Biomolecules and Chemistry in Everyday Life - Result Question 25
26. The Fischer presentation of $D$-glucose is given below.
The correct structure(s) of $\beta$-L-glucopyranose is (are)
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Answer:
Correct Answer: 26. (d)
Solution:
- (d) A pyranose ring is a $6$ membered ring having $5$ carbon atoms and one oxygen atom. In glucose, it is formed by the reaction between $>C=O$ group at position $1$ and $-OH$ group at 5 th carbon atom. In general reaction between $>C=O$ group
The product formed in called hemiacetal
(if $>C=O$ group belongs to an aldehyde) or hemiketal (if $>C=O$ group belongs to a ketone). $L$ - glucose has the mirror image configuration of D-glucose i.e.,
So, $\beta$ - $L$ glucopyranose is formed as
The $\alpha$-$L$-glucopyranose has configurational change at $C _1$ only and looks like
BETA
