Download 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!
1
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.
18
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
19
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.
20
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)
22
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
24
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.
26
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).
30