Reaction of carbon disulfide and o-phenylene diamine by tertiary amine in the presence of potassium hydroxide

The reaction of carbon disulfide and o-phenylene diamine catalyzed by tertiary amine in the presence of KOH in an aqueous solution/ organic solvent two-phase medium was carried out. The reaction was greatly enhanced by adding a small amount of tertiary amine in the presence of KOH. The reaction of synthesizing 2-mercaptobenzimidazole (MBI) first took place in the organic phase. However, the potassium salt of MBI, which was produced from the reaction of MRI and KOH at the interface between CH2Cl2 and H2O, dissolved in the aqueous phase. The greatest advantage of using this process is that MBI in crystal form can then be precipitated from the aqueous solution by adding an acidic compound. Based on the experimental data, a reaction mechanism was proposed. The reaction of synthesizing MBI was first initiated by reacting CS2 and R3N to produce an active intermediate (R3N-CS2). This active intermediate further reacted with o-phenylene diamine to produce the desired MBI product. In addition, potassium hydroxide also reacted with H2S, which is a byproduct from the synthesis of MBI, to enhance the reaction. The reaction of CS2 and C6H4(NH2)(2) in a two-phase medium is described by a pseudo-first-order rate law.