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  • 1
    ISSN: 0894-3230
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The crystal structure at 200 K of the complex formed by the optically active host (R,R)-(-)-trans-4,5-bis(hydroxydiphenylmethyl)-2,2-dimethyl-1,3-dioxolane (2) and 4-nitro-5-methylpyrazole (1b) and toluene as guests was determined by x-ray analysis. Although only the NH protons corresponding to tautomer 1b were found in the structure, some anomalies in the bond angles involving the nitrogen atoms of the pyrazole ring suggested the presence of about 25% of a structure containing the 3-methyl-4-nitropyrazole tautomer (1a). This hypothesis was confirmed by 13C cross polarization magic angle spinning NMR spectroscopy.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 10 (1997), S. 637-645 
    ISSN: 0894-3230
    Keywords: 3-nitropyrazole ; structure ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: ---The molecular and crystal structure of 3-nitropyrazole was determined by X-ray analysis. The triclinic unit cell contains 12 molecules which form four hydrogen-bonded (N - H···N) trimers. Each trimer comprises of pseudo-ring in a flattened envelope distorted towards a chair conformation. The crystal packing consists of layers formed by centrosymmetric related trimers joined through C - H···O interactions. Ab initio calculations were performed on 3(5)-nitro- and 4-nitropyrazole and their corresponding protonated forms up to the MP2/6-31G** level of theory. The origin of the difference in aqueous basicities between both nitropyrazoles is discussed. © 1997 John Wiley & Sons, Ltd.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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