Transcript CH_12_3_Reactions_Alcohols_Thiols

Chapter 12 Organic Compounds with
Oxygen and Sulfur
1
12.3
Reactions of Alcohols and Thiols
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Dehydration of Alcohols
2
Alcohols undergo
• dehydration when heated with an acid catalyst
• the loss of –H and –OH from adjacent carbon atoms,
producing an alkene
H OH
| |
H—C—C—H
| |
H H
alcohol
H+, heat
H—C=C—H + H2O
| |
H H
alkene
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Oxidation of 1 Alcohols
3
Alcohols undergo oxidation, increasing the number of
carbon and oxygen bonds.
Primary alcohols are oxidized to produce an aldehyde.
1 bond to O
H OH
|
|
H—C—C—H
| |
H H
1 alcohol
2 bonds to O
oxidation
H O
| ||
H—C—C—H
|
H
aldehyde
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Oxidation of 1 Alcohols
4
Alcohols undergo oxidation, increasing the number of
carbon and oxygen bonds.
Aldehydes can further oxidize to produce a carboxylic acid.
1 bond to O
H O
|
||
H—C—C—H
|
H
aldehyde
2 bonds to O
oxidation
H O
| ||
H—C—C—OH
|
H
carboxylic acid
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Oxidation of 2 Alcohols
5
Secondary alcohols are oxidized to produce a ketone.
To indicate the process of oxidation, [O] is placed over the
reaction arrow.
1 bond to O
2 bonds to O
H OH H
|
| |
H—C—C—C—H
|
| |
H H H
H O H
| || |
H—C—C—C—H
|
|
H
H
[O]
2 alcohol
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
ketone
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Oxidation of Tertiary 3 Alcohols
6
Tertiary (3) alcohols do not readily oxidize.
OH
CH3CCH3
CH3
3 alcohol
[O]
no product
no H to oxidize
no reaction
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Oxidation and Reduction
7
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 a decrease in the number of C–O bonds
• there is a gain of H
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Oxidation and Reduction
8
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Methanol Poisoning
9
Methanol
• is also known as methyl alcohol
• is highly toxic and found in windshield washer fluid, Sterno,
and paint strippers
• is rapidly absorbed and oxidized to formaldehyde and then
formic acid
O
[O]
CH3OH
O
[O]
HCH
methyl alcohol formaldehyde
HCOH
formic acid
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Ethanol, CH3CH2OH
10
Ethanol
• acts as a depressant and 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
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Effect of Alcohol on the Body
11
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Oxidation of Thiols
12
When thiols undergo oxidation,
• an H atom is lost from each of two –SH groups
• the product is a disulfide
• protein in hair is cross-linked by disulfide bonds found in the
amino acid cysteine
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Learning Check
13
Select the product for the oxidation of
OH
CH3CHCH2CH3
[O]
O
A. CH3CH=CHCH3
B. CH3CCH2CH3
OH
C. CO2 + H2O
D. CH3CHCH2CH3
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Solution
14
Select the product for the oxidation of
OH
[O]
CH3CHCH2CH3
O
The answer is B.
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
CH3CCH2CH3
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Learning Check
15
Select the product when CH3–CH2–CH2–OH undergoes each of
the following reactions:
[O]
[O]
CH3—CH2 —CH2OH
B.
C.
1) CH3—CH=CH2
2) CO2 + H2O
O
||
3) CH3—CH2—C—H
O
||
4) CH3—CH2—C—OH
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Solution
16
Select the product when CH3–CH2–CH2–OH undergoes each of
the following reactions:
O
[O]
B. 3)
||
CH3—CH2—CH2OH
CH3—CH2—C—H
[O]
O
C. 4)
||
CH3—CH2—C—OH
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Learning Check
17
Give the primary product for the reaction of
2-propanol when it undergoes
A. oxidation
B. dehydration
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Solution
18
OH
CH3CHCH3 = 2-propanol = C3H8O
A. oxidation
OH
O
2CH3CHCH3 + 9O2
[O]
CH3CCH3 + 6CO2 + 8H2O
B. dehydration
OH
CH3CHCH3
H+, heat
CH3CH=CH2 + H2O
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.