In the given reaction
`CH_(2)=CH-CHOoverset([X])rarrCH_(2)=CH-CH_(2)OH`
[X] will be

Options

A. `H_(2), Ni`
B. `H_(2), Pt`
C. `NaBH_(4)`
D. `H_(2)//"Wilkinson catalyst"`

Answer

To solve the problem, we need to identify the reagent [X] that can convert CH2=CH-CHO to CH2=CH-CH2OH without reducing the double bond. Let's go through the steps systematically.

### Step 1: Understand the Reaction
We start with the compound CH2=CH-CHO, which has both an alkene (double bond) and an aldehyde (CHO group). The product we want is CH2=CH-CH2OH, which retains the double bond but converts the aldehyde to an alcohol.

### Step 2: Identify the Requirements for Reagent [X]
The reagent must:
- Reduce the aldehyde (CHO) to an alcohol (CH2OH).
- Not reduce the double bond (CH=CH) in the molecule.

### Step 3: Evaluate Possible Reagents
Let's consider the common reducing agents:
1. **Hydrogen with Nickel (H2/Ni)**: This will reduce both the aldehyde and the double bond, which is not what we want.
2. **Hydrogen with Platinum (H2/Pt)**: Similar to Nickel, this will also reduce both the aldehyde and the double bond.
3. **Sodium Borohydride (NaBH4)**: This reagent is known for selectively reducing aldehydes to alcohols without affecting alkenes. This fits our requirement perfectly.
4. **Hydrogen with Wilkinson's Catalyst**: This catalyst can reduce alkenes without affecting functional groups, but it does not selectively reduce aldehydes.

### Step 4: Conclusion
Based on the evaluation, the reagent that meets the criteria of reducing the aldehyde to an alcohol while leaving the double bond intact is **Sodium Borohydride (NaBH4)**.

### Final Answer
Therefore, the reagent [X] is **Sodium Borohydride (NaBH4)**.

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