分析大二有机下chapter-11

1、SupplementCram Rule: 羰基位于M和S两个基团中间，亲核试剂主要从立体障碍较小的一侧 (S侧)进攻羰基碳原子67-80%20-33%SupplementReviewComplete the following reaction:1)2)Review3)The Aldol Reactions (羟醛缩合反应)The carbon chain increase doubled.(1)-H; (2) base (3) reversible Chemical Properties of Aldehydes and Ketones The aldol equilibrium gener

2、ally favors condensation product in case of aldehydes with no substituent (RCH2CHO) but favors reactant for disubstituted aldehydes (R2CHCHO) Chemical Properties of Aldehydes and KetonesThe aldol equilibrium favors reactant for most ketones.A good method to prepare ,-unsaturated aldehydes.Chemical P

3、roperties of Aldehydes and KetonesChemical Properties of Aldehydes and Ketones21. Predicate the main products of the following reaction:Chemical Properties of Aldehydes and KetonesExercise：Chemical Properties of Aldehydes and Ketones In general, a mixed aldol reaction between two different aldehyde

4、or ketone partners leads to a mixture of four possible products. Mixed Aldol ReactionClearly, such a reaction is of little practical value. Mixed aldol reactions can lead cleanly to a single product if either of two conditions is met.Chemical Properties of Aldehydes and Ketones If one of the carbony

5、l partners contains no - hydrogens but does contains a reactive carbonyl group that is a good acceptor of nucleophiles- Claisen-Schmidt condensationsDonorAcceptorAcceptorDonorChemical Properties of Aldehydes and KetonesOHOHChemical Properties of Aldehydes and Ketones(2) If one of the carbonyl partne

6、rs is much more acidic than the other one- Knoevenagel condensationsDonorAcceptorChemical Properties of Aldehydes and KetonesPerkin Condensation The Perkin condensation is an aldol-type condensation in which an aromatic aldehydes (ArCHO) react with a carboxylicacid anhydride(酸酐), (RCH2CO) 2O, to giv

7、e an , -unsaturated acid (ArCH=CRCOOH).Chemical Properties of Aldehydes and KetonesIntramolecular Aldol ReactionsChemical Properties of Aldehydes and Ketones When certain dicarbonyl compounds are treated with base, however, an intramolecular aldol reaction can occur, leading to the formation of a cy

8、clic product.Chemical Properties of Aldehydes and KetonesPredicate the main products of the following reactions(2) Exercise：Chemical Properties of Aldehydes and KetonesThe Mannich Reaction Compounds capable of forming an enol (烯醇) react with formaldehyde (甲醛) and a primary or secondary amine to yiel

9、d aminoalkyl carbonyl compoundsCan you propose the mechanism?Mannich base， -氨基酮A method to prepare ,-unsaturated aldehydes. The Mannich reaction is a kind of ponent reaction (MCR). MCRs have attracted considerable interest owing to their synthetic efficiency.Chemical Properties of Aldehydes and Keto

10、nesIn this reaction, two C-N bonds and two C-C bonds are formed. 3. Alpha Halogenation(卤代) of Aldehydes and KetonesChemical Properties of Aldehydes and Ketones Halogenation of aldehydes and ketones occurs under basic conditions. If excess base and halogen are used, a methyl ketone is triply halogena

11、ted.Mechanism：Chemical Properties of Aldehydes and Ketones A methyl ketone is triply halogenated and then cleaved bybase in the haloform reaction(卤仿反应). The products are a carboxylic acid plus a so-called haloform (卤仿).no reaction Haloform (卤仿)Chemical Properties of Aldehydes and KetonesIodoformA me

12、thyl ketone or acetaldehyde Iodoform is a yellow precipitate, this reaction can be used to distinguish the compounds having the following structure： Chemical Properties of Aldehydes and KetonesChloroformBromoformThis reaction can also be used to prepare carboxylic acidChemical Properties of Aldehyde

13、s and KetonesExercise: 1. Which of the following compounds can carry out the Iodoform reaction? Halogenation of aldehydes and ketones also occurs under acidic conditions.Chemical Properties of Aldehydes and KetonesMechanismChemical Properties of Aldehydes and Ketones-+CC HHOReactions of -HNucleophil

14、ic AdditionOxidation reactionReduction reaction4. Oxidation of Aldehydes and KetonesChemical Properties of Aldehydes and Ketones1). Aldehydes are readily oxidized to yield carboxylic acids Many oxidizing agents, including KMnO4 and hot HNO3, convert aldehydes into carboxylic acids, but CrO3 in aqueo

15、us acid is a more common choice in the laboratory. The oxidation occurs rapidly at room temperature and results in good yields. Aldehydes are oxidized by the Tollens reagent in high yield without harming carbon-carbon double bonds or other functional groups in the molecule. Chemical Properties of Al

16、dehydes and KetonesCH3CH=CHCHOKMnO4Ag(NH3)2+CH3CH=CHCOO-+AgTollens reagent Tollens reagent can be used to distinguish aldehydes and ketonesAliphatic(脂肪族) aldehydes can be oxidized by Fehling reagent.Chemical Properties of Aldehydes and KetonesFehling reagent Fehling reagent(菲林试剂) can be used to dist

17、inguish aliphatic and aromatic aldehydes.2). Ketones are inert to most oxidizing agents but undergo a slow cleavage reaction when treated with HNO3. The C-C bond next to the carbonyl group is broken, and carboxylic acids are produced.Chemical Properties of Aldehydes and Ketonessymmetrical ketoneChem

18、ical Properties of Aldehydes and KetonesBaeyer-Villiger rearrangement（拜耶尔-维利格重排）Chemical Properties of Aldehydes and KetonesMechanism: 酮在过氧酸的作用下,过氧酸中的氧原子插入到羰基与迁移基团之间生成酯的反应.The shift of R and its electron pairThe migration sequence of groups:Chemical Properties of Aldehydes and Ketones氢 叔烷基 仲烷基 苯基 伯烷基 甲基