McGhie, A. R.; McCauley, J. P.; Smith, A. B.; Hochstraseer, R. M. J. Phys. Chem. 1991,95,6075-6078. (47) Letokbw, V. S. In h e r spectmcopy of highly vibrationally excited molecules; Lctokhov, V. S., Ed.; Adam Hilga: New York, 1989; pp 1-54. (48) Hare, J. P.; Kroto, H. W.; Taylor, R. Chem. Phys. Lett. 1991,177, 394-398. (49) Levine, R. D.; Banetein. R. B. In M d c c~l a r Reaction Dynamics andThe preparation, characterization, infrared ahrption, and vibrational circular dichroism (VCD) spectra of the title compound are presented. From ab initio quantum mechanical energy minimization, geometry optimization calculations, the lowest energy conformation is a slightly distorted envelope form, so that deuteration give rise to both pseudoaxially and pseudoequatorially substituted conformers. The vibrational spectra (IR and Raman) have been assigned by comparison of frequencies and overall intensity patterns to those calculated by using an ab initio force field obtained for both conformers. This force field was subsequently modified by refining scale factors to improve the fit to frequencies of assigned bands for both the do and d2 isotopomers. The absorption intensities and VCD signs and magnitudes were calculated by the ab initio magnetic field perturbation theory of Stephens using the distributed origin gauge with origins at the nuclei. Good qualitative agreement was found between the experimental and theoretical dipole strengths and rotational strengths when the average of the calculated valuar for the two conformers was used. The best calculations used a 6-31G** basis set for for the force field and the intensities, but the refined force field did not lead to a significant improvement in the intensity or VCD pattern (other than frequency alignment) as compared to the unscaled ab initio result. For purposes of comparison to previous reports, calculations were also made for the planar conformation. Test calculations with variants of more approximate methods that do not allow for charge reorganization associated with nuclear motion gave distinctly unsatisfactory results, particularly in the mid-infrared portion of the spectrum.
