Organic reactions in microemulsions

Microemulsions are useful as reaction media to overcome the reagent incompatibility that one frequently encounters in organic synthesis. In this respect microemulsions can be regarded as an alternative to two-phase systems with added phase transfer agent (phase transfer catalysis). Recent work has shown that the two approaches, i.e. use of microemulsions and addition of a phase transfer agent, can be combined, leading to very high reactivity. It has also been demonstrated that an extra acceleration of a reaction may be obtained by proper choice of surfactant in the formulation. Only a small amount of a surfactant with a charge opposite the charge of one reactant may lead to a rate enhancement due to an increased local concentration of that reactant in the interfacial zone, where the reaction takes place (microemulsion catalysis). The oil–water interface of a microemulsion can also be used as a template to impart regioselectivity.