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Question #44640
The Question
Consider the reaction of 1-bromoheptane-2,6-dione with 1.0 equivalent of tert-butylmagnesium chloride (-BuMgCl) in anhydrous THF at , followed by warming to . What is the major organic product formed?
Options
- A.
6-methyl-7-oxabicyclo[4.1.0]heptan-2-one
- B.
1-oxaspiro[2.5]octan-5-one
- C.
1-bromo-6-tert-butyl-6-hydroxyheptan-2-one
- D.
1-methyl-7-oxabicyclo[4.1.0]heptan-2-one
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
Grignard Reagent Sensitivity|Aldol Condensation Directionality|Enolate Regioselectivity
Why This Question Is Tricky
Common Mistakes
This question tests the Hard-Soft Acid-Base (HSAB) principle and kinetic vs thermodynamic acidity in the context of Grignard reagents.
The 'Hidden Variable' is that bulky Grignards like t-BuMgCl act as bases, not nucleophiles, when reacting with enolizable ketones.
Students often fall into the trap of predicting nucleophilic addition (Option C).
Furthermore, the student must identify the most acidic proton (C1 over C7) to avoid the spiro-epoxide trap (Option B).
The resulting cascade is an elegant intramolecular Darzens condensation, testing stereochemical and regiochemical numbering of bicyclic systems.
Quick Facts About This Question
Question Information
| Subject | Chemistry |
| Chapter | Haloalkanes and Haloarenes - Class 12 |
| Concept | Grignard Reagent Sensitivity |
| Difficulty | 8 |
| Cognitive Load | 7 |
| Target Solve Time | 160 sec |
| Access | Free |