ether

Ether is a term used in chemistry and physics with several related meanings. In organic chemistry, ethers are a class of compounds in which an oxygen atom is connected to two carbon-containing groups, giving the general structure R-O-R'. The simplest representative is diethyl ether (ethyl ether), historically a common solvent. Ethers are typically colorless liquids or gases at room temperature and are valued for their ability to dissolve a wide range of organic substances. They are relatively inert toward many reagents, but can form peroxides on prolonged storage in air, and are highly flammable. Reactions of ethers include cleavage by strong acids to yield alcohols or alkyl halides, and the Williamson ether synthesis, which forms ethers from alkoxides and alkyl halides.

In practical use, ethers such as diethyl ether, tetrahydrofuran (THF), and dimethyl ether serve as solvents in laboratories and industry. Their relatively low boiling points and affinity for organic compounds make them useful, but safety concerns—particularly flammability and peroxide formation—require careful handling and storage.

Historically, the term ether is also associated with the luminiferous aether (often spelled aether), a hypothetical medium once believed to carry light waves through space. In the 19th century, experiments like Michelson–Morley failed to detect such a medium, and the development of Einstein’s theory of relativity rendered the concept unnecessary in modern physics. The word persists in various names and cultural references, but no physical medium for light propagation beyond the vacuum is required by current theory.