共查询到20条相似文献,搜索用时 640 毫秒
1.
Anderson JL Ding J Welton T Armstrong DW 《Journal of the American Chemical Society》2002,124(47):14247-14254
Room-temperature ionic liquids (RTILs) are useful in many chemical applications. Recent publications have attempted to determine the polarity of RTILs using empirical solvent polarity scales. The results have indicated that most RTILs have similar polarities. Nevertheless, RTILs are capable of behaving quite differently when used as solvents in organic synthesis, matrixes in matrix-assisted laser desorption/ionization (MALDI) mass spectrometry, liquid-liquid extraction, and as stationary phases in gas chromatography. The work presented in this study uses a linear free energy approach to characterize 17 RTILs on the basis of their distinct multiple solvation interactions with probe solute molecules. This model provides data that can be used to help identify the interactions and properties that are important for specific chemical applications. 相似文献
2.
Domínguez de María P 《Angewandte Chemie (International ed. in English)》2008,47(37):6960-6968
The application of room-temperature ionic liquids (RTILs) as (co)solvents and/or reagents is well documented. However, RTILS also have "nonsolvent" applications in biotransformations and organocatalysis. Examples are the anchoring of substrates to RTILs; ionic-liquid-coated enzymes (ILCE) and enzyme-IL colyophilization; the construction of biocatalytic ternary reaction systems; the combination of enzymes, RTILs, membranes, and (bio)electrochemistry; and ionic-liquid-supported organocatalysts. These strategies provide more robust, more efficient, and more enantioselective bio- and organocatalysts with many practical applications. As shown herein, RTILs offer a wide range of promising alternatives to conventional chemistry. 相似文献
3.
Ashraf Ghanem Author Vitae 《Tetrahedron》2007,63(8):1721-1754
Over the last few years, there has been a dramatic increase in the number of publications in the field of lipase-catalyzed reactions performed in common organic solvents, ionic liquids or even non-conventional solvents. A fairly large percentage of these publications have emerged from organic chemists who have recognized the potential of biocatalysis as a viable and popular technique in organic synthesis. Considerable research has shown that reactions catalyzed by enzymes are more selective and efficiently performed than many of their analogues in the organic chemistry laboratory. This review article focuses on some of the recent developments in the rapidly growing field of lipase-catalyzed asymmetric access to enantiomerically pure/enriched compounds. The literature search is dated back to the last five years and covers some comprehensive examples. 相似文献
4.
Many important applications of room temperature ionic liquids(RTILs), e.g., lubrication, energy storage and catalysis, involve RTILs confined to solid surfaces. In order to optimize the performance, it is critical to understand the wettability of nanometer-thick RTILs on solid surfaces. In this review, the recent progress in this filed is presented. First, the macroscopic wettability of RTILs on solids will be discussed briefly.Afterwards, the wetting of nanometer-thick RTILs will be discussed with the emphasis on RTIL/mica and RTIL/graphite interfaces since mica and graphite not only are mostly studied but also have important real-life applications. For RTIL/mica interface, the extended layering that promotes the wetting has been extensively reported and it is generally accepted that the electrostatic interaction at the RTIL/mica interface is the key. However, recent works from others and us highlight the unexpected effect of water:Water enables ion exchange between K+and the cations of RTILs on the mica surface and thus triggers the ordered packing of cations/anions in RTILs, resulting in extended layering. Different from mica, there is no electrical charge on the graphite surface. Interestingly, previous reports showed inconsistent results on the wettability of RTILs on graphite. Recent research from others and us suggested that π-π~+stacking between sp~2 carbon and the imidazoliumcation in the RTILs is the key to the extended layering and enhanced wettability of RTILs. Lastly, the future research directions will be briefly discussed. 相似文献
5.
《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(13):2938-2944
Room temperature ionic liquids (RTILs) have attracted a great deal of interest as environmentally benign (green) solvents for organic synthesis. More recently, RTILs that are chiral, less expensive, or functionalized (protic or Lewis basic) have been developed. In many cases, these new solvents are based on the modification of natural products. This paper is an overview of these new biorenewable RTILs. 相似文献
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7.
Aurora Martín-CaleroVerónica Pino Ana M. Afonso 《Trends in analytical chemistry : TRAC》2011,30(10):1598-1619
Ionic liquids (ILs) are non-molecular solvents, which are mainly characterized as possessing low melting points, low-to-negligible vapor pressures, and high thermal stability. Their unique solvation properties, coupled to the fact that they can be structurally tailored for specific applications, have increased study of ILs in many areas of fundamental and applied chemistry. Thus, ILs have successfully been utilized as novel solvents in different extraction and microextraction schemes in recent years, but mainly with environmental samples.Food samples are quite complicated matrices from an analytical point of view. They contain a large range of chemical substances, and sometimes they also have a high fat content. Even with the most advanced analytical techniques, food sampling and food-sample preparation prior to the analytical determination are labor-intensive and time-consuming, and normally require relatively large amounts of organic solvents.In this review, we summarize the most recent analytical developments aimed at employing ILs as a tool in food analysis. We discuss practical applications to determine metals and organic compounds in food samples of quite different natures, with special emphasis to the extraction step at which the IL is introduced, and the advantages of the IL-based methods developed over conventional extraction methods. 相似文献
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9.
Photoexcitation of (neat) room temperature ionic liquids (RTILs) leads to the observation of transient species that are reminiscent of the composition of the RTILs themselves. In this minireview, we summarize state-of-the-art in the understanding of the underlying elementary processes. By varying the anion or cation, one aim is to generally predict radiation-induced chemistry and physics of RTILs. One major task is to address the fate of excess electrons (and holes) after photoexcitation, which implies an overview of various formation mechanisms considering structural and dynamical aspects. Therefore, transient studies on time scales from femtoseconds to microseconds can greatly help to elucidate the most relevant steps after photoexcitation. Sometimes, radiation may eventually result in destruction of the RTILs making photostability another important issue to be discussed. Finally, characteristic heterogeneities can be associated with specific physicochemical properties. Influencing these properties by adding conventional solvents, like water, can open a wide field of application, which is briefly summarized. 相似文献
10.
In recent years, room temperature ionic liquids (RTILs) have proven to be of great interest to analytical chemists. One important
development is the use of RTILs as highly thermally stable GLC stationary phases. To date, nearly all of the RTIL stationary
phases have been nitrogen-based (ammonium, pyrrolidinium, imidazolium, etc.). In this work, eight new monocationic and three
new dicationic phosphonium-based RTILs are used as gas–liquid chromatography (GLC) stationary phases. Inverse gas chromatography
(GC) analyses are used to study the solvation properties of the phosphonium RTILs through a linear solvation energy model.
This model describes the multiple solvation interactions that the phosphonium RTILs can undergo and is useful in understanding
their properties. In addition, the phosphonium-based stationary phases are used to separate complex analyte mixtures by GLC.
Results show that the small differences in the solvent properties of the phosphonium ILs compared with ammonium-based ILs
will allow for different and unique separation selectivities. Also, the phosphonium-based stationary phases tend to be more
thermally stable than nitrogen-based ILs, which is an advantage in many GC applications. 相似文献
11.
Koch M Rosspeintner A Angulo G Vauthey E 《Journal of the American Chemical Society》2012,134(8):3729-3736
The fluorescence quenching of 3-cyanoperylene upon electron transfer from N,N-dimethylaniline in three room-temperature ionic liquids (RTILs) and in binary solvent mixtures of identical viscosity has been investigated using steady-state and time-resolved fluorescence spectroscopy. This study was stimulated by previous reports of bimolecular electron transfer reactions faster by one or several orders of magnitude in RTILs than in conventional polar solvents. These conclusions were usually based on a comparison with data obtained in low-viscous organic solvents and extrapolated to higher viscosities and not by performing experiments at similar viscosities as those of the RTILs, which we show to be essential. Our results reveal that (i) the diffusive motion of solutes in both types of solvents is comparable, (ii) the intrinsic electron transfer step is controlled by the solvent dynamics in both cases, being slower in the RTILs than in the conventional organic solvent of similar viscosity, and (iii) the previously reported reaction rates much larger than the diffusion limit at low quencher concentration in RTILs originate from a neglect of the static and transient stages of the quenching, which are dominant in solvents as viscous as RTILs. 相似文献
12.
Ionic liquids in analytical chemistry 总被引:1,自引:0,他引:1
Ping Sun 《Analytica chimica acta》2010,661(1):1-753
Ionic liquids (ILs) are composed entirely of ions and they possess fascinating properties, including low volatility, tunable viscosity and miscibility, and electrolytic conductivity, which make ILs unique and useful for many applications in chemical analysis. The dramatic increase in the number of publications on ILs is indicative of the tremendous interest in this field from analytical chemists. This review summarizes recent efforts in the major subdisciplines of analytical chemistry, including extractions, gas chromatography, liquid chromatography, capillary electrophoresis, mass spectrometry, electrochemistry, sensors, and spectroscopy. 相似文献
13.
Observer 《Trends in analytical chemistry : TRAC》1982,1(16):VII-VIII
This month sees the introduction of a new feature to TrAC — OBSERVER. A panel of expert correspondents will contribute short reports on significant recent publications in analytical chemistry and related areas. The reports will take the form of critical commentaries. OBSERVER is thus designed to expand TrAC's current awareness function and will complement the information found elsewhere in the journal. 相似文献
14.
Green analytical chemistry is a comprehensive perspective that aims to reduce or eliminate the toxic and harmful solvents, reagents, and techniques in the preparation, pre-treatment, and determination steps of an analysis process. With the increase in environmental pollution in recent years, awareness has been increasing in terms of both the contamination analysis of environmental sources and the more environmentally friendly analysis methods. This review evaluates the solvents such as bio-based solvents and deep eutectic solvents, nanomaterials synthesized by non-toxic methods, the greener changes in the extraction methods, and chromatographic techniques considering the most recent studies. In particular, trying to make the methods used to analyze environmental samples safer and less toxic is an important point that overlaps with the green approach, which aims to minimize environmental pollution. In this context, this review provides information on green analytical chemistry-based environmental applications covering the last ten years so that the applications of this approach can be examined and understood in more detail and can be applied by other researchers. 相似文献
15.
Feng G Huang J Sumpter BG Meunier V Qiao R 《Physical chemistry chemical physics : PCCP》2011,13(32):14723-14734
Room-temperature ionic liquids (RTILs) have received significant attention as electrolytes due to a number of attractive properties such as their wide electrochemical windows. Since electrical double layers (EDLs) are the cornerstone for the applications of RTILs in electrochemical systems such as supercapacitors, it is important to develop an understanding of the structure-capacitance relationships for the EDLs of these systems. Here we present a theoretical framework termed "counter-charge layer in generalized solvents" (CGS) for describing the structure and capacitance of the EDLs in neat RTILs and in RTILs mixed with different mass fractions of organic solvents. Within this framework, an EDL is made up of a counter-charge layer exactly balancing the electrode charge, and of polarized generalized solvents (in the form of layers of ion pairs, each of which has a zero net charge but has a dipole moment--the ion pairs thus can be considered as a generalized solvent) consisting of all RTILs inside the system except the counter-ions in the counter-charge layer, together with solvent molecules if present. Several key features of the EDLs that originate from the strong ion-ion correlation in RTILs, e.g., overscreening of electrode charge and alternating layering of counter-ions and co-ions, are explicitly incorporated into this framework. We show that the dielectric screening in EDLs is governed predominantly by the polarization of generalized solvents (or ion pairs) in the EDL, and the capacitance of an EDL can be related to its microstructure with few a priori assumptions or simplifications. We use this framework to understand two interesting phenomena observed in molecular dynamics simulations of EDLs in a neat IL of 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF(4)]) and in a mixture of [BMIM][BF(4)] and acetonitrile (ACN): (1) the capacitance of the EDLs in the [BMIM][BF(4)]/ACN mixture increases only slightly when the mass fraction of ACN in the mixture increases from zero to 50% although the dielectric constant of bulk ACN is more than two times higher than that of neat [BMIM][BF(4)]; (2) the capacitance of EDLs near negative electrodes (with BMIM(+) ion as the counter-ion) is smaller than that near positive electrodes (with BF(4)(-) as the counter-ion) although the closest approaches of both ions to the electrode surface are nearly identical. 相似文献
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17.
Lippens G Warrass R Wieruszeski JM Rousselot-Pailley P Chessari G 《Combinatorial chemistry & high throughput screening》2001,4(4):333-351
Solid phase organic chemistry coupled with combinatorial methods promises to increase dramatically the diversity and number of small molecules available for medical and biological applications. However, optimizing the reaction conditions can be a time consuming step, especially since analytical tools to monitor reaction progress and detect impurities for solid phase chemistry are less developed than for solution chemistry. The use of high resolution magic angle spinning (HRMAS) NMR is described here as such an analytical tool. Whereas initial applications of molecular identification using deuterated organic solvents to swell the resins presented a significant gain in time over the cleave-and-analysis methods, the introduction of a differential diffusion filter has made immediate recording of spectra possible without any sample treatment. The applications of HRMAS NMR to different solid supports that are used in combinatorial chemistry will be described in terms of rapidity, robustness and sensitivity. 相似文献
18.
Miniaturization continues to be one of the leading trends in analytical chemistry and one that brings advantages that can be particularly beneficial in biochemical research. Use of a miniaturized scale enables efficient analysis in a short time and requires very small amounts of samples, solvents, and reagents. This can result in a remarkable decrease in costs of enzyme kinetics studies, especially when expensive or rare enzymes and/or substrates are involved. Free zone electrophoresis is without a doubt the most common microscale separation technique for capillary and on-chip enzyme assays. Progress and applications in this field are reviewed frequently whereas other modes of separation, although successfully applied, receive only marginal interest in such publications. This review summarizes applications of less common modes of separation in capillary or chip formats, namely micellar electrokinetic chromatography, liquid chromatography, gel electrophoresis, isoelectric focusing, and isotachophoresis. Because these techniques are based on separation mechanisms different from those of free zone electrophoresis, they can be, and have been, successfully used in cases where zone electrophoresis fails. Advantages and drawbacks of these alternative separation techniques are discussed, as also are the difficulties encountered most often and solutions proposed by different research groups. 相似文献
19.
Le Rouzo G Lamouroux C Bresson C Guichard A Moisy P Moutiers G 《Journal of chromatography. A》2007,1164(1-2):139-144
Hydrophilic interaction liquid chromatography (HILIC) is an alternative technique to ion pairing-reversed-phase liquid chromatography (IP-RPLC) and classical RPLC for separation of alkylimidazolium room-temperature ionic liquids (RTILs). Particularly, HILIC offers better retention and selectivity for short-chains RTILs imidazolium compounds. HILIC mechanisms were investigated by studying the influence of organic modifier content and salt concentration in the mobile phase. HILIC method was validated by quantifying 1-butyl-3-methylimidazolium cation (BMIM) degradation under gamma radiation at 2.5MGy. Development of separative reproducible analytical methods, including for low concentration, applicable to RTILs are today mandatory to improve RTILs chemistry. 相似文献
20.
lvaro Fernndez-Ochoa María de la Luz Cdiz-Gurrea Patricia Fernndez-Moreno Alejandro Rojas-García David Arrez-Romn Antonio Segura-Carretero 《Molecules (Basel, Switzerland)》2022,27(3)
The study of the bioavailability of bioactive compounds is a fundamental step for the development of applications based on them, such as nutraceuticals, functional foods or cosmeceuticals. It is well-known that these compounds can undergo metabolic reactions before reaching therapeutic targets, which may also affect their bioactivity and possible applications. All recent studies that have focused on bioavailability and metabolism of phenolic and terpenoid compounds have been developed because of the advances in analytical chemistry and metabolomics approaches. The purpose of this review is to show the role of analytical chemistry and metabolomics in this field of knowledge. In this context, the different steps of the analytical chemistry workflow (design study, sample treatment, analytical techniques and data processing) applied in bioavailability and metabolism in vivo studies are detailed, as well as the most relevant results obtained from them. 相似文献