Bond dissociation enthalpies in chlorinated benzenes and phenols and enthalpies of formation of their free radicals: A Gaussian-4 prediction

Abstract

The bond dissociation enthalpies (BDEs) in chlorinated benzenes and phenols and the standard gas-phase enthalpies of formation of chlorinated phenyl and phenoxy radicals are predicted by using Gaussian-4 (G4) and Gaussian-3X (G3X) model chemistries. The predicted G4 BDEs are systematically smaller than the G3X ones, with difference as much as ∼15 kJ/mol for the C6Cl5-Cl bond, and the G4 enthalpies of formation of the free radicals are systematically smaller than the G3X ones. The discrepancies increase gradually with the degree of chlorination; whereas for the closed-shell species, G4 and G3X enthalpies of formation agree closely within 2 kJ/mol. The difference between G4 and G3X arises mainly from the noncanceling high-level correction terms in G4. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 43: 62–69, 2011