Kinetic study of the gas-Phase reaction of the nitrate radical with methyl-substituted thiophenes

The gas-phase reactions of the NO3 radical with 2-methylthiophene, 3-methylthiophene, and 2,5-dimethylthiophene have been studied, using relative and absolute methods at 298 K. Determination of relative rate was performed using Teflon collapsible bag as the reaction chamber and gas chromatography as the analytical tool. For the absolute method, experiments were carried out using fast-flow-discharge technique with detection of NO3 by laser-induced fluorescence. The temperature dependence was studied by the absolute technique for the reactions of NO3 with 2-methylthiophene and 3-methylthiophene in the range 263-335 K. The proposed Arrhenius expressions for the reaction of the nitrate radical with 2-methylthiophene and 3-methylthiophene are k = (4 +/- 2) x 10(-16) exp[-(2200 +/- 100)/TI] cm(3) molecule(-1) s(-1) and k = (3 +/- 2) x 10(-15) exp(-(1700 +/- 200)/T]] cm(3) molecule(-1) s(-1), respectively. (C) 2003 Wiley Periodicals, Inc.