CATALYTIC-OXIDATION OF POLYOLS BY MOLECULAR-OXYGEN IN ALKALINE MEDIA

The low-temperature oxidation of alkaline solutions of polyols (among them, hexahydric alcohols derived from hexane and cyclohexane and nonr educible sugars) by molecular oxygen is studied in the presence of cop per compounds. In contrast to the majority of primary and secondary al cohols, polyols are oxidized at high rates in aqueous solutions contai ning Cu2+ ions. It is found that a hydroxide cation enters the composi tion of catalytically active intermediate complexes and controls the r ate and selectivity of the oxidation. The extremely strong dependence of the rates of the polyol oxidation on their structure, the character of the base used, and the oxygen partial pressure is established. It is shown that O-2 participates in a limiting step of the process. A re action mechanism different from the traditional one is suggested. Acco rding to this mechanism, the oxidation of polyols proceeds through the formation of triple complexes [Cu2+... RO(-m)... O-2] The kinetic dat a obtained agree well with the hypothesis on the formation of an unsta ble intermediate alpha-oxyperoxide. The pathways of its decomposition to yield different acids are determined by the nature of polyols to be oxidized and by the nature of a base.