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gauche-3-Butenenitrile is higher in energy than
syn-3-butenenitrile. The conversion does not
require a formal rotation around a double bond. Therefore,
the two species should be considered as conformers.
There are two equivalent gauche-configurations
separated by the anti-transition state.
Experimental results by
(1) J. R. Durig, G. A. Guirgis, and A. S. Drew,
1994, J. Raman. Spectrosc. 25, 907
suggest gauche to be higher than syn by
336 ± 61 cm–1 in the gas phase.
However, since gauche was also detected in a
cold environment, it is necessary to treat the two
conformers separately.
The millimeter data were taken from
(2) J. Demaison, J. Burie, D. Boucher, and G. Wlodarczak,
1991, J. Mol. Spectrosc. 146, 455.
Also included in the fit were microwave transitions
from
(3) M. C. McCarthy, K. L. K. Lee, P. B. Carroll, J. P.
Porterfield, P. B. Changala, J. H. Thorpe, and J. F. Stanton,
2020, J. Phys. Chem. A 124, 5170.
Some additional spectroscopic parameters were used,
in part estimated. The calculation should be suitable
for most observational purposes.
Transition frequencies with calculated uncertainties
exceeding 0.2 MHz should be viewed with caution.
The 14N hyperfine splitting can be resolved
for low values of J. Therefore, a separate
hyperfine calculation is provided up to J' = 25
and up to 120 GHz. Please note that the 14N spin
multuplicity was also considered in the hyperfine free calculation.
Please note: the quantum number
range in the HFS file has been extended in April 2024 so that
a-type transitions occur at higher frequencies.
The dipole moment components are from
(4) E. Zeisberger and I. Botskor,
1983, J. Mol. Struct. 97, 323.
Please note that the old dipole moment components are
incorrect, and the new data are compatible with quantum
chemical calculations in (1).
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