1) Olefins 
Unsaturated hydrocarbons that contain one or more carboncarbon double bonds.These compounds are similar to alkanes, in that they can be straight or branched aliphatic hydrocarbons. The only difference is that the alkenes (also known as olefins) contain a carbon-carbon double bond, and have the general formula C2H2n. The simplest
(Olefins) Unsaturated hydrocarbons that contain one or more carbon-carbon double bonds.
Unsaturated hydrocarbons that contain one or more double carbon-carbon bonds. Alkenes with just one double C-C bond form an homologous series with the general formula CnH2n. The first few in this series are ethene, propene, butene, and pentene. Higher me...
hydrocarbon molecules with the general formula C H which contain one or more double bonds.
Unsaturated hydrocarbons of the type cn-h2n, indicated by the suffix -ene. ... (12 Dec 1998) ... 
These compounds are similar to alkanes, in that they can be straight or branched aliphatic hydrocarbons. The only difference is that the alkenes (also known as olefins) contain a carbon-carbon double bond, and have the general formula C2H2n. The simplest group member is ethene which is a gas. The double bond can be anywhere within the length of the carbon chain, resulting in a large number of possible isomers. The double bond means that these compounds are 'unsaturated' and react readily with compounds capable of adding across the double bond. Some simple alkenes are listed below:
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