Abstract
Kinetics of reaction involving two low-spin iron(II) di-imine complexes, Fe(phen)2+3 and Fe(hxsbH)2+, are reported where the solvent media include three microemulsions and a range of aqueous 2-butoxyethanol mixtures. In certain systems containing Fe(hxsbH)2+ the rate of reaction follows zero-order kinetics for a considerable part of the reaction. The kinetics are accounted for using a reaction scheme in which the complex metal ion is adsorbed at an interphase between organic-rich and water-rich domains. The same model is used to account for the marked acceleration in the rate of reaction between Fe(phen)2+3 and hydroxide ions in these systems. The kinetics of a scheme in which reaction takes place in both domains are examined, the distribution of the substrate being at all times in equilibrium between the two microphases. In such cases a plot of In k(obs.) against 1/T can be S-shaped, where k(obs.) is the overall first-order rate constant. Effects of changes in acid, acid concentration and added surfactant on the rate of reaction in the microemulsions are reported.
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