Knowledge Bank

The infrared and Raman spectra of oxalyl bromide, $(COBr)2$, have been recorded between 4000 and $33cm-1$. The infrared spectra have been examined in the solid, liquid, and gaseous states. The Raman spectra of the solid and liquid states have been observed and qualitative depolarization ratios have been measured. The vibrational spectrum of the crystalline materials has been interpreted on the basis of $C2h$ molecular symmetry and a $C2h5$ space group symmetry. However, in the fluid states both the $C2h$ and $C2v$ molecular symmetries appear to be present, in contrast to earlier work reported on this system. In support of the crystallographic workers' report of an intermolecular charge-transfer phenomenon involving the bromine and oxygen atoms, we have observed a continual decrease in the $Ag$ carbonyl stretching frequency by means of a variable temperature laser Raman cell. Furthermore, all symmetry allowed external lattice modes have been observed in the far infrared spectrum and at least four of the six Raman active external lattice modes have also been recorded.