The axial and equatorial hydrogen bonds in the tetrahydropyran∙∙∙HF complex.

Characterized by microwave spectroscopy after their formation in a supersonic jet, the axial and equatorial hydrogen bond conformers of the title complex were studied. The axial form--shown in the picture--has been found to be the most stable one. The experimental data are consistent with a C(s) symmetry for both conformers, in which linear hydrogen bonds lying in the symmetry plane bisect the C-O-C angle. The structure of tetrahydropyran subunit in the axial form was also determined and no significant structural distortion occurs upon complexation.