Download CHAPTER 18 KETONES AND ALDEHYDES

CHAPTER 18
KETONES AND ALDEHYDES
PROBLEMS 1,3,4,6,7-11,12C
15,17,19,20,24,27A,C,31,33,34A,B,D,
35A,C,39A-E,45A,B,51A-D,61,65,66
CARBONYL COMPOUNDS
O
CONTAIN A C=O GROUP
IMPORTANT MEMBERS
O
R
O
H
R
ALDEHYDE
R
KETONE
CHAPTER 18
O
O
R
OH
CARBOXYLIC
ACID
CHAPTER 20
R
O
OR
ESTER
R
O
NH2
AMIDE
CHAPTER 21
R
Cl
ACID
CHLORIDE
STRUCTURE OF THE CARBONYL GROUP
DIPOLE MOMENT
E+
C
O
H
:NUC
BASE:
CHAPTER 22
NOTE: NUC ATTACK
OCCURS AT PI ORBITAL
NOT BACKSIDE OF C=O
NOMENCLATURE
IUPAC SYSTEM
KETONES: ALKANONE, MUST NUMBER TO GIVE
CARBONYL LOWEST NUMBER
1
2
3
4
5
6
O
5,5-DIMETHYL-3-HEXANONE
(5,5-DIMETHYLHEXAN-3ONE)
O
O
OH
4-HYDROXY-2-BUTANONE
BUT
O
OH
3-OXOBUTANOIC ACID
ALDEHYDES - IUPAC
ALDEHYDE CARBON IS NUMBERED “ONE”
6
4
5
2
3
1
O
3-ISOPROPYLHEXANAL
H
O
H
FORMYLCYCLPENTANE
6
4
3
2
5
1
O
O
H
3-ISOPROPYL-5-OXOHEXANAL
ALDEHYDES COMMON NAMES
STEM PLUS ALDEHYDE
R-CHO
R-CO2H
HCHO
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
Ketones common names
RADICAL SYSTEM
NAME RADICALS IN ALPHA ORDER + KETONE
O
Me
Methyl phenyl ketone
STEM CONVENTION - ALKYL METHYL KETONES
NAME STEM OF ALKYL GROUP ACCORDING tTO THE PREVIOUS SLIDE FOLLOWED BY PHENONE
ACETOPHENONE
O
Write the structure for butyrophenone
CH3CH2CH2
Ph
SPECTROSCOPY OF ALDEHYDES AND KETONES
1. IR READ PAGE 780
2. NMR Read pp 780-782
MASS SPECTRA
H3C
ALPHA CLEAVAGE
O
H3C
CH3CH2
+
O
H2
C
H3C
CH3
H2
C
O
CH3
+
CH3
O
TWO ACYLIUM IONS ARE ABOUT THE SAME
H2
C
CH3
O
THEREFORE
ETHYL RADICAL IS MORE STABLE THAN METHYL
RADICAL STABILITY CONTROLS FRAGMENTATION
McLAFFERTY REARRANGEMENT
CHARACTERISTICS
A GAMMA HYDROGEN IN THE PARENT CATION-RADICAL IS TRANSFERRED
TO CARBONYL OXYGEN ATOM INTRAMOLECULARLY
CLEAVAGE OF ALPHA-BETA CARBON (WITH RESPECT TO C=O
OCCURS
A STABLE ALKENE IS LOST AND A NEW RESONANCE STABILIZED CATION
RADICAL(ENOL) IS FORMED
NOTE- THE PARENT CATION, STABLE ALKENE LOST, AND
THE NEW STABILIZED CATION RADICAL HAVE EVEN MOLECULAR MASSES
EXAMPLE
O
a
H3C
C
H2
H2
C
b
g
CH2
OH
H
H3C
CH2
even mw
Even mw
+
CH2=CH2
g
b
Even mw
MECHANISM OF
McLAFFERTY
REARRANGEMENT
g
O
H3C
C
C
H2
H
CH2
CH2
OH
H3C
C
+
H2C
CH2
CH2
THERE IS A NICE SUMMARY ON BOTTOM OF PAGE 784. LOOK IT OVER.
REVIEW OF SYNTHESIS OF
KETONES AND ALDEHYDES
OXIDATION OF ALCOHOLS - LAST SEMESTER
OZONOLYSIS OF ALKENES - LAST SEMESTER
FRIEDEL ACEYLATION AND GATTERMAN KOCH
WILL BE COVERED ON NEXT TEST
HYDRATION OF ALKYNES - LAST SEMESTER
HYDROBORATION AND OXIDATION - LAST SEMESTER
1,3-DITHIANE METHOD
PREPARATION OF 1,3-DITHIANES
O
H
HS-CH2CH2CH2SH
H
H+
S S
HH
Dream up a mechanism for this reaction.
WHY HIGH ACIDITY OF 1,3DITHIANES?
Old explanation
S S
H H
S S
n-BuLi
S
H
RECALL
A-B has bonding mo and non-bonding mo

neg charge
A
B
Thus
C
S=C
Vacant d-orbitals
Modern explanation

C
S
C
Synthetic Methodology
1. Deprotonation of 1,3-dithiane with n-BuLi
n-BuLi
S
S
H
S
S
H
H
Li
2. Alkylation or dithane anion (SN2)
SN2
H
S
S
S
S
+ R-X
Li
H
R
R must be methyl or primary
R can not be Ar, CH2=CH
3. Hydrolysis of alkylated dithiane.
S
H
S
R
H+ / HgCl2
O
H
R
Preparation of Ketones via 1,3dithianes
INSTEAD OF STOPPING AT MONO-ALKYLATION
STEP, ONE CAN REPEAT PROCESS USING THE
REMAINING ACIDIC HYDROGEN ATOM
S
H
S
R
R'X
S
R'
S
R
O
H+
HgCl2
R'
R
UMPOLUNG OF C=O
O
H
S -S
R
electrophilic carbonyl
H
nucleophilic "masked"
carbonyl
"acyl anion equivalent"
Retrosynthetic analysis
Prepare 1-phenyl-2-pentanone
From
O
H
HSCH2CH2CH2SH
H H
S
H
S
n-BuLi
PhH2C
n-BuLi
S
H
S
PhCH2B
CH3CH2CH2Br
PhH2C
S
CH2CH2CH3
S
hydrolysis
Ph
O