मराठी
Karnataka Board PUCPUC Science 2nd PUC Class 12

Reactions of Haloarenes - Nucleophilic Substitution

Advertisements

Topics

Estimated time: 5 minutes
CBSE: Class 12

Key Points: Reactions of Haloarenes - Nucleophilic Substitution

Aryl halides are less reactive than alkyl halides in nucleophilic substitution. Due to resonance effect, lone pair on halogen is delocalized into benzene ring.

This gives partial double bond character to C–X bond → bond becomes shorter & stronger.
Strong electron-withdrawing groups (EWGs) like –NO₂ increase reactivity.
EWGs must be at ortho or para positions for effective substitution.

Example reaction:
p-chloronitrobenzene + OH⁻ → p-nitrophenol (Cl replaced by OH).

Mechanism is SNAr (Addition–Elimination).

  • Step 1: Nucleophile attacks carbon bearing halogen → forms intermediate.
  • Step 2: Leaving group (Cl⁻) departs → aromaticity restored.
  • Reactivity order:
    More –NO₂ groups = higher reactivity
    (Tri-NO₂ > Di-NO₂ > Mono-NO₂ > no EWG)

Shaalaa.com | Reactions of Haloarenes

Shaalaa.com


Next video


Shaalaa.com


Reactions of Haloarenes [00:01:42]
S
Advertisements
Share
Notifications

Englishहिंदीमराठी


      Forgot password?
Use app×