Question

Draw the mechanism for addition of Br2 to an alkene.

Answer 1

Addition of bromine to an alkene is an elctrophilic addition whose final product is a vicinal dibromide. It has 2 steps.

Step 1: electrons (from C=C) of the alkene approach bromine molecule, one of the Br atoms accepts the electrons and releases the shared pair of electrons to the other Br atom. This is followed by the formation of a cyclic brominium ion.

Step 2: Br ^- attacks a carbon atom of the brominium ion thus breaking the ring. This forms a vicinal dibromide (Br atoms are on adjacent carbon atoms).