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 ~1H NMR-Shifts
Electron densities ρ, the respective laplacians ~2ρ, and ellipticities ∈ 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 ∈ values of BCPs of dissolved or liquid substances, the relations between DFT-calculated ρ, ~2ρ, and ∈ 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 ∈ reliable predictions of ρ, ~2ρ, and ∈ 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 ∈ 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 e in the certain CH BCPs of the phenyl ring are presented.
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