In this section, we investigate an apparent outlier in the reported experimental KIE values in chloroform as solvent, 1.98 vs 2.08-2.17 for aprotic solvents @250K. There was no supporting evidence for this anomaly from the continuum solvent model calculations (Table ). Chloroform, unlike the other solvents, has the ability to form weak hydrogen bonds and this suggests that we may have to consider solvent models in which one or more explicit molecules supplement the continuum solvent. A model including just one chloroform hydrogen-bonded to oxygen (Figure ) shows a KIE250 reduced to 1.952 from 2.124 (B3LYP/Def2-TZVPP) and to 1.758 if a third-generation dispersion correction model such as B3LYP+GD3+BJ/Def2-TZVPP is used, for which KIE250 = 1.800 (Table ).