Chapter 25 Lipids - Welcome to Terry Sherlock's Web Site

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Transcript Chapter 25 Lipids - Welcome to Terry Sherlock's Web Site

CHE 242
Unit VIII
The Structure, Properties,
Reactions and Mechanisms of
Carboxylic Acids and Their
Derivatives
CHAPTER TWENTY-FIVE
Terrence P. Sherlock
Burlington County College
2004
Examples of Lipids
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Waxes
• Esters of long-chain fatty acids with
long-chain alcohols.
• Spermaceti is found in the head of the
sperm whale and is probably used to
control buoyancy.
• Most natural waxes are protective coats
for plants’ leaves, insects’ exoskeleton,
mammals’ fur, and birds’ feathers. =>
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Triglycerides
• Fatty acid esters of glycerol.
• Fats
Solid at room temperature
Most are derived from mammals
• Oils
Liquid at room temperature
Most are derived from plants or coldblooded animals.
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4
Fatty Acids
• Unbranched carboxylic acids with
12-20 carbons.
• Most contain an even number of
carbons because they are built from
acetic acid units.
• Melting points increase with increasing
molecular weights.
• Unsaturation greatly lowers the melting
point.
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Melting Points
• A cis double bond bends the molecule
so it cannot pack efficiently.
• A trans double bond has less effect.
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Fats and Oils
• Most fats have saturated fatty acids.
• Most oils have unsaturated fatty acids.
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Saponification
• “Soap-making”
• Base-catalyzed hydrolysis of ester
linkages in fats and oils.
CH2 OH
O
CH2 O C
O
(CH2)16CH3
CH O C
O
(CH2)16CH3
CH2 O C
CH OH
CH2 OH
+ 3 NaO H
O
+-
+ 3 Na O C
(CH2)16CH3
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A soap
(CH2)16CH3
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Soap Structure
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Grease in Soap Solution
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Detergents
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18
12 CH3
Steroids
2
3
17
11
19
CH3 C 13 16
D
1
9 8 14
15
10
H
A
B
5
7
4 H 6
• Polycyclic, usually all trans.
• Common structural features:
=O or -OH at C3
Side chain at C17
Double bond from C5 to either C4 or C6.
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A-B Ring Junction
May be cis, but usually is trans.
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Cholesterol
CH3
CH3
3
HO
5
H
17
H
H
H
6
H
• Common biological intermediate.
• Probably a precursor to other steroids.
• Side chain at C17 and double bond C5-C6.
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Sex Hormones
CH3
CH3
H
OH
H
CH3
H
OH
H
H
H
O
H
H
HO
testosterone
estradiol
• Female hormone has an aromatic ring
and one less methyl group than the
male hormone.
• Testosterone is converted to estradiol
in the ovaries.
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POWER POINT IMAGES FROM
“ORGANIC CHEMISTRY, 5TH EDITION”
L.G. WADE
ALL MATERIALS USED WITH PERMISSION OF AUTHOR
PRESENTATION ADAPTED FOR BURLINGTON COUNTY COLLEGE
ORGANIC CHEMISTRY COURSE
BY:
ANNALICIA POEHLER STEFANIE LAYMAN
CALY MARTIN
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