E1 and E2 Reactions

Add yours
Organic Chemistry | E1, E2, SN1 and SN2 Practice Question - Rearrangement.

Tip: This isn't the place to ask a question because the teacher can't reply.

1 of 2 videos by Dr. Hayek

Key Questions

  • Answer:

    The video below gives a quick description of what is involved in an elimination reaction.

  • Answer:

    E1 reactions are unimolecular elimination reactions.


    A carbon-leaving group bond will be homolytically broken creating a carbocation intermediate. The carbocation and leaving group anion are stabilized by a polar, protic solvent. A nucleophile (usually weak and can also be the same as the solvent) will attack the adjacent, beta hydrogen, and the C-H bond electrons will move to form a new pi C-C bond. The leaving group and the beta hydrogen were eliminated from the starting material.

  • First of all, an elimination reaction is a type of organic reaction in which two substituents are removed from a molecule in either a one or two-step mechanism.

    • The one-step mechanism is known as the E2 reaction
    • The two-step mechanism is known as the E1 reaction.

    Note: The numbers do not have to do with the number of steps in the mechanism, but rather the kinetics of the reaction, bimolecular and unimolecular respectively.

    What is E2 mechanism?

    • E2 is the first step of elimination with a single transition state .

    • Typically undergone by primary substituted alkyl halides, but is possible with some secondary alkyl halides.

    • The reaction rate is second order.
    • E2 typically uses a strong base, it needs a chemical strong enough to pull off a weakly acidic hydrogen.
    • E2 competes with the SN2 reaction mechanism.


Videos on topic View all (20)

Nucleophilic Substitution Reactions (SN1 and SN2) and Elimination Reactions (E1 and E2)