Acetamide planarity revisited: Density functional and second order Moeller-Plesset perturbation studies

Density functional theory (DFT) with nonlocal functionals, BLYP, BP86, B3LY P and ACM, with split-valence basis sets has been applied to the prediction of molecular structure and torsional barrier of acetamide, a peptide mimic . Moeller-Plesset calculations truncated to the second order (MP2) have bee n performed on acetamide for comparison with DFT results. The conformation of the methyl group observed in MP2 calculations is different from that in DFT calculations. DFT promises to be a powerful method for molecular struct ure determination and conformational analysis of peptides in future at the same level of accuracy as NMR, X-ray crystallography and neutron diffractio n.