Question

Which of the following groups is deactivating ortho-para directing in aromatic electrophilic substitution?

• A. \(-NO_2\)
• B. \(-OCH_3\)
• C. \(-CH_3\)
• D. \(-Cl\)
• E. \(-CHO\)

Hint:

Remember, halogens are unique in that they are deactivating yet ortho-para directing due to their dual electronic effects.

Answer 1

The Correct Option is D

Step 1: Halogens, including chlorine, are generally deactivating because of their strong electronegativity, which tends to withdraw electron density from the benzene ring through the inductive effect. 
Step 2: Despite being deactivating, halogens are ortho-para directors because they can donate electron density back to the ring through resonance (mesomeric effect). 
Step 3: Chlorine, therefore, is an ortho-para director but is overall deactivating due to its electron-withdrawing inductive effect being stronger than its electron-donating resonance effect.