Hydrogen bonding vibrational spectroscopic study

Vibrational, spectroscopic studies of water and carbohydrate solutions have been performed, in order to provide information on the nature and variety of hydrogen bonding between molecules (see Sections 11,3 and V,2). It is generally accepted208,209 that i.r.- and Raman-spectral results concerning... 

Q. Du, E. Freysz, and Y. R. Shen, Surface vibrational spectroscopic studies of hydrogen bonding and hydropohobicity. Science 264 (1994) 826. 

In summary, vibrational spectroscopic studies have shown that in the enzyme catalyzed hydride transfer reaction, the substrate C=0 or C=N bond in the Michaelis complex may first be activated in two different ways for the subsequent hydride transfer. For a substrate that contains a C=0 bond to be reduced by the enzyme, strong electron withdrawing interaction due to hydrogen bonding (in LDH) or electrostatic interaction (in LADH) can polarize this bond to reduce the electron cloud near the carbonyl carbon to facilitate the hydride transfer. This is consistent with theoretical studies that one of the driving forces for the hydride transfer is the large... 

Mention should be made of infrared spectroscopic studies performed to determine the strength of hydrogen-bonded solvation these studies characterized the strength of the interaction by means of the shift in the X—H vibration (where X may be oxygen, nitrogen or fluorine) and by the changes in width and intensity of the band [Bu 59, Bu 61, Ha 72, Hy 62, Lu 58, Sc 59]. 

Bll. Vibrational spectroscopic studies on the Hydrogen Bonding and Aggregation in Surfactant Solutions. 

Studies of the X—Y stretching vibration in complexes of XY with different Lewis bases reveal a characteristic decrease in frequency as the strength of the base increases [35, 36]. Hence spectroscopic scales of halogen-bond basicity can be built [37] in the manner described in Chapter 4 for the O—H stretching vibration in hydrogen-bonded complexes. Spectroscopic scales based on the shifts of the v(I—I) band of diiodine at 211 cm , the u(I—Cl) band of iodine monochloride at 376 cm and the v(I—CN) band of iodine cyanide at 485 cm will be presented and compared with thermodynamic basicity and/or affinity scales. 

The simplest unsaturated alcohol with ip3-carbon O—H is allyl alcohol (propenol). The monomer occurs in two energetically similar conformations in the gas phase [145, 240], which are both stabilized by intramolecular O—H- -n interactions. The dimer has only been studied in matrix isolation [241]. Spectroscopic evidence for an intermolecular O—H ji hydrogen bond was found. A vibrational (IR and Raman) supersonic jet measurement would be able to unravel the different monomer and dimer conformations involved. 

S. Jarmelo, N. Maiti, V. Anderson, P. R. Carey, and R. Fausto, Ca H bond stretching frequency in alcohols as a probe of hydrogen bonding strength A combined vibrational spectroscopic and theoretical study of n [1 Djpropanol. J. Phys. Chem. A 109, 2069 2077 (2005). 

The EFG data from the multipole parameters are, in principle, for the static crystal while the spectroscopic data are affected by vibrations. There may therefore by a systematic difference between the two sets of values, which is evident for a number of hydrogen-bonded hydroxyl groups and water molecules studied by Tegenfeldt and Hermansson (1985), but is not apparent in the data in Table 8.3. The EFG values for H atoms in hydrogen-bonds is further discussed in chapter 12. 

The complexity of the physical properties of liquid water is largely determined by the presence of a three-dimensional hydrogen bond (HB) network [1]. The HB s undergo continuous transformations that occur on ultrafast timescales. The molecular vibrations are especially sensitive to the presence of the HB network. For example, the spectrum of the OH-stretch vibrational mode is substantially broadened and shifted towards lower frequencies if the OH-group is involved in the HB. Therefore, the microscopic structure and the dynamics of water are expected to manifest themselves in the IR vibrational spectrum, and, therefore, can be studied by methods of ultrafast infrared spectroscopy. It has been shown in a number of ultrafast spectroscopic experiments and computer simulations that dephasing dynamics of the OH-stretch vibrations of water molecules in the liquid phase occurs on sub-picosecond timescales [2-14],... 

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