ALDEHYDES%20AND%20KETONES

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ALDEHYDES AND KETONES
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Aldehydes and Ketones
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d
d-
Most Reactive Group p-electrons polarisation
al aldehydes, one - ketones
Names
Propanal
Methanal (formaldehyde)
Ethanal (acetaldehyde)
Pentanal
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Nomenclature of Aldehydes
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If the aldehyde group is attached to a ring,
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Nomenclature of Ketones
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Oxidation
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An aldehyde has a greater partial positive charge
on its carbonyl carbon than does a ketone
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• Steric factors contribute to the reactivity of
  an aldehyde

• The carbonyl carbon of an aldehyde is more
  accessible
• to the nucleophile

• Ketones have greater steric crowding in their
  transition
• states, so they have less stable transition
  states

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Reactions

• 1. Redox reactions

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• 2. Addition AN

Addition of water
Addition of bisulfite
Bisulfite
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Addition of NH3
Addition of HCN
Cyanohydrine
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• 3. Condensation reactions (addition followed by
  elimination)

Ammonia derivatives
Primary amine
Schiff base
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Hydroxylamine
Oxime
Hydrazine
Hydrazone
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Phenylhydrazine
Phenylhydrazone
2,4-dinitrophenylhydrazine
2,4-dinitrophenylhydrazone
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Aldol condensation
Aldol
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Reaction with alcohol
Hemiacetal (addition!)
Acetal (condensation!)
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KetoEnol Tautomerism
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Oxidation of a Primary Alcohol
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Reduction by Addition of a Hydride Ion and a
Proton
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Aldehydes and ketones react with nucleophiles to
form addition products nucleophile addition
reactions
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Water adds to an aldehyde or ketone to form a
hydrate
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Hydration of Aldehydes and Ketones
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Alcohols Under Analogous Reactionwith Aldehydes
and Ketones

• Product is called a hemiacetal.

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Example

2CH3CH2OH
HCl
H2O
Benzaldehyde diethyl acetal (66)
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Reaction with Primary AminesImines
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If the nucleophile that adds to the aldehyde or
ketone is an O or an N, a nucleophilic
additionelimination reaction will occur
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Imine (Schiff's Base) Formation
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Example

CH3NH2
CHNCH3
H2O
N-Benzylidenemethylamine (70)
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Reaction with Derivatives of Ammonia
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Reaction with Derivatives of Ammonia
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Example
H2NNH2
H2O
(73)
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Example
CCH3
phenylhydrazine
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An aldol addition product loses water to form an
aldol condensation product
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Aldol Condensation
NaOH
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Aldol Addition of Acetaldehyde
Acetaldol(50)
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Hemiacetal reacts further in acid to yield an
acetal

• Product is called an acetal.

ROH, H
Product is called a hemiacetal.
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Formaldehyde

• formaldehyde cannot form an enolate
• formaldehyde is extremely reactive
• toward nucleophilic addition

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Acrolein
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Acrolein
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Acrolein