Question

Arrange the following compounds in increasing order of their acidic strength: (A) 3-nitrophenol
(B) 3,5-Dinitrophenol
(C) 2,4,6-Trinitrophenol
(D) Phenol

• A. (D), (C), (B), (A)
• B. (C), (A), (B), (D)
• C. (D), (A), (B), (C)
• D. (A), (B), (C), (D)

Hint:

Electron-withdrawing groups like nitro groups (-NO2) increase the acidity of phenols by stabilizing the conjugate base. The more nitro groups, the stronger the acidity.

Answer 1

The Correct Option is A

Step 1: Understanding acidic strength.
The acidic strength of a compound is affected by the presence of electron-withdrawing groups (EWGs), which increase acidity by stabilizing the conjugate base. In phenolic compounds, the more nitro groups (strong electron-withdrawing groups) present, the stronger the acidity.
Step 2: Analyzing the compounds.
- Phenol (D): Phenol has a hydroxyl group (-OH) attached to a benzene ring. The hydroxyl group is weakly electron-donating, which makes phenol less acidic.
- 3-nitrophenol (A): Nitro group at the para position increases acidity by withdrawing electrons from the benzene ring.
- 3,5-Dinitrophenol (B): Two nitro groups further increase the electron-withdrawing effect, making it more acidic than 3-nitrophenol.
- 2,4,6-Trinitrophenol (C): Three nitro groups provide the greatest electron-withdrawing effect, leading to the highest acidity.
Step 3: Conclusion.
The increasing order of acidity is:
(D)<(A)<(B)<(C).
Final Answer: \[ \boxed{\text{The correct answer is (1) (D), (C), (B), (A).}} \]