Electrochemical Reduction of the Simplest Monosaccharides: Dihydroxyacetone and Glyceraldehyde

Abstract

Dihydroxyacetone (DHA) and glyceraldehyde (GA) - the simplest monosaccharides in nature - are both essential building blocks in organic synthesis. There have been detailed investigations on the selective production of DHA and GA through the platinum-catalyzed electrochemical oxidation of glycerol, which is a surplus byproduct from biodiesel. However, less attention has been paid to the electrochemical behavior of DHA and GA themselves. Here, we report the electrochemical reduction of DHA and GA at different pH on platinum and palladium electrodes. Palladium exhibits a superior activity toward both the dehydroxylation and hydrogenation of DHA and GA. Using online high-performance liquid chromatography, we show that both DHA and GA display a two-step reduction. In particular, DHA is reduced first to acetol and then sequentially to acetone, while GA is first reduced to 3-hydroxypropionaldehyde (3-HPA), followed by hydrogenation to 1,3-propanediol. The reduction of both molecules is accompanied by a poisoning of the catalyst surface. In situ Fourier-transform infrared spectroscopy measurements suggest adsorbed carbon monoxide as the poisoning species, resulting from the dissociative adsorption of DHA and GA. Mechanistic reaction pathways for both DHA and GA reduction are proposed and discussed.