Bromine Water

In the laboratory, bromine water is employed in several analytical and synthetic applications due to its strong oxidizing properties and ability to react with various organic compounds. Here are the main laboratory uses of bromine water:

1. Testing for Unsaturation in Organic Compounds

Bromine water is widely used to test for the presence of unsaturated compounds (alkenes and alkynes). When added to an unsaturated compound, the bromine adds across the double or triple bonds, leading to the decolorization of the bromine water.

• Example Reaction: C2H4(ethene)+Br2→C2H4Br2(1,2-dibromoethane)\text{C}_2\text{H}_4 (\text{ethene}) + \text{Br}_2 \rightarrow \text{C}_2\text{H}_4\text{Br}_2 (\text{1,2-dibromoethane})C2​H4​(ethene)+Br2​→C2​H4​Br2​(1,2-dibromoethane)

2. Detection of Phenols

Phenols react with bromine water to form a white precipitate of 2,4,6-tribromophenol, indicating the presence of a phenolic group.

• Example Reaction: C6H5OH(phenol)+3Br2→C6H2Br3OH(2,4,6-tribromophenol)+3HBr\text{C}_6\text{H}_5\text{OH} (\text{phenol}) + 3\text{Br}_2 \rightarrow \text{C}_6\text{H}_2\text{Br}_3\text{OH} (\text{2,4,6-tribromophenol}) + 3\text{HBr}C6​H5​OH(phenol)+3Br2​→C6​H2​Br3​OH(2,4,6-tribromophenol)+3HBr

3. Oxidation Reactions

Bromine water can oxidize certain functional groups in organic compounds, such as converting aldehydes to carboxylic acids.

• Example Reaction: RCHO(aldehyde)+Br2+H2O→RCOOH(carboxylic acid)+2HBr\text{RCHO} (\text{aldehyde}) + \text{Br}_2 + \text{H}_2\text{O} \rightarrow \text{RCOOH} (\text{carboxylic acid}) + 2\text{HBr}RCHO(aldehyde)+Br2​+H2​O→RCOOH(carboxylic acid)+2HBr

4. Identification of Aliphatic Amines

Primary and secondary aliphatic amines can be distinguished from tertiary amines using bromine water. Primary and secondary amines react with bromine to form N-bromoamines, while tertiary amines do not react.

5. Detection of Aniline and Its Derivatives

Aniline and its derivatives react with bromine water to form a precipitate of 2,4,6-tribromoaniline, which is a useful test for identifying these compounds.

• Example Reaction: C6H5NH2(aniline)+3Br2→C6H2Br3NH2(2,4,6-tribromoaniline)+3HBr\text{C}_6\text{H}_5\text{NH}_2 (\text{aniline}) + 3\text{Br}_2 \rightarrow \text{C}_6\text{H}_2\text{Br}_3\text{NH}_2 (\text{2,4,6-tribromoaniline}) + 3\text{HBr}C6​H5​NH2​(aniline)+3Br2​→C6​H2​Br3​NH2​(2,4,6-tribromoaniline)+3HBr

6. Bleaching and Disinfection

Due to its strong oxidizing properties, bromine water can be used for bleaching certain substances and as a disinfectant in laboratory settings.

7. Analytical Chemistry

Bromine water is used in various qualitative and quantitative analyses to identify and measure specific organic and inorganic substances.