Thermodynamic study of electrochemical oxidation of some pdihydroxybenzenes in the presence of p-toluenesulfinic acid

In this investigation, electrochemical oxidation of some p-dihydroxybenzenes (1-3) in the presence of p-toluenesulfinic acid as a nucleophile was studied experimentally and theoretically. The experimental results were obtained using cyclic voltammetry and controlled-potential coulometry (CPC), and the computational data was obtained by the use of density functional theory (B3LYP level of theory and 6-311G(p,d) basis set). The CPC was performed in an aqueous solution containing Methylhydroquinone (1) and p-toluenesulfinic acid (2), and monitoring of the electrolysis progress was performed by the use of the cyclic voltammetry. The coulometry was terminated after consumption of about two electrons per molecule of 1 and 1a is produced as a final product. Also, the electrochemical oxidation of 1 in the presence of 2 was studied theoretically. Firstly the effect of the substituents on the oxidation potential of the studied species (1-3) was investigated using computational study. It was found that species with larger ΔGtot value have more positive oxidation potential [1, 2]. Secondly calculated ΔGtot of the electrochemical oxidation of 1a indicates that because ΔGtot of the product (1a) is more than starting molecule (1), mechanism of the electrolysis is EC and produced 1a is not electroactive in the CPC [3].