An electronegativity model for vibrational intensities of substituted methanes

Abstract

The mean dipole moment derivatives of the carbon polar tensors of the halogenated methanes are shown to be linearly related to the carbon partial charges calculated using the equalization of the electronegativity principle. The relationship is quantitative and allows the calculation of mean dipole derivatives of carbon atoms from valence state ionization potentials and electron affinities of the atoms in the halogenated methanes. The methyl group electronegativity in ethane calculated from the carbon mean dipole derivative is in excellent agreement with the previously reported value obtained from electronic transition data. Ab initio charge, charge flux, and overlap contributions to the carbon mean dipole derivatives are shown to be useful in the interpretation of the relation between the derivatives and the partial charges.