Q5 / 180 · COMEDK 2024 (Morning Shift) · Chemistry
From the following compounds, identify the one which is most acidic.
- AD
- BB
- CA
- Correct answerDC
Solution
The acidity of a compound is determined by the stability of its conjugate base. The more stable the conjugate base, the more acidic the compound.
Compound [A] is phenol, which forms a phenoxide ion. The negative charge on the oxygen is delocalized into the benzene ring.
Compound [B] is dicyclohexylmethanol, an aliphatic alcohol. It lacks resonance stabilization for its conjugate base and is the least acidic.
Compound [C] is p-nitrophenol. The nitro group ($-NO_2$) is a strong electron-withdrawing group (EWG) due to both its inductive effect ($-I$) and resonance effect ($-M$). This group significantly stabilizes the phenoxide ion by dispersing the negative charge, making p-nitrophenol more acidic than phenol.
Compound [D] is cyclohexanol, an aliphatic alcohol, which is less acidic than phenol.
Comparing the compounds, the presence of the strong electron-withdrawing $-NO_2$ group in [C] makes it the most acidic among the given options.
Answer: C
Compound [A] is phenol, which forms a phenoxide ion. The negative charge on the oxygen is delocalized into the benzene ring.
Compound [B] is dicyclohexylmethanol, an aliphatic alcohol. It lacks resonance stabilization for its conjugate base and is the least acidic.
Compound [C] is p-nitrophenol. The nitro group ($-NO_2$) is a strong electron-withdrawing group (EWG) due to both its inductive effect ($-I$) and resonance effect ($-M$). This group significantly stabilizes the phenoxide ion by dispersing the negative charge, making p-nitrophenol more acidic than phenol.
Compound [D] is cyclohexanol, an aliphatic alcohol, which is less acidic than phenol.
Comparing the compounds, the presence of the strong electron-withdrawing $-NO_2$ group in [C] makes it the most acidic among the given options.
Answer: C
Hence, the correct answer is option: 'D'.