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JEE Advanced levelOne or more correct optionsDifficulty 3 of 3hx107

For the reaction with in methanol (nucleophilic aromatic substitution by addition-elimination), select the correct statements.

  1. AThe rate-determining step is the breaking of the C-halogen bond in the Meisenheimer complex.
  2. B1-Chloro-3-nitrobenzene is much less reactive than 1-chloro-4-nitrobenzene.
  3. C1-Chloro-2,4-dinitrobenzene reacts faster than 1-chloro-4-nitrobenzene.
  4. D1-Fluoro-2,4-dinitrobenzene reacts faster than 1-chloro-2,4-dinitrobenzene.

Answer: B, C, D

Nitro groups at ortho and para positions stabilise the negative charge of the Meisenheimer complex by resonance, so two such groups are better than one, while a meta nitro group cannot delocalise the charge onto itself. The slow step is the attack of the nucleophile to form the complex, which is why F, the most electron-withdrawing halogen, gives the fastest reaction. The fourth statement is therefore false.
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