The reaction CH3+ CD4? CH3D + CD3

Abstract

A precision, recording, mass spectrometer of the Graham, Harkness and Thode4 type has been constructed and used to identify and measure the products formed in the photolysis of pure acetone and of acetone + deuteromethane mixtures. Applying well-established arguments to the results on the photolysis of pure acetone the velocity constant of the reaction CH3* + CH3COCH3 -+ CH4 + CH2COCH3 is found to be 5 x 10s exp (-9.8 kcaI/RT) I. mole-1 sec-1, Traces of ethylene but no ketene were detected in the products of reaction over the range 155 to 369" C inclusive. Deuterium is only slowly exchanged between CD4 and CH3COCH3 at 354" C. The products of photolysis of CD4 + CH3COCH3 mixtures in the temperature range 153 to 428" C include CH4, CH3D, CD3H, C2H6, CzH3D3 and barely detectable traces of C2D6. From the observed temperature dependence of the initial rates of formation of CH3D and CH4 the rate constant of the reaction CH3* + CD4 -+ CH3D + CD3 is calculated to be 1.8 x 108 exp (-12-93 f 0.65 kcal/RT) 1. mole-1 sec-1. These results are discussed in relation to current views concerning hydrogen-atom abstraction reactions.

Reduced Dimensionality Quantum Dynamics of CH3 + CH4 → CH4 + CH3: Symmetric Hydrogen Exchange on an Ab Initio Potential

“…2 This heavy-light-heavy (HLH) reaction has been the focus of many previous experimental and theoretical characterizations. Several experimental studies have been done on this system and isotopic variants, [3][4][5][6][7] although, because of symmetry considerations, all of these experiments were indirect measurements involving derivation of a suitable rate constant by comparison with the rate of a well-characterized reference reaction. Kerr and Parsonage, 8 and Arthur and Bell 9 both independently presented useful evaluations of kinetic experiments prior to 1974 and 1977, respectively.…”

Generation of Ketene With High Quantum Yield by a KrF Laser

“…This value in turn implies Eke 155 kJ/mol, which we have adopted in Table 2 instead of Brinton's value of 171 kJ/mol. Then k2 3.8.10 s sexp (-387 kJ/mol/RT) (12) The rate of decay into two fragments can either be estimated to k2a-10 2 to 10 TM S -1 exp (-333 kJ/mol/RT) (13) or be assumed to be equal to (11). With these rates the direct decay into 3 fragments is predicted to be faster than the stepwise decay above about 505 K, 615 K or 800 K, respectively.…”