A. Phenol
B. P-nitrophenol
C. O-nitrophenol
D. M-nitrophenol
¨ Among the given options, p-nitrophenol is the most acidic.
¨ The acidity of phenols is due to the ability of the hydroxyl group (-OH) to release a proton (H+) and form a negatively charged phenoxide ion (PhO-). The strength of the acid depends on the stability of the phenoxide ion that is formed.
¨ In p-nitrophenol, the nitro group (-NO2) has electron-withdrawing effects and reduces the electron density on the oxygen atom of the -OH group. This makes the oxygen atom more willing to release a proton and form the corresponding phenoxide ion, thereby increasing the acidity of p-nitrophenol.
¨ In comparison, o-nitrophenol and m-nitrophenol have a lower acidity than p-nitrophenol because the position of the nitro group on the aromatic ring affects the stability of the phenoxide ion that is formed, and in these cases, the positions of the nitro groups are less favorable for stabilizing the ion.
¨ Phenol itself has a moderate acidity, but it is weaker than p-nitrophenol due to the absence of electron-withdrawing groups on the aromatic ring.
Submitted by :- Jamil Ahmed