`D`-Glucose and `D`-fructose both form the same osazone, Which statements are correct about the above reaciton?

Options

A. D-glucose, D-mannose and D-fructose all form the same osazone derivative because all of them have
(1) the same constitution and configuration at `C - 3`, `C - 4, C - 5` and `C - 6` but different constitution and configuration at `C - 1` and `C - 2` which become identical by osazone formation
B. the same configuration at `C - 5`
C. the same configuration at `C - 1` and `C - 2`
D. the same configuration at `C - 3` and `C - 4`

Answer

A

Explanation

Osazone formation results in a loss of the stereocenter at `C2` but does not affect other stereocentres. For example, `D-` glucose and `D-` mannose yield the same phenylosazone:

This experiment established that `D-` glucose and `D-` mannose have the same constitution and configuration about `C3, C4` and `C5`. Similarly `D-` fructose yields the same osazone because in the formation of osazone derivatives of aldohexoses and ketohexoses, the carbon atoms the participate in the reaction are `C -1` and `C - 2`
Diastereomeric aldoses that differ in configuration at only one carbon (such as `D-` glucose and `D-` mannose) are called epimers. In general, any pair of disastereomers that differ in configuration at only a single stereocenter can be called epimers.