FOURIER-TRANSFORM IR AND RAMAN-SPECTROSCOPY AND STRUCTURE OF CARBOHYDRATES

To determine the role of the skeletal base configuration of carbohydra te molecules, a comparative study was made, using IR and Raman spectro scopy, of theoretical calculations of the vibrational spectra of a ser ies of carbohydrates differing in the configuration of CO (CH) bonds i n various positions of the pyranose ring. The normal vibrations of car bohydrate molecules have, with few exceptions, close or coinciding fre quencies; however, they differ greatly in the shape and contribution t o the potential energy distribution (PED) of individual groups and bon ds. Despite the cooperative character of the vibrations, each compound is characterized by a specific set of frequencies with a prevailing c ontribution to the PED of particular CO and CC bonds of the molecule. It is concluded that vibrations have a peculiar localization and that steric factors play an important role in the vibrational spectra of ca rbohydrates. (C) 1997 Elsevier Science B.V.