VIBRATIONAL-SPECTRA AND NORMAL COORDINATE ANALYSIS OF SOME DIETHYL TERTIARY AMIDES

The Raman and infrared spectra of N,N‐diethylformamide, N,N‐diethylacetamide, N,N‐diethylchloroacetamide and N,N‐diethylpropionamide were measured. Raman polarization measurements were also made. A normal coordinate analysis was carried out for N,N‐diethylformamide, N,N‐diethylacetamide and N,N‐diethylchloroacetamide using a 63‐parameter modified valence force field. The force constants were refined in an overlay least‐squares technique using vibrational frequencies of the molecules to obtain a converged set of meaningful force constants. The reliability of the force constants so obtained was tested by making a zero‐order calculation for N,N‐diethylpropionamide. The potential energy distributions and eigenvectors calculated in the process were used to make unambiguous vibrational assignments. Copyright © 1990 John Wiley & Sons, Ltd.