Reaction of Benzyl Chloride with Aqueous Ammonium Sulfide under Liquid–Liquid Phase Transfer Catalysis

Abstract

The reaction of benzyl chloride with aqueous ammonium sulfide was carried out in an organic solvent – toluene, using tetrabutylammonium bromide (TBAB) as phase transfer catalyst (PTC). Benzyl mercaptan (BM), dibenzyl sulfide (DBS), and dibenzyl disulfide (DBDS) are formed during the reaction. The reaction was found to be kinetically controlled. The selectivity of DBS was maximized in this study by changing the different parameters such as NH3/H2S mole ratio, concentration of catalyst, concentration of benzyl chloride, and temperature. The selectivity of DBDS remained at low values and was unaffected by any of the parameters studied. The selective formation of DBS was achieved with excess benzyl chloride in the organic phase with the efficient sulfide utilization although the conversion of benzyl chloride remains low. The complete conversion of benzyl chloride could be achieved with very low selectivity of DBS and very high selectivity of BM at low benzyl chloride concentration. The apparent activation energy of the reaction was calculated as 10.30 kcal/mol.