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IR DAVID LIONEL
GOLDSMID STERN SALOMONS

of Broomhill K^nr
aronet




A TREATISE ON CHEMISTRY



$. K. OGDElf



TREATISE ON CHEMISTRY



SIR H. E. ROSCOE F.R.S. AND C. SCHORLEMMER F.R.S.



VOLUME HI
THE CHEMISTRY OF THE HYDROCARBONS AND THEIR DERIVATIVES

OR

ORGANIC CHEMISTRY

PART IV



" Chymia, alias Alchemia el Spagirica, est ars corpora vcl mixta, ml oomposita,
vcl aggregata etiam in principia sua resolvendi, aut ex prindpiis in talia
comlrinandi."&rAHL, 1723



Eontion
MACMILLAN AND CO.

AND NEW YORK
1892

The Kiyltt of Translation and Reproduction is Reterved



RICHARD CLAY AND SONS, LIMITED,

LONDON AND BHNGAY. '



First Edition printed 1887 (dated 1888), Reprinted with corrections 1692.



1 894-
IT, 3



PREFACE TO VOL. III., PART 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.



TOLUENE GROUP . . ........ ..'... . . . -. . 3

Toluene or Methylbenzene . . . 8

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 18

Fluorine Substitution Products of Toluene . _ . .. ( . : .. . . . 19
Nitro-Substitution Products of Toluene . . . . . . . 13.

Mononitrotoluenes 18

Dinitrotoluenes . .16

Trinitrotoluenes .... .... 17

Chloronitrotoluenes 19

Bromonitrotoluenes .... 19

Toluenesulphonic Acids . .20

Toluenemonosulphonic Acids ... 20

Toluenedisulphonic Acids 22

Toluenetrisulphonic Acids , 2

Monohydroxytoluenes 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 .... . J 1

Iodine Substitution Products .41

Nitro-Substitution Products . . . 41

Crcsorciuol 47

Toluquinol or Toluhydroquinonc .... .48

Toluquinono 49

Substitution Products of Toluquinone ... 50

Toluquinonoxime Compounds . . 50

Trihydroxytoluenes 53



CONTENTS.



TOLUENE GROUP continued.

Amido-Derivatives of Toluene 54

Amidotoluenes or Toluidines '54

Halogen Substitution Products of the Toluidines 67

Chlorotoluidiues 68

Brotnotoluidines 68

Todotoluidines 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

HippuricAcid 181

Benzenyl Compounds 194

Benzonitril and its Derivatives 197

Benzimido-Ethers 200

Benzenylamidines . .. 202

Benzenyloxime Compounds 207

Halogen-Substitution Products of Benzoic Acid . . . . . 216

Monochlorobenzoic Acids 217

Dichlorobenzoic Acids 221

Trichlorobenzoic Acids . 222



CONTENTS.



BEXZOYL GROUP continued.

Tetrachlorobenzoic Acid 222

Monobromobenzoic Acids 223

Dibromobenzoic Acids 224

Tribromobenzoic Acids 225

Mono-Iodobenzoic Acids 225

llonofluorbenzoic 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

Diamidobenzoic 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

Nitrosulphobenzoic Acids . , v . . . . 275

Amidosulphobenzoic Acids . <. 275

Benzophosphinic Acid . . 275

Benzarsenic Acids . .... .. ......:. . . 277

HYDROXYBENZYL GROUP . . ^ . . . '. ' . . . . 279

Hydroxybenzyl Alcohols >. . . ' . . . . ... . . 279

Hydroxybenzaldehydes . .285

Orthohydroxybenzaldehyde or Salicylaldehyde . . .... . 285

Substitution Products of Salicylaldehydo . . .. : . : . " . .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.



II YDROXY BENZYL GROUP contimwd.

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 -Resorcylic Acid . . 359

Adjacent Metadihydroxybenzoic Acid or 7-Resorcylic Acid . . . 360
Hydroxysalicylic Auid 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

Xylcnesulplionic 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 . 411

Xylylamines .... 412

The Tolualdehydes .... . 413

The Toluic Acids 414

Hydroxytolualdehydes 422

Hydroxytoluic Acids 423

Dihydroxytolualdehydes . . . . . .427

Dihydroxytoluic Acids ..,...' 428

Xylylene Alcohols 439

Hydroxymethylbenzoic Acids '. . . . 442

Aldehydes and Aldehydo-Acida 447

The Phthalic Acids .450

PhthalicAcid 452

Addition Products of Phthalic Acid -. .469

Halogen Substitution Products of Phthalic Acid 471

Nitrophthalic Acids .. '.. . .473

Amidophthalic Acids . 475

Sulphophthalic Acids .... ... 476



CONTENTS.



XYLENE GROUP continued.

Isophthalic Acid or Mctaphthalic 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

Hydroxymethyldihydroxybcnzoic Acids ... ... 497

Aldehydodihydroxybenzoic Acids . ....... 502

Dihydroxyphthalic Acids . . . " 510

Trihydroxyphthalic Acids . ... 519

Tetrahydroxyphthalic Acids 519



ORGANIC CHEMISTRY.



VOL. III. PART IV.



OEGANIO OHEMISTEY,

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 Ifeptacarbure quadrihydriquc,
7 H^ (67=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 (benzofrne), 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. Chcm. xviii. 165.

3 Ann. Chim. Phys. [3] iii. 168 ; Journ. Prakt. Clwm. xxv. 336.

4 Tolubalsam is obtained by incisions made in the bark of the Myroxylon
toluifera, 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 Oarthagena (Fliickiger and
Han bury , Pharmacograph ?' ).

B 2



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}?
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
Glenard 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 O 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 Jahresb. xxii. 354.

3 Chem. Soc. Mem.. (1845) ii. 367. 4 Ibid. iii. 421.

c Ann. Chem. Pharm. xc. 252. . 6 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. 75). 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 110'3 and does
not solidify at 20. Oxidizing agents convert it into benzoic
acid. It combines with aluminium chloride forming the com-
pound AL>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 :

C 6 H 6 + A1 2 C1 6 = C 6 H 5 A1 2 C1 5 + HC1
2C 6 H 5 A1,C1 5 +- 2HC1 = C 12 H 10 + 2 A1 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 n fi .CH, + A1,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 = C H 5 A1 2 C1 5 + CH.CL

1 Journ. Prakt. Chtm. Ixi. 74. - Ann. Chcm. Phnrm. Ixxvi. 286.

3 Jjid. Ixxxvi. 335. 4 JoUrn. Prakt. Chcm. Ixx. 300.

c Greville Williams, Chem. News, xlix. 197.
G C4ustavson, Bcr. Dcutsch. Chem. Gcs. xi. 2152. 7 Compt. rend. c. 692.



AROMATIC COMPOUNDS.



When one part of chromium oxychloride is dissolved m 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 +2Cr0 2 Cl 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 :



C 6 H 5 .CH< + H 2 = C 6 H 5 .CHO + 4HC1 + 2CrO.,

\OCrCl 2 .OH

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 Dihydrotolucne, 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, olefines, 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 4 2H 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 titard, Ann. Chim. Phys. [5] xxii. 223.

2 Baeyer, Ann. Cham. Pharm. civ. 271.

3 Kelbe, ibid. ccx. 10 ; Kelbe and Bauer, Bcr. Deutsch. CJicm. Gcs. xvi. 2559 ;
Renard, Aim. Chim. Phys. [6], i. 22,3.

4 Chem. News, xx. 76.



TOLUENE SUBSTITUTION PRODUCTS.



ing to Tichborne, colophonin hydrate, C 10 H 22 O 3 + H 2 O, is formed,
and loses water on heating. 1

HcxJiydrotoluenc, 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 Benzobne 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 stre'am 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 chlorobeiizene. These enigmatical results were explained by
Beilstein 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 Chcm. New*, xx. 38.

2 Wreden and Znatowicz, Ann. Chcm. Pharm. clxxxvii. 161.

3 Beilstein and Kurbatow, ibid. xiii. 1818 ; see also xiv. 1620.

4 Ann. Chim. Phys. [3], iii. 178.

5 Ann. Chcm. Pliarm,. xcvi. 246 ; ibid. cxli. 198.
c 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. 18) 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, G H 4 (CH 3 )
NH(C 2 H 3 O), 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



NH 2 .

1 Beilstein and Kuhlberg, Ann. Chcm. P/utrm. cl. 286.

2 Ibid. clvi. 79 ; Gascorowski and Wayss, Bar. Deutsch. Chem. Gcs. xviii.
1939.

3 Emmerling, Ber. Deutsch. Chcm. Gcs. viii. 830.

4 Wroblevsky, Ann. Chcm. Pharm. clxviii. 199.



CHLOKOTOLUENES.



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 156 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.



DICHLOROTOLUENES, 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 .CO 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 Beilstoin and Geitner, loc. cit.

2 Aronheim and Dietrich, Bar. Dcutsch. C'hcm. Gcs. viii. 1402.

3 Hiibner and Majert, ibid. vi. 794.

4 Beilstein and Geitner ; Beilstein and Kuhlbcrg, Ann. Chcm. Pkarm. cl. 313 ;
Schultz, ibid, clxxxvii. 263. Aronheim and Dietrich.



10 AROMATIC COMPOUNDS.

dichlorotoluene, (CH 3 :C1:C1 1 :3 : 4), which yields the cor-



Online LibraryHenry E. (Henry Enfield) RoscoeA treatise on chemistry (Volume 3) → online text (page 1 of 50)