The final components needed for calculating kinetic isotope effects are the normal vibrational modes for the reactant, which require all 3N-6 modes to be all real, deriving from only positive eigenvalues for the force constant matrix. The total and free gas phase energies of both the exo-and endo-isomers matched those reported, with gradient norms < 10 -5 au. When a solvent field is applied, the result again differs. For example for dichloromethane, although the total reactant energies for 2 and 3 match the reported values, the presence of two negative force constants resulted in two imaginary modes for both the 3 and 2 of respectively 36.3i/17.7i cm -1 and 143.7i/2.8i cm -1 , with relatively large associated gradient norms of 0.000732 and 0.000766 au. One further example illustrates the general nature of this issue. For chlorobenzene as solvent, the endo- and exo-29 transition states at the original geometries have respectively three (1467.8i/331.2i/183.2i) and two (366.6i/126.9i) imaginary modes, whilst the reactants have respectively two (49.7i/26.0i) and zero, suggesting the effect of unwanted imaginary modes is unpredictable.