Role of geometrical relaxation in solution of simple molecules exhibiting anomeric effects

Abstract

The conformational equilibria in the gas phase and in solution of dimethoxymethane (DMM), MeOC(H 2)OMe, and dimethoxyethane (DME), MeOC(HMe)OMe, have been studied by means of quantum-chemical calculations. The influence of the anomeric effect on these equilibria and their interconversion processes has been investigated. Solvent effects have been described using the continuum cavity model of Nancy's group. Geometry optimizations have been performed in both gas-phase and solution media (water permittivity was used). For DMM three stable conformers exist, but for DME the potential energy surface in solution shows a new minimum which corresponds to a fourth stable conformer. Energy profiles corresponding to rotation around the COMe bond, for interconversion of α- and β-anomers, have been calculated for processes in the gas phase and in solution. One-electron and polyelectron population analyses in terms of the natural hybrid orbitals of Weinhold have been performed to understand the evolution of the electronic structure with torsion about the CO bonds.