Since 3N-6 real modes for reactants and 3N-7 for transition states are required to evaluate the Bigeleisen-Mayer equation for harmonic kinetic isotope effects, we cannot directly replicate the previously reported KIE values, in part because we do not have access to the normal mode wavenumbers obtained in the original work. Instead, we will use new values obtained by geometry re-optimisation which do satisfy the condition, whilst still using G03 settings. The relative energies in dichloromethane replicate well; for endo-exo (TS) DDG298 = 0.52, DDG250 0.51 and DDE 0.42 kcal/mol, the latter comparing with DDE = 0.40 kcal/mol reported 9 (gas phase). The transition state normal mode wavenumbers are respectively 281.5i and 271.5i vs literature values 9 of 286i and 272i cm -1 .