The easiest way to draw equatorial bonds on the chair conformation is to make them parallel to the cyclohexane ring line that is the second line moving clockwise or counter-clockwise around the ring plane from the carbon you’re drawing the equatorial bond on (see the highlighted lines below).
Can you flip the ring of a cyclohexane chair?
The equilibrium will tend to lie toward the more stable chair conformation. A common exam question tests the student’s ability to “flip” the ring of a cyclohexane chair conformation. The arrows in the figure below are meant to show how the structure physically moves to get from one conformation to the other.
What are chair conformations in cyclohexane?
Chair conformations are the most stable conformations cyclohexane can form. The basic structure is shown below. Each point represents carbon. To help visualize, it should be noted that carbon 1 is pointing up above the plane and carbon 4 is pointing down below the plane.
Is cyclohexane flat or curved?
Although the hydrocarbon cyclohexane is typically drawn as if it were flat, in reality the structure is not flat at all. Most of the time, the structure exists in what is called the chair conformation. This conformation is called the chair because it looks (sort of) like a reclining lounge chair, as shown here.
What are the axial substituents of the chair conformation?
This is your first axial substituent. The chair conformation has alternating axial up, axial down… so once you have that single axial substituent move on to.. Every carbon on the chair conformation has 1 substituent axial and the other equatorial. If axial is up equatorial is down, if equatorial is up then axial is down.
What are the two positions of substituents in cyclohexane?
Substituents in a Chair. There are two general positions that a substituent can be in for a chair conformation of cyclohexane: axial and equatorial. Axial substituents are labeled in red below. Equatorial substituents are in blue.
What is the purpose of the arrows in the cyclohexane chair?
The arrows in the figure below are meant to show how the structure physically moves to get from one conformation to the other. The arrows do not represent electrons moving. Note how the carbons move from one flipped structure to the other (following the red and blue circles). The carbons are also numbered to more easily depict the locations of the carbons before and after the flip.
Why are axial substituents more stable than equatorial substituents?
These 1,3-diaxial interactions cause axial substituents much higher energy than equatorial substituents. Because equatorial positions have less energy (due to the lack of 1,3-diaxial interactions), they are much more stable, so substituents prefer to be in the equatorial positions. Your textbook will have a table containing ...
How many substituents are there in a cyclohexane?
At each carbon on the cyclohexane, there is a one substituent that points up and one that points down, which is something we will utilize in this step. If the substituent is a wedge () on the 2-D cyclohexane, then place the substituent so it is going upward on the chair at the corresponding carbon (e.g.
Which way do axial substituents point?
One the other hand, all axial substituents point either straight up or straight down.
Can a chair be numbered?
We then draw a regular chair conformation and a chair conformation in its flipped formed. The first chair can be arbitrarily numbered, but it’s important the numbering stays with the same carbon during the course of the flip.
Can both conformation and chair conformation be used to draw the same molecule?
Both can be used to draw the exact same molecule, but they are simply different ways of representing it. For this majority of this section, we will focus on the chair conformation.
What are chair conformations?
Chair conformations are the most stable conformations cyclohexane can form . The basic structure is shown below. Each point represents carbon. To help visualize, it should be noted that carbon 1 is pointing up above the plane and carbon 4 is pointing down below the plane. Every other carbon lies in the same plane. Moreover, the conformation continuously jumps back and forth between its most stable forms. This swap is called the chair flip and it is explained further down this article!
What type of bonds are used in chair conformations?
Carbon-carbon bonds that are a part of the cyclohexane are drawn as part of the chair’s basic structure. Apart from these are two types of bonds we use in chair conformations: axial and equatorial. These bonds attach to hydrogens, functional groups, and other substituents. In the figure above, axial bonds are positioned perpendicular (straight) to the structure and are shown in red. Meanwhile, equatorial bonds stand slanted and are shown in blue. When drawing chair conformations, the type of bond alternates. If carbon one is axial, then carbon two is equatorial.
How to draw alternate chairs?
Draw 2 parallel lines slightly offset from each other. Top left or top right will give you alternate chairs.
What does a professor look for in a chair?
When it comes to exams, you won't be graded on how ‘pretty' your chair looks. Instead your professor will look for clarity and the ability to distinguish your axial and equatorial substituents.
What happens if a substituent is up on carbon?
If there's a substituent up on carbon #1, it says up on carbon #1. If it's down it stays down.
Can you copy chair conformation?
This is where the messiness and confusion arises. Most books will show a chair conformation slightly sideways, making it impossible to copy. Worse, it's really difficult to show which substituents are axial vs equatorial.
CORE Concepts
Covered in Other Articles
- Newman Projections
- Fischer Projections
- Naming Cycloalkanes
What Are Chair Conformations?
- Chair conformations are the most stable conformations cyclohexane can form. The basic structure is shown below. Each point represents carbon. To help visualize, it should be noted that carbon 1 is pointing up above the plane and carbon 4 is pointing down below the plane. Every other carbon lies in the same plane. Moreover, the conformation continuo...
Stability and Ring Flips
- Some chair conformations are more stable than the others and therefore preferred. A key factor for determining stability is to calculate the 1,3-diaxial strain. This is a type of steric interactionthat occurs when bulky attachments are located on axial bonds. To calculate the 1,3-diaxial strain, you must add the strain energies of substituents located on the axial bonds. You can find strain ener…
Further Reading