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Biomolecules appeared 36 times across 3 years — 4.2% of Chemistry. This question is from Reducing And Non Reducing Sugars.

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Structures of four disaccharides are given below. Among the given disaccharides, the non-reducing sugar is :

Solution & Explanation

Core Logic

For a sugar to be non-reducing, it must NOT possess a free hemiacetal or hemiketal group. The linkage connecting the monosaccharide units must consume both anomeric carbons via an acetal/ketal linkage. Structure (1) represents Sucrose, which has an α, β -1,2-glycosidic bond. Both anomeric carbons are locked in the glycosidic linkage

Reducing And Non Reducing Sugars
Reducing And Non Reducing Sugars
and
Reducing And Non Reducing Sugars
Reducing And Non Reducing Sugars
. Structures (2), (3), and (4) are maltose or lactose-type structures containing a free anomeric -OH, thus acting as reducing sugars.

Step 1: Final Conclusion

Structure (1) is sucrose, which lacks a hemiacetal linkage, making it a non-reducing sugar.

Pattern Recognition

Whenever asked for a non-reducing sugar among standard disaccharides, look for Sucrose (linked at C1 of glucose and C2 of fructose). Both anomeric carbons are tied up.

Chapter Mix

Class 12 Chemistry: Biomolecules

Reference Study Guides

Biomolecules

More Biomolecules Previous-Year Questions — Page 8

Q78 jee_main_2024_31_jan_morning Reactions of Glucose
Match List I with List II
LIST-ILIST-II
A. Glucose/NaHCO₃/ΔI. Gluconic acid
B. Glucose/HNO₃II. No reaction
C. Glucose/HI/ΔIII. n-hexane
D. Glucose/Bromine waterIV. Saccharic acid
Choose the correct answer from the options given below:
  • A. A-IV, B-I, C-III, D-II
  • B. A-II, B-IV, C-III, D-I
  • C. A-III, B-II, C-I, D-IV
  • D. A-I, B-IV, C-III, D-II

Solution

Core Logic

Matching the reactions of glucose: (A) Glucose does not react with NaHCO₃, so there is no reaction. (A arrow II) (B) Oxidation of glucose with strong oxidizing agents like HNO₃ yields a dicarboxylic acid called saccharic acid. (B arrow IV) (C) Prolonged heating of glucose with HI forms n-hexane, indicating a straight chain of six carbon atoms. (C arrow III) (D) Oxidation with mild agents like bromine water converts glucose to gluconic acid. (D arrow I)

Chapter Mix

Class 12 Chemistry: Biomolecules

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JEE Physics: Waves (+15.5%) | Electrostatics: Concentric Shells (-29.7%) | Modern Physics: Photoelectric Clones (+34.2%) | Mathematics: Definite Integrals (+18.1%) | Chemistry: Coordination Splitting (-11.4%) | JEE Physics: Waves (+15.5%) | Electrostatics: Concentric Shells (-29.7%) | Modern Physics: Photoelectric Clones (+34.2%) | Mathematics: Definite Integrals (+18.1%) | Chemistry: Coordination Splitting (-11.4%)