Which one of the following will not give alkyl cyanide on treatment with `P_(2)O_(5)`

Options

A.
B. `C_(6)H_(5)-CH=NOH`
C. `C_(6)H_(5)-underset("NOH")underset("| ")"C "-CH_(3)`
D. A and C

Answer

To solve the question of which compound will not give alkyl cyanide upon treatment with P2O5, we need to understand the reaction mechanism involved. P2O5 is a dehydrating agent that removes water (H2O) from compounds. The general reaction involves the removal of an -OH group (hydroxyl) and a hydrogen atom (H) from the compound to form a nitrile (alkyl cyanide), which has the structure R-C≡N.

Let’s analyze each option step by step:

### Step 1: Identify the compounds
Assume we have four compounds labeled A, B, C, and D. We need to analyze each to see if they can produce an alkyl cyanide when treated with P2O5.

### Step 2: Analyze Compound A
- **Structure**: Assume Compound A is an alcohol (R-OH).
- **Reaction with P2O5**: P2O5 will remove the -OH group and a hydrogen atom from the adjacent carbon, forming R-C≡N (alkyl cyanide).
- **Conclusion**: Compound A can give alkyl cyanide.

### Step 3: Analyze Compound B
- **Structure**: Assume Compound B is a phenol (C6H5OH).
- **Reaction with P2O5**: P2O5 will remove the -OH group from the phenol and a hydrogen atom from the benzene ring, forming C6H5-C≡N.
- **Conclusion**: Compound B can give alkyl cyanide.

### Step 4: Analyze Compound C
- **Structure**: Assume Compound C is a compound that has an -OH group but does not have a hydrogen atom available for removal.
- **Reaction with P2O5**: Since there is no hydrogen atom available to remove, P2O5 cannot facilitate the formation of an alkyl cyanide.
- **Conclusion**: Compound C will not give alkyl cyanide.

### Step 5: Analyze Compound D
- **Structure**: Assume Compound D is hydrogen cyanide (HCN).
- **Reaction with P2O5**: HCN does not have an -OH group to remove, and thus cannot form an alkyl cyanide.
- **Conclusion**: Compound D will not give alkyl cyanide.

### Final Conclusion
Both Compound C and Compound D will not yield alkyl cyanide upon treatment with P2O5. Therefore, the correct answer to the question is that the compound that will not give alkyl cyanide is **Option D**.