Appreciating Errors in Computation of Selectivity
Paton, Robert · Figshare · 2014
The figure ilustrates how errors in estimating the free energy difference between competing transition structures affect the resulting prediction of enantioselectivity at 298K. For an unselective reaction (measured ee = 0%), an error of up to 0.5 kcal/mol in the relative free energies of competing transition structures results in a predicted selectivity between +40 and -40% ee; increasing the error up to 1 kcal/mol results in a prediction between +70 and -70% ee. Due to the exponential relationship between enantioselectivity and free energy difference, and assuming a certain error in calculating relative energies, uncertainty in predicted ee values will be smaller for more highly selective reactions . Depending on the system being studied, a 1 kcal/mol error (or even larger) may be a reasonable estimate and so comparison of computed with experimental ee values should be performed with this variation in mind.