Which reagent will produce 1, 1-dichloroethane from ethanal?

Options

A. `Cl_(2)`
B. `SOCl_(2)//Py`
C. HCl
D. any of above.

Explanation

To produce 1,1-dichloroethane from ethanal (acetaldehyde), we need to follow a specific reaction pathway. Here’s a step-by-step solution:

### Step 1: Identify the structure of ethanal
Ethanal, also known as acetaldehyde, has the chemical formula CH3CHO. Its structure consists of a carbonyl group (C=O) attached to a methyl group (CH3).

### Step 2: Understand the target product
The target product is 1,1-dichloroethane, which has the structure CH2Cl-CH2Cl. This means we need to introduce two chlorine atoms to the same carbon atom in the molecule.

### Step 3: Choose the appropriate reagent
To achieve the conversion from ethanal to 1,1-dichloroethane, we can use thionyl chloride (SOCl2) in the presence of a base like pyridine. Thionyl chloride is a reagent that can convert alcohols and aldehydes into chlorinated products.

### Step 4: Reaction mechanism
1. **Formation of the intermediate**: When ethanal reacts with thionyl chloride (SOCl2), the carbonyl oxygen is protonated, and the carbonyl group is converted into a better leaving group.
2. **Chlorination**: The chloride ion from thionyl chloride attacks the carbon atom of the carbonyl group, leading to the formation of a chlorinated intermediate.
3. **Formation of 1,1-dichloroethane**: In the presence of pyridine, the reaction facilitates the addition of another chlorine atom, resulting in the formation of 1,1-dichloroethane.

### Step 5: Conclusion
Thus, the reagent that will produce 1,1-dichloroethane from ethanal is thionyl chloride (SOCl2) in the presence of pyridine.

### Final Answer
The reagent that will produce 1,1-dichloroethane from ethanal is **thionyl chloride (SOCl2) in the presence of pyridine**.

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