What are two types of substituent positions around a chair?

1 Answer
Sep 24, 2015

A cyclohexane ring commonly has a chair conformation. Each carbon has an axial hydrogen, and an equatorial hydrogen.


This is one instance where a molecular model would really come in useful. When the carbon ring is in a chair conformation, each carbon bears 2 substituents (in this case hydrogen) axial and equatorial to the plane of the ring.

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The red hydrogens are axial, and the blue hydrogens are equatorial. Note that when the chair swaps conformation (which a model will easily demonstrate) axial and equatorial substituents interchange their orientation.

Should a cyclohexyl ring bear a bulky substituent, such as #Bu^t#, or even #Me#, the equatorially placed substituent enjoys a substantial steric advantage due to the minimization of trans-annular axial interactions, and the conformations tend to keep the alkyl group in an equatorial position.

Here is a video that fully explain the cyclohexane chair conformation and the type of bonds: axials and equatorials