Bromine test for double bonds. Bromine solution can be used to detect for the presence of carbon-carbon double bonds within unsaturated organic molecules, here cyclohexene. Bromine atoms in the Br2 molecules are capable of adding across the double bonds. This type of addition is known as halogen-addition or halogenation. The resulting molecule is known as a haloalkane (saturated). When this occurs, the orange-red colour of the bromine solution is decolourised and a colourless mixture results. The two layers seen is due to the varying polarities of the water (from the bromine solution) and the resulting haloalkane.