In which of the following reaction migration of alkyl group from `''C''` to `''N''` terminus is not occuring

Options

A. Pinacol-Pinacolone rearrangement
B. Curitius rearrangement
C. Lossen Rearrangement
D. Beckmann Rearrangement

Explanation

To determine in which of the given reactions the migration of an alkyl group from the carbon to the nitrogen terminus is not occurring, we will analyze each rearrangement step by step.

### Step 1: Analyze Pinacol-Pinacolone Rearrangement
1. **Starting Compound**: Pinacol (a diol with two -OH groups).
2. **Reaction Conditions**: Treatment with an acid (H⁺).
3. **Mechanism**:
- Protonation of one -OH group leads to the formation of a carbocation.
- Rearrangement occurs where a methyl group migrates to stabilize the carbocation.
4. **Final Product**: Pinacolone (a ketone).
5. **Conclusion**: There is no nitrogen present in this reaction, so no migration of an alkyl group to nitrogen occurs.

### Step 2: Analyze Curtius Rearrangement
1. **Starting Compound**: An azide compound (R-CH₂-CO-N₃).
2. **Reaction Conditions**: Heating or treatment with acid.
3. **Mechanism**:
- The azide group decomposes, leading to the formation of an isocyanate.
- The alkyl group (R) migrates from the carbon to the nitrogen.
4. **Final Product**: R-C(=O)-N.
5. **Conclusion**: There is a migration of the alkyl group from carbon to nitrogen.

### Step 3: Analyze Lawson Rearrangement
1. **Starting Compound**: Hydroxylamine (NH₂OH).
2. **Reaction Conditions**: Acidic medium.
3. **Mechanism**:
- The hydroxylamine loses water, forming a carbon-nitrogen double bond.
- The alkyl group migrates from the carbon to the nitrogen.
4. **Final Product**: R-C(=N)-OH.
5. **Conclusion**: There is a migration of the alkyl group from carbon to nitrogen.

### Step 4: Analyze Bachmann Rearrangement
1. **Starting Compound**: An oxime (R-C(=NOH)).
2. **Reaction Conditions**: Acidic medium.
3. **Mechanism**:
- The oxime undergoes rearrangement to form a nitrile.
- The alkyl group migrates from the carbon to the nitrogen.
4. **Final Product**: R-C≡N.
5. **Conclusion**: There is a migration of the alkyl group from carbon to nitrogen.

### Final Conclusion
After analyzing all four rearrangements, we find that:
- **Pinacol-Pinacolone Rearrangement** is the only reaction where the migration of the alkyl group from carbon to nitrogen does not occur.

### Answer
**The correct answer is the Pinacol-Pinacolone rearrangement.**