Crown ethers are a class of cyclic chemical compounds that consist of a ring of atoms, typically oxygen or nitrogen, which can selectively bind to cations, such as sodium or potassium. Their unique structure allows them to form stable complexes with these ions, making them useful in various chemical applications, including separation processes and ion transport. These compounds are named for their crown-like shape, which resembles a crown with a central cavity that can accommodate metal ions. Crown ethers are widely used in fields like organic chemistry, analytical chemistry, and medicinal chemistry due to their ability to enhance solubility and facilitate reactions.