ORGANIC CHEMISTRY Chapter 17 17. 4 The Aldol reaction: The addition of Enolate anions to aldehydes and stones Department of Chemistry, Xiamen University
ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 17 17.4 The Aldol Reaction: The Addition of Enolate Anions to Aldehydes and Ketones
ORGANIC CHEMISTRY Chapter 17 10% NaoH. H,o OH 2 CHCHO ChrCHCHoCHo 3-Hydroxybutanal (50%) B-hydroxyaldehyde Aldol addition(aldol reaction) ("aldol") OH Naoh 2 PhChoCHO PhCh,CH— CHCHO Etoh Ph 90 Department of Chemistry, Xiamen University
ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 17 Aldol addition (aldol reaction) 2 CH3CHO CH3CHCH2CHO OH 10% NaOH, H2O 5°C 3-Hydroxybutanal (50%) β−hydroxyaldehyde ("aldol") 2 PhCH2CHO PhCH2CH OH CHCHO Ph 90% EtOH NaOH
ORGANIC CHEMISTRY Chapter 17 Mechanism CH2-C一H=CH2-C-H CH=C-H+ H-OH H OH CH3 H + CH,-C-H CH,=C-H H-OH OH CH3CH一CH2-C-H—CH3CH-CH2-C-H+OH Department of Chemistry, Xiamen University
ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 17 Mechanism Mechanism OH CH2 C H O H CH2 C H O CH2 C H O + CH2 C H O CH3 C H O + CH3 CH O CH2 C H O CH2 C H O H OH CH3 CH OH CH2 C H O + OH H OH
ORGANIC CHEMISTRY Chapter 17 17. 4a Dehydration of the aldol Addition product g The aldols formed in aldol additions can be easily dehydrated to yield conjugated enals(enones). oH O h or oh + h2o H An aldo A conjugated enal(enone) Aldol condensation -A condensation reaction is one in which molecules are joined through the intermolecular elimination of a small molecule such as water or an alcohol Department of Chemistry, Xiamen University
ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 17 17.4A Dehydration of the Aldol Addition Product The aldols formed in aldol additions can be easily dehydrated to yield conjugated enals (enones). C OH C C O H C C C O H+ or OH ∆ + H2O An aldol A conjugated enal (enone) Aldol condensation — A condensation reaction is one in which molecules are joined through the intermolecular elimination of a small molecule such as water or an alcohol
ORGANIC CHEMISTRY Chapter 17 Mechanism OH CH3 -CHTCH-C-H CH2ch=ch-C-H OH + H-oh oh o The conditions needed for aldol dehydration are often only a bit more vigorous(slightly higher temperature for example)than the conditions needed for the aldol dimerization itself o As a result, conjugated enals(enones are often obtained directly from aldol reactions and the intermediate B-hydroxy carbonyl compounds arent usually isolated Department of Chemistry, Xiamen University
ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 17 Mechanism Mechanism CH3 CH OH CH C H O OH H CH3 CH CH C H O + H OH + OH The conditions needed for aldol dehydration are often only a bit more vigorous (slightly higher temperature, for example) than the conditions needed for the aldol dimerization itself. As a result, conjugated enals (enones) are often obtained directly from aldol reactions, and the intermediate β-hydroxy carbonyl compounds aren’t usually isolated