Which of the following does not exit as a zwitter ion ?

Options

A. Glycine
B. Alanine
C. Sulphanilic acid
D. Picric acid

Answer

To determine which of the given compounds does not exist as a zwitterion, we first need to understand what a zwitterion is.

### Step 1: Define Zwitterion
A zwitterion is a molecule that has both positive and negative charges but is overall electrically neutral. This typically occurs in compounds that contain both an acidic group (which can donate a proton, H⁺) and a basic group (which can accept a proton).

### Step 2: Analyze Each Compound
1. **Glycine**:
- Glycine is an amino acid with the structure: NH₂-CH₂-COOH.
- In solution, it can exist as a zwitterion where the carboxylic acid group (COOH) donates a proton to the amino group (NH₂), resulting in NH₃⁺-CH₂-COO⁻.
- Thus, glycine exists as a zwitterion.

2. **Alanine**:
- Alanine is another amino acid with the structure: NH₂-CH(CH₃)-COOH.
- Similar to glycine, alanine can also form a zwitterion by the transfer of a proton from the carboxylic acid group to the amino group, resulting in NH₃⁺-CH(CH₃)-COO⁻.
- Therefore, alanine exists as a zwitterion.

3. **Sulfanilic Acid**:
- Sulfanilic acid has the structure: C₆H₄(NH₂)(SO₃H).
- The sulfonic acid group (SO₃H) can donate a proton to the amino group (NH₂), forming a zwitterion: C₆H₄(NH₃⁺)(SO₃⁻).
- Hence, sulfanilic acid exists as a zwitterion.

4. **Picric Acid**:
- Picric acid has the structure: C₆H₃N₃O₇ (with three nitro groups and one hydroxyl group).
- In this case, there is no basic amino group to accept a proton, and the structure does not allow for the formation of a zwitterion since the acidic groups cannot transfer a proton to create both positive and negative charges simultaneously.
- Therefore, picric acid does not exist as a zwitterion.

### Conclusion
The compound that does not exist as a zwitterion is **picric acid** (Option 4).

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