RATE CONSTANTS FOR THE GAS-PHASE REACTIONS OF CL-ATOMS WITH C-2-C-8 ALKANES AT T=296+/-2K

Relative rate constants for the gas-phase reactions of Cl-atom with thirteen atmospherically interesting alkanes (C-2-C-8) have been determined at 296 +/- 2 K based on GC/FID measurements of their relative decays in the UV (lambda greater than or equal to 300 nm) photolysis of mixtures containing Cl-2 and the entire series of the selected alkanes in the mtorr range in 750 torr of N-2. The following absolute rate constants (in units of 10(-10) cm(3) molecule(-1) s(-1)) have been derived from the relative rate constants combined with the value of 1.94 x 10(-10) cm(3) molecule(-1) s(-1) for the Cl + n-butane reaction: ethane (0.57 +/- 0.05); propane (1.27 +/- 0.02); 2-methyl propane (1.30 +/- 0.01), 2-methyl butane(1.96 +/- 0.02), n-pentane (2.50 +/- 0.02); 2,3-dimethyl butane (2.00 +/- 0.06); 2-methyl pentane (2.58 +/- 0.08); n-hexane (3.05 +/- 0.04); 2-methyl hexane (3.12 +/- 0.04); n-heptane (3.65 +/- 0.06); 2,2,4-trimethyl pentane (2.25 +/- 0.08); and n-octane (4.09 +/- 0.12). The uncertainties indicated are two least-squares standard deviations (2 sigma). These rate constants are compared with literature values and their applicability to Arctic tropospheric conditions is discussed. (C) 1995 John Wiley & Sons, Inc.