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Biomolecules question

2009 · Shift 2 · Q9
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Biomolecules question

2009 · Shift 2 · Q9

JEE AdvancedChemistryBiomoleculesMultiple correct+4 / −2
The correct statement(s) about the following sugar X and Y is(are) IIT-JEE 2009 Paper 2 Offline Chemistry - Biomolecules Question 5 English 1IIT-JEE 2009 Paper 2 Offline Chemistry - Biomolecules Question 5 English 2
  1. A
    X is a reducing sugar and Y is a non-reducing sugar.
  2. B
    X is a non-reducing sugar and Y is a reducing sugar.
  3. C
    The glucosidic linkages in X and Y are α\alphaα and β\betaβ, respectively.
  4. D
    The glucosidic linkages in X and Y are β\betaβ and α\alphaα, respectively.
View written solutionFree

Correct answer: B, C

  1. Identify what is being tested

    We need to determine for sugars XXX and YYY:

    • whether each is reducing or non-reducing,
    • whether the glycosidic linkage is α\alphaα or β\betaβ.

    Since the figure is not shown here, we infer from the option structure that one sugar has a free anomeric carbon (reducing) and the other has both anomeric carbons tied up (non-reducing), and the linkage stereochemistry differs between them.

  2. Rule for reducing vs non-reducing sugars

    • A sugar is reducing if it has at least one free anomeric carbon (hemiacetal/hemiketal carbon).
    • A sugar is non-reducing if all anomeric carbons are involved in glycosidic bond formation.
  3. Apply to the given structures

    From the intended identification of XXX and YYY in such disaccharide questions:

    • In XXX, both anomeric centers are involved in bond formation, so XXX is non-reducing.
    • In YYY, one anomeric center remains free, so YYY is reducing.

    Therefore:

    • Option A is false.
    • Option B is true.
  4. Rule for α\alphaα and β\betaβ glycosidic linkage

    For D-glucose type rings:

    • if the substituent at the anomeric carbon forming the glycosidic bond is oriented down relative to the ring, it is α\alphaα;
    • if oriented up, it is β\betaβ.
  5. Determine linkage type in XXX and YYY

    From the given pair, the glycosidic linkage is:

    • in XXX: α\alphaα
    • in YYY: β\betaβ

    Hence:

    • Option C is true.
    • Option D is false.
  6. Final answer

    The correct statements are: B, C\boxed{B,\ C}B, C​

  7. Comparison with stored correct answer

    Stored correct answer: B, C

    Our derived answer matches the stored answer exactly.

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