Hemicellulose chemical structure

Moreover, an absorption band near 1375 cm-i is detected and it is assigned to the CH bending vibration present in cellulose and hemicellulose chemical structures (Sim et al., 1998). The prominent band at 1044 cm-i is also associated with hemicelluloses and is attributed to the C-OH bending. Finally, a sharp band at 897 cm-i, which is typical of b-glycosidic linkages between the sugar units in hemicelluloses, was detected in the anomeric region (Sun et al., 2005). 

FIGURE 9.20 Chemical structure of cellulose (a), which is a glucose polymer, and xylan (b), a typical component of hemicellulose. 

Analyses of the hemicelluloses of woods indicate the presence of a high proportion of D-xylose residues in association with those of a methyl ether of a hexuronic acid.64 The first evidence for the chemical structure of such wood xylans came from the isolation of xylobiose, xylotriose,65 and the aldobiouronic acid 0-(4-0-methyl-a-D-glucosyluronic)-(l —> 2)-D-xylose acid (IX)22 from partial hydrolyzates of aspen wood. The role of such oligosaccharide fragments in wood xylans became more apparent as the result of a study of a xylan from European beechwood,26 in which it was shown... 

Figure 2.1.1 Schematic illustration of the chemical structure of the major compounds of lignocellulose, namely, cellulose, hemicellulose, and lignin.

Meshitsuka, G, and Isogai, A. 1996. Chemical structure of cellulose, hemicellulose, and lignin. In Hon, D. N.-S. (Ed.), Chemical modification of lignocellulosic materials (pp. 11-34). New York Marcel Dekker. 

Wood is composed of three major polymeric materials cellulose, hemicelluloses, and lignin. Cellulose is the common name used for the glucan present in wood, which constitutes about 42 percent of wood s dry weight. Cellulose is the primary component of the walls of cells making up wood fibers and is the main structural material of wood and other plants. Paper, paperboard, and other wood fiber products thus also are composed mostly of cellulose. The chemical structure of the cellulose macromolecule is shown in Fig. 28.4. In the plant the degree of polymerization (DP) of cellulose is approximately 14,000.5... 

Chemical Structure in the Hemicellulose Group, E. L. Hirst, Fundamentals Papermaking Fibers, Trans. Symp. Cambridge, Engl. 1957, 93 (1958). 

The Chemical Structure of the Hemicelluloses, E. L. Hirst, Pure Appl. Chem., 5,53 (1962). 

Although the approximate contents of major lignin linkages are now reasonably well understood [23,277], the chemical structure of lignin, unlike cellulose or hemicellulose, still cannot be precisely defined. Since carbon-carbon... 

C) Partial chemical structure of O-acelyl-4-O-methylglucuronoxylan (a hardwood hemicellulose). 

Garcia D.B. et al. (2008) Cellulose Hemicellulose Phenolic compounds Some hours 30% 40% Huge dependency of the adsorption process on the chemical structure of the sorbate... 

Glucomannan is the most commonly used form of the hemicelluloses. The chain structure consists of a linear backbone of (l,4)-linked p-D-mannopyranosyl units to which (l,6)-linked a-D-galactopyranosyl units are snbstituted. The Man Gal ratio in the chemical structure of glucomannan shown in Figure 28.4 is 2 1. Glucomannan is a water-soluble polysaccharide that is considered a dietary fiber. It is commonly nsed as a food additive, as an emulsifier, and a thickener. It is also used in drug delivery applications. Glucomannans have been specifically derived from softwoods. 

The chemical structure of hemicelluloses is the most important factor that influences their properties [1,4,7]. 

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