Transition state distortion energies correlate with activation energies of 1,4-dihydrogenations and Diels-Alder cycloadditions of aromatic molecules.

The reaction energetics of 43 1,4-dihydrogenation reactions of polycyclic aromatic hydrocarbons and nitrogen-containing heterocycles as well as the 43 analogous Diels-Alder reactions with ethylene (C(2)H(4)) have been computed using B3LYP/6-31G(d) density functional theory (DFT). The transition state distortion energies are found to correlate with the activation energies of these reactions, even for cases when energies of reaction do not correlate with reactivities.