Question

$D-$Glucose and $D-$fructose both form the same osazone. Which statements are correct about the above reaction?

• A. Glucose and fructose are epimers
• B. Glucose and fructose are anomers
• C. The configurations of the $OH$ group at $C-3$ and $C-4$ in glucose and fructose are same
• D. The configurations of the $OH$ group at $C-4$ and $C-5$ in glucose and fructose are same.

Answer 1

Answer: (C), (D)

The correct options are
C The configurations of the $OH$ group at $C-4$ and $C-5$ in glucose and fructose are same.
D The configurations of the $OH$ group at $C-3$ and $C-4$ in glucose and fructose are same

The statements $C$ and $D$ are correct.
(A) Glucose and fructose are not epimers.
Epimers are diastereomers that contain more than one chiral center but differ from each other in the absolute configuration at only one chiral center.
(B) Glucose and fructose are not anomers.
an anomer is a special type of epimer. It is one of two stereoisomers of a cyclic saccharide that differs only in its configuration at the hemiacetal/acetal carbon, also called the anomeric carbon.
(C) The configurations of the $OH$ group at $C-3$ and $C-4$ in glucose and fructose are same. This can be seen from the figure.
(D) The configurations of the $OH$ group at $C-4$ and $C-5$ in glucose and fructose are same. This can be seen from the figure.