The cis and trans rotational isomers of 3-fluorostyrene. What is the energy difference between them?

Abstract

Results obtained for 3-fluorostyrene from single vibronic level fluorescence in a supersonic jet, microwave spectroscopy and ab initio calculations have been interpreted to give cis-trans energy differences of 220±50, 26±45, and 43 cm −1 with cis the more stable. Calculations have suggested that the torsional potential may include a V 3 term, in addition to the V 1, V 2 and V 4 terms used to interpret the fluorescence data. It is shown that it is possible that all three results can be reconciled in this way.