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Bromine water, Br 2. Bromine water is an oxidizing, intense brown mixture containing diatomic bromine (Br 2) dissolved in water (H 2 O). [1] It is often used as a reactive in chemical assays of recognition for substances which react with bromine in an aqueous environment with the halogenation mechanism, mainly unsaturated carbon compounds (carbon compounds with 1 or more double or triple bond(s)).
The formation of a brominated phenol (i.e. 2,4,6-tribromophenol) or aniline (i.e. 2,4,6-tribromoaniline) in form of a white precipitate indicates that the unknown was a phenol or aniline. The more unsaturated an unknown is, the more bromine it reacts with, and the less coloured the solution will appear. [1]
The bromine test is useful to confirm the result, although modern spectroscopic techniques (e.g. NMR and IR spectroscopy) are far superior in determining the identity of the unknown. The quantity of total phenols may be spectroscopically determined by the Folin–Ciocalteau assay.
If bromine water is added to aniline, the bromine water is decolourised and a white precipitate of 2,4,6-tribromoaniline is formed. To generate the mono-substituted product, a protection with acetyl chloride is required: Aniline can react with bromine even in room temperatures in water. Acetyl chloride is added to prevent tribromination.
This Wikipedia page provides a comprehensive list of boiling and freezing points for various solvents.
A few types of aromatic compounds, such as phenol, will react without a catalyst, but for typical benzene derivatives with less reactive substrates, a Lewis acid is required as a catalyst. Typical Lewis acid catalysts include AlCl 3, FeCl 3, FeBr 3 and ZnCl 2. These work by forming a highly electrophilic complex which is attacked by the benzene ...
Phenol is an organic compound appreciably soluble in water, with about 84.2 g dissolving in 1000 ml (0.895 M). Homogeneous mixtures of phenol and water at phenol to water mass ratios of ~2.6 and higher are possible. The sodium salt of phenol, sodium phenoxide, is far more water-soluble. It is a combustible solid (NFPA rating = 2).
Bromine readily reacts with water, i.e. it undergoes hydrolysis: Br 2 + H 2 O → HOBr + HBr. This forms hypobromous acid (HOBr), and hydrobromic acid (HBr in water). The solution is called "bromine water". The hydrolysis of bromine is more favorable in the presence of base, for example sodium hydroxide: Br 2 + NaOH → NaOBr + NaBr