Question

D-Glucose (structure given below) and its stereoisomers undergo oxidation with conc. HNO$_3$ to give the corresponding dicarboxylic acidsThe number of stereoisomers of glucose that would give meso-dicarboxylic acid is

• A. 2
• B. 4
• C. 6
• D. 8

Hint:

Oxidation of aldoses with concHNO$_3$ gives aldaric acidsIf the two ends become identical and the configuration is internally symmetrical, the aldaric acid is meso

Answer 1

The Correct Option is B

Step 1: What nitric acid does.
Strong nitric acid oxidises both ends of an aldohexose to give a diacid with the same group at each end.

Step 2: Condition for a meso product.
Such a diacid is meso when its hydroxyl pattern has an internal mirror plane, so its optical activity cancels.

Step 3: Count.
An aldohexose has four stereocentres giving sixteen isomers, and four of them oxidise to internally symmetric, that is meso, diacids.

Step 4: Answer.
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