Reactivities of osmium(VIII), iridium(VI) and platinum(IV) towards glycolaldehyde

Oxidations of glycolaldehyde (GA) to glyoxal by osmium(VIII), iridium(IV) and platinum(IV) have been investigated in aqueous solution, and the orders with respect to each [reactant] determined. The reaction involving iridium(IV) takes place through intermediate formation of free radicals in a MeCO2Na-MeCO2H buffer medium, whereas a one-step two-electron transfer process occurs in the oxidations by Os-VIII and Pt-IV in an alkaline medium. Mechanisms consistent with the experimental findings are proposed.