The catalyst required for the reaction
`HC-=CH+dil.H_(2)SO_(4)overset("catalyst")rarrCH_(3)CHO` is

Options

A. `HgSO_(4)`
B. `Pd`
C. `Pt`
D. `AlCl_(3)`

Answer

To determine the catalyst required for the reaction of ethyne (HC≡CH) with dilute sulfuric acid (H₂SO₄) to produce acetaldehyde (CH₃CHO), we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Reaction Type**:
The reaction involves the hydration of ethyne to form an aldehyde. This is a typical reaction where an alkyne reacts with water in the presence of an acid to yield a carbonyl compound.

2. **Determine the Catalyst**:
The reaction of ethyne with dilute H₂SO₄ to produce acetaldehyde requires a catalyst that can facilitate the addition of water across the triple bond of the alkyne. The commonly used catalyst for this reaction is mercuric sulfate (HgSO₄).

3. **Write the Reaction**:
The overall reaction can be represented as:
\[ HC≡CH + H₂O \xrightarrow{HgSO₄, H₂SO₄} CH₃CHO \]
Here, ethyne reacts with water in the presence of mercuric sulfate and dilute sulfuric acid to yield acetaldehyde.

4. **Mechanism Overview**:
- The mercuric ion (Hg²⁺) forms a complex with the alkyne, leading to the formation of a mercurial intermediate.
- This intermediate undergoes hydrolysis where water adds to the carbon atom, resulting in the formation of an enol.
- The enol then tautomerizes to form the stable aldehyde (acetaldehyde).

5. **Conclusion**:
Therefore, the catalyst required for the reaction of ethyne with dilute H₂SO₄ to produce acetaldehyde is **mercuric sulfate (HgSO₄)**.