Predominantly orbital effects determine the pre ferred syn attack of electrophiles on the norbornane derivative 1 bearing an electron‐withdrawing endo substituent. This finding is the result of topological analyses of the electrostatic potentials from ab initio calculations and a comparison of the energies of the transition states calculated with semiempirical methods. R = CN, COOCH3. (Figure Presented.) Copyright © 1994 by VCH Verlagsgesellschaft mbH, Germany