Kinetic model for synthesizing 4,4′-diethanoxy biphenyl by phase transfer catalysis

Abstract

The reaction between 4,4′-biphenol (HO(Ph) 2OH) and bromoethane (C 2H 5Br) was first carried out to synthesize 4,4′-diethanoxy biphenyl in an organic solvent/alkaline solution of NaOH two-phase medium under phase transfer catalytic condition. Rational reaction mechanism and kinetic model were built up by considering the reactions from which two sites of nucleophiles on a molecule attacked the organic phase reactant. The mass transfer and the phase equilibrium of the catalysts between two phases were constructed by the two-film theory. In this system, two active catalysts (QO(Ph) 2OQ produced from the aqueous phase, and QO(Ph) 2OR produced from the organic phase) were proposed to synthesize in using tetrabutylammonium bromide (TBAB or QBr) as the regenerated catalyst. The first active catalyst 4,4′-di-tetrabutylammonium biphenoxide ((C 4H 9) 4N +–OC 6H 4C 6H 4O −2–N +(C 4H 9) 4, QO(Ph) 2OQ), could be identified, whereas the second active catalyst p-(tetrabutylammonium phenoxy) alkanoxy benzene ((C 4H 9) 4N +–OC 6H 4C 6H 4O −2–C 2H 5, QO(Ph) 2OR) was not detected during the reaction. The first apparent constant of the organic phase reaction was obtained via experimental data. Effect of agitation, temperature, amount of water, organic solvents, catalysts, amount of TBAHS catalyst, amount of sodium hydroxide and volume of alkaline solution on the reaction rate and the conversion were investigated in detail. The results were explained satisfactorily by considering the interaction between the reactants and the environmental species.