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  • Electronic Resource  (3)
  • 2D INADEQUATE  (1)
  • Bond orders  (1)
  • Chemical shift anisotropy  (1)
  • Highly strained compounds  (1)
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  • Electronic Resource  (3)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical chemistry accounts 71 (1987), S. 277-288 
    ISSN: 1432-2234
    Keywords: Shielding tensors ; MNDO ; Bond orders ; Aromaticity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The Pople model for chemical shielding is applied to calculate the in-plane components of the 13C shielding tensors of condensed aromatic hydrocarbons. The wave functions are evaluated using the MNDO method and the calculated results are supported by the very good agreement with the experimental results in the few cases in which experimental information is available. The relationship found between the calculated bond orders and the in-plane components of the 13C shielding tensors suggest that the experimental study of the 13C shielding tensors in these compounds may provide a powerful technique for studying aromaticity. The in-plane components are found to be directly affected by the degree of delocalization of the π-electrons in the adjacent bonds. Rules are given for estimating the orientation of the two in-plane components of the shielding tensor.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2234
    Keywords: Chemical shift anisotropy ; Highly strained compounds ; Quantum chemical calculation of shielding tensors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The solid state 13C NMR spectra of bicyclo[1.1.0]butane and [1.1.1]propellane have been measured at low temperature. The orientation of the principal axes of the chemical shielding tensor have been determined with ab initio calculations based on the IGLO (Individual Gauge for Localized Orbitals) method when they are not determined by symmetry. Excellent agreement is obtained between the calculated and experimental principal values of the shielding tensor when basis sets containing polarization functions are used. In most cases the agreement is such that the calculated values are within the experimental error.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 33 (1995), S. 803-811 
    ISSN: 0749-1581
    Keywords: NMR ; 13C NMR ; 2D INADEQUATE ; polycyclic benzenoid aromatics ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A computerized analysis of a single 2D INADEQUATE spectra assigns all of the 13C chemical shifts in fairly complex aromatic systems. Without the aid of the computer this information is often difficult, if not impossible, to retrieve owing to overlap of the signals in the double quantum dimension. In addition, the use of the computerized analysis allows for the interpretation of INADEQUATE spectra with much lower signal-to-noise ratios than are practical if the analysis were to be done visually. Finally, narrowing the spectral window to a subset of the entire spectrum and the companion advantages are demonstrated. The assignments of the aromatic chemical shifts in 2-methoxydibenzofuran, 6-methylchrysene, 1-decylpyrene, and 7-methylbenzo[a]pyrene illustrate the power of automated pattern recognition methods while supplying previously unavailable chemical shift assignments on these complex fused polycyclic aromatic systems.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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