The product of which of the following reactions is not a vicinal dihalide?

Options

A. Reaction of ethylene glycol with P + `Br_(2)`
B. Reaction of HCl with ethyne
C. Reaction of HBr with ethyne in the presence of peroxide
D. Reaction of `Cl_(2)` with propene at `60^(@)C`

Answer

To determine which reaction produces a product that is not a vicinal dihalide, we first need to understand what vicinal dihalides are. Vicinal dihalides are compounds that have two halogen atoms (X) attached to adjacent carbon atoms in a molecule.

### Step-by-Step Solution:

1. **Identify the Reactions**: We need to analyze the reactions given in the question. The reactions involve:
- Ethylene glycol with PBr2
- Ethyne (acetylene) with HCl
- Ethyne with HBr in the presence of peroxide

2. **Reaction of Ethylene Glycol with PBr2**:
- Ethylene glycol (HO-CH2-CH2-OH) reacts with PBr2.
- The hydroxyl groups (OH) are replaced by bromine (Br) atoms.
- The product formed is CH2Br-CH2Br, which has bromine atoms on adjacent carbons.
- **Conclusion**: This is a vicinal dihalide.

3. **Reaction of Ethyne with HCl**:
- Ethyne (HC≡CH) reacts with HCl.
- The reaction proceeds through the formation of a carbocation, and both chlorine atoms end up on the same carbon atom.
- The product is H2C=CCl2, which has both Cl atoms on the same carbon.
- **Conclusion**: This is a geminal dihalide, not a vicinal dihalide.

4. **Reaction of Ethyne with HBr in the Presence of Peroxide**:
- Ethyne (HC≡CH) reacts with HBr in the presence of peroxide.
- The reaction leads to the formation of vinyl bromide (H2C=CHBr) first, and then a second equivalent of HBr adds to form 1,2-dibromide (Br-CH2-CHBr).
- The product has bromine atoms on adjacent carbons.
- **Conclusion**: This is a vicinal dihalide.

5. **Final Conclusion**:
- The reaction of ethyne with HCl produces a geminal dihalide, while the other reactions produce vicinal dihalides.
- Therefore, the answer to the question is that the product of the reaction of ethyne with HCl is not a vicinal dihalide.

### Summary:
The product of the reaction of ethyne with HCl is not a vicinal dihalide; it is a geminal dihalide.

---