Acetaldehyde and benzaldehyde may be distinguished by reacting with

Options

A. DNP
B. `NH_(2)OH`
C. Grignard reagent
D. Benedict's reagent

Answer

To distinguish between acetaldehyde and benzaldehyde, we can use the Benedict's test. Here’s a step-by-step explanation of the process:

### Step-by-Step Solution:

1. **Understanding the Compounds**:
- Acetaldehyde (CH₃CHO) is an aldehyde with an alpha hydrogen (the hydrogen atom attached to the carbon adjacent to the carbonyl group).
- Benzaldehyde (C₆H₅CHO) is also an aldehyde but does not have an alpha hydrogen.

2. **Benedict's Test**:
- The Benedict's test is a qualitative test for the presence of reducing sugars and aldehydes. It involves the reaction of the aldehyde with the Benedict's reagent, which contains copper(II) ions.
- For an aldehyde to react with Benedict's reagent, it must be able to form an enolate ion. This requires the presence of an alpha hydrogen.

3. **Enolate Formation**:
- Acetaldehyde has 3 alpha hydrogens (the three hydrogen atoms on the methyl group). This allows it to form an enolate ion when it reacts with the Benedict's reagent.
- Benzaldehyde, on the other hand, has no alpha hydrogen. Therefore, it cannot form an enolate ion and will not react with the Benedict's reagent.

4. **Performing the Test**:
- When acetaldehyde is mixed with Benedict's reagent, a color change occurs, indicating a positive test (usually a brick-red precipitate of copper(I) oxide).
- When benzaldehyde is mixed with Benedict's reagent, there is no color change, indicating a negative test.

5. **Conclusion**:
- By performing the Benedict's test, we can distinguish between acetaldehyde and benzaldehyde. Acetaldehyde will give a positive result, while benzaldehyde will not react.

### Final Answer:
Acetaldehyde and benzaldehyde may be distinguished by reacting with **Benedict's reagent**.

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