Ethylene is converted to X on passing through a mixture of acidified aqueous solution of palladium chloride and cupric chloride. Which of the following reagents readily takes part addition reaction with X

Options

A. `Br_2`
B. HBr
C. HCl
D. HCN

Answer

To solve the question, we need to follow these steps:

### Step 1: Identify the starting compound
The starting compound is ethylene (C2H4), which has a double bond between the two carbon atoms.

### Step 2: Understand the reaction conditions
Ethylene is passed through a mixture of acidified aqueous solutions of palladium chloride (PdCl2) and cupric chloride (CuCl2). This process is known as the Wacker process.

### Step 3: Determine the product (X)
In the Wacker process, ethylene is oxidized to form an aldehyde. The reaction can be represented as follows:
\[ \text{C}_2\text{H}_4 + \text{Pd}^{2+} + \text{Cu}^{2+} \rightarrow \text{CH}_3\text{CHO} \]
Thus, the product X is acetaldehyde (CH3CHO).

### Step 4: Identify the reagents for addition reactions
Next, we need to determine which of the provided reagents can readily participate in an addition reaction with the aldehyde (X = CH3CHO). The reagents given are Br2, HBr, HCl, and CN.

### Step 5: Analyze the reactivity of the reagents
- **Br2**: Typically reacts with alkenes and alkynes but not directly with aldehydes in a straightforward manner.
- **HBr**: Can react with aldehydes, but it is not the strongest nucleophile.
- **HCl**: Similar to HBr, it can react with aldehydes.
- **CN (Cyanide ion)**: This is a strong nucleophile and will readily react with the carbonyl group in aldehydes.

### Step 6: Determine the strongest nucleophile
Among the reagents, CN (from HCN) is the strongest nucleophile. When it reacts with the carbonyl group of the aldehyde, it will form a cyanohydrin.

### Conclusion
The reagent that readily takes part in an addition reaction with X (acetaldehyde) is **CN** (from HCN).

### Final Answer
The correct answer is CN (Cyanide ion).

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