HARDNESS PROFILES OF SOME 1,2-HYDROGEN SHIFT REACTIONS

Ab initio SCF/6-31G* calculations are performed on the 1,2-hydrogen s hift reaction in some HAB molecules and HAB(+) ions (AB = CN, SiN, BO, AlO, BS, AlS, BeF, CO, SiO, CS, N-2) in order to test the validity of the maximum hardness principle. The hardness is found to be a good in dicator of the more stable isomer in most cases, as is the chemical po tential. Profiles of these quantities, as a function of the reaction c oordinate, do not exhibit extrema at the transition state, but other e xtrema are noted at unexpected points. While the total energy does not exhibit the same behavior as the hardness or the chemical potential, the individual electronic and nuclear repulsion energies are in close parallel with them.