The microwave spectrum and molecular structure of the hydrogen-bonded aniline-methanol complex

The rotational spectrum of aniline-methanol was investigated in the frequen cy region 3-19 GHz using a pulsed molecular beam Fourier transform microwav e spectrometer. Sixty-three measured a- and b-type transitions show a fine structure due to internal rotation of the methyl group. The resulting A and E lines are additionally split into hyperfine components arising from quad rupole coupling of the N-14 nucleus. The torsional motion of the methyl gro up is hindered by an effective barrier V-3 of nearly 215 cm(-1), which is a lmost one-half of the methanol barrier height. The structure of the complex was calculated assuming a common symmetry plane for the monomers. These fo rm a linear N ... H-O hydrogen bond. Its distance was found to be 3.03 Angs trom, which is identical with that of aniline-water. (C) 1999 Academic Pres s.