Simulation of Pyramidal Inversion of Nitrogen in Tetrahydro-1,3-Oxazines in Polar Medium

Abstract

A hybrid DFT PBE/3ζ method is used to simulate pyramidal inversion of the nitrogen atom in unsubstituted- and N-methyltetrahydro-1,3-oxazines in vacuum and in the presence of water and difluorodichloromethane. Relative energies of the equatorial and axial conformers are studied as functions of the number of solvent molecules. It is shown that calculated and experimental NMR values of the barrier of pyramidal nitrogen inversion coincide for the cluster 3-methyltetrahydro-1,3-oxazine-4 difluorodichloromethane molecules. It is concluded that the optimal number of molecules in the solvation shell does not exceed 10 for both solvents.