Which of the following alcohol can not be oxidized by `KMnO_4`

Options

A.
B.
C.
D.

Answer

To determine which alcohol cannot be oxidized by KMnO4, we need to understand the oxidation behavior of different types of alcohols. Here’s a step-by-step solution:

### Step 1: Identify the Types of Alcohols
Alcohols can be classified into three categories based on the carbon atom to which the hydroxyl (-OH) group is attached:
- **Primary Alcohols**: The -OH group is attached to a carbon that is bonded to one other carbon.
- **Secondary Alcohols**: The -OH group is attached to a carbon that is bonded to two other carbons.
- **Tertiary Alcohols**: The -OH group is attached to a carbon that is bonded to three other carbons.

### Step 2: Understand Oxidation with KMnO4
KMnO4 (potassium permanganate) is a strong oxidizing agent.
- **Primary Alcohols** can be oxidized to aldehydes and further to carboxylic acids.
- **Secondary Alcohols** can be oxidized to ketones.
- **Tertiary Alcohols** generally do not undergo oxidation under mild conditions because they lack a hydrogen atom on the carbon bearing the -OH group (no alpha hydrogen).

### Step 3: Analyze the Given Alcohols
Assuming we have a list of alcohols to analyze, we need to check each one for the presence of alpha hydrogen:
1. **Primary Alcohol**: Will oxidize.
2. **Secondary Alcohol**: Will oxidize.
3. **Tertiary Alcohol**: Will NOT oxidize (no alpha hydrogen).

### Step 4: Conclusion
Based on the analysis, the alcohol that cannot be oxidized by KMnO4 is the **tertiary alcohol**.