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）第十章 自由基反应（10.3-10.6）The Reactions of Alkanes with Halogens

ORGANIC CHEMISTRY Chapter 10 10. 3 The reactions of alkanes with Halogens Department of Chemistry, Xiamen University

ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 10 10.3 The Reactions of Alkanes with Halogens

ORGANIC CHEMISTRY Chapter 10 CH4 +X CHrx+ ch,X2+ chX or nv XEF C + CX+HX or Br Department of Chemistry, Xiamen University

ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 10 CH4 + X2 or hv ∆ CH3X + CH2X2 + CHX3 + CX4 + HX X= F, Cl, or Br

ORGANIC CHEMISTRY Chapter 10 10.3A Multiple substitution reactions Versus Selectivity CH CI CH CH CH2CHCH CH3 CHCH2CI CH3 CCH3 48 29% polychlorinated products +hCI 23% Department of Chemistry, Xiamen University

ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 10 10.3A Multiple Substitution Reactions Versus Selectivity CH3CHCH3 CH3 Cl2 hv CH3CHCH2Cl CH3 CH3CCH3 CH3 Cl + + polychlorinated products + HCl 48% 29% 23%

ORGANIC CHEMISTRY Chapter 10 10.4 Chlorination of methane Mechanism of reaction Department of Chemistry, Xiamen University

ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 10 10.4 Chlorination of Methane: Mechanism of Reaction

ORGANIC CHEMISTRY Chapter 10 Mechanism hy 2Cl· Chain Initiation CH 4 cl CH2 Hc Chain CH3 F Cl2-CH3CI Cl)Propagation C1·+Cl CH3+“CH Ch2 ch Chain Termination CH3·+C1 CH2C Department of Chemistry, Xiamen University

ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 10 Mechanism Mechanism hv CH4 + Cl CH3 ＋ HCl CH3 ＋ Cl2 CH3Cl ＋ Cl Cl ＋ Cl CH3 ＋ CH3 CH3 ＋ Cl Chain Initiation Chain Propagation Chain Termination Cl2 2Cl Cl2 CH3CH3 CH3Cl

ORGANIC CHEMISTRY Chapter 10 10.5 Chlorination of Methane: Energy Changes Department of Chemistry, Xiamen University

ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 10 10.5 Chlorination of Methane: Energy Changes

ORGANIC CHEMISTRY Chapter 10 Chain Initiation 2Cl·△H°=+243kJ/mol DH°=243 Chain Propagation CH3-H+Cl→CH3+HCl△H°=+4kJ/mol DH°=435 DH°=431 CH3+Cl2—CH3C1+Cl·△H°=106kJ/mol DH°=243DH=349 Chain Termination △H°=102 kJ/mol CH.+ Cl CHCI DH°=349 CH2 +CH CHCH DH°=368 Cl·+Cl Cl DH°=243 Department of Chemistry, Xiamen University

ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 10 hv Cl2 2Cl ∆H° = + 243 kJ/mol DH°= 243 Chain Initiation CH3 ＋ HCl CH3 ＋ Cl2 CH3Cl ＋ Cl ∆H° = 106 kJ/mol DH°= 435 CH3 H ＋ Cl DH°= 431 DH°= 243 DH°= 349 ∆H° = + 4 kJ/mol Chain Propagation Cl ＋ Cl CH3 ＋ CH3 CH3 ＋ Cl Cl2 CH3CH3 CH3Cl Chain Termination DH°= 349 DH°= 368 DH°= 243 ∆H° = 102 kJ/mol

ORGANIC CHEMISTRY Chapter 10 Reaction of methane with other halogens △H°( kJ/mol) Chain initiation X=F CI Br 2X. +159+243+192+151 Chain Propagation CH3-H+X·→CH3+HX134+4+69+138 CH3 t X2 CH3X+X.29310610084 Overall 4△H°=42710231+54 Department of Chemistry, Xiamen University

ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 10 Reaction of methane with other halogens hv X2 2X ∆H° (kJ/mol) Chain Initiation CH3 ＋ HX CH3 ＋ X2 CH3X ＋ X CH3 H ＋ X Chain Propagation X= F Cl Br I +159 +243 +192 +151 134 +4 +69 +138 293 106 100 84 Overall ∆H° = 427 102 31 +54

ORGANIC CHEMISTRY Chapter 10 10.6 Halogenation of higher Alkanes Department of Chemistry, Xiamen University

ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 10 10.6 Halogenation of Higher Alkanes

ORGANIC CHEMISTRY Chapter 10 hy CH3CHCH2CH3+C235° ChaCH CHCHCI 28% CH3 CH2 CHCH3 72% C V(1°H):V(2°H)=28/6:72/4=1:4 hv CHr chcha t c 35 o(CH3)2 CHCh2Cl+(Ch3)3 CCI CH 63 37% V(1°H:V(3H)=63/9:37/1=1:53 V(1°H):V(2H):V(3°H)=1:4:53 Department of Chemistry, Xiamen University

ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 10 CH3CH2CH2CH3 + Cl2 hv 35 72% CH3CHCH3 + Cl2 (CH3)2CHCH2Cl + (CH3)3CCl hv 35 CH 63% 37% 3 V(1 H)：V(2 H) = 28 / 6 ：72 / 4 =1：4 V(1 H)：V(3 H) = 63 / 9 ：37 / 1 =1：5.3 V(1 H)：V(2 H) ： V(3 H) =1：4：5.3 CH3CH2CHCH3 Cl CH3CH2CH2CH2Cl + 28%