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 determine which reagents react with `C6H5CH2CONH2` (benzylamide) to form `C6H5CH2CN` (benzyl cyanide), we need to analyze the reactions with the given reagents: P2O5, SOCl2, and POCl3.

### Step-by-Step Solution:

1. **Identify the Structure of Benzylamide**:
- The compound `C6H5CH2CONH2` is benzylamide, where `C6H5` is the phenyl group, `CH2` is the benzyl group, and `CONH2` is the amide functional group.

2. **Reagent 1: P2O5 (Phosphorus Pentoxide)**:
- P2O5 is a dehydrating agent. When benzylamide reacts with P2O5, it removes water (dehydrates) and converts the amide (CONH2) to a nitrile (CN).
- Mechanism: The nitrogen atom donates its lone pair to the phosphorus atom, leading to the formation of an intermediate. After rearrangement and loss of a leaving group, the final product is `C6H5CH2CN`.

3. **Reagent 2: SOCl2 (Thionyl Chloride)**:
- SOCl2 is also a dehydrating agent and converts amides to nitriles.
- Mechanism: The nitrogen donates its lone pair to the sulfur in SOCl2, leading to the formation of an intermediate. Chloride ion is eliminated, and the final product is again `C6H5CH2CN`.

4. **Reagent 3: POCl3 (Phosphoryl Chloride)**:
- POCl3 can also facilitate the conversion of amides to nitriles.
- Mechanism: Similar to the previous reagents, nitrogen donates its lone pair to phosphorus, leading to the formation of an intermediate. Chloride is eliminated, resulting in the formation of `C6H5CH2CN`.

5. **Conclusion**:
- All three reagents (P2O5, SOCl2, and POCl3) can convert benzylamide to benzyl cyanide. Therefore, the answer is that all of the above reagents can react with `C6H5CH2CONH2` to form `C6H5CH2CN`.

### Final Answer:
The answer is option 4: All of the above.