11.5 - Reactions of Alkenes
The bromine water test
- Alkenes are unsaturated because they contain a carbon-carbon double bond, making them much more reactive than saturated alkanes.
- Bromine water is an orange solution of bromine in water.
Carrying out the test
- Put a sample of the hydrocarbon in a test tube.
- Add a few drops of bromine water.
- Stopper the tube and shake it so the liquids mix.
Reading the result
- Alkane (saturated) - No reaction; the bromine water stays orange.
- Alkene (unsaturated) - The orange colour disappears, turning the mixture colourless.
The change must be described as orange to colourless, not "clear", because the starting solution is already clear.
