Cellulose chemically reacts with oxidants to produce a series of substances with different structures from the original cellulose. This reaction process is called cellulose oxidation. (Quoted from Guo Lizhu Archives Protection Technology) The base ring of cellulose macromolecule is a macromolecular polysaccharide composed of D-glucose with β-1,4 glycosidic bonds, and its chemical composition contains 44.44% carbon, 6.17% hydrogen, and 49.39% oxygen. Due to different sources, glucose residues in cellulose molecules
The number of groups, the degree of polymerization (DP), is in a wide range. It is the main component of cell walls of vascular plants, lichen plants and some algae. Cellulose is also found in the capsules of Acetobaeter and caudate animals. Cotton is high-purity (98%) cellulose. The so-called α-cellulose (α-cellulose) refers to the part that cannot be extracted from the complete cellulose standard sample of the original cell wall with 17.5% NaOH. β-cellulose (β-cellulose) and γ-cellulose (γ-cellulose) are cellulose corresponding to hemicellulose. Although α-cellulose is usually mostly crystalline cellulose, β-cellulose, γ-cellulose chemically contains not only cellulose, but also various polysaccharides. The cellulose of the cell wall forms microfibrils. The width is 10-30 nanometers, and some are several micrometers in length. Using X-ray diffraction and negative dyeing method (negative dyeing method), according to electron microscope observation, the crystalline part of the chain molecules arranged in parallel constitutes basic microfibers with a width of 3-4 nanometers. It is speculated that these basic microfibers collectively constitute microfibers. Cellulose can be dissolved in Schwitzer reagent or concentrated sulfuric acid. Although it is not easy to use acid hydrolysis, dilute acid or cellulase can make cellulose produce D-glucose, cellobiose and oligosaccharides. There is an enzyme (cellulose synthase (UDPforming EC 220.127.116.11)) that transfers glycosides to synthesize cellulose from UDP glucose primers in acetic acid bacteria. Standard samples of granular enzymes with the same activity have been obtained in higher plants. This enzyme is usually It uses GDP glucose (cellulose synthase (GDP forming) EC18.104.22.168), in the case of UDP glucose transfer, the mixing of β-1, 3 bonds occurs. The formation site of microfibers and the mechanism of controlling the arrangement of cellulose are still It is not very clear. On the other hand, in terms of the decomposition of cellulose, it is estimated that when the primary cell wall stretches and grows, a part of the microfiber is decomposed by the action of cellulase and becomes soluble.
Water can cause limited swelling of cellulose, and some aqueous solutions of acids, alkalis and salts can penetrate into the crystalline area of the fiber to produce infinite swelling and dissolve the cellulose. The cellulose does not change significantly when heated to about 150°C. If the temperature is exceeded, it will gradually coke due to dehydration. Cellulose hydrolyzes with concentrated inorganic acid to generate glucose, etc., reacts with concentrated caustic solution to generate alkali cellulose, and reacts with strong oxidant to generate oxidized cellulose.
Post time: Aug-07-2020