OH-induced oxidation mechanisms of ethyl and n-propyl acetates have been investigated at room temperature (298 ^5 K) and atmospheric pressure by photolysing mixtures with FTIR CH 3 ONO/acetate/NO spectroscopy as analytical device. The main oxidation products and their yields were as follows : from ethyl acetate, acetic acid (0.75 ^0.13), acetoxyacetaldehyde (0.15 ^0.05), acetic anhydride (0.02 ^0.01), formic acetic anhydride (0.02 ^0.01) and peroxyacetyl nitrate (PAN) ; from n-propyl acetate, acetoxyacetaldehyde (0.22 ^0.06), formic acetic anhydride (0.28 ^0.03), acetic acid (0.15 ^0.02), acetaldehyde (0.35 ^0.10), peroxypropionyl nitrate (PPN) and probably acetoxypropionaldehyde (0.30 ^0.10). From these data, oxidation schemes of these two acetates were elucidated. This study reveals in particular the speciÐc reactivity of acetates by conÐrming the novel a-ester rearrangement proposed recently by Tuazon et al. (J. Phys. Chem. A, 1998, 102, 2316 and then by showing that oxygenated alkoxyl radicals may not follow the same rules of reactivity as other alkoxyl radicals. This last observation shows the necessity for further experiments to understand the inÑuence of the oxygenated function on alkoxyl reactivity.

Vinyl acetate is widely used in industry. It has been classified as a high-production volume (HPV) chemical in the United States. To evaluate its impact on the environment and air quality, its atmospheric reactivity toward the three main tropospheric oxidants (OH, NO(3), and O(3)) has been investigated. Kinetic and mechanistic experiments have been conducted at room temperature and atmospheric pressure using an indoor Pyrex simulation chamber coupled to Fourier transform infrared (FTIR) and UV-visible spectrometers. Rate constants for the reactions of vinyl acetate with OH, NO(3), and O(3) were equal to (2.3 +/- 0.3) x 10(-11), (7.3 +/- 1.8) x 10(-15), and (3.0 +/- 0.4) x 10(-18) cm(3) molecule(-1) s(-1), respectively. From these data, tropospheric lifetimes of vinyl acetate have been estimated as follows: tau(OH) = 6 h, tau(NO(3)) = 6 days, and tau(O(3)) = 5 days. This demonstrates that reaction with OH radicals is the main tropospheric loss process of this compound. From the mechanistic experiments, main oxidation products have been identified and quantified and oxidation schemes have been proposed for each studied reaction.