Hydrocarbons with double or triple covalent bonds between neighboring carbon atoms are said to be unsaturated hydrocarbons.
The term "unsaturated" denotes the possibility of adding extra hydrogen atoms to the hydrocarbon to make it saturated.
Alkynes and alkenes are unsaturated hydrocarbons.
Bromine test used for
The bromine test is also known as the bromine water test.
It is an unsaturation test.
Alkene or alkyne unsaturated carbon-carbon bonds can be detected using the bromine test.
An organic molecule is given to a reactant, in this case, bromine, to break a double- or triple-bond.
This type of chemical reaction is known as an addition.
Bromine test reaction
When bromine is in solution, it has an orange-brownish color, but when bromine reacts with an alkene or an alkyne, the color of the solution disappears.
Alkanes can't react with bromine since they only have single bonds.
Therefore, when they are combined, there is no color change.
However, bromine will react with aromatic compounds like phenol.
Benzene is insufficiently reactive without a catalyst to undergo a bromine reaction.
However, this reaction can occur in the presence of a catalyst.
Since phenol has more reactivity than benzene, it can interact with bromine without a catalyst.
This is because the alcohol group contributes electron density to the delocalized benzene ring.
Reaction
When ethene reacts with bromine react with bromine it can form which causes decolouration.