Kinetics and mechanism of oxidation of aurate(I) by peroxydisulphate in aqueous hydrochloric acid

✍ Scribed by R. M. Babshet; G. S. Gokavi

• Publisher: John Wiley and Sons
• Year: 2002
• Tongue: English
• Weight: 132 KB
• Volume: 34
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/kin.10088

✦ Synopsis

Abstract

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