Fatty acids and triglycerides

CHM4201:SPECIAL TOPIC IN
ORGANIC CHEMISTRY

Triglycerides and Chemistry
of Fatty acids
Group Members:

Nur Fatihah binti Abas (154120)
Faridah binti Sulaiman (154603)
Wan Fatihah Nasuha binti Wan Nor (154115)

Lecturer’s Name:

Prof. Mawardi Rahmadi

Learning outcomes:

1) To understand about fatty acid and triglycerides.

2) To know the physical and chemical properties of
fatty acid and triglycerides.

3) To distinguish between fatty acid and triglycerides.

Fatty Acids
• Long straight-chain carboxylic acids
▫ no branching
• Most common chains range from 10–20 carbons in
length
• Usually, an even number of carbons in the chain,
including the carboxyl carbon
• Can be saturated or unsaturated, but usually no other
functional groups present
▫ Any fatty acid that cannot be synthesized by the body
is called an essential fatty acid

Structure of fatty acids
• A fatty acid is nothing
more than a long C-H
chain with a carboxyl
group (COOH) on the
end.

• The COOH gives it an
acid property.

• The 3….dots represent
the chain is very long.

Physical Properties of Fatty Acids
• Solubility
>Longer chains
• more hydrophobic, less soluble.
>Double bonds increase solubility.
• Melting points
• Depend on chain length and saturation
• Double bonds lead chain disorder and low melting
temperature.
• Unsaturated FAs are solids at Room Temperature.

Fatty Acids
• The most common fatty acids.
Carbon Atoms: Common Melting Point
Double Bonds Name (°C)
Satur ated Fatty Acids
12:0 Lauric acid 44
Higher mp
14:0 Myristic acid 58
16:0 Palmitic acid 63
18:0 Ste aric acid 70
20:0 Arachidic acid 77
Uns aturated Fatty Acids
Lower mp 16:1 Palmitoleic acid 1
18:1 Oleic acid 16
18:2 Linole ic acid -5
18:3 Linole nic acid -11
20:4 Arachidonic acid -49

Types of fatty acids
The Length of • long-chain
the Carbon • medium-chain
Chain • short-chain

The Degree of • saturated
Unsaturation • unsaturated

The Location of • omega-3 fatty acid
Double Bonds • omega-6 fatty acid

The Length of the Carbon Chain

Short-chain Fatty Acid
(less than 6 carbons)

Medium-chain Fatty Acid
(6-10 carbons)

Long-chain Fatty Acid
(12 or more carbons)

Saturated

The Degree of
Unsaturation
Monounsaturated
Unsaturated
(cis or trans
configuration)
Polyunsaturated

Saturated and Unsaturated FAs

• Saturated FAs have no
double bonds. (C-C)
Double bonds lower the
melting temperature

• Unsaturated FAs have at
least one double bond
(C=C) in one of the fatty
acids

Saturated Fatty Acid
 All single bonds between carbons

Monounsaturated Fatty Acid

One carbon-carbon double bond

Polyunsaturated Fatty Acid

More than one carbon-carbon double bond

Structure
• Stearic acid: a typical saturated fatty acid with
18 carbons in the chain

• Oleic acid: a typical unsaturated fatty acid with
18 carbons in the chain

Cis-fatty acid: H’s on same side of the double bond; fold into
U-like formation; naturally occurring.
Trans-fatty acid: H’s on opposite side of double bond; more
linear; occur in partially hydrogenated foods

Location of Double Bonds
• Polyunsaturated fatty acid (PUFA) are identified by
position of the double bond nearest the methyl end
(CH3) of the carbon chain; this is described as a
omega number.

• If PUFA has first double bond 3 carbons away from
the methyl end => omega 3 FA

• 6 carbons from methyl end => omega 6 FA

Fatty Acid Nomenclature

• Nomenclature reflects location of double
bonds
• Also used are common names (e.g: oleic,
stearic, palmitic)
• Linoleic is also known as 18:2 n-6
• This means the FA is 18 carbons in length, has
2 double bonds, the first of which is on the 6th
carbon
• Arachidonic => 20:4 n-6

Classification and Structure-Saturated Fatty Acids

Common Name Systematic Name Formula
O
Butyric acid n-butanoic CH3(CH2)2C OH
O
Caproic acid n-hexanoic CH3(CH2)4C OH
O
Caprylic acid n-octanoic CH3(CH2)6C OH

O
Capric acid n-decanoic CH3(CH2)8C OH
O
Lauric acid n-dodecanoic CH3(CH2)10C OH

Common Name Systematic Name Formula
O
Myristic acid n-tetradecanoic CH3(CH2)12C OH

O
Palmitic acid n-hexadecanoic CH3(CH2)14C OH

O
Stearic acid n-octadecanoic CH3(CH2)16C OH

O
Arachidic acid n-eicosanoic CH3(CH2)18C OH
O
Behenic acid n-docosanoic CH3(CH2)20C OH

O
Lignoceric acid n-tetracosanoic CH3(CH2)22C OH

Naming for Unsaturated FAs

10 9 8 7 6 5 4 3 2 1
O
1 9
C H3(C H2)7 HC CH C H2 CH2 CH2 CH2 C H2 CH2 C H2 C OH

Δ 9, 10 - Octadecenoic acid
9 - Octadecenoic acid

Common Name of Fatty Acids

Common Name Systematic Name

Myristoleic 9-tetradecenoic acid

Palmitoleic 9-hexadecenoic acid

Oleic 9-octadecenoic acid

Vaccenic 11-octadecenoic acid

Erucic 13-docosenoic acid

Chemical Reactions of Fatty
Acids

Esterification reacts fatty acids with alcohols to
form esters and water

Fatty Acid Hydrolysis
• Acid Hydrolysis reverses esterification
▫ Fatty acids are produced from esters

Saponification
• Saponification is the base-catalyzed hydrolysis of
an ester
• Products of the reaction are
▫ An alcohol
▫ An ionized salt which is a soap
 Soaps have a long uncharged hydrocarbon tail
 Also have a negatively charged carboxylate group at
end
 Form micelles that dissolve oil and dirt particles

Reaction at the Double Bond

• Hydrogenation is an addition reaction
• Unsaturated fatty acids can be converted to
saturated fatty acids
• Hydrogenation is used in the food industry

O
CH3 CH2 4CH CH CH2CH CH CH2 7 C OH
2 H2, Ni
O
CH3 CH2 16 C OH

Triglycerides

• An ester of glycerol with
three fatty acids.
• Also known as
triacylglycerols
• One type of lipid
categorised as simple lipid.

Structure of Triglycerides
• Glycerides are lipid esters
• A triglyceride places fatty acid chains at each
alcohol group of the glycerol

O
CH2O C R1
Glycerol O
part
CH O C R2 Fatty acid
O chains
CH2O C R3

Glycerol

• Glycerol Always
looks the same

• 3 C’s with 3 OH’s and
everything else H’s.

Example of triglycerides
▫ Triglyceride derived from one molecule each of
palmitic acid, oleic acid, and stearic acid, the three
most abundant fatty acids in the biological world.

O p almitate (16:0)
oleate (18:1)
O CH2 OC(CH2 ) 1 4 CH3
stearate (18:0)
CH3 ( CH2 ) 7 CH=CH(CH2 ) 7 COCH O
CH2 OC(CH2 ) 1 6 CH3

Physical properties of triglycerides
• Physical properties depend on the fatty acid
components.
▫ Melting point increases as the number of carbons in
its hydrocarbon chains increases and as the number
of double bonds decreases.
▫ Oils: Triglycerides rich in unsaturated fatty acids
are generally liquid at room.
▫ Fats: Triglycerides rich in saturated fatty acids are
generally semisolids or solids at room temperature.

Physical properties of triglycerides

▫ Hydrocarbon chains of saturated fatty acids can lie
parallel with strong dispersion forces between their
chains; they pack into well-ordered, compact
crystalline forms and melt above room temperature.

▫ Because of the cis configuration of the double bonds in
unsaturated fatty acids, their hydrocarbon chains have
a less ordered structure and dispersion forces between
them are weaker; these triglycerides have melting
points below room temperature.

Chemical Properties

Triglycerides have typical ester and alkene chemical
properties as they are composed of these two groups:-

▫ Saponification: replace H with salt from a strong
base
▫ Hydrolysis: produces the fatty acids and glycerol, a
reverse of formation
▫ Hydrogenation: saturates the double bonds

Triglyceride Reactions
• Triglycerides undergo three basic reactions
• These reactions are identical to those studied in
carboxylic acids

Triglyceride
H2O, H+ H2, Ni
NaOH
Glycerol
Fatty Acids More saturated
Glycerol triglyceride
Fatty Acid Salts

What’s What?
• Identify the glycerol
molecule
• The fatty acids

Fatty acids and triglycerides

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