E2 - Mechanism Introduction

Time to discuss the most complicated mechanism of the bunch, E2. It’s an awesome reaction, but there are a few extra details we’re gonna have to keep track of!

Summary: A negatively charged nucleophile reacts with an inaccessible leaving group to produce beta-elimination in one-step.

Properties of E2 reactions:

  • Nucleophile =  Strong
  • Leaving Group =  Substituted
  • Reaction coordinate = Transition State
  • Reaction = Concerted
  • Rate =  Bimolecular
  • Rate =  k[Nu][RX]
  • Stereochemistry = Anti-Coplanar

Example: Rank the following alkyl halides in order of reactivity toward E2 reaction.