Conjugate base of B is more stable than conjugate acid of A. A is more acidic than B Consider compound A: resonance form 2 is more stable than 1. Conjugate base of A is more stable than conjugate acid of B. B is more acidic than A. Consider compound A: resonance form 1 is more stable than 2.
The Correct Answer and Explanation is:
Correct answer: ✅ B is more acidic than A.
Explanation:
To determine the acidity of compounds A and B, we analyze the stability of their conjugate bases, since a more stable conjugate base corresponds to a stronger acid.
Structural Overview:
Both A and B are nitro-substituted benzoic acid derivatives. Upon deprotonation by a base (PT), they yield conjugate bases that can resonate. The resonance forms (1 and 2) help delocalize the negative charge, contributing to stability.
Comparing Resonance in A vs. B:
Compound A:
- Resonance forms 1 and 2 show delocalization of the negative charge.
- In form 2, the lone pair from the negatively charged oxygen interacts with the carbon bearing the nitro group.
- However, this interaction places a negative charge on the nitrogen of the nitro group, which is already electron-withdrawing. This is less favorable, making resonance form 2 less stable.
Compound B:
- In the conjugate base of B, the negative charge is more delocalized, especially in resonance form 2.
- The nitro group is in the ortho position to the carboxylate, allowing for better electron delocalization via resonance and inductive effects.
- Nitro groups are strong electron-withdrawing groups; they stabilize nearby negative charges through inductive and resonance effects.
Conclusion:
- Compound B’s conjugate base is more stabilized due to stronger resonance and inductive effects from the nitro group.
- Therefore, B is more acidic than A because its conjugate base is more stable.
Incorrect Statements:
- “A is more acidic than B” is false.
- “Consider compound A: resonance form 2 is more stable than 1” is false (form 1 is more stable).
- “Conjugate base of A is more stable than conjugate acid of B” is irrelevant and misleading.
Final Note:
When analyzing acidity, always prioritize the stability of the conjugate base, which depends on resonance, inductive effects, and electron-withdrawing groups.
