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  • 1
    Electronic Resource
    Electronic Resource
    EFFECT OF RING SIZE ON THE COMPLEXATION AND DECOMPOSITION OF BENZENEDIAZONIUM ION IN THE PRESENCE OF CROWN ETHERS IN 1,2-DICHLOROETHANE AND THE GAS PHASE (1997)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 10 (1997), S. 67-75 
    Details
    ISSN: 0894-3230
    Keywords: benzenediazonium ion ; host-guest complexation ; dediazoniation ; crown ethers ; ring size ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: ---The host-guest complexation and the kinetics of the thermal dediazoniation of benzenediazonium tetrafluoroborate in the presence of unsubstituted and (di)benzene- and dicyclohexane-substituted crown ethers containing 4-10 oxygen atoms were studied by UV spectrophotometry in 1,2-dichloroethane at 40°C. The complexation equilibrium constants K and the stabilizing ability of the complexation (k2/k1) were calculated by a kinetic method. Complexation in the gas phase was observed and characterized by fast atom bombardment mass spectrometry (FAB-MS). All complexing agents except 12-crown-4 formed 1:1 complexes [crown ether-PhN2]+ under FAB conditions. The complexation caused a hypsochromic shift Δλmax in the UV spectrum of the benzenediazonium salt, which was largest for hosts containing six oxygen atoms. The thermodynamic and kinetic stability were much greater for insertion-type complexes containing six or more oxygen atoms in the host molecule than for the charge-transfer complexes formed with 15-crown-5. In contrast, 12-crown-4 destabilized benzenediazonium ion owing to the increase in homolytic dediazoniation. 21-Crown-7 was the strongest complexing and stabilizing agent for benzenediazonium ion; with a larger hole size in the host the effects weakened. The effects of benzene and cyclohexane substituents in crown ethers on the thermodynamic and kinetic stability were small compared with the effects of the number of oxygen atoms. © 1997 by John Wiley & Sons, Ltd.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 2
    Electronic Resource
    Electronic Resource
    Complexation of tropylium ions with crown ethers and acyclic polyethers examined by fast atom bombardment mass spectrometry (1995)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 377-384 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The molecular complex formation of six macrocyclic and six acyclic polyethers with tropylium and 4-methoxyphenyltropylium tetrafluoroborates was observed and characterized in the gas phase by fast atom bombardment mass spectrometry (FABMS), to obtain information on intrinsic molecular interactions in the absence of the complicating effect of solvation. The stoichiometry of the complexes was assessed on the basis of corresponding peaks in FAB mass spectra. In addition to the expected 1 : 1 complexes between polyether and tropylium ion, some 2 : 1 complexes were also formed. The stability order of selected complexes was studied in competition experiments. The complexation equilibrium constant and thermodynamic parameters for the interaction of dibenzo-18-crown-6 with tropylium ion were determined in 1,2-dichloroethane solution by UV-visible spectrophotometry. Complexation of polyethers with tropylium salts has not been reported previously.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610080511
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Molecular complexes in solution containing benzene-substituted crown ethers and tropylium ions (1996)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 9 (1996), S. 21-28 
    Details
    ISSN: 0894-3230
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The interaction of benzo-15-crown-5, benzo-18-crown-6, dibenzo-18-crown-6, dibenzo-24-crown-8, and dibenzo-30-crown-10 with tropylium tetrafluoroborate in 1,2-dichloroethane was studied by spectroscopic methods. The stoichiometries of the complexes in the gas phase were investigated by fast atom bombardment mass spectrometry. The crown ethers formed 1:1 molecular complexes with the acceptors, apparently by a charge-transfer mechanism. The stability constant K and the molar absorptivity of the complex εc were determined by the method of Rose and Drago. The magnitudes of the thermodynamic parameters of complexation were calculated. A discussion of the thermodynamic parameters is included.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
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