This tag is for questions relating to ethers: compounds containing an $\ce{R-O-R}$ fragment. It can be applied to the synthesis of, synthesis from and properties of ethers. If one of the $\ce{R}$ groups noted above is a carbonyl group, use *esters* instead. If both are, *carbonyl-compounds* is appropriate. This tag should not be used if the ether functionality is minor compared to others, or if it does not take part in the reaction in question.

Ethers are formally organic derivatives of water, wherein both hydrogens have been replaced by organic residues. The simplest linear ether is dimethyl ether $\ce{CH3OCH3}$. Simplest cyclic, saturated ether is oxiran.

The properties of ethers are typically very similar to the corresponding hydrocarbons in which the ether oxygen has been replaced by a $\ce{CH2}$ group. They are, however, more polar due to the high electronegativity of oxygen.

The most commonly used ethers in a laboratory environment are diethyl ether (the one commonly known simply as ‘ether’), tetrahydrofurane (a cyclic ether) and tert-butyl methyl ether (also known as MTBE, TBME or ± ether). Tetrahydrofuran and diethyl ether are often the solvent of choice for organometallic reactions, as they have very low melting points and the oxygens are able to complex metal cations well.

The most simple synthesis of ethers commences from the corresponding alcohols and proceeds with catalytic strong acids via a nucleophilic substitution mechanism. To selectively synthesise unsymmetrical ethers, strategies such as the Williamson ether synthesis or Meerwein salts are used.

Ether functionalities are often found in natural products or pharmaceuticals; however, they typically appear as methyl ethers or other very simple ethers. Thus, these are rarely considered as ethers.