In the following reaction sequence
`Ph -C -= CH underset(Hg^(2+)) overset(aq.H_(2)SO_(4)) rarr A underset(2.H_(2)O)overset(1.CH_(3)MgI)rarr B`
the product `(B)` is

Options

A. `PhCOCH_(3)`
B. `PhCH_(2)CHOHCH_(3)`
C.
D. `PhCH_(2)COCH_(3)`

Answer

To solve the given reaction sequence, we will break down each step in detail.

### Step 1: Reaction of Phenylacetylene with Hg²⁺ and H₂SO₄
The starting compound is phenylacetylene (Ph-C≡C-H). When phenylacetylene reacts with mercuric ion (Hg²⁺) in the presence of aqueous sulfuric acid (H₂SO₄), it undergoes a hydration reaction.

1. **Formation of a Mercurinium Ion**:
- The triple bond (C≡C) reacts with Hg²⁺, forming a mercurinium ion. This ion is a cyclic structure where the mercury atom is bonded to one of the carbons of the triple bond.
- The structure can be represented as:
```
Ph-C(Hg)-C
```

2. **Nucleophilic Attack by Water**:
- Water (H₂O) acts as a nucleophile and attacks the more substituted carbon atom of the mercurinium ion, leading to the formation of an intermediate.
- This gives us a compound with a hydroxyl group (OH) and a hydrogen atom on the other carbon:
```
Ph-C(OH)-C(Hg)-H
```

3. **Deprotonation**:
- The intermediate loses a proton (H⁺), leading to the formation of an enol:
```
Ph-C(=C)-OH
```

4. **Tautomerization**:
- The enol tautomerizes to form a ketone (A). The double bond shifts, and we end up with:
```
Ph-C(=O)-CH₃
```
- This compound is a phenyl ketone (acetophenone).

### Step 2: Reaction of Compound A with CH₃MgI
Now, we take the product A (acetophenone) and react it with methylmagnesium iodide (CH₃MgI).

1. **Nucleophilic Addition**:
- The Grignard reagent (CH₃MgI) acts as a nucleophile and attacks the carbonyl carbon of the ketone (A).
- This results in the formation of a tetrahedral intermediate:
```
Ph-C(OH)(CH₃)-CH₃
```

2. **Protonation**:
- The intermediate is then protonated by water (H₂O) to yield the final product (B):
```
Ph-C(OH)(CH₃)-CH₃
```
- This compound is a tertiary alcohol.

### Final Product
The final product B is a tertiary alcohol, specifically 1-phenyl-2-propanol.

### Summary of the Reaction Sequence
1. **Starting Material**: Ph-C≡C-H (Phenylacetylene)
2. **Intermediate A**: Ph-C(=O)-CH₃ (Acetophenone)
3. **Final Product B**: Ph-C(OH)(CH₃)-CH₃ (1-phenyl-2-propanol)

### Answer
The product B is **1-phenyl-2-propanol**.

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