Hydrochloric Acid → 5-(Trifluoromethyl)-1,3,4-thiadiazole-2(3H)-thione

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699 g (3 moles) of 2-bromo-5-trifluoromethyl-1,3,4-thiadiazole and 248 g (3.3 moles) of thiourea in a mixture of 600 ml of ethanol and 75 ml of water were heated for 2 hours under reflux. A solution of 223 g of potassium hydroxide in 2 liters of water was rapidly added dropwise to the reaction solution while it was still hot, and the mixture was once more heated under reflux, for 5 minutes. The cooled solution was adjusted to pH 5 with dilute hydrochloric acid and extracted repeatedly with methylene chloride. After drying and concentrating, the residue was recrystallized from a litte petroleum ether. The mother liquor yielded further product. 330 g (59% of theory) of 2-mercapto-5-trifluoromethyl-1,3,4-thiadiazole of melting point 73° C were obtained. ##STR85##

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