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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 35 (1999), S. 431-449 
    ISSN: 1573-1111
    Keywords: Triphenylmethanol ; inclusion ; structure ; 2H NMR ; dynamics ; thermal stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The crystal structure of an inclusion compound formed by triphenylmethanol with di-methylformamide was determined (space group P1 with a = 898.8(3) pm, b = 1022.3 pm, c = 1177.3pm, α =104.57(1)°, β = 110.32(1)°, γ = 96.76(1)°, Z = 2 at T = 300 K). The structure of compounds formed with acetone and dimethylsulfoxide were rerefined. A new assignment for the acetone compound in space group P21/n allowed a better ordered description of the molecule. The structure of the dimethylsulfoxide compound at 100 K did not indicate a phase transition and reproduced basically the room temperature structure. The results were compared with the known structures of clathrates formed by triphenylmethanol with methanol and 1,4-dioxane. All triphenylmethanol inclusion compounds are unstable, and therefore their decomposition during heating was analysed by both thermalanalysis and X-ray powder diffraction. Vapor pressure measurements of the inclusion compounds were performed from 283 to 376 K. For the pure host no marked vapor pressure was detected in this temperature range with the setup used. From the logarithmic plots of vapor pressures versus temperature the heats of vaporization were determined. The dynamics of the deuterated guest molecules were studied by measurement of the temperature dependence of the 2H NMR signals derived from powder spectra in the range 120–335 K.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0947-3440
    Keywords: Pyridinethione ; Thiohydroxyamic acid ester ; Pyridone ; Alkoxyl radical precursor ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Although Barton's radical precursors, the O-acyl derivatives of 1-hydroxypyridine-2(1H)-thione 2, have been studied in detail for more than a decade, to date nothing has been reported on the solid state or the solution geometries of these molecules or the analogous oxo derivatives, the pyridones 7, 8. In view of this, selected O-alkyl and O-acyl derivatives of pyridinethiones and of 2-(1H)pyridones have been prepared and investigated by X-ray diffraction and NMR (COSY, NOE) experiments. The X-ray data indicate alternating bond lengths in the carbon framework of the heterocycles 2d, 3b, 7b, and 8 and long N—O bonds [1.394(4)-1.398(2) Å]. In all the compounds studied, the O-alkyl and the O-acyl groups are twisted out of the plane of the heterocycles, which is in accord with the VSEPR concept. Further, the thermal stabilities of thiohydroxamic acid derivatives 2, 3 and of substituted pyridones 7, 8 were studied by differential scanning calorimetry (DSC).
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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