Hydrogenolysis and Dimerization of Thiobenzoic Acid with Molybdenum Trisulfide Catalyst

Abstract

In the hydrogenolysis of thiobenzoic acid catalyzed by molybdenum trisulfide (MoS₃) at 160280°C under the hydrogen pressure of 80 kg/cm², 90 min, toluene and dibenzyl were obtained at final products. During the course of the reaction, appreciable amount of S-benzyl benzothioate and benzoic acid were obtained as main intermediates, whereas α-toluenethiol and didenzyl sulfides were scarcely obtained as intermediates.
In order to elucidate the course of the reaction, the related intermediates of thiobenzoic acid were synthesized, and these hydrogenolyses or heat-treatment were carried under the various conditions. It was considered that S-benzyl benzothioate might be produced by the reduction of dibenzoyl sulfide, and benzoic acid might be produced by the hydrolysis of thiobenzoic acid and/or dibenzoyl sulfide. It was presumed that dibenzoyl sulfide might be produced by dehydrogensulfurization of thiobenzoic acid and partially by desulfurization of dibenzoyl disulfide which might be produced by dehydrogenation of thiobenzoic acid.
The whole reaction path for the hydrogenolysis of thiobenzoic acid are suggested.