Which one of the following organic compounds decolourizes an alkaline `KMnO_4` solution

Options

A. `CS_2`
B. `C_3H_6`
C. `C_3H_8`
D. `CH_3OH`

Explanation

To determine which organic compound decolorizes an alkaline KMnO4 solution, we need to understand the nature of the compounds that can do so. Alkaline KMnO4 is a strong oxidizing agent and is typically purple in color. When it reacts with certain organic compounds, it can lose its color, indicating a reduction of the KMnO4.

### Step-by-Step Solution:

1. **Identify the Compounds**: First, we need to know the organic compounds that are being considered for this reaction. Common candidates include alcohols, aldehydes, ketones, and alkenes.

2. **Understand the Reaction**: Alkaline KMnO4 can oxidize certain functional groups. For example:
- **Alkenes**: They can be oxidized to diols, which will decolorize KMnO4.
- **Aldehydes**: They can be oxidized to carboxylic acids, which will also decolorize KMnO4.
- **Alcohols**: Primary alcohols can be oxidized to aldehydes, and secondary alcohols can be oxidized to ketones.

3. **Check for Unsaturation**: Compounds that contain double bonds (alkenes) or functional groups that are easily oxidizable (like aldehydes) are likely to decolorize the solution.

4. **Perform the Test**: If we have a specific compound in mind, we can perform a test by adding it to an alkaline KMnO4 solution and observing the color change. If the purple color disappears, the compound is indeed capable of reducing KMnO4.

5. **Conclusion**: Based on the knowledge of organic chemistry, alkenes and aldehydes are the most likely candidates to decolorize alkaline KMnO4.

### Final Answer:
The organic compound that decolorizes an alkaline KMnO4 solution is typically an alkene or an aldehyde.