Arrange the following compounds in decreasing order of their acidity.

(A) Acetic acid
(B) Chloroacetic acid
(C) Dichloroacetic acid
(D) Trichloroacetic acid

Choose the correct answer from the options given below:

(D), (C), (B), (A)

The correct answer is Option (1) → (D), (C), (B), (A)

Acidity of carboxylic acids increases with the presence of electron-withdrawing substituents, because they stabilize the conjugate base via the –I (inductive) effect.

Chlorine is strongly electron-withdrawing, and more Cl atoms ⇒ stronger –I effect ⇒ higher acidity.

Given:

• Acetic acid (no Cl) → least acidic
• Chloroacetic acid (1 Cl)
• Dichloroacetic acid (2 Cl)
• Trichloroacetic acid (3 Cl) → most acidic

Decreasing order of acidity: $(D) > (C) > (B) > (A)$