Kinetics of the reactions of halogenated methyl radicals (CF₃, CF₂Cl, CFCl₂, and CCl₃) with molecular chlorine

The kinetics of four gas‐phase reactions involving halogenated methyl radicals (R  CF 3 , CF 2 Cl, CFCI 2 , and CCI 3 ) with molecular chlorine have been studied using a tubular reactor coupled to a photoionization mass spectrometer. The radicals were homogeneously generated by the pulsed photolysis of precursor molecules at 193 nm. The subsequent decays of the radical concentration were monitored in real‐time experiments as a function of Cl 2 concentration to obtain the rate constants of these R + Cl 2 reactions. Where possible, the rate constants were measured as a function of temperature to determine Arrhenius parameters. Apparent discrepancies between these measured rate constants for CF 3 and CCl 3 with Cl 2 and ones obtained in prior indirect studies are explained. The higher activation energies for these R + Cl 2 reactions compared to that of the CH 3 + Cl 2 reaction are attributed in part to the different polarities of the transition states formed.