Green Conversion of Phenolic Compound to Benzoate Over Polymer-Supported Phase-Transfer Catalysts
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The conversion of sodium phenoxide into benzoates over polymer-supported phase-transfer catalysts with trialkylamines as the functional groups (triphase catalysis) was investigated. The yield of product phenyl benzoate was 100% in 1 h of reaction using a small amount of tributylamine catalyst supported on 1.38% divinylbenzene (DVB) cross-linked copolymer (40–80 mesh) of styrene and chloromethylstyrene. During the reaction, the catalyst stays between the aqueous and organic phases. The overall reaction rate was strongly dependent on the stirring speed and the ionic exchange of Cl− of the catalyst with PhO− in the interfacial region. The reaction rate decreased with increasing the mean particle sizes for 1.38% DVB catalyst. The variation of the catalytic intermediate within the catalyst was determined to verify the reaction mechanism. A kinetic model was also proposed to correlate the reaction rate constants. The efficient conversion of phenolic compounds over polymer-supported catalysts shows that triphase catalysis is an efficient green technology in chemical synthesis.
KeywordsEsterification Polymer-supported phase-transfer catalyst Trialkylamines Phenyl benzoate Triphase catalysis
The authors acknowledge the financial support of the National Science Council, Taiwan, Republic of China (Grant No. NSC 93-2214-E-005-001). This work is also supported in part by the Ministry of Education, Taiwan, ROC, under the ATU plan.