Peculiarities of the mechanism of electroreduction of cinnamic acid in DMF and DMF-H2O mixture

Abstract

The electrochemical behavior of cinnamic acid (CA) on the cathodes with a high hydrogen overpotential (Hg, glassy carbon, and carbositall) in the aprotic solvent (DMF) and in DMF with additions of H2O or Et4NOH is studied by the methods of polarography, preparative electrolysis, cyclic voltammetry (CVA), coulometry, and chronoammetry. It is found that the mechanism of CA electroreduction is in conflict with the classical notion of the mechanism of electroreduction of α,β-unsaturated carboxyl compounds. It is shown that in the aprotic solution, in contrast to similar carbonyl compounds or ethers, which are the derivatives of organic acids, the products of double-bond hydrogenation, rather than the dimeric compounds, are the only products of CA electroreduction, i.e the presence of carboxyl group changes essentially the direction of electrochemical process. From the data of CVA, it is concluded that stable dimeric associates are present in the DMF solutions in the equilibrium with nondissociated CA.