To determine the correct Fischer projection representation for L-(-)-glucose, we analyze the stereochemical relationship between D-(+)-glucose and L-(-)-glucose.
1. Relationship Between D- and L-Enantiomers
L-(-)-glucose is the enantiomer (non-superimposable mirror image) of D-(+)-glucose.
In a Fischer projection, the structure of an enantiomer is obtained by taking the mirror image across a vertical mirror plane. This corresponds to reversing (inverting) the positions of the groups attached to every chiral center (C2,C3,C4, and C5).
2. Analysis of Chiral Centers in D-(+)-glucose
The structure of D-(+)-glucose is given as:
CHO∣H−C2−OH∣HO−C3−H∣H−C4−OH∣H−C5−OH∣CH2OH
The positions of the −H and −OH groups at each chiral center from top to bottom are:
- C2: −H on the left, −OH on the right.
- C3: −OH on the left, −H on the right.
- C4: −H on the left, −OH on the right.
- C5: −H on the left, −OH on the right.
3. Deriving the Structure of L-(-)-glucose
Inverting the configuration at all four chiral centers (C2,C3,C4, and C5) gives:
- C2: −OH on the left, −H on the right.
- C3: −H on the left, −OH on the right.
- C4: −OH on the left, −H on the right.
- C5: −OH on the left, −H on the right.
Thus, the Fischer projection of L-(-)-glucose is:
CHO∣HO−C2−H∣H−C3−OH∣HO−C4−H∣HO−C5−H∣CH2OH
This structure corresponds to option (A).
Correct Answer: A
