 Factors that affect the rate determining step are stereochemistry, leaving groups, and base strength.A theory, for an E2 reaction, by Joseph Bunnett suggests the lowest pass through the energy barrier between reactants and products is gained by an adjustment between the degrees of Cβ-H and Cα-X rupture at the transition state.The adjustment involves much breaking of the bond more easily broken, and a small amount of breaking of the bond which requires more energy.