The kinetics of Baeyer-Villiger oxidation of biacetyl and benzil by peroxomonophosphoric acid and peroxomonosulfuric acid have been studied in different pH ranges at 308 K. The reactions are second order; first order each in peroxy acid and in diketone concentrations at constant pH. The oxidation rate is strongly pH-dependent; the rate increases with increase in pH. From the pH-rate data the reactivity of different peroxo species, in the oxidation, has been determined. A mechanism consistent with rate-determining nucleophilic attack of peroxo species on carbonyl carbon of the diketone molecule has been proposed. Acetic acid and benzoic acid are respectively found to be the products of oxidation of biacetyl and benzil.

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The kinetics of dimethyl sulfoxide (DMSO) oxidation by peroxomonophosphoric acid (PMPA) in aqueous medium a t 308 K and I = 0.4 mol/dm3 follow the rate expressionsIn the pH range from 0 to 2, where k l and kz are 5.092 X 10-1 dm3/mol sec and = 0, respectively; in the pH range from 4 to 7, where k2 = 8.127 X lo-" and kn = 2.90 X and dm3/mol sec;in the pH range from 10 to 13.6, where k4 N 0, and k:, = 3.08 X The reaction is interpreted in terms of mechanisms involving an electrophilic and a nucleophilic attack of the peroxomonophosphoric acid species, respectively, in acid and alkaline regions, on the sulfur atom of the sulfoxide molecule giving rise to SNZ-type transition states followed hy oxygen-oxygen bond fission to form the products. dm3/mol sec.

The oxidation of benzaldehydes by peroxomonophosphoric acid has been found to proceed by (i) −d[peroxomonophosphoric acid]⁄dt∝ [benzaldehyde][peroxomonophosphoric acid][H+]x where x=a fraction at [H+]<0.5 M and x=0 at [H+]>0.5 M and (ii) −d[peroxomonophosphate]⁄dt∝ [benzaldehyde][peroxomonophosphate][OH−]y where y=a fraction at [OH−]<0.1 M and y=0 at [OH−]>0.1 M. In the alkaline oxidation Hammett relationship is obeyed excellently, unlike the oxidation in the acid medium. The oxidation mechanisms are discussed in terms of a nucleophilic attack of the peroxomonophosphoric acid species on the carbonyl carbon centre. Thermodynamic parameters have been evaluated to substantiate the mechanisms.