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Chapter 12 Aldehydes and Ketones Nucleophilic Addition to Carbonyl Group
12.1 Nomenclature 12.2 Structure of Carbonyl Group12.3 Preparation of aldehydes and ketones12.4 Nucleophilic addition of aldehydes and ketones 12.4.1 Hydration of aldehydes and ketones 12.4.2 The addition of hydrogen cyanide 12.4.3 The addition of alcohols 12.4.4 The addition of amines
12. 5 The Addition of Ylides: the Wittig Reaction12.5.1 Ylides ( 叶立德 )and Preparation of phosphorous ylides12.5.2 Mechanism of the Wittig reaction 12.5.3 Synthesis of alkenes by Wittig reactions12.6 Oxidation of Aldehydes and ketones12.6.1 Oxidation of Aldehydes12.6.2 Baeyer-Villiger oxidation of ketones12.7 Spectroscopic analysis of aldehydes and ketones
General role:• The longest continuous chain with
carbonyl group is as a parent, suffix: e al or one. To ketones, numbered
the number of carbonyl group.
Aldehydes and KetonesO
CCarbonyl group
羰基Formaldehyde
甲醛Aldehyde
醛Ketone
酮12.1 Nomenclature
C H
OC H
O
Formyl醛基
O
CR
O
CR
Acyl 酰基
H C
O
H R C
O
H R C
O
R
C
O
Ar C
O
ArC
O
PhC
O
Ph
Aroyl芳酰基
Benzoyl芳酰基
Benzyl ethyl ketone乙基苄基甲酮
CH2CCH2CH3
O
CH2CCH2CH3
O
CH2 CHCH CH C H
O
CH3 CH3
CH2 CHCH CH C H
O
CH3 CH3
3-Methylbutanal3- 甲基丁醛
4-Methyl-3-hexanone4- 甲基 -3- 己酮
CH3CHCH2C
O
H
CH3
CH3CHCH2C
O
H
CH3
CH3CH2CCHCH2CH3
O
CH3CH3CH2CCHCH2CH3
O
CH3
2,3-Dimethyl-4-pentenal2,3- 二甲基 -4- 戊烯醛
2. When –CHO is attached to a ring, suffix is -aldehyde or -carbaldehyde ( 以甲醛为母体 )
3. Alkyl groups are as substitutes, “ketone” are as parent
CHOCHO
Benzaldehyde苯甲醛
C
O
C
OBenzophenone
二苯甲酮
O
CH3
O
CH3
P2849.3P2849.3
4-Methylcyclohexanone4- 甲基环己酮
sp2- hybridizedπbond
C O¦Ä ¦ÄC O
¦Ä ¦Ä
Dipole momentμ = 2.3 ~ 2.9D Dipole momentμ = 2.3 ~ 2.9D
Trigonal plane
C O C OC O C O
A B
Electron delocalization
Resonance structures:
CH3 C
O
CH3
Polar solvent
P283,9.2
P283,9.2
Acetaldehyde( 乙醛 )
Acetone( 丙酮 )
Polarized
C
O+
-
C
O+
- Nucleophilic
ElectrophilicH+,E+
OH-,Nu:-
Reaction sites and reactions of aldehydes and ketones
O
C R (H)C
H
Nucleophilic additionNucleophilic additionOxidation
And reductionOxidation
And reduction
Reaction of α -hydrogenReaction of α -hydrogen
C O
Nu
12.4 Nucleophilic Addition of Aldehydes and Ketones
Nu
C O H Nu +¦Ä ¦Ä
C O H
Nu
H Nu
The trigonal planar structure of C=O is relatively open to attack from above or below by Nu−.:
Nu:−
OH−, H− , R3C − ,H2O, NH3, ROH
:
sp2 sp3
Intermediate:an alkoxide ion
P2889.6
P2889.6
12.4.1 Hydration of Aldehydes and ketones
Geminal diol(同碳二醇)
Hydrate( 水合物 )
Reversible
K =[RCH(OH)2]
[RCHO] [H2O]
R C
O
H (CH3) + H2O COH
OHR
(CH3) H
K
CF3 C
O
CF3 H C
O
H CH3 C
O
H CH3 C
O
CH3 (CH3)3C C
O
C(CH3)3> > > >
Khydr22,000 41 1.8 × 10-2 4.1 × 10-3 2.5 × 10-5
Reactivity decreasesReactivity decreases
P2909.7P2909.7
Factors affecting the reactivity:1. Electronic effects of alkyl groups
CF3 C
O
CF3
CH3 C
O
CH3CH3 C
O
CH3
2. Steric effect of alkyl groups
C
O
R R CH2OOH
OHRR
C
O
R R CH2OOH
OHRR
Hybridization: sp2 sp3
The bond angle: 120° 109.5° H < CH3 < tert-Butyl
The crowding in the products is increased by the larger group
Electron-donating effect of alkylSubstituents stabilizes the carbonyl group;Electron-withdrawing effect destabilizes the carbonyl group
Mechanism of HydrationThe addition of water is subject to catalysis by both an acid and a base.
The mechanism for the base-catalyzed reaction:
A hydroxide ion attacks the carbon of the carbonyl group.
This step is rate-determining.Nucleophile:HO - > H2ONucleophile:HO - > H2O
A hydroxideion
An alkoxideion
HO + CH
H3CO C
OH
OHH3C
slowStep 1
An alkoxide ion attracts a proton from water, yielding geminal diol.
The mechanism for the acid-catalyzed reaction:Step 1
H
ROC + C O
R
H H+HH O
H
¦Ä ¦Ä H2Ofast
H
ROC + C O
R
H H+HH O
H
¦Ä ¦Ä H2Ofast
Protonation of carbonyl group:
HC O
R
HC O
R
HHH
C OR
HC O
R
HH
Step 2C
OH
OHH3C
+ H OHfast C
OH
OHH3C
H + OHC
OH
OHH3C
+ H OHfast C
OH
OHH3C
H + OH
Step 2H O
H
C OR
H H+
Slow
C
H
R
OHH
O HH O
H
C OR
H H+
Slow
C
H
R
OHH
O H
Water as a nucleophile attacks the protonated carbonyl group
The step is rate-determiningStep 3
CH
R
OHH
O H HO
O
R
H C +
H
OH H
O
H
H H
CH
R
OHH
O H HO
O
R
H C +
H
OH H
O
H
H H
Transformation of the proton
R C
O
H (CH3) + HCN CCN
OHR
(CH3) H
Characteristics of the reaction1. Base-catalyzed,reagent: KCN2. Formation of C - C bond3.- CN COOH, - NH2
C
O
CH3CH2 CH3HCN CH3CH2 C
OH
CN
CH3
95%H2SO4
¡÷CH3CH2 C
CH3
COOH
12.4.2 The addition of hydrogen cyanide ( 氢氰酸 ) - Cyanohydrin ( 氰基醇 )formation
12.4.3 The addition of alcohols Acid catalysis Aldehydes react with alcohols
to yeld hemiacetals ( 半缩醛 ) or acetals( 缩醛 )
R C
OC
OR'
OHR
HH R'OH / H+ R'OH / H+
COR'
OR'R
H+ H2OR C
OC
OR'
OHR
HH R'OH / H+ R'OH / H+
COR'
OR'R
H+ H2O
Aldehyde hemiacetal acetal
C
O
H + 2 CH3CH2OHHCl CH
OCH2CH3
OCH2CH3C
O
H + 2 CH3CH2OHHCl CH
OCH2CH3
OCH2CH3
Benzaldehyde Ethanol Benzaldehydediethyl acetal
苯甲醛缩 二乙醇 (60%)
Mechanism of the reaction:
H
ROC +¦Ä ¦Ä
C OR
HH + R'O
H
R'H O
H
CH
R
OR'H
O H HO
R'O
R
H C +
H
OH R'
R'O
H
H
O R'
CH
R
O R'
O H
H
OH2
R'O
R
H C-H2O
R'H
ROC
C OR
HR'
R' O H
C
R
O
R'
OH
H
R'HOR'
H O
R'O
R
C R' + R' OH2
The position of equilibrium is favorable for acetal formation from most aldehydes.
For most ketones, the position of equilibrium is unfavorable.
excess alcohol as solvent
Diols react with aldehydes or ketones to formcyclic acetals by removing the water:
O + HOCH2
HOCH2
对甲苯磺酸 CH2
CH2
OOO +
HOCH2
HOCH2
对甲苯磺酸 CH2
CH2
OO
COR'
OR'
R
(R")H+ H2O H C
R
(R")HO + 2 R'OH C
OR'
OR'
R
(R")H+ H2O H C
R
(R")HO + 2 R'OH
Acetal hydrolysis is favored by excess water.Acetals as protecting groupsAcetals as protecting groups
O CH2OH O C
O
OC2H5O CH2OH O C
O
OC2H5
Acetals arestable in basicsolution
Acetals arestable in basicsolution
Acetals are susceptible to hydrolysis in aqueous acid:
O C
O
OC2H5H+
HOCH2CH2OH
C
O
OC2H5OOO C
O
OC2H5H+
HOCH2CH2OH
C
O
OC2H5OO
(a) Protection of carbonyl group
(b) Reduction of the ester group1) LiAlH4 / Et2O
2) H2OCH2OHO
O1) LiAlH4 / Et2O
2) H2OCH2OHO
O(c) Unmasking of the carbonyl group
CH2OHOO
H+
H2O
O CH2OHCH2OHO
O
H+
H2O
O CH2OH
12.4.4 The addition of amines (胺)1. Reaction with primary amines: imides ( 亚胺 )
Aldehydes and ketones react with primary amines to yield imides
Step 1. Nucleophlic addition
Step 2. Elimination
NR H
H
+ C O NR
H
H
C O NR
H
HC O
Primary amine
Aldehydeor ketone
Carbinoamine (氨基甲醇)
NR CNR
H
HC O + H2O Imide(亚胺)
N-Substituted imides:Schiff’s bases ( 西佛碱 )N-Substituted imides:Schiff’s bases ( 西佛碱 )
C O + H+ C OH C OH
The reactions are accelerated by acid-catalysis
C OHNR H
H
+ NR
H
C OH-H+
NR
H
HC OH
NR
H
HC O +H+
NR
H
HC O
H
NR C + H2O
(a) Protonation of carbonyl group
(b) Nucleophile attacks carbonyl group
(c) Elimination with acid-catalysis
Carefulcontrolof pH!
Carefulcontrolof pH!
pH: 4~5pH: 4~5
O + (CH3)2CHCH2NH2
H+
NCH2CH(CH3)2O + (CH3)2CHCH2NH2
H+
NCH2CH(CH3)2
Cyclo-hexanone
Isobutylamine(异丙胺)
N-Cyclohexylide-Isobutylamine
( N- 亚环己基异丙胺) Reaction with derivatives of ammonia
C O C N YNY H
H
+ + H2O
C O H2N OH C OHN + H2O
Hydroxylamine(羟胺)
An oxime(肟)
C O H2N NH2 C NH2N + H2O
Hydrazine(肼)
A hydrazone(腙)
C O H2NNH CC6H5
HNO2
O2N NNH NO2
O2N
C6H5
H£«H2O
2,4-DinitrophenylHydrazine
( 2,4- 二硝基苯肼)2,4-dinitrophenylhydrazone ( 腙 )
The products are insoluble and have sharp characteristic melting point. The reaction are often used to identify unknown aldehydes and ketones.
O + H2NNHCNH2 + H2O
O
NNHCNH2
O
Semicarbazine(氨基脲)
Semicarbazone (缩氨基脲)(半卡巴腙)
Reactions with secondary aminesAldehydes and ketones react with secondary amine (R2NH), to form enamines (烯胺)
RCH2CR'
O
+ RCH2CR"2NH
OH
R'
NR"2
-H2O RCH CR'
NR"
Obenzene
¡÷+ H2ON
H
N
Cyclopentanone(环戊酮)
Pyrrolidine(吡咯烷)
N-(1-Cyclopentenyl)Pyrrodine
[N-(1- 环戊烯基 ) 吡咯烷 ]
12. 5 The Addition of Ylides: the Wittig Reaction
CR
R'O + (C6H5)3P C
R"R"'
CR
R'C
R"R"' + (C6H5)3P O
Solvents: THF, DMSO S
O
CH3 CH3
Dimethyl sulfoxide(二甲亚砜)
The characteristics of Wittig reaction: Regioselectivity
Aldehydes and ketones react withphosphorous ylides to yield alkenes and triphenyl phosphine oxide (三苯基氧膦)
O + Ph3P CH2CH3SCH3
O
CH2+ Ph3P O
86%
14.5.1 Ylides and the Preparation of Phosphorous Ylides
Ylides ( 叶立德 ): Molecules with two oppositely charged atoms
(C6H5)3P CR"
R(C6H5)3P C
R"
RA hybrid of the two resonance structures
Preparation of phosphorous ylides:Step1 Alkyl halides Triphenyphosphine
SN2 reaction
(C6H5)3P + CH XR"
R"'(C6H5)3P CH X
R"
R"Substrates: 1°, 2°Alkyl halides
Ch.P346( 己 )Ch.P346( 己 )
X(C6H5)3P C H
R"
R"C6H5 Li (C6H5)3P C
R"
R"+ C6H6 + LiX
Step 2 An acid-base reaction
The strong base: Alkyllithiun or phenyllithium
Br(C6H5)3P CH3 C6H5 Li (C6H5)3P CH2+ C6H6 + LiX
12.5.2 Mechanism of the Wittig reaction
CH3
CCH3
O
+ C
H
CH3
P(C6H5)3
H3C
CCH3
O
C
H
CH3
P(C6H5)3
H3C
CCH3
O
C
H
CH3
P(C6H5)3
Aldehydeor ketone
Triphenylphosphoniumyelid
Oxaphosphetane(氧膦烷)
( 内膦盐 )A betaine( 甜菜碱 )
CCH3
CH3C
H
CH3
+ O P(C6H5)3
TriphenlphosphineOxaide( 三苯基氧膦)
12.5.3 Synthesis of alkenes by Wittig reactions
C6H5CH C
CH3
CH3
CC6H5
HO + C
X
H
CH3
CH3
CC6H5
H X
H+ O C
CH3
CH3
(CH3)2CHBr + (C6H5)3P (C6H5)3P CH(CH3)2Br
RLi (C6H5)3P C(CH3)2C6H5CHO C6H5CH CH(CH3)2 + (C6H5)3P O
Georg F. K. Wittig received the Nobel Prize in Chemistryin 1979.Georg F. K. Wittig received the Nobel Prize in Chemistryin 1979.
CH P(C6H5)3+2 O CH CHO
Synthesis of β-Carotene ( β- 胡萝卜 素)
12.6 Oxidation of Aldehydes and ketones
RCH
OOxidize
RCOH
O The strong oxidizing reagents:K2Cr2O7 / H+, KMnO4 / OH-;The mild oxidizing reagent: Ag2O/OH-.
O
O CHK2Cr2O7
O
O COHH2SO4,H2O
Furfural(糠醛)
Furoic acid(糠酸) (75%)
P2879.5P2879.5
CO
HAgNO3
NH4OH
CO
OH + Ag
Tollens reagent
Georg Wittig 1/2 of the prize
University of Heidelberg Heidelberg, Federal
Republic of Germany b. 1897d. 1987
German chemist whose method of synthesizing olefins (alkenes) from carbonyl compounds is a reaction often termed the Wittig synthesis. For this achievement he shared the 1979 Nobel Prize for Chemistry.Wittig was born in Berlin and studied at Kassel and Marburg. He was professor at Freiburg 1937-44, Tubingen 1944-56, and Heidelberg 1956-67.In the Wittig reaction, which he first demonstrated 1954, a carbonyl compound (aldehyde or ketone) reacts with an organic phosphorus compound, an alkylidene-triphenylphosphorane, (C6H5)3P=CR2, where R is a hydrogen atom or an organic radical. The alkylidene group (=CR2) of the reagent reacts with the oxygen atom of the carbonyl group to form a hydrocarbon with a double bond, an olefin (alkene). In general:(C6H5)3P=CR2 + R2'CO (C6H5)3PO + R2C=CR2The reaction is widely used in organic synthesis, for example to make squalene (the synthetic precursor of cholesterol) and vitamin D3
German chemist whose method of synthesizing olefins (alkenes) from carbonyl compounds is a reaction often termed the Wittig synthesis. For this achievement he shared the 1979 Nobel Prize for Chemistry.Wittig was born in Berlin and studied at Kassel and Marburg. He was professor at Freiburg 1937-44, Tubingen 1944-56, and Heidelberg 1956-67.In the Wittig reaction, which he first demonstrated 1954, a carbonyl compound (aldehyde or ketone) reacts with an organic phosphorus compound, an alkylidene-triphenylphosphorane, (C6H5)3P=CR2, where R is a hydrogen atom or an organic radical. The alkylidene group (=CR2) of the reagent reacts with the oxygen atom of the carbonyl group to form a hydrocarbon with a double bond, an olefin (alkene). In general:(C6H5)3P=CR2 + R2'CO (C6H5)3PO + R2C=CR2The reaction is widely used in organic synthesis, for example to make squalene (the synthetic precursor of cholesterol) and vitamin D3
Bernhard Tollens(1841-1918)
Bernhard Tollens Was born in Hamburg,Germany, receivedHis Ph.D. at University of Göttingen,and thenbecame professorat the same institution.
12.6.2 Baeyer-Villiger oxidation of ketonesKetones react with peroxy acides to give esters:
C6H5 C
OCH3 + RCOOH
OCH3 C O C6H5
O+ RCOH
O
The oxygen atom is inserted between the carbonyl group and the larger of two groups attached to it.
The migratory aptitude of groups: H > phenyl > 3°alkyl > 2°alkyl > 1°alkyl > methyl
CCH3
O
+ PhCOOHO
CHCl3 OCCH3
O+ PhCOH
O
(67%)
Mechanism of the Baeyer-Villiger oxidation:
C
O
CH3
C6H5
+ O O
H
C
O
R C
O
CH3
C6H5
H
O O C
O
R(1)
(2) H+
C
O
CH3
C6H5
H
O O C
O
R
H-RC
O
OH C
O
CH3
C6H5
H
O(3a)
phenylmigration
(3b) CH3C
O
O C6H5 + H+
Adolf von Baeyer was awarded the Nobel Prize in Chemistry in 1905.
Adolf von Baeyer was awarded the Nobel Prize in Chemistry in 1905.
CCH3CH2CH3CH2
C
O
CC
O
NHNH
OCCH3CH2CH3CH2
C
O
CC
O
NHNH
OBabiturate
( 巴比妥 )
Johann Friedrich WilhelmAdolf von Baeyer
Germany Munich University b. 1835d. 1917
A great German organic chemist of histime, he received the 1905 Nobel Prize in Chemistry for his researches on organic dyes and hydroaromatic compounds. Most famous were his researches on theconstitution and synthesis of the plant pigment indigo (1883), the discovery of barbituric acid (1863) phenolphthalein and fluorescein (1871), and the "straintheory" of triple bonds and small carbon rings.Three of his students (E. Fischer, E. Büchner, R. Willstätter) received Nobel prizes.
A great German organic chemist of histime, he received the 1905 Nobel Prize in Chemistry for his researches on organic dyes and hydroaromatic compounds. Most famous were his researches on theconstitution and synthesis of the plant pigment indigo (1883), the discovery of barbituric acid (1863) phenolphthalein and fluorescein (1871), and the "straintheory" of triple bonds and small carbon rings.Three of his students (E. Fischer, E. Büchner, R. Willstätter) received Nobel prizes.
12.7 Spectroscopic analysis of aldehydes and ketonesC
O
1665 ~ 1780 cm -1 (s) Stretching vibration
HC
O
2820, 2720 cm -1 (m) Stretching vibration
(CH3)2CHCH2 C
O
CH3 O (CH3)2C CH CH3C
O O
C H
σ / cm -1 1717 1715 1690 1700
When the carbonyl groups conjugate with carbon-carbon double bond, the location of the pick shifts to the direction of lower frequency (低频)
Ch.P336( 四 )
Ch.P336( 四 )
RCHO ~1730 cm-1 RCOR 1705 ~1720 cm-1
ArCHO 1695 ~1715 cm-1 ArCOR 1680 ~1700 cm-1
C C CHO 1680~1690 cm-1 C C COR 1665~1690cm-1
The characteristic absorption of aldehydic proton:
HC
O 1H NMR, δ: 9 ~ 10 ppm
1H NMR spectrum of acetaldehyde
13C NMR :
200 180 160 140 120 100 80 60 40 20 0
CH3CH2CCH2CH2CH2CH3
O
C
O
CH2
CH2
CH2
CH2 CH3
CH3
Chemical shift (δ, ppm)
190-220 ppm
The signal for the carbon of C=O in aldehydes And ketones appears at verylow field:
Problems to Chapter 12P3039.21(b),(e),(f),(g),(h)9.25(b),(c),(e)9.29(b)~(d)9.32(a),(b)9.34((b),(d)9.36(c)9.38(b)9.39(c)9.40(b)
P3039.21(b),(e),(f),(g),(h)9.25(b),(c),(e)9.29(b)~(d)9.32(a),(b)9.34((b),(d)9.36(c)9.38(b)9.39(c)9.40(b)
9.41(b),(c)9.449.459.48*9.499.509.51
9.41(b),(c)9.449.459.48*9.499.509.51
Ch.P363( 十四 )( 十五 )( 十六 )(B)
Ch.P363( 十四 )( 十五 )( 十六 )(B)