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.
<y-Nitro-OTthocresol (1:4: 2) is formed together with the a-com-
pound when orthocresol is nitrated at as low a temperature as
possible. On distillation with steam it remains behind. It is
only very slightly soluble in water, readily in alcohol and ben-
zene, and crystallizes in white needles united to form bushy
aggregates, or in small, hexagonal tablets, being, therefore,
dimorphous like paranitrophenol. It melts at 82 85, and
forms a potassium salt, crystallizing in small brass-yellow
plates. On reduction it is converted into y-am'ido-orthophenol,
crystallizing in tablets which have a silvery lustre and melt at
175. When oxidized in an acid solution, it is converted into
toluquinone. Hirsch has been unable to obtain the liquid nitro-
cresol mentioned above. 4
Dinitro-orthocresol, C 6 H 2 (CH 3 ) (NO 2 ) 2 OH (1 : 3 : 5 : 2), was
first obtained from orthotoluidine, nitro-orthotoluidine (NH 2 :
NO 2 = 2 : 5), and orthotoluidinesulphonic acid (NH 2 : S0 3 H =2:3),
by converting them into diazo-compounds and heating these with
dilute nitric acid. 5 It is also formed by the further nitration of
Ladenburg, Per. Deutsch. Chem. Gfes. ix. 1524; x. 1124.
Hofmann and Miller, ibid. xiv. 467.
Neville and Winther, ibid. xv. 2978.
Hirsch, ibid, xviii. 1511.
Neville and Winther, ibid. xiii. 1496 ; Nblting, and Salis, ibid. xiv. 987.
METACRESOL. 27
a- and <y-nitro-orthocresol (Hirsch), and of orthocresyl ether.'
It crystallizes from alcohol in long, yellow prisms, and from
petroleum-spirit in broad, golden-yellow needles, which have a
blue surface-lustre and melt at 86.
On the reduction of its ethyl ether the diamido- ether is
obtained, and this compound forms a chrysoidine with diazo-
benzene (Part III. p. 301), thus affording a further proof that the
nitroxyl groups in dinitrocresol have the meta-relation to each
other.
2032 Metacresol. In order to prepare this compound, 100
grammes of thymol are heated for ten or twelve hours with 35
grammes of phosphorus pentoxide, the propylene which is
evolved being passed into bromine in order to obtain its bromide
as a by-product. The syrupy mass is brought into 115 120
grammes of fused caustic potash, and the mixture kept in a
state of fusion and well agitated for five or ten minutes. It is
then dissolved in water and extracted with ether in order to
remove cresyl phosphate and other substances ; the residue is
then decomposed with hydrochloric acid, the metacresol taken
up with ether, the latter distilled off, and the product purified
by distillation in a current of carbon dioxide (Schotten and
Tiemann).
It is a liquid which smells like phenol, boils at 201 and does
not solidify in a freezing mixture ; if, however, a crystal of phenol
be thrown into the cooled liquid it solidifies immediately, form-
ing crystals resembling those of phenol and melting at 3 4. 2
Its aqueous solution is coloured violet to blue by ferric chloride ;
by the action of potassium chlorate and hydrochloric acid, it is
converted into dichlorotoluquinone (South worth).
Metacresyl oxide, (CH 3 .C 6 H 4 ) 2 O, is formed, together with pro-
pylene and other products by the dry distillation of aluminium
thymol, (C 3 H 7 (CH 3 )C 6 H 3 O) 6 A1<,, and is a liquid boiling at
284 288 . 3
Bromometacresol, C 6 H 2 Br(CH 3 )OH (1 : 3 : 5), has been pre-
pared from the corresponding bromotoluidine, and crystallizes
from hot water in white needles melting at 56 57. 4
Nitrometacresol, C 6 H 3 (CH 3 )(N0 2 )OH (1:3: 5), is prepared
from symmetric dinitrotoluene ; it crystallizes from hot water in
light yellow, lustrous prisms, containing one molecule of water
1 Stadel, Ann. Chem. Pharm. ccxvii. 158.
2 Stadel, Ber. Deutsch. Chem. Ges. xviii. 3443.
3 Gladstone and Tribe, Journ. Chem. Soc. 1882, i. 5.
* Neville and Winther, Ber. Deutsch. Chem. Ges. xv. 2991.
28 AROMATIC COMPOUNDS.
of crystallization. It is deposited from solution in benzene in
anhydrous crystals melting at 90 91. On reduction it yields
amidometacresol, the hydrochloride of which is readily soluble. 1
Trinitrometacresol, C 6 H(NO 2 ) 3 (CH 3 )OH (N0 2 : N0 2 : NO 2 = 2 :
4:6), was obtained by Duclos from crude cresol ; N biting and Salis
have prepared it from metacresol, which is readily converted into
the trinitro-compound, while its isomerides yield the dinitrocresols
as final products. In order to prepare it, coal-tar cresol is
dissolved in 3 parts of concentrated sulphuric acid, and allowed
to stand in a warm place until cresol no longer separates out on
the addition of water. Crude nitric acid is then gradually
added to the aqueous solution, which is subsequently evaporated,
the residue being extracted with a little water to remove picric
and oxalic acids, and repeatedly re-crystallized from alcohol. 2
Liebermann and van Dorp obtained it by heating nitrococ-
cussic acid, 3 C 6 (N0 2 ) 3 (CH 3 )(C0 2 H)OH, and Emmerling and
Oppenheim by the action of nitric acid on hydroxyuvitic acid,
C 6 H 2 (CH 3 )(C0 2 H) OH. 4 Trinitrometacresol is slightly soluble
in cold, somewhat more readily in hot water, and crystallizes in
long, yellow needles melting at 105 106.
When its ethyl ether is heated with alcoholic ammonia, no
nitrous acid is removed (Nolting and Salis), which proves that it
contains no nitroxyl groups in the ortho-relation (Part III.
p. 63), and, therefore, that trinitrometacresol has the following
constitution :
CH 3
NO/NNO,
H\/OH
N0 2
2033 Paracresol is most readily obtained from paratoluidine, as
orthocresol is from orthotoluidine ; it crystallizes in prisms melting
at 36, and boils at 198 ; its aqueous solution is coloured blue
by ferric chloride. It differs from its isomerides in not yielding
a chlorinated toluquinone by the action of potassium chlorate and
hydrochloric acid.
Paracresyl oxide (CH 3 .C 6 H 4 ) 2 0, has been prepared by
Gladstone and Tribe in the same mariner as the ortho-compound,
1 Bcr. Deutsch. Chtm. Ges. xv. 2978.
2 Beilstcin and Kellner, Ann. Chem. Pharm. cxxviii. 165.
8 Ibid, clxiii. 101.
4 Ber. Deutsch. Chem. Ges. ix. 1094.
PARACRESOL. 2 9
and is also formed by heating paracresol to 300 with zinc chloride.
It crystallizes from alcohol in small lustrous plates, and from
petroleum spirit in needles which have a silky lustre, and melt
at 165, but readily volatilize at 100 . 1
Chloroparacresol, C 6 H 3 (CH 3 )C1(OH) (1:3: 4), is formed by
the action of dry chlorine on anhydrous sodium paracresate. It
is a colourless liquid which boils at 195 196, and has a peculiar,
unpleasant, persistent odour. Phosphorus pentachloride converts
it into a dichlorotoluene, which yields on oxidation the ortho-
dichlorobenzoic acid melting at 200 . 2
Dichloroparacresol, C 6 H 2 (CH 3 )C1 2 .OH, is formed by the
action of chlorine on boiling paracresol ; it crystallizes from
alcohol in monoclinic needles, and from a hot, concentrated
solution in petroleum-ether in long needles melting at 39 ; on
the gradual evaporation of a dilute solution, it is obtained in
transparent prisms with a melting point of 42 ; these, however,
soon fall to pieces, and the product then melts at 39. On
oxidation the dichlorobenzoic acid melting at 156 is formed
(Glaus and Riemann).
Bromoparacresol, C 6 H 3 (CH 3 )Br(OH) (1:3: 4), is obtained
by the action of bromine on potassium paracresate. It is a
liquid which does not solidify in a freezing mixture, boils at
213 214, and has a less unpleasant smell than the chlorine
compound (Schall and Dralle).
Bromoparacresol (1 : 2 : 4) may be readily obtained by the
action of bromine on a solution of paracresol in chloroform ; it
crystallizes in needles, melting at 17 18, and boils at
218 220. On fusion with caustic potash it is converted into
lutorcinol, C 6 H 3 (CH S ) (OH) 2 . 3
Dibromoparacresol, C 6 H 2 (CH 3 )Br 2 (OH), is also formed when
potassium paracresate is treated with bromine. It crystallizes
from alcohol in prisms which are isomorphous with dichloropara-
cresol and melt at 49 (Schall and Dralle).
lodoparacresol, C 6 H 3 (CH 3 )I(OH) (1:3: 4), is an oily liquid,
and is obtained by the action of iodine on potassium paracresate ;
on fusion with potash it yields protocatechuic acid, C 6 H 3 (OH) 2
C0 2 H, and catechol.
Di-iodoparacresol, C 6 H 2 (CH 3 )I 2 (OH), is formed in the pre-
paration of the mono-compound, and crystallizes in small tablets
melting at 61'5 (Schall and Dralle).
1 Buch, Ser. Deutsch. Chem. Ges. xvii. 2638.
3 Schall and Dralle, ibid. xvii. 2528. 3 Vogt and Henninger, ibid. xv. 1081.
30 AROMATIC COMPOUNDS.
a-Nitroparacrcsol, C 6 H 3 (CH 3 )(N0 2 )OH (1:3: 4), is obtained
by boiling nitracetparatoluide with caustic soda, 1 and by the
nitration of paracresol. 2 It is slightly soluble in water, readily
in alcohol, and crystallizes in flat, yellow needles, which melt at
33*5, and are volatile in steam.
a-Amidoparacresol, C 6 H 3 (CH 3 )(NH 2 )OH (1:3:4) is formed
by the reduction of the nitro-compound with tin and hydro-
chloric acid ; it crystallizes from ether in monoclinic prisms, and
when heated with formic acid yields methenylamidoparacresol,
melting at 45 (Hofmann and Miller).
/3-Nitroparacresol, (CH 3 : NO 2 : OH = 1 : 2 : 4), is prepared from
ordinary dinitrotoluene by reducing it with ammonium sulphide
to nitrotoluidine and then replacing the amido-group by hy-
droxyl. It forms long yellow crystals which melt at 78 and are
readily soluble in hot water and alcohol. 3
(3-Amidoparacresol, (CH 3 : NH 2 : OH =1:2:4), is obtained
by the reduction of the preceding compound, and crystallizes
from hot water in small plates melting at 143 144 . 4
y-Amidoparacresol, (CH 3 : NH 2 : OH = 1 : 4 : 2). The hydro-
chloride of this base is obtained by converting the monacetyl
compound of the corresponding diamidotoluene into acetamido-
cresol, C 6 H 3 (CH 3 )OH(NH.C 2 H 3 0) and boiling this with hydro-
chloric acid. It crystallizes in small glistening plates, and on
treatment with potassium bicarbonate yields the free base,
which forms small lustrous plates or needles, melting at
159 161 (Wallach).
The constitution of the substituted paracresols follows from
their conversion into dihydroxytoluenes.
Dinitroparacresol, C 6 H 2 (CH 3 )(NO 2 ) 2 OH(1 :3 :5 :4), has been
prepared from the corresponding dinitrotoluidine and by the
nitration of cresolsulphonic acid. 5 It is also obtained by warming
the diazo-compound prepared from paratoluidinesulphonic acid
with nitric acid (Neville and Winther), and by the nitration of
paracresol ethyl ether; it crystallizes from dilute alcohol in
yellow needles melting at 85. On the reduction of its ethyl
compound, diamidoparacresyl ether, C 6 H 2 (CH 3 )(NH 2 ) 2 OC 2 H 6 , is
1 Wagner, Ber. Deutsch. Chem. Ges. vii. 537 ; Neville and Winther, ibid. xv.
2893.
2 Armstrong and Thorpe, Jahresb. Chem. 1876, 452 ; Hofmann and Miller,
loc. cit.
3 Knecht, Ann. Chem. Pharm. ccxv. 83 ; Ber. Deutsch. Chem. Ges. xv. 298.
Neville and Winther, ibid. xv. 2980.
4 Wallach, ibid. xv. 2831.
5 Armstrong and Field, Ber. Deutsch. Chem. Ges. vi. 974.
DIHYDROXYTOLUENES. 31
obtained ; this compound forms a chrysoidine with diazobenzene
chloride, proving that the nitroxyls of the dinitrocresol are in
the meta-relation to each other.
Potassium dinitroparacresate, C 6 H 2 (CH 3 )(NO 2 ) 2 OK, crystallizes
in red needles and forms the "golden yellow," which was
exhibited as a new dye in the Belgian section of the Vienna
Exhibition in 1873. 1
It is also, together with the potassium salt of dinitro-ortho-
cresol, contained in " safronsurrogate," which is used for colouring
milk, butter, and cheese. 2
Victoria yellow or aniline orange, which formerly came into
the market as a red powder, is the salt of a third dinitrocresol,
the constitution of which is unknown. It crystallizes from hot
water in yellowish needles, melting at 109 110 . 3
Thiocresols, C 6 H 4 (CH 3 )SH, are obtained by the reduction of
the corresponding sulphonic chlorides.
Melting- Boiling-
point, point.
Orthothiocresol 4 small, delicate plates . 15 188
Metathiocresol 5 liquid 188
Parathiocresol 6 large plates 43 189
DIHYDROXYTOLUENES AND ALLIED BODIES.
HOMOCATECHOL, OR HOMOPYROCATECHIN, C 6 H 3 (CH 3 )(OH) 2
(1:3:4).
2034 Hugo Miiller obtained this compound by heating its
monomethyl ether, creosol, with hydriodic acid : 7
6
It is also formed by fusing creosol with caustic potash, 8 by
boiling the diazo-compound of a-amidocresol with water (Neville
1 Piccard, Ber. Deutsch. Chem. Ges. viii. 685
2 Wichelhaus, ibid. vii. 770.
8 Martius and Wichelhaus, ibid. ii. 206.
4 Hiibner and Post, Ann. Chcm. Pharm. clxix. 30.
5 KM- Marcker, ibid, cxxxvi. 79.
7 Chem. News, x. 269.
8 Tiemann and Koppe, Ber. Deutsch. Chem. Ges. xiv. 2025.
AROMATIC COMPOUNDS.
and Whither), and by submitting a-homoprotocatechuic acid,
C 6 H 2 (CH 3 )(OH) 2 CO 2 H, to dry distillation.*
Homocatechol is a syrup which readily dissolves in water,
alcohol, ether, and benzene, and can be distilled without
decomposition. It reduces silver salts and Fehling's solution
in the cold, and gives a green colouration with ferric chloride,
which is converted into a reddish violet by the addition of a
little ammonia or carbonate of soda.
Homocatechol monomethyl ether or Creosol, C 6 H 3 (CH 3 )(OCH 3 )
OH(1 : 3 : 4), occurs in beechwood-tar-creosote and in the pro-
ducts of distillation of guaiacum resin. 2 In order to prepare
it, the portion of creosote boiling at about 220 is dissolved in
ether and treated with very concentrated alcoholic potash ; potas-
sium creosate, C 8 H 9 K0 2 -f- 2H 2 O, separates out in needles and is
then decomposed by dilute sulphuric acid. It may also be
prepared by heating a-homovanillic acid, C 6 H 3 (OH)(OCH 3 )CH 2 .
CO 2 H, with lime (Tiemann and Nagai). It is a strongly re-
fractive liquid boiling at 220, and possesses a feeble odour which
resembles that of vanilla and is very pleasant when the vapour
is dilute. It produces a metallic mirror when warmed with a
solution of a silver salt, and its alcoholic solution is coloured
emerald-green by ferric chloride. Phosphorus chloride converts
it into parachlorometacresol methyl ether, C 6 H 3 C1(CH 3 )OCH 3 ,
(CH 3 : OCH 3 : Cl=l : 3 : 4), a liquid boiling at 185 . 3
Homocatechol dimethyl ether, C 6 H 3 (CH 3 )(OCH 3 ) 2 , also occurs in
creosote, and is obtained pure by boiling potassium creosate with
methyl iodide and wood-spirit. It is a liquid which boils at
214 215 and possesses the characteristic smell of the indif-
ferent oils which are obtained from crude wood-tar. It is
insoluble in water and alkalis, and is not coloured by ferric
chloride. 4
2035 Creosote was discovered by Reichenbach in the year
1832, both in the tar and the pyroligneous acid obtained by the
distillation of beech-wood. 5 He describes it as a colourless,
strongly refractive liquid, which begins to boil at 203 and
possesses an unpleasant penetrating odour, at the same time
resembling that of smoked meat, and a burning taste. He
investigated its properties very carefully, and found that it
1 Tiemann and Nagai, Ber. Deutsch. Chem. Ges. x. 210.
2 Hlasiwetz, Ann. Chem. Pharm. cvi. 339.
3 Biechele, ibid. cli. 115.
4 Tiemann and Mendelsohn, Ber. Deutsch. Chem. Ges. viii. 1136.
8 Schweiger's N. Jahrb. Chem. Phys. vi. 301, 345 ; vii. 1, 57 ; viii. 57, 399.
CREOSOTE. 33
coagulates albumin, and that fresh meat which has been soaked
in creosote for half an hour to an hour can be dried without
undergoing putrefaction. Such meat is very tasty, and
Reichenbach therefore concluded that creosote is the antiseptic
principle contained in smoke. He derived its name from this
power of preserving meat, its most peculiar and most striking pro-
perty, one too which had been known from the earliest times ; he
remarks, " The Greek word /cpeas, meat, has a genitive /cpeaTos,
or Kpea&s, contracted to /cpeo)? ; <7<wf&> 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.
<y- Diamidotoluene hydrochloride, C 7 H 10 N 2 (HC1) 2 , crystallizes
from hot hydrochloric acid in small plates with a nacreous
lustre.
^-Diamidotoluene sulphate, C 7 H 10 N 2 .S0 4 H 2 , is slightly soluble
in cold, more readily in hot water, and is precipitated from this
solution by alcohol as a white powder.
1 Beilstein and Kuhlberg, Ann. Chem. Pharm. clviii. 351.
2 Nietzki, Ber. Deutsch. Chem. Ocs. x. 832, 1158.
74 AROMATIC COMPOUNDS.
As already mentioned, solutions of its salts to which a little
orthotoluidine has been added are coloured a deep green by
ferric chloride. Nietzki at first attributed the colouration to
paratoluylene-diamine alone, but he afterwards found that the
colour was only produced in samples prepared from ortho-amido-
azotoluene, which had not been completely freed from ortho-
toluidine ; the pure compound only gives the reaction after the
addition of the latter base.
B-Diamidotoluene (1 : 2 : 3) is formed by the reduction of /3-
orthonitro-orthotoluidine. It forms red crystals, which are
readily taken up by the usual solvents, smell like acetamide,
melt at 61 P 62 and boil at 255 . 1
DIAZO-DERIVATIVES OF TOLUENE.
2054. Only the derivatives of paratoluidine have hitherto
been prepared pure ; they are obtained by the methods used in
the preparation of the corresponding benzene derivatives. 2
The diazo-compounds of the two other toluidines have only
been obtained as intermediate products in the preparation of
derivatives ; many examples of this kind have already been
given.
Diazotoluene nitrate, CH 3 .C 6 H 4 N=nNO.N0 2 , crystallizes in
white needles.
Diazotoluene sulphate, CH 3 .C 6 H 4 N=N.O.SO 2 .OH, forms lus-
trous needles or prisms.
Diazo-amidotoluene, CH 3 .C 6 H 4 N=N.NH.C 6 H 4 .CH 3 , is pre-
pared by passing nitrogen trioxide into a solution of paratolu-
idine in a mixture of alcohol and ether. 3 It crystallizes in
yellow or reddish yellow needles or prisms, and gives a platini-
chloride (C 14 H 16 N 3 ) 2 PtCl 6 , which forms yellow tablets.
Diazobenzene-amidotoluene, C 6 H 5 N 2 .NH.C 6 H 4 .CH 3 , was ob-
tained by Griess as a product of the action of diazobenzene
nitrate on paratoluidine, 4 as well as of that of diazotoluene nitrate
on aniline. 5 It crystallizes in narrow, yellow plates. The
formation of the same compound by two different reactions
1 Lellmann and Wurthner, Anti. Chem. Pharm. ccxxviii. 243.
2 Griess, Jahresb. Cficm. 1866, 458.
3 Griess, Ann. Chem. Pharm. cxxi. 277
4 Ibid, cxxxvii. 60.
6 cr. Deutsch. Chem. Ges. vii. 1619.
AZOTOLUENES. 75
which should yield isomeric substances, is analogous to the case
of diazobromobenzene-amidobenzene, which has been already
discussed.
HYDRAZINE-DERIVATIVES OF TOLUENE.
2055 Paratolylhydrazine, CH 3 .C 6 H 4 .NH=NH 2 , is prepared
from paratoluidine just as is phenylhydrazine from aniline.
It crystallizes from ethereal solution in rhombic tablets, melts
at 61, boils with slight decomposition between 240 244, and
is slightly soluble in water, but readily in alcohol. 1
Diparatolylhydrazine, (CH 3 .C 6 H 4 ) 2 N=z:NH 2 , is formed by the
action of zinc-dust and acetic acid on diparatolylnitrosamine ;
it crystallizes from benzene in colourless plates melting at 171
172, and is a weak monacid base. Mercuric oxide converts it
into diparatolylamine without the formation of a tetrazone-com-
pound (Pt. III. p. 29). 2
AZO-DERIVATIVES OF TOLUENE.
2056 Azotoluenes, CH 3 .C 6 H 4 N="NC 6 H 4 .CH 3 , are formed by
reduction of the nitrotoluenes or oxidation of the toluidines, and
are converted into hydrazotoluenes, C 7 H 7 .NH NH.C 7 H 7 , by
further reduction.
Ortho-azotoluene is obtained by the action of zinc-dust and
alcoholic potash, or sodium amalgam and alcohol on orthonitro-
toluene, 3 as well as by the oxidation of orthotoluidine with
potassium permanganate, ammonia and oxalic acid being simul-
taneously formed. 4 It is volatile with steam and crystallizes from
ether in red prisms melting at 55. It is reduced to orthohydro-
azotoluene by the further action of sodium amalgam ; this forms
colourless crystals melting at 165, which decompose at a
higher temperature into orthotoluidine and ortho-azotoluene, and
are readily oxidized to the latter in the air.
1 E. Fischer, Bcr. Deutsch. Chem. Ges. ix. 890.
5 Lehne, ibid. xiii. 1546.
1 Petriew, Beilstein's Org. Chem. 976 ; Ber. Deutsch. Chem. Ges. vi. 557.
4 Hoogewerff and van Dorp, ibid. xi. 1203.
76 AROMATIC COMPOUNDS.
Meta-azotolucne is most readily formed by treating metanitro-
toluene with zinc-dust and alcoholic potash. 1 It crystallizes from
weak alcohol in orange-coloured rhombic prisms melting at 55.
When it is heated with alcoholic ammonium sulphide, the liquid
metahydrazotoluene is formed and rapidly re-oxidizes in the air.
Para-azotoluene may be best obtained by dissolving 1 part of
paranitrotoluene in 10 parts of alcohol and gradually adding 22
parts of 4 per cent, sodium amalgam together with a sufficient
quantity of acetic acid. 2 The oxidation of paratoluidine with
potassium permanganate affords a very poor yield of the azo-
compound, but better results may be obtained by oxidizing the
sulphate of the base with potassium ferricyanide (Barsilowsky).
It is also formed by the action of chromic acid on a solution of
paratoluidine in glacial acetic acid, 3 and by that of bleaching
. powder on the base dissolved in chloroform. 4
It is slightly soluble in alcohol, readily in ether and petroleum-
spirit, crystallizing from the latter in orange-yellow needles
which melt at 144. When it is heated to 100 with alcoholic
ammonia in a closed vessel, parahydrazotoluene is formed and
crystallizes in large needles or tablets which melt at 124 and
decompose into paratoluidine and parazotoluene when more
strongly heated. It rapidly becomes oxidized to the latter when
its alcoholic solution is exposed to the air (Melms).
Barsilowsky, by the oxidation of paratoluidine with potassium
ferricyanide, obtained parazotoluene and an isomeric substance, 5
which Perkin also obtained by the action of potassium dichromate
on a solution of toluidine sulphate. 6 It forms red, hexagonal
crystals and is a weak base ; Perkin was only able to prepare its
platinichloride, from the composition of which he concluded that
the compound was a triparatolylenediamine, C 21 H 21 N 3 , while
Barsilowsky found that it is reduced by alcoholic ammonium
sulphide to a compound isomeric with hydrazotoluene, which
crystallizes in small colourless plates and readily oxidizes in the
air. It is a weak base and forms a very characteristic oxalate,
(C 14 H 16 N 2 ) 2 C 2 H 2 O 4 -hH 2 O, which separates from dilute alcohol
in star-like aggregates, which are very similar to the seed
feathers of the dandelion.
1 Barsilowsky, Ann. Chem. Pharm. ccvii. 114.
2 Helms', Ber. Dcutsch. Chem. Gcs. iii. 549.
3 Perkin, Journ. Chem. Soc. 1880, i. 553.
* Schmitt, Journ. PraJct. Chem. [2] xviii. 198.
5 Ann. Chem. Pharm. ccvii. 102.
6 Journ. Chem. Soc. 1880, i. 546.
AMIDO-AZOTOLUENES. 77
Klinger and Pitschke have now found that the red substance
is an amido-azo-compound of the formula CggH^N^ 1 It is
decomposed into paratoluidine and paraleucotoluidine, C 21 H 25 N 3 ,
by energetic reduction with tin and hydrochloric acid. This
compound crystallizes in small colourless plates, and is readily
oxidized topararosotoluidine, C 21 H 23 N 3 , which forms small lustrous
red plates, and dissolves in water with an intense violet-red
colour. The red substance has, therefore, the following con-
stitution, C 21 H 17 (NH 2 ) 2 N = N.C 6 H 5 .CH 3 . These compounds
will be more fully described in the sequel.
Ortho-azoxytoluenefl^f^^f), is formed when orthonitrotoluene.
is heated with a solution of sodium in methyl alcohol, and
crystallizes from warm petroleum-ether in yellow, monoclinic
needles melting at 59 60. It is not converted into the
isomeric hydroxyazotoluene, C 7 H 7 .N 2 .C 7 H 6 .OH, on heating
with concentrated sulphuric acid, but a large quantity of ortho-
toluidine is formed, the oxygen thus liberated producing the
oxidation of a portion of the ortho-azoxy toluene to a mixture of
amorphous acids.
Klinger and Pitschke consider that the conversion of azoxy-
benzene into hydroxyazobenzene (Pt. III. p. 297) is brought
about in a similar manner, and may be looked upon as " hy-
droxylation by direct oxidation." 2
Amido - azotoluenes, CH 3 .C 6 H 4 N N.C 6 H 3 (CH 3 )NH 2 , are
formed by the action of nitrous acid on orthotoluidine and
metatoluidine, while paratoluidine, as already mentioned, is thus
converted into diazo-amidotoluene. Compounds belonging to
this group are also formed by the action of a diazoparatoluene
salt on orthotoluidine or metatoluidine, as well as on aniline,
etc. 3
AmidortJio-azotoluene is obtained by passing nitrogen trioxide
into orthotoluidine floating on a saturated solution of common salt.
The product is allowed to stand for some time, washed with
water to remove any orthocresol which has been formed, treated
with dilute caustic soda and finally boiled with dilute hydrochloric
acid, the hydrochloride thus obtained being then decomposed by
ammonia.
Amidortho-azotoluene is slightly soluble in water, readily in
alcohol, and crystallizes in lustrous, golden plates or tablets,
1 Ber. Dcutsch. Chem. Ges. xvii. 2439.
* Ibid, xviii. 2551.
3 Nietzki, ibid. x. 662, 832, 1156.
78 AROMATIC COMPOUNDS.
melting at 100. The hydrochloride, C 14 H 15 N 3 .C1H, is only
slightly soluble in water, and crystallizes in long, thin tablets
with a silver lustre.
This compound is decomposed into orthotoluidine and para-
tolylenediamine by the action of hydrochloric acid and tin or zinc
dust, and has therefore the following constitution :
~CH 3 ~CH 3
Amidometa-azotoluene crystallizes from alcohol in broad,
golden-yellow needles melting at 80. The hydrochloride forms
long, dark blue needles, which are only slightly soluble in hot
alcohol, and, like all the other salts of this class, is decomposed
by water. On reduction with tin and hydrochloric acid, para-
tolylenediamine is formed.
Ortho-amido2Jara-azotolnene forms yellow tablets melting at 127
128; its hydrochloride crystallizes in cinnabar-red needles,
which appear of a steel-blue colour when seen by reflected light.
Metamidoparazotoluene crystallizes from alcohol in large, yellow,
plates, melting at 127; the hydrochloride forms small, steel-blue
needles.
Para-amidopara-azotoluene. In order to prepare this compound,
the isomeric diazo-amidoparatoluene is heated for twelve hours to
65 with five times its weight of paratoluidine and one equiva-
lent of paratoluidine hydrochloride. It crystallizes from alcohol
or acetic ether, in orange-red lustrous needles melting at 118'5.
Its hydrochloride crystallizes in light yellow needles and forms
a green solution in water. It is converted into paratoluidine
and orthotolylenediamine by reduction. 1
On treatment with fuming sulphuric acid, a mixture of di-
sulphonic acids is formed, which comes into the market as
"Acid yellow R," since it dyes a redder shade than the colouring
matter obtained from amido-azobenzene (Part III. p. 307),
which is therefore called " Acid yellow G."
a-Azoxytoluidine, C 14 H 12 N 2 (NH 2 ) 2 O, is formed by the action
of sodium amalgam on a solution of orthonitroparatoluidine in
absolute alcohol, and crystallizes from hot water in small, yellow
needles melting at 148. It is a diacid base, and on further
reduction yields the following compounds :
1 Nolting and Witt, Bcr. Deutsch. Chem. Gcs. xvii. 77.
AZOXYTOLUIDINES. 79
a-Azotoluidine, or Symmetric a-diamido-azotoluene, C 14 H 12 N 2
(NH 2 ) 2 , crystallizes from hot water in red needles which are
readily soluble in alcohol and melt at 159.
a-Hydrazotoluidine, C 14 H 12 (N 2 H 2 )(NH 2 ) 2 , is almost insoluble
in cold water and alcohol, but is slightly soluble in hot alcohol ;
it forms small, colourless, rhombic tablets which melt at 180.
It is tolerably stable in contact with cold water and alcohol,
but rapidly oxidizes when heated with them in the air. 1
ft-Azoxytoluidine, C 14 H 12 N 2 (NH 2 ) 2 O, is obtained from para-
nitro-orthotoluidine and crystallizes in long, yellow to yellowish
red, silky needles melting at 168; its salts crystallize well.
When heated with concentrated sulphuric acid, it is converted
into the isomeric hydroxyazo-compound, just as is the case with
azoxybenzene (Part III. p. 296) :
N.C 7 H 6 .NH 2 NC 7 H 5 (OH)NH 2
I = II
N.C 7 H 6 .NH 2 NC 7 H 6 .NH 2 .
This compound crystallizes from alcohol in small, dark red
needles, which melt at 212 with decomposition. Its hydro-
chloride and sulphate are only slightly soluble in water. On
treatment with stannous chloride and hydrochloric acid, it
is resolved into ordinary diamidotoluene and diamidocresol,
C 6 H 2 (CH 3 )(NH 2 ) 2 OH, the hydrochloride of which crystallizes in
white needles which become coloured blue in the air ; the free
base immediately becomes resinous.
@-Azotoluidine, or Symmetric /3-diamido-azotoluene, C 14 H 12 N 2
(NH 2 ) 2 , crystallizes from hot water in small, yellow needles, and
is deposited on the gradual evaporation of its alcoholic solution
in long, red needles, which melt at 197, and are slightly soluble
in water, readily in alcohol. The sulphate is only slightly
soluble in water, the hydrochloride being somewhat more readily
dissolved.
(3-Hydrazotoluidine, C 14 H 12 (N 2 H 2 )(NH 2 ) 2 , forms yellow needles
which rapidly oxidize when exposed to the air in a moist state.
It decomposes without melting when heated, and burns with a
brilliant flame. It is almost insoluble in absolute alcohol, but
dissolves readily in dilute alcohol and water. 2
:xix. 340.
kBuckney, .ibid. xi. 1451.
Limpricht, Ber. Dcutsch. Chem. Ges. xviii. 1403 ; Graff, Ann. Chem. Pharm.
80 AROMATIC COMPOUNDS.
The constitutions of the two azotoluidines are expressed by
the following formulae :
NH
Metanitroparatoluidine is immediately converted by sodium
amalgam into the corresponding diamidotoluene, while metanitro-
ortho- and a-orthonitrometa-toluidine yield resinous products on
oxidation (Limpricht).
Asymmetric diamido-azotoluene, C 7 H 7 NnzNC 7 H 6 (NH 2 ) 2 , cor-
responds to chrysoidine (Part III. p. 301) and is formed by the
action of diazotoluene nitrate on a-diamidotoluene. It crystal-
lizes from alcohol in orange-yellow needles melting at 183. Its
hydrochloride, (C 14 H 16 N 4 )C1H, forms red needles. 1
2057 Tolusafranine, C 21 H 90 N 4 . The history of this dye, which
is simply known as " safranine " in commerce, has already been
briefly indicated. Phenosafranine chloride, the lower homologue
of tolusafranine, has been, proved 2 to have the following con-
stitution :
NH 2 .
This formula explains all the facts which have been already
given (Part III. p. 369) concerning this substance, and also its
formation from one molecule of paradiamidobenzene and two
molecules of aniline.
Hofmann and Geyger were the first to subject the com-
mercial product to a searching examination ; they ascertained
1 Hofmann, Ann. Chem. Pharm. x. 218.
2 Witt, Ber. Deutsch. Chem. Ges. xix. 3121. Nietzki, ibid. 3163.
TOLUSAFRANINE. 81
that it is a hydrochloride of the formula C 21 H 21 N 4 C1, which
is not attacked by alkalis, but is readily decomposed by moist
silver oxide, and that it is not a derivative of aniline, as had
been up to that time assumed, but of orthotoluidine, from which
it can be obtained by the action of nitrous acid and oxidation
of the products with arsenic or chromic acids. 1 Witt then
found that it is formed by heating amido-ortho-azotoluene with
orthotoluidine hydrochloride, 2 and by the oxidation of a mixture
of orthotoluidine and paratoluylenediamine. 3 In order to prepare
it, a solution of equal molecules of orthotoluidine and hydrochloric
acid is treated with the calculated quantity of sodium nitrate, to
obtain amido-ortho-azotoluene ; the product, after the addition of
some orthotoluidine hydrochloride, is allowed to stand and is
then reduced with zinc-dust and hydrochloric acid, a mixture of
fy-diamidotoluene and orthotoluidine being formed, which is then
neutralized and oxidized with potassium dichromate ; if the
solution were kept acid, toluquinone would be formed. 4 The
safranine is then precipitated with common salt, filtered off,
pressed, dried and brought into the market. 5
Tolusafranine hydrochloride, C 21 H 21 N 4 C1, is tolerably soluble
in water and alcohol, forming red solutions which possess a
characteristic fluorescence ; the salt is precipitated from its
aqueous solution by the addition of hydrochloric acid in red
crystals, which are best obtained by crystallizing the commercial
product from boiling, dilute alcohol. The free base, obtained
from this compound by means of silver oxide, probably has the
formula C 21 H 21 N 4 OH, and forms reddish brown crystals which
take a faint green metallic lustre on drying, but have not yet
been obtained free from silver chloride ; they are soluble in
water and alcohol, but not in ether.
Tohtsafranine nitrate, C 21 H 21 N 4 .NO 3 , crystallizes in reddish
brown needles which are only very slightly soluble in cold
water.
Tolusafranine picrate, C 21 H 20 N 4 .C 6 H 3 (NO 2 ) 3 O, is obtained by
the addition of picric acid to a solution of one of the salts of
the base, and forms brownish red needles, insoluble in water,
alcohol and ether.
1 Bar. Deutsch. Chem. Ges. v. 526.
2 Ibid. x. 874.
3 Ibid. xii. 939 ; Bindschedler, ibid. xiii. 207.
4 Nolting, Schultz, Steinkohlentheer, 1049.
5 Ibid. 527.
82 AROMATIC COMPOUNDS.
Tolusafranine shows all the characteristic reactions of the
safranines (Part III. p. 323).
It is employed as a substitute for saffron for dyeing silk and
cotton mordanted with tannin.
2058 Toluykne-blue, C 15 H 18 N 4 .HC1 + H 2 O, is formed when 36
rjrms. of nitrosodimethylaniline hydrochloride, and 24 grms. of
metatoluylenediamine, each dissolved in 500 c.cm. of water at
30, are mixed. ; evolution of heat takes place and a deep green
colouration is produced. If the solution be now allowed to stand,
flat, lustrous brown prisms separate out, but gradually fall into a
fine crystalline powder. These readily form blue solutions in
water, alcohol and acetic acid ; traces of free mineral acids change
the colour into reddish brown, the original shade being restored
by alkalis. The base is precipitated by alkalis from its solution
as a resinous mass which takes a cupreous lustre in the air.
Toluylene-blue is converted by tin and hydrochloric acid into
the leuco-compound, C 15 H 20 N 4 HC1, which is a deliquescent
crystalline substance and is very readily re-oxidized.
Toluylene-red, C 15 H 16 N 4 , is formed, together with the leuco-
compound, when toluylene-blue is boiled with water for 15-20
minutes. Stannous chloride precipitates the colouring matter
as a double tin salt in crystals, which are then decomposed by
an alkali.
Toluylene-red crystallizes in orange-red needles containing
four moleculQS of water, which they lose at 150 160. The
anhydrous base is blood-red and only slightly soluble in alcohol ;
it forms rose-red normal salts, which are stable and readily
soluble in water, while its acid salts are coloured blue and are
decomposed by water.
Toluylene-violet, C 14 H 14 N 4 , is formed by warming toluylene-
blue with metatoluylenediamine dissolved in dilute acetic acid
for twelve hours to 35 40, the leuco-base of the blue compound
being simultaneously formed :
Toluylene-violet forms red crystals with a green reflection
and is even less soluble than toluylene-red ; its solution is flesh-
coloured and shows a remarkable orange-yellow fluorescence.
Its slightly soluble normal salts are coloured violet and crystal-
lize well, while the acid salts have a grass-green colour.
TOLUYLENE COLOURS. 83
Witt gives the following constitutional formulae for these
compounds : l
Toluylene-blue. Toluylene-red. Toluylene- violet.
C.H,
N(OH,),
, N
JJ
C.HKH, O.H .
PHOSPHORUS DERIVATIVES OF TOLUENE.
2059 Paratolylphosphorus dichloride, CH 3 .C 6 H 4 PC1 2 , is obtained
the continued heating of 15 parts of toluene with 200 parts
of phosphorus trichloride and 3 parts of aluminium chloride,
or by heating mercury paratolyl with phosphorus trichloride to
180 190 . 2 It is a crystalline mass, which fumes slightly in
the air, melts at 25, and boils at 245.
Paratolylphosphorus tetrachloride, CH 3 .C 6 H 4 PC1 4 , is formed by
the combination of the compound just described with chlorine,
and crystallizes from benzene in pointed prisms melting at 42.
When heated in a sealed tube to 200, it decomposes with
formation of the dichloride and parachlorobenzyl chloride :
;H 3 .C 6 H 4 PC1 4 = CH 3 .C 6 H 4 PC1 2 + CH 2 C1.C 6 H 4 C1 + PC1 3 + HC1.
It rapidly deliquesces in the air, forming paratolylphosphorus
tchloride, CH 3 .C 6 H 4 POC1 2 , which is, however, best obtained
in a similar manner to phenylphosphorus oxychloride, by the
action of sulphur dioxide on the tetrachloride. It is a thick
liquid, boiling at 284 285.
Paratolyl phosphenylous acid, CH 3 .C 6 H 4 P0 2 H 2 , is formed by
the action of water on the dichloride. It is slightly soluble
in water and crystallizes from alcohol in tablets melting at
104 105.
Paratolylphosphenilic acid, CH 3 .C 6 H 4 PO(OH) 2 , is obtained by
decomposing the tetrachloride or the oxychloride with water. It
is readily soluble in alcohol and crystallizes from water in matted,
woolly needles which melt at 181. It is decomposed by ignitioa
1 Bcr. Dcutsch. Chcm. Ges xii. 931.
2 Michaelis and Paneck, Liebig's Ann. ccxii. 203.
84 AROMATIC COMPOUNDS.
with lime, with formation of toluene and calcium phosphate.
Potassium permanganate oxidizes it to parabenzoplwsplwnilw acid,
C0 2 H.C 6 H 4 PO(OH) 2 , which will be described under benzoic acid.
Paratolylphosphine, CH 3 .C 6 H 4 .PH 2 , is obtained by heating
tolylphosphenylous acid in an atmosphere of carbon dioxide. It
is a liquid which possesses a most intense smell, inhalation of its
vapour producing headache and bleeding of the nose. It boils
at 178 and solidities at a lower temperature to a crystalline mass
which melts at 4. It is rapidly oxidized to tolylphosphenylous
acid in the air. It combines with hydriodic acid to form
paratolylphosphonium iodide, CH 3 .C 6 H 4 .PH 3 I, crystallizing in
broad, lustrous needles which deliquesce in the air and sublime
in cubes when heated to 340 in a current of carbon dioxide.
Dimethylparatolyl phospliine, CH 3 .C 6 H 4 .P(CH 3 ) 2 , is obtained
by the action of zinc methyl on the dichloride, and is a liquid
which has an unpleasant smell, boils at 210, dissolves in acids
and is not oxidized by exposure to the air. Mercuric oxide con-
verts it into dimethyltolylphosphine oxide, CH 3 .C 6 H 4 .P(CH 3 ) 2 )
which is a thick liquid. The phosphine combines with methyl
iodide to form CH 3 .C 6 H 4 P(CH 3 )I, crystallizing in needles which
melt at 225 and yield a strongly alkaline, deliquescent
hydroxide. 1 The corresponding chloride is a very hygroscopic
crystalline body. 2
Orthotolylphosphorus dichloride, CH 3 .C 6 H 4 PC1 2 , is obtained by
heating orthomercury tolyl with phosphorus trichloride. It is
a liquid which boils at 244 and does not solidify even at -20.
It combines with chlorine forming the tetrachloride as a solid
yellow mass. It is decomposed by water with formation of
orthotolylpkosphenylous acid, which is a liquid but forms crystal-
line salts, while the orthotolylphosphenilic acid obtained from the
tetrachloride consists of small crystalline grains which melt at
141 (Michaelis and Paneck).
ARSENIC DERIVATIVES OF TOLUENE.
2060 Arsenparatolyl chloride, CH 3 .C 6 H 4 AsCl 2 , is obtained by
heating mercury paratolyl with arsenic trichloride. 3 It crystal-
lizes in tablets, melts at 31, and boils in an atmosphere of carbon
dioxide at 2 6 7 without decomposition. It combines with chlorine
1 Czimatis, Bcr. Dcutsch. Chem. Ges. xv. 2014.
2 Ibid. 2018.
3 Michaelis and La Coste, Ann. Chem. Pharm, cci. 246.
ARSENIC DERIVATIVES OF TOLUENE. 85
forming the tetrachloride, a yellow crystalline mass, which is
semi-fluid at the ordinary temperature but solidifies completely
on cooling. It is converted by water into tolylarsenic add,
CH 3 .C 6 H 4 AsO(OH) 2 , which crystallizes in long, thin needles.
When the dichloride is boiled with caustic soda solution, arsen-
tolyl oxide, CH 3 .C 6 H 4 AsO, is formed as a powder melting at
156.
Arsendiparatolyl chloride, (CH 3 .C 6 H 4 ) 2 AsCl, is formed when
mercury tolyl is boiled for a long time with three or four times its
amount of arsentolyl chloride. 1 It is an oily, yellow liquid which
is converted by boiling alcoholic potash into arsenditolyl oxide
((CH 3 .C 6 H 4 ) 2 As) 2 0, which crystallizes from ether in silky needles
melting at 98. The monochloride combines with chlorine to
form arsendiparatolyl trichloride, (CH 3 .C 6 H 4 ) 2 AsCl 3 , a yellow
powder which is immediately converted by water into dipara-
tolylarsenic acid, (C 7 H 7 ) 2 AsO(OH), a white crystalline mass
which is slightly soluble in water, readily in alcohol, from which
it crystallizes in granules melting at 167. It is oxidized
by an alkaline solution of potassium permanganate to dibenzo-
arsenic acid, (CO 2 H.C 6 H 4 ) 2 As0 2 H.
Triparatolylarsine, (CH 3 .C 6 H 4 ) 3 As, is formed by heating
arsenparatolyl oxide to 360 :
3CH 3 .C 6 H 4 AsO = (CH 3 .C 6 H 4 ) 3 As+ As 2 3 .
It separates from ethereal solution in large crystals which
melt at 145 and only volatilize at temperatures above 360.
When chlorine is passed into its chloroform solution, arsentri-
tolyl dichloride, (CH 3 .C 6 H 4 ) 2 AsCl 2 , is formed as a white crystal-
line mass which is dissolved almost without decomposition by
boiling water.
Tritolylarsine is oxidized by alkaline potassium permanganate
solution to tribenzo-arsenic acid, (CO 2 H.C 6 H 4 ) 3 As(OH) 2 , which
will be described under benzoic acid.
Arsenorthotolyl chloride, C 6 H 3 .C 6 H 4 AsCl 2 , has been obtained
from mercury orthotolyl and arsenic trichloride, and is a faintly
smelling liquid which boils at 264 265 in an atmosphere of
carbon dioxide without undergoing decomposition. It combines
with chlorine to form the tetrachloride, which is a thick honey-
yellow liquid. When the dichloride is boiled with soda solution,
arsenorthotolyl oxide, CH 3 C 6 H 4 AsO, is formed as a powder which
1 La Coste, ibid, ccviii. 18.
237
86 AROMATIC COMPOUNDS.
is readily soluble in hot water, slightly in alkalis, and melts
at 145 146.
Ortliotolylarsenic acid, CH 3 .C 6 H 4 As.O(OH) 2 , is obtained by the
action of water on the tetrachloride, and crystallizes from hot
water in fine needles, which melt at 159 160 and are con-
verted by prolonged heating into the crystalline anhydride,
arsenorlhotolyl dioxide, CH 3 .C 6 H 4 AsO 2 (La Coste and Michaelis).
ANTIMONY DERIVATIVES OF TOLUENE.
2061 These compounds are obtained by the action of sodium
on a mixture of antimony trichloride with bromotoluene
dissolved in benzene. 1 .
Paratolylstibine, Sb(C 6 H 4 .CH 3 ) 3 , is readily soluble in benzene,
slightly in alcohol, and crystallizes in large, transparent, lustrous
tablets melting at 127*5. It forms compounds with the
elements of the chlorine group, which crystallize from benzene
in lustrous prisms.
Melting-point.
Paratolylstibine chloride, Sb(C 7 H 7 ) 3 Cl 2 . . 156-5
Paratolylstibine bromide, Sb(C 7 H 7 ) 3 Br 2 . . 233'5
Paratolylstibine iodide, Sb(C 7 H 7 ) 3 I 2 . . 182'5
Paratolylstibine oxide, Sb(C 7 H 7 ) 3 0, is obtained by treating the
bromide with alcoholic potash and washing the residue with
water ; it is slightly soluble in benzene, from which it crystallizes
in small needles melting at 223*5. If it be dissolved in hot
glacial acetic acid and treated with sufficient water to produce
turbidity, fine, transparent crystals of paratolylstibine hydroxide,
Sb(C 7 H 7 ) 3 (OH) 2 , are deposited on cooling ; this compound melts
at 169*5.
Metatolylstibine, Sb(C 6 H 4 .CH 3 ) 3 , forms large tablets melting at
64*5 ; the bromide, which melts at 113 and crystallizes well, is
much more readily soluble in ether than its isomerides.
Orthotolylstibine is a thick liquid, and forms a crystalline
bromide. 2
3 Michaelis and Genzken, Ber. Deutsch. Chem. Ges. xvii. 924.
2 Ibid.
MERCURY DERIVATIVES OF TOLUENE. 87
BORON AND SILICON DERIVATIVES OF
TOLUENE.
2062 Paratolylboron chloride, CH 3 .C 6 H 4 BCL>, 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. J<nirn. ii. 95. 3 Ibid. 4 Ibid.
5 Jackson and Lowry, Per. Dcutsch. Chem. Ges. x. 1211.
6 Jackson and Mabery, Amer. CJiem. Journ. ii. 257.
7 Ber. Dcutsch. Chem. Ges. xi. 58.
9 Jackson and White, Amer. Chem. Journ. ii. 317.
8 Ibid.
NITROBENZYLAMINES. 119
Melting-point.
Orthodibromo- 1 /p TT T>r. 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.
<y-Tribenzhydroxylamine is only formed in small quantity; it
crystallizes in short, monoclinic prisms, melting at 112, and is
to a large extent converted into the /3-cOmpound by dilute
hydrochloric acid.
All the three modifications are resolved on dry distillation
into benzoic anhydride and phenyl isocyanate :
,NO.COC 6 H 5
C 6 H 5 .C<; ' = C 6 H 5 NCO+(CO.C 6 H 5 ) 2 0.
\O.CO.C 6 H 5
They are decomposed by alcoholic potash into dibenzhydrox-
amic acid and benzoic acid.
The chemical behaviour of these substances is therefore iden-
tical, and they present an instance of trimorphism, for although
they all crystallize in forms belonging to the monoclinic system,
these forms are distinct ones and cannot be derived from one
another.
Benzenylamidoxime, or Benzhydroxamide, C 6 H 5 .C(NOH)NH 2 ,
is formed when a solution of hydroxylamine and benzonitril in
dilute alcohol is heated to 80 for about eighteen hours : 2
_N.OH
C 6 H 5 .C=N + H 2 N. OH = C 6 H 5 .C7~
X NH 2 .
1 Klein and Trechmann, Ann. Chem. Pharm. clxxxvi. 104.
2 Kriiger and Tiemann, Ber. Dcutsch. Chem. Ges. xvii. 126, 1687 ; xviii. 727,
1053.
BENZHYDROXAMIDE. 213
It is also formed by the action of hydroxylamine on benz-
amidine, C 6 H 5 .C(NH)NH 2 , and was described by Pinner as
benzoxamidine. 1
It is readily soluble in alcohol and ether, and crystallizes from
hot water in long, flat, acute prisms, melting at 79 80. It is
precipitated by petroleum spirit from its solution in benzene in
needles. Its solution is coloured deep red by ferric chloride ; it
forms salts both with acids and bases. Benzamide and nitrous
oxide are formed by the action of sodium nitrite on its hydro -
chloride, while when heated to 200 with hydrochloric acid, it
decomposes into ammonium chloride and benzoic acid.
Benzenylamidoxime is poisonous ; thus, 0'5 grm. proved fatal
to a dog, O'l grm. to a rabbit, and 0'Q3 grm. to a frog.
Its alkyl ethers are formed by heating the sodium salt with
the corresponding iodide.
Ethyl ether of lenzenylamidoxime, C 6 H 5 .C(NOC 2 H 5 )NH 2 , is
almost insoluble in water, but readily soluble in alcohol and
ether, and crystallizes in rhombic plates, which melt at 67, and
dissolve in acids but not in alkalis. Its hydrochloride crystal-
lizes well.
Benzcnylethoxime chloride, C 6 H 5 .C(NOC 2 H 5 )C1, is formed when
sodium nitrite is added to a well-cooled solution of the ether :
C 6 H 5 .C(NOC 2 H 5 )NH + HC1 + NaNO 2 = C 6 H 5 .C(NOC 2 H 5 )OH
+ NaCl + H 2 + Ng.
C 6 H 6 .C(NOC 2 H 5 )OH + HC1 = C 6 H 5 (NOC 2 H 5 )C1 + H 2 O.
According to Lossen, a diazo-compound is probably formed at
first, and then decomposes in the following mariner : 2
X>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.
<y-Dichlorobenzoic acid, (2:6), is obtained, together with the
preceding compounds, when dichlorobenzyl chloride is heated
with water to 200 ; it crystallizes from alcohol in small needles,
melting at 126'5. 3
S-Dichlorobenzoic acid, (2 : 4), is formed by the oxidation of the
corresponding dichlorotoluene with nitric acid, and crystallizes
in long, pliable needles, melting at 158.
e-Dichlorobcnzoic acid, (3 : 5), has also been prepared from
symmetric dichlorotoluene, and forms long needles, melting at
182 (Lellmann and Klotz).
TKICHLOROBENZOIC ACIDS, C 6 H 2 C1 3 .CO 2 H.
2126 a-Trichlorobenzoic acid, (2:4:6), is obtained by the
oxidation of a-trichlorotoluene, 4 and by heating a-trichloro-
benzyl chloride 5 to 260 with water ; it crystallizes in needles
which melt at 163,
ft-Trichlorobcnzoic acid has been obtained from the corre-
sponding aldehyde by oxidation with potassium permanganate ;
it melts at 129 . 6
y-Trichlorobenzoic acid, (3:4: 5), is formed when chrysanisic
acid, C 6 H 2 (NO 2 ) 2 (NH 2 )CO 2 H, is heated with fuming nitric acid.
It forms fine needles, melting at 203 . 7
TETRACHLOROBENZOIC ACID, C 6 HC1 4 .C0 2 H.
Beilstein and Kuhlberg prepared this compound by heating
tetrachlorobenzyl chloride with water to 280
1 Beilstein, Ann. Chem. Pharm. clxxix. 285.
2 Rack and Wilkens, ibid, ccxxii. 201.
* Schultz, ibid, clxxxvii. 269.
4 Jannasch, ibid, cxlii. 301
6 Beilstein and Kuhlberg, Ber. Deutsch. Chem. Gcs. xviii. 420.
6 Seelig, ibid, xviii. 420.
7 Salkowski, Ann. Chem. Pharm. clxiii. 28.
THE MONOBROMOBENZOIC ACIDS.
MONOBROMOBENZOIC ACIDS, C 6 H 4 Br.CO 2 H.
2127 Orihobromobenzoic acid was first prepared by Griess
from anthranilic acid or ortho-amidobenzoic acid by the diazo-
reaction, but was not further investigated by him. 1 It was, how-
ever, examined by v. Bichter, who found it to be identical
with that which he had obtained from metabromonitrobenzene
by means of the reaction already mentioned (p. 21 7). 2 Zincke
obtained it by boiling orthobromotoluene with dilute nitric
acid ; 3 it is, however, better to employ a dilute solution of
potassium permanganate. 4
It is more readily soluble in cold water than its isomerides,
and is still more soluble in hot water, from which it crystallizes
in long needles, which melt at 150 and sublime in small plates.
Barium orthobromobenzoate, (C 7 H 4 Br0 2 ) 2 Ba, is very readily
soluble in water, and crystallizes from alcohol in long needles
containing two molecules of alcohol.
Mctabromobenzoic acid. Peligot obtained this substance in the
year 1838 by the action of bromine on silver benzoate, 5 and
Herzog, in 1842, by acting upon benzoic acid with bromine in
the sunlight. 6 The compound thus prepared, however, was not
pure. Reinecke then found that the pure compound can readily
be obtained by heating benzoic acid to 100 with bromine and
water ; 7 it may also be prepared in this manner from benzamide,
the reaction taking place at 120, 8 and bromanil being formed
at the same time :
C 6 H 5 .CO.NH 2 + Br 2 + H 2 O = C 6 H 4 Br.C0 2 H + N H 4 Br.
;
According to Hiibner and Angerstein, it can also be prepared
by Peligot's method, if dry silver benzoate be submitted to the
action of bromine vapour in the sunlight. 9 Griess also obtained
it from metamidobenzoic acid 10 and Sandmeyer from meta-
bromaniline, which he diazotized and brought into a solution of
potassium cuprous bromide heated to 90 ; the nitril, which was
1 Ann. Chcm. Pharm. cxxxv. 121.
2 Bcr. Dcutsch. Chcm. Gcs. iv. 464 ; v. 428; 3 Ibid, vii. 1502.
1 Rhalis, Ann. Chcm. Pharm. cxcviii. 102. 6 Ibid, xxviii. 246.
6 Brandes, Arch. Pharm. xxiii. 16.
Zeitschr. Chcm. 1865, 116; 1869, 100.
* Friedberg, Ann. Chcm. Pharm. clviii. 26.
6 Ibid, clviii. 2. 10 Ibid, cxvii. 25.
224 AROMATIC COMPOUNDS.
thus formed, was then decomposed by boiling soda- solution; 1
Wroblewsky prepared it by the oxidation of metabromotoluene. 2
Metabromobenzoic acid is very slightly soluble in water,
readily in alcohol, crystallizes in needles, melts at 155, sublimes
at a higher temperature and boils above 280. On fusion with
caustic potash, metahydroxybenzoic acid is formed together with
a little salicylic acid, and, probably, some parahydroxybenzoic
acid.
Barium mctabromdbenzoate, (C 7 H 4 BrO 2 ) 2 Ba + 4H 2 O, is very
slightly soluble in water and crystallizes in small, flat needles.
Parabromobenzoic acid was first obtained by Griess from par-
amidobenzoic acid. 3 It is formed by the oxidation of parabromo-
toluene, 4 parabromo-ethylbenzene, 5 etc., with dilute nitric acid
or chromic acid, and may also be obtained from parabromaniline
by means of Weith's reaction (Part III. p. 31). 6 It is almost
insoluble in cold water, and only slightly soluble in boiling water,
from which it crystallizes in small plates. It is readily soluble
in alcohol and ether, and separates from them in small needles,
melting at 251.
Barium parabromobenzoate, (C 7 H 4 Br0 2 ) 2 Ba, crystallizes in
nacreous plates, which are readily soluble in water.
DIBROMOBENZOIC ACIDS, C 6 H 3 Br 2 CO 2 H.
Br. : Br. Melting-point.
a) 3 : 4 small needles, 7 229 230
/5) 2 : 3 small needles, 8 147
7) 3 : 5 flat needles, 9 213 214
8) 2 : 5 flat needles, 10 153
e) 2 : 4 needles or tablets, 11 . . . 168 170
Bcr. Dcntsch. Chem. Ges. xviii. 1495.
Ann. Chem. Pharm. clxviii. 156.
Ibid, cxxxv. 121.
Hiibner, Ohly and Philipp, ibid, cxliii. 247.
Fittig and Kbnig, ibid, cxliv. 283.
Weith and Landolt, Bcr. Ueutsch. Chem. Ges. viii. 717.
Burghardt and Beutnagel, Ann. Chem. Pharm. ccxxii. 184.
Beutnagcl, ibid, ccxxii. 105.
Beilstein and Geitner, ibid, cxxxix. 4 ; Neville and Whither, Bcr. Deutsch.
Chem. Ges. xiii. 970.
10 Holzapfel, Ann. Chem. Pharm. ccxxii. 107.
11 Neville and Winther, loc. cit.
IODOBENZOIC ACIDS. 225
TRIBROMOBENZOIC ACIDS, C 6 H 2 Br 3 .C0 2 H.
Melting-point,
a) silky needles l 234 235 s
/3) small needles 2 195
7) needles 3 186'5
8) needles 4 . . 178
Pentabromobenzoic acid, C 6 Br 5 .CO 2 H. When metabromo-
benzoic acid is heated to 150 with bromine and water,
a-tribromobenzoic acid is formed, and on further heating with
bromine at 200 is converted into pentabromobenzoic acid. It
crystallizes from alcohol in thin plates or long, broad needles
which become brown and melt at 234 235 (Reinecke).
MONO-IODOBENZOIC ACIDS, C 6 H 4 I.CO 2 H.
2128 Ortho-ioddbenzoic acid was obtained by Griess and Bichter
from anthranilic acid, and by the latter also from meta-iodo-
nitrobenzene. Kekule prepared it by the oxidation of ortho-
iodotoluene with dilute nitric acid. It is slightly soluble in
water, readily in alcohol, and crystallizes in long, white needles,
which melt at 157 and readily sublime. On fusion with potash,
salicylic acid is formed.
Heta-iodobenzoic acid has been prepared by Griess, Lunge, and
Hiibner, and by Grothe from metamidobenzoic acid. It is also
formed when benzoic acid is heated with potassium iodate and
dilute sulphuric acid, and by the action of iodine and iodic acid
on sodium benzoate. It forms small plates or needles, melting
at 186 187; on heating with caustic potash solution it is con-
verted into metahydroxybenzoic acid, and with ammonia into
metamidobenzoic acid.
Para-iodobenzoic acid was obtained by Griess 5 from par-
amidobenzoic acid, and by Korner 6 by the oxidation of para-
iodotoluene. It crystallizes in small plates melting at 256 . 7
1 Reinecke, Zeitechr. Chem. 1869, 110.
2 Smith, er. Deuisch. Chem. Gcs. x. 1706.
3 Volbrecht, ibid. x. 1708.
4 Lawrie, ibid. x. 1705.
6 Ber. Dcutsch. Chem. Gcs. iv. 522.
6 Zcitschr. Chem. 1868, 327.
7 Schmidt and Schultz, Ann. Chem. Pharm. ccvii. 333.
226 ABOMATIC COMPOUNDS.
According to Beran it cannot be obtained perfectly pure by
recrystallization, but must be sublimed, plates which melt at
265 266 l being obtained in this way.
MONOFLUORBENZOIC ACIDS, C 6 H 4 F.C0 2 H.
2129 These compounds are obtained by passing nitrogen
trioxide into solutions of the amidobenzoic acids in alcohol,
a diazo-amidobenzoic acid being formed, which is decomposed
into fluorbenzoic acid and amidobenzoic acid hydrofluoride on
warming with fuming hydrofluoric acid : 2
N.C 6 H 4 .C0 2 H
II + HF = C 6 H 4 F.C0 2 H + NH 2 .C 6 H 4 .C0 2 H+N 2 .
N.NH.C 6 H 4 .C0 2 H
They can be still more simply obtained from the diazobenzoic
acid sulphates (p. 260).
As much as 5 grms. of these compounds may be administered
daily to a dog without injuring it; they appear in the urine as
the fluorhippuric acids, 3 C 9 H 8 FNO 3 , which crystallize in needles
or prisms.
Orthofluorbcnzoic acid crystallizes in fine needles, is readily
soluble in alcohol, more readily in water, and melts at 117
118.
Orthofluorhippuric acid melts at 121'5.
Metafluorbenzoic acid crystallizes from hot water in broad,
lustrous plates or needles, which resemble those of benzoic acid
and melt at 123 124.
Metafluorhippuric acid melts at 152 153.
Parafluorbenzoic acid resembles the meta-compound, and melts
at 180 181. This substance was first prepared by Schmitt
and v. Gehren from ordinary amidobenzoic acid, and was there-
fore looked upon as metafluorbenzoic acid. The amido-acid
employed probably contained the para-compound as an im-
purity. The fluorbenzoic acid crystallizes, according to their
account, in pointed rhombic prisms, which have a characteristic
sweet taste, and melt at 182. On distillation with lime it yields
phenol, which was mistaken by Schmitt and v. Gehren for fluor-
1 Per. Dculsch.Chcm Ges. xviii. IS 7.
3 Schmitt and v. Gehren, Journ. Prdkt. Chem. [2] i. 394 ; Patern6 and Oliveri,
Gaz. CTiim. 1882, 95. 8 Coppola, ibid. xiii. 521.
THE NITROBENZOIC ACIDS. 227
benzene ; a high boiling compound is also formed, which probably
consists chiefly of diphenyl oxide : 1
(C 6 H 4 F.C0 2 ) 2 Ca + 2Ca(OH) 2 = 2C 6 H 5 .OH + CaF 2 4 2CaC0 3 .
Parafluorhippuric acid melts at 161'5.
Difluorbenzoic acid, C 6 H 3 F 2 .C0 2 H, is formed, together with
chromic fluoride, when benzoic acid is treated with chromium
hexfluoride. It is scarcely soluble in cold, only slightly in boil-
ing water, but more readily in hot benzene, and sublimes
less readily than benzoic acid, in flat, white needles, melting
at 232.
Calcium diftuorbenzoate, (C 6 H 3 F 2 .CO 2 ) 2 Ca 4- 3H 2 O, crystallizes
from hot water in fascicular aggregates of white, lustrous needles,
which dissolve in 200 parts of water at 15. 2
NITRO-SUBSTITUTION PRODUCTS OF
BENZOIC ACID.
2130 In the year 1839, Plantamour obtained an acid very rich
in oxygen by the action of nitric acid on cinnamic acid, benzalde-
hyde being also formed. He gave no name to the new substance,
since he wished to ascertain by investigation whether it could be
classed along with any known acid. Analysis led to the formula
C 13 H 10 9 , and this formula was confirmed by the composition of
the silver salt. 3
In the next year, Mulder found that nitrobenzinic acid is
formed by the action of nitric acid on benzoic acid, cinnamic
acid and oil of cinnamon. He determined the correct com-
position of the compound and formulated it as C 14 H 8 O 4 -f N 2 O 3
+ H 2 O, according to which it is a compound of nitrous acid with
an organic substance containing two atoms of hydrogen less, and
one atom of oxygen more than benzoic acid. He also found it
to be identical with the acid discovered by Plantamour, who had
overlooked the presence of nitrogen. 4
The same acid was prepared by Blyth and Hofmann by the
distillation of styrolene (phenylethylene) with strong nitric acid. 5
1 Patern6 and Oliver!, Gaz. Chim, xiii. 5?3.
2 Jackson and Hartshorn, Ber. Deutsch. Chem. Gcs. xviii. 1993.
3 Ann. Chem. Pharm. xxx. 348. 4 Ibid, xxxiv. 297.
5 Ibid. liii. 304.
2<J8 AROMATIC COMPOUNDS.
Abel detected it among the products of the action of nitric acid
on cumene (isopropylbenzene), 1 and Blumenau obtained it in
the same way from dragon's blood. 2 The acid formed by the
nitration of benzoic acid was then investigated by Zinin, 3
Gerland, 4 Voit 5 and Ernst, 6 the three last-mentioned giving
directions for its preparation.
Glenard and Boudault had, in 1843, obtained nitrodracylic
acid, C 8 H 6 (NO 2 )O 2 , by the action of fuming nitric acid on the
dracyl (toluene) obtained from dragon's blood, and Gerhardt
considered it to be nitrobenzoic acid. 7 Wilbrand and Beilstein
showed, however, that it is not identical, but isomeric with
the latter, and that another acid is formed in small quantity,
which appears to be ordinary nitrobenzoic acid. 8 It was ob-
tained about the same time by Fischer, who named it para-
nitrobenzoic acid, 9 while that derived from benzoic acid was
known as orthonitrobenzoic acid until it was recognized as
oelonging to the meta-series (Part III., p. 41).
The third isomeride, now known as orthonitrobenzoic acid,
was first prepared by Radziswesky from phenylacetic acid, but
was believed to be ordinary nitrobenzoic acid. 10 Beilstein and
Kuhlberg then prepared the ortho-acid from cinnamic acid
(phenylacrylic acid), 11 and considered it as identical with
Radziswesky's compound, this being confirmed by Pirogow. 12
Griess was the first to recognize the fact that not only
metanitrobenzoic acid, but also its two isomerides are formed by
the nitration of benzoic acid ; from 4,000 grms. of benzoic acid
he obtained, in addition to the chief product, 347 grms. of
orthonitrobenzoic acid and 35 grms. of paranitrobenzoic acid, 13
while according to Widnmann, the ortho-acid formed amounts to
25 per cent, of the weight of benzoic acid employed. 14 The older
investigators had all the three nitrobenzoic acids under their obser-
vation, but their purest compounds were probably specimens in
which one or other of the isomerides simply predominated. This
is shown by the following facts ; toluene, cumene, styrolene, oil
of cinnamon and cinnamic acid are oxidized by dilute nitric acid
1 Ann. Chem. Pharm. Ixiii. 308. 2 Ibid. Ixvii. 313.
3 Journ. Prakt. Chem,. xxxvi. 93.
4 Ann. Chem. Pharm. Ixxxvi. 143 ; xci. 185.
5 Ibid. xcix. 100. 6 Zeituchr. Chem. 1860, 477.
1 Ann. Chem. Pharm. xlviii. 343. 8 Ibid, cxxvi. 255 ; cxxviii. 257.
9 Fischer, ibid, cxxvii. 137. 10 Ber. Deutsch. Chem. Ges. iii. 648.
11 Ann. Chum. Pharm. clxiii. 121. 12 Ibid, clxiii. 140.
13 Ibid, clxvi. 129 ; Ber. Deutsch. Chem. Ges. x. 1868.
14 Ann. Chem. Pharm. cxcliii. 223.
ORTHONITROBENZOIC ACID, 229
to benzole acid, which is converted by the concentrated acid into
the nitrobenzoic acids. Toluene is converted by strong nitric
acid into the three isomeric nitrotoluenes, the chief product being
the para-compound, the meta-compound being only formed
in small quantity (p. 15), while on the nitration of benzoic
acid, the meta-acid forms the chief product, anol the para-
compound only occurs in small quantity. Concentrated nitric
acid converts cinnamic acid, and probably styrolene and cumene,
into para- and ortho-nitro-compounds, the meta-compound
being possibly formed in small quantity. All these nitro-
derivatives of the hydrocarbons, as well as the nitro-cinnamic
acids, yield the corresponding nitrobenzoic acids on oxidation.
Which of these predominated, therefore, in the mixtures in
question, depended, in the first instance, upon the concentration
of the nitric acid employed. The nitrobenzoic acid obtained
from cinnamic acid and styrolene was probably a mixture of the
para- and ortho-acids, and this would also be the composition of
that obtained from dragon's blood and cumene by the aid of
fuming nitric acid. These mixtures may, however, have also
contained dinitrobenzoic acids and styphnic acid, both of which
are formed by the action of nitric acid on benzoic acid.
MONONITROBENZOIC ACIDS, C 6 H 4 (N0 2 )C(XH.
2131 OrtJionitrobenzoic acid. In order to prepare this com-
pound, the mixture obtained by the nitration of benzoic acid
is converted into the barium salts, from which the barium ortho-
nitrobenzoate can readily be obtained in crystals, which are then
decomposed by dilute sulphuric acid. 1
Orthonitrobenzoic acid can also be readily obtained by boiling
orthonitrotoluene for a long time with a solution of potassium
permanganate. 2 Crude nitrotoluene may also be employed since
the larger portion of the slightly soluble paranitrobenzoic acid
can easily be separated. The barium salts are prepared from the
mother-liquors of this and separated as described below. 3
Orthonitrobenzoic acid dissolves in 100 parts of water at 165 ;
it is more readily soluble in hot water and crystallizes from it
in large colourless needles. It is obtained in asymmetric tablets
1 Widnmann, Ann. Chem. Pharm. cxciii. 202.
2 Widnmann, Bcr. Deutsch. Chem. Ges. viii. 892.
8 Moirnet, Reverdin and Nolting, ibid. xii. 443.
246
230 AROMATIC COMPOUNDS.
or prisms by the spontaneous evaporation of its alcoholic solution.
It melts at 147, and has an intensely sweet taste, which also
characterizes its salts.
Barium orthonitrobenzoate, (C 6 H 4 .NO 2 .C0 2 ) 2 Ba + 3H 2 O, crys-
tallizes on the spontaneous evaporation of its solution in water,
in which it is more readily soluble than the acid, in large,
yellow, asymmetric tablets, which lose their water over sulphuric
acid.
Ethyl orthonitrobenzoate, C 6 H 4 (NO 2 )CO 2 .C 2 H 5 , forms asym-
metric crystals, melting at 30.
Orthonitrobenzoyl chloride, C 6 H 4 (N0 9 )COC1, is a faint yellow
liquid, which solidifies at a low temperature to a crystalline mass,
and decomposes on heating. When heated with silver cyanide,
the nitril of nitrophenylglyoxylic acid is formed, and this is
converted by reduction into isatin, an oxidation product of
indigo. 1
Orthonitrobenzonitril, C 6 H 4 (NO 2 )CN. By the action of am-
monia on orthonitrobenzoyl chloride, orthonitrobenzamide,
C 6 H 4 (N0 2 )CO.NH 2 , is formed, and crystallizes in long needles,
melting at 174 ; it is converted into the nitril on heating with
phosphorus pentoxide. 2 The latter may also be obtained syn-
thetically from orthonitraniline by diazotizing it with hydro-
chloric acid and sodium nitrite, and bringing the compound
thus obtained into an almost boiling solution of copper sulphate
and potassium cyanide : 3
2C 6 H 4 (N0 2 )N 2 C1 + Cu 2 (CN) 2 = 2C 6 H 4 (N0 2 )CN + N 2 + Cu 2 Cl 2 .
It crystallizes in needles which are readily soluble in alcohol
and hot water, melt at 109, and sublime when more strongly
heated.
2132 Metanitrobenzoic acid is best obtained by bringing an in-
timate mixture of one part of previously fused and finely powdered
benzoic acid with two parts of nitre into three or four parts oi
sulphuric acid, the mixture being well stirred, and then heating
until the nitrobenzoic acids have separated out as an oily layer. 4
In a well-conducted operation these contain little or no unaltered
benzoic acid. Should this be present in large quantity, it is
1 Claissen and Shadwell, Ber. Dcutech. Chem. Ges. xii. 350.
2 Barthlein, ibid. x. 1713.
3 Sandmeyer, ibid, xviii. 1492.
4 Ernst, loc. cit. ; Leo Liebermann, Ber. Deutsch. Chem. Ges. x. 862 ; Widn-
mann, Ann. Chem. Pharm. cxciii. 216.
METANITROBENZOIC ACID. 231
removed by distillation with water, and the product then heated
to boiling with 20 parts of water and neutralized with barium
hydroxide. Barium metanitrobenzoate crystallizes out on cool-
ing. The mother liquor is evaporated and the residue repeatedly
extracted with small quantities of cold water, the salt of the
ortho-acid being obtained on the evaporation of the solution. A
further crop of crystals of the meta-compound are obtained by
dissolving the residue in 20 parts of boiling water and cooling
the solution, the barium salts of paranitrobenzoic acid, benzoic
acid and styphnic acid remaining in solution.
Metanitrobenzoic acid dissolves at 16'5 in 425, and at 100
in 10 parts of water ; on cooling it separates from the solution in
small plates ; it crystallizes from dilute alcohol in monoclinic
tablets, melting at 140 141 ; when gradually cooled the
melting-point falls to 135 136, but rises again after some
time, or when the remelted acid is allowed to cool rapidly
(Widnmann). It possesses the characteristic property of melting
under hot water ; it commences to sublime at temperatures above
100, and its vapour provokes coughing.
Sodium metanitrobenzoate, C 6 H 4 (NO 2 )C0 2 Na -f- 3H 2 O, crystal-
lizes in coarse, colourless or yellowish tablets, and may be
employed for the purification of the crude acid. 1
Barium metanitrobenzoate, (C 6 H 4 .NO 2 .CO 2 ) 2 Ba + 4H 2 O, crys-
tallizes in thin prisms, and is less soluble than the free acid.
Ethyl metanitrobenzoate, C 6 H 4 (NO 2 )C0 2 .C 2 H 5 , has been pre-
pared by the action of hydrochloric acid on an alcoholic solution
of the acid, by that of alcohol on its chloride, and by the nitra-
tion of ethyl benzoate. It is also formed when ethyl nitrate
and benzoic acid in ethereal solution are treated with sulphuric
acid. 2 It crystallizes in monoclinic prisms, which melt at 41
and have an aromatic smell, boils at 298, and decomposes into
ethylene bromide and metanitrobenzoic acid when heated to
170 200 with bromine. 3
Metanitrobenzoyl chloride, C 6 H 4 (N0 2 )COC1, crystallizes in
pyramids with a diamond lustre or in long, fine prisms, which
melt at 33 34 4 and smell like benzoyl chloride.
Metanitrolenzamide, C 6 H 4 (NO 2 )CO.NH 2 , forms yellow, mono-
clinic needles, and melts at 140 142.
1 Hiibner, Ann. Chcm. Pharm. ccxxii. 72.
2 Fittica, Journ. Prakt. Chem. [2] xvii, 221.
3 Naumann, Ann. Chcm. Pharm. cxxxiii. 202.
4 Claissen and Thompson, Ber. Dcutsch. Chem. Ges. xii, 1943.
AROMATIC COMPOUNDS.
Metanitrohippuric acid, C 6 H 4 (N0 2 )CO.NH.CH 2 .CO 2 H. Ber-
tagnini obtained this compound in the year 1851 by taking 6 grms.
of nitrobenzoic acid daily and isolating the nitrohippuric acid from
his very acid urine. He also prepared it by adding sulphuric
acid to a solution of hippuric acid in cold, fuming nitric acid. It
crystallizes from alcohol in silky needles, melting at 162. It is
decomposed by boiling fuming hydrochloric acid into glycocoll
and nitrobenzoic acid. 1
Metanitrobenzonitril, C 6 H 4 (NO 2 )CN, is formed by the action
of phosphorus pentoxide or phosphorus chloride on the amide,
as well as by the nitration of benzonitril and, synthetically, from
metanitraniline in a similar manner to the ortho-compound. It
crystallizes in needles, melting at 117 118 . 2
2133 Paranilrobenzoic acid is prepared by the oxidation of
paranitrotoluene with strong nitric acid (Beilstein and Wilbrand ;
Fischer), with potassium dichromate and dilute sulphuric acid 3
or with potassium permanganate. 4
It dissolves in 1200 parts of water at 17, and in 140 parts at
100 without melting, is more readily soluble in alcohol and
crystallizes in yellowish white, lustrous plates, which melt at
238 and sublime in needles.
Barium paranitrdbenzoate, (C 6 H 4 .N0 2 .C0 2 ) 2 Ba + 5H 2 O, crys-
tallizes in yellow, transparent, monoclinic prisms, which dissolve
in 250 parts of cold and 8 parts of boiling water. It forms an
anhydrous double salt with barium benzoate, (C 6 H f) .CO 2 ). 2 Ba
-f (C 6 H 4 .NO 2 .C0 2 ) 2 Ba, which crystallizes in large, colourless or
brownish, lenticular aggregates. The calcium salt and calcium
metanitrobenzoate both form double salts with calcium benzoate. 5
Ethyl paranitrol>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.
<y-Dinitrobenzoic acid, (2:6), is very freely soluble in boiling
water, crystallizes in fine, matted, white needles, melts at 202,
and, like its isomerides, has a very bitter taste. It decomposes
on distillation into carbon dioxide and metadinitrobenzene, and
on reduction yields metadiamidobenzene.
Barium ry-dinitrobenzoate, (C 6 H 3 (NO 2 ) 2 CO 2 \Ba + 2H 2 O, is
veiy readily soluble in water and crystallizes in needles.
1 Bcr. Deutsch. Chem. Ges. xii. 1983 ; Zeitschr. Kryst. iv. 58.
2 Ber. Deutsch. Chem. Ges. vii. 1223.
3 Tiemann and Judson, ibid. in. 223 ; "Wurater, ibid. vii. 148.
4 Glaus and Halberstadt, ibid. xiii. 815 ; Stromeyer, Ann. Chem. Pharm.
ccxxii. 79.
THE DINITEOBENZOIC ACIDS. 235
S-Dinitrolcnzoic acid, (3 : 5), or Ordinary dinitrobenzoic acid.,
was first prepared by Cahours : l it is obtained by heating ben-
zoic acid 2 or metanitrobenzoic acid 3 with a mixture of nitric
and sulphuric acids, or by oxidizing symmetric dinitrotoluene
with chromic acid 4 or nitric acid (Hiibner).
In order to prepare it, 20 grms. of benzoic acid are dissolved
in 180 grms. of concentrated sulphuric acid, one-third of the
volume of fuming nitric acid added, and the whole heated nearly
to boiling for four hours and then poured into two volumes of
cold water ; a yield of 30 grms is obtained. 5
It crystallizes from hot water in thin, quadratic tablets, and
from alcohol in prisms, which melt at 204 205, and sublime
in needles. On reduction it yields S-diamidobenzoic acid. Its
salts detonate violently when heated.
Barium -dinitrobenzoate, (C 6 H 3 (NO 2 ) 2 CO 2 ) 2 Ba + H 2 0, forms
small crystals, readily soluble in hot water (Hiibner).
e-Dinitrobenzoic acid, (3:4), is formed at the same time as the
/3-acid by the action of a mixture of nitric and sulphuric acids
on paranitrobenzoic acid. It has an intensely bitter taste, is
only slightly soluble in cold water, fuses under hot water and
crystallizes from it in stellate groups, melting at 161. These
crystals sublime at a higher temperature, and detonate violently
when heated on platinum foil. 6
Barium e-dinitrobenzoatv, (C 6 H 3 (N0 2 ) 2 C0 2 ) 2 Ba + 4H 9 0, forms
a white, radiating crystalline mass.
TRINITROBENZOIC ACID, C 6 H 2 (N0 2 ) 3 C0 2 H.
2135 This compound is obtained by heating trinitrotoluene to
100 with fuming nitric acid for a week. It crystallizes from
hot water in rhombic prisms, melts at 190 and sublimes at a
higher temperature. 7
1 Ann. Chcm. Pharm. Ixix. 241.
2 Michler, ibid, clxxv. 152.
3 Muretow, Zeitschr. Chcm. 1870, 641.
4 Stadel, Ber. Deutsch. Chcm. Ges. xiv. 902.
6 Hiibner, Ann. Chcm. Pharm. ccxxii. 72.
6 Glaus and Halberstadt, Ann. Chcm. Pharm. xiii. 815.
7 Tiemann and Judson, ibid. iii. 224.
236 AEOMATIC COMPOUNDS.
CHLORONITROBENZOIC ACIDS, C 6 H 3 C1(N0 2 )C0 2 H.
Cl : N0 2 Melting-point.
a) 2:5 silky needles or rhombic tablets l . . 164 165
) 3:6 prisms 2 137 138
7) 3:2 long, thin needles or six-sided tablets 3 235
5) 3:5 small needles 4 147
e) 4:3 small needles 5 1 79 180
f) 2:4 readily soluble crystals 6 136 137
The first three of these acids have been obtained by the
nitration of ortho- and meta-chlorobenzoic acid. The fourth
acid is prepared from the corresponding amidonitrobenzoic acid
and the fifth by the nitration of parachlorobenzoic acid ; this
compound and the last have also been obtained by the oxida-
tion of the corresponding chloronitrotoluenes. Since the f-acid
melts at the same temperature as the yS-acid, they were
considered to be identical, but this is not the case, as the
-acid is derived from paranitrotoluene, and can be converted
into orthochlorobenzoic acid.
BROMONITROBENZOIC ACIDS, C 6 H 3 Br(NO 2 )CO 2 H.
Br : NO 2 Melting-point.
a) 2:5 long needles 7 177 178
/3) 3 6 monoclinic prisms 8 ....... 140 140
7) 3:2 monoclinic crystals 9 250
8) 4:3 small plates or needles 10 199
e) 3:5 long needles or thin, six-sided tablets n 161
2:4 long needles 12 163 164
1 Kekule, Ann. Chem. Pharm. cxvii. 135; Hiibner, Zeitschr. Chem. 1886, 614 ;
Hiibner and Biedermann, Ann. Chem. Pharm. cxlvii. 263 ; "Wilkens and Rack,
ibid, ccxxii. 192.
2 Ulrich, ibid, ccxxii. 95. 3 Ibid.
4 Grube, Ber. Deutsch. Chem. Ges. x. 1703.
5 Hiibner and Biedermann ; Raveill, Ann. Chem. Pharm. ccxxii. 182.
6 Wachendorff, ibid, clxxxv. 275,
7 Burghard, Ber. Deutsch. Chem. Ges. viii. 560 ; Rahlis, Ann. Chem. Pharm.
cxcviii. 109 ; Scheufelen, ibid, ccxxxi. 181.
8 Hiibner, Ohly and Philipp, ibid, cxliii. 233 ; Hiibner and Meeker, Zeitschr.
Chem. 1867, 565 ; Hiibner and Petermann, Ann. Chem. Pharm. cxlix. 132 ;
ccxxii. 101. 9 Ibid.
10 Ibid. ; Raveill, Ber. Deutsch. Chem. Ges. x. 1707 ; Ann. Chem. Pharm.
ecxxii. 177 ; Scheufelen.
11 Hesemann and Kb'hler, ibid, ccxxii. 166. 12 Scheufelen.
ORTHO-AMIDOBENZOIC ACID. 237
The first is formed by the nitration of orthobromobenzoic
acid, as well as by the oxidation of the corresponding bromo-
nitrotoluene, and yields 8-dibromobenzoic acid when the
nitroxyl is replaced by bromine. The following two have been
prepared from rnetabromobenzoic acid and are converted into
anthranilic acid by reduction (Part III., p. 50). The S-acid is
obtained from parabromobenzoic acid and from metanitrobromo-
toluene, the e-acid from the corresponding amidonitrobenzoic
acid, and the f-acid by the oxidation of the corresponding
bromonitrotoluene.
IODONITROBENZOIC ACIDS, C 6 H 3 I(N0 2 )C0 2 H.
I : NO 2 Melting-point
a) 3:2 slightly soluble crystals l 235
/3) 3 : 6 readily soluble, melts under water 2 . . . 179
7) 3:4 readily soluble, does not melt under water 3 192
8) 4:3 readily soluble in alcohol, very slightly in
water* 210
The first three are formed by the nitration of meta-iodobenzoic
acid, and the last one from para-iodobenzoic acid.
MONAMIDOBENZOIC ACIDS, C 6 H 4 (NH 2 )C0 2 H.
2136 Ortho-amidobenzoic acid. Fritzsche, in his research on
aniline, mentioned that the product of the first action of potash
on indigo is a characteristic acid, which he subsequently obtained
pure by employing indigo-blue in the place of crude indigo.
He determined its composition, and his results were confirmed
by the remarkable decomposition which occurred on heating.
"Anthranilic acid decomposes when it is heated to a tempera-
ture just exceeding its melting-point into carbon dioxide, which
is given off as a gas, and aniline." 5
Liebig looked upon this research as of exceptional interest,
and its confirmation appeared to him to be so important and
1 Cunze and Hiibner, ibid, cxxxv. 106 ; Grothe, Journ. PraU. Chem. [2] xviii.
324. 2 Ibidf
4 Glassner, Her. Deutsch. Chem. Ges. viii. 562.
5 Journ. Prakt. Chem. xxiii. 67 ; Ann. Chem. Pharm. xxxix. 76.
238 AROMATIC COMPOUNDS.
necessary, that lie instituted further investigations, which cor-
roborated the results obtained by Fritsche. 1 At the same time
he discovered an excellent method for the preparation of
anthranilic acid, which will be described below.
Gerland subsequently showed that the acid in question is
isomeric with benzamic acid (metamidobenzoic acid). 2 Hiibner
and Petermann succeeded in preparing anthranilic acid syn-
thetically from benzoic acid ; by the nitration of metabromo-
benzoic acid, they obtained two isomeric nitrobromobenzoic
acids, C 6 H 3 Br(N0 2 )C0 2 H, both of which yielded anthranilic
acid on reduction (Part III., p. 50). It may be more simply
obtained by the reduction of orthonitrobenzoic acid with tin and
hydrochloric acid; 3 the tin is precipitated with sulphuretted
hydrogen and the filtrate evaporated to dryness, the residue
treated with an excess of ammonia and the solution then
acidified with acetic acid. The greater portion of the anthra-
nilic acid crystallizes out ; the remainder is then obtained as the
copper salt by the method described below.
Sandmeyer observed that almost half of the nitrobenzoic
acid is converted into salicylic, acid on reduction with tin and
hydrochloric acid. 4
In order to prepare it from indigo, the crude material is finely
powdered and boiled for ten hours with ten times its amount of
strong caustic potash solution, a small quantity of manganese
dioxide being occasionally added, and the original volume of the
solution maintained throughout the operation by the repeated
addition of small quantities of water. The solution is then
neutralized with sulphuric acid, freed from most of the potassium
sulphate by crystallization and evaporated to dryness. Potassium
anthranilate is extracted from the residue by alcohol and is then
converted into the copper salt, which is obtained as a light green
precipitate by distilling off the alcohol, acidifying with acetic
acid and adding copper acetate or sulphate; the free acid is
obtained from this by the action of sulphuretted hydrogen. 5
Bottinger found that the only definite compound formed in this
reaction, in addition to 28 per cent, of anthranilic acid, is formic
acid : 6
C 16 H 10 N 2 2 + 2O + 4H 2 O = 2C 7 H 7 N0 2 + 2CH 2 2 .
Ann. Chem. Pharm. xxxix. 91. 2 Ibid. Ixxxvi. 143.
Beilstein and Kuhlbcrg, Ann. Chcm. Pharm. clxiii. 138.
Ber. Dcutsch. Chem. Gcs. xviii. 1494.
Hiibner and Petermann, Ann. Chem. Pharm. cxlix. 142.
Ber. Dcutsch. Chcm. Gcs. x. 269.
PROPERTIES OF ORTHO-AMIDOBENZOIC ACID. 239
Ortho-amidobenzoic acid dissolves in about 250 parts of cold,
more readily in hot water, and readily in alcohol. The solution
has a sweet taste, but is acid to litmus paper, and shows a blue
fluorescence when the acid is pure. It crystallizes in small
plates, or on the gradual evaporation of its solution, in rhombic
needles, melts at 145, and sublimes when carefully heated, but
decomposes into carbon dioxide and aniline when distilled, more
completely when mixed with powdered glass (Liebig). On
treatment with sodium amalgam, benzoic acid and ammonia are
formed (Hiibner and Petermann) :
C 6 H 4 (NH 2 )C0 2 H + 2H=C 6 H 5 .C0 2 H + NH 3 .
Most of its metallic salts crystallize well.
Ortho-amidobenzoic acid hydrockloride, C 7 H 7 NO 2 .HC1, is readily
soluble in water and alcohol, slightly in ether, and crystallizes in
needles or four-sided prisms, melting at 191; its solution is not
precipitated by platinum chloride.
Formortho-amidobenzoic acid, 2C 6 H 4 (NH.CHO)C0 2 H + H 2 O,
is obtained by heating ortho-amidobenzoic acid with formic acid,
and crystallizes from chloroform in fine, matted needles, which,
after drying, form a light, very readily electrified mass, and melt
at 168. When it is heated with phosphorus pentoxide, phenyl
carbamine is formed. 1
Acctortlio-amidobenzoic acid, C 6 H 4 (NH.C 2 H 3 0)C0 2 H, is formed
by the oxidation of acetorthotoluide with potassium perman-
ganate, 2 and by heating a mixture of equal molecules of
anthranilic acid and acetic anhydride. 3 It is slightly soluble in
cold, readily in hot water, and crystallizes from acetic acid in
flat, rhombic needles, which melt at 179 180.
Diacetortho-amidobenzoic acid, C 6 H 4 N(C 2 H 3 O) 2 CO 2 H, is ob-
tained by boiling anthranilic acid with an excess of acetic
anhydride, and forms crystals, melting at 220 (Bedson and
King).
Benzortho-amidobenzoic acid, C 6 H 4 (NH.CO.C 6 H 5 )CO 2 H, is
formed by the action of benzoyl chloride on anthranilic acid
id by the oxidation of benzoylorthotoluide. It crystallizes
:om alcohol in long needles, melting at 182 . 4
1 v. Meyer and Bellmann, Journ. PraH. Chem. [2] xxxiii. 24.
2 Bedson and King, Ber. Deutsch. Chem. Ges. xiv. 263.
3 Jackson, ibid. xiv. 886.
4 Bruckner, Ann. Chem. Pharm. ccv. 134.
240 AROMATIC COMPOUNDS.
Ortho-amidobenzamide, C 6 H 4 (NH 2 )CO.NH 2 , is formed when
anthranilcarboxylic acid is dissolved in aqueous ammonia :
CO CO.NH 2
C 6 H 4 | + NH 3 = C 6 H + C0
N.C0H
It crystallizes from hot water in nacreous plates, and from
chloroform in large, white plates, melts at 108, and boils with
slight decomposition at about 300. It is converted into ortho-
amidobenzoic acid by acids and alkalis. 1
Ortho-amidobenzonitril, C 6 H 4 (NH 2 )CN, is obtained by the
action of tin and hydrochloric acid on orthonitrobenzonitril ; it
crystallizes in yellowish needles, melts at 103, and forms readily
soluble salts. 2
2137 Anthranil, C 7 H 5 NO, is formed by the action of tin on a
solution of orthonitrobenzaldehyde in glacial acetic acid, and is
a colourless, oily liquid, which has a characteristic, penetrating
smell, is volatile with steam, and commences to boil at 210 215,
the greater portion of it being decomposed. It rapidly becomes
brown and resinous when exposed to the air or to light. It is a
very feeble base, and combines with mercuric chloride to form the
compound C 7 H 5 NO + HgCl 2 , which crystallizes in fine needles
and is readily soluble in alcohol and hot water, but on heating
with a solution of potassium chloride, is resolved into its
constituents. 3
Anthranil is converted into anthranilic acid by the action of
alkalis :
/CO /CO.OH
C 6 H 4 < |
\NH
When heated with ammonia and ferrous sulphate it is con-
verted into orthonitrobenzaldehyde, while antkranilcarboxylic
acid is formed when it is heated with ethyl chlorocarbonate :
/CO /CO
C 6 H 4 < | +COC1(OC 2 H 6 ) = C 6 H 4 < | +C 2 H 5 C1.
\KCO.OH
This compound crystallizes from hot water in fine needles,
which decompose into carbon dioxide and anthranil at 230. It
1 Kolbe, Journ. PraU. Chem. [2] xxx. 475.
2 Barthlein, Ber. Dcutsch. Chem. Gei. x. 1713.
3 Friedlanderand Henriques, ibid. xv. 2105.
BENZOYLANTHRANIL. 241
dissolves in dilute caustic soda, forming a solution which possesses
a splendid blue fluorescence; this, however, soon disappears,
anthranilic acid being formed. Anthranilcarboxylic acid is also
obtained by the oxidation of isatin, and will be more fully
described along with this substance.
Benzoylanthranil is readily obtained by the action of benzoyl
chloride on anthranil :
/CO /CO
C 6 H 4 < | + COC1.C 6 H 5 = C 6 H 4 < | + HC1.
\NH \N.CO.C 6 H 5
It crystallizes from a mixture of benzene and ligroin in long
needles, which melt at 122 123, and dissolve when heated
with dilute alkalis, benzortho-amidobenzoic acid being formed. 1
Dicyanamidobenzoyl, C 9 H 5 N 3 0, is the name given by Griess to
a compound which he obtained by passing cyanogen into a cold
aqueous solution of anthranilic acid :
NH-C-CN
^2=C 6 H 4 < || +H 2 0.
X CO.OH XX) - N
It is slightly soluble in water, readily in hot alcohol, and
crystallizes in small, yellowish prisms ; although it does not
contain a carboxyl group, it has an acid reaction and is a
monobasic acid. 2
Carboxamidocyanamidobenzoyl, C 9 H 7 N 3 2 , is formed when the
preceding compound is heated with strong ammonia in a sealed
tube :
/NH-C-CN /NH-C-CO.NIL.
C 6 H 4 || +H 2 = C 6 H 4 ||
XX) -N X CO-N
It crystallizes from hot water in fine needles and from alcohol in
plates, has an acid reaction and forms salts with bases, the hydrogen
of the imido-group being probably replaced by the metal.
Carboxylcyanamiddbenzoyl, 2C 9 H 6 N 2 O 3 +H 2 O, is obtained by
heating dicyanamidobenzoyl with baryta water:
NH-C-CN /NH-C-CO.OH
C 6 H 4 < || +2H 2 = C 6 H/ || +NH 3 .
\CO-N XX) -N
1 Friedlander and Wleiigel, Ber. Dcutsch. Chem. Ges. xvi. 2227.
2 Ibid. xi. 1986 and 2180.
242 AROMATIC COMPOUNDS.
It crystallizes in small, white plates, which are slightly soluble
in cold water and alcohol; it is a dibasic acid. When it is boiled
with water or acids, or simply heated, carbon dioxide is evolved
and carbimidamidobenzoyl, C 8 H 6 N 2 O 2 , formed. This compound
crystallizes from hot water in needles melting at 214. It
possesses basic properties and has the following constitution :
CH
||
CO-N.
Griess has also prepared various other derivatives of dicyan-
amidobenzoyl. 1
Ethoxycyanamidobenzoyl, C 10 H 10 N 2 O 2 , is formed when an
alcoholic solution of anthranilic acid is saturated with cyanogen,
allowed to stand for some time and then evaporated :
,
C 6 H 4 <
X CO.OH
/NH C OC 2 H 5
C 6 H 4 < ||
\CO-N
It crystallizes from hot alcohol in needles, melts at 173, and
can be distilled in small quantities without undergoing
decomposition. 2
2138 Uramidobenzoyl, C 8 H 6 N 2 O 2 , is prepared by fusing
anthranilic acid with urea or by boiling the preceding com-
pound with hydrochloric acid :
NH C OC 2 H 5 ,NH CO
It is slightly soluble in water and alcohol, crystallizes in lustrous
plates melting above 350, dissolves in caustic potash solution
and is reprecipitated by carbon dioxide. Fuming nitric acid
converts it into nitro-uramidobenzoyl, C 8 H 5 (N0 2 )N 2 O 2 , which
crystallizes in honey-yellow prisms, and is converted by reduction
into the slightly soluble amido-uramidobenzoyl, C 8 H 5 (NH2)N 2 O 2 ,
1 Bcr. Deutsch. Chem. Ges. xviii. 2417.
2 Griess, ibid. ii. 415.
BENZOYLGUANIDINE. 243
which forms yellow needles and yields salts, which are also only
slightly soluble and crystallize well (Griess).
Ortho-uramidobenzoic acid, C 8 H 8 N 2 3 . This compound, which
is the acid corresponding to the anhydride just described, is
formed by the action of potassium cyanate on ortho-amidobenzoic
acid hydrochloride : l
/NH 2 /NH.CO.NH 2
C 6 H 4 < +CONH=C 6 H 4 <
\C0 2 H \C0 2 H.
It crystallizes in needles, and on treatment with nitric acid
only yields one dinitro-compound, which will be subsequently
mentioned.
Orthobenzoglycocyamidine, or Benzoylguanidine, C 8 H 7 N 3 O, is
obtained by heating ethoxycyanamidobenzoyl with alcoholic
ammonia :
^NH-C OC 2 H 5
l \CO N
[ C=NH
It may also be obtained by allowing a solution containing
cyanamide and anthranilic acid to stand : 2
C 6 H 4 .NH 2 C 6 H 4 NH
+ CN.NH 2 = | >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 <f is formed
\CH(OCO.CH 3 ) 2 ,
when salicylaldehyde is heated to 150 with acetic anhydride;
it crystallizes from alcohol in thick, hard, transparent tablets,
which melt at 103 104, and distil with slight decom-
position. 2
Perkin has obtained the following compounds in a similar
manner :
/OCH 3 Melting-point.
C 6 H 4 <^ , lustrous prisms ..... 75
\CH(OCO.CH 3 ) 2
/OC 2 H 5
C 6 H 4 < , small prisms ...... 88 89
\CH(OCO.CH 3 ) 2
C 6 H 4 <( , needles or pointed tablets 100 101
\CH(O.CO.CH 3 ) 2
The last compound may also be obtained by heating salicyl-
aldehyde to 180 with acetic anhydride. 3 Tolerably concentrated
caustic potash decomposes it into acetic acid and orthohydroxy-
benzidene acetate, while it splits up- on distillation into acetyl-
salicylaldehyde and acetic anhydride. 4
Orthohydroxylenzidenoxime, or Salicylaldoxime, C 6 H 4 (OH)
CH:=N.OH, is formed by the action of hydroxylamine on
salicylaldehyde, and forms white crystals which dissolve readily
in alcohol, ether and benzene, but are insoluble in petroleum
spirit, and melt at 57. 5 Its compounds resemble those of
benzaldoxime (p. 139).
1 Rossing, Ber. Deutsch. Chem. Ges. xvii. 2988.
2 Perkin, Ann. Chem. Pharm. cxlvi. 371.
3 Barbier, Bull. Soc. Chim. xxxiii. 53.
* Perkin, Ann. Chem. Pharm. cxlviii. 203.
6 Lach, Ber. Deutsch. Chem. Ges. xvi. 1782.
HYDROSALICYL AMIDE. 29 1
Hydroxylenzidene-amidobenzoic acid, C 6 H 4 (OH)CH=:NC 6 H 4
C0 2 H, is prepared by mixing warm, dilute, aqueous solutions
of salicylaldehyde and metamidobenzoic acid. It crystallizes in
long, yellow needles, which are very soluble in alcohol and
benzene. Its aqueous solution gives off salicylaldehyde on
evaporation. 1
Helicin combines with metamidobenzoic acid to form the
analogous compound C 6 H 4 (OC 6 H n 5 )CH:=NC 6 H 4 .C0 2 H, which
crystallizes from alcohol in lustrous plates, melting at 142 ; 2 it
is resolved into the preceding compound and grape sugar by
heating with an aqueous solution of emulsin.
Hydrosalicylamide, N 2 (CH.C 6 H 4 .OH) 3 . This compound, cor-
responding to hydrobenzamide (p. 140), was prepared by Ettling
by the action of ammonia on an alcoholic solution of salicylalde-
hyde, and named by him salicylimide. 3 It forms heavy, light
yellow crystals, melting at 300, and is insoluble in water, slightly
in cold, more readily in hot alcohol, and decomposes into salicyl-
aldehyde and ammonia when heated with concentrated caustic
potash solution or strong acids. It absorbs three molecules
of hydrochloric acid, forming a compound which decomposes
in moist air into salicylaldehyde and ammonium chloride. 4
As a phenol it forms metallic salts ; when an ammoniacal
solution of copper acetate is added to its cold alcoholic solu-
tion, the liquid becomes coloured emerald-green, and after a
few minutes becomes decolourized, cruciform plates being de-
posited, which after drying have a strong satin lustre; their
composition is represented by the formula (C 21 H 15 N 2 3 ) 2 Cu 3
(NH 3 ) 2 . They are almost insoluble in water and alcohol, and
form a green solution in hydrochloric acid, from which they are
reprecipitated by alkalis. They are not attacked by cold caustic
potash, and decomposition only proceeds slowly on boiling ;
salicylaldehyde is formed when it is heated with strong acids.
Orthobenzidenephenylhydmzine, C 6 H 4 (OH)CH=N 2 H.C 6 H 5 ,
crystallizes from hot, dilute alcohol in yellow needles or plates,
melting at 142 143. When it is heated with chloracetic
acid a colouring matter, C 9 H 7 NO 3 , is produced, which forms a
deep bluish green solution in alcohol and is coloured cherry-red
by alkalis. 5
1 Schiff, Ann. Chem. Pharm. ccx. 114.
2 Ber. Deutsch. Chem. Ges. xii. 2032.
3 Ann. Chem. Pharm. xxxv. 261.
4 Bode, Jahresb. Chem. 1857, 318.
6 Fischer, Ber. Deutsch. Chem. Ges. xvii. 575 ; Rossing, ibid. 3004.
292 AROMATIC COMPOUNDS.
SUBSTITUTION PRODUCTS OF SALICYL-
ALDEHYDE.
2167 ChlorosalicylaldeJiyde, C 6 H 3 C1(OH)CHO, is formed by
the action of chlorine on salicylaldehyde. 1 It is insoluble in
water, and crystallizes from alcohol in rectangular tablets.
Bromosalicylaldehyde, C 6 H 3 Br(OH)CHO, is not only formed by
the direct action of bromine 2 but also when salicylaldehyde is
treated with phosphorus pentabromide, the latter compound act-
ing in the same manner as a mixture of bromine and phosphorus
pentabromide. 3 It crystallizes from ether in small plates, melt-
ing at 98 99 ; its alcoholic solution is coloured violet by ferric
chloride.
Melting-point.
Methylbromosalicylaldehyde, flat prisms )-,-,QO n A -
C 6 H 3 Br(OCH 3 )CHO. j 1
Ethylbromosalicylaldehyde, 4 sharp prisms ] a ^ aQO
C 6 H 3 Br(OC 2 H 5 )CHO. j b7 "
a-Nitrosalicylaldehyde, C 6 H 3 (NO 2 )(OH)CHO, is formed, to-
gether with the /3-compound, by boiling salicylaldehyde with
dilute nitric acid ; 5 the two substances are separated by means
of their barium salts. a-Nitrosalicylaldehyde crystallizes in
small yellow prisms, which melt at 105 107, while its barium
salt, (C 7 H 4 NO 4 ) 2 Ba + 2H 2 0, forms slightly soluble, yellowish red
columns.
ft-Nitrosalicylaldeliyde forms needles, melting at 123 125;
its barium salt, (C 7 H 4 N0 4 ) 2 Ba + 6H 2 O, crystallizes in yellow
prisms.
Methylnitrosalicylaldehyde, C 6 H 3 (N0 2 )(OCH 3 )CHO, forms fine,
white needles, melting at 88. 6
1 Piria, Ann. Chem. Pharm. xxx. 169 ; Lbwig, Bcrz. Jahresb. xx. 311.
2 Piria ; Lowig, Pogg. Ann. xlvi. 57 ; Heberlein, Berz. Jahresb. xxv. 484.
3 Henry, Ber. Deutsch. Chem. Ges. ii. 274.
4 Perkin, Ann. Chem. Pharm. cxlv. 304.
5 Mazzara, Gazz. Chim. Ital. vi. 460.
6 Voswinkel, Ber. Deutsch. Chem. Ges. xv. 2027 ; Schnell, ibid. xvii. 1381.
METAHYDROXYBENZALDEHYDE. 293
METAHYDROXYBENZALDEHYDE.
2168 This compound is formed, together with metahydroxy-
benzyl alcohol, by the action of sodium amalgam on a faintly
acid solution of metahydroxybenzoic acid. It can be more
readily obtained from metamidobenzaldehyde by treating its
well-cooled solution in hydrochloric acid with the calculated
quantity of sodium nitrite and then heating. 1 It crystallizes
from hot water in white needles, melting at 104; its aqueous
solution is coloured a faint violet by ferric chloride, and it differs
from the isomeric para-compound in giving a precipitate with
lead acetate.
Methylmetahydroxylenzaldehyde, C 6 H 4 (OCH 3 )CHO, is obtained
by heating the aldehyde with caustic potash, methyl iodide and
wood-spirit. It is an oily liquid, which boils at 230 and has a
pleasant odour.
Acetylmetaliydroxylienzaldehyde, C 6 H 4 (OCO.CH 3 )CHO, is
formed by the action of acetic anhydride on the potassium
compound of the aldehyde, and is an oily liquid, boiling
at 263.
Acetometahydroxylenzidene acetate, C 6 H 4 (OCO.CH 3 )CH(O.
CO.CH 3 ) 9 , is produced when the aldehyde is boiled with an
excess of acetic anhydride. It is slightly soluble in water,
readily in alcohol, and crystallizes in lustrous, white plates,
melting at 76.
Nitro-8ub$tttution products. The three following compounds
are all formed by the direct nitration of the aldehyde ; they
may be separated by re -crystallization from hot water, chloro-
form, &c.
a-Nitrometahydroxylenzaldehyde, C 6 H 3 (N0 2 )(OH)CHO, crys-
tallizes in yellowish plates, melting at 128, which are slightly
soluble in cold, more readily in hot water, and readily in
chloroform and petroleum ether.
f$-Nitrometahydroxyl)enzaldehyde forms needles which melt at
166, and is more readily soluble in water than the a-compound,
but only very slightly soluble in chloroform and benzene.
y-Nitrometahydroxylenzaldehyde melts at 138, and crystallizes
1 Tiemann and Ludwig, Ber. Deutsch. Chem. Ges. xv. 2043 and 3052.
250
294 AROMATIC COMPOUNDS.
in prisms, which dissolve readily in hot water, chloroform and
benzene, but only with difficulty in petroleum ether.
When these compounds are heated with caustic potash, wood-
spirit and methyl iodide, their methyl ethers, C 6 H 3 (N0 2 ) (OCH 3 )
CHO, are formed (Tiemann and Ludwig) ; these can also be
obtained by the nitration of metamethoxybenzaldehyde. 1
a-Orthonitroniethylmetahydroxybenzaldehyde crystallizes from
chloroform in thick, yellow prisms, melting at 107.
(3-Orthonitromethylmetahydroxybenzaldehyde forms white plates
or needles, which melt at 82 83.'
These bodies are known to be orthonitro-compounds because
they give the indigo reaction (p. 146).
Metanitromethylmetahydroxybenzaldehyde crystallizes in needles
or prisms, and melts at 98.
ParanitrometTiylmetahydroxybenzaldehyde was obtained by
Ulrich by the oxidation of paranitromethoxycinnamic acid ; it
crystallizes in hair-like needles and melts at 62.
PARAHYDROXYBENZALDEHYDE.
2169 This body was first prepared by Bucking by heating the
methyl ether, anisaldehyde, with hydrochloric acid. 2 It may be
synthetically obtained by the action of chloroform on an alkaline
solution of phenol, salicylaldehyde being formed at the same time.
In order to prepare it, 30 parts of chloroform are gradually
added to a solution of 20 parts of phenol in 120 parts of water
heated to 50 60 ; the liquid becomes coloured blue and then
deep red, a considerable rise of temperature taking place, the
use of an inverted condenser being thus rendered necessary.
The mixture is finally boiled for half an hour, the excess of
chloroform distilled off, an excess of sulphuric acid added, and
the whole distilled in steam, salicylaldehyde passing over along
with any free phenol, from which it is subsequently separated by
means of acid sodium sulphite. The residual liquid is filtered while
hot from the deep red coloured resin which is formed, and after
cooling is extracted with ether ; on evaporation of the ether, the
parahydroxybenzaldehyde is left behind, and is then re-crystall-
ized from boiling water. 3 It is slightly soluble in cold, more readily
1 M. Ulrich, Ber. Deutsch. Chem. Ges. xviii. 2571. 2 Ibid. ix. 527.
3 Reimer and Tiemann, ibid. ix. 824 ; Tiemann and Herzfeld, ibid. x. 63.
PARAHYDROXYBENZALDEHYDE. 295
in hot water, and readily in alcohol, ether, &c., and crystallizes
in fine needles, which have a faint but pleasant aromatic odour,
melt at 115 116, and sublime unaltered. Its aqueous solu-
tion is coloured a dirty violet by ferric chloride ; if its ethereal
solution be shaken up with a solution of acid sodium sulphite,
combination ensues, but the double compound is readily soluble.
Its solution is not easily attacked by oxidizing agents, but it is
converted into parahydroxybenzoic acid by fusion with caustic
potash at a low temperature.
Methylparahydroxybenzaldeliyde, C 6 H 4 (OCH 3 )CHO. Cahours
prepared this compound by the oxidation of oil of anise seed, 1
while Cannizzaro and Bertagnini obtained it by oxidizing anise
alcohol (p. 284), and named it anisaldehyde. 2 Piria then showed
that it is also formed by distilling a mixture of calcium formate
and calcium anisate (methylparahydroxybenzoate) ; 3 and Tie-
mann and Herzfeld obtained it by heating parahydroxybenz-
aldehyde with methyl iodide, wood -spirit and caustic potash.
It may be most readily prepared from oil of anise, which
consists for the most part of anethol, C 3 H 5 .C 6 H 5 .OCH 3 , the
methyl ether of allylphenol. One part of this is brought into a
cold solution of 2 parts of potassium dichromate, 3 parts of
sulphuric acid, and 8 parts of water. As soon as the temperature
ceases to rise, the mixture is diluted with half its volume of
water and distilled, the quantity of liquid in the distilling flask
being kept at its original volume by the gradual addition of
water. The distillate is repeatedly rectified, the aldehyde
coming over in the first portions, which are then shaken up with
a concentrated solution of acid sodium sulphite. The crystals,
which separate after some time, are washed with alcohol and
decomposed by carbonate of soda solution. 4
Anisaldehyde is a liquid which has an aromatic odour, boils at
247 248, and dissolves slightly in cold, more readily in hot
water ; it readily takes up oxygen from the air and is converted
by alcoholic potash into a mixture of anise alcohol and anisic
acid. When heated with dilute hydrochloric acid to 200, it
decomposes into parahydroxybenzaldehyde and methyl chloride
(Bucking).
Acetylparahydroxylenzaldehyde, C 6 H 4 (OCO.CH 3 )CHO, is ob-
tained by dissolving 2 parts of parahydroxybenzaldehyde and
1 part of caustic potash in water, evaporating and treating the
1 Ann. Chem. Pkarm. Ivi. 307. 2 Ibid, xcviii. 189.
3 ibid. c. 105. 4 Rossel, ibid. cli. 28.
296 AROMATIC COMPOUNDS.
residue with acetic anhydride in presence of ether (Tiemann
and Herzfeld).
It is also formed by the action of acetic anhydride on the
aldehyde, 1 and is a liquid, boiling at 264 265, which forms an
almost insoluble compound with acid sodium sulphite.
Acetylparakydroxybenzidene acetate, C 6 H 4 (OCO.CH 3 )CH(OCO.
CH 3 ) 2 , is prepared by heating the aldehyde with three times its
weight of acetic anhydride. It is readily soluble in hot water
and alcohol, and crystallizes from ether in flat prisms, melting
at 93 94 (Tiemann and Herzfeld).
Parahydroxybenzaldoxime, C 6 H 4 (OH)CH=:NOH, forms odour-
less, white needles. 2
Chloroparahydroxylenzaldehyde, C 6 H 3 C1(OH)CHO, crystallizes
from hot water in silky needles melting at 148 149 ; its aqueous
solution is coloured violet by ferric chloride.
Bromoparahydroxybenzaldehyde, C 6 H 3 Br(OH)CHO, is almost
insoluble in water, crystallizes from alcohol in long, strongly
refractive needles, melting at 179- 180, and does not give any
colouration with feme chloride.
lodoparahydroxylenzaldeliyde, C 6 H 3 I(OH)CHO, is formed
when parahydroxybenzaldehyde is boiled with iodine and dilute
alcohol. It is slightly soluble in water, readily in alcohol, and
separates from chloroform in white crystals, melting at 198
199. On heating with caustic potash it yields protocatechuic
acid. 3
Nitroparahydroxylenzaldehyde, C 6 H 3 (N0 2 )(OH)CHO. Maz-
zara obtained this substance by boiling the aldehyde with dilute
sulphuric acid, 4 and Herzfeld by adding concentrated nitric
acid to a solution of parahydroxybenzaldehyde in concentrated
sulphuric acid. 5 It is soluble in boiling water and alcohol, and
crystallizes in yellowish needles melting at 139 140. Its
aqueous solution gives a fugitive red colouration with ferric
chloride. It decomposes carbonates ; the potassium salt, C 6 H 3
(NO 2 )(OK)CHO + H 2 0, forms golden-yellow tablets.
1 Barbier, Bull. Soc. CMm. xxxiii. 54.
2 Lach, Ber. Deutsch. Chem. Ges. xvi. 1785.
3 Herzfeld, ibid. x. 2196.
4 Gfaz. Chim. Ital. vii. 285.
6 Ber. Dcutsch, Chem. Ges. x. 1269.
SALICYLIC ACID. 297
/OH
HYDROXYBENZOIC ACIDS, C 6 H 4 <
X C0 2 H.
OETHOHYDROXYBENZOIC ACID, OR SALICYLIC ACID.
2170 The history of this important substance is of special
interest because its genetic relations to the benzoyl and cinnamyl
groups and to indigo blue were known at a very early period.
Piria, who prepared it in 1838, by heating the aldehyde with
caustic potash, 1 pointed out that the radicals benzoyl and salicyl
are different oxidation products of the hydrocarbon or radical
C 7 H 5 (p. 285). Marchand 2 and Gerhardt 3 found that it is also
formed when salicin is melted with potash, and is converted by
dilute nitric acid into nitrosalicylic acid, which is identical with
indigotic or anilotic acid, a substance obtained by the action of
nitric acid on indigo which had long been familiar to chemists.
This compound on fusion with potash at a low temperature
yields anthranilic acid (p. 237), while Cahours, by carrying out
the operation at a higher temperature, obtained salicylic acid ; 4 it
was obtained, together with acetic acid, in a similar manner
from cumaric acid by Delalande, who remarked that this latter
compound bears the same relation to cinnamic acid as salicylic
to benzoic acid. 5 Ettling, who prepared salicylic acid by
oxidizing its aldehyde with potassium dichromate and sulphuric
acid, found that it can also be obtained by heating the copper
salt of this or of benzoic acid, and is therefore an oxidation
product of the latter. 6 Gerhardt had previously observed that
salicylic acid decomposes on heating into phenol and carbon
dioxide, just as anthranilic acid is split up into aniline and
carbon dioxide. A series of relations was thus established
among the following compounds:
Benzene Benzoic acid Cinnamic acid
C 6 H 6 C 7 H 6 O 2 C 9 H 8 O 2
Phenol Salicylic acid Cumaric acid
C e H 6 C 7 H 6 S C 9 H 8 3
Aniline Anthranilic acid
C 6 H 7 N C 7 H 7 N0 2
1 Ann. Chim. Phys. Ixix. 298 ; Ann. Chem. Pharm. xxx. 1 65.
2 Journ. Prakt. Chem. [1] xxvi. 396. 3 Ann. Chem. Pharm. xlv. 19.
* Ibid. lii. 343. s Ibid. xlv. 336. 6 Ibid. liii. 77.
298 AEOMATIC COMPOUNDS.
Hofmann found that aniline is converted into phenol by the
action of nitrous acid, and suggested that anthranilic acid would
probably yield salicylic acid when treated in a similar manner,
this suggestion being experimentally verified by Gerland. 1
Salicylic acid was obtained synthetically by Kolbe and Laute-
mann by the action of carbon dioxide on a mixture of phenol
and sodium. 2 The former chemist found that it is also formed
when carbon dioxide is passed over heated sodium phenate, half
of the phenol being set free : 3
/ONa
2C 6 H 5 .ONa + CO 2 = C 6 H / + C 6 H 5 OH.
\C0 2 Na
Ethyl salicylate may be prepared by the action of sodium on
a mixture of phenol and ethyl chloroformate : 4
/OH
C 6 H 5 .ONa 4- C1C0 2 .CLH 6 = C 6 H 4 < + NaCl.
X C0 2 .C 2 H 5
The acid is also formed, together with parahydroxybenzoic
acid, when a mixture of tetrachloromethane and phenol is heated
to 100 with alcoholic potash (Part III. p. 32). 5
It may also be obtained by fusing orthocresol, 6 toluene-
orthosulphonic acid, 7 &c., with caustic potash, as well as by
heating copper benzoate to 180 with water, 8 and when sodium
is allowed to remain in contact with ethyl succinate for a long
time. 9 It has also been observed as a product of the action
of hydrogen dioxide on a solution of benzoic acid in sulphuric
acid. 10
Salicylic acid also occurs in nature. Lb'wig and Weidmann
detected it in the flowers of Spircea Ulmaria, accompanied by
salicylaldehyde, but did not actually identify it. Its methyl
ether is contained in the ethereal oils of the various species of
Gaultheria.
21 j i It was formerly prepared exclusively from the winter-
1 Ann. Chem. Pharm. Ixxxvi. 147.
2 Ibid. cxv. 201.
3 J&urn. Prakt. Chem. [2] x. 89.
4 Wilm and Wischin, Zcitschr. Chem. 1868, 6.
3 Reimer and Tiemann, Ber. Deutsch. Chem. Ges. ix. 1285.
6 Earth, Ann. Chem. Pharm. cliv. 360.
7 Wolkow, Zeitschr. Chem. 1870, 326.
8 Smith, Amer. Chem. Journ. ii. 338.
9 Herrmann, Ber. Deutsch. Chem. Ges. x. 646.
10 Hanriot, Compt. Rend. cii. 1250.
SALICYLIC ACID.
green oil obtained from Gaulthcria procumbms by saponifying
with potash and decomposing the product with hydrochloric
acid. It is now manufactured by Kolbe's process.
The calculated quantity of pure phenol is dissolved in strong
caustic soda solution, the whole evaporated to dryness and the
residue rubbed into a dry powder ; this is then gradually heated
up to 180 in a metal retort in a current of carbon dioxide which
has been previously warmed. After some time phenol com-
mences to distil over, and is subsequently given off in larger
quantity; the temperature is then raised to 200, and the
operation continued until no more phenol comes over. The
residue is dissolved in water and fractionally precipitated with
hydrochloric acid ; resinous and colouring matters are first thrown
down, followed by tolerably pure acid, which is re-crystallized
from water and purified by distillation with superheated steam. 1
According to another patented process, carbonyl chloride,
which is now manufactured on a large scale, is passed into a
mixture of sodium carbonate and phenate heated to 140, the
temperature being finally raised to 200 . 2
Various hypotheses were proposed to explain the course of
the reaction which occurs when sodium phenate is heated in a
stream of carbon dioxide. The correct explanation was found
by R. Schmitt. 3 Pure dry sodium phenate absorbs carbon
dioxide with formation of sodium phenylcarbonate,CoH. 5 O.CQ.O]$a,,
as a white powder which is instantly decomposed by water,
phenol and sodium bicarbonate being formed. When heated in
a closed tube to 120 130, it is converted quantitatively into
monosodium salicylate. In Kolbe's reaction, this complete decom-
position does not take place, and the monosodium salicylate
reacts with the sodium phenate at a higher temperature, phenol
being liberated :
O.C 6 H 5 C 6 H 4 .OH
NaO.C 6 H 5 + CO 9 =
CCXNa CO Na.
C 6 H 4 .OH C 6 H 4 ONa
| + NaO.C 6 H 5 = | +C 6 H 5 .OH.
C0 2 Na C0 2 Na
Salicylic acid is, therefore, best prepared by bringing abso-
lutely dry sodium phenate into an autoclave, pumping in rather
1 Rautert, Compt. Rend. viii. 537.
2 Ibid, xviii. Ref. 90.
3 Journ. Prakt. Chcm. [2] xxxi. 397.
300 AROMATIC COMPOUNDS.
more than the calculated quantity of carbon dioxide, the mass
being kept cool during the absorption, or, better, adding it in
the solid form, agitating for some time and then heating to
120 ISO . 1
2172 Salicylic acid has a slightly acid,, astringent and at the
same time sweet taste ; it dissolves slightly in cold, more readily
in hot water, from which it crystallizes in fine needles, while it
is deposited in monoclinic prisms from an alcoholic solution
which is allowed to evaporate spontaneously.
100 parts of water dissolve at :
15 100
0-085 0-225 7-925 parts.
Absolute alcohol and ether dissolve about half their weight of
the acid ; 2 it is also readily soluble in chloroform, differing in
this respect from its isomerides, and is dissolved by solutions
of the acetates and citrates of the alkali metals. 3
Its aqueous solution is coloured deep violet by ferric chloride ;
free acids, especially acetic and hydrochloric acids, hinder the re-
action. 4 It prevents the precipitation of copper salts by alkalis,
while its isomerides have not this property. 5 Strong boiling
nitric acid converts it into picric acid, and chromic acid oxidizes
it to water, carbon dioxide and a little formic acid. 6
It melts at 155 156 , 7 and sublimes on gradual heating, but
partially decomposes into carbon dioxide and phenol when
rapidly heated. It is completely split up when heated to
250 260 for two hours in a sealed tube ; on cooling, the
compound of these two substances, which has already been
described, separates out (Part III. p. 102). 8 This decomposition
also occurs when the acid is heated for a long time to 220 2.30
with water, and more rapidly in presence of hydrochloric -acid at
140 150 . 9 Sodium amalgam only acts upon it in acid solu-
tion ; a resinous substance, probably saliretin, being formed. 10 In
order to test the purity of salicylic acid, a piece the size of a pea
Bcr. Deutsch. Chem. Gcs. xvii. Kef. 624 ; Schmitt, loc. cit.
On Solubility, &c., see Ost, Juurn. Prakt. Chem. [2] xvii. 232 ; Bourgoin,
Bull. Soc. Ghim. xxix. 247 ; xxxi. 57.
R other, Pharm. Journ Trans. 1886, 328.
Pagliani, Bcr. Deutsch. Chem. Gcs. xii. 385. 5 Weith, ibid. ix. 342.
Kraut, Ann. Chem. Pharm. cl. 9. 7 Hiibner, ibid, clxii. 74.
Klepl, Journ. Prakt. Chem. [2] xxv. 464.
Grabe, ibid, cxxxix. 143.
10 Velden, Journ. Prakt. Chem. [2] xv. 164.
THE SALICYLATES. 301
is ground up with five ccs. of concentrated sulphuric acid, in
which it should form a perfectly colourless solution. 1 Its alcoholic
solution evaporated on a watch-glass should yield perfectly
clear and colourless crystals : if they are yellow or brown, the
sample contains admixed resins or colouring matters, while if
they are pink or violet, iron is present.
As salicylic acid decomposes so readily into carbon dioxide and
phenol, Kolbe considered that it would, like the latter, be a
powerful antiseptic, and subsequently verified this conclusion by
experiment. It has very rapidly come into favour both for
technical and household purposes, and is preferable to phenol
because it has no smell and is not poisonous. Its isomerides,
according to Kolbe, are not antiseptics. 2 Salicylic acid is also
employed in medicine, both for external and internal application.
Several physicians have observed that the acid prepared from
winter-green oil acts more powerfully than that obtained
artificially, but this may possibly be due to the fact that the
acid which first came into the market contained a considerable
amount of impurity. 3
2173 The Salicylates. Salicylic acid was first thought to be a
monobasic acid, but was afterwards regarded as dibasic. Piria
observes on this point : " Salicylic acid differs in a most striking
manner from other monobasic acids in forming acid ethers, which
are more fitly compared with the acid ethers of polybasic acids
than with the neutral ethers. In the course of researches which
I have instituted upon this question, I have succeeded in finding
the cause of this exception, or rather in showing that the behaviour
of this acid is not exceptional. Salicylic acid, which has
hitherto been looked upon as monobasic, is actually dibasic, and
very markedly so ; it forms salts with two equivalents of a base
so readily that it is singular that they have remained so long
unnoticed. In the following, I shall call salts containing one
equivalent of base, which have been previously described, acid
salicylates, and those discovered by me, containing two equivalents
of base, neutral salicylates." 4
This view was accepted by most chemists, but Kolbe con-
sidered it to be a monobasic hydroxy-acid. Further researches
have shown that it is both a monobasic acid and a phenol, and
1 Hager, Frcsenius' Zeitschr xvi. 259.
2 Journ. Prakt. Chem. [2] xi. 9.
3 Williams, Yearbook of Pharm. 1884, 424.
4 Ann. Chem. Pharm. xciii. 262.
302 AROMATIC COMPOUNDS.
therefore contains two hydrogen atoms which are easily replaced
by metals. The salts thus obtained are usually called basic
salicylates, while those formed by the replacement of the
hydrogen of the carboxyl group are known as normal salicylates.
The latter have recently been carefully examined by Milone. 1
Potassium salicylate, C 6 H 4 (OH)CO 2 K, is obtained by dissolving
the acid in potassium carbonate solution, evaporating and ex-
tracting the residue with alcohol. It is deposited in needles on
the spontaneous evaporation of its aqueous solution. When
heated to 210 220, it decomposes quantitatively into basic
potassium parahydroxybenzoate, phenol and carbon dioxide :
/OH /OK
2C 6 H/ = C 6 H 4 <( + C 6 H 5 .OH + CO 2 .
\C0 8 K \C0 2 K
If a solution of one molecule of the acid and two molecules
of caustic potash be evaporated to dryness, and the residue
heated to 220, the basic salt of parahydroxybenzoic acid is also
formed, together with phenol :
/OK /OK
2C 6 H 4 <( + H 9 = C 6 H 4 <; + C 6 H 6 .OH + K 2 C0 3 .
X C0 2 K \C0 2 K
If, however, three or more molecules of potash are employed,
the salicylic acid is not changed ; if four are taken, complete
decomposition into carbon dioxide and phenol sets in at 300,
while in the presence of six molecules, the acid remains quite
unaltered even at this temperature. 2 Rubidium salicylate
behaves in a precisely similar manner on heating. 3
Sodium salicylate, C 6 H 4 (OH)CO 2 Na, forms silky tablets or a
crystalline powder, and has an unpleasant sweet taste. It
dissolves in its own weight of water and is used in medicine.
On heating to above 200, phenol and carbon dioxide are given
off, the basic salt remaining behind, but not a trace of the para-
acid is formed even at 300. When salicylic acid is heated to
this temperature with four molecules of caustic soda, it decom-
poses into phenol and carbon dioxide, while if eight molecules
are added the greater portion of it remains unaltered (Ost).
1 Gaz. Chim. Ital. xv. 219.
2 Ost, Journ. Prakt. Chem. [2] xi. 391.
3 v. d. Velden, ibid. [2] xv. 151.
THE SALICYLATES. 303
Inversely, sodium parahydroxybenzoate is converted into
basic sodium salicylate, phenol and carbon dioxide, when it is
heated to 290 in a current of carbon dioxide, 1 while hydroxy-
isophthalic acid, C 6 H 3 (OH)(CO 2 H) 2 , and hydroxytrimesic acid,
C 6 H 2 (OH)(C0 2 H) 3 , are formed at temperatures above 300.
When equal molecules of salicylic acid and its normal salt
are dissolved in alcohol and the solution concentrated, hard,
clear crystals of C 7 H 6 3 -f C 7 H 5 NaO 3 are obtained, which are
converted by water into pseudomorphs of salicylic acid. 2
Lithium salicylate is converted into the basic salt at 300
without any formation of parahydroxybenzoic acid.
Thallium salicylate, C 6 H 4 (OH)C0 2 T1, is obtained by neutra-
lizing the acid with thallium carbonate ; its hot, concentrated
solution deposits coarse needles on cooling. If the calculated
quantity of thallium hydroxide be added to the solution, the
basic salt, C 6 H 4 (OT1)CO 2 T1, separates out in yellow, nacreous,
rhombic tablets, which are only very slightly soluble in water.
This compound is also formed, together with phenol, when the
normal salt is heated to 300, while at a higher temperature the
salicylic acid is partially converted into parahydroxybenzoic
acid and hydroxyisophthalic acid (v. d. Velden).
Ammonium salicylate, 2C 6 H 4 (OH)CO 2 NH 4 + H 2 0, forms
readily soluble, monoclinic crystals ; when heated in a current of
ammonia it decomposes into phenol and ammonium carbonate.
The methylamine and aniline salts behave in a similar manner,
while tetra-ethylammonium salicylate decomposes on heating
into tri-ethylamine and ethyl salicylate. 3
Calcium salicylate, (C 7 H 5 3 ) 2 Ca + 2H 2 O, is readily soluble in
water, and crystallizes in octohedra ; when it is heated with a
solution of calcium sucrate, or when salicylic acid is heated with
an excess of milk of lime, the basic salt, C 7 H 4 3 Ca + H 2 O, is
formed as a sandy, crystalline powder, which is almost insoluble
in water and has an alkaline reaction (Piria).
Barium salicylate, (C 7 H 5 O 3 ) 2 Ba + H 2 O, is obtained by boiling
the acid with water and barium carbonate ; it crystallizes in
stellate aggregates of silky needles. When baryta water is
added to its boiling concentrated solution., the slightly soluble,
alkaline, basic salt, C 7 H 4 O 3 Ba + 2H 2 O, separates out in small
plates or needles.
* Kupferberg, Journ. Prakt. Chem. [2] xiii. 104.
2 Hofraann, Arch. Pharm. [3] xii. 226.
3 Kupferberg, Journ. Prakt. Chem. [2] xvi. 437.
304 AROMATIC COMPOUNDS,
Lead salicylate, (C 7 H 5 O 3 ) 2 Pb 4- H 2 O, separates from boiling
water in transparent crystals ; when it is boiled with water, or
when lead acetate is added to its hot solution, a slightly soluble,
crystalline precipitate of C 7 H 4 O 3 Pb is formed. If, however,
ammonia be added, and the solution boiled, the basic salt,
2(C 7 H 4 3 )Pb + 3PbO, is formed ; it is a light powder consisting
of micaceous plates.
Copper salicylate, (C 7 H 5 O 3 ) 2 Cu + 4H 2 O, is best prepared by
decomposing the barium salt with copper sulphate ; it crystal-
lizes in long, bluish green needles, which are readily soluble in
water, and on boiling with it form the basic salt, C 7 H 4 O 3 Cu -f H 2 O,
which is a yellowish green powder.
Basic copper potassium salicylate, C 7 H 4 O 3 Cu -f- C 7 H 4 3 K 2 +
4H 2 O, is formed by adding salicylic acid to a solution of copper
tartarate in tolerably strong caustic potash; a green mass of
crystals is formed, which is dried on a porous plate and re-
crystallized from a little lukewarm water. Small, emerald-green,
rhombic tablets are thus obtained, which are insoluble in alcohol,
and form a dark blue solution in caustic potash. When the
aqueous solution is boiled it becomes colourless and deposits
black copper oxide. Barium chloride produces, on standing, a
green, crystalline precipitate of C 7 H 4 O 3 Cu + C 7 H 4 O 3 Ba + 4H 2 O.
Silver salicylate, C 7 H 5 O 3 Ag, is a precipitate which crystallizes
from boiling water in very lustrous, transparent needles.
Borondisalicylic acid, B(OH)(OC 6 H 4 .C0 2 H) 2 , is not known in
the free state ; its sodium salt is formed, along with free boric
acid, when four molecules of salicylic acid are added to a boiling
solution of one molecule of borax, as well as by dissolving a
mixture of equal molecules of boric acid, salicylic acid and
sodium salicylate :
/OH
HO - B< + HO.C 6 H 4 .C0 2 H + HO.C 6 H 4 .C0 2 Na =
/OC 6 H 4 .C0 2 H
HO-B< +2H 2 0.
\OC 6 H 4 .C0 2 Na
It forms crystalline crusts and is readily soluble in hot water
and alcohol. Its aqueous solution turns turmeric paper brown,
reddens litmus paper, and is coloured violet by ferric chloride ;
hydrochloric acid gives a precipitate of salicylic acid. Several
METHYLSALICYLIC ACID. 305
other of its salts have been prepared ; its barium salt is only
slightly soluble in boiling water. 1
2174 Methyl salicylate, C 6 H 4 (OH)C0 2 .CH 3 . Cahours, in 1843,
found that winter-green oil, obtained from Gaultheria procumbens
(Canadian tea), one of the Ericaceae, which occurs abundantly in
the north of the United States and in Canada, consists of this
compound together with small quantities of a terpene, and he
prepared the ether by distilling salicylic acid with wood-spirit
and sulphuric acid in order to compare the two products. 2 Since
as a phenol it forms metallic salts, it was called gaultheriaic
acid and methylsalicylic acid, the latter name being now given
to the following compound.
The ethereal oils of Gaultheria punctata and G-aultheria
leucocarpa, which grow on the summits of extinct volcanoes
in Java, 3 and of Andromeda Lechenaultii, one of the Ericaceae,
which occurs abundantly in the Neilgherry Mountains in India, 4
consist almost entirely of methyl salicylate.
It is a liquid with a pleasant, refreshing odour, and, boils at
217. Winter-green oil is largely used in America as a perfume ;
that obtained artificially, by heating salicylic acid with methyl
alcohol and sulphuric acid, does not possess the fine odour of the
natural product.
Methylsalicylic acid, C 6 H 4 (OCH 3 )CO 2 H. Cahours obtained
the methyl ether of this compound by the action of methyl
iodide and caustic potash on winter-green oil. It is a liquid
boiling at 244 246 (Schreiner). In order to prepare the acid,
two parts of methyl salicylate are heated to 100 120 with one
part of caustic potash and three or four parts of methyl iodide,
the product distilled in order to remove* methyl alcohol and
methyl, iodide, and the residue then extracted with caustic soda
and precipitated with hydrochloric acid. Any adhering salicylic
acid is removed by boiling with an excess of milk of lime,
insoluble basic calcium salicylate being precipitated, while
calcium methylsalicylate remains in solution, and is then
decomposed by hydrochloric acid. 5
Methylsalicylic acid crystallizes from hot water in large,
monoclinic tablets, and from alcohol in prisms, which melt at
98'5 and decompose above 200 into carbon dioxide and anisol.
1 Jahns, Arch. Pharm. [3] xii. 212.
2 Ann. Chem. Pharm. xlviii. 83 ; liii. 327.
3 de Vrij, Pharm. Journ. Trans. [3] ii. 503 ; Kohler, Ber. Deutsch. Chem. Ges.
"\. 246. 4 Broughton, Pharm. Journ. Trans. [3] ii. 281.
6 Grabe, Ann. Chem. Pharm. cxxxix. 137.
06 AROMATIC COMPOUNDS.
On heating with concentrated hydrochloric acid, it is resolved
into salicylic acid and methyl chloride; hydriodic acid has a
similar action.
The sodium salt of the acid is formed, together with a little
of the methyl ether and sodium salicylate, when winter-green
oil is heated with sodium :
C 6 H 4 .ONa C 6 H 4 .OH C 6 H 4 .OCH 3 C 6 H 4 .OH
+ 1 =1 +1
C0 2 .CH 3 CO 2 .CH 3 C0 2 .CH 3 C0 2 Na.
Two molecules of the sodium compound then react in a
similar manner :
C 6 H 4 .ONa C0 2 .CH 3 C 6 H 4 .OCH 3 C0 2 Na
+ 1 +1
2 .CH 3 C 6 H 4 .ONa CO 2 Na C 6 H 4 .OCH 3 .
ETHEREAL SALTS OF SALICYLIC ACID.
Melting Boiling
point. point.
2 Ethyl salicylate, C 6 H 4 (OH)C0 2 .C 2 H 5 , liquid 223
3 Propyl salicylate, C 6 H 4 (OH)C0 2 .C 3 H 7 , liquid 239
4 Amyl salicylate, C 6 H 4 (OH)CO 2 .C 5 H n , liquid . 270
5 Ethylene salicylate, (C 6 H 4 (OH)C0 2 ) 2 C 2 H 4 , needles 83
6 Propenyl salicylate, C 6 H 4 (OH)C0 2 C 3 H 5 (OH) 2 , liquid
SALICYLIC ETHERS.
Melting-point.
7 Ethysalicylic acid, C 6 H 4 (OC 2 H 5 )CO 2 H, gradually ) 19<4 o
solidifying oil j
8 Isopropylsalicylic acid, C 6 H 4 (OC 3 H 7 )CO 2 H, liquid .
9 Benzylsalicylic acid, C 6 H 4 (OC 7 H 7 )C0 2 H, small tablets 75
10 Ethylenesalicylic acid, C 6 H 4 (OC 6 H 4 .CO 2 H) 2 , long ) 1 5 1 o_ 152
needles J
1 Ann. Chem. Pharm. cxlii. 327.
2 Baly, ibid. Ixx. 269 ; Schreiner, ibid, cxcvii. 17 ; Gottig, Ber. Deutsch.
Chem. Ges. ix. 1473. 3 Cahours, Jahresb. Chem. 1874, 333.
4 Drion, Ann. Chem. Pharm. xcii. 313. 5 Gilmer, ibid, cxxvii. 377.
6 Gottig, Ber. Deutsch. Chem. Ges. x. 1817.
7 Kraut, Ann. Chem. Pharm. cl. 1 ; Gottig, Ber. Deutsch. Chem. Ges. ix. 1474.
8 Kraut. 9 Perkin, Journ. Chem. Soc. xxi. 125.
10 Weddige, Journ. Prakt. Chem. [2] xxi. 128.
ETHYL METHYLSALICYLATE. 307
ETHEREAL SALTS OF SALICYLIC ETHERS.
Boiling-point.
1 Ethyl methylsalicylate, C 6 H 4 (OCH 3 )C0 2 .C 2 H 5 , . 260
2 Methyl ethylsalicylate, C 6 H 4 (OC 2 H 5 )CO 2 .CH 3 , . 256 257
3 Ethyl ethylsalicylate, C 6 H 4 (OC 2 H 5 )C0 2 .C 2 H 5 , . 258 259
4 Methyl isopropylsalicylate, C 6 H 4 (OC 3 H 7 )C0 2 .CH 3 , 250
5 Methyl benzylsalicylate,C 6 H 4 (OC 7 H 7 )C0 2 .CH 3 , above 320
Melting-point.
6 Ethyl ethylenesalicylate, C 2 H 4 (OC 6 H 4< C0 2 C 2 H 5 ) 2 , ) 96 _ 97 o
thick plates j
Phenyl salicylate, C 6 H 4 (OH)C0 2 .C 6 H 5 . Seifert 7 obtained this
compound by heating salicylic acid and phenol with phosphorus
oxychloride :
2C 6 H 4 (OH)C0 2 H + 2C 6 H 5 .OH + POC1 3 =
2C 6 H 4 (OH)C0 2 .C 6 H 5 + 3HC1 + HP0 3 .
A better yield is obtained by employing the sodium salts ; this
ethereal salt, known as salol, is manufactured by heating the
product of the action of carbon dioxide on sodium phenate with
phosphorus pentachloride or oxychloride :
C 6 H 4 (OH)C0 2 Na + C 6 H 6 .ONa + PC1 5 =
C 6 H 4 (OH)C0 2 .C 6 H 5 + 2NaCl + POC1 3 .
2C 6 H 4 (OH)C0 2 Na+ 2C 6 H 5 .ONa+POCl 3 -
2C 6 H 4 (OH)C0 2 .C 6 H 5 + SNaCl + NaP0 3 .
Salol crystallizes in rhombic prisms, which are odourless and
melt at 42 42*5 ; the dilute alcoholic solution, however, has
a smell resembling that of winter-green oil. It is employed in
medicine as a substitute for salicylic acid, because, as it is not
decomposed until it reaches the duodenum, it does not attack
the stomach like the former : when applied externally it has no
corrosive action, and, on account of its lower melting-point, it
can be more conveniently used for dressings, &c., than salicylic
acid.
1 Grabe ; Schreiner ; loc. cif. 2 Schreiner ; loc. cit.
3 Gbttig ; Schreiner ; Zoc. cit. 4 Kraut ; loc. cit.
5 Perkin ; loc. cit. 6 Weddige ; loc. cit.
7 Journ. Prakt. Chem. [2] xxxi. 462.
308 AROMATIC COMPOUNDS.
Phenyl methylsalicylate, C 6 H 4 (OCH 3 )C0 2 .C 6 H 5 , was prepared by
Seifert in a similar manner ; it crystallizes in six-sided prisms,
melting at 59.
Acetylsalicylic acid, C 6 H 4 (O.CO.CH 3 )CO 2 H, is formed by the
action of acetyl chloride on salicylic acid or its sodium salt, and
crystallizes from hot water in fine needles, melting at 118
118'5. Its aqueous solution gives a violet colouration with
ferric chloride ; when the acid is heated with ammonia, ammo-
nium salicylate is formed, but no salicylamide (Kraut).
/\
Salicyl chloraldide, 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 <cci 3 + PC1 - c < ccl3 +2 ^-
2176 Salicylamide, C 6 H 4 (OH)CO.NH 2 , is obtained by the
action of concentrated ammonia on methyl salicylate ; 2 it cry-
stallizes from ether in lustrous, yellow plates, melting at 142 , 3
and sublimes when carefully heated. As a phenol it forms
metallic salts ; its ethers are formed when ammonia is allowed to
act upon the ethers of salicylic acid.
Benzoylsalicylamide, C 6 H 5 (O.CO.C 6 H 5 )NH 2 , is formed when
salicylamide is heated to 180 with benzoyl chloride, or fused
with benzamide. 4 It is slightly soluble in alcohol, but almost
insoluble in ether, and crystallizes in needles melting at 200.
Disalicylamide, (C 6 H 4 (OH)CO) 2 NH, is prepared by heating
salicylic acid in a current of hydrochloric acid. It crystallizes
in yellowish white needles, which resemble asbestos in appearance,
and melt at 197 199 with partial decomposition; it is in-
soluble in water, but readily dissolves in alcohol and alkalis. The
alcoholic solution is coloured red by ferric chloride. 5
Salicylanilide, C 6 H 4 (OH)CO.NH(C 6 H 5 ), is obtained by gently
warming aniline with salicylic acid and then gradually adding
phosphorus trichloride to the cooled mass. It crystallizes from
dilute alcohol in small prisms, melting at 184 135; ferric
chloride colours the solution violet. 6
Salicyluric acid, C 6 H 4 (OH)CO.NH.CH 2 .C0 2 H. When salicylic
acid is administered internally, it appears in the urine partly in
an unaltered state and partly as salicyluric acid. This is slightly
soluble in water, readily in alcohol, and crystallizes in fine
needles, which melt at 160 and give a violet colouration with
feme chloride. On heating with concentrated hydrochloric acid,
1 Anschiitz, Ann. Chem. Pharm. ccxxviii. 308, and private communication.
2 Limpricht, ibid, xcviii. 258.
3 Grimaux, Bull. Soc. Chim. xiii. 25.
4 Chiozzaand Gerhardt, Jahresb. Chem. 1856, 502.
6 Schulerud, Journ. PraU. Chem. [2] xxii. 298.
6 Kupferberg, ibid. [2] xvi. 442 ; Wanstrat, Ber. Deulsch. Chem. Gcs. vi. 336,
CHLOROSALICYLIC ACID. 313
it decomposes into salicylic acid and amido-acetic acid. Its
barium salt forms prisms, which are only slightly soluble in
water. 1
SaUcylnitril, C 6 H 4 (OH)CN, is formed by heating the amide
with phosphorus pentoxide, and is a colourless, crystalline
substance, which melts at 195, and on boiling with dilute
caustic potash is converted into salicylic acid. 2
Polysalicylnitril, (C 7 H 5 ON) X . Limpricht obtained this com-
pound by heating salicylamide to 270, and looked upon it as an
imide of the dibasic salicylic acid. 3 It is a yellow, crystalline
powder, which melts at 280 285 (Grimaux), and is only
converted into salicylic acid by fusion with caustic potash. On
heating with phosphorus pentachloride, orthochlorobenzonitril
is formed. 4
Benzoylsalicylnitril, C 6 H 4 (OCO.C 6 H 6 )CN, was prepared by
Limpricht by heating benzosalicylamide, and called by him
benzoylsalicylimide. 5 Henry obtained it by heating the poly-
nitril with benzoyl chloride. It. crystallizes from hot alcohol in
small, brittle, lustrous plates, melting at 148 149. The hot
alcoholic solution is coloured red by ferric chloride.
SUBSTITUTION PRODUCTS OF SALICYLIC
ACID.
2177 Chlorosalicylic acid, C 6 H 3 C1(OH)C0 2 H (5 : 2 : 1), is formed
by passing chlorine into a solution of salicylic acid in carbon
disulphide, 6 as well as by the action of nitrous acid upon
/3-chloramidobenzoic acid. 7 It may also be obtained by replacing
the amido-group of the corresponding amid osalicy lie acid by
chlorine, 8 and by heating parachlorophenol with tetrachloro-
methane and alcoholic potash. 9 It dissolves in 1100 parts of
water at 20, and in 80 parts at 100, and crystallizes in small
1 Bertagrrini, Ann. Chem. Pharm. xcvii. 249.
2 Grimaux, Bull. Soc. Chim. xiii. 26.
3 Ann. Chem. Pharm. xcviii. 261.
4 Henry, Ber.Deutsch. Chem. Ges. ii. 491.
8 Ann. Chem. Pharm. xcix. 250.
6 Hiibner and Brenkeu, Ber. Deutwh. Chem. Ges. vi. 174.
7 Hiibner and "Weiss, ibid. vi. 175.
8 Schmitt, Jahresb. Chem. 1864, 385 ; Beilstein, Ber. Deutsch. Chem. Ges.
viii. 816.
9 Hasse, ibid. x. 2190.
314 AROMATIC COMPOUNDS.
needles, melting at 172. The aqueous solution is coloured violet
by ferric chloride.
Dichlorosalicylic acid, C 6 H 2 C1 ? (OH)CO 2 H(3 : 5 : 2 : 1), may be
prepared by heating salicylic acid with antimony pentachloride, 1
as well as by the action of chlorine on a solution of salicylic
acid in glacial acetic acid. 2 It is also slightly soluble in boiling
water, and crystallizes from dilute alcohol in small prisms, which
melt at 214, and are coloured dark violet by ferric chloride. Con-
centrated nitric acid converts it into the same dichloronitrophenol
as is formed by the nitration of a-dichlorophenol. 3
a-Br&mosalicylic acid, C 6 H 3 Br(OH)CO 2 H(3 : 2 . 1), has been
obtained from the corresponding amidobromobenzoic acid. 4 It
crystallizes in small, soluble needles, melting at 219 220, and
gives a dark reddish blue colouration with ferric chloride.
ft-Bromosalicylic acid (5:2:1) is formed by the direct
bromination of salicylic acid, 5 and also by treating /3-bromamido-
benzoic acid with nitrous acid (Hiibner and Heinzerling). It
crystallizes from hot water in long needles, melting at 164
165 ; ferric chloride colours it violet.
Three dibromosalicylic acids are also known. 6
lodosalicylic acid, C 6 H 3 I(OH)CO 2 H(5 : 2 : 1), has been prepared
from the corresponding amido-salicylic acid by means of the
diazo-reaction. 7 It is almost insoluble in cold water, and crystal-
lizes from alcohol in needles, which melt at 196, and decompose
into iodophenol and carbon dioxide when they are rapidly heated.
The same acid had previously been obtained by Lautemann by
treating salicylic acid with iodine and caustic potash solution, 8
while Liechti 9 and Demole, 10 by the action of iodine and iodic
acid on salicylic acid, prepared an iodosalicylic acid which is
slightly soluble in cold, somewhat more readily in hot water, and
crystallizes in needles, melting at 183.
Two isomeric acids are therefore produced by the direct action
of iodine on salicylic acid, 11 and probably in varying proportions.
The following compounds are also formed in this reaction :
1 Lossner, Joum. Prdkt. Cham. [2] xiii. 429.
2 Smith, Bcr. Deutsch. Chem. Ges. xi. 1225.
3 Smith and Knerr, Amer. Chem. Journ. viii. 95.
4 Hiibuer and Heinzerling, Zcitschr. Chem. 1871, 709.
5 Henry, Ber. Deutsch. Chem. Ges. ii. 275 ; Hiibner and Heinzerling.
6 Rollwage, ibid. x. 1707; Smith, ibid. 1706 ; Hiibner, ibid. 1706.
7 Goldberg, Journ. PraJct. Chem. [2] xix. 368 ; Hiibner, Ber. Deutsch. Chem.
Ges. xii. 1347. 8 Ann. Chem. Pharm. cxx. 302.
9 Ibid. Suppl. vii. 136. 10 Ber. Deutsch. Chem. Ges. vii. 1437.
11 Fischer, Ann. Chem. Pharm. clxxx. 346.
NITROSALICYLIC ACIDS. 315
Di-iodosalicylic acid, C 6 H 2 I 2 (OH)CO 2 H, is best obtained by
the action of iodine and mercuric oxide upon an alcoholic
solution of salicylic acid. 1 It is slightly soluble in cold, more
readily in hot water and alcohol, crystallizes in needles, melting
at 220 280, and, like moniodosalicylic acid, is coloured violet
by ferric chloride.
Tri-iodosalicylic acid, C 6 HI 3 (OH)CO 2 H, is insoluble in water,
and crystallizes from alcohol in yellow needles.
2178 Nitrosalicylic acids. In the year 1806, Fourcroy and
Vauquelin obtained a volatile, crystalline acid, which they
thought was benzoic acid, by treating indigo blue with dilute
nitric acid. Chevreul recognized the individuality of this sub-
stance, which was called indigotic acid, and it was then carefully
examined by Buff, 2 and correctly analysed by Dumas. 3 Marchand 4
confirmed the results obtained by Dumas, and found, as also
did Gerhardt, 5 that indigotic acid is identical with nitrosalicylic
acid. Piria, by the action of nitric acid on salicin, obtained
helicin and anilotic acid, which, according to Major, is identical
with nitrosalicylic acid, although Piria himself was convinced
that the two acids were different substances. 6 In spite of this,
it was generally assumed that only one nitrosalicylic acid existed,
until Hiibner found that two are formed by the nitration of
salicylic acid. 7 One of these is identical with anilotic acid, while
indigotic acid proves to be a mixture of both. 8 These acids are
also formed when the vapour of nitric acid is passed into methyl
salicylate. 9
a-Nitrosalicylic acid, (CO 2 H : OH :NO 2 = 1 : 2 : 5), may be
obtained, in addition to the methods given above, by heating
paranitrophenol with tetrachlorom ethane and alcoholic potash
to 100 , 10 by boiling e-nitro-amidobenzoic acid with caustic potash
solution, 11 and by passing nitrogen tetroxide into a cold aqueous
solution of salicylic acid (Hiibner). In order to prepare it, 100
parts of salicylic acid are dissolved in 800 parts of glacial acetic
acid, 50 parts of pure nitric acid, of sp. gr. of 1'5, being then
1 Weselsky, Ann. Chem. Pharm. clxxiv. 103.
2 Schweigg, Journ. Chem. Phys. li. 38 ; liv. 163.
8 Ann. Chim. Phys. [3] ii. 224.
4 Journ. Prakt. Chem. xxvi. 385.
5 Ann. Chem. Pharm. xlv. 19.
6 Ibid, xcvii. 253.
7 Ibid. cxcv. 1.
8 Masino and Schiff, ibid, cxcviii. 256.
9 Smith and Kiierr ; Amer. Chem. Journ. viii. 99.
10 Hasse, Ber. Deutsch. Chem. Ges. x. 2188.
11 Griess, ibid. xi. 1730.
316 AROMATIC COMPOUNDS.
gradually added in the cold ; the solution is then diluted with
two or three volumes of water, and the acid, which separates
out after some time, purified by repeated crystallization from hot
water. The barium salt of the yS-acid may be prepared from
the mother-liquor; it is only slightly soluble in water.
a-Nitrosalicylic acid crystallizes in long needles, which melt
at 228 and dissolve in 1475 parts of water at 15; it is more
easily soluble in alcohol or hot water. Its solution is coloured
blood-red by ferric chloride. Boiling nitric acid converts it into
picric acid, and when its diethyl ether is heated to 130 with
alcoholic ammonia, the amide of e-amidonitrobenzoic acid is
obtained. On heating with lime it decomposes into carbon
dioxide and paranitrophenol.
Normal barium a-nitrosalicylate, (C 7 H 4 N0 5 ) 2 Ba H- fflgO, 1 is
obtained by heating the acid with water and barium carbonate ;
it is readily soluble in water, and crystallizes in compact, yel-
low needles which form fascicular aggregates. The basic salt,
C 7 H 3 NO 6 Ba 4- 2H 2 O, is formed by boiling the acid with baryta
water, and crystallizes in citron-yellow plates, which have a satin
lustre and are only slightly soluble in water.
ft-Nitrosalicylic acid, or Anilotic acid, (C0 2 H : OH : N0 2 =
1:2: 3), is formed in largest quantity by the action of the most
concentrated nitric acid upon salicylic acid at a low temperature, 2
and has also been obtained by heating orthonitrophenol with
tetrachloromethane and alcoholic potash (Hasse). In order to
prepare it, 10 grms. of salicylic acid are gradually brought into
a mixture of 10 grms. of concentrated nitric acid with 10 12
grms. of glacial acetic acid at a temperature of about 6. The
solution is then poured into 250 ccm. of water and the
precipitated acids separated by means of their barium salts.
/3-Nitrosalicylic acid dissolves in 770 parts of water at 15 "5,
readily in alcohol and ether, and crystallizes in long needles,
which contain a molecule of water, and melt at 125. The
anhydrous acid melts at 144; its solution is coloured blood-red
by ferric chloride ; on heating with lime it decomposes into
carbon dioxide and orthonitrophenol, while the amide of f-amido-
nitrobenzoic acid is formed by the action of alcoholic ammonia
on its diethyl ether.
Normal barium fB-nitrosalicylate, (C 7 H 4 N0 5 ) 2 Ba, crystallizes
in golden yellow plates or compact, refractive needles, which are
1 Ann. Chem. Pkarm. ccr. 344.
2 Schaumann, Ber. Deutsch. Chem. Ges. xii. 1346.
DINITROSALICYLIC ACID. 317
only very slightly soluble in cold, more readily in hot water.
Ammonia added to the solution produces a deep-red colouration
and then a precipitate of the basic salt, 2C 7 H 3 NO 5 Ba + 3H 2 O, in
thick, blood-red needles.
Dinitrosalicylic acid, C 6 H 2 (NO. 2 ) 2 (OH)C0 2 H. The methyl
ether of this compound was obtained by Cahours by dropping
winter-green oil into a mixture of fuming nitric and sulphuric
acids. 1 It crystallizes in yellow scales, which melt at 127 128
(Salkowski), and are easily saponified by caustic potash. Sten-
house then prepared dinitrosalicylic acid by the action of nitric
acid on the aqueous extracts of Populus nigra and P. balsam-
ifera, which contain populin. 2 It is also formed by the
further nitration of both the mononitrosalicylic acids, their
constitution being thus shown. It is best prepared by bringing
10 grms. of salicylic acid into 70 grms. of the most concentrated
nitric acid at 0, and pouring the clear solution into 300 ccm. of
water; after standing for 24 36 hours the separated acid is
filtered off, pressed, converted into the barium salt by boiling
with water and barium carbonate, and re-precipitated by hydro-
chloric acid. 3
Dinitrosalicylic acid is readily soluble in cold, very readily in
hot water, and crystallizes therefrom in thick, lustrous plates, or,
on rapid cooling, in fine needles containing one molecule of
water. Its solution is coloured dark-red by ferric chloride ; on
heating with water to 200 it decomposes into carbon dioxide
and ordinary dinitrophenol.
Potassium -dinitrosalicylate. When caustic potash is added in
excess to the aqueous solution of the acid, the salt C 6 H 2 (N0 2 ) 2
(OK)CO 2 K -f- H 2 O is formed; it crystallizes in long, dark-red
needles, which detonate violently when heated. Dilute hydro-
chloric acid or nitric acid added to its solution precipitates the
salt C 6 H 2 (NO 2 ) 2 (OH)CO 2 K, which crystallizes from boiling
water in compact, short, dark yellow needles.
Barium dinitrosalicylate, C 6 H 2 (NO 2 ) 2 OBaC0 2 + 3H 2 0, forms
compact, yellow needles, which are only slightly soluble in cold
water.
2179 a-Amidosalicylic acid, C 6 H 3 (NH 2 )(OH)C0 2 H, was ob-
tained by Beilstein by reducing nitrosalicylic acid with tin and
hydrochloric acid ; 4 it is better, however, to employ acetic acid
(Hiibner). It crystallizes in needles which have a satin lustre,
1 Ann. Chem. Pharm. Ixix. 232. 2 Ibid. Ixxviii. 1.
3 Hiibner, ibid. cxcv. 45. 4 Ann. Chem. Pharm. cxxx. 243.
318 AROMATIC COMPOUNDS.
and are insoluble in alcohol and cold water, but slightly soluble
in hot water ; the solution soon decomposes in the air, a brown,
amorphous substance being precipitated. Ferric chloride pro-
duces a cherry-red colouration, followed by a brownish black
precipitate.
Amidosalicylic acid forms salts both with bases and acids ; it
decomposes on heating into carbon dioxide and paramidophenol. 1
CO
TrimetJiylamidosalicylic acid, C 6 H 3 (OH)<; ^>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 <f . In order to prepare this compound, the
\C0 2 H
distillation is stopped as soon as the acid has lost about 15 per
cent, of its weight and before any turbidity has appeared. The
residue is boiled with chloroform and water, and the compound
then extracted with dilute alcohol and purified by re-crystal-
lization. It forms short, microscopic needles, which melt at
261 and are rapidly converted into parahydroxybenzoic acid in
alkaline solution. As a monobasic acid it forms a barium salt,
(C 14 H 9 5 ) 9 Ba, which crystallizes in long plates containing water
of crystallization. On heating with acetic anhydride, the mono-
acetyl compound, C 14 H 9 (C 2 H 3 O)O 5 , is formed ; it crystallizes in
small plates, melting at 216*5.
Diparahydroxybenzoylparahydroxybenzoic acid,
OCO.C 6 H 4 O.CO.C 6 H 4 .OH
, is contained in the residue ob-
tained in the preparation of the preceding compound, and also in
1 Klepl, Journ. Praki. Chem. [2] xxv. 525 ; xxviii. 193.
332 AROMATIC COMPOUNDS.
the amorphous mass formed by the distillation of parahydroxy-
benzoic acid, from which it may be extracted by absolute alcohol.
It is a white, non-crystalline powder, which is slightly soluble in
alcohol and ether, but insoluble in water and chloroform; it
melts at 280, and readily dissolves in alkalis, being gradually
converted into parahydroxybenzoic acid, while it is not altered
by boiling water. When the acid is suspended in a small
quantity of water and treated with sufficient caustic soda to
effect solution, the compound C 21 H 13 O 7 Na is precipitated in
needles after some time. The acetyl compound, C 21 H 13 (C 2 H 3 O)O 7 ,
is formed by heating the acid with acetic acid ; it crystallizes in
needles melting at 230.
Parahydroxylenzide, (C 7 H 4 O 2 ) n , is the final product of the
action of heat upon parahydroxybenzoic acid, and forms a white,
amorphous powder, which is insoluble in the ordinary solvents,
and carbonizes at 350 without previously melting. Boiling
concentrated caustic potash converts it into parahydroxybenzoic
acid ; on heating with concentrated sulphuric acid, parahydroxy-
benzoylsulphuric acid is obtained, while parachlorobenzenyl
trichloride is formed by the action of phosphorus chloride at 300
(p. 196).
Anisic anhydride, (C 6 H 4 (OCH 3 N / CO) 2 O, is obtained by the
action of phosphorus oxychloride on sodium anisate. It crys-
tallizes from ether in small, silky needles, which melt at 99
and volatilize at a higher temperature without decomposition. 1
Methylparahydroxybenzoyl chloride, or Anisyl chloride, C 6 H 4
(OCH 3 )COC1, is formed by the action of phosphorus penta-
chloride on anisic acid. 2 It forms long needles, which cannot be
volatilized. 3
Paracarbonylphenylphosplwryl chloride, C 6 H 4 (OPOC1 2 )COC1 >
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 .C<f
\OCO.C 6 H 6
Melting-point.
Large, monosymmetric crystals with many faces . 147'5 C
-o
^NO.CO.C 6 H 4 .OCH 3
BENZDIANISHYDROXYLAMINE, C 6 H 5 .Cr^
\O.CO.C 6 H 4 .OCH 3
Melting-point.
a) Sbort, asymmetric columns ....... 137'5 138'5
ft) Asymmetric tablets 137-5 138
Lossen remarks concerning these compounds : " The twelve
substances described above afford an additional proof of the well-
established fact that there are two kinds of isomerism, which
must be carefully distinguished from one another. Seven
isomeric substances were obtained as the products of three
different methods of preparation, three being yielded by one
method and two by each of the others ; three further methods
of preparation, different from the preceding, gave five isomeric
bodies, two being formed by each method. Isomerides are,
therefore, formed both by different methods and by one and the
same method, but the difference between two compounds which
are prepared by independent methods is not the same as that
existing between the isomeric products of a single method." ]
The latter, in fact, always give the same decomposition
products on treatment with hydrochloric acid or caustic potash.
1 Loc. cit. and Ber. Deutsch. Chem. Ges. xviii. 1189.
PKOTOCATECHUICALDEHYDE. 343
Thus benzole acid and dianishydroxamic acid are obtained by
the action of caustic potash upon the anisbenzanishydroxylamines,
the same products, together with anisic acid and anisbenzhydrox-
amic acid, being also formed from dianisbenzhydroxylamine,
while the benzdianishydroxylamines are resolved into anisic acid
and benzanishydroxamic acid.
The dibenzanishydroxylamines under the same circumstances
yield benzanishydroxamic acid, and not, as might have been
expected, a compound metameric with this :
NO.CO.C 6 H 5
C 6 H 6 .cf +2KOH =
\O.CO.C 7 H 7
NOK
C 6 H 5 .C<f + KO.CO.C 6 H 5 + H 2 0.
\O.CO.C 7 H 7
Lossen assumes that the decomposition first proceeds in this
way, and that the compound formed changes into :
" A similar exchange between a metal and an acid radical has
often been observed."
DIHYDROXYBENZYL AND DIHYDROXY-
BENZOYL, COMPOUNDS.
2190 Protocatechuicaldehyde, or a-Orfhodihydroxybenzaldehyde,
C 6 H 3 (OH) 2 CHO.(COH : OH : OH = 1 : 3 : 4), was first prepared
from piperonal (p. 347) and from vanillin or its methyl ether.
Tiemann and Reimer found that it is also formed by the action
of chloroform on an alkaline solution of catechol. 1 In order to
prepare it, a solution of 10 parts of the latter in 600 parts of 16
per cent, caustic soda solution is heated for 5 6 hours with 100
parts of chloroform in an apparatus connected with an inverted
condenser, acidified with hydrochloric acid, allowed to cool,
filtered from a black resinous substance and shaken out with
1 Be,r. Deutsch. Chem. Ges. ix. 1269.
314 AROMATIC COMPOUNDS.
ether. The aldehyde is extracted from the ethereal solution by
means of acid sodium sulphite, liberated by dilute sulphuric
acid, again dissolved in ether and the residue on evaporation
re- crystallized from boiling toluene. 1
It is readily soluble in water, alcohol and ether, very slightly
in cold, more readily in boiling toluene, and crystallizes from
water in flat, lustrous needles, melting at 150. Ferric chloride
added to its aqueous solution produces a green colouration, which
becomes first violet and then red on the addition of sodium
carbonate. Ammoniacal silver solution is immediately reduced
by it.
Vanillin, C 6 H 3 (OH)(OCH 3 )CHO(CHO : OCH 3 :OH = 1 : 3 : 4).
The crystalline coating of vanilla (givre de vanille) was mistaken
by Buchholz for benzoic acid, and by other chemists for cinnamic
acid, although Bley had previously pointed out that it is a
distinct substance. Gobley, who at first took it for cumarin,
subsequently found with Vee, that it differs from this substance,
and named it vanillin, 2 while Stokkebye, who obtained analytical
results differing from those of Gobley, termed it vanillaic acid. 3
The correct formula of vanillin was determined by Carles, who
investigated its properties and some of its derivatives, 4 without
being able to determine its relations to any known compounds.
Tiemann and Haarmann, however, were successful in this, and
prepared it artificially from coniferin, C 1G H 12 O 8 . This compound
occurs in the cambium sap of the fir-tree, and is decomposed by
emulsin in the presence of water into grape sugar and the
compound C 10 H 12 O 3 , forming odourless crystals, which after
standing in the air for some time have a faint smell of vanilla ;
Tiemann and Haarmann therefore oxidized it with chromic acid
and thus obtained vanillin. On fusion with caustic potash it is
converted into protocatechuic acid, and on heating to 200 with
hydrochloric acid is decomposed into methyl chloride and proto-
catechuicaldehyde, proving that it is the methyl ether of the
latter. 5
Reimer and Tiemann then obtained it by heating guaiacol
(Part III. p. 134) with caustic soda and chloroform, 6 the iso-
meric metamethoxysalicylaldehyde being simultaneously formed
(Tiemann and Koppe). 7
1 Tiemann and Koppe, Per. Deutsch. Chem. Ges. xiv. 2015.
2 Jahresber. Chcm. 1858, 534. 3 Ibid. 1864, 512.
4 Bull. Soc. Chim. xvii. 2. 8 Scr. Deutsch. Chem. Ges. vii. 608.
8 Ibid. ix. 424. 7 Ibid. xiv. 2023.
VANILLIN. 345
The decomposition product of coniferin, referred to above, is
coniferyl alcohol, C 6 H3(OH)(OCH 3 )CHz=CH.CH 2 OH, and its
conversion into vanillin by oxidation may readily be under-
stood. The latter is formed in a similar manner from eugenol,
C 6 H 3 (OH)(OCH 3 )CH=CH.CH 3 , a substance which is found in
oil of cloves.
Vanilla contains 1*5 2'5 per cent, of vanillin and a little
vanillic acid, C 6 H 3 (OH)(OCH 3 )C0 2 H, but no other aromatic
compounds. 1 It also occurs in Siam benzoin, 2 in Asa fcetida, 3
and frequently in small quantities in beet-sugar, 4 since the sugar
beet contains coniferin, which has also been found, together with
vanillin, in asparagus. 5
It is best obtained from coniferin. The trees containing this
substance, Abies excelsa, A. pectinata, Pinus strdbus, P. cembra,
Larix europaea, and other pines and firs, are felled during the
spring or early summer. The trunks are then sawn into pieces
and freed from bark, the cambium sap being removed by
means of a sharp knife. This is boiled with water, freed from
albumen, and the clear liquid evaporated to one-fifth of its bulk.
The crystals which separate after some time are filtered off,
pressed and re-crystallized after having been boiled with animal
charcoal.
The aqueous solution is then allowed to flow into a warm
mixture of potassium dichromate and dilute sulphuric acid,
the whole being heated for several hours in a flask con-
nected with an inverted condenser. After cooling, the solution
is filtered to remove a small quantity of a resinous substance
and extracted with ether. On evaporation a yellow oil is left,
which solidifies after some days to crystals which are boiled with
animal charcoal and re-crystallized from hot water. 6
Vanillin can also be readily obtained by replacing the nitroxyl
group in paranitromethylmetahydroxybenzaldehyde by hydroxyl }
by the oxidation of ferulaic acid, C 6 H 3 (OH)(OCH 3 )CH 2 .C()X
which can be prepared on the large scale without difficulty, 7 and
from olivil, 8 C 14 H 18 O 5 , the crystalline constituent of the Lecca
gum, or resin of the wild olive, which is used in Italy as
Tiemann and Haarmann, Ber. Deutsch. Chem. Ges. viii. 1118 ; ix. 1287.
Jannaschand Rump, ibid. xi. 1635.
E. Schmidt, ibid. xix. Ref. 706.
Scheibler, ibid. xiii. 335 ; Lippmann, ibid. xiii. 662.
Lippmann, ibid. xvi. 44 ; xviii. 3335.
Tiemann and Haarmann, ibid. vii. 609 and 614.
7 M. Ulrich, ibid, xviii. Ref. 682.
8 Scheidel, ibid, xviii. 685.
346 AROMATIC COMPOUNDS.
incense. 1 This substance will be further described along
with eugenol.
Properties. Vanillin forms white needles, generally occurring
in stellate aggregates, which possess a very strong taste and smell
of vanilla. It melts at 80 81, sublimes readily, boils at 285
without decomposition when heated in an atmosphere of carbon
dioxide, and dissolves in 90 100 parts of water at 14, and in 20
parts at 75 80. It is scarcely soluble in cold, more readily in
hot petroleum spirit. Its aqueous solution is coloured bluish
violet by ferric chloride ; if this solution be heated, white needles
of dihydrovanillin separate out. This body, which will be
described among the compounds containing two aromatic nuclei,
has the following constitution : 2
C 6 H 2 (OHXOCH 3 )CHO
C 6 H 2 (OH)(OCH 3 )CHO'
Vanillin is reduced in dilute alcoholic solution by sodium
amalgam to vanillyl alcohol, C 6 H 3 (OH)(OCH 3 )CH 2 .OH, which
crystallizes in prisms, melting at 115 . 3
Vanillin has an acid reaction and forms salts, which have
been investigated by Carles, and by Tiernann and Haarmann ;
the former has also prepared bromine and iodine substitution
compounds.
2191 Isovanillin, C 6 H 3 (COH)(OH)(OCH 3 ) (1: 3: 4), is
formed by heating opianic acid, C 6 H 2 (COH)(OCH 3 ) 2 CO 2 H, to
160 170 with dilute hydrochloric acid ; it crystallizes from hot
water in monosymmetric prisms, which possess a vitreous lustre,
and its solution is not coloured by ferric chloride ; it sublimes
when heated, undergoing slight decomposition ; 4 its vapour has
a pleasant smell, resembling that of vanilla and anise.
Mcthylvanillin, or Dimethylprotocatechuicaldehyde, C H 3 (OCH 3 ) 2
CHO, is formed by heating potassium vanillin with methyl
iodide and wood-spirit. 5 Beckett and Wright prepared it by
distilling opianic acid with soda lime. 6 It is slightly soluble in
hot water, readily in alcohol, and crystallizes in needles, which
smell like vanilla ; it melts at 42 43 and boils at 280 285.
1 Pelletier, Ann. Chem. Pharm. vi. 31 ; Sobrero, ibid. liv. 67.
Tiemann, Ber. Deutsch. Chem. Gcs. xviii. 3493.
Ibid. viii. 1125 ; ix. 415 ; xviii. 1597.
Wegscheider, Monatsch. Chem. iii. 789.
Tiemann, Ber. Deutsch. Chem. Ges. viii. 1135-
Journ. Chem. Soc. 1876, i. 287.
VANILLIN COMPOUNDS. 347
Acetylvanillin, C 6 H 3 (OCO.CH 3 )(OCH 3 )CHO, is obtained by
the action of sodium vanillin .on an ethereal solution of acetic
anhydride. It crystallizes in large, flat needles, melting at 77 . 1
Glucovanttlin, or Vanillin glucoside, C 6 H 3 (OCH 3 )(OC 6 H U O 5 )
CHO + 2H 0, is formed by the oxidation of coniferin with a
dilute solution of chromic acid. It is tolerably soluble in water,
less readily in alcohol, and crystallizes from dilute alcohol in
white needles which lose their water at 100 and melt at 192. It
is readily decomposed by emulsin into grape sugar and vanillin,
and is converted by sodium amalgam and water into glucovanillyl
alcohol, C 6 H 3 (OCH 3 )(OC 6 H n O 5 )CH 2 .OH + H 2 O, which crys-
tallizes in white needles, melting at 120. When its aqueous
solution is treated with a little emulsin and allowed to stand for
four or five days at 30 40, vanillyl alcohol is formed, and can
most easily be obtained pure by this method. 2
Piperonal, or Methyleneprotocatechuicaldehyde, C 6 H 3 (O 2 CH 2 )
CHO, was prepared by Fittig and Mielk by the oxidation of
piperic acid, C 6 H 3 (0 2 CH 2 )C 4 H 4 .CO 2 H, with potassium per-
manganate. 3 It is slightly soluble in cold, more readily in hot
water and forms long, thin, lustrous plates, which have a very
pleasant smell, resembling that of the heliotrope ; 4 it is on this
account employed in perfumery. 5
Piperonal melts at 37, boils at 263 and forms a vapour which
has a specific gravity of 5'18. 6 A very characteristic reaction of
this substance is that it decomposes into protocatechuicaldehyde
and finely divided carbon when it is heated to 200 with dilute
hydrochloric acid : 7
/CHO /CHO
Oxidizing agents convert it into piperonylic acid, while sodium
amalgam reduces it in boiling aqueous solution to piperonyl
1 Tiemann and Nagai, Ber. Deutsch. Chem. Ges. xi. 647.
Tiemann, ibid, xviii. 1595. Ann. Chem. Pharm. clii. 35.
* This same smell is possessed by "vanillon," a kind of vanilla, which forms
thick, fleshy capsules, and is obtained from the West Indies. It is only employed
in perfumery for the preparation of essence of heliotrope ; it contains no piperonal,
but vanillin and an oil which is probably benzaldehyde. The perfumers in
preparing essence of heliotrope add a little of this oil to the extract of vanillon.
If a little be added to a solution of pure vanillin, both substances can be
recognized by their smell for some time, but after standing for months, the
mixture acquires the smell of heliotrope (Tiemann and Haarmann, Ber. Deutsch.
Chem. Ges. ix. 1287.) * Chem. Zeit. 1884, 173.
5 Knecht, Ber. Deutsch. Chem. Ges. x. 1274.
7 Fittig and Kem.sen, Ann. Chem. Pharm. clxviii. 97.
348 AROMATIC COMPOUNDS.
alcohol, C 6 H 3 (O 2 CH 2 )CH 2 .OH, which is slightly soluble in cold,
more readily in hot water, and forms long, colourless crystals,
melting at 5 1 . 1
Dicliloropiperonal, C 6 H 3 (O 2 CC1 2 )COH. When one molecule
of piperonal is heated with three molecules of phosphorus
pentachloride, the compound C 6 H 3 (O 2 CC1 2 )CHC1 2 is formed.
It is an oily liquid, which is decomposed by water into hydro-
chloric acid and dichloropiperonal ; the latter crystallizes from
toluene in needles, which melt at 90 and undergo the following
decomposition when heated with water :
/CHO /CHO
C 6 H 3 ^ )\ ccla + 2H 2 = C 6 H 3 ^( [ + C0 2 + 2HC1.
Protocatechuicaldehyde was first prepared according to this
method by Fittig and Remsen.
2192 /3 Methylorthodihydroxybenzaldehydc, or (B-Metamethoxy-
salicylaldehyde, C 6 H 3 (OH)(OCH 3 )CHO (CHO: OH: OCH 3 =
t : 2 : 3), is formed together with vanillin by heating guaiacol
with caustic soda and chloroform. On distillation with steam it
passes over first as a liquid, which smells like salicylaldehyde,
boils at 264 265 in a current of carbon dioxide, stains the
skin yellow and forms a deep yellow solution in alkalis. Ferric
chloride added to an alcoholic solution produces a green coloura-
tion containing a shade of violet. 2
Metadihydroxybenzaldchyde, or (3-Rcsorcylaldehyde, C 6 H 3 (OH) 2
CHO (CHO : HO : HO = 1 : 2 : 4), is obtained, along with
resorcyldialdehyde, C 6 H 2 (OH) 2 (CHO) 2 , by heating resorcinol
with caustic soda and chloroform. 3 It crystallizes from water in
yellowish needles, which melt at 134 135; its solution is
coloured reddish brown by ferric chloride. It is an unstable
substance and gradually decomposes in moist air into a red
powder.
Orthomethoxyparahydroxybenzaldehyde, C 6 H 3 (OH)(OCH 3 )CHO
(CHO : OCH 3 : OH = 1 : 2 : 4), is formed, together with the
following compound and two resorcyldiaidehydes, by heating
methylresorcinol with caustic soda and chloroform. 4 It is readily
soluble in alcohol, slightly in water and benzene, and crystallizes
1 Fittig and Remsen, Ann. Chan. Pharm. clix. 138.
2 Tiemann and Koppe, Her. Deutsch. Chem. Ges. xiv. 2020.
3 Tiemann and Lewy, ibid. x. 2212.
4 Tiemann and Parrisius, ibid. xiii. 2365.
PARAMETHOXYSALICYLALDEHYDE. 349
from the latter in lustrous plates melting at 153. Its aqueous
solution is coloured a faint violet by ferric chloride. The acetyl-
derivative, C 6 H 3 (OC 2 H 3 0)(OCH 3 )CHO, is formed by adding the
potassium compound to an ethereal solution of acetic anhydride ;
it crystallizes in needles, melting at 86.
Paramethoxysalicylaldchyde, (COH: OH: OCH 3 = 1: 2: 4),
may also be obtained by heating 7-resorcyldialdehyde with caustic
potash and methyl iodide. It is almost insoluble in water and
crystallizes in plates, which have a characteristic, pleasant,
aromatic odour, melt at 62 63 and are very readily volatile.
It forms an intensely yellow solution in alkalis ; ferric chloride
produces a deep reddish yellow colouration in an alcoholic
solution.
Melting-point.
Dimethyl-/3-resorcylaldehyde, needles 68 69.
Diethylr/3-resorcylaldehyde, lustrous plates . . . 71 72.
Paradihydroxybenzaldeliyde, or Gentisinaldehyde, (CHO : OH :
OHz=l : 2 : 5), has been prepared from quinol by the action of
chloroform and caustic soda. It is readily soluble in water and
alcohol, and crystallizes in flat, lustrous yellow needles, melting
at 99 ; its aqueous solution is coloured a transient bluish green
by ferric chloride and intensely yellow by alkalis. 1
MethylparadiJiydroxylenzaldehyde, or Metamethoxysalicylalde-
hyde, (CHO : OH : OCH 3 =1 : 3 : 5), has been obtained from
methylquinol. 2 It is a yellow oil which has an aromatic odour,
solidifies in a freezing mixture to a radiating mass and then melts
at 4; it boils at 247 248 in a current of carbon dioxide. It
stains the skin yellow, forms an intensely yellow solution in
alkalis and in alcoholic solution is coloured a permanent bluish
green by ferric chloride. Its acetyl-compound crystallizes in
needles, melting at 63.
Melting-
point.
Dimethylparadihydroxybenzaldehyde, fine needles . .51
Ethylparadihydroxybenzaldehyde, thick, yellow prisms. 51 '5
Diethylparadihydroxybenzaldehyde, small needles 3 . . 60
1 Tiemann and Miiller, Ber. Deutsch. Chem. Ges. xiv. 1986.
2 Ibid. 1990.
3 Hantzsch, Journ. Prakt. Chem. [2] xxii. 464.
350 AROMATIC COMPOUNDS.
/OH
DIHYDROXYBENZOIC ACIDS, C 6 H/-CO.OH
\OH.
2193 The numbers appended designate the positions of the
groups C0 2 H: OH: OH.
PROTOCATECHUIC ACID, OR ORTHODIHYDROXYBENZOIC
- ACID (1:3:4).
In the year 1859, Hesse, by the action of bromine on an
aqueous solution of quinic acid, C 7 H 12 O 6 , obtained " carbohydro-
kinonic acid," C 7 H 6 O 4 , which decomposed into hydroquinone
and carbon dioxide on heating. 1 Two years later Strecker found
that an acid is formed by fusing piperic acid with potash, which
resembles catechuic acid so closely that he at first thought that
they were identical, but as he subsequently found less carbon in
the new compound he named it protocatechuic acid. 2 It decom-
poses on heating into carbon dioxide and catechol, and should
therefore be isomeric with Hesse's acid. All the other properties
of the two acids, however, agreed so completely that most
chemists assumed their identity, the more so as catechol had been
previously found among the decomposition products of carbo-
hydrokinonic acid. Fittig and Macalpine then proved decisively
that they are identical, and that the differences observed by
Hesse were due to some error. 3
Protocatechuic acid has been obtained from various carbon
compounds by fusion with caustic potash. Catechin or catechuic
acid, 4 the maclurin which occurs in fustic, 5 and the luteolin
obtained from woad also yield phloroglucinol, while many resins
give parahydroxybenzoic acid in addition 6 (p. 326).
Its synthetical formation from sulphanisic acid, 7 paracresol-
1 Ann. Chem. Pharm. cxii. 52 ; cxxii. 221.
2 Ibid, cxviii. 280. Strecker supposed that catechu contained two homologous
acids, which he named deutero- and trito-catechuic acids ; but this view has not
been confirmed.
3 Ibid, clxviii. 111.
4 Kraut and Delden, ibid, cxxviii. 285 ; Malin, ibid, cxxxiv. 118.
5 Barth and Pfaundler, ibid, cxxvii. 357.
6 Barth and Hlasiwetz, ibid. cxxx. 346 ; cxxxiv. 277 ; cxxxix. 78.
7 Malin, ibid. clii. 109.
PROTOCATECHUIC ACID. 351
sulphonic acid, 1 bromanisic acid, iodoparahydroxybenzoic acid,
sulphoparahydroxybenzoic acid and sulphometahydroxybenzoic
acid, 2 is of theoretical interest.
It is best prepared from East Indian kino, which is obtained
by making incisions in the bark of Pterocarpus Marsupium ; the
sap flows out and dries to a dark red, transparent mass, which is
employed in medicine as an adhesive, and for many purposes as
a substitute for catechu. One part of the finely-powered kino is
then gradually brought into a well-stirred melt of three parts of
caustic soda kept at a low temperature. When the mass has
become coloured a light orange brown, it is dissolved in 20 parts
of water, and the solution acidified with sulphuric acid, and
allowed to stand for twenty-four hours. The filtrate is extracted
with ether, the latter evaporated and the residue repeatedly
crystallized from water. 3 The aqueous solution of the acid may
also be precipitated with lead acetate, the precipitate washed
and finally decomposed by sulphuretted hydrogen (Barth and
Hlasiwetz).
According to Eijkman, protocatechuic acid occurs in the fruit
of Illicium religiosum.*
It crystallizes in monoclinic needles, containing one molecule of
water which is lost at 100, and melts at 194 ; 5 it dissolves in
5355 parts of water at 14 and in 3537 parts at 75 80, 6
is very soluble in alcohol, less so in ether, and almost insoluble
in boiling benzene. Its aqueous solution is coloured an intense
bluish green by ferric chloride, the colour being changed to dark
red by the addition of sodium carbonate. The solutions of its
salts are coloured violet by ferrous sulphate. It reduces an
ammoniacal silver solution, but not Fehling's solution ; on dry
distillation, or when heated to 330 350 with caustic soda, it
decomposes into carbon dioxide and catechol. When nitrogen
trioxide is passed into its ethereal solution, oxalic and dihydroxy-
tartaric acids are formed (Part III. p. 58), together with smaller
quantities of dinitrophenol, picric acid, dinitrodihydroxyquinone
and nitroparahydroxybenzoic acid. 7
Protocatechuic acid is produced along with benzoic acid when
gum benzoin is fused with caustic potash; a compound of the
1 Earth, Ann. Chem. Pharm. cliv. 364.
2 Ibid. clix. 232.
3 Stenhouse, ibid, clxxvii. 188.
4 Ber. Deutsch. Chem. Ges. xviii. Ref. 281.
5 Barth and Schmidt, ibid. xii. 1265.
6 Tiemann and Nagai, ibid. x. 211.
7 Gruber, ibid. xii. 514.
352 AROMATIC COMPOUNDS.
formula C 7 H 6 3 + C 7 H 6 4 + 2H 2 is formed, crystallizing in short
prisms, and the two acids cannot be separated by re-crystallization
or by fractional precipitation with lead acetate. On treatment
with bromine, however, the parahydroxybenzoic acid is converted
into tribromophenol, while the protocatechuic acid remains
unaltered (Earth and Hlasiwetz).
Barium protocatechuate, (C 6 H 3 (OH) 2 C0 2 ) 2 Ba -f 5H 2 0, forms
granular crystals ; when its solution is treated with concentrated
baryta water, the basic salt separates out in warty crystals, which,
after drying at 130, have the formula (C 6 H 3 (0 2 Ba)C0 2 ) 2 Ba. 1
Lead protocatechuate, (C (5 H 3 (OH) 2 C0 2 )Pb + 2H 2 O. An amor-
phous precipitate of (C 6 H 3 (OPb.OH) 2 CO 2 ) 2 Pb is obtained by the
addition of lead acetate to an aqueous solution of the acid ; the
solution of this in dilute acetic acid deposits the normal salt in
small crystals.
Methyl protocatechuate, C 6 H 3 (OH) 2 CO 2 .CH 3 , crystallizes from
hot water in needles, which melt at 134-5; ferric chloride colours
its aqueous solution green. 2
2194 Vanillic acid, C 6 H 3 (OCH 3 )(OH)C0 2 H,(CO 2 H : OCH 3 : OH
= 1 : 3 : 4), was first obtained by Tiemann by the oxidation of
coniferin with potassium permanganate ; 3 it is also formed by
the action of air on finely divided, moist vanillin, 4 and has been
prepared by various other reactions, which will be described
below. It crystallizes in needles, melting at 207 , 5 and sublimes
without decomposition; it dissolves in 850 parts of water at 14,
and in 39 parts at 100, is very readily soluble in alcohol, but
somewhat le*ss so in ether ; it is not coloured by ferric chloride,
and in the pure state is quite odourless. 6 On heating with caustic
soda and chloroform, vanillin is formed and only one aldehydo-
vanillic acid, 7 proving that the hydroxyl-group is in the para-
position, since both ortho- and para-compounds may be formed
in this reaction (p. 286).
Methyl vanillate, C 6 H 3 (OCH 3 )(OH)C0 2 .CH 3 , crystallizes from
dilute alcohol in lustrous needles, melts at 62 63, and boils
at 285 287 . 8
Vanillic acid ghicoside, or Glucovanillic acid, (C 6 H 3 (OCH 3 )
OC 6 H n O 5 )CO 2 H + H 2 O, is formed, together with glucovanillin, 9
Barth, Ann. Chem. Pharm. cxlii. 246.
P. Meyer, Bar. Dcutsch. Chem. Ges. xi. 129.
Ibid. viii. 509. 4 Ibid. viii. 1123.
Ibid. ix. 414. 6 Ibid. x. 60.
Tiemann and Mendelsohn, ibid. ix. 1278.
Matsmoto, ibid. xi. 128. 9 Tiemann, ibid, xviii. 1595.
ISOVANILLIC ACID. 353
by the action of potassium permanganate on coniferin, and
crystallizes from hot water in fine prisms, which lose their
water of crystallization at 100, and melt at 210 9 212.
It is decomposed by emulsin or by boiling with dilute acids
into grape sugar and vanillic acid. 1
Acetylvanillic acid, C 6 H 3 (OCH 3 )(OCO.CH 3 )C0 2 H, is formed
by heating vanillic acid with acetic anhydride, 2 and from
eugenol acetate, C 6 H 3 (OCH 3 )(OC 2 H 3 0)C 3 H 5 , acetylferulic acid, 3
C 6 H 3 (OCH 3 )(OC 2 H 3 O)C 2 H 2 .C0 2 H, acetylcreosol,* C 6 H 3 (OCH 3 )
(OC 2 H 3 0)CH 3 and acetylhomovanillic acid 5 by oxidation with
potassium permanganate. It crystallizes from dilute alcohol in
fine needles, which melt at 142, and are decomposed on boiling
with caustic potash into acetic and vanillic acids.
Benzoyhanillic acid, C 6 H 3 (OCH 3 )(OCO.C 6 H 5 )C0 2 H, is pre-
pared by the oxidation of benzoyleugenol, and crystallizes from
dilute alcohol in small plates which have a peculiar surface
lustre, and melt at 178 . 6
Isovanillic acid, C 6 H 3 (OH)(OCH 3 )CO 2 H, (C0 2 H :OH: OCH 3
m 1 : 3 : 4). Tiemann found that when dime thy Iprotocatechuic
acid is heated with dilute hydrochloric acid, vanillic acid and
an isomeric methylprotocatechuic acid are formed, 7 the latter
being, as was proved by Beckett and Wright, 8 identical with
an acid which Matthiessen and Foster had previously ob-
tained by heating hemipinic acid, C 6 H 2 (OCH 3 ) 2 (C0 2 H) 2 , with
hydrochloric acid. 9 According to Matsmoto, who proposed the
name isovanillic acid, it is most readily prepared by heating
2 parts of di methylprotocatechuic acid to 160 170 with a
mixture of 25 parts of hydrochloric acid of specific gravity 1'2
and 50 parts of water for four to five hours. The product
is repeatedly crystallized from water in order to remove vanillic
and protocatechuic acids which are formed in the reaction, and
is then freed from any unaltered dimethylprotocatechuic acid by
conversion into the acetyl compound, which is then recrystallized
and saponified by dilute caustic potash. 10
1 Tiemann and Reimer, Ber. Deutsch. Chem. Ges. viii. 515.
2 Tiemann and Nagai, ibid. viii. 1142.
3 Tiemann, ibid. ix. 409.
4 Tiemann and Mendelsohn, ibid. x. 57.
5 Tiemann and Nagai, ibid.x. 201.
6 Kraaz and Tiemann, ibid. xv. 2068.
7 Ibid. viii. 513.
8 Journ. Chcm. Soc. 1876, i. 302.
9 Proc. Roy. Soc. xii. 502.
10 Bcr. Deutsch. Chem. Gcs. xi. 125.
354 AROMATIC COMPOUNDS.
Isovanillic acid crystallizes in lustrous, transparent prisms,
melting at 250, which dissolve in 1,700 parts of water at 14,
and in 160 parts at 100. It is readily soluble in alcohol and
ether ; it gives no colour reaction with ferric chloride.
Acetylisovanillic acid, C 6 H 3 (OCO.CH 3 )(OCH 3 )CO 2 H, crystal-
lizes from dilute alcohol in scales, melting at 206 207.
2195 Veratric acid or Dimethylprotocatechuic acid, C 6 H 3 (OCH 3 ) 2
C0 2 H. In the year 1839, E. Merck discovered veratric acid,
C 9 H 10 O 4 , 1 in the seeds of Veratrum Sdbadilla, and W. Merck
then observed that it decomposes into carbon dioxide and
veratrol, C 8 H 10 O 2 , on heating with caustic baryta. 2 By the
oxidation of methyleugenol, Grabe and Borgmann obtained
bimethoxybenzoic acid, 3 which was shown by Tiemann 4 and by
Erlenmeyer and Wassermann 5 to be identical with the di-
methylprotocatechuic acid which Kolle had prepared by
heating protocatechuic acid with caustic potash, methyl iodide
and wood-spirit ; 6 Korner then showed that this compound is
also identical with veratric acid, veratrol being dimethylcate-
chol. 7 Veratric acid is also formed when veratrin and pseudo-
aconitine are heated with alcoholic potash. 8 In order to prepare
it, 1 part of methyleugenol, C 6 H 3 (OCH 3 ) 2 C 3 H 5 , is shaken up
with 10 15 parts of water, and a solution of 3'5 parts of potas-
sium permanganate in 20 30 parts of water heated to 80 90
gradually added. The filtrate is concentrated by evaporation
and precipitated with hydrochloric acid. 9 Yeratric acid dissolves
in 2,100 parts of water at 14, and in 160 parts at 100, and
crystallizes from a concentrated solution at a temperature above
50 in anhydrous needles, while crystals containing a molecule of
water are obtained from very dilute solutions at any temperature
below this. It melts at 174 175 and can be sublimed. It
dissolves readily in alcohol and ether ; ferric chloride produces
no colouration.
Methyl veratrate, C 6 H 3 (OCH 3 ) 2 C0 2 .CH 3 , is formed, together
with methyl protocatechuate and methyl isovanillate, when
protocatechuic acid is heated with caustic potash, methyl iodide
and wood spirit, 10 no methyl vanillate being formed. 11
I Ann. Chem. Pharm. xxix. 188. 2 Ibid, cviii. 60.
3 Ibid, clviii. 282. 4 Ber. Deutsch. Chem. Gcs. viii. 514.
5 Ann. Chem. Pharm. clxxix. 366. 6 Ibid. clix. 240.
f Ber. Deutsch. Chem. Gcs. ix. 582.
8 Wright and Luff, Journ. Chem. Soc. 1878, i. 160 and 352.
9 Tiemann and Matsmoto, Ber. Deutsch. Chem. Ges. ix. 937.
10 Matsmoto, ibid. xi. 122.
II Tiemann, Ber. Deutsch. Chem Ges. viii. 513.
PIPERONIC ACID. 355
The ether is obtained pure when a solution of the acid in
anhydrous methyl alcohol is saturated with hydrochloric acid,
or when vanillic acid is heated with caustic potash and methyl
iodide. It crystallizes in odourless needles, melts at 59 60
and boils at about 300 (Matsmoto).
Melting- Boiling-
point, point.
Ethyl veratrate, 1
C 6 H 3 (OCH 3 ) 2 C0 2 .C 2 H 5 43 44 295 296
Ethylvanillic acid, 2
C 6 H 3 (OC 2 H 5 )(OCH 3 )C0 2 H . . . 193 194
Diethylprotocatechuic acid, 3
C 6 H 3 (OC 2 H 5 ) 2 C0 2 H, . . . . . 149
Piper onic acid, C 6 H 3 (O 2 CH 2 )C0 2 H, was prepared by Fittig
and Mielk by the oxidation of piperic acid or piperonal with
potassium permanganate, 4 while Fittig and Remsen obtained it
by heating protocatechuic acid with caustic potash and methy-
lene iodide : 5
/OK \CH 2
C 6 H / OK + CH 2 I 2 = C 6 H 3 -- O / + 2KI.
\C0 2 K \C0 2 K
It occurs in small quantity in Paracoto bark, which is collected
on the river Mapiri in Bolivia, and has been detected in true
Goto bark, which is also found in Bolivia. 6
Piperonic acid is scarcely soluble in cold water, slightly in
boiling water, from which it separates in small needles, or, on
very gradual cooling, in characteristic crystals, which resemble
in appearance small twisted threads of sewing cotton. It is also
slightly soluble in ether and cold alcohol, separating from a
hot alcoholic solution in larger crystals. It is obtained in the
purest state by sublimation, which yields large, compact, glitter-
ing prisms with acute terminal planes ; it melts at 227*5
228'5, but sublimes at a lower temperature.
When it is heated with phosphorus pentachloride, a liquid
chloride is formed which yields a chlorinated acid on decom-
position with cold water ; this substance is probably a dichloro-
piperonic acid and is resolved on heating with water into
1 Tiemann and Matsmoto, Ber. Dcutsch. Chcm. Ges. ix. 942.
2 Tiemann, ibid. viii. 1130 ; Wassermann, Ann. Chem. Pharm. clxxix. 379.
3 Kolle, ibid, clix.' 245. 4 Kolle, ibid. clii. 40.
8 Ibid, clxviii. 93. 6 Hesse and Jobst, ibid, cxcix. 63.
356 AROMATIC COMPOUNDS.
hydrochloric acid, carbon dioxide and protocatechuic acid.
Piperonic acid is decomposed by dilute hydrochloric acid at
170, or by water at 210, into carbon dioxide and protocatechuic
acid, so that it behaves in an analogous manner to its aldehyde 1
(p. 347). _
Potassium piperonate, C 8 H 5 O 4 K + H 2 O, crystallizes in long
needles, which are readily soluble in water.
Calcium piperonate, (C 8 H 5 4 ) 2 Ca + 3H 2 0, is slightly soluble
in cold, readily in hot water, and crystallizes in fascicular groups
of needles or plates.
Silver piperonate, C 8 H 5 O 4 Ag, is a granular precipitate, which
crystallizes from hot water in large, narrow plates.
Ethyl piperonate, C 8 H 5 O 4 .C 2 H 5 , is a mobile, strongly refractive
liquid, which has a pleasant fruity odour (Jobst and Hesse).
Ethyleneprotocatechuic acid, C 6 H 3 (O 2 C 2 H 4 )C0 2 H, is formed by
heating protocatechuic acid with caustic potash and ethylene
bromide. 2 It is slightly soluble in cold water and crystallizes
from a boiling solution in splendid, broad, lustrous needles. It
dissolves in almost every proportion in alcohol, from which it
separates on dilution in druses composed of short, lustrous
prisms, which melt at 133'5, and sublime in lustrous prisms
when carefully heated.
The calcium salt, (C 9 H 7 O 4 ) 2 Ca + 2H 2 O, crystallizes from hot
water in well-developed, compact, monoclinic prisms.
Bromoprotocateckuic acid, C 6 H 2 Br(OH) 2 CO 2 H, is prepared by
triturating protocatechuic acid with bromine ; it crystallizes
from hot water in fine, rhombic needles, and is converted into
gallic acid by fusion with potash. 8
2196 Maclurin, C 13 H 10 O 6 + H 2 0, occurs in fustic (Morus,s. Ma-
dura tinctoria), and was described by Wagner as morintannic
acid. 4 " Its correct formula has been determined by Hlasiwetz
and Pfaundler. 5 According to Wagner, the dirty yellow, crys-
talline masses found in the centre of the logs consist almost
entirely of impure maclurin, which can readily be purified
by repeated crystallization from slightly acidified water. Bene-
dikt employs as his raw material the muddy deposit which
is obtained as a by-product in the manufacture of fustic
extract, and which consists of maclurin and its calcium
1 Fittig and Remsen, Ann. Chem. Pharm. clix. 129.
2 Fittig and Macalpine, ibid, clxviii. 99.
3 Barth, ibid, cxlii. 246 ; Ber. Dcutsch. Chem. Gcs. viii. 1484.
4 Journ. Prakt. Chem. li. 82 ; Hi. 449.
5 Ann. Chem. Pharm. cxxvii. 352.
MACLURIN AND LUTEOLIN. 357
salt. It is ground up with dilute hydrochloric acid pressed, and
repeatedly crystallized from hot water. In order to remove any
adhering colouring matter, it is dissolved in water and treated
with lead acetate. A current of sulphuretted hydrogen is then
passed through the hot liquid, which is subsequently filtered and
allowed to cool ; the pure maclurin is thus obtained as a light
yellow, crystalline powder. It becomes anhydrous at 130, and
melts at 200. On boiling with water and barium carbonate
one molecule of carbon dioxide is evolved for every two
molecules of maclurin present (Benedikt), while the salt
C 13 H 8 PbO 6 + H 2 O is deposited in yellow plates when lead
acetate is, added to the boiling solution (Hlasiwetz and
Pfaundler).
When maclurin is boiled with concentrated caustic potash solu-
tion or heated to 120 with dilute sulphuric acid, it decomposes
smoothly into protocatechuic acid and phloroglucinol.
Benedikt therefore proposes the following formulae for maclurin
and its lead salt : 1
OH /OH
co.
Luteolin, C 20 H 14 8 , was discovered by Chevreul in weld
la lutea), 2 and analyzed by Moldenhauer, 3 who obtained
lumbers which led to the formula given above, while Paraf
id Schiitzenberger calculated the composition 2C 12 H 8 O 5 -|-3H 2 O
from the results of their investigation and somewhat unsatis-
factory analyses. 4 It is obtained by extracting the dried plant
with water containing 5 6 per cent, of alcohol, concentrating
the filtrate by evaporation and purifying the crude luteolin thus
obtained by recrystallization from alcohol or a mixture of water
and glycerol.
It crystallizes in small, yellow needles, which dissolve in
14,000 parts of cold water, in 5,000 parts at 100 and in 37
parts of alcohol. It readily forms a deep yellow solution in
alkalis, and dissolves in cold sulphuric acid forming a reddish
yellow solution from which it is precipitated by water. A small
1 Ann. Chem. Pharm. clxxx. 114. 2 Berzelius, Jahresb. xi. 280.
3 Ann. Chem. Pharm. c. 180. 4 Compt. Rend. lii. 92.
254
358 AROMATIC COMPOUNDS.
quantity of ferric chloride produces a green colouration, which
passes into brownish red on the addition of more of the reagent.
Its hot aqueous solution dyes wool, mordanted with alum, a
beautiful daffodil-yellow (Chevreul). On fusion with potash it
is decomposed with evolution of hydrogen into phloroglucinol
and protocatechuic acid : 1
CHO + 3H) = 2CH0 + CH0 + H
MMg 764 663 2 .
Rochleder states, however, that the amount of phloroglucinol
formed is much greater than corresponds to this equation. The
formula of luteolin is by no means accurately determined and
its constitution is quite unknown.
SYMMETRIC METADIHYDROXYBENZOIC ACID
OR a-RESORCYLIC ACID (1:3: 5).
2197 This substance is obtained by fusing /3-disulphobenzoic
acid, 2 metabromosulphobenzoic acid and parabromosulphobenzoic
acid 3 with caustic potash. It crystallizes with one and a half
molecules of water in needles or prisms, which melt at 232
233, are tolerably soluble in cold, ^ readily in hot water,
alcohol and ether, and give no colouration with ferric chloride.
On fusion with caustic soda it decomposes above 300 into
resorcinol and carbon dioxide. 4 A very characteristic reaction
is that when heated with 4 parts of sulphuric acid to 140, a
deep red solution is formed from which water precipitates green
flocks of anthrachrysone, C 14 H 4 (OH) 4 2 , which is a derivative of
anthracene, and is also formed by the dry distillation of the
acid. Lead acetate does not produce a precipitate when added
to an aqueous solution of the acid.
Ethyl a-resorcylate, C 6 H 3 (OH) 2 CO 2 .C 2 H 5 , crystallizes from
water in long prisms which melt below 100.
Dimethyl-a-resorcylic acid, C 6 H 3 (OCH 3 ) 2 CO 2 H, is formed when
a-resorcylic acid is heated with caustic potash, methyl iodide and
wood-spirit, and when dimethylorcinol is oxidized with potassium
1 Rochleder, Journ. Prakt. Chcm. xcix. 433.
2 Earth and Senhofer, Ann. Chcm. Pharm. clix. 217.
8 Bottinger, Bcr. Deutech. Chem. Ges. viii. 374.
4 Barth and Schreder, ibid. xii. 1258.
RESORCYLIC ACIDS. 359
permanganate. 1 It crystallizes from hot water in fine needles,
which melt at 175 176.
Diethyl-a-resorcylic acid, C 6 H 3 (OC 2 H 5 ) 2 CO 2 H, was prepared
by Earth and Senhofer from the acid by the action of ethyl
iodide. 2 It forms elongated prisms, which melt at 87 88, and
are decomposed by distillation with lime into carbon dioxide and,,,
diethylresorcinol. 3
a-Bromoresorcylic acid, G 6 H 2 Br(OH) 2 C0 2 H, is formed by the
action of bromine water on an aqueous solution of a-resorcylic
acid, and crystallizes from hot water in long needles, which melt at
253, and give a yellowish brown colouration with ferric chloride.
It gives the same reaction with sulphuric acid as a-resorcylic
acid, and is converted into gallic acid by fusion with caustic
potash (Barth and Senhofer).
ASYMMETRIC METADIHYDROXYBENZOIC
ACID OR ^-RESORCYLIC ACID, (1:2:4).
2198 This acid is formed when paracresolsulphonic acid, 4 and
a-disulphobenzoic acid 5 are fused with caustic potash, and may
also be obtained, together with a large amount of resorcinol,
when its aldehyde is fused for a short time with caustic potash. 6
It may also be prepared, together with 7-resorcylic acid and
dihydroxyphthalic acid, C H 2 (OH) 2 (C0 2 H) 2 , by heating 1 part
of resorcinol with 4 parts of ammonium carbonate and 5 parts
of water to 120 130 , 7 and still more readily by heating
resorcinol in an open flask with a concentrated solution of
potassium bicarbonate. It is very slightly soluble in cold water,
and crystallizes from a hot solution in needles containing one
and a half molecules of water, one of which is lost on exposure
to the air (Fahlberg). It melts at 204 206, and simultane-
ously decomposes into carbon dioxide and resorcinol. Its
1 Tiemann and Streng, Ber. Deutsch. Chem. Ges. xiv. 2002.
2 Ann. Chem. Pharm. clxiv. 121.
3 Barth, Ber. Deutsch. Chem. Ges. xi. 1569.
4 Ascher, Ann. Chem. Pharm. clxiv. 11.
8 Blomstrand, Ber. Deutsch. Chem. Ges. v. 1088 ; Fahlberg, Amer. Chem,. Journ.
ii. 196.
8 Tiemann and Reimer, Ber. Deutsch. Chem. Ges. xii. 997 ; Tiemann and
Parrisius, ibid. xiii. 2358.
7 Brunner and Senhofer, ibid. xiii. 2356 ; Ber. Wien. AJcad. 1879, ii 504.
360 AROMATIC COMPOUNDS.
solution is coloured dark red by ferric chloride, and does not
give a precipitate with lead acetate.
Orthor)iethyl-@-resorcylic acid, C 6 H 3 (OH)(OCH 3 )C0 2 H(OCH 3 :
OH = 2 : 4), is formed when the acetyl-derivative of its aldehyde
is oxidized with potassium permanganate and the product
decomposed by caustic potash. It is tolerably soluble in water,
does not crystallize well, and gives no colouration with ferric
chloride. 1
Paramethyl-0-resorcylic acid, (OH : OCH 3 =2 : 4). The methyl
ether is prepared by adding sodium to a solution of /3-resorcylic
acid in wood-spirit and then heating with methyl iodide, the
acid being obtained from this by boiling with caustic potash
(Tiemann and Parrisius) ; it is also formed when sodium rnethyl-
resorcinol is heated to 215 in a current of carbon dioxide : 2
C 6 H 4 (OCH 3 )ONa + CO 2 = C 6 H 3 (OCH 3 )(OH)CO 2 Na.
It crystallizes from hot water in lustrous needles, which melt
at 151'5, and decompose into methylresorcinol and carbon
dioxide when rapidly heated. Its aqueous solution is coloured
an intense reddish violet by ferric chloride.
Dimethyl- ft-resorcy lie acid, C 6 H 3 (OCH,) 2 CO 2 H, is not readily
formed by the further methylation of the preceding compound,
but may be obtained by the oxidation of its aldehyde with
potassium permanganate ; it crystallizes from hot water in fine
needles, melting at 108 (Tiemann and Parrisius).
Diethyl-@-resorcylic acid, C 6 H 3 (()C 2 H 5 ) 2 C0 2 H, was prepared in
a similar manner ; it forms needles which melt at 99. 3
ADJACENT METADIHYDROXYBENZOIC ACID
OR 7-RESORCYLIC ACID (1:2:6).
2199 The formation of this acid has already been mentioned ;
it is very soluble in water, and crystallizes in fine, fascicular
needles, which contain one molecule of water and commence to
fuse at 140, a partial decomposition into resorcinol and carbon
dioxide occurring, which becomes complete at a higher tempera-
1 Tiemann and Parrisius, Bcr. JDewtsch. Chem. Ges. xiii. 2375.
2 Korner and Bertoni, ibid. xiv. 847.
3 Tiemann and Lewy, ibid. x. 2215.
HYDROXYSALICYLIC ACID. 361
ture. Its aqueous solution is coloured a deep bluish violet by
ferric chloride.
ry-BromoTesorcylic acid, C 6 H 2 Br(OH) 2 C0 2 H + H 2 O, is formed
by the action of bromine on an ethereal solution of the acid. It
is slightly soluble in cold water, readily in alcohol, and crystallizes
in fine prisms, which lose their water at 100 and melt at
184 with decomposition. It is coloured violet by ferric
chloride.
Dimethyl->y-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 <to prepare gallic acid, Scheele's method, which is
stated by Liebig to give the best yield, is made use of. Finely
powdered nut-galls are extracted with cold water and the solution
allowed to stand in a warm place, the precipitated acid being
recrystallized from boiling water.
According to Braconnot, the entire nut-galls may be moistened
with water in summer or allowed to stand in a warm place until
they form a paste, which is then extracted with boiling water. 8
The spores of Penicillium glaucum or Aspergillus niger are
necessary to set up fermentation. 9 Wittstein recommends the
addition of beer yeast ; he thus obtained almost 50 per cent,
from Chinese nut-galls, while without the yeast the yield only
amounted to 17 per cent. 10 One hundred pounds of Turkish
nut-galls, treated by Scheele's method, give 24 pounds of gallic
acid. 11
It crystallizes in silky needles or asymmetric prisms, containing
one molecule of water, which is lost at 120, has an acid,
astringent taste, and dissolves in 130 parts of water at 12'5, and
in 3 parts at 100. It is more readily soluble in alcohol, since
27'95 parts dissolve in 100 parts of absolute alcohol at 15,
and 18*90 parts in 100 parts of 90 per cent, alcohol, while 100
parts of ether only dissolve 2 '5 parts. 12
Gallic acid commences to melt above 220 and decomposes
into carbon dioxide and pyrogallol when more strongly heated.
It is readily oxidized, reduces Fehling's solution and the salts of
the noble metals, and in alkaline solution absorbs oxygen. When
1 Ber. Deutsch, Chem. Ges. xi. 1881.
2 Earth and Senhofer, ibid. viii. 1884.
3 Ibid. 4 Matmoso, ibid. xi. 140.
6 Barth and Senhofer, Ann. Chem. Pharm. clxiv. 118.
6 Ibid. cxx. 137.
7 Ber. Dcutfteh. Chem. Gcs. vii. 1441.
8 Ann. Chim. Phys. ix. 181.
9 Tieghem, Zeitschr. Chem. 1868, 222.
10 Vierteljahrsschr. Pharm. ii. 72.
11 Steer, Jahresber. Chem. 1856, 482.
12 Bourgoin, Bull. Soc. Chim. xxix. 245.
368 AROMATIC COMPOUNDS.
it is added to feme chloride, a partial reduction ensues
and a black-blue precipitate is formed, which dissolves in the
excess of ferric chloride with a green colour. According to
Etti, the colouration depends mainly on the concentration of
the solutions, and varies between black-blue, black -green, blue,
greenish and brownish green. An excess of gallic acid destroys
the colour and effects complete reduction to ferrous chloride ; a
solution of pure ferrous sulphate in absence of air is therefore
not altered by it, but on exposure to air is coloured a bright blue,
and deposits a black precipitate without becoming decolourized.
Gallic acid in alcoholic or alkaline solution reduces paranitro-
benzyl chloride to paranitrotoluene. Digallic acid and pyro-
gallol have a similar action. 1
It is converted by the action of potassium chlorate and
hydrochloric acid into tricarballylic acid, C 3 H 5 (CO 2 H) 3 , and
isotrichloroglyceric acid, CC1 3 .C(OH) 2 .C0 2 H, which crystallizes in
needles and is readily decomposed by alkalis into chloroform and
oxalic acid. 2
When gallic acid is heated with sulphuric acid, rufigallic acid
or hexyhydroxyanthraquinone, C U H 2 O 2 (OH) 6 , is formed, while an
acid solution of potassium permanganate produces hydrorufigallic
acid, C 14 H 8 O 5 .
Gallic acid is not precipitated by gelatine solution, and can
thus be distinguished from tannic acid and other similar
substances.
2203 The G-allates have been chiefly investigated by Buchner.
Sodium gallate, C 6 H 2 (OH) 3 C0 2 Na + 3H 2 O, is obtained by
adding alcoholic soda to a solution of the acid in alcohol as a
granular, crystalline precipitate, which crystallizes from a very
concentrated aqueous solution in pointed yellow plates.
Potassium gallate, C 6 H 2 (OH) 3 CO 2 K + C 6 H 2 (OH) 3 C0 2 H+H 2 0,
is a light, crystalline powder which is prepared in a similar
manner to the sodium salt ; the normal salt has not yet been
obtained.
Ammonium gallate, C 6 H 2 (OH) 3 CO 2 NH 4 + H 2 O, is formed
when ammonia is passed into a solution of the acid in absolute
alcohol, and crystallizes from water in fine needles. When its
solution is boiled, the acid salt, C 6 H 2 (OH) 3 C0 2 NH 4 + C 6 H 2 (OH) 3
C0 2 H, is deposited on cooling in splendid crystals. 3 It is also
1 Pellizzari, Gazz Chem. Itnl. xiv. 481.
2 Schreder, Ann. Chem. Pharm. clxxvii. 282 ; see also Claisen and Antweiler,
Ber. Deutsch. Chem. Ges. xiii. 1938.
3 Etti, Ber. Deutsch. Chem. Ges. xvii. 1821.
SALTS OF GALLIC ACID.
formed when dry gallic acid is saturated with ammonia, the
excess of the latter allowed to evaporate in a vacuum and the
residue crystallized from water ; it contains water of crystallization
(Kobiquet).
Calcium gallate, (C 7 H 5 5 ) 2 Ca 4- 3H 2 0, forms thin, crystalline
crusts, consisting of needles. When lime-water is added to a
solution of the acid a dirty green precipitate is produced.
Barium gallate, (C 7 H 5 O 5 ) 2 Ba + 3H 2 O, is obtained by neutra-
lizing a boiling solution of the acid with barium carbonate ; it
crystallizes in small plates, which do not readily redissolve in
water. If the freshly-prepared solution be treated with baryta-
water, a precipitate of C 7 H 2 5 Ba 2 + 5H 2 O is formed, which
rapidly becomes coloured dark blue on exposure to the air in the
moist state (Hlasiwetz).
Lead gallate. Lead acetate added to a hot solution of an
excess of the acid produces a precipitate of 2C 7 H 4 O 5 Pb -f H 2 O,
which soon changes to a lustrous, crystalline powder. If, how-
ever, an excess of the lead acetate be employed, a flocculent
precipitate is formed, which becomes yellow and crystalline on
boiling and has the formula C 7 H 2 5 Pb 2 (Liebig).
Iron gallate. A splendid blue precipitate is obtained when
the acid is added to a mixture of three molecules of a ferrous
salt with two molecules of a ferric salt. 1
Ethyl gallate, 2C 6 H 2 (OH) 3 C0 2 .C 2 H 5 + 5H 2 O, is formed when
hydrochloric acid is passed into the alcoholic solution of the acid.
It is slightly soluble in cold, readily in hot water and alcohol,
and crystallizes in pointed prisms, which lose their water at
100 . 2 It is slightly soluble in chloroform, from which it
separates in anhydrous crystals. 3 It behaves towards ferric
chloride, silver nitrate, &c., in the same manner as the free
acid, and on heating decomposes into alcohol and pyrogallol,
accompanied, however, by other products. 4 When acid sodium
carbonate is added to its aqueous solution, small crystals of
C 6 H 2 (OH) 3 C0 2 .C 2 H 5 + C 6 H 2 (OH) 2 (ONa)C0 2 .C 2 H 5 , are formed,
which are scarcely soluble in cold water (Ernst and Zwenger).
Lead acetate added to an aqueous solution of the ether produces
a finely divided precipitate of (C 6 H 2 (CO 2 .C 2 H 5 )0 3 ) 2 Pb 3 (Schiff).
Triethylgallic acid, C 6 H 2 (OC 2 H 5 ) 3 CO 2 H. The ethyl ether of
this substance is obtained by heating ethyl gallate with caustic
1 Barreswill, Compt. Rend. xvii. 739.
2 Grimaux, Bull. Soc. Chim. ii. 94.
3 Ernst and Zwenger, Ann. Chem. Fharm. clix. 28.
4 Schiff, ibid, clxiii. 209.
370 AROMATIC COMPOUNDS.
potash, ethyl iodide and alcohol ; water precipitates it from alco-
holic solution in lustrous needles, which melt at 51 and are easily
decomposed by alcoholic potash ; hydrochloric acid separates the
triethylgallic acid from the product as a crystalline precipitate.
It is slightly soluble in cold, readily in hot water, and separates
from the latter in crystals melting at 112 . 1
Triacetylgcillic acid, C 6 H 2 (OC 2 H 3 O) 3 CO 2 H, is prepared by
boiling gallic acid with acetyl chloride and acetic anhydride. It
is only slightly soluble in hot water, separates from alcohol in
small, lustrous needles and gives no colouration with ferric
chloride (Schiff).
Bromogallic acid, C 6 HBr(OH) 3 CO 2 H, is obtained by triturating
equal molecules of gallic acid and bromine. 2 It separates from
the hot, aqueous solution in monoclinic crystals, resembling those of
gypsum ; its solution gives a splendid violet colouration with ferric
chloride and a fiery red, soon changing to brown with ammonia.
Dibromogallic acid, C 6 Br 2 (OH) 3 CO 2 H 4- H 2 0, is formed when
an excess of bromine is employed (Grimaux). It crystallizes
from hot water in long plates or needles, melting at 150 . 3 Ferric
chloride produces a black-blue colouration ; moist silver oxide
decomposes it with formation of pyrogallol, carbon dioxide and
silver bromide, while on heating with water and potassium silver
cyanide it is reconverted into gallic acid : 4
C 6 Br 2 (OH),C0 2 H + 2AgCN + 4H 2 O =
C 6 H 2 (OH 3 )C0 2 H + 2C0 2 + 2NH 3 + 2AgBr.
Gallamide, C 6 H 2 (OH) 3 CO.NH 2 . This compound, which is also
called gallamic acid, is formed together with gallic acid when a
solution of tannin in ammonia is rapidly boiled :
H(X OH
H(X /OH
x + NH = X C H /
HO^ /O HO/ \CO.NHj
\CO.OH
HO. /OH
CO.OH.
. Ges. xvii.
9 ; Grimaux
8 Etti, Bcr. Deuisch. Chem. Ges. xi. 1182. 4 Priwoznik, ibid. iii. 645.
1 Albrecht and Will, Bcr. Dcutsch. Chem. Ges. xvii. 2098.
2 Hlasiwetz, Ann. Chem. Pharm. cxlii. 249 ; Grimaux, Zeitschr. Chem. 1867, 431.
TANNIC ACID. 371
In order to avoid oxidation, ammonium sulphite must be
added to the solution or the operation must be conducted in
an atmosphere free from oxygen. 1 It crystallizes from hot water
in large, colourless plates and decomposes on boiling with
hydrochloric acid into gallic acid and ammonia.
2204 Digallic acid, Tannic acid or Tannin, C 6 H 2 (OH) 3 CO.
OC 6 H 2 (OH) 2 C0 2 H. The name of tannic acids has been applied
to a whole series of substances, which are weak acids, "have an
astringent taste, give black-blue or dark green compounds with
salts of iron, and combine with animal skins to form leather, for
which purpose they are largely employed. These bodies do not
stand in any intimate chemical relation to each other, and the
tannic acid derived from nut-galls, the constitution of which is
known, is alone referred to here.
The nut-galls in which it occurs are of two kinds : the ordinary,
Turkish or Levant variety, which are produced by the puncture
of the gall-fly (Cynips G-allae tinctoriae) in the young shoots of
Quercus hisitanica, var. infectoria and probably some other
species, and the Chinese or Japanese nut-galls, which are formed
by a plant-louse (Aphis chinensis) on the leaf-stalks and young
twigs of Rhus semialata. In addition to these modes of occur-
rence, tannic acid has hitherto only been observed in sumach,
the leaves and twigs of Rhus coriaria. 2
Stenhouse, who found that tannic acid from sumach is con-
verted into gallic acid by dilute sulphuric acid, says : " Sumach,
therefore, appears to approach the nature of nut-galls more
closely than any of the other astringent substances. This fact
is well known to Turkey-red dyers, who have long successfully
employed sumach as a substitute for galls."
In order to prepare tannin, the method of Pelouze was formerly
employed, according to which the nut-galls are extracted with
ordinary ether, containing both alcohol and water. The
solution thus obtained separates into two layers, the upper of
which consists of water and ether containing gallic acid and a
little tannin, while the syrupy lower layer is a solution of tannin
in water and ether and is evaporated to dryness.
A mixture of 12 parts of ether and 3 parts of alcohol is now
used for the extraction, 12 parts of water being added to the
extract and the alcohol and ether removed by distillation. The
1 Knop, Jahrcsber. Chem. 1854, 431 ; Schiff and Pons, Per. Deutsch. Chem.
Ges. xv. 2591 ; xviii. 487 ; Etti, ibid. xvii. 1820.
2 Stenhouse, C/WM. Soc. Mem. i. 137 ; Lowe, Fres. Zeitschr. xii. 128.
372 AROMATIC COMPOUNDS.
residual aqueous solution is then filtered and evaporated, the
crude tannin being further purified by solution in water and
treatment with animal charcoal. 1
Pure tannin may also be obtained by extracting nut-galls
with anhydrous ether, to which 5 per cent, of alcohol has been
added (Schiff).
While the tannin prepared by Pelouze's method contains more
or less grape sugar or a substance yielding dextrose, this is not
the case with that obtained by the more modern process, and
hence it follows that tannin is not a glucoside, but that the older
specimens contained, as was suggested by Rochleder, an admix-
ture of sugar or a glucoside which was brought into solution by
the water present. 2
Schiff, as already mentioned, found that gallic acid is converted
into tannic acid when it is heated with phosphorus oxychloride
or when its solution is evaporated with arsenic acid. According
to Freda, the product obtained by the latter method gives all
the characteristic reactions of tannin, but is nothing more than
gallic acid containing arsenic acid, 3 while Schiff has shown that
this is not the case, but that arsenic acid adheres to the tannin
so obstinately that it cannot be removed without a simultaneous
conversion of a portion of the latter into gallic acid. 4 The
constitution of tannin or digallic acid is expressed by the
following formula :
HOv ,HO
" 2 \co>
/
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.
<y-Dinitroparaxylene (1:4:2:5) is slightly soluble in cold ,
more readily injiot alcohol, and forms long, yellow needles with
a vitreous lustre, which melt at 147 148 . 5
Lellmann determined the constitutions of these three isomerides
by the methods already described (Part III., p. 245) ; the first
two, which are formed in largest quantity, were converted into
the hydrochlorides of the corresponding diamines, their solutions
evaporated with ammonium thiocyanate,'and the residues heated
to 120, ground up with water, washed, dissolved in caustic soda,
and these solutions heated with lead acetate'. The a- compound
gave a precipitate of lead sulphide while the /3-compound did
not, and was thus proved to be an orthodiamine.
He then prepared the free a-diamidoparaxylene, which is a
crystalline mass, and combines with allyl mustard oil to form the
compound C 6 H 2 (CH 3 ) 2 (NH.CS.NH.C 3 H 5 ) 2 , which crystallizes in
1 Luhmann, Ann. Chem. Pharm. cxliv. 276 ; Fittig, loc. cit. ; Grevingk, loc cit.
2 Jannasch, Ann. Chem. Pharm. clxxvi. 55 ; Nblting and Forel, loc. cit.
3 Fittig and Glinzer, Ann. Chem. Pharm. cxxxvi. 307 ; Fittig, Ahrens and
Mattheides, ibid, cxlvii. 17.
4 Jannasch and Stiinkel, Ber. Deutsch. Chem. Ges. xiv. 1146.
6 Lellmann, Ann. Chem. Pharm. ccxxviii. 250.
398 AROMATIC COMPOUNDS.
small needles, melting without decomposition at 112'5. It is
therefore a metadiamine, and the ^-compound must, accordingly,
contain the nitroxyl groups in the para-position.
Trinitroparaxylene, C 6 H(CH 3 ) 2 (NO 2 ) 3 (1:4:2:3: 5), may
readily be prepared by nitrating with a mixture of nitric and
sulphuric acids, the whole being gently heated at the close of the
operation. It crystallizes from alcohol in stellate aggregates of
dazzling white needles, which melt at 139 140 . 1
XYLENESULPHONIC ACIDS, C 6 H 3 (CH 3 ) 2 S0 3 H.
2212 Orthoxylenesulphonic acid (1:2:4) is formed by dis-
solving orthoxylene in tolerably hot sulphuric acid. It crystal-
lizes from a somewhat dilute acid solution with two molecules
of water in long, rectangular tablets or thicker, flat prisms with
pointed ends. Its salts crystallize extremely well. When its
potassium salt is heated with sodium formate, paraxylic acid is
formed.
Sodium orthoxylenesulphonate, C 6 H 2 (CH 3 ) 2 S0 3 Na + 5H 2 O,
separates from a concentrated solution in flat prisms, the size of
which seems only to be limited by that of the containing vessel ;
they soon effloresce on exposure to the air.
Orthoxylenesulphonic chloride, C 6 H 3 (CH 3 ) 2 S0 2 C1, crystallizes
from ether in prisms, melting at 51 52.
Orthoxylenesulphonamide, C 6 H 3 (CH 3 ) 2 S0 2 .NH 2 , separates from
hot alcohol in prisms, which melt at 144 . 2
a-Metaxylenesulphonic acid (1:3: 4) is formed, together with
a small quantity of the isomeric compound, when metaxylene is
dissolved in sulphuric acid. It separates on the addition of a
little water in large plates or prisms, which contain two molecules
of water. Xylic acid is formed when potassium salt is heated
with sodium formate (p. 391).
Sodium metaxylenesulphonate, C 6 H 3 (CH 3 ) 2 S0 3 Na, crystallizes
from water in scales, and from alcohol in small plates possessing
a silver lustre.
a-Metaxylenesul phonic chloride solidifies in the cold to a radiating
mass, or to prisms which melt at 34.
1 Fittig and Glinzer ; Nolting and Geissmann, Ber. Dcutf.ch. Chnn. Oes. xix.
144. 2 Jacobsen, -ib-ul. x. 1010 ; xi. 22.
XYLENOLS. 399
a-Metaxylenesulphamide crystallizes from water in long
pointed needles and melts at 137.
v-Metaxylenesulphonic acid (1:3:2) has not been prepared
pure ; its calcium salt when heated with sodium formate yields
a xylic acid, which decomposes on distillation with lime
into carbon dioxide and metaxylene. Its chloride is an oily
liquid, and the amide crystallizes in needles, melting at
95 96. 1
ParaxylenesulpJionic acid is formed when paraxylene is dis-
solved at a gentle heat in slightly fuming sulphuric acid. It
crystallizes with two molecules of water in large plates or very
long, flat prisms.
Sodium paraxylenesidphonate, C 6 H 3 (CH 3 ) 2 S0 3 Na + H 2 O, crys-
tallizes in large, flat, striated prisms, which do not effloresce in
the air.
ParaxylenesulpJionic chloride forms flat prisms, which melt
at 24 26
Paraxylenesnlphamide is readily soluble in alcohol, slightly
in boiling water, from which it crystallizes in splendid, long
needles, melting at 147 148 (Jacobsen).
HYDROXY-XYLENES, OR XYLENOLS,
C 6 H 3 (CH 3 ) 2 OH.
2213 After Dusart, Kekule and Wurtz had shown that
sulphonic acids are converted into phenols by fusion with potash,
the last-named of these chemists applied the reaction to xylene,
and discovered the interesting fact that this hydrocarbon yields
two isomeric phenols, a solid and a liquid xylenol. This iso-
merism is explained by him as due to the different positions of
the hydroxyl with relation to the two methyl groups. " This
isomerism," he adds, "could, according to Kekule's beautiful
theory, also exist in xylene itself, as a result of a different
arrangement of the side chains in the nucleus." 2 After this
supposition had been proved correct and these xylenes were
known, it was seen that six xylenols must exist, and these have
all now been prepared. Jacobsen obtained four of them from
1 Jacobsen, Ann. Chem. Pharm. clxxxiv. 188 ; loc. cit.
2 Ann. Chem. Pharm. cxlvii. 372 ; see also Wroblewsky, Zeitschr. Chem. 1868,
232.
400 AROMATIC COMPOUNDS.
the sulphonic acids just described, 1 and the two others have been
prepared from the xylidines by means of the diazo-reaction. 2
Like ordinary phenol, they readily form tribromo-derivatives.
The xylenols also occur in coal-tar. They have not, in-
deed been isolated, but their derivatives have been prepared
from it.
The tar obtained as a by-product from blast furnaces
which are worked with coal seems to be especially rich in
xylenols ; the creosote oil fraction, boiling at 210 240, when
distilled over heated zinc dust, yielded a mixture of hydrocarbons,
which consisted chiefly of metaxylene. 3
a-OrtJwxylcnol (1:2:4) crystallizes from hot water in very
long needles and from very dilute alcohol in rhombic pyramids,
melting at 62*5 ; 4 it boils at 225 and forms an aqueous solution
which is not coloured by ferric chloride.
a-Tribromorthoxylenol, C 6 Br 3 (CH 3 ) 2 OH, crystallizes from
alcohol in fine, snow-white, matted needles, melting at 169.
v-Orthoxylenol (1:2: 3) crystallizes from water in white
needles, melts at 75 and boils at 218; its aqueous solution
is coloured blue by ferric chloride, but is not affected by
bleaching-powder solution.
a-Metaxylenol (1:3:4) is, according to Jacobsen, a strongly
refractive liquid, which smells like phenol, boils at 211 '5 and
becomes viscid at 20, without, however, solidifying. These are
also the properties of the liquid xylenol discovered by Wurtz,
while Stadel and Holz showed that the xylenol prepared from
pure a-metaxylidine solidifies at the ordinary temperature. 5
Jacobsen, on reinvestigation, found that his preparation crystal-
lized after repeated cooling or on the addition of a small crystal. 6
It forms white needles, melting at 26. It dissolves slightly
in water, yielding a solution which is coloured blue by ferric
chloride ; the alcoholic solution, on the other hand, is coloured
a splendid dark green, which passes into blue when water is
added.
a-Metaxylenyl methyl ether, C 6 H 3 (CH 3 ) 2 OCH 3 , is a liquid
which has a faint smell resembling that of benzene, and boils
at 192.
1 Bcr. Deutsch. Chem. Gcs. xi. 23.
2 Thol, ibid, xviii. 359, 2561 ; Nolting and Forel, ibid, xviii. 2668.
3 Smith, Coutts and Brothers, Journ. Chem. Soc. 1886, i. 17.
4 Jacobsen, Ber. Deutsch. Chem. Ges. xvii. 161.
8 Ber. Deutsch. Chem. Ges. xviii. 2921.
6 Ibid, xviii. 3463.
PARAXYLENOL. 401
a-Metaxylenyl acetate, C 6 H 3 (CH 3 ) 2 O.CO.CH 3 , is a liquid
boiling at 226, which has a faint odour of oil of bergamot.
Melting-point.
a-Bromometaxylenol, C 8 H 8 Br.OH, oily liquid . . .
a-Dibromometaxylenol, C 8 H 7 Br 2 .OH, fine, colourless ) ,-<>
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 <thrin , C 21 H 24 O ]0 -f-H 2 O, was discovered
in a stunted specimen of E. fuciformis* It crystallizes in
1 Ann. CJiem. Pharm. Ixviii. 83 ; civ. 56. 2 Ibid, cxvii. 297.
3 Stenhouse and Groves, Jaurn. Chcm. Soc. 1880, 407.
4 Menschutkin, Bull. Soc. Chim. [2] ii. 424 ; Lamparter, Ann. Chem. Pharm.
cxxxiv. 234.
436 AROMATIC COMPOUNDS.
concentrically arranged needles, which are very readily soluble in
alcohol. On boiling with baryta water it is resolved into carbon
dioxide, erythrol and homorcinol :
C 13 H 16 6 + 2H 2 = C0 2 + C 4 H 10 4 + C 8 H 10 O 2 .
It is not homologous with picroerythrin, but is the anhydride
of such a compound, which would probably have the following
constitution :
X CO.O V
(CH 3 ) 2 C 6 H(OH)<( >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 <g = C 6 H0 X)H + 2H 2 0.
CO CO
2242 PJithalyl chloride, C 8 H 4 O 2 C1 2 , was first prepared by Hugo
Miiller from phthalic acid by the action of phosphorus penta-
1 Schultz, Sleinkohlcntheerc.
2 Wislicenus, Ber.Deutsch. Chem. Gcs. xvii. 2178.
PHTHALYL CHLORIDE.
459
!3 2
er- 0}
*^ >
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 <cc,> C ' H <c>
+ 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 <co>
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 A<T ' >0 + 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<f NO + 2KSH = C 6 H / NO + 2KC1 + SH 9 .
\ CO / \CO/
It crystallizes from alcohol in small plates or needles, melts at
114 and boils at 284.
1 Bcr. Dfiutsch. CJiem. Ge*, xix 1137. 2 Ibid. xvii. 817.
8 Schreder, ibid. vii. 705. 4 Griibe and Zschokke, ibid. xvii. 1175.
PHTHALAMIC ACID. 463
2243 Phihalimide, C 8 H 4 O 2 (NH), is obtained by heating acid
ammonium phthalate : 1
X CO.ONH 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 :
<HN" PO NTT
CH/ - +HO = CH/
\CO.OH \CO.OH '
This is then resolved into phthalimide and water. 3
The conversion may however be simply explained by an
intermolecular change : 4
C 6 H 4 =C 6 H 4 <; >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) <CO.OH
2262 Noropianic acid, 2C 8 H 6 O 5 + 3H 2 O, was obtained by
Wright, together with methyl iodide, by boiling opianic acid
with four times its weight of 50 per cent, hydriodic acid. It is
readily soluble in water and crystallizes in fine prisms, which
become anhydrous at 100 and melt at 171. Its solution is
coloured greenish blue by ferric chloride, the addition of
ammonia or carbonate of sodium changing the colour to
brownish red. It reduces ammoniacal silver solution in the cold
and forms a yellow or brown solution in alkalis. The lead salt
is a canary-yellow precipitate. 2
Methylnoropianic acid, C 6 H 2 (OCH 3 )OH(COH)C0 2 H, was
prepared by Matthiessen and Foster from opianic acid by
heating it with hydrochloric or hydriodic acid. In order to
prepare it, hydrochloric acid is passed into a warm solution of
50 grms. of opianic acid in 600 cb. cms. of strong hydrochloric
acid until no opianic acid separates after standing for about two
days. The solution is then concentrated, the paste of crystals
thus obtained dissolved in water, the solution neutralized
exactly with ammonia and* treated with barium chloride, which
produces a brown precipitate. The addition of ammonia to the
filtrate precipitates the barium salt of the acid, which is then
washed and decomposed with sulphuric acid. 3
It is readily soluble in water and crystallizes in nacreous
plates, long prisms, or transparent vitreous columns, which contain
different amounts of water, but all readily effloresce in the air.
The anhydrous acid melts at 154 ; its aqueous solution is
coloured dark blue by ferric chloride, and on the addition of
ammonia light red.
1 T. and H. Smith, Pharm. Journ. Trans. [3] viii. 981.
2 Journ. Chem. Soc. 1877, ii. 545.
3 Prinz, Journ. Prakt. Chem. [2] xxiv. 368.
OPIANIC ACID. 503
As a phenol-acid it forms two series of salts.
Silver methylnoropianate, C 9 H 7 5 Ag, is a gelatinous precipitate,
which becomes crystalline on standing. It is soluble in hot
water and separates in crystals when the solution is cooled.
Barium methylnoropianate, C 9 H 6 O 5 Ba + H 2 O, is also thrown
down in the gelatinous state and changes into granular crystals
on standing.
CUoromethylnoropianic acid, C 6 HC1(OCH 3 )OH(COH)C0 2 H,
is obtained by the action of potassium chlorate and hydrochloric
acid on methylnoropianic acid, and crystallizes from hot water in
large, lustrous needles, which melt at 206 (Prinz).
Nitromethylnoropianic acid, C 6 H(N0 2 )(OCH 3 )OH(COH)CO 2 H
+ H 2 O, is formed when methylnoropianic acid is treated with
dilute nitric acid (Matthiessen and Foster). It is also obtained
by heating nitro-opianic acid for some time with hydrochloric
acid. It crystallizes in radiating needles, which lose their water
at 120 and melt at 203 . 1
2263 Dimethylnoropianic acid or Opianic acid, C 6 H 2 (OCH 3 ) 2
(COH)CO 2 H, was prepared by Wb'hler and Liebig from narcotin
by boiling it with dilute sulphuric acid and manganese dioxide.
Blyth found that it is also formed by heating with platinum
chloride, 2 and Anderson obtained it by oxidizing narcotin with
dilute nitric acid. In order to prepare it according to the
method proposed by Matthiessen and Foster, 100 grms. of
narcotin are heated with 1,500 grms. of water and 150 grms. of
sulphuric acid until the mixture boils ; 150 grms. of finely
powdered pyrolusite, corresponding to 90 grms. of manganese
dioxide, are then added somewhat rapidly and the hot solution
filtered.
Opianic acid separates out on cooling and is purified by
recrystallization. Wohler, in order to obtain it perfectly colour-
less, dissolved it in sodium hypochlorite, heated to boiling, and
then added an excess of the hypochlorite. The decolourization
may also be effected, according to Prinz, by passing the gases
evolved from nitric acid and arsenic trioxide through the hot
solution ; and it may also be obtained perfectly white by running
potassium permanganate into the hot solution acidified with
sulphuric acid until it becomes sherry-yellow. 3 The portion
which is left in the mother-liquor from its preparation can be
1 Elbel, Bcr. Deutsch. Chem. Ges. xix. 2306.
2 Ann. Chem. Pharm. 1. 29.
3 Prinz, Journ. Prakt. Chem. [2] xxiv. 353.
504 AROMATIC COMPOUNDS.
removed by ether, which does not dissolve the colouring matter
(Wegscheider).
It is slightly soluble in cold, readily in hot water, alcohol and
ether, and crystallizes in thin, narrow prisms or silky needles, which
melt at 150 (Wegscheider) and decompose on further heating,
giving off a vapour which smells like vanilla (Wohler). It
has a faint acid reaction and a slightly bitter taste. Sodium
amalgam and water reduce it to meconin, while on evaporation
with caustic potash it is converted into the latter and hemipinic
acid (Matthiessen and Foster, Beckett and Wright). When its
sodium salt is heated with soda lime methylvanillin is formed,
and isovanillin when it is heated with dilute sulphuric acid to
160 170. Concentrated sulphuric acid converts it on heating
into a red colouring matter, which Anderson mistook for alizarin,
C 14 H 8 O 4 , but which was shown by Liebermann and Chojnacki to
be the closely allied substance rufiopin, 1 C 14 H 8 O 6 .
The salts of opianic acid have been investigated by Wohler
and Wegscheider. 2
Potassium opianate. C 10 H 9 5 K, is readily soluble in water and
crystallizes in several forms, which differ in the amount of water
they contain. It crystallizes from ordinary alcohol in compact,
white prisms containing two and a half molecules, or transparent,
rhombic tablets with one molecule of water of crystallization.
Barium opianate, (C 10 H 9 O 5 ) 2 Ba + 2H 2 O, forms a radiating mass
of prisms, which are readily soluble in water and effloresce when
kept in a warm place.
Lead opianate, (C 10 H 9 O 5 ) 2 Pb -f 2H 2 O, is only slightly soluble,
and forms very lustrous, transparent crystals, apparently of the
same form as sphenite.
Silver opianate, 2C 10 H 9 O 5 Ag + H 2 0, is described by Wohler as
forming short prisms, which readily become coloured yellow.
Wegscheider found that when the acid is rapidly dissolved in
presence of silver carbonate, complete saturation does not take
place, and that reduction ensues on boiling. On precipitating
the potassium salt with silver nitrate, he found that the greater
portion of the silver salt was removed by washing, and therefore
prepared it by mixing concentrated solutions of silver fluoride
and potassium opianate. The tough, amorphous, yellowish pre-
cipitate changes on stirring into hemispherical or warty masses
consisting of small prisms, which can be completely washed
with a small quantity of water.
1 Ann. Chem. Pharm. clxii. 321. 2 Monatsh. Chem. iii. 348.
OPIANIC ANHYDRIDE. 505
Methyl opianate, C 10 H 9 5 (CH 3 ), was prepared by Wegscheider
from the silver salt by the action of methyl iodide. It is also
formed, as found by Liebermann and Kleemann, when opianic
acid is boiled with methyl alcohol. 1 It crystallizes from alcohol
in flat, monosymmetric needles, and from ether in thick, vitreous
tablets or short prisms, which melt at 102 and partially sublime
on careful heating. It rapidly decomposes into methyl alcohol
and opianic acid when boiled with water, the latter being ob-
tained pure by this method (Liebermann and Kleemann).
Ethyl opianate, C 10 H 9 O 5 (C 2 H 5 ), is readily formed, according to
Wohler, by saturating a hot, alcoholic solution of opianic acid
with sulphur dioxide, while it could not be prepared by means
of hydrochloric acid. Anderson, however, noticed its formation
when hydrochloric acid was added to an alcoholic solution of
the potassium salt, and Prinz prepared it by the action of the
chloride on absolute alcohol. According to Liebermann and
Kleemann, it may be most simply obtained by boiling the acid
with absolute alcohol.
It crystallizes from alcohol in needles or fine prisms, which
melt at 92 and sublime when carefully heated.
2264 Opianic anhydride, C 20 H 18 O 9 . Wohler found that
opianic acid undergoes a remarkable change when it is kept in
a state of fusion for some time, becoming insoluble in water,
and he assumed that it is thus converted into an isomeric modi-
fication, while Matthiessen and Wright concluded that it loses
water and forms the compound C 40 H 38 19 . 2 Wegscheider, on the
other hand, considered the substance to be formed from three
molecules of opianic acid, and named it triopianide, C 30 H 18 O U . 3 ;
Liebermann has, however, found 4 that it is formed when opianic
acid is heated for two hours at 160 in a current of air, and
explains the reaction by the following equation :
2(CH 3 0) 2 (COH)C 6 H 2 ,CO.OH =
(CH 3 0) 2 (COH)C 6 H 2 .CO V
>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
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