Which of the following compounds would give positive Fehling's solution test ?

Options

A. `C_(6)H_(5)-overset(O)overset(||)C-CH_(3)`
B.
C.
D.

Answer

To determine which of the given compounds would give a positive Fehling's solution test, we need to understand the nature of the compounds that react positively with Fehling's solution. Here's a step-by-step solution:

### Step 1: Understand Fehling's Solution
Fehling's solution consists of two components:
- **Fehling's A**: Copper(II) sulfate (CuSO4)
- **Fehling's B**: Sodium potassium tartrate (Rochelle salt)

This solution is used to test for the presence of aldehydes and certain other reducing sugars.

### Step 2: Identify the Reaction
When an aldehyde is present, it reduces the copper(II) ions (Cu²⁺) in Fehling's solution to copper(I) oxide (Cu₂O), which precipitates as a red solid. Therefore, compounds that can be oxidized to carboxylic acids (like aldehydes) will give a positive test.

### Step 3: Analyze the Given Compounds
We need to evaluate each compound to see if it can give a positive Fehling's test:

1. **Aldehydes**:
- Aldehydes generally give a positive Fehling's test because they can be oxidized to carboxylic acids.
- **Conclusion**: Positive test.

2. **Aromatic Aldehydes (e.g., Benzaldehyde)**:
- Aromatic aldehydes do not react with Fehling's solution as they are less reactive compared to aliphatic aldehydes.
- **Conclusion**: Negative test.

3. **Ketones**:
- Ketones do not react with Fehling's solution and do not give a positive test.
- **Conclusion**: Negative test.

4. **Carboxylic Acids**:
- Only formic acid (HCOOH) can give a positive test as it can be oxidized to carbon dioxide and water.
- **Conclusion**: Positive test.

5. **Hemiacetals**:
- Hemiacetals can be converted to aldehydes under certain conditions, thus they can give a positive test.
- **Conclusion**: Positive test.

### Step 4: Final Evaluation
From the analysis:
- **Aldehydes**: Positive
- **Aromatic Aldehydes**: Negative
- **Ketones**: Negative
- **Formic Acid**: Positive
- **Hemiacetals**: Positive

### Step 5: Identify the Correct Answer
Based on the evaluation, the compounds that give a positive Fehling's solution test are:
- Aliphatic aldehydes
- Formic acid
- Hemiacetals

Thus, the correct answer from the options provided would be the compound that is either an aliphatic aldehyde, formic acid, or a hemiacetal.