Chapter 6.6, Problem 6.40P

Interpretation Introduction

Interpretation:

The most stable chair conformation for the given compound has to be drawn.

Concept Introduction:

When a compound contains a cyclohexane ring in it, then there are three possibilities of conformations.  They are chair, boat and twist-boat.  Among these three conformations of cyclohexane ring, the most stable one is the chair conformation.

In the above structure, there are twelve substituents that can be placed.  Among the twelve, six are axial substituents and six are equatorial substituents.  The axial substituents can be represented as shown below,

The equatorial substituents can be represented as,

To draw a group in a correct configuration, we have to understand what is coming towards us and what is going away from us (wedge and dash bonds).

For drawing the other chair conformation, a ring flip has to be done.  Ring flipping makes the skeleton as shown below,

During this ring flip from one chair conformation to another, all the substituents present in axial position goes to equatorial position and vice-versa.

The most stable conformation among the two chair conformations can be found by looking into the bulky groups that are present in the ring.  The chair conformation which has the bulky group in equatorial position will be the more stable one as there wont be steric interaction.  If the bulky group is present in axial position, then there will be axial-axial interaction, which makes the conformation less stable.  In simple words, we can say that the bulky group will prefer to be in equatorial position.