Question

Which of the following is the most acidic compound?

• A. p-Nitrophenol
• B. o-Nitrophenol
• C. o-Cresol
• D. p-Cresol
• E. Phenol

Hint:

Remember that the presence of electron-withdrawing groups like nitro enhances the acidity of phenols by stabilizing the resulting anion.

Answer 1

The Correct Option is A

Step 1: The acidity of phenols is significantly influenced by substituents on the aromatic ring. 
Step 2: Nitro groups are strong electron-withdrawing groups due to their -I (inductive) and -R (resonance) effects, which stabilize the phenoxide ion formed upon deprotonation. 
Step 3: In para positions, the nitro group exerts a stronger electron-withdrawing effect compared to the ortho position due to better resonance stabilization of the negative charge on the oxygen atom of the phenoxide ion. 
Step 4: Therefore, p-nitrophenol is more acidic than o-nitrophenol, cresols, and phenol, making it the most acidic compound among the given options.