Exhaustive Study of the Electrodimerization of 2-Mercaptobenzoxazole; From Electrochemical Behavior to Electrosynthesis

Organic compounds possessing S–S bonds, often called disulfides or more specifically disulfanes, have been widely employed in the various fields ranging from biochemistry to industrial chemistry [1]. It is known that the oxidative coupling of the 2-mercaptobenzoxazole (MBO) to the 2,2-disbenzoxazole disulfide (BBOD) passes through a radical path [2,3]. However, there has been a little discussion concerning the electrodimerization of this compound on the various conditions and without paying attention to the significant optimizations. This can be due to the problems caused by the adsorption of thiols and related dimers on the electrode surface. So, the precise and comprehensive electrochemical survey is necessary in order to the better understanding of the proposed mechanisms and the fine electrosynthesis. Our initial studies showed two essential point; pH–dependent behavior and typical adsorption pattern. At the critical acidic to mild basic conditions, two anodic and one cathodic processes are observed. The MBO undergoes 1H+, 1e- oxidation of adsorbed and dissolved forms at the forward and low scan rate. It is leading to the formation of related disulfide (S-S) by dimerization of the electrogenerated thiyl radicals. The typical adsorption peak at the backward scan rate is related to the produced dimer (BBOD) owning to its extremely low solubility, which is easy to understand by the scan rate diagnostic test. At the critical basic conditions, the cathodic adsorption peak has disappeared that can be assigned to the related sulfonate because of over oxidation processes. The pH-dependence, scan rate effect and various solvents have evaluated for obtaining of the optimal condition. According to the above-mentioned contents, the first aim of this study is the voltammetric analysis as an easy-to-apply electrochemical technique for the oxidation of different thiols in more details in order to shed more lights on the mechanistic aspect of this green electrochemical transformation under various conditions. On the other hand, the obtained optimal parameters will be employed for the electrodimerization of the various type of thiols in the electrosynthesis condition.