CH3C(O)OCH(O˙)CH3 alkoxy radical derived from ethyl acetate: Novel rearrangement confirmed by computational chemistry

Abstract

The reactivity of the CH₃C(O)OCH(O˙)CH₃ secondary alkoxy radical, main intermediate derived from the oxydation by OH of ethyl acetate has been studied using the quantum chemistry density functional theory. Our calculations show that the major reaction pathway is a one-step mechanism where the H-atom α to the oxygenated function is abstracted by the carbonyl oxygen while the C–O bond of the ester function is breaking. This is the first computational evidence of the occurrence of the α-ester rearrangement proposed by Tuazon et al. (E. C. Tuazon, W. P. L. Carter, S. M. Aschmann, R. Atkinson, Int. J. Chem. Kinet., 1991, 24, 1003) leading to the formation of acetic acid observed experimentally. Compared to the other possible reactions, our calculations predict that, among all the unimolecular processes that the alkoxy radical can undergo, this rearrangement is, by far, the most favoured one. Moreover, in the conditions of the lower troposphere (1 atm and 298 K), this chemical process is expected to occur, rather than reaction with O₂.