Kinetic Study of Boric Acid-Borate Interchange in Aqueous Solution by 11B NMR Spectroscopy

Koji Ishihara, Akira Nagasawa, Kimiko Umemoto, Hideaki Ito, Kazuo Saito

Research output: Contribution to journalArticle

41 Citations (Scopus)

Abstract

Kinetics of interchange between boric acid and tetrahydroxyborate has been studied by the band shape analysis of 11B NMR signals in aqueous solution of pH 8–10 at 20–52 °C and 0.1–250 MPa. The system was analyzed as two-site exchange B(OH)3 ⇌ B(OH)4-. The observed first-order rate constant toward the right (kX) is related to the second-order exchange rate constant (kex) by the equation kX = kexCT[OH-]/(kb + [OH-]), where kb = [B(OH)3][OH-]/[B(OH)4-], and CT is the total concentration of boron. Under the given conditions kex is (2–7) × 106 dm3 mol-1 s-1 and ΔH‡, ΔS‡, and ΔV‡ are 20.1 ± 1.0 kJ mol-1, -55.0 ± 3.1 J mol-1 K-1, and -9.9 ± 0.5 cm3 mol-1, respectively. The activation parameters reflect the transition state forming dimeric [(OH)3B(μ-OH)B(OH)3]-. The results are compared with those of related reactions.

Original languageEnglish
Pages (from-to)3811-3816
Number of pages6
JournalInorganic Chemistry
Volume33
Issue number17
DOIs
Publication statusPublished - 1994 Aug 1

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

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