A QUANTITATIVE TREATMENT OF MICELLAR EFFECTS IN MODERATELY CONCENTRATED HYDROXIDE ION

Cationic micelles increase first-order rate constants of reactions of OH- with p-nitrophenyl diphenyl phosphate (pNPDPP), 2,4-dinitrochloronaphthalene (DNCN), and 1,1,1-trichloro-2,2-bis(p-chlorophenyl)-ethane (DDT). The micellar rate effects with moderately concentrated OH- (<0.5 M) are larger than predicted by pseudophase ion-exchange treatments with constant fractional micellar ionization, alpha. A treatment based on solution of the Poisson-Boltzmann equation (PBE), which includes both nonspecific, Coulombic and specific ion-micelle interactions, fits the data reasonably well with a modest increase of the aggregation number and a "rough", rather than a "smooth", micellar surface. Estimated second-order rate constants of reactions of dilute OH- with pNPDPP and DNCN at the micellar surface based on a smooth micelle agree with the new values for reactions with 0.5 M OH-.