Which compound will yield 5-keto -2 methyl hexanal upon treatment with `O_(3)`?

Options

A.
B.
C.
D.

Answer

To determine which compound will yield 5-keto-2-methylhexanal upon treatment with ozone (O3), we need to analyze the structure of the desired product and trace back to the corresponding alkene that would produce it through ozonolysis.

### Step-by-Step Solution:

1. **Identify the Product Structure:**
- The desired product is 5-keto-2-methylhexanal.
- This indicates that the compound has six carbon atoms (hexanal), with:
- An aldehyde (−CHO) group at the first carbon.
- A methyl (−CH3) group at the second carbon.
- A keto (C=O) group at the fifth carbon.

2. **Draw the Structure of the Product:**
- The structure can be represented as follows:
```
CH3-CH-CHO
|
C=O
|
CH2-CH3
```
- This corresponds to the linear structure:
```
CH3-CH(CH3)-CH2-CO-CH2-CHO
```

3. **Determine the Alkene Precursor:**
- Ozonolysis of alkenes cleaves the double bond and forms carbonyl compounds.
- To obtain the desired product, we need to consider where the double bond must be located in the precursor alkene.
- The double bond should be between the first and fifth carbons to yield the aldehyde and keto groups in the product.

4. **Analyze the Given Options:**
- We have four options to consider:
1. 1,3-dimethylcyclopentene
2. 1,4-dimethylcyclopentene
3. 1,5-dimethylcyclopentene
4. 1,2-dimethylcyclopentene

5. **Perform Ozonolysis on Each Option:**
- **Option 1: 1,3-dimethylcyclopentene**
- The double bond is between carbon 1 and 2.
- Cleavage yields the desired product structure.
- **Option 2: 1,4-dimethylcyclopentene**
- The double bond is between carbon 1 and 4.
- The resulting product does not match the desired structure.
- **Option 3: 1,5-dimethylcyclopentene**
- The double bond is between carbon 1 and 5.
- The resulting product does not match the desired structure.
- **Option 4: 1,2-dimethylcyclopentene**
- The double bond is between carbon 1 and 2.
- The resulting product does not match the desired structure.

6. **Conclusion:**
- After analyzing all options, **Option 1: 1,3-dimethylcyclopentene** is the only compound that yields 5-keto-2-methylhexanal upon ozonolysis.