Chapter 13 Alcohols, Phenols,
and Thiols
13.1
Alcohols, Phenols, and Thiols
Copyright © 2007 by Pearson Education, Inc.
Publishing as Benjamin Cummings
Alcohols and PhenolsAn 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
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) Secondary (2º) Tertiary (3º)
1 group 2 groups 3 groups
H CH3 CH3
| | |
CH3—C—OH CH3—C—OH CH3—C—OH| | |H H CH3
Classification of Alcohols
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
Learning Check
OH|
1. CH3—CH—CH2—CH3 (S) secondary
2. CH3—CH2—CH2—OH (P) primary
OH |
3. CH3—CH2—C—CH2—CH3 (T) tertiaryCH3
Solution
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 methyl alcohol
CH3─CH3 ethane
CH3─CH2─OH ethanol ethyl alcohol
More Names of AlcoholsIn 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
Some Typical AlcoholsOH|
“rubbing alcohol” CH3—CH—CH3
2-propanol (isopropyl alcohol)
antifreeze HO—CH2—CH2—OH
1,2-ethanediol (ethylene glycol)
OH
|
glycerol HO—CH2—CH—CH2—
OH
1,2,3-propanetriol
Copyright © 2007 by Pearson Education, Inc.
Publishing as Benjamin Cummings
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
3.
OH
Solution1. CH3—CH2—CH2—CH2—OH 1-butanol
OH CH3
| |
2. CH3—CH—CH—CH2—CH3 3-methyl-2-pentanol
3. cyclopentanol OH
Write the structure of the following:
A. 3-pentanol
B. ethyl alcohol
C. 3-methylcyclohexanol
Learning Check
SolutionWrite the structure of the following:
A. 3-pentanol OH
|
CH3—CH2—CH—CH2—CH3
B. ethyl alcohol CH3 —CH2 —OH
C. 3-methylcyclohexanol
CH3
OH
Phenols in Medicine
Phenol
• Is the IUPAC name for benzene with a
hydroxyl group.
• Is used in antiseptics and disinfectants.
phenol resorcinol 4-hexylresorcinol
OH
OH
CH2CH2CH2CH2CH2CH3
OH OH
OH
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-butanolCH3
| B. CH3—CH2—CH—CH2—CH2—OH
3-methyl-1-pentanol
C. CH3—CH2—CH2—SH1-propanethiol
Chapter 13 Alcohols, Phenols,
Ethers, and Thiols
13.2
Ethers
Copyright © 2005 by Pearson Education, Inc.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—CH31 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
MTBEMethyl 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 etherCH3—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 O
furan tetrahydrofuran pyran 1,4-dioxane
O
O
Dioxins
Dioxins are
• A group of ethers that are highly toxic.
• Formed during forest fires and as industrial by-products.
• Often carcinogenic.
Cl
Cl Cl
OCH2 OHC
O
Cl
Cl
O
O
Cl
Cl
2,4,5-trichlorophenoxyacetic acid 2,3,7,8-tetrachlorodibenzodioxin
(2,4,5-T; agent orange) (TTCC, “dioxin”)
Learning Check
Name each of the following:
1.
2.
O
O
OCH3
Solution
1. methoxy cyclopentane
(cyclopentyl methyl ether)
2. 1,4-dioxaneO
O
OCH3
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 Molar Boiling Soluble
Mass Point (°C) in Water?
Alkane CH3─CH2─CH3 44 -42 No
Ether CH3─O─CH3 46 -23 Yes
Alcohol CH3─CH2─OH 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.
2CH3OH + 3O2 2CO2 + 4H2O + Heat
Copyright © 2007 by Pearson Education, Inc.
Publishing as Benjamin Cummings
Dehydration of an alcohol occurs
• When heated with an acid catalyst.
• With the loss of —H and —OH from adjacentcarbon atoms.
H OH| | H+, heat
H—C—C—H H—C=C—H + H2O| | | |H H H H
alcohol alkene
Dehydration of Alcohols
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 6CO2 + 8H2O
2. dehydration
OH
│ H+
CH3─CH─CH3 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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