Mechanism of the dimethyldioxirane oxidation of N,N-dimethylanilines

Relative rates of dimethyldioxirane oxidation of a number of para-substituted N,N-dimethylanilines in acetone at 5 degrees C are compared with those of reactions with methyl iodide and other oxidants, The reactions with dimethyldioxirane followed the Hammett relationship with ap value of -1.0. Measurement of the second order rate constants for the dimethyldioxirane reactions in aqueous acetonitrile containing potassium nitrate at 21 degrees C, showed better correlation with the Hammett relationship (rho = 0.89) than with the Okamoto-Brown model (rho(+) = 0.56). The reaction rates are accelerated greatly in the presence of water such that the respective pseudo first order rate constants for the oxidation of N,N-dimethyl-4-nitroaniline in acetone and water are 6.3 x 10(-3) and 5.86 s(-1), respectively, All of the data are consistent with a concerted electrophilic mechanism and there is no evidence of free radical or electron transfer reactions.