Kinetics and mechanism of reduction of thallium(III) with glyoxal in perchloric acid medium

The kinetics and mechanism of reduction of thallium(III) with glyoxal has been studied in 0.5 mol dm - 3 perchloric acid medium. The reaction is first order with respect to thallium(III) and glyoxal. An inverse hydrogen ion effect is observed. A plausible mechanistic pathway for the reaction is suggested which leads to the following rate law: rate=k 1 [Tl 3 + ][H 2 C 2 O 2 ]+k 2 [TlOH 2 + ] [Gly] where k 1 and k 2 are the formation constants of the complex between thallium(III), TlOH 2 + and glyoxal. The computed values of E a and ΔS* are 39.04+1.04 kJ mol - 1 and -11.66′7.36 JK - 1 mol - 1 , respectively.