Which of the following compounds reacts with ethylmagnesium bromide and also decolourizes bromine water solution:

Options

A.
B.
C.
D.

Answer

To solve the problem, we need to determine which compound reacts with ethylmagnesium bromide (a Grignard reagent) and also decolorizes bromine water. Here’s a step-by-step breakdown of the solution:

### Step 1: Understand the Reactivity of Grignard Reagents
Grignard reagents, such as ethylmagnesium bromide (C2H5MgBr), are highly reactive and can react with:
- Carbonyl compounds (like aldehydes and ketones)
- Compounds containing acidic hydrogen (like alcohols, carboxylic acids, etc.)

### Step 2: Analyze the Decolorization of Bromine Water
Bromine water (Br2 in H2O) is used to test for unsaturation (double or triple bonds). Compounds with double bonds (C=C) or triple bonds (C≡C) will decolorize bromine water due to the addition reaction with bromine.

### Step 3: Evaluate Each Compound
We need to evaluate each of the given compounds to see if they can react with the Grignard reagent and decolorize bromine water.

1. **Compound 1**: Check for double bonds and acidic hydrogens.
- If it lacks a double bond and does not have acidic hydrogens, it will not decolorize bromine water and will not react with Grignard.

2. **Compound 2**: Check for carbonyl groups and acidic hydrogens.
- If it has a carbonyl group, it will react with Grignard. If it has no double bonds or acidic hydrogens, it will not decolorize bromine water.

3. **Compound 3**: Look for double bonds and acidic hydrogens.
- If it has a double bond, it may decolorize bromine water. If it has no carbonyl groups or acidic hydrogens, it will not react with Grignard.

4. **Compound 4**: Check for both double bonds and acidic hydrogens.
- If it has both a double bond and an acidic hydrogen, it will decolorize bromine water and react with Grignard.

### Step 4: Conclusion
After analyzing all the compounds:
- Compound 4 has a double bond and an acidic hydrogen, which allows it to react with ethylmagnesium bromide and decolorize bromine water.
- Therefore, the correct answer is **Option D**.