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Haworth representations

An important characterization parameter for ceUulose ethers, in addition to the chemical nature of the substituent, is the extent of substitution. As the Haworth representation of the ceUulose polymer shows, it is a linear, unbranched polysaccharide composed of glucopyranose (anhydroglucose) monosaccharide units linked through thek 1,4 positions by the P anomeric configuration. [Pg.271]

The orientation of the model described above results in a clockwise numbering of the ring atoms. Groups that appear to the right of the modified Fischer projection appear below the plane of the ring those on the left appear above. In the common Haworth representation of the pyranose form of D-aldohexoses, C-6 is above the plane. [Pg.62]

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 ... [Pg.63]

Chart II. P-D-GIucopyranose in the twelve possible Haworth representations (the hydrogen atoms are frequently omitted)... [Pg.64]

The variants are distinguished by the locants of those ring atoms that lie outside a reference plane (defined below) and are listed for some examples in Table 1. The locants of ring atoms that lie on the side of the reference plane from which numbering appears clockwise (i.e. the upper side in the normal Haworth representation of furanoses and pyranoses) are written as superscripts and precede the letter those that lie on the other side are written as subscripts and follow the letter. Heteroatoms (e.g. O, S) are indicated by their subscript or superscript atomic symbols. Table 1 gives the notations and Chart III some examples. [Pg.69]

Haworth representation, cyclic monosaccharides, 61-63 Hemiacetal groups disaccharides with, 149-150 without, 148-149 nomenclature, 122-123 oligosaccharides with, 153-154 without, 151-153... [Pg.486]

The net result is a cyclic system looking like the Haworth representation that is commonly used, especially in biochemistry books. The Haworth representation nicely reflects the up-down relationships of the various substituent groups, but is uninformative about whether these are equatorial or axial. The last step, therefore, is to transcribe this representation into a chair conformation, as shown, so that we see the conformational consequences. [Pg.105]

Note that you may also encounter another version of the cyclic form referred to as the Haworth representation (see Box 3.16). This shows the ring as a planar system, and is commonly used in biochemistry books. However, we know that five-membered and six-membered rings are certainly not planar. The Haworth representation nicely reflects the up-down relationships of the various substituent... [Pg.472]

Whereas furanose rings are almost, but not quite, flat, pyranose rings are not, thus Haworth representations do not show the actual molecular shape. Pyranose rings assume one of two chair forms designated the chair because C-4 is up and C-l is down or the 1C4 form. The 4C1 chair is by far the most... [Pg.475]

You should be able to satisfy yourself that the configuration at C5 is the same in both Fischer and Haworth representations. This amounts to asking if 18 and 19 represent the same configurations ... [Pg.915]

A major drawback of cyclic Fischer projections is the unrealistic manner in which the structures are depicted. In 1929, Haworth designed a representation to address this deficiency. Haworth projections provide a simple way to represent cyclic monosaccharides with a three-dimensional perspective. The following process allows the conversion of a Fischer projection into a Haworth representation ... [Pg.6]

Figure 9.5 Haworth representation of glucose and fructose. (A) Both the a and /3 anomers of glucose. (B) For fructose, the /3 anomer of fructofuranose. In the a anomer, the -OH on carbon 2 of fructose would be pointing down and the -CH2OH would be up. (C) The /3 anomer of D-fructopyranose. (Reproduced by permission from Diem K, Lentner C. Scientific Tables. Basel Ciba-Geigy, 1971.)... Figure 9.5 Haworth representation of glucose and fructose. (A) Both the a and /3 anomers of glucose. (B) For fructose, the /3 anomer of fructofuranose. In the a anomer, the -OH on carbon 2 of fructose would be pointing down and the -CH2OH would be up. (C) The /3 anomer of D-fructopyranose. (Reproduced by permission from Diem K, Lentner C. Scientific Tables. Basel Ciba-Geigy, 1971.)...
After the introduction of the Fischer formulas came the use of the Haworth representation, which was an attempt to give a more accurate spatial view of the molecule. Because the Haworth formula does not account for the actual bond angles, the modem con-... [Pg.102]

Figure 1.13 Fischer and Mills representations of a- and P-xylofuranose and a- and P-xylopyranose. Also shown are full and abbreviated Haworth representations of P-D-xylopyranose. Figure 1.13 Fischer and Mills representations of a- and P-xylofuranose and a- and P-xylopyranose. Also shown are full and abbreviated Haworth representations of P-D-xylopyranose.
Like aldopentoses, aldohexoses such as D-glucose are capable of forming two fura-nose forms (a and (3) and two pyranose forms (a and (3). The Haworth representations of the pyranose forms of D-glucose are constructed as shown in Figure 25.4 each has a CH2OH group as a substituent on the six-membered ring. [Pg.982]

FIGURE 16.7 Haworth representations of sugar structures, (a) A comparison of the structure offuran with Haworth representations offuranoses. (b) A comparison of the structure of pyran with Haworth representations of pyranoses. (c) Ot-D-Glucopyranose in the Haworth representation (left), in the chair conformation (middle), and as a space-filling model (right). [Pg.468]

FIGURE 16.8 A comparison of the Fischer, complete Haworth, and abbreviated Haworth representations of a- and [i-D lucose (glucopyranose) and 3-D-ribose (ribofuranose). [Pg.468]

In the Haworth representation, the a-anomer is represented with the OH group (red) downward, and the P-anomer is represented with the OH group (red) upward. [Pg.468]


See other pages where Haworth representations is mentioned: [Pg.1037]    [Pg.475]    [Pg.475]    [Pg.475]    [Pg.478]    [Pg.1037]    [Pg.44]    [Pg.44]    [Pg.61]    [Pg.61]    [Pg.63]    [Pg.487]    [Pg.105]    [Pg.105]    [Pg.105]    [Pg.472]    [Pg.472]    [Pg.475]    [Pg.475]    [Pg.478]    [Pg.1044]    [Pg.47]    [Pg.56]    [Pg.1422]    [Pg.36]    [Pg.75]    [Pg.335]    [Pg.70]   
See also in sourсe #XX -- [ Pg.80 ]

See also in sourсe #XX -- [ Pg.116 ]




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