Transcript Reactions of Alcohols and Thiols

Chapter 13 Organic Compounds
with Oxygen and Sulfur
13.3
Reactions of Alcohols and Thiols
Copyright © 2005 by Pearson Education, Inc.
Publishing as Benjamin Cummings
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Combustion of Alcohols
Alcohols undergo combustion with O2 to produce
CO2 and H2O.
2CH3OH + 3O2
2CO2 + 4H2O + Heat
Copyright © 2005 by
Pearson Education, Inc.
Publishing as Benjamin
Cummings
2
Dehydration of Alcohols
Alcohols undergo
• dehydration when heated with an acid catalyst.
• 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
3
Learning Check
Write the equations for the reaction of 2-propanol when it
undergoes
1. combustion.
2. dehydration.
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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
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Oxidation and Reduction
In an oxidation,
• there is an increase in the number of C-O bonds.
• there is a loss of H.
In a reduction,
• there is an decrease in the number of C-O bonds.
• there is a gain of H.
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Oxidation and Reduction
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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)
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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
│
CH3─C─CH3
│
H
O
║
CH3─C─CH3 + H2O
[O]
2-propanol (isopropyl alcohol)
2-propanol (dimethyl ketone)
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Oxidation of Tertiary ( 3)Alcohols
Tertiary 3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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Oxidation of Ethanol in the Body
In the body,
• enzymes in the liver oxidize ethanol.
• aldehyde product impairs coordination.
• blood alcohol over 0.4% can be fatal.
O
O
║
║
CH3CH2OH
CH3CH
CH3COH
ethyl alcohol
acetaldehyde
2CO2 + H2O
acetic acid
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Ethanol CH3CH2OH
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.
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Effect of Alcohol on the Body
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Alcohol Contents in Common
Products
% Ethanol
50%
40%
15-25%
12%
3-9%
Product
Whiskey, rum, brandy
Flavoring extracts
Listerine, Nyquil, Scope
Wine, Dristan, Cepacol
Beer, Lavoris
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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
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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
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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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Learning Check
Select the product when CH3—CH2—CH2—OH undergoes
each of the following reactions:
A) H+, heat
B)
[O]
C) + O2
1) CH3—CH=CH2
2) CO2 + H2O
O
||
3) CH3—CH2—C—H
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Solution
B.
1) CH3—CH=CH2
O
||
3) CH3—CH2—C—H
C. + O2
2) CO2 + H2O
A. H+, heat
[O]
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