Arrange the following compounds in decreasing order of acidity:
(A) o-cresol
(B) Phenol
(C) m-nitrophenol
(D) o-nitrophenol
(E) Ethanol
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → D>C>B>A>E
The acidity of a phenol depends on the stability of its phenoxide ion:
Electron-withdrawing –NO2 increases acidity; the effect is stronger at the ortho/para positions (charge reaches the nitro group by resonance) than at meta (inductive effect only).
Electron-releasing –CH3 decreases acidity.
Alcohols are much weaker acids than phenols, because the charge on the alkoxide ion is not delocalised.
Combined order: nitrophenol (o/p) > nitrophenol (m) > phenol > cresol > alcohol
(D) o-nitrophenol: pKa 7.2
(C) m-nitrophenol: pKa 8.3
(B) phenol: pKa 10.0
(A) o-cresol: pKa 10.2
(E) ethanol: pKa 15.9
Shortcut: the order must start with the nitrophenol D and end with ethanol E; only Option (4) does both.
NCERT (2026-27 edition):
Acidity of Phenols – …
