Laser Raman and infrared spectra of (b-alanine) b-alaninium nitrate were recorded and analyzed at room temperature. The proposed assignment of normal modes is based on group theoretical analysis. The hydrogen atom is shared by two amino acids, leading to switching of roles of the cation and zwitterion. The two alanine groups share one proton and become monoprotonated. The presence of an ionized carboxylic group and carbonyl was identified. The extensive hydrogen bonding in the crystal is responsible for the changes in the position and intensity of several bands. The nitrate anion fundamentals, however, continue to be degenerate.
Infrared and Raman spectra of DL-threoninium dihydrogenphosphate crystal were recorded at room temperature and vibrational assignments of the observed wavenumbers were made. The extensive intermolecular hydrogen bonding in the crystal was identified by the shifting of bands due to the stretching and bending modes of the various functional groups. The T d symmetry of the phosphate anion is reduced to the lower symmetry C 2v owing to the intermolecular hydrogen bonding and coordination. The splitting of degenerate modes and the appearance of infrared-inactive modes indicate the effect of the crystalline field on molecular vibrations.
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