KINETICS OF THE REACTIONS OF OH WITH ALKANES

The rate coefficients for the reactions of OH With ethane (k(1)), prop ane (K-2), n-butane (K-3), iso-butane (k(4)), and n-pentane (k(5)) hav e been measured over the temperature range 212-380 K using the pulsed photolysis-laser induced fluorescence (PP-LIF) technique. The 298 K va lues 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 1 0(-12) cm(3) molecule(-1) s(-1) for k(1), k(2), k(3), K-4, and k(5), r espectively. The temperature dependence of k(1) and k(2) can be expres sed 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]. T he Arrhenius plots for k(3) - k(5) were clearly curved and they were f it 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 esti mated systematic errors. The present measurements are in excellent agr eement with previous studies and the best values for atmospheric calcu lations are recommended. (C) 1994 John Wiley & Sons, Inc.