Why are alkenes unsaturated?

5 ml of highly diluted bromine water are placed in a test tube. Ethene is then passed through the liquid. The color continues to lighten until the yellow color disappears completely. Alternatively, you can also detect unsaturated fatty acids. These also discolor diluted bromine water after a longer retention period.


Alkenes and alkynes are unsaturated hydrocarbons because they have double or triple bonds that are relatively unstable and tend to break. When ethene is introduced into bromine water, the bromine reacts in an addition reaction with the ethene to form dibromoethane. The double bonds of unsaturated fatty acids can also add bromine.




The storage and handling of bromine in schools is very problematic. Bromine is highly toxic and causes wounds on the skin that are difficult to heal. Diluted bromine water can also release toxic fumes when heated or when the container breaks and falls to the floor. Experiments with bromine are only allowed in one Deduction be performed. Student exercises with bromine water are not recommended. They are not allowed with bromine. safety goggles and suitableProtective gloves made of fluororubber are necessary! Alternatively, a film can be used.