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JEE Advanced levelSingle correct optionDifficulty 3 of 3g1208

Which statement about the phenyl anion, , formed by removing H+ from benzene is correct?

  1. AThe anion has 8 pi electrons and is antiaromatic
  2. BThe lone pair is in an sp2 orbital in the plane of the ring, perpendicular to the pi cloud, so it is not delocalised into the ring
  3. CThe lone pair occupies a p orbital and is delocalised over the ring like the benzyl anion
  4. DThe lone pair is delocalised to the ortho and para carbons, so it is as stable as the benzyl anion

Answer: B

The C-H bond of benzene lies in the ring plane, so after removal of H+ the lone pair sits in an sp2 orbital in that plane. It is orthogonal to the pi system and cannot be delocalised; the pi sextet is unchanged and the ring stays aromatic. In the benzyl anion the lone pair is in a p orbital and is delocalised.
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