Ncert Exercises & Solutions

Discuss the role of Lewis acids in the preparation of aryl bromides and

chlorides in the dark.

Lewis acids are electron deficient species. They are responsible for, inducing heterolytic

fission in halogen molecule.

Role of Lewis acid is to produce an electrophile. The eletrophile praduce will attack on

electron rich benzene ring to produce aryl bromides and chlorides.

$A l C l_{3} + C l \to {[A l C l_{4}]}^{-} + C l^{+}$
$A l B r_{3} + B r_{2} \to {[A l B r_{4}]}^{-} + B r^{+}$

This electrophile wil further attack on benzene.