Organic Syntheses, Coll. Vol. 1, p.82 (1941); Vol. 7, p.6 (1927).
In a 3-l. round-bottomed flask
are placed 750 g. (8.1 moles) of aniline (Note 1)
and 1 kg. (8.2 moles) of benzoic acid
. When about two-thirds of the benzoic acid
is in the flask the mixture is melted to make room for the rest. The flask is placed in a large oil bath
and connected to a condenser
for distillation. The temperature of the oil is raised quickly to 180–190°, at which point distillation starts. The bath is held at this temperature until practically no more aniline
and water distil (about two hours), and then the temperature is slowly raised to 225° and maintained at this temperature until no further distillation takes place (one to two hours). The oil bath is now removed and the contents of the flask are allowed to cool below 180° and 550 g. (5.9 moles) of aniline
is added. The distillations at 190° and 225° are repeated (about six hours). The hot mixture is poured into two 20-cm. evaporating dishes
(Hood) and is allowed to cool. The crude product weighs 1600–2000 g.
, depending on the amount of aniline
The purplish-gray solid is ground (Note 2)
in a large mortar
and is poured with vigorous stirring into a 12-l. (3-gallon) crock
containing 6 l. of approximately normal hydrochloric acid
(5.5 l. of water and 500 cc. of concentrated hydrochloric acid
). The stirring is continued for one hour after all the benzanilide
has been added, and then the solid is filtered on a 20-cm. Büchner funnel
. The process of stirring with acid and filtering is repeated twice to remove the excess of aniline
. The solid is stirred for two hours with 6 l. of water and is filtered. It is stirred for one hour with 6 l. of normal sodium hydroxide
solution to remove the excess of benzoic acid
and is then filtered. The stirring with alkali and filtering is repeated. The solid is next stirred for two hours with 7 l. of water and is filtered, sucked dry, and air-dried overnight on paper.
After drying on paper the purplish solid is dried to constant weight in three 20-cm. evaporating dishes at 90–100° (about two days) and is then repowdered. The product is light purplish-gray and weighs 1270–1325 g.
per cent of the theoretical amount). It melts at 157–160°
. The product is pure enough for use in the preparation of p-dimethylaminobenzophenone (p. 217)
and for most synthetic purposes. When 100 g. of benzanilide
is dissolved in 750 cc. of hot alcohol (Note 3)
and the solution is boiled with about 10 g. of decolorizing carbon (Norite)
, filtered, and cooled at 10° overnight, 80–86 g.
of an almost colorless product melting at 160–161°
separates. A second crystallization from alcohol using decolorizing carbon
gives a white product with approximately the same loss in the mother liquors as in the first crystallization.
The ordinary "pure" aniline
of commerce gives as good yields and as pure a product as redistilled aniline
Very little of the solid fails to go into solution. The hot solution must be filtered rapidly as the benzanilide
This preparation is referenced from:
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