Choose the correct order of increasing acidic strength of following c…

The correct answer is Option (2) → (C), (B), (A), (D)

Core Concept

Acidity depends on the stability of the conjugate base.

• Electron withdrawing groups increase acidity

• Nitro groups strongly withdraw electrons

• More nitro groups → greater stabilization → stronger acid

Explanation

Option C: Propan-1-ol

Alcohols are very weak acids because the alkoxide ion formed after losing H⁺ is not resonance stabilized.

Also, the alkyl group shows +I effect which destabilizes the conjugate base.

Option B: Phenol

Phenol is more acidic than alcohol because the phenoxide ion formed is stabilized by resonance. The negative charge is delocalized over the aromatic ring.

Option A: 3-Nitrophenol

Nitro group is an electron withdrawing group. At meta position, it withdraws electrons via –I effect. This stabilizes the phenoxide ion, increasing acidity compared to phenol.

Option D: 3,5-Dinitrophenol

Presence of two nitro groups greatly enhances electron withdrawal. Both –I and resonance effects stabilize the conjugate base strongly. Hence, it is the strongest acid among the given.