. Although chlorine is an electron withdrawing group
Although chlorine is an electron withdrawing group, yet it is ortho-, para-directing in electrophilic aromatic substitution reactions. Explain why it is so
Chlorine withdraws electrons through negative inductive effect and releases electron through resonance. Through negative inductive effect, chlorine destabilizes the intermediate carbocation formed during the electrophilic substitution. Through resonance effect, chlorine tends to stabilize the carbocation and the effect is more pronounced at ortho and para-positions
The negative inductive effect is stronger than resonance effect and causes net electron withdrawal and thus causes net deactivation. The resonance effect tends to oppose the inductive effect for the attack at ortho and para positions and hence makes the deactivation less for ortho and para attack. Thus the electrophilic substitution takes place at ortho and para positions.