In a
3-l. round-bottomed, three-necked flask fitted with a
liquid-sealed mechanical stirrer, a
thermometer, and a
500-cc. separatory funnel are placed
1.7 l. of dry benzene and
160 g. (1.2 moles) of powdered, anhydrous aluminum chloride (Note
1). The mixture is cooled to 10° by means of an
ice-water bath and maintained at 10–20° during the addition of a solution of
120 g. (0.58 mole) of benzalacetophenone (Note
2) in
300 cc. of dry benzene. This addition requires about thirty minutes. The cooling bath is then removed and stirring continued at room temperature until all the dense, yellow precipitate formed at first has gone into solution (Note
3). The reaction is complete after stirring for an additional hour.
The bulk of the brown-colored
benzene solution is decanted into a cold mixture of
100 cc. of concentrated hydrochloric acid and 1.5 l. of water in a
5-l. round-bottomed flask. The remainder is filtered on a Büchner funnel, and the lumps of
aluminum chloride are washed with two
100-cc. portions of benzene. The filtrates are added to the main solution and the whole is washed thoroughly with the dilute acid. If the layers do not separate readily the mixture is filtered with gentle suction and the water separated by siphoning. The solution is washed twice with 1.5-l. portions of water and filtered again if necessary.
The clear, light yellow
benzene solution is subjected to rapid steam distillation (Note
4) in the same 5-l. flask, and when no more
benzene passes over the flask is cooled under the tap with shaking. The residual oil solidifies to light brown pellets. These are collected, separated from water as much as possible, and dissolved in
2250 cc. of boiling alcohol.
Five grams of decolorizing carbon is added; the hot solution is filtered with suction and allowed to cool. The best results are obtained if the alcoholic solution is stirred slowly with a
mechanical stirrer while cooling to room temperature. Stirring is stopped when the mixture becomes semi-solid, and the mass is then allowed to stand for twenty-four hours. The fine, colorless needles are filtered on a
15-cm. Büchner funnel and pressed as dry as possible. The yield of thoroughly air-dried, colorless material melting at
91–92° (Note
5) amounts to
125–140 g. (
76–85 per cent of the theoretical amount) (Note
6).