91Ó°ÊÓ

The energy of the conformation is based upon the repulsion of the bulky groups. The more the repulsion, the more will be energy.

Also, the conformation will be unstable.

The given compound is 1,2-dichloroethane. The Newman projection for the given compound is shown below:

Newman projection for 1,2-dichloroethane

a.

By fixing the front carbon, the back carbon is rotated by ${60}^0$. As a result, three staggered and three eclipsed conformations are produced as shown below:

Conformation of 1,2-dichloroethane

b.

The relation between the positions of the bulky groups with energy and stability is mentioned below:

• When the two bulkier groups (chlorine) are anti or opposite to each other, the energy of the conformation is the minimum, and it is stable.
• When the two bulkier groups (chlorine) are at ${120}^0$, the energy of the conformation is larger as above, and it is slightly stable.
• When the two bulkier groups (chlorine) are at ${60}^0$, the energy of the conformation is the largest as the above two conformations, and it is unstable.

The graph between energy and dihedral angle is shown below:

Graph representing energy and dihedral angle