Acid Strength Carboxylic Substituents
Mediumchemistry
p-Nitrobenzoic acid vs benzoic acid acidity order:
Select the correct option:
Solution
Incorrect! Answer:
p-nitrobenzoic > benzoic
- Acidity Principle: Acidity increases with anything that stabilizes the conjugate base (carboxylate anion).
- Electronic Effects of −NO2: The nitro group is one of the most powerful electron-withdrawing groups.
- Mechanisms: It exerts a strong Inductive effect (−I) and a strong Resonance effect (−R or −M) from the para position.
- Stabilization: These effects pull electron density away from the carboxylate group, effectively dispersing the negative charge and making the anion more stable.
- Comparison: Consequently, p-nitrobenzoic acid is significantly more acidic (lower pKa) than unsubstituted benzoic acid.
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About This Question
- Subject
- chemistry
- Chapter
- oxygen organics
- Topic
- acid strength carboxylic substituents
- Difficulty
- Medium
- Year
- 2025
Solution
Correct Answer:
p-nitrobenzoic > benzoic
- Acidity Principle: Acidity increases with anything that stabilizes the conjugate base (carboxylate anion).
- Electronic Effects of −NO2: The nitro group is one of the most powerful electron-withdrawing groups.
- Mechanisms: It exerts a strong Inductive effect (−I) and a strong Resonance effect (−R or −M) from the para position.
- Stabilization: These effects pull electron density away from the carboxylate group, effectively dispersing the negative charge and making the anion more stable.
- Comparison: Consequently, p-nitrobenzoic acid is significantly more acidic (lower pKa) than unsubstituted benzoic acid.
This medium difficulty chemistry question is from the chapter oxygen organics, covering the topic of acid strength carboxylic substituents. It appeared in the 2025 exam.
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