Electroreduction of some naphthylazo compounds using polarography and cyclic voltammetry techniques

ABSTRACT

The polarographic and cyclic voltammetric reduction of alpha-, beta- and 4-sulphonaphthylazochromotropic acid dyes were studied in aqueous B.R. buffer solutions of pH = 2-12. Over the entire pH range, alpha- and beta-naphthylazo compounds were reduced through an irreversible diffusion-controlled 2-electron wave representing the saturation of the N = N center to the hydrazo stage. For 4-sulpho compound an irreversible diffusion-controlled 4-electron wave was obtained corresponding to complete reduction of its azocenter to the amino stage. The voltammograms of alpha-and-beta-naphthylazo compounds in solution of different pH's exhibit a single cathodic peak, whereas 2 cathodic peaks are observed for 4-sulpho compound. The mechanistic pathway of the electrode reaction was suggested and the kinetic parameters were calculated and discussed