Initial conformations of the neutral, protonated and carbamate forms of the amines were generated using the Spartan v.18 software package with the default Merck Molecular Force Field (MMFF94). The 10 lowest energy conformers of each solute at the MMFF94 level were further optimized using the Gaussian 16 package, followed by frequency calculations using high-level composite methods (G4, G3, CBS-QB3 and CBS-APNO) to find the lowestfree-energy conformer for each QM method at 298.15 K. For a given QM method, the free energies of the most stable conformers were then used to calculate the ideal-gas reaction free energies at T = 298.15 K; to save computational time, the effect of temperature on the reaction free energy was implemented only using G4 calculations over the temperature range of 283.15-373.15 K according to: ∆G 0 j (T ; P 0 ) = ∆G 0 j (298.15; P 0 ) avg + [∆G 0 j (T ; P 0 ) -∆G 0 j (298.15;