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Structure of aqueous sodium acetate solutions by X-Ray scattering and density functional theory.
- Source :
- Pure & Applied Chemistry; Oct2020, Vol. 92 Issue 10, p1627-1641, 15p
- Publication Year :
- 2020
-
Abstract
- The structure of aq. sodium acetate solution (CH<subscript>3</subscript>COONa, NaOAc) was studied by X-ray scattering and density function theory (DFT). For the first hydrated layer of Na<superscript>+</superscript>, coordination number (CN) between Na<superscript>+</superscript> and O(W, I) decreases from 5.02 ± 0.85 at 0.976 mol/L to 3.62 ± 1.21 at 4.453 mol/L. The hydration of carbonyl oxygen (OC) and hydroxyl oxygen (OOC) of CH<subscript>3</subscript>COO<superscript>−</superscript> were investigated separately and the OC shows a stronger hydration bonds comparing with OOC. With concentrations increasing, the hydration shell structures of CH<subscript>3</subscript>COO<superscript>−</superscript> are not affected by the presence of large number of ions, each CH<subscript>3</subscript>COO<superscript>−</superscript> group binds about 6.23 ± 2.01 to 7.35 ± 1.73 water molecules, which indicates a relatively strong interaction between CH<subscript>3</subscript>COO<superscript>−</superscript> and water molecules. The larger uncertainty of the CN of Na<superscript>+</superscript> and OC(OOC) reflects the relative looseness of Na-OC and Na-OOC ion pairs in aq. NaOAc solutions, even at the highest concentration (4.453 mol/L), suggesting the lack of contact ion pair (CIP) formation. In aq. NaOAc solutions, the so called "structure breaking" property of Na<superscript>+</superscript> and CH<subscript>3</subscript>COO<superscript>−</superscript> become effective only for the second hydration sphere of bulk water. The DFT calculations of CH<subscript>3</subscript>COONa (H<subscript>2</subscript>O)<subscript>n=5–7</subscript> clusters suggest that the solvent-shared ion pair (SIP) structures appear at n = 6 and become dominant at n = 7, which is well consistent with the result from X-ray scattering. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 00334545
- Volume :
- 92
- Issue :
- 10
- Database :
- Complementary Index
- Journal :
- Pure & Applied Chemistry
- Publication Type :
- Academic Journal
- Accession number :
- 146468070
- Full Text :
- https://doi.org/10.1515/pac-2020-0402