Which of the following alkenes on ozonolysis give a mixture of ketones only?

Options

A. `CH_(3)-CH=CH-CH_(3)`
B. `CH_(3)-underset(CH_(3))underset(|)C-CH=CH_(3)`
C.
D. `CH_(3)-CH=CH_(2)`

Explanation

To determine which alkenes give a mixture of ketones only upon ozonolysis, we will analyze the ozonolysis process step by step.

### Step-by-Step Solution:

1. **Understanding Ozonolysis**:
Ozonolysis is a reaction where alkenes react with ozone (O3) to form ozonides, which upon reduction (commonly with zinc and water) yield carbonyl compounds (aldehydes or ketones).

2. **Identifying the Alkene Structure**:
We need to analyze the given alkenes. The key is to identify whether the double bond is terminal or internal:
- Terminal alkenes typically yield aldehydes.
- Internal alkenes can yield ketones.

3. **Analyzing Each Alkene**:
- **Alkene 1**: If the alkene is something like CH3-CH=CH2 (propene), ozonolysis will yield CH3CHO (acetaldehyde) and CH3CHO (acetaldehyde), which are aldehydes.
- **Alkene 2**: If the alkene is CH3-CH=CH-CH3 (butene), ozonolysis will yield CH3COCH3 (acetone) and CH3COCH3 (acetone), which are ketones.
- **Alkene 3**: If the alkene is CH3-CH=CH2 (propene) again, it will yield aldehydes.
- **Alkene 4**: If the alkene is CH3-CH=CH-CH3 (butene), it will yield ketones.

4. **Conclusion**:
The alkenes that yield a mixture of ketones only upon ozonolysis are those that do not have terminal double bonds. Therefore, alkenes like CH3-CH=CH-CH3 yield only ketones.

### Final Answer:
The alkenes that give a mixture of ketones only upon ozonolysis are those that are internal alkenes, such as CH3-CH=CH-CH3.