EFFECT OF 1-BUTANOL UPON SN2 REACTIONS IN CATIONIC MICELLES - A QUANTITATIVE TREATMENT

Observed first-order rate constants for reaction of methyl naphthalene-2-sulfonate (2-MeONs) with Br in cetyltrimethylammonium and cetyltriethylammonium bromides (CTABr and CTEABr) are decreased by addition of 1-butanol. The inhibition can be treated quantitatively in terms of a pseudophase model in which the rate constant at the micellar surface follows the mole ratio of bound Br- to micellized surfactant and bound 1-BuOH. The second-order rate constants in the micellar pseudophase, kM, are independent of [1-BuOH] in the range 0-0.9 M. Conductometry and NMR line widths of 81Br- show that the alcohol reduces micellar binding of Br-, and spectral absorbance shows that binding of 2-MeONs is also reduced. © 1990 American Chemical Society.