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 of the given compounds does not form a Grignard reagent when reacted with magnesium in the presence of ether, we will analyze each option step by step.

### Step 1: Understanding Grignard Reagents
Grignard reagents are formed when haloalkanes or aryl halides react with magnesium in dry ether. The general reaction can be represented as:
\[ R-X + Mg \xrightarrow{\text{dry ether}} R-MgX \]
where \( R \) is an alkyl or aryl group, and \( X \) is a halogen.

### Step 2: Analyzing Each Option
1. **Chloroethane (C2H5Cl)**:
- Structure: CH3-CH2-Cl
- Reaction:
\[ \text{CH}_3\text{CH}_2\text{Cl} + Mg \xrightarrow{\text{dry ether}} \text{CH}_3\text{CH}_2\text{MgCl} \]
- Conclusion: Chloroethane forms a Grignard reagent.

2. **1-Chloropropane (C3H7Cl)**:
- Structure: CH3-CH2-CH2-Cl
- Reaction:
\[ \text{CH}_3\text{CH}_2\text{CH}_2\text{Cl} + Mg \xrightarrow{\text{dry ether}} \text{CH}_3\text{CH}_2\text{CH}_2\text{MgCl} \]
- Conclusion: 1-Chloropropane forms a Grignard reagent.

3. **Bromobenzene (C6H5Br)**:
- Structure: C6H5-Br
- Reaction:
\[ \text{C}_6\text{H}_5\text{Br} + Mg \xrightarrow{\text{dry ether}} \text{C}_6\text{H}_5\text{MgBr} \]
- Conclusion: Bromobenzene forms a Grignard reagent.

4. **Vinyl Chloride (C2H3Cl)**:
- Structure: CH2=CH-Cl
- Reaction:
- Vinyl chloride has a double bond and the chlorine atom is involved in resonance, leading to a partial double bond character between the carbon and chlorine.
- This resonance stabilizes the molecule and prevents the formation of a Grignard reagent.
- Conclusion: Vinyl chloride does not form a Grignard reagent.

### Final Answer
The compound that does not form a Grignard reagent is **Vinyl Chloride (D)**.

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