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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 nitrodracylic
acid (Part III. p. 38). 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 chloronicnnic acid, C 6 H 5 C1O 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 added
to benzoic acid suspended in hydrochloric acid ; the reaction,

1 Henry, Eer. Deutsch. Chem. Ges. vi. 492.

2 Brandes, Arch. Pharm. xxiii. 15.

3 Ann. Chem. P/iarm. xli. 48 ; xlii. 265.

4 Handb. Org. Chem. iii. 92.

5 Phil. Mag. xxvii. 129 ; Ann. Chem. Pharm. Ixv. 55.

6 Ibid, cxxii. 142. * Ibid. cii. 259.
8 Ibid, cxxxiii. 293. 9 Ibid. Ixx. 257.

10 Gerharclt, TraM Chim. Org iii. 214.

11 WroMewsky, Ann. Chem. Pharm, elxviii. 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 metachlorobenzoale, (C 7 H 4 ClO 2 ) 2 Ca + 3H 2 O, forms
scaly crystals, which dissolve in 82'6 parts of water at 12.

Metaclilorobenzoyl chloride, C 6 H 4 C1.COC1, is a strongly refrac-
tive liquid, boiling at 225 . 3

MctacUorohippuric acid, C 6 H 4 C1.CO.NHCH 2 .C0 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. 6
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.

Mctachlorobcnzonitril, 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 .^H 2) and metasulphamidobenzoic acid,
C e H 4 (CO 2 H)SO 2 .NH 2 , with phosphorus chloride. It crystallizes



Rc,r. Dcutsch. Che.m. Gcs. vi. 175.

Dembey, Ann. Chem. Pharm. cxlviii. 221.

Limpricht and Uslar, ibid. cii. 262 ; Graebe ; ibid, cxxxviii. 197.

Otto, ibid, cxxii. 129.

Ibid, cxlii. 346.






PARACHLOROBENZOIC ACID. 221

from alcohol in prisms, which smell like benzaldehyde, melt
at 40, and readily volatilize with steam. 1

Pa.racldoro'bcnzoic acid, or Chlorodracylic 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 parachlorotoluene 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 Miiller 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 parachlorobcnzoate, (C 7 H 4 C10 2 ) 2 Ca + 8H 2 O, crystal-
lizes in small plates or needles, and is even less soluble in water
than the corresponding salt of the meta-acid.

Parachlorobcnzoyl 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).



DlCHLOROBENZOIC ACIDS, C 6 H 3 C1.,.CO 2 H.

2125 a-fiichlorobenzoic acid, (3 : 4). Otto first prepared this
compound by boiling dichlorohippuric acid with hydrochloric
acid ; (i 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 20l 202.

Ann. Chcm. PJuirm. cvi. 32. 2 Ibid, cxxviii. 270.

Ibid, cxxxix. 336. * Bcr. Deutsch. Chcm. Gcs. viii. 880.

Zcitschr. Cham. 1869, 137. 6 Ann. Clwm. Pharm. cxxii. 147.

Beflgtein and Kuhlberg. ibid. clii. 225 ; Lellinann and Klotz, ibid, ccxxxi. 308.

Beilstein, ibid, clxxix. 284.

Glaus and Thiel, 1 Bc.r. Deutsch. Cham. Gcs. viii. 948.

Clans and Pfeifer, ibid. v. 658 ; vi. 721.



222 AKOMATIC COMPOUNDS.

fi-Dichlorobenzoic 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 : G), 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

&-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).



TRICHLOROBENZOIC ACIDS, C 6 H 2 C1 3 .C0 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.

fi-TriMofobenzoic acid has been obtained from the corre-
sponding aldehyde by oxidation with potassium permanganate ;
it melts at 129 . 6

y-Trichlorolenzoic 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 .CO 2 H.

Beilstein and Kuhlberg prepared this compound by heating
tetrachlorobenzyl chloride with water to 280 ; it melts at 187.

Beilstein, Ann. Chem. Pharm. clxxix. 285.

Rack and Wilkens, ibid, ccxxii. 201.

Schultz, ibid, clxxxvii. 269.

Jannasch, ibid, cxlii. 301

Beilstein and Kuhlberg, Ber. Deutsch. Chem. Gcs. xviii. 420.

Seelig, ibid, xviii. 420.

Salkowski, Ann. Chem. Pharm. clxiii. 28.



THE MOXOBROMOBEXZOIC ACIDS. 223



MONOBROMOBENZOIC ACIDS, C 6 H 4 Br.CO 2 H.

2127 Orthobromobcnzoic 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. 217). 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.

Jlarium orthobromobenzoate, (C 7 H 4 BrO 2 ) 2 Ba, is very readily
soluble in water, and crystallizes from alcohol in long needles
containing two molecules of alcohol.

Metabromobenzoic 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.N H 2 + Br 2 + H 2 = C 6 H 4 Br. CO 2 H + NH 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-
brornaniline, which he diazotized and brought into a solution of
potassium cuprous bromide heated to 90 ; the nitril, which was

Ann. Chcin. Pfinrm. cxxxv. 121.

Ber. Dcutsch. Chem Ges. iv. 464 ; v. 428. * Tbid. vii. 1502.

Rhalis, Ann. Chem. Phann. cxcviii. 102. s Ibid, xxviii. 246.

Brandes, Arch. Phann. xxiii. 16.
Zeitschr. Che.m. 1865, 116; 1869, 100.
1 Friedberg, Ann. Chem. Pharm. clviii. 26.
Ibid, clviii. 2. 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 mctabromobenzoatc, (C 7 H 4 BrO 2 ) 2 Ba -+- 4H 2 O, is very
slightly soluble in water and crystallizes in small, flat needles.

Pardbromobenzoic 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. 35 ). 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 Acii>j, C G H 3 Br 2 CO 2 H.

Br. : Br. Melting-point.

a) 3 : 4 small needles, 7 229 C 230

/3) 2 : 3 small needles, 8 147

7) 3 : 5 flat needles, 9 213 214

S) 2 : 5 flat needles, 10 153

e) 2 : 4 needles or tablets, 11 . . . 168 170

far. Dcutsch. Chcm. Gen. xviii. 1495.
Ann. Chcm. Phct,rm. clxviii. 156.
Ibid, cxxxv. 121.

Hiibner, Ohly and Philipp, ibid, cxliii. 247.
Fittig and Konig, ibid, cxliv. 283.
Weith and Landolt, Ber. Ucutuch. Chcm. Ges. viii. 717.
Burghardt and Beutnagel, Ann. Chcm. Pharm. ccxxii. 184.
Bputnagel, ibid, ccxxii. 105.

Beilstein and Geitner, ibid, cxxxix. 4 ; Neville and Winther, Bcr. Dcutsch.
Chcm. Ges. xiii. 970.

10 Holzapfel, Ann. Chcm. Pharm. ccxxii. 107.

11 Neville and Wiuther, loc. cit.



IODOBENZOIC ACIDS. 225



TRIBROMOBENZOIC ACIDS, C 6 H 2 Br 3 .C0 2 H.



a) silky needles l . .
/3) small needles -


Melting-point.

234 235 '
195


7) needles 3 ....
S) needles 4 ....


186-5
..... 178



Pentdbromobenzoic 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 Orthv-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.

Mda-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 metahydroxy benzoic acid, and with ammonia into
metamidobenzoic acid.

Para-iodobcnzoic 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






Reinecke, Zeitxhr. Chem. 1869, 110.
Smith, Ber. Deutsch. Chem. Gcs. x. 1706.
Voorecht, ibid. x. 1708.
Lawrie, ibid. x. 1705.
Ber. Deutsch. Clicm. Gcs. iv. 522.
Zeitschr. Chem. 1868, 327.

Schmidt and Schultz, Ann. Chem. Pharm. ccvii. 333.
VOL. HI. PAET IV. Q



AROMATIC COMPOUNDS.



According to Beran it cannot be obtained perfectly pure by
recrystallization, but must be sub'imed, plates which melt at
265 266 * being obtained in this way.



MONOFLUORBENZOIC ACIDS, C 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

+ HF = C 6 H 4 F.CO,H+NH .C 6 H 4 .C0 2 H+N .
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.

Metafliiorbenzoic acid crystallizes from hot water in broad,
lustrous plates or needles, which resemble those of benzoic acid
and melt at 123 124 D .

Metafluorhippuric acid melts at 152 153.

Parqfluorbenzoic 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 Bcr. Df,utsch.Chem. Ges. xviii. 137.

2 Schmitt and v. Gehren, Journ. Prakt. Chem. [2] i. 394 ; Paterno and Oliver!,
Gaz. Chim. 1882, 95. 3 Coppola, ibid. xiii. 121.



THE NITROBENZOIC ACIDS. 227



benzene ; a high boiling compound is also formed, which probably
consists chiefly of diphenyl oxide : l

(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.

Difluorlenzoic 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 difluorbenzoate, (C 6 H 3 F 2 .CO 2 ) 2 Ca + 3H 2 0, 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 U H 8 4 -f N 2 3
+ H 2 0, 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 Paternb and Oliver!, Gaz. Chim, xiii. 533.
'-' Jacks Jii and Hartshorn, Bcr. Deukch. Chem. Ges. xviii. 1993.
3 Ann. CJv-m. r/tarm. xxx. 348. * Ibid, xxxiv. 297.

5 Ibid. liii. 304.

Q 2



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 iiitrobenzoic 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
belonging to the meta-series (Part III., p. 45).

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

Ann. Chem. Pharm. Ixiii. 308. - Ibid. Ixvii. 313.
Journ. Prakt. Chcm. xxxvi. 93.

Ann. Chcm. Pharm. Ixxxvi. 143 ; xci. 185.

Ibid. xcix. 100. Zeitechr. Cliem. 1860, 477.

Ann. Chem. Pharm. xlviii. 343. Ibid, cxxvi. 255 ; cxxviii. 257.

Fischer, ibid, cxxvii. 137. ]0 Eer. Deutsch. Chem. Ges. iii. 648.

11 Ann. Chcm. 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 tire 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-compouiid being only formed
in small quantity (p. 15), while on the. .nitration of be'nzoic
acid, the meta-acid forms the chief product, and the para-
compound only occurs in small quantity. Concentrated nitric
acid converts cinnamic acid, and probably styrolene and cumene,
into para- and or tho-nitro-com pounds, 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, CgH

2131 Orthonitrobenzoic 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 16'5 ;
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. Ghem. Pharm. cxciii. 202.
3 Widnmann, Ber. Deutsch. Ghem.. Ges. viii. 8*92.
3 Moniiet, Reverdiu and Noltiug, ibid. -xii. 443.



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 C H 4 (NO 2 )CO 2 .C 2 H 5 , forms asym-
metric crystals, melting at 30.

Orthonitrobenzoyl chloride, C 6 H 4 (N0 2 )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

Orthonitrobcnzonitril, C C H 4 (N0 2 )CN. By the action of am-
monia on Orthonitrobenzoyl chloride, orthonitrobenzamide,
C 6 H 4 (NO 2 )CO.NH,, is formed, and crystallizes in long needles,



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