Question

Which one is least reactive towards nucleophilic substitution reaction?

• A. o-aminochlorobenzene
• B. Chlorobenzene
• C. o-nitrochlorobenzene
• D. 2, 4-dinitrochlorobenzene

Answer 1

Answer: (A)

o-aminochlorobenzene

Answer 2

Aryl halides are less reactive towards nucleophiiic substitution reactions because $C - X$bond in them has double bond character due to conjugation between lone pair of halogenand benzene.
Due to this following resonating structures are formed.
Due to presence of such double bond character aryl halides show nucleophiiic
substitution reactions with difficulty.
However, aryl halides can be made to undergo
nucleophiiic substitution by the presence of electron withdrawing groups (such as $- NO _{2}$) at the o and p-positions to the nuclear halogen,
But in the presence of electron donatinggroups (such as $-N H_{2}$ ) at o or p-position, it is very difficult to show nucleophiiicsubstitution reaction.
Therefore, is least reactive towards nucleophiiic substitution reaction.