Kinetic study of the reaction of chlorine atoms with CF 3 I and the reactions of CF 3 radicals with O 2 , Cl 2 and NO at 296 K

The kinetics of the gas‐phase reaction of Cl atoms with CF 3 I have been studied relative to the reaction of Cl atoms with CH 4 over the temperature range 271–363 K. Using k (Cl + CH 4 ) = 9.6 × 10 −12 exp(−2680/ RT ) cm 3 molecule −1 s −1 , we derive k (Cl + CF 3 I) = 6.25 × 10 −11 exp(−2970/ RT ) in which E a has units of cal mol −1 . CF 3 radicals are produced from the reaction of Cl with CF 3 I in a yield which was indistinguishable from 100%. Other relative rate constant ratios measured at 296 K during these experiments were k (Cl + C 2 F 5 I)/ k (Cl + CF 3 I) = 11.0 ± 0.6 and k (Cl + C 2 F 5 I)/ k (Cl + C 2 H 5 Cl) = 0.49 ± 0.02. The reaction of CF 3 radicals with Cl 2 was studied relative to that with O 2 at pressures from 4 to 700 torr of N 2 diluent. By using the published absolute rate constants for k (CF 3 + O 2 ) 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: k 0 (CF 3 + O 2 ) = (4.8 ± 1.2) × 10 −29 cm 6 molecule −2 s −1 ; k ∞ (CF 3 + O 2 ) = (3.95 ± 0.25) × 10 −12 cm 3 molecule −1 s −1 ; F c = 0.46. The value of the rate constant k (CF 3 + Cl 2 ) was determined to be (3.5 ± 0.4) × 10 −14 cm 3 molecule −1 s −1 at 296 K. The reaction of Cl atoms with CF 3 I is a convenient way to prepare CF 3 radicals for laboratory study. © 1995 John Wiley & Sons, Inc.