THE KINETICS, KINETIC ISOTOPE EFFECTS, AND SUBSTRATE SELECTIVITY OF ALKYLBENZENE OXIDATION IN AQUEOUS PERMANGANATE SOLUTIONS .2. REACTION WITH HMNO4

The kinetics of toluene and toluene-d8 oxidation by permanganate in aqueous solutions of perchloric acid (0 - 1.2 M) and the substrate selectivity of benzene and alkylbenzene (ArH) oxidation in the HClO4 solution (0.5 M) at 70-degrees-C are studied by the kinetic distribution method. The rate constants of toluene oxidation k = W/[ArH][KMnO4] are shown to increase with enhancement of the acidity h- in accordance with the equation k = k- + k0h-/K(a), where k- and k0 are the rate constants of toluene oxidation by MnO4 and HMnO4, respectively, and K(a) is the acidity constant of HMnO4. The kinetic isotope effect is reduced from 13.6 to 1.5 when [HClO4] increases in the range of 0 - 1.2 mol/l. The contributions of the reactions of alkylbenzenes with the MnO4 and HMnO4 species are determined; the routes of the side-chain and ring attacks by HMnO4 are discriminated. The substrate selectivity of the latter route is simultaneously governed by the basicity and by the values of the ionization potentials (I(ArH)) of the substrates and is expressed by the equation log(k0/k0(PhH) = a'DELTAlogK(B) + b'DELTAI(ArH).