Question

Find the strongest carboxylic acid from the following:

• A. 1
• B. 2
• C. 3
• D. 4

Hint:

Stronger –I effect → stronger acid due to stabilization of conjugate base.

Answer 1

The Correct Option is C

Step 1: Acidity determinants in carboxylic acids.
Electron-withdrawing substituents enhance acidity by stabilizing the carboxylate conjugate base through inductive effects.

Step 2: Halogen electronegativity trend.
Fluorine exerts the strongest –I effect due to its highest electronegativity, followed by chlorine and bromine.

Step 3: Comparing the acids.
Benzoic acid lacks a powerful –I group; Cl₃CCOOH and Br₃CCOOH show moderate stabilization; F₃CCOOH benefits from maximal electron withdrawal.

Step 4: Conjugate base stability.
The trifluoromethyl group profoundly stabilizes the carboxylate anion, making trifluoroacetic acid the strongest acid listed.

Step 5: Conclusion.
F₃CCOOH is the most acidic among the choices.