Variable-Pressure Kinetic and Equilibrium Study of the Complexation of the Beryllium(II) Ion with 4-Isopropyltropolone in Acidic Aqueous Solution

Masahiko Inamo, Koji Ishihara, Shigenobu Funahashi, Yves Ducommun, André E. Merbach, Motoharu Tanaka

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Abstract

Kinetics and equilibria for the formation and dissociation of the 1:1 complex of the beryllium(II) ion with 4-isopropyltropolone (Hipt) in acidic aqueous solution have been studied spectrophotometrically at various temperatures and pressures at an ionic strength of 0.100 M ((Na,H)ClO4). Equilibrium measurements gave the following results: K = [Be(ipt)+] [H+] [Be2+]−1 [Hipt]−1 = 1.17 ± 0.06 (25.0 °C), ΔH° = 2.4 ± 0.3 kJ mol−1, ΔS° = 9.2 ± 1.1 J K−1 mol−1, ΔV° = +5.3 ± 0.2 cm3 mol−1 (25.0 °C). The reaction volumes for the proton dissociation of Hipt and for the complexation of Be2+ with ipt are -8.2 ± 0.5 and +13.5 ± 0.6 cm3 mol−1, respectively, at 25.0 °C. The rate constants and activation parameters for formation and dissociation of the complex are as follows: kf = 58.1 ± 0.5 M−1 s−1 (25.0 °C), kr = 49.8 ± 0.5 M−1 s−1 (25.0 °C), ΔHf* = 38.1 ± 0.4 kJ mol−1, ΔH,* = 35.7 ± 0.4 kJ mol−1, ΔSf* = -83.5 ± 1.3 J K−1 mol−1, ΔSr* = -92.7 ± 1.2 J K−1 mol−1, ΔVf* = −7.1 ± 0.2 cm3 mol−1 (25.0 °C), ΔKr* = −12.4 ± 0.2 cm3 mol−1 (25.0 °C). The negative values of entropy and volume of activation indicate that the reaction proceeds with an associative mode of activation.

Original languageEnglish
Pages (from-to)1580-1583
Number of pages4
JournalInorganic Chemistry
Volume30
Issue number7
DOIs
Publication statusPublished - 1991 Apr 1

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ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

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