DETA-H2O (secondary amine), a widely used amine-solvent solution, is first taken as an example, along with its three typical conformers of transition states (Fig. ). The IGMH results for the transition state conformers in the DETA-H2O system is shown in and the N atom in amine (1C-7N), as well as the relative activation Gibbs free energies of the transition state conformers in the DETA-H2O system, are given in Tab. 2. From Figs. and, it is seen that the O atom in CO2 has a weak interaction (hydrogenbonding interaction) with the H atom in amine among three conformers. This hydrogenbonding interaction is beneficial to the attractions between 1C-7N reactive sites, the interaction of which is also identified in Fig. . From Tab. 2 it is found that the ADCH charge difference of 1C-7N in the conformer (Fig. ). This result is also consistent with the qualitative ranking of relative activation Gibbs free energies, which confirms the validity of the calculated results regarding activation Gibbs free energies to some extent. The ADCH charge differences among reactive sites could provide an explanation for the variations in energy caused by conformational changes. the ADCH charge differences between the C atom in CO2 and the O atom in water (1C-5O), those between the N atom in amine and the H atom in water (7N-4H), as well as the summation of the 1C-5O and 7N-4H charge differences are considered in this example. The ADCH charge differences, as well as the relative activation Gibbs free energies of the transition state conformers in the MDEA-H2O system, are given in Tab.