Question

Which of the following is least acidic?

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

Answer 1

The correct option is D o-Cresol

o-cresol $(o-(C{H}_3)C_6{H}_4-(OH\left)\right)$ is least acidic. $-OH$ group and ${}_C{H}_3$ groups are electron releasing group. It increases the electron density on a benzene ring and does not delocalize the negative charge of phenoxide ion.

Hence, it decreases the acidity of phenol. $-Cl$ and $-N{O}_2$ groups are electron-withdrawing groups. They delocalize the electron density of phenoxide ion. It increases the acidity of phenol.