Calculating Energy of Newman Projection Rotation

Sometimes we’ll be asked to actually calculate the amount of energy a Newman Projection “spends” while rotating. 

Important Barrier of Rotation Values

These are the values we’ll need so we can solve for the unknown interactions in these questions. 

Example: The barrier to rotation for the following molecule is 22 kJ/mol . Determine the energy cost associated with the eclipsing interaction between a bromine and hydrogen atom.

3m

Now it’s time to put your knowledge to the test. Remember to draw the eclipsed version to know what the interactions are!

Problem: The barrier to rotation for 1,2 -dibromopropane along the C1—C2 bond is 28 kJ/mol. Determine the energy cost associated with the eclipsing dibromine interaction.

4m