(4)反应机理 1ROH (SN2) HH CHCH2—OH+ -Br Br CH3 Sx2.BrCH.CH HO-KBF Br1 oROH (SN2) SN2 SN2 Br Br BrCH HO P 2CH3 + CH3CH2 OH + P Br Br Br Br - + C O P H CH3 Br Br H H + (4)反应机理