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1967年帕得逊(Poderson)首次合成了大环冠醚化合物,并发现此类物质对碱金属这类难以络合的离子,都有良好的络合能力.此后许多化学家研究了多种王冠醚对碱金属、碱土金属的萃取,并认为这类萃取是“离子对萃取”,即冠醚和碱金属离子形成—嵌入式络阳离子,在有适当的低电子密度大阴离子存在时,可成对地萃取入有机相。碱金属离子的萃取能力与所用王冠醚有密切关系,当王冠的孔穴半在与金属离子的半径相近时,生成的络合物最稳定,萃取能力也最高;此外萃取能力和所用大阴离子及稀释剂介电常数有密切关系.Y.玛库斯(Marcus)和L.E.阿歇(Asher)的研究表明,若选择适当的王冠醚溶剂,则没有大阴离子存在时,对碱金属的某些无机盐类也可达到相当程度的萃取.
In 1967, Poderson first synthesized macrocyclic crown ether compounds and found that such compounds have good complexing properties for difficult to complex ions such as alkali metals. Many chemists have since studied many kinds of diades Ether for the extraction of alkali metals and alkaline earth metals, and this type of extraction is considered “ion-pair extraction”, ie the formation of a crown ether and an alkali metal ion - an embedded cations cation which, when present in the presence of a suitably large anion of low electron density, Extract the organic phase to the earth. The extraction ability of alkali metal ions is closely related to the crown ether used. When the radius of the hole in the crown is close to the radius of the metal ions, the complex formed is the most stable and has the highest extraction capacity. In addition, the extraction ability and the large anion and dilution Agent dielectric constant is closely related.Y Marcus (Marcus) and LE Asher (Asher) studies have shown that if the choice of the appropriate crown ether solvent, then there is no large anion in the presence of certain inorganic salts of alkali metals Classes can also achieve a considerable degree of extraction.