The relative rate technique has been used to determine the rate constants for the reaction of chlorine atoms with a series of oxygenated organic species. Experiments were performed a t 295 t 2 K and atmospheric pressure of synthetic air or nitrogen. The decay rates of the organic species were measured relative to that of ethane or n-butane. Using rate constants of 5.7 x lo-" cm3 molecule-'s-', and 2.25 x lo-'' cm3 molecule-' s-l for the reaction of C1 with ethane and n-butane respectively the following rate constants were derived, in units of lo-" cm3 molecule-' s-': propane, (16.0 2 0.4); i-butane, (15.1 -t 0.9); n-pentane, (31.0 .t 1.6); n-hexane, (34.5 2 2.3); cyclohexane, (36.1 f 1.5); methanol, (4.57 2 0.40); ethanol, (8.45 t 0.91); n-propanol, (14.4 f 1.2); tbutylalcohol, (3.26 f 0.19); acetaldehyde, (8.45 t 0.79); propionaldehyde, (11.3 2 0.9); dimethylether, (20.5 t 0.8); diethylether, (35.6 t 2.8); and methyl-t-butylether, (16.6 2 1.2). Quoted errors represent 20, and do not include any errors due to uncertainties in the rate constants used to place our relative measurements on an absolute basis. The results are discussed with respect to the mechanisms of these reactions and to previous literature data.
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 atmosphere, 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 (2740 torr) in synthetic air a t 295 K. Using rate constants of 2.53 x lo-", and 1.35 x lo-'' cm3 molecule-' s-l for the reaction of OH radicals with n-butane and diethyl ether, the following rate constants were derived, in units of lo-" cm3 molecule-' sf': dimethylether, (0.232 2 0.023); di-n-propylether, (1.97 2 0.08); di-n-butylether, (2.74 2 0.32); di-n-pentylether, (3.09 5 0.26); methyl-t-butylether, (0.324 2 0.008); methyl-nbutylether, (1.29 * 0.03); ethyl-n-butylether, (2.27 2 0.09); and ethyl-t-butylether, (0.883 0.026). Quoted errors represent 2u 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.
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