Crown ethers are a class of cyclic chemical compounds that consist of a ring of atoms, typically oxygen and carbon, with a specific number of ethylene units. They are named for their crown-like shape, which allows them to selectively bind certain cations, such as sodium or potassium, due to the size of their central cavity. This unique property makes them useful in various applications, including separation processes and as ion-selective electrodes. These compounds are often used in organic synthesis and analytical chemistry because they can enhance the solubility of ionic compounds in organic solvents. Crown ethers can also facilitate the transport of ions across membranes, making them valuable in biological and environmental studies. Their ability to form stable complexes with metal ions has led to their use in catalysis and material science.