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Aldehydes and ketones
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Outline
 Structure and Bonding
 Nomenclature
 Physical Properties
 Preparation
 Reactions
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Structure and Bonding
 The functional group of an aldehyde is a carbonyl group bonded to a
hydrogen atom and a carbon atom
 The functional group of a ketone is a carbonyl group bonded to two
carbon atoms
 Many compounds found in nature have aldehyde or ketone functional
groups. Aldehydes have pungent odors, whereas ketones tend to smell
sweet. Vanillin and cinnamaldehyde are examples of naturally occurring
aldehydes. A whiff of vanilla extract will allow you to appreciate the
pungent odor of vanillin. The ketones camphor and carvone are
responsible for the characteristic sweet odors of the leaves of camphor
trees, spearmint leaves, and caraway seeds.
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IUPAC Nomenclature of aldehyde
 Select the longest chain of carbon atoms that contains the functional group.
 changing the suffix -e of the parent alkane to –al.
 Number must start with carbonyl group of an aldehyde as carbon-1.
 For unsaturated aldehydes, the presence of a carbon-carbon double or triple
bond is indicated by the infix -en- or -yn-. As with other molecules with both an infix
and a suffix, the location of the group corresponding to the suffix determines the
numbering pattern.
 The functional group priority order in nomenclature system is as following:
Acid and derivatives > aldehyde > ketone > alcohol > amine > alkene > alkyne >
ether
 For cyclic molecules in which }CHO is bonded directly to the ring, the molecule is
named by adding the suffix -carbaldehyde to the name of the ring. The atom of
the ring to which the aldehyde group is bonded is numbered 1.
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 The common name for an aldehyde is derived from the common name of
the corresponding carboxylic acid by dropping the word acid and
changing the suffix -ic or –oic to -aldehyde.
 In common names carbon atoms near the carbonyl group are often
designated using Greek letters (α, ᵝ, ɣ , δ…..) beginning with carbon next
the carbonyl group.
Butanal
a
(𝛂340 Chem 1st 1439
3-Methylbutanal
a
7
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Br
8
O
O
O
O
O 2N
β-Bromo- α-methyl butyraldehyde
Cyclohexanecarbaldehyde
3-Bromo-2-methyl-butanal
O
OH
O
Cl
β-Chloro-  -ethyl valeraldehyde
3-Chloro-2-ethyl-pentanal
p-Methyl-benzaldehyde
p-Tolualdehyde
4-Methyl-benzaldehyde
p-Nitro-benzaldehyde
4-Nitro-benzaldehyde
O
O
H 3CO
 -Phenyl-acetaldehyde
Salicylaldehyde
p-Methoxy-benzaldehyde
2-Phenylethanal
o-Hydroxy-benzaldehyde
Anisaldehyde
2-Hydroxy-benzaldehyde
4-Methoxy-benzaldehyde
O
O
O
O
O
HO
O
OH
3,4-Dioxobutanoic acid
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COOH
2-Formylbenzoic acid
benzene carbaldehyde
3-Hydroxypopanal
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IUPAC Nomenclature of Ketone
 ketones are named by selecting as the parent alkane the longest chain
that contains the carbonyl group changing the suffix from -e to –one
 The parent chain is numbered from the direction that gives the carbonyl
carbon the smaller number.
 If a ketone has a second functional group of higher naming priority, the
ketone oxygen is indicated by the prefix “oxo.”
 Common names for ketones are derived by naming the two alkyl or aryl
groups bonded to the carbonyl group as separate words followed by the
word ketone.
 A ketone or aldehyde group can also be named as a substituent on a
molecule with a higher priority functional group as its root. A ketone or
aldehyde carbonyl is named by the prefix oxo- if it is included as part of the
longest chain in the root name. When an aldehyde group is a substituent
and not part of the longest chain, it is named by the prefix formyl.
Carboxylic acids frequently contain ketone or aldehyde groups named as
substituents.
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Phenyl ethanone
Dimethyl Ketone
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Diphenylmethanone
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Physical Properties
 Oxygen is more electronegative than carbon; therefore, a carbon-oxygen
double bond is polar, with oxygen bearing a partial negative charge and
carbon bearing a partial positive charge.
 In general, aldehydes and ketones have higher boiling points than alkenes
because they are more polar and the dipole–dipole attractive forces
between molecules are stronger. But they have lower boiling points than
alcohols because, unlike alcohols, two carbonyl groups can’t form
hydrogen bonds to each other.
 Aldehydes and ketones can form hydrogen bonds with the protons of OH
groups. This makes them more soluble in water than alkenes, but less soluble
than alcohols.
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CH3CH2CH2CH3 CH3OCH2CH3
Butane
bp 0 °C
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methoxyethane
bp 8 °C
CH3CH2CHO
CH3COCH3
propanal
acetone
bp 49 °C
bp 56 °C
CH3CH2CH2OH
propan-1-ol
bp 97 °C
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Syntheses of Ketones and Aldehydes
Oxidation of Alcohols
 Sodium dichromate in sulfuric acid (“chromic acid,” H2CrO4) is the oxidizing reagent
for secondary alcohols to ketones. Bleach (NaOCl sodium hypochlorite) is an
inexpensive. Primary alcohols are usually oxidized by Pyridinium chlorochromate
(PCC), a complex of chromium trioxide CrO3 with pyridine and HCl, provides good
yields of aldehydes
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Ozonolysis of Alkenes
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Friedel–Crafts Acylation
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Hydration of Alkynes
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Reactions of aldehydes and Ketones
Nucleophilic Addition to the Carbon–Oxygen Double Bond
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Addition of Grignard Reagents
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Reduction of carbonyl group
Addition of metal hydrides( formation of alcohol)
O
1) LiAlH 4 or NaBH 4
R
2) H 3 O +
R
CH 2
H
O
OH
1) LiAlH 4 or NaBH 4
R
2) H 3 O +
R`
R
CH
R`
OH
2H2 / Pt
O
1) NaBH4
2) H2O
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OH
OH
The Addition of Alcohols: Hemiacetals
and Acetals
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R
H
`R
+
O
R
+
`R
R ``O H
R ` = H
A ld e h y d e
R ` = a lk y l K e to n e
+
O
+
H
C 2H 5O H
O R ``
O H
H e m ia c e ta l
H
O H
5
H
H e m ia c e ta l
O
+
C 2H 5O H
+
O H
+
C 2H 5O H
O C 2H
5
H e m iK e ta l o ld
H e m ia c e ta l n e w
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`R
+
C 2H 5O H
O C 2H
H
R
R ```O H
H
+
O R ``
O R ```
A c e ta l
O C 2H
5
O C 2H
H y d r o ly s is
5
O
+ 2 C 2H 5O H
A c e ta l
O C 2H
5
H y d r o ly s is
O C 2H
5
K e ta l o ld
A c e ta l n e w
O + 2 C 2H 5O H
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Addition of Hydrogen Cyanide: Formation
of cynohydrins
R
`R
R
+ HCN
O
`R
Cyanohydrine
OH
CN
CN
CH2NH2
O
+ HCN
OH
H2 / Pt
OH
or LiAlH4 and H3O +
O
+ HCN
Benzaldehyde cyanohydrine
CN
H3O +
OH
heat
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COOH
OH
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Addition of acetylide ions:
R
R
H3 O +
`R
O + ``R
`R
CNa
R``
OH
O
H3
+
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CNa
O+
OH
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Addition of Ammonia and Ammonia
Derivatives
NH3
NH
I m in e
OH
O
N H 2O H
N
O x im e
H y d r o x y a m in e
H 2 N -N H 2
NH2
N
H y d r a z in e
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H y d ra z o n e
Oxidation of Aldehydes
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K
M
n
O
4
r
C
O
O
H
R
C
O
O
H
o
rA
R
C
H
O
r
C
H
O
o
rA
o
r
K
C
r
O
2
2
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Iodoform reaction: The reaction occurs in any aldehyde or ketone
containing CH3CO.
ONa
R
+ 3 I2
O
+ 4 NaOH
I 2 / NaOH
O
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R
O
COONa
+ CHI 3
+ 3 NaI
+ CHI 3
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Cannizaro Reaction
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A) Nucleophilic addition
of an OH - ion to the 1st
aldehyde molecule
gives a tetrahedral
intermediate.
B
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A
B) Hydride shift: The tetrahedral
intermediate I , expels a hydride
ion as a leaving group and is
thereby oxidized. A second
aldehyde molecule accepts
the hydride ion in another
nucleophilic addition step and
is thereby reduced.
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Aldol condensation:
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Tollens’ Test
 Tollens’ reagent oxidizes an aldehyde into the corresponding carboxylic
acid. The reaction is accompanied by the reduction of silver ions in Tollens’
reagent into metallic silver, which, if the test is carried out in a clean glass
test tube, forms a mirror on the test tube.
 Ketones are not oxidized by Tollens’ reagent, so the treatment of a ketone
with Tollens’ reagent in a glass test tube does not result in a silver mirror.
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