Acetates are emitted to the atmosphere from vegetation and through their use in industry. Another potential source is emission from automobiles; a number of acetates, including vinyl acetate (CH3C(O)OCH=CH2, VA) and allyl acetate (CH3C(O)OCH2CH=CH2, AA), have been detected as products in the combustion of rape methyl esters used as fuel alternatives or additives. Little information exists concerning the atmospheric degradation of unsaturated esters, which are mainly initiated by OH radicals. Limited information is available on the degradation of alkenes by Cl atoms, and therefore for the reactions of these acetates with Cl atoms. This data is necessary to assess the impact of such reactions in maritime environments where, under circumstances, OH radical and Cl atom initiated oxidation of the compounds can be important.
A product study is reported on the gas-phase reactions of OH radicals and Cl atoms with VA and AA. The experiments were performed in a 1080 L quartz-glass chamber in synthetic air at 298 ± 2 K and 760 ± 10 torr using long path in situ FTIR spectroscopy for the analysis of the reactants and products.
The major products observed in the VA with OH and Cl reactions are formic acetic anhydride together with formaldehyde and formyl chloride as co-products, respectively and for the reactions of allyl acetate with OH and Cl we observed acetoxyacetaldehyde as major products together with formaldehyde and formyl chloride, respectively.
The results are used to postulate atmospheric chemical mechanisms which can be incorporated into chemistry transport models to obtain estimations of the contributions of emissions of such compounds to ozone and other photooxidant formation in the troposphere.
