Chapter 17
Aldehydes and Ketones:
Nucleophilic Addition
to the
Carbonyl Group
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
17.1
Nomenclature
IUPAC Nomenclature of Aldehydes
O
O
H
H
O
O
HCCHCH
Base the name on the
chain that contains
the carbonyl group
and replace the -e
ending of the
hydrocarbon with -al.
IUPAC Nomenclature of Aldehydes
O
O
H
H
4,4-dimethylpentanal
O
O
HCCHCH
5-hexenal
or hex-5-enal
2-phenylpropanedial
(keep the -e ending
before -dial)
IUPAC Nomenclature of Aldehydes
O
when named as
a substituent
formyl group
C
H
when named
as a suffix
carbaldehyde or
carboxaldehyde
Substitutive IUPAC Nomenclature of Ketones
O
O
CH3CH2CCH2CH2CH3
CH3CHCH2CCH3
CH3
H3C
Base the name on the chain
that contains the carbonyl group
O and replace -e with -one.
Number the chain in the
direction that gives the lowest
number to the carbonyl carbon.
Substitutive IUPAC Nomenclature of Ketones
O
O
CH3CH2CCH2CH2CH3
3-hexanone
or hexan-3-one
H3C
O
4-methylcyclohexanone
CH3CHCH2CCH3
CH3
4-methyl-2-pentanone
or 4-methylpentan-2-one
Functional Class IUPAC Nomenclature of Ketones
O
O
CH3CH2CCH2CH2CH3
O
H2C
CHC CH
CH2
CH2CCH2CH3
List the groups
attached to the
carbonyl separately in
alphabetical order, and
add the word ketone.
Functional Class IUPAC Nomenclature of Ketones
O
O
CH3CH2CCH2CH2CH3
ethyl propyl ketone
CH2CCH2CH3
benzyl ethyl ketone
O
divinyl ketone
H2C
CHC CH
CH2
17.2
Structure and Bonding:
The Carbonyl Group
Structure of Formaldehyde
planar
bond angles: close to 120°
C=O bond distance: 122 pm
The Carbonyl Group
very polar double bond
O
1-butene
propanal
dipole moment = 0.3D
dipole moment = 2.5D
Carbonyl Group of a Ketone is More
Stable than that of an Aldehyde
heat of combustion
O
2475 kJ/mol
H
2442 kJ/mol
O
Alkyl groups stabilize carbonyl groups the same
way they stabilize carbon-carbon double bonds,
carbocations, and free radicals.
Spread is Greater for
Aldehydes and
Ketones than for Alkenes
O
H
2475 kJ/mol
Heats of combustion of
C4H8 isomeric alkenes
CH3CH2CH=CH2
2717 kJ/mol
cis-CH3CH=CHCH3
2710 kJ/mol
trans-CH3CH=CHCH3
2707 kJ/mol
O
2442 kJ/mol
(CH3)2C=CH2
2700 kJ/mol
Resonance Description of
Carbonyl Group
••
•• –
O ••
•• O ••
C
C
+
Nucleophiles attack carbon;
electrophiles attack oxygen.
Bonding in Formaldehyde
Carbon and oxygen are sp2 hybridized.
Bonding in Formaldehyde
The half-filled
2p orbitals on
carbon and
oxygen overlap
to form a  bond.
17.3
Physical Properties
Aldehydes and Ketones have Higher Boiling Points
than Alkenes, but Lower Boiling Points than Alcohols
boiling point
–6°C
O
49°C
OH
97°C
More polar than alkenes,
but cannot form
intermolecular hydrogen
bonds to other carbonyl
groups.
17.4
Sources of Aldehydes and Ketones
Many Aldehydes and Ketones Occur Naturally
O
2-heptanone
(component of alarm pheromone of bees)
Many Aldehydes and Ketones Occur Naturally
O
H
trans-2-hexenal
(alarm pheromone of myrmicine ant)
Many Aldehydes and Ketones Occur Naturally
O
H
citral (from lemon grass oil)
Table 17.1 Synthesis of Aldehydes and Ketones
from alkenes
A number of
reactions already
studied provide
efficient synthetic
routes to
aldehydes and
ketones.
ozonolysis
from alkynes
hydration (via enol)
from arenes
Friedel-Crafts acylation
from alcohols
oxidation
What About..?
aldehydes from carboxylic acids
R
1. LiAlH4
2. H2O
O
O
C
C
OH
R
H
PDC, CH2Cl2
RCH2OH
Example
Benzaldehyde from benzoic acid
O
O
COH
CH
1. LiAlH4
2. H2O
(81%)
CH2OH
PDC
CH2Cl2
(83%)
What About..?
Ketones from aldehydes
R
1. R'MgX
2. H3O+
O
O
C
C
R
H
OH
RCHR'
R'
PDC, CH2Cl2
Example
3-heptanone from propanal
O
O
C
CH3CH2
CH3CH2C(CH2)3 CH3
H
(57%)
1. CH3(CH2)3MgX
2. H3
O+
OH
CH3CH2CH(CH2)3 CH3
H2CrO4