Which of the following compounds can form a zwitterion ?

Options

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

Explanation

To determine which of the given compounds can form a zwitterion, we need to analyze the structures of each compound and identify if they contain both an acidic group (like a carboxylic acid) and a basic group (like an amine) that can ionize to form a dipolar ion.

### Step-by-step Solution:

1. **Understand the Definition of Zwitterion**:
A zwitterion is a molecule that has both positive and negative charges but is overall electrically neutral. This typically occurs in amino acids where the amino group (–NH2) can accept a proton (H+) to become –NH3+, and the carboxylic acid group (–COOH) can lose a proton to become –COO−.

2. **Analyze Each Compound**:
- **Benzoic Acid (C6H5COOH)**: This compound has a carboxylic acid group but does not have an amine group. Therefore, it cannot form a zwitterion.
- **Acetyl Anilide (C6H5NHCOCH3)**: This compound contains an amide group and does not have a carboxylic acid group. Hence, it cannot form a zwitterion.
- **Aniline (C6H5NH2)**: This compound has an amine group but lacks a carboxylic acid group. Thus, it cannot form a zwitterion.
- **Glycine (NH2CH2COOH)**: Glycine is an amino acid that contains both an amine group (–NH2) and a carboxylic acid group (–COOH). At a neutral pH, the amino group can accept a proton to become –NH3+, and the carboxylic acid group can lose a proton to become –COO−, resulting in a zwitterion.

3. **Conclusion**:
Among the given compounds, only glycine can form a zwitterion due to the presence of both the amine and carboxylic acid functional groups.

### Final Answer:
The compound that can form a zwitterion is **Glycine**.