Question

D-Glucose and D-mannose are C-2 epimers.
A. True
B. False

Answer 1

Hint:Epimers are the compounds which are optical isomers of each other as they differ from each other by configuration of the group or atom of a single carbon atom. D-galactose and D-mannose are epimer of D-glucose.

Complete step by step answer:
In stereochemistry epimer denotes that at a stereogenic centre, the two isomers of the molecule differ from each other and the rest of the structure remains the same. Epimer defines one of the pairs of stereoisomers.
Stereoisomers are those molecules which have the same molecular formula but they differ in their three-dimensional orientation of the atoms or molecules.
The structure of D-Glucose, D-mannose and D-galactose is shown below.

As we can see in the structure, D-mannose and D-glucose, the two sugars differ from each other by the configuration of atoms in the second carbon. Therefore, they are called C-2 epimers.
From the structure of D-glucose and D-galactose, we can see that the two sugars differ from each other by the configuration of atoms at the forth position. Therefore, they are called C-2 epimers.
Therefore, it is a TRUE statement that D-Glucose and D-mannose are C-2 epimers.

Note:
Epimers are the stereoisomers which contain multiple stereogenic centres. The stereogenic centres are the carbon atoms which are joined to four different atoms or molecules. In the epimer, out of all the stereogenic centres only one stereogenic centre differs in the configuration.