Download 4. Reactions of Alcohols and Thiols

Chapter 13 Alcohols, Phenols, and
Thiols
13.4
Reactions of Alcohols and Thiols
General, Organic, and Biological Chemistry
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Combustion of Alcohols
Combustion is the reaction of an alcohol with O2 to
produce CO2 and H2O.
General, Organic, and Biological Chemistry
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2
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
alcohol
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alkene
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Saytzeff’s Rule
According to Saytzeff’s rule, the dehydration of a
secondary alcohol favors the product in which
 hydrogen is removed from the adjacent carbon atom
in the chain with the smaller number of H atoms
General, Organic, and Biological Chemistry
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4
Learning Check
Write the equations for the reactions when 2-propanol
undergoes:
A. combustion
B. dehydration
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5
Solution
A. dombustion:
B. dehydration:
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Formation of Ethers
 Ethers form when dehydration takes place at low
temperature.
two methanol molecules
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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
(continued)
General, Organic, and Biological Chemistry
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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 –OH
 an aldehyde is produced
Ethanol (ethyl alcohol)
General, Organic, and Biological Chemistry
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
2-Propanol (isopropyl alcohol)
General, Organic, and Biological Chemistry
2-Propanone(dimethyl ketone,
“acetone”)
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Oxidation of Tertiary (3)
Alcohols
Tertiary alcohols do not readily oxidize.
There is no H on the C—OH to oxidize.
2-Methyl-2-propanol
General, Organic, and Biological Chemistry
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Learning Check
Select the compound that would result for each reaction
of CH3—CH2—CH2—OH.
1) CH3—CH ═ CH2 2) CO2 + H2O 3)
A. H+, heat
B. [O]
C. O2, heat
General, Organic, and Biological Chemistry
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Solution
Select the compound that would result for each reaction
of CH3—CH2—CH2—OH.
A. H+, heat
1) CH3—CH ═ CH2
B. [O]
3)
C. O2, heat
2) CO2 + H2O
General, Organic, and Biological Chemistry
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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
General, Organic, and Biological Chemistry
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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
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Effect of Ethanol on the Body
General, Organic, and Biological Chemistry
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Learning Check
Select the product from the oxidation of
?
1) CH3—CH ═ CH—CH3
3) CO2 + H2O
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2)
4)
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Solution
Select the product from the oxidation of
2)
General, Organic, and Biological Chemistry
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Oxidation of Thiols
When thiols undergo oxidation,
 an H atom is lost from two –SH groups
 the product is a disulfide
disulfide
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