Shown below is an interactive image of cyclohexane. You can rotate this picture by "dragging" your mouse on a blank portion
of the drawing window. "Clicking" on one atom gives the name for that atom. If you then click on a second atom, the distance
between these two atoms will be shown. Selecting the Axial and Equatorial buttons below the image allow highlighting of these
types of atoms.
Note that the emphasis of this activity is to look at interactions controlled by conformational changes.
When looking at "neighboring" atoms for any hydrogen, we recognize that the carbon atoms all have approximately
tetrahedral geometries. Conformational changes involve rotation around single bonds and do NOT change
bond lengths or bond angles. When determining which atoms are "neighboring", all atoms directly bonded
to the carbon atom attached to the hydrogen atom of interest are ignored (not highlighted).
Perform each of the tasks listed below.
Highlight the "Axial" atoms and view down any carbon-carbon bond. Notice that
these atoms are arranged in an "anti" conformation relative to each other, but are "gauche" to
the rest of the ring.
Similarly, by highlighting the "Equatorial" atoms, you should be able to see
the "gauche" arrangement with each other and the "anti" arrangement with the rest of the ring.
Press the "Equatorial Atom" button. One of the equatorial hydrogen atoms will
change color to blue and all neighboring atoms within 3 Angstroms will be highlighted. You
should see that there are 4 hydrogen atoms on neighboring atoms that are highlighted.
Next, press the "Axial Atom" button. One of the axial hydrogen atoms will change
color to blue and all neighboring atoms within 3 Angstroms will be highlighted. In this case, you
will notice that, in addition to 4 hydrogen atoms, there are also two carbon atoms highlighted.
This is a result of the "gauche" interaction of this hydrogen with the ring. This is the reason
bulky groups are more stable on axial positions and tend to avoid equatorial positions.
Finally, press the "Axial" button and orient the molecule so the six carbon atoms
are approximately horizontal. Note that the axial atoms alternate from "up" to "down" going around
the ring. While not as obvious, the equatorial atoms also alternate in the same manner.