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responding dichlorobenzoic acid on oxidation.

Dichlorotoluene hexchloride, C 6 H 3 C1 2 (CH 3 )C1 C , 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- Boilitig-

point. point.

a-Trichlorotoluene 2 C 6 H 2 C1 3 .CH 3 (2 : 4 : 5) 82 230

/3-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.

MONOBKOMOTOLUENES, C 6 H 4 Br.CH 3 .

Orthobromotoluene 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. Chem. Pharm. cxlii. 304

Dietrich; Seelig,



.

' Sein and KuW1.org. ' ^^ > ^^ ** KnhlbM *

6 Hubner and Jannasch, Ann. Chem. Pharm. clxx 117

? Luginin, Bull. Soc. Chim. iv. 514. * Reymann, ibid. xxvi. 535.



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.

Metalromotoluenc 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.

Paralromotolucnc. 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

Boiling-
point.

240
246
236

















Melting-


CH 3


:Br :


: Br










point.


1


3


4


liquid,


does not


solidify at


-20





1


2


6


,.


M


H


})





1


2


5




)}


n


M





1


2


4


M


M


n


M





1


2


3


solid








28


1


3


5


longr needles


39



246

Wroblevsky, Ann. Cfam. Pharm. clxviii. 171.

See also Grete, ibid, elxxvii. 231.

Hiibner and Wallach, Ann. Chem. Pharm. cliv. 293.

Htibner and Post, ibid, clxix. 6.

Wroblevsky, ibid, clxviii. 161 ; Neville and Wintlier, Bar. Dcutsch. CItcm.
w. xiii. 962 ; xiv. 417.
6 Jannasch, Ann. C/icm. 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-

point, point.

88 89
46

66 200

52-5
112

58 59



TETRABROMOTOLUENES, C 6 HBr 4 .CH 3 . 2



CH 3 : Br : Br : Br :




1345


crystals . .


1234


crystals . .


1 2 4 G


long needles


1235


flat needles


1245


long needles


1256


flat needles















Melting-


Boiling-


CH 3 i


Br


:Br :


: Br :


:Br:




point.


point.




2


3


4


5


thin needles .


Ill lll-5





1


2


3


5


6


fine needles .


116 117





1


2


3


4


6


crystals . . .


105 108






Pcntabromotoluene, 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. Dcutsch. Chcm. Gcs. ix. 1508.



NITROTOLUENES. 13



IODINE SUBSTITUTION PRODUCTS OF
TOLUENE.

Only the mono-iodotoluenes, C G 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.

MONONITROTOLUENES, C e H 4 (NO. 2 )CH 3 .

2024 By dissolving toluene in fuming nitric acid and pre-
cipitating with water, Deville obtained nitrotoluene (protonitro-
lenzo&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. Chem. Pharm. clviii. 147 ; Korner, Zeitschr.
Chcm. clxxxviii. 327.
- Patenio and Olivcri, Gas. 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,
lie 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. Chem. 1865, 222. 2 Ibid. 1866, 269.

3 Bull. Soc. Chim. vii. 376. 4 Zcitschr. Chem. 1867, 225.

6 Ibid. 1868, 557. * Ibid. 1869, 190,

7 Ibid.



NITROTOLUENES. 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 foi 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 )(NO 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 I 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.

Orthonitrotoluene is obtained pure when the amido-group of
the isomeric nitrotoluidines, which contain the nitroxyl in the

1 Ann. CJicm. Pharm. civ. i.

- Monnct, Keverdin and Nlilting, Her. Dcutsch. Chcm. 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.

Mctanitrotoluene 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

Paranitrotoluenc, 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, : NO 2 = 1 : 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 N biting
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.
- Ibid. olvi. 13.

8 Rosenstiehl, Ann. Chim. Pliys. [4] xxvii. 407. Cunerth, Ann. Chem. Pharm.
clxxii. 222.

4 Clans and Becker, Bcr. Deutsch. Chem. Ges. xvi. 1596.
6 Ibid, xviii. 1400.



TRINITROTOLUENES.



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 6 1 . 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 (NOg^ + C 6 H 6 , crystallizing in
large prisms which effloresce in the air. 3

y-Dinitrotolucne. 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 (1 : 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 Stadel and Becker, Ann. Chem. Pharm. ccxvii. 205 ; Stadel, ibid, ccxxv. 384.

3 Stadel, Ber. Deutsch. Chem. Ges. xiv. 901 ; Liebiq' s Ann. ccxvii. 189 ; Hiibuer,
ibid, ccxxii. 74 ; Neville and Winther, Ber. Dc.utsch. Chem.'- Ges. xvi. 2985.

4 Wilbrandt, Ann. Chem. Pharm. cxxviii. 178.

5 Tiemann, Ber. Deutsch. Chem. Ges. iii. 217.
* H. Schmitt, private communication.

VOL. III. PART IV. O



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 + C 6 H 7 N
is obtained in long, red, lustrous needles melting at 83 84. 2

^-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.

^-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 y-trinitro-
toluene, combination does not occur as in the case of the
symmetric trinitrotoluene, but 7-dmitrotolylphenylamine is ob-
tained, diazo-amidobenzene beingprobably simultaneously formed :

CH 3 .C 6 H 2 (N0 2 ) 3 4- 3C 6 H 5 .NH ? =
CH 3 .C 6 H 2 (N0 2 ) 2 N(C 6 H 6 )H + C 6 H 5 N 2 .NH.C 6 H 5 + 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, Per. Deutsch Chem. Ges. xvi. 1596.

2 Hepp, Ann. Chem. Pharm. ccxv. 344.



CHLORONITKOTOLUENES. 19



CHLORONITROTOLUENES, C C H 3 C1(NO 2 )CH 3 .

2027 Paracldworthonilrotoluenc, (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

Ortlwchloroparanitrotoluene (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-
chlorotoluene, 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



BROMONITROTOLUENES, C C H 3 B<NO.^.CH 3 . 7



Br : NO,
2: 5
2 : 4
.> : 2
3 : 5
5 : 2
4: 2
4 : 3


crystals


Melting-point.

76-3

74_75


needles


liquid
prisms 8
rhombic crystals 9 . . . .


86
55


fine needles 10
crystals


45'o
31 32



Beilstein and Kuhlberg, Ann. Chcm. Pharm. clviii. 336.
Ibid, clxxxv. 273. 3 Ber. Deutsch. Cfiem. Ges. xvii. 534.

Ann. Chcm. Pharm. clxviii. 203. 5 Ber. Deutsch. Chem. Qes. vii. 797.

Gattermann and Kaiser, ibid, xviii. 2599.
Neville and Winther, ibid. xiv. 417.
Wroblevsky, Ann. Chem. Pharm. cxcii. 203.
Grete, ibid, clxxvii. 246.

u Beilstein and Kuhlberg, Hiibner and Roos, Ber. Deutsch. Chcm. Ges. vi. 799.

c i'



20 AROMATIC COMPOUNDS.



TOLUENESULPHONIC ACIDS

TOLUENEMONOSULPHONIC ACIDS, C 6 H 4 ^SO S H).CH 3 .

2028 By the action of fuming sulphuric acid on toluene,
Deville obtained a monosulphonic acid (Acide sulfobcnzo&niquc)
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

/Cl
2C 6 H 5 .CH 3 +3SO <

" M)H

/CH 3 /CH 3 /OH

C 6 H 4 < +C 6 H 4 < + S0 2 < +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 Latscliinow, Zeifschr. Chcm. 1869, 67.

2 Chrustschow, Ber. Deutsch. Chem. Ges. vii. 1167.

* Claessonand Wallin, ibid. aii. 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 :



3 H

o \/ A

NH 2

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.,0 = C 6 H 4 < + HC1 + N 2 .

\N = NCI \S0 2 .OH.

Tolueneparasulphonic acid, C 6 H 4 (CH 3 )S0 3 H4-H 2 O, 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



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