1. Solubility
At normal temperature, cellulose is not soluble in water, nor in general organic solvents, such as alcohol, ether, acetone, benzene, etc. It is also insoluble in dilute alkali solution, and can be soluble in copper ammonia Cu (NH3) 4 (OH) 2 solution and copper ethylenediamine [NH2CH2CH2NH2] Cu (OH) 2 solution. Therefore, it is relatively stable at room temperature because of hydrogen bonds between cellulose molecules.
2. Cellulose hydrolysis
Under certain conditions, cellulose reacts with water. During the reaction, the oxygen bridge breaks, and water molecules are added at the same time. Cellulose changes from long-chain molecules to short-chain molecules, until the oxygen bridge breaks completely and becomes glucose.
3. Cellulose oxidation
The chemical reaction between cellulose and oxidant produces a series of substances with different structure from the original cellulose. This reaction process is called cellulose oxidation. The base ring of cellulose macromolecule is D-glucose β- The chemical composition of macromolecular polysaccharides composed of 1,4 glycosidic bonds contains 44.44% carbon, 6.17% hydrogen and 49.39% oxygen. Due to different sources, the number of glucose residues in cellulose molecules, that is, the degree of polymerization (DP), is in a wide range and is the main component of vascular plants, lichens and some algae cell walls. Cellulose is also found in the capsule of Acetobacter and in the capsule of cercospora. Cotton is high purity (98%) cellulose. so-called α- Cellulose（ α- Cellulose) refers to the part that cannot be extracted with 17.5% NaOH from the complete cellulose standard sample of the original cell wall. β- Cellulose（ β- cellulose）、 γ- Cellulose（ γ- Cellulose) is cellulose corresponding to hemicellulose. Although, α- Cellulose is usually mostly crystalline cellulose, β- Cellulose γ- In addition to cellulose, cellulose also contains various polysaccharides. Cellulose in the cell wall forms microfibers. The width is 10-30 nanometers, and the length is several microns. Using X-ray diffraction and negative staining method (negative staining method), according to the observation of electron microscope, the crystalline part of chain molecules arranged in parallel forms a basic microfiber with a width of 3-4 nanometers. It is speculated that these basic microfibers together form microfibers. Cellulose can be dissolved in Schwitzer reagent or concentrated sulfuric acid. Although it is not easy to hydrolyze with acid, dilute acid or cellulase can make cellulose produce D-glucose, cellobiose and oligosaccharide. In acetic acid bacteria, there are enzymes that transfer glycosides from UDP glucose primer to synthesize cellulose. Standard samples of granular enzymes with the same activity have been obtained in higher plants. This enzyme usually takes advantage of GDP glucose and occurs when it is transferred from UDP glucose β- Mixing of 1,3 bonds. The formation site of microfibers and the mechanism of controlling cellulose arrangement are still unclear. On the other hand, in terms of cellulose decomposition, it is estimated that when the primary cell wall expands and grows, a part of the microfiber is decomposed and becomes soluble due to the action of cellulase.
Water can cause limited swelling of cellulose, and some acid, alkali and salt aqueous solutions can penetrate into the fiber crystallization zone to produce infinite swelling and dissolve cellulose. Cellulose does not change significantly when heated to about 150 ℃, and will gradually coking due to dehydration above this temperature. Cellulose hydrolyzes with concentrated inorganic acid to form glucose, reacts with concentrated caustic solution to form alkali cellulose, and reacts with strong oxidant to form oxidized cellulose.
4. Compliance
Cellulose has poor flexibility and is rigid because:
(1) Cellulose molecules have polarity and strong interaction between molecular chains;
(2) The six-membered pyran ring structure in cellulose makes internal rotation difficult;
(3) Both intramolecular and intermolecular hydrogen bonds can be formed in cellulose, especially the intramolecular hydrogen bonds can not rotate the glycosidic bonds, which greatly increases its rigidity.
