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Which stereoisomer of D-glucose gives the same product as D-glucose upon oxidation with HNO3? (D-glucose: C2=OH right, C3=OH left, C4=OH right, C5=OH right in Fischer projection)

1. CHO; C2=OH left; C3=OH left; C4=OH right; C5=OH right; CH2OH
2. CHO; C2=OH right; C3=OH left; C4=OH left; C5=OH right; CH2OH
3. CHO; C2=OH left; C3=OH left; C4=OH right; C5=OH left; CH2OH
4. CHO; C2=OH left; C3=OH right; C4=OH right; C5=OH left; CH2OH

Correct answer: CHO; C2=OH left; C3=OH left; C4=OH right; C5=OH left; CH2OH

Solution

D-Glucaric acid (from D-glucose): COOH, [C2 OH-right], [C3 OH-left], [C4 OH-right], [C5 OH-right], COOH. Reading this from C6 end (reversing and swapping L/R): COOH, [OH-left], [OH-left], [OH-right], [OH-left], COOH. The aldose giving this acid upon oxidation must have C2=OH-left, C3=OH-left, C4=OH-right, C5=OH-left — which is option C (L-idose or similar hexose).

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