Class 12 Chemistry - Chapter Biomolecules NCERT Solutions | Enumerate the reactions of D-glucose whi

Welcome to the NCERT Solutions for Class 12th Chemistry - Chapter Biomolecules. This page offers a step-by-step solution to the specific question from Exercise 2, Question 10: enumerate the reactions of d glucose which cannot....
Question 10

Enumerate the reactions of D-glucose which cannot be explained by its open chain structure.

Answer

 

(1) Aldehydes give 2, 4-DNP test, Schiff's test, and react with NaHSO4 to form the hydrogen sulphite addition product. However, glucose does not undergo these reactions.

(2) The pentaacetate of glucose does not react with hydroxylamine. This indicates that a free -CHO group is absent from glucose.

(3) Glucose exists in two crystalline forms - ∝ and β. The ∝-form (m.p. = 419 K) crystallises from a concentrated solution of glucose at 303 K and the β-form (m.p = 423 K) crystallises from a hot and saturated aqueous solution at 371 K. This behaviour cannot be explained by the open chain structure of glucose.

 

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