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

doi:10.1016/S0020-1693(97)05499-6

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

^*Corresponding author for this work

School of Advanced Science and Engineering

Research output: Contribution to journal › Article › peer-review

15 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=(k_ex[CH₃B(OH)₃^-]+k _X2)[CH₃B(OH)₂]=(k_ex[CH ₃B(OH)₂]+k_Y2)[CH₃B(OH) ₃^-]. The second-order rate constant, k_ex (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 k_X2 and k_Y2 depend on the hydroxide ion concentration indicating alternative routes for the interchange.

Original language	English
Pages (from-to)	91-96
Number of pages	6
Journal	Inorganica Chimica Acta
Volume	262
Issue number	1
DOIs	https://doi.org/10.1016/S0020-1693(97)05499-6
Publication status	Published - 1997 Sept 30

Keywords

B NMR spectroscpoy
Kinetics and mechanism
Methylboronate
Methylboronic acid

ASJC Scopus subject areas

Physical and Theoretical Chemistry
Inorganic Chemistry
Materials Chemistry

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10.1016/S0020-1693(97)05499-6

Cite this

@article{fa1d10ec662a49179ca2d8ca016f7620,

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

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.",

keywords = "B NMR spectroscpoy, Kinetics and mechanism, Methylboronate, Methylboronic acid",

author = "Yoko Kono and Koji Ishihara and Akira Nagasawa and Kimiko Umemoto and Kazuo Saito",

year = "1997",

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language = "English",

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T1 - An 11B NMR study of the kinetics of methylboronic acid-methylboronate interchange in aqueous solution

AU - Kono, Yoko

AU - Ishihara, Koji

AU - Nagasawa, Akira

AU - Umemoto, Kimiko

AU - Saito, Kazuo

PY - 1997/9/30

Y1 - 1997/9/30

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.

AB - 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.

KW - B NMR spectroscpoy

KW - Kinetics and mechanism

KW - Methylboronate

KW - Methylboronic acid

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