Chapter 5, Problem 5.36P

Interpretation Introduction

Interpretation:

The Newman projections of $\text{1, 2 - dichloroethane}$ for its anti-conformer and each of its gauche conformer are to be drawn. Those conformers that possess a plane of symmetry are to be determined and indicated using a dashed line.

Concept introduction:

Newman projections are used to show the relative positions of the groups attached to the two carbon atoms of the bond of interest. The representation is drawn looking along the bond. The carbon in front is represented by a point, while the carbon at the back is represented by a concentric circle. The bonds to the three groups on the front carbon converge on the point. Bonds to the three groups on the back carbon end on the circle. Depending on the dihedral angles, the conformers are classified as eclipsed or staggered with angles of ${\text{0}}^{\text{o}}$ and ${\text{60}}^{\text{o}}$ respectively.

Depending on the relative positions of the bulkiest groups on the front and back carbon, the staggered conformers are further divided into anti and gauche. In anti-conformers, the bulkiest groups on the front and back carbons are directly across from each other with a ${\text{180}}^{\text{o}}$ dihedral angle. In gauche conformer, ${\text{60}}^{\text{o}}$ is the dihedral angle between the two.

A molecule possesses a plane of symmetry if a plane passing through its center divides it into halves that are mirror images of each other.