Question

What is halogenation of alkenes?

Answer 1

Hint: Alkenes are the unsaturated hydrocarbons consisting of one or more double bonded carbon atoms. Halogenation of alkenes means the addition of a halogen like bromine, or chlorine on the double bond of alkenes. Halogen dissociates into an ion consisting of opposite charges and attacks on the double bond to form dihalide.

Complete answer:
Hydrocarbons are the compounds consisting of only carbon and hydrogen atoms. Alkanes, alkenes, and alkynes are the important hydrocarbons. Alkenes are the unsaturated hydrocarbons consisting of one or more double bonded carbon atoms.
Halogenation means the addition of a diatomic halogen like bromine or chlorine. Fluorine and iodine do not readily participate in the halogenation reaction.
When the molecule of bromine is added to an alkene, cyclic bromonium transition state is formed. Later the other bromine atom attacks to form a dihalide compound.
At the double bond of alkenes, the two bromine atoms were added. As the two bromine atoms were added at the adjacent carbon atoms, the compound formed is known as vicinal dihalide.
The chemical reaction that involved the halogenation of alkenes is as follows:
 $ C{H_3} - CH = C{H_2} + B{r_2} \to C{H_3} - CH\left( {Br} \right) - C{H_2}Br $
The compound formed is known as vicinal dibromide. Thus, halogenation of alkenes means the addition of halogen to an alkene.

Note:
All the halogens readily are not involved in the halogenation of alkenes, as fluorine is small in size it does not exist as a diatomic. Iodine also does not readily participate in the halogenation of alkene. When halogenation of alkenes is done in presence of $ CC{l_4} $ the syn products will be formed.