22:21 - 
No comments
No comments
EXPERIMENT 5: EXPERIMENT USING LIPID
INTRODUCTION
Triglyceride is an ester
composed glycerol and three fatty acids. Saponification number
primarily serves to determine the proportion of fatty acid esters in the
sample. In this experiment we
prepare soap from vegetable oil. Vegetable oil are esters of carboxylic acids
which have a high molecular weight and contain the alcohol, glycerol.
Chemically, these fats and oils are called triglycerides. The principal acids
in vegetable oils can be prepared from the natural triglycerides by alkaline
hydrolysis (saponification). The saponification reaction is a base usually NaoH
or KOH hydrolysis of triglycerids to make three salts (soap) and glycerol. The
molecules crystallize differently depending on the base used.
MATERIALS:
Triglyceride sample: e.g. Coconut oil, corn oil, palm oil, margarine,
butter
Solvent (1:1 ethanol/ether)
0.5M KOH
Phenolphthalein
0.5M HCl
1.Saponification of tryglyceride
\
2. Application : making Soap
RESULT:
1.Saponification of triglyceride
Sample
|
Blank
(V
HCl used in liter)
|
Sample
(V HCl used in liter)
|
Mol
for blank
Molarity
x V HCl (blank)
|
Mol
for sample
Molarity
x V HCl (sample)
|
Mol
of reacted KOH or MolKOH
|
Saponification
number = MolKOH x 56.1 x 103 gram of fat
|
Palm
|
0.025
|
0.025
|
0.013
|
0.012
|
0.0003
|
14.0 g
|
Corn
|
0.026
|
0.024
|
0.013
|
0.012
|
0.0010
|
56.1 g
|
Sunflower
|
0.027
|
0.022
|
0.014
|
0.011
|
0.0030
|
168.3 g
|
Table 1: Result of Saponification Number of
Different Types of Oils
2.Application : Making Soap
DISCUSSION:
1.
Saponification
of triglycerides
Triglycerides or triacylglycerols are
composed of three fatty acids each in ester linkage with a single glycerol. Since the polar hydroxyls of
glycerol and the polar carboxylates of the fatty acids are bound in ester
linkages, triacyl glycerols are non polar hydrophobic molecules, which are
insoluble in water. Saponification is the hydrolysis of fats or oils under
basic conditions to afford glycerol and the salt of the corresponding fatty
acid.
The saponification number is the number
of milligrams of potassium hydroxide required to neutralize the fatty acids
resulting from the complete hydrolysis of 1 g of fat. It gives information
concerning the character of the fatty acids of the fat. The longer the carbon
chain, the less acid is liberated per gram of fat hydrolyzed. It is also
considered as a measure of the average molecular weight or chain length of all
the fatty acid present. The long chain fatty acids found in fats have low
saponification value because they have a relatively fewer of carboxylic
functional groups per unit mass of the fat and therefore high molecular weight.
The principle in this experiment is fats (triglycerides) upon alkaline
hydrolysis (either with KOH or NaOH) yield glycerol and potassium or sodium
salts of fatty acids (soap).
In this experiment, there are 3 types of
oil or fat are used such as palm oil, corn oil and sunflower oil. The result shows
that sunflower oil has the highest saponification number. So that, it means
that sunflower oil has the shortest chain of fatty acid and lower molecular
weight. Corn oil is the shorter fatty acid chains and the long fatty acid chains is the palm oil
with high molecular weight. However, all the results obtained are differ from
the theoretical value. The actual saponification number of these oils is shown
in the Table 2:
Sample (Oil)
|
Saponification Number
|
Palm oil
|
196-205
|
Sunflower oil
|
188-194
|
Corn oil
|
188-193
|
Table 2: Actual
Saponification Number
Actually, the highest saponification
number should be the palm oil and followed by the sunflower oil and the lowest
is the corn oil. From the saponification number, we will know that palm oil has
the shortest fatty acid chains while the corn oil has the long fatty acid
chains. In this experiment, the result obtained is differ from the theory due
to error occurred while carrying out the experiment. The titration process may
have contributed to an error for this result as the volume of HCl used in the
titration might be excess after the indicator pink color turn to colorless.
Application : making soap
Making soap was a long process. Since water
and oil do not mix, this mixture had to be continuously stirred and heated
sufficiently to keep the fat melted. Slowly a chemical reaction called
saponification would take place between the fat and the hydroxide which
resulted in a liquid soap. When the fat and water no longer separated,
the mixture was allowed to cool. At this point salt, such as sodium
chloride, was added to separate the soap from the excess water. The soap
came to the top, was skimmed off, and placed in wooden molds to cure. It
was often aged many months to allow the reaction between the fat and hydroxide
to run to completion. Poorly make soap could contain excess alkali and
could dry and chap people's skin
Soaps have hydrocarbon and ionic ends. The
hydrocarbon ends are hydrophobic and non-polar. The ionic ends are hydrophilic
and polar. When both oil and water present and mix with the soap. The
hydrophobic part of the soap mixes with the oil, while the hydrophilic part of
the soap mixes with the water. The attraction of the polar end of the soap is
strong enough to pull the grease molecules into the water. Therefore, the
grease molecules associated with the non-polar ends are pulled into the water
along with the soap molecules. The soap and grease combine and arrange in the
form of micelles. Finally the micelles will disperse in the water.
QUESTION:
1.
What is the
relationship between saponification and phase (liquid / solid) of a
triglyceride?
For any chemical
reaction to occur, including saponification, the reactant should be in the same
phase. Hydroxide will almost entirely exist in the aqueous phase, and the
triglyceride will be almost entirely in the organic phase. Increasing stirring
will create more interface for the reaction to proceed. As the reaction goes,
glycerin and fatty acid salts will be produced, which can have appreciable
solubility in both phases. So, the regents will increase in concentration in
the phase most favored by the other as the reaction progresses. The higher the
concentration of the reactants, the more opportunity they have to react and the
faster the reaction will go.
2.
Why do triglycerides
with longer fatty acids have a lower saponification number than those with
shorter fatty acids?
Triglycerides are composed of
three fatty
acids linked to glycerol.
The fatty acids may be saturated or unsaturated. Triglycerides with longer fatty acid have a lower
saponification number because the number of carboxylic functional groups per
unit mass is low. It results in a higher molecular weight. So, less volume of
HCl is needed per gram of fat hydrolyzed. KOH volume to hydrolyzed the ester
bond also less as the saponification number is low.
3.
Why
is the difference in the molar amount of HCl used to neutralize the control and
the amount of HCl used to neutralize the sample equivalent to the molar amount
of KOH used to saponify the test sample?
Because one mole of HCl reacts with 1 mole of
KOH. Thus the test sample will require more acid to neutralize it because it
contains more alkali than the control.
Soap contain hydrophilic (‘water-loving’) and
hydrophobic (‘water-hating’). The dispersing of grease of soap is determined by
its polar and non-polar structures in conjunction with an application of
solubility properties. The long hydrocarbon chain non-polar hydrophobic
(repelled by water). The “salt’ end of soap molecule is ionic and hydrophilic
(water soluble). When grease or oil (non-polar hydrocarbons) are mixed with a
soap-water solution, the soap molecules work as a bridge between polar water
molecules and non-polar oil molecules. Since soap molecules have both
properties of non-polar and polar molecules, the soap can act as an emulsifier.
An emulsifier is capable of dispersing one liquid into another immiscible
liquid. This means that oil doesn’t naturally mix with water, soap can suspend
oil/grease in such a way that it can be removed. Therefore, the soap will form
micelles and trap the fats within the micelle. Since the micelle is soluble in
water, it can easily be washed away.
CONCLUSION
In a conclusion, the highest saponification number indicates its fatty acid chain length in triglyceride is lower. Soap is produced by undergo the saponification reaction
In a conclusion, the highest saponification number indicates its fatty acid chain length in triglyceride is lower. Soap is produced by undergo the saponification reaction
REFERENCE
0 comments:
Post a Comment