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JEE Main levelSingle correct optionDifficulty 2 of 3o2128

Halogens are deactivating yet ortho/para directing in electrophilic aromatic substitution because

  1. Athe halogen has no lone pair available for delocalisation
  2. Bthe halogen donates electrons by hyperconjugation
  3. Cthe +M effect dominates the -I effect, but only at the meta position
  4. Dthe -I effect lowers overall ring reactivity, while the +M effect of the lone pairs stabilises the ortho and para arenium ions

Answer: D

Inductive withdrawal reduces the electron density of the whole ring, so reaction is slower than for benzene. In the arenium ions from ortho and para attack a resonance form puts the positive charge on the carbon bearing the halogen, where its lone pair can stabilise it. This directing effect is not available for meta attack.
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