Perturbation theory of chemical reactivity

Klopman, G. "The Generalized Perturbation Theory of Chemical Reactivity and Its Applications , in "Chemical Reactivity and Reaction Paths", G. Klopman, Ed. Wiley-Interscience New York, 1974, pp. 55-166... 

Klopman, G. 1974. The generalized perturbational theory of chemical reactivity and its applications. In Chemical Reactivity and Reaction Paths, (Ed.) G. Klopman, pp. 55-165. New York Wiley-Interscience. 

The paucity of information on the mechanism of reactions, and on the structure of the transition state, and the role of the anomeric effect in its stabilization, constitutes the main reason why qualitative interpretation of reactivity as shown in the aforementioned examples is still very rare. An alternative, more-popular estimation of the relative reaction-rates of con-formers is based on the lone-pair orbital interactions, and their symmetry and energy in the ground state, and could be loosely associated with the perturbation theory of chemical reactivity. ... 

This perturbation theory of chemical reactivity is based upon an early stage of the reactant mutual approach, when the molecules are still distinct though close enough for the MO description of the combined reactive system to be valid, say separated by a distance of the order of 5-10 a.u. The implicit assumption is that the reaction profiles for the compared reaction paths are of similar shape, so that the trend of the predicted energy differences at an early point on the reaction coordinate is expected to reflect the difference in the activation energy. 

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