How do sn1 reactions differ from sn2 reactions?

1 Answer

Consider the following points of difference.


SN1 Reaction

  • It is Substitution Nucleophilic Unimolecular reaction.
  • Proceeds in two steps.
  • First step is the slow one involving dissociation of the substrate to form carbocation intermediate. Second step is the fast one in which the carbocation combines with the attacking Nucleophile.
  • More stable carbocation #rarr# faster is the reaction
  • It is favored by polar solvents.
  • Mostly given by tertiary alkyl halides.
  • It occurs with Racemization.
  • It follows #1^(st)# order kinetics.
  • Rate=k[R-X]
(Image source only)

SN2 Reaction

  • It is Substitution Nucleophilic Bimolecular reaction.
  • Proceeds in a single step which is the rate determining step.
  • It is favored by non polar solvents.
  • Mostly given by primary alkyl halides.
  • Nucleophilic addition takes place from the opposite side of the Leaving group.
  • It occurs with 100% inversion of configuration.
  • It follows #2^(nd)# order kinetics.
  • Rate=k[R-X][Nu]
(Image source only)