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1、第十一章 醛和酮,Aldehyde醛,Ketone酮,Carbonyl羰基,1 命名,一、醛,Rule:选主链,定母体；编号；排序,甲醛 methanalformaldehyde,乙醛 ethanalacetaldehyde,4-甲基-2-乙基戊醛2-ethyl-4-methylpetanal,烷醛ane-al,b-甲基戊醛 或 3-甲基戊醛b-methylpetanal,3-甲基环己基甲醛3-methylcyclohexanecarbaldyhyde,苯甲醛benzenecarbaldehyde benzaldehyde,p-硝基苯甲醛p-nitrobenzenecarbaldehyde,3
2、-甲基-4-己烯醛3-methyl-4-hexenal,二、酮的命名,Rule:选主链,定母体；编号；排序,烷酮ane-anone,丙酮propanone acetone,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-one,2 醛酮的物质性质,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,二、羰基的亲核加成反应,1.加HCN,a
3、-羟基酸,a-氨基醇,Mechanism,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,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,CABED,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,ACB,芳香族醛酮与HCN反应活性，主要受电子效应的影响,反应范围,RCHO RCOCH3 8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：RCHO RCOCH3 8碳以下的环酮,3.与RO
4、H加成,Mechanism,半缩醛,酸的作用活化羰基，增大羰基的碳正性,缩醛,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,保护羰基,4.与RSH（硫醇）加成,硫代缩醛（酮）,Problem,5.与H2O加成,K平衡的大小取决于羰基上的取代基,6.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,7.与氨的衍生物加成,反应通式：,活化羰基,NH2失活,羰基试剂,水解,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,2.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
5、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,Mechanism,fast,slow,酸催化烯醇化,fast,fast,自动催化反应,B.碱催化下的卤代反应,Mechanism,fast,slow,卤仿,碘仿反应,黄色,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,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,Mechanism,slo
6、w,羟酮缩合,B.酸催化下的羟醛缩合反应,C.分子内的羟醛缩合反应,D.交叉羟醛缩合反应,四种产物,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-H,不对称的酮Aldol反应的取向,四、氧化反应,1.强氧化剂：KMnO4/H+,K2Cr2O7/H+,HNO3,2.弱氧化剂：Tollens试剂 AgNO3/NH3.H2O Ag(NH3)2+OH-Fehling试剂 CuSO4/OH-+酒石酸钾钠,3.拜尔维立格氧化(Baeyer-Villiger),Mechanism,反应方向,R迁移能力：Ar3o2o1oCH3,氢优先迁移,五、还原反应,1.还原为醇,A.催化氢化,催化氢化活性：
7、CHO C=C RCOR,选择性差,B.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,C.麦尔外因彭多夫还原(Meerwein-Ponndorf),可逆,Mechanism,负氢转移,欧芬脑氧化(Oppenauer),可逆,Mechanism,醇交换,D.金属还原,单分子还原：Na/C2H5OH;Fe/CH3CO2H,Mechanism,负离子自由基,双分子还原：Mg,Mg-Hg齐/非质子性溶剂,还原偶联,Mechanism,2.还原为烃,A.Clemmensen还原,B.Wolff-Kischer还原,黄鸣龙改
8、进,Mechanism,C.硫代缩酮的还原,3.歧化反应Cannizzaro反应,无a-H,Mechanism,负氢转移,亲核加成,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,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,B.Wittig反应的机理,C.Wittig反应的应用,2.安息香缩合反应,Mechanism,失去质子,决速步骤,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,3.贝克曼重排(Beckman)-反酮
9、肟重排,Mechanism,特点：分子内的反式重排,手性碳构型保持,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,Cram规则:不对称醛酮与亲核试剂加成时，亲核试剂优先从醛酮加成 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,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,A.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,C.与RLi加成
10、,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,2.亲电加成,与HX加成，一般为1,4-加成,Br2褪色,4 醛酮的制备,一、醛的合成,1.炔水合，胞二卤代物水解,2.芳烃氧化,3.伯醇氧化,4.Reimer-Tiemer反应,5.酰氯的部分还原,A.Rosenmund还原,B.化学还原LiAlH(OC(CH3)33,6.酯与腈的部分还原,二、酮的制备,1.甲基酮的合成RCOCH3,2.仲醇的氧化,3.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,Key Reactions Reaction with Grignard
11、ReagentsTreatment of formaldehyde with a Grignard reagent followed by hydrolysis gives a primary alcohol.Similar treatment of any other aldehyde gives a secondary alcohol.Treatment of a ketone gives a tertiary alcohol.,2.Reaction with Organolithium ReagentsReactions of aldehydes and ketones with org
12、anolithium reagents are similar to those with Grignars reagents.,3Reactions with Anions of Terminal AlkynesTreatment of an aldehyde or ketone with the alkali metal salt of a terminal alkyne followed by hydrolysis gives an a-alkynyalchol.,4.Reaction with HCN to form Cyanohydrins For aldehydes and mos
13、t sterically unhindered aliphatic ketones,equilibrium favors formation of the cyanohydrin.For aryl ketones,equilibrium favors starting materials,and little cyanohydrin is obtained.,5.The Wittig Reaction Treatment of an aldehyde or ketone with a triphenylphosphonium ylide gives an oxaphosphetane inte
14、rmediate,which fragments to give triphenylphosphine oxide and an alkene.,6.HydrationThe degree of hydration is greater for aldehydes than for ketones.,7.Addition of Alcohols to Form Hemiacetals Hemiacetals are only minor components of an equilibrium mixture of aldehyde or ketone and alcohol,except w
15、here the OH and the C=O are parts of the same molecule and a five-or six-membered ring can form.,8.Addition of alcohols to Form Acetals Formation of acetals is catalyzed by acid.Acetals are stable to water and aqueous base but are hydrolyzed in aqueous acid.Acetals are valuable as carbonyl-protectin
16、g groups.,9.Addition of Sulfur Nucleophiles:Formation of 1,3-Dithianes The most commonly used thiol for preparation of thioacetals is 1,3-propanedithiol.The product is called a 1,3-dithiane.,10.Alkylation of Anions Derived from Aldehyde 1,3-Dithianes Treatment of an aldehyde 1,3-dithiane(pKa 31)with
17、 butyllithium gives an anion.This anion can enter into substitution reactions with primary alkyl,allylic,and benzylic halides and addition reactions with the carbonyl group pf aldehydes and ketones.,11.Addition of Ammonia and Its Derivatives:Formation of Imines Addition of ammonia or a primary amine
18、 to the carbonyl group of an aldehyde or ketone forms a tetrahedral carbonyl addition compound.Loss of water from this intermediate gives an imine.,12.Addition of Secondary Amines:Formation of Enamines Addition of Secondary amine to the carbonyl group of an aldehyde or ketone forms a tetrahedral car
19、bonyl addition intermediate.Acid-catalyzed dehydration of this intermediate gives an enamine.,13.Addition of Hydrazine and Its Derivatives Treatment of an aldehyde or ketone with hydrazine gives a hydrazone.Derivatives of hydrazine react similarly.,14.Keto-Enol Tautomerism The keto form predominates
20、 at equilibrium,except for those aldehydes and ketones in which the enol is stabilized by resonance or hydrogen bonding.,15.Deuterium Exchange at the a-Carbon Acid-or base-catalyzed deuterium exchange at an a-carbon involves formation of an enol or enolate anion intermediate.,16.Halogenation at the
21、a-carbon The rate-limiting step in acid-catalyzed a-halogenation is formation of an enol.In base-promoted a-halogenation,it is formation of an enolate anion.,17.The haloform Reaction The haloform reaction oxidizes a methyl ketone to a carboxylic acid.,18.Oxidation of an Aldehyde to a Carboxylic Acid
22、 The aldehyde group is among the most easily oxidized functional groups.Oxidizing agents include KMnO4,K2Cr2O7,Tollens reagent,H2O2,and O2.,19.Oxidation of a Ketone to an Ester:The Baeyer-Villiger RearrangementOxidation of a ketone by a peroxyacid involves nucleaophilic addition to the carbonyl grou
23、p of the ketone to form a tetrahedral carbonyl addition intermediate followed by molecular rearrangement to give an ester.,20.Catalytic Reduction Catalytic reduction of the carbonyl group of an aldehyde or ketone to an alcohol group is simple to carry out and yields of alcohol are high.A disadvantag
24、e of this method is that some other functional groups,including carbon-carbon double and triple bonds,may also be reduced.,21.Metal Hydride Reduction Both LiAlH4 and NaBH4 are selective in that neither reduces isolated carbon-carbon double or triple bonds.,22.Clemmensen Reduction of an aldehyde or k
25、etone Reduction of the carbonyl group of an aldehyde or ketone using amalgamated zinc in the presence of concentrated hydrochloric acid gives a methylene group.,23.Wolff-Kishner Reduction of an Aldehyde or Ketone Formation of a hydrazone followed by treatment with base,commonly KOH in diethylene glycol or potassium tert-butoxide in dimethyl sulfoxide,reduces the carbonyl group of an aldehyde or ketone to a methylene group.,作业：P412 2 4 5 10 11 13 14 15 17 19 20 22 23,
