Infrared spectroscopy and theoretical calculations as tools for the conformational analysis of 2-methoxycyclohexanone

The conformational equilibrium of 2-methoxycyclohexanone has been analyzed through infrared spectroscopy and theoretical calculations. These calculations indicate that six conformations may be present in the vapor phase, due to the rotation of the methoxy group around the OC 2 bond, leading to axial (g +, g − and anti) and equatorial (g +, g − and anti) conformers. However, the infrared spectrum in CCl 4 solution shows just three carbonyl stretching bands, corresponding to the conformers of lower energies. An additional band is observed for the CH 3CN solution, attributed to a fourth conformer stabilized by a dipole–dipole interaction between this conformer, having a high dipole moment, and the very polar solvent. An interpretation of the governing factors of 2-methoxycyclohexanone equilibria is also given.