Mechanism of electrochemical reduction of oxamide analytical applications

Oxamide is electrochemically reduced at mercury electrodes between pH 5.6 and 11.6. The overall mechanism proceeds by an initial 2e reduction of the 1,2-carbonyl groups of oxamide to give a dianion. This then protonates, rearranges, and loses ammonia to glyoxylamide, which is reduced in a further 2e/2H⁺ reaction giving glycolamide as the ultimate product. The reaction thus proceeds by a typical e.c.e. mechanism. The overall homogeneous rate contant for the chemical reaction(s) interposed between the two charge-transfer steps was measured by peak voltammetric, potentiostatic and d.c. polarographic methods. The d.c. polarographic wave of oxamide between pH 5.6 and 11 provides the basis for a very simple analytical method for the determination of oxamide.