Arrange the following compounds in increasing order of their acidity.
(A) Phenol
(B) Ethanol
(C) Benzoic acid
(D) p-Nitrobenzoic acid
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → (B), (A), (C), (D)
Acidity depends on the stability of the conjugate base.
- Ethanol (B) – aliphatic alcohol, conjugate base (ethoxide) not stabilized → least acidic
- Phenol (A) – conjugate base (phenoxide) stabilized by resonance → more acidic than ethanol
- Benzoic acid (C) – carboxylate ion stabilized by resonance → more acidic than phenol
- p-Nitrobenzoic acid (D) – carboxylate stabilized by electron-withdrawing NO₂ group → most acidic
Increasing order of acidity: $\text{B < A < C < D}$
Ethanol < Phenol < Benzoic acid < p-Nitrobenzoic acid