Intramolecular Twisting Effects in Substituted Benzenes. II. Ground-State Properties

Abstract

The effects on ground‐state properties of twisting a substituent group about the substituent‐ring bond in substituted benzenes are discussed from the viewpoint of semiempirical MO theory. The ground‐state properties are discussed with reference to a parameter θ, which generally increases as the substituent is twisted. The substituent‐ring bond order varies approximately as cosθ, and the following vary approximately as cos²θ: the resonance energy, charge densities, ring C–C bond orders and the π‐electronic dipole moment. The θ dependence of the total dipole moment is discussed. Numerical applications to N,N‐dimethylaniline and related molecules are described, including a detailed treatment of the dipole moments of N,N‐dimethylaniline and some of its ortho‐substituted derivatives. A brief discussion of the valence state of the dimethylamino group is included.