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Typical at glance but interesting when analyzed in detail: A story of Tris hydration.
- Source :
- Journal of Chemical Physics; 12/14/2022, Vol. 157 Issue 22, p1-15, 15p
- Publication Year :
- 2022
-
Abstract
- This paper provides results of dielectric relaxation (DR) spectroscopy of aqueous solutions of tris(hydroxymethyl)aminomethane (Tris) covering frequencies of 0.05 ≤ ν/GHz ≤ 89. The DR spectra can be well fit by a sum of Cole–Cole relaxation, assigned to the solute, and 2 Debye modes already observed for neat water. Analysis of the amplitudes reveals that Tris is hydrated by 7 H<subscript>2</subscript>Os up to its solubility limit. However, the rather high effective solute dipole moment of ≈12 D suggests that H<subscript>2</subscript>O dipoles in contact with Tris should reorient independently from it. Accordingly, an alternative description of the DR spectra with a superposition of 4 Debyerelaxations was attempted. In this model, the slowest mode at ∼4 GHz arises from solute reorientation and that at ∼8 GHz was assigned to dynamically retarded hydration water, whereas relaxations at ∼18 and ∼500 GHz are again those of (rather unperturbed) bulk water. Analysis of the solvent-related modes shows that Tris indeed slows down 7–8 H<subscript>2</subscript>O molecules. However, the solute–solvent interaction strength is rather weak, excluding the rotation of an alleged Tris-(7–8) H<subscript>2</subscript>O cluster as an entity. The now derived effective dipole moment of (6.3 ± 0.5) D for the bare Tris molecule allows speculations on its conformation. With the help of computational methods, we suggest that Tris dissolved in water most likely possesses an intramolecular H-bond between the nitrogen and hydrogen atoms of amino and hydroxyl groups, respectively. In addition, computational results indicate that the seven hydration H<subscript>2</subscript>Os found by DR bind directly to the Tris OH groups. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 00219606
- Volume :
- 157
- Issue :
- 22
- Database :
- Complementary Index
- Journal :
- Journal of Chemical Physics
- Publication Type :
- Academic Journal
- Accession number :
- 160822570
- Full Text :
- https://doi.org/10.1063/5.0128391