Which compound can exist in a dipolar (zwitter ion) state

Options

A. `C_(6)H_(5)CH_(2)CH(N=CH_(2))COOH`
B. `(CH_(3))_(2)CHCH(NH_(2))COOH`
C. `C_(6)H_(5)CONHCH_(2)COOH`
D. `HOO"CC"H_(2)CH_(2)COCOOH`

Explanation

To determine which compound can exist in a dipolar (zwitter ion) state, we need to understand the characteristics of zwitter ions.

### Step-by-Step Solution:

1. **Definition of Zwitter Ion**:
A zwitter ion is a molecule that has both a positive and a negative charge, but the overall charge of the molecule is neutral. This typically occurs when a molecule has both an acidic functional group and a basic functional group.

2. **Identify Functional Groups**:
To find zwitter ions, we need to look for compounds that contain:
- A basic site (like an amino group, -NH2)
- An acidic site (like a carboxylic acid group, -COOH)

3. **Analyze the Options**:
Let's analyze the given options to see which one contains both functional groups.

- **Option 1**: This compound has a carboxylic group (-COOH) but lacks an amino group. Therefore, it cannot form a zwitter ion.

- **Option 2**: This compound has both a carboxylic group (-COOH) and an amino group (-NH2). This means it has both an acidic and a basic site, allowing it to exist as a zwitter ion.

- **Option 3**: This compound contains an amide group, which does not have the same basic properties as an amino group. Thus, it cannot form a zwitter ion.

- **Option 4**: This compound has only a carboxylic group and lacks a basic site. Therefore, it cannot form a zwitter ion.

4. **Conclusion**:
The only compound that can exist in a zwitter ion state is **Option 2**, as it contains both the necessary functional groups (an amino group and a carboxylic group).

### Final Answer:
**Option 2** is the compound that can exist in a dipolar (zwitter ion) state.