English: Cyclohexane chair flip (ring inversion) reaction. Structures of the significant conformations (A, B, C & D) of the reaction are shown & plotted against their energy differences. Inversion happens quickly & constantly in room temperature.

Conformations:

A (A1, A2): chair

B (B1, B2): twist-boat

C: boat

D (D1, D2): half-chair

When ring flip happens completely from chair-to-chair, hydrogens that were previously axial (blue H) turn equatorial & equatorial ones (red H) turn axial.

Valleys of the pink graph are conformations lowest in energy (shown as A & B). Peaks are conformations highest in energy (shown as C & D). Energies are A<B<C<D with D highest & A lowest in energy. A is thus the most stable conformation &, of all the other conformations, occurs most often in room temperature.

Valleys A & B are local energy minima & A is global minima. A & B can thus be classified as conformers. Peaks are not conformers. Energy differences are mostly caused by anglular strain.

Source for conformer classification:

Pure & Appl. Chem., Vol. 68, No. 12, pp. 2193-2222, 1996

Source for the relative energy differences & other info in this description:

J Clayden, N Greeves, SG Warren (2001). Organic chemistry. (2nd ed.). p. 373. ISBN 9780191666216.