See image — Biomolecules Chemistry Question

💡 Solution & Explanation

Concept: Oxidation of monosaccharides with nitric acid (HNO3). Step 1: Identify the reagent. HNO3 (nitric acid) with heat (Delta) is a strong oxidizing agent. Step 2: Determine what HNO3 does to D-Glucose. When D-Glucose is treated with dilute HNO3 (a mild oxidizing agent like Br2/H2O), only the aldehyde group (-CHO) is oxidized to give D-Gluconic acid. However, concentrated HNO3 (a stronger oxidizing agent) oxidizes BOTH the aldehyde group at C1 AND the primary alcohol group at C6 to carboxylic acid groups (-COOH), yielding a dicarboxylic acid called a saccharic acid (aldaric acid). Step 3: D-Glucose oxidized at both ends by HNO3/heat gives D-Glucaric acid (also called D-saccharic acid), which is a dicarboxylic acid (aldaric acid) with -COOH groups at both C1 and C6. Step 4: Eliminate wrong options: - (a) D-Gluconic acid: This is the product of mild oxidation (only -CHO oxidized, e.g., by Br2/H2O), not HNO3. - (b) D-Glucitol: This is the reduction product (using NaBH4 or H2/Ni), not oxidation. - (c) D-Fructose: This is an isomer obtained by isomerization, not by HNO3 oxidation. - (d) D-Glucaric acid: Correct — both terminal groups oxidized by HNO3/Delta to give the aldaric acid. Therefore, the correct answer is D.