Asymmetrical nonbridgehead nitrogen—30 geminal systems—21

The vicinal n - σ* interaction stabilizes the pyramidal state of the nitrogen geminal system where X and Y are electronegative substituents with high-lying levels of nonbonding n orbitals. A approximate value for the energy of n - σ* stabilization of pyramidal state in N , N -dialkoxyamines, equal to ∼5.7 kcal/mol, has been found by comparing the average experimental value of the inversion barrier for these compounds with the one calculated according to the additive scheme. The influence of the vicinal n - σ* interaction on the structural peculiarities of N -alkoxyisoxazolidines manifests itself in the conformations with the greatest overlapping of n and σ* orbitals being predominantly populated and in a change in NO bond lengths and valence angles. The combination of a ligand having the highest-lying level of n orbital with a ligand, which forms the σ bond with a N atom, having the lowest-lying antibonding level results in the dissociation of a nitrogen geminal system into an ionic planar form of the type. From this is inferred the dual nature of the influence exerted by the vicinal n - σ* interaction upon the inversion barrier of the geminal system.