17O and 1H- 15N heteronuclear multiple quantum coherence ( 1H- 15N HMQC) NMR of linear amides: evidence of an out-of-plane (torsion angle) deformation of the amide bond and pyramidicity at the amide nitrogen

Abstract

17O and 1H- 15N heteronuclear multiple quantum coherence NMR studies of linear amides demonstrate the ready occurence of an out-of-plane (torsion angle) deformation of the amide bond and pyramidicity at the amide nitrogen for the sterically hindered trans-isomer of N-tert-butylformamide. Solvent accessibility, steric hindrance and, thus, torsion angle deformation is shown to be strongly solvent dependent.