The crude
p-acetaminobenzenesulfonyl chloride (p. 8) obtained from
67.5 g. (0.5 mole) of acetanilide is shaken for two hours with a solution of
252 g. (1 mole) of crystallized sodium sulfite (Na
2SO
3 · 7H
2O) in 500 cc. of water. The reaction mixture is kept slightly alkaline by the addition at intervals of small portions of
50 per cent sodium hydroxide solution. The total volume of alkali used varies from 10 to 50 cc. After the alkaline mixture has been shaken for the two-hour period (Note
1) it is filtered, and the filtrate is acidified with
60 per cent sulfuric acid. If the acid is added slowly, the
sulfinic acid comes down in fine crystals which, after filtering and drying, melt at
155° with decomposition (Note
2). The yield is
50–55 g.. (
43–47 per cent of the theoretical amount based on the
acetanilide used).
The product may be purified by crystallization from 400 cc. of hot water, but this is unnecessary when the above procedure is followed carefully.