Bromine test
Encyclopedia
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.
Saturation (chemistry)
In chemistry, saturation has six different meanings, all based on reaching a maximum capacity...
C=C bonds and phenols
Phenols
In organic chemistry, phenols, sometimes called phenolics, are a class of chemical compounds consisting of a hydroxyl group bonded directly to an aromatic hydrocarbon group...
.
In this laboratory method, an unknown sample is treated with a small amount of elemental bromine
Bromine
Bromine ") is a chemical element with the symbol Br, an atomic number of 35, and an atomic mass of 79.904. It is in the halogen element group. The element was isolated independently by two chemists, Carl Jacob Löwig and Antoine Jerome Balard, in 1825–1826...
— either as an aqueous solution, or as a solution in dichloromethane
Dichloromethane
Dichloromethane is an organic compound with the formula CH2Cl2. This colorless, volatile liquid with a moderately sweet aroma is widely used as a solvent. Although it is not miscible with water, it is miscible with many organic solvents...
or carbon tetrachloride
Carbon tetrachloride
Carbon tetrachloride, also known by many other names is the organic compound with the formula CCl4. It was formerly widely used in fire extinguishers, as a precursor to refrigerants, and as a cleaning agent...
. 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
Baeyer's reagent
Baeyer's reagent, named after the German organic chemist Adolf von Baeyer, is used in organic chemistry as a qualitative test for the presence of unsaturation, such as double bonds. The bromine test is also able to determine the presence of unsaturation....
. 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
NMR spectroscopy
Nuclear magnetic resonance spectroscopy, most commonly known as NMR spectroscopy, is a research technique that exploits the magnetic properties of certain atomic nuclei to determine physical and chemical properties of atoms or the molecules in which they are contained...
and infrared spectroscopy
Infrared spectroscopy
Infrared spectroscopy is the spectroscopy that deals with the infrared region of the electromagnetic spectrum, that is light with a longer wavelength and lower frequency than visible light. It covers a range of techniques, mostly based on absorption spectroscopy. As with all spectroscopic...
) are better at determining the structural features and identity of unknown compounds.