12-16 1. CH3 CH SN2 SN2 CI H OH (R) (R) 2 CHs CH C玛 CH3 “CL C+K C.HS HO H H C2Hs (R) SN1反应历程 HO 12-17 1.A>B>C>D 2.A>B>C>D 12-18 有3个立体异构体（一对对映体和一个内消旋体）》 Br CH3 B氏CH H ·HBr -CH3 -Br 三H H Br ∠BrCH H CH3 (内消旋体) Br Br CH Br CH H -Br Br CH -H CH CH Z- (外消旋体2S,3SR3) 6 12-16 2. 12-17 1.A>B>C>D 2. A>B>C>D 12-18 { 3 }Ƀ‚[ƒ²;€€ƒ„;}…†‡ƒµ Br Br CH3 Br H CH3 CH3 CH3 H H H Br CH3 CH3 H Br Br H CH3 Br H CH3 ✷✹✸✬✺✑✻✛✼✾✽ (E ) - HBr Br H CH3 CH3 H Br H Br CH3 CH3 Br H Br H CH3 Br H ✿❁❀❃❂✞❄❃❅ ❆❈❇❉❆✌❊●❋❍❇❃❋✹■ H CH3 CH3 Br -HBr (Z ) CH3 2 3 2 3 SN2 (R) (S) (R) H C2H5 CH3 OH C H OH - I C2H5 CH3 C SN2 I H C2H5 CH3 Cl C
HO - HO H CH3 C + C2H5 + - Cl SN 1
 (R) (S) H C2H5 CH3 OH C H C2H5 CH3 C H C2H5 CH3 Cl C