Post on 03-Dec-2015
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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 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
R COH
O
Carboxylic acids, common names:
…
CH3(CH2)4CO2H caproic acid L. caper goat
CH3(CH2)5CO2H ---
CH3(CH2)6CO2H caprylic acid
CH3(CH2)7CO2H ---
CH3(CH2)8CO2H capric acid
CH3(CH2)9CO2H ---
CH3(CH2)10CO2H lauric acid oil of lauryl
5 4 3 2 1C—C—C—C—C=Oδ γ β α used in common names
CH3CH2CH2CHCOOH
BrCH3CHCH2COOH
CH3
bromovaleric acid -methylbutyric acid
isovaleric acid
COOH
COOH COOH COOH
CH3
CH3CH3
benzoic acid
o-toluic acid m-toluic acid p-toluic acid
Special names!
ALDEHYDES AND KETONES
“carbonyl” functional group:
Aldehydes Ketones
HC
H
O
RC
H
O
RC
R'
O
R can be Ar
C
O
Nomenclature:
Aldehydes, common names:
Derived from the common names of carboxylic acids;
drop –ic acid suffix and add –aldehyde.
CH3
CH3CH2CH2CH=O CH3CHCH=O
butyraldehyde isobutyraldehyde (α-methylpropionaldehyde)
CHO
benzaldehyde
CHO
CH3
o-tolualdehyde
HC
H
O
formaldehyde
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.)
CH3
CH3CH2CH2CH=O CH3CHCH=O
butanal 2-methylpropanal
H2C=O CH3CH=O
methanal ethanal
Ketones, common names:
Special name: acetone
“alkyl alkyl ketone” or “dialkyl ketone”
H3CC
CH3
O
CH3CH2CCH3
O
CH3CH2CCH2CH3
O
ethyl methyl ketone diethyl ketone
CH3CCH2CH2CH3
O
methyl n-propyl ketone
(o)phenones:
Derived from common name of carboxylic acid, drop –ic acid, add –(o)phenone.
CR
O
C
O
H3CC
O
benzophenone 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.
CH3CH2CCH3
O
CH3CH2CCH2CH3
O
2-butanone 3-pentanone
CH3CCH2CH2CH3
O
2-pentanone
Physical properties:
polar, no hydrogen bonding
mp/bp are relatively moderate for covalent substances
water insoluble
(except: four-carbons or less)
C O sp2 120o
C O C O
Spectroscopy:
IR: C=O stretch, strong ~1700 cm-1
RCHO 1725 ArCHO 1700
R2CO 1710 ArCOR 1690
C—H stretch for aldehydes 2720
nmr: -CHO 9-10 ppm
C=Ostretch
acetophenone
valeraldehyde
CHOC—Hstretch2720 cm-1
C=O stretch
valeraldehyde
CH3CH2CH2CH2CH=O
a b c d e
-CHO
Oxidation/Reduction:
oxidation numbers:
oxidation
-4 -2 0 +2 +4 CH4 CH3OH H2C=O HCO2H CO2
alkane alcohol aldehyde carboxylic acid
reduction
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 CH3CH2CH2CH2CO2H
1-pentanol
pentanoic acid
K2Cr2O7, special conditions!CH3CH2CH2CH2CH=O
pentanalvaleraldehyde
CH2OHC5H5NHCrO3Cl
pyridinium chlorochromate
CH=O
benzaldehydebenzyl alcohol
CH3CH2CH2CH2CH2OH
1-pentanol
Aldehyde synthesis: 2) oxidation of methylaromatics:
+ CrO3, (CH3CO)2O
geminal diacetate
H2O, H+
CH3
BrBr
CH OOC C
H3C
OO
H3C
Br
CHO
p-bromobenzaldehyde
Aromatic aldehydes only!
CH3
CH3O CH3
CrO3
(CH3CO)2O
CrO3
(CH3CO)2O
H2O
H2O
CHO
CH3O CH=O
2-methylnaphthalene 2-naphthaldehyde
p-methylanisole p-anisaldehyde
Aldehyde synthesis: 3) reduction of acid chloride
LiAlH(O-t-Bu)3
lithium aluminum hydride tri-tert-butoxide
O
Cl
isovaleryl chloride
O
Hisovaleraldehyde
RC
O
Cl
LiAlH(O-t-Bu)3
RC
O
H
CO
Cl
LiAlH(O-t-Bu)3C
O
H
LiAlH(O-t-Bu)3
benzoyl chloride benzaldehyde
CH3CHCH2CO
Cl
CH3
CH3CHCH2CO
H
CH3
isovaleryl chloride isovaleraldehyde
Ketone synthesis: 1) oxidation of secondary alcohols
NaOCl
cyclohexanol cyclohexanone
isopropyl alcohol acetone
K2Cr2O7
H OH O
H3CC
CH3
O
CH3CHCH3
OH
Ketone synthesis: 2) Friedel-Crafts acylation
RCOCl, AlCl3 + ArH + HClAlCl3
ArCR
O
Aromatic ketones (phenones) only!
CH3CH2CH2CO
Cl+
AlCl3CH3CH2CH2C
O
butyrophenone
+AlCl3
m-nitrobenzophenone
O2N
C Cl
O
CO
O2N
+AlCl3
C Cl
O
NO2
NR
Friedel Crafts acylation does not work on deactivated rings.
Mechanism for Friedel-Crafts acylation EAS
RC
Cl
O+ AlCl3 RC=O + AlCl4
+ RC=ORDS
H
CR
O
H
CR
O
+ AlCl4 C R
O+ HCl + AlCl3
Ketone synthesis: 3) coupling of RCOCl and R2CuLi
RCOCl + R'2CuLiR
C
O
R'
Cl
O
+ (CH3CH2)2CuLi
O
Isobutyryl chloride 2-Methyl-3-pentanone
lithium diethylcuprate
CuLi
2
+ CHCH2CH2CH3
O
ClCCH2CH2CH3
O
butyrophenone
CH3CH2CH2CO
Cl+ CH3CH
CH3
2
CuLi CH3CH2CH2CCHCH3
O
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
aldehyde
1o alcohol
Ar-CH3
acid chloride
CrO3 H2O
(AcO)2O
LiAlH(O-t-Bu)3
K2Cr2O7, special cond.
or C5H5NHCrO3Cl
ketone
2o alcohol
acid chloride + ArH
acid chloride + R2CuLi
NaOCl, etc.
AlCl3
Reaksi adisi heteroatom nukleofil:
Reaksi adisi karbon nukleofil:
C
O
C
OHH+, H2O
OH
C
O
C
OH
CN
HCN
REAKSI PADA SENYAWA KARBONIL
Reaksi Oksidasi Senyawa karbonil:
Zat Pengoksidasi:
RC
H
O[O]
RC
OH
O
RC
R
O[O]
tidak bereaksi
Prinsip:
Zat pengoksidasi kuat Zat pengoksidasi lemah
1. KMnO4 1. CrO3/piridin dalam CH2Cl2, 25 C
2. HNO3 pekat3. H2CrO4 ( CrO3/Na2Cr2O7 + H2SO4 pekat)
2. Pereaksi Tollens (Ag+)3. Pereaksi Fehling (Cu2+)4. Pereaksi Benedict
Reaksi Adisi Nukleofil Senyawa karbonil:
RC
H
O
+ NH3 R CH
NH Suatu Imina tak tersubstitusi
RC
R
OR C NR'
Suatu Imina tersubstitusiR' NH2+
R
Reaksi senyawa karbonil dengan Ammonia (NH3) atau Amina menghasilkan senyawa Imina
Mekanisme reaksi (pH optimum 3-4):
H3CC
H
O
H2N CH3
..H3C C
O-
N+
H
H
CH3
-
H
H3C C
OH
N
H
CH3
H
..
..:
H+
H3C C
+OH2
N
H
CH3
H
.. H3C C N
H
CH3-H+
+ H2O
SOAL-SOAL
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,
CH2OH
K2Cr2O7
special conditions
CH3
CrO3
(CH3CO)2O
CH(OOCCH3)2
H2O
C
O
Cl
LiAlH(O-t-Bu)3
CH=O
benzaldehyde
Synthesize benzaldehyde three different ways.
CH
OH NaOCl
CO
Cl+
AlCl3
CO
Cl+ CuLi
2
C
O
Synthesize benzophenone three different ways.
cyclohexanone, 4-bromobenzaldehyde, 2-pentanone, valeraldehyde, acetophenone, isobutyraldehyde, using a different method for each one.
OBr CHO
CH3CH2CH2CCH3
OCH3CH2CH2CH2CHO
CH3C
O
CH3CHCHO
CH3
oxidation of 2o alcohol oxidation of Ar-CH3
R2CuLi + R'COCl
Friedel-Crafts acylation
oxidation of 1o alcohol
reduction of acid chloride
O
CH3CH2CH2CCH3
O
CH3C
O
OHH
K2Cr2O7
CH3 CCl
O+
AlCl3
(CH3CH2CH2)CuLi + CH3 CCl
O
Br CHO
CH3CH2CH2CH2CHO
CH3CHCHO
CH3
Br CH3
CH3CH2CH2CH2CH2-OHK2Cr2O7
special conditions
CrO3
(CH3CO)2O
H2O
CH3CHC
CH3 O
Cl
LiAlH(O-t-bu)3
The methods could be reversed for the last two syntheses.