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Published February 1979 | public
Journal Article

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 k_1^(298) = (0.93 ± 0.05) x 10^(-13) cm^3/molec • sec 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 ΔH°_(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.

Additional Information

© 1979 John Wiley & Sons. Received February 22, 1978, Revised June 12, 1978. The authors are much indebted to Dr. R. T. Watson for his cogent criticisms in the preparation of this manuscript. This work was supported in part by the Army Office of Scientific Research under contract DAAG29-76-g-0195 and by the National Science Foundation under grant CHE-76-16787A01.

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October 23, 2023