On reduction of the drug diflunisal in non-acqueous media

The electrochemical reduction of diflunisal was studied in dimethyl sulfoxide on static mercury drop electrode. Diflunisal yields one irreversible wave at -1.2 V (vs. Ag | AgCl | 1 M LiCl electrode) due to the reduction of the carboxylic functional group in the molecule. The electrochemical properties of the drug were compared with the ones of the chlorinated analogue. The study is based on cyclic voltammetry, tast polarography, and constant potential electrolysis. The experimental findings are supported by molecular orbital calculations. The mechanism of reduction of the carboxylic moiety was found to involve two electrons and two protons. The reduction pathway leads to formation of an aldehyde derivative.