S2反应的影响因素 CH CH3 CH HaC =0 M+ o=s CH3 O CH3 CH3 CH 3 3+CH 3 CH, CH,CH,-Br 3-CH,CH, CH2CH 3 Br Solvent CH3OH H,O DMSO DMF CH3CN HMPA relative re activity 1,3002,8005,000200,000 ess More re active re active
SN2反应的影响因素 N3 - N3 - CH2CH2CH2CH 3 + Br - + CH 3CH2CH2CH2 - Br Solvent CH3OH H2O DMSO DMF CH3CN HMPA relative reactivity 1 7 1,300 2,800 5,000 200,000 More reactive Less reactive S H3 C H3 C O S CH3 CH3 O S CH3 CH3 O S CH3 CH3 O S CH3 CH3 O S CH3 CH3 O S CH3 CH3 M+ O
2反应的影响因素 一 Hindered subs trate Poor leaving group Unhindered Good le aving subs trate group Poor nucleophile Protic solvent Good nucleon polar apron solvent
SN2反应的影响因素 Summary: The SN2 reaction is worst when carried out with a hindered substrate, a neutral nucleophile, and a protic solvent. 即位阻大的底物、中性（弱的）亲核试剂、 和质子性溶剂不利于SN2反应 Hindered substrate Unhindered substrate Poor leaving group Good leaving group Poor nucleophile Good nucleophile Protic solvent polar aprotic solvent
The s reaction R-Br +ho R-oH HBr H3C C—B C—B Br C-Br HRC H2c H H3C Relative reactivity <1 12 1200,000 Less M reactive reactive e What's going on here?---- an alternative substitution mechanism
The SN1 Reaction What’s going on here? ---- an alternative substitution mechanism H C Br H H H3 C C Br H H H3 C C Br H3 C H H3 C C Br H3 C H3 C R-Br + H2O R-OH + HBr Relative reactivity < 1 1 12 1200,000 Less reactive More reactive
The su reaction 1.SN1反应的动力学 级反应 V=k[R为] 2SN1反应的机理 般两步反应 ●—限速步骤是碳正离子的形成
The SN1 Reaction 1. SN1 反应的动力学 —— 一级反应 —— v = k [RX] 2. SN1 反应的机理 —— 一般两步反应 —— 限速步骤是碳正离子的形成
The s reaction CH3 CH3 H2C一C-Br H2C—C-OH CH3 CH3 Rate limiti ep OH 2 CH3 CH3 Fast H H2C一C Br H2C—C-0+ step OH2 CH
The SN1 Reaction H3 C C B r C H3 C H3 H3 C C + C H3 C H3 + Br - H3 C C O C H3 C H3 H H Rate -limiting step Fast step OH2 OH2 H3 C C OH C H3 C H3