Question

One of the following functional group makes benzoic acid weaker

• A. Nitro group
• B. Hydroxy group
• C. Chloro group
• D. Acetyl group

Answer 1

The Correct Option is B

The question asks which functional group makes benzoic acid weaker. Let's analyze the options:

• Nitro group: The nitro group (\text{-NO}_2) is an electron-withdrawing group. It increases the acidity of benzoic acid by stabilizing the carboxylate anion through resonance and inductive effects. Therefore, it does not make benzoic acid weaker.
• Hydroxy group: The hydroxy group (\text{-OH}) is an electron-donating group. It decreases the acidity of benzoic acid by destabilizing the carboxylate anion through resonance donation of electron density. This makes benzoic acid a weaker acid.
• Chloro group: The chloro group (\text{-Cl}) is an electron-withdrawing group, though weaker than the nitro group. It increases the acidity of benzoic acid, so it does not make benzoic acid weaker.
• Acetyl group: The acetyl group (\text{-C(O)CH}_3) is generally considered an electron-withdrawing group due to the presence of the carbonyl. Thus, it tends to increase acidity, not decrease it.

Based on the above analysis, the hydroxy group is the correct answer as it is the functional group that makes benzoic acid weaker by decreasing its acidity due to its electron-donating nature.