Download Aldehydes and Ketones

ALDEHYDES AND KETONES
By:
Dr. Siham Lahsasni
ALDEHYDES: STRUCTURE AND NOMENCLATURE
 General
formula: RCHO or RCH=O
 The aldehyde group is always at the end of a
chain
 IUPAC system: Select the longest continuous
carbon chain that contains the C=O group
and replace the ending by the suffix al.
 The CHO group is assigned the number 1
position and takes precedence over other
functional groups that may the present such
as –OH, C=C for example.
O
H
C
H
H3C
Common Formaldehyde
IUPAC
H3C
Methanal
O
Cl
CH
H
Acetaldehyde
Ethanal
HO
H3C CH2
C
O
H
Propionaldehyde
O
C
H
2-Chloropropanal

O
O
H3CH2CH2C
Butyraldehyde
Propanal
H
Butanal
O
H3CHC=HC
3-Hydroxypropanal
C
C
H
2-Butenal
Aromatic aldehydes are usually designated as derivatives of
the simplest aromatic aldehyde, Benzaldehyde.
O
O
H
H
OH
H
H
O 2N
Benzaldehyde
O
O
p-Nitrobenzaldehyde o-Hydroxybenzaldehyde
Salicylaldehyde
H3CO
p-Methoxtbenzaldehyde
Anisaldehyde
H
KETONES: STRUCTURE AND NOMENCLATURE
General formula: RCOR’ (R and R’=alkyl or aryl)
 Common name: listing the alkyl substitutents attached to the
carbonyl group, followed by the word ketone.
 IUPAC system: relpace the ending –e by the suffix –one. The
chain is numbred in such a way as give the lowest number to
the C=O group.

O
H3C
C
O
CH3
Common Dimethyl ketone
IUPAC
H3C
C
O
C6 H5
Methyl phenyl ketone
Acetone
Acetophenone
Propanone
Phenyl ethanone
H3C
C
O
CH=CH 2 H5C6
Methyl vinyl ketone
C
C6 H5
Diphenyl ketone
Benzophenone
3-Buten-2-one
Diphenylmethanone
O
O
C2 H 5
O
OH
CHO
C
C2 H 5
Cyclopentylpropanone 3-Ethyl-2-hydroxycyclohexanone
5-Oxohexanal
PHYSICAL PROPERTIES OF KETONES
AND ALDEHYDE



O
C
+
O
C
O

C
-
C
O



Because the polarity of the carbonyl group, aldehydes and
ketones are polar compounds.
 Dipole-dipole attractions, although important, are not as
strong as intractions due to hydrogen bonding. As a result,
the boiling points of aldehydes and ketones are higher than
those of nonpolar alkanes, but lower than those of alcohols.


C


O


H
O


H


O
C
The lower aldehydes and ketones are soluble.
PREPARATION OF ALDEHYDES AND KETONES
1- Oxidation of alcohols
RCH 2
OH
CrO 3/ pyridine
O
R
Cu / heat
H
O
CrO 3/ pyridine
R2CH
R
OH
C
R
Cu / heat
2- Reduction of acid chloride
H2 / Pd(BaSO4)
O
R-H 2C-C
R-CH2-CHO
Cl
O
O
LiAlH[O(CH3)3] 3
Cl
H
3- Ozonolysis of alkenes
A
A
A
1)O 3
A
O
2)Zn / H 2O
A
A
+
A
O
A
4- Hydration of alkynes
H
C
C
+
HO H
H2SO4, HgSO4
H
C
C
OH
an enol unstable
C
C
H
O
carbonyl more stable
-78 C
H 3C
C
CH
CH3-CH=CH
(Sia)2BH
+
ether
O
H 2O2/ OH H 2O
CH3-CH 2-CH
CH 3
CH 3
Sia= CH 3-C
C
H
H
: disiamyl
(Sia) 2BH
5- Friedel Grafts acylation
O
O
+
CH3
AlCl 3
R
Cl
6-Oxo reaction - Hydroformylation reaction
CH3-CH=CH2
+
H2
+
CH3-CH2-CH2-CHO
CO
CH3-CH-CH3
+
CHO
7- Gattermann-Koch reaction
75 %
25 %
CHO
+
-
C
O+
+
HCl +
AlCl3
CO
H-C
H+
O+
H-C+
CHO
+
H-C+
O
O
8- Oxidation of an Alkyl Side of aromatic ring
H3 COCO
CH 3
OCOCH3
HC
CHO
H2O / H+
CrO3 / 10 C
(CH3CO)2O
9- From acid chloride and lithium dialkyl cuperate or R2 cd
O
R
C
O
Cl
+
R2CuLi
O
C
Cl
+
(CH3-CH2)2CuLi
-78 C
ether
-78 C
ether
O
H3 C
C
R
C
R2
O
C
CH2 -CH 3
O
Cl
+
(Ph)2Cd
-78 C
ether
C
CH 3
10- From Carboxylic acid and RLi
O
R
O
C
1) Ether
2 R'Li
+
OH
R
C
R'
+
R'H + 2 LiOH
2) H3O+
O
O
C
OH
+
1) Ether
2 CH3Li
C
CH3
2) H3O+
11- From nitrile and Grignard reagent or alkyl lithium
O
NMgX
R
C
N
H3O+
Ether
+ R'MgX
R
C
R
R'
C
N
+ R'Li
H3O+
Ether
R
C
R'
R
C
O
H 3C
H 3C
H
C
C
N
+
PhLi
1) Ether
2) H3O+
R'
O
NLi
R
C
C
R'
CH 3
H
C
CH 3
REACTIONS OF ALDEHYDES AND KETONES
H
R
R
C+
O -
H
C+
>
O -
C+
>
O -
R'
H
Activity of the carbonyl group
Nu-
C+
O -
Nu
C
O-
E+
Nu
C
OE
1- reduction of carbonyl group
a- Addition of metal hydride
C
O
+
M+H-
H
C
H2O
H
OAl
O
+
H
C
OH
OH
H2O
LiAlH4
H
2 H2 / Pd
H3C
O -M+
H+
OH
H3C
O
H
1) NaBH 4
2) H 2O
H3C
OH
b- Addition of Grignard Reagents: Formation of alcohols
R'
O
R
+
C
R'MgX
H
1) Dry ether
R
HO
+
C
OH
2) H 2O
O
H3C
CH
C2H5MgX
H
1) Dry ether
2) H 2O
H3C
CH
C2H5
R'
O
R
C
R'
+
R''MgX
1) Dry ether
2) H 2O
R
C
OH
R''
CH3
O
+
CH 3MgX
1) Dry ether
2) H 2O
OH
c- Clemmenson reduction
O
H
COOH
H
HCl / Zn(Hg)
COOH
d- The Wolf-kishner reduction
O
N-NH 2
NH2NH2
COOH
COOH
H
NaOH

H
COOH
e- Wittig reaction
O
C
+
CH2=P(C6H5)3
O
P(C 6H 5) 3
C
CH 2
O-
P(C 6H 5) 3
C
CH 2
THF
C
CH 2
(C6H5)3P=O
+
O
O
H
+
(Ph)3P=CH
C
OC 2 H5
O
OC2 H 5
2- Oxidation reaction
aR-CHO or
Ar-CHO
KMnO4
or
RCOOH
or K Cr O
2 2 7
ArCOOH
b- Tollenis test
RCHO
+ 2 Ag(NH3)+2 +
OH-
RCOO- + 2 Ag + 4 NH3 + 3 H2O
c- Iodoform reaction
O
H3C
C O
+
3 I2
+
4 NaOH
R
O Na
R
CH3
H3C
O
I 2 / NaOH
-
H3C
COONa
+
+ CHI3 +
+
CHI3
3 NaI
3- Addition of Hydrogen Cyanide: Formation of cynohydrins
R'
O
R
C
+
R'
R
HCN
C
OH
CN
Cyanohydrin
CN
O
H
NH2
OH
+
OH
H2 / Pt
+
or LiAlH 4 and H 3O
HCN
Benzaldehyde cyanohydrin
O
OH
+
H3O
CN
HCN
OH
+
COOH
Heat
4- Addition of acetylide ions:
R'
O
R
C
R'
+
-
2
C Na
R C
H3O
+
+
R
C
C
C
R
OH
O
+ H3C
C
-
C Na
+
H3O
+
OH
C
C
CH3
2
5- Addition of alcohols:
R'O
O
R
C
2
R =H:
2
R =Alkyl
+
2
R'OH
H
R
R''OH
C
OH
R
Aldehyde
R
Hemiacetal
Ketone
Hemiketal
+
C2H5OH
H3C
C
H5 C2 O
CH
OC 2H5
CH3
C2H5OH
C2H5OH
+
H
H3C
C
OC 2H5
H5C2O
H
H3C
CH
Acetal
HO
+
+
2
Ketal
Hemiacetal
H3C
OR''
R
Acetal
H
H
O
C
HO
+
C
R
+
H
2
O
H3C
R'O
+
OC 2H5
CH3
Hemiketal
C2H5OH
+
H
H3C
C
CH3
Ketal
OC 2H5
6- Addition of Ammonia and Ammonia Derivatives
NH3
C
NH
Imine
NH 2OH
Hydroxylamine
H2N
C N OH
Oxime
NH2
C
Hydrazine
C
N
NH2
Hydrazone
O
H2N
NH
C
Phenylhydrazine
NO 2
O 2N
NO 2
NH
C
NH C
Semicarbazide
NH
N
-
O
H2N
NH
Phenylhydrazone
O 2N
H2N
N
NH2
2,4 Dinitrophenylhydrazone
O
C
N
NH
C
Semicarbazone
NH2
7- Aldol condensation
The reaction occurs in any aldehyde or ketone containing α hydrogen:
2
O
H3C
2
dil. NaOH
C O
R
C
OH
CH2 C
R
R
CH3
CH3
H3C
dil. NaOH
CH3
H3C
O
O
OH
CH3
O
O
O
OHCH3
O
CH2
CH3
-
O
O-
H2O
OH
8- Cannizzaro reaction
Aldehyde which does not contain α hydrogen undergoes
Cannizzaro reaction.
CHO
CH 2 OH

NaOH (30 %)
+
COO-Na+
+
O
O
O-
CH
C
+
C
H
OH
OH-
H
O
O
C
CH2 OOH
CH2 OH
C
+
O-
more stable anion
+