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FATTY ACIDSFATTY ACIDS

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Learning objectives The two basic components of fatty acids &

their groups on the basis of number of carbon atoms in fatty acid.

Essential and non-essential fatty acids. The well known examples of saturated &

unsaturated fatty acids. Preparation of fatty acid in vitro.

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Fatty acidsFatty acids Fatty acids are the most Fatty acids are the most important componentimportant component

of the of the lipidslipids.. These are water insoluble, These are water insoluble, long chainlong chain

hydrocarbonshydrocarbons having having carboxyl groupcarboxyl group (COOH)(COOH) on one end & on one end & methylmethyl (CH3)(CH3) group on the other group on the other end of the chain. end of the chain.

Fatty acids in human body are of great variety.Fatty acids in human body are of great variety. All fatty acids are All fatty acids are building blocksbuilding blocks of of lipidslipids

including including neutral fatsneutral fats, , phospholipidsphospholipids, , glycolipidsglycolipids, , cholesterolcholesterol, , waxeswaxes etc. etc.

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Fatty acids having Fatty acids having carboncarbon atom from atom from 1 – 121 – 12 are called are called short chainshort chain fatty acids. fatty acids. 13 – 1813 – 18 are are moderate chainmoderate chain FAs. FAs. 19 – onward long chain19 – onward long chain FAs. FAs. In the body In the body short chainshort chain FA with 2 C are in FA with 2 C are in

abundanceabundance & with 4, 6 & 8 are present in very & with 4, 6 & 8 are present in very small amount.small amount.

Moderate chainModerate chain FAs are FAs are also abundancealso abundance in in human body fluid, most frequent is human body fluid, most frequent is 16 C16 C ((Palmitic acidPalmitic acid). ).

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Classification of fatty acidsClassification of fatty acids Fatty acids are classified Fatty acids are classified accordingaccording to the to the

number of carbonnumber of carbon atoms & presence or atoms & presence or absence of absence of double bonddouble bond etc. etc.

1-1- Saturated acids. Saturated acids. 2-2- Unsaturated acids. Unsaturated acids. 3-3- Branched chain acids. Branched chain acids. 4-4- Cyclic acids. Cyclic acids. 5-5- Hydroxy & keto-derivatives. Hydroxy & keto-derivatives.

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1- Saturated Acids1- Saturated Acids These are the fatty acids which These are the fatty acids which contain single contain single

bonds,bonds, there will be there will be nono any any double bonddouble bond. . Usually contain Usually contain even numbereven number of C atoms. of C atoms. SomeSome FAsFAs with odd number of C atoms have with odd number of C atoms have

also been discovered in plants & animal fats.also been discovered in plants & animal fats. A A few typical FAsfew typical FAs obtained from different fats obtained from different fats

are given along with sources. are given along with sources.

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NameName FormulaFormula Source Source i- Butyric acidi- Butyric acid-4-4 CH CH33 (CH (CH22))22 COOH Butter COOH Butter ii- Caproic acidii- Caproic acid-6-6 CH CH33 (CH (CH22))44 COOH Butter COOH Butter iii- Caprylic acidiii- Caprylic acid-8 -8 CH CH33 (CH (CH22))66 COOH Butter COOH Butter iv- Capric acidiv- Capric acid-10-10 CH CH33 (CH (CH22))88 COOH Butter, COOH Butter,

coconut oilcoconut oil v- Lauric acid CHv- Lauric acid CH33 (CH (CH22))1010COOH SpermacetiCOOH Spermaceti vi- vi- Myristic acidMyristic acid CH CH33 (CH (CH22))1212COOH ButterCOOH Butter vii- vii- Palmitic acidPalmitic acid CH CH33 (CH (CH22))1414COOH animal & COOH animal & vegetable fats vegetable fats viii- viii- Stearic acidStearic acid CH CH33 (CH (CH22))1616COOH = COOH = All above acids contain even number of carbon atomsAll above acids contain even number of carbon atoms

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Non essential fatty acids:Non essential fatty acids: From From dietarydietary point of view, point of view, saturated FAssaturated FAs are are

synthesizedsynthesized by human body, by human body, no needno need to to provide as provide as externalexternal source & not so essential source & not so essential as unsaturated FAs. as unsaturated FAs.

So they are called non-essential fatty acids. So they are called non-essential fatty acids.

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2- Unsaturated Fatty acids2- Unsaturated Fatty acids These contain These contain one or more double bondsone or more double bonds & are & are

more more reactivereactive than saturated fatty acids. than saturated fatty acids. They are further They are further classifiedclassified in to in to A)- One Double Bond acids (mono-enoic)A)- One Double Bond acids (mono-enoic) i- Palmitoleic acids:i- Palmitoleic acids: C C1515HH2929COOHCOOH CHCH33 (CH (CH22))55 CH= CH (CH CH= CH (CH22))77 COOH COOH Source;Source; Animal & vegetable fats & oils. Animal & vegetable fats & oils.

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ii- Oleic acid:ii- Oleic acid: C C1717HH3333COOHCOOH CHCH33 (CH (CH22))77 CH= CH (CH CH= CH (CH22))77COOHCOOH Animal & vegetable fats & oilsAnimal & vegetable fats & oils

iii- Erucic acid:iii- Erucic acid: C C2121HH4141COOHCOOH CHCH33 (CH (CH22))77 CH= CH (CH CH= CH (CH22))1111COOHCOOH Rapeseed oil Rapeseed oil

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B)- Two Double Bond Acids (Di-enoic)B)- Two Double Bond Acids (Di-enoic) Linoleic acidLinoleic acid – C – C1717HH3131COOH COOH CHCH33(CH(CH22))44CH=CHCHCH=CHCH22 – CH=CH(CH – CH=CH(CH22))77COOH COOH Source;Source; Linseed & cotton seed oil. Linseed & cotton seed oil.

C)- Three Double Bond Acids (Tri-enoic)C)- Three Double Bond Acids (Tri-enoic) Linolinic acidLinolinic acid – C – C1717HH2929COOHCOOH CHCH33CHCH22CH=CHCHCH=CHCH22CH=CHCHCH=CHCH22CH=CH(CHCH=CH(CH22))77COOHCOOH Linseed oil.Linseed oil.

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D)- Four Double Bond AcidsD)- Four Double Bond Acids Archidonic acid:Archidonic acid: C C1919HH3131COOHCOOH CHCH33(CH(CH22))44CH=(CHCHCH=(CHCH22CH=)CH=)33CH(CHCH(CH22))33COOHCOOH Animal and plant source. Animal and plant source. Essential Fatty Acids:Essential Fatty Acids: From From dietarydietary point of view, unsaturated fatty point of view, unsaturated fatty

acids must be acids must be taken by humantaken by human ( (external external sourcesource) because these can ) because these can notnot be be synthesizedsynthesized in the body. in the body.

So they are very essential – called essential FASo they are very essential – called essential FA

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3- Branched Chain Fatty acids3- Branched Chain Fatty acids Branched chain FA are often present in Branched chain FA are often present in waxeswaxes

than fat.than fat. These are These are i. Isoseriesi. Isoseries CHCH33 CH – (CHCH – (CH22)n – COOH )n – COOH CHCH33

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ii. Anti-isoseriesii. Anti-isoseries

(CH(CH22)n – COOH )n – COOH

CHCH33 – CH – CH22 – CH – CH

CHCH33

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4- Cyclic Fatty acids4- Cyclic Fatty acids Fatty acids having cyclic structure are Fatty acids having cyclic structure are rarerare but but

have been identified to be have been identified to be presentpresent in certain in certain seeds oilsseeds oils..

Ring structure is present at the Ring structure is present at the endend of of FA chainFA chain CH = CHCH = CH

HH22C CH(CHC CH(CH22))1212COOH COOH

CHCH2 2 Tridecanoic acidTridecanoic acid

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5- Hydroxy & Keto derivatives 5- Hydroxy & Keto derivatives The hydroxy derivatives of C2, C3, & C4 FA The hydroxy derivatives of C2, C3, & C4 FA

do not exist in lipids. do not exist in lipids. Many hydroxy derivatives of higher acids are Many hydroxy derivatives of higher acids are

known. known.

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Preparation of Fatty acidsPreparation of Fatty acids All the acids are obtained by the All the acids are obtained by the hydrolysishydrolysis of of

estersesters with super heated with super heated steamsteam or or alkalialkali. . The The saltsalt obtained is obtained is treatedtreated with some with some mineral mineral

acidacid to get the acid. to get the acid. O O CHCH22 – O – C – R CH – O – C – R CH22OH OOH O OO CH – O – C – R + 3HCH – O – C – R + 3H22O CHOH + 3R – C – OH O CHOH + 3R – C – OH OO CHCH2 2 – O – C – R CH – O – C – R CH22OHOH

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PHYSICAL PROPERTIES OF FATTY ACIDSPHYSICAL PROPERTIES OF FATTY ACIDS 1- Physical state & Melting point1- Physical state & Melting point:: The melting of FAs The melting of FAs dependsdepends upon the upon the chain chain

lengthlength & & degree of unsaturationdegree of unsaturation. . Chain length:Chain length: The The longerlonger is the chain , the is the chain , the

higherhigher is MP & vice versa. is MP & vice versa. e.g. The MP of Butyric acid is -8C while e.g. The MP of Butyric acid is -8C while Palmitic acid is 62C & Stearic acid is 70C. Palmitic acid is 62C & Stearic acid is 70C.

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Unsaturation:Unsaturation: The The greatergreater the the numbernumber of of double bonds, the double bonds, the lowerlower the MP. the MP.

e.g. the MP of Oleic acid is 14C while e.g. the MP of Oleic acid is 14C while Linolenic acid have -10C. Linolenic acid have -10C.

That is why the That is why the acids withacids with small chainsmall chain length length & with & with high unsaturationhigh unsaturation are generally are generally liquidsliquids at room temperature. at room temperature.

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2- Isomerism of Fatty acids:2- Isomerism of Fatty acids: The The unsaturatedunsaturated FAs containing FAs containing double bondsdouble bonds

show geometrical isomerism. show geometrical isomerism. Cis Isomer:Cis Isomer: Oleic acid is a cis acid Oleic acid is a cis acid both chainboth chain

on the on the same sidesame side. . CHCH33(CH(CH22))77 – C – H – C – H

HOOC(CHHOOC(CH22))77 – C – H – C – H cis form (oleic acid)cis form (oleic acid)

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Trans Isomer:Trans Isomer: trans isomer is called elaidic trans isomer is called elaidic acid, acid, both chainsboth chains are on are on oppositeopposite direction. direction.

H – C – (CHH – C – (CH22))77CHCH33

HOOC(CHHOOC(CH22))77 – C – H – C – H 3- Solubility3- Solubility Also depends upon the Also depends upon the chain lengthchain length & degree & degree

of of unsaturationunsaturation. . Chain length:Chain length: solubility of FAs solubility of FAs decreasesdecreases

with with increaseincrease in chain length. e.g. Butyric acid in chain length. e.g. Butyric acid is more soluble than palmitic acid.is more soluble than palmitic acid.

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Degree of unsaturation:Degree of unsaturation: solubility of FAs solubility of FAs increasesincreases with with increaseincrease in double bond. in double bond.

e.g. palmitoleic acid is more soluble than e.g. palmitoleic acid is more soluble than palmitic acid. palmitic acid.

4- Boiling Point4- Boiling Point The boiling points of FAs The boiling points of FAs increasesincreases with the with the

increaseincrease in chain length. in chain length.

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5- Absorption Spectra5- Absorption Spectra The The naturallynaturally occurring FAs occurring FAs do not absorbdo not absorb

light in UV/visible region. light in UV/visible region. Conjugated doubleConjugated double bonds show an appreciable bonds show an appreciable

absorptionabsorption in UV/visible region (230-260nm). in UV/visible region (230-260nm). Thus Thus spectroscopic analysisspectroscopic analysis is helpful in their is helpful in their

characterizationcharacterization. .

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CHEMICAL PROPERTIES OF FATTY ACIDS CHEMICAL PROPERTIES OF FATTY ACIDS 1- Salt Formation1- Salt Formation Fatty acids when Fatty acids when reactedreacted with with alkaliesalkalies form form

their salts. their salts. R – COOH + HO Na R – COONa+ HR – COOH + HO Na R – COONa+ H22OO Soap: Soap: Metallic saltsMetallic salts of higher FAs are called of higher FAs are called

soapsoap. . These may be salts of Na, K, Mg & Ca.These may be salts of Na, K, Mg & Ca. Na & K salts are solubleNa & K salts are soluble & are good & are good

emulsifyingemulsifying agents, While Ca or Mg salts are agents, While Ca or Mg salts are insoluble in water. insoluble in water.

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2- Detergent Formation2- Detergent Formation ReductionReduction of COOH group of FAs produces of COOH group of FAs produces

alkyl alcoholsalkyl alcohols, which can be , which can be sulphatedsulphated or or sulphonated to form alkyl sulphates or sulphonated to form alkyl sulphates or sulphonates which act as sulphonates which act as detergentdetergent. .

R – COOH + 2HR – COOH + 2H22 R – CH R – CH22OH + HOH + H22O O

R – CHR – CH22OH + Na R – CHOH + Na R – CH22 – ONa R – CH – ONa R – CH22 – SO – SO22ONaONa Sod alkyl sulphonateSod alkyl sulphonate Unlike soaps the detergents are stable & do Unlike soaps the detergents are stable & do

not form insoluble salts with Ca & Mg. not form insoluble salts with Ca & Mg.

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3- Ester Formation3- Ester Formation Fatty acids form esters when Fatty acids form esters when treatedtreated with with

alcoholsalcohols in the presence of dehydrating agents in the presence of dehydrating agents like like conc. Hconc. H22SOSO44 or or anhydrous HClanhydrous HCl..

R – COOH + HO – R R – C O– OR + H2OR – COOH + HO – R R – C O– OR + H2O Most important esters are with Most important esters are with glycerolglycerol. . Mono, di, tri Mono, di, tri glyceridesglycerides are the are the essential essential

constituentsconstituents of fats & oils. of fats & oils.

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4- Hydrogenation4- Hydrogenation Unsaturated acidsUnsaturated acids are are hydrogenatedhydrogenated in the in the

presence of Pt, Ni or Cu. presence of Pt, Ni or Cu. Raney nickleRaney nickle is of commercial importance for is of commercial importance for

the manufacture of the manufacture of vegetable fatsvegetable fats from from oilsoils.. CHCH33(CH(CH22))77CH=CH(CHCH=CH(CH22))77COOH CHCOOH CH33(CH(CH22))1616COOH COOH Oleic acid Stearic acid Oleic acid Stearic acid

H2

Ni

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5- Addition of Halogen:5- Addition of Halogen: Halogen under mild condition readily Halogen under mild condition readily add to add to

double bonddouble bond.. The The orderorder of reactivity is of reactivity is FF22>Cl>Cl22>Br>Br22>I>I22.. Elaidic & oleic acids yield Elaidic & oleic acids yield differentdifferent

dibromides. dibromides. With oleic acid the bromine atoms will be on With oleic acid the bromine atoms will be on

the same side the same side (erythro form)(erythro form) & with elaidic & with elaidic acid on opposite sides acid on opposite sides (threo form)(threo form). .

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BrBr22

CHCH33(CH(CH22))77CH=CH(CHCH=CH(CH22))77COOH COOH Oleic acid Br BrOleic acid Br Br CHCH33(CH(CH22))77CHCH(CHCHCH(CH22))77COOHCOOH erythro formerythro form

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6- Formation of prostaglandin:6- Formation of prostaglandin: Prostaglandins are synthesize Prostaglandins are synthesize withinwithin the body the body

from from unsaturated fatty acidsunsaturated fatty acids & have been & have been found to occur in found to occur in many organsmany organs..

e.g. seminal plasma, genital glands. e.g. seminal plasma, genital glands. They play a They play a hormonal rolehormonal role & thus control & thus control

different biological phenomenon. different biological phenomenon. OH OH - CH- CH22(CH(CH22))55COOHCOOH

- CH=CH – CH(CH- CH=CH – CH(CH22))44CHCH33 O O PGE1PGE1

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Smooth musclesmuscles contraction. Labour inducingLabour inducing agent. Involved in blood clottingblood clotting. Mucosal protectiveprotective agent.

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7- Rancidation:7- Rancidation: AdditionAddition of O of O22 on double bond gives on double bond gives

peroxidesperoxides. . Peroxides can undergo Peroxides can undergo cleavagecleavage to form to form bad bad

smellingsmelling aldehyde, ketonses & acids. aldehyde, ketonses & acids. Thus on Thus on exposure to airexposure to air, light & warmth, fats , light & warmth, fats

undergo undergo autoxidationautoxidation. The process is known as . The process is known as rancidationrancidation which is prevented by vitamin E. which is prevented by vitamin E.

O2O2 CHCH33(CH(CH22))77CH=CH(CHCH=CH(CH22))77COOH COOH CHCH33(CH(CH22))77CHO + CHO + COOH(CHCOOH(CH22))77COOHCOOH

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Lecture - feedback Define lipids? Fatty acids are the building block of……..? Palmitic acid is ………..carbon fatty acid? From From dietarydietary point of view, unsaturated fatty acids point of view, unsaturated fatty acids

are ……?are ……? All FAs are obtained by the All FAs are obtained by the hydrolysishydrolysis of ….. with of ….. with

super heated super heated steamsteam or or alkalialkali?? The The longerlonger is the chain , the …….. the MP? is the chain , the …….. the MP? Elaidic acid is a trans or cis isomer of oleic acid?Elaidic acid is a trans or cis isomer of oleic acid? The commercial manufacturing of vegetable fat by The commercial manufacturing of vegetable fat by

the method ….…?the method ….…? The process of auto oxidation of fat called…..?The process of auto oxidation of fat called…..?

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References and keys:References and keys: Dr.M.Rafiq, and Muashtaq Ahmad.Dr.M.Rafiq, and Muashtaq Ahmad.

Rapeseed Rapeseed = oil seed plant of mustard family -Brasica napus= oil seed plant of mustard family -Brasica napus SpermacetiSpermaceti = = waxy solid from sperm whales: a white waxy solid. Source: oil in waxy solid from sperm whales: a white waxy solid. Source: oil in

the head of sperm whales and other cetaceans.the head of sperm whales and other cetaceans. Raney nickleRaney nickle = special form of nickel prepared by treating Al – Ni alloy with = special form of nickel prepared by treating Al – Ni alloy with

NaOH sol. Nickel is left in the form of spongy mass which is more powerful NaOH sol. Nickel is left in the form of spongy mass which is more powerful catalyst especially for hydrogenation. catalyst especially for hydrogenation.