As shown in Figs. , for the molecules with multiple hydroxyl groups, namely TBAE, 2AEE, EAE, AEPD, AMPD, DEA, SAPD, the pK a simulations overestimate the experimental results. Since the ideal gas and the residual chemical potentials both contribute to the resulting pK a values, we are not able to pinpoint the source of the error, and it could be due to the well-known issue with the amine hydroxyl parameters of the GAFF and its hydration free energy prediction, or due to the error in the ideal gas QM prediction for species with multiple oxygen atoms, which are subjected to relatively larger uncertainty, as in the case of TEA with three hydroxyl groups. triangle left 8 plus 36 and star, and the curves are our simulation results. The error bar indicates the uncertainty at 298.15 K from the caption to Table . Deprotonation constant of methyldiethanolamine (MDEA), nethyldiethanolamine (EDEA),2-piperidinemethanol (2PIPM) and tert-butyldiethanolamine (t-BDEA) as function of temperature. Experimental data is shown by square, 6 diamond, triangle left 8 plus 36 and star, and the curves are our simulation results. The error bar indicates the uncertainty at 298.15 K from the caption to Table .