Question

In-Class Worksheet In the box below each molecule, draw Newman projections for the structures A, B, and C shown from the perspective indicated. For each Newman projection that you've drawn, indicate if there are any eclipsed bonds or 1. gauche butane interactions. H H CH3 H3C CH3 CH3 H. H3C CH3 H CH3 H H Structure C Structure B Structure A Structure A can exist in a lower energy conformation by undergoing a bond rotation; draw the Newman projection of this conformation. 2. 3. You might have noticed that structures A, B and C are really just different conformations of the same molecule. In the graph of this molecule, starting with the conformation shown in structure C (this will be 0° on your graph). For each eclipsed or staggered conformation, draw the Newman projection and calculate the expected energy of the conformer. Rotate the front carbon clockwise while keeping the back carbon stationary. It might be helpful to use Figure 1.7 as a guide. area on the back of this page, draw an energy diagram for the rotation

Answer 1

Thus after rotation the Newman's projection has lower energy.

Newman gauche arxlhe gauche Structure Structure R - eclipsed Gauche & Eclipsed Interactions are labelled cu eclipsed on the Spictures : structure C Couche Maul CH3 Bond rotation m by 1200 H Has 2 Gauche Interactions Has only I gauche