Structure, conformation and NMR studies on 1,2-dioxane and halogen substituted 1,2-dioxane molecules.

Molecular structure and conformational stability of chair and twist conformers of 1,2-dioxane and halogen substituted compounds of the 1,2-dioxane have been studied using ab initio and density functional theory (DFT) methods. The molecular geometries of 1,2-dioxane, 3,6-difluoro, 3,6-dichloro, 3,3,6,6-tetrafluoro and 3,3,6,6-tetrachloro 1,2-dioxane compounds were optimized at HF, MP2, B3LYP and B3PW91 levels of theory by implementing 6-31G* basis set. To study the effect of polar medium, self-consistent reaction field theory is used to optimize the conformers at B3LYP/6-31G* level of theory. The geometrical parameters of chair and twist conformers have been discussed in the light of interaction between lone pair electrons present in the oxygen and substituted halogen atoms. The relative stability of the conformers have been studied using relative energy, maximum hardness principle and thermodynamical quantities. The 13C-NMR chemical shift study for carbon atoms in the title compounds are calculated and the results have been discussed.