Knowledge Bank

The far-infrared and Raman spectra of cyclohexene and five of its deuterated derivatives have been recorded. In the gas-phase infrared spectrum of cyclohexene, two series of bands originating at 165 $cm-1$ and 276 $cm-1$ were assigned to the ring-bending and ring-twisting vibrations, respectively. Overtone, sum, and difference bands provided additional data for the assignment of the energy states. A potential energy surface of the form $$ V = a_{1}{x_{1}}^{4} +b_{1}{x_{1}}^{2} + a_{2}{x_{2}}^{4} +b_{2}{x_{2}}^{2} + c{x_{1}}^{2}{x_{2}}^{2} $$ was used to represent the potential energy surface, and appropriate kinetic energy expansions were determined for these computations. Cyclohexene has a twisted (halfchair) conformational minimum. The planar and bent conformations were calculated to be 4700 and 1100 $cm-1$ higher in energy, respectively. These results will be compared to those recently determined for related oxygen containing $compounds.1$