In the reaction sequence `CH_3CHOoverset(NH_2OH//overset(o+)H)rarr(A)overset(P_2O_5//Delta)rarr(B)`, B will be

Options

A. `CH_3CH=NOH`
B. `H_2C=NOH`
C. `CH_3CN`
D. `CH_3CH_2NH_2`

Answer

To solve the problem step by step, let's analyze the reaction sequence provided:

1. **Identify the Reactants and Products**:
- The starting compound is acetaldehyde (CH₃CHO).
- The first reagent is hydroxylamine (NH₂OH), which will react with the carbonyl group of acetaldehyde.
- The second reagent is phosphorus pentoxide (P₂O₅) under heating conditions.

2. **First Reaction: Formation of A**:
- When acetaldehyde (CH₃CHO) reacts with hydroxylamine (NH₂OH), it forms an oxime. The reaction can be represented as:
\[ CH_3CHO + NH_2OH \rightarrow CH_3C(=N-OH)H \]
- Here, the carbonyl oxygen (C=O) of acetaldehyde reacts with the nitrogen of hydroxylamine, resulting in the elimination of a water molecule (H₂O) and forming the oxime (A).

3. **Second Reaction: Conversion of A to B**:
- The oxime (A) is then treated with phosphorus pentoxide (P₂O₅) and heated. P₂O₅ is a dehydrating agent, which means it will remove water from the oxime.
- The dehydration of the oxime leads to the formation of a nitrile. The reaction can be represented as:
\[ CH_3C(=N-OH)H \overset{P_2O_5}{\Delta} \rightarrow CH_3CN + H_2O \]
- In this step, the hydroxyl group (-OH) is removed, and the nitrogen forms a triple bond with the carbon, resulting in the formation of acetonitrile (CH₃CN).

4. **Final Product (B)**:
- Therefore, the final product B after the dehydration step is acetonitrile (CH₃CN).

**Final Answer**: B will be CH₃CN (acetonitrile).

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