Alchemical Methods. Simulation parameters were reconsidered after submission to examine which variables are more reliable for quantitatively accurate predictions. While the box size and type have negligible effects on the solvation free energy, these include using more walkers, longer and consistent simulation times for all systems, as well as changing the van der Waals and Coulomb interactions independently for a longer λ path (see ESI). These parameters were shown to increase the robustness of the AWH method in the original publication modeling the solvation free energy of ethanol in water. These simulations ran for 5 ns with a timestep of 2 fs in quintuplicate to generate error estimates. This method will be denoted as the MM-1 method.