Reaction in micellar solutions: Part 10+-Effects of surfactants on kinetics of formation and dissociation of monothiocyanatoiron(III) complex

Abstract

The kinetics of reversible complexation of iron(III) with thiocyanate (SCN^-) has been investigated at 25°C in aqueous micellar media by stopped flow technique. The rate of reaction of Fe(OH₂)<img src='http://www.niscair.res.in/jinfo/equation142.gif' border=0> + with SCN^- is decelerated 400 times by the anionic micelles of sodium dodecyl sulphate (SDS). The major path of dissociation of monothiocyanatoiron(III) species in the anionic micellar pseudo-phase is revealed to be Fe(OH)NCS⁺ → Fe(OH)²⁺+ SCN^- and the dissociation rate of Fe(OH)NCS⁺ is moderately accelerated by the anionic micelles. The neutral micelles of Triton x 100 have only little effect on the rate of formation and dissociation of FeNCS²⁺ or Fe(OH)NCS⁺. The results indicate that micelles may be useful probes to throw light on the mechanism of inorganic substitution reactions.