The kinetics and mechanism of the oxidation of phenylthioacetic acid and thiodiglycolic acid by potassium ferrate

The kinetics and mechanism of the oxidation of phenylthioacetic acid and thiodiglycolic acid by potassium ferrate were investigated under pseudo and non pseudo first-order conditions. Phenylthioacetic acid was oxidized to the sulfone and Fe(II) within 300s and thiodiglycolic acid was oxidized to the sulfoxide and Fe(III) within 1000s. Above a pH value of 8.7 for phenylthioacetic acid and 8.3 for thiodiglycolic acid the kinetics were first-order in the concentration of the hydrogen ions, the organosulfur compound and the ferrate ions, whereas below these pH values the kinetics were independent of the hydrogen ion concentration. A possible mechanism involves reaction between protonated ferrate and the organosulfur compound as the rate-determining step with a rate constant of 35 M(-1)s(-1). These results are comparable with other similar compounds.