As we learned already, we use Newman projections to visualize the rotations of conformers. Now we will learn the steps involved to draw the perfect one.
Example #1: Introduction to Drawing Newman Projections
Worked Example: Draw the most energetically favorable Newman Projection for CH3CH2CH2CH2CH3 down the C2 – C3 bond.
1. Convert problem into bondline structure
Concept #1: Step 1
2. Highlight the bond of interest
Concept #2: Step 2
3. Draw an eyeball glaring down the length of the bond
Concept #3: Step 3
4. Surround only the bond of interest with ALL implied hydrogens
Concept #4: Step 4
5. Draw a front carbon with 3 groups in the front and a back carbon with 3 groups in the back
Concept #5: Step 5
6. Determine which dihedral angle would correspond
Concept #6: Step 6
Hint: This question asked for the most energetically favorable = most stable. Which conformation is most stable?
The right answer was anti. You got it. So it turns out this time we drew it correctly on the first try. But there will be other examples where we will have to rotate the Newman Projection into the correct position.
Practice: Draw the most energetic Newman Projection of CH3CH(C6H5)CH3
Hint: Not all Newman Projections can form an anti, gauche and eclipsed conformation. If you have no clear large group on one side of the projection, you’ll just be stuck with projections called staggered (not overlapping) and eclipsed (overlapping).
Practice: Draw the most stable Newman Projection of CH3CH2 CH2OH through the C2 – C1 bond.