Chapter 26.6, Problem 21CC

(a)

Interpretation Introduction

Interpretation:

Chair conformations and the position of substituents need to be identified for the given set of compounds.

Concept introduction:

Ring-flipping is a phenomenon known as ring inversion that involves rotation about the single bonds of cyclic conformers.  Usually this happens in cyclohexane ring.  When ring flip happens in the cyclohexane, the axially and equatorially substituted groups are inverted.  The ring-flipping also happens in a fused ring system.  Decalin is a fused ring system.  There are two stereoisomers for decalin, namely cis-decalin and trans-decalin.  If the substituent is facing away from the ring or which makes $90°$ with the ring plane means it is in axial position and the substituent which makes a small angle with the ring plane is said to be in equatorial position.  The chair-conformation of cyclohexane is the most stable one as there is a less strain on the ring and no steric hindrance.  The cyclohexane fused system can be drawn in chair conformation as given below.

When viewing the molecule from the top the bonds which are said to be in parallel with the viewing angle are in axial position and which are not parallel are known to be in equatorial position.

To draw and explain: chair conformation and identify the substituent position.

(b)

Interpretation Introduction

Interpretation:

Chair conformations and the position of substituents need to be identified for the given set of compounds.

Concept introduction:

Ring-flipping is a phenomenon known as ring inversion that involves rotation about the single bonds of cyclic conformers.  Usually this happens in cyclohexane ring.  When ring flip happens in the cyclohexane, the axially and equatorially substituted groups are inverted.  The ring-flipping also happens in a fused ring system.  Decalin is a fused ring system.  There are two stereoisomers for decalin, namely cis-decalin and trans-decalin.  If the substituent is facing away from the ring or which makes $90°$ with the ring plane means it is in axial position and the substituent which makes a small angle with the ring plane is said to be in equatorial position.  The chair-conformation of cyclohexane is the most stable one as there is a less strain on the ring and no steric hindrance.  The cyclohexane fused system can be drawn in chair conformation as given below.

When viewing the molecule from the top the bonds which are said to be in parallel with the viewing angle are in axial position and which are not parallel are known to be in equatorial position.

To draw and explain: chair conformation and identify the substituent position.

(c)

Interpretation Introduction

Interpretation:

Chair conformations and the position of substituents need to be identified for the given set of compounds.

Concept introduction:

Ring-flipping is a phenomenon known as ring inversion that involves rotation about the single bonds of cyclic conformers.  Usually this happens in cyclohexane ring.  When ring flip happens in the cyclohexane, the axially and equatorially substituted groups are inverted.  The ring-flipping also happens in a fused ring system.  Decalin is a fused ring system.  There are two stereoisomers for decalin, namely cis-decalin and trans-decalin.  If the substituent is facing away from the ring or which makes $90°$ with the ring plane means it is in axial position and the substituent which makes a small angle with the ring plane is said to be in equatorial position.  The chair-conformation of cyclohexane is the most stable one as there is a less strain on the ring and no steric hindrance.  The cyclohexane fused system can be drawn in chair conformation as given below.

When viewing the molecule from the top the bonds which are said to be in parallel with the viewing angle are in axial position and which are not parallel are known to be in equatorial position.

To draw and explain: chair conformation and identify the substituent position.