Department of Pure and Applied Chemistry

College of Arts and Sciences

Visayas State University
Visca, Baybay City, Leyte

Name: Ana Luisa C. Laurente Date Performed: June 18, 2019

Lab Schedule: 7:00 – 10:00 (M-F) Date Submitted: July 15, 2019

Group No: 6 Score:

Experiment No. 4

Lipids

A. Abstract

This experimental procedure was basically geared towards understanding the physical
and chemical properties of lipids and how to differentiate them based on their different
properties. Different tests were done to observe the different characteristics or behaviours
of lipids which are as follows; Test for solubility, test for unsaturation, the saponification
and lastly the observation of reactions of soaps.

B. Introduction

The lipids are a large and diverse group of naturally occurring organic compounds that
are related by their solubility in non-polar organic solvents (e.g. ether, chloroform, acetone
& benzene) and general insolubility in water. Lipids are defined by their physical behavior
rather than by their chemical structures. As a resultm there is great structural variety
among the lipid class.

Fats and oils are made from two kinds of molecules: glycerol (a type of alcohol with a
hydroxyl group on each of its three carbons) and three fatty acids joined by dehydration
synthesis. Since there are three fatty acids attached, these are known as triglycerides.
The main distinction between fats and oils is whether they’re solid or liquid at room
temperature, and this is based on differences in the structures of the fatty acids they
contain.

The main functions of lipids include: source of energy, some fat soluble vitamins have
regulatory or coenzyme functions, and structural functions (cell membrane).

C. Methodology

Materials

 Test tubes  Fat or oil for soap

 Fatty acids  95% ethanol
 Lipids  Aluminium foil
 Organic model kits  Saturated NaCL solution
 5% bromine solution  Detergent soap
 Methylene chloride  5% CaCl
 Methods

SOLUBILITY OF LIPIDS

2 mL of water was prepared on each of the 5 test tubes prepared. After preparation of the
2 mL of water on each test tube, 5 drops of each lipids were added on each test tube using a
microspatula. After the addition of the different lipids on each tet tube shaking was done and
observation were recorded. Same procedure goes to the solubility of lipids in hexane using 2
mL of hexane.

TEST FOR UNSATURATION

This part of the experiment was performed in the fume hood for safety purposes. 5 drops
of each lipids were prepared in each test tube using a dropper. For the solid lipids, 0.1 g were
used and were dissolved in 1 mL methylene chloride. After dissolving, 2 mL of methylene
chloride were added to each sample. After all the preparation, bromine was added slowly drop
by drop until a permanent color of orange was obtained on each test. Each drop done on the
addition of bromine was recorded on each sample.

SAPONIFICATION: PREPARATION OF SOAP

A 6 grams of fat was withdrawn from the source and transferred in a 125-mL Erlenmeyer
flask. After preparation of the 6 grams of fat an addition of a 95% ethanol in the amount of 20
mL and 20% NaOH in the same amount was added. Covering the mouth of the Erlenmeyer
flask with aluminium foil with a small poke a hole was done after the addition. Erlenmeyer flask
was placed in a hot bath for 30 minutes or more until the solution became clear. In a separate
test tube, a few drops of the saponified solution was placed and was added with a 10 mL of
cold water. Observation were done and by the time that fat droplets were formed, careful
adding of an amount of 5 mL of 20% NaOH and 5 mL 95% ethanol to the flask and continuation
of the heating process was done carefully for 10 more minutes. When the solution became
clear, the mixture was let to cool.

REACTION OF SOAPS

A solution of both commercial and prepared soap was done by dissolving 1 g of each soap
in separate beakers with a 50 mL distilled water. For E-1, 10 mL of each solution were
prepared in separate test tubes. After preparation shaking then observation was done. For E-
2, pH of each solution were tested using the pH paper. For E-3 10 mL of each soap solution
were prepared separately in separate test tubes. For the 3rd test tube, a 10 mL water was
placed and an addition of 5 drops of cedar oil was done to all three test tubes. Shaking was
done afterwards for 5 minutes and then observations were recorded. For E-4, 10 mL of each
solution were prepared in separate test tubes and 2 mL of 5% CaCl2 was added on each
solution. Stopper and shaking was done then observation were recorded. Same procedure
was done using a 2 mL of 5% MgCl2.

D. Results
a. Equations for the Formation and Hydrolysis of a Triacylglycerol
 b. Solubility

Solubility of Lipids
SOLVENTS
LIPID TYPE Water Hexane

Vegetable oil Fatty acid (oil) insoluble soluble

Coconut oil Triacylglycerol (oil) insoluble soluble
Canol Triacylglycerol (oil) insoluble soluble
Olive oil Triacylglycerol (oil) insoluble soluble
Vitamin A Terpene insoluble soluble

 Explain why the above compounds are classified as lipids.

The above compounds are classified as lipids because of its inability to mix with water
and ability to mix with hexane since hexane is nonpolar like lipids. Solubility of the above
compounds to hexane explains the ‘’ like dissolves like’’ concept.

 What type of solvent is needed to remove an oil spot? Why?

A nonpolar organic solvent, Hexane is needed to remove oil spot because of its attributes
such as simply recovery, non-polar nature, low latent heat of vaporization.

c. TEST FOR UNSATURATION

FATTY ACID DROPS OF BROMINE SOLUTION

Stearic acid 5 drops
Oleic Acid 53 drops
Linoleic Acid 20 drops

TRIACYLGLYCEROL (FATS AND OILS)

Canola 15 drops
Olive oil 52 drops
Vegetable oil 40 drops
Coconut oil 20 drops
Vitamin E 40 drops

STRUCTURE OF Stearic acid, Oleic acid, and Linoleic acid.

Stearic acid

Oleic acid

Linoleic acid
 Which is the most unsaturated fatty acid? Linoleic acid
Which is the most saturated fatty acid? Stearic acid
Which is the most unsaturated triacylglycerol?
Which is the most saturated triacylglycerol? Lard

d. SAPONIFICATION: FORMATION OF SOAP

Write an equation for saponification of tristearin (glycerol) tristearate.

e. REACTION OF SOAPS

Commercial Product: Surf

OBSERVATIONS
TEST SOAP (prepared) COMMERCIAL
PRODUCT
E–1 Shaking Foam was present Foam was present
E–2 pH 12.1 11.7
E–3 Oil Negative on oil Negative on oil
presence presence
E–4 CaCl2 Floating precipitate Precipitate was
present observed
MgCl2 Precipitate was Precipitate was
observed observed

 What is the effect of soap on a layer of oil?

Soap has a hydrophobic end and hydrophilic end, they arrange themselves into
clusters called micelle, and surrounds and oil particle. The hydrophobic end sticks to
the oil while the hydrophilic ends stick out to the water making the oil into smaller drops
and mixing it with water.

 How does soap react with the salts CaCl2 or MgCl2?

Soap reacts with salts forming lime soaps and Na+ ion being replaced by Mg2+
and Cl2- to form insoluble compounds.

DISCUSSION

Based on the chemical equation 1.1 above, 3 moles of fatty acids are required to react
with 1 mole of glycerol and yields 1 mole of triacylglycerol and 3 moles of water. This reaction
is also termed as dehydration reaction because water molecules are released after the
reaction has occurred effectively forming the triacylglycerol. When the triacylglycerol is
hydrolyzed, 3 moles of water is required to break the three –O- bonds between glycerol and
fatty acids, and produce 3 moles of fatty acids and 1 mole of glycerol.

Between the two fatty acids used in the test for unsaturation, it is the oleic acid together
with bromine solution produce an orange solution. It’s the double bond in the oleic molecule
that reacted with the said solution causing the production of the color orange. Therefore, oleic
acid is an unsaturated fatty acid while stearic acid is a saturated fatty acid since there were
no notable changes. Among linoleic acid, oleic acid, and stearic acid, linoleic acid is classified
as the most unsaturated fatty acid because of the presence of double bonds in carbons 9 &
12, and stearic acid is classified as the most saturated fatty acid since double bond is absent
in its structure. And among the triacylglycerols, only the coconut oil that reacted effectively
with the bromine solution, and therefore, is classified as the most unsaturated triacylglycerol
among the group. And butter, although not included in the test, is the most saturated
triacylglycerol because it is the one that is solid at room temperature, which is one of the
properties of saturated fats.

From the chemical equation 2 of formation of soap, 3 moles of sodium hydroxide, NaOH,
are required to react with a fatty acid to produce a soap and 1 mole of glycerol. The hydrolysis
and neutralization process is termed as saponification and ethanol was added in order to hard
soap batches to better mix the soap making materials during the saponification process. It is
a vital additive for attaining the most clarity in transparent glycerin soap. It helps the chemical
reaction between the sodium hydroxide solution and the fatty oils.

The reaction of the prepared soap was compared with the reaction of the commercial soap,
specifically Ariel. When the two soap samples were shook, they both produced bubbles. Upon
measuring the pH of the two soap samples using pH meter, the prepared soap has a pH of
7.80 while the commercial soap has pH of 10.92 which is very basic. When 5 drops of oil were
added into each of the soap solutions and was shook for a while, it was found out that the oil
mixed with water. This was because soap allows oil to dissolve in water. Soap is a surfactant,
which means that it has properties similar to water and oil. When the oil, soap, and water are
mixed together, soap breaks the oil and water molecules into very small droplets, thus, the
substances appeared to be mixed. Lastly, when the two soap samples were added with CaCl2
and MgCl2 salts, both produced white precipitates. The precipitates can be seen in the soapy
water and are referred to as soap scum.

E. Conclusion

Lipids are slippery when touched and/or in contact with the skin and are water-insoluble
but soluble in organic solvents. They appear in two forms. They could be solids or liquids
substances and can be also be described as greasy substances.

Saturated fats can directly be distinguished from unsaturated fats by looking or examining
their physical appearance. Unsaturated fats appeared to be liquid at room temperature in the
form of oil because of the double bond(s) that is/are present in its molecule. While saturated
fatty acids are solids at room temperature. They are also determined through the use of
bromine. If an orange solution is produced, then, that fatty acid is unsaturated and saturated
in the other way.

In the saponification process, fatty acids are released as sodium salts with sufficient
sodium hydroxide and the mixture of these salts of long-chain fatty acids is soap. Which is
fully precipitated out by adding saturated NaCl.

Soap with soft water will more likely produce bubbles when shake. With oil, it tends to
produce a homogenous solution, as if there is no oil added to the solution. And soap will
produce white precipitates when reacted with salts which are visible even one drop is added..
 F. References

http://www.oit.edu/docs/default-source/library-documents/library-publishing/che102-
introorganic-chemistry/chapter-4-9.pdf?sfvrsn=2

http://www.ehow.com/about_6384669_ethanol-used-make-soap_.html

Answers to Questions.

1. Explain why the above compounds are classified as lipids.

They are classified as lipids because they are insoluble in water and soluble in hexane
which is an organic substance, which best fitted with the characteristic of lipids which
water insoluble compounds but soluble in organic solvents.

2. What type of solvent is needed to remove an oil spot? Why?

A nonpolar solvent. It is because oil is a nonpolar substance which dissolves in another
nonpolar substance. As stated by the Rule of Thumb, “like dissolves like”. This means
that liquid polar substances dissolves polar substances and liquid nonpolar substances
dissolves nonpolar substances.

3. Which is the most unsaturated fatty acid?

Linoleic acid is the most unsaturated fatty acid.

4. Which is the most saturated fatty acid?

Stearic acid is the most saturated fatty acid.

5. Which is the most unsaturated triacylglycerol?

Coconut oil is the most unsaturated triacylglycerol.

6. Which is the most saturated triacylglycerol?

Butter is the most saturated triacylglycerol.

7. What is the effect of soap on a layer of oil?

Soap allows oil to dissolve in water.

8. How does soap react with the salts CaCl2 and MgCl2?
Soap reacts with the salts CaCl2 and MgCl2 by producing white precipitate.