Download Chapter 14 Aldehydes, Ketones, and Chiral Molecules

Chapter 14 Aldehydes, Ketones,
and Chiral Molecules
14.1
Aldehydes and Ketones
Copyright © 2007 by Pearson Education, Inc.
Publishing as Benjamin Cummings
Carbonyl Group in Aldehydes
and Ketones
A carbonyl group
• In an aldehyde is
attached to at least one H
atom.
• In a ketone is attached to
two carbon groups.
Copyright © 2007 by Pearson Education, Inc.
Publishing as Benjamin Cummings
Naming Aldehydes
An aldehyde
• Has an IUPAC name in which the -e in the alkane name is
changed to -al.
• Has a common name for the first four aldehydes that use the
prefixes form- (1C), acet- (2C), propion- (3C), and butyr(4C), followed by aldehyde.
O
O
O
║
║
║
H−C−H
CH3−C−H
CH3−CH2−C−H
methanal
ethanal
propanal
(formaldehyde)
(acetaldehyde)
(propionaldehyde)
Naming Aldehydes
Copyright © 2007 by Pearson Education, Inc.
Publishing as Benjamin Cummings
Aldehydes in Flavorings
• Several naturally occurring aldehydes are used
as flavorings for foods and fragrances.
O
H
C
Benzaldehyde
(almonds)
O
CH=CH C
H
Cinnamaldehyde (cinnamon)
Naming Ketones
Ketones are named
• In the IUPAC system by replacing the -e in the alkane
name with -one. The carbonyl carbon is indicated by a
number.
• With a common name by indicating the alkyl groups
attached to the carbonyl group in alphabetical order
followed by ketone.
O
O
║
║
CH3−C−CH3
CH3−C−CH2−CH3
propanone
2-butanone
(dimethyl ketone)
(ethyl methyl ketone)
Ketones in Common Use
Butter
flavoring
Nail polish remover,
Solvent
Propanone,
Dimethylketone,
Acetone
Copyright © 2007 by Pearson Education, Inc.
Publishing as Benjamin Cummings
Learning Check
Classify each as 1) aldehyde or 2) ketone.
O
O
||
||
A. CH3—CH2—C—CH3
B. CH3—C—H
CH3
O
|
||
C. CH3—C—CH2—C—H
|
CH3
O
D.
Solution
A. 2) ketone
B. 1) aldehyde
C. 1) aldehyde
D. 2) ketone
Learning Check
Classify each as an aldehyde (1), ketone (2), alcohol
(3), or ether (4).
O
║
A. CH3─CH2─C─CH3
B. CH3─O─CH3
CH3
O
│
║
C. CH3─C─CH2─C─H
│
CH3
OH
│
D. CH3─CH─CH3
Solution
Classify each as an aldehyde (1), ketone (2),
alcohol (3), or ether (4).
O
║
A. CH3─CH2─C─CH3
B. CH3─O─CH3
(2) ketone
(4) ether
CH3
O
OH
│
║
│
C. CH3─C─CH2─C─H
D. CH3─CH─CH3
│
CH3
(1) aldehyde
(3) alcohol
Learning Check
Name each of the following:
O
║
1. CH3─CH2─CH2─CH2─C─H
O
║
2. Cl─CH2─CH2─C─H
O
║
3.
CH3─CH2─C─CH3
Solution
O
║
1. CH3─CH2─CH2─CH2─C─H
pentanal
O
║
2. Cl─CH2─CH2─C─H
3-chloropropanal
O
║
3. CH3─CH2─C─CH3
2-butanone;
ethyl methyl ketone
Learning Check
Name the following compounds.
O
||
A. CH3—CH2—CH2—C—CH3
B.
O
CH3
O
|
||
C. CH3—C—CH2—C—H
|
CH3
Solution
A. 2-pentanone; methyl propyl ketone
B. cyclohexanone
C, 3,3-dimethylbutanal
Chapter 14 Aldehydes, Ketones,
and Chiral Molecules
14.2
Physical Properties
Copyright © 2007 by Pearson Education, Inc.
Publishing as Benjamin Cummings
Polar Carbonyl Group
The polar carbonyl group
• Provides dipole-dipole interactions.
δ+ δδ+ δC=O
C=O
• Does not have H on the oxygen atom.
• Cannot form hydrogen bonds.
Boiling Points
Aldehydes and ketones have
• Polar carbonyl groups (C=O).
δ+ δC=O
• Attractions between polar groups.
δ+ δδ+ δC=O
C=O
• Higher boiling points than alkanes and ethers of similar
mass.
• Lower boiling points than alcohols of similar mass.
Comparison of Boiling Points
58
Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings
Learning Check
Select the compound in each pair that would have the
Higher boiling point.
A. CH3—CH2—CH3 or CH3—CH2—OH
O
B.
or
C. CH3—CH2—OH or CH3—O—CH3
Solution
A. CH3—CH2—OH
O
B.
C. CH3—CH2—OH
Solubility in Water
The electronegative O atom of the
carbonyl group in aldehydes and
ketones forms hydrogen bonds with
water.
Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings
Learning Check
Indicate if each is soluble or insoluble in water.
A. CH3—CH2—CH3
B. CH3—CH2—OH
O
||
C. CH3—CH2—CH2—C—H
O
||
D. CH3—C—CH3
Solution
A. CH3—CH2—CH3
insoluble
B. CH3—CH2—OH
soluble
O
||
C. CH3—CH2—CH2—C—H
soluble
O
||
D. CH3—C—CH3
soluble
Chapter 14 Aldehydes,
Ketones and Chiral Molecules
Oxidation and Reduction
Copyright © 2007 by Pearson Education, Inc.
Publishing as Benjamin Cummings
Oxidation
• Aldehydes are easily oxidized to carboxylic acids.
O
O
||
[O]
||
CH3—C—H
CH3—C—OH
Acetaldehyde
Acetic acid
Tollens’ Test
• Tollens’ reagent,
which contains
Ag+, oxidizes
aldehydes, but not
ketones.
• Ag+ is reduced to
metallic Ag,
which appears as a
“mirror” in the
test tube.
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