What does ethoxide mean?
Ethoxide is the name given to the negatively charged ion C₂H₅O⁻ and to the salts that contain it. It arises when ethanol loses its acidic hydrogen from the oxygen atom, making it the conjugate base of ordinary drinking alcohol. Because that negative charge makes it both a powerful base and a useful nucleophile, ethoxide occupies a central place in organic chemistry: sodium ethoxide and potassium ethoxide are routine reagents for deprotonating compounds and for driving reactions such as the Williamson ether synthesis, ester formation, and eliminations. In practice chemists almost always encounter ethoxide paired with a metal counter-ion rather than as a bare ion, so phrases like 'sodium ethoxide in ethanol' are common in laboratory usage. The word belongs firmly to technical register — it appears in textbooks, research papers, and safety data sheets, not in general conversation. Its structure mirrors that of other '-oxide' ions such as hydroxide and methoxide, which makes it easy to situate once those relatives are known.
nounAn alkoxide anion with the formula C₂H₅O⁻, the conjugate base of ethanol; also any metal salt containing this anion, such as sodium ethoxide.
- The negatively charged C₂H₅O⁻ ion, the conjugate base of ethanol.
- Any salt formed between this anion and a metal cation, e.g. sodium ethoxide.
"Sodium ethoxide is commonly used as a strong base in organic synthesis."
"Treating the haloalkane with sodium ethoxide gave the desired ether via the Williamson synthesis."
"In solution, potassium ethoxide acts as both a strong base and a nucleophile."
The plural typically refers collectively to different metal salts of the ethoxide anion.
"Alkali-metal ethoxides such as sodium and potassium ethoxide are widely available reagents."
Swap the hydrogen of ethanol for sodium and you get sodium ethoxide — a base strong enough to strip protons yet gentle enough to build ethers.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of ethoxide
The word ethoxide is a transparent chemical coinage combining 'ethyl' — itself derived from 'ether', which traces back through German Äther to Greek aithēr, meaning upper air or clear sky — with the suffix '-oxide' from 'oxygen', coined by French chemists from Greek oxys (sharp, acid). It was formed in the nineteenth century as systematic nomenclature for alcohol-derived ions developed alongside modern organic chemistry. Its closest relatives are the parallel terms methoxide, hydroxide, and oxide, all built on the same naming pattern.
How ethoxide is actually used
Strictly a technical term confined to chemistry — organic chemistry lectures, lab protocols, and research literature. Chemists often specify the counter-ion ('sodium ethoxide', 'potassium ethoxide') since free ethoxide ions do not exist on their own. In everyday speech it is essentially unknown, and it should not be confused with the neutral 'ethoxy' prefix seen in names like ethoxyethane.
Easily confused with ethoxide
The ethoxy group (–OC₂H₅) is a neutral substituent attached within a molecule, whereas ethoxide is a negatively charged ion or salt of that group.
Hydroxide is the OH⁻ ion derived from water, while ethoxide is the analogous C₂H₅O⁻ ion derived from ethanol.