Conformers of cis-N-methylacetamide : Ab initio study of geometries and vibrational spectra

Abstract

Energies and geometries have been obtained, at the Hartree-Fock 4-31G* level, for the four stable conformers of cis-N-methylacetamide that result from conformational isomerism of the CH3 groups. Ab initio force fields were obtained for these four structures, the scale factors being transferred from the experimentally refined ones for the trans molecule with the minimum change required to give agreement with the available data on the cis molecule. The latter required a change only in the scale factor for the CN stretch, and resulted in good agreement between observed and calculated bands. Comparisons of properties are made between the four cis confonners and between the lowest energy conformers of trans- and cis-N-methylacetamide.