Advices For Studying Organic Chemistry

Table 6C Relative rates for the reaction of 2-chloro-2-methylpropane with

different solvents

Solvent Relative rate

Ethanol 1

Acetic acid 2

Aqueous ethanol (40%) 100

Aqueous ethanol (80%) 14,000

Water 105

6.14E THE NATURE OF THE LEAVING GROUP

1. Good Leaving Group:
   
   
   1. The best leaving groups are those that become the most stable ions after they
      depart.
   
   
   2. Most leaving groups leave as a negative ion ⇒ the best leaving groups are those
      ions that stabilize a negative charge most effectively ⇒ the best leaving groups
      are weak bases.
   
   
   
   


2. The leaving group begins to acquire a negative charge as the transition state is
   reached in either an SN1 or SN2 reaction.
   SN1 Reaction (rate-limiting step)

C X Cδ+ Xδ− C+ + X−

Transition state
SN2 Reaction

C X C X

Nu − δ−Nu δ− Nu C + X−

Transition state

1) Stabilization of the developing negative charge at the leaving group stabilizes