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
    A Comparative 1H- and 13C-NMR Study of the Dianion and Dication of Biphenylene (1986)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 69 (1986), S. 955-961 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Biphenylene dianion has been prepared by Li reduction of the parent hydrocarbon. It is stable below -30° and was characterized by its 1H- and 13C-NMR spectra. A comparison of these data with those of the dication indicates the existence of ion pairs in the dianion case which are responsible for a different charge distribution. The diamagnetic ring currents of both ions, however, are of comparable magnitude, and both are more diatropic than the parent hydrocarbon. Predictions of the π-charge-density effect on 1H chemical shifts are improved by calculations that use the linear and quadratic electric-field effect equation instead of the simple Spiesecke-Schneider relation.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19860690502
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Solvation of indenyllithium and indenylpotassium studied by 13C NMR spectroscopy (1990)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 3 (1990), S. 9-12 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Polarization of the π-electron systems of indenyllithium (In -Li+) and indenylpotassium (In -K+), which is generally indicative of the degree and tightness of contact ion pairing, was investigated by 13C NMR spectroscopy. The effect of changing solvent is about two thirds as great for In -K+ as for In -Li+. The indenyl anion is more strongly polarized with Li+/dimethyl sulfoxide than with Li+/ammonia, whereas the reverse is observed for In -K+. Complexation of In -K+ in tetrahydrofuran (THF) by cryptand(2,2,2) results in a π-electron distribution identical with that of In -Li+ in hexamethylphosphoramide, indicative of solvent- or agent-separated ion pairs or free ions. Small but significant cation-anion interactions are observed for In -K+ in hexamethylphosphoramide and for In -N+Me4 in THF.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610030103
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Structural examination of some polychlorinated 2-phenoxyphenols by 1H and 13C nuclear magnetic resonance (1980)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 13 (1980), S. 391-395 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Carbon-13 NMR spectra of some polychlorinated 2-phenoxyphenols have been obtained. The substituent chemical shifts obtained by varying the chlorine substitution pattern of one ring are very similar to those reported for the corresponding diphenyl ethers. Thus, the replacement of a 2-chlorine atom by a hydroxyl group only induces minor shielding changes at the adjacent aryl moiety and the 13C chemical shift changes are mainly determined by the preferred conformations governed by the steric demand of the ortho substituents. An 1H NMR/IR study revealed an equilibrium between intermolecular aggregates and intramolecular OH…π species in the concentration interval 2-0.005 M. Any hydrogen bonding effects on 13C NMR shieldings are, therefore, minor compared to shielding variations caused by steric perturbations.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270130602
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Solvent and temperature studies of some indenyl- and fluorenyllithiums using 13C NMR spectroscopy (1979)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 12 (1979), S. 661-666 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 13C NMR spectra of indenyl- and fluorenyllithium and some of their methyl substituted derivatives have been obtained. The shielding differentials induced by varying the temperature or coordinating ability of the solvent are discussed in terms of an equilibrium between discrete ion pairs or differences in external solvation. An increase of the coordinating ability of the solvent induces shift differentials of similar signs as those given by lowering the temperature. Methyl substituents close to the cation location are found to have only a minor effect on the observed ion pair ratio but seem to influence the preferred cation position in the tight ion pair structure.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270121203
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Carbon-13 nuclear magnetic resonance spectroscopy of polychlorinated diphenyl ethers (1977)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 9 (1977), S. 196-202 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Carbon-13 n.m.r. chemical shifts are reported for diphenyl ether and several of its chlorinated analogs. Carbon shieldings were found to be dependent on the degree of steric interference to conjugative release by the oxygen atom. Substituent effects due to attached chlorine atoms seem to be more easily transmitted into the adjacent aryl moiety if the number of ortho chlorines is reduced. These results were clearly seen by a variable-by-variable plot display or by using a pattern recognition computer program. Spin-lattice relaxation times have been measured for several compounds mainly for assignment purposes, but they are also briefly discussed in view of possible interconversion mechanisms.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270090405
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    A carbon-13 NMR study of some alkyl-substituted indenes. An experimental study of the baker-nathan order of hyperconjugation in the neutral ground state (1978)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 11 (1978), S. 516-519 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Carbon-13 NMR spectra of several alkyl-substituted indenes have been assigned and analysed. For structures having an alkyl substituent in the C-2 position an increased shielding was observed for the remote conjugated positions C-4 and C-6, an alternating trend similar to that found for the 2-cycloaminoindenes. The hyperconjugative behaviour was slightly more pronounced for the methyl group compared with an isopropyl or tert-butyl substituent, a fact which supports a model where C—H σ-π interactions are more efficient than those involving C—C bonds.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270111009
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Carbon-13 n.m.r. characterization of indenyllithium in solution (1977)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 9 (1977), S. 593-595 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 13C N.m.r. chemical shifts obtained for indenyl- and cyclopentadienyllithium in several, mostly ethereal, solvents are presented. The chemical shift changes induced by varying the solvent are assumed to probe the actual π-electron density distribution, thus providing an insight into the structure of the ion-pair. The increase in the estimated π-electron densities obtained for the protonated aromatic carbons of indenyllithium by increasing the coordinating ability of the solvent gives evidence of a change of the ion-pair equilibrium towards solvent-separated species. The average chemical shifts for indenyl- and cyclopentadienyllithium were independent of the choice of solvent, a fact which supports the ion-pair model in all studied media.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270091009
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    The interaction between paramagnetic relaxation reagents and carbon tetrachloride (1982)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 18 (1982), S. 207-210 
    Details
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 13C spin-lattice relaxation times for carbon tetrachloride have been measured in the presence of various paramagnetic chromium (III) chelates (PARRs). The T1 values were compared with those of an inert standard, cyclohexane. A specific PARR: carbon tetrachloride interaction was clearly indicated, which is less obvious for bulky ligands or ligands having electron-withdrawing substituents. The electron-nuclear relaxation model and the quantitative description of outer-sphere complexation is briefly discussed.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1270180407
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    A carbon-13 NMR study of the ion pair structure of the dibenzo[b,f]pentalene dianion (1983)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 21 (1983), S. 322-327 
    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 chemical shifts of dibenzo[b, f]pentalene and its 5,10-dimethyl derivative are presented and compared with those of the corresponding dilithium dianions. As probed by the relative 13C NMR chemical shifts, the charge distribution within the dianion system is clearly dependent on the actual ion pair state. This condition is demonstrated by varying the solvent and temperature. The polarization of charge towards the pentalene carbons, i.e. the preferred cation positions, is observed on going to tight ion pair conditions. Further support for this model is gained from 7Li NMR. The limitations of the use of 1H and 13C NMR chemical shifts to measure charge distributions within anion systems are discussed.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/omr.1270210508
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Natural abundance one-bond 13C—13C coupling constants and unambiguous assignments of 13C NMR chemical shifts of dithieno[b,d]pyridines; a multivariate data analysis (1990)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 28 (1990), S. 33-41 
    Details
    ISSN: 0749-1581
    Keywords: Dithieno[b,d]pyridines ; 13C NMR ; 1D-INADEQUATE ; Multivariate data analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The one-bond 13C—13C coupling constants (1JCC) in all nine possible dithieno[b,d]pyridines were measured at natural isotope abundance by using the INADEQUATE pulse sequence technique. The unambiguous assignments of the 13C NMR shifts of these compounds are also reported. Assignments are based on proton decoupled 13C spectra, heteronuclear correlation spectra (HETCOR) and 1D-INADEQUATE 13C NMR spectroscopy. The effect of the fusion pattern and the influence of the heteroatoms in the ring skeleton on the NMR parameters are discussed. By a multivariate principal components data analysis, it was shown that the magnitude of 1J(CC) of the pyridine subunit could be satisfactorily predicted from shift data, the azomethine C—H coupling constant and MNDO bond orders. The last parameter gave only a minor contribution to the coupling variability.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260280108
    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...