Force Constants and Structure

Abstract

IN a recent letter in NATURE¹, Duchesne has discussed the values of the force constants of the potential energy function of the molecules ethylene and tetrachlorethylene, and has attempted to draw inferences from the calculated data about structural properties. In a paper at present in the press², we have examined the values of the force constants of the linkages in different molecules of a given series, such as the methyl and ethyl derivatives of a metal, in so far as these are given by the values of their normal vibration frequencies. The results suggested that in different molecules of a particular type variation in the force constant of a given link or of the bending constant of a given angle might throw light on the electronic arrangements in the different linkages. We have accordingly now calculated the force constants of linkages in a very large number of molecules from the known vibration frequencies. It becomes clear that in some cases, structural problems, such as the phenomenon of resonance, may be studied by this procedure. The detailed results will appear shortly elsewhere, but since our conclusions with the two molecules mentioned above appear to go further than those given by Duchesne, it may be fitting to summarize them here.