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 × 10−12 exp(−2680/RT) cm3 molecule−1 s−1, we derive k(Cl + CF3I) = 6.25 × 10−11 exp(−2970/RT) in which Ea 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) = (4.8 ± 1.2) × 10−29 cm6 molecule−2 s−1; k∞(CF3 + O2) = (3.95 ± 0.25) × 10−12 cm3 molecule−1 s−1; Fc = 0.46. The value of the rate constant k(CF3 + Cl2) was determined to be (3.5 ± 0.4) × 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.