The computed free energies of binding for both IBU and KET are presented in Table . In the same table, we also present computed enthalpies of binding (∆H bind ) and entropies of binding (T ∆S bind ). We observe that the free energies of binding of the down configurations are -3.6 ± 0.3 kcal/mol and -2.3 ± 0.3 kcal/mol for IBU and KET, respectively. Within the presented uncertainties, IBU is thus predicted to be a better binder than KET. We note that there is no difference (∆G bind = -0.8 ± 0.3 kcal/mol) between either compound when placed in the up orientation and from this we deduce that for both IBU and KET the preference for the down orientation is most likely due to the hydroxy groups on the primary side interacts favorably with the negative charge of the carboxylate on either guest molecule.