APPLICATION OF FOURIER-TRANSFORM RAMAN-SPECTROSCOPY TO A RANGE OF COMPOUNDS OF PHARMACEUTICAL INTEREST

Fourier transform (FT) Raman spectra have been obtained for a range of synthetic and semisynthetic samples to evaluate the utility of the technique for the characterization of compounds of pharmaceutical interest. These spectra are compared with the IR KBr disc spectra. Examples of the additional, important information which may be extracted from Raman data in comparison with IR spectroscopy are reported for the range of chemical structures studied. The superior ability of Raman to characterize the stretching modes of the C-H bond compared with IR spectroscopy is demonstrated for several compounds. The characterization of highly symmetric vibrational modes is one of the most prominent and useful advantages of Raman spectroscopy and several examples of this primary application are also cited. These include the assignment of the ring breathing frequency of monosubstituted benzene rings, the C-C-C symmetric skeletal mode of a tricyclic fused ring system, the N = O symmetric stretch of aromatic nitro groups and the stretching vibrations of various double bonds, several of which possess a high degree of local symmetry.