Monosaccharides conformation representations

Fig. 1 Various representations of the monosaccharide Glucose (a) extended Fischer projection (b) Haworth projection (c) pyranoside Cj chair representation (d) 3D conformational representation. The numbers indicate the standard designations of each carbon atom in the monosaccharide. This numbering is also used to identify the OH groups, OHn being the OH group bound to Cn...

The Haworth representation implies a planar ring. However, monosaccharides assume conformations that are not planar these may be represented by Haworth conformational formulae. The nomenclature of conformations is described in 2-Carb-7. For example, (5-D-glucopyranose assumes a chair conformation ... 

William Mills described a similar convention to depict the structures of monosaccharides. While the ring atoms of the Haworth projections are oriented perpendicular to the paper, Mills chose to depict the carbon skeleton in the plane of the paper (Fig. 1.5). Although Fischer, Haworth, and Mills projections are useful tools for depicting the structures of carbohydrates, the planar nature of these representations does not provide an accurate picture of the actual geometry of the molecules. In order to understand carbohydrate function and reactivity, recognition of each distinct conformation and the properties associated with it is required [15]. 

CONFORMATIONAL STRUCTURES Although Haworth projection formulas are often used to represent carbohydrate structure, they are oversimplifications. Bond angle analysis and X-ray analysis demonstrate that conformational formulas are more accurate representations of monosaccharide structure (Figure 7.10). Conformational structures are more accurate because they illustrate the puckered nature of sugar rings. 

---