Kinetic studies of the complex formation of iron(III) with 4-isopropyltropolone by a high-pressure stopped-flow technique. Mechanistic difference between the hexaaquairon(III) ion and the pentaaquahydroxoiron(III) ion in their complexation

Koji Ishihara, Shigenobu Funahashi, Motoharu Tanaka

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Abstract

The formation rate of the 1:1 iron(III) complex with 4-isopropyltropolone (Hipt) has been studied spectrophotometrically in aqueous solution of low pH at various temperatures and pressures by a stopped-flow technique. The rate law is expressed as d[Fe(ipt)2+]/dt = (k1 + k2KFeOH [H+]-1)(1 + KH [H+])-1[Fe3+][Hipt], with k1 = 21.7 ± 1.1 M-1 s-1 and k2 = (6.30 ± 0.31) × 103 M-1 s-1 at 25°C and I = 1.00 M at atmospheric pressure. The activation parameters for the reaction of Fe(OH2)6 3+ (k1 path) and the reaction of Fe(OH2)5OH2+ (k2 path) are as follows: ΔH 1 = 59.5 ± 3.0 kJ mol-1, ΔS 1 = -19.8 ± 3.0 J mol-1 K-1, ΔV 1 = -8.7 ± 0.8 cm3 mol-1; ΔH 2 = 29.2 ± 3.6 kJ mol-1, ΔS 2 = -72.3 ± 5.0 J mol-1 K-1, ΔV 2 = 4.1 ± 0.6 cm3 mol-1. Associative- and dissociative-interchange mechanisms are most probably operative for the k1 and k2 paths, respectively.

Original languageEnglish
Pages (from-to)194-198
Number of pages5
JournalInorganic Chemistry
Volume22
Issue number2
Publication statusPublished - 1983
Externally publishedYes

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Interchanges
Complexation
Atmospheric pressure
Iron
Chemical activation
Ions
iron
Kinetics
kinetics
ions
Temperature
atmospheric pressure
activation
aqueous solutions
beta-thujaplicin
temperature

ASJC Scopus subject areas

  • Inorganic Chemistry

Cite this

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title = "Kinetic studies of the complex formation of iron(III) with 4-isopropyltropolone by a high-pressure stopped-flow technique. Mechanistic difference between the hexaaquairon(III) ion and the pentaaquahydroxoiron(III) ion in their complexation",
abstract = "The formation rate of the 1:1 iron(III) complex with 4-isopropyltropolone (Hipt) has been studied spectrophotometrically in aqueous solution of low pH at various temperatures and pressures by a stopped-flow technique. The rate law is expressed as d[Fe(ipt)2+]/dt = (k1 + k2KFeOH [H+]-1)(1 + KH [H+])-1[Fe3+][Hipt], with k1 = 21.7 ± 1.1 M-1 s-1 and k2 = (6.30 ± 0.31) × 103 M-1 s-1 at 25°C and I = 1.00 M at atmospheric pressure. The activation parameters for the reaction of Fe(OH2)6 3+ (k1 path) and the reaction of Fe(OH2)5OH2+ (k2 path) are as follows: ΔH‡ 1 = 59.5 ± 3.0 kJ mol-1, ΔS‡ 1 = -19.8 ± 3.0 J mol-1 K-1, ΔV‡ 1 = -8.7 ± 0.8 cm3 mol-1; ΔH‡ 2 = 29.2 ± 3.6 kJ mol-1, ΔS‡ 2 = -72.3 ± 5.0 J mol-1 K-1, ΔV‡ 2 = 4.1 ± 0.6 cm3 mol-1. Associative- and dissociative-interchange mechanisms are most probably operative for the k1 and k2 paths, respectively.",
author = "Koji Ishihara and Shigenobu Funahashi and Motoharu Tanaka",
year = "1983",
language = "English",
volume = "22",
pages = "194--198",
journal = "Inorganic Chemistry",
issn = "0020-1669",
publisher = "American Chemical Society",
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T1 - Kinetic studies of the complex formation of iron(III) with 4-isopropyltropolone by a high-pressure stopped-flow technique. Mechanistic difference between the hexaaquairon(III) ion and the pentaaquahydroxoiron(III) ion in their complexation

AU - Ishihara, Koji

AU - Funahashi, Shigenobu

AU - Tanaka, Motoharu

PY - 1983

Y1 - 1983

N2 - The formation rate of the 1:1 iron(III) complex with 4-isopropyltropolone (Hipt) has been studied spectrophotometrically in aqueous solution of low pH at various temperatures and pressures by a stopped-flow technique. The rate law is expressed as d[Fe(ipt)2+]/dt = (k1 + k2KFeOH [H+]-1)(1 + KH [H+])-1[Fe3+][Hipt], with k1 = 21.7 ± 1.1 M-1 s-1 and k2 = (6.30 ± 0.31) × 103 M-1 s-1 at 25°C and I = 1.00 M at atmospheric pressure. The activation parameters for the reaction of Fe(OH2)6 3+ (k1 path) and the reaction of Fe(OH2)5OH2+ (k2 path) are as follows: ΔH‡ 1 = 59.5 ± 3.0 kJ mol-1, ΔS‡ 1 = -19.8 ± 3.0 J mol-1 K-1, ΔV‡ 1 = -8.7 ± 0.8 cm3 mol-1; ΔH‡ 2 = 29.2 ± 3.6 kJ mol-1, ΔS‡ 2 = -72.3 ± 5.0 J mol-1 K-1, ΔV‡ 2 = 4.1 ± 0.6 cm3 mol-1. Associative- and dissociative-interchange mechanisms are most probably operative for the k1 and k2 paths, respectively.

AB - The formation rate of the 1:1 iron(III) complex with 4-isopropyltropolone (Hipt) has been studied spectrophotometrically in aqueous solution of low pH at various temperatures and pressures by a stopped-flow technique. The rate law is expressed as d[Fe(ipt)2+]/dt = (k1 + k2KFeOH [H+]-1)(1 + KH [H+])-1[Fe3+][Hipt], with k1 = 21.7 ± 1.1 M-1 s-1 and k2 = (6.30 ± 0.31) × 103 M-1 s-1 at 25°C and I = 1.00 M at atmospheric pressure. The activation parameters for the reaction of Fe(OH2)6 3+ (k1 path) and the reaction of Fe(OH2)5OH2+ (k2 path) are as follows: ΔH‡ 1 = 59.5 ± 3.0 kJ mol-1, ΔS‡ 1 = -19.8 ± 3.0 J mol-1 K-1, ΔV‡ 1 = -8.7 ± 0.8 cm3 mol-1; ΔH‡ 2 = 29.2 ± 3.6 kJ mol-1, ΔS‡ 2 = -72.3 ± 5.0 J mol-1 K-1, ΔV‡ 2 = 4.1 ± 0.6 cm3 mol-1. Associative- and dissociative-interchange mechanisms are most probably operative for the k1 and k2 paths, respectively.

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