The infrared and Raman spectra of trans- and cis-tetrachloro-tetramethylbicyclopropylidene

The title compounds trans- and cis-2,2,2′,2′-tetrachloro-3,3,3′,3′-tetramethyl-bicyclopopylidene were synthesized, and their infrared and Raman spectra were recorded. Non-coincidence between the IR and Raman bands of the trans compound suggested C2h symmetry and a planar ring system. In the cis compound most of the IR and Raman bands coincided and a C2v symmetry seems likely. The exocyclic CC double bond gave rise to a medium/weak Raman band at 1847 cm−1 in the trans compound. In the cis derivative IR and Raman bands both at 1825 cm−1 were observed. From similarities with related molecules, the ring breathing, the antisymmetric ring stretch, the CCl2 out-of-phase and in-phase stretch and the out-of-plane ring bending modes have been tentatively assigned for the trans and cis compounds.