Question

Which of the following has the most acidic Hydrogen?

• A. Dichloroacetic acid
• B. Trichloroacetic acid
• C. Chloroacetic acid
• D. Propanoic acid

Hint:

The more electron-withdrawing groups (such as halogens) attached to the α-carbon of a carboxylic acid, the more acidic the compound will be.

Answer 1

The Correct Option is B

The acidity of a carboxylic acid is influenced by the electron-withdrawing or electron-donating groups attached to the carboxyl group. Electron-withdrawing groups such as halogens (Cl, Br, I) stabilize the negative charge on the conjugate base (carboxylate ion), increasing the acid strength. The more halogen atoms attached to the α-carbon of the carboxyl group, the more acidic the compound. In the given options: - Trichloroacetic acid (CCl₃COOH) has three chlorine atoms attached to the α-carbon, which is highly electron-withdrawing, making it the most acidic. - Dichloroacetic acid (CCl₂COOH) has two chlorine atoms, followed by Chloroacetic acid (CClCOOH), which has only one chlorine atom. - Propanoic acid (CH₃CH₂COOH), with no electron-withdrawing groups, is the least acidic. Thus, Trichloroacetic acid has the most acidic hydrogen.