Kinetic, mechanistic and temperature dependence study of Cl reactions with CH3OC(O)H and CH3CH2OC(O)H. Atmospheric implications

Abstract

Reactions of Cl atoms with CH(3)OC(O)H (1) and CH(3)CH(2)OC(O)H (2) have been studied using the Discharge Flow-Mass Spectrometric (DF-MS) method. The study has been carried out at 1 Torr total pressure under pseudo-first-order conditions in the temperature range 253 K to 333 K to approach the tropospheric temperature profile. The measured room temperature rate coefficients are k(1)=(1.01+/-0.15) x 10(-12) cm(3) molecule(-1) s(-1) and k(2)=(8.78+/-1.22) x 10(-12) cm(3) molecule(-1) s(-1) (errors are 2sigma) and the fitted Arrhenius expressions, k(1)=(1.7+/-1.4) x 10(-11) exp -(810+/-250)/T cm(3) molecule(-1) s(-1) and k(2)=(5.5+/-4.8) x 10(-11) exp -(556+/-268)/T cm(3) molecule(-1) s(-1) (errors are 2sigma). The reactions proceed through the abstraction of an H atom to form HCl and the corresponding radical. At 298 K and 1 Torr, yields on HCl of 0.95+/-0.09 (error is 2sigma) for reaction (1) and 0.96+/-0.11 (error is 2sigma) for reaction (2) have been measured. The tropospheric lifetimes are calculated and discussed.