Bond dissociation energies and the Hammett correlation, Part 1: Remotely substituted aromatic compounds and vitamin E

Abstract

AbstractFour hundred and seventy nine experimental values of XZ bond dissociation energies (BDEs) of para‐, ortho‐, meta‐, and multisubstituted aromatic compounds were reproduced by the following simple equations: equation image Here X represents a wide variety of univalent atoms or groups; Y is one or several various remote substituents; and Z represents an oxygen, nitrogen, carbon, or sulfur atom. DH0(XZC5H6) is a known reference/anchor point for a series of XZ bonds. Esr is the remote conjugation energy between the substituents and the reaction center (broken bond), and can be expressed as a Hammett‐type correlation. σ+(Y) is the Brown–Okamoto constant of a substituent Y or the sum of several substituent constants. The Hammett slope or reaction constant ρ is a linear function of the difference between the covalent potentials Vx(Z) and Vx(X). It has been found that equation image and equation image The set of equations are very powerful for the prediction of BDEs, chemical reactivity, and reaction center (or active site) in antioxidants, nutrients, pharmaceuticals, toxicants, carcinogens, and explosives. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 453–466, 2002