Organic Syntheses, Coll. Vol. 1, p.111 (1941); Vol. 6, p.8 (1926).
is prepared by refluxing 214 g. (2 moles) of commercial p-toluidine
with 800 cc. of glacial acetic acid
in a 2-l. round-bottomed flask
for two hours. The reflux condenser
is replaced by a mechanical stirrer
and the mixture is stirred and cooled to 45°. Part of the product may separate in small crystalline flakes. The mixture is thoroughly stirred and 325 g. (102 cc., 2.03 moles) of bromine
is added slowly from a separatory funnel
at such a rate that the temperature of the mixture is maintained at 50–55°. During the course of this addition, which requires about forty minutes, a precipitate may separate; this later dissolves. The mixture is stirred one-half hour after the bromine
has been added, and is then poured in a thin stream (Note 1)
with efficient stirring into 10 l. of cold water to which has been added 25 g. of sodium bisulfite (Note 2)
separates in crystalline flocks. It is filtered by suction and washed well with water and pressed dry. The wet crude material is dried until its weight does not exceed 500 g. before proceeding with the hydrolysis (Note 3)
The partially dried 3-bromo-4-acetaminotoluene
is refluxed with 500 cc. of 95 per cent ethyl alcohol
in a 3-l. round-bottomed flask
. To the boiling solution is added 500 cc. of concentrated hydrochloric acid
and the refluxing is continued for three hours. During this time, crystals of the hydrochloride of 3-bromo-4-aminotoluene
separate. The hot mixture is poured into a 2-l. beaker
and cooled thoroughly in running water. The hydrochloride is filtered by suction and washed rapidly with two 100-cc. portions of chilled alcohol. The weight of the hydrochloride is 250–300 g. (Note 4)
The hydrochloride is suspended in 800 cc. of water in a 2-l. beaker provided with a mechanical stirrer. The base is liberated by the addition of a solution of 140 g. of technical sodium hydroxide
in 700 cc. of water, and settles as a heavy brownish oil. After cooling to room temperature, the oil is separated and weighed. The yield of the crude base is 225–250 g.
per cent of the theoretical amount based on the amount of p-toluidine
used). The crude material may be used directly for the preparation of m-bromotoluene (p. 133)
The base may be purified by steam distillation but distillation under reduced pressure is more satisfactory. The oil is dried over 5 g. of solid sodium hydroxide
and distilled under reduced pressure. The first portion of the distillate may contain p-toluidine
and must be carefully separated, as it causes rapid discoloration. The 3-bromo-4-aminotoluene
is obtained as a colorless liquid of b.p. 120–122°/30 mm.
or 92–94°/3 mm.
It solidifies on cooling and melts at 16–18°
. The loss on purification is about 15 per cent of the weight of the crude base.
compound often separates at first as a heavy oil. To avoid the formation of lumps, this material should be seeded or allowed to crystallize spontaneously before the main portion is poured into water.
If the material is not partly dried before hydrolysis, the yield of the hydrochloride is diminished because of its solubility. If pure 3-bromo-4-acetaminotoluene
is desired, the crude material may be crystallized from 50 per cent alcohol
with the addition of decolorizing carbon (Norite)
as almost colorless needles, m.p. 116–117°
. The yield is 360 g.
(79 per cent
of the theoretical amount). This purification has no advantage when the acetamino compound is to be hydrolyzed to the amine.
The dark filtrate from the hydrochloride does not contain enough dissolved salt to justify recovery unless the acetamino compound is insufficiently dried before the hydrolysis.
This preparation is referenced from:
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