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Jai Ganesh

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Registered: 2005-06-28

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Bromine water

Bromine water

Gist

Bromine water is a solution of bromine (Br₂) dissolved in water, typically appearing as a vivid yellow-to-red liquid. It's a strong oxidizing agent and is used to test for unsaturation in organic compounds, with the color of the solution changing when it reacts with unsaturated compounds.

Summary

Bromine water is an oxidizing, intense brown mixture containing diatomic bromine (Br2) dissolved in water (H2O). 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 most common compounds that react well with bromine water are phenols, alkenes, enols, the acetyl group, aniline, and glucose. In addition, bromine water is commonly used to test for the presence of an alkene which contains a double covalent bond, reacting with the bromine water, changing its color from an intense yellow to a colorless solution. Bromine water is also commonly used to check for the presence of an aldehyde group in compounds. In this reaction, the color of bromine water is changed to yellow from colorless (oxidation process).

Details

An aqueous solution containing bromine molecule is the bromine water.

Bromine water solution can be prepared by two ways-

* Shake a few (2 to 6) drops of bromine liquid with 50mL of water in a brown bottle. Addition of very small amounts of sodium bromide and sodium bromate will help in the test for unsaturation.
* Mix sodium bromide and sodium bromate salts in the ratio of about 10:1 and add dil.sulphuric acid slowly.
Bromine water has yellow to red colour depending on the bromine concentration.

Inhaling the vapours may cause lung problems. May cause eye irritation and severe skin burns when it comes in contact with. Having a 5% sodium thiosulphate for washing is advisable first aid for external bromine contact.

Bromine Water Test

Bromine water is an oxidizing agent and reacts with reducing compounds like glucose-containing aldehydes, and as brominating agents with aromatic compounds like phenols and amines. It is used primarily to test the unsaturation present in organic compounds.

Additional Information

About 3.41 grams (0.12 ounce) of bromine dissolve in 100 milliliters (0.1 quart) of water at room temperature. The solution is known as bromine water. Like chlorine water, it is a good oxidizing agent, and it is more useful because it does not decompose so readily.

Bromine water is used as a test for alkenes and alkanes. When an alkene is added to bromine water, a halogen, and shaken the double bond in the alkene reacts with the bromine. After being allowed to stand, the layers separate again. The bromine water has been decoloured by the reaction to form water (lower layer). The bromine has added to the alkene to form the corresponding bromoalkane (upper layer). An alkane has been added to bromine water and the test tube shaken. The alkane used here is hexane which, as a hydrocarbon, is immiscible with water. After shaking and being allowed to stand, the two layers separate again, but the bromine is now dissolved in the hexane (top layer) rather than the water (bottom layer). Alkanes do not decolorize bromine.

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