Which of the following is not a nucleophile ?

Options

A. `H_(2)O`
B. `CH_(3)OH`
C. `H_(2)`
D. `NH_(3)`

Explanation

To determine which of the following options is not a nucleophile, we first need to understand what a nucleophile is. A nucleophile is defined as a species that has an electron pair available for donation, making it a Lewis base. Nucleophiles can either have a negative charge or be neutral, but they must possess at least one lone pair of electrons.

### Step-by-Step Solution:

1. **Define Nucleophile**:
- A nucleophile is a species that donates an electron pair to form a chemical bond. It is characterized as a Lewis base.

2. **Identify Characteristics of Nucleophiles**:
- Nucleophiles can have:
- A negative charge (e.g., OH⁻, CN⁻)
- A neutral charge with lone pairs (e.g., H2O, NH3)
- They must have at least one lone pair of electrons to act as a nucleophile.

3. **Evaluate Each Option**:
- **Option A: H2O (Water)**:
- Water has two lone pairs on the oxygen atom, making it a nucleophile.
- **Option B: CH3OH (Methanol)**:
- Methanol also has a lone pair on the oxygen atom, so it is a nucleophile.
- **Option C: H2 (Hydrogen)**:
- Hydrogen (H2) has no lone pairs and is not electron-rich. It cannot act as a nucleophile.
- **Option D: NH3 (Ammonia)**:
- Ammonia has one lone pair on the nitrogen atom, making it a nucleophile.

4. **Conclusion**:
- Among the given options, H2 (Hydrogen) is the only species that does not qualify as a nucleophile because it lacks lone pairs and is not electron-rich.

### Final Answer:
- The option that is not a nucleophile is **Option C: H2 (Hydrogen)**.