Chap 15 Electrophilic aromatic substitution(芳香族 亲电取代) 15.1 Electrophilic aromatic substitution reactions These reactions are of the general type shown below: +E Ar-E H E+- Electrophilic reagent亲电试剂
Chap 15 Electrophilic aromatic substitution (芳香族 亲电取代） 15.1 Electrophilic aromatic substitution reactions These reactions are of the general type shown below; + E + E + H + ArH + E + Ar-E + H + E+ -------Electrophilic reagent 亲电试剂
Fig 15.1 Electrophilic aromatic substitution reactions (X=CL, Br) + hX Halogenation 卤化 HNO HSO H20 Nitration 硝化 So, SO3H H2SO4 Sulfonation 磺化 RCL, AICI3 R Friedel-Crafts Alkylation (R can rearrange) HC弗瑞德尔克拉伏茨 烷基化 RC-CL, AlCI R Friedel-Crafts Acylation 弗瑞德尔-克拉伏茨 酰基化
Fig 15.1 Electrophilic aromatic substitution X2 , Freactions. eX3 (X = Cl, Br) X + HX Halogenation 卤 化 NO2 HNO3 H2SO4 + H2O SO2 H2SO4 SO3H RCl, AlCl3 (R can rearrange) R + HCl RC-Cl, AlCl3 O R O Nitration 硝 化 Sulfonation 磺 化 Friedel-Crafts Alkylation 弗瑞德尔-克拉伏茨 烷基化 Friedel-Crafts Acylation 弗瑞德尔-克拉伏茨 酰基化
15.2 A general mechanism for electrophilic aromatic substitution(芳香族亲电取代反 应机理): Arenium ions(芳基离 子) a considerable body of experimental evidence indicates that electrophiles attack the Isystem of benzene to form a delocalized nonaromatic carbocation known as an arenium ion or sometimes as a complex)
15.2 A general mechanism for electrophilic aromatic substitution（芳香族亲电取代反 应机理）: Arenium ions（芳基离 子） A considerable body of experimental evidence indicates that electrophiles attack the πsystem of benzene to form a delocalized nonaromatic carbocation known as an arenium ion (or sometimes as a σcomplex) π
+E H Arenium ion(芳基正离子) σ- complex(o络合物) E E H H
E + H + H + E + E + E H + E H + E H + Arenium ion (芳 基 正 离 子 ） σ- complex (σ-络 合 物 ）
We wish to show the mechanism using the modern formula for benzene Rate-determining Step 1 Slow Arenium ion(芳基正离子) E σ- complex(-络合物) Fast E Step 2 H+
We wish to show the mechanism using the modern formula for benzene. + E + Arenium ion (芳 基 正 离 子 ） σ- complex (σ-络 合 物 ） Step 1 E + H Step 2 E + H E + H + Rate-determining Slow Fast