Aldehydes and Ketones
Before you can learn about aldehydes and
ketones, you must first know something about
the nomenclature of carboxylic acids since many
of the names of aldehydes and ketones are
derived from the names of the corresponding
carboxylic acids.
Carboxylic acids:
R-COOH, R-CO2H,
O
R C
OH
Common names:
HCO2H
formic acid
L. formica ant
CH3CO2H
acetic acid
L. acetum vinegar
CH3CH2CO2H
propionic acid G. “first salt”
CH3CH2CH2CO2H
butyric acid
L. butyrum butter
CH3CH2CH2CH2CO2H
valeric acid
L. valerans
Carboxylic acids, common names:
…
CH3(CH2)4CO2H
caproic acid
CH3(CH2)5CO2H
---
CH3(CH2)6CO2H
caprylic acid
CH3(CH2)7CO2H
---
CH3(CH2)8CO2H
capric acid
CH3(CH2)9CO2H
---
CH3(CH2)10CO2H
lauric acid
L. caper goat
oil of lauryl
5 4 3 2 1
C—C—C—C—C=O
δ γ β α
Br
CH3CH2CH2CHCOOH
 bromovaleric acid
used in common names
CH3
CH3CHCH2COOH
 -methylbutyric acid
isovaleric acid
COOH
Special names!
benzoic acid
COOH
CH3
COOH
COOH
CH3
CH3
o-toluic acid
m-toluic acid
p-toluic acid
ALDEHYDES AND KETONES
“carbonyl” functional group:
O
C
Aldehydes
H
O
C
H
Ketones
R
O
C
H
R can be Ar
R
O
C
R'
Nomenclature:
Aldehydes, common names:
Derived from the common names of carboxylic acids;
drop –ic acid suffix and add –aldehyde.
CH3CH2CH2CH=O
butyraldehyde
CH3
CH3CHCH=O
isobutyraldehyde
(α-methylpropionaldehyde)
CHO
CHO
CH3
benzaldehyde
H
O
C
H
formaldehyde
o-tolualdehyde
CH2CH=O
phenylacetaldehyde
Aldehydes, IUPAC nomenclature:
Parent chain = longest continuous carbon chain containing
the carbonyl group; alkane, drop –e, add –al. (note: no
locant, -CH=O is carbon #1.)
CH3CH2CH2CH=O
butanal
H2C=O
methanal
CH3
CH3CHCH=O
2-methylpropanal
CH3CH=O
ethanal
Ketones, common names:
Special name:
H3C
O
C
CH3
acetone
“alkyl alkyl ketone” or “dialkyl ketone”
O
CH3CH2CCH3
ethyl methyl ketone
O
CH3CH2CCH2CH3
diethyl ketone
O
CH3CCH2CH2CH3
methyl n-propyl ketone
(o)phenones:
O
R C
Derived from common name of carboxylic acid, drop –ic
acid, add –(o)phenone.
O
C
benzophenone
H3C
O
C
acetophenone
Ketones: IUPAC nomenclature:
Parent = longest continuous carbon chain containing the
carbonyl group. Alkane, drop –e, add –one. Prefix a locant
for the position of the carbonyl using the principle of lower
number.
O
CH3CH2CCH3
O
CH3CH2CCH2CH3
2-butanone
3-pentanone
O
CH3CCH2CH2CH3
2-pentanone
Physical properties:
C O
sp
2
120
o

C O
C O
polar, no hydrogen bonding
mp/bp are relatively moderate for covalent substances
water insoluble
(except: four-carbons or less)
Spectroscopy:
IR:
C=O stretch, strong ~1700 cm-1
RCHO
1725
ArCHO
1700
R2CO
1710
ArCOR
1690
C—H stretch for aldehydes
nmr:
-CHO 9-10 ppm
2720
acetophenone
C=O
stretch
valeraldehyde
CHO
C—H
stretch
2720 cm-1
C=O stretch
valeraldehyde
CH3CH2CH2CH2CH=O
a b c d e
-CHO
Oxidation/Reduction:
oxidation numbers:
oxidation
-4
CH4
-2
CH3OH
0
H2C=O
+2
HCO2H
alkane
alcohol
aldehyde
carboxylic acid
reduction
+4
CO2
Aldehydes, syntheses:
1. Oxidation of 1o alcohols
2. Oxidation of methylaromatics
3. Reduction of acid chlorides
Ketones, syntheses:
1. Oxidation of 2o alcohols
2. Friedel-Crafts acylation
3. Coupling of R2CuLi with acid chloride
Aldehydes synthesis 1) oxidation of primary alcohols:
RCH2-OH
+
K2Cr2O7, special conditions  RCH=O
RCH2-OH
+
C5H5NHCrO3Cl
 RCH=O
(pyridinium chlorochromate)
[With other oxidizing agents, primary alcohols  RCOOH]
CH3CH2CH2CH2CH2OH
K2Cr2O7, special conditions!
1-pentanol
CH2OH
CH3CH2CH2CH2CH=O
pentanal
valeraldehyde
C5H5NHCrO3Cl
CH=O
pyridinium chlorochromate
benzyl alcohol
CH3CH2CH2CH2CH2OH + K2Cr2O7
1-pentanol
benzaldehyde
CH3CH2CH2CH2CO2H
pentanoic acid
Aldehyde synthesis: 2) oxidation of methylaromatics:
O
H3C
C O
C O
H3C
CH O
CH3
+ CrO3, (CH3CO)2O
Br
Br
geminal diacetate
CHO
H2O, H+
Br
p-bromobenzaldehyde
Aromatic aldehydes only!
CH3
CrO3
CHO
H2O
(CH3CO)2O
2-methylnaphthalene
2-naphthaldehyde
CrO3
CH3O
CH3
p-methylanisole
(CH3CO)2O
H2O
CH3O
CH=O
p-anisaldehyde
Aldehyde synthesis: 3) reduction of acid chloride
R
O
C
LiAlH(O-t-Bu)3
Cl
lithium aluminum hydride tri-tert-butoxide
O
LiAlH(O-t-Bu)3
Cl
isovaleryl chloride
R
O
C
H
O
H
isovaleraldehyde
O
LiAlH(O-t-Bu)3
C
Cl
benzoyl chloride
CH3
O
CH3CHCH2C
Cl
isovaleryl chloride
O
C
H
benzaldehyde
LiAlH(O-t-Bu)3
CH3
O
CH3CHCH2C
H
isovaleraldehyde
Ketone synthesis: 1) oxidation of secondary alcohols
H
O
OH
NaOCl
cyclohexanone
cyclohexanol
OH
CH3CHCH3
isopropyl alcohol
K2Cr2O7
H3C
O
C
CH3
acetone
Ketone synthesis:
2) Friedel-Crafts acylation
AlCl3
RCOCl, AlCl3 + ArH
O
CH3CH2CH2C
Cl
+
O
R C Ar
AlCl3
+ HCl
O
CH3CH2CH2C
butyrophenone
Aromatic ketones (phenones) only!
O
C Cl
O
C
AlCl3
+
O2N
O2N
m-nitrobenzophenone
O
C Cl
AlCl3
+
NR
NO2
Friedel Crafts acylation does not work on deactivated rings.
Mechanism for Friedel-Crafts acylation EAS
R
O
C
+
Cl
AlCl3
RC=O + AlCl4
RDS
+ RC=O
O
CR
H
+ AlCl4
O
CR
H
O
C R
+ HCl + AlCl3
Ketone synthesis:
3) coupling of RCOCl and R2CuLi
O
RCOCl + R'2CuLi
C
R
R'
O
O
Cl
+
(CH3CH2)2CuLi
lithium diethylcuprate
Isobutyryl chloride
2-Methyl-3-pentanone
CuLi
+
O
Cl
2
CHCH2CH2CH3
O
CCH2CH2CH3
butyrophenone
O
CH3CH2CH2C
Cl
+
CH3
CH3CH CuLi
2
O
CH3CH2CH2CCHCH3
CH3
2-methyl-3-hexanone
Aldehydes, syntheses:
1. Oxidation of 1o alcohols
2. Oxidation of methylaromatics
aromatic only
3. Reduction of acid chlorides
Ketones, syntheses:
1. Oxidation of 2o alcohols
2. Friedel-Crafts acylation
aromatic only
3. Coupling of R2CuLi with acid chloride
1o alcohol
Ar-CH3
acid chloride
K2Cr2O7, special cond.
or C5H5NHCrO3Cl
CrO3
H2O
(AcO)2O
LiAlH(O-t-Bu)3
aldehyde
2o
alcohol
acid chloride + ArH
NaOCl, etc.
AlCl3
acid chloride + R2CuLi
ketone
1. outline three different syntheses for benzaldehyde
2. outline three different syntheses for benzophenone
3. outline a different synthesis for each of the
following compounds:
cyclohexanone, 4-bromobenzaldehyde, 2-pentanone,
valeraldehyde, acetophenone, isobutyraldehyde,
Synthesize benzaldehyde three different ways.
CH2OH
K2Cr2O7
special conditions
CH(OOCCH3)2
CH3
CrO3
CH=O
H2O
(CH3CO)2O
benzaldehyde
O
C Cl
LiAlH(O-t-Bu)3
Synthesize benzophenone three different ways.
OH
CH
O
+
C
Cl
O
+
C
Cl
NaOCl
AlCl3
CuLi
2
O
C
cyclohexanone, 4-bromobenzaldehyde, 2-pentanone,
valeraldehyde, acetophenone, isobutyraldehyde, using a
different method for each one.
O
Br
oxidation of 2o alcohol
O
CH3CH2CH2CCH3
R2CuLi + R'COCl
O
CH3C
Friedel-Crafts acylation
CHO
oxidation of Ar-CH3
CH3CH2CH2CH2CHO
oxidation of 1o alcohol
CH3
CH3CHCHO
reduction of acid chloride
H
OH
(CH3CH2CH2)CuLi
CH3
O
C
Cl
O
K2Cr2O7
+
CH3
AlCl3
+
O
CH3CH2CH2CCH3
O
C
Cl
O
CH3C
Br
CH3
(CH3CO)2O
CH3CH2CH2CH2CH2-OH
CH3 O
CH3CHC
Cl
H2O
CrO3
Br
K2Cr2O7
CHO
CH3CH2CH2CH2CHO
special conditions
LiAlH(O-t-bu)3
CH3
CH3CHCHO
The methods could be reversed for the last two syntheses.