A theoretical study of vibrational spectra of tetranitrate-methyl-β-D-glucopyranoside and 2,3-di-O-nitro-methyl-β-D-glucopyranoside

Coupled calculations were carried out of normal vibration frequencies from the point of view of the valence-force field scheme and of absolute IR band intensities by the CNDO/2 method for the tetranitrate-methyl-beta-D-glucopyranoside molecule. A good agreement was achieved with the experiments. Normal coordinate analysis was made for 2,3-di-O-nitro-methyl-beta-D-glucopyranoside molecule with force constants obtained for the tetra-nitrate-methyl-beta-D-glucopyranoside. Before proceeding to the calculation of the spectra of such complex molecules of nitrates of monosaccharides, a complete experimental and theoretical investigation was performed of the vibrational spectra of methylnitrate, which made it possible to determine the deficit of force constants for the calculations of the spectra of nitrosubstituted glucopyranosides. Detailed interpretations of the observable IR spectra of both the nitro-glucopyranosides compounds considered are given. The absorption spectra sensitivity to the spot of the nitrate group localization was discovered. Special attention was focused on analyzing the spectra of nitrates of saccharides for the characteristic split of the band due to the asymmetric stretching vibrations of the ONO2 groups in the region of 1700-1600 cm(-1). (C) 1998 Elsevier Science B.V.