Ultrasound-assisted phase-transfer catalysis: benzoylation of sodium 4-acetylphenoxide by dual-site phase-transfer catalyst in a tri-liquid system.
A novel dual-site phase-transfer catalyst (PTC) was prepared and used to conduct the benzoylation of sodium 4-acetylphenoxide by ultrasound-assisted third-liquid phase-transfer catalysis. The catalyst 1,4-bis(tributylammoniomethyl)benzene dibromide (BTBAMBB) was synthesized from the reaction of p-xylylene dibromide and tributylamine in toluene at 70°C. The dual-site PTC was employed to form the third-liquid phase by extra addition of 0.04-0.05 mol of NaCl into 10 cm(3) of water. In the condition of 0.0425 mol of NaCl at 30°C, the catalytic intermediate in the third-liquid phase reached a maximum value. Almost 80% of the catalyst was transferred from the aqueous phase into the third-liquid phase. The distributions of the catalytic intermediate and dual-site PTC between phases and the kinetics of benzoylation of sodium 4-acetylphenoxide catalyzed by BTBAMBB with ultrasound irradiation were performed. The pseudo-first-order kinetic equation was applied to describe the overall reaction. Under ultrasound irradiation (28 kHz/300 W) in a batch reactor, the yield of product 4-acetylphenyl benzoate in the organic phase was 98.1% in 2 min at 30°C and 250 rpm with the apparent rate constant k(app) to be 0.0075 s(-1), which was 6 times faster than that without using ultrasound (yield=14.4%, k(app)=0.0013 s(-1)). The present study provides a green method to synthesize esters by ultrasound-assisted third-liquid phase-transfer catalysis.
Yang
Hung-Ming
HM
Department of Chemical Engineering, National Chung Hsing University, 250 Kuo-kuang Road, Taichung 402, Taiwan, ROC. hmyang@dragon.nchu.edu.tw
Chiu
Chun-Cheng
CC
D000098:Acetophenones / Q000737:chemistry*; D002384:Catalysis; D044367:Phase Transition; D000644:Quaternary Ammonium Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D012965:Sodium Chloride / Q000737:chemistry; D014465:Ultrasonics; D014867:Water / Q000737:chemistry; D014992:Xylenes / Q000138:chemical synthesis* / Q000737:chemistry
C554929:1,4-bis(tributylammoniomethyl)benzene; D000098:Acetophenones; D000644:Quaternary Ammonium Compounds; D014992:Xylenes; D014867:Water; D012965:Sodium Chloride