In a
3-l. round-bottomed flask fitted with a
mechanical stirrer are placed
200 g. of technical flake sodium hydroxide,
200 g. of benzophenone,
2 l. of 95 per cent alcohol, and
200 g. of technical zinc dust. The stirrer is started and the mixture slowly warms to about 70° spontaneously. After two to three hours the mixture, which has started to cool, is filtered with suction, and the residue is washed twice with
100-cc. portions of hot alcohol (Note
1).
The filtrate is poured into five volumes of ice water acidified with about
425 cc. of concentrated commercial hydrochloric acid. The
benzohydrol separates as a white crystalline mass and is filtered by suction. The yield of crude air-dried product melting at
65° is
194–196 g. (
96–97 per cent of the theoretical amount). From
200 g. of crude product in
200 cc. of hot alcohol there is obtained, after cooling in an ice-salt mixture, filtering, and drying,
140–145 g. of product melting at
68°. The
benzohydrol remaining in the mother liquors may be precipitated with water.