Question

Why is bromine used when dissolved in ccl4 or water in the reactions with alkenes?

Answer 1

Explanation:

In free radical substitution, the bromine reacts at a slow rate with C-H bond. The $CCl_{4}$, helps to retain bromine solution for a longer period of time as $CCl_{4}$ doesn't react with bromine.

Water helps in the formation of bromohydrins which further helps in the addition of Br and OH to the double bond. As a result, the double bond breaks and each carbon atom gets attached to the bromine atom.

During this reaction, the dark brown color of bromine becomes colourless. This change in color shows conversion of a double bond into a single bond.