Which of the following is not a nucleophile?

Options

A. `CN^(-)`
B. `OH^(-)`
C. `NH_(3)`
D. `BF_(3)`

Explanation

To determine which of the given options is not a nucleophile, we need to understand what a nucleophile is. A nucleophile is a species that has a lone pair of electrons or a negative charge, allowing it to donate electrons to an electrophile in a chemical reaction.

Let's analyze each option step by step:

1. **Option 1: CN⁻ (Cyanide ion)**
- The cyanide ion has a negative charge (CN⁻).
- Since it has a negative charge, it can donate electrons.
- Therefore, CN⁻ is a nucleophile.

2. **Option 2: OH⁻ (Hydroxide ion)**
- The hydroxide ion also has a negative charge (OH⁻).
- Similar to CN⁻, it can donate electrons due to its negative charge.
- Thus, OH⁻ is also a nucleophile.

3. **Option 3: NH₃ (Ammonia)**
- Ammonia (NH₃) has a lone pair of electrons on the nitrogen atom.
- This lone pair allows NH₃ to act as a nucleophile by donating electrons.
- Therefore, NH₃ is a nucleophile.

4. **Option 4: BF₃ (Boron trifluoride)**
- Boron trifluoride (BF₃) is an electron-deficient compound.
- It does not have a lone pair of electrons or a negative charge; instead, it acts as an electron acceptor.
- Thus, BF₃ is not a nucleophile; it is an electrophile.

Based on this analysis, the answer to the question "Which of the following is not a nucleophile?" is **BF₃**.

### Summary of Steps:
1. Identify the nature of each species (negative charge or lone pair).
2. Determine if each species can donate electrons (nucleophile) or accept electrons (electrophile).
3. Conclude which species does not fit the definition of a nucleophile.