Micellar Effects on S(N)2 Reactions of Alkyl Naphthalene-2-sulfonates:The Role of Hydrophobic Substituents.

Reactivities of methyl naphthalene-2-sulfonate, MeONs, and its 6-alkyl derivatives, alkyl=Me, n-C(6)H(13) and n-C(12)H(25), 6-Me-MeONs, 6-Hex-MeONs, and 6-Do-MeONs, respectively, are compared for reactions in cetyl trialkylammonium bromide micelles, n-C(16)H(33)NR(3)Br, R=Me, Et, n-Pr, n-Bu, CTABr, CTEABr, CTPABr, CTBABr, respectively. Similar experiments were made on reactions of Br(-) with n-butyl and n-decyl naphthalene-2-sulfonates, BuONs, and DeONs, respectively. Reactions with OH(-) were followed in cetyl trialkylammonium hydroxide, alkyl=Me, Et, n-Pr, CTAOH, CTEAOH, and CTPAOH, solubility permitting. Some reactions with OH(-) or Br(-) were also followed in mixed-ion systems of CTAOMs or CTPAOMs (OMs=MeSO(3)). Micellar rate effects were analyzed by using pseudophase treatments including interionic competition in mixed-ion systems. Second-order rate constants in the micellar pseudophase increase systematically with increases in substrate hydrophobicity and for reactions with Br(-), but not OH(-), they also increase with bulk of the cationic head group. Copyright 2001 Academic Press.