Final answer:
In E2 eliminations, the β-hydrogen atom and the leaving group must be antiperiplanar to each other to facilitate the transition state needed for the elimination to occur. The E2 mechanism is a bimolecular reaction favored by steric hindrance and strong bases.
Step-by-step explanation:
For most E2 eliminations, a transition state conformation where the leaving group and the β-hydrogen atom are antiperiplanar to one another is necessary. This arrangement of space makes it easier for the base to remove the proton at the same time as the leaving group leaves, which results in the formation of a double bond. The base and the substrate are the two molecular entities involved in this fundamental reaction step, as indicated by the E2 mechanism, which is a bimolecular reaction. Additionally, because both of these mechanisms require a base and an electronegative leaving group, they frequently compete with one another. Stronger bases and increased steric hindrance, however, are in favor of the E2 mechanism.