 A cyclohexane molecule in chair conformation, with hydrogen atoms in axial position in red, equatorial in blue. Cyclohexane is a molecule with the molecular formula C6H12 consisting of six carbon atoms linked to each other to form a ring, with each carbon atom bearing two hydrogen atoms.
Half of the 12 hydrogens are in axial position, which means their C-H bonds are parallel and appear to stick up and down from the structure, the other half are in equatorial positions; meaning that they are splayed out.
The axial hydrogens can simultaneously swap places with the equatorial hydrogens. This phenomenon is known as ring flipping.
Due to the inherent need of the sp3 single bonds on carbons to reach 109.5 degrees cyclohexane is not a "flat" 3-D form. chair and boat cyclohexanes exist with chair being the most stable, virtually strain free. (111 degrees IIRC). Odd Hassel received the Nobel Prize for work on the conformations of cyclohexane.
Cis/Trans isomers of Cyclohexane.
- (A=axial, E=equatorial substituents)
- AA/EE---------AE/EA
- Trans-1,2-----Cis---1,2
- Cis---1,3-----Trans-1,3
- Trans-1,4-----Cis---1,4
Each conformation will differ in its stability depending upon what functional groups are present. As a rule substituents are most stable when they are in their equatorial positions. This is due to torsional strains placed upon groups at opposing angles.
For example, if there is a methyl group on carbon 1 in an axial position, it will interact with the axial hydrogens on carbon 3 and carbon 5.
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