Download Chapter 13 Alcohols, Phenols, and Thiols

Chapter 13 Alcohols, Phenols,
and Thiols
13.1
Alcohols, Phenols, and Thiols
Copyright © 2007 by Pearson Education, Inc.
Publishing as Benjamin Cummings
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
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)
2 groups
CH3
|
CH3—C—OH
|
H
Tertiary (3º)
3 groups
CH3
|
CH3—C—OH
|
CH3
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
Solution
OH
|
1. CH3—CH—CH2—CH3
(S) secondary
2. CH3—CH2—CH2—OH
(P) primary
OH
|
3. CH3—CH2—C—CH2—CH3
CH3
(T) tertiary
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
IUPAC
Common Name
CH4
methane
CH3─OH
methanol
CH3─CH3
ethane
CH3─CH2─OH
ethanol
methyl alcohol
ethyl alcohol
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
6
5
4
3
2
1
5-methyl-2-hexanol
Some Typical Alcohols
OH
|
“rubbing alcohol” CH3—CH—CH3
2-propanol (isopropyl alcohol)
antifreeze HO—CH2—CH2—OH
1,2-ethanediol (ethylene glycol)
glycerol
OH
OH
|
HO—CH2—CH—CH2—
Copyright © 2007 by Pearson Education, Inc.
Publishing as Benjamin Cummings
1,2,3-propanetriol
Learning Check
Give the IUPAC name for each of the following:
1. CH3—CH2—CH2—CH2—OH
OH CH3
|
|
2. CH3—CH—CH—CH2—CH3
OH
3.
Solution
1. CH3—CH2—CH2—CH2—OH
1-butanol
OH CH3
|
|
2. CH3—CH—CH—CH2—CH3
3-methyl-2-pentanol
3. OH
cyclopentanol
Learning Check
Write the structure of the following:
A. 3-pentanol
B.
ethyl alcohol
C.
3-methylcyclohexanol
Solution
Write the structure of the following:
A. 3-pentanol
OH
|
CH3—CH2—CH—CH2—CH3
B. ethyl alcohol
CH3 —CH2 —OH
C. 3-methylcyclohexanol
OH
CH 3
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
CH 2 CH 2 CH 2 CH 2 CH 2 CH 3
phenol
resorcinol
4-hexylresorcinol
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
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
Solution
Name each of the following compounds:
OH
|
A. CH3—CH2 —CH—CH3 2-butanol
CH3
|
B. CH3—CH2—CH—CH2—CH2—OH
3-methyl-1-pentanol
C. CH3—CH2—CH2—SH
1-propanethiol
Chapter 13 Alcohols, Phenols,
Ethers, and Thiols
13.2
Ethers
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Publishing as Benjamin Cummings
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
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
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
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.
Learning Check
Draw the structure of each compound.
A. diethyl ether
B. ethyl methyl ether
C. 2-methoxybutane
Solution
Draw the structure of each compound.
A. diethyl ether
CH3—CH2—O—CH2—CH3
B. ethyl methyl ether CH3—CH2—O—CH3
C. 2-methoxybutane
O—CH3
|
CH3—CH—CH2—CH3
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
O
pyran
1,4-dioxane
Dioxins
Dioxins are
• A group of ethers that are highly toxic.
• Formed during forest fires and as industrial by-products.
• Often carcinogenic.
O
Cl
O
Cl
Cl
CH 2
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”)
Learning Check
Name each of the following:
O
1.
O
2.
O
CH 3
Solution
1.
O
2.
O
O
CH 3
methoxy cyclopentane
(cyclopentyl methyl ether)
1,4-dioxane
Chapter 13 Alcohols, Phenols, Ethers,
and Thiols
13.3
Physical Properties of Alcohols,
Phenols, and Ethers
Copyright © 2007 by Pearson Education, Inc.
Publishing as Benjamin Cummings
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
Boiling Points of Ethers
Ethers
• Have an O atom, but
no H is attached.
• Cannot form
hydrogen bonds
between ether
molecules.
• Have boiling points
similar to alkanes of
similar mass.
Copyright © 2007 by Pearson Education, Inc.
Publishing as Benjamin Cummings
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
Comparing Solubility and Boiling
Points
Compound
Alkane
CH3─CH2─CH3
Ether
CH3─O─CH3
Alcohol CH3─CH2─OH
Molar
Mass
44
Boiling
Point (°C)
-42
Soluble
in Water?
No
46
-23
Yes
46
78
Yes
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+
Learning Check
Which compound would have the higher
boiling point? Explain.
ethyl methyl ether or 1-propanol
Solution
1-propanol would have the higher boiling
point because an alcohol can form hydrogen
bonds, but the ether cannot.
Learning Check
Which compound would be more soluble in
water?
Explain.
ethanol or 2-pentanol
Solution
Ethanol. An alcohol with two carbons in its
carbon chain is more soluble than one with
5 carbons. The longer alkyl chain
diminishes the effect of the –OH group.
Chapter 13 Alcohols, Phenols,
Ethers, and Thiols
Reactions of Alcohols and Thiols
Copyright © 2007 by Pearson Education, Inc.
Publishing as Benjamin Cummings
Combustion of Alcohols
Combustion is the reaction of an alcohol
with O2 to produce CO2 and H2O.
2CO2 + 4H2O + Heat
2CH3OH + 3O2
Copyright © 2007 by Pearson Education, Inc.
Publishing as Benjamin Cummings
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
Learning Check
Write the equations for the reactions when
2-propanol undergoes:
1. combustion
2. dehydration
Solution
OH
│
CH3─CH─CH3 = 2-propanol = C3H8O
1. combustion
2C3H8O + 9O2
2. dehydration
OH
│
CH3─CH─CH3
6CO2 + 8H2O
H+
CH3─CH=CH2 + H2O
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
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.
Oxidation and Reduction
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