Micellar effects on the reactions of complex ions in solution: Part 12ǂ-Kinetics of reversible complexation of oxalatopentaammineco-balt(II) with nickel(II) and iron(III) in the presence of anionic micelles of sodium dodecyl sulphate in aqueous medium

Abstract

The kinetics of reversible complexation of Ni(II) and Fe(II) with oxalatopentaamminecobalt(ill) has been investigated in aqeous micellar medium of sodium dodecyl sulphate at 25&deg;C by stopped flow spectrophotometry, The reaction occurs exclusively on the micellar surface, Analysis of the rate data is consistent with the reversible formation of the hinuclear species via the paths:<br /><br /> (NH₃)₅CoC₂O<img src="http://www.niscair.res.in/jinfo/plusfour.gif" alt="" border="0" />+ Ni²⁺<img src="http://www.niscair.res.in/jinfo/harpoon.gif" alt="" border="0" />(NH&lt;sub3)₅CoC₂O₄Ni³⁺ and<br /><br /> (NH₃)₅CoC₂O₄H²⁺ + FeOH²⁺<img src="http://www.niscair.res.in/jinfo/harpoon.gif" alt="" border="0" />(NH₃)₅CoC₂O₄Fe⁴⁺.<br /><br /> Comparison of the formation and dissociation rate constants for the micellar medium with those for the aqueous medium indicates that anionic micelles exert retarding influence on the rates of the formation and dissociation of the binuclear species. Coulombic forces are largely responsible for the observed micellar effect.