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Lecture 4 Alcohols, Phenols, and Thiols
Alcohols, Phenols, and Thiols
Copyright © 2007 by Pearson Education, Inc.
Publishing as Benjamin Cummings
1
Midterm II Outcome
30%
25%
% Student
20%
15%
10%
5%
0%
> 90
80-90
70-79
50-70
< 50
Score on Test
Class Average: 75
High Score: 103
Low Score: 32
2
Alcohols and Phenols
An alcohol contains
 A hydroxyl group
(—OH) attached to
a carbon chain.
A phenol contains
 A hydroxyl group
(—OH) attached to
a benzene ring.
Copyright © 2007 by Pearson Education, Inc.
Publishing as Benjamin Cummings
3
Classification of Alcohols
Alcohols are classified
 By the number of alkyl groups attached to the carbon
bonded to the hydroxyl.
 As primary (1°), secondary (2°), or tertiary (3°).
Primary (1º)
1 group
H
|
CH3—C—OH
|
H
Secondary (2º)
Tertiary (3º)
2 groups
3 groups
CH3
CH3
|
|
CH3—C—OH
CH3—C—OH
|
|
H
CH3
4
Learning Check
Classify each alcohol as
(P) primary, (S) secondary, or (T) tertiary.
OH
|
1. CH3—CH—CH2—CH3
2. CH3—CH2—CH2—OH
OH
|
3. CH3—CH2—C—CH2—CH3
|
CH3
5
Naming Alcohols
The names of alcohols
 In the IUPAC system replace -e of alkane name with ol.
 that are common names use the name of the alkyl
group followed by alcohol.
Formula
IUPACCommon Name
CH4
methane
CH3─OH
methanol
CH3─CH3
ethane
CH3─CH2─OH
ethanol
methyl alcohol
ethyl alcohol
6
More Names of Alcohols
In IUPAC names for longer carbon chains, the chain is
numbered from the end nearest the ─OH group.
CH3─CH2─CH2─OH
1-propanol
OH
│
CH3─CH─CH2─CH3
2-butanol
CH3
OH
│
│
CH3─CH─CH2─CH2─CH─CH3
5-methyl-2-hexanol
6
5
4
3
2
1
7
Some Typical Alcohols
“rubbing alcohol”
OH
|
CH3—CH—CH3
2-propanol (isopropyl alcohol)
antifreeze
HO—CH2—CH2—OH
1,2-ethanediol (ethylene glycol)
glycerol
OH
|
HO—CH2—CH—CH2—OH
1,2,3-propanetriol
Copyright © 2007 by Pearson Education, Inc.
Publishing as Benjamin Cummings
8
Learning Check
Give the IUPAC name for each of the following:
1. CH3—CH2—CH2—CH2—OH
2.
OH CH3
|
|
CH3—CH—CH—CH2—CH3
OH
3.
9
Learning Check
Write the structure of the following:
A. 3-pentanol
B.
ethyl alcohol
C.
3-methylcyclohexanol
10
Naming Phenols
To name a phenol with two substituents,
 Assign C-1 to the carbon attached to the –OH.
 Number the ring to give the lowest numbers.
 Use prefixes o, m, and p for common names.
OH
OH
OH
Cl
Br
Phenol
3-chlorophenol
(m-chlorophenol)
4-bromophenol
(p-bromophenol)
11
Phenols in Medicine
Phenol
 Is the IUPAC name for benzene with a hydroxyl
group.
 Is used in antiseptics and disinfectants.
OH
OH
OH
OH
OH
CH2CH2CH2CH2CH2CH3
phenol
resorcinol
4-hexylresorcinol
12
Derivatives of Phenol
 Compounds of phenol are the active ingredients in the
essential oils of cloves, vanilla, nutmeg, and mint.
Copyright © 2007 by Pearson Education, Inc.
Publishing as Benjamin Cummings
13
Learning Check
Write the structure of each of the following:
A.
3-pentanol
B.
ethyl alcohol
C.
p-methylphenol
14
Thiols
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.
15
Naming Thiols
 In thiols with long carbon chains, the chain is numbered
to locate the –SH group.
CH3—CH2—CH2—SH
1-propanethiol
SH
|
CH3—CH—CH3
2-propanethiol
16
Thiols
Thiols
 Often have
strong odors.
 Are used to
detect gas leaks.
 Are found in
onions, oysters,
and garlic.
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Publishing as Benjamin Cummings
17
Learning Check
Draw the structure of each compound.
A. 2-butanethiol
B. 2-methyl-1-butanol
18
Learning Check
Name each of the following compounds:
OH
|
A. CH3—CH2 —CH—CH3
CH3
|
B. CH3—CH2—CH—CH2—CH2—OH
C. CH3—CH2—CH2—SH
19
Pause: Group Activity
Do the following problems on ALE 4
 Problem # 1, parts A to F
 Problem # 2, parts A to D
20
Ethers
Ethers
 Contain an ─O─ between two carbon groups.
 That are simple are named by listing the alkyl names
in alphabetical order followed by ether
CH3─O─CH3
CH3─CH2─O─CH3
dimethyl ether
ethyl methyl ether
21
IUPAC Names for Ethers
 In the IUPAC system, the shorter alkyl group and the
oxygen are named as an alkoxy group attached to the
longer alkane.
methoxy
propane
CH3—O—CH2—CH2—CH3
1
2
3
 Numbering the longer alkane gives
1-methoxypropane
22
Ethers as Anesthetics
Anesthetics
 Inhibit pain signals to the brain.
 Such as ethyl ether CH3─CH2─O─CH2─CH3 were used
for over a century, but caused nausea and were
flammable.
 Developed by 1960s 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
23
MTBE
Methyl tert-butyl ether
CH3
│
CH3─O─C─CH3
│
CH3
 Is one of the most produced organic chemicals.
 Is a fuel additive
 Is used to improve gasoline combustion.
 Use is questioned since the discovery that MTBE has
contaminated water supplies.
24
Learning Check
Draw the structure of each compound.
A. diethyl ether
B. ethyl methyl ether
C. 2-methoxybutane
25
Cyclic Ethers
A cyclic ether
 Contains an O atom in a carbon ring.
 Is called a heterocyclic compound.
 Typically has 5 (furan) or 6 atoms (pyran) in the
ring.
O
O
furan
O
tetrahydrofuran
O
pyran
O
1,4-dioxane
26
Dioxins
Dioxins are
 A group of ethers that are highly toxic.
 Formed during forest fires and as industrial byproducts.
 Often carcinogenic.
O
Cl
O
Cl
Cl
CH2
C OH
2,4,5-trichlorophenoxyacetic acid
(2,4,5-T; agent orange)
Cl
O
Cl
Cl
O
Cl
2,3,7,8-tetrachlorodibenzodioxin
(TTCC, “dioxin”)
27
Learning Check
Name each of the following:
O
1.
2.
CH3
O
O
28
Pause: Group Activity
Do the following problems on ALE 4
 Problem # 1, parts G to I
 Problem # 2, parts E to F
29
Lecture 4
13.3
Physical Properties of Alcohols,
Phenols, and Ethers
Copyright © 2007 by Pearson Education, Inc.
Publishing as Benjamin Cummings
30
Boiling Points of Alcohols
Alcohols
 Contain a strongly
electronegative O in the OH
groups.
 Form hydrogen bonds between
alcohol molecules.
 Have higher boiling points than
alkanes and ethers of similar
mass.
Copyright © 2007 by Pearson Education, Inc.
Publishing as Benjamin Cummings
31
Boiling Points of Ethers
Ethers
 Have an O atom, but
no H is attached.
 Cannot form hydrogen
bonds between ether
molecules.
Copyright © 2007 by Pearson Education, Inc.
Publishing as Benjamin Cummings
32
Solubility of Alcohols and Ethers
in Water
 Alcohols and ethers are more soluble in water than
alkanes because the oxygen atom hydrogen bonds
with water.
 Alcohols with 1-4 C atoms are soluble, but alcohols
with 5 or more C atoms are not.
Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings
33
Comparing Solubility and Boiling
Points
Compound
Alkane
CH3─CH2─CH3
Molar Boiling
Mass Point (°C)
44
-42
Ether
CH3─O─CH3
46
-23
Yes
46
78
Yes
Alcohol CH3─CH2─OH
Soluble
in Water?
No
34
Solubility of Phenol
Phenol
 Is soluble in water.
 Has a hydroxyl group that ionizes slightly (weak
acid).
 Is corrosive and irritating to the skin.
OH
O-
+ H2O
+ H3O+
35
Learning Check
Which compound would have the higher boiling
point? Explain.
ethyl methyl ether or 1-propanol
36
Learning Check
Which compound would be more soluble in water?
Explain.
ethanol or 2-pentanol
37
Pause: Group Activity
Do the following problems on ALE 4
 Problem # 3
 Problem # 4
38
Lecture 4
13.4
Reactions of Alcohols and Thiols
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39
Combustion of Alcohols
Combustion is the reaction of an alcohol
with O2 to produce CO2 and H2O.
2CH3OH + 3O2
2CO2 + 4H2O + Heat
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Publishing as Benjamin Cummings
40
Dehydration of Alcohols
Dehydration of an alcohol occurs
 When heated with an acid catalyst.
 With the loss of —H and —OH from adjacent carbon
atoms.
H OH
|
|
H+, heat
H—C—C—H
H—C=C—H + H2O
|
|
| |
H H
H H
alcohol
alkene
41
Learning Check
Write the equations for the reactions when
2-propanol undergoes:
1. combustion
2. dehydration
42
Formation of Ethers
 Ethers form when dehydration takes place at low
temperature.
H+
CH3—OH + HO—CH3
CH3—O—CH3 + H2O
two methanol
dimethyl ether
43
Oxidation and Reduction
In the oxidation of an organic compound
 There is an increase in the number of C—O
bonds.
 There is a loss of H.
In the reduction of an organic compound
 There is an decrease in the number of C—O
bonds.
 There is a gain of H.
44
Oxidation and Reduction
Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings
45
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 carbon bonded to the OH.
 An aldehyde is produced.
[O]
Primary alcohol
Aldehyde
OH
O
|
[O]
||
CH3—C—H
CH3—C—H + H2O
|
H
Ethanol
(ethyl alcohol)
Ethanal
(acetaldehyde)
46
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 carbon bonded to the OH.
 A ketone is produced.
[O]
secondary alcohol
ketone
OH
O
│
[O]
║
CH3—C—CH3
CH3—C—CH3 + H2O
│
H
2-propanol (isopropyl alcohol)
2-propanone(dimethyl ketone,
“acetone”) 47
Oxidation of Tertiary (3)Alcohols
Tertiary 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
48
Learning Check
Select the compound that would result for each reaction
of CH3—CH2—CH2—OH.
1) CH3—CH=CH2
A. H+, heat
B.
2) CO2 + H2O
O
||
3) CH3—CH2—C—H
[O]
C. O2, heat
49
Oxidation of Ethanol in the Body
In the body,
 Ethanol is oxidized by enzymes in the liver.
 Aldehyde product impairs coordination.
O
O
║
║
CH3─CH2─OH
CH3─C─H
CH3─C─OH
ethyl alcohol
acetaldehyde
acetic acid
2CO2 + H2O
50
Ethanol CH3─CH2─OH
Ethanol
 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.
Copyright © 2007 by Pearson Education, Inc.
Publishing as Benjamin Cummings
51
Effect of Alcohol on the Body
TABLE 13.2
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52
Learning Check
Select the product for the oxidation of
OH
│
[O]
CH3—CH—CH2—CH3
1) CH3—CH=CH—CH3
3) CO2 + H2O
O
║
2) CH3—C—CH2 —CH3
OH
│
4) CH3—CH—CH2—CH3
53
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
54
Pause: Group Activity
Do the following problems on ALE 4
 Problem # 5
55