Thank you for the opportunity to help you with your question!
projections are drawn by looking directly along a particular bond in the system
(here a C-C bond) and arranging the substituents symmetrically around the atoms
at each end of that bond. The protocol requires that the atoms within the central
bond are defined as shown below:
In order to draw a Newman projection from a wedge-dash diagram,
it is useful to imagine putting your "eye" in line with the central bond in
order to look along it.
Let's work through an example, consider drawing a Newman
projection by looking at the following wedge-dash diagram of propane from the
left hand side.
- First draw the dot and circle to represent the front
and back C respectively
- Since the front carbon atom has an H atom in the
plane of the page pointing up we can add that first
- The back carbon atom has an H atom in the plane
of the page pointing down
- Now add the other bonds to each C so that it is symmetrical
- The groups / bonds that were forward of the plane of the page in
the original wedge-dash diagram are now to our right
- Those behind the plane are now to our left
- Now you try the same thing, but looking from the right
to generate the other Newman projection.
are used mainly for determining
conformational relationships. Recall that conformers are molecules that
can be converted into one another by a rotation around a single bond. Newman Projections
are also useful when studying a reaction involving prochiral molecules
that have a double bond, in which the addition of a new group creates a
In this notation, you are actually viewing a molecule by looking
down a particular carbon-carbon bond. The front carbon of this bond is
represented by a dot, and the back carbon is represented by a large
circle. The three remaining bonds are drawn as sticks
coming off the dot (or circle), separated by one another by 120 degrees. A Newman Projection
can be drawn such that the groups on the front carbon are staggered
(60 degrees apart) or eclipsed
(directly overlapping) with the groups on the back carbon. Below are two Newman Projections
of ethane, C2
. The structure on the left is staggered, and the structure on the right is eclipsed. These are the simplest Newman Projections
because they have only two carbons, and all of the groups on both carbons are identical.
Please let me know if you need any clarification. I'm always happy to answer your questions.