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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.