Question

Why is interconversion of cyclohexane called ring flip?

Answer 1

Because during the interconversion, the substituents DO actually flip from axial to equatorial and vice versa.

Explanation:

My google-fu is too weak to post a nice animation of the process. I will attempt to describe it, and advize that you really should obtain a good set of molecular models (which of course you can take into exams).

A cyclohexane ring, `C_6H_12`, has the one preferred conformation, a chair conformation. In this conformation (which I have always thought of a folding beach chair!) EACH carbon atom has ONE axial substituent, and one equatorial substituent - these are trivial to recognize on a model. On each FACE of the ring, there are 3 axial substituents, and 3 equatorial substituents. Axial substituents interfere with each other sterically ACROSS the ring (these are so-called trans-annular ineractions). For cyclohexane, the ring-flip, which involves interconversion between axial and equatorial substituents is fairly soft thermodynamically, and able to be performed at RT.

Should the cyclohexane bear an alkyl group, even something as small as `CH_3`, the steric bulk of this group dictates the group lie in an equatorial conformation because of unfavourable transannular interaction.

I urge you to get a set of molecular models so that you can appreciate this process. You must also be able to represent this on the printed page. This is non-trivial. Remember, for the preferred chair confomation, there are axial and equatorial positions.