Bromine test

In organic chemistry, the bromine test is a qualitative test for the presence of unsaturation (carbon to carbon double or triple bonds) and phenols.

An unknown sample is treated with a small amount of elemental bromine in an organic solvent, such as dichloromethane or carbon tetrachloride. Presence of unsaturation and/or phenol in the sample is shown by disappearance of the deep brown coloration of bromine when it has reacted with the unknown sample. The formation of a brominated phenol in form of a white precipitate indicates that the unknown was a phenol. The more unsaturated an unknown is, the more bromine it reacts with, and the less coloured the solution will appear.