Which of the following is capable of forming a zwitter ion ?

Options

A. `C_(6)H_(5)-OH`
B. `C_(6)H_(4)(NH_(2))_(2)`
C. `underset(" "CH_(2)OH)underset(|)(" "CH_(2)OH)`
D. `H_(2)N-CH_(2)-COOH`

Explanation

To determine which of the given compounds is capable of forming a zwitterion, we first need to understand what a zwitterion is. A zwitterion is a molecule that contains both a positive and a negative charge, but overall is neutral. Specifically, it typically consists of a carboxylate ion (–COO⁻) and an ammonium ion (–NH₃⁺).

### Step-by-Step Solution:

1. **Identify the Definition of Zwitterion**:
- A zwitterion is characterized by having both a positive charge (from an ammonium ion) and a negative charge (from a carboxylate ion) in the same molecule.

2. **Analyze the Given Compounds**:
- We need to check each compound to see if it contains both a carboxylate group and an ammonium group.

3. **Evaluate Each Option**:
- **Option A: C6H5OH (Phenol)**:
- This compound contains a hydroxyl group (-OH) but lacks both a carboxylate ion and an ammonium ion. Thus, it cannot form a zwitterion.
- **Option B: C6H4(NH2)2 (Diaminobenzene)**:
- This compound has two amino groups (-NH2) but does not contain a carboxylate group. Therefore, it cannot form a zwitterion.
- **Option C: CH2OH-CH2OH (Glycol)**:
- This compound contains hydroxyl groups but lacks both a carboxylate ion and an ammonium ion. Hence, it cannot form a zwitterion.
- **Option D: NH2-CH2-COOH (Amino Acetic Acid or Glycine)**:
- This compound contains an amino group (-NH2) and a carboxylic acid group (-COOH). The carboxylic acid can lose a proton (H⁺) to form a carboxylate ion (–COO⁻), while the amino group can gain a proton to become an ammonium ion (–NH3⁺). Thus, it can exist as a zwitterion.

4. **Conclusion**:
- The only compound that can form a zwitterion is **Option D: NH2-CH2-COOH**.

### Final Answer:
- The correct option is **D: NH2-CH2-COOH**.