What is significance of reaction of bromine in with alkenes and alkynes?
Unsaturated hydrocarbons such as alkenes and alkynes are much more reactive than the parent alkanes. They react rapidly with bromine, for example, to add a Br2 molecule across the C=C double bond.
This reaction provides a way to test for alkenes or alkynes. Solutions of bromine in CCl4 have an intense red-orange color. When Br2 in CCl4 is mixed with a sample of an alkane, no change is initially observed. When it is mixed with an alkene or alkyne, the color of Br2 rapidly disappears.
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