Crown Ether And Its Application

Dec. 08, 2020

Crown Ether And Its Application

Crown ether is a general term for heterocyclic compounds containing ether groups, also known as "macrocyclic ethers". In organic chemistry, crown ethers are defined as a general term for a class of macrocyclic compounds containing multiple oxygen atoms. The basic unit of crown ether is ethyleneoxy (-CH2CH2O-). If this structural unit is repeated twice, the simplest crown ether, a cyclic oligomer of dioxane, can be obtained. Repeated four times It is 12-Crown-4, and so on. At present, there are tens of thousands of crown ether compounds in the world, among which the most common are 15-crown-5 and 18-crown-6. According to its structure, crown ethers can be divided into large monocyclic polyethers, namely crown ethers and large dicyclic polyethers, namely cryptethers.

In 1967, Pedersen reported for the first time a new class of compounds-crown ethers, and he also discovered that crown ethers can form stable complexes with metals. Since then, the special properties of crown ether compounds have aroused great research interest. American chemist Cram and French chemist Lehn studied crown ethers from various angles. Lehn synthesized the cryptether for the first time. For this, Pedersen, Cram and Lehn won the 1987 Nobel Prize in Chemistry.

Application of crown ether

The biggest feature of crown ethers is that they can complex with positive ions, especially alkali metal ions, and complex with different metal ions depending on the size of the ring. The special properties of crown ethers have attracted the attention of chemists, because crown ether chemistry has gradually become an emerging subject that has attracted much attention. It has penetrated into many fields of chemistry and has developed and widely used in organic synthesis, biochemistry, analytical chemistry and other fields.

1. Application in analysis, testing and medical diagnosis

Forming complexes with cations is one of the main characteristics of crown ethers. According to the theory of host-guest chemistry, crown ethers act as host molecules and form stable host-guests with various metal ions as guest, such as alkali metals, alkaline earth metals, Ag+, Au+, etc. Complex, this complex is formed by the interaction of cations with the negatively charged oxygen atoms on the crown ether ring. Generally, the more suitable the size of the cation and the pore size of the crown ether ring are, the more stable the resulting coordination compound will be. By selectively combining metal ions, it can be used in the fields of medical diagnosis, analysis and detection, and can quantitatively detect the content of trace elements.

2. Application in organic synthesis

Because the outer side of the crown ether ring is surrounded by a hydrophobic shell, it can be dissolved in organic solvent even if it contains cations in the cavity. This property can promote the transfer of the oxidant, so that the reactant can be in good contact with the oxidant. Thus the reaction proceeded smoothly.

3. Application in soil chemistry

The ions enter the cavities of the crown ether to form a polymer-immobilized reagent, which is easy to handle and can be recycled. Therefore, it can be used to remove toxic ions in the environment, as well as water purification, soil purification, and target metal ion removal.

Crown ether

4. Application in ion selective electrode

Since the first discovery of crown ethers in 1967, people have successfully applied them to ion selective electrodes, thus opening up a new field of ion selective electron research, that is, neutral carrier electrodes. There have been various cyclic polyethers successively, including monocyclic, polycyclic, open-ring, bridged crown ethers and various other components used in ion selective electrodes.

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