• The reaction between?alkenes?and halogens is known as?halogenation
• It is an example of an?electrophilic?addition?where an electrophile ('electron seeker') joins onto to a double bond
• The C=C double bond is broken, and a new single bond is formed from each of the two carbon atoms
• The result of this reaction is a?dihalogenoalkane
• The reaction occurs readily at room temperature and is the basis for the test for?unsaturation in molecules

Halogenation in alkenes

• Halogens can be used to test if a molecule is?unsaturated?(i.e. contain a double bond)
• Br₂?is an orange or yellow solution, called?bromine water
• The unknown compound is?shaken?with the bromine water
• If the compound is unsaturated, an addition reaction will take place and the coloured solution will decolourise

The?bromine water test is the standard test for unsaturation in alkenes