Force Constants for the Fluoromethanes

Abstract

A calculation, involving vibrational potential functions of a general quadratic type restricted to small displacements, has been used to evaluate force constants, singly or in linear combination, for the fluoromethanes, and simultaneously, to confirm new assignments of the fundamentals of CF3H and CF2H2 arising from a detailed experimental study of their Raman spectra. The results indicate considerably greater bond strengths than expected from a mere extrapolation of the properties of analogous halogen derivatives. Particularly significant is the order of interaction terms involving the C–F stretching and the F–C–F bending motions of the molecules.