Reactivity indices for radical reactions involving polyaromatics

The reactivity of polyaromatics involved in various radical reactions is studied. The reactions under study are hydrogen abstractions by a methyl radical and additions to double bonds both intra- and intermolecular. The chemical reactivity of the involved molecules is described through different properties, which are calculated within the density functional theory (DFT) framework. The softness reactivity index is tested on its usefulness and reliability to provide information about the reactivity of the global molecule or about chemical selectivity. The applicability of the hard and soft acids and bases (HSAB) principle for bimolecular radical reactions is illustrated by comparing the results of the softness-matching criterion with kinetic and thermodynamic data. For large polyaromatic molecules several magnetic indices, in particular, magnetic susceptibilities, chemical shifts, and nucleus independent chemical shifts (NICS), are computed to quantify the aromatic character of the involved species. The applicability of these magnetic indices in the case of radical reactions is validated by comparing with kinetic results obtained from transition state theory.