Consider the following sequence of reactions
`[A](C_(3)H_(9)N) overset(NaNO_(2)//HCl) to [B] (C_(3)H_(8)O) overset(K_(2)Cr_(2)O_(7))underset(H_(2)SO_(4))to (C_(3)H_(6)O_(2))[C]`
The compound [A] is

Options

A. `CH_(3)CH_(2)NHCH_(3)`
B. `CH_(3)CH_(2)CH_(2)NH_(2)`
C. `(CH_(3))_(2)CHNH_(2)`
D. `(CH_(3))_(2)N`

Answer

To solve the question, we need to identify the compound [A] (C₃H₉N) based on the given sequence of reactions.

### Step-by-step Solution:

1. **Identify the structure of compound A (C₃H₉N)**:
- The molecular formula C₃H₉N suggests that it is an amine.
- Possible structures for C₃H₉N include:
- CH₃CH₂CH₂NH₂ (1-propylamine)
- CH₃CH(NH₂)CH₃ (isopropylamine)
- (CH₃)₂NH (dimethylamine)
- We need to determine which of these can be converted to an alcohol (C₃H₈O) upon treatment with NaNO₂ and HCl.

2. **Reaction of A with NaNO₂ and HCl**:
- When a primary amine reacts with NaNO₂ and HCl at low temperatures (0°C), it forms an alcohol.
- Among the options, only CH₃CH₂CH₂NH₂ (1-propylamine) is a primary amine.
- Therefore, when CH₃CH₂CH₂NH₂ is treated with NaNO₂ and HCl, it will produce CH₃CH₂CH₂OH (1-propanol), which corresponds to the formula C₃H₈O.

3. **Identify compound B (C₃H₈O)**:
- From the reaction, we have established that compound B is CH₃CH₂CH₂OH (1-propanol).

4. **Reaction of B with K₂Cr₂O₇ and H₂SO₄**:
- K₂Cr₂O₇ in the presence of H₂SO₄ is a strong oxidizing agent that can oxidize alcohols to carboxylic acids.
- 1-Propanol (B) will be oxidized to propanoic acid (C₃H₆O₂), which is CH₃CH₂COOH.

5. **Conclusion**:
- Based on the above reactions, we conclude that the compound A is CH₃CH₂CH₂NH₂ (1-propylamine).

### Final Answer:
The compound [A] is **CH₃CH₂CH₂NH₂** (1-propylamine).

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