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In electrophilic substitution reactions of haloarenes (e.g., chlorination of chlorobenzene), the halogen substituent is:
AStrongly activating + ortho-directing only
BSlightly deactivating BUT ortho/para-directing — due to +M (resonance, lone-pair donation) being slightly outweighed by -I
CStrongly deactivating + meta-directing
DActivating + meta-directing
Answer & Solution
Correct answer: B. Slightly deactivating BUT ortho/para-directing — due to +M (resonance, lone-pair donation) being slightly outweighed by -I
Halogens are **deactivating** (-I effect makes the ring electron-poor) but **ortho/para-directing** (lone pairs donate by resonance to o/p positions, raising electron density there). Reactions are slower than benzene but go to o/p products (e.g., chlorination of chlorobenzene → 1,4-dichlorobenzene major).
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