Solvent Modification in Ion-Pair Extraction: Effect on Sodium Nitrate Transport in Nitrobenzene Using a Crown Ether
A comparative quantitative analysis of the effect of solvent modifiers on an ion-pair extraction of an inorganic salt by a crown ether was conducted. Two classes of the solvent modifiers that possess electron-pair donor (EPD) or hydrogen-bond donor (HBD) groups were investigated. The equilibrium constants corresponding to the extraction of sodium nitrate into nitrobenzene (NB) employing model neutral host cis-syn-cis-dicyclohexano-18-crown-6 (1) with and without solvent modifier were determined using the SXLSQI computer model. For a series of EPD modifiers—including tri-n-butyl- and tri-phenylphosphate, tri-n-butyl- and tri-phenylphosphine oxide, N,N-di-n-butyl- and N,N-di-phenyl acetamide—the enhancement of the NaNO3 extraction by 1 was found to be dependent on the hydrogen-bond acceptance ability of the modifier quantified by the b solvatochromic parameter. Application of the solvent EPD modifier improved solvation of the sodium ion, lowering the large energy barrier of Na+ partitioning into the extraction phase. A HBD modifier 3,5-di-t-butylphenol 8 that forms strong hydrogen bonds with nitrate anion in NB, exhibited even greater enhancement of the NaNO3 extraction by 1. The determined extraction constants were correlated with the b or a solvatochromic parameters of the solvent modifiers and linear trends were observed. Hydrogen bond interaction between 3,5-di-t-butylphenol 8 and nitrate anion in the presence of the sodium-loaded crown ether in the extraction phases was studied by vibrational spectroscopy. Formation of the simple 1:1 adduct was demonstrated.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 876899
- Report Number(s):
- PNNL-SA-44252; JSLCAG; KP1302000; TRN: US200608%%282
- Journal Information:
- Journal of Solution Chemistry, 34(10):1145-1166, Vol. 34, Issue 10; ISSN 0095-9782
- Country of Publication:
- United States
- Language:
- English
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