Product Selectivity in Photoelectrochemical Reduction of Benzyl Halides on Semiconductor Photocathodes

Abstract

Electrochemical reduction of benzyl halides on various cathodes was examined under illumination and in the dark. Product selectivity control in the reduction by illumination was accomplished onIy whenp-type semiconductor photocathodes were uscd. By estimating the electrophilicity of benzyl halides from their rate constants for rnethanolysis under illumination and in the dark, it was proposed that the mechanism for the selectivity control by illumination invoIves a photo-assisted process for the nucleophilic attack of carbanion intermediate species formed by the two-electron reduction of the benzyl halides to the unreacted ones as electrophilcs.