Kinetics and Mechanism of Formation of [Fe(CN) 5 D-PA] by Ligand Substitution Reaction in the Presence of Surfactant Micelle in Acidic Media.

The kinetics and mechanism of formation of [Fe(CN)5D-PA]3− by ligand substitution reaction between aquapentacyanoferrate(II) ion, and D-pencillamine (D-PA) has been investigated spectrophothmetrically in presence of anionic surfactant micelle, sodium dodecylsulphate (SDS) at 421 nm (λmax of product) under pseudo-first order conditions using excess of D-PA over [Fe(CN)5H2O]3−. The reaction was studied as a function of [Fe(CN)5H2O3−], [D-PA], [SDS], pH, ionic strength, and temperature, by varying only one of these variables at a time while the other variables held constant. The reaction exhibited first order kinetics in [D-PA] while it was independent of [Fe(CN)5H2O3−] in the chosen concentration range. The sodium dodecylsulphate (SDS) micelle, being of negatively charged, does not reveal any regular effect except at or near its critical micelle concentration (cmc). The effect of temperature on the reaction rate was also studied to calculate the activation parameters, computed by Arrhenius and Eyring plots. The most plausible mechanism consistent with the experimental results has also been proposed. [ABSTRACT FROM PUBLISHER]