Question

Product of D-aldotetroses with conc. \(HNO_3\) gives optically inactive dicarboxylic acid. Which among the following will be D-Aldotetrose in the given structures? 

• A. Structure (1)
• B. Structure (2)
• C. Structure (3)
• D. Structure (4)

Answer 1

The Correct Option is A

To determine which structure is a D-aldo tetrose, we need to understand the characteristics of D-aldo tetroses and their reactions:

Characteristics of D-Aldotetroses:

• D-aldo tetroses are sugars having four carbon atoms with an aldehyde group at one end.
• They have the "D" configuration, which means that the hydroxyl group on the chiral carbon farthest from the aldehyde group is on the right side in a standard Fischer projection.

Reaction with Conc. \(HNO_3\):

• When treated with concentrated nitric acid (\(HNO_3\)), aldo tetroses are oxidized to form dicarboxylic acids.
• The oxidation of D-aldo tetroses should yield optically inactive (i.e., achiral) dicarboxylic acids.

Based on the given structures in the image, the one that fits these criteria is:

1. The structure must be a tetrose (4 carbons, starting with an aldehyde group).
2. The structure must have a D-configuration, with the hydroxyl group on the right at the farthest chiral center.
3. The D-aldotetrose should form an achiral dicarboxylic acid upon oxidation.

Analysis of Options:

• Structure (1): It has the D-configuration and the hydroxyl group on the right at the farthest chiral center. Upon oxidation, it will form an optically inactive dicarboxylic acid.
• Structure (2) and (3): These are L-configurations, not matching D-aldo tetrose criteria.
• Structure (4): Although it is a tetrose, it does not conform to the D-configuration.

Conclusion: The correct answer is Structure (1) as it is the D-aldo tetrose that forms an optically inactive dicarboxylic acid when treated with concentrated \(HNO_3\).