C. Siswanto et al., SYNTHESIS OF ALKYLPHENYL ETHERS IN AQUEOUS SURFACTANT SOLUTIONS BY MICELLAR PHASE-TRANSFER CATALYSIS .1. SINGLE-PHASE SYSTEMS, Langmuir, 13(23), 1997, pp. 6047-6052
Phase-transfer catalysis and micellar catalysis are two conventional m
ethods of promoting reactions between lipophilic and hydrophilic react
ants. Phase-transfer catalysis employs organic solvents that may be un
desirable for both economic and:environmental reasons, while applicati
on of micellar catalysis is limited by the relatively low solubilizati
on capacities of surfactant solutions. Micellar phase-transfer catalys
is is a process that combines the best aspects of both conventional me
thods while avoiding some of the associated problems. Reaction systems
consist of reactants, water, surfactant and a phase-transfer catalyst
--no organic solvent is used. The surfactant acts to solubilize and em
ulsify the lipophilic reactant, while the role of phase-transfer catal
yst is to shuttle the hydrophilic reactant from the aqueous phase into
the micellar environment where the reaction primarily takes place. Al
kylation of phenol with 1-bromobutane was studied under phase-transfer
, micellar, and micellar phase-transfer conditions in single-phase sol
utions at relatively high reactant loadings. Cationic (dodecyltrimethy
lammonium bromide), anionic (sodium dodecyl sulfate), and nonionic (di
methyldodecylamine oxide) surfactants were compared. Higher conversion
s with micellar phase-transfer catalysis over conventional micellar an
d phase-transfer catalysis were observed in nonionic and anionic surfa
ctant systems. For cationic surfactant systems, no significant advanta
ge was observed for micellar phase-transfer catalysis in comparison to
conventional micellar catalysis. The effect of cationic surfactant co
ncentration was studied and an optimum surfactant concentration was ob
served. Effects of initial reactant concentrations and two types of mi
xing were also studied. Mixing effects were significant, suggesting th
at mass transport rates of components between the aqueous and micellar
pseudophases in these microheterogeneous systems at high reactant con
centrations may affect reaction kinetics.