Prediction of Electron Densities, the Respective Laplacians, and Ellipticities in Bond-Critical Points of Phenyl-CH-Bonds via Linear Relations to Parameters of Inherently Localized CD Stretching Vibrations and H-1 NMR-Shifts

Electron densities ρ, the respective laplacians ▽2ρ, and ellipticities ϵ in bond-critical points (BCPs) are reactivity-determining characteristics according to the theory of atoms in molecules. These quantities are experimentally detectable only for substances in the crystalline state. To facilitate the determination of ρ, ▽2ρ, and ϵ values of BCPs of dissolved or liquid substances, the relations between DFT-calculated ρ, ▽2ρ, and ϵ and DFT-calculated vibrational and 1H NMR spectroscopic quantities were studied for a set of 18 monosubstituted benzene derivatives. We found that via linear functions of ρ, ▽2ρ, or ϵ reliable predictions of ρ, ▽2ρ, and ϵ are possible, dependent on at least one of the variables vibrational transition energy, IR intensity, Raman activity of an inherently localized CD-stretching vibration, and the 1H NMR shift. For the determination of ρ, ▽2ρ, and ϵ values in the ph−CH BCPs, the most important variables are the vibrational transition energy of the CD-stretching vibration and the corresponding 1H NMR shift. The parameters of the functions best suited to predict ρ, ▽2ρ, and ϵ in the certain CH BCPs of the phenyl ring are presented.