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  • 1
    ISSN: 1572-879X
    Keywords: hydrogen bonding, measurement by NMR ; NMR, hydrogen bonding evaluation by ; solids, hydrogen bonding ability of ; solvents, hydrogen bonding ability of ; supports, hydrogen bonding ability of
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The chemical shift difference between signals of C(β) and C(α) of unsaturated ketones, Δδ, which we used before to measure acid strengths, has now been used to evaluate the hydrogen bond donor ability of solvents which are not acidic enough to hydronate the indicator. For such solvents there is no general correlation between H-bond donor ability and acid strength: hexa-fluoroisopropanol is a much weaker acid than acetic acid, but it is a stronger H-bond donor. The method can be applied to evaluate the H-bonding properties of solid surfaces, and it was thus found that silica gel has a much stronger H-bond donor ability than methanol or acetic acid.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 2 (1989), S. 425-427 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Distribution between pentane and trifluoromethanesulfonic acid (TFMSA) and carbon-13 NMR measurements showed that benzene and toluene are not protonated to any significant extent in TFMSA. This finding contradicts previous reports, and validates the ranking of superacids based on the extent of benzene protonation.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 3 (1990), S. 639-642 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The second ionization of the 4-chloro-3-methylbutanoyl ion forms a primary alkyl acyl dication, as a tight ion pair. Methyl and hydrogen shifts occur to comparable extents indicating that the relative stability of the product (sec- or tert-carbocation) does not influence the energy barrier for the shift. The product of methyl shift (1,3-sec-alkyl acyl dication) loses the proton closest to the counterion in the tight ion pair and forms the pent-3-enoyl cation. Protonation-deprotonation of the latter, followed by internal acylation, gives the protonated cyclopent-2-enone. The dication resulting from hydrogen shift loses a proton from C-2 and gives the 3-methylbut-2-enoyl cation.
    Type of Medium: Electronic Resource
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