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Question #45074
The Question
Consider the following two-step reaction sequence:
\ce{(2S)-2-bromopropanal ->[NaCN, HCN][0^\circ C] X (Major)}
\ce{X ->[K_2CO_3, DMF][25^\circ C] Y (Major)}
Identify the absolute configuration of the major product \textbf{Y}.
Options
- A.
\ce{(2R, 3S)-2-cyano-3-methyloxirane}
- B.
\ce{(2S, 3S)-2-cyano-3-methyloxirane}
- C.
\ce{(2R, 3R)-2-cyano-3-methyloxirane}
- D.
\ce{(2S, 3R)-2-cyano-3-methyloxirane}
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
Electrophile vs Nucleophile|Cyanohydrin Stereochemistry|Aldehydes, Ketones, and Carboxylic Acids
Why This Question Is Tricky
Common Mistakes
This problem tests the Polar Felkin-Anh model for nucleophilic addition to alpha-halo carbonyls, followed by a stereospecific intramolecular SN2 reaction.
Students often mistakenly apply the standard Felkin-Anh or Cram's rule without accounting for the strong dipole of the C-Br bond, or they fail to correctly rotate the resulting Newman projection to the antiperiplanar conformation required for epoxide formation, leading them to incorrectly predict the thermodynamically more stable trans-epoxide.
Quick Facts About This Question
Question Information
| Subject | Chemistry |
| Chapter | Organic Chemistry – Some Basic Principles and Techniques - Class 11 Part 2 |
| Concept | Electrophile vs Nucleophile |
| Difficulty | 8 |
| Cognitive Load | 7 |
| Target Solve Time | 160 sec |
| Access | Free |