Kinetics of the Reaction of CCl3 + Br2 and Thermochemistry of CCl3 Radical and Cation

Article abstract of DOI:10.1021/j100164a043

The rate constant of the CCl3 + Br2 -> CCl3Br + Br reaction was determined as a function of temperature between 300 and 532 K and fit to an Arrhenius expression: k₁ (L mol^-1 s^-1) = (1.8 +/- 0.4) x 10⁸ exp<(-1.43 +/- 0.29) kcal mol^-1/RT>.The reaction was studied in a tubular flow reactor by using laser photolysis to produce the CCl3 reactant and photoionization mass spectrometry to monitor CCl3 in time-resolved experiments.Previously published kinetic data were reevaluated to obtain k_-1, the rate constant for the reverse reaction, and recent spectroscopic data were used to calculate accurate entropies and heat capacities.The values of k_-1, k₁, and these calculated thermodynamic properties were used in a third law determination to obtain ΔH⁰_f,298.15(CCl3) = 17.0 +/- 0.6 kcal mol^-1 and ΔH⁰_f,0(CCl3) = 16.7 +/- 0.6 kcal mol^-1.This information was combined with spectroscopic data on CCl3+ to obtain ΔH⁰_f,298.15(CCl3+) = 205.2 +/- 0.6 kcal mol^-1 and ΔH⁰_f,0(CCl3+) = 203.7 +/- 0.6 kcal mol^-1.Bond energies of several relevant compounds and tables of thermodynamic functions for CCl3 and CCl3+ are presented.An improved heat of formation for the CCl3O2 radical, ΔH⁰_f,298.15(CCl3O2) = 2.7 +/- 1.1 kcal mol^-1, is also reported.