Enumerate the reactions of D-glucose which cannot be explained by its open chain structure.
(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.
The reaction between A and B is first order with respect to A and zero order with respect to B. Fill in the blanks in the following table:
| Experiment |
A/ mol L - 1 |
B/ mol L - 1 |
Initial rate/mol L - 1 min - 1 |
| I | 0.1 | 0.1 |
2.0 × 10 - 2 |
| II | -- | 0.2 |
4.0 × 10 - 2 |
| III | 0.4 | 0.4 | -- |
| IV | -- | 0.2 |
2.0 × 10 - 2 |
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(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 d...
Step-by-step explanation:
•
•
• (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
•
Students often lose marks by skipping steps, writing incomplete explanations, or misunderstanding keywords used in the question.
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