Oxidation reactions of cellulose

J.C. Artur, 0. Hinojosa, Oxidative reactions of cellulose initiated by free radicalsZZ J. Polym. Sci. part C (1971), No 36, 53-71. 

Takahashi, A. and Takahashi, S. (1973) Oxycellulose. II. Oxidation reaction of cellulose with nitrogen... 

In this chapter, the state of the art on the pyrolysis and thermo-oxidation reactions of cellulose and of two very common cellulosic substrates (namely, cotton and paper) has been thoroughly reviewed. The reaction mechanisms involved in the degradation processes have been extensively described, taking into consideration the conditions that may favour the formation of either volatile species, or char. More specifically, the... 

Oxidation Reaction of Cellulose Samples 2.1) Choice of oxidation reaction... 

Hydroxyalkylcellulose. Reaction of cellulose with ethylene or propylene oxides produces hydroxyethyl or hydroxypropyl derivatives. By forming the hydroxyethyl derivative about the same ratio of hydrogen bonding sites to carbon atoms is provided as in the underivatized cellulose, but the substituent groups reduce the fit between polymer chains so that the derivative can be dissolved in water to produce stable solutions. The cellulose derivative has many of the solution properties of guaran. 

Typical reactions of cellulose, such as oxidation or chain cleavage, can be caused by many different reagents and conditions. It will thus be difficult to relate the reaction outcome to the presence of a specific intermediate. 

Hydroxyalkyl celluloses are obtained in the reaction of cellulose with alkene oxides or their corresponding chlorohydrins. The reaction is a base-catalyzed SN2-type substitution, and the reaction rate is proportional to the product [epoxide][CelI—O3]. The commercial preparations include hy-droxyethyl- and hydroxypropylcellulose for which ethylene oxide and propylene oxide are used as reagents. Hydroxyethylcellulose is formed according to the following equation ... 

In this book, he emphasized the importance of the microscopic and the submicroscopic structure of fibrous high polymers. The reactions of cellulose with water, aqueous alkalis, organic bases, ammonia, and strong salt solutions were all stressed. Special attention was given to various types of cellulose esters, to cellulose xanthate, and to the cellulose ethers. The oxidation of cellulose under a variety of conditions was described, as were the hydrolysis reactions. The latter included discussions on reversion and on the kinetics of acid hydrolysis. It is interesting to note that Heuser, who earlier had criticized the terms hydrocellulose and oxycellulose, and had... 

When cellulose is exposed to the unlimited supply of oxygen present as 21% of the air, unstable peroxide radicals form. In the autocatalytic reaction of cellulose oxidation, decomposition of peroxide forms cellulose radicals that react with oxygen to form R02- radicals. These radicals attack other cellulose molecules to form oxycelluloses (carbonyl, aldehyde, and carboxyl acid groups) along with more cellulose free radicals (34). 

The experiments of Schwenker and Beck also throw further light on the mechanism of the secondary reactions. In these experiments, cellulose was pyrolyzed in atmospheres of air, nitrogen, and helium, and essentially the same products were obtained, regardless of the conditions of pyrolysis. Therefore, it was concluded that the secondary decomposition reactions must, by-and-large, be non-oxidative in nature, in contrast with the primary reactions of cellulose on slow heating, which involve oxidation of the compound to provide carbonyl and carboxyl groups. 

It has long been known that, during the reaction of cellulose with ethylene oxide, the 2-hydroxyethyl subtituents react further, to give... 

Some fungi can also secrete enzymes that catalyze oxidation reactions of either cellulose itself or the lower molecular weight oligomers from the enzymatic hydrolysis of cellulose. Of these, the peroxidases can provide hydrogen peroxides for free radical attack on the C2-C3 positions of cellulose to form... 

The reaction of cellulose with various oxidizing agents under acidic, neutral or alkaline conditions not only leads to chemical modification, but invariably to decreases in molecular weight (or degree of polymerization (D.P.)), which in turn leads to losses in strength properties. Indeed, this is one of the principal problems encountered in the bleaching, an oxidative reaction, of cotton and wood fibers to improve their brightness. 

The formation of cuprous oxide fiom reaction of cellulose with Fehling s solution provide a number known as the copper number. The test is well- standardized and gives a quantitative measure of the reducing ability of a cellulose sample (10). 

Oxidative depolymerization of cellulose occurs during the bleaching of wood pulp under alkaline conditions (alkali-oxygen and alkali-peroxide bleaching processes) leading to losses in pulp strength and involve the reactions outlined above. The oxidation at the C-2, -3 or -6 hydrot ls usually is initiated by hydroxyl radicals... 

Prepared by the reaction of cellulose with ethylene oxide or 2-chloroethanol. 

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