When cyclohexane is in the chair conformation, explain the difference between axial position and equatorial position. Hand-drawn the chair conformation and place the hydrogens (using different color) to axial and equatorial. 1 6. Draw a chair conformation of 1,4-dimethylcyclohexane in which on methyl group is equatorial and the other is axial. Draw a ring flip. From the drawing, determine whether it is a trans or cis. (Be sure to number all carbons for clarification)
The Correct Answer and Explanation is:
In cyclohexane’s chair conformation, there are two types of positions for substituents: axial and equatorial.
- Axial position: These hydrogens or substituents point straight up or down along the axis of the ring, alternating between the two directions as you move around the ring. Axial positions are less stable because they cause steric hindrance (called 1,3-diaxial interactions) with other substituents in the axial positions on non-adjacent carbons.
- Equatorial position: These hydrogens or substituents point outward, roughly parallel to the plane of the ring. This position is more stable because there is less steric hindrance and less crowding between substituents.
For 1,4-dimethylcyclohexane:
Consider a chair conformation of cyclohexane where two methyl groups are attached at the 1 and 4 positions. If one methyl group is in the equatorial position and the other in the axial position, the molecule is considered trans (because the two substituents are on opposite sides of the ring).
Chair Flip:
When the chair conformation flips, the axial and equatorial positions switch. In this flipped conformation:
- The methyl group that was equatorial becomes axial.
- The methyl group that was axial becomes equatorial.
So, after a ring flip, the molecule will still be trans, because the two methyl groups will remain on opposite sides of the ring.
Cis vs. Trans:
- Cis: The two substituents are on the same side of the ring.
- Trans: The two substituents are on opposite sides of the ring.
Given that the positions switch upon the chair flip, we see that the methyl groups are always positioned on opposite sides, hence the molecule is trans.
Drawing:
For this, I’d need to generate an image for you. Do you want me to create the chair conformation of 1,4-dimethylcyclohexane with the positions labeled and colored differently for axial and equatorial?
