3.2. Newman Projections

It is often challenging to look at a line-angle structure and determine at a glance the angles between groups. Instead a special kind of drawing, Newman Projections, are used to visualize looking down a σ bond (Figure 3.2). This makes it easier to compare conformations.

Figure 3.2 – Example of 60° Rotations Around a σ Bond and Newman Projections of the Resulting Conformations.

In a Newman Projection the atom closer to the viewer becomes a point, with the other bonds from that atom being lines radiating from there in the directions their respective bonds point to. Drawing the other atom in the bond as a point would be ambiguous and confusing. Instead, the atom further from the viewer becomes a circle and its other bonds radiate from there.

In some conformations two atoms are directly in front of each other from the viewer’s perspective (Figure 3.3). To avoid confusion the Newman Projection is drawn with them slightly offset (clockwise or counterclockwise). It is important to remember that this is an imperfect representation; although it looks like we are discussing a conformation with a small angle between the groups, they are actually directly in front of each other.

Figure 3.3 – Newman Projections Showing Atoms Directly in Front of One Another.