cyclohexane

Cyclohexane is one of the most common rings that carbon forms, due to its lack of bond angle strain that smaller or larger rings have. The lowest-energy conformation of cyclohexane is called the "chair" conformation. This conformation has six positions called "axial" positions, which are pointing straight up or down and perpendicular to the plane of the molecule. It also has six "equatorial" positions that point out from the center of the molecule. Cyclohexane can undergo an inversion, or "ring-flip", which reverses the positions - axials become equatorials, and vice versa. This requires very little energy.

Another conformation cyclohexane can attain is the "boat" conformation.

This conformation is less energetically favored (requires more energy to attain) versus the chair conformation. There are no axial or equatorial positions in the boat conformation.