Kinetics of the reduction of hexachloroiridate (IV) by <img src='http://www.niscair.res.in/jinfo/small.gif' border=0> -methionine in aqueous solutions

Abstract

The kinetics of the reduction of hexachloroiridate (IV) by <img src='http://www.niscair.res.in/jinfo/small.gif' border=0> -methionine in aqueous solution has been studied. The data are consistent with the rate law:<br><br> - <em>d</em>[oxidant]/<em>dt= k</em>₃[oxidant][reductant][H⁺]<br><br> with <em>k</em>₃ = 1.58 ± 0.06 mol^-2dm⁶ s^-1, <img src='http://www.niscair.res.in/jinfo/delta.gif' border=0><em> H</em>^≠ = 31.3 ± 2.1 kJ mol^-1, <img src='http://www.niscair.res.in/jinfo/delta.gif' border=0><em> S</em>^≠= 210±11.6 JK^-1 mol^-1 at <em>I</em> =1.0 mol dm³ (NaCI) and T = 25.5ᵒC<em>. </em>Free radicals are unimportant in the reaction and the reduction is rationalised in terms of an outer-sphere mechanism.