Hydrogen bonded bimolecular complexes of carboxylic acids in the vapor phase : Observation and characterization by low resolution microwave spectroscopy

Various carboxylic acids and amides are shown to form H-bonded bimolecules with trifluoroacetic acid in the vapor phase. These bimolecules have been observed directly by low resolution microwave spectroscopy which gives rotational constants in agreement with those calculated with the assumption of a planar, 8-membered ring geometry for the H-bonded portion of the structure. A number of combinations did not provide observable spectra, and reasons are proposed why the bimolecules probably did not form in certain of these cases. Approximate dipole moments are obtained for the H-bonded bimolecular complexes.