KINETIC-STUDY OF THE REACTION OF CHLORINE ATOMS WITH CF3I AND THE REACTIONS OF CF3 RADICALS WITH O2, CL2 AND NO AT 296-K

The kinetics of the gas-phase reaction of Cl atoms with CF3I have been studied relative to the reaction of Cl atoms with CH4 over the temperature range 271 - 363 K. Using k(Cl + CH4) = 9.6 x 10(-12) exp(-2680/RT)cm3 molecule-1 s-1, we derive k(Cl + CF3I) = 6.25 x 10(-11) exp(-2970/RT) in which E(a) has units of cal mol-1. CF3 radicals are produced from the reaction of CL with CF3I in a yield which was indistinguishable from 100%. Other relative rate constant ratios measured at 296 K during these experiments were k(Cl + C2F5I)/k(Cl + CF3I) = 11.0 +/- 0.6 and k(Cl + C2F5I)k(cl + C2H5Cl) = 0.49 +/- 0.02. The reaction of CF3 radicals with Cl2 was studied relative to that with O2 at pressures from 4 to 700 torr of N2 diluent. By using the published absolute rate constants for k(CF3 + O2) at 1-10 torr to calibrate the pressure dependence of these relative rate constants, values of the low- and high-pressure limiting rate constants have been determined at 296 K using a Troe expression: k0(CF3 + O2) C (4.8 +/- 1.2) x 10(-29) cm6 molecule-2 s-1; k(infinity)(CF3 + O2) = (3.95 +/ 0.25) x 10(-12) cm3 molecule-1 s-1; F(c) = 0.46. The value of the rate constant k(CF3 + Cl2) was determined to be (3.5 +/- 0.4) x 10(-14) cm3 molecule-1 s-1 at 296 K. The reaction of Cl atoms with CF3I is a convenient way to prepare CF3 radicals for laboratory study. (C) 1995 John Wiley & Sons, Inc.