Spectroelectrochemical investigations of the reduction of benzaldehyde and p-cyano-and p-phenylbenzaldehyde in sulfolane

Spectroelectrochemical investigations are presented for the reduction of benzaldehyde and p-cyano- and p-phenylbenzaldehyde in the solvent sulfolane. Two reduction intermediates were observed for the p-cyanobenzaldehyde reduction. One intermediate was the radical anion which was consumed in a dimerization reaction, k₂ = 85-88 M^-1 s^-1. The other intermediate was the electrochemically inactive complex between the radical anion and the unreduced parent. The verification of this complexation clarifies previous voltammetric studies of this type of reduction mechanism.