Which of the following reagents may not be used to convert alkyl chlorides and alkyl bromides into alkylfluorides?

Options

A. `Hg_(2)F_(2)`
B. `SbF_(5)`
C. `AgF`
D. `CaF_(2)`

Answer

To solve the question of which reagent may not be used to convert alkyl chlorides and alkyl bromides into alkyl fluorides, we can follow these steps:

### Step 1: Understand the Reaction
The conversion of alkyl chlorides (R-Cl) and alkyl bromides (R-Br) to alkyl fluorides (R-F) typically involves a reaction known as the Schwartz reaction. In this reaction, alkyl halides react with metal fluorides.

**Hint:** Identify the type of reaction and the general formula involved.

### Step 2: Identify the Required Characteristics of Metal Fluorides
For the metal fluoride to effectively convert alkyl halides into alkyl fluorides, it should have covalent character. Covalent metal fluorides are more soluble in organic solvents and can react more readily with alkyl halides.

**Hint:** Consider the properties of covalent versus ionic compounds.

### Step 3: Analyze the Given Reagents
We have the following reagents to consider:
1. Hg2F2 (Mercury(II) fluoride)
2. SbF5 (Antimony pentafluoride)
3. AgF (Silver fluoride)
4. CaF2 (Calcium fluoride)

We need to determine which of these has ionic character and may not be suitable for the reaction.

**Hint:** Recall the nature of the bonds in these compounds and their solubility.

### Step 4: Determine the Nature of Each Reagent
- **Hg2F2**: This has covalent character.
- **SbF5**: This also has covalent character.
- **AgF**: This is a covalent fluoride.
- **CaF2**: This is primarily ionic in nature.

**Hint:** Compare the bonding characteristics of each reagent.

### Step 5: Conclusion
Since CaF2 has ionic character, it may not be effective in converting alkyl chlorides and alkyl bromides into alkyl fluorides. Therefore, the reagent that may not be used is **CaF2**.

**Final Answer:** CaF2