Electrochemical reduction of the 4,4′-azobis-benzaldehyde and its bis-methylacetal in methanol at a mercury cathode

Abstract

The electrochemical behaviour of the 4,4′-azobis-benzaldehyde and its bis-methylacetal in methanol solutions, is studied by d.c. polarography, controlled-potential coulometry, and cyclic voltammetry. The polarographic reduction of the 4,4′-azobis-benzaldehyde involves a two-electron and a four-electron wave, corresponding to the reduction of the azo group and the two aldehydic groups, respectively. The addition of HCl in small concentrations, results in the decrease with time of the second wave due to the acetalization of the two aldehydic groups occurring in bulk. The polarographic curves of the 4,4′-azobis-benzaldehyde-bis-methylacetal in methanol, in excess of any strong acid, show a second reduction wave corresponding to the further reduction of the hydrazo compound formed in the first step. This further reduction proceeds via an intermediate step, consisting in the protonation of the hydrazo group, which exhibits an electrosorption current peak in the corresponding cyclic voltammogram.