Mechanistic study and computational analysis of the electrochemical oxidation of some hydroquinone derivatives in the presence of p-toluenesulfinic acid and green synthesis of new derivatives

The mechanism of electrochemical oxidation of methoxyhydroquinone, methylhydroquinone, tert-butylhydroquinone, and chlorohydroquinone in the presence of p-toluenesulfinic acid as a nucleophile has been investigated both experimentally and theoretically. Electrolysis of these species in the presence of p-toluenesulfinic acid indicates that the final products are produced via an EC mechanism. The electrochemical synthesis of the final products has been performed in good yields and purity. Using density functional theory (BP86 method) and 6-31G(d,p) basis set, ∆G_tot of the species have been calculated. Because the ∆G_tot of products are higher than that of starting molecules, the electrolysis after consumption 2e⁻ per molecule has been terminated. Also, by the use of NBO analysis at the mentioned level of theory, the effect of the charge of the reaction sites on site selectivity has been studied.