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Question #44802
The Question
The acid-catalyzed hydrolysis of sucrose to D-glucose and D-fructose at 298 K is monitored by polarimetry. The apparent pseudo-first-order rate constant is calculated as . In a very dilute acid, the mutarotation rate of the products is comparable to the hydrolysis rate, causing to deviate from the true hydrolysis rate constant during the early stages of the reaction. Given the specific rotations : Sucrose = , -D-Glucopyranose = , -D-Glucopyranose = , equilibrium D-Glucose = . Assuming the hydrolysis proceeds via the most stable oxocarbenium ion intermediate, identify the specific rotation of the D-glucose anomer initially released, and the relationship between and at early times ().
Options
- A.
- B.
- C.
- D.
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Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Exception_Exposure
Learn to identify edge cases and boundary exceptions that JEE examiners hide in math problems.
Concepts Behind This Question
Pseudo-First Order Kinetics|D-Glucose Anomeric Equilibrium|Reducing Sugar Criteria
Why This Question Is Tricky
Common Mistakes
Tests the intersection of carbohydrate reaction mechanisms (oxocarbenium ion stability determining the cleavage site) and chemical kinetics (the assumption of instantaneous mutarotation in polarimetric rate determination).
Students often rote-learn the inversion of cane sugar without realizing that the transient intermediates (-D-glucose) have different optical properties, causing a kinetic trap if mutarotation is not infinitely fast.
Quick Facts About This Question
Question Information
| Subject | Chemistry |
| Chapter | Chemical Kinetics - Class 12 |
| Concept | Pseudo-First Order Kinetics |
| Difficulty | 8 |
| Cognitive Load | 7 |
| Target Solve Time | 160 sec |
| Access | Free |