Homogeneous isotope exchange reactions. Part 2.—CH4/D2

Abstract

The kinetics of the early stages of the exchange reaction in CH₄+ D₂ mixtures have been studied in a static system at 957–1118 K. Methane pressures between 0.30 and 29.4 Torr (1 Torr = 133 N m^–2) and D₂ pressures between 0.28 and 23.6 Torr were studied. The initial rate is described by d[CH₃D]/dt=k[CH₄][D₂]^½(1 +C[CH₄]/[D₂])^–½, where log₁₀(_3/2k/dm^3/2mol^–½ s^–1)= 12.41 ± 0.4 –(64 485 ± 1880)^†;/4.5757(T/K) is independent of total pressure and s/v, and C depends on both these variables. The results are in good agreement with a homogeneous radical chain mechanism with heterogeneous initiation and termination. The rate constant for [graphic omitted] + D₂ [graphic omitted] CH₃+ D deduced is in good agreement with low temperature measurements and the combined results give, log₁₀(k₆/dm³ mol^–1 s^–1)= 9.204 ± 0.035 –(12 655 ± 81)/4.5757(T/K) over the range 300–1118 K.