The rapid disappearance of the amber color of the bromine at room temperature is characteristic of reaction with alkenes. (colorless) (purple) (colorless) (brown ppt.) Reaction of an alkene with ...

Bromine water is an orange solution of bromine. It becomes colourless when it is shaken with an alkene. Alkenes can decolourise bromine water, but alkanes cannot. The slideshow shows this process.