It has been long known that all forms of energy are not equal in promoting reactions, particularly those in the gas phase. The non-statistical nature of such reactions often manifests in terms of mode specificity and bond selectivity. Here, we introduce a simple and general model for predicting mode specificity and bond selectivity in chemical reactions. This so-called Sudden Vector Projection (SVP) model is based on the premise that the collision time for an activated reaction is often much shorter than that needed for intramolecular vibrational energy redistribution (IVR) in the reactants. In this sudden limit, the coupling of a reactant mode, whether it is vibration, rotation, or translation, with the reaction coordinate at the transition state dictates its ability to promote the reaction. This coupling can be quantified by projecting the reactant mode vector onto the reaction coordinate vector. This SVP model has been tested in atom-diatom reactive systems and is found to be consistent with the venerable Polanyi’s Rules. It has also been applied to reactions involving polyatomic reactants with general success. In addition to predict mode specificity and bond selectivity, the SVP model can also be used to predict product energy disposal by invoking microscopic reversibility.

Sudden vector projection model: Mode specificity and bond selectivity made easy

249th National Meeting (2015)

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