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 cyclohexane. 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. However, when a molecule is already saturated, bromine atoms cannot add into the molecule. This results in no visible colour change.