Question

The electrophile, `E^((o+))` attacks the benzene ring to generate the intermediate `sigma`-complex. Of the following which `sigma`-complex is of lowest energy?
A.
B.
C.
D.

Answer 1

Correct Answer - 3
The `NO_(2)` group has a powerful electron-withdrawing influenece as it exerts both `-R` and `-I` effects `(-Rgt -I)`. This distabilizes the arenium cation 1,2, and 4 by intensifying their positive charge.On the other hand arenium ion (3) is most stable due to the absence of `NO_(2)` group.