Which of the following can not be obtained when alkenes are oxidised with `KMnO_(4)` and then followed by acid hydrolysis ?

Options

A. alkanoic acids
B. alkanals
C. alkanones
D. carbon dioxide

Answer

To solve the question, we need to analyze the oxidation of alkenes with potassium permanganate (KMnO4) followed by acid hydrolysis. Here’s a step-by-step breakdown:

### Step 1: Understand the Reaction
When alkenes are treated with KMnO4, a strong oxidizing agent, they undergo oxidation. This reaction can lead to the formation of various products depending on the structure of the alkene.

### Step 2: Identify Possible Products
1. **Alkanoic Acids (Carboxylic Acids)**: Alkenes can be oxidized to form carboxylic acids when they have terminal double bonds.
2. **Alkanals (Aldehydes)**: Alkenes can also be oxidized to form aldehydes, particularly when the double bond is between a primary carbon and a secondary carbon.
3. **Alkanones (Ketones)**: If the alkene has a double bond between two secondary carbons, it can be oxidized to form ketones.
4. **Carbon Dioxide**: Complete oxidation of alkenes can lead to the formation of carbon dioxide, especially in the case of more complex alkenes.

### Step 3: Analyze Each Option
- **Alkanoic Acids**: Can be formed from the oxidation of alkenes.
- **Alkanals**: Can be formed, but they are not the primary product of oxidation with KMnO4.
- **Alkanones**: Can definitely be formed from the oxidation of alkenes.
- **Carbon Dioxide**: While possible in complete oxidation, it is not a direct product of the oxidation followed by acid hydrolysis.

### Step 4: Conclusion
Based on the analysis, the product that **cannot** be obtained directly when alkenes are oxidized with KMnO4 followed by acid hydrolysis is **Alkanals**.

### Final Answer
The correct option is **Alkanals**.

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