Treatment of Micellar Reactions of UNI and Divalent Ions

摘要

Rates of biomolecular ionic reactions in aqueous micelles can be treated quantitatively by estimating the concentrations of each reactant at the micellar surface. The concentration of nonionic substrates can be measured directly or estimated, and that of hydrophilic counterions is calculated in terms of coulombic and specific effects. The coulombic effects are calculated by solving the Poisson-Boltzman equation in spherical symmetry and the specific effects are calculated using Volmer or Langmuir isotherms with an ion-specific binding parameter. The treatment permits calculation of second order rate constants at the micellar surface for reactions of mono- and dianions. Inhibition by inert anions can also be treated quantitatively although it is necessary to postulate a distance of closest approach for the hydrophilic sulfate ion. The treatment has been applied to reactions of 2,4-dinitrochloronaphthalene, p-nitrophenyl diphenyl phosphate and methyl naphthalene-2-sulfonate with OH- in cetyl trimethylammonium sulfate and of methyl naphthalene-2-sulfonate with Br in cetyl trimethylammonium bromide or mesylate.