S(N)2 REACTIONS OF A SULFONATE ESTER IN MIXED CATIONIC PHOSPHINE OXIDE MICELLES

Addition of the nonionic surfactant, dodecyl(dimethyl)phosphine oxide (C12PO) to aqueous cetyltrimethylammonium bromide (CTABr) inhibits the micellar-mediated reaction of Br- with fully bound methyl naphthalene -2-sulfonate (MeONs). Reaction in the micellar pseudophase depends on the concentration of Br - in the interfacial surface region, which is decreased;on addition of C12PO by increases in both the fractional mic ellar ionization, alpha, and the volume of the micellar pseudophase. T he inhibition of the reaction is partially offset by an increase in th e second-order rate constant in the micellar pseudophase on addition o f C12PO which appears to be related to a solvent-like effect at the mi celle-water interface. Interactions of CTABr and C12PO in the mixed mi celles were explored by using H-1 and P-31 NMR spectroscopy.