Download CHM 103 Lecture 23 S07

Last Time: Aromatic Compounds
“Special Conjugation”
Announcements & Agenda (03/09/07)
Exam next Wednesday!
„
„
„
„
One Important Example: Benzene (Know This One!)
Covers Ch 7, 8, 1010-12 (not 12.6, on Exam 3)
Practice Exam Posted!
Review Monday @ 6:30p (Room TBA)
Come visit Bob!!!
• 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.
Today
„
„
„
„
Quiz!
Properties & Reactions of Alcohols (12.1(12.1-12.3)
Ethers & Thiols (12.1(12.1-12.3)
Aldehydes & Ketones (12.4(12.4-12.5) (?)
1
By the way, aromatics are called as such b/c many of
them have noticeable odors!
2
Last Time: A color debate!
Last Time: Polymerization
Highly conjugated pi bonds!
CH2
In polymerization, small repeating units
called monomers join to form a long chain
polymer.
CH3
H3C
CH2
N
N
Fen+
N
N
H3C
It’s the HEME in
hemoglobin!!!
H
H
H
CH3
H
+
C C
H
H
C C
H
H
+
H
H
monomer unit repeats
C C
H
H
Ethylene monomers
H H H
HO
O
HO
chain continues
O
Note: Highly conjugated molecules are
typically colored!
H H H
C C C
C C C
H H H
HnH H
chain continues
Polyethylene
3
4
1
Last Time: Alcohols
Properties of 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.
• contain polar OH groups.
• form hydrogen bonds with
other alcohol molecules.
• Short alcohols (1(1-4 C
atoms) are soluble in
water
•
> 4 C atoms less soluble
• have much higher BPs
than alkanes of similar
mass.
water alcohol
phenol
5
Some Typical Alcohols (Know These)
OH
|
“rubbing alcohol” CH3—CH—
CH—CH3
2-propanol (isopropyl
(isopropyl alcohol)
alcohol)
Could make you sick
antifreeze
HO—
HO—CH2—CH2—OH
6
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
1,21,2-ethanediol (ethylene
(ethylene glycol)
glycol)
OH
Will kill you
|
glycerol
HO—
CH—CH2—OH
HO—CH2—CH—
1,2,31,2,3-propanetriol
Part of cooking oil
7
8
2
Properties of Phenol
Derivatives of Phenol
Compounds of phenol are the active
ingredients in the essential oils of cloves,
vanilla, nutmeg, and mint.
• is soluble in water.
• has a hydroxyl group that ionizes slightly
(weak acid).
• is corrosive and irritating to skin.
OH
O-
+ H2O
+ H3O+
9
Naming Alcohols
Drawing structures revisited
Traditional drawing
OH
• IUPAC: Alcohols will be called somethingol
somethingol
• If other functional groups present, the -OH group
will sometimes be named as a “hydroxyl
“hydroxyl”” group
Abbreviated drawing
OH
Formula
CH3CH2CH2CHCH3
2-pentanol
H
C
HC
CH
HC
CH
C
H
Benzene
H
C
HC
CH
HC
CH
C
Phenol
OH
10
IUPAC
CH4
methane
methane
CH3─OH
methanol
methanol
CH3─CH3
ethane
ethane
CH3─CH2─OH
ethanol
ethanol
Common Name
methyl alcohol
ethyl alcohol
• Also know common names for propyl alcohol and
OH
11
those mentioned earlier
12
3
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
Reactions of Alcohols
Tertiary (3º)
(3º)
3 groups
CH3
|
CH3—C—OH
|
CH3
13
Dehydration of Alcohols
Combustion of Alcohols
• Alcohols dehydrate when heated with an acid
catalyst
• Lose —H and —OH from adjacent carbon
atoms
Alcohols undergo combustion with O2 to produce
CO2 and H2O.
2CH3OH + 3O2
14
2CO2 + 4H2O + Heat
H OH
|
|
H—C—C—H
|
|
H H
alcohol
15
H+, heat
H—C=C—
C=C—H + H2O
| |
H H
alkene
16
4
Learning Check
Solution
OH
│
CH3─CH─
CH─CH3 = 2-propanol = C3H8O
Write the equations for the reaction of 22propanol when it undergoes
1. combustion.
1. combustion
2C3H8O + 9O2
2. dehydration.
17
2. dehydration
OH
│
CH3─CH─
CH─CH3
6CO2 + 8H2O
Major Product: Alkene w/
more alkyl substiuents
H+
CH3─CH=CH2 + H2O
18
Oxidation of Primary (1°) Alcohols
Oxidation of Secondary (2°
(2°) 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 + H2O
CH3—C—H
|
H
Ethanol
Ethanal
(ethyl alcohol)
(acetaldehyde)
19
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 + H2O
CH3─C─CH3
│
H
2-propanol (isopropyl alcohol)
22-propanol
20
(dimethyl ketone)
ketone)
5
Oxidation of Tertiary ( 3)°Alcohols
Oxidation of Ethanol in the Body
Tertiary 3°
3° alcohols do not readily oxidize.
[O]
Tertiary alcohol
no reaction
OH
│
[O]
no product
CH3─C─CH3
│
CH3
no H on the CC-OH to oxidize
In the body,
• enzymes in the liver oxidize ethanol.
• aldehyde product impairs coordination.
• blood alcohol over 0.4% can be fatal.
O
O
║
║
CH3CH
CH3COH
2CO2 + H2O
CH3CH2OH
ethanol
acetaldehyde
acetic acid
2-methylmethyl-2-propanol
21
Ethanol CH3CH2OH
• acts as a depressant.
• kills or disables more
people than any other
drug.
• is metabolized at a rate of
1212-15 mg/dL per hour by
a social drinker.
• is metabolized at a rate of
30 mg/dL per hour by an
alcoholic.
22
Effect of Alcohol on the Body
23
24
6
Ethers
Alcohol Contents in Common Products
% Ethanol
50%
40%
1515-25%
12%
3-9%
• contains an ─O─ between two carbon
groups (R(R-O-R’).
• has a common name that gives the alkyl
names of the attached groups followed
by ether.
ether.
CH3─O─CH3 CH3─CH2─O─CH3
Product
Whiskey, rum, brandy
Flavoring extracts
Listerine, Nyquil, Scope
Wine, Dristan, Cepacol
Beer, Lavoris
25
Boiling Points of Ethers
26
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 11-4 C atoms are soluble, but not with 5 or
more C atoms.
Ethers
• are only modestly
polar.
• have an O atom,
but there is no H
attached.
• cannot form
hydrogen bonds
between ether
molecules.
27
28
7
Comparing Solubility & Boiling Points
Molar
Compound
Mass
Alkane CH3─CH2─CH3 44
Ether
CH3─O─CH3
Alcohol CH3─CH2─OH
Boiling
Point (°C)
-42
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
Soluble
in Water?
No
46
-23
Yes
46
78
Yes
29
MTBE
Ethane(enflurane)
Ethane(enflurane)
Penthrane
30
Thiols
Methyl terttert-butyl ether
CH3
│
CH3─O─C─CH3
│
CH3
• 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.
• is second in production of organic chemicals.
• is an additive used to improve gasoline
performance.
• the -SH group may
also be called a
“mercapto”
mercapto” group
• use is questioned since the discovery that MTBE
has contaminated water supplies.
31
32
8
Thiols
Oxidation of Thiols
Thiols
• often have
strong odors.
When thiols undergo oxidation,
• an H atom is lost from each of two –SH groups.
• the product is a disulfide.
disulfide.
[O]
CH3─S─S─CH3 + H2O
CH3─SH + HS─CH3
• are used to
detect gas
leaks.
• are found in
onions,
oysters, and
garlic.
33
Aldehydes and Ketones
34
Naming Aldehydes
An aldehyde contains a
carbonyl group (C=O),
which is a carbon atom
with a double bond to an
oxygen atom.
In a ketone,
ketone, the carbon of
the carbonyl group is
attached to two other
carbon atoms.
35
36
9
Naming Ketones
Aldehydes in Flavorings
• as IUPAC, the -e in the alkane name is replaced with
–one.
one.
• With a common name, the alkyl groups attached to the
carbonyl group are named alphabetically followed
by ketone.
O
O
║
║
CH3─C─CH2─CH3
CH3 ─C─CH3
Several naturally occurring aldehydes are
used as flavorings for foods and fragrances.
O
C
H
Benzaldehyde (almonds)
O
CH=CH C
propanone
H
2-butanone
(dimethyl ketone)
(ethyl methyl ketone)
Cinnamaldehyde (cinnamon)
37
38
Learning Check
Ketones in Common Use
Classify each as 1) aldehyde or 2) ketone.
O
O
||
||
A. CH3—CH2—C—CH3
B. CH3—C—H
Nail polish remover,
solvent
O
CH3
|
||
C. CH3—C—CH2—C—H
|
CH3
Butter flavoring
Propanone,
Dimethylketone, Acetone
39
O
D.
40
10
Properties of Aldehydes & Ketones
• The polar carbonyl group provides dipoledipole-dipole
interactions.
δ+ δ-
C=O
δ+ δ-
Boiling Points
Aldehydes and ketones have
• polar carbonyl groups (C=O).
C=O
δ+ δ-
C=O
• attractions between polar groups.
• Without an H on the oxygen, aldehydes and
ketones cannot form hydrogen bonds to each
other.
δ+ δ-
δ+ δ-
C=O
C=O
• higher bp’s than alkanes and ethers of similar
mass.
• lower bp’s than alcohols of similar mass.
41
Comparison of Boiling Points
42
Solubility in Water
The electronegative O atom of the carbonyl
group of aldehydes and ketones forms
hydrogen bonds with water.
43
44
11
Tollens’ Test
Benedict’s Test
• Benedict’s reagent,
which contains Cu2+,
reacts with aldehydes
that have an adjacent
OH group.
• Tollens’
Tollens’ reagent,
which contains
Ag+, oxidizes
aldehydes, but
not ketones.
ketones.
• An aldehyde is
oxidized to a
carboxylic acid, while
Cu2+ is reduced to
give red Cu2O(s).
• Ag+ is reduced
to metallic Ag,
which appears
as a “mirror” in
the test tube.
45
46
12