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1、Aldehyde Fe/CH3CO2HMechanism负离子自由基47双分子还原： Mg, Mg-Hg齐/非质子性溶剂还原偶联Mechanism482. 还原为烃A. Clemmensen还原B. Wolff-Kischer还原黄鸣龙改进49MechanismC. 硫代缩酮的还原503. 歧化反应Cannizzaro反应无a-HMechanism负氢转移亲核加成51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52六、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53B. Wittig反应的机理54C. Wittig反应的应
2、用552. 安息香缩合反应Mechanism失去质子决速步骤56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573. 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58七、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59Cram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6061八、a,b-不饱和醛
3、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62A. 与HCN加成B. 与RMgX加成RMgX与a,b-不饱和醛酮作用，1,2-加成倾向大，但如羰基上有较大 位阻的取代基，则倾向于1,4-加成63C. 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642. 亲电加成与HX加成，一般为1,4-加成Br2褪色654 醛酮的制备一、醛的合成1.炔水合，胞二卤代物水解662.芳烃氧化3.伯醇氧化674. Reimer-Tiemer反应5. 酰氯的部分还原A. Rosenmund还原68B. 化学还原LiAlH(OC
4、(CH3)336. 酯与腈的部分还原69二、酮的制备1. 甲基酮的合成RCOCH32. 仲醇的氧化703. 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7172Key Reactions 1. Reaction with Grignard Reagents 2.Treatment of formaldehyde with a Grignard reagent followed by hydrolysis gives a primary alcohol. Similar treatment of any other aldehyde gives a secondary
5、alcohol. Treatment of a ketone gives a tertiary alcohol.2. Reaction with Organolithium Reagents Reactions of aldehydes ane ketones with organolithium reagents are similar to those with Grignars reagents.3Reactions with Anions of Terminal Alkynes Treatment of an aldehyde or ketone with the alkali met
6、al salt of a terminal alkyne followed by hydrolysis gives an a-alkynyalchol. 4. Reaction with HCN to form Cyanohydrins For aldehydes and most sterically unhindered aliphatic ketones, equilibrium favors formation of the cyanohydrin. For aryl ketones, equilibrium favors starting materials, and little
7、cyanohydrin is obtained.735. The Wittig Reaction Treatment of an aldehyde or ketone with a triphenylphosphonium ylide gives an oxaphosphetane intermediate, which fragments to give triphenylphosphine oxide and an alkene.6. Hydration The degree of hydration is greater for aldehydes than for ketones. 7
8、. Addition of Alcohols to Form Hemiacetals Hemiacetals are only minor components of an equilibrium mixture of aldehyde or ketone and alcohol, except where 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
9、 acetals is catalyzed by acid. Acetals are stable to water and aqueous base but are hydrolyzed in aqueous acid. Acetals are valuable as carbonyl-protecting groups. 749. Addition of Sulfur Nucleophiles: Formation of 1,3-Dithianes The most commonly used thiol for preparation of thioacetals is 1,3-prop
10、anedithiol. 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 butyllithium gives an anion. This anion can enter into substitution reactions with primary alkyl, allylic, and benzylic halides and addit
11、ion 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 to the carbonyl group of an aldehyde or ketone forms a tetrahedral carbonyl addition compound. Loss of water from this intermediate
12、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 carbonyl addition intermediate. Acid-catalyzed dehydration of this intermediate gives an enamine. 7513. Addition of Hydrazine and Its
13、 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 at equilibrium, except for those aldehydes and ketones in which the enol is stabilized by resonance or hydrogen bonding. 15
14、. 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 a-carbon The rate-limiting step in acid-catalyzed a-halogenation is formation of an enol. In base-promoted a- halogenati
15、on, it is formation of an enolate anion. 7617. The haloform Reaction The haloform reaction oxidizes a methyl ketone to a carboxylic acid. 18. Oxidation of an Aldehyde to a Carboxylic Acid The aldehyde group is among the most easily oxidized functional groups. Oxidizing agents include KMnO4, K2Cr2O7,
16、 Tollens reagent, H2O2, and O2. 19. Oxidation of a Ketone to an Ester: The Baeyer-Villiger Rearrangement Oxidation of a ketone by a peroxyacid involves nucleaophilic addition to the carbonyl group 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
