FAR-INFRARED SPECTRA AND TWO-DIMENSIONAL POTENTIAL ENERGY SURFACE FOR THE RING-TWISTING AND RING-BENDING VIBRATIONS OF CYCLOHEXENE AND ITS DEUTERATED DERIVATIVES.

$^{1}$ M. M. Tecklenburg and J. Laane, J. Am. Chem. Soc., 111, 6920 (1989).""Author Institution: Texas A\&M University, College Station; Bristol-Meyers, College StationThe 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}