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JEE Main · 2023 · 11 Apr 2023 · Shift 1 · Biomolecules

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L-isomer of tetrose gives positive Schiff's test and has two chiral carbons. On acetylation. ' X ' yields triacetate. ' X ' also undergoes following reactions
'
' X ' is
  1. (A)(see structure)
  2. (B)(see structure)
    ✓ Correct
  3. (C)(see structure)
  4. (D)(see structure)

Answer: (B)

Solution

The formula with a positive Schiff's test indicates a free aldehyde group, and formation of a triacetate indicates three hydroxyl groups, so X is the open-chain aldotetrose with two chiral carbons. Reduction with converts the to , giving the corresponding tetritol; this product B is chiral only for threitol, since the erythritol from an erythrose would be a meso (optically inactive) compound. Therefore X is a threose, and with the hydroxyl on the lowest chiral carbon drawn to the left it is the L-threose, in which the two secondary hydroxyls lie on opposite sides of the Fischer projection.

JEE Main · 2023 · 11 Apr 2023 · Shift 1 · Single correct option

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