Rate constants for the reactions of OH radicals and Cl atoms with 1-propanol (1-C 3 H 7 OH) have been determined over the temperature range 273-343 K by the use of a relative rate technique. The value of k(Cl + 1-C 3 H 7 OH) = (1.69 ± 0.19) × 10 −12 cm 3 molecule −1 s −1 at 298 K and shows a small increase of 10% between 273 and 342 K. The value of k(OH + 1-C 3 H 7 OH) increases by 14% between 273 and 343 K with a value of (5.50 ± 0.55) × 10 −12 cm 3 molecule −1 s −1 at 298 K, and further when combined with a single independent experimentally determined value at 753 K gives k(OH + 1-C 3 H 7 OH) = 4.69 × 10 −17 T 1.8 exp(422/T) cm 3 molecule −1 s −1 , which fits each data point to better than 2%. Two well-established structure-activity relationships for H abstraction by OH radicals give accurate predictions of the rate constant for OH + 1-C 3 H 7 OH, provided the β-CH 2 group is given an increased reactivity of a factor of about 2 over that for the structurally equivalent CH 2 group in alkanes at 298 K. REACTIONS OF HYDROXYL RADICALS AND CHLORINE ATOMS WITH 1-PROPANOL 111A quantitative product analysis was carried out at 298 K for the Cl-initiated photooxidation of 1-C 3 H 7 OH, using both FTIR and gas chromatography. HCHO, CH 3 CHO, and C 2 H 5 CHO were the only major organic primary products observed, although HCOOH was found in much smaller amounts as a secondary product. A key characteristic of the analysis was that the initial values of the product ratio [CH 3 CHO]/[C 2 H 5 CHO] were effectively constant for NO pressures between 0.15 and 0.3 Torr, but fell by about 35% as the pressure fell to 0.0375 Torr. From a detailed consideration of the mechanism for the oxidation, it is suggested that C 2 H 5 CHO, CH 3 CHO (+HCHO), and 3 molecules of HCHO are formed uniquely from CH 3 CH 2 CHOH, CH 3 CHCH 2 OH, and CH 2 CH 2 CH 2 OH radicals, respectively. On this basis, use of the product yields gives the branching ratios of 56, 30, and 14% for Cl atom reaction at the α-, β-, and γ-C H positions in 1-C 3 H 7 OH at 298 K. Given the very low temperature coefficients involved, little change will occur over tropospheric temperature ranges.

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to be ca. 1000 times lower than the average tropospheric OH radical concentrations [5]. The amount of data concerning the reactions of ethers and other oxygenated compounds with Cl atoms [1,6 -12] is not as extensive as that for the reaction with OH radicals and is increased by this study.By measurement of the rate constants for the reactions of methylethylether with OH radicals and Cl atoms the tropospheric lifetimes with respect to removal by each of these species can be estimated. Such information is important when calculating the ozone forming potential [13] of volatile organic compounds and thus assessing their contribution to atmospheric pollution.A relative rate technique has been used to obtain rate constants for the reactions of OH radicals and Cl INTRODUCTIONIn addition to being used as solvents, ethers are being added [1,2] to unleaded petrol in order to increase the octane rating and reduce the amounts of unburnt hydrocarbons, carbon monoxide, and other noxious emissions from exhausts. Ethers are mostly removed in the troposphere by their reaction with hydroxyl radicals, although chlorine atoms have recently been considered as potential tropospheric oxidants [3] ABSTRACT: The rate constants for the gas-phase reactions between methylethylether and hydroxyl radicals (OH) and methylethylether and chlorine atoms (Cl) have been determined over the temperature range 274 -345 K using a relative rate technique. In this range the rate constants vary little with temperature and average values of k MEEϩOH ϭ (6.60 Ϫ2.62 ϩ3.88 ) ϫ 10 Ϫ12 cm 3 molecule Ϫ1 s Ϫ1 and k MEEϩCl ϭ (34.9 Ϯ 6.7) ϫ 10 Ϫ11 cm 3 molecule Ϫ1 s Ϫ1 were obtained. The atmospheric lifetimes of methylethylether have been estimated with respect to removal by OH radicals and Cl atoms to be ca. 2 days and ca. 30 -40 days, respectively.

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