Haworthprojectie

Haworthprojection is a standardized two‑dimensional representation used to depict the cyclic forms of monosaccharides. It was introduced by the British chemist Walter Haworth in the early to mid-20th century as a convenient way to illustrate the stereochemistry of sugars that form hemiacetal or hemiketal rings. The projection simplifies the three‑dimensional shape of the ring into a planar polygon, usually a hexagon for pyranoses (six‑membered rings) and a pentagon for furanoses (five‑membered rings), with the ring oxygen shown as part of the ring.

In a Haworth projection, substituents such as hydroxyl groups and hydrogen atoms are drawn either above or below the plane of the ring. The anomeric carbon (the carbon that was carbonyl in the open-chain form) can adopt two configurations: alpha or beta, indicating the orientation of the anomeric hydroxyl relative to the ring plane. For most common D‑sugars, the CH2OH substituent is drawn above the plane, and the alpha/beta designation refers to whether the anomeric hydroxyl is below or above the plane, respectively. This notation also extends to glycosidic linkages in disaccharides, where the relative orientation of linked units is depicted.

Haworth projections are widely used in carbohydrate chemistry and biochemistry to convey stereochemistry quickly and to compare different sugars, particularly their pyranose and furanose forms. They are a simplification of the real, puckered three‑dimensional conformations (such as chair forms) and are most effective for illustrating connectivity and relative stereochemistry rather than detailed conformational geometry.