Transcript CHM 103 Lecture 22 S07

Announcements & Agenda (03/07/07)
Exam next Wednesday!
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Covers Ch 7, 8, 10-12 (not 12.6, on Exam 3)
Practice Exam Posted!
Come visit Bob!!!
Today
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Aromatic Compounds (11.5)
Polymers (11.4)
Properties & Reactions of Alcohols (12.1-12.3)
1
Last Time:
Bond Angles in Alkenes & Alkynes
According to VSEPR theory:
• the 3 groups bonded to C
atoms in a double bond are
at 120° angles.
• alkenes are flat because the
atoms in a double bond all
lie in the same plane.
• the 2 groups bonded to
each carbon in a triple bond
are at 180° angles.
2
Last Time: Cis-Trans Isomers
In an alkene, the double bond
• is rigid, i.e. NO ROTATION around the double bond!
• holds attached groups in fixed positions.
• makes cis/trans isomers possible.
• Important in nature – such as in pheromones
CH3
CH3
CH = CH
cis
CH3
CH = CH
trans
CH3
(similar groups on same side) (similar groups on opp. sides)3
By the way, cyclohexane & other cyclic
compounds are not flat.
H OH
HO
HO
H
O
Example: a monosaccharide
H
H
OH
OH
H
4
Geometric Isomerism in cycloalkanes:
H
Cl
H
H
H
H
H
H
H
H
H
Cl
H
H
H
Cl
H
H
H
Cl
Cl
Cyclobutane
chlorocyclobutane
Trans =
“across”
H
H
Cis = same
side
H
1,2-dichlorocyclobutane
5
Last Time: Addition Reactions
• The double/triple
bond can be broken
•
alkenes & alkynes are
very reactive.
• In addition reactions,
reactants are added
to the carbon atoms in
the double or triple
bond.
6
One Last Thing about Hydration…
Hydration is also reversible – the equilibrium amounts of
alkene compared to alcohol depend on how much water is
around.
Lots of water – the reaction tends to use up as much
water as it can, and most of the alkene forms
alcohol.
If water is removed, water can be pulled off from
alcohol to form the alkene. (concentrated acid).
7
Conjugated bonds
If you have alternating double & single bonds,
• you get “extended, conjugated” pi bonds.
• what looks like a single bond in between two double
bonds, is actually sort of a double bond itself.
• multiple pairs of electrons can spread out all the way
through the aligned parallel orbitals -> molecules like this!
H
C
H
H
C
C
C
H
H
H
H
H
H
C
C
C
C
H
H
H
8
Aromatic Compounds
“Special Conjugation”
One Important Example: Benzene (Know This One!)
• a ring of 6 C & 6 H atoms.
• a flat ring structure drawn with three double bonds.
• represented by 2 structures because electrons are
shared among all the C atoms.
By the way, aromatics are called as such b/c many of
them have noticeable odors!
9
Benzene and Aromaticity
Aromatics are compounds that have
conjugated pi bonds around a ring. Electrons
love this, and aromatics are very stable.
10
Occurrences in Nature & Health
Vanillin
O
O
Aspirin
CH
COH O
C O CH3
OCH3
O
OH
NH C CH3
CH3 O
CH3
H3C CH CH2
CH COH
OH
Ibuprofen
Acetaminophen
Aromatics can be bad too  Many are
carcinogens! Can interact with DNA.
11
Aromatic rings can include N atoms, too.
They can be 5 or 6 membered rings (and >), fused rings,
etc.
Pyridine
N
H
N
O
H2N
H2N
HN
N
O
CH C
OH
CH2
N
O
N
H
N
Adenine
Thymine
Phenylalanine
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By the way, why is blood red?
Highly conjugated pi bonds!
CH2
CH3
H3C
CH2
N
N
Fen+
N
N
H3C
HO
It’s the HEME in
hemoglobin!!!
CH3
O
HO
O
Note: Highly conjugated molecules are
typically colored!
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11.4
Polymers of Alkenes
14
Polymers: What are they?
• large, long-chain molecules.
• found in nature
• Examples: cellulose in plants, starches in food,
proteins, DNA, etc.
• also synthetic such as polyethylene and
polystyrene, Teflon, and nylon.
• have small repeating units called
monomers.
• can be made from reaction of small alkenes
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Common Synthetic Polymers
16
Common Synthetic Polymers
Important: Properties of polymers depend on
what monomers they are made from and how
they are put together!
17
Polymerization
In polymerization, small repeating units
called monomers join to form a long chain
polymer.
H
H
+
C C
H
H
H
H
C C
H
H
+
H
H
monomer unit repeats
C C
H
H
Ethylene monomers
chain continues
H H H
H H H
C C C
C C C
H H H
H nH H
chain continues
Polyethylene
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Recycling Plastics
Recycling is simplified by using codes on
plastic items.
1
2
3
4
5
6
PETE Polyethyleneterephtalate
HDPE High-density polyethylene
PV Polyvinyl chloride
LDPE Low-density polyethylene
PP Polypropylene
PS Polystyrene
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CHAPTER 12!
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28 Good Practice Problems (Ch 12)
12.01, 12.03, 12.07, 12.09, 12.11,
12.13, 12.15, 12.17, 12.19, 12.23,
12.25, 12.31, 12.33, 12.35, 12.37,
12.39, 12.41, 12.43, 12.45, 12.49,
12.51, 12.53, 12.55, 12.63, 12.65,
12.67, 12.71, 12.75
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Alcohols
An alcohol contains a hydroxyl group (—OH)
attached to a carbon chain.
•
occur in many important molecules like sugars and -ol
compounds (cholesterol, menthol, etc.)
A phenol contains a hydroxyl group (—OH) attached
to a benzene ring.
water alcohol
phenol
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Properties of Alcohols
• contain polar OH groups.
• form hydrogen bonds with
other alcohol molecules.
• Short alcohols (1-4 C
atoms) are soluble in
water
•
> 4 C atoms less soluble
• have much higher BPs
than alkanes of similar
mass.
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Some Typical Alcohols (Know These)
OH
|
“rubbing alcohol” CH3—CH—CH3
2-propanol (isopropyl alcohol)
Could make you sick
antifreeze
HO—CH2—CH2—OH
1,2-ethanediol (ethylene glycol)
OH
Will kill you
|
glycerol
HO—CH2—CH—CH2—OH
1,2,3-propanetriol
Part of cooking oil
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http://www.annals.org/cgi/content/full/122/6/456
The Elixir Sulfanilamide disaster of 1937
105 people died
1938 Federal Food, Drug and Cosmetic
Act, which required proof of safety before
the release of a new drug
In the 1980s similar incident happened in
Haiti killing dozens of Haitian infants
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Properties of Phenol
• is soluble in water.
• has a hydroxyl group that ionizes slightly
(weak acid).
• is corrosive and irritating to skin.
OH
O-
+ H2O
+ H3O+
26
Derivatives of Phenol
Compounds of phenol are the active
ingredients in the essential oils of cloves,
vanilla, nutmeg, and mint.
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Drawing structures revisited
Traditional drawing
OH
Abbreviated drawing
OH
CH3CH2CH2CHCH3
2-pentanol
H
C
HC
CH
HC
CH
C
H
Benzene
H
C
HC
CH
HC
CH
C
Phenol
OH
OH
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Naming Alcohols
• IUPAC: Alcohols will be called somethingol
• If other functional groups present, the -OH group
will sometimes be named as a “hydroxyl” group
Formula
IUPAC
CH4
methane
CH3─OH
methanol
CH3─CH3
ethane
CH3─CH2─OH
ethanol
Common Name
methyl alcohol
ethyl alcohol
• Also know common names for propyl alcohol and
those mentioned earlier
29
Classification of Alcohols
• determined by the number of alkyl groups attached
to the carbon bonded to the hydroxyl.
• primary (1°), secondary (2°), or tertiary(3).
Primary (1º)
1 group
H
|
CH3—C—OH
|
H
Secondary (2º)
2 groups
CH3
|
CH3—C—OH
|
H
Tertiary (3º)
3 groups
CH3
|
CH3—C—OH
|
CH3
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Reactions of Alcohols
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Combustion of Alcohols
Alcohols undergo combustion with O2 to produce
CO2 and H2O.
2CH3OH + 3O2
2CO2 + 4H2O + Heat
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Dehydration of Alcohols
• Alcohols dehydrate when heated with an acid
catalyst
• Lose —H and —OH from adjacent carbon
atoms
H OH
|
|
H—C—C—H
|
|
H H
alcohol
H+, heat
H—C=C—H + H2O
| |
H H
alkene
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Learning Check
Write the equations for the reaction of 2propanol when it undergoes
1. combustion.
2. dehydration.
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Solution
OH
│
CH3─CH─CH3 = 2-propanol = C3H8O
1. combustion
2C3H8O + 9O2
2. dehydration
OH
│
CH3─CH─CH3
6CO2 + 8H2O
Major Product: Alkene w/
more alkyl substiuents
H+
CH3─CH=CH2 + H2O
35
Oxidation of Primary (1) Alcohols
When a primary alcohol is oxidized, [O],
• one H is removed from the –OH.
• another H is removed from the C bonded to -OH.
• an aldehyde is produced.
This is a carbonyl
[O]
group…
Primary alcohol
Aldehyde
OH
O
|
[O]
||
CH3—C—H
CH3—C—H + H2O
|
H
Ethanol
Ethanal
(ethyl alcohol)
(acetaldehyde)
36
Oxidation of Secondary (2) Alcohols
When a secondary alcohol is oxidized, [O],
• one H is removed from the –OH.
• another H is removed from the C bonded to -OH.
• a ketone is produced.
ASK ME ABOUT “R”!!!
[O]
secondary alcohol
ketone
OH
O
│
[O]
║
CH3─C─CH3
CH3─C─CH3 + H2O
│
H
2-propanol (isopropyl alcohol)
(dimethyl ketone)
2-propanol
37
Oxidation of Tertiary ( 3)Alcohols
Tertiary 3 alcohols do not readily oxidize.
[O]
Tertiary alcohol
no reaction
OH
│
[O]
CH3─C─CH3
no product
│
CH3
no H on the C-OH to oxidize
2-methyl-2-propanol
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Oxidation of Ethanol in the Body
In the body,
• enzymes in the liver oxidize ethanol.
• aldehyde product impairs coordination.
• blood alcohol over 0.4% can be fatal.
O
O
║
║
CH3CH2OH
CH3CH
CH3COH
2CO2 + H2O
ethanol
acetaldehyde
acetic acid
39
Ethanol CH3CH2OH
• acts as a depressant.
• kills or disables more
people than any other
drug.
• is metabolized at a rate of
12-15 mg/dL per hour by
a social drinker.
• is metabolized at a rate of
30 mg/dL per hour by an
alcoholic.
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Effect of Alcohol on the Body
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Alcohol Contents in Common Products
% Ethanol
50%
40%
15-25%
12%
3-9%
Product
Whiskey, rum, brandy
Flavoring extracts
Listerine, Nyquil, Scope
Wine, Dristan, Cepacol
Beer, Lavoris
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