Chemistry / organic chemistry 1
The chair flip
Same molecule. A different seat.
Explore how a ring flip changes conformation.
Rotate. Compare. Flip.
Methylcyclohexane
Illustrative motion. Intermediate shapes are not a calculated reaction pathway.
Make your prediction below. Position labels and energy estimates will appear after you check.
Go to the question ↓Compare the two chairs
Relative energy · kcal/molAdditive A-value estimate. Additional group interactions and non-chair conformers are omitted. Model notes ↓
Follow the substituents
What changes in a flip?
A ring face describes configuration.
Axial or equatorial describes conformation.
| Group | Ring face | Chair A | Chair B |
|---|
Try it yourself
Predict before you flip.
Load a question to set up the molecule and hide the answers. Rotate and flip it, then check your reasoning.
Load this question to begin.
The chemistry
A different shape.
The same connections.
Cyclohexane puckers into a chair so its carbon bonds can sit near tetrahedral angles with staggered neighboring bonds. Each carbon has one axial position and one equatorial position.
Axial positions run parallel to the ring axis, alternating up and down. Equatorial positions point outward around the ring. Equatorial does not mean exactly horizontal.
Explore the molecular orbital builder →Why do larger groups prefer equatorial?
An axial group approaches the axial positions two carbons away, creating 1,3-diaxial steric interactions. Turn on the contact overlay to see those pairs. The dotted lines indicate crowding, not chemical bonds.
Cis and trans survive a ring flip
Two groups on the same ring face are cis; groups on opposite faces are trans. An up group can be axial in one chair and equatorial in the other. Changing an editor’s up/down setting changes the stereoisomer, while flipping the ring preserves it.
Model assumptions, energy values, and sources
The endpoint chairs use ideal tetrahedral geometry. Groups are labeled attachment markers rather than complete atomic models. In particular, a tert-butyl marker does not show its three methyl branches. Ring hydrogens are explicit only when requested, or when needed for a contact highlight.
The animation interpolates puckered shapes through a boat-like midpoint for teaching. It does not calculate the real chair, half-chair, twist-boat, and boat pathway, transition-state energies, or flip rates. Only the endpoint conformations receive axial/equatorial labels and energy estimates.
A-values are approximate free-energy penalties for placing a substituent axial instead of equatorial. This model uses the following textbook approximations in kcal/mol: methyl 1.8, ethyl 1.9, isopropyl 2.2, tert-butyl 5.4, hydroxyl 1.0, chloro 0.5, and bromo 0.5. These are twice the individual substituent–hydrogen interaction values tabulated in the source.
We sum axial penalties for each chair and subtract the lower sum to display relative energies. Estimated populations use p(A) = e−G(A)/RT / (e−G(A)/RT + e−G(B)/RT) at 298.15 K. They are predictions of this additive model, rather than measured composition. Solvent effects, neighboring-group interactions, and changes to A-values with temperature are omitted. Chairs predicted to tie may differ when those interactions matter. Bulky groups can also make non-chair conformers important.
Background and values: John McMurry, Organic Chemistry, OpenStax, axial and equatorial bonds, monosubstituted cyclohexanes (table 4.1), and disubstituted cyclohexanes.