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.
Acidic strength is influenced by electron-withdrawing groups (EWGs), which stabilize the conjugate base, thereby increasing acidity. For phenolic compounds, the presence of more nitro groups (strong EWGs) correlates with higher acidity.
Step 2: Analyzing the compounds.
- Phenol (D): The hydroxyl group (-OH) on the benzene ring is weakly electron-donating, reducing acidity.- 3-nitrophenol (A): A para-positioned nitro group enhances acidity by withdrawing electrons from the benzene ring.- 3,5-Dinitrophenol (B): Two nitro groups amplify the electron-withdrawing effect, resulting in greater acidity than 3-nitrophenol.- 2,4,6-Trinitrophenol (C): Three nitro groups provide the maximal electron-withdrawing effect, leading to the highest acidity.Step 3: Conclusion.
The order of increasing acidity is: (D)<(A)<(B)<(C). Final Answer: \[\boxed{\text{The correct answer is (1) (D), (C), (B), (A).}}\]