Ion Exchange in Micellar Solutions. 7. Effect of Detergent Structure on the Binding and Reactivity of OH- in Cationic Micellar Solutions

Article abstract of DOI:10.1021/j100222a022

Ion exchange selectivity coefficients for the binding of OH- to a series of homologous alkyltrimethylammonium bromides and chlorides and to hexadecylpyridinium chloride (HPCl) and bromide are reported.The magnitude of these selectivity coefficients is determined principally by the nature of the detergent counterion (Cl- or Br-).Although there appear to be secondary contributions from the head group type, variations in the detergent alkyl chain length (tetradecyl to octadecyl) have little or no effet on the observed OH- binding affinity.Quantitative analysis of kinetic data for a series of alkaline hydrolysis reactions in micellar HPCl provides intrinsic reactivity parameters in the micellar pseudophase which are in all cases comparable to those in micellar hexadecyltrimethylammonium bromide (CTAB).It is concluded that the factors which contribute to the binding and to the reactivity of OH- at the cationic micellar surface are distinct and that the intrinsic effects of nonfunctionalized cationic detergents on reactivity and equilibria are quite similar (as opposed to being highly surfactant specific).