ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Carbon-13 NMR spin-lattice relaxation in dithiarsolanes. Correlation between molecular motions and structural properties (1981)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 17 (1981), S. 285-289 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 13C NMR spin-lattice relaxation times (T1) and nuclear Overhauser enhancements (η) were measured for dithiarsolanes. The contributions of dipolar (T1DD) and spin-rotation (T1SR) mechanisms were determined. The T1 data were analysed to obtain information on the relative order of magnitude of the internal motion rates. The calculations were based on the isotropic, with internal rotation about the As—Ph bond, model of reorientation. In cis, trans-2-phenyl-4-methyl-1,3,2-dithiarsolane, the internal rotation of the phenyl ring is c. three times faster than overall molecular reorientation. The internal motion of the arsolane ring is slightly slower than the phenyl ring rotation. The rotation of the methyl groups in the compounds appears to be considerably hindered, with rotation energy barriers of c. 10 kJ mol-1. In contrast to the situation in the 4-methyldithiarsolane, the internal motion of the arsolane ring is twice as fast as the internal rotation of the phenyl ring for the methyl-unsubstituted analogue, 2-phenyl-1,3,2-dithiarsolane.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270170412
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    1H and 13C NMR studies on 1,3,2-dioxarsolanes (1983)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 21 (1983), S. 417-425 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 1H and 13C NMR spectra of a series of 1,3,2-dioxarsolanes have been obtained at 2.1 T and some at 9.4 T. The chemical shifts and spin-spin coupling constants have been obtained from complete spectral analyses of the 1H and proton-coupled 13C spectra. The spectral data are interpreted on the basis of two rapidly interconverting half-chair conformers with a pseudoaxial substituent at arsenic. Unique assignment of syn/anti or cis/trans geometries have been made from 1H or 13C NMR spectroscopy alone. The syn and trans isomers of the 4-methyl- and 4,5-dimethyl-1,3,2-dioxarsolanes, respectively, appear to be conformationally biased towards the forms with pseudoequatorial methyl groups. The general trends in the geminal and vicinal 1H—1H and 13C—1H coupling constants are interpreted in terms of stereospecific, electronegativity and lone-pair effects of the oxygen heteroatoms and conformational factors. The NMR data on the 1,3,2-dioxarsolanes are discussed with reference to related 1,3-dithoxa- and 1,3-dithia- five-membered rings with As, P, S or C at the 2-position.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/omr.1270210704
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Spectral analysis of the high-resolution proton-coupled carbon-13 NMR spectra of 1,3,2-dithiarsolanes (1982)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 18 (1982), S. 28-32 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The high-resolution proton-coupled 13C NMR spectra of 2-chloro- and 2-phenyl-4-methyl-1,3,2-dithiarsolane and 2-chloro- and 2-phenyl-1,3,2-dithiarsolane have been obtained and completely analysed. The spectral analysis has provided all the 13C chemical shifts and 13C—1H coupling constants, including their relative signs. The results of this work are adequately interpreted in terms of two rapidly equilibrating half-chair conformers with the 4-methyl pseudo-axial or pseudo-equatorial. The cis isomers appear to be conformationally biased towards the form with the 4-methyl pseudo-equatorial. The two one-bond 13C—1H coupling constants of the methylene group are distinctly different. For both the cis and trans isomers, the largest one-bond coupling always involves the methylene proton situated syn to the substituent at arsenic. The observed variation in the geminal and vicinal 13C—1H coupling constants are discussed in terms of a stereospecific inductive effect of the sulphur hetero-atoms and conformational factors.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270180107
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    13C—1H coupling constants in 9, 10-dihydroanthracene (1983)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 21 (1983), S. 287-292 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 1H and 13C NMR spectra of 9,10-dihydroanthracene have been obtained at 2.1 and 9.4 T using selective decoupling of the methylene protons. Complete spectral analyses of the experimental spectra have provided the chemical shifts and coupling constants. The 13C—1H coupling constants in 9, 10-dihydroanthracene and biphenylene have been well accounted for by MNDO theoretical calculations of the molecular geometries and bond orders in these compounds.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/omr.1270210413
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Carbon-13 NMR Spin-Lattice Relaxation and Molecular Motion in 2-Phenyl-1,3,2-dioxarsolane and its 4-Methyl and 4,5-Dimethyl Derivatives (1985)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 23 (1985), S. 253-258 
    Details
    ISSN: 0749-1581
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 13C NMR spin-lattice relaxation times (T1) have been measured as a function of temperature for three 2-phenyl-1,3,2-dioxarsolanes. The T1 data have been interpreted in terms of isotropic overall molecular reorientation, internal rotation about the As—Ph bond and internal methyl rotation. Information on the relative order of magnitude of the overall and internal reorientations has been obtained. The internal rotation of the phenyl ring is thus 2 - 4 times faster than the overall molecular tumbling. Further, the internal rotation of the arsolane ring appears to be comparable to, or slightly faster than, the phenyl ring rotation. The association process which is believed to take place in the unsubstituted parent compound is reflected in its very high activation energy for overall reorientation (39 kJ mol-1 compared with 24-25 kJ mol-1 for the methyl derivatives). The rotation of the methyl groups appears to be considerably more hindered in the cis isomer of 2-phenyl-4,5-dimethyl-1,3,2-dioxarsolane than in the trans isomer and, in particular, the mono-4-methyl compound.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260230409
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Proton and carbon-13 NMR relaxation studies of 2,2-dichloropropane and 2,2-dibromopropane (1987)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 25 (1987), S. 534-538 
    Details
    ISSN: 0749-1581
    Keywords: 1H and 13C NMR ; Relaxation studies ; Liquid and solid 2,2-dihalopropanes ; 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 spin-lattice relaxation times, T1, have been measured for liquid and solid 2,2-dichloropropane (1) and 2,2-dibromopropane (2). Molecular self-diffusion, with activation energies in the range 18-24 kJ mol-1, is responsible for the considerable line narrowing observed for the NMR spectra in solid I of these substances. The NMR data reveal a previously unreported phase transition point at 208 K for 2.An analysis of the proton and 13C T1 times in both the liquid and solid phases is reported. Effective correlation times, activation energies and pre-exponential factors for the appropriate motions have been obtained from the Arrhenius equation. The proton and 13C spin-lattice relaxation mechanisms in the liquid and solid I phases are governed by overall molecular reorientations, with activation energies in the range 9-11 kJ mol-1. The rotational correlation time increases slightly at the liquid → solid I boundary from 3.2 to 3.6 ps for 1 and from 5.1 to 5.4 ps for 2. The correlation time is observed to decrease by five orders of magnitude at the solid I → solid II transition point of 2. The dominant motion causing spin-lattice relaxation in phase II is methyl group reorientation with an activation energy of 18 kJ mol-1.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260250616
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Natural abundance carbon-13 and deuterium NMR studies on the liquid and solid phases of tert-butyl chloride and tert-butyl nitrate (1988)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 26 (1988), S. 1086-1092 
    Details
    ISSN: 0749-1581
    Keywords: 13 ; 2H ; NMR line width ; Relaxation ; Orientationally disordered disordered compounds ; Molecular motion ; Correlation times ; Activation energies ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: NMR line widths (13C) and spin-lattice relaxation times (13C and 2H) were measured over a wide temperature region in liquid and solid tert-butyl chloride (1) and tert-butyl nitrate (2). Molecular self-diffusion, with activation energies in the range 29-37 kJ mol-1, is responsible for the considerable line narrowing observed for the 13C resonances in solid I of these substances.An analysis of the 13C and 2H spin-lattice relaxation times (T1) in the liquid and solid phases of 1 and 2 is reported. Rotational correlation times, activation energies and pre-exponential factors for the appropriate motions were obtained from the Arrhenius equation. The 13C and 2H T1 data suggest that the overall reorientation occurring in solid I of 1 and 2 is slightly retarded by the melting process. The 13C T1 data show that the faster motion in the ordered phases of 1 and 2 is the uniaxial C3′ reorientation with an activation energy of 12-14 kJ mol-1, while the slower motion is the C3 methyl reorientation with an activation energy of 12-13 kJ mol-1.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260261210
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Natural abundance carbon-13 and deuterium NMR studies on the liquid and solid phases of tert-butyl iodide (1989)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 27 (1989), S. 830-835 
    Details
    ISSN: 0749-1581
    Keywords: NMR line shapes ; Spin-lattice relaxation ; Orientationally disordered tert-butyl compounds ; Molecular motion ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Carbon-13, deuterium and proton NMR line shapes of polycrystalline tert-butyl iodide (1) have been studied between 200 K and the melting point (239 K). Carbon-13 and deuterium spin-lattice relaxation times (T1) were measured between 313 and 200 K in the liquid and solid phases of 1.The NMR line shape data indicate the occurrence of two disordered phases of 1 between the melting point and 222 K. An analysis of the 13C and 2H T1 relaxation times is reported. The 13C and 2H T1 relaxation is governed by overall molecular tumbling in the liquid and disordered phases of 1, whereas the 13C T1 relaxation in the ordered solid is governed by uniaxial molecular reorientation of the tert-butyl group. Rotational correlation times, activation energies and pre-exponential factors were obtained from the T1 data by using the Arrhenius equation. Significantly different activation parameters were obtained for the two disordered solids. The effective correlation time at the melting point of 1 (ca. 5 ps) is 2-3 times longer than for other globular tert-butyl compounds.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260270904
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    High-field magnetic resonance studies of tert-butanol in liquid and solid phases (1991)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 29 (1991), S. 698-705 
    Details
    ISSN: 0749-1581
    Keywords: NMR line width ; Spin-lattice relaxation ; Molecular motion ; Orientationally disordered crystals ; Hydrogen bonding ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1H and 13C line widths and 1H, 2H, 13C and 17O spin-lattice relaxation (times (T1) of tert-butanol (TB) were studied at a field strength of 9.4 T in the liquid and solid states (160-299 K). The NMR line width data reveal the existence of at least two crystalline forms between 160 K and the metling point (299 K). The ordered phase (solid II) is observed throughout the whole temperature region on warming, indicating that the disordered phase (solid I), observed between ca. 210 K and the melting point, is monotropic. The line narrowing of the 1H resonances for solid I, observed around 225 and 280 K, is ascribed to the onset of overall molecular tumbling and translational diffusion, respectively. The 1H line width of solid II is constant between 160 and 284 K. Activation parameters for the overall molecular tumbling and/or internal methyl and tert-butyl reorientations were obtained from the T1 data. The long correlation time (75-92 ps at the melting point) and high activation energy (27-37 kJ mol-1) suggest that the overall tumbling in the disordered and liquid phases involves hydrogen-bonded aggregates. The dynamics of the methyl group, in contrast to the tert-butyl group, appear to be only slightly affected by change of state and phase (activation energy 11-12 kJ mol-1).
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260290712
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...