What do bromine molecules do in addition reactions?

Bromine molecules are known for their role in addition reactions, particularly in the context of alkenes, which contain carbon-carbon double bonds. When bromine reacts with these unsaturated hydrocarbons, the bromine molecules add across the double bond, resulting in a more saturated molecule. This process involves the bromine molecule acting as a source of bromine atoms that bind to the carbons at the ends of the double bond, converting the alkene into a dibromide. This reaction is a classic method of halogenation in organic chemistry and is indicative of the reactivity of alkenes, as they readily undergo addition reactions due to the presence of the double bond, which is a region of high electron density that can react with electrophiles such as bromine.

Understanding this reaction mechanism illustrates the significance of bromine in organic synthesis and highlights its utility in identifying the presence of double bonds through tests known as bromine water tests, where a color change indicates the conversion of an alkene to a saturated compound.