第十一章醛和酮

第十一章醛和酮Aldehyde醛Ketone酮Carbonyl羰基1§1命名一、醛Rule:选主链,定母体；编号；排序甲醛methanalformaldehyde乙醛ethanalacetaldehyde4-甲基-2-乙基戊醛2-ethyl-4-methylpetanal烷－醛ane--alb-甲基戊醛或3-甲基戊醛b-methylpetanal23-甲基环己基甲醛3-methylcyclohexanecarbaldyhyde苯甲醛benzenecarbaldehyde

benzaldehydep-硝基苯甲醛p-nitrobenzenecarbaldehyde3-甲基-4-己烯醛3-methyl-4-hexenal3二、酮的命名Rule:选主链,定母体；编号；排序烷－酮ane--anone丙酮propanoneacetone

5-甲基-3-己酮5-methyl-3-hexanone

4-甲基环己酮4-methylcyclohexanone

1-苯基-1-丙酮1-phenyl-1-propanone

2,4-己二酮2,4-hexanedione

4-己烯-2-酮4-hexen-2-one4化合物普通命名法IUPAC命名法熔点/℃沸点/℃溶解度g/100gH2O甲醛HCHOformaldehydeformaldehyde-9221易溶乙醛CH3CHOacetaldehydeacetaldehyde-1212116丙醛CH3CH2CHOpropionaldehydepropanal-81497丁醛CH3(CH2)2CHOn-butyraldehydebutanal-9976微溶戊醛CH3(CH2)3CHOn-valeraldehydepentanal-92103微溶苯甲醛PhCHObenzaldehydebenzaldehyde-261780.3丙酮CH3COCH3acetonepropanone-9556∞丁酮CH3CH2COCH3ethylmethylketone2-butanone-8680262-戊酮CH3(CH2)2COCH3methylpropyl

ketone2-pentanone-781026.33-戊酮C2H5COC2H5dimethyl

ketone3-pentanone-401025环己酮cyclohexanonecyclohexanone-451552.4苯乙酮PhCOCH3methylphenylketone1-phenyl-1-ethanone21202不溶苯丙酮PhCOCH2CH3ethylphenylketone1-phenyl-1-propanone21218不溶二苯酮PhCOPhdiphenyl

ketoneDiphenyl

methanone48306不溶§2醛酮的物质性质5§3醛酮的化学性质一、羰基的结构与反应特征sp2杂化，平面结构sp3杂化，四面体亲核加成反应6二、羰基的亲核加成反应1.加HCNa-羟基酸a-氨基醇7Mechanism实验证据：加少量碱加速反应的进行相对活性：>>Problems:比较如下化合物与HCN反应的活性大小>>芳环与羰基p-p共轭，减弱羰基碳正性8<叔丁基的立体位阻，妨碍亲核试剂接近羰基碳(4)将如下化合物与HCN反应的活性大小排序C>A>B>E>D脂肪族醛酮与HCN反应活性，主要受空间因素影响(5)将如下化合物与HCN反应的活性大小排序A>C>B芳香族醛酮与HCN反应活性，主要受电子效应的影响9反应范围RCHORCOCH38碳以下的环酮2.与饱和NaHSO3溶液反应亲核中心为S，不是O反应范围：RCHORCOCH38碳以下的环酮103.与ROH加成Mechanism半缩醛酸的作用活化羰基，增大羰基的碳正性缩醛11缩酮分水器缩醛缩醛(酮)的分解缩醛(酮)在碱性条件下是稳定的，但对酸敏感12保护羰基134.与RSH（硫醇）加成硫代缩醛（酮）14Problem155.与H2O加成K平衡的大小取决于羰基上的取代基166.与金属有机试剂RM加成RM:RMgBr,RLi,RC=CNa制备各种醇的方法RMgBr与RLi的区别177.与氨的衍生物加成反应通式：1819活化羰基NH2失活羰基试剂水解20三、涉及羰基a-H的反应1.a-H的酸性及烯醇平衡烯醇平衡212.a-卤代及卤仿反应A.酸催化下的卤代反应动力学实验：反应速度与羰基化合物以及酸的浓度相关，但与卤素的浓度无关结论：反应的决速步骤在卤素参与反应之前22Mechanismfastslow酸催化烯醇化fastfast自动催化反应23B.碱催化下的卤代反应Mechanismfastslow24卤仿碘仿反应黄色25碘仿反应的应用鉴别有机分子中是否具有结构单元反应的方向酸性条件：卤代反应发生在取代基多的a碳上稳定性<26碱性条件：卤代反应发生在取代基少的a碳上原因：决速步骤中碱夺取a-H形成烯醇负离子，取代少的a-C上H的酸性强，位阻小3.羟醛缩合(Aldol)反应A.碱催化下的羟醛缩合反应a,b-不饱和醛Mechanismslow27羟酮缩合B.酸催化下的羟醛缩合反应28C.分子内的羟醛缩合反应D.交叉羟醛缩合反应四种产物29交叉羟醛缩合反应－a,b-不饱和醛酮的合成提供羰基提供a-H30不对称的酮Aldol反应的取向31四、氧化反应1.强氧化剂：KMnO4/H+,K2Cr2O7/H+,HNO3322.弱氧化剂：Tollens试剂AgNO3/NH3.H2O[Ag(NH3)2]+OH-

Fehling试剂CuSO4/OH-+酒石酸钾钠333.拜尔－维立格氧化(Baeyer-Villiger)Mechanism反应方向34R迁移能力：Ar>3o>2o>1o>CH3氢优先迁移35五、还原反应1.还原为醇A.催化氢化催化氢化活性：CHO>C=C>RCOR选择性差36B.化学还原－LiAlH4,NaBH4选择性好LiAlH4:可还原COR,CO2H,CN,NO2NaBH4:一般只能还原醛酮羰基37C.麦尔外因－彭多夫还原(Meerwein-Ponndorf)可逆Mechanism负氢转移38欧芬脑氧化(Oppenauer)可逆Mechanism醇交换39D.金属还原单分子还原：Na/C2H5OH;Fe/CH3CO2HMechanism负离子自由基40双分子还原：Mg,Mg-Hg齐/非质子性溶剂还原偶联Mechanism412.还原为烃A.Clemmensen还原B.Wolff-Kischer还原黄鸣龙改进42MechanismC.硫代缩酮的还原433.歧化反应－Cannizzaro反应无a-HMechanism负氢转移亲核加成44交叉歧化反应四种反应方式甲醛羰基活性高，优先受到OH-的进攻45六、其它重要反应1.Wittig反应Wittig试剂－磷叶立德(Yilde)A.Wittig试剂的制备46B.Wittig反应的机理47C.Wittig反应的应用482.安息香缩合反应Mechanism失去质子决速步骤49原因：吸电子取代基减弱碳负离子的亲核性给电子取代基减弱羰基碳的碳正性决速步反应中提供碳负离子，亲核性大反应中提供羰基碳，其碳正性大503.贝克曼重排(Beckman)-反酮肟重排Mechanism特点：分子内的反式重排手性碳构型保持51七、羰基加成反应的立体化学产生一个新的手性中心R,R’中不含手性碳，则得到外消旋体52Cram规则:不对称醛酮与亲核试剂加成时，亲核试剂优先从醛酮优势构象中空间位阻较小的一边，既较小基团一边进攻羰基优势构象：手性碳原子上最大基团与羰基处于反式共平面时，其构象最稳定5354八、a,b-不饱和醛酮的反应1.亲核加成醛羰基活性高，倾向于1,2-加成；酮倾向于1,4-加成55A.与HCN加成B.与RMgX加成RMgX与加成a,b-不饱和醛酮作用，1,2-加成倾向大，但如羰基上有较大位阻取代基，则倾向于1,4-加成56C.与RLi加成RLi试剂活性高，倾向于1,2-加成D.与R2CuLi加成R2CuLi倾向于1,4-加成572.亲电加成与HX加成，一般为1,4-加成Br2褪色58§4醛酮的制备一、醛的合成1.炔水合，胞二卤代物水解592.芳烃氧化3.伯醇氧化604.Reimer-Tiemer反应5.酰氯的部分还原A.Rosenmund还原61B.化学还原－LiAlH[(OC(CH3)3]36.酯与腈的部分还原62二、酮的制备1.甲基酮的合成RCOCH32.仲醇的氧化633.芳香酮的合成4.酰氯与有机铜化合物的反应5.腈与有机镁(锂)的反应6465KeyReactionsReactionwithGrignardReagentsTreatmentofformaldehydewithaGrignardreagentfollowedbyhydrolysisgivesaprimaryalcohol.Similartreatmentofanyotheraldehydegivesasecondaryalcohol.Treatmentofaketonegivesatertiaryalcohol.2.ReactionwithOrganolithiumReagentsReactionsofaldehydesandketoneswithorganolithiumreagentsaresimilartothosewithGrignarsreagents.3．ReactionswithAnionsofTerminalAlkynesTreatmentofanaldehydeorketonewiththealkalimetalsaltofaterminalalkynefollowedbyhydrolysisgivesana-alkynyalchol.4.ReactionwithHCNtoformCyanohydrins

Foraldehydesandmoststericallyunhinderedaliphaticketones,equilibriumfavorsformationofthecyanohydrin.Forarylketones,equilibriumfavorsstartingmaterials,andlittlecyanohydrinisobtained.665.TheWittigReaction

Treatmentofanaldehydeorketonewithatriphenylphosphonium

ylidegivesanoxaphosphetaneintermediate,whichfragmentstogivetriphenylphosphineoxideandanalkene.6.HydrationThedegreeofhydrationisgreaterforaldehydesthanforketones.7.AdditionofAlcoholstoFormHemiacetals

Hemiacetalsareonlyminorcomponentsofanequilibriummixtureofaldehydeorketoneandalcohol,exceptwherethe–OHandtheC=Oarepartsofthesamemoleculeandafive-orsix-memberedringcanform.8.AdditionofalcoholstoFormAcetals

Formationofacetalsiscatalyzedbyacid.Acetalsarestabletowaterandaqueousbasebutarehydrolyzedinaqueousacid.Acetalsarevaluableascarbonyl-protectinggroups.679.AdditionofSulfurNucleophiles:Formationof1,3-Dithianes

Themostcommonlyusedthiolforpreparationofthioacetalsis1,3-propanedithiol.Theproductiscalleda1,3-dithiane.10.AlkylationofAnionsDerivedfromAldehyde1,3-Dithianes

Treatmentofanaldehyde1,3-dithiane(pKa

31)withbutyllithiumgivesananion.Thisanioncanenterintosubstitutionreactionswithprimaryalkyl,allylic,andbenzylichalidesandadditionreactionswiththecarbonylgrouppfaldehydesandketones.11.AdditionofAmmoniaandItsDerivatives:FormationofImines

Additionofammoniaoraprimaryaminetothecarbonylgroupofanaldehydeorketoneformsatetrahedralcarbonyladditioncompound.Lossofwaterfromthisintermediategivesanimine.12.AdditionofSecondaryAmines:FormationofEnamines

AdditionofSecondaryaminetothecarbonylgroupofanaldehydeorketoneformsatetrahedralcarbonyladditionintermediate.Acid-catalyzeddehydrationofthisintermediategivesanenamine.6813.AdditionofHydrazineandItsDerivatives

Treatmentofanaldehydeorketonewithhydrazinegivesahydrazone.Derivativesofhydrazinereactsimilarly.14.Keto-Enol

Tautomerism

Theketoformpredominatesatequilibrium,exceptforthosealdehydesandketonesinwhichtheenolisstabilizedbyresonanceorhydrogenbonding.15.DeuteriumExchangeatthea-Carbon

Acid-orbase-catalyzeddeuteriumexchangeatana-carboninvolvesformationofanenolorenolateanionintermediate.16.Halogenationatthea-carbon

Therate-limitingstepinacid-catalyzeda-halogenationisformationofanenol.Inbase-promoteda-halogenation,itisformationofanenolateanion.6917.ThehaloformReactionThehaloformreactionoxidizesamethylketonetoacarboxylicacid.18.OxidationofanAldehydetoaCarboxylicAcid

Thealdehydegroupisamongthemosteasilyoxidizedfunctionalgroups.OxidizingagentsincludeKMnO4,K2Cr2O7,Tollens’reagent,H2O2,andO2.19.OxidationofaKetonetoanEster:TheBaeyer-VilligerRearrangementOxidationofaketonebyaperoxyacidinvolvesnucleaophilicadditiontothecarbonylgroupoftheketonetoformatetrahedralcarbonyladditionintermediatefollowedbymolecularrearrangementtogiveanester.20.CatalyticReduction

Catalyticreductionof