Mechanism of the Reaction CH(+4) + CH4 = CH(+5) + CH3 as a Function of Energy: Rate Constants and Product Distributions for the Reactions of CH(+4) + CD4 and CD(+4) + CH4 at 80 and 300K.

摘要

The collision mechanism of the reaction CH4(+)+ Methane = CH5(+)+ CH3 has been investigated as a function of temperature by measuring rate constants and product distributions for the reactant pairs CD4(+) + CD4 and CD4(+) + CH4 at 80 and 300 K. At 80K, both reactions give the same product distribution, which is close to the statistical distribution and consistent with a long-lived complex mechanism. With increasing temperature, the product distributions change dramatically and, at 300 K, they already show strong contributions of the channels which dominate at higher energies > or = 0.15 eV)-namely the direct transfer of protons and hydrogen atoms. Together with results from ICR, tandem mass spectrometry, crossed beams, photoionization and quantum chemical calculations, the present low-temperature study is able to provide a unified description of the mechanism of this reaction and its energy dependence. Keywords: Proton transfer, Isotope effect; Reprints. (AW)