ALDEHYDES AND KETONES
May 11, 2015
ALDEHYDES AND KETONES
Ald h d STRUCTUREAldehyde
O
STRUCTURE
CR H
R = H, alkyl, aryl
Ketone
R H
O
R d R' lk l lC
R R'
R and R' = alkyl or arylR and R' cannot be hydrogen!
NOMENCLATURENOMENCLATURE
IUPAC Nomenclature of KetonesIUPAC Nomenclature of Ketones
Ch th l t ti b h i th t
IUPAC Nomenclature of KetonesIUPAC Nomenclature of Ketones
• Choose the longest continuous carbon chain that contains the carbonyl carbon
• Number from the end of the chain closest to the carbonyl carbon
• Ketone ending is -one
Do the ketones section of Organic Nomenclaturegprogram!
OEXAMPLES
C CH
O
CH 3
CCH 2
CH 2CH 3
2-Pentanone O
CCH2 CH
CH3 CH2CH3
CH2CH3CH3
4-Ethyl-3-hexanone
OO
CH CH3CH
CH3
3-Isopropylcyclopentanone
Common or Trivial NamesCommon or Trivial NamesKETONESKETONES
Common, or Trivial, NamesCommon, or Trivial, Names
• Name each group attached to the carbonyl group as an alkyl group
• Combine into a name, according to the pattern:
lk l lk l’ k talkyl alkyl’ ketone
NOTE This is not all one word!NOTE: This is not all one word!
Example of Common NamesExample of Common NamesO
CH 3
CCH 2
CH 2CH 3CH 3 CH 2 CH 3
Methyl propyl ketone OMethyl propyl ketone O
CCH3 CH3CCH2 CH2
CH3 CH3
Diethyl ketone
OSPECIAL CASESSPECIAL CASES
O
C CO
CCH3 CH3
di th l k t
C
diphenyl ketone
acetone
dimethyl ketonebenzophenone
diphenyl ketone
A common laboratorysolvent and cleaningagent C
OCH3g 3
methyl phenyl ketoneKNOW
acetophenoneKNOWTHESE
IUPAC Nomenclature of AldehydesIUPAC Nomenclature of Aldehydes
• Choose the longest continuous carbon chain that t i th b l bcontains the carbonyl carbon
• Number from the end of the chain closest to the • Number from the end of the chain closest to the carbonyl carbon (carbon #1!)
• Aldehyde ending is -al
Do the aldehydes section of Organic Nomenclatureprogram.
EXAMPLESEXAMPLES
CH CH Oaldehyde group is
CH3
CH2CH2
CH2C
O
H
always carbon 1
Hpentanal
CH CHCl
13CH3CH
CHC
O
HCH
1
2
3
4
HCH3
2-chloro-3-methylbutanal2 chloro 3 methylbutanal
Common Names of the AldehydesCommon Names of the AldehydesO
CH H
O
CCH H
O
CCH HCHH H CH3 H CH2 HCH3
O
Formaldehyde Acetaldehyde Propionaldehyde1 2 3
O
CC HCH2CH3
O
CC HCHCHCHC HCH2CH3 C HCH2CH2CH3
O
Butyraldehyde Valeraldehyde4 5
O
CCH2 HCH2CH2CH2CH3 RECOGNIZE22223
Caproaldehyde6
RECOGNIZETHESE
OSPECIAL CASESSPECIAL CASES
O
CCH H
CO
Hformaldehyde
O
C Hformaldehyde
CH CH
benzaldehyde
H CH3
acetaldehydeKNOWTHESEacetaldehyde
Forming Common Names of AldehydesForming Common Names of Aldehydes
OUSE OF GREEK LETTERS
C ω ε δ γ β α −−
C C C C C C H……. γ β
ω is always the end of the chain, no matter how long
CHO CHO
Cl
α-chlorocaproaldehyde
Cl
ω-chlorocaproaldehydeα chlorocaproaldehyde
( α-chlorohexanal )
ω chlorocaproaldehyde
( ω-chlorohexanal )
REACTIVITY OF THE C=O GROUPREACTIVITY OF THE C=O GROUP
NUCLEOPHILIC ADDITION
THE CARBONYL GROUPTHE CARBONYL GROUPGENERALIZED CHEMISTRY
THE CARBONYL GROUPTHE CARBONYL GROUP
nucleophilict at oxygen
H+ or E+electrophiles add here
O..
:δ+
δ-
O..
::-
C δ+
C+
electrophilic Nu:
nucleophiles attack here
electrophilic at carbon
NUCLEOPHILIC ADDITION TO C=ONUCLEOPHILIC ADDITION TO C=O
MECHANISMS
IN ACID AND IN BASEIN ACID AND IN BASE
Nucleophilic Addition to CarbonylNucleophilic Addition to CarbonylBasic or Neutral SolutionBasic or Neutral Solution
: :..
:_
OO..
Basic or Neutral SolutionBasic or Neutral Solution
an+ :Nu
slow:O
CC
Nu
analkoxideion
-
Nu
:..
:O :..O H
fast
_
C
Nu
+ H2O C
Nu
fast
or on adding acid
BASIC SOLUTIONGood nucleophiles
d t b BASIC SOLUTIONand strong bases(usually charged)
Nucleophilic Addition to Carbonyl Nucleophilic Addition to Carbonyl Acid CatalyzedAcid Catalyzed
O H:O fast
+:..
Acid CatalyzedAcid Catalyzedmore reactive toaddition than the un-
CC+ H+ fast
protonated precursor
slow:
..
O HO H+..
+ :NuCC
Nu (+)
Acid catalysis speeds the rate of addition of
k l hil d
ACIDIC SOLUTIONweak nucleophiles andweak bases (usually uncharged). pH 5-6
stronger acidprotonates thenucleophile
CYANOHYDRINSCYANOHYDRINS
Addition of CyanideAddition of Cyanide :C N:
O O: : : :.. _
yyBuffered to pH 6-8
+ CN_
R C R R C R
CN
O O H: : :.. _ ..
R C R
CN
+ R C R
CN
OH2
a cyanohydrin
A cyanohydrinIn acid solution there would be little CN-, and HCN (g) would be a problem (poison).
CYANIDE ION BONDS TO HEMOGLOBINCYANIDE ION BONDS TO HEMOGLOBIN
CN..
Cyanide bonds (irreversibly) to the
CYANIDE ISIS A POISON
CH3
C (irreversibly) to thesite (Fe II) whereoxygen usually bonds.
..
N NCH3
Y di fN
N
N
NCH3 CH3
FeYou die ofsuffocation -lack of oxygen.
CH3
CH CH COOH CH2CH2COOH
CH3
CH2CH2COOH 2 2
HCN is a gas that you can easily breathe into your lungs.
ORGANOMETALLICSORGANOMETALLICS
Addition of Organometallic ReagentsAddition of Organometallic ReagentsSynthesis of Alcohols
M_ +..
Addition of Organometallic ReagentsAddition of Organometallic Reagents
+
M
R M
O
C R C R
O: : : :ether
(R-MgBr)
H O
R RR
(R-Li)k
:R - H2OH +
O H:..These reagents cannot
exist in acid solution
workupstep
R C R
O H
+ M(OH)x
:exist in acid solution
l h lR
alcohol
Summary of Reactions of Summary of Reactions of Organometallics with Organometallics with Carbonyl CompoundsCarbonyl CompoundsCarbonyl CompoundsCarbonyl Compounds
All reviewt • Organometallics with ketones yield
tertiary alcohols• Organometallics with aldehydes yield
to you
• Organometallics with aldehydes yield secondary alcohols
• Organometallics with formaldehyde yieldOrganometallics with formaldehyde yieldprimary alcohols.
• Organometallics with carbon dioxide yieldcarboxylic acids.
etc.
HYDRATESHYDRATESHYDRATESHYDRATES
Addition of WaterAddition of Water
O O HH+
+ H2OCR R'
R C R'H
O H
a hydratealdehyde or ketonefavored
hydrates are unstableand cannot be isolatedin most cases
most hydrates revert to an aldehyde or ketone as soon as they formor ketone as soon as they form
+ H2O
O
CR C R'
O H
CR R'O H
ACID CATALYSISACID CATALYSIS
H+
ACID CATALYSISACID CATALYSIS
RECALL
O HO
OH
H..
: :+
+..
O H..OO: : O H
+
:
NAcid catalysis enhances the reactivity
:NuAcid catalysis enhances the reactivityof the carbonyl group - nucleophilicaddition proceeds more easily. weak nucleophiles
can react
Water is a weak nucleophile.
WATER ADDS TO THE CARBONYL GROUP OF WATER ADDS TO THE CARBONYL GROUP OF ALDEHYDES AND KETONES TO FORM HYDRATESALDEHYDES AND KETONES TO FORM HYDRATES
OH
HH
+
ALDEHYDES AND KETONES TO FORM HYDRATESALDEHYDES AND KETONES TO FORM HYDRATES
catalyzed by atrace of acid
O H
CO HO
CO HH.. .. .. ..
: : : :+
O HH
OHH
OH
H
....
....
.. :+ a hydrate
H O HH O
HH
H....
..
..+
for most compounds the equilibriumfavors the starting materials In a reaction where all steps are
MICROREVERSIBILITY:g
and you cannot isolate the hydratep
reversible, the steps in the reversereaction are the same as those inthe forward reaction, reversed!
ISOTOPE EXCHANGE REVEALS THE PRESENCE ISOTOPE EXCHANGE REVEALS THE PRESENCE OF THE HYDRATEOF THE HYDRATE
f H O18O O
OF THE HYDRATEOF THE HYDRATE
18 an excess of H2O18
shifts the equilibriumto the right
O
R ROH2
O
R R18
18
+ H+
excess
O H
R CO
RO
H
18
+H2O18 -H2O
OH
18exchange shows the presence of a symmetricintermediateintermediate
SOME STABLE HYDRATESSOME STABLE HYDRATESthese also indicate that hydrates are possible
Cl OHOClδ−
y p
CCl
Cl HOHC
HCl
Clδ+δ−
chloral chloral hydrateδ−
OHO
120o expected60o required
109o expected
OHO
l l
109 expected60o required
sp2 sp3
cyclopropanone cyclopropanonehydrate
SOME ADDITIONAL STABLE HYDRATESSOME ADDITIONAL STABLE HYDRATESSOME ADDITIONAL STABLE HYDRATESSOME ADDITIONAL STABLE HYDRATES
C CH
O
OH
OHC C
O
HH
O
HH
O O
glyoxal
C CO
HPh
O
C CPh
O
HOH
OH
H Hphenylglyoxal
ACETALS ANDACETALS ANDHEMIACETALSHEMIACETALSHEMIACETALSHEMIACETALS
ACID CATALYSISACID CATALYSIS
H+
ACID CATALYSISACID CATALYSIS
RECALL
O HO
OH
H..
: :+
+..
O H..OO: : O H
+
:
NAcid catalysis enhances the reactivity
:NuAcid catalysis enhances the reactivityof the carbonyl group - nucleophilicaddition proceeds more easily. weak nucleophiles
can react
Alcohols are weak nucleophiles.
Addition of AlcoholsAddition of AlcoholsTWO MOLES OF ALCOHOL WILL ADD
O O Haddition of one mole
TWO MOLES OF ALCOHOL WILL ADD
R C R'
OROH R C
OR'
O
H
R+ hemiketal
H+
O R
O H O Raddition of second mole
R CO
R'H
ROH R CO
R'R
+ H O+H+
O R O R H
an aketal
The equilibria normally favor the aldehyde or ketone startingmaterial, but we will show how they can be made.
ACETALS AND HEMIACETALSACETALS AND HEMIACETALS
C OR
CR OH
CR ORROH ROH
C OH
CH OR
CH ORaldehyde
hemiacetal acetal
CR OR
CR OH
C OR
ROH ROHC
R ORC
R ORC O
R ketone
(k t l)*(h ik t l)* (ketal)*(hemiketal)**older term *older term
R OH H 2SO4 R O HH
+ +..
Like a hydronium
H OR
H.. ..+
+
H yion
CO
R R
H
CO
R R
H
CO
R R
H.. .. ..: : :
+
OH R
RHO..
.. ....
+
ACID CATALYZEDACID CATALYZED ORH:ACID CATALYZEDACID CATALYZED
FORMATION OF AFORMATION OF AHEMIACETALHEMIACETAL
firstaddition
CO
R R
H..:
R OH
++
Normally the startingmaterial is favored -but a second molecule
hemiacetal RO..:
..R OHof alcohol can react
if in excess (next slide)
FORMATION OF THE ACETAL ( FORMATION OF THE ACETAL ( from the hemiacetal ))
remove
H OR
H HO HH ....+
second
remove
HO
R
H
CO H
CO HH
CR R
O
:..
....:..
CR R+
second addition
CR R
RO
CR R
RO
CR R
RO.. ::: ..
CR R
RO:+
+SN1
O RHR ...... :
Resonancestabilizedcarbocation
hemiacetal
ORH C
O
R R
RH
CO
R R
R
OR
H.... ::
:+ +
acetal RO
ROH .... ::
STABILITY OF ACETALS AND HEMIACETALSSTABILITY OF ACETALS AND HEMIACETALS
Most hemiacetals are not stable, except for those of sugars(see later)(see later).
Acetals are not stable in aqueous acid, but they are stable to aqueous baseaqueous base.
COR ROH
AQUEOUS H2SO4COR
C OROH
AQUEOUSACID
2 4
H2O+
COR
OR
AQUEOUSBASE no reaction
H2O
NaOH
OR
ADDITION OF WATER AND ALCOHOLSADDITION OF WATER AND ALCOHOLS
H2O
hydrate
WATER
CO OH OH
y
R O H R O H
ALCOHOLS
R-O-H
H2O
R-O-H
CO OH OR RO OR
hemiacetal acetal
RO OR OROH+2
H2OH+ acetals are
stable to basebut not to
no reactionNaOH
H2Obut not toaqueous acid
REAKSI OKSIDASIREAKSI OKSIDASI
OKSIDASI ALDEHID DAN KETON
• Keton tidak mudah dioksidasi• Aldehid sangat mudah dioksidasi menjadiAldehid sangat mudah dioksidasi, menjadi
asam karboksilat
Zat pengoksidasi : KMnO4, H, H2O
Reaksi ReduksiReaksi Reduksi
Reaksi Reduksi
• Reduksi aldehid menghasilkan alkohol primer• Reduksi keton menghasilkan alkohol sekunderReduksi keton menghasilkan alkohol sekunder• Zat pereduksi:
H2 k liH2, katalis Zn/Hg, HCl
Reaksi Adisi-eliminasiReaksi Adisi-eliminasi
Reaksi Adisi-eliminasi
• Aldehid + Amina Primer Imina• Aldehid + Amina sekunder EnaminaAldehid + Amina sekunder Enamina• Aldehid + Amina tersier hidrazon
Ramalkan produk hemiasetal atauRamalkan produk hemiasetal atau hemiasetal siklik dari:
1 5-hidroksi-2-heksanon dengan air1. 5 hidroksi 2 heksanon dengan air2. 1,3,4,5,6-pentahidroksi-2-heksanon
dengan airdengan air3. propanal dengan metanol4. Aseton dengan 1,2,3-propanatriol
Ramalkan apa produk reaksi sikloheksanonRamalkan apa produk reaksi sikloheksanon dengan :
1. CH3NH22. (CH3)2NH