See image — Aldehydes Ketones and Carboxylic Acids Chemistry Question

💡 Solution & Explanation

Concept: Epimers are monosaccharides that differ in configuration at only one specific chiral carbon. C2-epimers specifically differ only at carbon-2 (C2). Step 1: Recall the definition of C2-epimers. Two sugars are C2-epimers if they have identical configurations at all chiral centers except C2, where they have opposite configurations. Step 2: Analyze option (b) D-Glucose and D-Mannose. - D-Glucose has the configuration at C2 as R (OH on the right in Fischer projection). - D-Mannose has the configuration at C2 as S (OH on the left in Fischer projection). - At C3, C4, and C5, both D-Glucose and D-Mannose have identical configurations. - Therefore, D-Glucose and D-Mannose differ only at C2, making them C2-epimers. Step 3: Eliminate other options. - Option (a): D-Maltose is a disaccharide, not a monosaccharide, so it cannot be an epimer of D-Glucose in the classical sense. - Option (c): D-Allose is a hexose and D-Ribose is a pentose; they have different carbon chain lengths and cannot be epimers of each other. - Option (d): D-Glucose and D-Arabinose differ at C2 and C3 (and are also different chain lengths — hexose vs pentose), so they are not C2-epimers. Step 4: Confirm that D-Glucose and D-Mannose are the classic textbook example of C2-epimers among the aldohexoses, differing solely at the C2 hydroxyl group orientation. Therefore, the correct answer is B.