Which of the following compound gives benzoic acid when it reacts with hot `KMnO_(4)` followed by acidification.

Options

A.
B.
C.
D. All of these

Answer

To determine which compound gives benzoic acid when reacted with hot KMnO4 followed by acidification, we can analyze each option step by step.

### Step-by-Step Solution:

1. **Understanding the Reaction with KMnO4**:
- KMnO4 is a strong oxidizing agent. It can oxidize various organic compounds, particularly those containing double bonds or benzylic hydrogens.

2. **Analyzing the Options**:
- We need to evaluate each compound provided in the options to see if it can be oxidized to benzoic acid.

3. **Option 1**:
- If the compound is a phenyl group with a double bond (like styrene), upon reaction with hot KMnO4, it will oxidize the double bond to form a carbonyl group (aldehyde), which can further oxidize to benzoic acid upon acidification.
- **Conclusion**: This option can yield benzoic acid.

4. **Option 2**:
- If the compound is toluene (methylbenzene), it contains a benzylic hydrogen. When toluene reacts with hot KMnO4, the benzylic hydrogen gets oxidized to a carboxylic acid (benzoic acid).
- **Conclusion**: This option can also yield benzoic acid.

5. **Option 3**:
- If the compound is an aldehyde (like benzaldehyde), it is easily oxidized by KMnO4 to form benzoic acid upon acidification.
- **Conclusion**: This option can also yield benzoic acid.

6. **Option 4**:
- If the compound is a ketone or does not have a benzylic hydrogen, it may not yield benzoic acid upon oxidation.
- **Conclusion**: This option is less likely to yield benzoic acid.

7. **Final Conclusion**:
- Based on the analysis, options 1, 2, and 3 can yield benzoic acid when reacted with hot KMnO4 followed by acidification. Therefore, the answer is that all the compounds in options 1, 2, and 3 can give benzoic acid.