VIBRATIONAL-SPECTRA AND STEREOCHEMISTRY OF MONOSACCHARIDES AND POLYSACCHARIDES .3. BETA-METHYL-D-GLUCOSIDE, ALPHA-METHYL-D-GLUCOSIDE, AND BETA-METHYL-D-XYLOSIDE

The IR and Raman spectra of beta- and alpha-methyl-D-glucosides and be ta-methyl-D-xyloside are compared Experimental data are correlated wit h theoretical calculations of the frequencies of normal vibrations. Pr edominant contributions (20% and more) of particular CiOi and CiC(i+1) bonds to the potential energy distribution of normal vibrations (i.e. , localization of vibrations on these bonds, which form skeletons of m onosaccharide molecules) are estimated. This approach is used to inter pret the main distinctions between the IR and Raman spectra of the tes t compounds. The use of vibrational spectra in selective analysis of c ertain functional groups is discussed. It is shown that replacing the hydroxyl group at C1 has a specific effect on the predominant localiza tion of vibrational modes in particular skeletal bonds (mainly in C1O1 ) of the monosaccharide molecules.