With these two quantities, we can adequately explain stereoselectivity propensities for different species. As an illustrative example, shown in Fig. is the nucleophilic addition on the carbonyl group, whose stereoselectivity depends on the size of the groups at the Cα atom. The incoming electrophile prefers the side with a smaller group in the -carbon. This preference is unambiguously seen by the magnitude of the steric force shown for the two molecules in Fig. . We also applied the idea to SN2 reactions and justified the experimental finding that bulky groups on the central carbon substantially increase the reaction barrier height.