Transcript Chapter 17: Aldehydes and Ketones

CHAPTER 13: 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,
Common names:
HCO2H
formic acid
formica ant
CH3CO2H
acetic acid
acetum vinegar
CH3CH2CO2H
propionic acid
“first salt”
CH3CH2CH2CO2H
butyric acid
butyrum butter
CH3CH2CH2CH2CO2H
valeric acid
valerans
ALDEHYDES COMMON NAMES
STEM PLUS ALDEHYDE
R-CHO
R-CO2H
HCH
O
HCO2H
FORMALDEHYDE
FORMICA - ANTS
CH3CHO
ACETALDEHYDE
CH3COOH
ACETUM - SOUR
CH3CH2CHO
PROPIONALDEHYDE
PROTOS PION - FIRST FAT
PROPIONIC ACID
CH3CH2CH2CO2H
BUTRYM - BUTTER
CH3CH2CH2CH2CH2CHO
CAPROALDEHYDE
ACETIC ACID
CH3CH2CO2H
CH3CH2CH2CHO
BUTYRALDEHYDE
FORMIC ACID
BUTYRIC ACID
CH3CH2CH2CH2CH2CO2H
CAPER - GOAT
CAPROIC ACID
NAMING ALDEHYDES
IUPAC: Replace -e with -al.
 The aldehyde carbon is number 1.
 If -CHO is attached to a ring, use the suffix carbaldehyde.

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O
H
C
H
H3C
Common Formaldehyde
IUPAC
Methanal
Cl
H3C
O
O
2-Chloropropanal
Acetaldehyde
H
H3CH2CH2C
H
Butanal
O
C
C
Butyraldehyde
Propanal
HO
H
C
Propionaldehyde
Ethanal
O
CH
H3C CH2
H
O
O
H
3-Hy droxy propanal
H3CHC=HC
2-Butenal
C
H
NOMENCLATURE

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
H3CO
p-Methoxtbenzaldehyde
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
C6H5
Methyl phenyl ketone
Acetone
Acetophenone
Propanone
Phenyl ethanone
H3C
C
O
CH=CH2 H5C6
Methyl vinyl ketone
C
C6H5
Diphenyl ketone
Benzophenone
3-Buten-2-one
Diphenylmethanone
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
O
O
C2 H 5
O
OH
C
C2 H 5
CHO
O
O
C2 H 5
O
OH
CHO
C
C2 H 5
Cyclopentylpropanone 3-Ethyl-2-hydroxycyclohexanone
5-Oxohexanal
BOILING POINTS
More polar, so higher boiling point than comparable
alkane or ether.
 Cannot H-bond to each other, so lower boiling point
than comparable alcohol.

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SOLUBILITY
Good solvent for alcohols.
 Lone pair of electrons on oxygen of carbonyl can
accept a hydrogen bond from O-H or N-H.
 Acetone and acetaldehyde are miscible in water.

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Aldehydes synthesis 1) oxidation of primary alcohols:
RCH2-OH
+
K2Cr2O7 (potassium dichromate)  RCH=O+ H2
RCH2-OH
+
C5H5NHCrO3Cl

RCH=O+ H2
(pyridinium chlorochromate, or PCC)
[With other oxidizing agents, primary alcohols  RCOOH]
Aldehyde synthesis: Primary alcohols
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) 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
O
R C Ar
AlCl3
RCOCl, AlCl3 + ArH
O
CH3CH2CH2C
Cl
+
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.
ACETALS ANDHEMICETALS
Acetal: two –OR groups bonded to the same
carbon
 Hemiacetal: one –OR group and one –OH group
bonded to the same carbon

ENOLIZATION

Keto-Enol Tautomerism
Tautomerism: interconversion between two structures that
differ by the placement of an atom or group
 Slow in neutral conditions, sped up in acid or base catalyzed
systems
 Enol content is very small, <<<1% for most aldehydes and
ketones
