ORGANIC-REACTIVITY IN MICROEMULSION SYSTEMS

Sulfides are oxidized at a remarkably fast rate (< 15 s, 23-degrees-C) when dissolved in an oil-in-water microemulsion containing a 2-fold excess of hypochlorite. Sulfoxide is formed exclusively and quantitatively. As much as 1 mL of sulfide can be oxidized by 15 mL of microemulsion. The process is much faster than phase-transfer catalysis and requires no stirring since the microemulsions are homogeneous. The cosurfactant in the microemulsion (a low molecular weight alcohol) is shown to play a central role in the oxidation by acting as an intermediary between the oil-soluble mustard and the water-soluble hypochlorite. The microemulsion-based method is simple, cheap, mild, selective, and rapid. These properties arise from the fact that microemulsions represent a "community" of molecules that function only by virtue of cooperative action. Each of the six components (water, hydrocarbon, surfactant, cosurfactant, oxidant, and sulfide) has its own particular residence site and its own particular role in the reaction. Self-assembly converts what might have been a useless and intractable mixture into a functioning system that destroys objectionable compounds.