Bromine test
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The bromine test is a qualitative test for the presence of unsaturated C–C bonds and phenols.
In this laboratory method, an unknown sample is treated with a small amount of elemental bromine — either as an aqueous solution, or as a solution in dichloromethane or carbon tetrachloride. A positive test for the presence of unsaturation and/or phenol is indicated by the disappearance of the deep brown coloration of bromine, which happens because the bromine has been consumed by reaction with the unknown sample. The formation of a white precipitate indicates the formation of a brominated phenol.
The presence of unsaturation can also be determined using the Baeyer's reagent. The iodine value is way to determine the presence of unsaturation quantitatively.
The bromine test is simple and easily carried out at the bench top. Modern spectroscopic methods (e.g. NMR and infrared spectroscopy) are better at determining the structural features and identity of unknown compounds.
