Chapter 17 Aldehydes and Ketones Nucleophilic Addition to the Carbonyl Group

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Chapter 17Aldehydes and KetonesNucleophilic
Additionto theCarbonyl Group
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17.1Nomenclature
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IUPAC Nomenclature of Aldehydes
Base the name on the chain that contains the
carbonyl group and replace the -e ending of the
hydrocarbon with -al.
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IUPAC Nomenclature of Aldehydes
4,4-dimethylpentanal
5-hexenal or hex-5-enal
2-phenylpropanedial(keep the -e endingbefore
-dial)
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IUPAC Nomenclature of Aldehydes
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Substitutive IUPAC Nomenclature of Ketones
Base the name on the chain that contains the
carbonyl group and replace -e with -one. Number
the chain in the direction that gives the lowest
number to the carbonyl carbon.
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Substitutive IUPAC Nomenclature of Ketones
3-hexanone or Hexan-3-one
4-methyl-2-pentanone or 4-methylpentan-2-one
4-methylcyclohexanone
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Functional Class IUPAC Nomenclature of Ketones
List the groups attached to the carbonyl
separately in alphabetical order, and add the
word ketone.
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Functional Class IUPAC Nomenclature of Ketones
ethyl propyl ketone
benzyl ethyl ketone
divinyl ketone
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17.2Structure and BondingThe Carbonyl Group
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Structure of Formaldehyde

• planar
• bond angles close to 120
• CO bond distance 122 pm

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The Carbonyl Group
O
1-butene
propanal
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Carbonyl Group of a Ketone is MoreStable than
that of an Aldehyde
heat of combustion
2475 kJ/mol
2442 kJ/mol

• Alkyl groups stabilize carbonyl groups the
  sameway they stabilize carbon-carbon double
  bonds,carbocations, and free radicals.

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Spread is Greater forAldehydes andKetones than
for Alkenes

• Heats of combustion ofC4H8 isomeric alkenes
• CH3CH2CHCH2 2717 kJ/mol
• cis-CH3CHCHCH3 2710 kJ/mol
• trans-CH3CHCHCH3 2707 kJ/mol
• (CH3)2CCH2 2700 kJ/mol

2475 kJ/mol
2442 kJ/mol
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Resonance Description ofCarbonyl Group

• Nucleophiles attack carbon electrophiles
  attack oxygen.

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Bonding in Formaldehyde
Carbon and oxygen are sp2 hybridized.
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Bonding in Formaldehyde
The half-filledp orbitals oncarbon andoxygen
overlapto form a ? bond.
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17.3Physical Properties
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Aldehydes and Ketones have Higher Boiling
Pointsthan Alkenes, but Lower Boiling Points
than Alcohols
boiling point
6C

• More polar than alkenes, but cannot form
  intermolecular hydrogen bonds to other carbonyl
  groups.

49C
97C
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17.4Sources of Aldehydes and Ketones
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Many Aldehydes and Ketones Occur Naturally

2-heptanone(component of alarm pheromone of bees)
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Many Aldehydes and Ketones Occur Naturally
O
H
trans-2-hexenal (alarm pheromone of myrmicine
ant)
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Many Aldehydes and Ketones Occur Naturally
O
H
citral (from lemon grass oil)
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Table 17.1 Synthesis of Aldehydes and Ketones

• from alkenes
• ozonolysis
• from alkynes
• hydration (via enol)
• from arenes
• Friedel-Crafts acylation
• from alcohols
• oxidation

A number of reactions alreadystudied
provideefficient syntheticroutes to aldehydes
and ketones.
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What About..?

• aldehydes from carboxylic acids

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Example

• Benzaldehyde from benzoic acid

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What About..?

• Ketones from aldehydes

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Example

• 3-heptanone from propanal

O
C
CH3CH2
H
(57)