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 aq ueous solutions of perchloric acid (0 - 1.2 M) and the substrate selec tivity of benzene and alkylbenzene (ArH) oxidation in the HClO4 soluti on (0.5 M) at 70-degrees-C are studied by the kinetic distribution met hod. The rate constants of toluene oxidation k = W/[ArH][KMnO4] are sh own 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 constant s of toluene oxidation by MnO4 and HMnO4, respectively, and K(a) is th e acidity constant of HMnO4. The kinetic isotope effect is reduced fro m 13.6 to 1.5 when [HClO4] increases in the range of 0 - 1.2 mol/l. Th e contributions of the reactions of alkylbenzenes with the MnO4 and HM nO4 species are determined; the routes of the side-chain and ring atta cks by HMnO4 are discriminated. The substrate selectivity of the latte r route is simultaneously governed by the basicity and by the values o f the ionization potentials (I(ArH)) of the substrates and is expresse d by the equation log(k0/k0(PhH) = a'DELTAlogK(B) + b'DELTAI(ArH).