Newman Projection is useful in alkene stereochemistry. It is used for determining conformational relationships. (Conformers are molecules which are converted to one another by a rotation around a single bond).
Newman Projection visualizes the chemical conformations of a carbon to carbon chemical bond from front to back. The front carbon is represented by a dot.The back carbon is represented a circle. The name for front carbon atom is proximal. The back carbon atom is called distal. Other carbons are drawn as sticks coming off the dot or circle and they are separated by 120 degrees. Newman projection is useful to assess the torsional angle between bonds.
Below is a sample for Newman projections
A Newman projection can be ‘staggered’ or ‘eclipsed’. You could draw Newman projection such that the groups on the front carbon are staggered with 60 degrees apart. Or they could be eclipsed (overlapping directly) with the groups on the back carbon. Following are the samples of Newman projections of ethane for staggered and eclipsed ones.
New man projections can be made for butane so that its eclipsed, gauge and anti conformations could be seen. In this case, the front dot represents the second carbon in the butane chain. The back circle represents the third carbon in the butane chain. Newman projection is used to condense the bond between these two carbons.
Let us view the below picture for understanding our concept more clearly.
The sawhorse projection is similar to Newman projection. It visualizes the carbon to carbon bond from an oblique angle.
Following are the pictures of sawhorse projection