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  • 1
    Electronic Resource
    Electronic Resource
    Hydrogen resonance spectrum of cyclobutanone (1967)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 71 (1967), S. 1555-1557 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100865a001
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  • 2
    Electronic Resource
    Electronic Resource
    Structural effects on ESR hyperfine coupling constants of some dithiazolidinyl free radicals (1989)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 27 (1989), S. 288-294 
    Details
    ISSN: 0749-1581
    Keywords: ESR ; ENDOR/TRIPLE ; Dithiazolidinyl free radicals ; Sulphur-nitrogen heterocycles ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of related dithiazolidin-2-yl free radicals prepared from cyclic strained alkenes and tetrasulphur dinitride, and an attempt was made to relate the nitrogen and proton hyperfine coupling constants to the radical structures. The radical made from dimethoxybenzonorbornadiene was studied by ENDOR and it was found that isotopic substitution with 15N gives well resolved ENDOR spectra; the TRIPLE measurements showed that the 14N coupling constants are positive whereas all the resolved proton coupling constants are negative.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260270318
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  • 3
    Electronic Resource
    Electronic Resource
    Electron spin resonance spectroscopy of free radicals (1993)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 31 (1993), S. 1027-1030 
    Details
    ISSN: 0749-1581
    Keywords: ESR ; Isotropic spectra ; Powder spectra ; Dithiadiazolyl radicals ; Dimerization ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Solution and powder ESR spectra of the 4-trifluoromethyl-1,2,3,5-dithiadiazolyl and 4-pentafluorophenyl-1,2,3,5-dithiadiazolyl free radicals were analysed. Comparison of the ESR parameters with those obtained for the protonated equivalents shows that fluorination produces a drift of unpaired electron spin density away from the nitrogen 2px orbitals towards sulphur 3px orbitals (x is the direction perpendicular to the heterocyclic ring), consistent with an increase in electronegativity of the substituent. The fluorinated radicals dimerize more readily than their protonated counterparts.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260311114
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Stable conformations and energy barriers to rotation in perfluoro(4-sec-butylpyridine) (1990)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 28 (1990), S. 268-270 
    Details
    ISSN: 0749-1581
    Keywords: Perfluoro(4-sec-butylpyridine) ; Semi-empirical MO calculations ; PM3 Hamiltonian ; Conformational analysis ; Variable-temperature ; 19F NMR ; Perfluoroalkyl-aryl rotational barrier ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: All-valence-electron MNDO-SCF-MO calculations were carried out on perfluoro(4-sec-butylpyridine) in order to calculate the stable conformations of the perfluoroalkyl group and the energy barrier to rotation of this group around the Calkyl—Caryl, bond. Both the AM1 and PM3 Hamiltonians were used. The results were compared with the value obtained from a variable-temperature study of the 19F NMR spectrum of the compound. The PM3 method is shown to give a significant improvement compared with AM1.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260280314
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  • 5
    Electronic Resource
    Electronic Resource
    Carbon-13 NMR relaxation studies of some dicyclohexyl compounds (1991)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 29 (1991), S. 777-785 
    Details
    ISSN: 0749-1581
    Keywords: Carbon-13 relaxation ; Molecular motion ; Rotational barriers ; Dicyclohexyl compounds ; Traction fluids ; Molecular modelling ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Four dicyclohexyl compounds were studied, one of which is a traction fluid and the remainder have related structures in which the cyclohexane rings are separated by two or three carbon atoms. Carbon-13 NMR T1 and NOE data were obtained for the four compounds at 22.50 and 100.62 MHz over a wide temperature range. The data were fitted simultaneously to either a reduced Lorentzian spectral density or to a ‘model-free’ two-correlation time spectral density. For the first time it has been possible to observe the tracking from the full ‘model-free’ two-correlation time spectral density to the reduced Lorentzian spectral density. From the correlation times and activation energies derived from these fittings, it can be concluded that all the compounds have semi-rigid structures. Computer modelling of the structures and molecular mechanics calculations of the rotational barriers gave results in agreement with those from the NMR data. Similarly, it was found that the friction coefficients of the compounds correlate with the NMR and molecular mechanics conclusions, namely that the increased rigidity produced by the introduction of methyl groups into the linkage between the cyclohexane rings leads to a more effective traction fluids. Hence it seems to be feasible to design new traction fluids in the laboratory.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260290807
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  • 6
    Electronic Resource
    Electronic Resource
    Carbon-13 NMR relaxation studies of some dicyclohexyl compounds at high pressure (1991)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 29 (1991), S. 823-829 
    Details
    ISSN: 0749-1581
    Keywords: Dicyclohexyl derivatives ; 13C spin-lattice relaxation times ; High-pressure NMR ; Rotational-translational coupling ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Four dicyclohexyl compounds were investigated, one of which is a traction fluid and the remainder have related structures in which the cyclohexyl rings are separated by two or three carbon atoms. Carbon-13 spin-lattice relaxation times have been measured at 25.16 MHz at pressures up to 200 MPa over the temperature range 280-329 K. High-pressure relaxation data have been successfully interpreted in terms of the ‘model-free’ approximation. A pressure-dependent rotational coupling parameter, κ, was evaluated from a modified Stokes-Einstein-Debye relationship using experimentally determined pressure-dependent rotational correlation times. The smallest value of κ was found to be associated with the most rigid and least-extended molecule, showing that molecular shape has a significant effect on the rotational-translational coupling. The values obtained for the activation volumes derived from methyl group data suggest that barriers to internal motion are governed by intramolecular effects. It has been demonstrated that high-pressure 13C relaxation measurements can provide a powerful means of studying the relationship between molecular rigidity and the macroscopic behaviour of functional fluids.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260290813
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  • 7
    Electronic Resource
    Electronic Resource
    Comparison of the Woessner and the ‘model-free’ approaches for the analysis of carbon-13 spin-lattice relaxation data for methyl groups (1992)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 30 (1992), S. 259-262 
    Details
    ISSN: 0749-1581
    Keywords: Carbon-13 relaxation times ; NOE factors ; Methyl groups ; Dicyclohexyl compounds ; Alkyl chains ; Model lubricants ; Molecular dynamics ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Carbon-13 NMR relaxation data obtained for methyl groups in two dicyclohexane compounds were used to compare the Woessner and ‘model-free’ approaches. It is shown that the extra flexibility offered by the latter leads to a more successful analysis of the data.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260300312
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  • 8
    Electronic Resource
    Electronic Resource
    ESR spectroscopic investigation of some 4-substituted 1,3,2-dithiazolyl and 2,3,1-dithiazolyl radicals (1992)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 30 (1992), S. 666-672 
    Details
    ISSN: 0749-1581
    Keywords: Electron spin resonance spectroscopy ; Sulphur-nitrogen-containing radicals ; Dithiadiazolyl radicals ; Dithiadiazolyl radicals ; Dithiazophospholyl radicals ; Phosphaalkynes ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Further information has been obtained on the electronic structure of 1,3,2-dithiazol-2-yl radicals. The structure has been well characterized previously except for positions 4 and 5 in the ring. We have obtained solution and powder ESR spectra of radicals substituted with 13C in both positions and of radicals substituted with nitrogen or phosphorus in the 4-position. It is probably the first time that a compound has been prepared containing the ring. Two especially interesting facts emerged from the ESR spectra of these 1,3,2-dithiazolyl radicals: the 13C-substituted radical has a considerable amount of p spin density in the plane of the ring and the phosphorussubstituted radical has a very low unpaired spin density at the phosphorus atom. It is known that 1,3,2,4-dithiadiazolyl radicals isomerize readily by photolysis to the symmetrical 2,3,1,4-dithiadiazolyl radicals; we attempted the same reaction with But and a new radical was produced that we have been unable to identify.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260300717
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  • 9
    Electronic Resource
    Electronic Resource
    ESR spectroscopy of some dicyano-, pyrazino- and quinoxalino-1,3,2-dithiazolyl radicals (1992)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 30 (1992), S. 774-778 
    Details
    ISSN: 0749-1581
    Keywords: ESR ; 1,3,2-Dithiazol-2-yl radicals ; Pyrazine ; Quinoxaline ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Several symmetrical 1,3,2-dithiazol-2-yl radicals have been examined that have in common nitrogen-containing substituents at the 4- and 5-positions, namely 4,5-dicyano-1,3,2-dithiazol-2-yl, [15N2]-1,3,2-dithiazolo [4,5-b] pyrazin-2-yl and 1,3,2-dithiazoleo [4,5-b] quinoxalin-2-yl. The ESR spectrum of the 4,5-dicyano radical does not reveal any 14N splittings from the cyanide groups; however, the pyrazine and the quinoxaline derivatives do have multi-lined well resolved spectra arising from substantial hyperfine interactions with these nuclei. The interactions are sufficiently large to be observed in the powder spectra of the latter. The presence of proton hyperfine interactions shows that unpaired-electron spin density is delocalized over all the rings. It has been found that the radicals attached to pyrazine and quinoxaline can be incorporated into single crystals of naphthalene and phenazine, respectively.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260300814
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  • 10
    Electronic Resource
    Electronic Resource
    Multi-frequency, variable-temperature and high-pressure study of carbon-13 spin - lattice relaxation in tetraoctyltin (1991)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 29 (1991), S. 1221-1225 
    Details
    ISSN: 0749-1581
    Keywords: High pressure ; Molecular motion ; Carbon-13 relaxation ; Octyl chains ; Tetraoctyltin ; Polydecene ; Model lubricants ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Carbon-13 NMR spin-lattice relaxation times, T1, and nuclear Overhauser effect data were obtained for neat tetra-n-octyltin at 22.5 and 100.6 MHz over a wide temperature range. T1 values were also measured at 25.16 MHz at pressures up to 211 MPa. The ambient-pressure data were fitted to the ‘model-free’ two-correlation time spectral density with a temperature-dependent order parameter, S2. The pressure data were interpreted by assuming that internal motions of the octyl chain are independent of pressure while the overall (tumbling) motion and S2 are pressure dependent. The values of the motional parameters for tetra-n-octyltin lie in the ranges expected for compounds containing long n-alkyl chains. The results show that this approach is applicable to complex liquids such as synthetic lubricants of the polydecene type.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260291211
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