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General
Organic ChemistryTwo credits
Second Semester 2009
King Saud bin Abdulaziz University for Health Science
Reference Book: Organic Chemistry: A Brief Course, by Robert C. Atkins and Francis A. CareyThird Edition
Instructor: Rabih O. Al-Kaysi, PhD.
IUPAC Nomenclature of AldehydesIUPAC Nomenclature of Aldehydes HH
OO OO
HH
OO HCCHCHHCCHCH
OOBase the name on the Base the name on the chain that contains chain that contains the carbonyl group the carbonyl group and replace the and replace the -e-e ending of the ending of the hydrocarbon by hydrocarbon by -al-al..
4,4-dimethylpent4,4-dimethylpentananalal 5-hex5-hexenenalal
IUPAC Nomenclature of AldehydesIUPAC Nomenclature of Aldehydes HH
OO OO
HH
OO HCCHCHHCCHCH
OO
2-phenylprop2-phenylpropaneanedialdial(keep the (keep the -e -e endingendingbefore before -dial-dial))
when named as when named as a substituenta substituent
formyl groupformyl group carbaldehyde orcarbaldehyde orcarboxaldehydecarboxaldehyde
when named when named as a suffixas a suffix
CC HH
OO
IUPAC Nomenclature of Aldehydes IUPAC Nomenclature of Aldehydes
CHCH33CHCH22CCHCCH22CHCH22CHCH33
OO
CHCH33CHCHCHCH22CCHCCH33
OO
CHCH33 HH33CC OO
Base the name on the chain Base the name on the chain that contains the carbonyl that contains the carbonyl group and replace group and replace -e-e by by -one-one. . Number the chain in the Number the chain in the direction that gives the lowest direction that gives the lowest number to the carbonyl number to the carbonyl carbon.carbon.
Substitutive IUPAC Nomenclature of KetonesSubstitutive IUPAC Nomenclature of Ketones
Substitutive IUPAC Nomenclature of KetonesSubstitutive IUPAC Nomenclature of Ketones
CHCH33CHCH22CCHCCH22CHCH22CHCH33
OO
CHCH33CHCHCHCH22CCHCCH33
OO
CHCH33 HH33CC OO
3-3-hexanhexanoneone
4-methyl4-methyl-2--2-pentanpentanoneone
4-methylcyclohexan4-methylcyclohexanoneone
Functional Class IUPAC Nomenclature of KetonesFunctional Class IUPAC Nomenclature of Ketones
CHCH33CHCH22CCCHCH22CHCH22CHCH33
OO OO
CHCH22CCCHCH22CHCH33
CHCH CHCH22
OO
HH22CC CHCCHC
List the groups List the groups attached to the attached to the carbonyl separately in carbonyl separately in alphabetical order, and alphabetical order, and add the word add the word ketoneketone..
CHCH33CHCH22CCCHCH22CHCH22CHCH33
OO
ethylethyl propylpropyl ketone ketone benzylbenzyl ethylethyl ketone ketone
divinyl ketonedivinyl ketone
OO
CHCH22CCCHCH22CHCH33
CHCH CHCH22
OO
HH22CC CHCCHC
Functional Class IUPAC Nomenclature of KetonesFunctional Class IUPAC Nomenclature of Ketones
planarplanar
bond angles: close to 120°bond angles: close to 120°
C=O bond distance: 122 pmC=O bond distance: 122 pm
Structure of FormaldehydeStructure of Formaldehyde
1-butene1-butene propanalpropanal
The Carbonyl GroupThe Carbonyl Group OO
dipole moment = 0.3Ddipole moment = 0.3D dipole moment = 2.5Ddipole moment = 2.5D
very polar double bondvery polar double bond
nucleophiles attack carbon; nucleophiles attack carbon; electrophiles attack oxygenelectrophiles attack oxygen
Resonance Description ofResonance Description ofCarbonyl GroupCarbonyl Group
CC
OO •••• ••••
CC
OO
++
––•••••••• ••••
Carbon and oxygen are Carbon and oxygen are spsp22 hybridized hybridized
Bonding in FormaldehydeBonding in Formaldehyde
The half-filledThe half-filledpp orbitals on orbitals oncarbon andcarbon andoxygen oxygen overlapoverlapto form a to form a bondbond
Bonding in FormaldehydeBonding in Formaldehyde
boiling pointboiling point
––6°C6°C
49°C49°C
97°C97°C
Aldehydes and ketones have higher boilingAldehydes and ketones have higher boilingthan alkenes, but lower boiling points than alcohols.than alkenes, but lower boiling points than alcohols.
More polar than More polar than alkenes, but cannot alkenes, but cannot form intermolecular form intermolecular hydrogen bonds to hydrogen bonds to other carbonyl groupsother carbonyl groups
OO
OHOH
2-heptanone2-heptanone(component of alarm pheromone of bees)(component of alarm pheromone of bees)
OO
Many aldehydes and ketones occur naturallyMany aldehydes and ketones occur naturally
transtrans-2-hexenal -2-hexenal (alarm pheromone of myrmicine ant)(alarm pheromone of myrmicine ant)
Many aldehydes and ketones occur naturallyMany aldehydes and ketones occur naturally
OO
HH
citral (from lemon grass oil)citral (from lemon grass oil)
Many aldehydes and ketones occur naturallyMany aldehydes and ketones occur naturally OO
HH
from alkenesfrom alkenes
ozonolysisozonolysis
from alkynesfrom alkynes
hydration (via enol)hydration (via enol)
from arenesfrom arenes
Friedel-Crafts Friedel-Crafts acylationacylation
from alcoholsfrom alcohols
oxidationoxidation
Synthesis of Aldehydes and KetonesSynthesis of Aldehydes and Ketones
A number of A number of reactions alreadyreactions alreadystudied providestudied provide
efficient syntheticefficient syntheticroutes to routes to
aldehydes and aldehydes and ketones.ketones.
CC
OO
RR OHOH
aldehydes from carboxylic acidsaldehydes from carboxylic acids
RCHRCH22OHOH
1. LiAlH1. LiAlH44
2. H2. H22OOPDC, CHPDC, CH22ClCl22
HHCC
OO
RR
What about..?What about..?
benzaldehyde from benzoic benzaldehyde from benzoic acidacid
COHCOH
OO CHCH
OO
1. LiAlH1. LiAlH44
2. H2. H22OOPDCPDCCHCH22ClCl22
CHCH22OHOH
(81%)(81%) (83%)(83%)
ExampleExample
CC
OO
RR HH
ketones from aldehydesketones from aldehydes
R'R'CC
OO
RR
PDC, CHPDC, CH22ClCl221. 1. R'MgXR'MgX
2. H2. H33OO++
RCHRCHR'R'
OHOH
What about..?What about..?
CC
OO
CHCH33CHCH22 HH
3-heptanone from propanal3-heptanone from propanal
HH22CrOCrO44
1. 1. CHCH33(CH(CH22))33MgXMgX
2. H2. H33OO++
CHCH33CHCH22CHCH(CH(CH22))3 3 CHCH33
OHOH
OO
CHCH33CHCH22CC(CH(CH22))3 3 CHCH33
(57%)(57%)
ExampleExample
Reactions of Aldehydes and Reactions of Aldehydes and
Ketones:Ketones:
A Review and a PreviewA Review and a Preview
Already covered in earlier chapters:Already covered in earlier chapters:
reduction of C=O to CHreduction of C=O to CH22
Clemmensen reductionClemmensen reduction
Wolff-Kishner reductionWolff-Kishner reduction
reduction of C=O to CHOHreduction of C=O to CHOH
addition of Grignard and organolithiumaddition of Grignard and organolithium
reagentsreagents
Reactions of Aldehydes and KetonesReactions of Aldehydes and Ketones
Principles of Nucleophilic Principles of Nucleophilic
Addition to Carbonyl Groups:Addition to Carbonyl Groups:
Hydration of Aldehydes and Hydration of Aldehydes and
KetonesKetones
HH22OO
Hydration of Aldehydes and KetonesHydration of Aldehydes and Ketones
CC••••OO ••••
HOHO CC OO HH••••
••••
••••
••••
compared to Hcompared to H
electronic: electronic: alkyl groups stabilize alkyl groups stabilize reactantsreactants
steric: steric: alkyl groups crowdalkyl groups crowdproductproduct
OHOH
OHOH
RR R'R'++ HH22OO CCCCRR R'R'
OO
Substituent Effects on Hydration EquilibriaSubstituent Effects on Hydration Equilibria
C=OC=O hydratehydrate KK %%RelativeRelative
raterate
CHCH22=O=O CHCH22(OH)(OH)22 23002300 >99.9>99.9 22002200
CHCH33CH=OCH=O CHCH33CH(OH)CH(OH)22 1.01.0 5050 1.01.0
(CH(CH33))33CCH=OCCH=O (CH(CH33))33CCH(OH)CCH(OH)22 0.20.2 1717 0.090.09
(CH(CH33))22C=OC=O (CH(CH33))22C(OH)C(OH)22 0.00140.0014 0.140.14 0.00180.0018
Equilibrium Constants and Relative RatesEquilibrium Constants and Relative Ratesof Hydrationof Hydration
when carbonyl group is when carbonyl group is destabilizeddestabilized
alkyl groups alkyl groups stabilizestabilize C=O C=O
electron-withdrawing groups electron-withdrawing groups destabilizedestabilize C=O C=O
When does equilibrium favor hydrate?When does equilibrium favor hydrate?
OHOH
OHOH
RR RR++ HH22OO CCCCRR RR
OO
Substituent Effects on Hydration EquilibriaSubstituent Effects on Hydration Equilibria
RR = CH = CH33: : KK = 0.000025 = 0.000025
RR = CF = CF33: : KK = 22,000 = 22,000
Mechanism of Hydration (base)Mechanism of Hydration (base)
CC••••OO •••••••• OO ••••
HH
••••
––
Step 1:Step 1:Step 1:Step 1:
++
••••
HOHO CC OO••••
••••
••••••••––
Mechanism of Hydration (base)Mechanism of Hydration (base)
Step 2:Step 2:Step 2:Step 2:
••••OOHH
HH
••••
••••HOHO CC OO
••••
••••
••••••••––
++••••
••••OO
HH
••••––••••
HOHO CC OOHH••••
••••
••••
Mechanism of Hydration (acid)Mechanism of Hydration (acid)
CC••••OO ••••
Step 1:Step 1:Step 1:Step 1:
++ ••••
HH
OOHH
HH++
++
CC
••••OOHH++
•••• ••••
HH
OO
HH
Mechanism of Hydration (acid)Mechanism of Hydration (acid)
Step 2:Step 2:Step 2:Step 2:
CC••••OOHH++
++••••
HH
OO
HH
••••CC OOHH
••••
••••
HH
OO
HH
•••• ++
Mechanism of Hydration (acid)Mechanism of Hydration (acid)
Step 3:Step 3:Step 3:Step 3:
++••••
HH
OO
HH
••••CC OOHH
••••
HHOO
HH
••••
•••• •••• OO
HH
••••CC OOHH
••••
••••
++
HH
HHOO
HH ••••
++
Cyanohydrin FormationCyanohydrin Formation
––OONN CC CC••••
•••• ••••••••
HH HH
HH
++OO ••••
HH
HH
OO ••••••••OONN CC CC••••
•••••••• HH
2,4-Dichlorobenzaldehyde2,4-Dichlorobenzaldehydecyanohydrin (100%)cyanohydrin (100%)
ExampleExample
ClCl ClCl CHCH
OOClCl
ClCl CHCNCHCN
OHOHNaCN, waterNaCN, water
then Hthen H22SOSO44