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  • Wiley-Blackwell  (2)
  • 1990-1994  (2)
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  • 1
    Electronic Resource
    Electronic Resource
    Does the ipso-carbon chemical shift tell us anything about the structure of phenylated phosphorus compounds?This article is dedicated to Leopold Horner on the occasion of his eightieth birthday. (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Heteroatom Chemistry 2 (1991), S. 515-519 
    Details
    ISSN: 1042-7163
    Keywords: Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The nuclear magnetic resonance signals exhibited by the ipso-carbon atoms of a variety of phenylated phosphorus compounds were found to span over the remarkably wide range of + 162 to + 117 ppm. Nevertheless, these changes in chemical shifts have little diagnostic value. They are tentatively attributed to a charge-mediated contraction and expansion of the C,P σ-bond orbital on one hand and to a σ-bond induced deformation of the aromatic π-electron cloud on the other.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hc.520020503
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    About the structure of phosphorus ylids: Electron distribution and geometry (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Heteroatom Chemistry 1 (1990), S. 151-156 
    Details
    ISSN: 1042-7163
    Keywords: Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Using 13C-chemical shifts as a probe for the electronic environment of carbon centers, triphenylphosphoniomethanide, the model case of a “reactive” phosphorus ylid, was found to have much more zwitterion than PC double bond character (resonance structure 1a being dominant). Triphenylphosphonio-propenide (“triphenylphosphonium-allylid”), a “moderated” ylid, accumulates electron excess mainly at the α-carbon atom (resonance structure 6a being dominant) whereas triphenylphosphonio-ethenoate (formyl-methylene-triphenylphosphorane) and other “stabilized” ylids carry roughly equal fractions of negative charge at the α-carbon and the oxygen atom (resonance formulas a and b being of comparable importance). The one-bond C,H coupling constant of triphenylphosphonio-methanide (1) argues against a perfectly planar ylid center. The three-bond P,C coupling constants permit the assignment of endo- or exo-configurations to ylids having an allyl-type side-chain.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hc.520010205
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    Paper (German National Licenses)
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