The Fischer projection enables us to simply read or represent enantiomer or diastereomer relations among complex acyclic molecules containing several asymmetric C atoms. This is its foremost advantage. For example, D-mannose differs from D-glucose in the configuration at C² only (two diastereomers), while L-glucose is the enantiomer of D-glucose.

D-mannose

D-glucose

L-glucose

• Exchange of any two substituents at an asymmetric C atom in a Fischer projection results in the projection of the compound with inverted configuration of this atom.
• A Fischer projection in its entirety may be rotated by 180°, but not by 90°.

Verify these statements by performing the said operations on a Fischer projection (e.g. of D-glyceraldehyde OCH-CH(OH)-CH₂OH) and translating the obtained projection into a 3D formula.