Theoretical Investigation of the Ring Flipping and Conformational Properties of 2-Methoxy-2-Oxo-1,3,2-Dioxaphosphorinane and its Analogous Containing S and Se Atoms

The ring-flipping potential energy surfaces and conformational properties of 2-methoxy- 2-oxo-1,3,2-dioxaphosphorinane (1), 2-(methylthio)-2-oxo-1,3,2-dioxaphosphorinane (2), 2- (methylselanyl)-2-oxo-1,3,2-dioxaphosphorinane (3) have been explored by means of the long range corrected hybrid-density functional theory [1], with the 6-311+G** basis set and natural bond orbital (NBO) analysis [2]. Results of potential level optimization using the computational levels listed above, indicate that the stability of the axial-conformations at ambient temperature is greater than the equatorial-conformations and the axial-conformation preference decreases from compound 1 to compound 3. In this investigation, the participation of the exo- endo- hyperconjugative anomeric effect (HCAE), Pauli exchange-type repulsions, dipole-dipole interaction effect, the global electronegativity and the global hardness on structural and conformational properties of compounds1-3, have been studied to determine the origin of this conformational behavior. Based on the results, hyperconjugative interactions play a decisive role in the stability and axial-conformation preference of these compounds. This effect can be verified by deleting the donor-acceptor matrix elements of the HCAE from the Fock matrices.