Converting between Newman and Sawhorse
Newman and Sawhorse conversion:
Conversion of Newman to Sawhorse projection is very easy. By applying simple rules one can convert Sawhorse to Newman projection and Newman to sawhorse projection.
Conversion of Newman to Sawhorse:
For this conversion, the Newman projection is considered in its staggered form. And as in the Newman projection, the central C-C double bond having front and rare carbon is not visible, and the rare carbon is rotated to get eclipsed conformation. After this, the molecule is placed or viewed such that the central C-C double bond becomes visible and the front carbon is at the lower position.
The groups attached to both carbons are written such that the groups which are on the right side in the Newman projection are written on the right side in the sawhorse project and the groups on left in the Newman projection are mentioned on the left side of the sawhorse projection.
If both OH groups are opposite in the Newman projection then;
For a standard sawhorse projection, if the Newman projection is in eclipsed conformation, then first convert it into staggered conformation before going to sawhorse conformation.
Sawhorse to Newman Projection:
The conversion of sawhorse to Newman projection is also easy. The side from which the structure is seen is marked as front carbon and the side opposite to this is marked as rare carbon. The groups on the left side of carbon-carbon central bond are written on the left in Newman projection and the groups on the right side are written on the right side of Newman projection.
Examples;
This eclipsed conformation is highly unstable. It is converted to the stable staggered conformation as shown below;
Other examples:
