Elimination in sulfobetaine micelles: effects of head group bulk

Zwitterionic micelles of tetradecyldimethylammoniopropanesulfonate and tetr adecyldibutylammoniopropanesulfonate SB3-14 and SBBu3-14, respectively, acc elerate the E2 reaction of OH- with 4-nitrophenethyl bromide (1b), but the reaction of phenethyl bromide (1a) is inhibited by SB3-14 and is only sligh tly accelerated by SBBu3-14. Analysis of these data allows the separation o f the association constants for transfer of reactants from water to micelle s from the second-order rate constants in the micelles. These second-order rate constants are, as in water, larger for Ib than la, and for both substr ates are higher in SBB u3-14 than in SB3-14, as found for reactions in othe rwise similar cationic micelles. Rate constants in micelles, relative to th ose in water, are consistently higher in E2 than in S(N)2 reactions. Copyri ght (C) 1999 John Wiley & Sons, Ltd.