厦门大学化学化工学院：《有机化学》课程教学资源（课件讲稿，双语版）第六章 离子反应 —卤代烃的亲核取代和消除反应（6.1-6.9）Introduction

Chapter 6. loniGReactiohs mucleophilic Substitution and Elimination Reactions of Alkyl Halides 离争反一卤代烃的亲核取代 和消除反应

Chapter 6 Ionic Reactions — Nucleophilic Substitution and Elimination Reactions of Alkyl Halides 离子反应 —— 卤代烃的亲核取代 和消除反应

ORGANIC CHEMISTRY Chapter 6 6.1 ntroduction Department of Chemistry, Xiamen University

ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 6 6.1 Introduction

ORGANIC CHEMISTRY Chapter 6 o The c-x bond of alkyl halides is polarized o The carbon atom bears a partial positive charge 9 Ihe halogen atom a partial negative charge C->Ⅹ The size of halogen atoms: I>Br>cI>F Thec-X bond length Bond C-F C-Cl C-Br C- Bond length(A) 1.39 1.78 1.93 2.14 Department of Chemistry, Xiamen University

ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 6 The C—X bond of alkyl halides is polarized. The carbon atom bears a partial positive charge, The halogen atom a partial negative charge C > X δ δ The size of halogen atoms: I > Br > Cl > F The C—X bond length Bond C—F C—Cl C—Br C—I Bond length (Å) 1.39 1.78 1.93 2.14

ORGANIC CHEMISTRY Chapter 6 o Compounds in which a halogen atom is bonded to an sp -hybridized carbon are called vinylic halides or phenyl halides a vinylic halide a phenyl halide or aryl halide CH=CH Vinyl group 乙烯基 Department of Chemistry, Xiamen University

ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 6 Compounds in which a halogen atom is bonded to an sp2-hybridized carbon are called vinylic halides or phenyl halides. C C X X A vinylic halide A phenyl halide or aryl halide CH2 CH Vinyl group 乙烯基

ORGANIC CHEMISTRY Chapter 6 6.2 Physical Properties of Organic Halides Department of Chemistry, Xiamen University

ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 6 6.2 Physical Properties of Organic Halides

ORGANIC CHEMISTRY Chapter 6 Physical Properties o Solubil o Very low solubilities in water o Relatively nonpolar solvents ° Toxicity o Many chloroalkanes have a cumulative toxicity and are carcinogenIc o Boiling points o chCL CH Br. chchcl cha=chcl cha=chBr are gas o In general, higher alkyl halides(Xcl, Br, Iare all quids Department of Chemistry, Xiamen University

ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 6 Physical Properties Solubility Very low solubilities in water. Relatively nonpolar solvents. Toxicity Many chloroalkanes have a cumulative toxicity and are carcinogenic. Boiling points CH3Cl, CH3Br, CH3CH2Cl, CH2=CHCl, CH2=CHBr are gas. In general, higher alkyl halides(X=Cl,Br,I) are all liquids

ORGANIC CHEMISTRY Chapter 6 6.3 Nucleophilic Substitution Reactions 亲核取代反应 Department of Chemistry, Xiamen University

ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 6 6.3 Nucleophilic Substitution Reactions 亲核取代反应

ORGANIC CHEMISTRY Chapter 6 N R-X R-Nu+Ⅹ Nucleophile Alkyl halide Product Halide ion (substrate) Heterolysis Leaving group Nucleophilic substitution reaction HO:+ CH2-Cl- CH2-OH Cl CH20:+ CH, CHo-Br CHr CHo-oCH2 Br I:+CH3 CH, CH, -CI CH CHCHo-I CI Department of Chemistry, Xiamen University

ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 6 Nu + R X R Nu + X Nucleophile Alkyl halide Product Halide ion (substrate) Heterolysis Leaving group Nucleophilic substitution reaction HO + CH3 Cl CH3 OH + Cl CH3O + CH3CH2 Br CH3CH2 OCH3 + Br CH3CH2CH2 Cl CH3CH2CH2 + I + Cl I

ORGANIC CHEMISTRY Chapter 6 Questions When does the carbon-halogen bond break? Does it break at the same time that the new bond between the nucleophile and the carbon forms? Nu: +R-X Nu--R--X R-Nu+X g Or does carbon-halogen bond break first? R-X—R++X And then Nu:+R+—-R-Nu Department of Chemistry, Xiamen University

ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 6 Questions When does the carbon-halogen bond break? Does it break at the same time that the new bond between the nucleophile and the carbon forms? Nu + R X Nu R X R Nu + X δ δ Or does carbon-halogen bond break first? R X R + X And then Nu + R R Nu

ORGANIC CHEMISTRY Chapter 6 6.4 Nucleophiles 亲核试剂 Department of Chemistry, Xiamen University

ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 6 6.4 Nucleophiles 亲核试剂