When is it useful to convert bond line views to Fischer projections?
It is useful to convert bond line views to Fischer projections when you want to show the absolute configurations at each chiral centre.
Consider the bond-line structure of D-glucose.
It gives only the connectivity of the atoms. It gives no information on stereochemistry.
There are four chiral centres, so there are
To show stereochemistry, we must use wedge-dash formulas.
These formulas give the stereochemical information.
But it is easiest to compare structures using Fischer projections, because they are always written in the same way.
If we make the wedge-dash formula vertical with C-1 at the top, it becomes structure B above. It is then easy to convert B into the Fischer projection A.
Here’s a video on converting line drawings to Fischer projections.