Mechanism of the dimethyldioxirane oxidation of N,N-dimethylanilines

Abstract

Relative rates of dimethyldioxirane oxidation of a number of para-substituted N,N-dimethylanilines in acetone at 5 °C are compared with those of reactions with methyl iodide and other oxidants. The reactions with dimethyldioxirane followed the Hammett relationship with a ρ value of –1.0. Measurement of the second order rate constants for the dimethyldioxirane reactions in aqueous acetonitrile containing potassium nitrate at 21 °C, showed better correlation with the Hammett relationship (ρ = 0.89) than with the Okamoto–Brown model (ρ⁺ = 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 × 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.