Structural Reorganization in Degenerate Reactions

Since the reaction usually occurs in a polar medium, the reorganization energy AEq S ) of the solvent shell has to be taken into account as well. 

Apart from the amount of charge transferred (Ae) and the static and optical dielectric constants, (A. Ap) only structural quantities are involved here the radii T2 and 

This example shows how electronic excitation energies (hv) and vibrational force constants combined with ground-state structural data (Ad) can lead to an estimate of activation energy and transition-state structure for thermal reactions. 

Excitation energies have also been incorporated, with appropriate modification, into a similar model of the reaction profile for organic Sn2 reactions [42]  

Note that in the region of the observed structures the activation energy shows a sharp decrease ( 50%) associated with only a relatively modest shift in molecular structure towards the transition state. The fourth-order dependence between structure and energy follows if the symmetric, double-well reaction profiles for the molecules involved are assumed to have the following simple algebraic form 

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