E1-Elimination

The E1 elimination reaction is a two-step mechanism in which the leaving group leaves first followed by deprotonation and formation of an alkene.  The rate-determining step (RDS) or slow step is the dissociation of the leaving group to form a carbocation intermediate.

• Typically only 3^o alkyl halides and tosylates undergo E1 elimination (carbocation intermediate).
• A weak or no base at all usually suffices.
• 3^o alcohols will eliminate under acidic conditions.
• Rate is proportional to the alkyl halide concentration and is independent of the nature and concentration of base..
  • Rate = =k [RX]
  • 1st order kinetics
• No stereochemistry but regiochemistry controlled by Zaitsev's Rule.
• Dissociation of halide or tosylate in the RDS.  The transition state resembles a carbocation explaining why 3^o halides are the fastest.