Equilibrium Dynamics in the Thallium(III)-Chloride System in Acidic Aqueous Solution

Julius Glaser, Istvan Banyai

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Abstract

Kinetics of ligand exchange in the thallium(III)-chloride system in aqueous three molar perchloric acid solution was studied by measuring 203Tl NMR line widths at 25 °C. The rate constants for the reactions are k01= 4.5 × 104 (7.8 × 103 at 0 °C), k12 = 5.2 × 104 (1.5 × 104), k23= 2.7 × 107 (3.3 × 106), k34< 3 X 107M-1 s-1; for the reaction k02 = 6.4 × 105M-1s-1 (1.7 × 105), and for the anation reactions k'01 < 1 × 108, k'12= 3.3 × 108(2.4 X 108), k'23 = 1.3 × 109, and k'34= 4.7 × 108M-1s-1. The first type of exchange dominates at low chloride to thallium ratios (Cltot/Tltot) = R ≤2, the second type is only observed when the species Tl3+and T1C12+ are present, whereas the third one dominates at all higher R values. The activation parameters for the reaction represented by k01are ΔH*= 49 (±2) kJ mol-1and ΔS* = +12 (±0.3) J mol-1K-1. A mechanism for this reaction is suggested to be a dissociatively activated interchange process. The activation parameters for the reaction represented by k'34are ΔH* = 6.6 kJ mol-1 and ΔS* = -107 J mol-1 K-1. An associatively activated interchange mechanism for this reaction is proposed. The stability constant for the complex T1C152-was estimated to be K5= [TlCl52-]/[TlCl4-] [Cl-]} ≈ 0.5 M-l.

Original languageEnglish
Pages (from-to)3186-3194
Number of pages9
JournalJournal of the American Chemical Society
Volume111
Issue number9
DOIs
Publication statusPublished - Apr 1989

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ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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