Which of the following is the best method for the preparation of compound cyclopentyl cyanide from cyclopentyl chloride ?

Options

A.
B. `(A)+overset(Theta)(C)Nto (B)`
C.
D. All

Explanation

To prepare cyclopentyl cyanide from cyclopentyl chloride, we need to consider the best method among the given options. Let's analyze the options step by step.

### Step-by-Step Solution:

1. **Identify the Reactants and Products**:
- Reactant: Cyclopentyl chloride (C5H9Cl)
- Product: Cyclopentyl cyanide (C5H9CN)

2. **Consider Option A**:
- Option A suggests treating cyclopentyl chloride with potassium iodide (KI).
- The reaction would involve the substitution of the chloride ion with the iodide ion.
- However, since chloride is a poorer leaving group compared to iodide, this reaction will not proceed effectively.
- **Conclusion**: Option A is not a viable method.

3. **Consider Option B**:
- Option B suggests treating cyclopentyl chloride with cyanide ion (CN⁻).
- The cyanide ion is a good nucleophile and can effectively displace the chloride ion, which is a good leaving group.
- The reaction can be represented as:
\[ \text{C5H9Cl} + \text{CN}^- \rightarrow \text{C5H9CN} + \text{Cl}^- \]
- **Conclusion**: Option B is a suitable method for preparing cyclopentyl cyanide.

4. **Consider Option C**:
- Option C involves a different reaction mechanism, likely involving a nitrogen compound that does not lead to the desired product.
- The formation of an intermediate compound that does not yield cyclopentyl cyanide indicates that this method is not effective.
- **Conclusion**: Option C is incorrect.

5. **Final Conclusion**:
- After analyzing all options, the best method for the preparation of cyclopentyl cyanide from cyclopentyl chloride is **Option B**.