Question

Which one of the following correctly represents the decreasing order of acidic nature of the given carboxylic acids:
[A] 2-Hydroxybenzoic acid
[B] Benzoic acid
[C] 3-Hydroxybenzoic acid
[D] 4-Hydroxybenzoic acid

• A. [D]>[C]>[B]>[A]
• B. [A]>[C]>[B]>[D]
• C. [D]>[B]>[C]>[A]
• D. [B]>[A]>[C]>[D]

Hint:

In aromatic acids, the position of substituents (such as \(-OH\)) influences the acidity of the compound by either stabilizing or destabilizing the carboxylate anion formed after deprotonation.

Answer 1

The Correct Option is B

The carboxylic acid group (\(-COOH\)) is electron-withdrawing and generally decreases the electron density on the aromatic ring, making the compound more acidi(C) However, the position of the hydroxyl group (\(-OH\)) on the benzene ring can influence the acidity. - When the hydroxyl group is in the ortho position (2-Hydroxybenzoic acid), it causes an intramolecular hydrogen bond that stabilizes the molecule, making it more acidi(C) - In the meta position (3-Hydroxybenzoic acid), the hydroxyl group has a weaker effect on the carboxyl group, making it less acidi(C) - The para position (4-Hydroxybenzoic acid) has a moderate effect compared to the ortho position. - Benzoic acid (without any substituents) is the least acidic since there is no electron-withdrawing or donating group affecting the carboxyl group. Thus, the order of acidity is: \[ \text{[A] 2-Hydroxybenzoic acid}>\text{[C] 3-Hydroxybenzoic acid}>\text{[B] Benzoic acid}>\text{[D] 4-Hydroxybenzoic acid} \]