ibid. x. 1570. 4 Jacobsen. 6 Heine, Ber. Deutsch. Chem. Ges. xii. 494 ; Lonnies, ibid. xiii. 705. 496 AROMATIC COMPOUNDS. the action of nitrous acid. 1 It is also formed when paraxylenol, 2 bromoterephthalic acid, 8 ortho-aldehydometahydroxybenzoic acid, 4 or metahydroxyparatoluic acid 5 is fused with caustic potash. In order to prepare it, amidoterephthalic acid is dissolved in dilute sulphuric acid, treated with sodium nitrite and boiled. 6 It forms a powder, which is slightly soluble in hot water, readily in alcohol, and sublimes on heating with partial decomposition without previously melting. Its aqueous solution is coloured an intense violet-red by ferric chloride. When it is mixed with sand and submitted to dry distillation, it decomposes into carbon dioxide and phenol, and on heating with hydrochloric acid to 220 is resolved into carbon dioxide and metahydroxybenzoic acid, while fusion with an excess of caustic potash converts it into salicylic acid, together with a smaller amount of metahy- droxybenzoic acid. 7 Methoxyterephthalic acid, C 6 H 3 (OCH 3 )(C0 2 H) 9 , is formed by the oxidation of methylmetahomosalicylic acid 8 and crystallizes from hot water in small prisms, which melt at 277 279, and are resolved into methyl chloride and hydroxyterephthalic acid by hydrochloric acid at 160. Dimethyl hydroxyterephthalate,Q^(Qi]) (CO 2 .CH 3 ) 2 , is obtained by passing hydrochloric acid into a solution of the acid in methyl alcohol, and crystallizes in splendid, silky needles, which melt at 94 and are soluble in hot water, readily in alcohol. Ferric chloride gives a somewhat fainter colouration than with the free acid. When the ethereal solution is shaken up with caustic soda solution, the sodium compound, C 6 H 3 (ONa)(C0 2 .CH 3 ) 2 , is formed as a white paste. On heating the acid with caustic soda, methyl iodide and wood-spirit, the trimethyl ether, C 6 H 3 (OCH 3 )(CO 2 .CH 3 ) 2 , is obtained as an oily, pleasant-smelling liquid. Dimethyl acetoxyterepUUate, C 6 H 3 (OCO.CH 3 )(CO 2 .CH 3 ) 2 , is prepared by heating the dimethyl ether with acetyl chloride, and crystallizes from alcohol in cauliflower-like masses of fine needles, melting at 76 (Burckhardt). Dinitrohydroxyterephthalic acid, C 6 H(NO,)(OH)(C0 2 H) 2 , is Ann. Clicm. Pharm. cxxi. 96. Jacobsen, Ber. Deutsch. Chem. Ges. xi. 570. Fischli, ibid. xii. 621. Tiemann and Landshoff, ibid. xii. 1336. Hall and Remsen, ibid. xii. 1433. Burckhardt, x. 144. Earth and Schreder, xii. 1260. 8 Schall, ibid. xii. 828. HYDROXYMETHYLDIHYDROXYBENZOIC ACIDS. 497 formed by the action of a mixture of concentrated nitric acid and fuming sulphuric acid on hydroxyterephthalic acid. It is readily soluble in water, from which it separates in golden yellow, trans- parent crystals, resembling those of calc-spar, which are, like the yellow and red salts of the acid, explosive. 1 HYDROXYMETHYLDIHYDROXYBENZOIC ACIDS, X CH 2 .OH C fl H 8 (OH) / \CO.OH 2260 In 1832, Couerbe detected meconin? C 10 H 10 4 , in opium, and Wohler and Liebig, in 1842, obtained opianic acid, 3 C 10 H 10 O 5 , by the oxidation of narcotin or opian, which is also an opium alkaloid. This acid was more closely investigated by Wohler, who found that it is converted by further oxidation into hemipinic acid, C 5 H 5 3 . He assumed that in its formation one molecule of opianic acid took up oxygen and formed two mole- cules of hemipinic acid ; he says : " It contains a radical which consists of half the radical of opianic acid, and this is referred to in its name." * Anderson, who also investigated the products of oxidation of narcotin, obtained a substance, opianyl, in addition to these acids, and pointed out that it shows an interesting relation to opianic and hemipinic acids when the formula of the latter of these is doubled, as his and Laurent's 5 researches had shown to be necessary. " For we have as follows : Opianyl ..... C 10 H 10 O 4 , Opianic acid . . . C 10 H 10 O 5 , Hemipinic acid . C 10 H 10 6 , as though these three compounds were different oxidation pro- ducts of the same radical." 6 He subsequently found that opianyl is identical with me- conin. 7 Matthiessen and Foster then made the important observation, 1 Burckhardt, Ber. De.utsch. Che.m. Ges. xii. 1273. 2 Ann. Chim. Phys. xlix. 44 ; 1. 337 ; lix. 148. 3 Ann. Chem. Pharm. xliv. 126. 4 Ibid. 1.1. 5 Compt. Rend, xx. 1118. 6 Ibid. Ixxxvi. 179. 7 Ibid, xcviii. 44. 49S AROMATIC COMPOUNDS. that when opiaiiic acid is evaporated with caustic potash solution it is resolved into meconin and hemipinic acid : They also found that opianic acid is reduced to meconin by the action of water and sodium amalgam : C 10 H 10 6 +2H = C 10 H 10 4 +H 2 0. These highly characteristic reactions receive, according to them, a simple explanation, if it be assumed that a very un- stable hydrate of meconin, C 10 H 12 O 6 , is first formed. The de- composition of opianic acid then becomes quite analogous to that of benzaldehyde into benzyl alcohol and benzoic acid, and the reduction of the former also corresponds to that of benzalde- hyde to benzyl alcohol. By heating hemipinic acid with concentrated hydriodic acid, they obtained carbon dioxide, methyl iodide and hypogallic acid, according to the equation : C 10 H 10 6 +2HI = C0 2 + 2CH 3 I + C 7 H 6 O 4 . If hydrochloric acid be employed, metliylhypogallic c^,C 8 H 8 O 4 is first formed, and is converted into hypogallic acid by further heating. Hemipinic acid, therefore, as well as opianic acid and meconin, contains two methyl groups, and the three bodies in question are derivatives of the still unknown normal compounds : Normeconin .... C g H 6 O 4 , Noropianic acid . . C 8 H 6 O 5 , Norhemipinic acid . C 8 H 6 O 6 , as they may be shortly designated, ordinary meconin being thus dimethylnormeconin, &c. They then succeeded in converting the latter, as well as opianic acid, into methylnor meconin, C 9 H 8 O 4 , and mdhylnor- opianic acid, C 9 H 8 O 5 , by heating with hydrochloric or hydriodic acid. They finally considered hemipinic acid to be dimethyl- dihydroxyterephthalic acid and looked upon opianic acid as the corresponding aldehy do-acid, 1 but, as shown by Matthiessen and Wright, the former can be readily converted into an anhydride, and must therefore be dimethyldihydroxyphthalic acid. 1 Phil. Trans. 1863, 345 ; Journ. Chem. Soc. [2] i. 342 ; ibid. vi. 357- MECONIN AND OPIANIC ACID. 499 Liebermann and Chojnacld proposed the following formula for opianic acid : /COH C 6 H 2 (OCH 3 ) 2 < \CO.OH and this was confirmed by the researches of Beckett and Wright, who also found that hypogallic acid is identical with protocatechuic acid. In the case of meconin there were two possibilities ; it might be either hemipinic aldehyde or the anhydride of an alcoholic acid: /COH /CH 2V C 6 H 2 (OCH 3 ) 2 < C 6 H 2 (OCH 3 ) 2 <; >O. CO / The facts that it is formed from opianic acid by the action of nascent hydrogen, and cannot be re-oxidized to opianic acid, while the latter is converted into meconin and hemipinic acid by heating with caustic potash, are in favour of the latter view. Beckett and Wright then proved that this view is correct, and their results were confirmed by the researches of Hessert. 1 Hemipinic acid is dimethylcatecholdicarboxylic acid, and can readily be converted into protocatechuic acid or catecholcarboxylic acid, in which the side-chains have the position C0 2 H : OH : OH = 1 : 3 : 4. Since hemipinic acid is simultaneously a derivative of phthalic acid, the second carboxyl group must be either in position 2 or 6 ; in the latter case it would yield only one acid methyl ether, while in the ' former two such compounds would be possible. Wegscheider has now found that two such isomerides exist, 2 and he has also obtained isovanillin by heating opianic acid with dilute hydrochloric acid, 3 while Beckett and Wright found that methylvanillin is formed when sodium opianate is distilled with soda-lime. It follows from these facts that the constitutions of the three compounds in question are represented by the following formulae : Meconin. Opianic acid. Hemipinic acid. CH 2>0 COH CO.OH o /NcO.OH /\CO.OH \/OCH 3 \/OCH 3 OCH 3 OCH 3 OCH 3 1 Journ. Chem. Soc. 1876, i. 164, 281, 461. 2 Monatsh. Chem. iii. 348. 3 Ibid. iii. 798. 500 AROMATIC COMPOUNDS. Meconin therefore stands to hemipinic acid in the same rela- tion as phthalide to phthalic acid. 2261 . Meconinic acid or Hydroxymetliyldimetlioxybenzoic acid, C 6 H 2 (OCH 3 ) 2 (CH 2 .OH)CO 2 H, is not known in the free state. When its lactone, meconin, is dissolved in baryta water, barium meconinate, (C 10 H n O 5 ) 2 Ba, is formed, and is left on evaporation as a gummy mass * (Kessert), while Prinz obtained it in fine, silky needles. 2 This salt, however, yields meconin on decom- position with a strong acid. The copper and silver salts are precipi- tates, which decompose on heating with formation of meconin. Meconin, C 10 H 10 O 4 , as already mentioned, occurs in opium. Anderson obtained it, accompanied by other products, by the oxidation of narcotin with nitric acid, and it is also formed by the reduction of opianic acid. In order to prepare it, the mother liquor of the opium alka- loids is extracted with ether, the solution evaporated, and the residue washed with hydrochloric acid and re-crystallized from water (Anderson). It forms white, lustrous needles, which have a bitter taste, melt at 102 102'5 (Wright), and when carefully heated sublime in splendid needles. It is readily soluble in alcohol and ether, and requires 22 parts of boiling water and 700 parts of water at 15'5 for solution. On heating with concentrated sulphuric acid, a purple-coloured solution is formed. It forms ethers when heated with stearic or be.nzoic acids, as was shown by Berthelot, who concluded from this that it is an alcohol. 3 Chloromeconin, C 10 H 9 C10 4 , was prepared by Anderson by the action of chlorine on fused meconin or on its aqueous solution. It crystallizes in colourless needles, which are scarcely soluble in cold, somewhat more readily in hot water, and more freely in alcohol, melt at 175 and sublime without decomposition. Bromomeconin, C 10 H 9 Br0 4 , crystallizes from alcohol in colour- less needles, melting at 167. lodomeconin, C 10 H 9 IO 4 , is formed by the action of chloride of iodine on an aqueous solution of meconin, and forms long crystals or needles, which melt at 112, and decompose when more strongly heated. Nitromeconin, C 10 H 9 (NO 2 ) 2 O 4 , is obtained by dissolving meconin in cold, concentrated nitric acid, and precipitating with water. It crystallizes from alcohol in white needles or prisms, which 1 Bcr. Dcutsch. Chem. Ges. xi. 240. 2 Journ. Prakt. Chem. [2] xxiv. 373. 8 Ann. Chim, Phys. [3] Ivi. 51 ; Ann. Chem. Pharm. cxii. 356. MECONINIC ACID. 501 melt at 160, and sublime when carefully heated. It forms a yellow solution in hot alkalis and is not re-precipitated by acids, nitromeconinic acid being probably formed. Amidomeconin, C 10 H 9 (NH 2 )O 4 , is prepared by warming the preceding compound with iron filings and acetic acid. It is precipitated by water as a yellowish powder, which is only slightly soluble in benzene, and melts at 171. Methyl normeconin, C 6 H 2 (OCH 3 )(OH)C 2 H 2 O 2 , is formed when meconin is heated with hydrochloric or hydriodic acid (Mat- thiessen and Foster), and when meconin or narcotin is carefully fused with caustic potash (Beckett and Wright). It crystallizes from hot water in prisms, which melt at 125; ferric chloride colours the aqueous solution a beautiful blue, which is converted into red by the addition of ammonia. On further fusion with potash it is converted into protocatechuic acid. ty-Meconin. When hemipinimide, which will be further de- scribed below, is boiled with tin and hydrochloric acid, hemi- pinimidine is formed : CO CH 2 (CH 3 0) 2 C 6 H 2 ( >0 + 4H = (CH 3 0) 2 <( >O \C=NH \0=NH +H0. This substance crystallizes from benzene in small plates, which melt at 181, and are converted into nitrosohemipinimidine, C 10 H 10 O 3 N(NO), by the action of sodium nitrite on their solution in hydrochloric acid. The latter compound crystallizes from hot alcohol in silky, yellow needles, and dissolves in caustic soda solution with evolution of nitrogen. Hydrochloric acid added to this solution precipitates ^-meconin, which crystallizes from hot water in colourless needles, melting at 123 124. Its isomerism with meconin is shown by the following formula : co >0 H. \/OCH ; OCH, Nitro-ty-meconin, C 10 H 9 (NO 2 )0 4 , crystallizes in splendid, yellowish needles, which melt at 166. Amido-ty-meconin, C 10 H 9 (NH 2 )O 4 , resembles amidomeconin, but is readily soluble in benzene, and melts at 165 . 1 1 Salomon, Ber. Deutsch. Chem. Gcs. xx. 883. 263 502 AROMATIC COMPOUNDS. Meconiosin, C 8 H 10 O 2 , also occurs in opium, and crystallizes in plates, which melt at 88 and dissolve in 27 parts of cold water, and in almost every proportion in boiling water. On heating with sulphuric acid a splendid green solution is formed. 1 ALDEHYDODIHYDROXYBENZOIC ACIDS, X COH CA( H) O + H 2 0. (CH 3 0) 2 (COH)C 6 H 2 .C(K Opianic anhydride is also obtained when opianic acid is heated with phosphorus pentachloride, and crystallizes from hot acetone in needles, which melt at 234. 1 Bcr. Dcutsch. Chcm. Gcs. xx. 881. 2 Ann. Chem. Pharm. Suppl. vii. 63. 3 Monatsh. Chcm. iv. 262. 4 Bcr. Dcutsch. Chcm. Gcs. xix. 2286. 506 AROMATIC COMPOUNDS. On heating with caustic potash and a little water, it decom- poses into meconin and hemipinic acid, while on boiling with caustic potash solution, or when it is dissolved in sulphuric acid and the solution poured into water, it is reconverted into opianic acid. Acetylopianic acid. When aromatic aldehydes or aldehydo- acids are heated with acetic anhydride and anhydrous sodium acetate, the aldehyde group CHO is converted into the acrylic acid residue CH=CH C0 2 H. Opianic acid does not behave in this way, but forms acetylopianic acid, which crystallizes from hot water in needles melting at 120 121. It is insoluble in cold alkalis and is only decomposed on boiling, acetic and opianic acids being formed ; it therefore does not contain a carboxyl group, and its constitution must be expressed by the following formula : /CO (CH 3 0) 2 C 6 H 2 < >0 \CH.O.CO.CH 3 It appears, therefore, that opianic acid can behave not only as an ortho-aldehydo-acid, but also as a lactone. 1 The one form can pass into the other according to the circumstances of the case: /CO.OH /CO (CH 3 0) 2 C 6 H / - (CH 3 0) 2 C 6 H 2 < >0 . \CH.OH Opianyl sulphurous acid, C 6 H 2 (OCH 3 ) 2 (CHO.S0 3 H 2 )CO 2 H, is formed when opianic acid is dissolved in a hot aqueous solution of sulphur dioxide : /CHO ^CO.OH (CH 3 0) 2 C 6 .H 2 / -hSO(OH), (CH 3 0) 2 C 6 H \CO.OH On evaporation at a gentle heat, the compound is left as a fine crystalline mass, which is resolved into its constituents by water. Its solution has a characteristic bitter taste, and leaves a persistent, sweet after-taste. 1 Liebermann and Kleemann, Ber. Dcutsch. Chem. Ges. xix. 2287. THIO-OPIANIC ACID. 507 Barium opianyhulphitc, (C 10 H 10 O 5 .SO 3 H) 2 Ba + 3H 2 0, is pre- pared by dissolving barium carbonate in a freshly -made solution of the acid, and crystallizes in lustrous, rhombohedral tablets. Lead opianylsulphite, (C 10 H 10 O 5 .SO 2 H) 2 Pb + 6H 2 0, is prepared in a similar manner, and forms very lustrous, four-sided prisms or six-sided tablets (Wohler). These salts correspond to the ethidene sulphites (Part II. p. 73). 2265 Thio-opianic acid, (CH 3 O) 2 C 6 H 2 (CHS)CO 2 H, was ob- tained by Wohler by passing sulphuretted hydrogen into a warm solution of opianic acid ; it forms a yellow powder which crystal- lizes from alcohol in fine, transparent, yellowish prisms, which melt below 100 and resemble opianic acid in forming an anhydride. Chloropianic acid, (CH 3 0) 2 CHC1(COH)CO 2 H, is formed by the action of potassium chlorate on a hot solution of opianic acid in hydrochloric acid, and crystallizes from hot water in small prisms melting at 210 211 (Prinz). Bromopianic acid, (CH 3 0) 2 C 6 HBr(COH)C0 2 H, is prepared by adding bromine to a boiling solution of opianic acid (Prinz) and by triturating opianic anhydride with bromine (Wegscheider). It crystallizes from hot water in small, arborescent needles which melt at 204. Nitro-opianic acid, (CH 3 O) 2 C 6 H(NO 2 )(COH)C0 2 H, is formed, together with nitrohemipinic acid, by the action of concentrated nitric acid on opianic acid. It is only slightly soluble in water, and crystallizes in lustrous yellow prisms, melting at 166. Its salts are readily soluble in water and crystallize well. Opianylplienylliydrazide, C 16 H 14 N 2 O 3 , is obtained by mixing hot solutions of opianic acid, phenylhydrazine hydrochloride, and sodium acetate (Part III. p. 283) : 5 N 2 H 3 = C 16 H 14 N 2 3 It crystallizes from alcohol in almost colourless needles, which melt at 175, and are insoluble in alkalis, but dissolve in con- centrated hydrochloric acid, from which solution they are pre- cipitated by water. It is therefore a weak base, and is very stable, being unattacked by concentrated sulphuric acid even at 130 ; it has probably the following constitution ; /CO N.C 6 H 6 508 AROMATIC COMPOUNDS. Phenylhydrazine nitro-opianic acid, C 16 H I5 N 3 6 , is formed in a similar manner, according to the equation : /CO.OH (CH 3 0) 2 C 6 H (NO,) < + NH 2 -NH.C 6 H 5 /CO.OH (CH 3 0) 2 C 6 H(N0 2 K +H 2 0. =iN NHC 6 H 5 It crystallizes in splendid, carmine-red needles, which melt at 184, and form a red solution in alkalis. Acids convert it into nitro-opianylphenylhydrazide, C 16 H 13 N 3 5 , which crystallizes in yellow, silky needles, melting at 173, is insoluble in alkalis, and behaves as a weak but stable base. 1 When it is boiled with alcoholic potash, it decomposes into methyl alcohol and nitromethylnoropianylwhenylhydrazide, C 15 H n N 3 5 , which has also been prepared from methylnor- opianic acid. 2 This substance crystallizes in glittering, yellow plates, melting at 191, and since it is a phenol, behaves as a weak acid. Amido-opianylphenylhydrazide, C 16 H 15 N 3 3 , is obtained by the reduction of the nitro-compound with tin and hydrochloric acid. It crystallizes in fine needles, and oxidizes in the air to amido- hemipinylphenylhydrazide. 2266 Isonoropianic acid, C 6 H 2 (OH) 2 (COH)C0 2 H(C0 2 H : OH : OH : COH 1:3:4:5), is formed when the following compound is heated to 170 180 with hydrochloric acid. It is tolerably soluble in cold, readily in hot water, and crystallizes in yellowish needles, which melt with decomposition a few degrees above 240. Its aqueous solution is coloured yellow by alkalis and dark green by ferric chloride, this colour being instantly changed to reddish violet by the addition of ammonia. It reduces ammoniacal silver solution in the cold, and Fehling's solution on boiling. 3 Methylisonoropianic acid or Aldehydovanillic acid, C 6 H 2 (OCH 3 ) (OH)COH(C0 2 H), is formed, together with vanillin, when vanillic acid is heated with caustic soda and chloroform. It is readily soluble in alcohol, very slightly in cold, somewhat more readily in boiling water, from which it crystallizes in fine, silky needles, which melt at 221 222. As an aldehydo-acid 1 Liebermann, Bcr. Deutsch. Chem. Gcs. xix. 763. 2 Elbel, ibid. xix. 2306. 3 Mendelsohn and Tiemann, ibid. x. 393. ISOPIANIC ACID. 509 it combines with acid sodium sulphite ; caustic soda colours the solution an intense yellow, while ferric chloride produces a dirty reddish violet colouration. Its constitution follows from the fact thai;, in the synthesis of aldehydes or aldehydo-acids from phenols by means of chloro- form, the aldehyde group always takes either the ortho- or para- position with regard to the hydroxyl. Since the latter is occupied in vanillic acid, the aldehyde group must lie next the hydroxyl, and the two groups are thus found in aldehydovanillic acid in the same relation as in salicyl aldehyde a view which is confirmed by its behaviour towards caustic soda and ferric chloride. 1 As a phenol it forms two series of salts. 2 Methyl aldeJiydovanillate, C 6 H 2 (OCH 3 )OH(COH)CO 2 .CH 3 , is prepared by heating the acid with caustic potash, wood-spirit and methyl iodide, and forms yellow needles, which melt at 134 135, and are soluble in carbonates of the alkalis. Isopianic acid, C 6 H 2 (OCH 3 ) 2 (COH)CO 2 H. The methyl ether of this compound is formed together with the foregoing com- pound. It crystallizes from boiling water in fine needles, which melt at 98 99, and are insoluble in the alkali carbonates. It is readily saponified by hot caustic potash solution. The free acid, which is precipitated by acids from this product, crystallizes from water in fine needles, melting at 210 211, which give no colouration with caustic soda or ferric chloride. It forms a slightly soluble compound with acid sodium sulphite. 3 Quercimeric acid, C 8 H 6 O 5 -hH 2 O. This substance, which is very similar to isonoropianic acid, was obtained by Hlasiwetz and Pfaundler by fusing quercitin with caustic potash. It forms crystalline granules or small prisms, is readily soluble in water, and reduces Fehling's solution and salts of silver. Ferric chloride produces a blue colouration in the aqueous solution, and an alkaline solution turns red in the air. On further fusion with potash protocatechuic acid is formed. 4 1 Ber. Deutsch. Ohem. Ges.ix.. 1278. 2 Mendelsohn and Tiemann, ibid. x. 395. , 3 Ibid. x. 397. 4 Mresber. 1864, 560. 510 AROMATIC COMPOUNDS. DIHYDROXYPHTHALIC ACIDS, C 6 H 2 (OH) 2 (C0 2 H) 2 . 2267 Hemipinic acid or Dimethoxyortliophthalic acid, C 6 H 2 (OCH 3 ) 2 (CO 2 H) 2 , is, as already mentioned, a product of the oxidation of opianic acid, and has also been obtained by the oxidation of the alkaloids contained in opium, oxynarcotin and narcein. 1 It is readily soluble in alcohol, very slightly in cold, more freely in boiling water, from which it crystallizes in colour- less, distorted prisms with acute basal planes, containing two molecules of water which are lost below 100. The anhydrous acid melts at 180, and sublimes in lustrous plates, resembling those of benzoic acid (Wohler). Crystals containing half a molecule of water are obtained by the spontaneous evaporation of its solution, while those deposited from a supersaturated solution contain one molecule (Matthiessen and Foster). It has a faint acid and slightly astringent taste, is decomposed into carbon dioxide and dimethylcatechol on heating with soda-lime, and is converted into rufiopin by hot sulphuric acid. Dilute hydrochloric acid decomposes it at 160 170 into methyl chloride, carbon dioxide, isovanillic acid and protocatechuic acid (Wegscheider). Its aqueous solution is coloured yellowish brown by ferric chloride, and gives a white precipitate with lead acetate. Normal potassium hemipinate, C w "H. 8 OoK 2 , is very soluble in water and does not easily crystallize. Acid potassium hemipinate, C 10 H 9 6 K, forms thick, six-sided tablets, which are readily soluble in water and alcohol, and have an acid reaction. Normal silver hemipinate, C 10 H 8 O 6 Ag 2 , is a white precipitate, insoluble in water. Acid a-mcthyl hemipinate, C 6 H 9 (OCH 3 ) 2 (CO 2 .CH 3 )C0 2 H + H 2 0(OCH 3 :OCH 3 :C0 2 CH 3 :C0 2 H^4: 3:2:1), is prepared by oxidizing methyl opianate with potassium permanganate, and crystallizes from hot water in lustrous, narrow, flat needles, which readily effloresce and when completely dehydrated melt at 121 122. Its solution gives a yellowish brown precipitate with ferric chloride. 1 Beckett and Wright, Journ. Chem. Soc. 1876, i. 461. HEMIPINIC ACID. 511 Acid IB-methyl hemipinate, C 6 H 2 (OCH 3 ) 2 (C0 2 H)C0 2 .CH 3 (4:3:2:1), is formed by passing hydrochloric acid into a solu- tion of hemipinic acid in methyl alcohol. It is readily soluble in water and crystallizes from alcohol in arborescent needles or stellate groups of prisms, and from benzene or chloroform in rhombic tablets, which melt at 137 138. Its solution is not precipitated by ferric chloride (Wegscheider). Add ethyl hemipinate, 2C 6 H 2 (OCH 3 ) 2 (CO 2 .C 2 H 5 )CO 2 H + 3H 2 O, was prepared by Anderson by passsing hydrochloric acid into the alcoholic solution of the acid. It is also formed by heating hemipinic anhydride with 90 per cent, alcohol (Matthiessen and Wright) and crystallizes from hot water in fascicular groups of needles, melting at 141 142 (Wegscheider). Its solution is precipitated by ferric chloride, so that it cor- responds to the a-methyl ether, and not, as might have been expected from its formation, to the ^-compound. Hemipinic anhydride, C 10 H 8 O 5 , is formed when the acid is heated for an hour to 180 (Beckett and Wright), by the action of phosphorus pentachloride on the acid (Prinz) and by the distillation of the methyl ether (Wegscheider). It crystallizes from absolute alcohol, benzene, and xylene in lustrous needles, which melt at 167 and readily sublime. On heating with zinc dust and glacial acetic acid it is reduced to ^-meconin (Salomon). 2268 Nitrohemipinic acid, C 6 H(NO 2 )(OCH 3 ) 2 (CO 2 H) 2 + H 2 0, is best prepared by boiling nitro-opianic acid with pure nitric acid. It is also formed when meconin or ijr-meconin is heated under pressure with nitric acid (Salomon), and crystallizes from hot water in hard, yellow, vitreous prisms which lose water on heating, melt at 155, and are converted into the anhydride at 160 165; the latter crystallizes from benzene incompact, light yellow prisms, and melts at 145 . 1 Amidohemipinic acid, C 6 H(NH 2 )(OCH 3 ) 2 (C0 2 H) 2 , was first prepared from its anhydride and was then obtained by Grime by reducing nitrohemipinic acid with caustic soda and ferrous sulphate. The free acid is only known in its aqueous solution, which is coloured yellow, showing a fine green fluorescence, has an acid reaction and decomposes on evaporation. Barium amidohemipinate, C 10 H 9 N0 6 Ba, is obtained by boiling the anhydride with baryta water ; it is a golden coloured crys- talline powder, which dissolves in dilute acids, but is insoluble in water. 1 Grime, Ber. Deutsch. Chem. Gcs. xix. 2299. 512 AROMATIC COMPOUNDS. Anhydro-amidohemipinic acid was prepared by Prinz by the action of an acid solution of stannous chloride on a boiling solution of nitro-opianic acid and was named azo-opianic acid. 1 Liebermann then pointed out that this substance is probably the anhydride or anthranil of amidohemipinic acid : 2 /CO.OH (CH 3 0) 2 C 6 H/NH >0 The accuracy of this view was proved by Grime. It crystallizes from alcohol in fine, colourless needles, which melt at 200 with decomposition. When its solution in concentrated hydrochloric acid is evaporated, the hydrochloride separates in stellate groups of prisms, which lose their hydrochloric acid on drying. Its potassium salt, (CH 3 0) 2 CH(CONH)CO 2 K, is a crystalline powder, insoluble in alcohol. When it is boiled with acetic anhydride and anhydrous sodium acetate the acetyl-compound is formed, and crystallizes in needles which form an aqueous solu- tion possessing a blue fluorescence. It readily decomposes with formation of free acetic acid, and has the following con- stitution : /CO (CH 3 0) 2 C 6 H(C0 2 H)< | X N.C 2 H 3 AmidohemipinylpTienylhydrazide is formed by the continued boiling of anhydro-amidohemipinic acid with alcohol, phenyl- hydrazine hydrochloride, and sodium acetate, and also by the oxidation of amido-opianylphenylhydrazide in the air : X CO-NC 6 H 5 (CH 3 0) 2 C 6 H^-CH=N + O = jGO NCJEL (CH 3 0) 2 C 6 H C = N + H 2 0. X NH It crystallizes from benzene or alcohol in small, vitreous, honey- yellow crystals belonging to the tetragonal system, which melt at 222. 8 1 Journ. Prakt. Chem. [2] xxiv. 362. 2 JSer. Dcutsch. Chcm. Ges. xix. 351. 8 Liebermaixn, ibid. xix. 2275. HEMIPINIMIDE. 513 Diazohemipinic acid, (CH 3 O) 2 C 6 H(CO 2 H)<^^>, is ob- tained by the addition of hydrochloric acid to a cooled solu- tion of sodium amidohemipinate and sodium nitrite. It forms a light yellow, crystalline powder, which explodes by percussion or on heating. When it is dissolved in warm hydrochloric acid, the chloride, (CH 3 0) 2 C 6 H(CO 2 H) 2 N 2 C1, separates on cooling in long needles, which are instantly converted by water into .their constituents (Griine). Opianoxime anhydride, C 10 H 9 N0 4 . is formed when an alcoholic solution of opianic acid and hydroxylamine hydrochloride is allowed to stand : /CO.OH C 6 H 2 (OCH 3 ) 2 < + H 2 N.OH = X COH /CO C 6 H 2 (OCH 3 ) 2 / _| +2H 2 0. It crystallizes from benzene in long needles, which on careful heating melt at 114 115, and are converted into acid ammonium hemipinate by boiling with water. 1 Hemipinimide, C 10 H 9 NO 4 . This compound, which corresponds to phthalimide, is formed when ammonium hemipinate is heated and when an alcoholic solution of opianic acid is boiled with hydroxylamine hydrochloride, the foregoing compound being first formed and then undergoing an intramolecular change, which also occurs when it is rapidly heated to 117; the temperature rises suddenly to 260, and the liquid solidifies on cooling to crystals of hemipinimide : CO O CO C 6 H 2 (OCH 3 ) 2 It crystallizes from hot water in splendid needles, which melt at 228 230 and readily sublime. Its aqueous solution has a fine blue fluorescence. When it is triturated with a cold alcoholic solution of potash, potassium Jiemipinimide, C 10 H 8 O 4 (NK), is formed as a crystalline powder, whose aqueous solution gives a white precipitate of silver hemipinimide, C 10 H 8 O 4 (NAg), with silver nitrate. 1 Licbermann, Ber. Deutsch. Chem. Ocs. xix. 2923. 514 AROMATIC COMPOUNDS. Ethyl hemipinimide, C 10 H 8 O 4 (NC 2 H 5 ), is obtained when the potassium compound is heated to 150 with ethyl iodide. It crystallizes from hot water or benzene in needles, which melt at 96 98. The solution also shows a blue fluorescence. 1 2269 Methylnorhemipinic acid, C 6 H 2 (OCH 3 )OH(CO 2 H) 2 + 2H 2 (4:3:2:1), is formed by heating hemipinic acid with hydriodic acid for a short time, 2 and by heating acid a-methyl hemipinate with hydrochloric acid. It forms warty crystals, which are readily soluble in water and alcohol. It reduces ammoniacal silver solution in the cold and Fehling's solution on heating, gives a deep blue colouration with ferric chloride, and melts at 152 155 with decomposition. It separates from ether as an anhydrous powder, which melts at 223 225 with evolution of gas (Wegscheider). On dry distillation it decom- poses into isovanillic acid and carbon dioxide, and is converted into protocatechuic acid by fusion with potash. In its preparation from hemipinic acid, the compound C 9 H 6 O 4 + 2H 2 is formed as a by-product. It crystallizes in lustrous prisms or thin tablets, which melt at 148. Its aqueous solution is coloured lilac by ferric chloride. This substance, which Liechti named opinic acid, might be methylnorhemipinic anhydride, but this is considered doubtful by Beckett and Wright since it contains water of crystallization, and they assume that it corresponds to salicylide and has the following constitution : /C0 2 H C 6 H(OCH 3 )^CO \O-> NitrometTiylnorhemipinic acid, C 6 H(NO 2 )(OCH 3 )OH(C0 2 H) 2 , is formed when methylnorhemipinic acid is evaporated with dilute nitric acid, and crystallizes from alcohol in almost white, silky needles, which are readily soluble in water, and melt at 220 . 3 Amidomethylnorhemipinic acid, C 6 H(NH 2 )(OCH 3 )OH(CO 2 H) 2 , is not known in the free state; its barium salt separates in lustrous, dull yellow plates when the anhydro-acid is boiled with baryta water. Anhydro-amidomethylnorhemipinic acid, (CH 3 0)(OH)C 6 H(C0 2 H)<^>0, is prepared by adding 1 Liebermann, Ber. Deutsch. Chem. Ges. xix. 2287. 2 Beckett and Wright, loc. cit. ; Liechti, Ann. Chem. Plwirm. Suppl. vii. 149. 8 Elbel, Ber. Deutsch. Chem. Ges. xix. 2306. DIHYDROXYISOPHTHALIC ACID. 515 stannous chloride and hydrochloric acid to a boiling, saturated solution of nitromethylnoropianic acid, and crystallizes in silky needles, which melt at 174 175 with decomposition. On boiling with acetic anhydride and sodium acetate, the diacetyl compound is formed : CH 3 (\ /CO )C 6 H(C0 2 H)< | CH 3 .CO. CK X N. CO.CH 3 It crystallizes in needles, melting at 205, and yields a solution in alcohol which has a blue fluorescence. Acetic anhydride is set free on standing, the monoacetyl derivative, C 6 H(OCH 3 ) (OC 2 H 3 O)(CO 2 H)(CONH), being formed. This body melts at 198 and does not form a fluorescent solution in alcohol. Isohemipinic acid, C 6 H 2 (OCH 3 ) 2 (CO 2 H) 2 , is formed by the oxi- dation of methyl isopionate with potassium permanganate. The methyl ether is thus obtained, which crystallizes in needles melting at 167, and yields the acid on saponification. The latter forms white needles, which are scarcely soluble in cold, more readily in hot water, and melt at 245 246 (Mendelsohn and Tiemann). 2270 Dihydroxyisophtlialic acid, or Resorcinoldicar'boxylic acid, C 6 H 2 (OH) 2 (CO 2 H) 2 . When resorcinol is heated with caustic soda and chloroform, dihydroxyisophthalaldehyde, C 6 H 2 (OH) 2 (COH) 2 , is formed, which is almost insoluble in cold water, but dissolves readily in alcohol and ether, from which it is removed by agitation with acid sodium sulphite without forming a difficultly soluble compound. It crystallizes from hot water in long, strongly refractive needles, which melt at 127 and readily sublime. It forms a yellow solution in alkalis. On fusion with caustic potash resorcinoldicarboxylic acid is formed ; this crys- tallizes from water in fine, white needles, which decompose on heating into resorcinol and carbon dioxide. 1 Its constitution has not been accurately determined, but the position of the side- chains is probably OH : OH : CO 2 H : CO 2 H = 1:3:4:6, since in this arrangement the carboxyls stand in both the ortho- and the para-relation to the hydroxyls. Dihydroxytercphthalic acid, (OH : OH : C0 2 H : C0 2 H =1:4:2:5). This body, which is also known as giiinoldicarboxylic acid, is ob- tained by passing air into an alkaline solution of succinosuccinic ether (Part II. p. 190 ; III. p. 146) and decomposing the pro- 1 Lewy and Tiemann, Ber. Deutsch. Chem. Ges. x. 2210. 516 AROMATIC COMPOUNDS. duct with sulphuric acid. 1 It may also be readily prepared by saponifying the ether, and crystallizes from hot water in brownish yellow, hair-like needles, but from alcohol in deep yellow plates, while it separates from ether in rhombic tablets or prisms, which are coloured greenish yellow and show a light blue fluorescence. A hot supersaturated solution, however, first deposits asymmetric white and green crystals, the latter of which are less acutely pointed than the former. On further cooling the rhombic prisms appear and replace the asymmetric crystals when the solution is again gently warmed. If, however, the latter are isolated, the white plates are. converted on cooling into the green, which again become white on warming, so that by alternate heating and cooling the same crystal can be obtained in either modification an in- definite number of times. Since the shape of the crystal alters with the colour, it can be made to present the appearance of a concertina, alternately elongated and compressed by causing the changes of temperature to follow one another rapidly. 2 The aqueous solution of the acid shows a faint emerald green fluorescence, while that of the alcoholic solution is light blue ; it is coloured a pure deep blue by ferric chloride. When rapidly heated the acid decomposes with formation of quinol and other products. 3 Normal sodium dihydroxyterephthalate, C 6 H 4 O 2 (C0 2 Na) 2 + 2H 2 O, crystallizes on the spontaneous evaporation of its aqueous solution, in flat, light brown prisms. Acid sodium diliydroxyterephthalate, C 6 H 4 O 2 (C0 2 Na)C0 2 H + 2H 2 O, forms light yellow, lustrous prisms. Basic sodium dihydroxyterephthalate, C 6 H 2 (ONa) 2 (CO 2 Na) 2 + 12H 2 O. The acid dissolves in caustic soda forming a deep yellow solution with a strong green fluorescence ; on the addition of very concentrated caustic soda the basic salt separates in large transparent crystals, which possess a large number of faces and appear a faint greenish yellow by transmitted, but light blue by reflected light. 2271 Diethyl diliydroxyterephthalate, C 6 H 4 O 2 (C0 2 .C 2 H 5 ) 2 , is formed by the addition of bromine to a solution of succinosuccinic ether in carbon disulphide, 4 and by the action of sodium on an ethereal solution of dibromaceto-acetic ether, 5 CH 3 .CO.CBr 2 .C0 2 . C 2 H 6 . The latter formation corresponds to that of succino- 1 Herrmann, Ber. Dcutsch. Chem. Ges. x. 111. 2 Lehmann, Zeitsch. Kryst. x. 3 ; Herrmann, Ber. Dcutsch. Chem. Ges. xix. 2229. 3 Herrmann, Ann. Chem. Pharm. ccxi. 335. 4 Herrmann, ibid. ccxi. 372 ; Ber. Deutsch. Chem. Ges. xvi. 1411 ; Duisberg, ibid. xvi. 133 ; Ebert, Ann. Chem. Pharm. ccxxix. 45. 6 Wedel, ibid, ccxix. 71. DIHYDROXYTEREPHTHALIC ACID. 517 succinic ether from monobromaceto-acelic ether. It crystallizes from ether in short, thick prisms or long flat needles, and from benzene in rectangular, rhombic tablets, which have the colour of uranium glass and show a light blue fluorescence. It melts at 133 133'5 and sublimes at a higher temperature in lustrous, green, flat plates possessing a beautiful blue fluorescence. Its alcoholic solution is coloured bluish green by traces of ferric chloride. It dissolves in alkalis forming a deep yellow solution, with which a concentrated solution of an alkali produces a deep orange-red precipitate. Diethyl diacetoxyterephtlialate, C 6 H 2 (OCO.CH 3 ) 2 (C0 2 .C 2 H 5 ) 2 , is prepared by heating the ethyl ether with acetyl chloride, and crystallizes from alcohol in colourless, lustrous plates, which melt at 115 (Wedel). Monethyl dihydroxyterephthalate, C 6 H 2 (OH) 2 (CO 2 .C 2 H 5 )C0 2 H. When the diethyl ether is dissolved in dilute caustic potash and the unattacked portion removed after some time by acetic acid, barium chloride precipitates the barium salt of the acid ether from the filtrate ; this salt can readily be recrystallized from hot water, and hydrochloric acid added to its solution precipitates the mono-ethyl ether of dihydroxyterephthalic acid. It is a strong monobasic acid, crystallizes from hot water in fine, yellow needles, and is deposited on the evaporation of its alcoholic solu- tion in light yellow, transparent, vitreous prisms, which melt at 184. Its solution is coloured bluish violet by ferric chloride. If the diethyl ether is boiled with alcoholic hydrochloric acid and zinc, it is again reduced to succinosuccinic ether, which can therefore be regarded as the ether of a dihydroxydihydrotere- phthalic acid. The latter is formed in the first stage of the reaction, but immediately changes into the isomeric compound: 1 X C0 2 .C 2 H 5 H x X C0 2 .C 2 H 5 C HC\/COH H 2 C\ /CO C C H/ \C0 2 .C 2 H 5 HX \C0 2 .C 2 H 5 The latter formula is rendered probable by the formation of the substance from bromaceto-acetic ether, CH 3 .CO.CHBr.CO 2 .C 2 H 5 , which occurs with elimination of hydrobromic acid ; it also forms a 1 Ber. Deutsch. Chem. Ges. xix. 428. 264 518 AROMATIC COMPOUNDS. di-imide, is converted into an oximido-compound by hydroxyl- amine (Baeyer), and yields both a phenylhydrazide and a di- phenylhydrazide. 1 On the other hand it yields a diacetyl-com- pound on heating with acetyl chloride ( Wedel) , which is more readily obtained by adding sodium ethylate to its ethereal solution, a rose-coloured precipitate of C 6 H 4 O 2 Na 2 (CO 2 .C 2 H 5 ) 2 being formed, which is immediately converted by acetyl chloride into the com- pound C 6 H 4 (OC 2 H 3 0) 2 (CO 2 .C 2 H 5 ) 2 (Baeyer). The latter com- pounds must be looked upon as derivatives of the dihydroxy- dihydroterephthalic acid into which succinosuccinic ether or quinonetetrahydrodicarboxylic acid so readily changes. Dihydroxyterephthalic acid also probably exists in two forms, as quinoldicarloxylic acid, C 6 H 2 (OH) 2 (CO 2 H) 2 , and as quinonedihydrodicarboxylic acid, C 6 2 H 4 (CO 2 H) 2 , which readily change into one another. The latter formula is required by its formation from dibromaceto-acetic ether, while its whole behaviour corresponds to the former. It may be assumed that the green modification is the quinone-acid, while the colourless is the quinol derivative (Herrmann). A similar case has been observed by Baeyer with regard to phloroglucinol, which forms a trioxime with hydroxylamine, the trihydroxybenzene being converted into triketohexhydrobenzene (Part III. p. 186.): 2 Phloroglucinol. Triketohexhydrobenzene. OH CO H 2 C/\CH 2 HO-C\/C-OH CH Analogous cases have long been known to chemists ; among the simplest are nitrous acid and cyanic acid, which are exceed- ingly unstable in the free state, but yield stable modifications of two kinds : Methyl nitrite. Potassium cyanate. CH 3 Ni=0 K O C=N Nitromethane. Methyl isocyanate. /\ CH 3 N/ \ CH 3 N=C=:0 1 Knorr, Ber. Deutsch. CTiem. Ges. xvii. 2055. 8 Ibid, xviii. 3454 ; xix. 159, 1800. TRI- AND TETRA-HYDROXYPHTHALIC ACIDS. 519 The constitution of these compounds can therefore be repre- sented with equal accuracy by different structural, or, as Laar l names them, tautomeric formulae. The atoms are in continual motion within the molecule, and one form is converted into the other when the light and most rapidly moving atoms of hydrogen are more strongly attracted by one or other of the remaining atoms. If, however, the hydrogen be replaced by a heavier atom or molecule, the latter no longer escapes from the sphere of attraction, and the mobile form is converted into a stable one. TRIHYDROXYPHTHALIC ACIDS, C 6 H(OH) 3 (C0 2 H) 2 . 2272 Gallocarloxylic acid, C 8 H 6 O 7 + 3H 2 0, is formed, together with pyrogallolcarboxylic acid (p. 378), when pyrogallol or gallic acid is heated to 130 with ammonium carbonate. It requires 3,000 parts of water at for solution, and crystallizes from hot water in very fine needles, which become anhydrous at 180 and melt above 270 with evolution of carbon dioxide. Dilute ferric chlorides colour its solution violet, while the concentrated reagent produces a greenish brown colouration. When heated in the air with water and an excess of calcium carbonate, the latter is coloured reddish violet, and when an ammoniacal solu- tion of the acid is mixed with a solution of bicarbonate of calcium, a deep violet coloured precipitate is formed, which may therefore be obtained with spring water containing calcium carbonate. 2 TETRAHYDROXYPHTHALIC ACIDS, C 6 (OH) 4 (C0 2 H) 2 , 2273 TetraJiydroxyterephthalic acid. When an ethereal or alcoholic solution of ethyl dihydroxyterephthalate is treated with anhydrous nitrogen trioxide, it is converted into ethyl . dihydr- oxyguinoneterephthalate, C 6 O 2 (OH) 2 (CO 2 .C. 2 H 5 ) 2 , crystallizing in yellow prisms, which are slightly soluble in cold water, alcohol and ether, more readily in chloroform. The solutions have a 1 Ber. Deutsch. Chem. Ges. xviii. 648 ; xix. 730. 2 Brunner and Senhofer, Monatsh. CJicm. i. 468. 520 AROMATIC COMPOUNDS. deep yellowish red colour. When the ether is heated with caustic soda, a basic salt of dihydroxyquinonetere.phthalic acid is formed, and immediately decomposes on the addition of acids into carbon dioxide and dihydroxyquinone, C 6 O 2 H 2 (OH) 2 , which forms small, black-brown crystals. Nitranilic acid, C b 2 (N0 2 ) 2 (OH) 2 , is always formed if dihydroxyterephthalic acid be submitted to the same treatment. Ethyl tetrahydroxyterephthalate, C ( .(OH) 4 (C0 2 .C 2 H 5 ) 2 , is ob- tained by passing sulphur dioxide into a faintly alkaline solution of the dihydroxyquinone ether, and crystallizes from hot chloro- form in golden yellow plates, melting at 178. It is converted by cold caustic soda solution into sodium tetrahydroxytere- phthalate, C 6 (OH) 4 (CO 2 Na) 2 , which crystallizes in yellow prisms. On decomposition with sulphuric or hydrochloric acid, tetra- hydroxyphthalic acid yields carbon dioxide and tetrahydroxy- benzene, C 6 H 2 (OH) 4 , which forms yellow needles, melting at 148 . 1 1 Loewy, Ber. Deutsch. Chem. Ges. xix. 2385. INDEX INDEX. A. ACETBROMAMIDE, 113 Acetmetamidobenzoic acid, 248 Acetmetatoluide, 62 a-Acetmetaxylide, 407 *-Acetmetaxylide, 407 u-Acetmetaxylide, 406 Acetmethylparatoluide, 65 Acetometahydroxybenzidene acetate, 293 Acetortho-amidobenzoic acid, 239 Acetorthotoluide, 59 a-Acetorthoxylide, 406 y-Acetorthoxylide, 406 Acetoxiine benzyl ether, 98 Acetparamidobenzoic acid, 253 Acetparatoluide, 66 Acet.paraxylide, 407 Acetphthalimide, 464 Acetylbenzenylamidoxime 214 Acetylisovanillic acid, 354 Acetylmetahydroxybenzaldehyde, 293 Acetylopianic acid, 506 Acetylorthamidobenzaldehyde, 149 Acetylparahydroxybenzaldehyde, 295 Acetylparahydroxybenzidene acetate, 296 Acetylparamidobenzaldehyde, 150 Acetylsalicylie acid, 308 Acetyl salicylaldehyde, 288 Acetylsinapic acid, 377 Acetylvanillic acid, 353 Acetylvanillin, 347 Acid ammonium hippurate, 189 Acid ammonium phthalate, 456 Acid barium hydroxamate, 208 Acid barium orthosulphobenzoate, 268 Acid bariumphthalate, 457 Acid calcium benzarsenate, 277 Acid ethyl hemipinate, 511 Acid ethyl metasulphobenzoate, 271 Acid ethyl o-nitrophthalate, 474 Acid ethyl v-nitrophthalate, 474 Acid metatoluidine oxalate, 61 Acid a-methyl hemipinate, 510 Acid /3-methyl hemipinate, 511 Acid methyl sulphinidephthalate, 478 Acid paratoluidine oxalate, 64 Acid potassium benzarsenate, 277 Acid potassium benzhydroxamate, 208 Acid potassium benzophosphinate, 276 Acid potassium hemipinate, 510 Acid potassium sulphinidephthalate, 477 Acid potassium sulphoparahydroxy- benzoate, 336 Acide quinique, 382 Acid silver sulphinidephthalate, 478 Acid sinapin sulphate, 375 Acid sodium benzhydroxamate, 208 Acid sodium dihydroxyterephthalate, 516 Addition products of isophthalic acid, 481 Addition products of phthalic acid, 469 Addition products of terephthalic acid, 486 Adjacent Dinitroparatoluidine, 71 Adjacent metadihydroxybenzoic acid, 360 Aes-cioxalic acid, 363 Aldehydes, 447 Aldehydovanillic acid, 508 Aldehydohydroxybenzoic acids, 491, 502 Alizaric acid, 450 Allyl benzoate, 162 Aloi'sol, 402 Amarine, 140 Amarythrin, 428 Amido-anisic acid, 338 Amido-azotoluenes, 77 Amid obenzenyl-phenylene-amidine, 206 Amidobenzoic acid percyanide, 248 Amidobenzylamines, 120 Amido-derivatives of the xylenes, 405 Amidohemipinic acid, 511 Amidohemipinylphenylphydrazide, 512 Amido-isophthalic acid, 482 Amidomeconin, 501 Amidometa-azotoluene, 78 Amidometatoluic acids, 418 524 INDEX. Amidomethylnorhemipinic acid, 514 Amido-opianylphenylhydrazide, 508 Amidortho-azotoluene, 77 0-Amido-orthocresol, 26, 51 7-Amido-orthophenol, 26 Amido-orthotoluic acids, 415 Ainido-\|/-meconin, 501 a-Amidoparacresol, 20 j8-Amidoparacresol, 30 7-Amidoparacresol, 30 Amidoparahydroxybenzoic acid, 335 a-amidoparatoluic acid, 421 Amidophenylmetabenzoglycocyamine, 253 Amidophthalic acids, 475 a-Amidophthalic acid, 475 v- Amidophthalic acid, 475 o-Amidosalicylic acid, 317 /8-Amidosalicylic acid, 318 Amido-substituted benzylamines, 116 Amidosulphobenzoic acids, 275 Amidoterephthalic acid, 489 Amidotoluenes, 54 Amido-uramidobenzoyl, 242 Amidoxylenes, 405 Ammonium benzidene sulphate, 137 Ammonium benzoate, 160 Ammonium gallate, 368 Ammonium metahydroxybenzoate, 321 Ammonium parahydroxybenzoate, 328 Ammonium salicylate, 303 Ammonium tcrephthalate, 484 Amyg-dalacese, 131 Amygdalin, 130 Amyl benzoate, 162 Amyl hippurate, 191 Amyl orsellinate, 433 Amyl salicylate, 306 Anhydrides of parahydroxybenzoic acid, 331 Anhydro-amidohemipinic acid, 512 Anhydro - amidomethylnorhemipinic acid, 514 Anhydrobenzodiamidobenzene, 205 Anhydrous benzoic acetic acid, 167 Aniletic acid, 316 Anilido-ethoxytolu-quinone anilide, 49 Anilidohydroxytoluquinone, 49 Anilidohydroxytoluquiuone anilide, 49 Aniline, 297 Aniline lourde speciale, 56 Aniline oil, 55 Aniline orange, 31 Anis-amide, 333 Anis-anilide, 333 Anisbenzanishydroxylamine, 312 Anisbenzethylhydroxylamine, 340 Anisbenzhydroxamic acid, 340 Anis-dibenzhydroxylamine, 341 Anise alcohol, 284 Anisenyloxime compounds, 339 Anisethylbenzhydroxylamine, 341 Anishydroxamic acid, 339 Anisic acid, 329 Anisic acid, substitution products of, 336 Anisic anhydride, 332 Anisonitril, 334 Anisuric acid, 333 Anisyl chloride, 332 Anthranil, 240 Anthranilcarboxylic acid, 240 Anthranilic acid, 297 Antimony derivatives of toluene, 86 Archil, 42 Arsendiparatolyl chloride, 85 Arsendiparatolyl trichloride, 85 Arsenditolyl oxide, 85 Arsenic Compounds of Benzyl, 125 Arsenic derivatives of toluene, 84 Arsenobenzoic acid, 277 Arsenorthotolyl chloride, 85 Arsenorthotolyl dioxide, 86 Arsenorthotolyl oxide, 85 Arsenparatolyl chloride, 84 Arsentolyl oxide, 85 Arsentribenzoic acid, 278 Arsentritolyl dichloride, 85 Asymmetric diamido-azotoluene, 80 Asymmetric dibenzyl thiocarbamide, 124 Asymmetric dibenzyl urea, 123 Asymmetric ethylbenzoyl urea, 178 Asymmetric metadihydroxy benzoic acid, 359 Asymmetric diphenylbenzenylamidine, 204 Azo-aceto-acetic benzoic acid, 267 Azobenzenesalicylic acid, 319 Azobenzoic acids, 265 Azo-derivatives of benzoic acid 265 Azo-derivatives of toluene, 75 Azomalonic-benzoic acid, 268 Azonitromethanebenzoic acid, 267 Azo-orcin, 52 Azophenylmethyl, 181 Azo-opianic acid, 512 Azotoluenes, 75 a-Azotoluidine, 79 0-Azotoluidine, 79 Azoxybenzoic acids, 265 o-Azoxytoluidine,78 /3-Azoxytoluidine, 79 B, BADIANIC ACID, 329 Barbatic acid, 402, 435 Barium amidohemipinate, 511 Barium benzoate, 161 Barium benzylsulphonate, 108 Barium chlorobenzylsulphonate, 108 Barium diamidobenzoate, 259 Barium o-dinitrobenzoate, 234 Barium )8-dinitrobenzoate, 234 Barium 7-dinitrobenzoate, 234 INDEX. 525 Barium 8-dinitrobenzoate, 235 Barium e-dinitrobenzoate, 235 Barium dinitrosalicylate, 317 Barium gallate, 369 Barium hippurate, 189 Barium homohydroxysalicylate, 438 Barium isophthalate, 479 Barium lecariorate-, 434 Barium meconinate, 500 Barium metabromobenzoate, 224 Barium metahydroxybenzoate, 321 Barium metanitrobenzoate, 231 Barium methylnoropianate, 503 Barium opianate, 504 Barium opianylsulphite, 507 Barium ornithurate, 193 Barium orsellinate, 432 Barium orthobromobenzoate, 223 Barium orthonitrobenzoate, 230 Barium parabromobenzoate, 224 Barium parahydroxybenzoate, 328 Barium paranitrobenzoate, 232 Barium para-orsellinate, 436 Barium protocatechuate, 352 Barium pyrogallolcarboxylate, 379 Barium quinate, 384 Barium salicylaldehyde, 287 Barium salicylate, 303 Barium terephthalate, 484 Basic barium nitroparahydroxybenzo- ate, 335 Basic copper potassium salicylate, 304 Basic copper quinate, 384 Basic lead pyro-gallolcarboxylate, 379 Basic sodium dihydroxyterephthalate, 516 Benzaldehyde, 129 Benzaldehyde-green, 135 Benzaldehyde oxyiodide, 137 Benzaldoxime, 139 Benzamic acid, 246 Benzamide, 172, 199 Benzamide hydrochloride, 174 Benzanilide, 174 Benzanilidimidocbloride, 203 Benzanisbenzhydroxylamine, 341 Benzanishydroxamic acid, 340 Benzarsene chloride, 277 Benzarsene iodide, 277 Benzarsenic acids, 277 Benzarsenious acid, 277 Benzdianishydroxylamine, 342 Benzene, 297 Benzenyl alcohol, 194 Benzenyl amidines, 1 95 Benzenylamidophenate, 206 Benzenylamidothiophenate, 206 Benzenylamidoxime, 212 Benzenylamidoximemetacarboxylic acid, 480 Benzenylamidoximeparacarboxylic acid, 485 Benzenylazoximebenzenylcarboxylic acid, 468 Benzenylazoxime carbinol, 215 Benzenylazoxime propenylcarboxylic acid, 215 Benzenyl compounds, 194 Benzenylethoxime chloride, 213 Benzenylethenylazoxime, 214 Benzenyl ethyl ether, 196 Benzenyloxime compounds, 207 Benzenyloximic acid, 208 Benzenyl triacetate, 196 Benzenyl tribromide, 196 Benzenyl trichloride, 195 Benzenyltrichlorophosphoryl chloride, 311 Benzethylanishydroxylamine, 341 Benzethylbenzhydroxylamine, 209 Benzhydroxamic acid, 208 Benzhydroxamide, 212 Benzhydroxylamine, 207 Benzidene-acetamide, 143 Benzidene-aniline, 140 Benzidene-aniline cyanhydrate, 141 Benzidene benzoate, 163 Benzidene benzobromohydrin, 170 Benzidene benzochlorohydrin, 169 Benzidene compounds, 136 Benzidene diacetate, 137 Benzidene di bromide, 136 Benzidene dichloride, 136 Benzidene dichlorochromic acid, 6 Benzidene diethyl ether, 136 Benzidene di-iodide, 137 Benzidenedimethylparadiamido- benzene, 142 Benzidenediphenylhydrazine, 141 Benzidenedi-ureide, 143 Benzidene-orthodiamidobenzene, 141 Benzideneparadiamidobenzene, 1 42 Benzidenephenylamine hydrochloride, 143 Benzidenephenylhydrazine, 141 Benzidenephenyldiamine, 142 Benzidene sulphide, 138 Benzidenetetra-ureide, 143 Benzidenetri-ureide, 143 Benzidene ureides, 143 Benzidene urethane, 143 Benzidenoxime, 139 Benzimido-acelic ether, 201 Benzimido-amide, 202 Benzimido-ethers, 200 Benzimido-ethyl ether, 201 Benzimido-isobutyl ether, 201 Benzimido-thiobenzyl ether, 202 Benzimido-thio-ethyl ether, 201 Benzoene, 3 Benzoene monochlore, 7 Benzoic acid, 7, 108, 151, 297, 383 Benzole acid, azo-derivatives of, 265 Benzoic acid, nitro-substitution pro- ducts of, 227 Benzoic acid, salts and ethers of, 160 Benzoic anhydride, 166 Benzoleic acid, 159 526 INDEX. Benzonitril, 122, 197 Beuzonitril and its derivatives, 197 Benzophosphine chloride, 276 Benzophosphinic acid, 275 Benzolorthoalcoholsame, 442 Benzortho-amidobenzoic acid, 239 o-benzothio-aldehyde, 138 0-benzothio-aldehyde, 138 7-benzothio-aldehyde, 139 Benzo-trichloride, 195 Benzoxamidine, 213 Benzoyl, 285 Benzoyl acetyl oxide, 167 Benzoylaniline, 174 Benzoylanthranil, 241 Benzoylazo benzene, 180 Benzoylbenzenylamidoxime, 214 Benzoyl-benzoic acid, 458 Benzoylbenzoximic acid, 209 Benzoyl bromide, 169 Benzoyl chloride, 168 Benzoyl derivatives of amines and amido- bases, 174 Benzoyl dioxide, 167 Benzoyldiphenylamine, 175 Benzoyldiphenylhydrazine, 181 Benzoyl disulphide, 171 Benzoyl ethylbenzhydroxamate, 209 Benzoyl fluoride, 170 Benzoyl-glycollic acid, 165 Benzoyl group, 128 Benzoylguanidine, 243 Benzoylguanidine, nitrate, 243 Benzoyl, halogen compounds of, 168 Benzoylhelicin, 289 Benzyl hydrosulphide, 138 Benzoyl iodide, 170 Benzoyl-lactic acid, 165 Benzoylmethylaniline, 175 Benzoylmethylpyrogallol dimethyl ether, 164 Benzoylnitranilines, 175 Benzoyl, nitrogen compounds of, 172 Benzoylornithine, 193 Benzoylorthotoluide, 175 Benzoyl oxide, 166 Benzoyl, oxides of, 166 Benzoyl paratoluide, 175 Benzoyl peroxide, 167 Benzoylphenylhydrazine, 179 Benzoylpropylpyro - gallol dimethyl ether, 164 Benzoyl pyro-gallol dimethyl ether, 164 Benzoylsalicin, 282 Benzoyl salicylaldehyde, 288 Benzoylsalicylarnide, 312 Benzoylsalicylnitril, 313 Benzoyl sulphide, 171 Benzoylsulphimide, 269 Benzoyl, sulphur compounds of, 170 Benzoyl thiocyanate, 172 Benzoyl thio-urea, 179 Benzoyl urea, 178 Benzoyl vanillic acid, 353 Benzyl, 89 Benzylacetamide, 121 Benzyl acetate, 97 Benzyl alcohol, 7, 89 ; properties, 93 ; substitution products of, 98 Benzylamidine, 202 Benzylamine, 112 ; properties, 113 Benzylamine hydrochloride, 113, 114 Benzylamine nitrite, 114 Benzylamines, 110 Benzylamines, amido-substituted, 116 Benzylamines, substitution products of, 118 Benzylammonium benzylcarbamate, 113, 114 Benzylaniline, 117 Benzyl, arsenic compounds of, 125 Benzyl benzoate, 162 Benzylbenzoyl thio-urea, 179 Benzyl bromide, 97 Benzyl bromophenyl ether, 95 Benzyl carbamate, 123 Benzyl-carbimide, 122 Benzyl chloride, 7, 96 Benzyl chlorophenyl ether, 95 Benzylcyananmide, 121 Benzylcyanuramide, 121 Benzyl-Derivatives of the Acid- Amides and Allied Bodies, 121 Benzyldimethylselenine tri-iodide, 110 Benzyldimethylsulphine iodide, 106 Benzyl dimethylsulphine platinichlor- ide, 107 Benzyl dioxysulphide, 107 Benzyl diphenylamine, 117 Benzyl diselenide, 109 Benzyl disulphide, 107 Benzyl, ethereal salts of, 96 Benzyl ethers, 94 Benzylethoxyl chloride, 100 Benzyl ethyl ether, 94 Benzyl ethyl sulphide, 106 Benzyl group, 89 Benzyl hydrosulphide, 105 Benzylhydroxyammomum chloride, 98 Benzyl iodide, 97 Benzyl-isocyanate, 122 Benzyl isocyanurate, 122 Benzyl isothiocyanate, 122 Benzylmetamine, 121 Benzyl methyl ether, 94 Benzyl mercaptan, 105 Benzyl mustard oil, 122 Benzyl nitrate, 97 Benzyl, nitrogen bases of, 110 Benzyl orthocresyl ether, 95 Benzyl oxalate, 98 Benzyl oxide, 94 Benzyl oxysulphide, 107 Benzyl paracresyl ether, 95 Benzylphenylamine, 117 Benzyl phenyldimethylammonium chloride, 117 Benzyl phenyl ether, 95 INDEX. 527 Benzylphosphine, 124 Benzylphosphonium iodide, 124 Benzylquinol, 96 Benzylsalicylic acid, 306 Benzyl salicylaldehyde, 287 Benzylselenic acid, 109 Benzyl selenide, 109 Benzyl, selenium compounds of, 109 Benzyl selenocyanate, 123 Benzyl, silicon compounds of, 127 Benzyl sulphide, 106 Benzylsulphonamide, 109 Benzylsulphonic acid, 108 Benzylsulphonic chloride, 108 Benzyl, sulphur compounds of, 105 Benzyl thiocarbamide, 124 Benzyl thiocyanate, 122 Benzyl thiobenzoate, 171 Benzyl urea, 123 Benzyl urethane, 123 Beta-orcinol, 402 Boron and Silicon derivatives of Tolu- ene, 87 Boron disalicylic acid, 304 Bromamidobenzoic acids, 255 Bromanisic acid, 336 Bromine substitution products, 41 Bromine substitution products of tolu- ene, 10 Bromobeuzidenedichlorochromyl chlo ride, 11 Bromobenzylbenzoate, 170 Bromogallic acid, 370 Bromomalophthalic acid, 470 Bromomeconin, 500 Bromometacresol, 27 a-Bromometatoluic acid, 417 j8-Bromometatoluic acid, 417 o-Bromometaxylene, 394 s-Bromometaxylene, 394 a-Bromometaxylenol, 401 Bromonitrobenzoic acids, 236 Bromonitro toluenes, 19 Bromoparacresol, 29 Bromoparahydvoxybenzaldehyde, 296 o-Bromoparatoluic acid, 420 /J-Bromoparatoluic acid, 420 Bromoparaxylene, 395 o-Bromophthalic acid, 472 v-Bromophthalic acid, 472 Bromopianic acid, 507 Bromoprotocatechuic acid, 356 a-Bromoresorcylic acid, 359 7-Bromoresorcylic acid, 361 Bromorthocresol, 25 a-Bromorthotoluic acid, 415 j8-Bromorthotoluic acid, 415 o-Bromorthoxylene, 393 Bromosalicylaldehyde, 292 a-Bromosalicylic acid, 314 0-Bromosalicylic acid, 314 Bromosulphobenzoic acids, 274 Bromoterephthalic acid, 488 Bromotoluidines, 68 Butyl benzoate, 162 Butyl hippurate, 191 C. CAFFEOL, 281 Calcium benzarsenite, 278 Calcium benzoate, 160 Calcium dibenzarsenite, 278 Calcium difluorbenzoate, 227 Calcium gallate, 369 Calcium hippurate, 189 Calcium isophthalate, 479 Calcium metachlorobenzoate, 220 Calcium metahydroxybenzoate, 321 Calcium metatoluate, 416 Calcium ornithurate, 193 Calcium orthochlorobenzoate, 218 Calcium orthotoluate, 414 Calcium parachlorobenzoate, 221 Calcium parahydroxybenzoate, 328 Calcium paratoluate, 419 Calcium phthalate, 457 Calcium piperonate, 356 Calcium pyrogallolcarboxylate, 379 Calcium quinate, 382, 384 Calcium salicylate, 303 Calcium terephthalate, 484 Cantharene, 391 Carbanilamide, 246 Carbanilidic acid, 246 Carbimidamidobenzoic acid, 250 Carbimidamidobenzoyl, 242 Carbohydrokinonic acid, 350 Carbonyl chloride, 462 Carbonyl dibenzenylamidoxime, 215 Carbotriphenyltriamine, 204 Carboxamidocyanamidobenzoyl, 241 Carboxamidobenzoic acid, 251 Carboxylcyanamidobenzoyl, 241 Catechol, 36 Chloranisic acid, 336 Chloramidobenzoic acids, 254 Chlorine substitution products, 41 Chlorine substitution products of toluene, 7 Chlorobenzol, 136 Chlorobenzoyl chloride, 310 Chlorobenzenyl trichloride, 310 Chlorodracylic acid, 221 Chloro-isophthalic acid, 481 Chloromeconin, 500 Chlorometatoluic acid, 417 Chlorometaxylenesulphamide, 393 Chloromethylnoropianic acid, 503 o-Chlorometaxylene, 393 Chloromichmic acid, 219 Chloroniceinic acid, 219 Chloronitrotoluenes, 19 Chloronitrobenzoic acids, 236 Chloroparacresol, 29 Chloroparahydroxybenzaldehyde, 296 Chloroparahydroxybenzoic acid, 334 Chloroparatoluic acid, 420 528 INDEX. Chloroparatoluidiue, 8 Chlorophthalic acid, 393 o-Chlorophthalic acid, 471 y-Chlorophthalic acid, 471 Chloroparaxylene, 393 Chloropiauic acid, 507 Chlororthotoluic acids, 415 - a-Chlororthoxylene, 392 y-Chlororthoxylene, 392 Chlorosalicylaldehyde, 292 Chlorosalicylic acid, 313 Chlorosulphobenzoic acids, 274 Chlorotorephthalic acid, 488 Chlorotoluene, 7 Chlorotoluic acid, 393 Chlorotoluidines, 68 Choline, 376 Cinnamei'n, 90 Cinnaraic acid, 90, 135, 297 Cinnamone, 135 Colophonin hydrate, 7 Colophonin, 6 Coniferyl alcohol, 345 Copper benzoate, 161 Copper hippuratc, 190 Copper metahydroxybenzoate, 321 Copper parahj-droxybenzoate, 328 Copper phthalate, 457 Copper quinate, 384 Copper salicylaldehyde, 287 Copper salicylate, 304 Couraaim, 186 Creosol, 32 Creosote, 32 et seq. o-Cresol, 23 j8-Cresol, 23 7-Cresol 24 Cresolcarboxylic acid, 438 Cresorcinol, 47, 437 Cresorcinolcarboxylic acid, 437 Cresorsellinic acid, 437 Cresotic acid, 423 a-Cresotic acid, 423 fi-Cresotic acid, 424 7-Cresotic acid, 424 Cresyl alcohol, 23 Cresyl benzoate, 164 Cresyl hydrate, 23 Cudbear, 44 Cumaric acid, 297 Cumic acid, 451 Cumino-cyminic acid, 451 Cumol, 386 Cyanobenzylamine, 121 Cyanocarbimidobcnzoic acid, 249 Cyanocarboxamidobenzoic acid, 249 Cynanphenin, 199 Cymene, 4 Cymol, 386 DlACETORTHO-AMIDOBENZOIC ACID, 239 Diacetotoluquinol, 48 Diamidobenzoic acids, 258 Diamidobenzoic acids, action of nitrous acid on the, 263 a-Diamidobenzoic acid, 258 /}-Diamidobenzoic acid, 259 5 -Diamidobenzoic acid, 267 7-Diamidobenzoic acid, 259 8 Diamidobenzoic acid, 259 5-Diamidobenzoic acid hydrochloride, 259 5-Diamidobenzoic acid sulphate, 259 Diamidobenzylsulphonic acid, 109 Diamidocresol, 79 Diamidohydro-acridine ketone, 245 o-Diamidometaxylene, 409 T-Diamidometaxylene, 409 s-Diamidometaxylene, 409 o-Diamidoparaxylene, 410 -Diamidoparaxylene, 410 7-Diamidoparaxylene, 410 Diamidosalicylic acid, 318 Diamidoterephthalic acid, 489 a-Diamidotoluene, 72 /3-Diamidotoluene, 72 7-Diamidotoluene, 73 5-Diamidotoluene, 74 a-Diamidotoluene di-hydrochloride, 72 -Diamidotoluene hydrochloride, 73 7-Diamidotoluene hydrochloride, 73 a-Diamidotoluene monohydrochloride, 72 a-Diamidotoluene sulphate, 72 -Diamidotoluene sulphate, 73 S-Diamidotoluene sulphate, 73 iamidotoluenes, 72 Diamidotriphenylmethane, 135 Diamines and Thamines of the Xylenes, 409 Dianilidotoluquinone, 49 Dianilidotoluquinone anilide, 49 Dianisbenzhydroxylamine, 342 Dianishydroxamic acid, 340 Diazo-amidobenzene, 18 Diazo-amidotoluene, 74 Diazo-amidotoluic acid, 421 Diazobenzene-amidobenzoic acid, 262 Diazobenzoic acid, 260 Diazobenzoic acid nitrate, 260 Diazobenzoic acid seminitrate, 260 Diazo-derivatives of benzoic acid, 260 Diazo-derivatives of toluene, 74 Diazohemipinic acid, 513 Diazo-imidobenzoic acids, 263 Diazooenzene-amidotoluene, 74 Diazo-salicylic acid, 319 Diazotoluene nitrate, 74 Diazotoluene sulphate, 74 Diazoxybenzoic acid, 267 Dibenzamide, 176 Dibenzamide hydrate, 177 Dibenzanilide, 177 . Dibenzanishhydroxylamine, 341 Dibenzarsene iodide, 278 Dibenzarsenic acid, 278 Dibenzarsenious acid, 278 INDEX. 529 Dibenzenylazoxime, 214 Dibenzenyltriamine, 202 Dibenzhydroxamic acid, 209 Dibenzhydroxylamine, 207 Dibenzidenediumidobenzoic acid, 142 Dibeuzidenemetadiamidotoluene, 142 Dibenzidene-orthodiamidotoluene, 1 42 Dibenziiaido-oxide, 197 Dibenzoarsenic acid, 85 Dibenzobenzoximate, 211 Dibenzoylcatechol, 164 Dibenzoylphenylhydrazinc, 180 Dibenzoylquinol, 164 Dibenzoylrescorciuol, 164 Dibenzoyl urea, 179 Dibenzenylamidine, 202 Dibenzylamine, 114 Dibenzylamine hydrochloride, 115 Dibenzylamine nitrate, 115 Dibenzylarsenic acid, 126 Dibenzylarsine trichloride, 125 Dibenzylcatechol, 96 Dibenzylcyanimide, 122 Dibenzyl ether, 94 Dibenzylguanidine, 121 Dibenzyloxamide, 121 Dibenzylphosphine, 125 Dibenzylquinol, 96 Dibenzylresorcinol, 96 Dibenzyl sul phone, 107 Dibenzyltolylamine, 118 Dibenzyl toluidine, 118 Dibromanisic acid, 336 Dibromobenzoic acids, 224 Dibromo-gallic acid, 370 Dibromohexhydroterephthalic acid, 486 Dibromolecanoric acid, 434 o-Dibromometaxylene, 394 /3-Dibromometaxylene, 394 a-Dibromometaxylenol, 401 Dibronioparacresol, 29 Dibromoparahydroxybenzoic acid, 334 Dibromoparatoluic acid, 420 Dibromoparaxylene, 395 o-Dibromophtnalic acid, 472 #-Dibromophlhalic acid, 473 Dibromophthalide, 444 Dibromorcinol, 41 Dibromorsellinic acid, 433 Dibromorthoxylene, solid, 394 liquid, 394 Dibromoterephthalic acid, 488 Dibromotoluenes, 11 Dibromotetrahydrophthalic acid, 470 Dichloraniaic acid, 336 Dichlorobenzaldehyde, 144 Dichlorobenzenyl trichloride, 196 o-Dichlorobenzoic acid, 221 /3-Dichlorobenzoic acid, 222 7-Dichlorobenzoic acid, 222 S-Dichlorobenzoic acid, 222 e-Dichlorobenzoic acid, 222 Dichlorobenzidene chloride, 145 Dichlorobenzoic acids, 221 Dichlorobenzyl alcohol, 100 Dichlorobenzyl chloride, 101 Dichlorohippuric acid, 220 Dichloroparacresol, 29 Dichloroparahydroxybenzoic acid, 334 Dichloroparaxylene, 393 Dichlorophthalic acid, 471 Dichloropiperonal, 348 Dichlororthocresol, 25 Dichlororthoxylene, 393 Dichloro-salicylic acid, 314 Dichlorosilicon orthoditoluide, 87 Dichlorotoluene hexchloride, 10 Dichlorotoluenes, 9 Dichlorotoluquinone, 27, 50 Dicinnyl ketone, 135 Dicyanamidobenzoyl, 241 Diethylbenzamide, 174 Diethylbenzylamine, 116 Diethyl diacetoxyterephthalate, 517 Diethyldiamidoterephthalate, 489 Diethyldibenzylammonium iodide, 117 Diethyl o-hydroxyisophthalate, 495 Diethyl s-hydroxyisophthalate, 495 Diethyl dihydroxyterephthalate, 516 Diethylorthotoluidine, 59 Diethylparadihydroxybenzaldehyde, 349 Di-ethylparatoluidine, 65 Diethylprotocatechuic acid, 355 Diethyl-/3-resorcylaldehyde, 349 Diethyl-a-resorcylic acid, 359 Diethyl--resorcylic acid, 360 Difluorbenzoic acid, 227 Digallic acid, 371 Dihydro-orthoxylene, 391 Dihydrophthalic acid, 469, 487 Dihydrotoluene, 6 Dihydroxybenzoic acids, 350 Dihydroxybenzyl and Dihydroxy- Benzoyl compounds, 343 Dihydroxyhexhydroterephthalic acid, 487 Dihydroxyisophthalaldehyde, 515 Dihydroxyisophthalic acid, 515 Dihydroxyphthalic acids, 510 Dihydroxyquinone, 520 Dihydroxyterephthalic acid, 515 Dihydroxytoluenes and allied bodies, 31 Dihydroxytolualdehydes, 427 Dihydroxytoluic acids, 428 Dihydroxytoluquinone, 49 Dihydroxy-xylenes, 402 Di-iodoparacresol, 29 Di-iodoparahydroxy ben zoic acid, 335 Di-iodosalicylic acid, 315 Dimetatolyl carbamide, 63 Dimetatolyl thiocarbamide, 63 Dimethoxybenzonitril, 361 Dimethoxyorthophthalic acid, 510 Dimethyl acetoxyterephthlate, 496 530 INDEX. Dimethylamidophenylhydroxytri- chlorethane, 151 Dimethylbenzamide, 174 Dimethylbenzenes, 390 Dimethyldiamidotoluene, 62 Dimethyldihydroxyphthalic acid, 498 Dimethyl a-hydroxyisophthalate, 495 Dimethyl s-hydroxyisophthalate, 495 Dimethylhydroxysalicylic acid, 362 Dimethyl hydroxyterephthalate, 496 Dimethylmetamidobenzoic acid, 247 Dimethylmetatoluidine, 61 Dimethylmethylene benzoate, 163 Dimethylnoropianic acid, 503 Dhnethylorthotoluidine, 58 Dimethylparadihydroxybenzaldehyde, 349 Dimethylparamidobenzaldehyde, 1 50 Dimethylparamidobenzoic acid, 253 Dime thy Iparatolui dine, 65 Dimethylparatolyl phosphine, 84 Dimethyltolylphosphine oxide, 84 Dimethylphenylenebenzenylamide am- monium iodide, 205 Dimethylphosphine-oxide benzoic acid, 277 Dimethylprotocatechuic acid, 354 Dimethylprotocatechuicaldehyde, 346 Dimethyl--resorcylaldehyde, 349 Dimethyl-o-resorcylic acid, 358 Dimethyl-/3-resorcylic acid, 360 Dimethyl-7-resorcylic acid, 361 Dinitro-amidobenzoic acids, 257 Dinitro-anisic acid. 337 Dinitro-anthranilic acid, 257 o-Dinitrobenzoic acid, 234 -Dinitrobenzoic acid, 234 7-Dinitrobenzoic acid, 234 8-Dinitrobenzoic acid, 235 e-Dinitrobenzoic acid, 235 Dinitrobenzoic acids, 234 Dinitrobenzysulphonic acid, 109 Dinitro-diphenylamine-orthocarboxylic acid, 245 Dinitro-i?-hydroxyphthalic acid, 493 Dinitrohydroxyterephthalic acid, 496 s-Dinitrometaxylene, 396 r-Dinitrometaxylene, 396 o-Dinitro-orcinol, 41 -Dinitro-orcinol, 42 Dinitro-ortharnidobenzoic acid, 257 Dinitro-orthocresol, 26 a-Dinitro-orthotoluiuine, 71 Dinitro-orthoxylene, 396 Dinitroparacresol, 30 Dinitroparahydroxybenzoic acid, 335 Dinitroparamidobenzoic acid, 258 Dinitroparaxylidine, 408 o-Dinitroparaxylene, 397 -Dinitropaiaxylene, 397 7-Dinitroparaxylene, 397 Dinitrophthalic acid, 475 Dinitrosalicylic acid, 317 7-Dinitrotoluene, 17 Dinitrotoluene, ordinary, 16 ; sym- metric, 17 Dinitrotoluenes, 16 Dinitrotoluidine, 18 -Dinitrotoluidine, 71 S Dinitrotoluidine, 71 initrotoluidines, 71 7-Dinitrotolylphenylamine, 18 Diorsellinic acid, 433 Di-orthotolylamine, 59 Di-orthotolylcarbamide, 59 Di-orthotolyl thiocarbamide, 60 Diparahydroxybenzoylparahydroxy- benzoic acid, 331 Diparatolylamine, 66 Diparatolylarsenic acid, 85 Diparatolyl carbamide, 66 Diparatolylhydrazine, 75 Diparatolylnitrosamine, 66 Diparatolyl thiocarbamide, 67 Diphenylbenzene, 452 Diphenylbenzenylamidine, 204 Diphenylorthoxylylenediamine, 440 Diphenylparamidobenzenylamidine,204 Diphenylphthalamic acid, 465 Diphenylphthalei'n, 465 Diphenylthiobenzamide, 178 Diphthalyl, 458, 460 Disalicylamide, 312 Disalicylic acid, 308 o-Disulphobenzoic acid, 274 -Disulphobenzoic acid, 274 Disulphobenzoic acids, 274 Disulphometahydroxy benzoic acid, 326 Disulphorthotoluic acid, 416 Dithiobenzoic acid, 172 Dithiometahydroxybenzoic acid, 325 Dixylylainine, 412 Dragonic acid, 329 Drupacese, 131 E. ERYTHRELINIC ACID, 429 Erythric acid, 429 Erythrinbitter, 428 Erythrylin, 428 Erythrin, 428, 431, 434 j8-Erythrin, 435 Erythroglucin, 430 Ethereal salts of Benzyl, 96 Ethereal salts of salicylic acid, 306 Ethereal salts of salicylic ethers, 307 Ethers of benzoic acid, 160 Ethers of benzyl with the dihydroxy- benzenes, 95 Ethers of phthalic acid, 457 Ethidenedibenzamide, 176 Ethoxycarbimidamidcbenzoic acid, 250 Ethoxycyanamidobenzoyl, 242 Ethoxymethoxybenzonitril, 361 Ethoxynitrobenzonitril, 361 Ethyl amido-isophthalate, 482 INDEX. 531 Ethyl a-amidophthalate, 476 k Ethyl iJ-amidophthalate, 475 'Ethyl anisbenzhydroxamate, 340 Ethyl anishydroxamate, 339 Ethylanishydroxamic acid, 339 o-Ethylbenzanishydroxamate, 340 -Ethylbenzanishydroxamate, 340 Ethyl benzenylamidoximecarboxylate, 214 Ethenylbenzenylazoxime, 214 a-Ethylbenzhydroxamic acid, 211 Ethyl benzhydroxamate, 209 Ethyl benzoate, 161 Ethyl benzoyl-glycollate, 165 Ethyl benzoyl-lactate, 165 Ethylbenzoyl thio-urea, 179 Ethyl-benzylamidine, 202 Ethylbromosalicylaldehyde, 292 Ethyleue benzoate, 162 Ethyl-#-diamidotoluene, 73 o-Ethyl dibenzhydroxaraate, 210 -Ethyl dibenzhydroxamate, 210 Ethyl dibenzylamine, 117 Ethyl dibromoterephthalate, 488 Ethyl dihydroxyquinoneterephthalate, 519 Ethylenebenzamide, 174 Ethyleneprotocatechuic acid, 356 Ethylene salicylate, 306 Ethylene salicylic acid, 306 Ethyl ether of benzenylamidoxime, 213 Ethyl ethylenesalicylate, 307 Ethyl ethylsalicylate, 307 Ethyl gallate, 369 Ethyl hemipinimide, 514 Ethyl hippurate, 190 j8-Ethylhydroxamic acid, 211 Ethyl hydroxysalicylate, 362 Ethyl isophthalate, 479 Ethyl metacyanobenzoate, 480 Ethyl meta-ethoxybenzoate, 322 Ethyl metahydroxybenzoate, 321 Ethyl metanitrobenzoate, 231 Ethyl metasulphamidobenzoate, 272 Ethyl metasulphobenzoic acid, 271 Ethyl metatoluate, 417 Ethyl methylsalicylate, 307 Ethyl nitro-isophthalate, 482 Ethylnitrolic acid, 468 Ethyl opianate, 505 Ethyl orsellinate, 433 Ethyl orthobenzoate, 194 Ethyl orthocyanobenzoate, 468 Ethyl orthonitrobenzoate, 230 Ethyl orthotoluate, 414 Ethylorthotoluidine, 59 Ethyl paracyanobenzoate, 485 Ethylparadihydroxybenzaldehyde, 349 Ethyl para-ethoxybenzoate, 330 Ethyl parahydroxybenzoate. 330 Ethyl paramethoxybenzoate, 330 Ethyl paranitrobenzoate, 232 Ethyl paratoluate, 419 Ethylparatoluidine, 65 Ethyl phthalate, 457 Ethyl phthalimide, 464 Ethylphthalylhydroxylamine, 467 Ethyl piperonate, 356 Ethyl pyro-gallolcarboxylate, 379 Ethyl quinate, 385 Ethyl a-resorcylate, 358 Ethyl salicylaldehyde, 287 Ethyl salicylate, 306 Ethyl terephthalate, 484 Ethyl tetracetylquinate, 385 Ethyl tetrachlorophthalate, 472 Ethyl tetrahydroxyterephthalate, 520 Ethyl thiobenzoate, 171 Ethyltolyl carbamate, 67 Ethylvanillic acid, 355 Ethyl veratrate, 355 Ethysalicylic acid, 306 Evernic acid, 435 Everninic acid, 435 P. FEKRIC benzoate, 161 Fluorine substitution products of toluene, 13 Formortho-arnidobenzoic acid, 239 Fluotoluene, 13 G. GALLAMIDE, 370 Gallates, the, 368 Gallic acid, 363, 381 Gallocarboxylic acid, 519 Gallocyanin, 377 Gentisic acid, 362 Gentisinaldehyde, 349 Glucovanillic acid, 352 Glucovanillin, 347 Glucovanillyl alcohol, 347 Guanidodibenzoic acid, 260 H. HALOGEN compounds of benzoyl, 168 Halogen substitution products, 118 Halogen substitution products of benzoic acid, 216 Halogen substitution products of phthalic acid, 471 Halogen substitution products of the Toluidines, 67 Halogen substitution products of the Xylenes, 392 Helicin, 288 Helicoi'din, 289 Hemipinic acid, 497, 510 Hemipinic anhydride, 511 Hemipinimide, 513 Hemipinimidine, 501 532 INDEX. Heptacarbure quadrihydrique, 3 Hexbromobenzene, 12 Hexchloroxylone, 34 Hexhydrometaxylene, 391 Hexhydroparaxylene, 392 Hexhydrophthalic acid, 470 Hexhydroterephthalic acid, 486 Hexhydrotoluene, 7 Hexmethyl-5-diamidobenzoic acid, 259 Hexnitrodiparatolylamine, 66 Hipparin, 175 Hippuramide, 191 Hippuramido-acetic acid, 191 Hippurates, the, 189 Hippurglycollamide, 192 Hippuric acid, 181, 383 ; properties, 188 Homocatechol, 31 Homocatechol dimethyl ether, 32 Homocatechol monomethyl ether, 32 Homo-erythrin, 435 Homohydroxysalicylic acid, 438 Homopyrocatechin, 31 Homorcinol, 402 Homosalicylic acids, 423 Homosaligenin, 422 Hydrazenebenzoic acids, 264 Hydrazine-derivatives of Toluene, 75 Hydrazobenzoic acids, 265 o-Hydrazotoiuidine, 79 0-Hydrazotoluidine, 79 Hydrobenzamide, 139, 140 Hydrobenzamide trijldehyde, 449 Hydrobenzamidetricarboxylic acid, 449 Hydrobenzoic acid, 159 Hydrobenzuric acid, 192 Hydrobenzyluric acid, 192 Hydro phlorone, 403 Hydrophthalide, 444 Hydrosalicylamide, 291 Hydroxybenzaldehydes, 285 Hyd roxybenzidene-amidobenzoic acid, 291 Hydroxybenzoic acids, 297 Hydroxybenzyl alcohols, 279 Hydroxybenzyl group, 279 Hydroxybcnzyluric acid, 192 o-Hydroxyisophthalic acid, 494 s-Hydroxyisophthalic acid, 495 v-Hydroxyisophthalic acid, 495 Hydroxyisophthalic acid, 303 Hydroxylamine derivatives containing three acid radicals, 341 Hydroxymetaxyloquinone, 404 Hydroxymethylbenzoic acids, 442 Hydroxymethyldihydroxybenzoic acids, 497 Hydroxymethyldimethoxybenzoic acid, 500 Hydroxymethylhydroxybenzoic acid, 490 v-Hydroxyorthophthalic acid, 493 Hydroxyphthalamic acid, 467 o-Hydroxyphthalic acid, 492 Hydroxyphthalic acids, 492 o-Hydroxyphthalic anhydride, 493 Hydroxyquinolcarboxylic acid, 380, 381 Hydroxysalicylic acid, 361 Hydroxyterephthalic acid, 495 Hydroxytolualdehydes, 422 s-Hydroxytoluic acid, 425 Hydroxytoluic acids, 423 Hydroxytoluquinonoxime, 52 Hydroxytrinesic acid, 303, 494 Hydroxy-xylenes, 399 Hypogallic acid, 498 I. IMIDE of metadiazobenzoic acid, 264 Insolinic acid, 451 lodamidobenzoic acids, 255 lodanisic acid, 337 Iodine substitution products, 41 Iodine substitution products of Toluene, 13 lodo-isophthalic acid, 481 lodomeconin, 500 lodometahydroxybenzoic acid, 323 lodonitrobenzoic acids, 237 lodoparacresol, 29 lodoparahydroxybenzaldehyde, 296 lodoparahydroxybenzoic acid, 335 lodoparatoluic acid, 420 lodosalicylic acid, 314 lodotoluenedisul phonic acid, 22 lodotoluidines, 68 Iron gallate, 369 Jsobutyl hippurate, 191 Isobutyl terephtlmlate, 484 Isodiazoxybenzoic acid, 267 Isohemipinic acid, 515 Isonitrosobenzyl ether, 98 Isonoropianic acid, 508 Isophthalalcohol, 440 Isophthalaldehyde, 447 Isophthalic acid, 451, 479 Isophthalic acid, addition products of, 481 Isophthalic acid, substitution products of, 481 Isophthalamide, 480 Isophthalonitril, 481 Isophthalyl chloride, 480 Isopianic acid, 509 Isopropyl benzoate, 162 Isopropylsalicylic acid, 306 Isopropyl terephthalate, 484 Isorcinol, 47 Isosulphometahydroxybenzoic acid, 325 Isotrichloroglyceric acid, 368 Isovanillic acid, 353 Isovanillin, 346 Isoxylol, 387 INDEX. 533 J. JUGLONIC acid, 493 K. KINOIN, 374 Kino-red, 374 LEAD benzoate, 161 Lead benzyl mercaptide, 106 Lead benzylsulphonate, 108 Lead dithiobenzoate, 172 Lead gallate, 369 Lead hippurate, 190 Lead opianate, 504 Lead opianylsulphite, 507 Lead parahydroxy benzoate, 328 Lead phthalate, 457 Lead proto-catechuate, 352 Lead quinate, 384 Lead salicylaldehyde, 287 Lead salicylate, 304 Lecanoric acid, 429, 432, 433 Lecanorin, 429 Lithium salicylate, 303 Litmus, 45 Luteolin, 357 M. MACLTTRIN, 356 Magnesium hippurate, 189 Maluchite-green, 135 Mandelic acid, 131 Meconin, 497, 500 ^-Meconin, 501 Meconinic acid, 500 Meconiosin, 502 Menyanthin, 423 Menyanthol, 423 Mercuric benzamide, 174 Mercuric benzoate, 161 Mercury benzyl mercaptide, 105 Mercury derivatives of Toluene, 87 Mercury orthotolyl, 88 Mercury paratolyl, 88 Meta-acetobenzyl acetate, 283 Meta-acetoxybenzoic acid, 322 Meta-azotoluene, 76 Meta-benzamoxalic acid, 248, 249 Metabenzenyltrichlorophosphoryl chloride, 322 Metabenzobetaine, 248 a-Metabenzo-creatine, 252 -Metabenzo-creatine, 252 Metabenzoglycocyamine, 251 Metabenzosarcosine, 247 Metabromobenzaldehyde, 145 Metabromobenzoic acid, 223 Metabromobenzyl bromide, 102 Metabromotoluene, 11 Metacarbamidobenzoic acid, 251 Metacarbonylphenylphosphoryl chloride, 322 Metacarboxyorthophosphoric acid, 322 Metachlorobenzaldehyde, 144 Metachlorobenzoic acid, 219 Metachlorobenzonitril, 220 Metachlorobenzoyl chloride, 220, 383 Metachlorohippuric acid, 220 Metachlorotoluene, 8 Metacresol, 24, 27 Metacresyl benzoate, 164 Metacresyl oxide, 27 Metacyanobenzoic acid, 480 Metadiamidobenzylarnine, 1 20 Metadiazo-amidobenzoic acid, 262 Metadiazobenzamide nitrate, 261 Metadiazobenzoic acid, 261 Metadiazobenzoic acid imide, 264 Metadiazobenzoic acid nitrate, 261 Metadiazobenzoic acid perbromide, 261 Metadiazobenzoic acid platinichloride, 261 Metadiazobenzoic acid sulphate, 261 Metadiazobenzonitril nitrate, 262 Metadihydroxybenzaldehyde, 348 Metadinitrobenzylamine, 119 Metadithiobenzoic acid, 272 Metaditolylamine, 62 Meta-ethoxybenzoic acid, 322 Metafluorbenzoic acid, 226 Metafluorhippuric acid, 226 Metaguanidobenzoic acid, 251 Metahomometahydroxybenzoic acid, 425 Metahomomethoxycalicylaldehyde, acid, 428 Metahomoparahydroxybenzaldehyde, 422 Metahomoparahydroxybenzoic acid, 426 Metahomosalicylaldehyde, 422 a-Metahomosalicylic acid, 424 /3-Metahomosalicylic acid, 424 Metahydrazinebenzoic acid, 264 Metahydrazobenzoic acid, 266 Metahydrazotoluene, 76 Metahydroxybenzaldehyde, 293 Metahydroxybenzamide, 323 Metahydroxybenzanilide, 323 Metahydroxybenzenylamidoxime, 216 Metahydroxybenzoates, 320 Metahydroxybenzoic acid, substitution products of, 323 Metahydroxybenzonitril, 323 Metahydroxybenzoic acid, 320 Metahydroxybenzoylsulphuric acid, 326 Metahydroxybenzuric acid, 323 Metahydroxybenzyl acetate, 283 Metahydroxybenzyl alcohol, 283 205 534 INDEX. Metahydroxybenzyl diacetate, 283 Metahydroxyovthotoluic acid, 425 Metahydroxyparatoluic acid, 426 Meta-iodobenzoic acid, 225 Meta-iodotoluene, 13 Metamethoxybenzoic acid, 321 Metamethoxysalicylaldehyde, 349 #-Metamethoxysalicylaldehyde, 348 Metamidobenzaldoxime, 150 Metamidobenzaldehyde, 150 Metamidobenzamide, 247 Metamidobenzenylamidoxime, 216 Metamidobenzoic acid, 246, 248, 252 Metamidobenzoic acid hydrochloride, 247 Metamidobenzonitril, 247 Metamidobenzylphenylamine, 120 Metamidoparamethyltoluidine, 73 Metamidoparazotoluene, 78 Metanitrobenzaldehyde, 147 Metanitrobenzaldoxime, 147 Metanitrobenzamide, 231 Metanitrobenzenylamidoxime, 216 Metanitrobenzidene bromide, 147 Metanitrobenzidene chloride, 147 Metanitrobenzoic, 230 Metanitrobenzoic acid, 228 Metanitrobeuzonitril, 232 Metanitrobenzoyl chloride, 231 Metanitrobenzyl alcohol, 104 Metanitrobenzylamine, 119 Metanitrobenzylamines, 119 Metanitrobenzyl chloride, 104 Metanitrobenzylphenylamine, 119 Metanitrohippuric acid, 232 Metanitromethylmetahydroxybenzalde- hyde, 294 Metanitro-orthotoluidine, 69 Metanitropara-ethyltoluidine, 71 Metanitroparamethyltoluidine, 7 1 Metanitroparatoluidine, 70 Metanitrotoluene, 16 Metaphlorone, 404 Metaphthalic acid, 479 Metasulphamidobenzoic acid, 272 Metasulphamido-orthotoluic acid, 416 Metasulphobenzamide, 271 Metasulphobenzoates, 270 Metasulphobenzoic acid, 269 Metasulphobenzoyl chloride, 271 Metathiocresol, 31 Metathiohydrobenzoic acid, 272 Metatoluaidehyde, 413 Metatoluic acid, 416 Metatoluidine, 60 Metatoluidine hydrochloride, 61 Metatoluidine nitrate, 61 Metatoluidine sulphate, 61 Metatolunitril, 417 Metatoluyl chloride, 417 Metatoluylenediamine, 72 Metatolyl carliamide, 63 Metatolyl mustard oil, 63 Metatolylstibine, 86 Metatolyl thiocarbamide, 63 Metatriamidobenzylamine, 120 Metatrinitrobenzy lamine, 1 1 9 Meta-uramidobenzoic acid, 250 Meta-urethanebenzoic acid, 251 Metaxylene, 388, 389, 391 a-Metaxylenesulphamide, 399 a-Metaxylenesulphonic acid, 398 v-Metaxylenesul phonic acid, 399 o-Metaxylenesulphonic chloride, 398 o-Metaxylenol, 400 s-Metaxylenol, 401 w-Metaxylenol, 401 o-Metaxylenyl acetate, 401 Metaxylidenehydrazine, 413 Metaxylidene tetrachloride, 447 Metaxylylene alcohol, 440 Metaxylylene bromide, 441 Metaxylylene chloride, 441 Metaxylylene ethyl ether, 440 o-Metaxylenyl methyl ether, 400 o-Metaxylidine, 406 s-Metaxylidine, 407 u-Metaxylidine, 406 Metazobenzoic acid, 266 Metazoxybenzoic acid, 266 Methenylamidorthocresol, 26 MetAxyloquinol, 403 Metaxyloquinone, 404 Metaxylorcinol, 402 Metaxylyl acetate, 412 Metaxylyl alcohol, 411 Metaxylyl bromide, 412 Metaxylyl chloride, 412 Metaxylyl ethyl ether, 411 o-Methoxyisophthalic acid, 494 u-Methoxyisophthalic acid, 495 Methoxynitrobenzonitril, 361 Methoxyterephthalic acid, 496 Methyl aldehydovanillate, 509 Methyl amido-anisate, 338 Methylamido-anisic acid, 338 Methyl amido-isophthalate, 482 Methyl amido-terephthalate, 489 Methylbenzene, 3 Methyl benzoate, 161 Methylbenzoylphenylhydrazine, 180 Methylbenzyl, 387 Methyl benzyJsalicylate, 307 Methylbromosalicylaldehyde, 292 Methyl bromoterephthalatc, 488 Methyl chloroterephthalate, 488 Methylcinnyl ketone, 135 Methyl cresolcarboxylate, 439 Methyl-j8-diamidotoiuene, 73 Methyldibenzoylphenylhydrazine, 1 80 Methyl dimethylamidosalicylate, 318 Methylenedibenzamide, 175 Methyleneprotocatechuicaldehyde, 347 Methyl ethylsalicylate, 307 Methyl hippurate, 190 a-Methylhydroquinoneformic acid, 362 a-Methylhydroxyphthalic acid, 493 u-Methylhydroxyphthalic acid, 493 INDEX. 535 Methylhydroxysalicylic acid, 362 Methylhypogallic acid, 498 Methyl iodide, 36 Methyl isocyanate, 518 Methylisonoropianic acid, 508 Methylisophthalate, 479 Methyl isopropylsalicylate, 307 Methylmetahomoparahydroxybenzoic acid, 427 o-Methylmetahomosalicylic acid, 424 Methylmetahydroxybeuzaldehyde, 293 Methylmetamidobenzoic acid, 247 Methylmetatoluidine, 61 Methyl nitrite, 578 Methyl-nitro-isophthalate, 482 Methylnitrosalicylaldehyde, 292 Methyl nitroterephthalate, 489 Methyl norhemipinic acid, 514 Methylnormecouin, 498, 501 Methylnoropianic acid, 498, 502 Methyl opianate, 505 Methyl orsellinate, 432 /3-Methylorthodihydroxybenzaldehyde, 348 o-Methylorthobenzoglycocyamidine, 243 -Methylorthohomometahydroxyben- zoic acid, 426 Methylorthohomoparahydroxybenzoic acid, 427 Methylorthohomosalicylic acid, 424 Methylorthotoluidine, 58 Methylorthotolylnitrosamine, 58 Methyl paradihydroxybenzaldehyde, 349 Methylparahomosalicylic acid, 424 Methylparahydroxybenzaldehyde, 295 Methylparahydroxybenzoate, 295, 328 Methylparahydroxybenzoyl chloride, 332 Methyl paramethoxybenzoate, 330 Methyl paratoluate, 419 Methylparatoluidine, 64 Methylphthalate, 457 Methylphthalimidine, 445 Methylprotocatechuate, 352 Methylpyrogallic acid, 53 Methylpyrogallol, 53 Methyl pyrogallol dimethyl ether, 54 Methyl salicylaldehyde, 287 Methyl salicylate, 305 Methyl salicylic acid, 305 Methyl terephthalate, 484 Methyl tetrahydrotcrephthalate, 486 Methyltoluol, 387 Methyl vanillate, 352 Methylvanillin, 346 Methyl veratrate,354 Monamidobenzoic acids, 237 Monethyl dihydroxy terephthalate, 517 Monobromobenzoic acids, 223 Monobromoparaxylcnol, 401 Monobromophthalide, 443 Monobromorcinol, 41 Monobromo toluenes, 10 Monochlorobenzoic acids, 217 Monochlorobenzenyl trichloride, 196 Monochlorotoluenes, 8 Monofluorbenzoic acids, 226 Monohydroxy toluenes and allied bodies, 23 ' Mono-iodobenzoic acids, 225 Mono-iodorcinol, 41 Mononitrobenzoic acids, 229 Mononitrotoluenes, 13 Monosulphobenzoic acids, 268 Monoxylylamine, 412 Morintannic acid, 356 N. NAPHTHALAMIDE, 463 Naphthalic acid, 450 Naphthesic acid, 450 Nitradiazobenzoic acid, 262 Nitranilic acid, 520 e-Nitro-amidobenzamide, 257 o-Nitvo-amidobenzoic acid, 256 -Nitro-amidobenzoic acid, 256 7-Nitro-amidobenzoic acid, 256 8-Nitro-amidobenzoic acid, 256 e-Nitro-amidobenzoic acid, 257 -Nitro-amidobenzoic acid, 257 77-Nitro-amidobenzoic acid, 257 Nitro-amidobenzoic acids, 255 Nitro-amidosalicylic acid, 318 Nitro-anisic acid, 337 Nitrobenzinic acid, 227 Nitrobenzoene, 4 Nitrobenzoic acids, 233 Nitrobenzylsulphonic acid, 109 Nitrococcusic acid, 425 Nitro-diamidometaxylene, 409 Nitro-dimethylmetatoluidine, 62 Nitro-dracyl, 4 Nitro-dracy lie acid, 228 Nitrogen bases of benzyl, 110 Nitrogen compounds of benzoyl, 172 Nitrohemipinic acid, 511 Nitro-isophthalic acid, 482 Nitromeconin, 500 Nitro-^-meconin, 501 Nitrometacresol, 27 o-Nitrometahydroxybenzaldehyde, 293 j8-Nitrometahydroxybenzaldehyde, 293 7-Nitrometahydroxybenzaldehyde, 293 Nitrometahydroxybenzoic acids, 323 o-Nitrometahydroxybenzoic acid, 324 )8-Nitrometahydroxybenzoic acid, 324 7-Nitrometahydroxybenzoic acid, 324 Tj-Nitrometahydroxybenzoic acid, 324 Nitrometatoluic acids, 417 o-Nitrometaxylene, 396 s-Nitrometaxylene, 396 r-Nitrometaxylene, 396 a-Nitro-a-metaxylidine, 408 s-Nitro-s-metaxylidine, 408 v-Nitrol-a-metaxylidine, 408 536 INDEX. a-Nitro-s-metaxylidine, 408 Nitromethane, 518 Nitromethylnoropianylhydrazide, 508 Nitromethylnoropianic acid, 503 Nitromethylnorhemipinic acid, 514 Nitro-opianic aci(l, 507 Nitro-opianylphenylhydrazide, 508 a-Nitro-orcinol, 41 /3-Nitro-orcinol, 41 a-Nitro-orthocresol, 25 /8-Nitro-orthocresol, 26, 51 7-Nitro-orthocresol, 26 Nitro-orthotoluic acids, 415 o-Nitro-orthoxylene, 395 y-Nitro-orthoxylene, 395 a-Nitroparaciesol, 30 0-Nitroparacresol, 30 Nitroparahydroxybenzoic acid, 335 Nitroparahydroxybcnzaldehyde, 296 a-Nitroparatoluic acid, 421 0-Nitroparatoluic acid, 421 /8-Nitroparatolunitril, 421 Nitroparaxylene, 397 o-Nitroparaxylidine, 408 jS-Nitroparaxylidine, 408 7-Nitroparaxylidine, 408 a-Nitrophthalic acid, 474 v-Nitrophthalic acid, 473 Nitrophthalic acids, 473 a-Nitrophthalicanhydride, 475 a-Nitro-salicylaldehyde, 292 /3-Nitrosalicylaldehyde, 292 Nitrosalicylic acids, 315 a-Nitrosalicylic acid, 315 /3-Nitrosalicylic acid, 316 Nitrosodibenzylamine, 116 Nitroso-dimethylmetatoluidine, 62 Nitrosohemipinimidine, 501 Nitrosomethylmetanitrobenzene, 147 Nitrosomethylnitrobenzene, 147 Nitrosomethylparatoluidine, 65 Nitrosometracresol, 51 Nitrosoparaxylorcinol, 402 Nitrosophthalimidine, 444 Nitro-substitution products, 41, 293 Nitro-sub.stitution products of benzoic acid, 227 Nitro-substitution products of toluene, 13 Nitre-substitution products of the xylenes, 395 Nitrosulphobenzoic acids, 275 Nitroterephthalamide, 489 Nitro-terephthalaldehyde, 449 Nitroterephthalaldehydic acid, 449 Nitro-terephthalic acid, 488 Nitrotolueno, 13 /3-Nitrotoluene, 15 Nitrotoluidine, 15 Nitrotoluidines, 69 Nitro-uramidobenzoyl, 242 Nitroxylidines, 408 Norhemipinic acid, 498 Normal barium hydroxamate, 208 Normal barium metasulphobenzoate, 270 Normal barium a-nitrosalicylate, 316 Normal barium /8-nitrosalicylate, 316 Normal barium parasu]phobenzoate,273 Normal barium phthalate, 457 Normal calcium benzamoxalate, 245 Normal ethyl metasulphobenzoate, 270 Normal ethyl a-nitrophthalate, 475 Nonr.al ethyl y-nitrophthalate, 474 Normal lead metasulphobenzoate, 270 Normal methyl sulphinidephthalate, 478 Normal potassium hemipinate, 510 Normal potassium metasulphobenzoate, 270 Normal potassium sulphinidephthalate, 477 Normal silver hemipinate, 510 Normal silver sulphinidephthalate, 477 Normal sodium dihydroxyterephtha- late, 516 Normeconin, 498 Noropianic acid, 498, 502 0. OCTYL BENZOATE, 162 Octacetylhelicoidin, 289 Oil of bitter almonds, 132 Opianic acid, 497, 503 Opianic anhydride, 505 Opianoxime anhydride, 513 Opianyl, 497 Opianylphenylhydrazide, 507 Opianyl sulphurous acid, 506 Opinic acid, 514 Orcein, 44 a-Orcein, 44 j8-0rcein, 44 Orcin, 37 /3-Orcin, 402 Orcinol, 37, 429 ; properties, 39 Orcinol acetate, 40 Orcinolazobeuzene, 40 Orcinol diethylcarbonate, 40 Orcinol dimethyl ether, 40 Orcinol monomethyl ether, 40 Orcinol, substitution products of, 41 Orcylaldehyde, 427 Orn'ithine, 193 Ornithuric acid, 192, 193 a-Orsellic acid, 429 Orsellinic acid, 432, 438 a-0rsel!inic acid, 429 Orthamidobenzaldoxime, 149 Orthamidobenzaldehydc, 149 Orthamidobenzyl alcohol, 105 Ortho - aldehydometahydroxybenzoie acid, 492 Ortho - aldehydoparahydroxybenzoic acid, 491 INDEX. 537 Ortho aldehydophenoxyacetic acid, 289 Ortho-aldehydosalicylic acid, 491 Ortho-amidobenzamide, 240 Ortho-amidobenzoic acid, 237 Ortho-amidobenzoic acid, hydrochlor- ide, 239 Ortho- amidobenzonitril, 240 Ortho-amidopara-azotoluene, 78 Ortho -azobenzoic acid, 265 Ortho-azotoluene, 75 Ortho-azoxybenzoic acid, 265 Ortho-azoxytoluene, 77 Orthobenzaraoxalic acid, 244 Orthobenzidenephenylhydrazine, 291 a-Orthobenzocreatinine, 243 j8-0rtbobenzocreatinine, 244 Orthobenzoglycocyamidine, 243 Orthobenzoic acid, 194 Orthobenzoylliydrazide, 264 Orthobeuzyl thioformate, 106 Orthobromobenzaldehyde, 145 Orthobromobenzoic acid, 223 Orthobromobenzyl alcohol, 102 Orthobromo-benzylamine, 118 Orthobromobenzyl bromide, 102 Orthobromotoluene, 10 Orthocarbonylphenylphosphoryl chlo- ride, 311 Orthocarboxylphenylphosphoric acid, 311 Orthochlorobonzaldehyde, 143 Orthochlorobenzidene chloride, 143 Orthochlorobenzoic acid, 144, 217 Orthochlorobenzonitril, 218 Orthochlorobenzoyl chloride, 218, 462 Orthochlorocarbonylphenyl metaphos- phate, 311 Orthochloroparanitrotoluene, 19 Orthochlorotoluene, 8 Orthocresol, 24, 25 Orthocresyl benzoate, 164 Orthocresyl oxide, 25 Orthocyanobenzoic acid, 468 Orthodiazobenzoic acid nitrate, 261 Orthodiazobenzoic acid seminitrate, 261 Orthodibroino-benzylamine, 119 o-Orthodihydroxybenzaldehyde, 343 Orthodihydroxybenzoic acid, 350 Orthodinitrotoluene, 17 Orthofluorbenzoic acid, 226 Orthofluorhippuric acid, 226 o-Orthohomometahydroxybenzoic acid, 426 /3-Orthohomometahydroxybenzoic acid, 426. Orthohomoparahydroxybenzaldehyde, 422 Or th oh omoparahy droxybenzoic acid, 427 Orthohomosalicylaldehyde, 422 Orthohomosalicylic acid, 424 Orthohydrazinebenzoic acid, 264 Orthohydrazobenzoic acid, 265 Orthohydroazotoluene, 75 Orthohydroxybenzaldehyde, 285 Orthohydroxybenzidene acetate, 290 Orthohydroxybenzidene compounds, 290 Orthohydroxybenzidenoxime, 290 Orthohydroxybenzoic acid, 297 Orthohydroxy benzyl alcohol, 279 Orthohydroxybenzyl ethyl ether, 280 Orthohydroxybenzyl glucoside, 281 Orthohydroxybenzyl methyl ether, 280 Orthohydroxymetatolualdehyde, 422 a-Orthohydroxymetatoluic acid, 423 Orthohydroxymetaxylyl alcohol, 422 Orthohydroxymethylbenzoic acid, 442 Orthohydroxymethylparahydroxyben- zoic acid, 490 Orthohydroxymethylsalicylic acid, 490 Orthohydroxyparatolualdehyde, 422 Orthohydroxyparatoluic acid, 424 Orthohydroxymetatolualdehyd e, 422 i/-0rthohydroxymetatcluic acid, 424 Ortho-iodobenzoic acid, 225 Ortho-iodotoluene, 13 Orthomethoxybenzyl alcohol, 280 Orthomethoxyparahydroxybenzalde- hyde, 348 Orthomethyl-j8-resorcylic acid, 360 Orthonitrobenzoyl chloride, 230 Orthonitrobenzyl alcohol, 104 Orthonitrobenzaldehyde, 146, 240 Orthonitrobenzaldoxime, 146 Orthonitrobenzoic acid, 228, 229 Orthonitrobenzonitril, 230 Orthonitrobenzyl chloride, 105 Orthonitrobenzyl iodide, 105 Orthonitrometatolualdehyde, 413 o-Orthonitrometatoluidine, 70 -Orthonitrometatoluidine, 70 o-Orthonitromethylmetahydroxybenz- aldehyde, 294 j3-0rthonitromethylmetahydroxybenz- aldehyde, 294 a-Orthonitro-orthotoluidine, 69 -Orthonitro-orthotoluidine, 69 Orthonitroparatoluidine, 70 Orthonitrophthalide, 446 Orthonitrotoluene, 15 Orthosulphamidobenzoic acid, 268 Orthosulphobenzoic acid, 268 Orthothiocresol, 31 Orthotolualdehyde, 413 Orthotoluamide, 414 Orthotoluic acid, 414 Orthotoluidine, 57 Orthotoluidine hydrobromide, 58 Orthotoluidine hydrochloride, 58 Orthotoluidine nitrate, 58 Orthotoluidine oxalate, 58 Orthotoluidine sulphate, 58 Orthotolunitril, 414 Orthotoluyl chloride, 414 538 INDEX. Orthotoluyl arsenic acid, 86 Orthotoluylenediamine, 72 Orthotolyl carbamide, 59 Orthotolyl isocyanate, 59 Orthotolyl mustard oil, 60 Orthotolylphosphenilic acid, 84 Orthotolylphosphenylons acid, 84 Orthotolylphosphorus dichloride, 84 Orthotolylstibine, 86 Orthotolyl thiocarbamide, 59 Orthotribromo-benzylamine, 119 Ortho-uramidobenzoic acid, 243 Orthoxylene, 388, 389, 390 a-Orthoxylenol, 400, 401 u-Orthoxylenol, 400 Orthoxylenesulphonamide, 398 Orthoxylouesulphonic acid, 398 Orthoxyienesulphonic chloride, 398 Orthoxylidene tetrachloride, 447 o-Orthoxylidine, 406 u-Orthoxylidine, 406 Orthoxyloquinol, 403 Orthoxyloquinone, 404 Orthoxylyl alcohol, 411 Orthoxylyl bromide, 412 Orthoxylyl chloride, 412 Orthoxylylene acetate, 440 Orthoxylylene alcohol, 439 Orthoxylylene bromide, 440 Orthoxylylene chloride, 439 Orthoxylylene ethyl ether, 439 Orthoxylylene iodide, 440 Orthoxylylene sulphide, 440 Orthrin, 128 Orthylene, 439 Oxalamidobenzoic acid, 249 Oxalanthranilic acid, 244 Oxides of benzoyl, 166 Oxybenzonitrisulphuric acid, 199 Oxybenzuramic acid, 250 P. PARA-ACETOBENZYL ACETATE, 284 Para-acetoxybenzoic acid, 330 Para- aid ehy dome tahydroxybenzoic acid, 492 Para-aldehydosalicylic acid, 491 Para-amidohydroxymethylbenzoic acid, 446 Para-amidopara-azotoluene, 78 Para-azotoluene, 76 Parabenzidene sulphide, 138 Parabenzophosphenilic acid, 84 Parabromobenzaldehyde, 145 Parabromobenzoic acid, 224 Parabromobenzyl acetate, 102 Parabromobenzyl alcohol, 101 Parabromobenzyl bromide, 101 Parabromotoluene, 11 Paracarbamidobenzoic acid, 254 Paracarbonylorthophosphoric acid, 332 Paracarbonylphenylphosphoryl chlor- ide, 332 Parachlorobenzaldehyde, 144 Parachlorobenzoic acid, 9, 221 Parachlorobenzoic acid, 221 Parachlorobenzyl acetate, 101 Parachlorobenzyl alcohol, 99, 100 Parachloro-benzylamine, 118 Parachlorobenzyl bromide, 101 Parachlorobenzyl chloride, 100 Parachlorobenzyl ethyl ether, 100 Parachlorobenzyl hydrosulphide, 106 Parachlorometacresol methyl ether, 32 Parachlorometatoluene, 19 Parachlororthonitrotoluene, 1 9 Parachlorotoluene, 9 Paracresol, 23, 24, 25, 28 Paracresyl benzoate, 164 Paracresyl oxide, 28 Paradiamidobenzylamine, 120 Paradiazo-amidobenzoic acid, 263 Paradiazobenzoic acid nitrate, 262 Paradichloro-benzylamine, 118 Paradihydroxybenzaldehyde, 349 Paradihydroxybenzoic acid, 361 Paradi-iodo-benzylamine, 118 Paradinitrobenzylamine, 119 Para-ethoxybenzoic acid, 330 Parafluorhippuric acid, 227 Parafluorbenzoic acid, 226 Parahomometahydroxybenzoic acid, 425 Parahomosalicylaldehyde, 422 Parahomosalicylic acid, 423 Parahydrazobenzoic acid, 266 Parahydrazotoluene, 76 Parahydroxybenzalclehyde, 294 Parahydroxybenzaldoxime, 296 Parahydroxybenzamide, 333 Parahydroxybenzanilide, 333 Parahydroxybenzide, 332 Parahydroxybenzoates, 328 Parahydroxybenzoic acid, 108 Paradroxybenzoic acid, 326 ; substitu- tion products of, 334 Parahydroxybenzonitril, 334 Parahydroxybenzoylparahydroxy-ben- zoic acid, 331 Parahydroxybenzoyl sulphuric acid, 336 Parahydrox} benzuric acid, 333 Parahydroxybenzyl acetate, 284 Parahydroxy benzyl alcohol, 283 Parahydroxybenzyi methyl ether, 284 P.irahydroxybenzyl thio-carbimide, 284 Parahydroxymetatoluic acid, 427 Parahydroxymetatolualdehyde, 422 Parahydroxymethylbenzoic acid, 442 Parahydroxymcthylsalicylic acid, 490 Parahydroxyorthotolualdehyde, 422 Parahydroxyorthotoluic acid, 426 Parahydroxyphenylacetonitril, 284 Para-iodobenzaldehyde, 146 Para-iodobenzoic acid, 225 INDEX. 539 Para-iodobenzyl alcohol, 102 Para-iodo-benzylamine, 118 Para-iodobenzyl bromide, 102 Para-iodotoluene, 13 Paraleucaniline, 148 ParaleucotoluHine, 77 Paramethoxybenzoic acid, 329 Paramethoxybenzylamine, 284 Paramethoxybenzyl chloride, 284 Paramethyl-#-resorcylic acid, 360 Paramethoxysalicylaldehyde, 349 Paramidobenzaldehyde, 150 Paramidobenzaldoxime, 150 Paramidobenzamide, 253 Paramidobenzanitril, 253 Paramidobenzoic acid, 253 Paramidobenzoic acid hydrochloride, 253 Paramidobenzylphenylamine, 120 Paramidodiazobenzoic acid, 263 Paramidophthalide, 446 Paranitrobenzaldehyde, 148 Paranitrobenzaldoxiine, 149 Paranitrobenzamide, 232 Paranitrobenzidene bromide, 148 Paranitrobenzidene chloride, 148 Parauitrobenzoic acid, 232 Paranitrobenzonitril, 233 Paranitrobenzoyl chloride, 232 Paranitrobenzyl acetate, 104 Paranitrobenzyl alcohol, 99, 103 Paranitrobenzylamines, 119 Paranitrobeazyl bromide, 99, 103 Paranitrobenzyl chloride, 103 Paranitrobenzyl hydrosulphide, 106 Paranitrobenzyl iodide, 103 Paranitrobenzyl nitrate, ] 03 Paranitrobenzyl oxalate, 104 Paranitrobenzyl thiocyanate, 123 Paranitrobenzylyphenylamine, 119 Paranitro-diamidotriphenylmethane, 148 Paranitrohippuric acid, 233 Paranitrohydroxymethylbenzoic acid, 446 Paranitroinethylmetahydroxybenzalde- hyde, 294 Paranitrotoluene, 15, 16 Paranitro-orthotoluidine, 69 Paranitrophthalide, 445 Para-orsellinaldehyde, 427 Para-orsellinic acid, 436, 438 Paraph enoxybenzoic acid, 331 Paraphosphorsellinic acid, 436 Pararosaniline, 148 Pararosotoluidine, 77 Parasulphamidobenzoic acid, 273 Parasulphamido-orthotoluic acid, 416 Parathiocresol, 31 Paratolualdehyde, 413 Paratoluamide, 419 Paratoluylenediamine, 73 Paratoluic acid, 418 Paratoluidine, 63 Paratoluidine hydrobromide, 64 Paratoluidine hydrochloride, 64 Paratoluidine nitrate, 64 Paratoluidine phenate, 64 Paratoluidine sulphate, 64 Paratolunitril, 420 Paratoluylamido-acetic acid, 419 Paratoluyl chloride, 419 Paratolylbenzoyl thio-urea, 179 Paratolylboron chloride, 87 Paratolyl carbamide, 66 Paratolylhydrazine, 75 Paratolyl mustard oil, 67 Paratolylphosphenilic acid, 83 Paratolylphosphenylous acid, 83 Paratolylphosphine, 84 Paratolylphosphonium iodide, 84 Paratolylphosphorus dichloride, 83 Paratolylphosphorus oxychloride, 83 Paratolylphosphorus tetrachloride, 83 Paratolylsilicic acid, 87 Paratolylsilicon chloride, 87 Paratolylsilicon oxide, 87 Paratolylstibine, 86 Paratolylstibine bromide, 86 Paratolylstibine chloride, 86 Paratolylstibine hydroxide, 86 Paratolylstibine iodide, 86 Paratolylstibine oxide, 86 Paratolyl thiocarbamide, 67 Paratolyl thiocarbimides, 67 Paratolyl urethane, 67 Paratriamidobenzylamino, 120 Paratribromo-benzylamine, 118 Paratrichloro-benzylamine, 118 Paratri-iodo-benzylamine, 118 Paratrinitrobenzylamine, 119 Para-uramidobenzoic acid, 254 Paraxylyl alcohol, 412 Paraxylenol, 401 Paraxylene, 388, 389, 391 'Paraxylenesulphamide, 399 Paraxylenesulphonic acid, 399 Paraxylenesulphonic chloride, 399 Paraxylidine, 407 Paraxylidene tetrachloride, 448 Paraxyloquinol, 403 Paraxyloquinone, 404 Paraxylorcinol, 402 Paraxylylene acetate, 441 Paraxylylene alcohol, 441 Paraxylyl bromide, 412 Paraxylylene bromide, 441 Paraxylylene chloride, 441 Paraxylylene iodide, 441 Paraxylylene monobenzoate, 442 Paraxylylene mono-ethyl ether, 441 Paraxylyl ethyl ether, 412 Parazobenzoic acid, 266 Penta-acetyltannin, 374 Pentabromobenzoic acid, 225 Pentabromorcinol, 41 Pentabromotoluene, 12 Pentachlorobenzidene chloride, 8, 145 540 INDEX. Pentachlorobeuzyl alcohol, 100 Pentachlorobenzyl chloride, 101 Pentachlororcinol, 41 Pentachlorotoluene, 10 Pentachloroxyloue, 34 Persio, 44 Peruvin, 90 Petrol, 387 Phenol, 297 Phenylacetamide, 113 Phenylacetonitril, 113 Phenylaceturic acid, 186 Phenylamido-acetonitril, 113 Phenylbenzaldehydine, 141 Phenylbenzaldehydine hydrochloride, 141 Phenylbenzenylamidine, 203 Phenyl benzoate, 163 Phenylbenzoyl thio-urea, 179 Phenylchlorocarbylethyl ether, 100 Phenylchloroform, 195 Phenylene benzoate, 164 Phenylenebenzcnylaraidine, 205 Phenylenediethylacetone, 462 Phenylenenitrobenzenylamidine, 206 Phenylhydrazine nitro-opianic acid, 508 Phenylhydroxyacetic acid, 132 Phenylhydroxyacetonitril, 113, 131 Phenyl isophtiialate, 480 Phenylorthotolylamine, 59 Phenylmetabenzoglycocyamine, 252 Phenylraethyl, 89 Phenyl methylsalicylate, 308 Phenylnitro-ethylene, 135 Phenylorthotolyl thiocarbamide, 60 Phenyl paraphenoxy benzoate, 331 Phenyl parahydroxy benzoate, 330 Phenyl paratoluate, 419 Phenylparatoluidine, 65 Phenylparatolylamine, 65 Phenylphthalimide, 464 Phenyl phthalimidine 445 Phenyl propionic acid, 186 Phenylpropionitril, 122 Phenyl salicylate, 307 Phenyl terephthalate, 484 Phenylthiobenzamide, 178 Phenylthiobenzoate, 171 Phloroglucinol, 357 Phloroglucinolcarboxylic acid, 380, 381 Phlorone, 404 Phosphorsellinanilide, 433 Phosphorsellinic acid, 433 Phosphorus compounds of benzyl, 124 Phosphorus derivatives of toluene, 83 Phosphorus pentachloride and its action upon salicylic acid, 309 Phospho-salicylic acid, 309 Phthalalcohol, 439 Phthalaldehyde, 442, 447 Phthalaldehydic acid, 447 Phthalamic acid, 463 Phthalamil, 464 Phthalanilic acid, 464 Phthaldns, 458 Phthalic acid, 439, 451, 452 Phthalic acid, addition products of, 469 Phthalic acid, halogen substitution products of, 471 Phthalic acids, 450 Phthalic anhydride, 457 ; apparatus for the sublimation of, 459 o-Phthalicsulphaniic acid, 477 Phthalide, 442, 458 Phthalide-anil, 445 Phthalidehydrazide, 445 Phthalimide, 463 Phthalimide oxime, 469 Phthalimidine, 444 Phthalinic acid, 464 Phthalylacetic acid, 458 Phthalyl chloride, 458 Phthalyldiamide, 466 Plithalylhydroxylamine, 466, 468 Phthalyloxide, 457 Phthalyl sulphide, 462 Picranyl, 129 Picroerythrin, 429, 431, 434 Picrorocellin, 436 Piperonal, 347 Piperonic acid, 355 Piperonyl alcohol, 347 Polysalicylnitril, 313 Pomacese, 131 Populin, 282, 317 Potassium benzidene sulphite, 137 Potassium benzoate, 160 Potassium benzylsulphonate, 108 Potassium chlorobenzylsulphonate, 108 Potassium cyauate, 518 Potassium dibenzhydroxamate, 210 Potassium dinitroparacresate, 31 Potassium dinitrosalicylate, 317 Potassium gallate, 368 Potassium hemipiiiimide, 513 Potassium hippurate, 189 hydroxyphthala: Potassium isophthalate, 479 Potassium hydroxyphthalamate, 467 Potassium opianate, 504 Potassium parahydroxybcnzoate, 328 Potassium phthalimide, 463 Potassium piperonate, 356 Potassium salicylaldehyde, 287 Potassium salicylate, 302 Potassium thiobenzoate, 170 Potassium o-toluquinonoximate, 51 Potassium tribenzarsenate, 278 Proin, 128 Propenyl salicylate, 306 Propyl benzoate, 162 Propylene, 24 Propylene benzoate, 163 Propyl salicylate, 306 Propyl terephthalate, 484 Protocatechuic acid, 350, 357 INDEX. 541 Protocatechuicaldehyde, 343 Protomtrobenzoine, 13 Pseudoery tin-in, 428 Pseudotoiuidine, 55 Pyrogallocarboxylates, 379 Pyrogallolcarboxylic acid, 378, 381 Q. QTJERCIMERIC acid, 509 Quinates, the, 384 Quinic acid, 186, 381 Quinoldicaiboxylic acid, 515, 518 Quinonedihydrodicarboxylic acid, 518 Quinonoximo benzoate, 165 R. RESORCINOLPICARBOXYLIC acid, 515 0-Resorcylaldehyde, 348 a-Resorcylic acid, 358 /3-Resorcylic acid, 359, 437 7-Resorcylic acid, 360 Retinaphtha, 3 Ribbon Litmus, 46 S. SACCHARIN, 269 Safranine, 80 Salicin, 281 Salicyl, 285 Salicyl alcohol, 279 Salicylaldehyde, 285 ; properties, 286 Salicylaldehyde, substitution products of, 292* Salicylaldoxime, 290 Salicylamide, 312 Salicylates, 301 Salicyl chloraldide, 308 Salicyl chloride, 310 Salicyl hydride, 285 Salicylhydroxyacetic acid, 309 Salicylic acid, 108, 157, 297 Salicylic acid, ethereal salts of, 306 Salicylic acid, substitution products of, 313 Salicylic ethers, 306 Salicylic ethers, ethereal salts of, 307 Salicylide, 308 Salicyl monochlorophosphate, 309 Salicylnitril, 313 Salicyl parazobenzenesul phonic acid, 319 Salicylsulphuric acid, 319 Salicyluric acid, 312 Saligesion, 279 Saliretin, 280 Salireton, 280 Salol, 307 Salts and ethers of benzoic acid, 160 Selenium compounds of benzyl, 109 Silicon compounds of benzyl, 127 Silicon paratolyl, 87 Silicon tetrabenzyl, 127 Silicotetrabenzylmethane, 127 Silver benzarsenate, 277 Silver benzarsenite, 278 Silver benzoate, 161 Silver benzophosphinatc, 276 Silver hemipinimide, 513 Silver hippurate, 190 Silver isophthalate, 479 Silver metasulphobenzoate, 270 Silver methylnoropianate, 503 Silver opianite, 504 Silver orthohydroxymethylbenzoate, 442 Silver parahydroxybenzoate, 328 Silver phthalate, 457 Silver phthalimide, 463 Silver piperonate, 356 Silver quinate, 384 Silver salicylate, 304 Silver terephthalate, 484 Sinalbin, 377 Sinapic acid, 376 Sinapin, 375 Sinapin thiocj T anate, 375 Sodium arsenetribenzoate, 278 Sodium benzidene sulphite, 137 Sodium benzoate, 160 Sodium gallate, 368 Sodium hippurate, 189 Sodium metanitrobenzoate, 231 Sodium metaxylenesulphonate, 398 Sodium orthoxylenesulphonate, 398 Sodium parahydroxybenzoate, 328 Sodium paraxylenesulphonate, 399 Sodium phenylenecarbonate, 299 Sodium quinate, 384 Sodium salicylate, 302 Sodium tetrahydroxyterephthalate, 520 Sodium a-toluquinonoxirnate, 51 Spirasic acid, 285 Spiroyl hydride, 285 Spiroylous acid, 285 Spiroyl wasserstoflsaure, 285 Strontium hippurate, 189 Substitution products of benzyl alcohol and its derivatives, 98 Substitution products of anisic acid, 336 Substitution products of benzidene compounds, 143 Substitution products of benzylamines, 118 Substitution products of isophthalic acid, 481 Substitution products of metahydroxy- benzoic acid, 323 Substitution products of parahydroxy- benzoic acid, 334 Substitution products of salicyl-alde- hyde, 292 542 INDEX. Substitution products of salicylic acid, 313 Substitution products of terephthalic acid, 488 Substitution products of the xylenes, 392 Sulphamicphthalic anhydride, 477 Sulphamidobenzonitril, 272 o-Sulpharnidouietatoluic acid, 418 v-Sulphamidometatoluic acid, 418 Sulphamidoparatoluic acid, 421 Sulphinidephthalic acid, 477 Sulphobenzoic acid, 20 Sulphobenzoyl hydride, 138 o-Sulpho-isophthalic acid, 482 s-Sulpho-isophthalic acid, 482 Sulphometahydroxybenzoic acid, 325 Sulphoparahydroxybenzoic acid, 335 Sulphoparatoluic acid, 421 o-Sulphophthalic acid, 476 v-Sulphophthalic acid, 477 Sulphophthalic acids, 476 Sulphorthot,oluic acid, 415 Sulphosalicylic acid, 318 Sulphoterephthalicacid, 490 Sulphur compounds of benzoyl, 170 Sulphur compounds of benzyl, 105 Symmetric a-diamido-azotoluene, 79 Symmetric /3-diamido-azotoluene, 79 Symmetric dibenzyl thiocarlamide, 124 Symmetric dibenzyl urea, 123 Symmetric dinitroparatoluidine, 71 Symmetric diphenylbenzenylarnidine, 203 Symmetric ethylbenzoyl urea, 178 Symmetric metadihydroxybenzoic acid, 358 T. TANNATES, 374 Tannic acid, 365, 371 Tannin, 371 ; properties, 373 Tartrophthalic acid, 470 Taurylic acid, 23 Telerythrin, 428 Terephthalaldehyde, 447 Terephthalaldehydic acid, 449 Terephthalamic acid, 485 Terephthalamide, 485 Terephthalic acid, 451, 483 ; addition products of, 486 ; substitution pro- ducts of, 488 Tereplithalonitril, 435 Terephthalyl chloride, 485 Tetrabromolecanoric acid, 434 Tetrabromometaxylene, 394 Tetrabromomethane, 12 Tetrabromoparaxylene, 395 Tetrabiomophthalic acid, 473 Tetrabromorthoxylene, 394 Tetrabromoluenes, 12 Tetracetylhelicin, 289 Tetrachlorobenzal chloride, 8 Tetrachlorobenzidene chloiide, 145 Tetrachlorobenzoic acid, 222 Tetrachlorobenzyl alcohol, 100 Tetrachlorobenzyl chloride, 101 Tetrachlorobenzenyl trichloride, 196 Tetrachlorocreocone, 36 Tetrachloroguaiacone, 36 Tetrachlorophthalic acid, 472 Tetrachlororthoxylene, 393 Tetrachlorotoluene, 10 Tetrachlorotoluquinone, 50 Tetrahydro-isophthalic acid, 481, 487 Tetrabydrometaxylene, 391 Tetrahydrophthalic acid, 470 Tetrahydroterephthalic acid, 486 Tetrahydrotoluene, 6 Tetrahydroxyhexhydrobenzoic acid, 383 Tctrahydroxyphthalic acids, 519 Tetrahydroxy terephthalic acid, 519 Tetrasalicyli'de, 308 Thallium metahydroxybenzoate, 321 Thallium salicylate, 303 Thiobenzaldine, 140 Thiobenzamide, 177 Thiobenzanilide, 178 Thiobenzoic acid, 170 Thiobenzoic anhydride, 171 Thiocresolo, 31 Thiometahydroxybenzoicacid, 325 Thio-opianic acid, 507 ThiophthalicaTdiydride, 462 Thiotoluidine, 72 Tolualdehydes, the, 413 Tolubenzaldehydine, 142 Toluene 3 et sc.q. , properties, 5 Toluene, amido-derivatives of, 54 Toluene, antimony derivatives of, 86 Toluene, arsenic derivatives of, 84 Toluene, azo-derivatives of, 75 Toluene, boron and silicon derivatives of, 87 Toluene, diazo-derivatives of, 74 Toluenedisulphoriic acids, 22 o-Tolneiiedisulphonic acid, 22 j8-Toluencdisul[>honic acid, 22 7-Tolueiiedisulphonic acid, 22 Toluene group, 3 Toluene, hydrazine derivatives of, 75 Toluene, mercury derivatives of, 87 Toluene, phosphorus derivatives of, 83 Toluenemetasulphonamide, 21 Tolunemetasulphonic acid, 21 Toluenemetasulphonic chloride, 21 Toluenemonosulphonic acids, 20 Tolucneparasulphonamide, 21 Tolueneparasul phonic acid, 21 Tolueneparasulphonic chloride, 21 Toluene-orthrsulphonic acid, 21 7-Toluenesulplionic acid, 22 Toluenesulphonic acids, 20 Tolucnetrisul phonic acids, 22 Toluenyl alcohol, 412 Toluhydroquinonc, 48 INDEX. 543 Toluic acids, 414 Toluidine, 4, 14, 111 Toluidinedisulphonic acid, 22 Toluidines, 54 Tolui dines, halogen substitution pro- ducts of the, 67 Toluol, 386 Toluquinhydrone, 50 Toluquinol, 48 Toluquinol dimethyl ether, 48 Toluquinol monomethyl ether, 48 Toluquinone, 49 o-Toluquinone chlorimide, 51 Toluquinone, substitution products, 50 a-Toluquinonoxime, 50 j8-Toluquinonoxime, 51 )8-Toluquinonoxime acetate, 51 Toluquinonoxime compounds, 50 Toluric acid, 419 Tolusafranine, 80 Tolusafranine hydrochloride, 81 Tolusafranine nitrate, 81 Tolusafranine picrate, 81 Toluylene-blue, 82 Toluylene-red, 82 Toluylene-violet, 82 Tolyl, 410 Tolylarsenic acid, 85 Tolylboric acid, 87 Tolylenediamines, 72 Triacetoxymetaxylene, 403 Triacetylgallic acid, 370 Triamido-azobenzoic acid, 264 Tri-amidobenzoic acid, 260 Triamidometaxylene, 409 Tribenzhydroxylamine, 207 Tribenzhydroxylamine, 211 o-Tribenzhydroxylamine, 212 j8-Tribenzhy<]roxylamine, 212 y-Tribenzhydroxylamine, 212 Tribenzidenediamine, 139 Tribenzo-arsenic acid, 85 Tribenzoylphloro-glucinol, 164 Tribenzylamine, 110, 115 Tribenzylamine, hydrochloride, 116 Tribenzylamine nitrate, 116 Tribenzylamine sulphate, 116 Tribenzylarsine, 126 Tribenzylarsine dichloride, 125 Tribenzylarsine oxide, 126 Tribenzarsenic acid, 278 Tribenzarsenious acid, 278 Tribenzy^arsonium iodide, 126 Tribromobenzoic acids, 225 a-Tribromometaxylenol, 401 s-Tribromometaxylenol, 401 v-Tribromometaxylenol, 401 Tribromoparaxylenol, 401 Tribromnphthalic acid, 473 Tribroinorcinol, 41 a-Tribromorthoxylenol, 400 Tribromotoluencs, 12 Tribromotoluqmnone, 50 a-Tilchlorobenzaldehyde, 145 18-Trichlorobenzaldehyde, 145 o-Trichlorobenzidene chloride, 145 /3-Trichlorobenzidene chloride, 145 a-Trichlorobenzoic acid, 222 -Trichlorobenzoic acid, 222 7-Trichlorobenzoic acid, 222 Trichlorobenzoic acids, 222 Trichlorobenzyl alcohol, 100 Trichlorobenzyl chloride, 101 Trichlorobenzenyl trichloride, 196 Trichlorophthalic acid, 472 Trichlororcinol, 41 Trichlororthoxylene, 393 o-Trichlorotoluene, 10 /3-Trichlorotoluene, 10 Trichlorotoluquinone, 50 Trie thy 1 benzylammonium iodide, 116 Triethylgallic acid, 369 Triethylhydroxyquinolcarboxylic acid, 380 Triethylpyrogallolcarboxylic acid, 379 Trihydroxybenzoic acids, 363 Trihvdroxybenzcic acids, constitution of,' 381 Trihydroxymetaxylene, 403 Trihydroxyphthalic acids, 519 Trihydroxytoluenes, 53 Trihydroxy-xylenes, 403 Tri-iodorcinol, 41 Tri-iodosalicylic acid, 315 Triketohexhydrobenzene, 518 Trimethylamido-amsic acid, 338 Trimethylamidobenzoic acid, 248 Trimethylamidosalicylic acid, 318 Trimethyl anise-betaine, 338 Trimethylene benzoate, 163 Trimethyl ether, 478 Trimethylhydroxyquinolcarboxylic acid, 380 Trimethylorthotolylammonium iodide, 59 Trimethylparatolylammonium iodide, 65 Trimethyl phosphobenzobetaine, 276 Triuitro-amarme, 148 Trinitrobenzene, symmetric, 18 Trinitrobcnzoic acid, 235 Trinitrohydrobenzamide, 148 Trinitrometahydroxybenzoic acid, 324 s-Trinitrohydroxytoluic acid, 425 Trinitrometacresol, 28 Trinitrometaxylene, 396 Trinitroparaxylene, 398 Trinitrophenyl benzoate, 164 Trinitro-orcinol, 42 Trinitro-orthoxylene, 396 o-Trinitrotoluene, 17 j8-Trinitrotoluene, 18 7- Trinitrotoluene, 18 Trinitrotoluenes, 17 Triopianide, 505 Triparatolylarsine, 85 Triphenylbenzylphosphonium chloride, 125 544 INDEX. Trisul phometab ydroxy benzoic 326 Trixylylamine, 413 Tuluol, 4 U. UMBELLIO ACID, 329 Uramidobenzoic acid, 249, 252 TJramidobenzoyl, 242 Uronitrotoluic acid, 104 V. VANILLA, 345 Vanillic acid, 352 Vanillic acid glucoside, 352 Vanillin, 344 Vanillin glucoside, 347 Vanillyl alcohol, 346 Veratric acid, 354 Victoria yellow, 31 acid, Xylenes, amido-derivatives of the, 405 Xylencs, diamines and triamines of the, 409 Xylenes, halogen substitution products of the, 392 Xylenes, nitro substitution products of the, 395 Xylenes, substitution products of the, 392 Xylenesulphonic acids, 398 Xylenols, 399 Xylidenyl pentachloride, 447 Xylidines, 405 Xylol, 386 Xyloquinones, the, 404 Xyloylamines, 412 Xylyl, 410 Xylyl alcohols, 411 Xylyl bromides, 412 Xylyl chlorides, 412 Xylyl compounds, 410 Xylylene alcohols, 439 Xylylidenediamine, 448 XANTHAROCELLIN, 436 Xylene group, 386 Xylenes, 390 Z. ZINC HIPPURATE, 189 Zinc phthalate, 458 THE END. 3-3 L'XIVKRSITY OF CALIFORNIA LIBRAE? THIS BOOK IS DUE ON THE LAST DATE STAMPED BELOW 30m-6,'14 UNIVERSITY OF CALIFORNIA LIBRARY