Rearrangement is not possible in :-

Options

A.
B. `CH_(3)-underset(OCH_(3))underset(|)CH-overset(o+)CH-CH_(3)`
C.
D. `CH_(3)-underset(CH_(3))underset(|)CH-overset(o+)CH-CH_(3)`

Answer

To solve the question "Rearrangement is not possible in:", we need to analyze the stability of the carbocations formed in the given options. Rearrangement occurs to form more stable carbocations. Let's go through the options step-by-step.

### Step 1: Understand the concept of carbocation stability
Carbocations can rearrange to form more stable species. The stability order of carbocations is:
- Tertiary (most stable)
- Secondary
- Primary (least stable)

### Step 2: Analyze each option

#### Option A: Benzyl carbocation (C6H5-CH2^+)
- This is a primary carbocation.
- It can rearrange to a more stable secondary carbocation due to the presence of the benzene ring, which provides resonance stabilization.
- **Conclusion**: Rearrangement is possible.

#### Option B: CH3C^+(H)OCH3
- This is a secondary carbocation.
- A hydride shift can occur to form a more stable tertiary carbocation.
- **Conclusion**: Rearrangement is possible.

#### Option C: Cyclic carbocation
- This is a secondary carbocation in a cyclic structure.
- Any rearrangement (like a hydride shift) will still result in a secondary carbocation.
- **Conclusion**: Rearrangement is NOT possible since the stability does not increase.

#### Option D: CH3-CH^+(CH3)-CH2-CH3
- This is a secondary carbocation.
- A hydride shift can occur to form a tertiary carbocation.
- **Conclusion**: Rearrangement is possible.

### Final Answer
The compound in which rearrangement is not possible is **Option C** (the cyclic secondary carbocation).

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