Discussion Forum



1)

Arenes on treatment with chlorine in presence of ferric chloride as a catalyst undergo what type of reaction?


A) Electrophilic substitution

B) Nucleophilic substitution

C) Electrophilic substitution

D) Nucleophilic substitution

Answer:

Option A

Explanation:

 Arenes on treatment with chlorine in presence of Lewis acid catalyst, ferric chloride or aluminium chloride and in the absence of light undergoes halogenation. It involves an electrophilic substitution  reaction

 1662021104_1.PNG

Mechanism of electrophilic substitution in as follows:

Step I: Generation of an electrophile.

  $Cl-Cl+AlCl_{3}\rightarrow Cl^{+}+Cl ^{\delta+}.........Al^{\delta-}-Cl_{3}$

                                                                 $\rightarrow Cl^{+}+[AlCl_{4}]^{-}$    Chloronium ion

Step II. Formation of carbocation (arenium ion)

 1662021307_2.PNG

The arenium ion gets stabilised by resonance

 1662021370_3.PNG

Step III  removal of proton

1662021479_4.PNG