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46 Hydroxymethylfurfural condenses with resorcinolunder the influence of HCl, forming a colored compound: O C HOH 2 C O H HO OH + 2 O C HOH 2 C OH OH O OH chromophore of red color H + - H 2 O resorcinol LESSON 21. CHEMISTRY OF OLIGOSACHARIDES AND POLYSACCHARIDES Required basic level of knowledge. Structure and properties of polyhydric alcohols. Structure and properties of aldehydes and ketones. The reaction of aldehydes with alcohols to form hemi- acetals. Qualitative reactions to aldehyde group (reaction of silver «mirror», re- duction of copper (II) hydroxide). Structure and properties of monosaccharides. Condensation reaction. Questions for the preparation for the lesson. 1. Oligosaccharides. Disaccharides. Definition. Examples (maltose, sucrose, lactose). Physical and chemical properties of disaccharides. Hydrolysis of di- saccharides. Reducing properties of disaccharides. 2. Polysaccharides. Definition. Classification. 3. Homopolysaccharides. Definition. The structure of starch (amylose, amy- lopectin), glycogen, cellulose. Pectin substances. Aqualitative reaction to starch and glycogen. Reactions of hydrolysis of starch and glycogen. The medico- biological role of homopolysaccharides 4. Heteropolysaccharides. Definition. Glycosaminoglycans. Definition, classification, fragments of formulas of hyaluronic acid, chondroitin sulfate. Polyanionic properties of glycosaminoglycans. The medico-biological role of glycosaminoglycans. Test-control on the topic «Carbohydrate Chemistry».