Relative kinetic measurements of rate coefficients for the gas-phase reactions of Cl atoms and OH radicals with a series of methyl alkyl esters

Abstract

Abstract Relative kinetic studies have been performed on the reactions of Cl atoms with a series of methyl alkyl esters in a 405-liter borosilicate glass chamber at (298 ± 3) K and one atmosphere of synthetic air using in situ FTIR spectroscopy to monitor the reactants. Rate coefficients (in units of cm3 molecule−1 s−1) were determined for the following compounds: methyl acetate (2.48 ± 0.58) × 10−12; methyl propanoate (1.68 ± 0.36) × 10−11; methyl butanoate (4.77 ± 0.87) × 10−11; methyl pentanoate (7.84 ± 1.15) × 10−11; methyl hexanoate (1.09 ± 0.31) × 10−10; methyl heptanoate (1.56 ± 0.37) × 10−10; methyl cyclohexane carboxylate (3.32 ± 0.76) × 10−10; methyl-2-methyl butanoate (9.41 ± 1.39) × 10−11. In addition rate coefficients (in units of 10−11 cm3 molecule−1 s−1) have been obtained for the reactions of OH radicals with the following compounds: methyl butanoate (3.55 ± 0.71), methyl pentanoate (5.41 ± 1.08), and methyl-2-methyl butanoate (4.08 ± 0.82). Using the kinetic rate data tropospheric lifetimes for the methyl alkyl esters with respect to their reactions with OH, and Cl have been estimated for typical ambient air concentrations of these oxidants.