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Question #44448
The Question
Consider the reaction of (E)-1-phenylhept-2-ene-1,6-dione with excess \ce{KCN} in aqueous ethanol at reflux temperature. The reaction yields a major organic product \textbf{P}. Identify the IUPAC name of \textbf{P}.
Options
- A.
2-benzoyl-3-methylcyclopent-2-ene-1-carbonitrile
- B.
4-acetyl-3-phenylcyclopent-2-ene-1-carbonitrile
- C.
2-(2-oxo-2-phenylethyl)-5-oxohexanenitrile
- D.
2-hydroxy-7-oxo-2-phenyloct-3-enenitrile
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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
Cyanohydrin Stereochemistry|Aldol Condensation Directionality|Alpha-Hydrogen Acidity
Why This Question Is Tricky
Common Mistakes
The problem tests the competition between kinetic 1,2-addition and thermodynamic 1,4-addition of cyanide to an enone, followed by an intramolecular Aldol condensation.
Students often fall into the trap of predicting the simple cyanohydrin (1,2-addition) or stopping at the Michael addition product.
The 'hidden mechanism' is the base-catalyzed intramolecular Aldol condensation of the resulting saturated diketone.
Furthermore, the regioselectivity of the Aldol condensation is tested: the enolate forms at the most acidic position (alpha to the phenyl ketone) and attacks the more electrophilic carbonyl (the aliphatic methyl ketone), leading to the thermodynamically most stable tetrasubstituted cyclopentene derivative.
Quick Facts About This Question
Question Information
| Subject | Chemistry |
| Chapter | Aldehydes, Ketones, and Carboxylic Acids - Class 12 |
| Concept | Cyanohydrin Stereochemistry |
| Difficulty | 8 |
| Cognitive Load | 7 |
| Target Solve Time | 160 sec |
| Access | Free |