Oils and Fats
Major Component (%95-99)
Minor Components (%1-5)
Triglycerides
Triglyceride Derivatives
Glycerol
Free Fatty Acids
Mono- and Diglycerides
Non-Triglyceride
Derivatives
Phospholipids
Sterols
Pigments
Vitamins
Antioxidants
Oxidation Products
Trace Metals
Triglyceride Structure
H2C
OH
3 fatty acids
O
O
O C - R1
O
O HO - C - R1
HC OH +
= HC O C- R2 +3H20
HO - C - R2
O
H2C OH
O
glycerol
H2C O C - R3
HO - C - R3
triacylglycerol
H2C
–One chiral carbon with 1-3 acyl groups
–simpler stereochemistry than sugars
–more possible substituents
O
-C
R acyl
Saponification
General reaction
Fat + Base  Soap + glycerine
Base = chemical that contains OH at the end
Creating soap from fats or oils.
Soaps are usually made from vegetable fats and oils. These consist of
3 fatty acid chains, held together by a glycerol molecule.
Fatty acid
glycerine
Triglycerides differ from each other in
regard to
• Number of Carbon Atoms in fatty acid
chains
• Number of double bonds
• Isomerization
• Distribution of FA on glycerol backbone
How are soaps made?
This reaction is basically the opposite of an esterification
Esterification – remove HOH to connect molecules
Saponification – Add NaOH to break molecules
Esterification
H
HO
Saponification
Na HO
What is a soap?
Because a soap molecule has a long carbon chain, it is
partially nonpolar.
Nonpolar
-
+
Polar
Na
Attracts oil
Attracts water
The sodium part has a + and – charge, so it’s polar at this
end.
On end can attract polar molecules like water
(hydrophilic), the other end can attract nonpolar molecules
like oil (hydrophobic)
Saponification Reaction:
Fat + Lye  Soap + Glycerol
Lye - Caustic solution made from ashes.
Soda Lye = NaOH
Potash Lye = KOH
Combining potash K2CO3 with slaked lime
Ca(OH)2 yields KOH and CaCO3
NaOH obtained from reacting sodium
compounds.
O H
C17H35-C-O-C-H
O
C17H35-C-O-C-H
O
C17H35-C-O-C-H
H
Fat
(Triglyceride)
+
NaOH 
+
NaOH 
+
NaOH 
Lye
O
C17H35-C-ONa
O
C17H35-C-ONa
O
C17H35-C-ONa
Soap!
H
H-C-OH
+
H-C-OH
H-C-OH
H
Glycerol
How does it happen??
O
• Break the ester linkages C – O- by
hydrolyzing the bonds between the carbon
backbone and the fatty acid chains.
• (Reversal of esterification reaction)
• Form the sodium salt of a fatty acid (soap) and
a trihydroxy alcohol (glycerol).
The Chemistry
http://en.wikipedia.org/wiki/Saponification
If oil is added to water, the two liquids do not mix.
Because of this, grease stains can be difficult to remove
during washing.
Soaps are compounds
which act as emulsifiers.
soap molecule
water
This means that they
help the oil to mix
with the water.
oil
How do soaps work?
• Organic Reaction: Slow!
• Must break covalent bonds.
• Refluxing: Technique which allows a
volatile solvent to boil, condense and
return to the reaction vessel. It helps to
maintain a fairly constant temperature
throughout the reaction period.
Strange but true…
Fat in cadavers: saponifies if conditions
are right. Alkalai environment, moist,
minimal oxygen.
Adipocere or grave wax is formed.
Saponification Value
Saponification - hydrolysis of ester under alkaline
condition.
The saponification value of an oil or fat is defined
as the number of mg of potassium hydroxide
(KOH) required to neutralize the fatty acids
resulting from the complete hydrolysis of 1 g of
the sample.
Saponification Value
Determination
Saponification # --mgs of KOH required to saponify 1 g of fat.
1.
5 g in 250 ml Erlenmeyer.
2.
50 ml KOH (0.5 N) in Erlenmeyer.
3.
Boil for saponification.
4.
Titrate with HCl (0.5 N) using phenolphthalein.
5.
Conduct blank determination.
SP# =
56.1(B - S) x N of HCl
Gram of Sample
B - ml of HCl required by Blank.
S - ml of HCl required by Sample.
N- Factor of 0.5 N HCL.