Nucleophilic Reactions in Zwitterionic Micelles of Amine Oxide or Betaine Sulfonate Surfactants

摘要

Ionic micelles in water concentrate counterions at their surface and repel co-ions due to Coulombic interactions. But non-Coulombic interactions are also important because hydrophilic, high charge density counterions are bound less strongly than polarizable, low charge density counterions. The concentration of reactants at miceller surfaces is the major source of enhancements of the rates of bimolecular reactions involving counterions, and examination of reaction rates and equilibria provides information on micelle-ion interactions. The specificity of counterion binding to micelles can be described in terms of a competition between ions. In one widely used treatment one for one competition is assumed and ion-exchange parameters are calculated as for binding to ion-exchange resins. An alternative treatment uses a Langmuir equation without stipulating one for one exchange. Other treatments involve calculation of Coulombic effects by solving the Poisson-Boltzmann equation, if necessary with inclusion of separate, non-Coulombic, interactions. Reprints. (JES)