Temperature and pressure effects on the kinetics of the Bromate ion‐iodide ion‐L‐ascorbic acid clock reaction

I. Fábián, Rudi Van Eldik

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8 Citations (Scopus)

Abstract

The kinetics of the bromate ion‐iodide ion‐L‐ascorbic acid clock reaction was investigated as a function of temperature and pressure using stopped‐flow techniques. Kinetic results were obtained for the uncatalyzed as well as for the Mo(VI) and V(V) catalyzed reactions. While molybdenum catalyzes the BrO 3−‐I reaction, vanadium catalyzes the direct oxidation of ascorbic acid by bromate ion. The corresponding rate laws and kinetic parameters are as follows. Uncatalyzed reaction: r2 = k2[BrO 3−] [I][H+]2, k2 = 38.6 ± 2.0 dm9 mol−3 s−1, ΔH‡ = 41.3 ± 4.2 kJmol−1, ΔS‡ = −75.9 ± 11.4 Jmol−1 K−1, ΔV‡ = −14.2 ± 2.9 cm3 mol−1. Molybdenum‐catalyzed reaction: r′2 = k2[BrO 3−] [I] [H+]2 + kMo[BrO 3−] [I] [ H+]2[M0(VI)], kMo = (2.9 ± 0.3)106 dm12 mol−4 s−1, ΔH‡ = 27.2 ± 2.5 kJmol−1, ΔS‡ = −30.1 ± 4.5 Jmol−1K−1, ΔV‡ = 14.2 ± 2.1 cm3 mol−1. Vanadium‐catalyzed reaction: r′1 = kV[BrO 3−] [V(V)], kV = 9.1 ± 0.6 dm3 mol−1 s−1, ΔH‡ = 61.4 ± 5.4 kJmol−1, ΔS‡ = −20.7 ± 3.1 Jmol−1K−1, ΔV‡ = 5.2 ± 1.5 cm3 mol−1. On the basis of the results, mechanistic details of the BrO 3−‐I reaction and the catalytic oxidation of ascorbic acid by BrO 3− are elaborated. © 1995 John Wiley & Sons, Inc.

Original languageEnglish
Pages (from-to)491-498
Number of pages8
JournalInternational Journal of Chemical Kinetics
Volume27
Issue number5
DOIs
Publication statusPublished - 1995

ASJC Scopus subject areas

  • Biochemistry
  • Physical and Theoretical Chemistry
  • Organic Chemistry
  • Inorganic Chemistry

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