Electrochemical oxidation of some dihydroxybenzoic acid derivatives in the presence of various nucleophiles: Experimental and theoretical analysis

In this work, mechanistic study of the electrochemical oxidation of 2,5-dihydroxybenzoic acid (2,5-DHBA) and 2,3-dihydroxybenzoic acid (2,3-DHBA) in the presence of various nucleophiles have been investigated both experimentally and theoretically. The study was done by the use of cyclic voltammetry, controlled-potential coulometry and Density Functional Theory (DFT). The theoretical results were calculated at DFT (B3LYP and BP86) levels of theory and 6-311+G (p,d) basis set. Results showed that two-electron oxidation of studied species is followed by a Michael addition reaction of nucleophiles and new dihydroxybenzoic acids are produced. Considering several mechanisms indicates that electrochemical oxidation potentials (Ep) of studied species are directly dependent on the ΔGtot of electrochemical oxidation. It was found that the products which are produced on the surface of electrode, depending on their ΔGtot of the electrochemical oxidation, will participate in the electrochemical or chemical following reactions.