Microwave studies of the three conformers of butyl cyanide

Three conformers of n-butyl cyanide have been characterized by microwave spectroscopy. Low and medium resolution studies on static gas samples in Stark-modulated spectrometers revealed the presence of three conformational species and identified them. High resolution pulsed-jet Fourier transform spectra allowed the assignment of individual transitions of each species yielding rotational and centrifugal distortion constants, N-14 quadrupole coupling constants, and qualitative relative energies of the species. The anti-anti and gauche(CN end)-anti forms are more stable than the anti-gauche(methyl end) conformer. The N-14 quadrupole coupling constants, which appear so different among the different conformers, are consistent with a reference electric field gradient, that in methyl cyanide, rotated to the inertial axes of each conformer of butyl cyanide. (C) 1997 Elsevier Science B.V.