Characteristic features of interaction between atoms in chloro-substituted 1,4-dioxane fromab initio calculations

Abstract

Ab initio calculations in a split-valence shell 6-31G(d) basis for the 2-chloro-1,4-dioxane (with axial and equatorial Cl atom) and 2,3-cis-dichloro-1,4-dioxane molecules with full optimization of their geometry were performed. The major contribution to the lowering of the NQR frequencies of the axial Cl atoms compared with the equatorial Cl atoms comes from the higher pσ-electron population of the former in these molecules. The populations of the orbitals for the unshared electron pairs of the axial and equatorial Cl atoms are identical in these molecules. But these orbitals are polarized differently, which also has some effect on the ratio of the NQR frequencies of these atoms. The differences in the electron populations of the axial and equatorial Cl atoms for the studied molecules are due to the asymmetry of the electron distribution in the Cl atoms geminal to them, which is responsible for the different polarization of the valence p-orbitals of the axial and equatorial Cl atoms.