Cellulose chemical classification

This chemical classification is of little use with respect to the various applications as biopolymers, in which most of the time interactions with solvents are involved. This is illustrated by the fact that the solubility of a given compound may change completely with the degree of substitution and/or with the molar substitution. This is for example the case of HPC and NaCMC which are commercially available as insoluble and water-soluble products. We therefore use a classification of cellulose-based biopolymers made according to their behavior in water and to their ionic character (Table 2). 

As indicated in the first part of the chapter, this type of classification based on the occurrence of polysaccharides offers some disadvantages, particularly in that some materials such as chitin, hyaluronic acid, and cellulose occur in plants or microorganisms as well as in animals. However, until more chemical work is done, a strictly chemical classification does not seem feasible. The conflicting classifications and nomenclature in this field need standardization and agreement. 

DOT CLASSIFICATION 8 Label Corrosive SAFETY PROFILE Poison by intraperitoneal route. Moderately toxic by ingestion, skin contact, subcutaneous, intravenous, and intramuscular routes. A corrosive irritant to skin, eyes, and mucous membranes. Human mutation data reported. Flammable when exposed to heat or flame. A powerful base. Reacts violently with acetic acid, acetic anhydride, acrolein, acrylic acid, acrylonitrile, cellulose, chlorosulfonic acid, epichlorohydrin, HCl, HF, mesityl oxide, HNO3, oleum, H2SO4, p-propiolactone, vinyl acetate. To fight fire, use foam, alcohol foam, dry chemical. When heated to decomposition it emits toxic fumes of NOx. See also AMINES. 

The classification of polymers previously described has been used in this book for the discussion of pyrolysis results. An important class of polymers that is not discussed here is that of chemically modified natural polymers (or semisynthetic polymers). Examples of such polymers are the modified celluloses (carboxymethyl cellulose, ethyl cellulose, etc ), modified starches, casein plastics (Galalith), etc. These types of compounds were discussed in the book on pyrolysis of natural organic polymers [2]. 

Another important limitation is the practical necessity of limiting the number of groupings that are established. In practice this works out so that only a small portion of the totality of logically valid classes and subclasses are set up. Dyestuffs, for example, might be classified on the basis of their chemical constitution, materials which they are used to color, methods of application, and the color imparted. When the classification is affected on the basis of chemical constitution, then a person who may be interested in dyes as chemical substances finds that his purpose is served very well. On the other hand, such classification may provide little assistance to a searcher who is interested in finding all the dyes used to color a certain type of material such as cellulose ester textiles. In establishing a classification system based on fixed compartments, arbitrary decisions must be made as to the basis for classification. If such decisions are in line with the user s... 

If the sponge is left to dry in the sun, this adsorbed water will evaporate, leaving only a small proportion of water bound chemically to the salts and to the cellulose of the sponge fibers. Like water in sponge, water is held in food by various physical and chemical mechanisms (Table 3.1). It is a convenient oversimplification to distinguish between free and bound water. The definition of bound water in such a classification poses problems. Fennema (1985) reports seven different definitions of bound water. Some of these definitions are based on the freezability of the bound component, and others rely on its availability as a solvent. He prefers a definition in which bound water is that which exists in the vicinity of solutes and other non-aqueous constituents, exhibits reduced molecular activity and other significantly altered properties as compared with bulk water in the same system, and does not freeze at -40"C."... 

Tomme P, Warren AJ, Miller Jr. RC, KUburn DG, GUkes NR (1995) Cellulose-binding domains classification and properties. In Saddler JN, Penner MH (eds) Enzymatic degradation of insoluble carbohydrates. American Chemical Society, Washington, DC, pl42 Irwin D, Walker L, Spezio M, Wilson D (1993) Biotech Bioengin 42 1002... 

While the methods for characterizing celluloses on the basis of their accessibility have been useful, they do not provide a basis for understanding the level of structure at which the response of a particular cellulose is determined. This follows from the ratlier simple categorization of the substrate cellulose into ordered and disordered fractions corresponding to the fractions that are thought to be crystalline and those that are not. This classification does not allow discrimination between effects that have their origin at the level of secondary structure and those that arise from the nature of the tertiary structure. Thus, in terms of chemical reactions, this approach does not facilitate separation of steric effects that follow from the conformation of the molecule as it is approached by a reacting species, from the effects of accessibility, which is inherently a consequence of the tertiary structure. 

The classification system is describing not only the chemical family belonging to a specific mode of action but all compounds via their common names counted to each family, as shown in Table 1.2 for the modes of action such as Inhibition of DHP (dihydropteroate) synthase , Microtubule assembly inhibition , Inhibition of mitosis/microtubule organization , Inhibition of VLCFAs (Inhibition of cell division) and Inhibition of cell wall (cellulose) synthesis as examples (not mentioned in other chapters of this book) (for a detailed table see www. plantprotection.org/HRAC/). The scheme The World of Herbicides available under this internet address also shows all chemical structures of the different herbicides belonging to the different chemical families. 

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