The General Valence Force Field of Ethylene

During the course of studies of the vibrational spectra of type molecules, it was found that differences in the results of force constant calculations were obtained by various workers. This diversity in results can be attributed not only to differences in frequency assignments and in assumed force fields, but also in choice of coordinates. The present note deals with the two different sets of symmetry coordinates in common use by various authors for ethylene-type molecules.