Question

Which of these is most acidic?

• A. CF\(_3\)COOH
• B. CCl\(_3\)COOH
• C. CBr\(_3\)COOH
• D. CH\(_3\)COOH

Hint:

Greater the electron-withdrawing power of the substituent attached to COOH, greater is the acidity of the carboxylic acid.

Answer 1

The Correct Option is A

Step 1: Acidity of carboxylic acids depends on the stability of the carboxylate ion formed after loss of a proton.
Step 2: Electron-withdrawing groups increase acidity by stabilizing the negative charge through the –I (inductive) effect.
Step 3: The inductive effect of halogens follows the order: \[ \text{F}>\text{Cl}>\text{Br}>\text{CH}_3 \]
Step 4: CF\(_3\)COOH has the strongest electron-withdrawing effect, providing maximum stabilization to the conjugate base.
Step 5: Hence, CF\(_3\)COOH is the most acidic among the given compounds.