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  • 1
    Electronic Resource
    Electronic Resource
    An NMR study of some N-arylaminopropenylylidenearylammonium salts (1975)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 7 (1975), S. 401-404 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The preparation, characterisation and 1H NMR spectra of some N-arylaminopropenylylidenearylammonium salts are reported. The NMR data show that in DMSO the cations exist as conjugated amino-imines, generally as the ‘all-trans’ geometrical isomer. An exception is found in the case of the 4-nitrophenyl derivative which produces a mixture of the ‘all-trans’ and ‘cis-trans’ isomers with slow exchange between them at room temperature. The relative stability of the ‘all-trans’ isomer increases as the salt becomes more ionic. By varying the temperature, pH and nature of the anion it is found that exchange of the N—H protons on the cation controls the appearance of spin-spin coupling between the N—H and 1,3-propene protons.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270070809
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  • 2
    Electronic Resource
    Electronic Resource
    Calculation of some fluorine nuclear screening constants (1977)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 10 (1977), S. 70-74 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 19F screening constants and their anisotropies have been calculated for 50 fluorine molecular environments. The calculations have been performed within a framework in which gauge-dependent atomic orbitals are used in the molecular orbital description. Calculations employing both INDO and CNDO/S standard parameterizations are reported. The molecules considered include simple binary fluorides and fluorocarbons. Both sets of calculations provide reasonable accounts of the 19F screening data for the binary fluorides. The presence of electric field effects in the aliphatic fluorocarbons are not accounted for by the present calculations. In the conjugated fluorocarbons the gross 19F chemical shift trend is reproduced except for ortho fluorines where electric field contributions are significant. The most highly screened component of σ is calculated to lie along the C—F bond of various fluorobenzenes but perpendicular to the plane of 4,4′-difluorobiphenyl, in agreement with experiment.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270100118
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  • 3
    Electronic Resource
    Electronic Resource
    NMR studies on some 1,3,5-triazaadamantane derivatives (1978)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 11 (1978), S. 103-105 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1H and 13C data are presented for eleven 1,3,5-triazaadamantane derivatives. Ring protonation produces a decrease in 1H screening and the opposite effect in the corresponding 13C spectrum. The trisaryl substituted compounds appear to exist as a single isomer with diequatorial and monoaxial substituents.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270110209
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  • 4
    Electronic Resource
    Electronic Resource
    13C NMR: Substituent effects on one-bond 15N—13C coupling constants in anilines and anilinium ions (1979)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 12 (1979), S. 1-4 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1J(15N13C) values obtained from FT 13C NMR spectra were measured for a number of 15N-enriched aniline derivatives and are found to exhibit varying degrees of dependence on the nature of the ring substituent. Theoretical calculations of 1J(15N13C) values for representative members of the systems examined were made using INDO parameters and a ‘sum-over-states’ perturbation approach. The calculated coupling constants are generally in fair agreement with experimental values when the integral products SN2(o)SC2(o) and (r-3)N(r-3)C have values of 34.437 au-6 and 2.770 au-6, respectively.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270120102
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  • 5
    Electronic Resource
    Electronic Resource
    A study of the use of MINDO/3 parameters in calculations of carbon and nitrogen screening constants (1979)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 12 (1979), S. 174-177 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The calculation of some carbon and nitrogen screening constants and chemical shifts is reported. The independent electron theory developed by Pople is used as the basis of the calculations. Within this framework the MINDO/3 parameterization scheme is employed and shown to provide quantitatively unreliable results. Improved agreement with the experimental data is found when the electronic excitation energies are taken from INDO/S parameterized calculations. The relative lack of success achieved by the MINDO/3 calculations is probably a reflection on the inability to reproduce the electronic excited states satisfactorily.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270120310
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  • 6
    Electronic Resource
    Electronic Resource
    Application of 15N spectroscopy and dynamic NMR to the study of ureas, thioureas and their lewis acid adducts (1980)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 13 (1980), S. 396-402 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Rotational barriers and 15N chemical shifts have been measured in a number of ureas and thioureas. As anticipated on the basis of the 15N shifts, several previously unobserved rotational barriers could be detected by using lanthanide reagents or a high field spectrometer. Nearly constant effects on both the rotational activation energy and the 15N shift are produced on going from ureas to the corresponding thioureas, and correlations are found between the ΔG
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270130603
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  • 7
    Electronic Resource
    Electronic Resource
    Some calculations of solvent effects on 17O and 19F chemical shifts (1980)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 14 (1980), S. 92-97 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Sum-over-states perturbation and finite perturbation calculations, within the ‘Solvaton’ model, are presented for the variation of some 17O and 19F chemical shifts as a function of the dielectric constant of the medium. In general, the nuclear screening and charge are predicted to increase as the dielectric constant increases. The effects of hydrogen bonding are included by means of minimum energy dimer models in some of the sum-over-states calculations.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270140204
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  • 8
    Electronic Resource
    Electronic Resource
    Some INDO calculations of the dependence of one-bond phosphorus-phosphorus coupling upon molecular geometry (1983)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 21 (1983), S. 199-202 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Some INDO parameterized SCPT calculations of 1J(P—P) and 1J(P≡P) are reported as a function of geometry. At structures corresponding to the gas-phase equilibrium configuration of diphosphine, all of the substituted diphosphines considered are predicted to have negative values of 1J(P—P). Both contact and non-contact contributions to 1J(P—P) are significant, whereas the angular variation of 1J(P—P) is mainly due to the contact term. The non-contact interactions are dominant in determining the value of 1J(P≡P).
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/omr.1270210312
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  • 9
    Electronic Resource
    Electronic Resource
    Some calculations of the solvent dependences of phosphorus nuclear shielding (1983)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 21 (1983), S. 399-402 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Some CNDO/S parameterized calculations of phosphorus shielding, as a function of the dielectric constant of the medium, are presented. Pople's SOS perturbation approach together with the solvaton model are employed. For trivalent phosphorus compounds a shielding decrease by up to 15 ppm is predicted as ε increases from 1 to 80. For pentavalent phosphorus a much smaller shielding variation, in the opposite direction, is predicted. In general, a consideration of changes in phosphorus charge density is insufficient to account for the variation in nuclear shielding.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/omr.1270210613
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  • 10
    Electronic Resource
    Electronic Resource
    Some CNDO/S parameterized calculations of intramolecular effects on nuclear shielding (1984)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 22 (1984), S. 90-92 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Some shielding calculations, using Pople's SOS model, are reported for B, C, N, F, P and Si as a function of changes in bond length and pyramidal bond angle. In all cases considered, the shielding is predicted to decrease as the bond length increases, which is in line with the available experimental data. The observed temperature variation of the nitrogen and phosphorus shieldings of NH3, PH3 and PF3 could be accounted for by a decrease in the pyramidal angle at higher temperatures. A similar angular variation for NF3 is predicted to cause a shielding variation, with temperature, in the same sense as that reported for NH3 and PH3, but opposite to that for PF3.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270220207
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