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Kinetics and mechanism of oxidation of aurate(I) by peroxydisulphate in aqueous hydrochloric acid
Author(s) -
Babshet R. M.,
Gokavi G. S.
Publication year - 2002
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/kin.10088
Subject(s) - chemistry , protonation , reaction rate constant , hydrochloric acid , aqueous solution , ion , inorganic chemistry , kinetics , chloride , electron transfer , reaction mechanism , reaction rate , catalysis , organic chemistry , physics , quantum mechanics
The reaction between Au(I), generated by reaction of thallium(I) with Au(III), and peroxydisulphate was studied in 5 mol dm −3 hydrochloric acid. The reaction proceeds with the formation of an ion‐pair between peroxydisulphate and chloride ion as the Michealis–Menten plot was linear with intercept. The ion‐pair thus formed oxidizes AuCl 2 − in a slow two‐electron transfer step without any formation of free radicals. The ion‐pair formation constant and the rate constant for the slow step were determined as 113 ± 20 dm −3 mol −1 and 5.0 ± 1.0 × 10 −2 dm 3 mol −1 s −1 , respectively. The reaction was retarded by hydrogen ion, and formation of unreactive protonated form of the reductant, HAuCl 2 , causes the rate inhibition. From the hydrogen ion dependence of the reaction rate, the protonation constant was calculated to be as 0.6 ± 0.1 dm 3 mol −1 . The activation parameters were determined and the values support the proposed mechanism. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 589–594, 2002