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  • 1
    ISSN: 1572-879X
    Keywords: acid strength and catalytic activity ; acid strength and H‐bond donor strength ; catalytic activity and acid strength ; catalytic activity and H‐bond donor strength ; H‐bond donor strength and acid strength ; H‐bond donor strength and catalytic activity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Two liquids, acetic acid and hexafluoroisopropanol (HFIP), and two solids, silica gel and polymethacrylic acid (PMA), were compared for hydrogen bond donor ability, acid strength, and catalytic activity in typical acid‐catalyzed reactions, inversion of sugar and cleavage of acetone dimethyl ketal. In each pair, the weaker acid (HFIP and silica gel, respectively) was much the stronger hydrogen bond donor, but was totally devoid of catalytic activity, which the poor hydrogen bond donor but stronger acids (acetic and methacrylic acid, respectively) exhibited. A strong hydrogen bond donor (e.g., HFIP) enhances, however, the catalytic activity of the acid catalyst (AcOH). Thus, hydrogen bond donor ability is not a measure of acid strength. A correlation of the two properties is possible only when each group (acids and bases) involved in the comparison consists of very close structural relatives. Such a correlation cannot be extrapolated to any other case.
    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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