Which of the following does not form Grignard reagent on reaction with Mg in the presence of ether?

Options

A. Chloroethane
B. 1-chloropropane
C. Bromobenzene
D. Vinyl chloride

Answer

To determine which compound does not form a Grignard reagent upon reaction with magnesium (Mg) in the presence of ether, we need to analyze the nature of the carbon-halogen bond in each compound. Grignard reagents are formed when the carbon-halogen bond is weak enough to break, allowing the carbon to bond with magnesium.

### Step-by-Step Solution:

1. **Understanding Grignard Reagents**:
- Grignard reagents are formed by the reaction of alkyl or aryl halides with magnesium in dry ether. The general reaction can be represented as:
\[ R-X + Mg \rightarrow R-MgX \]
- Here, \( R \) is the alkyl or aryl group, and \( X \) is the halogen (Cl, Br, or I).

2. **Analyzing the Compounds**:
- We need to evaluate the strength of the carbon-halogen bond in the given compounds. The weaker the bond, the more likely it is to react with magnesium.

3. **Compounds to Consider**:
- **Chloroethane (C2H5Cl)**: The C-Cl bond is relatively weak, and it can form a Grignard reagent.
- **1-Chloropropane (C3H7Cl)**: Similar to chloroethane, the C-Cl bond is weak enough to allow the formation of a Grignard reagent.
- **Vinyl Chloride (CH2=CHCl)**: The C-Cl bond here is stabilized by resonance due to the double bond, making it less likely to break and thus it does not form a Grignard reagent.
- **Bromobenzene (C6H5Br)**: The C-Br bond is also stabilized by resonance in the aromatic system, making it difficult to break and therefore it does not form a Grignard reagent.

4. **Conclusion**:
- Among the compounds analyzed, **Vinyl Chloride (CH2=CHCl)** and **Bromobenzene (C6H5Br)** do not form Grignard reagents due to the resonance stabilization of the carbon-halogen bond. However, since the question asks for a single answer, **Vinyl Chloride** is the primary compound that does not form a Grignard reagent.

### Final Answer:
**Vinyl Chloride (CH2=CHCl)** does not form a Grignard reagent on reaction with Mg in the presence of ether.