Which on heating with aqueous KOH, produces acetaldehyde?

Options

A. `CH_3-CH-Cl_2`
B. `CH_3 -CO-Cl`
C. `CH_3 -CH_2 -Cl`
D. `CH_2-Cl-CH_2 -Cl`

Explanation

To determine which compound, when heated with aqueous KOH, produces acetaldehyde, we can analyze the given options step by step.

### Step 1: Identify the structure of acetaldehyde
Acetaldehyde has the molecular formula CH3CHO. It is a two-carbon aldehyde, where the functional group -CHO is attached to the second carbon.

### Step 2: Analyze the options
We need to evaluate each option to see which one can yield acetaldehyde upon reaction with aqueous KOH.

#### Option D: CH2Cl2 (Dichloromethane)
- When CH2Cl2 is treated with aqueous KOH, the hydroxide ion (OH-) acts as a nucleophile and can replace one of the chlorine atoms. However, this will not lead to the formation of acetaldehyde. Instead, it may produce alcohols or other products.

#### Option C: CH3CH2Cl (Ethyl chloride)
- In this case, the OH- will replace the chlorine atom, leading to the formation of ethanol (CH3CH2OH). This does not yield acetaldehyde.

#### Option B: CH3COCH3 (Acetone)
- Here, the OH- will attack the carbonyl carbon, but it will not lead to the formation of an aldehyde. Instead, it may lead to other reactions that do not produce acetaldehyde.

#### Option A: CH3CCl2 (Dichloroethane)
- In this case, when CH3CCl2 is treated with aqueous KOH, the OH- can attack the carbon bonded to the chlorine atoms. The reaction will lead to the formation of acetaldehyde through the elimination of Cl- ions and rearrangement.

### Conclusion
The compound that produces acetaldehyde when heated with aqueous KOH is **CH3CCl2**.