鎓盐的固液相转移平衡研究(Ⅰ)——溴化四丁铵和羧酸钾的平衡常数测定

SOLID-LIQUID PHASE TRANSFER EQUILIBRIUM OF ONIUM SALTS(Ⅰ)

目前广泛应用的液-液相转移催化反应有两个主要的缺点:一是有一些水分子会随着离子对一起萃入有机相并在其周围形成水化膜,这不仅会降低反应速度有时还会引起种种副反应。另一个缺点是这种方法不适用于强亲水性的离子。在这两种情况下改用固液相反应可能有良好的效果。但是鎓盐为催化剂的固液相转移是否真正的可逆过程,它的相转移规律如何,至今尚未见文献报导。本文研究了溴化四丁铵与某些羧酸钾盐之间的反应平衡常数,其它工作正在进行中。

The liquid-liquid phase transfer catalysis suffers from two shortcomings:(1)The water molecules coextracted form a hydration shell,which retards the reaction and,sometimes,results in side reactions.(2)It seems to be not applicable for highly hydrophilic anions.For such reactions the solid-liquid phase transfer may be more suitable.But the factors affecting these reactions have not been reported as yet.This paper is the first effort in this area.From the data listed the following conclusions may be obtained:1.The solid-liquid phase transfer is a truely reversible reaction.2.In solvent with higher polarity and/or with higher hydrogen bonddonorability the equilibrium constant increases.3.Decrease of the electron density on the carboxylate group,either by electron withdrawing group or by intramolecular hydrogen bonding,favours the transfer of the carboxylate into solution.The intermolecular hydrogen bonding disfavours it.4.Transfer of salts of divalent anions is negligible or hardly detectable.