See image — Biomolecules Chemistry Question

💡 Solution & Explanation

Step 1 - Identify the structures: The two structures shown are cyclic forms of a sugar (appears to be fructose in furanose form) connected by an equilibrium arrow. They differ only at the anomeric carbon (C2 in fructose), where the -OH group is on opposite faces in the two structures. Step 2 - Determine the stereochemical relationship: The two structures differ at only ONE stereocenter (the anomeric carbon), while all other stereocenters remain identical. Two compounds that differ at one or more stereocenters but not all stereocenters are diastereomers, not enantiomers. Enantiomers would require inversion at ALL stereocenters. Since only the anomeric center differs, these are diastereomers (specifically, they are anomers - alpha and beta anomers). Step 3 - Identify the interconversion process: The interconversion of alpha and beta anomers of a sugar in solution is called mutarotation. This process involves opening of the ring (breaking the C-O bond at the anomeric position), rotation, and re-closing, which results in a change in optical rotation over time until equilibrium is reached. Step 4 - Evaluate why other options fail: - Options (a) and (b) are incorrect because the structures are NOT enantiomers; they are diastereomers (anomers). Enantiomers require mirror-image relationship at every stereocenter. - Option (d) is incorrect because the interconversion DOES require breaking and making bonds (the ring opens and closes at the anomeric carbon, breaking and forming a C-O bond). It is NOT merely a conformational change. - Option (c) correctly identifies them as diastereomers and names the interconversion as mutarotation. Therefore, the correct answer is C.