Question

Although chlorine is an electron withdrawing group, yet it is ortho-para directing in electrophilic aromatic reactions. Why?

Answer 1

Chlorine is an electron withdrawing group, and has a strong $-I$ effect, but the $+R$ of the ring causes the incoming group to attach at the ortho and para positions.

Complete step-by-step answer: In order to answer the question, let us first know about electron donating and electron withdrawing groups. Whenever a group is attached to a ring or a main branch, then there is an uneven distribution of electrons. As the atoms are different, so is the electron content and there can be cases where there is excess or deficiency of electrons. Now, a group which pulls the electron cloud towards it, from the ring is called electron withdrawing group and the group which donates the electron cloud towards the ring is called electron donating group.
Electrons are drawn from the benzene ring due to its $-I$ effect. This makes it harder and stability of the intermediate carbocation is compromised, which is formed during the electrophilic reaction. Chlorine, being electron rich, donates its electrons which get distributed in the ortho and para position. So, the lone pair helps in stabilising the intermediate carbocation.
Chlorine causes net deactivation as the $+R$ effect of chlorine is weaker than its $-I$ effect. Resonance effect opposed the inductive effect and so, ortho and para positions have less deactivation.
So, in chlorobenzene, we can say that the reaction is responsible due to the strong $-I$ effect of chlorine, whereas the position the incoming group will attach, is controlled by the weaker resonating effect.

Note: As inductive effect has partial charge delocalisation, it is less stronger than hyperconjugative effect. In resonance, interaction with only the pi bonds occur.