Stability of silver 2-mercapto-benzimidazole complexes in aqueous-methanol solutions

The values of acid ionization of 2-mercaptobenzimidazole in aqueous-methanol solutions were determined. It was shown that the ionization constant of 2-mercaptobenzimidazole decreases when going from aqueous to aqueous-methanol solutions. It was found that the ionization constant of 2-mercaptobenzimidazole depends on nature of the alcohol. In order to determine the area of dominance of various forms of 2-mercaptobenzimidazole in a wide ph range, diagrams of the fractional distribution of 2-mercaptobenzimidazole were constructed experimentally using the found values in aqueous-methanol solutions. It was revealed that the maximum fraction of accumulation of molecular form occurs at 5-11.5. Below 5, the protonated form of 2-mercaptobenzimidazole begins to accumulate in the solution. The number of formed complex particles of silver with 2-mercaptobenzimidazole was found depending on content of non-aqueous solvent, and the constants of their stability were calculated. It was found that interaction of silver with 2-mercaptobenzimidazole in an aqueous methanol solution gives rise to two complex forms stepwise. It was shown that with an increase of methanol content in the solution, the values of the general stability constants increase. (author)