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  • 1
    Electronic Resource
    Electronic Resource
    Molecular structure of 4-(3,5-dimethylpyrazol-1-yl)benzoic acid trifluoroacetate (1996)
    Springer
    Journal of chemical crystallography 26 (1996), S. 579-584 
    Details
    ISSN: 1572-8854
    Keywords: Hydrogen bonds ; 13C CPMAS NMR ; benzoic acid ; pyrazoles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal and molecular structure of the title compound has been determined by X-ray analysis. 4-(3,5-Dimethylpyrazol-l-yl)benzoic acid trifluoroacetate crystallizes in the 12/a space group witha=20.6584(13),b=9.9068(3),c=14.9467(6) Å, β=106.195(4),V=2937.6(2) Å3, Dc=1.494 g/cm3 andZ=8. The ions pack in chains parallel to thea axis through O−H⋯O and N−H⋯O hydrogen bond interactions. Solid-state13C CPMASNMR spectroscopy has been used to compare the structure of the trifluoracetate with that of the neutral molecule [4-(3,5-dimethylpyrazol-l-yl)benzoic acid].
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01668419
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  • 2
    Electronic Resource
    Electronic Resource
    Tautomerism and the Mills-Nixon-like effect in pyrazoles (1997)
    Springer
    Structural chemistry 8 (1997), S. 189-195 
    Details
    ISSN: 1572-9001
    Keywords: Mills-Nixon-like effect ; AM1 calculations ; ab initio calculations ; annular tautomerism ; NH-pyrazoles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Theoretical calculations on a wide variety of NH-pyrazoles clearly show a relationship between ring strain and annular tautomerism, i.e., the most stable tautomer is that having the largest singleond character in the C3-C4 bond.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02263506
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  • 3
    Electronic Resource
    Electronic Resource
    A General Equation Holds for the Geometry of Hydrogen Bonds with O and N Acceptors (1999)
    Springer
    Structural chemistry 10 (1999), S. 157-159 
    Details
    ISSN: 1572-9001
    Keywords: Hydrogen bonds ; bond length relationships ; ab initio and crystallographic data
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A unique equation able to correlate two geometrical parameters in hydrogen-bonded (HB) systems, the X—H covalent bond distance of the donor and the H•••Y distance of the acceptor, has been devised. The equation is able to fit high-quality crystallographic data of different HB donors and several nitrogen and oxygen acceptors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022041532090
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  • 4
    Electronic Resource
    Electronic Resource
    Bond Length–Electron Density Relationships: From Covalent Bonds to Hydrogen Bond Interactions (1998)
    Springer
    Structural chemistry 9 (1998), S. 243-247 
    Details
    ISSN: 1572-9001
    Keywords: Hydrogen bonds ; electron density ; bond critical points ; DFT calculations ; Pauling's bond order ; bond length
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract It is possible to treat bond distances of covalent C-H bonds and C⋯H hydrogen bonds simultaneously assuming a logarithmic relationship with the electron density at the bond critical point. Similar relationships have been found for other X-H/X⋯H bonds. The data used for obtaining these equations have been determined theoretically. All the systems have been fully optimized and their electron densities calculated at the B3LYP/6-311 + + G(d,p) level.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022424228462
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  • 5
    Electronic Resource
    Electronic Resource
    On the Tautomerism of 2-Phenacyl-4-pyrimidinones and Related Compounds (1989)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 122 (1989), S. 919-924 
    Details
    ISSN: 0009-2940
    Keywords: Pyrimidinones ; Tautomerism ; AM1 calculations ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zur Tautomerie von 2-Phenacyl-4-pyrimidinonen und verwandten Verbindungen3-Methyl-2-phenacyl-4-pyrimidinone 1, 2 werden durch Sulfidkontraktion synthetisiert. Aufgrund der NMR-Daten existieren die Verbindungen ausschließlich in der Benzoylmethylen-Form, sowohl in Lösung als auch als Festkörper. Diese Ergebnisse werden durch AM1-Berechnungen für die Stammverbindung bestätigt. Die Untersuchung des Tautomeren-Gleichgewichts mittels dieser semiempirischen Methode wurde auf andere Fälle von Enaminoketon/Enolimin-Tautomerie erweitert.
    Notes: 3-Methyl-2-phenacyl-4-pyrimidinones 1, 2 have been synthesized using the sulfide contraction. According to the NMR data, the compounds 1, 2 exist exclusively as the benzoylmethylene tautomers a both in solution and in the solid state. AM1 calculations of the parent system are in agreement with the experimental observations. The study of the tautomeric equilibrium by this semiempirical method has been extended to other cases of enamino-ketone/enolimine tautomerism.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19891220521
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  • 6
    Electronic Resource
    Electronic Resource
    15N NMR chemical shifts of NH-pyrazoles in the solid state and in solution at low temperature (1994)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 32 (1994), S. 699-702 
    Details
    ISSN: 0749-1581
    Keywords: 15N CP MAS NMR ; Tautomerism ; Pyrazoles ; Hydrogen bonds ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 15N chemical shifts of thirteen NH-pyrazoles in the solid state and of seven NH-pyrazoles in [2H8] THF solution at 170-175 K (with frozen annular tautomerism) are reported. The solid-state values are discussed using an additive model. The differences in chemical shifts between the solid state and solution are due to the different intermolecular hydrogen bonds present in the various environments.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260321110
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