What does epoxide mean?
An epoxide is a type of cyclic ether in which an oxygen atom is bonded to two adjacent carbon atoms, forming a small, triangular three-membered ring. This unusual geometry places considerable strain on the bonds, making epoxides among the most reactive compounds in organic chemistry — they readily undergo ring-opening reactions with acids, bases, and nucleophiles. Chemists value them as versatile intermediates for synthesizing alcohols, glycols, polymers, and pharmaceutical ingredients. The simplest example is ethylene oxide, produced industrially on a vast scale as a precursor to antifreeze and detergents. Epoxides are typically prepared by oxidizing alkenes with peracids, a transformation known as epoxidation. Although the word is essentially confined to laboratory and industrial settings, its everyday cousin appears in every hardware store: many strong adhesives are called epoxy resins because they are built from epoxide-containing precursors. Understanding epoxides therefore connects fundamental reaction mechanisms to materials people use daily.
nounA cyclic organic compound containing a three-membered ring consisting of an oxygen atom bonded to two carbon atoms; also called an oxirane.
- A cyclic ether with a three-membered ring containing one oxygen and two carbon atoms (an oxirane).
- Such a compound regarded as the oxidation product of an alkene, formed by reaction with a peracid.
"The chemist opened the epoxide ring by adding a nucleophile under basic conditions."
"Ethylene oxide is the simplest epoxide, its ring strained into high reactivity."
"Treating the alkene with mCPBA converts it cleanly to the corresponding epoxide."
Standard regular plural, used when referring to multiple compounds of this class.
"Terminal epoxides are generally more susceptible to nucleophilic attack than internal ones."
That tiny three-membered ring in an epoxide is so strained that it's one of the most reactive structures in all of organic chemistry — chemists exploit it to build everything from pharmaceuticals to epoxy glue.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of epoxide
The term combines the prefix 'epi-', from Greek meaning 'upon' or 'over', with 'oxide', denoting a compound of oxygen. It arose in late nineteenth- and early twentieth-century organic chemistry to describe oxygen bridging across a carbon–carbon double bond. The root 'oxys' (Greek for 'sharp' or 'acidic') also gives us 'oxygen', 'oxide', and 'epoxy'. Cognates sharing this heritage include 'oxidize' and 'epoxy'.
Related word forms
How epoxide is actually used
A technical term used almost exclusively in organic chemistry and related scientific fields; rare in everyday speech. In industrial contexts 'epoxy' is more commonly heard, but strictly speaking that term denotes the functional group or resins rather than the compound class itself.
Easily confused with epoxide
An oxide is a binary compound of oxygen with another element, whereas an epoxide is a specific three-membered cyclic ether within organic molecules.
Epoxy refers to a reactive group or the familiar adhesive/resin made from such compounds, while an epoxide is the individual cyclic ether molecule itself.