With respect to the compounds I-V, choose the correct statement(s).IIIIIIIVV
(A)The acidity of compound I is due to delocalization in the conjugate base.✓ Correct
(B)The conjugate base of compound IV is aromatic.✓ Correct
(C)Compound II becomes more acidic, when it has a −NO2 substituent.✓ Correct
(D)The acidity of compounds follows the order I>IV>V> II > III.
Answer: (A), (B), (C)
Solution
(A) Compound I (triphenylmethane) forms a resonance-stabilized conjugate base (triphenylmethyl anion) where the negative charge is delocalized over three benzene rings. This is correct.
(B) Compound IV (cyclopentadiene) forms the cyclopentadienyl anion, which is aromatic with 6 π-electrons (Hückel's rule). This is correct.
(C) The −NOX2 group is electron-withdrawing (-I effect), which stabilizes the conjugate base and increases acidity. This is correct.
(D) The correct acidity order based on pKa values is: IV (pKa ≈ 15) > V (pKa ≈ 25) > I (pKa ≈ 33) > II (pKa ≈ 43) > III (pKa ≈ 50). The given order is incorrect.
JEE Advanced · 2020 · 27 Sep 2020 · Paper 1 · One or more correct options
