Transition state theory inertia

For radical-radical reactions, the full mode coupling and anharmonicity effects for the relative and overall rotational motions must be explicitly accounted for. We have derived a direct variable reaction coordinate transition state theory approach that appears to 3deld accurate rate coefficients for a number of alkyl radical reactions.This approach is analogous to that embodied in Eq. (4.10) for the long-range transition state, but includes variational optimizations of the form of the reaction coordinate and does not make the large orbital moment of inertia assumption. A detailed description of this approach was provided in some of our recent articles. 

The procedure adopted here is to make use again of RRKM theory to calculate k2/k l as a function of the relative barrier height. In this case, the transition state for the, reaction is taken as the loose ion-molecule complex at the Langevin capture distance. The transition state for the reaction k2 is taken as the tetrahedral intermediate RCOYX ". By a suitable choice of the vibrational frequencies and moments of inertia, this type of calculation shows that E 0-E0 for Cl- + CH3COCl should be around — 7 kcal mol 1 in order to reproduce the experimental efficiency. This amounts to an E 0 of 4 kcal mol-1. 

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