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Q-15. For an electrophilic substitution reaction, the presence of a halogen atom in the benzene ring         .

(i) deactivates the ring by inductive effect

(ii) deactivates the ring by resonance

(iii) increases the charge density at ortho and para position relative to meta position by resonance

(iv) directs the incoming electrophile to meta position by increasing the charge density relative to ortho and para position.

 

Ans. (i) and (iii)

Explanation:

Presence of chlorine on benzene ring, deactivates the benzene ring inductive effect and increases the electron density on benzene ring at ortho and para positions.

According to inductive effect, chlorine is a electron withdrawing  group(-I), so it pulls the electrons from benzene ring through C à Cl sigma bond.

According to resonance, chlorine is electron donating group (+R), due to the presence of loan pairs. So it increases the electron density at ortho and para positions than meta, hence electrophile attacks on ortho and para positions in electrophilic substitution reactions.