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EFN-313 Lífræn efnafræði
11. kafli
“The most important hypothesis in all of
biology…is that everything that animals do,atoms do. In other words, there is nothingthat living things do that cannot be understood from the point of view that they are made of atoms acting according to the laws of physics.”
Richard Feynman (1918-1988)
Lífræn efni byggjast öll á kolefni
• C, CO, CO2 og CO3 teljast ólífræn
• Önnur C sambönd kallast lífræn
• Annaðhvort sameindir eða sameindajónir
• Óendanlega mörg lífræn efni til, á öllum formum með mismunandi eiginleika.
C-atóm eru einstök
• Mynda óskautað samgild tengi við Vetni
• Mynda samgild tengi sín á milli og mynda langar keðjur
• Mynda samgild tengi við aðra málmleysingja t.d. P,O,N,S og halogena
• C-C og C-H tengi eru óskautuð (nonpolar)
Fjögur sp3 hybridised orbitals mynda ferflötung
sp3 hybridised orbitals frá 2 C atómum geta skarast og myndað C-C σ-tengi
C-C bond
Each sp3 orbital
contributes one electron
to form C-C [C..C]
Raun lögun etan sameindar
sp3 svigrúmablanda (rafeindir) flýr eins langt frá kjarnanum og hægt er og tengist í þær áttir.
Carbon sp3 orbitals can overlap with Hydrogen 1s orbitals to
form Carbon-Hydrogen bonds
HC C
HH
H
H
H=
bonds: symmetrical about the bond axis
Each sp3 orbital contributes one electron; each s orbital
contributes one electron to form C-H [C..H]
C-C N-N O-O
Bond Dissociation Energy(kJ mol-1) 348 163 157
•Carbon-Carbon bonds: especially Sterk samgild tengi
•Kolefni: Einstakt, myndar catenate [Keðjur]
•Forms molecules composed of C-C bonds
CC
CC
CC
C CC
CC
C
C
C
C
C C
CC
Línulaga/Linear Greinótt/Branched Hring/Cyclic
•Organic molecules = Carbon-based molecules
•Organic chemistry = Chemistry of carbon-based molecules
Some properties of organic molecules
•Stability: composed of stable C-C covalent bonds
•Defined molecular structures
•Defined three-dimensional shapes
Organic chemicals are universal
OrganicOrganicChemicalsChemicals
Biological matter•Plants•Animals•Microbes
Geological matter•Fossil Fuels•Other
Atmosphericand
cosmic matter
Manufacturedproducts
Biological organic chemicals
• Sugars• Proteins• Fats & oils• Vitamins• DNA & RNA• Wood• Natural rubber• Essential oils
• Natural fibres• Antibiotics• Fermentation
products• Natural flavours• Natural
fragrances• Plant & microbial
products• Bio-matter
Organic chemicals in manufactured products
Bio-activeproducts
Medicines Veterinary medicines
Herbicides
Pesticides
Fungicides
Plant growth hormones
Imaging agents
Fertilizers
Antiseptics
Disinfectants
Organic chemicals in manufactured products
Materials
Fibres & clothings
Plastics
Coatings & lacquers
Packaging
Paper
Films
Medical implants
Wound dressings
Organic chemicals in manufactured products
FoodsSugars
Fats & Oils
Anti-oxidantsColourants
Flavourings
Vitamins
Dietary supplements
Fibre
Fuels
“Petrol”
“Diesel”
LPG
Natural gas
Coal
Peat/Turf
Methanol/Ethanol
Organic chemicals in manufactured products
Miscellaneous• Lubricants• Cosmetics• Fragrances• Pigments• Dyes• Inks• Adhesives• Explosives
• Detergents• Surfactants• Emulsifiers• Coolants• Photographic agents• Anti-scalants• Forensic chemicals• Liquid crystal displays
Hydrocarbons - Kolvetni
• Kolvetni eru einföldustu lífrænu efnin
• Kolvetni eru gerð úr Kolefni og Vetni
• Kolvetni þar sem öll tengi milli atóma eru einföld kallast ALKANar
• Öll eintengi eru sigmatengi (σ-bonds) og um þau frjás snúningur.
• Einföldustu: CH4, C2H6, C3H8
Um kolvetni
• Mettað kolvetni (Saturated hydrocarbon):Mettað kolvetni (Saturated hydrocarbon): Kolvetni eingöngu með eintengi
• Alkane:Alkane: Mettuð kolvetni þar sem kolefnin raða sér í opna keðju.
• Aliphatic hydrocarbon:Aliphatic hydrocarbon: Annað nafn á alkan
Hydrocarbons
H-C C-HH-C-C-H
H
H
H
H HC C
H
H H
Hydrocarbons
Alkanes(Chapter 2)
Alkenes(Chapters 5-6)
Alkynes(Chapter 7)
Arenes(Chapter 21-22)
Only carbon-carbon single
bonds
One or more carbon-carbondouble bonds
One or morecarbon-carbontriple bonds
One or morebenzenelike
rings
Class
Example
Carbon-carbon
bonding
Name Ethane Ethene Acetylene Benzene
Saturated Unsaturated
Bygging
• Lögun– Ferflötungslaga– Öll horn tengja um 109.5°
Drawing Alkanes
• Nokkrar aðferðir við að teikna byggingu– Endi og horn eru kolefnisatóm (line-angle)
CH3CH2CH2CH3CH3CH2CH3 CH3CH2CH2CH2CH3
PentaneButanePropane PentanePropane
Structuralformula
Line-angle formula
Ball-and-stickmodel
IUPAC
• International Union of Pure and Applied Chemistry
• Látum nægja að læra utanað upp í 10 en allt ofar þarf að kannast við.
• Sjá annars töflu 11.1 í bók.
Línulaga - Beinkeðjualkanar
Nafn # Kolefni Byggingaformúla
Methane 1 CH4
Ethane 2 CH3CH3
Propane 3 CH3CH2CH3
Butane 4 CH3CH2CH2CH3
Pentane 5 CH3CH2CH2CH2CH3
IUPAC NAMES
Nafn # C-atóma Byggingaformúla
Hexane 6 CH3CH2CH2CH2CH2CH3
Heptane 7 CH3CH2CH2CH2CH2CH2CH3
Octane 8 CH3CH2CH2CH2CH2CH2CH2CH3
Nonane 9 CH3 CH2 CH2CH2CH2CH2CH2CH2CH3
Decane 10 CH3CH2CH2CH2CH2CH2CH2CH2CH2CH3
Dæmi
A. Hver er byggingaformúla… H H H H
H C C C C H
H H H H
B. Hver er mólikúlformúlan?C. Hvert er nafnið?
Lausn
A. CH3CH2CH2CH3
B. C4H10
C. butane
Nafnakerfi - IUPAC
• Forskeyti/Prefix segir fjölda C-atóma
undec-dodec-
tetradec-pentadec-hexadec-heptadec-
nonadec-eicos-
tridec-
11121314151617
octadec- 181920
Prefixmeth-eth-prop-but-pent-hex-
oct-non-dec-
1234567hept-89
10
Carbons CarbonsPrefix
Nöfn: Greinóttra alkana1. Finndu lengstu kolefniskeðjuna.2. Númera keðjuna, byrja þaðan sem
styst er í fyrstu hliðargrein.3. Nefnið hliðarhópa og notið númer á C
sem staðsetningu.4. Raðið hliðarhópum (substituents) í
stafrófsröð.5. Notið di-, tri-, ef sami hópur kemur oft
fyrir.
Lengsta keðjan
6. Fjöldi kolefnisatóma í lengstu keðju ræður orðstofni/Nafni
7. Ef það eru tvær keðjur jafnlangar velst sú keðja sem hefur fleiri hliðarhópa.
C
CH3
CH2
CH3
CH CH2 CH2 CH3
CH CH2 CH3H3C
H3C
=>
Númera C -atóm
• Byrjið við endann næst fyrsta hliðarhóp.
• Ef tveir hl.hópar eru jafn langt frá skoðið þá aðra hópa.
1
2
3 4 5
6 7CHH3C
CH3
CH
CH2CH3
CH2 CH2 CH
CH3
CH3
=>
Nöfn hliðarhópa – ALKYL hópar
• CH3-, methyl
• CH3CH2-, ethyl
• CH3CH2CH2-, n-propyl
• CH3CH2CH2CH2-, n-butyl
CH3 CH CH2 CH3
sec-butyl
CH3 CH
CH3
CH2
isobutyl
CH3 CH CH3
isopropyl
CH3C
CH3
CH3
tert-butyl
=>
Alphabetize
• Raðið í stafrófsröð.
• Ignore di-, tri-, í stafrófsröðinni.
CHH3C
CH3
CH
CH2CH3
CH2 CH2 CH
CH3
CH3
3-ethyl-2,6-dimethylheptane =>
Flóknari hliðarhópar• Ef greinin er greinótt, númerið C in frá tengi
við aðalkeðju.• Nefnið og númerið hliðarkeðju í hliðarkeðju.
• Setjið sviga utanum flókna hliðarhópinn.
12
31-methyl-3-(1,2-dimethylpropyl)cyclohexane =>
Nomenclature - IUPAC
• Parent name:Parent name: the longest carbon chain• Substituent:Substituent: a group bonded to the parent chain
– alkyl groupalkyl group:: a substituent derived by removal of a hydrogen from an alkane; given the symbol R-
Alkane Alkyl group
CH4
Name Name
Methane CH3- Methyl group
CH3CH3 Ethane CH3CH2- Ethyl group
Nomenclature - IUPAC1.The name of a saturated hydrocarbon with an
unbranched chain consists of a prefix and suffix
2. The parent chain is the longest chain of carbon atoms
3. Each substituent is given a name and a number
4. If there is one substituent, number the chain from the end that gives it the lower number
CH3CHCH3
CH3
2-Methylpropane
12 3
CH3CH2CH2CHCH3
CH3
2-Methylpentane
123
45 5
432
1
(not 4-methylpentane)
Nomenclature - IUPAC
5. If there are two or more identical substituents, number the chain from the end that gives the lower number to the substituent encountered first
– indicate the number of times the substituent appears by a prefix di-, tri-, tetra-, etc.
– use commas to separate position numbers
2,4-Dimethylhexane1
23
45
66
54
32
1
(not 3,5-dimethylhexane)
Nomenclature - IUPAC
6. If there are two or more different substituents,– list them in alphabetical order– number from the end of the chain that gives
the substituent encountered first the lower number
3-Ethyl-5-methylheptane
12
34
5 67 7
65
43 2
1
(not 3-methyl-5-ethylheptane)
Nomenclature - IUPAC
7. The prefixes di-, tri-, tetra-, etc. are not included in alphabetization
– alphabetize the names of substituents first and then insert these prefixes
4-Ethyl-2,2-dimethylhexane(not 2,2-dimethyl-4-ethylhexane)
12 3
45
6
Nomenclature - IUPAC
• Alkyl groups
1-methylethyl (isopropyl)
propyl
ethyl
methyl
CondensedStructural FormulaName
CH3
-CH2CH3
-CH3
-CH2CH2CH3
-CHCH3
1,1-dimethylethyl (tert-butyl)
1-methylpropyl (sec-butyl)
2-methylpropyl (isobutyl)
butyl
CH3
CH3
CH3
CH3
-CH2CH2CH2CH3
-CH2CHCH3
-CHCH2CH3
-CCH3
CondensedStructural FormulaName
Nomenclature - Common• The number of carbons in the alkane determines the
name– all alkanes with four carbons are butanes, those with
five carbons are pentanes, etc.
– iso- indicates the chain terminates in -CH(CH3)2; neo- that it terminates in -C(CH3)3
CH3CH2CH2CH2CH3
CH3CHCH3
CH3
CH3CH2CHCH3
CH3
CH3CH2CH2CH3
CH3CCH3
CH3
CH3
Pentane Isopentane
IsobutaneButane
Neopentane
Propyl Groups
C
H
H
H
C
H
H
C
H
H
H
n-propyl
C
H
H
H
C
H
C
H
H
H
isopropyl
H
A primary carbon A secondary carbon
=>
Butyl Groups
C
H
H
H
C
H
C
H
H
C
H
H
H
C
H
H
H
C
H
C
H
HH
C
H
H
n-butyl sec-butyl
H
H
A primary carbon A secondary carbon
=>
Isobutyl Groups
CH
H
H
C
CH H
C
HH
H H
CH
H
H
C
CH H
C H
HH
H
H
H
A primary carbon A tertiary carbon
=>
isobutyl tert-butyl
Alkyl Groups
Branches on carbon chains H
H C CH3 methyl H H H
H C C CH3CH2 ethyl H H
Branched Alkanes
CH3
CH3CHCH3
methyl groups
CH3 CH3
CH3CHCH2CHCH3
Naming Branched Alkanes
CH3 methyl branch
CH3CH2CH2CHCH2CH3
6 5 4 3 2 1 Count
Naming Branched Alkanes
CH3 methyl branch
CH3CH2CH2CHCH2CH3
6 5 4 3 2 1 Count
3-Methylhexane
on third C CH3 six carbon chain group
Naming Summary
1. Count the C’s in the longest chain
2. Name each attached group
3 Count the longest carbon chain to
give the first attached group the
smallest number
4. Name and locate each group
Dæmi
A. CH3 CH3
CH3CHCH2CHCH3
B. CH3 CH3
CH3CH2CHCH2CCH2CH3
CH3
Svör
A. CH3 CH3
CH3CHCH2CHCH3 2,4-dimethylpentane
B. CH3 CH3
CH3CH2CHCH2CCH2CH3
CH3 3,3,5-trimethylheptane
Dæmi
Write a condensed structure for
A. 3,4-dimethylheptane
B. 2,2-dimethyloctane
Solution Alk5
A. 3,4-dimethylheptane CH3
CH3CH2CHCHCH2CH2CH3
CH3
B. 2,2-dimethyloctane CH3
CH3CCH2CH2CH2CH2CH2CH3
CH3
Constitutional/structural Isomerism
• Byggingaisomerur:Byggingaisomerur: Efni með sömu mólikúlformúlu en ólíka byggingaformúlu t.d.: C4H10
CH3CH2CH2CH3
Butane(bp -0.5°C)
CH3
CH3CHCH3
2-Methylpropane(bp -11.6°C)
Byggingaisomerur 11.6
– Eru þetta byggingaisomerur?
– Finndu lengstu keðjuna– Númerið að fyrsta hliðarhóp – Berið saman lengd og greinar
CH3CHCH2CHCH3 CH3
CH3
CH3CH2CHCHCH3
CH3
CH3
and (each is C7H16)
CH3CH2CHCHCH3
CH3
CH3
CH3CHCH2CHCH3
CH3
CH3
4
454
31and
5
1 12 23
3
52
5 4 3
2 1
Constitutional Isomerism
World populationWorld populationis aboutis about6,000,000,0006,000,000,000
4,111,846,763
4,347
75
31
Constitutional Isomers
MolecularFormula
CH4
C5H12
C10H22
C15H32
C30H62
36,797,588C25H52
Learning Check Alk6
Write 3 isomers of C5H12 and name each.
Solution Alk6
CH3CH2CH2CH2CH3 pentane
CH3
CH3CHCH2CH3 2-methylbutane
CH3
CH3CCH3 2,2-dimethylpropane
CH3
Dæmi
Write a condensed structure for
A. 3,4-dimethylheptane
B. 2,2-dimethyloctane
Svör
A. 3,4-dimethylheptane CH3
CH3CH2CHCHCH2CH2CH3
CH3
B. 2,2-dimethyloctane CH3
CH3CCH2CH2CH2CH2CH2CH3
CH3
Dæmi
Write 3 isomers of C5H12 and name each.
Svör
CH3CH2CH2CH2CH3 pentane
CH3
CH3CHCH2CH3 2-methylbutane
CH3
CH3CCH3 2,2-dimethylpropane
CH3
Cycloalkanes
• Hringmyndanir (CH2 groups)
• Formula: CnH2n
• Óskautaðir og óleysanlegir í vatni eins og alkanar
• Bræðslu, suðumörk og flestir eiginleikar svipaðir og hjá samsvarandi alkönum =>
Nafnakerfi• Sykloalkanar eru venjulega orðstofninn• Hringur á hvorki upphaf né endi – en sé
hliðarhópur þarf að númera….• Raða í stafrófsröð.• Stöku sinnum finnast cyklo sem
hliðarhópar eins og syklopentyl.
CH2CH3
CH2CH3
CH3=>
Cycloalkanes
• Hringir með 5 og 6 C algengastir
• Structure and nomenclature– if two substituents, number from the
substituent of lower alphabetical order– if three or more substituents, number to give
them the lowest set of numbers and then list substituents in alphabetical order
Cycloalkanes
• Teiknaðir– Lína er C-C bond– Horn og lína þýðir C
C
C CC
CC
C
C H2C
H2C CH2
CH
CH2
CH
CH3
CH3
C8H16
Cycloalkanes
• Example:Example: name these cycloalkanes
(a) (b)
(c) (d)
Bicycloalkanes
• Bicycloalkane:Bicycloalkane: an alkane that contains two rings that share two carbons
Bicyclo[4.4.0]decane(Decalin)
Bicyclo[4.3.0]nonane(Hydrindane)
Bicyclo[2.2.1]heptane(Norbornane)
Bicycloalkanes
• Nomenclature– parent is the alkane of the same number of carbons as are in the
rings– number from a bridgehead, along longest bridge back to the
bridgehead, then along the next longest bridge, etc.– show the lengths of bridges in brackets, from longest to shortest
Bicyclo[2.2.1]heptane
1
2
3
4
5
67
Chair Conformer
=>
Boat Conformer
=>
Conformational Energy
=>
Axial and Equatorial Positions
=>
Monosubstituted Cyclohexanes
=>
1,3-Diaxial Interactions
=>
Disubstituted Cyclohexanes
=>
Cycloalkanes
Cyclopropane CH2
CH2 CH2
CyclobutaneCH2 CH2
CH2 CH2
More Cycloalkanes
Cyclopentane CH2
CH2 CH2
CH2 CH2
Cyclohexane
CH2
CH2 CH2
CH2 CH2
CH2
Naming Cycloalkanes with Side Groups
Number of Naming
side groups
One Side group name goes in front of the cycloalkane name.
Two Number the ring in the direction that gives the lowest numbers to the side groups.
Cycloalkanes with Side Groups
CH3
CH3
CH3
CH3
CH3
CH3
methylcyclopentane
1,2-dimethylcyclopentane
1,2,4-trimethylcyclohexane
DæmiCH3
CH3
CH3
CH3
CH3
Lausn
1,3-dimethylcyclohexane
methylcyclopentane
1,2-dimethylcyclobutane
CH3
CH3
CH3
CH3
CH3
Chapter 11.8 Alkenes and Alkynes
Alkenes and Alkynes
Geometric Isomers / rúmísomerur Alkena
Alken hefur C=C tvítengi
Alkýn hefur CC
Mettuð/Saturated og ómettuð/Unsaturated
Mettuð kolvetni hafa mesta mögulega fjölda vetnisatóma. CnH2n+2 fyrir alkan
Ómettuð kolvetni hafa færri vetnisatóm en mettuð
Ómettuð kolvetni hafa tví eða þrítengi milli C atóma
Milli tví og þrítengja er enginn snúningur
ALKEN
C=C tvítengi Endar á EN
H2C=CH2 ethen (ethylen)
H2C=CH-CH3 propen (propylen)
cyclohexen
Alkyn
Carbon-carbon triple bonds Endar á -yn
HCCH ethyn (acetylen)
HCC-CH3 propyn
Alken mun algengari en alkyn
Nafnakerfi alken/alkyn
Þegar keðja hefur 4 eða fleiri C, þá númera keðju þaðan sem styst er í tvítengi án tillits til alkýl hliðarhópa.
1 2 3 4
CH2=CHCH2CH3 1-buten eða But-1-en
CH3CH=CHCH3 2-buten eða But-2-en
CH3CHCHCH3 2-butyn eða But-2-yn
Dæmi
Ritið nöfn þessara efna:
A. CH3CH2CCCH3
CH3
B. CH3C=CHCH3 C.
CH3
Lausn
IUPAC nöfnin eru:
A. CH3CH2CH=CHCH3 2-pentyne
CH3
B. CH3C=CHCH3 C.
3-methyl-2-butene 3-methylcyclopentene
CH3
• Þar sem engin snúningur er um tvítengi geta myndast rúmísomerur (geometric isomers)
• Rúmisomerur geta myndast ef keðja er 4C eða lengri. Rúmisomerur myndast á C no. 2 eða ofar
• Sömu megin úr tvítengi er CIS
• Sitthvoru megin úr tvítengi er Trans
Cis and Trans Isomers
Efnið er 2-buten Cis/trans eru mögulegar
CH3 CH3 CH3
CH = CH CH = CH
cis trans CH3
Cis/trans
• Cis/trans isomerur hafa mikil áhrif á lögun sameinda
• Náttúran notar oftast Cis í lífverum og allar fitusýrur í náttúrunni eru Cis
• Cis og trans hafa líka ólík bræðslu og suðumörk
Trans fitusýrur - ómettaðar
Sömu ómettuðu – CIS
12.8 Alkenar och Alkynar
• π orkumeira, • Léttara brjóta - hvargjarnara Stöðugra, orkulægra• óhvarfgjarnt
Nafnareglur
• Liknar det för alkaner –en -yn• 1. Namnge den kolkedja som innehåller längsta kedja
med dubbel trippel bindning• 2. Numrera kedjan från den ände som ger dubbel trippel
bindning lägst siffra.
3. Placera siffra och namnet på substituenter framför alken-alkyn namn
•2-etyl-1-buten
• Cykloalkanar, þar er talið yfir tvíbinding til hliðarhóps
• Hefur efnið tvo tvíbindinga kallast það DÍEN
• Hexatrien
Butadien
Cis-trans isomer
• stereoisomeri,cis-trans• Almennt er trans stöðugra
Cis-trans isomer
• Cis och trans isomeri kräver att de grupper som binder till kolet är OLIKA
11.9 Aromatic Compounds
Aromatic compounds innihalda benzene. Benzene C6H6 has 6 C atoms and 6 H Atoms
Two possible ring structures show benzene.
HH
H
H
H
H
H
H
H
H
H
H
Benzene Structure
The structures for benzene are also written as one formula with a circle within the ring to represented the alternating double bonds.
Benzene
structure
Aromatic Compounds in Nature and Health
Many aromatic compounds are common in nature and in medicine.
Ibuprofen
CHCOOH
CH3
CH3CHCH2
CH3
Aspirin Vanillin
CHO
OCH3
OH
COOH
COOCH3
Naming Aromatic Compounds
Aromatar hafa Bensen sem orðstofn og hliðarhópar settir fyrir fram. (stundum!!!!).
methylbenzene chlorobenzene
ClCH3
Þegar bensen er tvískipt
(tveir hliðarhópar) er hringur númeraður þannig að hóparnir fái sem lægst númer.
Forskeytin ortho (1,2), meta (1,3-) and para (1,4-) eru einnig notuð.
(para-chloromethylbenzene)(meta-dichlorobenzene)(ortho-dimethylbenzene)
1,2-dimethylbenzene 1,3-dichlorobenzene 1-chloro-4-methylbenzene
Cl
CH3
Cl
Cl
CH3
CH3
Aromatar hafa verslunarnöfn
(common name). Ef tvískipt, þá oft með
ortho-, meta-, para-.
(Methylbenzene) (meta-chloromethylbenzene) (hydroxybenzene) Toluene meta-chlorotoluene phenol
OH
Cl
CH3CH3
Dæmi
Select the names for each structure:
1. Chlorocyclohexane2. Chlorobenzene3. 1-chlorobenzene
1. Meta-methyltoluene2. Meta-dimethylbenzene3. 1,3-dimethylbenzene
CH3
CH3
Cl
Svör
Select the names for each structure:
2. Chlorobenzene
1. Meta-methyltoluene
2. Meta-dimethylbenzene
3. 1,3-dimethylbenzene
CH3
CH3
Cl
Dæmi
Ritið byggingaformúlur:
A. 1,3-dichlorobenzene
B. Ortho-chlorotoluene
Svör
Byggingaformúlurnar:
A. 1,3-dichlorobenzene
B. Ortho-chlorotoluene
Cl
Cl
CH3
Cl
Learning Check Alk11
Identify the organic family for each:
CH3CH2CH3
B.
C.
A.
Solution Alk11
Identify the organic family for each:
alkane
cycloalkane
aromatic
CH3CH2CH3
B.
C.
A.
Fused Benzene Rings
Naphthalene
3,4-Benzpyrene
Carcinogens
• Fused ring of benzene cause cancer• Contain four or more fused rings• Present in tobacco smoke, auto exhaust, and
burned food• The more a person smokes, the greater the
risk of developing cancer
Unsaturated Fatty Acids
Fatty acids in vegetable oils are omega-6 acids (the first double bond occurs at carbon 6 counting from the methyl group)
A common omega-6 acid is linoleic acid
CH3CH2CH2CH2CH2CH=CHCH2CH=CH(CH2)7COOH
6
linoleic acid, a fatty acid
Trans Fats
In vegetable oils, the unsaturated fats usually contain cis double bonds.
During hydrogenation, some cis double bonds are converted to trans double bonds (more stable) causing a change in the fatty acid structure
If a label states “partially” or “fully hydrogenated”, the fats contain trans fatty acids.
Trans Fats
In the US, it is estimated that 2-4% of our total Calories is in the form of trans fatty acid.
trans fatty acids behave like saturated fatty acids in the body.
Several studies reported that trans fatty acids raise LDL-cholesterol. Some studies also report that trans fatty acid lower HDL-cholesterol
The trans fatty acids controversy will continue to be debated.
Fats and AtheroschlerosisInuit people of Alaska have a high fat diet
and high blood cholesterol levels, but a very
low occurrence of atherosclerosis and heart
attacks.
Fat in the Intuit diet was primarily from fish
such as salmon, tuna and herring rather than
from land animals (as in the American diet).
Omega-3 Fatty Acids
Fatty acids in the fish oils are mostly the omega-3 type (first double bond occurs at the third carbon counting from the methyl group).
linolenic acid 18 carbon atoms
CH3CH2CH=CHCH2CH=CHCH2CH=CH(CH2)7COOH
eicosapentaenoic acid (EPA) 20 carbon atoms
CH3CH2(CH=CHCH2)5(CH2)2COOH
Atherosclerosis
Plaques of cholesterol adhere to the walls of the
blood vessels
Blood pressure rises as blood squeezes through
smaller blood vessels
Blood clots may form
Omega-3 fatty acids decrease the “sticking” of
blood platelets (fewer blood clots)
Omega-3 fatty acids can increase bleeding time
Learning Check HA6
(1) Ture or (2) False
A. ____ There are more unsaturated fats in vegetable oils.
B. ____ Vegetable oils have more omega-3 oils than found in fish.
C. ____ Hydrogenation of oils converts some cis-double bonds to trans- double bonds.
D. ____ Animal fats have more saturated fats.
Solution HA6
(1) True or (2) False
A. _T__ There are more unsaturated fats in vegetable oils.
B. _F__ Vegetable oils have more omega-3 oils than found in fish.
C. _T__ Hydrogenation of oils converts some cis-double bonds to trans- double bonds.
D. _T__ Animal fats have more saturated fats.
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