This presentation covers fats and oils chapter as per PCI syllabus. It contains all reactions and topics and have tried to explain it well.

1. Pharmaceutical Organic
Chemistry-II
By-
Mrs. Vastvikta Sahai
M. Pharm (Pharmaceutical Chemistry)
1

2. Topicstobecovered-
• Fats and Oils
• a. Fatty acids – reactions.
• b. Hydrolysis, Hydrogenation, Saponification and Rancidity of oils, Drying oils.
• c. Analytical constants – Acid value, Saponification value, Ester value, Iodine value, Acetyl value,
Reichert Meissl (RM) value – significance and principle involved in their determination.
2

3. FATS & OILS
3

4. Yields long-chain
fatty acids and
glycerol upon
hydrolysis
Most important
lipids found in
nature
One of the major
‘food factors’
needed for human
body
Fats & Oils belong to the group of naturally
occurring compounds known as Lipids (Greek-
lipos=fat)

5. 1gm of
metabolised
Fats or oils yields 9 Kcal
Carbohydrates yields 4 Kcal
Proteins yields 5.5 Kcal
5

6. 6

7. Animal & Vegetable fats & oils have similar chemical structures. They
are tri-esters formed from glycerol and long chain carboxylic acids
(often known as fatty acids).
7

8. Reaction:
8

9. A tri-ester of glyceride is known as glyceride or triglyceride. If all the
groups in above general formula are identical then it is a SIMPLE
glyceride, else MIXED glyceride.
9

10. Glyceride can be SATURATED or UNSATURATED, depending on
whether the fatty acid component chains are saturated or contain
double bonds.
10
Saturated
Fatty Acids
Unsaturated
Fatty Acids
Most
common
Most
common

11. Nomenclature:
11
Glycerol Tributyrate/ Tributyrin Glyceral palmito stearoleate

12. Physical Properties -Fats
Saturated
Fatty acids
Solids and
semisolids
Melts at
higher
temperature
Obtained
from animals
Structure
have no
unsaturation
More stable
than oils
Oils
Unsaturated
fatty acids
Liquids
Melts at
lower
temperature
Obtained
from
vegetables
Structure
have
unsaturation
Less stable
than fats
12

13. 13
May be either liquids or non crystalline solids at room temperature
Colourless, Odourless and tasteless in pure form
Lighter than water; insoluble in water
Soluble in organic solvents like acetone, benzene, chloroform etc.
Form emulsion when mixed vigorously with water in presence of soap/gelatin/emulsifier
Poor conductors of heat and electricity and serve as excellent insulator for animal body
Because of tight packing in fats, they have higher m.p. compared to oils

14. Animal fats are solids because
they have saturated fatty acids
in their structure and are
tightly packed to form solid
substances.
Oils are liquid because of
unsaturated fatty acids which
are slightly packed (or less
tightly packed) hence are
liquids.
14

15. Chemical Properties of Fats & Oils-
15

16. Hydrolysis- Triglycerides easily hydrolyse by enzyme called lipases in
the digestive tract of humans & animals into FATTY ACIDS &
GLYCEROL. The fatty acids produced are important in metabolic
processes in body.
16

17. 17
Stearic acid
HYDROLYS
IS/H2O

18. Saponification- when triglycerides are saponified by alkalis, glycerol and salts of
fatty acids are produced. Generally sodium or potassium salts are obtained known
as soaps.
18

19. 19

20. 20

21. Hydrogenation- Unsaturated glycerides react with hydrogen in the presence of
metal catalyst to yield saturated glycerides.
Hydrogenation results in transformation of a liquid glyceride (oil) into a semi
solid glyceride (fat).
This process resulting in hardening of oil owing to the formation of fats, is
known as Hardening of Oils.
This reaction is commercially used to harden vegetable oil for production of
cooking fat (vegetable ghee). Hardened oils are also used for making soaps and
candles.
21

22. 22
Type of
Hydrogenation
of ALKENES
An Oil (Unsaturated) A Fat (Saturated)

23. 23
Vanaspati and Margarineare productsof Hydrogenation.
The Hydrogenationreaction is generally stopped nearthe
end point of the reactionotherwise it forms isomers and is
difficult to isolate the pure products.

24. Hydrogenolysis- Glycerides split up like other esters into glycerol + long chain
alcohol (reduction products of fatty acids), when treated at high temperature
and pressure in the presence of copper chromite as catalyst with Hydrogen.
24

25. 25

26. Halogenation- Unsaturated glyceride on treatment with Iodine in the
presence of mercuric chlorides as catalyst, give iodides by addition at the
double bonds in the acid component chain.
26
It is very important property to determine the degree/extent of
unsaturation of fats and oils. Amount of Iodine consumed by a glyceride
is directly proportional to the number of double bonds in fatty acid
components.

27. 27

28. Drying of Oils-
A drying oil is an oil that hardens
to a tough, solid film after a
period of exposure to air
Oil hardens through a chemical
reaction in which the
components crosslink
Hence polymerize by the action
of Oxygen
28

29. Drying oils are
key component
of oil paints
and some
varnishes.
Some common used drying oil
– linseed oil, poppy seed oil.
Linseed oil have
high content of
di & tri
unsaturated
esters.
Which is particularly
susceptible to polymerization
reactions upon exposure to
oxygen in air.
The Oxygen
gets attached
to the C-H bond
adjacent to C-
double bond.
29

30. 30
Co2+
Co2+ + OH-
Cobalt
catalysed
drying process
Drying
Hyperoxide formation,
which can easily undergo
cross-linking reaction
between several
molecules of fatty acids
resulting in polymer
network

31. 31
E.g. Linseed oil

32. Depending on fatty acid pattern, vegetable oils can be
divided into-
Non-Drying Oils : contains mostly saturated fatty acids which
are unable to react, to form a cross-linked film by air oxidation.
E.g. Olive oil.
Semi-Drying Oils : contain fatty acids with only one or two
double bonds. E.g. Soya bean Oil , Sunflower Oil.
Drying Oils : are highly unsaturated oils, consisting of fatty acids
containing 2 or 3 double bonds. E.g. Linseed Oil, Perilla Oil.
32

33. Rancidity-
33

34. Hydrolytic
Rancidity
Hydrolysis will split fatty acid chains
away from the glycerol backbone in
glycerides. These fatty acids then
further undergo Autoxidation.
Oxidative
Rancidity
Oxidation primarily occurs with
unsaturated fats by a free-radical-
mediated process.
34
These chemical
processes can
generate highly
reactive
molecules in
rancid food and
oils, which are
responsible for
producing
unpleasant and
noxious odours
and flavours.

35.  Hydrolytic Rancidity
35
• It is due to the liberation of lower fatty acids by hydrolysis of ester links of
triglycerides.
• Particularly applicable to butter. Under moist and warm conditions,
hydrolysis of the glycerides in butter liberates butyric acid, caproic acid,
caprylic acid which have offensive odours.
• Micro-organisms present in the air provide the enzyme (lipase) that
catalyses the hydrolytic process.
• Rancidity so caused can be prevented by keeping butter covered in
refrigerator.

36. E.g.-
36

37.  Oxidative Rancidity
37
Occurs in triglycerides containing unsaturated acid components.
First, the ester linkage is hydrolysed to yield unsaturated acids.
Acid produced are subjective to oxidative cleavage at the double
bonds forming short chain aldehydes and acids.
Oxidation leading to rancidity in fats & oils is catalysed by the
presence of certain metallic salts.

38. E.g.-
38

39. Saponification Value -
39
oIs the number of mg of potassium hydroxide
required to saponify 1gm of fat or oil.
The oil sample is saponified by refluxing with excess of
alcoholic KOH solution. The alkali required for saponification
is determined by titration of the excess KOH with standard
solution.
The saponification value is an index of mean molecular
weight of fatty acids of glycerides comprising a fat. Lower the
SV, larger the MW of fatty acids in the glycerides and vice-
versa.
Definitio
n
Principle
Analytical
Importan
ce

40. Method -
Weigh 2gm of oil
in glass flask
Add 25ml of 0.5 N
alcoholic KOH
solution+ pumic
powder
Boil for 1hr under
a condenser with
frequent shakings
Determine the excess
of alkali by titration
with 0.5N HCl(A ml)
using 0.5ml of
phenolphthalein
Set a blank test upon the
same quantity of KOH at
the same time & under
same conditions i.e.
sample (B ml)
40

41. Formula-
𝑆𝑉 = 28.05 𝐵 − 𝐴 ÷ 𝑊
Where,
B= ml of HCl used for blank titration
A= ml of 0.5N HCl used for titration
W= weight of sample (gm)
1ml of 0.5N HCl=28.05 mg of KOH
E.g.
SV of castor oil=0.1811
SV of almond oil= 0.1925
41

42. 42
𝐾𝑂𝐻 + 𝐻𝐶𝑙 → 𝐾𝐶𝑙 + 𝐻2 𝑂
End Point

43. 43
S.V. is important in determining adulteration in fats or
oils. Amount of alkali required for converting a given
amount of fat or oil. Hence, helps in detection of
adulteration extent.

44. Acid Value-
Defined as number of mg of KOH required
to neutralize 1gm of oil & fat.
Indicated the amount of free fatty acids
present in oil or fat.
Is the measure of breakdown of the
triacylglycerols into free fatty acids which
has an adverse & undesirable effect.
Acid Value
44

45. Procedure-
Weigh accurately
specific quantity of
fat or oil in a CF
Add 50ml of
ethanol-ether
solution
Shake well
Titrate the solution
with KOH using
phenolphthalein
as indicator until
pink colour is
obtained
Measure the
amount of KOH
used and calculate
AV
45

46. Formula -
Where,
TV= Total Volume
N= Actual Normality of KOH
W= Weight of the Sample
N1= Approximate Normality of KOH
E.g.
AV of Soya oil= 0.6
AV of Olive oil= 6.6
46
A. 𝑉. = 5.61 × 𝑇𝑉 × 𝑁 ÷ 𝑊𝑁1
High AV indicates that
the given sample of
fat & oils is of low
quality & stored
under improper
conditions.

47. Ester Value-
Number of mg of KOH required to react the
esters in 1gm of a fat or oil.
The difference between S.V & A.V is known as
E.V.
Definition
E.V= S.V - A.V
E.V is calculated as percentage
ester.
Formula
47

48. Iodine Value-
Number of grams of iodine
taken up by 100gm of fat or
oil.
It is the number of grams of
iodine which will combine
with 100 gm of fat or oil.
Principle- it is determined by treating the given
sample of fat or oil with Iodine monochloride or
iodine in ethanol in presence of mercuric chloride.
Unreacted iodine is then calculated. It gives the
idea of degree of unsaturation present in the
sample.
48

49. Procedure- Fat or oil
sample is
taken
Dissolve in
CCl4
Treat with
excess of std
ethanolic iodide
in presence of
mercuric
chloride
Unused iodine
is then
calculated by
titration with
std. sodium
thiosulphate sol. 49
Hubl’s
Method

50. 50
Wij’s Method
This method uses
iodine
monochloride in
acetic acid in place
of Iodine
ICl readily
combines with the
double bonds
present in fat & oil
The unreacted
iodine is then
calculated by the
addition of KI &
titration with std sol
of sodium
thiosulphate using
starch indicator
Excess

51. Equation-
Iodine Value= 𝑎 − 𝑏 × 1.27 ÷ 𝑊
Where,
a= reading for blank titration
b= reading for actual titration
W= weight of fat or oil taken
Significance – tells degree of unsaturation present in fat or oil. Higher the iodine value,
high is unsaturation of fat or oil.
Also, gives an idea of drying character of drying of fat/oil.
Helps in determining adulteration of fat/oils.
51

52. Non-
Drying
oils 85-
105
Semi-
drying
oils 105-
120
Iodin
e
Value
Drying
oils
Above
120
52

53. Acetyl Value
53
Defined as the number of
milligrams of potassium
hydroxide (KOH) required to
neutralize acetic acid produced
by the saponification of 1gm of
completely acetylated fat or oil.

54. Procedure-
54
Titrate with
0.5N KOH +
phenolphthal
ein indicator
Cool
Put on water
bath for 30
mins
5ml of H2O
Sample+5ml
acetic
anhydride &
pyridine
mixture (1:7)

55. Formula-
𝑨𝒄𝒆𝒕𝒚𝒍 𝑽𝒂𝒍𝒖𝒆 = 𝐸 × 4.3 ÷ 𝐴
Where,
A= weight of sample acetylated in grams
E= Acidity equivalent
Significance-
Helps in determining the number of alcoholic group present in fats and oils
increased number of acetyl value indicates more amount of free fatty acids.
55

56. Reichert-Meissl Number
56
Defined as the
number of mg of
0.1N KOH
solution required
to neutralize 5gm
of fat or oil
RM Number of a fat
is determined by
treating a known
weight of it with
ethanolic alkali &
distilling the volatile
oil

57. 57
These are titrated against M/10
KOH & RM Number is calculated.
Known sample of oil or fat is
completely saponified with alkali.
The resulting solution is acidified
with dil H2SO4 & steam distilled.
The distillate which contains
volatile acid is then titrated against
0.1N KOH solution.

58. Procedure-
58
10gm
sample
Add
excess
0.1N
NaOH to
saponify
Acidify
with
Dil
H2SO4
Steam
distille
d
Distillate
measured
By
titrating
With 0.1N
KOH &
phenolphth
alein

59. Formula-
𝑅𝑀 𝑉𝑎𝑙𝑢𝑒 = 1.10[𝑇1− 𝑇2]
Where,
𝑇1 = volume of 0.1N KOH used for titration
𝑇2 = volume of 0.1N KOH used for blank titration
Significance-
Used for testing the purity of butter & desi ghee which may contain high amount
of glycerides of butyric acid & other steam volatile fatty acid residues.
E.g. adulterated butter has low RM Value than pure butter. RM Value is indicator of
non-fat compounds in edible fats like ghee, butter (purity determination).
59

60. THANK YOU!!
60
Mrs. Vastvikta Sahai