E2 Stereochemistry

When the beta-carbon has two protons, the more stable alkene will be formed (the one with less steric interference, like trans over cis). When there is only one beta-proton, the substrate must be in a rotational conformation in which the torsion angle between the beta-proton and the leaving group are "anti-periplanar" to each other, thus determining whether the alkene formed is (E) or (Z)