Effect of fluorine substitution, pressure and temperature on the tautomeric equilibria of acetylacetonate β-diketones

Wallen, Scott L.; Yonker, Clement R.; Phelps, Cindy L.; Wai, C. M.

doi:10.1039/a701851g

Cited by 56 publications

(46 citation statements)

References 3 publications

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“…The actual keto-enol tautomerisation is the exchange between the vinylic CH and enol OH sites [11]. By keeping the nuclei in a radio frequency (RF) (1-600 MHz) field of appropriate frequency, two different energy states are produced due to the alignment of the nuclear magnetic moments relative to the applied field and a transition between these energy states takes place.…”

Section: Nuclear Magnetic Resonance Spectroscopymentioning

confidence: 99%

Direct in situ supercritical fluid extraction of neodymium ion from its oxide using thenoyl tri fluoro acetone–tri butyl phosphate–methanol in carbon dioxide

Vincent

Mukhopadhyay

Wattal

2009

The Journal of Supercritical Fluids

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Section: Nuclear Magnetic Resonance Spectroscopymentioning

confidence: 99%

Direct in situ supercritical fluid extraction of neodymium ion from its oxide using thenoyl tri fluoro acetone–tri butyl phosphate–methanol in carbon dioxide

Vincent

Mukhopadhyay

Wattal

2009

The Journal of Supercritical Fluids

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“…), easy to determine by NMR, has been used to study solvent effects [5], relationships between NMR and IR [6], electronic effects (for other substituents) [7] [8], as well as pressure and temperature effects [8] [9]. The kinetics part of the proton transfer through the intramolecular H-bond between 1a and 1c (k 3 À k À3 ; K ee [1a]/[1c] 1) remains unknown.…”

mentioning

confidence: 99%

Solid‐State NMR Study of the Tautomerism of Acetylacetone Included in a Host Matrix

Claramunt

López

Lott

et al. 2005

Helvetica Chimica Acta

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The tautomerism of the enol form of acetylacetone (=pentane‐2,4‐dione; 1) inside a host cavity has been studied by means of solid‐state 13C‐NMR spectroscopy (SSNMR) using the variable‐temperature CPMAS technique. It appears that the enol form, 4‐hydroxypent‐3‐en‐2‐one (1a), exists in an equilibrium with an identical tautomer (1c) trough OH ⋅⋅⋅O proton transfer. The experimental results (energy barrier and chemical shifts) were rationalized by means of MP2 and GIAO calculations.

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“…TTA is a solid at room temperature and is easy to handle compared to the other liquid fluorinated β-diketones such as hexafluoroacetyl acetone (HFA) and trifluoroacetyl acetone (TFA). Recent NMR studies show that the fluorinated β-diketones HFA and TTA are almost exclusively in the enol form under the temperature and pressure conditions relevant to SFE systems (17). The nonfluorinated ligand AA is found to be only partly in the enolate form in supercritical C0 2 .…”

Section: Supercritical Fluid Extraction Of Mobile Uranium From Enviromentioning

confidence: 98%

Extraction and Separation of Uranium and Lanthanides with Supercritical Fluids

Wai

Lin

et al. 1999

ACS Symposium Series

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Uranyl ions in nitric acid solutions can be effectively extracted by supercritical CO 2 containing tributyl phosphate (TBP) or organophosphine oxides. The form of the extracted uranyl nitrate-TBP complex and the kinetics of the supercritical extraction are similar to those reported for the conventional solvent extraction of uranyl nitrate with TBP. On-line back-extraction of uranium in supercritical CO 2 with an aqueous solution has also been demonstrated. The results suggest that supercritical CO 2 could be as effective as the organic solvents used in the PUREX process. Supercritical CO 2 containing organophosphinic acids such as Cyanex 301 and Cyanex 302 has been shown to extract heavy lanthanides selectively from the light lanthanides in aqueous solutions. This in situ chelation-SFE technique is also capable of removing leachable uranium from solid samples such as mine tailings as indicated by the EPA Toxicity Characteristics Leaching Procedure.There has been considerable interest in the past two decades to utilize supercritical fluids as solvents for chemical separations (i). The reasons for developing supercritical fluid extraction (SFE) technologies are mostly due to the environmental regulations and waste disposal costs for conventional solvents. Supercritical fluids have both gas-like and liquid-like properties. The solvation power of a supercritical fluid depends on pressure and temperature; thus, one can achieve the optimum conditions for a particular separation process by manipulating the temperature and pressure of the fluid phase. The high diffusivity and low viscosity of supercritical fluids enable them to penetrate and transport solutes from solid matrices. Carbon dioxide is the most widely used gas for SFE because of its moderate critical constants (T c = 31.3 °C, P c = 72.9 atm), nontoxic nature, and availability in pure form. In SFE processes, solutes dissolved in supercritical carbon dioxide are separated by reducing 390 In Metal-Ion Separation and Preconcentration; Bond, A., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1999. 391the pressure of the fluid phase causing precipitation of the solutes. The fluid phase is usually expanded into a collection vessel to remove the solutes and the gas is recycled for repeated use. Typical examples of large-scale industrial applications of the SFE technology using supercritical C0 2 include the preparation of decaffeinated coffee and hop extracts (1).Until recently, little information was available in the literature regarding SFE of metal species. Direct extraction of metal ions is highly inefficient because of the charge neutralization requirement and the weak solute-solvent interactions. However, when metal ions are chelated with organic ligands, they may become quite soluble in supercritical C0 2 (2). This in situ chelation-SFE technique appears to have a wide range of applications including the treatment of metal contaminated or radioactive waste materials and mineral processing.Background

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Effect of fluorine substitution, pressure and temperature on the tautomeric equilibria of acetylacetonate β-diketones

Cited by 56 publications

References 3 publications

Direct in situ supercritical fluid extraction of neodymium ion from its oxide using thenoyl tri fluoro acetone–tri butyl phosphate–methanol in carbon dioxide

Direct in situ supercritical fluid extraction of neodymium ion from its oxide using thenoyl tri fluoro acetone–tri butyl phosphate–methanol in carbon dioxide

Solid‐State NMR Study of the Tautomerism of Acetylacetone Included in a Host Matrix

Extraction and Separation of Uranium and Lanthanides with Supercritical Fluids

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