Toward the origin of the conformational preference of 2-methoxyoxane, a model useful to study the anomeric effect

Abstract

The potential energy curves resulting from the C2-O exo bond rotation of 2-OMeOxane were calculated. One minimum was found for the axial conformer at MP2/6-31G(d,p); B3LYP/6-31G(d,p); and HF/6-31G(d,p) levels, and two minima in the equatorial conformer. The difference in the entropy of mixing between both conformers has a positive value, close to zero, which means that the entropy is higher for the equatorial conformer. The Scheme of rotation of the methoxy group at position 2 of oxane with six conformers, usually employed to describe this conformational process, is inadequate.