Structure of D Aldotetrose Forming Optically Inactive Dicarboxylic Acid

To determine the correct structure of the D-aldotetrose, we analyze the configuration and the optical activity of the oxidation product step-by-step:

1. D-Configuration Criterion

In a Fischer projection, an aldotetrose is classified as a D-sugar if the hydroxyl group ($-\text{OH}$) on the highest-numbered chiral carbon ($\text{C-3}$) is directed to the right.

• Option A: $\text{C-3}$ has $-\text{OH}$ on the left $\rightarrow$ L-erythrose
• Option B: $\text{C-3}$ has $-\text{OH}$ on the left $\rightarrow$ L-threose
• Option C: $\text{C-3}$ has $-\text{OH}$ on the right $\rightarrow$ D-erythrose
• Option D: $\text{C-3}$ has $-\text{OH}$ on the right $\rightarrow$ D-threose

Thus, only options C and D represent D-aldotetroses.

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2. Oxidation Reaction with Concentrated $\text{HNO}_3$

Concentrated nitric acid ($\text{HNO}_3$) is a strong oxidizing agent. It oxidizes both the terminal aldehyde group ($-\text{CHO}$) at $\text{C-1}$ and the primary alcohol group ($-\text{CH}_2\text{OH}$) at $\text{C-4}$ into carboxylic acid ($-\text{COOH}$) groups, forming an aldaric acid (tartaric acid derivative).

$\text{CHO-CH(OH)-CH(OH)-CH}_2\text{OH} \xrightarrow{\text{conc. HNO}_3} \text{COOH-CH(OH)-CH(OH)-COOH}$

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3. Optical Activity of the Oxidation Products

• Oxidation of Option C (D-erythrose):

  $$\begin{array}{c} \text{COOH} \\ | \\ \text{H}-\text{C}-\text{OH} \\ | \\ \text{H}-\text{C}-\text{OH} \\ | \\ \text{COOH} \end{array}$$

  The resulting dicarboxylic acid is meso-tartaric acid. This molecule possesses a horizontal plane of symmetry passing between $\text{C-2}$ and $\text{C-3}$. Due to this internal symmetry, it is achiral and optically inactive.

• Oxidation of Option D (D-threose):

  $$\begin{array}{c} \text{COOH} \\ | \\ \text{HO}-\text{C}-\text{H} \\ | \\ \text{H}-\text{C}-\text{OH} \\ | \\ \text{COOH} \end{array}$$

  The resulting dicarboxylic acid lacks a plane of symmetry or center of inversion, making it chiral and optically active.

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Conclusion

The D-aldotetrose that gives an optically inactive dicarboxylic acid upon oxidation with concentrated $\text{HNO}_3$ is D-erythrose, shown in Option C.

Correct Answer: C