On the nature of the anomeric effect in XHn—CH2—OH systems, with X = F, O, N, C

Using geometry optimizations at the 6-31G** level, energies, bond distances, and charges were obtained for systems XHn—CH2—OH with X = F, O, N, C, for various rotational conformers of the OH group. Conformational analysis shows that systems with X = F and O receive anomeric stabilization due to a partial π-bond forming in the CH2—OH fragment of the molecule, amplified or diminished by lone pair repulsion (or dipole) energies. For the systems with N and C, no π-bond stabilization is found. However, the e-NH2—CH2—OH system is still stabilized due to favourable lone pair repulsion circumstances. Keywords: anomeric effect, abinitio studies, π-bonding model.