Page 29 - FPGEE Medicinal and Organic Chemistry Q&A Book
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Krisman
Acetone Isomers: 420. (a) The Iodine value or number is defined
as the number of grams of iodine that are
O OH consumed by carbon-carbon double bonds
(C=C) present in 100 grams of the fat or oil.
CH C CH CH C CH
3 3 3 2 The iodine number is used to determine the
Keto form Enol form amount of unsaturation contained in fatty acids.
The higher the iodine number, the more unsat-
urated fatty acid bonds are present in a fat. Since
418. (b) Hydrogenation is the chemical reaction saturated fatty acids have no double bonds, its
that results in the addition of hydrogen (H ). The iodine number is zero.
2
process is usually employed to a reduced or satu-
rated organic compound. The process typically 421. (c) A fatty acid is a carboxylic acid often
constitutes the addition of pairs of hydrogen with a long unbranched aliphatic tail (chain),
atoms to a molecule. which is either saturated or unsaturated. Car-
The hydrogenation of an oil to a fat is boxylic acids as short as butyric acid (4 carbon
called hardening. Hydrogenation is widely atoms) are considered to be fatty acids, whereas
applied to the processing of vegetable oils and fatty acids derived from natural fats and oils may
fats. Complete hydrogenation converts unsat- be assumed to have at least 8 carbon atoms, e.g.
urated fatty acids to saturated ones. Hydroge- caprylic acid or octanoic acid. Fatty acids are
nation results in the conversion of liquid veg- produced by the hydrolysis of the ester link-
etable oils to solid or semi-solid fats, such as ages in a fat or biological oil with the removal
those present in margarine. Changing the degree of glycerol.
of saturation of the fat changes some important
physical properties such as the melting point, 422. (c) Soap is a surfactant cleaning compound,
which is why liquid oils become semi-solid. used for personal or minor cleaning. It is a mix-
ture of salts of fatty acids. Detergent is defined
419. (b) Saponification is the hydrolysis of an as a cleaning compound with soap-like property.
ester under basic conditions to form an alcohol
and the salt of a carboxylic acid. Saponifica- 423. (d) Triglyceride is a glyceride in which the
tion value or saponification number represents glycerol is esterified with three fatty acids. It is
the number of milligrams of potassium hydrox- the main constituent of vegetable oil and ani-
ide or sodium hydroxide required to saponify mal fats. Triglycerides are formed from a single
1g of a fat or oil. In the saponification reaction, molecule of glycerol, combined with three fatty
one mole of a fat reacts with three moles of KOH acids on each of the OH groups, and make up
or NaOH since the fat has three ester groups. most of fats digested by humans. Ester bonds
form between each fatty acid and the glycerol
168000 molecule. This is where the enzyme pancreatic
Saponification number of fat =
MW of fat lipase acts, hydrolyzing the bond and
“releasing” the fatty acid. In triglyceride form,
A lower saponification number indicates lipids cannot be absorbed by the duodenum.
high- molecular-weight fatty acid residues in the Fatty acids, monoglycerides (one glycerol, one
given fat, whereas a higher saponification fatty acid) and some diglycerides are absorbed
number indicates the low molecular weight fatty by the duodenum, once the triglycerides have
acid residues. been broken down. In the human body, high
levels of triglycerides in the blood
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