Semiempirical SCF‐MO calculations of kinetic isotope effects

Carbon and deuterium kinetic isotope effects (KIEs) on the isomerization of methyl isocyanide were calculated by using the geometries and force fields obtained with MNDO, AM1 and PM3 Hamiltonians. These theoretical KIE values were compared with the corresponding experimental values. None of the hamiltonians used proved to be superior to any of the others. The best agreement for the carbon isotope effect was obtained by using the PM3 method; however, the deuterium isotope effect obtained by this method gave the poorest fit to the experimental data. The opposite is true when the MNDO Hamiltonian was used.