What is the purpose of the bromine water test?

The bromine water test is specifically used to distinguish between saturated and unsaturated hydrocarbons. When bromine water, which is a brown solution due to the presence of bromine, is added to an unsaturated hydrocarbon (like alkenes or alkynes), a reaction occurs that leads to decolorization of the bromine solution. This is because the double or triple bonds in unsaturated hydrocarbons react with bromine, forming colorless brominated products.

In contrast, saturated hydrocarbons (like alkanes) do not undergo this reaction and hence do not cause any change in the color of bromine water. Thus, the test serves as a qualitative method to assess the presence of double or triple bonds in organic compounds, providing clear evidence of unsaturation in the hydrocarbon chain. This makes it an essential tool in organic chemistry for identifying the nature of different hydrocarbons.