Unsaturated Hydrocarbons

  • 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 alkene functional group and is what allows alkenes to react in ways that alkanes cannot.
  • The names and structure of the first four alkenes are shown below.

Alkene structures table, IGCSE & GCSE Chemistry revision notes

Table showing the formulae and structures of the first four alkanes

  • Compounds that have a C=C double bond are also called unsaturated compounds.
  • That means they can make more bonds with other atoms by opening up the C=C bond and allowing incoming atoms to form another single bond with each carbon atom of the functional group.
  • Each of these carbon atoms now forms 4 single bonds instead of 1 double and 2 single bonds.
  • This makes them much more reactive than alkanes.

Double Bond Opening, IGCSE & GCSE Chemistry revision notes

A carbon carbon double can break and form a single bond, allowing more atoms to attach to the carbon atoms

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Morgan Curtin Chemistry

Author: Morgan

Morgan’s passion for the Periodic Table begun on his 10th birthday when he received his first Chemistry set. After studying the subject at university he went on to become a fully fledged Chemistry teacher, and now works in an international school in Madrid! In his spare time he helps create our fantastic resources to help you ace your exams.