An 11B NMR study of the kinetics of methylboronic acid-methylboronate interchange in aqueous solution

Yoko Kono, Koji Ishihara, Akira Nagasawa, Kimiko Umemoto, Kazuo Saito

    Research output: Contribution to journalArticle

    14 Citations (Scopus)

    Abstract

    Methylboronic acid-methylboronate interchange has been studied kinetically by the band shape analysis of 11B NMR signals. The system was analyzed as two-site exchange CH3B(OH)2⇌CH3B(OH)3 - for a self-buffered aqueous solution in pH 9.5-11.4 at 24-55°C. The exchange rate was expressed as: rate=(kex[CH3B(OH)3 -]+k X2)[CH3B(OH)2]=(kex[CH 3B(OH)2]+kY2)[CH3B(OH) 3 -]. The second-order rate constant, kex (dm3 mol-1 s-1) (24.2°C)=7.03×105, is independent of pH, and the kinetic parameters obtained at I=0.10 M are ΔH (kJ mol-1)=17.5±1.9 and ΔS (J mol-1 K-1)=-74.3±6.2. A dimeric transition state is suggested for the path similarly to the interchange between boric acid and borate. The first-order rate constants kX2 and kY2 depend on the hydroxide ion concentration indicating alternative routes for the interchange.

    Original languageEnglish
    Pages (from-to)91-96
    Number of pages6
    JournalInorganica Chimica Acta
    Volume262
    Issue number1
    Publication statusPublished - 1997 Sep 30

    Fingerprint

    Interchanges
    Nuclear magnetic resonance
    aqueous solutions
    nuclear magnetic resonance
    Borates
    acids
    Kinetics
    Acids
    Rate constants
    kinetics
    Boric acid
    Kinetic parameters
    boric acids
    ion concentration
    borates
    hydroxides
    routes
    Ions
    methylidyne
    methaneboronic acid

    Keywords

    • B NMR spectroscpoy
    • Kinetics and mechanism
    • Methylboronate
    • Methylboronic acid

    ASJC Scopus subject areas

    • Biochemistry
    • Inorganic Chemistry
    • Physical and Theoretical Chemistry
    • Materials Chemistry

    Cite this

    An 11B NMR study of the kinetics of methylboronic acid-methylboronate interchange in aqueous solution. / Kono, Yoko; Ishihara, Koji; Nagasawa, Akira; Umemoto, Kimiko; Saito, Kazuo.

    In: Inorganica Chimica Acta, Vol. 262, No. 1, 30.09.1997, p. 91-96.

    Research output: Contribution to journalArticle

    Kono, Yoko ; Ishihara, Koji ; Nagasawa, Akira ; Umemoto, Kimiko ; Saito, Kazuo. / An 11B NMR study of the kinetics of methylboronic acid-methylboronate interchange in aqueous solution. In: Inorganica Chimica Acta. 1997 ; Vol. 262, No. 1. pp. 91-96.
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    abstract = "Methylboronic acid-methylboronate interchange has been studied kinetically by the band shape analysis of 11B NMR signals. The system was analyzed as two-site exchange CH3B(OH)2⇌CH3B(OH)3 - for a self-buffered aqueous solution in pH 9.5-11.4 at 24-55°C. The exchange rate was expressed as: rate=(kex[CH3B(OH)3 -]+k X2)[CH3B(OH)2]=(kex[CH 3B(OH)2]+kY2)[CH3B(OH) 3 -]. The second-order rate constant, kex (dm3 mol-1 s-1) (24.2°C)=7.03×105, is independent of pH, and the kinetic parameters obtained at I=0.10 M are ΔH≠ (kJ mol-1)=17.5±1.9 and ΔS≠ (J mol-1 K-1)=-74.3±6.2. A dimeric transition state is suggested for the path similarly to the interchange between boric acid and borate. The first-order rate constants kX2 and kY2 depend on the hydroxide ion concentration indicating alternative routes for the interchange.",
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    AU - Saito, Kazuo

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    N2 - Methylboronic acid-methylboronate interchange has been studied kinetically by the band shape analysis of 11B NMR signals. The system was analyzed as two-site exchange CH3B(OH)2⇌CH3B(OH)3 - for a self-buffered aqueous solution in pH 9.5-11.4 at 24-55°C. The exchange rate was expressed as: rate=(kex[CH3B(OH)3 -]+k X2)[CH3B(OH)2]=(kex[CH 3B(OH)2]+kY2)[CH3B(OH) 3 -]. The second-order rate constant, kex (dm3 mol-1 s-1) (24.2°C)=7.03×105, is independent of pH, and the kinetic parameters obtained at I=0.10 M are ΔH≠ (kJ mol-1)=17.5±1.9 and ΔS≠ (J mol-1 K-1)=-74.3±6.2. A dimeric transition state is suggested for the path similarly to the interchange between boric acid and borate. The first-order rate constants kX2 and kY2 depend on the hydroxide ion concentration indicating alternative routes for the interchange.

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