Ph-C`equiv`C - `CH_(3) overset(Hg^(2+)//H^(+))(rarr)`A

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Answer

To solve the problem, we need to analyze the reaction of the given alkyne (Ph-C≡C-CH₃) with mercuric ion (Hg²⁺) in an acidic medium (H⁺). The process involves hydrolysis, which leads to the formation of a carbonyl compound. Let's break down the steps:

### Step-by-Step Solution:

1. **Identify the Reactant:**
The given alkyne is phenylacetylene, represented as Ph-C≡C-CH₃. This molecule contains a phenyl group (Ph) and a terminal alkyne.

2. **Reaction with Mercuric Ion:**
The alkyne reacts with mercuric ion (Hg²⁺) in the presence of an acid (H⁺). The reaction involves the formation of a mercuric alkyne complex. The triple bond (C≡C) will coordinate with the Hg²⁺ ion.

3. **Formation of Enol:**
After the coordination, the next step involves hydrolysis. Water (H₂O) attacks the carbon atom that is bonded to the mercuric ion, leading to the formation of an enol intermediate. The structure at this stage can be represented as:
- Ph-C(OH)=C(Hg)

4. **Tautomerization to Ketone:**
The enol form is not stable and undergoes tautomerization to form a ketone. In this case, the hydrogen atom from the hydroxyl group (OH) is transferred to the adjacent carbon atom, resulting in the formation of a carbonyl group (C=O). The final product after tautomerization will be:
- Ph-C(=O)-CH₃ (which is acetophenone)

5. **Final Product:**
The final product of the reaction is acetophenone (Ph-C(=O)-CH₃).

### Summary of the Reaction:
Ph-C≡C-CH₃ + Hg²⁺ + H⁺ → Ph-C(=O)-CH₃ (Acetophenone)