Normal Coordinate Analysis of Halogenated Ethylenes. II. Perhalogenated Ethylenes

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Abstract
The methods described in the preceding paper have been applied to the normal coordinate analysis of the fundamental vibrations of 27 perhalogenated ethylenes which contain F, Cl, or Br. Force constants for the planar modes of the key molecules, C2F4, C2Cl4, and C2Br4, have been obtained by an adjustment procedure based on the method of least squares. The agreement between the calculated and observed fundamentals is quite good. The constants established for the key molecules were then used, either directly or with a simple interpolation scheme, to calculate the fundamentals of the remaining 24 ethylenes. Comparisons with experimental results have been made where possible and indicate good agreement for the out‐of‐plane as well as inplane vibrations. The planar normal modes of C2F4, C2Cl4, and the 5 fluorochloroethylenes are depicted.