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 — either as an aqueous solution, or as a solution in dichloromethane or carbon tetrachloride. Unsaturation and/or phenol is shown by the disappearance of the deep brown coloration of bromine when the bromine has been used up by reaction with the unknown sample. The formation of a white precipitate (a brominated phenol) indicates that the unknown was a phenol. The more unsaturated an unknown is, the more bromine it can decolourise. It has more affinity towards carbon with less alpha hydrogens and has a ^[1]

The presence of unsaturation can also be determined using Baeyer's reagent. The iodine value is a way to determine the presence of unsaturation quantitatively.

The bromine test is a simple qualitative test. Modern spectroscopic methods (e.g. NMR and infrared spectroscopy) are better at determining the structural features and identity of unknown compounds.

Its used to check or saturate the alkenes from each other and for other reasons also.

References

1. ↑ "The Systematic Identification of Organic Compounds" R.L. Shriner, C.K.F. Hermann, T.C. Morrill, D.Y. Curtin, and R.C. Fuson John Wiley & Sons, 1997 ISBN 0-471-59748-1