Question

Assertion (A): Carboxylic acids are more acidic than phenols.
Reason (R): Resonance structures of carboxylate ion are equivalent, while resonance structures of phenoxide ion are not equivalent.

• A. \(\text{Both (A) and (R) are correct and (R) is the correct explanation of (A)} \)
• B. \(\text{Both (A) and (R) are correct But (R) is not the correct explanation of (A)} \)
• C. \(\text{(A) is correct but (R) is incorrect} \)
• D. \(\text{(A) is incorrect but (R) is correct} \)

Hint:

Carboxylate ion is more stable due to equivalent resonance, making carboxylic acids stronger acids than phenols.

Answer 1

The Correct Option is A

Step 1: Understanding the Acidity of Carboxylic Acids vs. Phenols 
- Carboxylic acids (\( R-COOH \)) are more acidic than phenols (\( C_6H_5OH \)) because they have a lower pKa.
- The carboxylate ion (\( R-COO^- \)) formed after deprotonation is highly stabilized by resonance.
Step 2: Resonance and Stability Comparison 
- Carboxylate ion (\( COO^- \)):
- Resonance structures are equivalent.
- The negative charge is delocalized equally between two oxygen atoms, making the carboxylate ion highly stable. \[ \text{O=C-O}^- \leftrightarrow ^-O-C=O \] - Phenoxide ion (\( C_6H_5O^- \)):
- Resonance is not equivalent.
- The negative charge is not equally delocalized across the oxygen and the benzene ring.
- Oxygen retains a significant part of the negative charge, making it less stable than the carboxylate ion.
Step 3: Conclusion 
- Since carboxylate ion is more stable than phenoxide ion, carboxylic acids are more acidic than phenols.
- The given reason correctly explains this fact.
Thus, the correct answer is:  Option (1): Both (A) and (R) are correct and (R) is the correct explanation of (A)