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Phase‐Transfer Agents as Catalysts for a Nucleophilic Substitution Reaction in Microemulsions
Author(s) -
Häger Maria,
Holmberg Krister
Publication year - 2004
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200306048
Subject(s) - microemulsion , chemistry , catalysis , transfer agent , phase transfer catalyst , inorganic chemistry , crown ether , solvent , phase (matter) , nucleophilic substitution , reaction rate , salt (chemistry) , ammonium bromide , bromide , organic chemistry , pulmonary surfactant , ion , biochemistry , polymer , monomer
The reaction between 4‐ tert ‐butylbenzyl bromide and potassium iodide was carried out in microemulsions based on different nonionic surfactants, and the reaction rates were compared with those obtained in two‐phase systems with added phase‐transfer agent, either a quaternary ammonium salt or a crown ether. The reactions were relatively fast in the microemulsions and extremely sluggish in the two‐phase systems without additional phase‐transfer agent. Addition of a phase‐transfer agent did not accelerate the reaction when a hydrocarbon was used as organic solvent, neither in the two‐phase system nor in the microemulsion. When a chlorinated hydrocarbon was used as solvent, phase‐transfer catalysis became effective and the rate obtained in the two‐phase system with an equimolar amount of phase‐transfer agent added was higher than that obtained in the microemulsion. When a catalytic amount of phase‐transfer agent was used, the rate in the two‐phase system was about the same as the rate obtained in the microemulsion without the phase‐transfer agent. The combined approach, that is, use of a microemulsion as the reaction medium and addition of a phase‐transfer agent, gave the highest reaction rate. The quaternary ammonium salt (tetrabutylammonium hydrogen sulfate) was a more efficient catalyst in the microemulsion system than the crown ether ([18]crown‐6).