A relative rate study of the reaction of chlorine atoms (Cl) and hydroxyl radicals (OH) with a series of ethers

Abstract

AbstractRate constants for the gas phase reactions of hydroxyl radicals and chlorine atoms with a number of ethers have been determined at 300 ± 3 K and at a total pressure of 1 atmosphere. Both OH radical and chlorine atom rate constants were determined using a relative rate technique. Values for the rate constants obtained are as follows. compound kOH×1012(cm3 molecule−1 s−1) kC1×1011(cm3 molecule−1 s−1) Hexane 5.53 ± 1.55 — 2‐Chloro ethyl methyl ether 4.92 ± 1.09 14.4 ± 5.0 2,2‐Dichloro ethyl methyl ether 2.37 ± 0.50 4.4 ± 1.6 2‐Bromo ethyl methyl ether 6.94 ± 1.38 16.3 ± 5.4 2‐Chloro,1,1,1‐trifluoro ethyl ethyl ether <0.3 0.30 ± 0.10 Isoflurane <0.3 <0.1 Enflurane <0.3 <0.1 Di‐i‐propyl ether 11.08 ± 2.26 16.3 ± 5.4 Diethyl ether — 25.8 ± 4.4 The above relative rate constants are based on the values of k(OH + pentane)=[3.94 ± 0.98]×10−12 and k(OH + diethyl ether)=[13.6 ± 2.26] × 10−12 cm3 molecule−1 s−1 in the case of the hydroxyl reactions. In the case of the chlorine atom reactions, the above rate constants are based on values of k(Cl + ethane)=[5.84 ± 0.88] × 10−11 and k(Cl + diethyl ether)=[25.4 ± 8.05] × 10−11 cm3 molecule−1 s−1. The quoted errors include ±2σ from a least squares analysis of our slopes plus the uncertainty associated with the reference rate constants.Atmospheric lifetimes calculated with respect to reaction with OH radicals are based on a tropospheric OH radical concentration of (7.7 ± 1.4) × 105 radicals cm−3, and lifetimes with respect to reaction with Cl atoms are based on a tropospheric Cl atom concentration of 1 × 103 atoms cm−3. Observed trends in the relative rates of reaction of hydroxyl radicals and chlorine atoms with the ethers studied is discussed. The significance of the calculated tropospheric lifetimes is also reviewed. © 1993 John Wiley & Sons, Inc.