A single reagent that can distinguish HCHO and `C_6H_5CHO` is

Options

A. Tollen’s reagent
B. `l_2`+NaOH
C. `50%` NaOH
D. Fehling’s reagent

Answer

To distinguish between formaldehyde (HCHO) and benzaldehyde (C6H5CHO), we can use a reagent that reacts differently with these two aldehydes.

### Step-by-Step Solution:

1. **Identify the Aldehydes**:
- Formaldehyde (HCHO) is a simple aldehyde with no aromatic ring.
- Benzaldehyde (C6H5CHO) contains a phenyl group (an aromatic ring).

2. **Select a Suitable Reagent**:
- A reagent that can distinguish between these two aldehydes is **2,4-dinitrophenylhydrazine (DNPH)**. This reagent reacts with carbonyl compounds to form hydrazones.

3. **Perform the Reaction**:
- When DNPH is added to HCHO, it will react to form a yellow/orange precipitate of 2,4-dinitrophenylhydrazone.
- When DNPH is added to C6H5CHO, it will also form a yellow/orange precipitate, but the melting point of the resulting hydrazone will be different from that of the hydrazone formed with HCHO.

4. **Analyze the Results**:
- By measuring the melting points of the hydrazones formed, we can distinguish between the two aldehydes. The melting point of the hydrazone from HCHO will be different from that of the hydrazone from C6H5CHO.

### Conclusion:
The single reagent that can distinguish HCHO and C6H5CHO is **2,4-dinitrophenylhydrazine (DNPH)**.

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