Question

Arrange the following in increasing order of acidity.

• A. I < II < III < IV < V
• B. II < I < IV < V < III
• C. III < V < IV < I < II
• D. II < IV < III < I < V

Answer 1

The Correct Option is B

To arrange the given compounds in increasing order of acidity, we need to analyze the effect of substituents on the aromatic ring. The acidity of phenols is influenced by the substituents because they affect the stability of the phenoxide ion formed after the deprotonation of the hydroxyl group.

Factors Affecting Acidity:

• Electron Withdrawing Groups (EWG): These groups stabilize the phenoxide ion by delocalizing the negative charge, thereby increasing acidity.
• Electron Donating Groups (EDG): These groups destabilize the phenoxide ion by increasing electron density, thereby decreasing acidity.

Now, let's analyze each compound:

1. 

   Compounds with simple phenol structure, usually more acidic than those with electron donating groups.

2. 

   Contains an electron donating group (OCH₃). This decreases acidity.

3. 

   Contains an electron withdrawing group (NO₂). This significantly increases acidity.

4. 

   Contains an OCH₃ group further from the hydroxyl group, less effect than in II.

5. 

   Also contains a NO₂ group but further from the hydroxyl group, still increases acidity but not as much as III.

Conclusion:

The increasing order of acidity considering the effects of substituents is:

II < I < IV < V < III

Therefore, the correct answer is: II < I < IV < V < III.