Henry E. (Henry Enfield) Roscoe.

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2 Grevingk, Ber. Dcutsch. Chcm. Gcs. xvii. 2425.

3 Hofmann, ibid. ix. 12P5 ; Wroblewsky, Ann. Chem. Pharm. ccvii. 91 ; Thbl,
Eer. Dcutsch. Chsm. Gcs, xviii. 359 ; Nolting and Forel, ibid, xviii. 2677.

4 Fittig, Ahrens and Mattheides, Ann. Chcm. Pharm. cxlvii. 22.

5 Nolting, Witt and Forel, Bcr. Dcutsch. Chem. Ges. xviii. 2664.



DIAMIDO XYLENE& 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 6 H 2 (CH 3 ) 2 (NH 2 ) 2 .

2219 a-Diamidomdaxylene, C 6 H 2 (CH 3 ) 2 (NH 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-Diamidomctaxylene (1 3:4:6) has been prepared from
s-dinitrometaxylene and the corresponding nitroxylidene ; it
sublimes in white crystals, melting at 104.

v-Diamidomctaxylene (1:3:4:2) sublimes in white needles
and melts at 64.

Nitrodiamidomelaxylene, C 6 H(CH 3 ) 2 (ISIH 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 arid 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. Chcm. Gcs. xix. 144.

2 Hofmann, ibid. ix. 1298.

3 Nolting and Forel, ibid, xviii. 2683.

4 Fittig and Vclguth, Ann. Chcm. Pfuirm. 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-DiamidGparaxyhne, C 6 H 2 (CH 3 ) 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.

P-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. 73), 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 .N2.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, Bcr. Dciitsch. Chcm. 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 ( .H 3 .C0. 2 H, are called xylic 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 a?t the boiling-point in a similar
manner ; 5 an energetic reaction also takes peaces in the sunlight,
the first product consisting of a mixture of xylyl bromides. 6



XYLYL ALCOHOLS, CH 3 .e 6 H 4 .CH 2 .OH.

Orilwxylyl 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,
readily in alcohol, and crystallizes in needles, melting at 54.
According to Colson, who prepared it by heating the bromide
with water, it melts at 34'2 and boils at 217. 7

Metaxylyl alcolwl has been obtained both from the acetate
and bromide ; it is a liquid, which boils at 215 and has a faint
odour.

Mdaxylyl ethyl ether, CH ? .C H 4 .CH 2 .O.C 2 H 5 , is a liquid and
boils at 202.

Jnhrcsb. CJicm. 1866, 605.

Kekule, Ann. Chem. PJmnn. cxxxvii. 186.

Bailstein, Org. Chem. 2nd Edition, ii. 672.

Rayinann, Bull. Soc. Chim. xxvi. 532 ; xxvii. 498 ; Gundelach, ibid. xxvi. 43.

Radziszewski and Wispek, Bcr. Dcutsch. Chem. Ges. xv. 1743 ; xviii. 1279.

Bchtamm, ibid, xviii. 1272.

Colson, Bull. Soc. Chim. xliii. 6 ; Ann. Chim. Phys. [6] vL 115.



412 AROMATIC COMPOUNDS.

Metaxylyl acetate, CH 3 .C C 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
5S'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 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 .CH2.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. * Ibid, cxxiv. 252.

3 Jannasch, ibid, cxlii. 303 ; Pieper, ibid. cli. 129.



THE TOLU ALDEHYDES. 413

Trixylylaminc, (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 tolu aldehydes. 1

3CH s .C 6 H 4 CH(OCrCl 2 .OH) 2 + 3H 2 =
3CH 3 .C 6 H 4 .CHO + 2Cr0 3 +Cr~(OH) 6 + 6HC1.

Ortliotolualdehyde 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

Mctatolualdchyde 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-
dcnehydrazine, CH 3 .C C H 4 .C H.N 2 H.C 6 H 5 , which crystallizes from
alcohol in thick, yellow prisms, melting at 91.

Orthonitromctatolualdehyde, CH 3 .C C 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 fit-mi, Ann. Chim. Phys. [5] xxii. 218, 1881 ; Bornomann, Ber. Dcutsch.
Chcm. Ges. xvii. 1462. '
- Kaymann, Lull. Soc. Chim. xxvii. 498.

3 Lauth and Grimaux, ibid. vii. 234 ; Gunclelach, ibid. xxvi. 44.

4 Meister, Lucius and Briuiing, Bcr. Deiikch. Chcm. Ges. xvi. 817 ; Bornemann,
Zoc. cit.

5 Ann. Chcm. Fharm. cxxiv. 254.



414 AROMATIC COMPOUNDS.



THE TOLUIC ACIDS, CJL/

\C0 2 H

2222 Orthotoluic acid was first obtained by Bieber and Fittig
by oxidizing orthoxylene with dilate nitric acid. 1 It may also ;
be easily prepared from its nitril, and its ethyl ether is formed
by the action of ethyl chloroformate on a mixture of ortho-i
iodotoluene and sodium amalgam. 2 It is best prepared by
heating phthalide with phosphorus and hydriodic acid : 3



CO \CO.OH

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 intophthalic
acic!.

Calcium orthotohiate, (C 8 H 7 2 ) 2 Ca + 2H 2 O, crystallizes in
small needles, which are readily soluble in water but only
slightly in alcohol.

Ethyl orthololuate, C 8 H 7 O 2 .C 2 H 5 , is a liquid which boils at
219'5, and has an aromatic odour. 6

Orthotoluyl chloride, OH 3 .C 6 H 4 .COC1, is a liquid which boils at
211 (Ador and Rilliet).

Orthotoluamide, 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.

Ann. Chcm. Pharm. clvi. 242.

Kekule, Bcr. Dcutsch. Chcm. Ges. vii. 1007.

Grjibe, ibid. xix. 778. 4 Weith, ibid. vii. 1057.

Piccard, ibid. xii. 579. 6 Ador and Rilliet, ibid. xii. 2298-

Fittig and Ramsay, Ann. Chcm. Pharm. clxviii. 246.

Weith, Bcr. Dcutsch. Chcm. Gcs. vi. 418.



THF TOLUIC ACIDS. 415

Chlororthotoluic acids, C e H 3 Cl(CH 3 )CO 2 H, are obtained by
oxidizing the chloroxylenes with dilute nitric acid : *

01 CH 3 CO,II Melting-point.

4.2:1 compact prisms 130

4:1 : 2 compact prisms 106

3:2:1 needles 154

a-Hromorthotoluic acid, C 6 H 3 Br(CH 3 )CO 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
I74 r 176- 2

ft-Bromortliotoluic 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

Mtro-orthotohiic 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.

NO, CH 3 CO 2 H Melting-point.



a) 4
/3) 6

7) *



1 : 2 needles or microscopic prisms . 179

1 : 2 needles 145

2 : 1 long, lustrous needles .... 152



Amido-orthotoluic acids, C C H 3 (NH 2 )(CH 3 )CO 2 H :
NH 2 CH 3 C0 2 H

a) 4 : 1 : 2 small prisms 196

/?) 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
metatomidine 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 Krii^cr, Bcr. Dculsch. Chcm. Gcs. xviii. 1755.
- .lacobsen, ibid. xvii. 2372.

3 Jacobsen and Wierss, ibid. xvi. 1956.

4 Fittig and Bieber, Ann. Chcm. Pharm. cxlvi. 245 ; Fittig and Ramsay, ibid.
clxviii. 250 ; Jacobsen and Wierss, er. Dcutsch. Chcm. Gcs. 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 (S0 3 H) 2 (CH 3 )CO 2 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 (SO 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 )(C0 2 H).,, 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 ono 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 mctatoluate, (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. Chem. Oes. xiv. 38.

2 Ahrens, Zeitschr. Chem. 1869 ; 106 ; Tawildarow, Ber. Deutsch. Chem. Ges.
iv. 410 ; Bruckner, ibid. ix. 405. 3 Schrbtter, KekuU's Org. Chem. iii. 701.

4 Ber. Deutsch. Clwm. Ges. v. 424. 5 Bottinger and Ramsay, ibid. ix. 405.



NITROMETATOLUIC ACIDS. 417

Ethyl mdaloluate, C a H 7 O 2 .C 2 H 5 , is a liquid, which boils at
224-5 226-5V

Metatoluyl chloride boils at 218 (Ador and Rilliet).

Metatolunitril, C 6 H 4 (CH 3 )CN, has been obtained by heating
motatolyl 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

Chlorometatoluic acid, C 6 H 3 C1(CH 3 )C0 2 H (4:3: 1), is formed
by boiling a-chlorometaxylene with chromic acid, 3 as well as by
replacing the amido-group of amidonietatoluic 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 ac-id, C e H 8 Br(CH 3 )CO 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-Bromomctatoluic 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 (NO 2 )(CH 3 )CO 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 210

/3) 2 : 1 : 3 compact prisms 182

7) G : 1 : 3 lustrous needles or crystalline

powder 214

5) 5 : 1 : 3 silky needles 167

Adov and Rilliet, Ber. Dcutsch. Chcm. Ges. xii. 2300.
Width and Landolt, ibid. viii. 719.

Volrath, Ann. Chcm. Pharm. cxliv. 266 ; Jacobsen, Ber. Dcutsch. Chcm,
G s. xviii. 1760.

Beilstein and Kriisler, Ann. Chem. Pha.rm. cxlir. 181.
Fittij,', A livens and Mattheides, ibid, cxlvii. 32.
Kolbe, Ber. Dcutsch.. Chcm. Ges. xv. 39.
Jacobsen, ibid. xiv. 2351.

Kclbe and C/arnomski, Ann. Chcm. PJuirm. ccxxxv. 291.
Jacobscn, Ber. Dcutsch. Chcm. Gcs. xiv. 2353.

Kreusler and Beilstein, loc. cit. ; Remsen and Kuliara, Amcr. Chcm. Journ.
421 ; Thol, Ber. Dcutsch. Chcm. Gc*. xviii. 359.
11 Kelbe and Warth, Ann. Chem. Pharm. ccxxi. 161.
VOL. III. PART IV. E E



418 AROMATIC COMPOUNDS.

Amidometatoluic acids, C 6 H 3 (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

yS) 2 : 1 : 3 small, flat prisms 132

7) 6 : 1 : 3 long needles 167

a-Sulphamidometatoluic acid, C 6 H 3 (SO 2 .NH 2 )(CH 3 )CO 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-SidpJiamidometatoluic 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 cymcne, 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- j
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 dihydrocymenes, 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-
formate. 9 It has also been synthetically prepared by many of
the reactions previously mentioned (Part III , p. 34).

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. Chcm. Ges. x. 1044 ; xi. 229 and 68 ;
Jacobsen, ibid. xi. 895 ; Coale and Remsen, Amer. Chcm. Journ. iii. 205.

Chcm. Soc. Mem. iii. 425.

Jannasch and Dieckmann, Ber. Deutsch. Chem. Gcs. vii. 1514.

Yssel de Schepper and Beilstein, Ann. Chem. Pharm. cxxxvii. 306.

Berthelot, Bull. Soc. Chim. vii. 134.

Cavstanjen, Ber. Deutsch. Chem. Ges. ii. 635.

Hirzel, Zcitschr. Chem. 1866, 205 ; Miclk, Ann. Chcm. PJiarm. clxxx. 49 ;
Hempel, ibid, clxxx. 74 ; Kbbig, ibid. cxcv. 106.

8 Ibid, cxxxvii. 184. 9 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.

Mdhyl 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 .CJF[ 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 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 C 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

Paratoluamidc, CH 3 C 6 H 4 .CO.NH 2 , crystallizes from hot water
in needles or plates, which melt at 151 (Fischli).

Paratoluylamido-acdic acid, CH 3 .C 6 H 4 .CO.NH.CH 2 .CO 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. Clwm. PJiann. clxii. 339 ; Bruckner, ibid. ccv.
113.

Fischli, Bcr. Dcutsch. Chem. Gen. xii. 615.

3 Kraut, Chem. Ccntralbl. 1859, 84.

4 Cahours, Ann. Chem. Pharm. cviii. 316 ; Bruckner, ibid. ccv. 114 ; Ador
and Killiet, Bcr. Deutsch. Chem. Gcs. xii. 2298.

E E 2



420 AROMATIC COMPOUNDS.

decomposed into paratoluic acid and amido-acetic acid by con-



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