OXIDATION BY METAL SALTS .V. COBALTIC ACETATE OXIDATION OF ALKYLBENZENES

The cobaltic acetate oxidation of alkyl aromatic hydrocarbons was studied and an electron-transfer mechanism involving the intermediacy of aromatic radical cations was proposed. This mechanism was indicated by the high ρ value of –2.4 (correlated with σ+ at 65°) obtained from the relative reactivity of substituted toluenes, and the unusually low reactivity of cumene relative to toluene. The radical cation intermediates were detected by epr flow techniques in a few cases. The addition of lithium chloride lead to a dramatic enhancement of the reactivity of cobaltic acetate. In the presence of chloride ions the relative reactivity of substituted toluenes yielded a ρ value of –1.35 (correlated with σ+ at 24°). The effect of chloride ions on the ρ value was attributed to the formation of a cobaltic complex of relatively high oxidation potential and lower selectivity. The effect of chloride ion concentrations on the nuclear vs. side-chain products was also studied. © 1969, American Chemical Society. All rights reserved.