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JEE Main · 2019 · 11 Jan 2019 · Shift 2 · Biomolecules

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In the following compound

The favourable site/s for protonation is/are
  1. (A)a and e
  2. (B)b, c and d✓ Correct
  3. (C)a and d
  4. (D)a

Answer: (B)

Solution

Protonation at these ring positions gives a conjugate acid whose positive charge is spread over the conjugated aromatic framework by resonance. Sites , and lead to such resonance-stabilised cations and so are protonated preferentially, whereas protonation at or gives no comparable stabilisation.

JEE Main · 2019 · 11 Jan 2019 · Shift 2 · Single correct option

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