Synthesis of n-butyl phenyl ether by tri-liquid-phase catalysis using poly(ethylene glycol)-600 as a catalyst -: analysis of factors affecting the reaction in a batch reactor

As the second part of a series of studies on the synthesis of n-butyl phenyl ether (ROPh) by tri-liquid-phase catalysis, this work examines the factors affecting the reaction between n-butyl bromide (RBr, organic substrate) and sodium phenolate (NaOPh, aqueous nucleophile) with poly(ethylene glycol)-600 (PEG-600) as a phase-transfer catalyst. The reaction is performed in a batch reactor at 45-85 degreesC for 2h while the agitation speed is fixed at 1000rpm. Experimental results indicate that the individual mole fractions of NaOPh and PEG-600 slightly affect the reaction, while the total amount of these components exerts significant influence. When the mole fraction of PEG-600 is 0.5, the reaction rate and the conversion of RBr are the highest. No byproducts are formed in the course of the reaction. The system using a non-polar organic solvent might obtain a higher conversion compared with a weakly polar one owing to a higher concentration of PEG-600 in the third liquid phase. Furthermore, adding NaOH facilitates the reaction to obtain a higher reaction rate than adding other kinds of salt because the addition of a base results in the formation of a third liquid phase. The catalytic ability of PEG with average molecular weight of 600gmol(-1) is far higher than that with average molecular weight of 200, 400 and 1000 because PEG-600 possesses an appropriate chain length which can tightly associate with Na. to form the complex of PEG-600-Na+OPh- for reacting with RBr. In addition, this nucleophilic substitution reaction is found to be pseudo-first-order with respect to RBr. (C) 2001 Society of Chemical Industry.