Decomposition of the CF₃CO Radical: Pressure and Temperature Dependencies of the Rate Constant

The decomposition rate constant of the CF₃CO radicals was investigated as a function of pressure and temperature, using both experimental and theoretical approaches. The rate constant was measured experimentally by flash photolysis/UV absorption at one atmosphere pressure and in the 298-443 K temperature range. Experiments were complemented by RRKM calculations combined with DFT quantum calculations. At one atmosphere pressure (N₂ + O₂), the rate expression derived from experiments is: k = 10^(11.0±0.7)exp(-(4214±600)K/T) s^-1, in fairly good agreement with previous results obtained at different temperatures and using different experimental methods. The rate constant is in the falloff at one atmosphere pressure, near the low pressure limit at the highest temperature and thus, the above expression should not be used at other pressures. This explains the apparent low pre-exponential factor. RRKM calculations were performed and fitted to the present results as well as to the previous ones obtained at different pressures. Those calculations have resulted in a comprehensive and consistent description of the kinetic properties of this decomposition reaction. The detailed results are presented using the temperature dependent parameters of the Troe´s equation: k₀ (T) = 1.55×10^-8 exp(-4420 K/T) cm³ molecule^-1 s^-1 (buffer gas N₂ + O₂) k_∞(T) = 1.45×10¹⁴ exp(-5878 K/T) s^-1 for F_c = 0.6.