有机化学及实验教学课件全套-醛酮的Alfa位反应-考研试题文档资料系列.ppt

Aldehyde&KetoneNucleophilicNucleophilic Addition Addition to to the Carbonyl Groupthe Carbonyl Group Oxygen Oxygen NucleophilesNucleophiles Sulfur Sulfur NucleophilesNucleophiles Carbon Carbon NucleophilesNucleophiles Nitrogen Nitrogen NucleophilesNucleophilesReactions at the -Carbon of Aldehyde&KetoneReactions at the Reactions at the -Carbon of Carbonyl Compounds-Carbon of Carbonyl Compounds Acidity of the Acidity of the -hydrogenshydrogens KetoKeto-Enol tautomerizationEnol tautomerization ApplicationsApplicationsAcidity of the -hydrogenspKpKa aC C2 2HH6 65050C C2 2HH4 44444NHNH3 33434C C2 2HH2 22525CHCH3 3COCHCOCH3 32020C C2 2HH5 5OHOH15.915.9HH2 2OO15.7415.74Ph-OHPh-OH1010HH2 2COCO3 36.56.5Keto-Enol TautomerizationKetoKetoEnolEnolWhich makes a greater contribution to the hybrid?A.A.InterconversionInterconversion：B.B.KetoKeto-enol tautomers enol tautomers in equilibriumin equilibrium K K enolenol ketoketo Monocarbonyl compounds(99%)(1.51099%)(1.510-4 4%)%)(100%)(100%)(extremely small)extremely small)(98.8%)(98.8%)(1.2%)1.2%)-dicarbonyl dicarbonyl compoundscompounds24%24%76%76%PhenolPhenolK K 10 101414C.C.Detection:Detection:+FeClFeCl3 3Purple or bluePurple or blueD.Formation of D.Formation of enolateenolate:Which “Base”?Which “Base”?enolateenolateE.E.Regioselective Regioselective Formation of Formation of Enolate Enolate Anions Anions?Kinetic enolateThermodynamic enolateGenerally:Generally:1.Low temperature gives the kinetic 1.Low temperature gives the kinetic enolateenolate.2.High temperature,relatively weak base in a 2.High temperature,relatively weak base in a protic protic solvent gives the thermodynamic solvent gives the thermodynamic enolateenolate.LDATwo special examples:Two special examples:1.The kinetically favored 1.The kinetically favored enolate enolate can be formed can be formed cleanly through the use of cleanly through the use of diisopropylamide diisopropylamide(LDA).(LDA).2.In acid condition,the thermodynamic 2.In acid condition,the thermodynamic enolenol is is formed predominantly.formed predominantly.enolenolenolateenolateF.F.RacemizationRacemization:ApplicationNucleophilic centerNucleophilic centerAmbident nucleophileAmbident nucleophilecarbanionalkoxide anionsReact as an React as an alkoxidealkoxide anions anionstrapped trapped React as aReact as a carbanion carbanionReact as a React as a carbanion carbanion 1:1:HalogenationHalogenationHaloform Haloform reactionreactioniodoformiodoform reaction reactionReact as aReact as a carbanion carbanion 2:2:AlkylationAlkylationside reaction:side reaction:solution:solution:React as aReact as a carbanion carbanion 3:3:Aldol Aldol ReactionReactionReversibleeasyeasydifficultdifficultSoxhlet Soxhlet ExtractorExtractorcatalystacetoneHow does it work?How does it work?CrossedCrossed Aldol Aldol Reaction ReactionPractical Crossed Aldol ReactionReact as aReact as a carbanion carbanion 4:4:glycolysisglycolysis