Advices For Studying Organic Chemistry

Substituent Compound Relative Rate

Methyl CH 3 X 30

1° CH 3 CH 2 X 1

2° (CH 3 ) 2 CHX 0.02

Neopentyl (CH 3 ) 3 CCH 2 X 0.00001

3° (CH 3 ) 3 CX ~0

i) Neopentyl halids are primary halides but are very unreactive.

H 3 C C CH 2

CH 3

CH 3

X A neopentyl halide

2. 
   

   Steric effect:
   i) A steric effect is an effect on relative rates caused by the space-filling
   properties of those parts of a molecule attached at or near the reacting site.
   ii) Steric hindrance: the spatial arrangement of the atoms or groups at or near the
   reacting site of a molecule hinders or retards a reaction.
   iii) Although most molecules are reasonably flexible, very large and bulky groups
   can often hinder the formation of the required transition state.

   
   


3. 
   

   An SN2 reaction requires an approach by the nucleophile to a distance within
   bonding range of the carbon atom bearing the leaving group.
   i) Substituents on or near the reacting carbon have a dramatic inhibiting effect.
   ii) Substituents cause the free energy of the required transition state to be
   increased and, consequently, they increase the free energy of activation for the
   reaction.