How to Draw the Ring-Flip of a Chair?

In summary, this is what you need to do:

Now, let’s go into more detail. The first thing you need to know before drawing the ring flip of a chair cyclohexane is the correct conformation of the carbon chain and the orientation of each axial and equatorial group:

There are different ways of drawing a chair conformation and you are free to choose the one you like – as long as at the end you have the structures correct.

One approach to master this is printing out a nicely drawn chair conformation and sketching it on a different sheet of paper placed on it:

Notice that the carbon chains of these two chairs look like mirror images:

The ring flip represents two conformations of the same compound that are obtained through rotation around single bonds. This means no bonds are broken and all the atoms stay where they are:

Here is also a short video clip for better visualization of the chair forms with the bond angles and perspectives. 

It is important to mention that the video does not represent a ring flip which occurs via rotation about single bonds and just simply looking at the molecule from a different angle. The two forms of chair conformations in the video are for cyclohexane with no other groups or atoms than hydrogen, and it is a general representation of the axial and equatorial positions. As we will see below, with substituted cyclohexanes, it is crucial to follow the relative position and orientation of the groups. 

Draw the Ring-Flip Step-by-Step

Assuming you have practiced drawing chairs, this is what you need to do to draw the ring flip of any substituted cyclohexane:

Step 1

Number the atoms in the ring (the starting point and the direction doesn’t matter). In this case, we will go clockwise:

Step 2

Label wedge groups as pointing Up and dash lines as pointing Down. “Up” and “Down” is relative as it depends on the direction you are looking from but let’s follow this notation.

Step 3

Draw a chair conformation. You can draw any of the two – doesn’t matter:

Step 4

Number the atoms starting wherever you want but, this is Important – you must follow the direction you had in Step 1:

Step 5

Add the groups based on the numbers pointing Up or Down as you labeled them in step 2:

It is a common mistake to number the atoms inconsistently. This, unfortunately, happens in some YouTube videos as well (as I was referred to by one of my students) and students learn the wrong way.

If you go in opposite directions numbering the atoms in the ring, for example, initially going clockwise and now-counterclockwise, you will draw the enantiomer of the cyclohexane (enantiomers are stereoisomers, so they are different compounds).

Let’s do it here and see: If we number the ring starting from the OH and going counterclockwise (CCW), this is what we get:

This is a different molecule than what we are working with:

You can see they are non-superimposable mirror images, meaning no matter how you move them, you can’t make them identical.

You can jump ahead and read about enantiomers. If you haven’t covered that in your class yet, the take-home message is that the direction for numbering atoms must be consistent.

Again, in the beginning, you can choose any direction (clockwise or counterclockwise) but once there, you must follow it.

Step 6

Draw the other conformation of the chair (Ring-Flip):

There is NO such thing as a wedge is always axial or a dash is always equatorial!

You only need to follow these rules:

• The atoms should stay where they are – left carbon on the left and right carbon on the right.
• All the groups pointing up should still be pointing up regardless of being axial or equatorial.
• Each Equatorial group becomes Axial and each Axial group becomes Equatorial.

That is about it for drawing the ring-flip of chair conformations.

And of course, only practice makes it possible: