Effective charges in transition states

We can extend the effective charge concept to the transition state provided we know the overall and either or P. If we assume that there is a monotonic change in charge on the atom in question from ground to product state then the effective charge calculated as in Eqn. 21 is a good measure of the charge relative to the two states [14]. 

A useful example of this calculation is that for the attack of aryl oxide ions on cyclic sulphonate esters (Eqn. 22) [15]. 

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