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Chair Conformations

Cyclic Chair Representations


6-membered rings (typically all-carbon rings called cyclohexane) are drawn in two-dimensions as hexagons. However, this is not how they occupy space in three-dimensions! To show how they occpy three-dimensions, we use the chair comformation. The chair conformation minizes steric repulsion. The substituents that point straight up and straight down are in the axial position, the substituents that are in the plane of the ring are in the equitorial position.


Image illustrating Chair Conformations



Steric Factors in Cyclohexanes


It is also important to note that if there are any bulky substituents on the ring, they will prefer to be in the equitorial position. This is because there is less steric interactions (called 1,3-diaxial interations) when the large substituents is in the equatorial position.


Image illustrating Chair Conformations



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Example: Chair Conformations


Draw each of the following molecules in two different chair conformations. Circle the most stable.


Image illustrating Example: Chair Conformations


Image illustrating Example: Chair Conformations


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Example: Chair Conformations


Draw the following molecules in two different chair conformations. Circle the most stable.


Image illustrating Example: Chair Conformations


Image illustrating Example: Chair Conformations


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Practice: Chair Conformations


Draw the following molecule in two different chair conformations. Circle the most stable.


Illustration for practice question: Isomers



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