Co-catalysis by transition metal ions in the hydrogen ion catalysed oxidation of iodide ions. A kinetic study
The reaction between KI and [Fe(CN)6]3− ion, catalysed by hydrogen ions, was found to be catalysed further by PdCl2. Separate reactions under similar conditions, studied in the absence as well as in the presence of PdCl2 catalyst, were found to follow first order kinetics w.r. to [Fe(CN)6]3− and [H+], while the order was two w.r. to [I−]. [Fe(CN)6]4− ions were found to have a negative effect while changes in ionic strength of the medium do not effect the reaction velocity. Reaction in the presence of PdCl2 showed direct proportionality w.r. to [PdCl2]. The rate and extent of the reaction, which takes place even at zero [PdCl2] in the co-catalysed reaction, was calculated and was found to be in accordance with the rate values of the separately studied reaction at similar concentrations without adding PdCl2.