Polysaccharides ethers, industrial

A variety of polysaccharide ethers are produced industrially. They include methyl, ethyl, hydroxyethyl, hydroxypropyl, and carboxymethyl ethers. Combinations of these with other subslitulions are often seen. Because of the wide range of properties produced and low cost, etherifications are among the most common industrial modifications. The mechanism for etherification varies, depending on the desired subslitulion. Methylalion can be achieved with a simple Williamson synthesis where the hydroxyl is exposed by the addition of caustic soda [Figure 2] (4). 

Taylor H. Evans and Harold Hibbert, Bacterial Polysaccharides 203 E. L. Hirst and J. K. N. Jones, The Chemistry of Pectic Materials 235 Emma J. McDonald, The Polyfructosans and Difructose Anhydrides 253 Joseph F. Haskins, Cellulose Ethers of Industrial Significance. 279... 

Abstract The telomerization of butadiene with alcohols is an elegant way to synthesize ethers with minimal environmental impact since this reaction is 100% atom efficient. Besides telomerization of butadiene with methanol and water that is industrially developed, the modification of polyols is still under development. Recently, a series of new substrates has been involved in this reaction, including diols, pure or crude glycerol, protected or unprotected monosaccharides, as well as polysaccharides. This opens up the formation of new products having specific physicochemical properties. We will describe recent advances in this field, focusing on the reaction of renewable products and more specifically on saccharides. The efficient catalytic systems as well as the optimized reaction conditions will be described and some physicochemical properties of the products will be reported. 

Introduction. Today nitrocellulose is one of most important derivatives of cellulose used in industry and commerce, and a major product of the chemical industry. Its wide and manifold applications are due mainly to its extraordinary physical properties. Thus a protective coating of nitrocellulose varnish, a nitrocellulose film or a tube of smokeless powder — all are characterized by relatively high elasticity and mechanical strength. These properties are a direct consequence of the microstructure of cellulose, which is composed of highly oriented long-chain molecules of polysaccharide. Not only nitrocellulose, but also other derivatives of cellulose, such as other esters and ethers, demonstrate similar characteristics. 

A much more extensive investigation of the effect of alkalies has been made in the case of polysaccharides, especially cellulose this is understandable in view of the industrial importance of mercerization, of the viscose process, and of cellulose ethers. Various complexes have been reported for cellulose and alkalies depending upon the nature of the alkali, upon its concentration, upon the washing treatment used, and upon the pretreatment of the cellulose. A discussion of this subject has been published by Nicoll and Conaway.84 There is general agreement on the formation of several compounds, which are susceptible to hydrolysis. The question as to whether these compounds are molecular complexes (XLVII), true alkoxides (XLVIII), or an equilibrium mixture of the two has not been answered. In recent studies Lauer65 has reached... 

In contrast, CSPs have achieved great repute in the chiral separation of enantiomers by chromatography and, today, are the tools of the choice of almost all analytical, biochemical, pharmaceutical, and pharmacological institutions and industries. The most important and useful CSPs are available in the form of open and tubular columns. However, some chiral capillaries and thin layer plates are also available for use in capillary electrophoresis and thin-layer chromatography. The chiral columns and capillaries are packed with several chiral selectors such as polysaccharides, cyclodextrins, antibiotics, Pirkle type, ligand exchangers, and crown ethers. 

Chiral separations can be considered as a special subset of HPLC. The FDA suggests that for drugs developed as a single enantiomer, the stereoisomeric composition should be evaluated in terms of identity and purity [6]. The undesired enantiomer should be treated as a structurally related impurity, and its level should be assessed by an enantioselective means. The interpretation is that methods should be in place that resolve the drug substance from its enantiomer and should have the ability to quantitate the enantiomer at the 0.1% level. Chiral separations can be performed in reversed phase, normal phase, and polar organic phase modes. Chiral stationary phases (CSP) range from small bonded synthetic selectors to large biopolymers. The classes of CSP that are most commonly utilized in the pharmaceutical industry include Pirkle type, crown ether, protein, polysaccharide, and antibiotic phases [7]. 

The ozonation method has provided novel insight into the stereo structure of lignin side chains. It has other important biological and industrial outcomes, such as the analysis of benzylic ether bonds established between lignins and polysaccharides [112],... 

The reaction of polysaccharides ivith aldehydes to give cross-linked products has been known and exploited industrially for some time. Starch acetals may also be prepared by a method that does not give rise to cross-links and involves treatment of starch with a cyclic vinyl ether, 3,4-dihydro-2H-pyran, to give a tetrahydropyran-2-yl derivative (16). At low levels of substitution, the acetals are water-soluble, at... 

Desmarais AJ, Wint RF. HydroxyaUcyl and ethyl ethers of cellulose. In Whistler RL, Be-Miller JN, eds. Industrial Gums Polysaccharides and Their Derivatives. San Diego Academic Press, 1993 505-535. 

Numerous ethers of cellulose, starch, and bacterial dextran are of established or potential industrial importance. (See also Chapter XII.) Treatment of the polysaccharides with alkali and methyl chloride, ethyl chloride, benzyl chloride, ethylene oxide (or ethylene chlorohydrin), sodium chloro-acetate, and allyl bromide gives, respectively, the methyl, ethyl, benzyl, hydroxy ethyl, carboxy methyl, and allyl ethers. The cellulose derivatives... 

Hydroxyl groups of polysaccharides are etherified readily by low-molec-ular-weight alkyl halides, alkyl sulfates, vinyl derivatives, and epoxides. Although a wide variety of ethers may be made, very few have found industrial importance. The cellulose ethers of industrial importance are the methyl, ethyl, cyanoethyl, and carboxymethyl ethers. 

There has been a worldwide realization diat nature-derived monosaccharides, disaccharides, oligosaccharides and polysaccharides can provide us with the raw materials needed for the production of numerous industrial consumer goods (Kunz, 1993 Varma, 2003 Pacitti, 2003). This section will deal with the role of sugar molecules anchored like pendants onto a synthetic polymer, reminiscent of the crown ether type molecules pendant on polystyrene and other synthetic chains which created a whole new area of research with far-reaching outcomes (Gokel and Durst, 1976 Varma, 1979 Varma et al, 1979 Smid et al, 1979a, Shah and Smid, 1978 Smid et al, 1979b Varma and Smid, 1977). 

---