Submitted by F. G. Willson and T. S. Wheeler.
Checked by Henry Gilman and R. McCracken.
1. Procedure
A
1500-cc. flask is fitted with a
reflux condenser, a
mechanical stirrer, and a
200-cc. separatory funnel. In the flask are placed
372 g. (4 moles) of aniline (Note
1),
105 g. (1.25 moles) of sodium bicarbonate (Note
2), and 100 cc. of water. The flask and contents are then heated on a
steam bath to 90–95°, and
127 g. (115 cc., 1 mole) of benzyl chloride (Note
3) is run in slowly from the separatory funnel, vigorous agitation being maintained. The addition of
benzyl chloride should take not less than one and one-half to two hours, and the reaction is complete in four hours.
The mixture is then cooled, filtered with suction, the layers of water and organic liquid separated, and the latter washed with saturated salt solution (Note
4). The amines are then dried by shaking with about
20 g. of anhydrous sodium sulfate, and again filtered with suction. The excess of
aniline is removed by distillation under reduced pressure (Note
5) using a modified
Claisen flask with a fractionating side arm
(p. 130). The
aniline distils at 81° /12 mm., and then the temperature rises quickly to the boiling point of
benzylaniline,
180° /12 mm. or
190° /16 mm. When the temperature has risen to within about 5° of the boiling point of the
benzylaniline, the
receiver is again changed and the
benzylaniline collected from 170–200° /12 mm., practically all boiling at
178–180° /12 mm. (Note
6).
The
aniline recovered amounts to
250–260 g. (
89–92 per cent of the theoretical amount), and the yield of
benzylaniline is
155–160 g. (
85–87 per cent of the theoretical amount based on the
benzyl chloride). The product solidifies on cooling and melts at
33–36°. It is practically colorless and sufficiently pure for most synthetic purposes. A pure compound melting at
36° may be obtained by crystallizing the product from about
100 cc. of ligroin (b.p.
85–90°). The solution is cooled in a freezing mixture to cause crystallization, the crystals filtered with suction, washed with a little cold ligroin, pressed, and dried. The recovery is about
90 per cent of the original product.
2. Notes
2.
Sodium bicarbonate is used on account of its high purity and convenience in handling. An equivalent amount of the normal carbonate may be substituted, but reagents of stronger basicity increase the proportion of high-boiling by-products.
3. The
benzyl chloride should be freshly distilled and collected at 176–178°.
4. Saturated salt solution is used here in preference to water, as separation of the liquids is more rapid and clean.
5. The
aniline may also be quite satisfactorily removed by distillation under atmospheric pressure, using an
efficient fractionating column, the distillation being interrupted when the
thermometer in the
still-head registers 235°.
6.
Benzylaniline distils without appreciable decomposition at atmospheric pressure at
298–300°. It assumes, however, a yellow color, and separation from any higher-boiling impurities is more difficult than when distillation is carried out under reduced pressure.
3. Discussion
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