Question

Which of the following compounds can form a zwitter ion?

• A. Benzoic acid
• B. Acetanilide
• C. Aniline
• D. Glycine

Answer 1

The correct option is D

Glycine

Zwitter ion:

• It is a cation in an acidic medium that migrates to the cathode on a passing electric current.
• It is an anion in basic medium and migrates to an anode on passing electric current.
• In an aqueous solution, the carboxyl group can lose a proton and the amino group can accept a proton giving rise to a dipolar ion known as the Zwitter ion.

Zwitter ion can be formed by Glycine. It is because glycine behaves as salts rather than simple amines or carboxylic acids.

Explanation for incorrect option:

Option A:

• Benzoic acid $\left({\mathrm{C}}_6{\mathrm{H}}_5{\mathrm{CO}}_2\mathrm{H}\right)$ is the simplest aromatic carboxylic acid.
• The structure of benzoic acid:

• Benzoic acid has a carboxyl group but no amino group, the carboxyl acid can lose the proton and gain a negative charge but there will be no zwitterion formation.

Option B:

• Acetanilide structure is as:

• Here we can see acetanilide has an amine group but no carboxylic group.
• Therefore this will neither form zwitterion.

Option C:

Structure of aniline:

• In aniline, there is an amine group but no presence of carboxylic group.
• Therefore it can also not form zwitterion

Conclusion Statement: Hence Option(D) is correct.