“Tropospheric degradation mechanism of vinyl acetate and alyl acetate initiated by OH radicals and Cl atoms”

M. B. BLANCO, I. BEJAN, I. BARNES, P. WIESEN AND M. TERUEL

San Francisco USA. University of California Davis

Congreso; 3rd Atmospheric Chemical Mechanisms.; 2010

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 for their reactions with OH radicals. On the other hand, product studies for the reactions of alkenes, unsaturated carbonyls and in particular acetates with other tropospheric photooxidants like Cl atoms are especially scarce. These 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 VOCs 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 and AA reactions were formic acetic anhydride and acetoxyacetaldehyde,   respectively. The results, in presence and absence of NOx, 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.