Electrochemical synthesis of thiocarbamates

Abstract

The possibility of indirect and direct electrosyntheses of thiocarbamates is studied. The indirect synthesis is based on producing monochloramines by the chlorination of an aqueous solution containing an amine and sodium chloride on a dimensionally stable anode (DSA) in diaphragm electrolysis and a subsequent interaction of monochloramines with potassium xanthate. Optimum synthesis conditions are found ensuring a current efficiency for thiocarbamates of 43-60%. These are:c _amine = 0.17-2 M, c_NaC1 = 4 M,j_a = 20-30 A dm^-2, electrolysis temperature 10‡C, the chloramine : potassium xanthate : amine molar ratio of 1 : 1.1 : 2, and the temperature of the reaction between chloramine and potassium xanthate of 8‡C. The direct synthesis of thiocarbamates is realized in diaphragm electrolysis when oxidizing an aqueous solution containing an amine, potassium xanthate, and sodium chloride on DSA. With the electrosynthesis of ethyl ester of methylthiocarbamic acid as an example, conditions are found that allow one to obtain a target product with a current efficiency of about 44%. However, the direct synthesis is accompanied by the destruction of the anode material.