Phase-transfer catalytic reaction of 2,4,6-tribrornophenol and alpha-bromxylene initiated by hydroxide ion at high alkalinity

摘要

In this work, the phase transfer catalytic reactions of alpha-bromoxylene (-o-, -p- and -m-) and 2,4,6-tribromophenol for producing alpha-bromoxyl-2,4,6-tribromophenoxide were carried out in an alkaline solution of KOH/organic solvent two-phase medium. High conversion is obtained only under high concentration of alkali, though the conversion (or the reaction rate) exhibits a peculiar phenomenon at high concentration of alkali. Here, the conversion is decreased with the increase in the agitation speed of low speed region for a high content of alkali solid in the two-phase solution. The characteristics of the organic solvents, which are affected by the concentration of alkali compound, are used to explain this phenomenon of the conversion. The concentration of alkaline compound directly influences the polarity and the characteristics of the Lewis base of the organic solvent. These two important factors affect the solvolysis of organic solvent and reactant or the activated intermediate. The concentration of tetrabutylammonium 2,4,6-tribromophenoxide (ArOQ) stays constant through the course of reaction. Both the concentration of the active intermediate (ArOQ) and its activity are important in affecting the conversion. The resistance of mass transfer of ArOQ between two phases is negligible compared to the rate of organic-phase reaction. Thermodynamic properties in conjunction with the solvolysis effect was used to explain the kinetic data satisfactorily.