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Question #44454
The Question
An acid-catalyzed thermodynamic equilibration is established between the \textit{cis} and \textit{trans} diastereomers of 2-methoxy-4-\textit{tert}-butyltetrahydropyran in anhydrous \ce{CCl4} at 298 K. Which of the following correctly identifies the major diastereomer present at equilibrium and the primary electronic interaction responsible for its stability?
Options
- A.
\textit{trans}-isomer; stabilization via hyperconjugation
- B.
\textit{cis}-isomer; minimization of 1,3-diaxial steric strain
- C.
\textit{trans}-isomer; stabilization via hyperconjugation
- D.
\textit{cis}-isomer; dipole-dipole stabilization between the oxygen atoms
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Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Exception_Exposure
Learn to identify edge cases and boundary exceptions that JEE examiners hide in math problems.
Concepts Behind This Question
Alkane Conformation Energy Barriers|Cycloalkane Ring Strain
Why This Question Is Tricky
Common Mistakes
Students typically assume that the cis-1,3-disubstituted (or equivalent) cyclohexane derivative is always more stable because both substituents can adopt equatorial positions, minimizing 1,3-diaxial strain.
The trap here is the Anomeric Effect in tetrahydropyran systems.
The hidden variable is the stereoelectronic requirement for hyperconjugation (), which provides sufficient stabilization energy to override the standard steric penalty of the axial conformation.
Consequently, the trans-isomer (with an axial methoxy group) becomes the thermodynamically favored product, defying basic steric rules.
Quick Facts About This Question
Question Information
| Subject | Chemistry |
| Chapter | Hydrocarbons - Class 11 Part 2 |
| Concept | Alkane Conformation Energy Barriers |
| Difficulty | 8 |
| Cognitive Load | 7 |
| Target Solve Time | 160 sec |
| Access | Free |