Kinetics of the reaction of OH radicals with a series of ethers under simulated atmospheric conditions at 295 K

Abstract

Abstract Ethers are being increasingly used as motor fuel additives to increase the octane number and to reduce CO emissions. Since their reaction with hydroxyl radicals (OH) is a major loss process for these oxygenated species in the atmoshpere, we have conducted a relative rate study of the kinetics of the reactions of OH radicals with a series of ethers and report the results of these measurements here. Experiments were performed under simulated atmospheric conditions; atmospheric pressure (≃ 740 torr) in synthetic air at 295 K. Using rate constants of 2.53 × 10 −12 , and 1.35 × 10 −11 cm 3 molecule −1 s −1 for the reaction of OH radicals with n ‐butane and diethyl ether, the following rate constants were derived, in units of 10 −11 cm 3 molecule −1 s −1 : dimethylether, (0.232 ± 0.023); di‐ n ‐propylether, (1.97 ± 0.08); di‐ n ‐butylether, (2.74 ± 0.32); di‐ n ‐pentylether, (3.09 ± 0.26); methyl‐ t ‐butylether, (0.324 ± 0.008); methyl‐ n ‐butylether, (1.29 ± 0.03); ethyl‐ n ‐butylether, (2.27 ± 0.09); and ethyl‐ t ‐butylether, (0.883 ± 0.026). Quoted errors represent 2σ from the least squares analysis and do not include any systematic errors associated with uncertainties in the reference rate constants used to place our relative measurements on an absolute basis. The implications of these results for the atmospheric chemistry of ethers are discussed.