Comparison of reactivities of methyl naphthalene-2-sulfonate, MeONs, and its 6-sulfonate derivative, MeONsS(-), toward H2O, OH-, and Br- in water and in cationic micelles of cetyl trialkylammonium surfactants, n-C16H33N+R3X-, R = Me, n-Pr, n-Bu, CTA(+), CTPA(+), CTBA(+), X = OH, Br, and CH3SO3 has been investigated. For reactions in water, the introduction of the negative charge accelerates hydrolysis by a factor of ca. 2, but does not affect reactivity of OH- and Br-. For reactions in micelles, the negative charge decreases values of km for reactions with water, with OH- and Br- by a factor of ca. 2; differences for the two substrates decrease with bulking the surfactant head group for a reaction with Br- but not for a reaction with OH-.