Which of the following is an electrophilic reagent ?

Options

A. `RO^(-)`
B. `BF_(3)`
C. `NH_(3)`
D. `ROH`.

Explanation

To determine which of the given options is an electrophilic reagent, we need to understand the characteristics of electrophiles and nucleophiles.

### Step-by-Step Solution:

1. **Define Electrophiles and Nucleophiles**:
- Electrophiles are species that are electron-deficient and can accept an electron pair. They are often positively charged or neutral species with an empty orbital.
- Nucleophiles are electron-rich species that can donate an electron pair. They typically have lone pairs of electrons or negative charges.

2. **Analyze the Given Options**:
- We will examine each option to identify whether it can act as an electrophile or a nucleophile.

3. **Evaluate BF3**:
- BF3 (Boron Trifluoride) has a boron atom that is electron-deficient because it has only six electrons in its valence shell. It has vacant orbitals and can accept an electron pair. Therefore, BF3 is an electrophile.

4. **Evaluate NH3**:
- NH3 (Ammonia) has a nitrogen atom with a lone pair of electrons. It can donate this lone pair to form bonds, making it a nucleophile.

5. **Evaluate RO-**:
- RO- (an alkoxide ion) has a negative charge and a lone pair of electrons. It can donate its lone pair, which classifies it as a nucleophile.

6. **Conclusion**:
- Among the options provided, only BF3 is an electrophilic reagent.

### Final Answer:
The correct answer is **BF3**.

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