Molecular Beam Rotational Spectrum of Cyclobutanone-Trifluoromethane: Nature of Weak CH···O=C and CH···F Hydrogen Bonds

The molecular beam Fourier transform microwave spectrum of cyclobutanone-trifluoromethane has been assigned and measured. The carbon atom of trifluoromethane lies in the plane of the heavy atoms of cyclobutanone. The complex is stabilized by one C-H···O=C and two C-H···F-C weak hydrogen bonds. The C-H···O=C interaction, involving one carbonylic oxygen, is studied for the first time in detail with rotationally resolved spectroscopy. The two C-H···F-C weak hydrogen bonds involve two fluorine atoms of trifluoromethane and two hydrogens of the same methylenic group in the ? position.