Aliphatic and aromatic aldehydes can be differentiated by the use of

Options

A. Fehling solution
B. Tollen's regent
C. `KMnO_(4)//H^(+)//Delta`
D. conc. `HNO_(3)//Delta`

Answer

To differentiate between aliphatic and aromatic aldehydes, we can use the following step-by-step solution:

### Step 1: Understanding Aldehydes
Aldehydes can be classified into two categories: aliphatic aldehydes and aromatic aldehydes. Aliphatic aldehydes have a straight or branched chain structure, while aromatic aldehydes contain a benzene ring.

### Step 2: Identifying the Differentiation Method
To differentiate between aliphatic and aromatic aldehydes, we can use specific reagents that react differently with these two types of compounds. One of the most effective reagents for this purpose is Fehling's solution.

### Step 3: Reaction with Fehling's Solution
Fehling's solution contains copper(II) ions (Cu²⁺) which can be reduced to copper(I) oxide (Cu₂O) in the presence of reducing sugars or aldehydes. When an aliphatic aldehyde is added to Fehling's solution, it reacts and forms a red precipitate of Cu₂O, indicating a positive test.

### Step 4: Lack of Reaction with Aromatic Aldehydes
In contrast, aromatic aldehydes do not react with Fehling's solution because they lack the necessary alpha hydrogen for enolate formation. Therefore, they do not produce the red precipitate.

### Step 5: Conclusion
Thus, the presence of a red precipitate when using Fehling's solution indicates the presence of an aliphatic aldehyde, while the absence of this reaction suggests an aromatic aldehyde. Therefore, we can conclude that aliphatic and aromatic aldehydes can be differentiated by the use of Fehling's solution.

### Final Answer
The correct answer is: **Fehling's solution.**

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