例2:下列消除反应是经过E1还是E2? CH3 EtoH CH 3 CH CH3CH2CCI CH3 CHECCH3 CH3 CH2C=CH2 Br 主要 次要 3°R-X EtOH碱性较弱 是E1机理,有两个β位立氢可消除 b CH CH CH3CH==CCH3 HBr CH Br CH3CH2CCH3 CH3CH--C-CH2 b CH3 CH3CH2C=CH 2+ HBr⚫ 例2：下列消除反应是经过E1还是E2？ CH3CH2CCH3 Br CH3 b b' CH3CH C CH2 H CH H 3 - Br a Br b a CH3CH CCH3 CH3 b CH3CH2C CH2 CH3 + HBr + HBr 3 o R－X EtOH 碱性较弱 CH3CH2CCH3 Br CH3CH CCH3 CH3CH2C CH2 + 主要 次要 CH3 CH3 CH3 b b' EtOH 是E1 机理，有两个b位氢可消除