Question:medium
Which of the following has lowest pK$_a$ value?
Which of the following has lowest pK$_a$ value?
Show Hint
To compare the acidity of substituted benzoic acids:
- Electron-withdrawing groups (-NO$_2$, -CN, -X) increase acidity (lower pK$_a$).
- Electron-donating groups (-OH, -OR, -NH$_2$, -R) decrease acidity (higher pK$_a$).
- The effect is generally stronger at the para position for resonance effects. Carboxylic acids are almost always stronger than phenols.
Updated On: Mar 30, 2026
- 4-Nitrophenol
- Benzoic acid
- 4-Methoxybenzoic acid
- 4-Nitrobenzoic acid
Show Solution
The Correct Option is D
Solution and Explanation
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