MECHANISM OF RUTHENIUM TETROXIDE-CATALYZED OXIDATION OF ALDOSES BY ALKALINE NORMAL-BROMOACETAMIDE

The kinetics of oxidation of three aldoses (glucose, mannose and galactose) by N-bromoacetamide (NBA) in the presence of an alkaline solution of RuO4 as catalyst and Hg(OAC)2 as co-catalyst and as a scavenger for bromide have been investigated. The main products of the oxidation are the corresponding aldonic acids. The reaction is zero order with respect to aldose and OH-. First order dependence of the reaction on both NBA and RuO4 at low concentrations shifts to zero order at higher concentrations. Addition of acetamide decreases the reaction rate, while addition of Hg(OAC)2 has the opposite effect. No significant effect of ionic strength was observed. OBr- is postulated as the reactive oxidising species and a mechanism involving co-catalysis by RuO4 and Hg(II) is proposed.