Henry E. (Henry Enfield) Roscoe.

A treatise on chemistry (Volume 3) online

. (page 16 of 50)
Online LibraryHenry E. (Henry Enfield) RoscoeA treatise on chemistry (Volume 3) → online text (page 16 of 50)
Font size
QR-code for this ebook


in transparent prisms, melting at 50. 4

The benzoic ethers of glycerol, erythrol, mannitol, the glucoses,
etc., have also been prepared. 5

2099 Phenyl benzoate, C 6 H 5 .CO.OC 6 H 5 . Ettling and Sten-
house observed a compound among the distillation products of
copper benzoate which they named benzoic oxide, C 7 H 5 0, 6 while
Gerhardt considered it to be the radical benzoyl. 7 List and
Limpricht then found that it has the formula C 13 H 10 O 2 , and is
decomposed by alcoholic potash into benzoic and carbolic acids,
so that it is a compound of benzoic acid and phenyl oxide. 8 They
further showed that it is identical with the benzophenide, which
Laurent and Gerhardt obtained by the action of benzoyl chloride
on phenol. 9

Phenyl benzoate is readily formed when benzoyl chloride is
heated with phenol until hydrochloric acid ceases to be evolved,
and also when phenol is heated with benzamide. 10 It is readily
soluble in alcohol and ether, and crystallizes from a mixture of
these in lustrous, monoclinic prisms, 11 which melt at 71 and
sublime at a higher temperature. Its smell resembles that of

1 Fricclel and Crafts, Zeitschr. Chcm. 1871, 489 ; Mayer, Ann. Chcm. Pharm.
rxxxiii. 255.

2 Rebcml, Ann. Chim. Phys. [5] xiv. 500.

3 Oppenheim, Ann. Chem. Pharm. Suppl. vi. 360 ; Friedel and Ladenburg,
ibid. cxlv. 195.

4 Engolhardt, Jahrrsbcr. Chcm. 1857, 471 ; Wicke, Ann. Chcm. Pharm. cii. 356.

5 Berthelot, ibid. Ixxxviii. 311 ; xcii. 302 : Jahrcsbcr. 1855. 677 ; 1856, 660 ;
I860, 509.

6 Ann. Chcm. Pharm. liii. 77, 94. 7 Ibid. Ixxxvii. 162.

8 Ibid. xc. 190. o Ibid. Ixxv. 75 ; Ixxxvii. 161.

10 Guaroschi, ibid, clxxi. 141. " Bodewig, Jnhresber. 1879, 675.

M 2



164 AROMATIC COMPOUNDS.



the geranium. Chlorine and bromine effect substitution in
the phenyl and not in the benzoyl group.

Trinitrophenyl benzoate, C 6 H 5 .CO.OC 6 H 2 (N0 2 ) 3 . Gerhardt
and Laurent prepared this compound by heating picric acid with
benzoyl chloride. It is insoluble in water, slightly soluble in
cold, more readily in hot alcohol, and crystallizes in lustrous,
golden-yellow, rhombic plates, which detonate when heated. 1

Gresyl benzoate, C 6 H 5 .CO.OC 6 H 4 .CH 3 . The three isomeric
ethers have been prepared by Engelhardt and Latschinow. 2

Melting- Boiling-

point, point.

Orthocresyl benzoate, oily liquid ...

Metacresyl benzoate, crystals .... 38 290 300

Paracresyl benzoate, six-sided tablets . 70

Phenylene benzoate, (C 6 H 5 .CO.O) 2 C 6 H 4 , is also known in three
isomeric forms, which are obtained from the dihydroxybenzenes.

Melting-point.
Dibenzoylcatechol, rhombic crystals 3 ...

Dibenzoylresorcinol, scales 4 117

Dibenzoylquinol, silky needles 5 199

Tribenzoylphloroglucinol, (C 6 H 5 .CO.O) 3 C 6 H 3 , forms small, lus-
trous scales, which are almost insoluble in alcohol. 6 The benzoic
ether of pyrogallol, according to Malin, does not crystallize, but
its dimethyl ether, and two homologues of the latter which
occur in the higher boiling portions of beech-wood-tar oil, give
very characteristic ethereal salts of benzoyl. 7 Since these three
ethereal salts, which are very similar in their properties, can be
separated by means of their different solubilities, they will be
mentioned here :

Melting-point.
Benzoylpyrogallol dimethyl ether :

C 6 H 5 .CO.OC 6 H 3 (OCH 3 ) 2 118

Benzoylmethyl pyrogallol dimethyl ether :

C 6 H 5 .CO.OC 6 H 2 (CH 3 )(OCH 3 ) 2 . . . . 118 119
Benzoylpropylpyrogallol dimethyl ether :
C 6 H 5 .CO.OC 6 H 2 (C 3 H 7 )(OCH 3 ) 2 ... 91

1 Ann. Chem. Pharm, Ixxv. 77.

2 Zeitschr. Chem. 1869, 615 ; see also Kekule, Ber. Deutsch. Chem. Ges. vii.
1007 ; Guareschi, Ann. Chem. Pharm. clxxi. 142.

3 Nachbauer, ibid. cvii. 243.

Malin, ibid, cxxxviii. 76 ; Dobner, Ber. Deutsch. Chem. Ges. xi. 2269.
s Dobner and Wolff, ibid. xii. 661.

Hlasiwetz and Pfaundler, Ann. Chtm. Pharm. cxix. 199.
' Hofmann, Ber. Deutsch. Chem. Ges. xii. 1373.



BENZOYL-LACTIC ACID. 165



Quinonoxime benzoate, C 6 H 4 O(NO.CO.C 6 H 5 ), is formed when
benzoyl chloride is added to sodium quinonoximate (Part III.
p. 297), which is covered with pure ether or chloroform. It
crystallizes in yellowish needles, which melt with decomposition
at 168 175, and give Lieberrnann's reaction with phenol and
sulphuric acid. 1

2100 Benzoyl-glycollic acid, C 6 H 5 .CO.OCH 2 .CO 2 H, has hitherto
only been prepared from hippuric acid or benzoylamido-acetic
acid, by treating it with nitrous acid, 2 or by passing chlorine
into its dilute alkaline solution. 3 It crystallizes from hot water
in thin tablets or large prisms, and decomposes on boiling with
water, or more rapidly with dilute mineral acids, into benzoic
and glycollic acids. Otto, by the action of sodium amalgam on
its aqueous solution, obtained benzoleic acid (p. 159) and two
other isomeric acids which have net yet been thoroughly
investigated.

Ethyl lenzoyl-gly collate, C 6 H 5 .CO.OCH 2 .C0 2 C 2 H 5 . Andrejew
obtained this substance by heating ethyl chloracetate with
sodium benzoate ; it is a liquid which boils at 277 279, and
decomposes into alcohol, benzoic acid and glycollic acid, when
boiled with alcoholic potash. 4

Benzoyl-lactic acid, CH 3 (CH.O.CO.C 6 H 5 )C0 2 H, is formed
when lactic acid is heated to 180 with benzoic acid, 5 as well as
by the action of benzoyl chloride on lactic acid or calcium lac-
tate. 6 It separates from a hot, aqueous solution in tablets or
needles, melting at 112. On boiling with water or a dilute
acid it is decomposed into lactic and benzoic acids.

Ethyl lenzoyl-lactate, C 10 H 9 O 4 .C 2 H 5 , is formed by the action of
benzoyl chloride on ethyl lactate, and by heating silver benzoyl -
lactate with ethyl iodide. It is a liquid which boils at 288.
and is decomposed into lactic acid and ethyl benzoate by heating
with water to 150.

Benzoyl compounds of tartaric and racemic acids have also
been prepared. 7

1 Walker, Ber. Deutsch. Chem. Ges. xvii. 399.

2 Strecker, Ann. Chem. Pharm. Ixviii. 54 ; Strecker and Sokolow, ibid. Ixxx.

3 Gbssmann, ibid. xcix. 181. * Ibid, cxxxiii. 284.

5 Strecker and Sokolow, loc. cit. ; Strecker, ibid. xci. 359.

6 Wislicenus, ibid, cxxxiii. 264.

J Dessaignes, Jahresber. 1857, 307 ; Perkin, Ann. Chem. Pharm. Suppl. v.
274 ; AiiscMtz and Pictet, Ber. Deutsch. Chem. Ges. xiii. 1178.



166 AROMATIC COMPOUNDS



OXIDES OF BENZOYL.

2101 Benzoyl oxide, or Benzoic anhydride, (C 6 H 5 .CO). 2 O, was
discovered by Gerhardt in 1853. He first prepared it by heating
benzoyl chloride with sodium benzoate, and named it anhydrous
benzoic acid or benzoyl benzoate ; l he subsequently found that it
can be more simply obtained by the action of phosphorus oxy-
chloride on an excess of sodium benzoate, a portion of this
being simultaneously converted into benzoyl chloride. 2 Phos-
phorus pentachloride 3 or chloride of sulphur 4 may be employed
instead of phosphorus oxychloride. It is also formed in small
quantity when benzoic acid is heated with phosphorus pent-
oxide, 5 and in larger amount by heating benzoyl chloride to
140 150 with barium oxide, 6 or to 160 220 with benzoic
acid. 7 Gerhardt had already found that it may easily be ob-
tained by the action of benzoyl chloride on potassium oxalate :

K 2 C 2 4 + 2C 6 H 5 .COC1 = (C 6 H 5 .CO) 2 + 2KC1 + CO + C0 2 ,

Anhydrous oxalic acid may be advantageously employed instead
of the potassium salt ; the reaction takes place at 50 60 ac-
companied by a regular evolution of gas, and 80 per cent, of the
theoretical yield is obtained, together with some unattacked
chloride and benzoic acid. 8 Finally, it can also be obtained by
heating benzenyl trichloride with silver oxide, or with concen-
trated sulphuric acid containing 4'6 per cent, of water : 9

C 6 H 5 .CO X

2C C H 5 .CC1 3 + 3H = >0 + 6HCL

C 6 H 5 .CCK

Anhydrous oxalic acid may be substituted for the sulphuric
acid : 10

2C 6 H 5 .CC1 3 + 3C 2 4 H 2 = (C C H 5 .CO) 2 + 3HC1 + 300 + 3CO 2 .

Ann. Chem. Pharm. Ixxxii. 127. 2 Ibid. Ixxxvii. 73.

Wunder, Journ. Prakt. Chem. Ixi. 280.
Heintz, Pogg. Ann. xcviii. 458.
Etard and Gal, Bull. Soc. Chim. xxv. 342.
Gal, Ann. Chem. Pharm. cxxviii. 127.
Anschiitz, Ber. Dcutsch. Chem, Gcs. x. 1882.
[bid.

Janssen, ibid. xii. 1495, Patent 30 Oct. 1878 (No. 6689).
JU Anschiitz, ibid, ccxxvi. 20.



BENZOIC ANHYDRIDE. 167



Benzole anhydride crystallizes in rhombic prisms (Bodewig),
melting at 42 ; it boils at 360 (Anschiitz), and is tolerably
soluble in alcohol and ether. It is scarcely attacked by cold
water, but when heated with water it gradually forms benzoic
acid, and with alcohol, ethyl benzoate. When heated in a
stream of hydrochloric acid, it decomposes into benzoyl chloride
and benzoic acid. 1 Chlorine and bromine exert a similar action,
substitution products being simultaneously formed.

Benzoyl acetyl oxide, CH 3 .CO.O.CO.C 6 H 5 . Gerhardt prepared
this compound by the action of acetyl chloride on sodium
benzoate, and named it anhydrous benzoic acetic acid. 2 It is
a heavy, oily liquid, which has a pleasant smell like that of
Spanish wine, is gradually attacked by water, more rapidly by
alkalis, and is completely decomposed by distillation into benzoic
anhydride and acetic anhydride. 3 It is also formed when ben-
zoic acid is heated to 220 with acetic anhydride. 4 According to
Loir, an anhydride is obtained by the action of benzoyl chloride
on sodium acetate, which differs from that prepared by Gerhardt's
method in yielding acetyl chloride when heated with hydro-
chloric acid to 130, while Gerhardt's compound is first attacked
at 160, with formation of benzoyl chloride. 5 This, however, is
inaccurate, and Greene has shown that the compound, in what-
ever way it is prepared, behaves in exactly the same manner
towards hydrochloric acid, the same products acetyl chloride and
acetic acid, benzoyl chloride and benzoic acid being formed as
in the case of the anhydrides themselves. 6

A number of other mixed anhydrides are now known, which,
like the foregoing, decompose on distillation into benzoic an-
hydride and another simple anhydride, 7 and must therefore be
looked upon rather as mixtures than definite compounds.

Benzoyl dioxide, or Benzoyl peroxide, (C 6 H 5 .CO) 2 O 2 , was prepared
by Brodie by the action of benzoyl chloride on barium dioxide ;
it separates from ether or carbon disulphide in rhombic crystals,
which melt at 103'5, detonate when more strongly heated, and
when boiled with caustic potash are converted into benzoic acid
with evolution of oxygen. 8

Mosling, Ann. Chcm. Pharm. cxviii. 303. 2 Ib'id. Ixxxvii. 81.

Anschiitz, ibid, ccxxvi. 12. * Ibid.

Ann. Chim. Phys. [5] xviii. 132.
Bull. Soc. Chim. xxxiii. 424.

Gerliardt, Ann. Chcm. Pharm. Ivxxii. 127 ; Ixxxvii. 163 ; Chiozza, ibid.
Ixxxiv. 106 ; Ixxxvi. 259 ; Chiozza and Malcrba, ibid. xci. 102.
3 Ann. Ckem. Pharm. cviii. 80 ; Lippmann, Monatsh. Chcm, v. 560.



168 AKOMATIC COMPOUNDS.



HALOGEN COMPOUNDS OF BENZOYL.

2102 Benzoyl chloride, C 6 H 3 .COC1, was discovered in 1832 by
Wo'hler and Liebig ; they obtained it by the action of dry
chlorine on pure oil of bitter almonds, and describe it as a trans-
parent liquid the vapour of which violently attacks the eyes, and
has a peculiar, very penetrating odour resembling the sharp smell
of horse-radish. 1 Cahours then prepared it by the action of
phosphorus pentachloride on benzoic acid, 2 Gerhardt by that of
phosphorus oxychloride on sodium benzoate, 3 and Bechamp by
heating benzoic acid with phosphorus trichloride. 4 Fried el sub-
sequently observed its formation when hydrochloric acid is passed
over a mixture of beuzoic acid and phosphorus pentoxide heated
to 200 , 5 this being an important general method for the forma-
tion of acid chlorides. Harnitz-Harnitzky stated that it might
also be obtained by exposing a mixture of carbonyl chloride and
benzene vapour to the action of sunlight, 6 but Berthelot was
unable to confirm this statement, 7 although it is undoubtedly
formed in this way when aluminium chloride is present,
(p. 30). 8

It also may be obtained by heating benzenyl trichloride with
anhydrous oxalic acid :

C 6 H 5 .CC1 3 + C 2 O 4 H 2 = C 6 H 5 .COC1 + 2HC1+CO 2 +CO.

Benzoic anhydride is also formed in this reaction. In order
to prepare the chloride, a mixture of two molecules of phosphorus
trichloride with three molecules of benzoic acid is heated until
hydrochloric acid ceases to be evolved, water is then added and
the oily liquid which separates purified by distillation ; accord-
ing to another method, benzoic acid is heated with one molecule
of phosphorus pentachloride, and the mixture distilled, the dis-
tillate consisting at first of phosphorus oxychloride mixed with
a little benzoyl chloride, followed by pure benzoyl chloride. The
phosphorus oxychloride is then employed for a further prepara-
tion by being heated with sodium benzoate, an excess of which

1 Monatsh. Chem. iii. 262.

Ann. Chem. Pharm. Ix. 251. " Ibid. Ixxxvii. 63.

4 Journ. Prakt. Chem. Ixviii. 489. 6 Bull. Soc. Chim. ii. 80.

6 Ann. Chem. Pharm. cxxxii. 72. * Bull. Soc. Chim. x ii. 9, 392.

8 A'lor, Crafts and Friedel, Bcr Peutsch. Chem. Ges. x. 1854.



BENZOYL CHLOKIDE. 169



must be avoided, as, otherwise, some benzoic anhydride would
be formed. The crude chloride, prepared by either of these
methods, is freed from adhering chlorides of phosphorus by
treatment with cold water, and is then purified by distillation.

Properties. It is a strongly refractive liquid, which fumes in
the air, has a sp. gr. of T2324 at and solidifies when cooled in
crystals melting at 1. It boils at 198 ; its vapour attacks
the lungs and mucous membrane very violently. It is gradually
decomposed by cold, more rapidly by hot water, with formation
of benzoic and hydrochloric acids ; it is rapidly converted into
ethyl benzoate by alcohol, and the other alcohols produce a
similar reaction. Since it undergoes double decomposition so
readily, it is largely employed for the preparation of other
benzoyl derivatives ; many examples of this have been already
given and others will be met with in the sequel. It is also
employed to a considerable extent in the same way as acetyl
chloride, for determining the number of hydroxyl groups con-
tained in carbon compounds.

Gerhardt and Laurent found that the compound C 6 H 5 .CHO -f
C 6 H 5 .COC1 is formed by the action of chlorine on benzaldehyde ;
this substance is insoluble in cold alcohol, crystallizes in lustrous
plates, is decomposed by distillation into its components, and by
boiling with water into hydrochloric acid and benzaldehydo-
benzoic acid ; l the latter compound corresponds to the ethidene-
chloracetin (Part II. p. 80) obtained in a similar manner from
acetaldehyde, and is, therefore, benzidene lenzochlorohydrin :



/Cl

C 6 H 5 .CH<

\OCO.CJL



Benzoyl bromide, C 6 H 5 .COBr. Wohler and Liebig, by the
action of bromine on oil of bitter almonds, obtained a crystalline
compound which they looked upon as benzoyl bromide. This
substance was subsequently shown by Claisen to be benzidene-
benzobromohydrin ; this chemist then prepared benzoyl bromide
by heating three molecules of benzoic acid with two molecules
of phosphorus tribromide ; it is a transparent, colourless liquid,
has an odour resembling that of the chloride, but fumes more
strongly in the air, is more readily attacked by water and boils at
218- 219 . 2 It combines with benzaldehyde to form the com-

1 Jahrcsber. Chem. 1850, 489. 2 Ber. Dcutsch. Chcm. Gcs. xiv. 2473.



170 AROMATIC COMPOUNDS.



pound just mentioned, lenzidcne benzobromohydrin or bromo-
benzylbenzoate, C 6 H 5 .CHBr.O.CO.C 6 H 5 , which crystallizes from
boiling petroleum ether in short prisms or thick tablets, which
melt at 69 70 and are decomposed by distillation into their
components. Paterno obtained the same compound, together
with ethyl bromide, benzyl bromide and benzaldehyde, by the
action of bromine on ethyl benzoate, but considered it to be
benzoyl bromide. 1

Benzoyl iodide, C 6 H 5 .COI. Wohler and Liebig obtained this
compound by heating the chloride with potassium iodide as a
colourless, foliated, crystalline mass, which readily melts, a little
iodine being set free, has a penetrating odour and is decom-
posed by water and alcohol. It has not been analyzed.

Benzoyl fluoride, C fJ H 5 .COF. Borodin prepared this compound
by the distillation of the chloride with acid potassium fluoride,
F 2 HK, in a platinum retort. It is a heavy, oily and colourless
liquid, which boils at 161'5, has a still more powerful odour
than the chloride, and is decomposed by water into benzoic and
hydrofluoric acids. 2



SULPHUR COMPOUNDS OF BENZOYL.

2103 Th'lobenzoic acid, C 6 H 5 .CO.SH. Cloe'z obtained salts of
this acid by the action of benzoyl chloride on potassium sulphide
and double decomposition of the potassium thiobenzoate thus
formed with other metallic salts. 3 The compound which he
separated from the potassium salt and looked upon as thio-
benzoic acid proved to be benzoyl disulphide. The free acid is
obtained by decomposing the potassium salt with dilute hydro-
chloric acid ; a yellow liquid, smelling of sulphur compounds,
separates out and soon solidifies to a crystalline mass, melting at
24, which decomposes on distillation but is volatile with steam.
It is readily oxidized to benzoyl disulphide, this action taking
place even when its alcoholic solution is evaporated in the air. 4

Potassium thiobenzoate, C 6 H 5 .CO.SK, crystallizes from alcohol
in yellowish tablets or prisms, and is very readily soluble in
water. The silver salt is a yellowish white, and the lead salt a



1 Gaz. Chim. Ital. i. 586. 2 Ann Clusm. Pharm. cxxvi. 6

3 Ibid. cxv. 27.

4 Engelhardt, Latschinow and Malysehew, Zciischr. Cliem. 1868, 353.






THIOBENZOIC ACID. 171

white precipitate ; both of these readily blacken and decompose.
Copper sulphate gives a greenish yellow precipitate which after
some time becomes red and then contains benzoyl disulphide :
ferric chloride yields a violet-brown precipitate which becomes
yellow on warming.

Ethyl thiobenzoate, C 6 H 5 .CO.SC 2 H 5 , is formed by the action of
benzoyl chloride on lead mercaptide, Pb(SC 2 H 5 ) 2 , 1 and of ethyl
iodide on silver thiobenzoate. It is a yellow, repulsive smell-
ing liquid, which boils at 242 243 and is decomposed by
saponification with caustic potash into ben zoic acid and ethyl
hydrosulphide, while potassium hydrosulphide yields the latter
compound and thiobenzoic acid. It is oxidized by potassium
permanganate and dilute sulphuric acid to benzoic acid and
ethylsulphonic acid. 2

Phenyl thiobenzoate, C 6 H 5 .CO.SC 6 H 5 , is obtained by heating
benzoyl chloride with phenyl hydrosulphide. 3 It crystallizes
from alcohol or benzene in long lustrous needles, melting at 56.

Benzyl thiobenzoate, C 6 H 5 .CO.S.CH 2 .C 6 H 5 , is readily soluble
in alcohol and benzene, and forms lustrous, asymmetric crystals,
melting at 39'5. Its behaviour towards reagents resembles that
of the ethyl ether. 4

Benzoyl sulphide, or Thiobenzoic anhydride, (C 6 H 5 .CO) 2 S, was
obtained by Wohler and Liebig in an impure condition by the
distillation of benzoyl chloride with lead sulphide. It is pre-
pared by treating potassium thiobenzoate with benzoyl chloride
(Engelhard t, Latschiuow and Malyschew). It crystallizes from
ether in large prisms, which melt at 48 and decompose on
distillation. When heated with ammonia it yields benzamide
and thiobenzoic acid ; the latter is also formed by the action of
potassium hydrosulphide, while benzoic acid is obtained in
addition when caustic potash is employed.

Benzoyl disulphide, (C 6 H 5 .CO) 2 S 2 , is formed by the oxidation
of thiobenzoic acid and by heating benzoic anhydride in a stream
of dry sulphuretted hydrogen. 5 It is prepared by adding a
solution of iodine in potassium iodide to an aqueous solution of
potassium thiobenzoate. It is only slightly soluble in alcohol
and ether, and crystallizes from hot carbon disulphide in large






1 Tiitschow, Jahrcsbcr. Chem. 1863, 483.

2 Beckmann, Journ. Prakt. Chem. [2] xvii. 463.

3 Schiller and Otto, Ber. Deutsch. Chem. Ges. ix. 1635.

4 Liiders and Otto, ibid. xiii. 1285.

5 Mosliug, Ann. Chem. Pharm. cxviii. 304.



172 AROMATIC COMPOUNDS.



prisms or six-sided tablets which melt at 128, and become
coloured violet-red at a slightly higher temperature.

Dithiobenzoic acid, C 6 H 5 .CS.SH, is formed in small quantity
when benzoyl chloride is heated with lead sulphide. It is more
easily obtained by treating benzenyl trichloride with a very
dilute alcoholic solution of potassium sulphide : l

C 6 H 5 .CC1 3 + 2K 2 S = C 6 H 5 .CS.SK + 3KC1.

Acetate of lead first precipitates lead sulphide from the
solution obtained, and then the lead salt of the acid, which is
finally decomposed by hydrochloric acid. It is a dark violet-red,
heavy, oily liquid, which gives a carmine-coloured solution in
ether, and rapidly forms a resinous mass when exposed to
the air.

Lead dithiobenzoatc, (C 6 H 5 .CS 2 ) 2 Pb, is a vermilion-coloured
precipitate, which crystallizes from boiling xylene in fine, red
needles.

Benzoyl thiocyanate, C 6 H 5 .CO.S.CN, is obtained by the action
of benzoyl chloride on lead thiocyanate in the cold. It is a
yellow liquid which has a penetrating odour resembling that of
bitter almonds, and can only be distilled without decomposition
in a vacuum. 2 It combines with ammonia, forming benzoyl
thiocarbamide, (C 6 H 5 .CO)HN.CS.NH 2 , and is, therefore, probably
benzoyl mustard oil, C 6 H 5 .CO.N.CS.



NITROGEN COMPOUNDS OF BENZOYL.

2104 Benzamide, C 6 H 5 .CO.NH 2 . Wohler and Liebig obtained
this compound by the action of benzoyl chloride on ammonia,
and Fehling subsequently prepared it by boiling hippuric acid
with water and lead dioxide. 3 Dumas found that it is also
formed when ethyl benzoate is brought into contact with aqueous
ammonia, the reaction taking place more rapidly when the
mixture is heated to 100. 4 It is also formed by a similar
reaction from benzoic anhydride. 5

1 Engelhardt and Latschinow, Zcitschr. Chem. 1863, 456 ; see also Fleischer,
Ann. Chcm. Pharm. cxl. 240.

2 Miquel, Ann. Chim. Phys. [5] xi. 300.

3 Fehling, Ann. Chem. Pharm. xxv. 48 ; Schwarz, ibid. Ixxv. 195.
* Compt. Rend. xxv. 734.

5 Scheitz, Marsh and Geuther, Zcitschr. Chcm. 1868, 302.



BENZAMIDE. 173



In order to prepare it, benzoyl chloride is triturated with solid
ammonium chloride, the product washed with cold water, and
crystallized from hot water or alcohol ; 1 or equal molecules of
benzoic acid and ammonium thiocyanate may be heated to 150
170, carbonyl sulphide, ammonia, sulphuretted hydrogen and
carbon dioxide being evolved, while benzamide remains behind
and only requires to be freed from benzoic acid by washing with
ammonia. 2

It is slightly soluble in cold, more readily in hot water,
especially when it contains ammonia, and dissolves readily in
both alcohol and ether. When its aqueous solution is rapidly
cooled, it separates out in small plates, while on more gradual
cooling it is deposited in fine needles, which gradually change
into larger crystals. The latter are also obtained by allowing a
mixture of ethyl benzoate and ammonia to stand, or by gradually
cooling the fused compound ; they consist of well-formed, mono-
clinic tablets, 3 melting at 128 . 4 It boils at 286 -290, a small
portion being decomposed into water and benzonitril, C 6 H 5 .CN.
The latter compound may be readily prepared from it by simply
heating with a dehydrating agent ; Wohler and Liebig had
observed that when heated with caustic baryta, an oily, aromatic
liquid having a sweet taste, was formed, and that it might also
be obtained by passing the vapour of the compound through a
red-hot tube. This substance was afterwards recognized as the
benzonitril discovered by Fehling in the year 1844. 5

Benzamide is not decomposed by heating with dilute alkalis ;
when it is boiled with strong caustic potash or hydrochloric acid
it decomposes into ammonia and benzoic acid, and on boiling
with phenol, ammonia and phenyl benzoate are formed. 6 When
heated with ethyl nitrite to 120, the following reaction takes
place : 7

C 6 H 5 .CO.NH 2 +NO.OC 2 H 5 = C 6 H 5 .CO.OC 2 H 5 +H 2 O + N 2 .

If its solution in aqueous ether be treated with sodium
amalgam and kept neutral by the addition of hydrochloric
acid, benzyl alcohol is formed. 8

Gerhardt, Chim. Orq. iii. 268.

Kekule, J3er. Deutsch. Chem. Ges. vi. 113.

Klein, Ann. Chem. Phmm. clxvi. 184.

Schiff and Tassinari, B<-.r. Dnitsch. Chem. Ges. x. 1785.

Wohler, Ann. Chf.m Pharm. cxcii. 362.



Online LibraryHenry E. (Henry Enfield) RoscoeA treatise on chemistry (Volume 3) → online text (page 16 of 50)