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 rho, the respective laplacians nabla(2)rho, and ellipticities epsilon 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 rho, nabla(2)rho, and epsilon values of BCPs of dissolved or liquid substances, the relations between DFT-calculated rho, nabla(2)rho, and epsilon and DFT-calculated vibrational and (1)H NMR spectroscopic quantities were studied for a set of 18 monosubstituted benzene derivatives. We found that via linear functions of rho, nabla(2)rho, or epsilon reliable predictions of rho, nabla(2)rho, and epsilon 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 (1)H NMR shift. For the determination of rho, nabla(2)rho, and epsilon values in the ph-CH BCPs, the most important variables are the vibrational transition energy of the CD-stretching vibration and the corresponding (1)H NMR shift. The parameters of the functions best suited to predict rho, nabla(2)rho, and epsilon in the certain CH BCPs of the phenyl ring are presented.
Presselt
Martin
M
Institute of Physical Chemistry, Friedrich-Schiller-University Jena, Helmholzweg 4, 07743 Jena, Germany.
Schnedermann
Christoph
C
Schmitt
Michael
M
Popp
Jürgen
J