Raman spectra and simulation of cis-and trans-cyclooctene for conformational analysis compared to inelastic neutron scattering

Simulated and measured Raman spectra are used to determine the molecular conformation of trans-cyclooctene. This is the first reported Raman spectrum of this highly strained species. A crown structure results in a computed Raman spectrum, which is in good agreement with the experiment; a chair structure does not. Comparison is made with the case of cis-cyclooctene. The computed structure and limitations of the method of conformational analysis are discussed. In particular, the relative merits of Raman spectroscopy in comparison with infrared and inelastic neutron scattering (INS) are evaluated using computed spectra for all three methods and comparison of the observed INS for cis-cyclooctene with that computed for two conformations. It is concluded that the combination of computed and observed Raman spectra provides a useful method for conformational analysis for cases of this type.