Nucleophilicity of bromide ion in mixed cationic/sulfoxide micelles

Addition of the non-ionic surfactant, n-decyl methylsulfoxide (C10SO) to aqueous cetyltrimethylammonium bromide (CTABr) inhibits the micellar-mediated reaction of Br– with bound methyl naphthalene-2-sulfonate (MeONs). The concentration of Br– at the micellar surface is reduced due to an increase in the fractional micellar ionization, α, and in the volume of the micellar pseudophase, which slows the reaction of Br–. These concentration effects are partially offset by an increase in the second-order rate constant in the micellar pseudophase on addition of C10SO.