Just like in Fischer projections, the main concern is to quickly convey stereochemical relationships. They seem to suggest a funny see-saw shape for the carbon atoms, but the idea here is not to convey the shape of the molecule perfectly. They are commonly used in biochemistry to depict the cyclic forms of sugars. These drawings, by the way, are called Haworth projections. That means they differ in 3D space at the anomeric center the anomeric center is the C=O carbon to which an oxygen binds to form the ring.
In carbohydrates, a five-membered ring with an oxygen in it is called a furanose (another common form, a six-membered ring, is called a pyranose). \): D-threose and its two possible five-membered-ring forms.įor example, D-threose can form two different five-membered rings (that is, rings made from a circle of five atoms).
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