Oxidation studies. I. Oxidation of primary alcohols by peroxydisulfate

Abstract

Results on the oxidation of primary alcohols (methanol, ethanol, n-propanol, n-butanol and isobutanol) by peroxydisulfate in aqueous solution in the temperature range 50°-80°, under uncatalysed, Ag⁺ catalysed and deaerated conditions are presented. Oxygen was found to have a retarding effect on the rate of peroxydisulfate disappearance, -R_S2O3⁻, and the inhibition period was a maximum in the case of ethanol and isobutanol. Both under uncatalysed and Ag⁺ catalysed conditions -R_S2O3⁻ varied with [S₂O₈^-]^3/2 for all the alcohols; -R_S2O3⁻ was independent of alcohol concentration for all the alcohols except for methanol and ethanol where a one-half order with respect to [alcohol] was observed. In the Ag⁺ catalysed oxidation -R_S2O3⁻ varied as [Ag⁺]^½ with all the alcohols. The effect of [H⁺], ionic strength, temperature, initially added product of the reaction on the rate are discussed and the stoichiometries of the reactions determined. In the light of the observed results, reaction mechanisms are postulated with SO₄^•− as the reactive species formed by thermal decomposition of S₂O₈⁻ under uncatalysed conditions and by the interaction of Ag⁺ and S₂O₈^- under Ag⁺ catalysed conditions. The existence of Ag⁺⁺ in catalysed reactions is postulated. The values of rate constants, frequency factors, energies of activation entropies of activation, etc., were evaluated.