FTIR Spectroscopic Study of the OH-Induced Oxidation of Isopropyl, Isobutyl, and tert-Butyl Acetates

OH-induced oxidation mechanisms of isopropyl, isobutyl, and tert -butyl acetates have been investigated at room temperature (298 ± 5 K) and atmospheric pressure by photolyzing CH 3 ONO/acetate/NO mixtures with FTIR spectrometry as analytical device. All main oxidation products of isopropyl and isobutyl acetates were detected and their formation yields were determined: from isopropyl acetate, acetic anhydride (0.72 ± 0.07), acetone (0.26 ± 0.03), acetic acid (0.06 ± 0.03), and peroxyacetyl nitrate; from isobutyl acetate, acetone (0.78 ± 0.12), formic acetic anhydride (0.52 ± 0.06), acetoxyacetaldehyde (0.18 ± 0.06), acetic acid (0.08 ± 0.02), and peroxyisobutyryl nitrate. For tert -butyl acetate, preliminary results have been obtained and two oxidation products were detected: acetic anhydride (0.49 ± 0.04) and acetone (0.24 ± 0.04). From these data, oxidation schemes of these acetates were elucidated. This study shows that the presence of the ester function promotes the H-atom abstraction on the carbon in the α-position of the oxygenated function. Concerning the reactivity of alkoxy radicals, this study confirms the α-ester rearrangement proposed recently by Tuazon et al. ( J. Phys. Chem. A, 1998, 102, 2316). Moreover, it has been shown that nonlinear alkoxy radicals formed by the oxidation of acetates predominantly decompose instead of reacting with O 2 and isomerizing.