Chapter 4, Problem 70IP

(a)

Interpretation Introduction

Interpretation:

The connection between the two rings (in chair conformation) analogous to that in cis- or trans-decalin has to be predicted.

Concept Introduction:

Conformations: Rotation about C-C single bonds allows a compound to adopt a variety of possible three-dimensional shapes.

Drawing Axial and Equatorial substituents:

Each carbon in cyclohexane can bear two substituents. One group is said to occupy an axial position, which is parallel to a vertical axis passing through the center of the ring. The other group is said to occupy an equatorial position, which is positioned approximately along the equator of the ring.

(b)

Interpretation Introduction

Interpretation:

Whether the aromatic ring is in an axial or equatorial position has to be identified.

Concept Introduction:

Nomenclature of organic compounds:

Conformations: Rotation about C-C single bonds allows a compound to adopt a variety of possible three-dimensional shapes.

Drawing Axial and Equatorial substituents:

Each carbon in cyclohexane can bear two substituents. One group is said to occupy an axial position, which is parallel to a vertical axis passing through the center of the ring. the other group is said to occupy an equatorial position, which is positioned approximately along the equator of the ring.

(c)

Interpretation Introduction

Interpretation:

On considering the six-carbon acyclic substituent bound to one of the bridgeheads carbons, the relationship (as axial or equatorial) to each of the chairs has to be predicted.

Concept Introduction:

Conformations: Rotation about C-C single bonds allows a compound to adopt a variety of possible three-dimensional shapes.

Drawing Axial and Equatorial substituents:

Each carbon in cyclohexane can bear two substituents. One group is said to occupy an axial position, which is parallel to a vertical axis passing through the center of the ring. the other group is said to occupy an equatorial position, which is positioned approximately along the equator of the ring.

(d)

Interpretation Introduction

Interpretation:

The approximate dihedral angle between the two methyl groups directly bound to the chair has to be interpreted.

Concept Introduction:

Drawing Axial and Equatorial substituents:

Each carbon in cyclohexane can bear two substituents. One group is said to occupy an axial position, which is parallel to a vertical axis passing through the center of the ring. the other group is said to occupy an equatorial position, which is positioned approximately along the equator of the ring.

Conformations: Rotation about C-C single bonds allows a compound to adopt a variety of possible three-dimensional shapes.

Newman projections: The new conformations of compounds can be drawn and analyzed by Newman projections. A Newman projection visualizes different conformations of Carbon-carbon chemical bond from front to back with the front carbon represented as a black dot and the back Carbon represented as a circle.

Dihedral angle: The angle between two hydrogens of a Newman projection is called as dihedral angle or torsional angle. This dihedral angle changes as the C-C bond rotates. Two conformations with special attentions are staggered and eclipsed conformation. Staggered conformation is the lowest in energy and the eclipsed conformation is the highest in energy.

For example,