Reaction of carbon disulfide and o‐phenylene diamine catalyzed by quaternary ammonium salt in the presence of potassium hydroxide

Abstract

The synthesis of 2‐mercaptobenzimidazole (MBI) from the reaction of carbon disulfide and o‐phenylene diamine (C6H4(NH2)2), catalyzed by tetrabutylammonium bromide (TBAB or QBr) in the presence of potassium hydroxide, was carried out in a homogeneous solution using protic or aprotic solvent. Water in a small amount was added to dissolve the KOH. The role of KOH in the reaction was investigated by conducting several independent experiments, which included a timed reaction of CS2 and KOH, and further reaction of C6H4(NH2)2 in the presence or absence of TBAB catalyst in various sequential orders. A homogeneous reaction mechanism was proposed which supports the kinetic reaction model. The reactions were situated in protic and aprotic solvent and are described by zero‐order and pseudo‐first‐order rate laws, respectively. The effect of the amount of KOH on the conversion of C6H4(NH2)2 was also studied. The reaction was greatly accelerated both in the presence of TBAB catalyst and KOH. Satisfactory explanations were provided for the enhanced catalytic reaction of CS2 and C6H4(NH2)2 by TBAB compared with KOH. The reaction rates in these processes are also discussed in detail.