Kinetics and mechanism of the interaction of thioglycolic acid with cis-diaquaethylenediamineplatinum(II) perchlorate in aqueous medium

The kinetics of the interaction of thioglycolic acid with [Pt en(H2O)(2)](2 +) has been studied spectrophotometrically as a function of [Pt en(H2O)(2+) (2)], [thioglycolir acid], pH and temperature. The reaction has been monito red at 224 nm, where the spectral difference between the reactants and prod uct is maximum. The reaction proceeds via rapid outersphere association com plex formation followed by two slow consecutive steps having first order de pendence on the aqua ion and thioglycolic acid. Activation parameters have been evaluated using Eyring equation. The low Delta H*(1) and large negativ e value of Delta S*(1) as well as Delta H*(2) and Delta S*(2) indicate an a ssociative mode of activation for both aqua molecule substitution process i n the two consecutive steps.