Knowledge Bank

Infrared $(400-200cm-1)$ and Raman spectra of 1,1-dibromo-2,2-dichlorocyclopropane (DBDCCP) have been recorded for the first time. These spectral data are consistent with the expected $Cs$ structure of this molecule. In most cyclopropyl derivatives containing only a plane of symmetry, the plane is perpendicular to the ring plane; in DBDCCP, however, the symmetry plane is the ring plane. This fact leads to all three ring modes being totally symmetric vibrations. Additionally, the $CH2$ rock and wag end up in uncharacteristic symmetry blocks. A vibrational assignment for the 21 normal modes of DBDCCP has been proposed and these results are compared to the vibrational spectra of 1,1,2,2-tetrabromocyclopropane and 1,1,2,2-tetrachlorocyclopropane (for which two molecules DBDCCP represents an ``average” structure).