A six-membered ring containing five carbon atoms and an oxygen atom. Pyranose rings are formed by any aldose sugars with five or more carbon atoms. In solution the aldehyde group at the first carbon atom reacts with the hydroxyl group on the fifth carbon atom. This reaction renders the first carbon atom asymmetric. The pyranose forms of aldoses can thus exist in two isomeric forms. For example, D-glucose in solution forms both α-D-glucopyranose and β-D-glucopyranose. These isomers differ in a number of properties, e.g. optical activity, solubility in water, and melting point. Compare furanose ring. |
