A
5-l. round-bottomed three-necked flask equipped with a
mechanical stirrer, a
reflux condenser (Note
1), and two
250-ml. dropping funnels (mounted with the aid of a Y-tube) is charged with
1.7 l. of dimethylformamide (Note
2). The flask is heated until the
dimethylformamide is almost refluxing. Then, with stirring,
280 ml. (318 g., 2.5 moles) of 1,4-dichlorobutane and a solution of
359 g. (2.75 moles) of 60% sodium sulfide (Note
2) in 1 l. of hot water are added simultaneously from the dropping funnels at such a rate that the mixture refluxes without application of heat (Note
3). After the addition is complete (about 1.5 hours), the mixture is heated at reflux with stirring for an additional 2 hours. The condenser is arranged for distillation, and 600 ml. of distillate is collected (Note
4). The distillate is made alkaline by adding
20 g. of sodium hydroxide, and
sodium chloride is added to the saturation point. The aqueous layer is separated and discarded, and the crude
tetrahydrothiophene layer is dried over solid
potassium hydroxide. Distillation through a
30-cm. Vigreux column gives, after a small fore-run (Note
5),
160–172 g. (
73–78%) of colorless
tetrahydrothiophene, b.p.
119–121°,
nD25 1.5000–1.5014 (Note
6) and (Note
7).