Electroreduction and related studies on 2-aminoacrylic acid derivatives. Part I. Electroreactivity of 2-acetamidocinnamic acid

Abstract

Polarographic, cyclic voltammetric, controlled potential electrolysis, and potentiometric evidence indicates that at low pH values (<4) the mechanism of electroreduction of ethyl α-acetamidocinnamate and α-acetamidocinnamic acid (pK_a–1·03 and –1·13, respectively) involves the protonation of a weak base in a thin layer near the electrode surface or at the surface. As the protonated form of the substrate is removed by electrolysis, the electroactive substrate is replenished by a chemical reaction between the non-protonated substrate and a hydrogen ion. As the pH is increased, the rate of this chemical reaction decreases and two polarographic waves appear. In addition, α-acetamidocinnamic acid exhibited an additional electrochemical acid–base equilibrium, believed to result from the dissociation of the carboxylic proton.