Ring flip

A conformational change in a cyclic molecule that interconverts axial and equatorial positions. In cyclohexane, it occurs without breaking bonds and exchanges the two chair conformations.

Cyclohexane: A saturated six-carbon ring whose low-energy conformations include the chair form. Its chair conformations provide the classic example of ring flipping.
Axial bond: A substituent bond oriented approximately parallel to a ring’s principal axis in a cyclohexane chair. Ring inversion changes each axial bond into an equatorial one.
1,3-Diaxial interaction: A steric interaction between an axial substituent on cyclohexane and axial hydrogens or groups two ring positions away. These interactions often make the conformer with an axial substituent less favorable.
Cyclopentane pseudorotation: A continuous change among puckered cyclopentane conformations that moves the ring’s flap position. It changes ring shape continuously rather than interconverting cyclohexane chair forms.
Cyclohexane chair conformation: A puckered cyclohexane shape with alternating carbon atoms above and below a roughly planar ring. The ring flip converts one chair into its alternative chair.
Equatorial bond: A substituent bond directed roughly outward around the perimeter of a cyclohexane chair. Ring inversion changes each equatorial bond into an axial one.
A-value: A measure of the free-energy preference of a substituent for an equatorial rather than axial position in cyclohexane. It estimates how strongly a substituent shifts the ring-flip equilibrium toward an equatorial position.
Nitrogen inversion: A pyramidal nitrogen atom changes configuration by passing through a flatter geometry. It is an inversion at one atom, not a coordinated conformational change of a ring.
Cyclohexane boat conformation: A higher-energy cyclohexane conformation with both ends of the ring raised like a boat. It is one of the less stable shapes along a chair-to-chair inversion pathway.
Cyclohexane stereochemistry: The spatial arrangement of atoms and substituents in cyclohexane and its conformations. The flip changes axial or equatorial orientation while preserving whether a substituent points up or down.

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Cyclohexane conformationRelated: Cyclohexane’s ring flip interconverts two chair forms and swaps axial and equatorial positions.