Alkenes

These are hydrocarbons that contain at least one carbon-carbon double bond C=C. Another series of compounds is called the alkenes. They have a general formula: C_nH_{2n where n is a positive whole number whic is equal or greater than 2}

Alkenes have fewer hydrogen atoms than the alkanes. The extra valencies left over occur as double bonds between a pair of carbon atoms. The double bonds are more reactive than single bonds making the alkenes chemically more reactive. They contain 2 hydrogen atoms lesser than the alkanes. Ethene, propene, but-1-ene and but-2-ene are colourless gases at ordinary temperatures and pressures, the next thirteen (C₅H₁₀ to C₁₇H₃₄) are liquids while he higher ones are solid. Alkenes tend to burn with a more luminous and smoky flame than alkanes. The availability of double bonds also make them more chemically active.

Ethene

The most important alkene. One of the main products of cracking of gas oil fraction of petroleum.