Thermal decomposition of benzotrifluoride. The CC bond strength and the heat of formation of the phenyl radical

The kinetics of the decomposition of benzotrifluoride was studied from 720°c to 859°c in a flow system with and without carrier gas. Consideration of the product distribution made possible the study of the decomposition into CF3 and C6H5 radicals, which appeared to be truly homogeneous in character. The first‐order rate constant of the CC bond fission, log k (sec−1) = (17.9 ± 0.5) (99.7 ± 2.5)/θ, did not change with change of initial concentration, pressure of the carrier gas, or contact time. The Arrhenius parameters have been related to the appropriate thermodynamic data. Assumption of 0 kcal/mole for the activation energy of the reverse combination reaction yielded DH (C6H5CF3) = 103.6 ± 2.5 kcal/mole and ΔH (C6H5) = 77.1 ± 3.0 kcal/mole. Applicability of the simple first‐order formula to calculation of the rate constant has been also dealt with.