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/dm3/2mol–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.