Infrared vibrational intensities and polar tensors of CF3Br and CF3I

Abstract

Listen

Translate article

The polar tensors of CF3Br and CF3I determined from experimental intensities are reported. The sign ambiguities in the dipole moment derivatives derived from the intensities give rise to several polar tensor solutions, the most physically significant of which being chosen upon comparison with the results of ab initio molecular orbital calculations. The comparison is made more efficient by projecting the polar tensor space in bidimensional principal component graphs. The carbon mean dipole moment derivatives and effective charges in both molecules are in good agreement with estimates from electronegativity model equations obtained from fluoro- and chloromethane polar tensor data. The sum intensities of the two molecules are in good agreement with values estimated from the G sum rule in which electronegativity model estimations for the effective charges are used. Moreover, the carbon mean dipole moment derivatives of these molecules can be taken as atomic charges in a simple model recently proposed for estimation of atomic 1s core electron energies in molecular environments in which a linear relationship is expected to exist between the charge of the atom and its 1s core electron energy corrected for the electrostatic potential from neighboring atoms. The carbon mean dipole moment derivatives of CF3Br and CF3I fit very well a previous model regression of the relationship based on values of mean dipole moment derivatives for several halomethanes containing sp3 carbon atoms.