Nucleophilic Substitutions And Eliminations 091114

  • June 2020
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CH 231 (Shaughnessy) 1  SN1 vs SN2 vs E1 vs E2  

1° RX  Reaction Type  Requirements    Small or straight‐chain, basic nucleophile  ( , , , , etc.)   

Only occurs with hindered strong bases  ,   2,2,6,6

Example  ,     



 

2° RX  Reaction Type  Requirements    Strong non‐basic nucleophiles   

,

,

:  

Basic nucleophiles 

 &  1 

 

,

 

Example  S‐2‐iodopentane 

 R‐2‐cyanopentane

2‐bromopropane 

2° allyli/benzylic (because of   stabilization)  Neutralor acidic conditions &/or protic solvents  1 perferred with better nucleophiles ( , , No good nucleophile present 

 

:

(7%;  2) 3‐methyl‐1‐butyne +   (93%;  2) propene + ethyne  3‐bromo‐1‐cyclohexene   .  

1,3‐cyclohexadiene ( 1  +  3‐hydroxyl‐1‐cyclohexene  cyclohexanol  ,   

 

cyclohexene + water + 

 

3° RX  Reaction Type  Requirements    Doesn’t happen    Basic conditions  ,  &  1 

 

 

Example    (R,R)‐3‐bromo‐3,4,5‐trimethylhexane  ,

,

:

 

Non‐basic or acidic conditions 

Z‐2,3,4‐trimethyl‐3‐hexene  2‐bromo‐2‐methylpropane 

No good nucleophile present 

(80%;  1) methyl‐tertbutyl‐ether +  (20%;  1) 2‐methyl‐propene    1‐methyl‐1‐hydroxylcyclohexane 

 

(minor;  1) 1‐methyl‐1‐( )‐cyclohexane +  (major;  1) 1‐methylcyclohexene  (because   is a poor nucleophile)   

Tom Bertalan 

 

[email protected] 

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