KINETICS OF THE REACTIONS OF OH WITH ALKANES

The rate coefficients for the reactions of OH With ethane (k(1)), propane (K-2), n-butane (K-3), iso-butane (k(4)), and n-pentane (k(5)) have been measured over the temperature range 212-380 K using the pulsed photolysis-laser induced fluorescence (PP-LIF) technique. The 298 K values are (2.43 +/- 0.20) x 10(-13), (1.11 +/- 0.08) X 10(-12), (2.46 +/- 0.15) X 10(-12), (2.06 +/- 0.14) X 10(-12), and (4.10 +/- 0.26) X 10(-12) cm(3) molecule(-1) s(-1) for k(1), k(2), k(3), K-4, and k(5), respectively. The temperature dependence of k(1) and k(2) can be expressed in the Arrhenius form: K-1 = (1.03 +/- 0.07) x 10(-11) exp[-1110 +/- 40)/T] and k(2) = (1.01 +/- 0.08) X 10(-11) exp[-(660 +/- 50)/T]. The Arrhenius plots for k(3) - k(5) were clearly curved and they were fit to three parameter expressions: k(3) = (2.04 +/- 0.05) X 10(-17) T-2 exp[(85 +/- 10)/T]; k(4) = (9.32 +/- 0.26) X 10(-18) T-2 exp[(275 +/- 20)/T]; and k(5) = (3.13 +/- 0.25) x 10(-17) T-2 exp[(115 +/- 30)/T]. The units of all rate constants are cm(3) molecule(-1) s(-1) and the quoted uncertainties are at the 95% confidence level and include estimated systematic errors. The present measurements are in excellent agreement with previous studies and the best values for atmospheric calculations are recommended. (C) 1994 John Wiley & Sons, Inc.