What sequence of reactions would best accomplish the following conversion?
`CH_(3)-overset(O)overset(||)C-CH_(2)-overset(O)overset(||)C-Hoverset(?)rarrCH_(3)overset(OH)overset("| ")"CH"CH_(2)CHO`

Options

A. `NaBH_(4)//H_(3)O^(+)`
B. `HOCH_(2)CH_(2)OH//H^(+), NaBH_(4), H^(+)//H_(2)O`
C. `KMnO_(4)//HO^(-)," heat"`
D. `LiAlH_(4)//H_(3)O^(+)`

Answer

To accomplish the conversion from the given compound to the desired product, we will follow a systematic sequence of reactions. The starting compound is a ketone and an aldehyde, and we want to convert the ketone into a secondary alcohol and the aldehyde into a primary alcohol.

### Step-by-Step Solution:

1. **Identify the Functional Groups**:
The starting compound has a ketone (C=O) and an aldehyde (C=O) functional group. The ketone is located between two carbon atoms, while the aldehyde is at the end of the carbon chain.

2. **Protection of the Aldehyde**:
To prevent the aldehyde from being reduced while we reduce the ketone, we will protect the aldehyde group. We can use ethylene glycol (HO-CH2-CH2-OH) as a protecting group. In the presence of an acid (H+), the aldehyde will react with ethylene glycol to form a cyclic acetal, thus protecting it.

Reaction:
\[ \text{Aldehyde} + \text{Ethylene Glycol} \xrightarrow{H^+} \text{Protected Aldehyde} \]

3. **Reduction of the Ketone**:
Now that the aldehyde is protected, we can reduce the ketone to a secondary alcohol. We can use sodium borohydride (NaBH4) as a reducing agent. This will convert the ketone into a secondary alcohol.

Reaction:
\[ \text{Ketone} + \text{NaBH}_4 \rightarrow \text{Secondary Alcohol} \]

4. **Deprotection of the Aldehyde**:
After the reduction step, we need to remove the protecting group to regenerate the aldehyde. This can be done through hydrolysis. We will use water in the presence of an acid (H3O+) to deprotect the aldehyde.

Reaction:
\[ \text{Protected Aldehyde} + \text{H}_2O \xrightarrow{H_3O^+} \text{Aldehyde} \]

5. **Final Product**:
After deprotection, we will have the secondary alcohol from the ketone and the aldehyde remains intact, giving us the final product.

### Summary of Reactions:
1. Protect the aldehyde using ethylene glycol in acidic medium.
2. Reduce the ketone using NaBH4 to form a secondary alcohol.
3. Deprotect the aldehyde using water and acid.

### Final Reaction Sequence:
\[ \text{CH}_3C(=O)CH_2C(=O)H \xrightarrow{H^+} \text{Protected Aldehyde} \xrightarrow{\text{NaBH}_4} \text{Secondary Alcohol} + \text{Aldehyde} \xrightarrow{H_2O/H_3O^+} \text{Final Product} \]