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NEET CHEMISTRYMedium

The correct corresponding order of names of four aldoses with configuration given below respectively, is:

A

L-erythrose, L-threose, L-erythrose, D-threose

B

D-threose, D-erythrose, L-threose, L-erythrose

C

L-erythrose, L-threose, D-erythrose, D-threose

D

D-erythrose, D-threose, L-erythrose, L-threose

Step-by-Step Solution

Aldotetroses contain two chiral carbon atoms. In the Fischer projection, if the hydroxyl (-OH) groups on the two chiral centers are on the same side, it is named erythrose. If they are on opposite sides, it is named threose. The D and L configuration is determined by the position of the -OH group on the highest-numbered chiral center (C3 in aldotetroses). If this -OH group is on the right side, it is a D-sugar; if it is on the left, it is an L-sugar.

  • D-erythrose: Both -OH groups are on the right side.
  • D-threose: The -OH group on C2 is on the left, and the -OH group on C3 is on the right.
  • L-erythrose: Both -OH groups are on the left side.
  • L-threose: The -OH group on C2 is on the right, and the -OH group on C3 is on the left.
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