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Proton Affinities of Organocatalysts Derived from Pyridine N-oxide

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    0441769 - ÚOCHB 2015 RIV HR eng J - Journal Article
    Váňa, J. - Roithová, J. - Kotora, Martin - Beran, Pavel - Rulíšek, Lubomír - Kočovský, Pavel
    Proton Affinities of Organocatalysts Derived from Pyridine N-oxide.
    Croatica Chemica Acta. Roč. 87, č. 4 (2014), s. 349-356. ISSN 0011-1643
    R&D Projects: GA ČR(CZ) GA14-31419S
    Grant - others:GA ČR(CZ) GAP207/11/0587
    Institutional support: RVO:61388963
    Keywords : density functional theory * isodesmic reactions * kinetic method * mass spectrometry * organocatalysis * proton affinity * superbases
    Subject RIV: CF - Physical ; Theoretical Chemistry
    Impact factor: 0.728, year: 2014

    Proton affinities of several efficient organocatalysts METHOX, QUINOX, ANETOX, KOTOX, FUREOX, and FUROOX bearing a pyridine N-oxide or 2,2'-bipyridyl N,N'-dioxide. moiety were determined by using extended kinetic method and density functional theory calculations. Proton affinities are in the range of 1030-1060 kJ mol(-1). Using isodesmic reactions, the effect of combining two pyridine N-oxide units in the neutral and the protonated molecule was studied: The combination of an unfavorable interaction in the former case and a favorable interaction in the latter accounts for the superbasic properties of 2,2'-bipyridyl N,N'-dioxides. Last but not least, the theoretically predicted pK(a) in ethanol are 0.1, -2.7, 0.9, 1.8, 1.9, and 2.3 for the METHOX, QUINOX, ANETOX, FUROOX, FUREOX, and KOTOX, respectively.
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