(exo) KIE ratios at 250K are 1.660 and 1.679 (Lit. 1.62 and 1.72, Table 9 ) using Gaussian 03 solvation models and at 195K they are 1.907 and 1.938 (Lit. 1.85 and 1.72; the temperature was not stated, but is here inferred 9 ). Using a value of DDG195= 0.495 kcal/mol gives the ratio of k4/k2 as 3.59, combining this with ) !