Kinetics of the Acid-Catalyzed Peroxide Oxidation of 4-Hydroxybenzaldehyde in Acetic Acid

Abstract The sulfuric acid-catalyzed oxidations of 4-hydroxybenzaldehyde with hydrogen peroxide in aqueous acetic acid were kinetically investigated at 15° and 20° by iodometric estimation of the peroxides. The rates of peroxide consumption were found to be proportional to the product of the concentrations of hydroxybenzaldehyde and peroxide, when the aldehyde was added after the equilibrium between hydrogen peroxide and peracetic acid was attained. The rate constant is a linear function of Hammett acidity function h0. Hydrogen peroxide itself reacts slowly with the aldehyde, but it reacts more easily through the formation of peracetic acid. A mechanism involving a ratedetermining attack of protonated and free peracetic acid was postulated and discussed.