Mechanism of the oxidation of cellulose with nitrogen oxides

Kaverzneva, E. D.; Salova, A. S.

doi:10.1007/bf00917382

Cited by 3 publications

(2 citation statements)

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“…6-carboxycellulose can be obtained by oxidation using nitrogen dioxide (NO 2 ) in a non-polar solvent, such as tetrachloromethane. This oxidation implies a rather complex mechanism, which includes adsorption of nitrogen oxides on the surface of cellulose, diffusion of oxidants into the structure of cellulose particles or fibers, whereby unstable cellulose nitrites are formed as intermediates (Kaverzneva & Salova, 1959). The literature provides a description of several oxidation processes with nitrogen oxides (Coseri et al, 2013), some of which are applied in industrial conditions, while some of them are used only in laboratories due to their complexity.…”

Section: Obtaining Oxidized Cellulose (6-carboxycellulose)mentioning

confidence: 99%

Medical and pharmaceutical application of oxidized cellulose

Grabovac

Sailović

Lipic

2020

GHTERS

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Cellulose is the most abundant natural polymer and versatile starting material for chemical modification for obtaining products with various applications. The oxidation of cellulose results in derivatives with improved properties, including the products with new, specific features that can be used for medical and pharmaceutical purposes. Due to its biocompatibility and biodegradibility, the oxidized cellulose (6-carboxycellulose) is widely used as a hemostatic agent, as a barrier for the prevention of postsurgical adhesion, in bandage products for covering different wounds, as an excipient in the production of tablets, various gels and pharmaceutical suspensions. In addition to these applications, the oxidized cellulose may be used for the production of surgical sutures, as a drug carrier in products with gradual/controlled release, and as a material in tissue engineering.

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Section: Obtaining Oxidized Cellulose (6-carboxycellulose)mentioning

confidence: 99%

Medical and pharmaceutical application of oxidized cellulose

Grabovac

Sailović

Lipic

2020

GHTERS

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“…Then CS was separated from the solution on a porous glass filter, washed with water:isopropanol (1:1 v/v) until the rinsings were neutral, and dried in air at room temperature. The number of carboxylic acids was determined by the Ba-acetate method [11]; the number of carbonyls, by a modified hydroxylamine method [12]. The degree of substitution (DS) of the COOH groups was calculated using the formula DS COOH = (162.15 × C COOH )/(4500 -14 × C COOH ) where 162.15 is the molecular weight of the GPU and C COOH is the number of carboxylic groups in mass %.…”

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Structural modification of potato starch by solutions of nitrogen(IV) oxide in CCl4

et al. 2007

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Structural transformations of potato starch by solutions of nitrogen(IV) oxide in CCl 4 were studied as a function of oxidant concentration, starch moisture content, reaction time, and molar ratio of reactants. Oxidized starches with various numbers of carboxylic acids were studied by x-ray phase analysis, 13 C NMR, and IR spectroscopy. It was found that carboxylic acids were formed primarily on C 6 in starch oxidation products that were x-ray amorphous. The number of carboxyls increased slightly with increased oxidation time and oxidant concentration. It was shown that moisture must be present in the starch for oxidation by nitrogen(IV) oxide to be effective.Starch production has recently become more interesting [1-6] because modified starches have a unique set of physical chemical properties and the starting material can be constantly renewed.The goal of the present work was to investigate the effect of various factors on oxidative transformations of starch by solutions of nitrogen(IV) oxide (N 2 O 4 ) in CCl 4 .Starch oxidation by N 2 O 4 follows mainly the following scheme:A study of the effect of the glucopyranose unit (GPU):N 2 O 4 mole ratio at constant N 2 O 4 concentration ( Fig. 1) on the rate of oxidative transformations of the polysaccharide revealed the effect of the reaction products (NO, H 2 O, HNO 3 , N 2 O 3 , HNO 2 ) on the reaction. The higher the mole ratio of reactants, the lower the oxidant concentration and the change of composition during the reaction. Increasing the amount of oxidant under otherwise equal conditions increased both the rate and the maximum degree of starch oxidation in the studied time interval. Further increasing (>10 moles) the excess of oxidant had no effect on the process. Therefore, all subsequent kinetic studies were carried out with a 10-fold excess of N 2 O 4 relative to the stoichiometric amount required for full oxidation of the primary hydroxyls to carboxylic acids.The results show ( Table 1) that changing the N 2 O 4 concentration from 5 to 20 mass % with a constant mole ratio of reactants increased the oxidation and the reaction rate to their upper limits. This can be explained by the activating action of N 2 O 4 , which can cleave intermolecular H-bonds and increase the rate of diffusion processes close to the quasihomogeneous value by penetrating into the starch granules. The activating action of N 2 O 4 is quite consistent with the observed morphology change of the starch granules (Fig. 2). As the N 2 O 4 solution concentration increased, the starch granules underwent greater changes.

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