Three carbohydrates P, Q, and R are subjected to reaction with excess phenylhydrazine. P is D-glucose. Q is an aldohexose that is an epimer of P. R is a ketohexose that is a functional isomer of P. If P, Q, and R all yield the exact same osazone derivative, identify carbohydrates Q and R.

Step-by-step solution

The formation of an osazone by the reaction of a monosaccharide with excess phenylhydrazine involves only the first two carbon atoms (C-1 and C-2). During this reaction, the stereocenter at C-2 is destroyed as it is converted into a hydrazone group ( C=N-NHPh ). Because the rest of the carbon chain (C-3 to C-6) remains unchanged, any two aldoses that differ only in their configuration at C-2 (i.e., C-2 epimers) will yield the exact same osazone. Since Q is an aldohexose epimer of P (D-glucose) and forms the same os