Kinetics of dissociation of tris-2, 2'-bipyridyl iron(II) in the water pools of CTAB reverse micelles

Abstract

The kinetics of dissociation of the complex [Fe(bipy)₃]²⁺ has been studied in the water pools of cetyltrimethylammonium bromide(CTAB) in a mixture of hexane and chloroform(1: 1). In the absence of acid, the reaction is immeasurably slow in conventional aqueous medium but proceeds with a measurable speed in the reverse micelles. At low acid concentration (&lt;0.01’<i>M</i>), the reaction does not go to completion and reaches equilibrium in aqueous medium whereas in the reverse micelles it goes to completion and the rate is much higher. The rate decreases with increase in <i>W </i>(=[H₂O]/[CT AB]) at constant [CT AB] but is insensitive to change in [CTAB] at constant <i>W. </i>The H⁺ ion has more pronounced acceleration (approximately 100 times) than in aqueous system. Anions like SCN^- and Cl^- accelerate the dissociation due to the low polarity of water pool leading to stable ion pair formation with the complex. The kinetics has been accounted for by the unique properties of the water pools.