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  • 13C NMR  (8)
  • Wiley-Blackwell  (8)
  • International Union of Crystallography
  • Oxford University Press
  • 2020-2022
  • 1985-1989  (8)
  • 1940-1944
  • 1987  (8)
  • 1
    Electronic Resource
    Electronic Resource
    13C NMR studies of the friedelane series of triterpenoids and the conformation of the D and E rings in friedelan-7-oneDedicated to Proof. Ajay K. Bose on his sixtieth birthday. (1987)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 25 (1987), S. 39-41 
    Details
    ISSN: 0749-1581
    Keywords: 13C NMR ; Friedelanes ; Triterpenoids ; D/E ring conformation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 13C chemical shifts in the spectra of friedelan-7-one (1), methyl 3-oxofriedelan-25-oate (2), methyl friedelan-25-oate (3), 7-oxofriedelan-3-α-yl acetate (4), friedelan-3-one (5), 2-hydroxy-3, 4-seco-friedelan-3-oic acid (6), methyl 2-oxo-3,4-seco-friedelan-3-oate (7), methyl 2-hydroxy-3,4-seco-friedelan-3-oate (8) and 3,4-seco-friedelan-2,3-diol (9) have been fully assigned using two-dimensional heteronuclear correlation NMR spectroscopy, BB proton decoupled, DEPT and selective heteronuclear spin decoupling methods. These assignments and the observation of substantial NOEs between 26-methyl and 28-methyl and between 28-methyl and 30-methyl support the boat to boat conformations for the D and E rings in 1. Corrections and correlations are made of some earlier literature assignments of friedelanones.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260250110
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  • 2
    Electronic Resource
    Electronic Resource
    NMR study of substituent effects in 4-substituted and 4,4′-disubstituted diphenyl sulphides (1987)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 25 (1987), S. 1001-1006 
    Details
    ISSN: 0749-1581
    Keywords: 1H NMR ; 13C NMR ; Diphenyl sulphides ; substituent effects ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The proton and carbon NMR spectra of nine 4-X-diphenyl sulphides (series 1), seven 4-X-4′-NO2-diphenyl sulphides (series 2) and eight 4,4′-X2-diphenyl sulphides (series 3) have been obtained. Correlation of the 13C chemical shifts with the appropriate substituent chemical shifts (SCS) for monosubstituted benzenes (Lynch plots) show an enhancement of substituent effect at C-1 (carbon para to the substituent) in series 1 and 2, but not in series 3. The carbons of the unsubstituted ring in series 1 also correlate with Cp-SCS, with slopes of less than unity; correlation for C-1′ has a negative slope. Dual substituent parameter (DSP) correlations of the 13C chemical shifts with σI/σoR are good to excellent for all the carbons of series 1 compounds, except those ortho to the substituent X. The carbons meta to the substituent X correlate well, but with negative values for ρI and ρR, although showing a scattered Lynch plot. Similar correlations are found with some carbon shifts in series 2, and with C-1 shifts in series 3.It is concluded that (a) reverse resonance effects are operative at the position meta to the variable substituent by virtue of the sulphur substituent ortho to that carbon; (b) there is transmission of inductive (field) and resonance effects from one aryl ring to the other, except when both rings carry substituents of the same electronic character (series 3); (c) there is some evidence for π-polarization in the unsubstituted phenyl ring of series 1 compounds.
    Additional Material: 10 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260251117
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  • 3
    Electronic Resource
    Electronic Resource
    13C NMR spectra of polyalkoxymethanes, and their sulphur- and nitrogen-containing analogues, of an aliphatic series. Inclusion of non-bonded interactions by the use of C—O bond increments (1987)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 25 (1987), S. 1-7 
    Details
    ISSN: 0749-1581
    Keywords: 13C NMR ; Acetals ; Carbonates ; Ortho ethers ; Hetero analogues ; Co bond increments ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 13C NMR spectra of 40 substituted acetals, carbonates, ortho ethers, 1,3-dioxocycloalkanes, 1,3-oxothiolanes and 1,3-oxazolidines were studied. The chemical shift of the C-α carbon atom was found to depend both on the number (K) and type of the hetero substituents at C-α. The effect of oxygen, nitrogen and sulphur atoms on the C-α chemical shift was shown to be a non-additive property relative to the unsubstituted isostructural hydrocarbons. The C-α chemical shift in the linear and cyclic polyalkoxymethanes can be described by an equation incorporating C—O bond increments and contributions from the RO substituents: \documentclass{article}\pagestyle{empty}\begin{document}$$ \delta \left({^{13} {\rm C} - \alpha } \right) = \delta \left({^{13} {\rm CH}_4 } \right) + K\Delta \delta \left({{\rm C} - {\rm O}} \right) + \sum _k \Delta {\rm RO} $$\end{document}The C—O increment depends quadratically on the number (K-1) of geminal neighbours of the oxygen atom under study. Good agreement between the experimental and calculated shifts can only be achieved by inclusion of nonbonded interactions between the geminal heteroatoms.
    Additional Material: 6 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260250102
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  • 4
    Electronic Resource
    Electronic Resource
    1H and 13C nuclear magnetic resonance study of 1,3-dipyridylthioureas for chemical shift assignments and conformational analysis (1987)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 25 (1987), S. 474-479 
    Details
    ISSN: 0749-1581
    Keywords: 1H NMR ; 13C NMR ; 1,3-Dipyridylthioureas ; Conformation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A study of molecular conformation by 1H and 13C NMR methods of three 1,3-dipyridyl thioureas namely, 1,3-di(2-pyridyl)thiourea (1), 1,3-di(3-pyridyl)thiourea (2), 1-(2-pyridyl)-3-(3-pyridyl)thiourea (3), and also of 1-phenyl-3-(2-pyridyl)thiourea (4) and 1,3-diphenylthiourea (5), included for the sake of comparison, was carried out. Evidence was obtained that 3 and 4 exist in solution solely in one form, in an internally hydrogen bonded E,Z conformation, whereas 1, 2 and 5 exist in two (or more) rotamer forms. The data reveal an interesting dynamic exchange phenomenon occurring in 1 between two intramolecularly hydrogen bonded conformers. The 1H and 13C chemical shifts, 1H,1H and 13C,1H coupling constants are reported. The 13C and 1H chemical shifts are correlated with the electron densities calculated by the CNDO method.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260250603
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  • 5
    Electronic Resource
    Electronic Resource
    13C NMR spectra of some sulphur dioxide - aromatic amine complexes (1987)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 25 (1987), S. 592-593 
    Details
    ISSN: 0749-1581
    Keywords: Molecular complexes ; Sulphur dioxide ; Aromatic amines ; 13C NMR ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 13C NMR spectra of equilibrium mixtures formed between sulphur dioxide and N-methylbenzenamine, N,N-dimethylbenzenamine and N,N-diethylbenzenamine were obtained. The analysis of the spectral data indicates that the interaction of the amines with the Lewis acid occurs by means of the lone pair mainly localized on the nitrogen atom, and that the complexes can be considered as labile on the time scale of the experiment.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260250708
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  • 6
    Electronic Resource
    Electronic Resource
    Triterpenoids. Part II - For Part I, see Acta Crystallogr. in press.Carbon-13 NMR spectra of 18β- and 18α-11-oxooleanolic acid derivatives (1987)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 25 (1987), S. 223-226 
    Details
    ISSN: 0749-1581
    Keywords: 13C NMR ; 18β-11-oxooleanolic acid derivatives ; 18α-11-oxooleanolic acid derivatives ; D/E ring junction ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 13C NMR spectra of five pairs of 18β- and 18°-11-oxooleanolic acid derivatives have been assigned. The chemical shifts of C-12, C-13, C-17, C-18 and C-28 are of diagnostic value for the determination of the D/E junction stereochemistry.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260250309
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  • 7
    Electronic Resource
    Electronic Resource
    A substituent chemical shift (SCS) effect study by 13C and 19F NMR of para-substituted phenylhalodiazirines (1987)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 25 (1987), S. 923-927 
    Details
    ISSN: 0749-1581
    Keywords: 13C NMR ; 19F NMR ; substituent induced ; chemical shifts ; p-substituted phenylhalodiazirines ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A range of 3-(para-substituted-phenyl)-3-halodiazirines have been prepared and their 13C and 19F NMR spectra measured. Calculated with these data were the susceptibility coefficients ρI and ρR of the inductive (σI) and resonance (σR0) effects, respectively, to substituent-induced chemical shift differences at the diazirine carbon (13C NMR) and the 3-fluorine (19F NMR of the 3-fluorodiazirine series). An inverse relationship was found between the susceptibility parameters and the electronegativity of the halo substituent at the diazirine carbon.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260251018
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  • 8
    Electronic Resource
    Electronic Resource
    Carbon-13 NMR line width and relaxation studies of tert-butyl bromide and tert-butyl cyanide (1987)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 25 (1987), S. 1063-1068 
    Details
    ISSN: 0749-1581
    Keywords: 13C NMR ; Line width Relaxation ; Orientationally disordered tert-butyl compounds ; Molecular motion Correlation times ; Activation energies ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Proton and 13C line widths and 13C spin-lattice relaxation times (T1) were measured over a wide temperature region in liquid and solid tert-butyl bromide (1) and tert-butyl cyanide (2). A striking feature of the proton and 13C NMR spectra of 1 is the abrupt line narrowing at the phase I → phase II transition point. In 2, however, the line width does not vary with temperature in phase I, indicating that the translational motion is too slow to affect the line width.An analysis of spin-lattice relaxation times in both the liquid and solid phases is reported. It is shown that 13C T1 measurements can distinguish between internal methyl group reorientation (C3 motion) and uniaxial molecular reorientation of tert-butyl groups (C3′ motion) if these motions are independent and responsible for the T1 relaxation over a large part of the temperature region. The 13C spin-lattice relaxation mechanism in the liquid and disordered phases of 1, and the liquid phase of 2, is governed by overall molecular tumbling with an activation energy of 8-11 kJ mol-1. The 13C T1 data show that the faster motion in the ordered phases of 1 and 2 is the C3′ reorientation with an activation energy of 15-18 kJ mol-1 while the slower motion is the C3 reorientation with an activation energy of ca 19 kJ mol-1.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260251209
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