有机化学教学课件：Chapter 4. Alkynes

1、Chapter 4 Alkynes,4.1 Nomenclature 4.2 Structure of Alkynes 4.3 Reactions of alkynes 4.3.1 Acidity of Terminal Alkynes （端位炔烃的酸性） 4.3.2 Application of the Acidity of Terminal Alkynes in Organic Synthesis （端位炔烃酸性在合成上的应用） 4.3.3 Hydrogenation of Alkynes 1. Syn-addition of H2: Synthesis of cis-Alkyenes 2

2、. Metal-Ammonia Reduction of Alkynes Synthesis of trans-Alkenes,4.3.4 Electrophilic Addition of Alkynes a. Addition of HX b. Hydration of Alkynes c. Addition of X2 d. Hydroboration and Oxidation of Alkynes 4.4 Oxidation of Alkynes 4.5 Preparation of Unsaturated Hydrocarbons 4.5.1 Preparation of alke

3、nes Dehydrohalogenation of alkyl halides 2. Dehydration (脱水)of alcohols 4.5.1 Preparation of Alkynes Dehydrohalogenation of vicinal alkyl dihalides b. Alkylation of alkynide ions,Alkynes,Hydrocarbons containing a carbon-carbon triple bond,4.1 Nomenclature,P128,4.13,1-Butyne,Alkenyne (烯炔,3-Penten-1-y

4、ne (3-戊烯-1-炔,1-penten-4-yne (1-戊烯-4-炔,1. Numbering starts from the end near the first multiple bond,2. When there is a choice, double bonds receive lower numbers than triple bonds,4， 8-壬二烯-1-炔,4.2 Structure of Alkynes,Acetylene (ethyne,sp Hybrid orbitals,C,Ground state,Promotion of electron,Excited

5、state,sp-hybridized state,Hybri- dization,Each sp hybrid orbital,50% s character 50% p character,P19, 1.9,The shape of an sp hybrid obital,The two sp hybride orbitals are oriented 180away from each other, perpendicular to the two remaining p orbitals,An sp-hybridized carbon atom,Geometric structure

6、of sp-hybridized C atoms is linear,H,H,bond,bond,bond,Carbon-carbon triple bonds,4.3 Physical properties of alkynes,4.4 Reactions of alkynes,4.4.1 Acidity of Terminal Alkynes(p131,Acetylene,Carbanion,Conjugate base (共轭碱,Acidity,pKa: 3.2 15.8 16-17 26 38,P128132,4.3.2 Application of the Acidity of Te

7、rminal Alkynes in Organic Synthesis,1. Preparation of Metal Alkynides,Acid-base reaction,P131,2. Formation of C-C Bonds,Synthesis of Alkynes,Sodium alkynides are useful intermediates as nucleophile,Primary halides,3. Formation of other metal alkynides,Ch. P77,4.3.3 Hydrogenation of Alkynes(p129,Ch.P

8、52(五)(1,Syn-addition of H2: Synthesis of cis-Alkyenes,Lindlar catalyst,Lindlar catalyst: Pd/ CaCO3, Pb(Ac)2-quinoline (喹啉,Quinoline,P-2 catalyst,96,Ch: P53,2. Metal-Ammonia Reduction of Alkynes Synthesis of trans-Alkenes : Mechanism,4.3.4 Electrophilic Addition of Alkynes,Reactivity: Alkynes Alkenes

9、,Regioselectivity: Follow Markov.s Rule,a. Addition of HX,b. Hydration of Alkynes,2-Hexanone,Keto-enol tautomerism(酮式烯醇式互变异构,Mechanism,c. Addition of X2,e. Hydroboration of Alkynes,d. Addition of HX,6.4 Oxidation of Alkynes,An internal alkynes,Identification of C-C triple bonds,4.5 Preparation of Un

10、saturated Hydrocarbons,4.5.1 Preparation of alkenes,a. Dehydrohalogenation of alkyl halides,脱卤化氢,Bromocyclohexane Cyclohexene (81,b. Dehydration (脱水)of alcohols,Elimination,Ch: P112,4.5.2 Preparation of Alkynes,Dehydrohalogenation of vicinal alkyl dihalides,Diphenylacetylene(85,b. Alkylation of metal alkynide,Additional problems: 1.Predict the products from reaction of 2- hexyne with the following reagents: 2 equiv Br2 (b) 1equiv HBr (c) Excess HBr (d) Li in NH