Download 4 Reactions Alcohol Thiols GOB Structures

13.4 Reactions of Alcohols and Thiols
A flaming dessert is prepared
using heat from the
combustion of an alcohol.
Δ
CH3—CH2—OH(g) + 3O2(g)  2CO2(g) + 3H2O(g) + energy
Learning Goal Write equations for the combustion,
dehydration, and oxidation of alcohols and thiols.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Dehydration of Alcohols
Alcohols undergo
• the loss of — H and — OH from adjacent carbon atoms from
the same alcohol, producing an alkene and a water molecule.
• dehydration when heated with an acid catalyst:
H+, heat
alcohol
+ H2O
alkene
Core Chemistry Skill Writing Equations for the Dehydration
of Alcohols
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Dehydration of Alcohols
The dehydration of a secondary alcohol can result in
the formation of a minor product and a major product.
Saytzeff’s rule states that
• the major product is the one that forms by removing
the hydrogen from the carbon atom that has the
smaller number of hydrogen atoms.
• hydrogen atoms are easier to remove from the
carbon atom adjacent to the carbon atom attached
to the — OH group that has fewer hydrogen atoms.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Study Check
Draw the condensed structural formula for the major alkene
produced by the dehydration of the following alcohol:
OH
H+, heat
CH3—CH—CH2—CH2—CH3
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Solution
Draw the condensed structural formula for the major alkene
produced by the dehydration of the following alcohol:
OH
H+, heat
CH3—CH—CH2—CH2—CH3
major product
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
CH3—CH
CH—CH2—CH3
© 2016 Pearson Education, Inc.
Oxidation and Reduction
In organic chemistry,
• oxidation reactions increase the number of carbon–oxygen
bonds by the addition of oxygen or a loss of hydrogen atoms.
• reduction reactions reduce the number of bonds between
carbon and oxygen atoms.
Core Chemistry Skill Writing Equations for the Oxidation of
Alcohols
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Oxidation of 1° Alcohols
Alcohols undergo oxidation, increasing the number of
carbon and oxygen bonds. To indicate the process of
oxidation, [O] is placed over the reaction arrow.
Primary alcohols are oxidized to produce an aldehyde.
1 bond to O
2 bonds to O
[O]
1° alcohol
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
aldehyde
© 2016 Pearson Education, Inc.
Oxidation of 1° Alcohols
Aldehydes can further oxidize to produce a carboxylic acid.
2 bond to O
3 bonds to O
[O]
aldehyde
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
carboxylic acid
© 2016 Pearson Education, Inc.
Oxidation of 2° Alcohols
Secondary alcohols are oxidized to produce a ketone.
1 bond to O
2 bonds to O
[O]
2° alcohol
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
ketone
© 2016 Pearson Education, Inc.
Oxidation of 3° Alcohols
Tertiary alcohols do not readily oxidize because there is no
hydrogen atom on the carbon bonded to the — OH group.
[O]
no product formed
no H to oxidize
3° alcohol
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Chemistry Link to Health:
Methanol Poisoning
Methanol is
• also known as methyl alcohol.
• highly toxic and found in windshield washer fluid,
Sterno, and paint strippers.
• rapidly absorbed and oxidized to formaldehyde and
then formic acid.
[O]
methyl alcohol
[O]
formaldehyde
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
formic acid
© 2016 Pearson Education, Inc.
Oxidation of Thiols
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.
CH3—S—H + H—S—CH3
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
[O]
CH3—S—S—CH3 + H2O
© 2016 Pearson Education, Inc.
Chemistry Link to Health:
Oxidation of Alcohol in the Body
Ethanol
• acts as a depressant and kills or
disables more people than does
any other drug.
• consumption can be analyzed
by using a breathalyzer.
• is metabolized by a social
drinker at a rate of 12–15 mg/dL
per hour.
• is metabolized by an alcoholic at
a rate of 30 mg/dL per hour.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Chemistry Link to Health:
Oxidation of Alcohol in the Body
The acetaldehyde produced from ethanol in the liver is
further oxidized to acetic acid, which is converted to
carbon dioxide and water in the citric acid cycle.
Liver enzymes can eventually break down ethanol, but
the aldehyde and carboxylic acid intermediates can
cause considerable damage to liver cells.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Chemistry Link to Health:
Oxidation of Alcohol in the Body
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Study Check
Select the product for the oxidation of
[O]
A.
B.
C. CO2 + H2O
D.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Solution
Select the product for the oxidation of
[O]
The correct answer is B.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Study Check
Select the product when CH3–CH2–CH2–OH undergoes each
of the following reactions:
[O]
[O]
A.
B. CO2 + H2O
C.
D.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Solution
Select the product when CH3–CH2–CH2–OH undergoes each
of the following reactions:
[O]
1.
[O]
2.
1. C.
2. D.
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.
Concept Map
General, Organic, and Biological Chemistry: Structures of Life, 5/e
Karen C. Timberlake
© 2016 Pearson Education, Inc.