In the following sequence of reaction :
`"A "overset("Reduction") to " B"overset(HNO_(2)) to CH_(3)CH_(2)OH`
The compound A is

Options

A. propane nitrile
B. ethane nitrile
C. nitromethane
D. methyl isocyanide

Explanation

To determine the compound A in the given sequence of reactions, we need to analyze the transformations step by step.

### Step 1: Identify Compound B
The question indicates that compound B is formed from compound A through a reduction process. The final product of the sequence is ethanol (CH3CH2OH), which is obtained from compound B by reacting it with HNO2 (Nitrous acid) and HCl.

From the video transcript, we learn that when compound B reacts with HNO2 and HCl, it produces ethanol. This suggests that compound B must be a primary amine, specifically ethylamine (CH3CH2NH2).

### Step 2: Determine Compound A
Next, we need to find out what compound A is, knowing that it reduces to ethylamine (B). The reduction of a nitrile (or other nitrogen-containing compound) to a primary amine is a common reaction.

The most straightforward precursor to ethylamine (B) is ethyl cyanide (propionitrile, CH3CH2CN). When propionitrile is reduced (for example, using lithium aluminum hydride, LiAlH4), it yields ethylamine.

### Conclusion
Thus, the compound A is propionitrile (CH3CH2CN).

### Summary of Steps:
1. Identify compound B as ethylamine (CH3CH2NH2) based on the final product (ethanol).
2. Determine that compound A must be propionitrile (CH3CH2CN) since it reduces to ethylamine.

### Final Answer:
The compound A is **propionitrile (CH3CH2CN)**.

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