Direct Electrochemical Reduction of 4,4′-(2,2,2-Trichloroethane-1,1-diyl)bis(methoxybenzene) (Methoxychlor) at Carbon and Silver Cathodes in Dimethylformamide

Abstract

Cyclic voltammetry and controlled-potential (bulk) electrolysis have been employed to investigate the electrochemical reduction of 4,4′-(2,2,2-trichloroethane-1,1-diyl)bis(methoxybenzene), commonly known as the pesticide methoxychlor, at glassy carbon and silver cathodes in dimethylformamide (DMF) containing 0.050 M tetra-n-butylammonium tetrafluoroborate (TBABF4). Reduction of methoxychlor at both glassy carbon and silver shows four voltammetric peaks, the first three of which are associated with cleavage of carbon–chlorine bonds; the fourth peak is assigned to reduction of 4,4′-(ethene-1,1-diyl)bis(methoxybenzene). Bulk electrolyses of methoxychlor at reticulated vitreous carbon and silver mesh cathodes at potentials corresponding to each of the first three voltammetric peaks were conducted; coulometric n values and product distributions (determined by means of GC and GC–MS techniques) depend on potential. In particular, two completely dechlorinated products, namely 4,4′-(ethane-1,1-diyl)bis(methoxybenzene) and 4,4′-(ethene-1,1-diyl)bis(methoxybenzene) have been identified and quantitated. A mechanistic scheme is proposed to account for the formation of the various products.