Normal Vibrations of N-Methylacetamide

The in-plane normal vibrations of N-methylacetamide and its deuterated compound were calculated as a six-body problem. The force constants were transferred from diformylhydrazine and other molecules with similar structures. The normal modes as well as the distributions of the potential energy among symmetry coordinates were also calculated. The result of these calculations allows quantitative discussions concerning the nature of the amide I, II, II′, III, III′, and IV vibrations and other normal vibrations of N-methylacetamide.