Effects of nonionic, cationic, and anionic micelles on the kinetics of the complexation reaction of nickel (II) with pyridine-2-azo-p-dimethylaniline

The stopped‐flow technique has been used to study the effect of cationic (CTAN), nonionic (Triton X‐100), andanionic (SDS) micelles on the rate of the reaction between nickel(II) ion and the ligand pyridine‐2‐azo‐p‐dimethylaniline (PADA) at 20.0°C and ionic strength 0.03 mol dm−3. The complex formation reaction is markedly inhibited by both CTAN and Triton X‐100 micelles. The kinetic dataare found to conform to a reaction mechanism which implies only partitioning of the ligand between water and the micellar phase, the estimated bindingconstant of PADA being significantly larger in the presence of CTAN aggregates. Anionic micelles strongly speed the complexation reaction, Which occurs in the micellar phase with the same rate and the same mechanism as in water. The extent of binding of PADA to anionic micelles is similar to that found for the cationic micellar aggregates.