In the preparation of alkyl halide from alcohol which of the following reagents preferred?

Options

A. `HX+ZnCl_(2)`
B. `PX_(3)`
C. `PCl_(5)`
D. `SOCl_(2)`

Answer

To determine the preferred reagent for the preparation of alkyl halides from alcohols, we will analyze the options provided and identify which one offers the most efficient and least labor-intensive method.

### Step-by-Step Solution:

1. **Identify the Reaction**: The general reaction for converting an alcohol (ROH) to an alkyl halide (R-X) involves replacing the hydroxyl group (-OH) with a halogen (X).

2. **Evaluate Option A**:
- Reagents: ROH, HX, ZnCl2
- Reaction: ROH + HX + ZnCl2 → R-X + H2
- This method produces an alkyl halide but involves the generation of hydrogen gas (H2) and may require additional purification steps.

3. **Evaluate Option B**:
- Reagents: ROH, PX3
- Reaction: ROH + PX3 → R-X + H3PO3
- This method also produces an alkyl halide, but it generates phosphorous acid (H3PO3) as a by-product, which may complicate purification.

4. **Evaluate Option C**:
- Reagents: ROH, PCl5
- Reaction: ROH + PCl5 → RCl + POCl3 + HCl
- This reaction yields an alkyl chloride and produces phosphorous oxychloride (POCl3) and hydrochloric acid (HCl) as by-products, requiring further purification.

5. **Evaluate Option D**:
- Reagents: ROH, SOCl2
- Reaction: ROH + SOCl2 → RCl + HCl + SO2
- This method produces an alkyl chloride along with gaseous by-products (HCl and SO2). Since both by-products are gases, they can easily escape from the reaction mixture, minimizing the need for purification.

6. **Conclusion**:
- Among the options, **Option D (SOCl2)** is preferred for the preparation of alkyl halides from alcohols because it produces gaseous by-products that can escape easily, leading to a purer product with minimal additional work required for purification.

### Final Answer:
**The preferred reagent for the preparation of alkyl halides from alcohol is Option D (SOCl2).**

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