Question

Chlorination can be done on
A. $C{{H}_{3}}-CH=C{{H}_{2}}$
B. ${{H}_{2}}C=C{{H}_{2}}$
C. $HC\equiv CH$
D. None of these

Answer 1

Hint: The halogenation of alkene occurs by breaking the carbon-carbon double bond. Specially chlorine or bromine molecules are added to the neighbouring carbon atoms from the opposite face of the molecules i.e, trans addition occurs. These types of electrophilic addition reactions can be done on alkenes and alkynes.

Complete Step by Step Answer:
The overall addition reaction involves the cleavage of carbon-carbon double bond or triple bond and thereby two chlorine atoms from the $C{{l}_{2}}$ molecule get attached to the carbons from the opposite face.

In case of (A) when chlorination is done, in the first step nucleophilic pi-bond of alkene attacks one of the chlorine atoms which acts as electrophile and the presence of chlorine molecule facilitates the cleavage of a double bond resulting in a halogen bridge. Another chlorine atom with a negative charge moves away.

In the next step, chloride ion acts as nucleophile attacks from the opposite side of the bridge, and the $$ 1$1,2-$dichloro propane is formed as the major product. Here anti addition of halogen to the alkene predominates.

When chlorination is done on ethylene, the vicinal halide is formed.

When chlorination occurs in acetylene, $1,1,2,2-tetrachloroethane$ is formed.

Hence chlorination can be done on propane, ethylene, and acetylene compounds.
Thus, option (D) is correct.

Note: Halogenation also can not be done on alkane compounds. This is because they have a strong sigma bond and are more stable. A huge amount of energy is required to break the sigma bond. Hence they do not participate in this kind of addition reaction like halogenations.