Distincton of Alkanes and Alkenes. On the left: Cyclohexane does not react with water bromide On the right: Cyclohexene
In organic chemistry, an alkene, olefin, or olefine is an unsaturated chemical compound containing at least one carbon-to-carbon double bond. The simplest alkenes, with only one double bond, no rings, and no other functional groups, are hydrocarbons with the general formula CnH2n.
Aromatic compounds are often drawn as cyclic alkenes, but their structure and properties are different and they are not considered to be alkenes.
The double bond in the middle makes them more reactive because the molecule is not saturated. An alkene's unsaturation means that it will take the color out of bromine. The names of alkenes always end with -ene.