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  • Analytical Chemistry and Spectroscopy  (6)
  • 1985-1989  (6)
  • 1965-1969
  • 1
    Electronic Resource
    Electronic Resource
    Indirect 1H—19F—1H and 1H—19F—13C nuclear overhauser enhancements: Anomalous intensity effects and applications in conformational analysis (1987)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 25 (1987), S. 539-543 
    Details
    ISSN: 0749-1581
    Keywords: Indirect heteronuclear NOEs ; 1H-19F-1H and 1H-19F-13C systems ; Three-spin effects ; Anomalous intensity effects ; Conformational analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Indirect nuclear Overhauser enhancements through 19F have been determined for the three-spin systems 1H-19F-1H and 1H-19F-13C by steady-state presaturation of the appropriate proton, and applied to the conformational analysis of 5-bromo-2-fluoro-4-nitroacetanilide. The 1H NOE difference spectra at 400 MHz showed antiphase doublets for protons undergoing simultaneous dipolar relaxation with, and scalar coupling to, 19F. Similarly, in the 13C selective NOE difference spectrum at 100 MHz, the two lines of the fluorine-bearing carbon showed negative enhancement factors of different magnitude on presaturation of the appropriate proton. The use of these anomalous intensity effects in conformational analysis is illustrated.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260250617
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  • 2
    Electronic Resource
    Electronic Resource
    Hydrogen-bonded 2-hydroxybenzalazines: Complete assignment of 1H and 13C NMR spectra (1985)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 23 (1985), S. 879-881 
    Details
    ISSN: 0749-1581
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 80 MHz 1H NMR and 20 MHz 13C NMR spectra of eleven substited benzalazines (subsituenst: α-methyl, α,α′-dimethyl, 2-hydroxy, 2,2′-dihydroxy, 4-n-octyloxy, 4,4′-di-n-octyloxy) possessing mesogenic acivity have been assigned using a variety of one-dimensional techniques. These include homonuclear NOE measurements, selective heteronuclear 13C{1H} NOE difference spectroscopy, singlefrequency off-resonance decoupling, spin - echo multiplicity sorting (SEFT) and long-range heteronuclear coupling constant determintion via both gated decoupling and selective excitation (DANTE).
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260231019
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  • 3
    Electronic Resource
    Electronic Resource
    Measurement of long-range heteronuclear selective 13{1H} NOE enhancements: 4- (α-arylethylidene)-2-phenyl-5(4H)-oxazolones (1985)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 23 (1985), S. 1072-1075 
    Details
    ISSN: 0749-1581
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The technique previously described as two-bond heteronuclear selective NOE difference was improved to yield quantitative data on NOE enhancement factors by recording separately the unperturbed and the perturbed FIDs. In this way the E and Z stereoisomers of 4(α-arylethylidene)-2-phenyl-5(4H)-oxazolones were easily distinguished. The latter showed positive NOE ehancements on quaternary carbons placed two, three and four bonds away from the irradiated methyl protons, as well as a negative NOE on a nearby protonated carbon.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260231209
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  • 4
    Electronic Resource
    Electronic Resource
    Selective heteronuclear NOE enhancements in benzoheterocycles. Effect of ring size on indirect three-spin effects (1988)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 26 (1988), S. 511-517 
    Details
    ISSN: 0749-1581
    Keywords: Heteronuclear NOE ; Selective heteronuclear 13C{1H} NOE ; Indirect Negative NOE ; 13C—1H—{1H} three-spin effects ; Coumarins ; 2(1H)-Quinolones ; Benzo[b]furans ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 80 MHz 1H NMR and 20 MHz 13C NMR spectra of five 4-methylcoumarins, six 4-methyl-2(1H)-quinolones and nine 3-methylbenzo[b]furans, including six new compounds, were fully assigned. Homonuclear 1H{1H} NOEs and selective heteronuclear 13C{1H} NOEs were measured after low-power pre-saturation of the methyl protons. Indirect, negative heteronuclear NOE enhancements were found in suitable three-spin systems of the 13C—1H—{1H} type, and their magnitude was found to be dependent on ring size. The first examples of indirect, heteronuclear NOE enhancements on non-protonated carbons are described.
    Additional Material: 12 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260260615
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  • 5
    Electronic Resource
    Electronic Resource
    Assignment of quaternary carbons via two-bond heteronuclear selective NOE difference, a useful structure elucidation aid (1985)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 23 (1985), S. 185-191 
    Details
    ISSN: 0749-1581
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Very low power irradiation of suitable narrow peaks in the proton frequency range generated NOE enhancement in neighbouring quaternary carbons, positioned two bonds from the irradiated protons. Subsequent FID acquisition under normal broad band decoupling yielded the NOE-containing FID, which, after subtraction of the unperturbed broad band decoupled FID (devoid of NOE), gave the final NOE difference FID to which only the carbons undergoing NOE enhancement had contributed. Fourier transformation of the latter gave the NOE difference spectrum, usually a one- or two-peak spectrum. This technique proved particularly useful for polysubstituted aromatic rings.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260230311
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  • 6
    Electronic Resource
    Electronic Resource
    3,6,9-trioxanthracenes and 3,6-dioxa-9-thianthracenes: Conformational analysis and complete assignment of 13C NMR spectra (1987)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 25 (1987), S. 985-986 
    Details
    ISSN: 0749-1581
    Keywords: 13C NMR ; Heteronuclear ; NOE ; Conformation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 20.15 MHz 13C NMR spectra of five 3,6,9-trioxanthracenes and four 3,6-dioxa-9-thianthracenes have been assigned using a variety of one-dimensional techniques. These include spin-echo multiplicity sorting (SEFT), long-range heteronuclear coupling constant determination via gated decoupling and selective heteronuclear 13C{1H} NOE difference spectroscopy. The axial position of substituents on C-10 has been demonstrated.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260251112
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