Gas-phase reaction of n-butyl acetate with the hydroxyl radical under simulated tropospheric conditions: Relative rate constant and product study

The gas-phase reaction of n-butyl acetate with hydroxyl radicals has been studied in an environmental smog chamber at 298 K, atmospheric pressure, and simulated tropospheric concentrations. The rate constant for this reaction has been determined by a relative method and the experimental result, relative to n-octane used as reference compound, is k = 5.2 +/- 0.5 X 10(-12) cm(3) molecule(-1) s(-1) This value appears to be about 25% higher than absolute rate constants found in the literature, but agrees very well with the other relative determination. Two reaction products have been identified and their production yield has been estimated, each accounting for about (15 +/- 5)% of the overall OH reaction processes. The two observed products are 2-oxobutyl acetate (CH3-CO-O-CH2-CO-CH2-CH3) and 3-oxobutyl acetate (CH3-CO-O-CH2-CH2-CO-CH3) The accuracy of the relative rate constant obtained is examined considering the evolution of the reactivity of the alkoxy end of the esters. Formation mechanisms for the two observed products are proposed and the likely other degradation channels are discussed. (C) 1996 John Wiley & Sons, Inc.