Organic halide electroreduction on silver

Silver, whose extraordinary electrocatalytical properties for organic halid e reduction have been recently evidenced, has been used as cathode material for systematic preparative electrolyses in membrane-divided cells. To bett er elucidate the substrate role on the remarkable positive shift of reducti on potentials, and on the "cage effect" i.e, the promotion of intermolecula r reaction on adsorbed intermediates, three halide substrate patterns are h ere compared in terms of both voltammetric characterization and preparative electroreduction products: aliphatic halides (adamantanes), aromatic halid es (phenols) and anomeric glycosyl halides. The preparative electroreductio ns result mainly in dimerization in the case of glycosyl halides, in H-->Br substitution in the case of bromophenols, in dimerization + substitution i n the case of haloadamantanes. The product analysis, both at the end of the reaction and at intermediate times, allows discussing the reaction pathway s in terms of intermediate stability and of active surface accessibility. T he possibility of complete dehalogenation on a wider substrate variety with remarkably lower energy consumption and almost quantitative current yields makes the process potentially very interesting for environmental purposes.