Question

What are the steps to convert bond line notations to Newman projections?

Answer 1

A bond-line notation gives no stereochemical information, but here's how to convert a wedge-dash notation to a Newman projection.

PROBLEM

Convert the following wedge-dash structure of 2-chloro-3-methylpentane to a Newman projection through the C2-C3 bond.

Step 1. Draw two Newman projection templates.

• Draw two circles.
• Put a dot in the centre of each. These represent C-2. C-3 is hiding behind the circles.
• On one circle, draw a Y with the spokes radiating from the dot at 120° angles. On the other circle, draw an inverted Y. These represent the bonds from C-2.
• Draw lines coming off each circle that bisect the angles of the Y. These represent the bonds from C-3.

You will choose one of these templates as the basis for your projection.

Step 2. View the molecule along the C2-C3 axis with your eye closest to C2.

Your eye will be at the lower left of the image.

The closest bonds make an inverted Y, so you will choose the second template for your projection.

Step 3. Place the groups onto your template.

• The groups on C-2 go on the front carbon, The groups on C-3 go on the back carbon.
• The "normal" groups go on the vertical lines: CH₃ in front; CH₂CH₃ behind.
• The wedged groups go on the right hand side: H in front; CH₃ in back.
• The dashed groups go on the left hand side: Cl in front; H in back.

And you have your Newman projection.