Bond dissociation energies from equilibrium studies. Part 4.—The equilibrium Br2+ CH4⇌ HBr + CH3Br. Determination of D(CH3—Br) and ΔH°f(CH3Br, g)

The equilibrium Br2+ CH4⇌ HBr + CH3Br (2) has been studied in the range 347–477°C, with equilibrium being approached from both sides. Products additional to those required by eqn (2) were formed but it is believed that reliable values of the equilibrium constant K2 have been measured. Third-law calculations lead to ΔH°2=–26.4 ± 0.7 kJ mol–1 at 298 K from which ΔH°f(CH3Br, g)=–34.3 ± 0.8 kJ mol–1.