Spectroscopy of Stereoisomeric forms of Mono- and Polysaccharides

To elucidate the role of the skeletal base configuration of carbohydrate molecules, a comparative study has been made by the methods of FT IR and Raman spectroscopy, of theoretical calculations of vibrational spectra of a series of carbohydrates differing in configuration of C-O (C-H) bonds in various positions of the pyranose cycle. It is shown that normal vibrations of carbohydrate molecules have, with few exceptions, close or coinciding frequencies, differing greatly, however, in shape and contribution to the potential energy distribution (PED) of individual groups and bonds. It has been found that despite the cooperative character of vibrations each compound is characterised by a specific set of frequencies with the prevailing contribution to the PED of particular C-O and C-C bonds of the molecules skeleton. It has been concluded that vibrations have peculiar localisation and the steric factors play an important part in the formation of vibrational spectra of carbohydrates [1].