What does alkene mean?
An alkene is a type of hydrocarbon — a compound made only of hydrogen and carbon — that contains at least one double bond between two carbon atoms. This double bond makes alkenes chemically unsaturated and far more reactive than their single-bonded counterparts, the alkanes. The simplest example is ethene (formerly called ethylene), a gas produced in enormous quantities worldwide because it is the starting material for polyethylene, one of the most widely manufactured plastics. Other familiar alkenes include propene, used to make polypropylene. Because of their reactivity, alkenes readily undergo addition reactions, in which atoms attach across the double bond, making them central intermediates in both industrial synthesis and classroom organic chemistry. The term belongs firmly to scientific vocabulary rather than everyday speech, but the substances themselves underpin much of modern materials production.
nounAn unsaturated hydrocarbon containing at least one carbon–carbon double bond, with the general formula CₙH₂ₙ. Alkenes are reactive compounds that readily undergo addition reactions and serve as key building blocks in industrial chemistry and plastics manufacture.
- A hydrocarbon containing one or more carbon–carbon double bonds (general formula CₙH₂ₙ for acyclic monoalkenes).
- Any member of this homologous series considered collectively in organic chemistry.
"Ethene, the simplest alkene, is produced on a massive scale to manufacture polyethylene plastic."
"Propene, another important alkene, is the raw material for polypropylene."
"In the laboratory, the students distinguished the alkene from the alkane by observing how it rapidly decolorized bromine water."
Regular plural; used when referring to multiple members of the class or to specific individual compounds within it.
"Terminal alkenes are generally more reactive toward electrophilic addition than internal ones."
The bag your groceries come home in exists because of an alkene — billions of tonnes of ethene are polymerized every year to make polyethylene.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of alkene
The word 'alkene' was formed in the late nineteenth century by combining elements of 'alkane' with the '-ene' suffix, which came to denote hydrocarbons containing a double bond. It derives ultimately from 'alkyl', itself rooted in Arabic 'al-' (the) plus 'kohl', via the German chemical nomenclature tradition. Its close relative 'olefin' ('olefine' in British usage) predates it, arising from the old name 'olefiant gas' for ethene, so called because it reacted with chlorine to form an oily liquid. The parallel terms 'alkane' and 'alkyne' were coined alongside it to label saturated and triple-bonded hydrocarbons respectively.
How alkene is actually used
A technical term used almost exclusively in organic chemistry and related sciences; rare in general conversation. In older British literature the synonym 'olefine' may appear, though 'alkene' is now standard.
Easily confused with alkene
An alkane is a saturated hydrocarbon with only single bonds between carbon atoms, whereas an alkene contains at least one carbon–carbon double bond.
An alkyne contains a carbon–carbon triple bond, whereas an alkene contains a carbon–carbon double bond.