Catalyzed reaction of carbon disulfide and o-phenylene diamine by tertiary amine

Abstract

The reaction of carbon disulfide and o-phenylene diamine in a two-phase solution to synthesize 2-mercaptobenzimidazole (MBI) catalyzed by the inexpensive tertiary amine was carried out. The reaction, which is accelerated by adding a small amount of tertiary amine, occurs in the organic phase. The mechanism was identified by two steps. First, the reaction of carbon disulfide and tertiary amine takes place to produce an active intermediate (R 3NCS 2) within a short time of reaction. Then, this active intermediate further reacts with o-phenylene diamine to produce MBI. A kinetic model based on the proposed mechanism was built up. The advantage of using two-phase reaction is that the product precipitates from the reaction solution. Only mechanical separation processes, such as: filtration and centrifugation, are required to remove the product from the solution. A pseudo-first-order rate law is sufficiently to describe the reaction. Factors, which affect the conversion of o-phenylene diamine and the reaction rate, were investigated in detail.