Electro-oxidation of meso-erythritol on platinum in acid medium:: analysis of the reaction products

The electrocatalytic oxidation of 1,2,3,3-butanetetrol (meso-erythritol) has been studied on polycrystalline platinum in 0.1 M HClO(4). A preliminary investigation by cyclic voltammetry, used to determine the optimized conditions of electrolysis, showed that the electro-oxidation of mesa-erythritol is a slow reaction on a bare platinum electrode. When the electrode surface is modified by underpotential deposition of lead or thallium adatoms, the current densities increase significantly. Otherwise, long-time electrolyses were carried out using a three potential plateau program with different values of the oxidation potentials. Chromatographic analyses showed that the oxidation of erythritol led mainly to 2,3,4-trihydroxybutanal (erythrose), 1,3,4-trihydroxy-2-butanone (erythrulose) and to the lactone of 2,3,4-trihydroxybutanoic acid (i.e. erythrono-gamma-lactone); this lactone is hydrolyzed in solution into erythronic acid. When increasing the oxidation potential, the degradation of the initial molecule skeleton becomes more and more important and the selectivity decreases. In situ FTIR reflectance spectroscopic investigations showed that the adsorption of erythritol is dissociative which is proved by the presence of CO species absorption bands. The identification of other kinds of adsorbed species and reaction products is also discussed. Finally, a reaction mechanism for the oxidation of erythritol is proposed. (C) 1999 Elsevier Science S.A. All rights reserved.