The major product obtained from photochemical chlorination of ethylbenzene (in excess) is hydrolyzed with aqueous KOH. The final product formed is :

Options

A. `PbCH_(2)CHO`
B. `PhCOCH_(3)`
C. `PhCHO`
D. PhCOOH

Answer

To solve the problem of determining the final product formed from the photochemical chlorination of ethylbenzene followed by hydrolysis with aqueous KOH, we can break down the process into a series of steps:

### Step 1: Photochemical Chlorination of Ethylbenzene
1. **Starting Material**: Ethylbenzene (C6H5-CH2-CH3).
2. **Chlorination Process**: Under the influence of light (photochemical conditions), chlorine (Cl2) will react with ethylbenzene.
3. **Mechanism**: The reaction proceeds via a free radical mechanism, where chlorine radicals (Cl•) abstract hydrogen atoms from the benzylic position (the carbon adjacent to the benzene ring).
4. **Formation of Products**: The major product of chlorination in excess chlorine will be 1,2-dichloroethylbenzene (C6H5-CHCl-CH2Cl), where two hydrogen atoms from the ethyl group are replaced by chlorine atoms.

### Step 2: Hydrolysis with Aqueous KOH
1. **Starting Material**: 1,2-Dichloroethylbenzene (C6H5-CHCl-CH2Cl).
2. **Hydrolysis Reaction**: When treated with aqueous KOH, the chlorine atoms will be replaced by hydroxyl groups (OH).
3. **Mechanism**: The reaction follows an SN1 mechanism due to the formation of a stable carbocation intermediate after the departure of a chlorine atom.
4. **Formation of Intermediate**: The first step involves the formation of a carbocation (C6H5-CH+-CH2Cl) after the loss of one Cl atom.
5. **Nucleophilic Attack**: The hydroxide ion (OH-) from KOH will then attack the carbocation, resulting in the formation of a secondary alcohol (C6H5-CHOH-CH2Cl).
6. **Second Hydrolysis**: The second chlorine atom will also be replaced by hydroxyl, leading to the formation of a diol (C6H5-CHOH-CH(OH)2).
7. **Dehydration**: The presence of two hydroxyl groups on the same carbon will lead to instability, resulting in the elimination of water (H2O) and forming a ketone.

### Final Product
The final product formed after the dehydration step will be acetophenone (C6H5-CO-CH3).

### Summary of the Final Product
The final product formed from the photochemical chlorination of ethylbenzene followed by hydrolysis with aqueous KOH is **acetophenone (C6H5-CO-CH3)**.

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