Knowledge Bank

“From the known crystal structure of hydrogen peroxide, one predicts under the unit cell approximation that each frequency of the free $H2O2$ molecule with $C2$ symmetry will contribute three components to the crystal spectrum. All components arising from the A frequencies will be Raman active but only two of the B components will be allowed. In view of the relatively strong intermolecular forces created by the network of hydrogen bonds in the crystal, one may also expect not only that these components will be split appreciably but that quite probably the accidental degeneracy of the stretching and bending hydrogen fundamentals of the free molecule may be removed. In support of these predictions, the Raman spectrum of large single crystals of $H2O2$ at -- $10\circ C$ is observed to be remarkably rich in bands as compared to the liquid spectrum. An assignment of the observed frequencies has been made which is consistent with the X-ray symmetry and shows splittings of $10-30cm-1$ between the crystalline components arising from any particular hydrogen frequency. Bands arising from, the accidentally degenerate A and B hydrogen stretching motions of the free molecule appear separated by somewhat more than $100cm-1$ in the crystal.”