Oxidation of alcohols involving two types of peroxyl radicals

Liquid-phase oxidation of alcohols ((RR2)-R-1 CHOH) occurs as a chain reaction involving two peroxyl radicals, namely, (RRC)-R-1-C-2(OH)O-2(center dot) and HO2 center dot. Using the model of crossing parabolas, the activation energy and the rate constant were calculated for the reactions of alpha-hydroperoxyl radicals with four alcohols. A kinetic analysis of this reaction as a two-center chain process in which two peroxyl radicals that differ in reactivity ((RRC)-R-1-C-2(OH) O-2(center dot) and HO2 center dot) participate in chain propagation was performed. The relative amounts of the peroxyl radicals and their contribution to chain propagation under different oxidation conditions (temperature, alcohol concentration) were calculated for the oxidation of four alcohols: ethanol, 2-propanol, cyclohexanol, and alpha-phenylethanol. A change in the ratio between radicals due to the accumulation of a carbonyl compound and the fast addition of hydroperoxyl radicals to the carbonyl group during alcohol oxidation was considered and its effect on the chain propagation step in the oxidation reaction was discussed.