Which reagent is used to differentiate between aldehyde and ketone ?

Options

A. Fehling's solution
B. Tollen's reagent
C. Schiff's reagent
D. All of these

Answer

To differentiate between aldehydes and ketones, we can use several reagents, including Fehling's solution, Tollens' reagent, and Schiff's reagent. Here’s a step-by-step breakdown of how these reagents work:

### Step 1: Understanding Aldehydes and Ketones
- **Aldehydes** have a carbonyl group (C=O) at the end of the carbon chain, while **ketones** have a carbonyl group within the carbon chain.
- Aldehydes are generally more reactive than ketones due to the presence of the hydrogen atom attached to the carbonyl carbon.

### Step 2: Using Fehling's Solution
- **Fehling's solution** consists of two solutions (A and B) that contain copper(II) sulfate and sodium potassium tartrate, respectively.
- When an aldehyde is added to Fehling's solution, it reduces the blue Cu²⁺ ions to red Cu₂O precipitate, indicating a positive test.
- Ketones typically do not react with Fehling's solution, so no color change occurs.

### Step 3: Using Tollens' Reagent
- **Tollens' reagent** is a solution of silver nitrate in ammonia (NH₄OH + AgNO₃).
- Aldehydes reduce the silver ions (Ag⁺) to metallic silver, forming a silver mirror on the test tube.
- Ketones do not react with Tollens' reagent, so no silver mirror forms.

### Step 4: Using Schiff's Reagent
- **Schiff's reagent** is a solution of fuchsine dye that has been decolorized by sulfur dioxide.
- Aldehydes will react with Schiff's reagent, restoring the pink color, while ketones will not cause any color change.

### Conclusion
- All three reagents (Fehling's solution, Tollens' reagent, and Schiff's reagent) can be used to differentiate between aldehydes and ketones.
- If a reaction occurs with any of these reagents, the compound is likely an aldehyde; if no reaction occurs, it is likely a ketone.

### Final Answer
The correct option is that all of these reagents (Fehling's solution, Tollens' reagent, and Schiff's reagent) can be used to differentiate between aldehydes and ketones.

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