Effect of short-chained sodium alkylsulfate micelles on the kinetics of metal complex formation

Abstract

The kinetics of the reaction between Ni aq 2+ and the bidentate ligand pyridine-2-azo-p-dimethylaniline (PADA) have been investigated in micellar solutions of sodium decyl-, octyl-, and hexylsulfates using the stopped-flow technique. The rate of enhancement decreased with decreasing alkyl-chain length and from the Berezin or Robinson model could be quantitatively related to the independently measured binding constants of Ni 2+ ion and PADA to the micelle surface. The dramatic effect of micelles upon the reaction rates in different directions of the Ni 2+ /PADA and the Ni 2+ /murexide reactions served as sensitive indicators of the cmc even at the very limit of micelle formation which relatively concentrated sodium hexylsulfate solutions represent.