Carbohydrates Haworth formulas

Structural drawings of carbohydrates of this type are called Haworth formulas, after the British chemist Sir Walter Norman Haworth (St Andrew s University and the University of Birmingham) Early m his career Haworth contributed to the discovery that carbohydrates exist as cyclic hemiacetals rather than m open chain forms Later he col laborated on an efficient synthesis of vitamin C from carbohydrate precursors This was the first chemical synthesis of a vitamin and provided an inexpensive route to its prepa ration on a commercial scale Haworth was a corecipient of the Nobel Prize for chem istry m 1937... 

Orienf fhe Haworth formula of the carbohydrate with the ring oxygen at the back and the anomeric carbon at the right... 

Haworth formulas are satisfactory for representing configurational relationships in pyranose forms but are uninformative as to carbohydrate conformations X ray crystal lographic studies of a large number of carbohydrates reveal that the six membered pyra nose ring of D glucose adopts a chair conformation... 

Haworth formulas (Section 25 6) Planar representations of furanose and pyranose forms of carbohydrates... 

The use of conformational analysis is essential to a rational approach to carbohydrate chemistry, but for simply representing carbohydrate structures most biochemists continue to use the Haworth formulae. 

PROBLEM 25.5 Write Haworth formulas corresponding to the furanose forms of each of the following carbohydrates ... 

Haworth formulas are satisfactory for representing configurational relationships in pyranose forms but are uninformative as to carbohydrate conformations. X-ray... 

Haworth formulas are named after the English chemist W. N. Haworth (University of Birmingham), who, in 1926, along with E. L. Hirst, demonstrated that the cyclic form of glucose acetals consists of a six-membered ring. Haworth received the Nobel Prize for his work in carbohydrate chemistry in 1937. For an excellent discussion of Haworth formulas and their relation to open-chain forms, see The Conversion of Open Chain Structures of Monosaccharides into the Corresponding Haworth Formulas, Wheeler, D. M. S., Wheeler, M. M., and Wheeler, T. S.,J. Chem. Educ. 1982, 59, 969-970. 

Inositols are hexahydroxycyclohexanes, with one hydroxyl group on each carbon atom of the ring. Although not strictly carbohydrates, they are obviously similar to pyranose sugars and do occur in nature. There are nine possible stereoisomers. Draw Haworth formulas for all possibilities (all are known), and tell which are chiral. 

In the usual writing of stereochemical formulas of carbohydrates by the Fischer and Haworth conventions, the hydroxyls in a ring are depicted as either cis or trans. It is well known, however, that these formulas do not necessarily give a true representation of the relative positions of the hydroxyls in space. The 6-member rings, and possibly to some extent the 5-member rings, generally are not planar but have a... 

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. 

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