The reagents which cannot convert primary alcohol to carboxylic acid?

Options

A. Potassium permanganate
B. Chromic acid
C. Pyridinium chlorochromate
D. Jones reagent

Answer

To determine which reagent cannot convert a primary alcohol to a carboxylic acid, we will evaluate each of the given reagents one by one.

### Step-by-Step Solution:

1. **Identify the Primary Alcohol**:
We start with a primary alcohol, which can be represented as R-OH, where R is an alkyl group.

2. **Evaluate Potassium Permanganate (KMnO4)**:
- KMnO4 is a strong oxidizing agent.
- It oxidizes primary alcohols to carboxylic acids.
- **Reaction**: R-OH → R-COOH (carboxylic acid)
- **Conclusion**: KMnO4 can convert primary alcohol to carboxylic acid.

3. **Evaluate Chromic Acid (H2CrO4)**:
- Chromic acid is also a strong oxidizing agent.
- It oxidizes primary alcohols to carboxylic acids.
- **Reaction**: R-OH → R-COOH (carboxylic acid)
- **Conclusion**: Chromic acid can convert primary alcohol to carboxylic acid.

4. **Evaluate Pyridinium Chlorochromate (PCC)**:
- PCC is a milder oxidizing agent compared to KMnO4 and chromic acid.
- It typically oxidizes primary alcohols to aldehydes, stopping at that stage.
- **Reaction**: R-OH → R-CHO (aldehyde)
- **Conclusion**: PCC cannot convert primary alcohol to carboxylic acid; it stops at the aldehyde stage.

5. **Evaluate Jones Reagent (Chromic Oxide in H+)**:
- Jones reagent is a strong oxidizing agent.
- It oxidizes primary alcohols to carboxylic acids.
- **Reaction**: R-OH → R-COOH (carboxylic acid)
- **Conclusion**: Jones reagent can convert primary alcohol to carboxylic acid.

### Final Conclusion:
The reagent that cannot convert a primary alcohol to a carboxylic acid is **Pyridinium Chlorochromate (PCC)**.

### Answer:
**Pyridinium Chlorochromate (PCC)**