One of our models, the Activation Strain Model (ASM) focuses on understanding reactivity: Why is a barrier high or low? How does this depend on the electronic structure and bonding capabilities of the reactants, on their structure and rigidity and on the characteristic distortivity of a particular reaction mechanism? The ASM decomposes the relative energy of a system of reactants along the reaction energy profile [ΔE(ζ), with ζ the reaction coordinate] into two terms, namely the total strain energy of the reactants and their mutual total interaction energy: ΔE(ζ) = ΔEstrain(ζ) + ΔEint(ζ), as illustrated below for metal-mediated C–X bond-activation via oxidative addition. Here, the total strain energy, ΔEstrain(ζ), is the energy needed to deform the reactants into the geometry they adopt in the interacting complex and is affected by their rigidity. The total interaction energy, ΔEint(ζ), is the actual interaction between the deformed reactants and can be further decomposed by using KS-MO and the EDA scheme.

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Understanding Chemical Reactivity Using the Activation Strain Model

P. Vermeeren, S. C. C. van der Lubbe, C. Fonseca Guerra, F. M. Bickelhaupt, T. A. Hamlin

Nature Protoc. 2020, 15, 649-667

Analyzing Reaction Rates with the Distortion/Interaction-Activation Strain Model

F. M. Bickelhaupt, K. N. Houk

Angew. Chem. Int. Ed. 2017, 56, 10070-10086 (Frontispiece & Cover)

The Activation Strain Model and Molecular Orbital Theory: Understanding and Designing Chemical Reactions

I. Fernandez, F. M. Bickelhaupt

Chem. Soc. Rev. 2014, 43, 4953-4967 (tutorial review)