We use Newman projections to visualize the rotations of conformers. Some are more stable than others.
So Newman projections are way of analyzing which sigma bond rotation will be the most stable. We have some rules about which rotations are better and which are worse!
The dihedral angle (theta), is equal to the angle between the two largest groups on either side of the projection.
As you’ll see, when we plot (theta) against energy, we wind up getting a predictable pattern of peaks and valleys that can be used to better understand the different rotations.
Concept: How to draw a Newman Projection Energy Diagram.8m
Professors may ask you to draw this, so don’t just tune it out! You need to understand the basics of energy diagrams for this topic.