Conformational analysis of N,N,N′,N′-tetramethylsuccinamide:: The role of C-H•••O hydrogen bonds

We report a conformational analysis of N,N,N',N'-tetramethylsuccinamide. An initial set of geometries was obtained through an exhaustive conformer search with molecular mechanics. The structures were further optimized using density functional theory (DFT) with the generalized-gradient approximation. Single-point energies on the DFT geometries are reported at the second-order Moller-Plesset (MP2) levels. The lowest energy conformations were further optimized at the MP2 level. Geometries and relative energies for 22 conformations are reported. The geometries are rationalized in terms of rotational potential energy surfaces in simple compounds, intramolecular C-H ... O hydrogen bonding, and dipole-dipole repulsion.