Question

Why is it difficult to undergo nucleophilic substitution in haloarene?​

Answer 1

In Haloarenes the C atom to which the X group is attached is SP2 hybridized thus it is become difficult to replace it by the Nucleophile. Since arenes and Vinyl halides are electron rich molecules due to presenceof n bonds, they repel Nucleophile attacking them.

Answer 2

Question:-

Why it is difficult for haloarenes to undergo nucleoplhilic subsituⁿ reaction?

Answer:-

Haloarenes are less reactive towards the nucleoplhilic substitution rxⁿ . This is due to following reasons :-

`\red{\bigstar}\underline{\textsf{ Reason 1 :- Partial double bond character .}}`

Halogen atom has one lone pair, and due to presence of π - σ - lp , resonance is established in the compound ( see attachment) . Due to resonance there is a partial double bond character in the carbon halogen bond , so it is difficult to break a double bond than a single bond.

`\rule{200}2`

`\red{\bigstar}\underline{\textsf{ Reason 2 :- $\pi$ cloud .}}`

When a nucleoplhile comes to attack , it is repelled by the π-cloud of the benzene ring.

`\rule{200}2`

`\red{\bigstar}\underline{\textsf{ Reason 3 :- Phenyl cation .}}`

If somehow the halogen atoms leaves the benzene ring ,being more electronegative than carbon , it takes away the electron , thus a positive charge is left on benzene ring and the phenyl cation so formed is very unstable .

`\rule{200}2`