Carbohydrates: classification, glucose structure, reactions

46 questions on Carbohydrates: classification, glucose structure, reactions from the Biomolecules chapter: 9 NEET level, 18 JEE Main, 19 JEE Advanced. Each one opens with its answer and solution.

• Glucose, C6H12O6, is classified as NEET level
• Oxidation of D-glucose with bromine water gives NEET level
• Prolonged heating of glucose with HI gives n-hexane. This shows that glucose has NEET level
• alpha-D-Glucopyranose and beta-D-glucopyranose differ in configuration at NEET level
• Glucose reacts with acetic anhydride to give a pentaacetate. This indicates that glucose contains NEET level
• The number of stereocentres in the open-chain form of D-fructose, HOCH2-CO-(CHOH)3-CH2OH, is JEE Main level
• Glucose reduces Tollens reagent but does not give the Schiff test or form an addition product with NaHSO3. The best explanation is that JEE Main level
• A freshly prepared solution of pure alpha-D-glucopyranose has specific rotation +112 degrees, which falls on standing to a constant +52.7 degrees. The best expl... JEE Main level
• D-Glucose, D-mannose and D-fructose all give the same osazone with excess phenylhydrazine because JEE Main level
• D-Fructose is a ketose, yet it reduces Tollens reagent. The reason is that JEE Main level
• Reduction of D-fructose with NaBH4 gives JEE Main level
• In the standard Haworth drawing of alpha-D-glucopyranose (the CH2OH group on C-5 is drawn upward, as for every D-sugar), the anomeric hydroxyl group at C-1 poin... JEE Main level
• D-Arabinose, an aldopentose, undergoes Kiliani-Fischer chain extension (HCN, hydrolysis, reduction). The aldohexoses obtained are JEE Main level
• Which of the following observations about glucose support the presence of a carbonyl (aldehyde) group in its open-chain form? JEE Main level
• Which of the following pairs are epimers? JEE Main level
• The open-chain aldohexose CHO-(CHOH)4-CH2OH has four stereocentres (C-2 to C-5), none of which is made equivalent by symmetry. How many stereoisomers (counting ... JEE Main level
• Consider aldohexoses in the pyranose ring form, where C-1 to C-5 are all stereocentres. The total number of stereoisomers (counting each anomer and each enantio... JEE Advanced level
• Assertion: D-Fructose gives a positive Tollens test. Reason: Fructose is a ketohexose, and ketones are oxidised by Tollens reagent. Choose the correct option. JEE Advanced level
• Counting every molecule of phenylhydrazine that reacts (including the one reduced to aniline and ammonia), the moles of phenylhydrazine consumed in converting 1... JEE Advanced level
• Which aldohexose gives an optically inactive (meso) aldaric acid on oxidation with hot dilute nitric acid? JEE Advanced level
• Pure alpha-D-glucopyranose has specific rotation +112.2 deg, the beta anomer +18.7 deg and the equilibrium mixture +52.7 deg. Ignoring the open-chain form, the ... JEE Advanced level
• D-Glucose, D-mannose and D-fructose are separately reduced with NaBH4. The total number of different alditols obtained from the three reactions is JEE Advanced level
• Which statement about methyl alpha-D-glucopyranoside is correct? JEE Advanced level
• Which reagent can be used to distinguish D-glucose from D-fructose? JEE Advanced level
• Which statements about alpha-D-glucopyranose are correct? JEE Advanced level
• Which sugars give the same osazone as D-glucose? JEE Advanced level
• Which observations about glucose are best explained by its cyclic hemiacetal structure? JEE Advanced level
• Which statements about D-fructose are correct? JEE Advanced level
• Which of the following is a ketohexose? NEET level
• D-glucose is warmed with bromine water. The main product is NEET level
• alpha-D-glucopyranose and beta-D-glucopyranose differ in configuration only at NEET level
• Glucose reacts with acetic anhydride to give a pentaacetate. This shows that glucose contains NEET level
• Which of the following pairs are epimers? Take epimers as sugars of the same constitution that differ in configuration at exactly one stereocentre. JEE Main level
• Assertion (A): D-glucose does not give Schiff's test although it is an aldohexose. Reason (R): In solution glucose exists mainly as cyclic hemiacetal forms and ... JEE Main level
• Match the reagent in List I with the product obtained from D-glucose in List II. List I: (P) HI with red P, heat; (Q) HCN; (R) bromine water; (S) conc. HNO3. Li... JEE Main level
• Which of the following pairs of sugars give the same osazone with excess phenylhydrazine? JEE Main level
• Sucrose (C12H22O11, molar mass 342 g mol^-1) has eight free hydroxyl groups. Assume all of them are acetylated by excess acetic anhydride and each -OH group con... JEE Main level
• Which of the following give a NEGATIVE Tollens' test (no silver mirror)? Take adenosine as the beta-N9-glycoside of D-ribofuranose with adenine. JEE Main level
• The specific rotations of alpha-D-glucopyranose and beta-D-glucopyranose are +112.2 deg and +18.7 deg. At mutarotation equilibrium the specific rotation is +52.... JEE Main level
• Which statements about D-fructose are correct? JEE Advanced level
• Methyl alpha-D-glucopyranoside is treated with excess periodic acid. Assume a ring-oxygen-bearing carbon is not cleaved, so the C-2, C-3, C-4 triol is cleaved a... JEE Advanced level
• Sucrose ([alpha]=+66.5 deg) is hydrolysed completely to a mixture of glucose and fructose. Take [alpha] of D-glucose as +52.7 deg and of D-fructose as -92.4 deg... JEE Advanced level
• Assertion (A): D-fructose gives a positive Fehling's test although it is a ketose. Reason (R): In alkaline medium fructose rearranges through an enediol to aldo... JEE Advanced level
• A branched polysaccharide, built only from glucose residues joined by alpha-1,4 linkages with some alpha-1,6 branch points, has molar mass 16218 g mol^-1. Take ... JEE Advanced level
• Count the stereocentres (chiral carbons) in each of: alpha-D-glucopyranose (ring form), open-chain D-fructose, and beta-D-fructofuranose (ring form, ring closur... JEE Advanced level
• Which statements are correct? JEE Advanced level