Which of the following regents react (s) with `C_6H_5CH_2CONH_2` to form `C_6H_5CH_2CN` ?

Options

A. `P_2O_5`
B. `SOCl_2`
C. `POCl_3 " or " PCl_5`
D. All of the above

Answer

To solve the question of which reagents react with `C6H5CH2CONH2` (benzylamide) to form `C6H5CH2CN` (benzyl cyanide), we can analyze the potential reagents one by one.

### Step-by-Step Solution:

1. **Identify the Reaction Type**:
The reaction we are looking at is the conversion of an amide (`C6H5CH2CONH2`) to a nitrile (`C6H5CH2CN`). This typically involves the removal of water (dehydration) and the introduction of a cyano group.

2. **Evaluate the Reagents**:
We have four reagents to consider:
- **P2O5**: This is a dehydrating agent known to remove water from amides, facilitating their conversion to nitriles.
- **SOCl2 (Thionyl Chloride)**: This reagent is also a dehydrating agent and can convert amides to nitriles by replacing the amide group with a cyano group.
- **POCl3 (Phosphoryl Chloride)** or **PCl5 (Phosphorus Pentachloride)**: Both of these reagents can act as chlorinating and dehydrating agents, which can also lead to the conversion of amides to nitriles.

3. **Reaction Mechanism**:
- When `C6H5CH2CONH2` reacts with any of the above reagents, the mechanism generally involves the formation of an intermediate that loses a molecule of water, resulting in the formation of the nitrile `C6H5CH2CN`.

4. **Conclusion**:
Since all three reagents (P2O5, SOCl2, and POCl3/PCl5) can facilitate the conversion of the amide to the nitrile through dehydration, the correct answer is that all of these reagents can react with `C6H5CH2CONH2` to form `C6H5CH2CN`.

### Final Answer:
**All of the above (Option 4)** are correct reagents that can convert `C6H5CH2CONH2` to `C6H5CH2CN`.