Page 39 Flashcards
What is the key requirement for an E2 reaction in terms of geometry?
A: The β-hydrogen and leaving group must be anti periplanar.
Why is anti periplanar geometry important for E2 reactions?
A: It aligns the bonds in a single plane for efficient overlap during the elimination process.
How does anti periplanar geometry affect cyclohexane reactions?
A: It dictates that elimination occurs only when the β-hydrogen and leaving group are in axial position
What are the two chair conformations of chlorocyclohexane?
A: Conformation A (more stable, equatorial Cl) and Conformation B (less stable, axial Cl).
Which conformation of chlorocyclohexane is more stable and why?
A: Conformation A is more stable because the bulkier chlorine group is in the equatorial position, minimizing steric strain.
Can E2 elimination occur in Conformation A of chlorocyclohexane?
A: No, because the chlorine in Conformation A is equatorial and not anti periplanar to the β-hydrogen.
Which conformation of chlorocyclohexane is reactive in E2 elimination?
A: Conformation B, where chlorine is in the axial position and anti periplanar to the β-hydrogen.
What happens to the stability when the leaving group is in the axial position?
A: The molecule becomes less stable due to increased steric and 1,3-diaxial interactions.
Why does E2 elimination prefer anti periplanar over syn periplanar geometry?
A: Anti periplanar geometry minimizes electron repulsion and allows for efficient orbital overlap.
What is the effect of substituents on cyclohexane’s anti periplanar geometry?
A: Bulky substituents tend to prefer equatorial positions, which can limit the availability of anti periplanar β-hydrogens for elimination.
