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  • 1
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The infrared absorption and Raman spectra of SrCl2·2H2O powder as well as SrCl2·2D2O, and partially deuterated and isotopically dilute samples, have been recorded in the range from 30 to 4000 cm-1 at 95 and 295 K and analysed with regard to the strongly asymmetric force field in the H2O molecules. This is shown by an unusually large splitting of the OH and OD stretching fundamentals of the HDO molecules: 3426 and 3243 cm-1 and 2534 and 2408 cm-1 respectively at 95 K. Uncoupled OD stretching frequencies of SrCl2·6H2O and SrCl2·H2O are also presented. In SrCl2·2H2O both a relatively strong and a weak hydrogen bond to chloride ions are present; these are essentially straight.The spectra of SrCl2·2H2O exhibit the following characteristics: (1) no intramolecular coupling of the OH stretching vibrations; (2) very large Fermi resonance of νOH and 2δH2O; (3) the same high intensity of H2O twisting librations in the infrared spectra as for wagging and rocking modes; (4) splitting of the librational fundamentals of the HDO molecules, as large as 100 cm-1, caused by different structural arrangements of the H and D atoms in the asymmetric H2O molecules; and (5) strong intermolecular coupling of bending and librational fundamentals, which results in correlation splittings up to 75 cm-1. Possibilities of assigning the librational modes of H2O molecules which are in an asymmetric force field are discussed.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Low temperature infrared and Raman spectra of polycrystalline BaBr2·2H2O at different degrees of deuteration are studied in the frequency range from 4000 to 30 cm-1. The single peaks observed for the bending fundamentals of isotopically dilute H2O and D2O show that the molecules of the water of crystallization are equivalent, as required by Bang's structure determination. The singlets observed for the three fundamentals of isotopically dilute HDO show that there is a symmetric force field in the water molecules which is not predicted from the structure determination. In BaBr2·2H2O weak hydrogen bonds to the bromine ions are present which are largely bent. From the shift of the stretching modes relative to the frequencies of free water the hydrogen bond enthalpy was found to be 20 kJ. The temperature shifts of all the stretching modes are positive, which is not in agreement with Falk's results on bent hydrogen bridges. The internal modes and the twisting libration of the water molecules show an unusual large correlation splitting due to intermolecular coupling of the vibrations of the two water molecules in the 2Br-·2H2O structure unit.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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