Use of self-assembled surfactant systems as media for a substitution reaction.

The reaction between 3-bromo-1-propanol and phenol and a series of phenols carrying substituents in 4-position was studied in micellar media and in microemulsions based on either a cationic or a nonionic surfactant. The reactivity and the yield were evaluated and compared to those obtained in a microhomogeneous medium, methanol-water. It was found that the micellar system based on the cationic surfactant dodecyltrimethylammonium bromide was particularly efficient as reaction medium in giving the highest yields. The high reactivity obtained in this system was attributed to formation of a pi-cation complex between the benzene ring of the phenol and the headgroup of the cationic surfactant, resulting in exposure of the phenolate oxygen to the aqueous subvolume where the substrate, 3-bromo-1-propanol, was situated. A highly distorted NMR spectrum of the cationic surfactant gave evidence for this hypothesis.