Which of the following gives an optically inactive aldaric acid on oxidation with dilute nitric acid ?

Options

A.
B.
C.
D.

Answer

To solve the problem of identifying which aldaric acid becomes optically inactive upon oxidation with dilute nitric acid, we will analyze each of the given options step by step.

### Step 1: Understanding Aldaric Acids
Aldaric acids are a type of sugar acid that contain both an aldehyde group (CHO) and a hydroxyl group (OH) on adjacent carbon atoms. When oxidized, the aldehyde group is converted to a carboxylic acid (COOH), and the hydroxymethyl group (CH2OH) is also oxidized to a carboxylic acid.

### Step 2: Oxidation with Dilute Nitric Acid
When an aldose sugar is treated with dilute nitric acid, the following transformations occur:
- The aldehyde group (CHO) at the first carbon oxidizes to a carboxylic acid (COOH).
- The hydroxymethyl group (CH2OH) at the last carbon also oxidizes to a carboxylic acid (COOH).

This results in the formation of a dicarboxylic acid, specifically an aldaric acid.

### Step 3: Checking for Optical Activity
A compound is optically inactive if it possesses a plane of symmetry. To determine if the resulting aldaric acid is optically inactive, we need to analyze the structure of each product after oxidation and check for symmetry.

### Step 4: Analyzing Each Option
1. **Option 1**:
- After oxidation, the structure does not have a plane of symmetry. Therefore, it is optically active.

2. **Option 2**:
- Similar to Option 1, this structure also lacks a plane of symmetry, making it optically active.

3. **Option 3**:
- Upon oxidation, this structure has a plane of symmetry. The arrangement of groups allows for mirror images, indicating that it is optically inactive.

4. **Option 4**:
- This structure also does not have a plane of symmetry, thus it is optically active.

### Conclusion
After analyzing all options, we find that **Option 3** produces an optically inactive aldaric acid upon oxidation with dilute nitric acid due to the presence of a plane of symmetry.

### Final Answer
The correct option is **Option 3**.

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