Conformation of dimethoxymethane: roles of anomeric effects and weak hydrogen bonds. A free jet microwave study

The rotational spectrum of dimethoxymethane has been measured by free jet millimetre-wave absorption spectroscopy. It corresponds to a distorted, but C-2 symmetric, configuration with the two methyl groups gauche with respect to the far oxygen atom. Each rotational transition is split into several, allowed and forbidden, component lines due to the two methyl groups internal rotations. The corresponding V-3 barrier has been determined to be 1.58 kcal mol(-1). The "distorted" shape is attributable to the anomeric effect, but also to intramolecular weak C-H...O hydrogen bonds.