Cyclic Forms of Monosaccharides

The present Recommendations deal with the acyclic and cyclic forms of monosaccharides and their simple derivatives, as well as with the nomenclature of oligosaccharides and polysaccharides. They are additional to the Definitive Rules for the Nomenclature of Organic Chemistry [13,14] and are intended to govern those aspects of the nomenclature of carbohydrates not covered by those rules. 

Glycosides were originally defined as mixed acetals (ketals) derived from cyclic forms of monosaccharides. 

Since in aqueous solutions the cyclic form of monosaccharides is in equilibrium with their corresponding open forms, the a and P structures continually interconvert. At equilibrium, one form usually predominates. For instance, glucose dissolved in water consists of about a 2 1... 

Since in aqueous solutions the cyclic form of monosaccharides is in equilibrium with their corresponding open forms, the a. and p structures continually interconvert. At equilibrium, one form usually predominates. For instance, glucose dissolved in water consists of about a 2 1 ratio of p-D-glucose to a-D-glucose. Although their chemical constituents are identical, the biochemical properties between the a and the P forms can be quite different. Monosaccharides linked together to form disaccharides and polysaccharides cannot continue to interconvert and are therefore frozen in the a or p forms. Changing one monosaccharide in a complex carbohydrate to its opposite... 

Haworth formulas are a useful way of representing the cyclic forms of monosaccharides. The rings are depicted as flat, with hydroxyl groups or other substituents above or below the ring plane. 

Explain the conventions for using a and /3 to designate the configurations of cyclic forms of monosaccharides. 

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