| 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 AuCl2? 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 dm3 mol?1 s?1, respectively. The reaction was retarded by hydrogen ion, and formation of unreactive protonated form of the reductant, HAuCl2, 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 dm3 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 |
