Arenediazonium Salts: New Probes of the Interfacial Compositions of Association Colloids. 6. Relationships between Interfacial Counterion and Water Concentrations and Surfactant Headgroup Size, Sphere-to-Rod Transitions, and Chemical Reactivity in Cationic Micelles

Abstract

Product yields measured by high-performance liquid chromatography from chemical trapping of Cl-, Br-, and H2O by an aggregate-bound arenediazonium ion in cetyltrialkylammonium halide {(CTRA)X, R = Me, Et, n-Pr, and n-Bu; X = Cl, Br}, micelles are used to estimate, simultaneously, interfacial counterion, Xm, and water, H2Om, concentrations as a function of [(CTRA)X] and tetramethylammonium halide concentrations, [(TMA)X]. The results are interpreted by using a two-site pseudophase model. Values of Xm and H2Om are estimated by assuming that when the product yields from reaction of a long-tail aggregate-bound arenediazonium ion in micelles are the same as the product yields from reaction of its short chain analogue in an aqueous quaternary ammonium ion salt solution, then Xm = [Xw] and H2Om = [H2Ow] in those solutions. The results show that Xm and H2Om are functions of headgroup size, surfactant concentration, and aqueous counterion concentration and type. Plots of Xm against [(CTRA)X] at a series of salt co...