The Reactions of Selected Acetates with the OH Radical in the Presence of NO:  Novel Rearrangement of Alkoxy Radicals of Structure RC(O)OCH(Ȯ)Ŕ

Abstract

Products of the gas-phase reactions of the OH radical with ethyl acetate, isopropyl acetate, tert -butyl acetate in the presence of NO were investigated using in situ Fourier transform infrared spectroscopy and gas chromatography. The products identified and their molar formation yields (corrected for secondary reactions with the OH radical) were acetic acid (0.96 ± 0.08) from ethyl acetate; acetic acid (0.09 ± 0.03), acetic anhydride (0.76 ± 0.07), and acetone (0.24 ± 0.02) from isopropyl acetate; and acetic anhydride (0.49 ± 0.05) and acetone (0.20 ± 0.02) from tert -butyl acetate. Consideration of the potential reaction pathways of the intermediate alkoxy radicals leads to the conclusion that alkoxy radicals of structure RC(O)OCH(Ȯ)Ŕ can undergo a rapid rearrangement and decomposition (α-ester rearrangement) to RC(O)OH plus ŔĊO, presumably via a five-membered ring transition state. However, our product studies provided no evidence for the analogous β-ester rearrangement proceeding via a six-membered transition state, although the possibility that this reaction could occur is not ruled out.