醛酮的Alfa位反应.ppt

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1、Aldehyde&KetoneNucleophilicAdditiontotheCarbonylGroupOxygenNucleophilesSulfurNucleophilesCarbonNucleophilesNitrogenNucleophilesReactionsatthe-CarbonofAldehyde&KetoneReactionsatthe-CarbonofCarbonylCompoundsAcidityofthe-hydrogensKeto-EnoltautomerizationA

2、pplicationsAcidityofthe-hydrogenspKaC2H650C2H444NH334C2H225CH3COCH320C2H5OH15.9H2O15.74Ph-OH10H2CO36.5Keto-EnolTautomerizationKetoEnolWhichmakesagreatercontributiontothehybrid?A.Interconversion：B.Keto-enoltautomersinequilibriumK＝[enol][keto]Monocarbonylc

3、ompounds(99%)(1.5×10-4%)(100%)(extremelysmall)(98.8%)(1.2%)-dicarbonylcompounds24%76%PhenolK1014C.Detection:+FeCl3PurpleorblueD.Formationofenolate:Which“Base”?enolateE.RegioselectiveFormationofEnolateAnions??KineticenolateThermodynamicenolateGenerally

4、:1.Lowtemperaturegivesthekineticenolate.2.Hightemperature,relativelyweakbaseinaproticsolventgivesthethermodynamicenolate.LDATwospecialexamples:1.Thekineticallyfavoredenolatecanbeformedcleanlythroughtheuseofdiisopropylamide(LDA).2.Inacidcondition,thethermo

5、dynamicenolisformedpredominantly.enolenolateF.Racemization:ApplicationNucleophiliccenterNucleophiliccenterAmbidentnucleophilecarbanionalkoxideanionsReactasanalkoxideanionstrappedReactasacarbanionReactasacarbanion1:HalogenationHaloformreactioniodoformreact

6、ionReactasacarbanion2:Alkylationsidereaction:solution:Reactasacarbanion3:AldolReactionReversibleeasydifficultSoxhletExtractorcatalystacetoneHowdoesitwork?CrossedAldolReactionPracticalCrossedAldolReactionReactasacarbanion4:glycolysis