Find the product when Phenyl acetylene reacts with dil. `H_2SO_4` in presence of `HgSO_4`

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Answer

To find the product when phenylacetylene reacts with dilute sulfuric acid in the presence of HgSO₄, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Reactants**:
- The reactants are phenylacetylene (C₆H₅C≡C-H) and dilute sulfuric acid (H₂SO₄) in the presence of mercuric sulfate (HgSO₄).

2. **Understand the Reaction Type**:
- This reaction is a hydration reaction, where water is added across the triple bond of phenylacetylene. The presence of HgSO₄ acts as a catalyst.

3. **Markovnikov's Rule**:
- According to Markovnikov's rule, when HX (where X is a nucleophile) is added to an alkene or alkyne, the more substituted carbon atom receives the nucleophile. In this case, the H⁺ from the acid will add to the less substituted carbon of the alkyne.

4. **Formation of Carbocation**:
- The triple bond in phenylacetylene will convert to a double bond after the addition of H⁺, forming a carbocation intermediate. The structure of the intermediate will be:
- C₆H₅-C(=C⁺)-H

5. **Nucleophilic Attack**:
- Water (acting as a nucleophile) will attack the carbocation. The hydroxyl group (OH) will attach to the more substituted carbon, leading to the formation of an enol intermediate:
- C₆H₅-C(OH)=C-H

6. **Tautomerization**:
- Enols are generally less stable than their keto forms. Therefore, the enol will undergo tautomerization to form the more stable keto form. In this case, the enol will convert to acetophenone (C₆H₅-C(=O)-CH₃):
- C₆H₅-C(=O)-CH₃

7. **Final Product**:
- The final product of the reaction is acetophenone.

### Final Answer:
The product formed when phenylacetylene reacts with dilute H₂SO₄ in the presence of HgSO₄ is **acetophenone (C₆H₅C(=O)CH₃)**.