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OH Stretching Vibrations (oh + stretching_vibration)
Selected AbstractsCharacteristics of hydrogen bond formation between sugar and polymer in freeze-dried mixtures under different rehumidification conditions and its impact on the glass transition temperatureJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 3 2008Koreyoshi Imamura Abstract The characteristics of hydrogen bond formation between trehalose and polyvinylpyrrolidone (PVP) in amorphous mixtures at different hydration states were quantitatively investigated. Amorphous trehalose,PVP mixtures were prepared by freeze-drying and equilibrated at different relative humidities (RH). Infrared (IR) spectra of the trehalose,PVP mixtures were obtained by Fourier transform IR spectroscopy,(FTIR) and the IR band corresponding to CO groups of PVP was deconvolved into the component bands responsible for CO groups that were free and restricted by hydrogen bonds, to estimate the degree of the trehalose,PVP interactions. The FTIR analysis indicated that approximately 80% of the CO groups of PVP formed hydrogen bonds with trehalose in the presence of more than 3 g of trehalose per gramme of PVP, independent of the RH. IR analysis of the OH stretching vibration of the sugar demonstrated that the presence of PVP lead to an increase in the free hydroxyl groups of trehalose that did not form hydrogen bonds at RH 0%. On the other hand, the water sorption behavior of the trehalose,PVP mixtures suggested that rehumidification diminished the effect of PVP on increasing the free OH groups. Thus a peculiar relationship may exist between Tg, RH and the composition of the mixture: The presence of PVP increased Tg at RHs 0 and above 23% but decreased Tg at 11%. © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97:1301,1312, 2008 [source] Raman spectroscopic study of the uranyl phosphate mineral dumontite Pb2 [(UO2)3O2(PO4)2]·5H2 OJOURNAL OF RAMAN SPECTROSCOPY, Issue 6 2009Ray L. Frost Abstract Raman spectra of dumontite were measured at 298 and 77 K. Observed bands were attributed to the stretching and bending vibrations of uranyl and phosphate units and OH stretching vibrations of water molecules. U,O bond lengths in uranyls and approximate O,H···O bond lengths were calculated. The values of the U,O bond lengths are in agreement with the data from the single crystal structure analysis of dumontite. Copyright © 2008 John Wiley & Sons, Ltd. [source] Pressure effects on inter- and intramolecular vibrations in hydrogen-bonded L -ascorbic acid crystalJOURNAL OF RAMAN SPECTROSCOPY, Issue 1 2008Hiroko Shimada Abstract Pressure effects on the Raman spectra due to the inter- and intramolecular vibrations of the L -ascorbic acid crystal were studied. The intensity of the Raman bands due to the intermolecular vibrations varies in three different ways by application of pressure. The bands of the first group become stronger, those of the second one become weaker and the third group shows no prominent change in their intensity with increasing pressure. The bands due to the intermolecular vibrations show a blue shift, while the bands due to the intramolecular vibrations shift to the blue or red depending on the vibrational modes by application of pressure. The bands assigned to the OH stretching vibrations shift to the red, the bands assigned to the CO and CC stretching vibrations shift a little to the red and the bands assigned to the other vibrations shift to the blue under high pressure. The following conclusions were derived. (1) The hydrogen bonds forming helixes become stronger and the isolated hydrogen bond becomes weaker with increasing pressure. (2) The bands of the first group owing to the intermolecular vibrations are ascribed to the vibrations related to the helix hydrogen bonds and the second group bands to the isolated hydrogen bond. (3) The CO stretching vibration couples with the CC stretching vibration. (4) The phase transitions take place at 1.8 and 4 GPa in the crystal. Copyright © 2007 John Wiley & Sons, Ltd. [source] Energy Transfer in Single Hydrogen-Bonded Water MoleculesCHEMPHYSCHEM, Issue 6 2005Huib J. Bakker Prof. Abstract We study the structure and dynamics of hydrogen-bonded complexes of H2O/HDO and acetone dissolved in carbon tetrachloride by probing the response of the OH stretching vibrations with linear mid-infrared spectroscopy and femtosecond mid-infrared pump,probe spectroscopy. We find that the hydrogen bonds in these complexes break and reform with a characteristic time scale of ,1 ps. These hydrogen-bond dynamics are observed to play an important role in the equilibration of vibrational energy over the two OH groups of the H2O molecule. For both H2O and HDO, the OH stretching vibrational excitation relaxes with a time constant of 6.3±0.3 ps, and the molecular reorientation has a time constant of 6±1 ps. [source] | ||||||||||