Draw the Newman projection energy diagram for butane

Here we draw an energy diagram for the Newman projections of butane showing the C:C:C:C dihedral (torsional) angles 0, 60, 120, and 180 degrees. In this case we discover that the two eclipsed conformations are of unequal energy and so are the two staggered conformations known as staggered anti and staggered gauche.

We list the strains of each conformation whether it be steric "bumping" strain or torsional strain due to bond repulsion, or both, or none. We also practiced converting a wedge/dash drawing (aka sawhorse) into a Newman projection.

Several tips were given if you see a problem like this. Start with the least stable conformation which will be an eclipse projection. Define that as the 0 degrees starting point. Also why not draw all the projection templates first without worrying about atom placement. Then hold the front carbon steady and fill in its bonds the same way for all four Newman conformations.

Four molecules were suggested at the end of the video for you to try drawing the energy diagram for. One of them is a challenge. I would not try to predict if the shape of the energy diagram will be similar to ethane, butane, or something totally different. Just work through your drawings and ask if any two Newman projections would actually have the same energy because the two have exactly the same strains.