Chapter 3.8, Problem 7P

Interpretation Introduction

Interpretation:

The $\text{A-C-C-X}$ torsion (dihedral) angle is to be determined when a substituent $\text{X}$ at $\text{C-1}$ satisfies the indicated stereochemical requirement in the given partial structure.

Concept introduction:

The anti and gauche bonds in cyclohexane are represented by sawhorse projections of staggered conformations of alkanes as

The substituents in anti-relationship are $\text{A}$ and $\text{B}$.

The substituents in gauche relationship are $\text{A}$ and $\text{Y}$, $\text{X}$ and $\text{Y}$, $\text{X}$ and $\text{B}$.

In the following structure, each path shows anti relationship where a substituent is equatorial.

In the following structure, each path shows gauche relationship where a substituent is axial.

The torsion (dihedral) angle for eclipsed conformation is ${\text{0}}^{\text{o}}$.

The torsion (dihedral) angle for gauche conformation is ${\text{60}}^{\text{o}}$.

The torsion (dihedral) angle for anti-conformation is ${\text{180}}^{\text{o}}$.