Complete the following reaction by identifying X and Y.
`CH_(3)CH_(2)C -= CH overset(NaNH_(2))to X overset(C_(2)H_(5)Br)toY`

Options

A. `X=CH_(3)CH_(2)COONa, Y=CH_(3)CH_(2)CH=CH_(2)`
B. `X=CH_(3)CH_(2)C-=CN a, Y=CH_(3)CH_(2)C-=C C_(2)H_(5)`
C. `X=CH_(3)CH_(2)CH_(2)CH_(2)Na,Y=CH_(3)CH_(2)CH_(2)CH_(3)`
D. `X=CH_(3)CH_(2)CH-=CN a, Y=CH_(3)CH_(2)-underset(C_(2)H_(5))underset(|)(C)H-CH_(3)`

Answer

To solve the question, we need to identify the compounds X and Y in the given reaction sequence. Let's break it down step by step.

### Step 1: Identify the starting compound
The starting compound is but-1-yne, which has the structure:
\[ \text{CH}_3\text{CH}_2\text{C} \equiv \text{CH} \]

### Step 2: Reaction with Sodium Amide (NaNH₂)
When but-1-yne reacts with sodium amide (NaNH₂), it acts as a strong base. The acidic hydrogen on the terminal alkyne (the hydrogen attached to the carbon that is triple-bonded) is removed, leading to the formation of a sodium acetylide. The reaction can be represented as:
\[ \text{CH}_3\text{CH}_2\text{C} \equiv \text{CH} + \text{NaNH}_2 \rightarrow \text{CH}_3\text{CH}_2\text{C} \equiv \text{C}^- \text{Na}^+ + \text{NH}_3 \]

Here, the product formed is sodium butynylide, which we can denote as X:
\[ X = \text{CH}_3\text{CH}_2\text{C} \equiv \text{C} \text{Na} \]

### Step 3: Reaction with Ethyl Bromide (C₂H₅Br)
Next, X reacts with ethyl bromide (C₂H₅Br). The sodium acetylide (X) will undergo an SN2 reaction with ethyl bromide. The nucleophilic carbon (C⁻) in the acetylide will attack the carbon in ethyl bromide, resulting in the displacement of the bromine atom:
\[ \text{CH}_3\text{CH}_2\text{C} \equiv \text{C}^- \text{Na}^+ + \text{C}_2\text{H}_5\text{Br} \rightarrow \text{CH}_3\text{CH}_2\text{C} \equiv \text{C} - \text{C}_2\text{H}_5 + \text{NaBr} \]

The product formed after this reaction is:
\[ Y = \text{CH}_3\text{CH}_2\text{C} \equiv \text{C} - \text{C}_2\text{H}_5 \]
This compound can be represented as but-2-yne:
\[ Y = \text{CH}_3\text{C} \equiv \text{C}\text{C}_2\text{H}_5 \]

### Final Answer
Thus, we have identified:
- \( X = \text{CH}_3\text{CH}_2\text{C} \equiv \text{C} \text{Na} \)
- \( Y = \text{CH}_3\text{C} \equiv \text{C}\text{C}_2\text{H}_5 \)