In organic chemistry, an alkene, olefin, or olefine is an unsaturated chemical compound containing at least one carbon–carbon double bond.[1]The simplest acyclic alkenes, with only one double bond and no other functional groups, known as mono-enes, form a homologous series ofhydrocarbons with the general formula CnH2n.[2] They have two hydrogen atoms less than the corresponding alkane (with the same number of carbon atoms).
The simplest alkene is ethylene (C2H4), which has the International Union of Pure and Applied Chemistry (IUPAC) name ethene. In thepetrochemical industry alkenes are often called olefins. For bridged alkenes, the Bredt's rule states that a double bond cannot be placed at the bridgehead of a bridged ring system, unless the rings are large enough (8 or more atoms). Aromatic compounds are often drawn as cyclic alkenes, but their structure and properties are different and they are not considered to be alkenes.