Fischer projection

The Fischer projection, devised by Hermann Emil Fischer in 1891, is a two-dimensional representation of a three-dimensional organic molecule by projection. They are used by chemists, particularly in organic chemistry and biochemistry. All bonds are depicted as horizontal or vertical lines. The carbon chain is depicted vertically, with carbon atoms represented by the center of crossing lines. The orientation of the carbon chain is so that the C1 carbon is at the top.



In a Fischer projection, all horizontal bonds project toward the viewer, while vertical bonds project away from the viewer. Therefore, a Fischer projection cannot be rotated by (2n+1)×90° in the plane of the page or the screen, as the orientation of bonds relative to one another can change, converting a molecule to its enantiomer.

Fischer projections are most commonly used in biochemistry and organic chemistry to represent monosaccharides, but can also be used for amino acids or for other organic molecules. Since Fischer projections depict the stereochemistry (three-dimensional structure) of a molecule, they are very useful for differentiating between enantiomers of chiral molecules. A computational approach to determining the chirality of a molecule based on computing the sign of a determinant is given by Cieplak and Wisniewski.

Haworth projections are a related chemical notation used to represent sugars in ring form. The groups on the right hand side of a Fischer projection are equivalent to those below the plane of the ring in Haworth projections. Fischer projections should not be confused with Lewis structures, which do not contain any information about three dimensional geometry.