Derivatives of cellulose

Several derivatives of cellulose, including cellulose acetate, can be prepared in solution in dimethylacetamide—lithium chloride (65). Reportedly, this combination does not react with the hydroxy groups, thus leaving them free for esterification or etherification reactions. In another homogeneous-solution method, cellulose is treated with dinitrogen tetroxide in DMF to form the soluble cellulose nitrite ester this is then ester-interchanged with acetic anhydride (66). With pyridine as the catalyst, this method yields cellulose acetate with DS < 2.0. 

The potential for use of chiral natural materials such as cellulose for separation of enantiomers has long been recognized, but development of efficient materials occurred relatively recently. Several acylated derivatives of cellulose are effective chiral stationary phases. Benzoate esters and aryl carbamates are particularly useful. These materials are commercially available on a silica support and imder the trademark Chiralcel. Figure 2.4 shows the resolution of y-phenyl-y-butyrolactone with the use of acetylated cellulose as the adsorbent material. 

The plastics industry was launched nearly 150 years ago with the production of certain derivatives of cellulose. However, its real emergence as a growth industry of immense proportions and importance has occurred since World War II with the sustained strong growth of thermoplastics and specialty elastomers. The importance of the polymers industry in modern society is underscored by the myriad of uses already developed for these materials, with more being developed almost daily. Although there are a multitude of polymers that are derived from hydrocarbons, we will only briefly discuss the more common thermoplastics that are made from relatively simple monomers from petroleum. 

Polysaccharide-based CSPs incorporate derivatives of cellulose and amylose adsorbed on silica gel. The selectivity of these CSPs depends upon the nature of the substituents introduced during the derivatization process. The secondary structure of the modified polysaccharide is believed to play a role in selectivity, but the chiral recognition mechanisms have not been fully elucidated [55]. 

Jones et al.S0, sl synthesized a guanine derivative of cellulose, 29 (G-Cellulose), and found that the affinity of biosynthetic polynucleotides for the cellulose is in the order, poly C > Poly A > Poly U. They claimed that hydrogen-bonding between guanine residues and Poly C was probably taking place. 

A comment on the properties of the base employed in reactions that involve the formation of the Vilsmeier-Haack adduct is in order, because several derivatives of cellulose are obtained by this route. Preparation of Cell-Tos has been attempted in LiCl/DMAc, by reacting the polymer with TosCl/base. Whereas the desired product was obtained by employing triethy-lamine, use of pyridine (Py) resulted in the formation of chlorodeoxycellu-lose. In order to explain these results, the following reaction pathways have been suggested [147] ... 

Figure 3.35 Optimized structures of (a) phenylcarbamate 23a and (b) 3,5-dimethylphenylcar-bamate 23x derivatives of cellulose. View along helix axis (top) and perpendicular to hebx axis (bottom).

Ester derivatives of cellulose, chitin, dextran, amylose, and amylopectin were prepared utilizing the acid chloride derivatives described in Part B of the Experimental Section. 

Preweighed 1.0 mg samples of each polysaccharide carbamate derivative were submerged in aqueous solutions at three pH values 3.1 7.0 and 11.3. Three milliliter aliquots were withdrawn at periodic intervals and analyzed by ultraviolet spectroscopy. Typical results are shown in Figures 3 and 4 for pendant hydrolysis rates of carbamate derivatives of cellulose and chitin respectively as a function of pH. 

Table I lists physical data for a number of the carbamate and ester derivatives of cellulose, chitin, amylose, amylopectin, and dextran synthesized as described in the Experimental Section. The solubility of the polysaccharide starting materials as well as that of the produced derivatives allows for macromolecular characterization through techniques including UV, NMR, IR, high pressure liquid chromatography, etc.

Figures 3 and 4 illustrate typical rates of hydrolysis for carbamate derivatives of cellulose and chitin. The rates of release at a pH value 11.3 were considerably higher in both systems than at pH values of 3.1 and 7.0. After seven days in the basic medium the cellulose derivative had delivered 27.3 percent of the available aniline. In the acidic medium and neutral medium 15.6 and 10.6 percent were delivered. After seven days the chitin derivative delivered 27.7, 10.0, and 9.5 percent of the available p-methylaniline in the basic, acidic, and neutral media, respectively.

Cellulose acetate is the most important ester derivative of cellulose. It is produced by acetylation of cellulose using acetic anhydride in acetic acid in the presence of a strong acid catalyst (usually sulfuric acid). In Eq. 9-29 the symbol is a general means of representing a polymer molecule minus the functional group of interest and —OH specifically... 

Various ether derivatives of cellulose, including some that are water-soluble, are important [Heinz and Liebert, 2001 Just and Majewicz, 1985 Zhang, 2001]. Methyl cellulose and car-boxymethyl cellulose (R = CH3 and CH2COOH, respectively) are synthesized by reaction of cellulose with sodium hydroxide followed by the appropriate alkyl halide ... 

The most useful CSPs for the resolution of many varied, structurally different racemates are the following the peracetates, benzoates (and derivatives) and carbamates (and derivatives) of cellulose and amylose coated on wide pore silica gel. Some of these polymer derivatives are also potentially useful as pure polymeric bead material, but mainly for preparative purposes. 

These contain natural or semisynthetic hydrophilic colloidal derivatives of cellulose. 

Many types of derivatives of cellulose have been used to prepare affinity adsorbents.51 0-(2-Aminoethyl)cellulose and 0-(carboxy-methyl)cellulose can be coupled to carbohydrates bearing carboxyl or primary amino groups by the carbodiimide method.52,53 Cellulose derivatives bearing amino groups can be coupled to reducing carbohydrates by reductive-amination reactions25 in which the Schiff base produced in the initial reaction is reduced with sodium cyanoborohy-dride.54... 

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 hypothesis has been published by de Waele [36] that nitrocotton combines with metallic oxides (pigments) through the carboxylic groups. The latter are present in partially oxidized derivatives of cellulose that accompany nitrocellulose. More recently Campbell and Johnson [37] have come to conclusions similar to those of Vodiakov and of de Waele. 

While regarding the formation of the O-nitro derivative of cellulose as an effective resultant from the nitration and denitration processes, the following picture of the course of reaction leading to the formation of nitrocellulose should be kept in mind. 

Other thickeners used include derivatives of cellulose such as methylcellulose, hydroxypropylmethylcellulose, and cellulose gum natural gums such as tragacanth and xanthan (see Cellulose ethers Gums) the carboxyvinyl polymers and the poly(vinyl alcohol)s. The magnesium aluminum silicates, glycol stearates, and fatty alcohols in shampoos also can affect viscosity. 

Richards, G. N. Diazonium derivatives of cellulose as initiators of graft copolymerization. J. Appl. Polymer Sci. 5, 553 (1961). 

Rogovin, Z. A., and U. Zhun-Zhui Structure and properties of cellulose and its esters. LXXXV. Synthesis of new derivatives of cellulose and other polysaccharides. IV. Synthesis of graft copolymers of carboxymethyl cellulose and caprolactam. Vysokomolekulyarnye Soedineniya 1, 1630 (1959). 

Some reactions and derivs of cellulose are given under Cellulose(above). The derivs of interest in the expl industry and allied applications are included here ... 

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