烯烃的亲电加成—HX和H2O .1 Mechanism of Electrophilic Addition slow fast C=C+H—Br: →=CC-+:: C-C H Br:H 亲电加成机理加 HX a carbocation dia two steps the formation of carbocation(碳正离 f) is the rate-determination step 活性、区域选择性、立体化学、重排反应
一、烯烃的亲电加成——HX 和 H 2 O 1.1 Mechanism of Electrophilic Addition 亲电加成机理－加HX —— two steps —— the formation of carbocation（碳正离 子）is the rate-determination step. 活性、区域选择性、立体化学、重排反应
mechanism for the acid-catalyzed addition of water CH3CH=CH2+H-OH、slow fast CH3 CHCH3 H2O:F CH3 CHCH H酸催化 OH H H2O: fast 亲电加成机理一加水 CHaCHCHa hO OH SlOw fast CH3CH=CH2 H--OCH3 CH3 CHCH3 CH3OH CH3 CHCH3 酸催化 OCH H CH3OH fast CH3CHCH3 CH3OH 亲电加成机理一加醇 OCH H
亲电加成机理－加水 酸催化 酸催化 亲电加成机理－加醇
烯烃的亲电加成—HX和H2O 1.2 Reactivity H-X C-C C-C fast H X 多烷基取代烯烃反应活性较高 当Y=C1时,△FP=-4142+431.0+2550=+271.8 kJ. mol-1 当YBr时,△F=-4112+3640+250=+2048kJmo1 当Y=I时,△F2=-414.2+2971+255.0=+1379kJmo1 当Y=OH时,△HO=-414,2+4644+255.0=+305.2 kJmol1 reaction activity HI> HBr> HCI 气相中烯烃与水加成活性最低 由于溶剂化作用,液相中的反应比气相快
一、烯烃的亲电加成——HX 和 H 2 O 1.2 Reactivity C C C C X C C H H X H X slo w fa st ——多烷基取代烯烃反应活性较高 当Y=Cl 时,Δ HӨ r= - 414.2 + 431.0 + 255.0 = + 271.8kJ·mol-1 当Y=Br 时,Δ HӨ r= - 414.2 + 364.0 + 255.0 = + 204.8 kJ·mol-1 当Y=I 时,Δ HӨ r= - 414.2 + 297.1 + 255.0 = + 137.9 kJ·mol-1 当Y=OH时,Δ HӨ r= - 414.2 + 464.4 + 255.0 = + 305.2 kJ·mol-1 —— reaction activity: HI > HBr > HCl ——气相中烯烃与水加成活性最低 ——由于溶剂化作用，液相中的反应比气相快
烯烃的亲电加成—HX和H2O 1.3 Regioselectivity ● Markovnikoy's rule(马氏规则) when an alkene undergoes electrophilic addition, the less highly substituted position is attached by the electrophile(亲电试剂) ●其本质的原因是碳正离子的形成是亲 电加成的限速步骤
一、烯烃的亲电加成——HX 和 H 2 O 1.3 Regioselectivity z Markovnikov ’s r ule （马氏规则 ） —— when an alkene undergoes electrophilic addition, the less highly substituted position is attached by the electrophile (亲电试剂). z 其本质的原因是——碳正离子的形成是亲 电加成的限速步骤
CH CH CH3 CCH3 CH3CCH tert-butyl cation CH More stable CH2C=CH Hcl only product formed CH CH3 CH2 CHCH2 C CHCHChCI isobutyl cation isobutyl chloride t formed H CHrCH-CH, H,O Ch2CHCH OH H CHrCH-CH+Choh CH3 CHCH3 OCH
More stable