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KFUPM-CHEMISTRY DEPARTMENT INDUSTRIAL ORGANIC CHEMISTRY CHEM 456_072 Homework 2 (Chapter 6) STUDENT NAME: Mosaab Al Sunaidi 1. STUDENT ID.: 259481 What types of polysaccharides are present in cotton? In which other plants these polysaccharides are also present? Give the structure and the characteristics of these polysaccharides. Cellulose, which is the most abundant type of polysaccharides. It exits in the cell wall of green plants, for example, trees. Cellulose is derived from D-glucose units, which condense through β(1→4)-glycosidic bonds. Cellulose is taste- and odorless, hydrophilic, not soluble in water or most organic solvents, chiral and biodegradable 2. What are the differences in terms of structures and properties between lactose and cellobiose? In terms of structure: both lactose and cellobiose have the same molecular formula and molecular mass. Cellobiose is consist of two glucose units joined with β(1→4) linkage, whereas lactose consist of β-D-galactose and β-D-glucose with β1-4 glycosidic linkage cellobiose In proparities: both lactose and cellobiose are disaccarides. Lactose is more soluble than cellobiose with a solubility of 21.4 g per 100 ml of water, while cellobiose is 12 g per 100 ml water (25'C). 3. Explain clearly the role of CO2, SO2, and Mg2+ in the sugar industry. In sugar industry, the process of purification of sugar involves the use of CO2 and SO2 with lime in order to produce plantation white sugar (or light brown color). SO2 and CO2 are bubbled through a mixture of sugar with other impurities. Some organic acids and phosphate will precipitate as calcium salts and colloid flocculate. Addition of excess carbon dioxide removes the excess lime, which is left in solution which will result in a solution called “thin juice”. In juice purification also, ion exchanger method is used. the substitution of Ca2+ and Mg2+ for the alkali ions (Na+, K+) softens the thin syrup and prevents the formation of hardness scale on the evaporator coil. The larger pore ion exchangers also help in bleaching of the thin juice due to the binding of pigments mainly by adsorption in the ion exchangers 4. How the conversion of starch into sugars is measured? How the concentration of sugar solution is measured? The extent of starch conversion into sugars is generally expressed as dextrose equivalents (DE value), i.e., the amount of reducing sugars produced, calculated as glucose (DE value: glucose = 100, starch = 0). The concentration of sugar solution is measured on the Brix scale which is a density scale for sugar (sucrose) solutions.The degrees on the scale Brix are numerically equal to the percentage of sucrose in the solution (e.g. 65 to 68 degrees Brix is 65-68% sucrose in solution). 5. Describe natural source of aspartame and the reactions of synthesis of the synthetic aspartame. Aspartame is metabolized in our bodies to its components: aspartic acid, phenylalanine, and methanol. Like other amino acids, it provides 4 calories per gram. Since it is about 180 times as sweet as sugar, the amount of aspartame needed to achieve a given level of sweetness is less than 1% of the amount of sugar required. Thus 99.4% of the calories can be replaced. In the synthesis of aspartame, the starting materials are a racemic mixture (equal quantities of both isomers) of phenylalanine, and aspartic acid. Only the L isomer of phenylalanine is deisred for use. This L isomer may be separated from the D isomer by a chemical pretreatment, followed by a reaction with the enzyme porcine kidney acylase. The final separation occurs with an acidic aqueous and organic extraction, where the L isomer is more soluble in the aqueous layer and the D isomer is more soluble in the organic layer. Ester Synthesis: Treatment of L-phenylalanine with methanol in the presence hydrochloric acid causes an ester reaction with the acid group on the phenylalanine. The product is the methyl ester of phenylalanine. Amide Synthesis: The final goal is to react the methyl ester of phenylalamine with aspartic acid to give the dipeptide amide structure. A series of reactions is required so that only the acid of the base amino acid is reacted. The acid group on the side chain is protected so that it does not react.