Which of the following will be obatined by the bromination of ethylbenzene is presence of light ?

Options

A.
B.
C.
D.

Answer

To determine the product obtained from the bromination of ethylbenzene in the presence of light, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Reactant**:
The compound we are starting with is ethylbenzene, which consists of a benzene ring with an ethyl group (C2H5) attached to it.

2. **Understand the Reaction Conditions**:
The reaction is performed in the presence of light, which indicates that a free radical mechanism will be involved. Light causes the homolytic cleavage of the bromine (Br2) molecule.

3. **Homolytic Cleavage of Bromine**:
When bromine is exposed to light, it undergoes homolytic cleavage to form two bromine radicals:
\[ \text{Br}_2 \xrightarrow{\text{light}} 2 \text{Br}^\cdot \]

4. **Formation of Free Radicals**:
The ethyl group (C2H5) in ethylbenzene can also undergo homolytic cleavage to form an ethyl radical (C2H5•). The hydrogen atom from the ethyl group can be abstracted by the bromine radical, leading to the formation of a benzyl radical (C6H5-CH2•) and HBr.

5. **Stability of Radicals**:
The benzyl radical (C6H5-CH2•) is more stable than other possible radicals due to resonance stabilization. This makes it the favored product.

6. **Final Product Formation**:
The benzyl radical can then react with a bromine radical to form the final product, which is bromobenzene with an ethyl group:
\[ \text{C}_6\text{H}_5\text{CH}_2\text{Br} + \text{HBr} \]
This product is known as bromethylbenzene (or 1-bromoethylbenzene).

7. **Select the Correct Option**:
Based on the analysis, the major product formed from the bromination of ethylbenzene in the presence of light is 1-bromoethylbenzene. If this matches option D in the provided choices, then option D is the correct answer.

### Conclusion:
The major product obtained from the bromination of ethylbenzene in the presence of light is **1-bromoethylbenzene**.