Reactivity of concerted pericyclic reactions follows the fundamental orbital symmetry conservations rules introduced by Woodward and Hoffmann almost half a century ago. Numerous experimental and theoretical studies show that these rules are valid even when asymmetric substitution destroys the symmetry of the reacting molecules. Intuitively, one may expect that a certain degree of the required symmetry will be sufficient to produce the desired product. Our calculations show that this intuition can be quantified by measuring the deviation from symmetry of the core atoms of the reactants that represent the reacting p orbitals. Calculations based on density functional theory and their analysis in terms of continuous symmetry measures, show that quantitative correlations exist for various Diels-Alder reactions of cyclic dienes with either cyano-substituted ethylenes or cycloalkenones derivatives, both in the gas phase and in the presence of solvents. These results demonstrate that when structural effects dominate over electronic effects, symmetry plays an important role in determining reactivity trends. I. Tuvi-Arad, and D. Avnir, Chem. Eur. J. 18  , 10014 (2012).

Symmetry-reactivity correlations in Diels-Alder reactions: Quantifying our intuition

246th National Meeting (2013)

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