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 con...

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Bibliographic Details
Published in:Journal of solution chemistry 2005-10, Vol.34 (10), p.1145-1166
Main Authors: LEVITSKAIA, Tatiana G, LUMETTA, Gregg J
Format: Article
Language:English
Subjects:
08 HYDROGEN
ADDUCTS
ANIONS
Chemistry
COMPUTERS
CROWN ETHERS
Exact sciences and technology
General and physical chemistry
HYDROGEN
MODIFICATIONS
NITRATES
NITROBENZENE
SODIUM IONS
SODIUM NITRATES
Solutions
SOLVATION
SOLVENTS
SPECTROSCOPY
TRANSPORT
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Summary: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.
ISSN:0095-9782
1572-8927
DOI:10.1007/s10953-005-7693-x