| Abstract: | The theory relating to hindered internal rotation is reviewed and expanded with special emphasis on selection rules and additional complications caused by considering higher terms in the potential energy expressions. Normal coordinate calculations are discussed on the basis of recent advances in the techniques of finding a unique set of force constants. In addition, the choice of the appropriate force field is discussed in light of recent findings. Formaldehyde is subjected to a normal coordinate analysis, using the most recent data. The relationship of the angular redundancy to the force constants is established. Force constants are calculated for the most general valency force field along with the Coriolis coupling coefficients for H₂CO and D₂CO. The far infrared and Raman spectra are obtained for tert-butyl chloride, tert-butyl bromide, tert-butyl iodide, tert-butyl amine, and neopentyl chloride. In addition, the far infrared spectrum of trimethylamine is reported. Normal coordinate calculations are carried out to confirm the assignment of the normal modes. Torsional frequencies are assigned for tert-butyl chloride, tert-butyl bromide, neopentyl chloride, and trimethylamine. Analysis of hindered internal rotation in tert-butyl systems is attempted. |
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