The very‐low‐pressure study of the kinetics and equilibrium: Cl + CH 4 ⇄ CH 3 + HCl at 298 K. The heat of formation of the CH 3 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\documentclass{article}\pagestyle{empty}\begin{document}$$ k_1^{298} = (0.93 \pm 0.05) \times 10^{ - 13} cm^3 /mole \cdot \sec $$\end{document}In addition, the ratio k 1 / k −1 was observed with about 25% accuracy: K 1(298) = 1.3 ± 0.3. This gives a heat of formation of the methyl radical Δ H ° f 298 (CH 3 ) = 35.1 ± 0.15 kcal/mol. A bond dissociation energy BDE (CH 3 H) = 105.1 ± 0.15 kcal/mol in good agreement with literature values was obtained.