Which of the following are not nucleophiles?

Options

A. `BF_3`
B. `RCOO^(-)`
C. `ROR`
D. `NO_(2)^(+)`

Answer

To determine which of the given molecules are not nucleophiles, we need to understand the characteristics of nucleophiles. Nucleophiles are electron-rich species that either possess a lone pair of electrons or carry a negative charge, allowing them to donate electrons to electron-deficient species.

### Step-by-Step Solution:

1. **Identify the Definition of Nucleophiles**:
- Nucleophiles are species that are rich in electrons. They can either have a lone pair of electrons or a negative charge.

2. **Analyze Each Given Option**:
- **Option A: BF3 (Boron Trifluoride)**
- Boron has three valence electrons and forms three bonds with fluorine atoms. After forming these bonds, boron has an incomplete octet and is electron-deficient. Therefore, BF3 is not a nucleophile.

- **Option B: RCOO- (Carboxylate Ion)**
- The carboxylate ion has a negative charge, indicating it has excess electrons. Thus, RCOO- can act as a nucleophile.

- **Option C: ROR (Ether)**
- In ethers, the oxygen atom has two lone pairs of electrons after forming two bonds. The presence of these lone pairs allows ethers to act as nucleophiles.

- **Option D: NO2+ (Nitronium Ion)**
- The nitronium ion has a positive charge, indicating a deficiency of electrons. Therefore, NO2+ is not a nucleophile.

3. **Conclusion**:
- Based on the analysis, the species that are not nucleophiles are:
- **A: BF3**
- **D: NO2+**

### Final Answer:
The molecules that are not nucleophiles are **BF3 (Option A)** and **NO2+ (Option D)**.