Anodic oxidation of amines. Part I. Cyclic voltammetry of aliphatic amines at a stationary glassy-carbon electrode

The anodic oxidations of seventeen aliphatic amines have been examined by cyclic voltammetry at a glassy-carbon electrode in aqueous alkaline solution. All are irreversibly oxidized. Primary amines show no wave. Secondary amines show one wave. Most tertiary amines show two waves and the peak potentials of the first waves are less positive than those of secondary amines. The peak potentials of the first wave of substituted tertiary amines shift to more positive values with increasing electronegativity of the substituent, and some amines with a strongly electron withdrawing group give one wave or no wave. A linear relationship is obtained between the pKa values and peak potentials of the first waves for tertiary amines. The postulated reaction mechanism for tertiary amines involves loss of two electrons, followed by reaction with water to form a secondary amine and an aldehyde.