Rate enhancement effect of third liquid phase on dibenzyl ether production in solid-liquid-liquid phase transfer catalytic system

To investigate the effect of polyethylene glycol (PEG) as a phase transfer catalyst (PTC) for a solid-liquid reaction, dibenzyl ether synthesis from benzyl chloride and benzyl alcohol in organic phase by using solid KOH. A third phase containing the catalyst PEG was formed when dodecane was used as an organic phase. Benzyl alcohol reactants and KOH were dissolved into the third phase. PEG, KOH and benzyl alcohol were combined to produce the alcoxide type complex in the third phase. The complex was transferred into the organic phase. Then, the reaction between the complex and benzyl chloride took place in the organic phase. The reaction rate of this system without water was nearly eight times higher than that of the PTC system with water. Furthermore, the amount of KOH could be reduced by this solid (KOH)-liquid (catalyst)-liquid (organic solvent) system. The difference of the reaction rate was explained by the variation of the base strength of the third phase containing the catalyst. The base strength in the system without water was higher than that in the system with water, which results in the higher concentration of the complex. (C) 2003 Elsevier Science B.V. All rights reserved.