The @[email protected] of a @[email protected] in solution by the addition of a surfactant at a concentration higher than its @[email protected] so that the reaction can proceed in the environment of surfactant aggregates (@[email protected]). (Rate enhancements may be due, for example, to higher concentration of the reactants in that environment, more favourable orientation and @[email protected] of the species, or enhanced rate constants in the micellar pseudophase of the surfactant aggregate.) @[email protected] formation can also lead to a decreased reaction rate.