The very-low-pressure study of the kinetics and equilibrium: Cl + CH4 ⇄ CH3 + HCl at 298 K. The heat of formation of the CH3 radical

The bimolecular rate constant for the direct reaction of chlorine atoms with methane was measured at 25°C by using the very-low-pressure-pyrolysis technique. The rate constant was found to be In addition, the ratio k₁/k_?1 was observed with about 25% accuracy: K₁₍₂₉₈₎ = 1.3 ± 0.3. This gives a heat of formation of the methyl radical ΔH° _{f 298}(CH₃) = 35.1 ± 0.15 kcal/mol. A bond dissociation energy BDE (CH₃ ? H) = 105.1 ± 0.15 kcal/mol in good agreement with literature values was obtained.