(1) K. Bolton, D. G. Lister, and J. Sheridan, 1974, J. Chem. Soc. Faraday Trans. 2 70, 113
determined the s-cis conformer to be lower than the s-trans conformer by 58 (17) cm^–1 or 0.7 (2) kJ/mol or 83 (24) K.
The experimental data were taken from (1) and from
(2) C. Calabrese, A. Vigorito, G. Feng, L. B. Favero, A. Maris, S. Melandri, W. D. Geppert, and W. Caminati, 2014, J. Mol. Spectrosc. 295, 37.
With respect to the first entry of Dec. 2013, extensive microwave and millimeter wave data were added. These were published by
(3) E. R. Alonso, L. Kolesniková, I. Peña, S. T. Shipman, B. Tercero, J. Cernicharo, and J. L. Alonso, 2015, J. Mol. Spectrosc. 316, 84.
Uncertainties of individual data sets were tested and adjusted if necessary. A very small number of transitions with large residuals from (3) were omitted. The effect on the calculated transition frequencies is small as the data set is dominated by the millimeter wave data from (3). The calculations should be sufficient for all observational purposes. Transitions with calculated uncertainties larger than 0.2 MHz should be viewed with caution.
The partition function values were calculated summing up the ground state contributions of both conformers. The uncertainty of the energy of the trans conformer leads to some probably modest uncertainty in the partition function.
The dipole moment componenets were measured in (1).