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Question #44463
The Question
An organic compound \textbf{X} (\ce{C7H15Br}), specifically 2-bromo-3,4-dimethylpentane, is treated with potassium \textit{tert}-butoxide (\ce{t-BuOK}) in \textit{tert}-butanol (\ce{t-BuOH}) at 350 K to yield a major hydrocarbon product \textbf{Y}. Compound \textbf{Y} is then subjected to hydroboration-oxidation using \ce{B2H6} in THF followed by alkaline \ce{H2O2}, producing compound \textbf{Z}. Finally, \textbf{Z} is treated with Jones reagent (\ce{CrO3} / \ce{H2SO4} / \ce{H2O}) to give the final major product \textbf{W}. Identify the correct IUPAC name of \textbf{W}.
Options
- A.
3,4-dimethylpentanoic acid
- B.
3,4-dimethylpentan-2-one
- C.
3,4-dimethylpentanal
- D.
2,3-dimethylpentan-3-ol
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
Alkene Addition Regioselectivity|Reaction Intermediates Stability|Enolate Regioselectivity
Why This Question Is Tricky
Common Mistakes
The question tests the student's ability to recognize when kinetic control overrides thermodynamic control due to steric hindrance.
The 'hidden variable' is the bulkiness of the tert-butoxide base, which forces the formation of the less stable Hofmann alkene (kinetic product) over the more stable Zaitsev alkene (thermodynamic textbook rule).
Students who blindly apply Zaitsev's rule will follow a completely different reaction pathway, leading to a secondary alcohol and ultimately a ketone, perfectly matching a distractor.
Furthermore, it tests chemoselectivity by ensuring students know Jones reagent oxidizes primary alcohols all the way to carboxylic acids, not stopping at aldehydes.
Quick Facts About This Question
Question Information
| Subject | Chemistry |
| Chapter | Hydrocarbons - Class 11 Part 2 |
| Concept | Alkene Addition Regioselectivity |
| Difficulty | 8 |
| Cognitive Load | 7 |
| Target Solve Time | 160 sec |
| Access | Free |