Describing Alkenes (Edexcel A Level Chemistry) : Revision Note

Describing Alkenes

• All alkenes contain a double carbon bond, which is shown as two lines between two of the carbon atoms i.e. C=C

• All alkenes contain a double carbon bond, which is the functional group and is what allows alkenes to react in ways that alkanes cannot

• Alkenes have the general molecular formula C_nH_2n

• They are said to be unsaturated hydrocarbons

  • They contain carbon-carbon double bonds

  • They are made up of hydrogen and carbon atoms only

• Alkenes are named using the nomenclature rule alk + ene

• In molecules with a straight chain of 4 or more carbon atoms, the position of the C=C double bond must be specified

• The carbon atoms on the straight chain must be numbered, starting with the end closest to the double bond

• The lowest-numbered carbon atom participating in the double bond is indicated just before the -ene:

The First Five Members of the Alkene Family