Transcript CHM 103 Lecture 24 S07

Announcements & Agenda (03/12/07)
Pick Up Quizzes
Exam THIS Wednesday!
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Covers Ch 7, 8, 10-12 (not 12.6, on Exam 3)
Practice Exam & Key Posted!
Review TONIGHT @ 6:30p (Room 1019)
Today
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Ethers & Thiols
Aldehydes & Ketones (12.4-12.5)
Note Benedict’s Test, Tollen’s Test, & Iodoform Test
will not be on Wednesday’s Exam!
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Last Time: Alcohol Classification
• determined by the number of alkyl groups directly
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
2
Last Time: 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
3
Last Time: Oxidation of 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
|
NOTE: If enough
H
oxidant around,
Ethanol
Ethanal
will go on to form
(ethyl alcohol)
(acetaldehyde)
4
carboxylic acid!
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.
[O]
secondary alcohol
ketone
OH
O
│
[O]
║
CH3─C─CH3
CH3─C─CH3 + H2O
│
H
2-propanol (isopropyl alcohol)
(dimethyl ketone)
2-propanol
5
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
6
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
7
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.
8
Effect of Alcohol on the Body
9
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
10
Ethers
• contains an ─O─ between two carbon
groups (R-O-R’).
• has a common name that gives the alkyl
names of the attached groups followed
by ether.
CH3─O─CH3 CH3─CH2─O─CH3
11
Boiling Points of Ethers
Ethers
• are only modestly
polar.
• have an O atom,
but there is no H
attached.
• cannot form
hydrogen bonds
between ether
molecules.
12
Solubility of Alcohols & Ethers in Water
Alcohols and ethers
• are more soluble in water than alkanes because
the oxygen atom can hydrogen bond with water.
• with 1-4 C atoms are soluble, but not with 5 or
more C atoms.
13
Comparing Solubility & Boiling Points
Molar
Compound
Mass
Alkane CH3─CH2─CH3 44
Ether
CH3─O─CH3
Alcohol CH3─CH2─OH
Boiling
Point (°C)
-42
Soluble
in Water?
No
46
-23
Yes
46
78
Yes
14
Ethers as Anesthetics
Anesthetics
• inhibit pain signals to the brain.
• like diethyl ether CH3─CH2─O─CH2─CH3 were used
for over a century, but caused nausea and were
flammable.
• developed by the 1960’s were nonflammable.
Cl F
F
Cl F
H
│ │
│
│ │
│
H─C─C─O─C─H
H─C─C─O─C─H
│ │
│
│ │
│
F F
F
H F
H
Ethane(enflurane)
Penthrane
15
MTBE
Methyl tert-butyl ether
CH3
│
CH3─O─C─CH3
│
CH3
• is second in production of organic chemicals.
• is an additive used to improve gasoline
performance.
• use is questioned since the discovery that MTBE
has contaminated water supplies.
16
Thiols
• are carbon
compounds that
contain a –SH group.
• are named in the
IUPAC system by
adding thiol to the
alkane name of the
longest carbon chain.
• the -SH group may
also be called a
“mercapto” group
17
Thiols
Thiols
• often have
strong odors.
• are used to
detect gas
leaks.
• are found in
onions,
oysters, and
garlic.
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Oxidation of Thiols
When thiols undergo oxidation,
• an H atom is lost from each of two –SH groups.
• the product is a disulfide.
[O]
CH3─SH + HS─CH3
CH3─S─S─CH3 + H2O
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Aldehydes and Ketones
An aldehyde contains a
carbonyl group (C=O),
which is a carbon atom
with a double bond to an
oxygen atom.
In a ketone, the carbon of
the carbonyl group is
attached to two other
carbon atoms.
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Naming Aldehydes
21
Aldehydes in Flavorings
Several naturally occurring aldehydes are
used as flavorings for foods and fragrances.
O
C
H
Benzaldehyde (almonds)
O
CH=CH C
H
Cinnamaldehyde (cinnamon)
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Naming Ketones
• as IUPAC, the -e in the alkane name is replaced with –
one.
• With a common name, the alkyl groups attached to the
carbonyl group are named alphabetically followed
by ketone.
O
O
║
║
CH3 ─C─CH3
CH3─C─CH2─CH3
propanone
(dimethyl ketone)
2-butanone
(ethyl methyl ketone)
23
Ketones in Common Use
Nail polish remover,
solvent
Butter flavoring
Propanone,
Dimethylketone, Acetone
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Properties of Aldehydes & Ketones
• The polar carbonyl group provides dipole-dipole
interactions.
+ -
C=O
+ -
C=O
• Without an H on the oxygen, aldehydes and
ketones cannot form hydrogen bonds to each
other.
25
Boiling Points
Aldehydes and ketones have
• polar carbonyl groups (C=O).
+ -
C=O
• attractions between polar groups.
+ -
+ -
C=O
C=O
• higher bp’s than alkanes and ethers of similar
mass.
• lower bp’s than alcohols of similar mass.
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Comparison of Boiling Points
27
Solubility in Water
The electronegative O atom of the carbonyl
group of aldehydes and ketones forms
hydrogen bonds with water.
28
Tollens’ Test
• Tollens’ reagent,
which contains
Ag+, oxidizes
aldehydes, but
not ketones.
• Ag+ is reduced
to metallic Ag,
which appears
as a “mirror” in
the test tube.
29
Benedict’s Test
• Benedict’s reagent,
which contains Cu2+,
reacts with aldehydes
that have an adjacent
OH group.
• An aldehyde is
oxidized to a
carboxylic acid, while
Cu2+ is reduced to
give red Cu2O(s).
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