VIBRATIONAL CIRCULAR DICHROISM SPECTRA AND CONFORMATIONAL ANALYSIS OF DIISOCYANANO-CYCLOPROPANE

Author Institution: U. S. Food and Drug Administration; Department of Chemistry, University of Illinois at ChicagoWe have measured the vibrational circular dichroism (VCD) spectrum of trans-1.2-di- isocyanocyclopropane using a dispersive spectrometer in the C-H stretching and N=C=O asymmetric stretching regions. The C-H region resembles the spectra obtained for dicyano-cyclopropane. which until now was a unique VCD pattern for the series of trans disubstituted cyclopropanes. This is also one of the few CH stretching VCD spectra that, to date, are not ammenable to theoretical analyses even at the a priori level. The isocyanate stretch gives rise to a distorted couplet that can be interpreted with the coupled oscillator model. Our preliminary results indicate that the pattern observed is only compatible with a cis-trans conformation of the two isocyanates with respect to the ring. Due to sample stability problems, it was not possible to obtain mid-ir VCD