INFRARED VIBRATIONAL INTENSITIES AND POLAR TENSORS OF THE FLUOROCHLOROMETHANES

The polar tensors of CFCl3, CF2Cl2, and CF3Cl determined from experime ntal infrared intensities are reported. The sign ambiguities in the di pole moment derivatives are resolved by comparing alternative polar te nser solutions with the results of MP2/6-311+G(3d) molecular orbital c alculations using bidimensional principal component projections of the polar tenser spaces. The carbon mean dipole moment derivatives of-the fluorochloromethanes are in good agreement with the values predicted by an electronegativity model equation obtained from both fluoro- and chloromethane polar tenser data. These values are shown to be intermed iate to those expected on the basis of separate fluoro- and chlorometh ane models. The mean dipole moment derivatives of the fluorine and chl orine atoms vary with the degree of fluorine-chlorine substitution. Th is contrasts with the almost constant values of these quantities alrea dy reported for the fluoro- and chloromethanes.