Identifying Strain

[ntruong2H]

When looking at a newman projection or structure, how can we tell which type of strain there is? I understand torsional strain occurs in eclipsed conformations and that steric strain occurs when two atoms are trying to be in the same volume. However, when just simply looking at a projection, how can we identify what kind of strain is present?

[Chem_Mod]

A Newman Projection just shows how a molecule looks/is oriented when looking down a specific C-C bond. Steric strain is very difficult to tell from a Newman Projection. You might be able to say that the two biggest groups are 180 degrees from each other and so the steric strain is at a minimum. However, if we are trying to actually visualize the physical bumping into of adjacent atoms, we would look at a space filling model rather than a Newman Projection.

[Bronson_Barretto_2C]

I don't think you're able to identify the exact type of strain. The Newman Projection is just a theoretical representation from a viewpoint against a carbon-carbon bond, so the strain visualized might not be entirely correct. If we had to define a strain on the final, I think we would have to be given the bond angles and the particular substituent to determine the strain based on size and relative space between the atoms.