Cocatalysis by ruthenium(III) in hydrogen ions catalyzed oxidation of iodide ions: A kinetic study

✍ Scribed by Praveen K. Tandon; Alka Mehrotra; Alok K. Singh; Ramesh Baboo; Priy B. Dwivedi

• Publisher: John Wiley and Sons
• Year: 2004
• Tongue: English
• Weight: 104 KB
• Volume: 36
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/kin.20030

✦ Synopsis

Abstract

RuCl~3~ further catalyzes the oxidation of iodide ion by K~3~Fe(CN)~6~, already catalyzed by hydrogen ions. The rate of reaction, when catalyzed only by hydrogen ions, was separated graphically from the rate when both Ru(III) and H^+^ ions catalyzed the reaction. Reactions studied separately in the presence as well as absence of RuCl~3~ under similar conditions were found to follow second‐order kinetics with respect to [I^−^], while the rate showed direct proportionality with respect to [Fe(CN)~6~]^3−^, [RuCl~3~], and [H^+^]. External addition of [Fe(CN)~6~]^4−^ ions retards the reaction velocity, while changing the ionic strength of the medium has no effect on the rate. With the help of the intercept of the catalyst graph, the extent of the reaction that takes place without adding Ru(III) was calculated and it was in accordance with the values obtained from the reaction in which only H^+^ ions catalyzed the reaction. It is proposed that ruthenium forms a complex, which slowly disproportionates into the rate‐determining step. Arrhenius parameters at four different temperatures were also calculated. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 545–553, 2004