Kinetics for benzoylation of sodium 4-acetylphenoxide via third-liquid phase in the phase-transfer catalysis

Abstract

In this research, the kinetics for synthesizing 4-acetylphenyl benzoate ((RCOOR)-C-*) from benzoylation of sodium 4-acetylphenoxide via third-liquid phase-transfer catalysis was investigated. The reaction rate was observed to be strongly dependent on agitation speeds in the third-phase catalytic reaction. By forming the third-liquid phase, the observed reaction can be greatly enhanced to give a product yield of 100 % in a duration of 3 min at 20 degrees C and 200 rpm. If a third-liquid phase was not formed in the liquid-liquid system, the reaction rate is very slow and the product yield is only 2 % in 3 min at 20 degrees C. The reaction conducted in third-liquid phase-transfer catalytic system is faster than that in LLPTC system by 25-28 times. The amount of catalytic intermediate (QOR) in the third-liquid phase was about 50 % of the catalyst initially added and kept about 30 % of it remained after 1 min, and only small amounts of a catalytic intermediate residing in the organic phase were observed during the reaction using methyl t-butyl ether as the solvent. The concentration of catalytic intermediate slightly decreased with increasing reaction time, while the molar ratio of QOR to benzyl tri-n-butylammonium cation in the third-liquid phase remained almost constant after I min and increased with increasing agitation speeds. The experimental results were well described by the pseudo-first-order kinetics. The present work shows an effective method to synthesize 4-acetylphenyl benzoate. (c) 2005 Elsevier B.V. All rights reserved.