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254 AROMATIC COMPOUNDS.

Para-uramidobenzoic acid, C 8 H 8 N 2 O 3 , is formed at the same
time as paracarbamidobenzoic acid by fusing paramidobenzoic
acid with urea, or potassium cyanate with paramidobenzoic acid
hydrochloride. It forms elongated plates, is scarcely soluble in
cold, only very slightly in boiling water, more readily in hot
alcohol. Concentrated nitric acid only forms one dinitro-com-
pound.

Paracarbamidobenzoic acid, C 15 H 12 N 2 O 5 , is obtained by heating
the preceding compound, and forms small needles which are
insoluble in the ordinary solvents.



CHLORAMIDOBENZOIC ACIDS, C 6 H 3 C1(NH 2 )C0 2 H.

Cl : NH 2 Melting-point,

a) 2:5 small, readily soluble needles, 1 . . 212
yS) 3:6 long, almost insoluble needles, 2 . . 148

8) 3:5 needles, 3 216

e) 4:3 small needles, 4 212

2145 The chloramidobenzoic acids corresponding to 7- and -
chloronitrobenzoic acids are unknown. Two others have, how-
ever, been prepared, one of which has been obtained from
chlorisatin, and should be identical with the /3-acid, but melts
at 204 ; 5 it will subsequently be mentioned. The second has
been prepared by Griess together with the e-acid by decomposing
metadiazobenzoic acid imide, C 6 H 4 N 3 .CO 2 H, with hydrochloric
acid ; it crystallizes in small prisms and has the constitution
C1:NH 2 = 2:3. 6

1 HiibnerandBiedermann, Ann. Chem. Pharm. cxlvii. 258 ; Rack and Wilken,
ibid, ccxxii. 198.

2 Cunzeand Hubner, ibid, cxxxv. Ill ; Hiibner and Weiss, Ber. Dcutsch, Cittern.
Gcs. vi. 175.

;< Grube, ibid. x. 1703.

4 Hubner and Biedermann ; Raveill, Ann. Chem. Pharm. ccxxii. 177.

5 Dorsch, Journ. Prakt. Chem. [2] xxxiii. 50.
c Griess, Ber. Deutsch. Chem. Ges. xix. 313.



NITRO-AMIDOBENZOIC ACIDS. 255



BROMAMIDOBENZOIC ACIDS,

Br : NH 2 Melting-point.

a) 2:5 broad needles 1 180

0) 3:6 long, slightly soluble needles 2 . . 208

7) 3:2 needles 3 172

8) 4:3 light yellow needles 4 . ..... 225

e) 3:5 colourless, tough needles 5 .... 215



IODAMIDOBENZOIC ACIDS, C 6 H 3 I(NH 2 )C0 2 H.

Melting-point.

a) 3:2 brown needles 137

/3) 3:6 needles melting with decomposition 209

These have been prepared from the iodonitrobenzoic acids
are converted by reduction into orthamidobenzoic acid.



NITRO-AMIDOBENZOIC ACIDS,

C 6 H 3 N0 2 (NH 2 )C0 2 H.

2146 Seven of the ten acids possessing this composition which
are possible according to theory are known, and their constitution
is shown on the next page. The first three have been obtained
from meta-uramidobenzoic acid, which, as already mentioned,
yields three dinitro-compounds. These cannot be directly separ-
ated, but on boiling with dilute ammonia are converted into the
mononitro-uramidobenzoic acids, which can be separated by
means of their barium salts :

C 8 H 6 (NO2) 2 N 2 3 + H 2 O = C 8 H 7 (NO2)N 2 O 3 + N0 2 .OH.
They are re-converted by concentrated nitric acid into the

N^

1 Burghard, Ber. Deutsch. Chem. Gea. viii. 560.

2 Hiibner and Meeker, Zeitschr. Chem. 1867, 564 ; Hiibner, Only and Philipp,
Ann. Chem. Pharm. cxliii. 241 : Hiibner and Petermann, ibid, cxlix. 133.

3 Ibid. 4 Burghard ; RaveilL
5 Hesemann and K5hler, Ann. Chem. Pharm. ccxxii. 169.



256 AROMATIC COMPOUNDS.

dinitro-compounds, which on boiling with water yield the nitro-
amidobenzoic acids : l

NH



C0 2 H C0 2 H



NO 2



C0 2 H C0 2 H C0 2 H



, ,NH,

> N0 2 NO' I
NH 2

a-Nitro-amidobenzoic acid is slightly soluble in water, readily
in alcohol, and crystallizes in yellow needles or prisms. 2 Nitrous
acid converts it into orthonitrobenzoic acid, and on reduction
with tin and hydrochloric acid it yields a-diamidobenzoic acid.

ft-Nitro-amido'bcnzoic acid forms lustrous, yellowish red needles
or plates, which are readily soluble in alcohol and slightly in
water, and when gently heated sublime in rhombic plates with-
out melting. Heated in a capillary tube it melts at 298 with
complete decomposition. 3 It is converted by nitrous acid into
paranitrobenzoic acid, and by tin and hydrochloric acid into
/3-diamidobenzoic acid.

y-Nitro-amidobenzoic acid crystallizes in thick, golden yellow
needles or prisms, which melt at 156 157, 4 and dissolve
readily in alcohol and hot water. Nitrous acid converts it into
orthonitrobenzoic acid, and reducing agents into 7-diamido-
benzoic acid.

S-Nitro-amidobenzoic acid was obtained by Griess from dinitro-
para-uramidobenzoic acid, 5 and by Salkowski by heating nitro-
anisic acid, C H 3 NO 2 (OCH 3 )C0 2 H, with ammonia to 140
170 . 6 It crystallizes in small, yellow needles, which are scarcely
soluble in water, only slightly in boiling alcohol, and melt at



1 Griess, Ber. Deutsch. Chem. Ges. ii. 434 ; v. 192 ; xi. I7i
[2] v. 235.
Chem. Ges. xviil 2947.



2 Journ. Prakt. Chew'. [2] v. 235.
:i Kaiser, J5cr. Deutsch. Chen



Ibid, xviii. 2951.

5 Loc. cit.

6 Ann. Chem. Pharm. clxxiii. 52.



DINITRO-AMIDOBENZOIC ACIDS. 257

284. It is converted by the diazo-reaction into metanitrobenzoio
acid, and by reduction into /3-diamidobenzoic acid.

e-Nitro-amidobenzoic acid was prepared by Griess from dinitro-
ortho-uramidobenzoic acid, and by Hiibner from the nitrosalicylic
acid which melts at 228 by heating the ethyl ether with
alcoholic ammonia; e-nitro-amidobenzamide, C 6 H 3 N0 2 (NH 2 )CO.
NH 9 , is thus obtained, and crystallizes in small, yellow needles,
melting at 140 ; it is converted into the acid by boiling with
baryta water. 1 Rhalis obtained it, together with paranitraniline,
by heating the nitrobromobenzoic acid which melts at 179
180 with ammonia. 2 It crystallizes from hot water in long,
lustrous, yellow needles, melting at 270. Ethyl nitrite con-
verts it into metanitrobenzoic acid, and on reduction it yields
a-diamidobenzoic acid.

%-Nitro-amidobenzoic acid. Hiibner obtained the amide of
this acid from the nitrosalicylic acid which melts at 144 ; it
crystallizes in yellow plates, melting at 109, and on boiling with
baryta water yields the acid, which is readily soluble in alcohol
and crystallizes from hot water in long, yellow, silky needles,
melting at 204. Nitrous acid converts it into metanitrobenzoic
acid.

7]-Nitro-amidobenzoic acid is formed by the reduction of
S-dinitrobenzoic acid with ammonium sulphide, 3 and crystallizes
from water in long, gold en yellow needles, or small, compact prisms,
melting at 208. It is converted into metanitrobenzoic acid by
ethyl nitrite, while metachlorobenzoic acid may be obtained from
it by replacing the amido-group by chlorine and the nitroxyl by
hydrogen ; its constitution is thus established.



DINITRO-AMIDOBENZOIC ACIDS,



2147 Dinitro-orthamidobenzoic acid or Dinitro-anthranilic acid
(NO 2 : N0 2 = 3 : 5) is prepared by the action of ammonia on
the ether of dinitrosalicylic acid. It is slightly soluble in
alcohol, and crystallizes from it in lustrous, golden scales, melting
at 256 . 4

1 Ann. CJicm. Pharm. xix. 21. - Ibid, cxcviii. 112.

3 Bocker, Grube and Rollwage, Ber. Deutsch. Ckem. Oes. x. 1703 ; Ann. Ghcm.
Pharm. ccxxii. 81.

4 Salkowski, Ann. Chem. Pharm. clxxiii. 40.

VOL. III. PART IV. S



258 AROMATIC COMPOUNDS.

Dinitroparamidobenzoic acid, (NO 2 : NO 2 = 2:6). Cahours,
in 1849, found that an acid soluble in ammonia is formed
by the action of fuming nitric acid on nitranisic acid, in addi-
tion to dinitro-anisoil and trinitro-anisoil. This substance
being of a splendid golden yellow colour, he named it chry-
sanisic acid, C 7 H 5 N 3 O 7 , looking upon it as a homologue of
picric acid. 1 After trinitrocresol had been prepared. Kolbe
suggested that it is identical with chrysanisic acid, 2 but Beil stein
and Kellner showed that this is not the case, since the latter has
the formula C 7 H 5 N 3 O 6 , and differs from the isomeric trinitro-
toluene, which was prepared and described by Wilbrand. 3

The actual constitution of chrysanisic acid was determined
by Salkowski, who found that it is not contained in the product of
the action of nitric acid on nitranisic acid, but is formed by the
action of ammonia on dinitro-anisic acid : 4

C 6 H 2 (OCH 3 )(N0 2 ) 2 C0 2 H + NH 3 = C 6 H 2 (NH 2 )(NO 2 ) 2 C0 2 H +
HO.CH 3 .

It may also be obtained by the oxidation of dinitropara-
toluidine, 5 and crystallizes from hot water, in which it is only
very slightly soluble, in fine needles, and from alcohol in lustrous,
golden, rhombic plates, melting at 259. On heating to 200
210 with fuming hydrochloric acid, /3-trichlorobenzoic acid is
formed, and with nitric acid it yields picric acid, while the
dinitro-anisic acid from which it is prepared is converted into
/3-dinitrophenol when heated with water to 170 . 6



DIAMIDOBENZOIC ACIDS, C 6 H 3 (NH 2 ) 2 CO 2 H.

2148 The formation of these has been already mentioned
under the dinitro- and nitro-amido-benzoic acids. The numbers
signify the position of the amido groups.

a-Diamidobenzoic acid (2 : 5) is slightly soluble in alcohol and
hot water, and crystallizes in very small prisms, which decompose
on heating with formation of paradiamidobenzene.

Ann. Chim. Phys. [3] xxvii. 454.

Lehrb. Or a. Chcm. ii. 145,

Ami. Chcm. Pharm. cxxviii. 164.

Ibid, clxiii. 1.

Friederici, Ber, Dcutsch. Chem. Ges. xi. 1975.

Salkowski and Rudolph, ibid. x. 1254.



DIAMIDOBENZOIC ACIDS. 259

@-Diamidobenzoic acid (3 : 4) crystallizes from hot water in
small plates, which melt at 211, and decompose at a higher
temperature, more easily when mixed with powdered glass or
lime, into carbon dioxide and orthodiamidobenzene.

y-Diamidobenzoic acid (2 : 3) forms long, yellowish white
needles, and also yields orthodiamidobenzene on heating.

S-Diamidobenzoic acid (3 : 5) is slightly soluble in water, more
readily in alcohol, and crystallizes in long needles which melt at
228 when gradually heated, but at 236 when rapidly heated, 1
and are carbonized at a higher temperature with evolution of
ammonia. On heating with caustic baryta, it decomposes into
carbon dioxide and metadiamidobenzene. It decomposes car-
bonates and forms salts which crystallize well. Its dilute
aqueous solution is coloured deep yellow by nitrous acid
(p. 263).

Barium diamidobenzoate, 2(CeH 3 (NH 2 ) 2 C0 2 ) 2 Ba -f 3H 2 O, cry-
stallizes in yellowish prisms, which are readily soluble in water.
Like its isomerides, it also combines with acids.

$-Diamidobenzoic acid hydrochloride, C 6 H 2 (CO 2 H)(NH 2 ) 2
(C1H) 2 , is readily soluble in water, but only slightly in hydro-
chloric acid, and crystallizes in needles.

B-Diamidobcnzoic acid sulphate, (C 6 H 3 (CO 2 H)(NH 2 ) 2 )SO 4 H 2 ,
forms white needles or prisms, which are slightly soluble in water
and still less so in alcohol. 2

ffexmethyl-S-diamid'Obenzoic acid, or, as Griess called it, six-
fold methylated diamidobenzoic acid, is not an acid in its
properties but a strongly alkaline ammonium hydroxide and, at
the same time, a salt. The iodide is formed by the action of
methyl iodide and caustic potash on a solution of 8-diamido-
benzoic acid in methyl alcohol. It crystallizes in six-sided
tablets or plates, and when treated in concentrated aqueous
solution with silver oxide yields the free base :

N(CH 8 ) S

/N(CH 3 ) 3 I , \

C 6 H / CO.OH + Ag 9 = C 6 H 3 f CO.O + 2AgT.

\N(CH 3 ) 3 I \N(CH 3 ) 3 OH

It is obtained on evaporation as a crystalline mass, which
consists of small plates, is very hygroscopic and behaves like

1 Hiibner, Ann. Chem. Pharm. ccxxii. 85.

2 Griess, ibid. cliv. 328.

S 2



AROMATIC COMPOUNDS.



caustic potash. The carbonate crystallizes from alcohol in
small plates, is readily soluble in water and has an alkaline
reaction. 1



TRI-AMIDOBENZOIC ACID, C H 2 (NH 2 ) 3 CO 2 H.

Salkowski obtained this compound by the reduction of
chrysanisic acid with tin and hydrochloric acid. It crystal-
lizes from boiling water in fine, lustrous needles, and decom-
poses on heating into carbon dioxide and triamidobenzene. Its
solution has an acid reaction, and it is at once a monobasic
acid and a diacid base.



DIAZO-DERIVATIVES OF BENZOIC ACID.

2149 The amidobenzoic acids behave in some respects like
amido-acetic acid and its homologues, and in others like aniline,
since they can be easily converted into diazobenzoic acids.
For this purpose, a magma of amidobenzoic acid and nitric
acid is well cooled by ice and saturated with nitrogen trioxide,
the nitrate formed being then precipitated with alcohol and
ether. Other salts are obtained in a similar manner. The
sulphates are best prepared by dissolving the nitrate in a cold
mixture of equal parts of water and sulphuric acid, and precipitat-
ing in crystals by the addition of strong alcohol and then ether. 2
The diazobenzoic acids, which, like the diazophenols, only exist as
anhydrides, are obtained from these salts by the action of caustic
potash. They also form double salts, which Griess looks upon
as basic salts :

Diazobenzoic acid. Diazobenzoic acid nitrate.

/N = N
C 6 H 4 < j C 6 H 4 <

\CO-0 \CO.OH.

Diazobenzoic acid seminitrate.

/N=N.O.CO.C 6 H 4
C 6 H/ |

N30.0H N=N.N0 3 .

1 Griess, Ser. Dcutech. Chcm. Gcs. vii. 39 ; Briihl, ibid. viii. 485.
3 Griess, ibid, xviii. 960.



DIAZO-DERIVATIVES. 261

The substituted amidobenzoic acids, as well as their amides,
nitrils, &c., also form diazo-compounds.

Orthodiazobenzoic acid nitrate, NO 3 .N .C 6 H 4 .CO 2 H, is readily
soluble in water, and crystallizes in rhombic or six-sided tablets,
or prisms, which explode violently on heating. When it is re-
peatedly dissolved in water and precipitated with alcohol and
ether, or when an alcoholic solution of anthranilic acid is treated
with nitrogen trioxide, orthodiazobenzoic acid seminitrate, NO 3 .N 2 .
C 6 H 4 ,CO 2 .N 2 .C 6 H 4 .C0 2 H, is formed ; it crystallizes in long, white
needles, and detonates violently when heated. 1

Metadiazobenzoic acid nitrate crystallizes in prisms, which are
slightly soluble in cold water. 2 On addi ng an alkali to its solution,

,N = N
a precipitate of metadiazdbenzoic acid, C 6 H 4 <^ | , is thrown



< | ,



down.

This forms a yellow mass which is very unstable.

Metadiazobenzoic acid sulphate, HSO 4 .N 2 .C 6 H 4 .C0 2 H, forms
long, narrow plates, which are readily soluble in water. When
it is repeatedly precipitated from aqueous solution by the
addition of alcohol and ether, it becomes converted into the
basic salt, to which Griess has given the formula 5C 7 H 4 N 2 O 2 ,
2S0 4 H 2 . 3 According to Beilstein it is probably 2(C 7 H 5 N 2 O 2 ) 2
S0 4 + C 7 H 5 N 2 O 2 (OH). 4 It crystallizes in small needles.

When the normal sulphate is heated, it decomposes with a
violent evolution of gas and formation of free sulphuric acid,
sulphoxybenzoic acid, and a very stable compound, C 14 H ]0 SO 8 , 5
which probably has the following constitution : SO 2 (C 6 H 3 (OH)
C0 2 H) 2 .

Metadiazobenzoic acid platinichloride, (C 7 H 5 N 2 O 2 ) 2 PtCl 6 , is
obtained by the addition of platinum chloride to a solution of
the nitrate ; it crystallizes in yellow prisms.

Metadiazobenzoic acid fterbromide, Br 9 N BrN.C 6 H 4 .CO 2 H, is
precipitated as an oil by the addition of a solution of bromine
in hydrobromic acid to a solution of the nitrate ; it soon solidifies
to a mass of yellow prisms, and is converted by ammonia into
diazobenzoic acid imide.

Metadiazobenzamide nitrate, NO 3 .N 2 .C 6 H 4 .CO.NH 2 , crystallizes
in white, explosive needles.

1 Griess, Ann. Chcm. Pharm. cxvii. 39, cxxxv. 121 ; Bcr. Deutsch. Chem. Ges.
x - 1653. 2 Griess, Ann. Chcm. Pharm. cxx. 126.

s her. Deutsch. Chem. Ges. ix. 165'5.
* JIandb. Org. Chem. 2nd Edition iii. 1239. s Jahrcsb. Chem. 1864, 351.



262 AROMATIC COMPOUNDS.

Metadiazobenzonitril nitrate, NO 3 .N 2 .C 6 H 4 .CN, forms explosive

needles or prisms which are only slightly soluble in cold water. 1

Paradiazobenzoic acid nitrate also crystallizes in white, explosive



Nitrodiazdbenzoic add, C 6 H 3 (NO.X X), is formed when

\C(K

S-nitro-amidobenzoic acid is brought into absolute alcohol nearly
saturated with nitrogen trioxide ; it forms light yellow, explosive
plates. 3

Diaznbenzene-amidobenzoic acid, C 6 H 5 .N N.NH.C 6 H 4 .C0 2 H,
is obtained by mixing aqueous solutions of diazobenzene nitrate
and metamidobenzoic acid. 4 According to Griess, this compound
is identical with that obtained by the action of aniline
on metadiazobenzoic acid, and which was therefore considered
to have the constitution C 6 H 5 .NH.N=N.C 6 H 4 .CO. 2 H. Griess,
however, expresses the constitution of both compounds by the
same formula, C 6 H 5 .NH=NH=NH.C 6 H 4 .CO 2 H (Part III,
p. 269). 5

By either process, a yellow, crystalline substance is obtained,
which separates from ether in small plates, and is decomposed
by hydrochloric acid with formation of metamidobenzoic acid,
metachlorobenzoic acid, metahydroxybenzoic acid, aniline, phenol
and nitrogen. The acid forms a yellow solution in alkalis ; on
the addition of barium chloride to its ammoniacal solution, which
must not be too dilute, the barium salt separates out in small,
light yellow crystals.



is formed by the action of metamidobenzoic acid on metadiazo-
benzoic acid, and therefore as an intermediate product when
nitrogen trioxide is passed into an alcoholic solution of metamido-
benzoic acid. 7 It forms orange-yellow, crystalline granules, which
are almost insoluble in water, alcohol, ether, &c., and detonate
at 180. It is soluble in alkalis, and is reprecipitated by
acids, even acetic acid. On boiling with hydrochloric acid,
it decomposes with evolution of nitrogen into metamidobenzoic
acid and metachlorobenzoic acid. It is a tolerably strong dibasic
acid and decomposes carbonates.

1 Griess, Ser. Deulsch. Chem. Ges. ii. 370.

2 Jahresb. Chem. 1864, 353.

3 Salkowski, Ann. Chem. Pharm. clxxiii. 63.

4 Griess, ibid, cxxxvii. 63. 5 Bcr. Deutsch. Chem. Ges. vii. 1619.
6 Jahresb. Chem. 1864, 353. 7 Ann. Chem. Pharm. cxvii. 1.



DIAMIDOBENZOIC ACIDS. 263

Paradiazo-amidobenzoic acid was obtained by Beilstein and
Wilbrand by treating a saturated alcoholic solution of paramido-
benzoic acid with a solution of nitrogen trioxide in alcohol. It
is an orange-yellow, crystalline powder, which is only slightly
soluble in boiling alcohol. 1

Isomeric compounds are formed from metadiazobenzoic acid
and paramidobenzoic acid, and from paradiazobenzoic acid and
metamidobenzoic acid (Griess).

2150 The Action of Nitrons Acid on the Diamidobenzoic Acids.
When sodium nitrite is added to a neutral solution of a-diamido-
benzoic acid, which contains the amido-group in the para-position,
paramidodiazobcnzoic acid is formed :

/NH 2 /NH 2

C 6 H 3 ^-NH 2 + N0 2 H = C C H 3 N=N + 2H 2 O.
\CO.OH \

CO O

It is insoluble in ether, slightly soluble in hot alcohol, readily
in hot water, and crystallizes in fine needles or four-sided plates,
which are brass coloured, have a very bitter taste, and detonate
on heating. It does not combine with bases, but forms crystal-
line salts with acids ; it also combines with amido-bases and
phenols to form azo-compounds. 2

Nitrous acid acts upon the two orthodiamidobenzoic acids
(/3 and 7) in the following manner :



C 6 HNH 2 + NO 2 H = C 6 H,;-N N + 2H 2 O.
\COOH \CO.OH

The diazo-imidobenzoic acids obtained in this manner crystal-
lize in needles and are powerful acids, the barium salts of which
are only slightly soluble in cold water. 3

Metadiamidobenzoic acid corresponds exactly with metadi-
amidobenzene in its behaviour towards nitrous acid. In a
very dilute solution a yellow colouration is produced, and this
reaction is so delicate that one part of nitrous acid can
be detected in five million parts of water. In concentrated

1 Ann. Chem. Pharm. cxxviii. 269.

2 Griess, Bar. Deutsch. Chcm. Gos. v. 200, xvii. 603.

3 Griess, ibid. ii. 436.



264 AROMATIC COMPOUNDS.

solutions a reddish-brown precipitate of triamido-azdbenzoic acid is
formed :



2C 6 H 3 NH 2 + N0 2 H=C 6 H 3 N=N-C 6 HNH 2 +2H 2 0.
\CO.OH \CO.OH \CO.OH

This substance is soluble in alkalis, and is reprecipitated by
acids. 1



HYDRAZINEBENZOIC ACIDS, C H.<;

\CO.OH.

2151 These compounds are obtained from the amidobenzoic
acids by the methods which are employed in the preparation of
phenylhydrazine from aniline (Part III., p. 330).

Orthohydrazinebenzoic acid is slightly soluble in alcohol and
ether, and crystallizes from hot water in fine needles. It reduces
Fehling's solution and salts of silver and mercury in the cold,
and combines with bases and acids. When it is gently heated
with concentrated hydrochloric acid or heated rapidly to
220 230 in a stream of carbon dioxide, the anhydride is
formed.

X NH \
Orthdbenzoi,lhydrazide, C 6 H.<^ /NH, forms crystals which

MX)/

are slightly soluble in alcohol, ether, and hot water, have an acid
reaction, and are readily dissolved by alkalis. It does not com-
bine with acids, and does not reduce salts of mercury or Fehling's
solution, but causes a precipitation of silver from an ammoniacal
solution. 2

Metahydrazinebenzoic acid is insoluble in ether, slightly soluble
in alcohol and hot water, and crystallizes in small, yellowish
plates, which melt with decomposition at 186. It has an acid
reaction, combines with acids and bases, and reduces Fehling's
solution. Nitrous acid converts it into the imide of metadiazo-
lenzoic acid :

CO 2 H /CO 2 H

=: C 6 H / + H 2 0.

\N N



V



1 Voit, ^4mi. Chem. Pharm. xcix. 100 ; Griess, ibid. cliv. 334; Bcr. Deutsch.
Chem. Oes. xvii. 606.
a Fischer, Her. Deutsch. Chem. Oes. xiii. 679.



AZO-DERIVATIVES OF BENZOIC ACID. 265

This is a monobasic acid, which is scarcely soluble in cold,
slightly in hot water, and readily in alcohol ; it crystallizes in thin
plates, melting at 160. Metahydrazinebenzoic acid is decom-
posed in presence of diazobenzene nitrate with formation of
diazobenzoic acid imide, metamidobenzoic acid, diazobenzene-
imide and aniline. 1



AZO-DERIVATIVES OF BENZOIC ACID.

2152 These are formed, like other azo-compounds, by the
reduction of the corresponding nitro-derivatives, the following
substances being obtained :

Azoxybenzoic acids. Azobenzoic acids. Hydrazotwnzoic acids.

.C0 2 H N.C 6 H 4 .C0 2 H HN.C 6 H 4 .CO 2 H



,.



HN.C 6 H 4 .



N.C 6 H 4 .CO 2 H HN.C 6 H 4 .CO 2 H.

Ortho-azoxylenzoic acid. Griess prepared this body by heating
equal parts of orthonitrobenzoic acid and caustic potash with
alcohol. 2 It may also be obtained, together with orthonitro-
toluene, by boiling orthonitrobenzyl alcohol with caustic potash. 8
It is only slightly soluble in water, and crystallizes from hot
alcohol in small, white, rhombic prisms, which decompose on
fusion. The barium salt is readily soluble in water and forms
pointed crystals.

Ortho-azdbenzoic acid is formed by the action of sodium
amalgam on a solution of sodium orthonitrobenzoate. It is
almost insoluble in water and crystallizes from hot alcohol
in fine, dark-yellow needles, which melt at 237 with partial
decomposition. Its yellow barium salt crystallizes with seven
molecules of water in prisms, or with nine molecules in
needles. 4

Orthohydrazobenzoic acid is obtained by treating a concentrated
alkaline solution of azoxybenzoic acid with sodium amalgam. 5
It crystallizes from alcohol in colourless, elliptical plates or

Griess, Ber. Dcutsch. Chem. Ges. ix. 1657 ; Fischer, ibid. xvi. 1335.

Ibid. vii. 1611.

Jaffe, Hoppc-Seyler's Zcitschr. ii. 57.

Griess, Bcr. Dcutsch. Chcm. Ges. x. 1869.

Griess, ibid. vii. 1612.



266 AEOMATIC COMPOUNDS.

microscopic prisms, and is readily oxidized to the preceding
compound.

Metazoxylenzoic acid is insoluble in water, slightly soluble in
alcohol and ether, and forms microscopic needles or plates. Its
barium salt is an almost insoluble precipitate. 1

Metazobenzoic acid was first prepared by Neubauer by the
oxidation of metamidobenzoic acid with potassium perman-
ganate, bat was not further investigated. 2 Beilstein and Wil-
brand then found that an acid is formed by the action of zinc
on an alkaline solution of metanitrobenzoic acid, which, according
to its composition, lies between nitro- and amido-benzoic acids. 3
Strecker, who prepared it by means of sodium amalgam,
named it azobenzoic acid. 4 It is dso formed by the action of
zinc on ammonium metanitrobenzoate. 5 Acids separate it from
its salts as a light-yellow, viscid precipitate, which becomes
granular when heated with alcohol, and is only slightly soluble
in water, alcohol, and ether. Its almost insoluble barium salt
crystallizes in microscopic, rhombic plates containing five mole-
cules of water.

On distillation with lime, azophenylene, C 12 H 8 N 2 , is formed,



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