Knowledge Bank

The preparation, infrared absorption and vibrational circular dichroism (VCD) spectra of the title compound will be presented. The absorption intensities and VCD signs and magnitudes were calculated using an ab initio force field and the a priori theory of Stephens, both carried out with a $6-31G\ast \ast$ basis set at the SCF level. Excellent agreement was found between theory and experiment for the single-signed VCD seen in the C-H(+) and C-D($-$) stretching regions. As predicted, no VCD was detectable in the $C=O$ stretching region. The mid-ir VCD pattern from 1300 to 900 $cm-1$, consisting of two large negative bands and several weak positive bands, was well-represented by the calculations. The single conformation of relatively high sysmmetry appears to have led to a relatively simple vibrational spectrum which is particularly susceptible to these analyses. Difficulties with isotopic and chemical impurity interference are shown to be less in VCD. Calculations on related four member ring molecules will also be presented as time permits.