OXIDATION BY METAL SALTS .3. REACTION OF MANGANIC ACETATE WITH AROMATIC HYDROCARBONS AND REACTIVITY OF CARBOXYMETHYL RADICAL

The manganic acetate oxidation of aromatic hydrocarbons proceeds by two competing mechanisms: (a) a free-radical mechanism resulting from the interaction of the aromatic hydrocarbon with the carboxymethyl radical (· CH2COOH) generated directly by the thermolysis of manganic acetate ; (b) an electron transfer mechanism which is of importance in the oxidation of aromatic hydrocarbons having ionization potentials of ≤8 eV. The relative extent of the electron transfer pathway can be suppressed by carrying out the reaction under anhydrous conditions or in the presence of potassium acetate. The relative reactivity of the carboxymethyl radical toward hydrogen abstraction from substituted toluenes was determined yielding a p value of –0.63 (correlated with σ+). The observed relative rate ratio of hydrogen atom abstraction from toluene-diphenylmethane-triphenylmethane is 1:12:39, respectively. A study of the relative rates of addition of the CH2COOH radical to substituted benzenes revealed that the reactivity toward addition is guided by the stability of the radical intermediate irrespective of whether the groups are electron withdrawing or electron donating. © 1969, American Chemical Society. All rights reserved.