lipids chemlab report
TRANSCRIPT
LipidsBayan, Charmaine Rose Jean L.
Himor, Jomarie Mhel P.Marquez, Ella Mae H.
Objectives:
• To distinguish the different properties of lipids through the different test performed and different reagents used.
Data and ResultsSAMPLE SOLVENT USED RESULT EXPLANATION
Cottonseed Oil Distilled Water
Ethyl Alcohol
Insoluble; formation of
globules
There are more hydrocarbons in a
lipid molecule which are largely hydrophobic than their polar side,
thus, making them insoluble especially
in polar solvent
EtherSoluble; clear; one
phaseThey are non-polar solvents, thus the lipid molecules are
soluble in them because of the
presence of Vander waals forces.
ChloroformSoluble;
translucent; one phase
Benzene Soluble; one phase
Data and ResultsMIXTURE RESULT EXPLANATION
Cottonseed oil-ethyl alcohol
Cottonseed oil-ether
Name for Test Sample Reagent needed
Results Explanation
Test for unsaturation Oleic Acid Bromine in
CCl4
3 drops needed to change
There is a lesser number
of double bonds in the oleic
acid, thus the color changed
right away
Palmitic Acid CholoroformHanus Iodine
Light pink to light yellow (30
minutes)It took a while for it to change since there are
more unsaturated
bonds in these group of lipids.
Oleic Acid ChloroformHanus Iodine
Light pink to light yellow (30
minutes)
Cottonseeed Oil
ChloroformHanus Iodine
Light pink to light yellow (30
minutes)
Name of Test Sample Reagent Added Result Explanation
a. Acrolein Test Glycerol KHSO4 No odor
There is no odor because fats are
odorless
Cottonseed KHSO4 No odorThere is no fat present in the
cottonseed oil, thus, it smelled like
chicharon/used oil
b. Rancidity Test Fresh
Coconut OilPhenolphtalein Colorless
There is no reaction
Methyl Orange Red
OrangeThe solution became
acidic
pH paperBlue color of
the litmus paper
remained the same
The fatty acids are still present in the fresh coconut oil. Thus changing the
blue litmus paper to red
Name of Test Sample Reagent Used Reaction Explanationb. Rancidity Test
Rancid Coconut Oil
Phenolphthalein No change, same color
with the rancid oil
The fatty acids are still present in the glycerol. Thus changing
the litmus paper into red.
Methyl Orange Red
Orange
pH paper Blue color of the litmus
paper remains the
same
Name of Test Sample Reagent Used Reaction Explanation
E. Saponification
Coconut Oil 10% Potassium Hydroxide(KOH)
Formation of gelatinous mass
Name of Test Sample Reagent Used Reaction ExplanationF. Properties of
Salting OutSoap Solution NaCl Crystallized
formed
White substance
Smells like coconut
Formation of Fatty Acids
Soap Solution 10% HCl Cloudy solution
Formation of bubbles on the walls of the test
tubeInsoluble Soaps Soap Solution 5% CaCl2 White
precipitate formed
Cloudy Solution
Name of Test Sample Reagent used Reaction ExplanationInsoluble Soaps Soap solution 5% MgCl2 White
precipitate formed
Cloudy Solution
Detergent 5% CaCl2 White precipitate
formed
Cloudy Solution
Name of Test Sample Reagent used Reaction Explanationa. Liebermann-Buchard Test
Cholesterol CHCl3 acetic anhydride;
concentrated sulfuric acid
From white cloudy solution
to dark
Blue to blue green in color
This test determines the
presence of cholesterol and
it indicated a positive test
when the color changed
Name of Test Sample Reagent used Reaction ExplanationE. Emulsifying
Action of Lecitihin
2% Albumin Cholesterol
Cholesterol lecithin
2 layers formed; soluble
in albumin
There was no layer formed
and the cholesterol
“mixed” with albumin
2 layers were formed since 2% albumin
and cholesterol do not mix.
Lecithin
Question and Answer:
1.Why are fatty acids insoluble in water?• Fatty acids are insoluble in water since
there are more hydrocarbons which are more hydrophobic than the carboxyl group which is soluble in water. The longer the chain of the fatty acid becomes, the more insoluble it gets.
2.Explain why the cis-form is more predominant configuration of unsaturated fatty acids?
• Cis-form configuration is more predominant in unsaturated fatty acids since most of the fatty acids are in liquid form, and most of these liquid form unsaturated fatty acids has this configuration.
3.Why is the acrolein test the general test for fats?
• Acrolein test is used because it is the product/result when a substance with a fat in it is reacted with the reagent, potassium bisulfate and heat. Thus, if an acrolein is produced from the reaction, fats are present in the substance.
4.What type of rancidity occurs in vegetable shortenings and how can it be prevented?
• The type of rancidity that occurs in vegetable shortenings is the oxidation rancidity In this ‘oxidation rancidity’, the oxygen molecules interact with molecules of the oil which causes damage or changes to the substance.
• The easiest way to prevent this from happening is to store these vegetable shortenings in a dark, cool place where it is less exposed to oxygen.
5.Explain the cleansing action of detergents• The cleansing action of the detergent is
caused by its molecular structure.the hydrophobic part of the molecule is attracted to other hydrophobic substances such as oils, and the like, and the hydrophilic part attaches itself to the water , and thus, when it is rinsed away with water the hydrophobic part that is attached to the water
6. Write the structure of the parent compound of cholesterol.
7.Explain the cooperative solvent effect of lecithin and albumin.
• Lecithin and albumin are good emulsifiers because they both have a non-polar and a polar portion which helps reduce the immiscibility of two substances. When they work hand-in-hand, they are able to hold polar substances through their hydrophilic molecules thus making the immiscibility of two substances possible.
Conclusion:• The different test performed in the lipids
determined some of its properties
Solubility test determined that lipids are largely non-polar(since they only dissolved or mixed with non-polar substances e.g. ether, benzene, chloroform) thus they tend dissolve in non-polar substances also.
• The test for unsaturation determined the varying number of double bonds that each fatty acid or lipid contain.
• In the acrolein test, it was determined that not all oils contain fats, since the cotton seed oil did not give off a positive result for the acrolein test.
• In the rancidity test, the test showed that it is acidic, thus there was no oxidation that occurred (especially in the rancid coconut oil.)
• In the liebermann-burchard test the cholesterol turned into blue-green which indicated the presence of cholesterol.
• Last but not the least with the presence of lipids (lecithin)which act as emulsifiers, two immiscible substances are able to mix together due to its hydrophilic and hydrophobic parts that aid in the mixing of the substances