Raman spectra and out-of-plane ring vibrations of bicyclo [3.1.0] hexane and its analogs

The low-frequency vapor phase Raman spectra have been recorded for bicyclo[3.1.0]hexane, 3-oxabicyclo[3.1.0]hexane, 6-oxabicyclo[3.1.0]hexane, and 3,6-dioxabicyclo[3.1.0]hexane. From the six observed ring-puckering transitions for bicyclo[3.1.0]hexane, the ring-puckering potential energy function was determined to be V(cm−1)=24.70(Z4+25.72Z2+ 9.28Z3), where Z is the reduced ring-puckering coordinate. For each of the oxabicyclohexanes three transitions were observed for the puckering mode and these were in agreement with previously reported far-infrared spectra. No puckering transitions were observed for the dioxabicyclohexane. For each of the four molecules, frequencies corresponding to twisting of the five-membered ring and rocking of the three-membered ring were also observed.