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Question #44964
The Question
A sample of D-arabinose () is dissolved in an aqueous buffer at and treated with of . The nucleophilic addition is allowed to reach completion. The resulting solution is immediately treated with an excess of Tollens' reagent () at . Assuming the cyanohydrin adducts do not undergo base-catalyzed reversion during the rapid Tollens' test, determine the mass of the silver precipitate formed and the stereochemical relationship of the newly formed cyanohydrin products. (Given: Atomic mass of )
Options
- A.
; Diastereomers
- B.
; Diastereomers
- C.
; Enantiomers
- D.
; Enantiomers
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Mechanism_Trap
Don't get tricked by the process! Learn the mechanical traps used in competitive exam questions.
Concepts Behind This Question
Reducing Sugar Criteria|Kiliani-Fischer Chain Extension|Nucleophilic Acyl Substitution
Why This Question Is Tricky
Common Mistakes
This problem tests the student's ability to recognize that nucleophilic addition at the anomeric carbon (forming a cyanohydrin in the first step of the Kiliani-Fischer synthesis) acts as a protecting group, destroying the hemiacetal/aldehyde equilibrium required for Tollens' oxidation.
The 'Hidden Variable' is the kinetic competition and stoichiometric limitation: students often blindly apply the Tollens' stoichiometry to the total initial mass of the sugar, failing to subtract the portion converted to the Tollens-negative cyanohydrin.
Additionally, it tests the stereochemical principle that nucleophilic attack on a chiral substrate yields diastereomers.
Quick Facts About This Question
Question Information
| Subject | Chemistry |
| Chapter | Biomolecules - Class 12 |
| Concept | Reducing Sugar Criteria |
| Difficulty | 8 |
| Cognitive Load | 7 |
| Target Solve Time | 160 sec |
| Access | Free |