Grignard reagent, a very useful starting compound for a number of organic reactions can be prepared by

Options

A. reaction of alkyl halides with a solution of magnesium hydroxide
B. reaction of alkyl halides with a solution of magnesium powder in presence of dry ether
C. reaction of `MgCl_2` with ether and alcohol
D. reaction of alkyl halide with magnesium in presence of alcohol.

Explanation

To prepare Grignard reagents, we need to follow a specific reaction involving alkyl halides and magnesium. Here’s the step-by-step solution:

### Step 1: Identify the Components
Grignard reagents are typically represented as R-Mg-X, where R is an alkyl or aryl group, Mg is magnesium, and X is a halogen (like Cl, Br, or I).

### Step 2: Choose the Correct Reaction
The formation of Grignard reagents involves the reaction of an alkyl halide (RX) with magnesium (Mg). The reaction must occur in an anhydrous (dry) ether solvent, which is crucial because Grignard reagents are highly reactive and can react with water.

### Step 3: Write the Reaction
The general reaction can be written as:
\[ \text{R-X} + \text{Mg} \xrightarrow{\text{Dry Ether}} \text{R-Mg-X} \]
Where:
- R-X is the alkyl halide
- Mg is magnesium
- Dry Ether is the solvent

### Step 4: Evaluate the Options
Now, let's evaluate the options given in the question:
1. **Reaction of alkyl halide with the solution of magnesium hydroxide**: This is incorrect because magnesium hydroxide does not produce Grignard reagents.
2. **Reaction of alkyl halide with the solution of magnesium powder in the presence of dry ether**: This is correct and will produce the desired Grignard reagent.
3. **Reaction of MgCl2 in ether or alcohol**: This is incorrect as it does not lead to the formation of Grignard reagents.
4. **Reaction of alkyl halide with magnesium in the presence of alcohol**: This is incorrect because alcohol will react with the Grignard reagent instead of allowing its formation.

### Conclusion
The correct method to prepare Grignard reagents is through the reaction of alkyl halides with magnesium powder in the presence of dry ether.

### Final Answer
Grignard reagent can be prepared by the reaction of alkyl halide with magnesium powder in the presence of dry ether.

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