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Chapter 13 Alcohols, Phenols, and Thiols
13.1
Alcohols, Phenols, and Thiols
Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings
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
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
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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
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OH |
1. CH3—CH—CH2—CH3 (S) secondary
2. CH3—CH2—CH2—OH (P) primary
OH |
3. CH3—CH2—C—CH2—CH3 (T) tertiary |
CH3
Solution
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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 methyl alcohol
CH3─CH3 ethane
CH3─CH2─OH ethanol ethyl alcohol
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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-
hexanol6 5 4 3 2 1
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Some Typical Alcohols
OH |“rubbing alcohol” CH3—CH—CH3
2-propanol (isopropyl alcohol)
antifreeze HO—CH2—CH2—OH
1,2-ethanediol (ethylene glycol) OH
| glycerolHO—CH2—CH—CH2—OH
1,2,3-propanetriol
Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings
9
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
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Solution
1. CH3—CH2—CH2—CH2—OH 1-butanol
OH CH3 | |2. CH3—CH—CH—CH2—CH3 3-methyl-2-pentanol
3. cyclopentanol OH
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Write the structure of the following:
A. 3-pentanol
B. ethyl alcohol
C. 3-methylcyclohexanol
Learning Check
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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
CH3
OH
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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
Cl
OHOH
Br
Phenol 3-chlorophenol 4-bromophenol (m-chlorophenol) (p-bromophenol)
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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
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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
16
Write the structure of each of the following:
A. 3-pentanol
B. ethyl alcohol
C. p-methylphenol
Learning Check
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Solution
Write the structure of each of the following:A. 3-pentanol OH
|CH3—CH2—CH—CH2—CH3
B. ethyl alcohol CH3—CH2—OH
C. p-methylphenol OH
CH3
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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.
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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
Naming Thiols
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Thiols
Thiols Often have
strong odors. Are used to
detect gas leaks. Are found in
onions, oysters, and garlic.
Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings
21
Learning Check
Draw the structure of each compound.
A. 2-butanethiol
B. 2-methyl-1-butanol
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Solution
Draw the structure of each compound.A. 2-butanethiol
SH|
CH3—CH—CH2—CH3
B. 2-methyl-1-butanol
CH3
| HO—CH2—CH—CH2—CH3
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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
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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
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Chapter 13 Alcohols, Phenols, Ethers, and Thiols
13.2
Ethers
Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings
26
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
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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
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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
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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.
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Learning Check
Draw the structure of each compound.
A. diethyl ether
B. ethyl methyl ether
C. 2-methoxybutane
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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
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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
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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”)
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Learning Check
Name each of the following:
1.
2. O
O
OCH3
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Solution
1. methoxy cyclopentane
(cyclopentyl methyl ether)
2. 1,4-dioxaneO
O
OCH3
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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
37
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
38
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
39
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
40
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
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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+
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Learning Check
Which compound would have the higher boiling
point? Explain.
ethyl methyl ether or 1-propanol
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Solution
1-propanol would have the higher boiling point because
an alcohol can form hydrogen bonds, but the ether
cannot.
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Learning Check
Which compound would be more soluble in water?
Explain.
ethanol or 2-pentanol
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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.
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Chapter 13 Alcohols, Phenols, Ethers, and Thiols
13.4
Reactions of Alcohols and Thiols
Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings
47
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
48
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+, heatH—C—C—H H—C=C—H + H2O
| | | | H H H H
alcohol alkene
Dehydration of Alcohols
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Learning Check
Write the equations for the reactions when
2-propanol undergoes:
1. combustion
2. dehydration
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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
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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
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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.
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Oxidation and Reduction
Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings
54
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 Ethanal (ethyl alcohol) (acetaldehyde)
Oxidation of Primary (1) Alcohols
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Oxidation of Secondary (2) AlcoholsWhen 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”)
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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
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Select the compound that would result for each reaction
of CH3—CH2—CH2—OH.
O
||1) CH3—CH=CH2 2) CO2 + H2O 3) CH3—CH2—C—H
A. H+, heat
B. [O]
C. O2, heat
Learning Check
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CH3—CH2—CH2—OH
A. H+, heat 1) CH3—CH=CH2
O ||
B. [O] 3) CH3—CH2—C—H
C. O2, heat 2) CO2 + H2O
Solution
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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
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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.
Ethanol CH3─CH2─OH
Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings
61
Effect of Alcohol on the Body
TABLE 13.2
Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings
62
Learning Check
Select the product for the oxidation of OH │ [O]
CH3—CH—CH2—CH3
O ║
1) CH3—CH=CH—CH3 2) CH3—C—CH2 —CH3
OH │
3) CO2 + H2O 4) CH3—CH—CH2—CH3
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Solution
Select the product for the oxidation of OH │ [O]
CH3—CH—CH2—CH3
O ║
2) CH3—C—CH2—CH3
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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