`H-C-=C-H underset(H_(2)SO_(4))overset(HgSO_(4))(rarr)overset("dil.NaOH")(rarr)overset(Delta)(rarr)P`. The final product P is

Options

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D.

Answer

To solve the problem step by step, we will analyze the reaction of the given compound and determine the final product \( P \).

### Step 1: Identify the Starting Compound
The starting compound is acetylene, represented as \( H-C \equiv C-H \).

### Step 2: Reaction with \( H_2SO_4 \) and \( HgSO_4 \)
When acetylene reacts with \( H_2SO_4 \) in the presence of \( HgSO_4 \), it undergoes hydration to form vinyl alcohol (also known as ethenol), which can be represented as:
\[ CH_2=CHOH \]
However, vinyl alcohol is not stable and will undergo tautomerization to form acetaldehyde:
\[ CH_2=CHOH \rightarrow CH_3CHO \]
So, the compound \( A \) formed is acetaldehyde \( (CH_3CHO) \).

### Step 3: Reaction with Dilute \( NaOH \)
Next, acetaldehyde \( (CH_3CHO) \) reacts with dilute \( NaOH \). This reaction is an aldol condensation where two molecules of acetaldehyde react. The mechanism involves the formation of an enolate ion, which then attacks another molecule of acetaldehyde:
1. The base \( NaOH \) abstracts a proton from the alpha carbon of acetaldehyde, forming an enolate ion.
2. This enolate ion then attacks the carbonyl carbon of another acetaldehyde molecule.

The product formed from this reaction is a beta-hydroxy aldehyde, which can be represented as:
\[ CH_3-CH(OH)-CH_2-CHO \]

### Step 4: Dehydration of the Beta-Hydroxy Aldehyde
The beta-hydroxy aldehyde undergoes dehydration (loss of water) when heated, resulting in the formation of a conjugated enone. The dehydration leads to the formation of:
\[ CH_3-CH=CH-CHO \]
This compound is but-2-enal (also known as crotonaldehyde).

### Final Product
Thus, the final product \( P \) is but-2-enal, which can be represented as:
\[ CH_3-CH=CH-CHO \]

### Summary of the Reaction
1. Acetylene \( (H-C \equiv C-H) \) reacts with \( H_2SO_4 \) and \( HgSO_4 \) to form acetaldehyde \( (CH_3CHO) \).
2. Acetaldehyde reacts with dilute \( NaOH \) to form a beta-hydroxy aldehyde.
3. The beta-hydroxy aldehyde undergoes dehydration to yield but-2-enal \( (CH_3-CH=CH-CHO) \).

### Final Answer
The final product \( P \) is but-2-enal.

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