Identify the most stable chair conformation of the most stable isomer of 1,4-diethylcyclohexane: IV B 0) IV 0 V
The Correct Answer and Explanation is:
The most stable chair conformation of 1,4-diethylcyclohexane corresponds to the isomer where the bulky ethyl groups are positioned in the equatorial positions, as this minimizes steric strain. Let’s break this down step-by-step.
Key Points:
- Chair Conformation of Cyclohexane: Cyclohexane can adopt two chair conformations that are interconvertible by a ring-flipping process. In each chair form, substituents on the cyclohexane ring can either be in axial or equatorial positions.
- Axial Position: Perpendicular to the ring’s plane.
- Equatorial Position: In the plane of the ring, more “sprawling.”
- Steric Strain: The axial positions introduce 1,3-diaxial interactions, which are unfavorable because bulky substituents in axial positions cause steric repulsion. The equatorial positions, on the other hand, minimize these interactions and are thus preferred for larger groups.
- Ethyl Substituents: For 1,4-diethylcyclohexane, the ethyl groups are the substituents, and they are relatively large. Placing these groups in axial positions would result in significant steric hindrance, increasing strain. Therefore, the most stable conformation places the ethyl groups in the equatorial positions.
- Flipping of the Cyclohexane Ring: When flipping the ring from one chair conformation to another, the positions of axial and equatorial substituents swap. The most stable conformation will have both ethyl groups in the equatorial positions, which minimizes steric interactions.
Conclusion:
Thus, the most stable isomer of 1,4-diethylcyclohexane will have both ethyl groups in equatorial positions. The corresponding chair conformation will be the one where both groups are in these positions, minimizing steric strain and making it the most stable conformation.
In terms of the specific isomer (IV or V), it depends on the structural context provided (e.g., drawing of the isomers). However, the key to determining the most stable chair conformation remains placing the ethyl groups in the equatorial positions for maximum stability.
