An insight into hydration structure of sodium glycinate from <Emphasis Type="Italic">ab initio</Emphasis> quantum chemical study

The hydration structure of sodium glycinate (Na⁺GL^?) is probed by the Monte-Carlo multiple minimum (MCMM) method combined with quantum mechanical (QM) calculations at the MP2/6-311++G(d,p) level. In the gas phase, the energy of Na⁺GL^?]_β is more than 30 kJ mol^?1 higher than Na⁺GL^?]_α. With higher degrees of hydration, our results indicate that the most stable conformers of Na⁺GL^?]?(H₂O)₈ were derived from Na⁺GL^?]_β instead of Na⁺GL^?]_α. The stable conformers determined by the conductor-like polarizable continuum model (CPCM) also show that Na⁺GL^?]_β is more stable than Na⁺GL^?]_α in the liquid phase. By analyzing the hydration process, water…water hydrogen bonding interaction will be more preferable than ion…water interaction as the number of water molecules increases. According to the electronic density at the bond critical point on the Na-X bonds (X?=?O1, O2, N) in the low-energy conformers, Na⁺GL^? will be dissociated as Na⁺ and GL^? in the bulk water, which is not predicted by the CPCM model. The structure features and the charge redistribution of Na⁺GL^? will provide a physical explanation for the weakening Na-O1 interaction.

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Graphical Abstract Hydration structure of sodium glycinate from ab initio quantum chemical study