Which of the following is NOT a nucleophile ?

Options

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

Answer

To determine which of the given options is NOT a nucleophile, we first need to understand what a nucleophile is. Nucleophiles are species that are rich in electrons and can donate a pair of electrons to form a new bond. They can be either neutral or negatively charged.

### Step-by-Step Solution:

1. **Identify the Nature of Nucleophiles**:
- Nucleophiles are electron-rich species that can donate electron pairs. They can be neutral (like water, ammonia) or negatively charged (like hydroxide ion).

2. **Analyze the Given Options**:
- Let's evaluate the options one by one to see which one does not fit the definition of a nucleophile.

3. **Option A: BF3 (Boron Trifluoride)**:
- Boron is a group 13 element with 3 valence electrons. In BF3, boron shares its electrons with fluorine atoms to form covalent bonds. However, boron has only 6 electrons in its valence shell (octet rule is not satisfied), making it electron deficient. Therefore, BF3 is not a nucleophile; it is an electrophile.

4. **Option B: NH3 (Ammonia)**:
- Nitrogen in ammonia has 5 valence electrons and forms three bonds with hydrogen atoms, leaving one lone pair. This lone pair makes NH3 a neutral nucleophile, capable of donating electrons.

5. **Option C: CH3CH2NH2 (Ethylamine)**:
- Ethylamine is a primary amine where nitrogen has a lone pair of electrons. This lone pair allows it to act as a neutral nucleophile.

6. **Option D: H2O (Water)**:
- Water has two lone pairs of electrons on the oxygen atom. This makes water a neutral nucleophile as well.

7. **Conclusion**:
- Among the options analyzed, BF3 is the only species that is not a nucleophile. It is an electron-deficient species, thus making it an electrophile.

### Final Answer:
**BF3 is NOT a nucleophile.**