Question

The configuration of the C-2 epimer of D-glucose is:
A.2R, 3S, 4R, 5S
B.2S, 3S, 4R, 5R
C.2S, 3R, 4S, 5R
D.2R, 3S, 4R, 5R

Answer 1

Hint: Epimers are the diastereomers which contain more than one chiral carbon but differ in their configuration from each other in the configuration at only one chiral carbon of their structures.
C-2 epimer means the structure or configuration of the epimers are different at carbon-2 position.

Complete answer:
To know the C-2 epimer of D-glucose we should know the structure of D-glucose.
The structure of D-glucose is

The C-2 epimer of D-glucose is

We know the configuration of all chiral carbons in D-glucose.

The configuration of all chiral carbons in D-glucose is 2R, 3S, 4R, 5R.
But coming to the C-2 epimer of D-glucose the configuration at Carbon-2 is going to change because the arrangement is different at carbon-2 of D-glucose and C-2 epimer of D-glucose.

In glucose at chiral carbon-2 the configuration is R, so in C-2 the epimer of D-glucose the configuration will be S.
Therefore the configuration of C-2 epimer of D-glucose is 2S, 3S, 4R, 5R.

So, the correct option is B.

Note: Epimers are not mirror images and non-super imposable to each other. So, epimers are also called as diastereomers.
The configuration at chiral carbon is going to identify by giving the numbers according to the groups attached to the chiral carbon.
After giving the numbers to all the groups we can say whether it is a R or S configuration.