Organic Chemistry

ORGANIC CHEMISTRY

Chapter 16

16.9 The Addition of Hydrogen Cyanide

Department of Chemistry, Xiamen University

ORGANIC CHEMISTRY

Chapter 16

R C O + HCN

CH3 (H)

CH3 (H)

OH

R CH3

C CN

R

H 2O +

H or OH

−

R

OH

OH

OH C

Cyanohydrin CN α−羟基腈

H2 O

C

CH3 CO2H α−Hydroxy acid α−羟基酸

R CH2 C CO2H α,β−Unsaturated acid α,β−不饱和酸


ORGANIC CHEMISTRY

Chapter 16

16.10 The Addition of Ylides: The Wittig Reaction


ORGANIC CHEMISTRY

Chapter 16

O

CH2 + CH2

P(C6H5)3

Phosphorus ylide 叶立德 Wittig reaction

CH3I + (C6H5)3P CH2

P(C6H5)3

CH3 P(C6H5)3

BuLi

CH2 P(C6H5)3

Phosphorus ylide 叶立德

(Wittig reagent)


ORGANIC CHEMISTRY

Chapter 16

Mechanism

O C + R2C

P(C6H5)3

O

P(C6H5)3

C

C

R R

THF

O

P(C6H5)3

C

C

R R

R C

+ O P(C6H5)3

C R


ORGANIC CHEMISTRY

Chapter 16

16.11 The Addition of Organometallic Reagents: The Reformatsky Reaction


ORGANIC CHEMISTRY

Chapter 16

O (CH3)2CH C CH(CH3)2 + CH3CH2MgBr

(1) Et2O (2) H3O

+

OH (CH3)2CH C CH(CH3)2

80%

CH2CH3

If a chiral atom attached to the carbonyl group, the stereoselectivity of nucleophilic addition follows the Cram’s rule. CH3CH2 CH3 C H

O C R Department of Chemistry, Xiamen University

ORGANIC CHEMISTRY

Chapter 16

Cram’s rule M

O

S

S

O

M

Nu RL

RL

O

O

M

L

M

L

Nu R

S

S

R


ORGANIC CHEMISTRY

Chapter 16

Ph H

H

Et C

H CH3

O

Et (1) CH3MgX (2) H3O+

O

HPh

Et

Ph OH

H H Et HO H H

Ph CH3 Ph

H

Et

HO

H

major

CH3 Ph H

Et

H

OH minor CH3 Department of Chemistry, Xiamen University

ORGANIC CHEMISTRY

Chapter 16

Reformasky Reaction Zn C O + Br C CO2R benzene

BrZnO C

C CO2R

α−Bromo ester

H3O+

OH C C CO2R

OH C C CO2R

β−Hydroxy ester

(1) OH, H2O +

(2) H

OH C C CO2H


ORGANIC CHEMISTRY

Chapter 16

16.12 Oxidation of Aldehydes and Ketones


ORGANIC CHEMISTRY

Chapter 16

Aldehydes are much more easily oxidized than ketones.

RCHO

[O]

RCO2H

Oxidizing agents：KMnO4, K2Cr2O7 , H2Cr2O7 , H2CrO4, Ag2O , H2O2, Br2-H2O Ketone are more resistant to oxidation.


ORGANIC CHEMISTRY

Chapter 16

16.12A The Baeyer-Villiger Oxidation of Aldehydes and Ketones O CH3 C C6H5

CH3CO3H

O CH3 C OC6H5

O R'' C O O + H+ R''CO3H O OH O O C R'' OH O + H R C R' O R C R' R C R' O O C R'' OH OH OH O + －H R C R' R C R C OR' R C OR' O

OR' Department of Chemistry, Xiamen University

ORGANIC CHEMISTRY

Chapter 16

Which group migrates? Migratory aptitude of groups: H > phenyl > 3ºalkyl > 2ºalkyl > 1ºalkyl > methyl

H > 3ºalkyl > 2ºalkyl ~ aryl > 1ºalkyl > methyl ——M. B. Smith, J. March; Advanced Organic Chemistry; 5th ed., John Wiley & Sons, Inc, 2001; pp1417~1418


ORGANIC CHEMISTRY

Chapter 16

O

O R

R

O

CF3CO3H

O

+ O R=

Yield (%)

Yield (%)

CH3

90

0

CH3CH2

87

6

(CH3)2CH

33

63

(CH3)3C

2

77

——Clayden, Greeves, Warren, and Wothers; Organic Chemistry; Oxford University Press; 2001; p993. Department of Chemistry, Xiamen University

R

ORGANIC CHEMISTRY

Chapter 16

CH3CO3H O

O O

O RCO3H

H

C 6 H5

CH3

O C C CH3

O

O

H

PhCO3H C6H5

O C O C CH3

CH3 Department of Chemistry, Xiamen University

ORGANIC CHEMISTRY

Chapter 16

16.12B Cannizarro reaction CHO

33%NaOH

CO2 +

CH2OH

Mechanism O PhCH

OH

O Ph C H

O PhCH

O

O

Ph C OH + PhCH2

OH O Ph C O

+ PhCH2OH Department of Chemistry, Xiamen University

ORGANIC CHEMISTRY

Chapter 16

Crossed cannizarro reaction CHO + CH2O

(CH3)3CCHO + CH2O

OH

OH

CH2OH + HCO2 (CH3)3CCH2OH + HCO2


ORGANIC CHEMISTRY

Chapter 16

16.13 Reduction of Aldehydes and Ketones


ORGANIC CHEMISTRY

Chapter 16

16.13A Catalytic Hydrogenation RCHO + H2 R2CO + H2

Pt or Pd, Ni 0.3 MPa, 25℃ Pt or Pd, Ni 0.3 MPa, 25℃

RCH2OH R2CH2OH

The stereoselectivity of reduction follows the Cram’s rule. CH3

CH3 N

H2 O

Ni

N H OH Department of Chemistry, Xiamen University

ORGANIC CHEMISTRY

Chapter 16

16.13B Reduction by Hydride Agents LiAlH4 4 CH3CH CHCH2CH2CHO + LiAlH4 (CH3CH CHCH2CH2CH2O)4AlLi 4 CH3CH CHCH2CH2CH2OH

Et2O H2O

+ Al(OH)3 + LiOH

Stereoselectivity: Cram’s rule Et O (1) LiAlH4 H C C (2) H2O Ph CH3

H Et OH H + C C C C Ph CH3 Ph CH3 75% 25%

Et H

OH H


ORGANIC CHEMISTRY

Chapter 16

O

t-Bu

[H] H

OH H

t-Bu

OH

t-Bu

[H] LiAlH4

10 ~ 20%

LiAlH(s-BuO)3 93%

86 ~ 90% 7% Department of Chemistry, Xiamen University

ORGANIC CHEMISTRY

Chapter 16

NaBH4 CH3

O

CH3

CO2CH3 (1) NaBH4 /MeOH (2) H3O+

Br

HO

Br

BH3 CH O

C O + BH3 O BH3 THF,0℃

H

OBH2 BH3

CO2CH3

3B

H2 O

H2O2

CH OH

H

OH OH

NaOH Department of Chemistry, Xiamen University

ORGANIC CHEMISTRY

Chapter 16

16.13C Reduction by Metals O

M

R C H(R)

HA

OH R CH H(R)

M = Na, Al, Mg, Al-Hg, Mg-Hg...... HA = acids, bases, ROH, H2O.... If the reaction was carried out in aprotic solvents, a bimolecular reduction product obtained.

O 2 R C H(R)

M Benzene

H2O

OH OH R C

C

R

H(R) H(R) Department of Chemistry, Xiamen University

ORGANIC CHEMISTRY

Chapter 16

Mechanism C O +M e e M HA C O H

C O C O

C O

C O C O

HA

H

C OH H

C O C O

H2O

C OH C OH


ORGANIC CHEMISTRY

2 CH3

H2SO4

∆

Chapter 16

O

Mg-Hg

C CH3

Benzene

H2O

OH OH CH3 C

C CH3

CH3 CH3 Pinacol

CH3O CH3 C

Pinacol rearrangment

C CH3

CH3 Pinacolone

O 2

Mg-Hg H2O Benzene

H2SO4 OH OH

∆ O


ORGANIC CHEMISTRY

Chapter 16

16.13D Meerwein-Ponndorf reduction C O + (CH3)2CHOH

[(CH3)2CHO]3Al

CH OH + (CH3)2C O

Benzene

Oppenauer oxidation OH

[(CH3)2CHO]3Al

+ CH3COCH3 O

OH + CH3CHCH3 Department of Chemistry, Xiamen University

ORGANIC CHEMISTRY

Chapter 16

16.14 Chemical Analysis for Aldehydes and Ketones


ORGANIC CHEMISTRY

Chapter 16

Derivatives of Aldehydes and Ketones: Aldehydes and ketones can be differentiated from noncarbonyl compounds through their reactions with derivatives of ammonia. Tollens’ Test RCO2NH4 + Ag Silver mirror O O O OH R C C R' + Ag R C CH R' + Ag(NH3)2 OH Silver mirror RCHO + Ag(NH3)2 OH


ORGANIC CHEMISTRY

Chapter 16

16.15 Spectroscopic Properties of Aldehydes and Ketones


ORGANIC CHEMISTRY

Chapter 16

IR: 1665 – 1780 cm-1(very strong, C=O) 2700 – 2775 cm-1 and 2820 – 2900 cm-1 (CHO) 1H

NMR:

CHO: δ 9 – 10 ppm CH—C=O: δ 2.0 – 2.3 ppm 13C

NMR:

C=O: δ 180 – 220 ppm

MS: M+•, M+•–1, RC≡O +•

UV: 270 – 300 nm, 300 – 350 nm(conjugated) Department of Chemistry, Xiamen University