厦门大学化学化工学院：《有机化学》课程教学资源（课件讲稿，英文版）Chapter 17 Aldehydes and Ketones II. Aldol Reactions（17.1-17.3）The Acidity of the α Hydrogens of Carbonyl Compounds：Enolate Anions

Chapter 17 Aldehydes and Ketones I Aldol Reactions

Chapter 17 Aldehydes and Ketones II. Aldol Reactions

ORGANIC CHEMISTRY Chapter 17 17.1 The Acidity of the a Hydrogens of Carbonyl Compounds: Enolate Anions Department of Chemistry, Xiamen University

ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 17 17.1 The Acidity of the α Hydrogens of Carbonyl Compounds: Enolate Anions

ORGANIC CHEMISTRY Chapter 17 C—C-C-R HH B Hydrogens are not acidic a Hydrogens are usually acidic (pKa=40~50 (pKa=19~20) CH3CH3 CH2=CHCH3 (C6H5)2CH2 CH3 CN pl 50 40 32.3 25 CH3SO2CH3 CHsCOCH3 CHINO HH 29 24.7 16.6 17.21 Department of Chemistry, Xiamen University

ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 17 C C H C O R H α Hydrogens are usually acidic (pKa = 19 ∼ 20) β Hydrogens are not acidic (pKa = 40 ∼ 50) CH2 CHCH3 pKa H H ~ 50 40 32.3 25 29 24.7 16.6 17.21 CH3CH3 (C6H5)2CH2 CH3CN CH3SO2CH3 C6H5COCH3 CH3NO2

ORGANIC CHEMISTRY Chapter 17 O C|H -C-R C-C-R C=C-R B: O R OH HB LO HB H B: C-C CC、+B: R R R Enol form Enolate anion Keto form 烯醇式 烯醇负离子 酮式 Department of Chemistry, Xiamen University

ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 17 C H C O R B C C O R C C O R C C O R δ δ C C O R δ δ Enolate anion 烯醇负离子 C C OH R C H C O R B + + B HB HB Keto form 酮式 Enol form 烯醇式

ORGANIC CHEMISTRY Chapter 17 17.2 Keto and Enol tautomers Department of Chemistry, Xiamen University

ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 17 17.2 Keto and Enol Tautomers

ORGANIC CHEMISTRY Chapter 17 Tautomerization(互变异构 OH Acetaldehyde CH2CH、—CH2=CH ( 100%)(extremely smal OH Acetone CH3CCH3 - CH2=CCH3 (>99) (1.5×104%) OH Cyclohexanone (988%) (1.2%) Department of Chemistry, Xiamen University

ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 17 Tautomerization (互变异构) CH3CH O CH3CCH3 O O OH CH2 CH OH CH2 CCH3 OH (~ 100%) (extremely small) (> 99%) (1.5×10 %) ( 98.8%) (1.2%) -4 Acetaldehyde Acetone Cyclohexanone

ORGANIC CHEMISTRY Chapter 17 O oH O C2HsO-C-CH2-C-OC2H5 C2H5O-C=CH-C-OC2H5 7.7×10 CH3-C-CH2-C-OC2H5 CH3 -C=CH-C-OC2H5 OH CH2-C-CHo-C-Cl CH2-c=ch-c-ch 76 H CH C-CH,3 H Department of Chemistry, Xiamen University

ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 17 C2H5O C CH2 O C OC2H5 O CH3 C CH2 O C CH3 O 7.3 76 C2H5O C CH OH C OC2H5 O 7.7 × 10-3 CH3 C CH2 O C OC2H5 O CH3 C CH OH C OC2H5 O CH3 C CH OH C CH3 O CH3 C C O C CH3 O H H

ORGANIC CHEMISTRY Chapter 17 17.3 Reactions via Enols and enolate Anions Department of Chemistry, Xiamen University

ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 17 17.3 Reactions via Enols and Enolate Anions

ORGANIC CHEMISTRY Chapter 17 173A Racemization CH2CH CHrCh OH or h2o OH HCC、n =( H (R) CHr CH2 CH3 CH2 O C-C-C6H4 C-C-C6Ha HrCt H (R) CH3 (S) Department of Chemistry, Xiamen University

ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 17 17.3A Racemization CH3CH2 C C H H3C C6H5 O OH or H3O+ CH3CH2 C C H3C C6H5 OH CH3CH2 C C H H3C C6H5 O CH3CH2 C C CH3 H C6H5 O + (R) (R) (S)

ORGANIC CHEMISTRY Chapter 17 Mechanism CH3 CH2 Ch2CH 0 H-OH CTC-C6H C=C HoC OH H HC CkH CH2CH OH Oh HrC 6115 CH3 CH2 O·H CHCH H C-C-C6H H2C√ Hrc C-cis CH3CH2 LOH H HrC Cshe Department of Chemistry, Xiamen University

ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 17 Mechanism Mechanism CH3CH2 C C H H3C C6H5 O OH CH3CH2 C C H3C C6H5 O H OH CH3CH2 C C H3C C6H5 OH + OH CH3CH2 C C H H3C C6H5 O CH3CH2 C C H H3C C6H5 H OH + H CH3CH2 C C H3C C6H5 OH