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Excess entropy scaling relationships for diffusivity of ions in room-temperature ionic liquids are tested using molecular dynamics simulations for a model ionic liquid, dimethyl imidazolium chloride. The thermodynamic excess entropy of the single ions (estimated from the ion-ion pair correlation functions) is shown to be very strongly correlated with the diffusivity. An essential feature of these systems, the fact that the heavier and larger cation has a greater diffusivity with respect to the anion, is correctly captured by the excess entropy calculations, which estimates the diffusivity ratio between the two ions with noticeable precision. [ABSTRACT FROM AUTHOR]

The conversion of cellulose into target chemicals is essential for the development of the sustainable chemical industry of the future. To this end, the single step transformation of cellulose into levulinic acid (LA) has been investigated in different aqueous systems and using either Brønsted acidic ILs, metal salts, or a mixture of these as catalysts with or without the formation of carbonic acid in situ. The effect of varying the reaction parameters, such as temperature, time, substrate concentration, and catalyst loading, on conversion and selectivity has been studied. A few different systems [(TMGH)(HSO4)–FeCl3 or (TMGH)(HSO4)–CrCl3 in H2O–CO2, (TMGH)(HSO4)–CrCl3 in H2O, FeCl3 in H2O, and FeCl3 or CrCl3 in H2O–CO2] allowed for the isolation of LA in good yields (41–55 mol%). The best and remarkably high yield of LA (69 mol%) has been obtained in water at 195 °C (4 h) by using TiOSO4 (0.375 wt%) as a catalyst. This new, environmentally friendly catalytic system retains high activity after five consecutive runs. Its catalytic activity has been discussed taking into account the hydrolysis process occurring under the reaction conditions. [ABSTRACT FROM AUTHOR]

The aim of this paper was to synthesize ionic liquids (ILs) that can play the double role of capping and reducing agents for the fabrication of silver nanoparticles (Ag NPs). A new simple method of synthesis of some ILs that have as counter ion citrate and their application in silver and gold nanoparticles preparation will be presented. AgNPs with a medium diameter of 8 nm, stable for more than 7 months in aqueous solution at room temperature were obtained with trioctyl ammonium citrate (TOM 3 Citr) at 1:7 molar ratio (AgNO 3 :TOM 3 Citr). The stability of these nanoparticles was investigated with UV–vis spectroscopy and the shape and diameter by TEM characterization. The effect of synthesis conditions was also investigated (molar ratio, temperature, pH) as well as the possibility to use the same IL to prepare Au NPs. [ABSTRACT FROM AUTHOR]

We report a green, facile chemical approach to isolate sporopollenin capsules from pollen grains based on the use of ionic liquids (ILs). Depending on the IL structure, it is possible to remove proteins and the cellulose-rich cell wall (intine) assuring grain integrity and simultaneously obtaining a direct functionalization of the sporopollenin. [ABSTRACT FROM AUTHOR]

The reaction paths and intermediate structures related to the formation of the Breslow intermediate and its oxidation along the oxidative/oxygenative lanes have been studied from a mechanistic point of view, with the support of gas-phase and computational studies. The results confirm the occurrence of a single-electron transfer from the Breslow intermediate to the molecular oxygen with formation of a radical couple that recombines either as a peroxide anion 7′ to afford the aldehyde-to-carboxylic acid product or as a hydroperoxy derivative 7″ that evolved into an electrophilic acyl azolium, opening to the aldehyde-to-ester conversion. Steric factors enter into determining the different reactivity. All of the intermediates of both catalytic paths have been observed and characterized under mass spectrometric conditions. In particular, for the imidazoline catalyst, the (+)ESI-MS/(MS) detection of the genuine Breslow intermediate was made possible in virtue of its limited reactivity. Mechanistic aspects of the N-heterocyclic carbenes catalyzed aerobic oxidation of aldehydes shares important similarities with that one of the recently revisited benzoin condensation. [ABSTRACT FROM AUTHOR]

There are still constraints to algae-sourced biodiesel commercialization owing to the high cost and energy consumption of biomass cultivation and lipid extraction. The use of “low-cost” protic ILs based on tetramethylguanidinium and 1,8-diazabicyclo[5.4.0]undec-7-ene cations (some of them generated in situ by reaction of the corresponding bases with CO2 in the presence of methanol) for lipid extraction was assessed using Scenedesmus obliquus and compared to conventional methods. High extraction yields (up to 88% compared to conventional solvents, hexane–methanol) were obtained in most of the investigated ILs using wet microalgae (85% water). Furthermore, [HDBU][MeOCO2/HCO3] and [HTMG][MeOCO2/HCO3] resulted in the direct isolation of fatty acid methyl esters ((FAMEs)-biodiesel), formed in situ through transesterification/esterification reactions. [ABSTRACT FROM AUTHOR]

Despite the weakly coordinating abilityof the bis(trifluoromethylsulfonyl)imideanion ([Tf2N]−) the corresponding ionicliquids (ILs) are able to dissolve relevant amounts of metal saltshaving the same anion, M[Tf2N]x. To better understand the metal dissolution process we evaluatedthe interaction ability of a set of metal cations (Y(III), Al(III),Co(II), Ni(II), Cu(II), Zn(II), Ag(I), Li(I), and Na(I)) toward the[Tf2N]−anion measuring the relativeaptitude to give the corresponding anionic monocharged complex, [M(Tf2N)x+1]−usingthe ESI-MS technique. UV–vis and NMR measurements were carriedout to verify the consistence between the liquid and the gas phase.Density functional theory calculations have been used to identifythe metal-containing species and determine their relative stability.An interesting correlation between interaction ability and chemicalproperties (Lewis acidity) was found. [ABSTRACT FROM AUTHOR]

In recent years, the designer nature of ionic liquids (ILs) has driven their exploration and exploitation in numerous fields. Undoubtedly, the most attractive feature of ILs is their tunability and the incorporation of functional groups into the cations or anions is the most efficient way to impart a particular property. Functionalized ILs are generally named 'task-specific ionic liquids' (TSILs). In this review, we survey some of the classes of TSILs, generally characterized by the presence of only one 'common' functional group, arising from slight modifications (here, defined as 'point-functionalization') that can be achieved through simple synthetic procedures. In particular, we will discuss their synthesis, immobilization and applications in some specific fields. Among these, we consider their use as solvent catalysts in organic synthesis and metal-catalysed processes, and as fluids in metal extraction processes and gas capture, highlighting their possible uses in materials sciences. The aim of this review is to provide, through a careful survey of the literature, indications of sustainable and rational developments in this extremely prolific field. [ABSTRACT FROM AUTHOR]

It is well known that ionic liquids (ILs) possess extraordinary characteristics, making them greener solvents with unique properties, which allow processes that would otherwise be difficult or impossible with common solvents to be carried out. In this review, we describe and discuss, in the light of possible future large scale applications, some fundamental studies showing the efficacy of ILs in several "hot" fields, from dissolution and transformation of biopolymers to extraction and capture of important inorganic components (metals) or pollutants (CO2). [ABSTRACT FROM AUTHOR]

Brønsted acidic ionic liquids (ILs) have been synthesized and investigated as catalysts in esterification and transesterification reactions: simple and non-corrosive salts characterized by aliphatic cations associated with an “acidic” anion (in particular, [HSO4]−) gave the higher yields. A quite good correlation between IL acidity (H0) and catalytic ability was found although also the hydrophilic nature of the ionic medium probably affects the process efficiency. [ABSTRACT FROM AUTHOR]

Abstract: A computational study of the catalytic activity exhibited by imidazolium based ionic liquids on the singlet oxygen promoted oxidation of thioethers is presented. The reaction of singlet oxygen with thioanisole and diethyl sulfide, in the absence and in the presence of 1-butyl-3-methylimidazolium cation, was followed along the reaction coordinate up to the formation of the persulfoxide intermediate that is widely recognized as the key intermediate in this process. In line with previous experimental observations, the results obtained show that the imidazolium cation strongly stabilizes the persulfoxide intermediate by hydrogen bonding thus depressing the unproductive intersystem crossing and favoring product formation. Evidence for a significant role played by exciplex intermediates in this reaction was also found. Surprisingly, the results for the singlet oxygen-sulfide system in the absence of imidazolium show that whereas diethyl sulfide can readily form the persulfoxide intermediate, from which S-oxidation products ensue, for thioanisole the persulfoxide formation is characterized by a high activation energy. A detailed investigation on the role played by the aromatic ring in this dramatic activation energy increase is presented suggesting, for the first time, a rationale for the well known low reactivity exhibited by aromatic sulfides in reactions with singlet oxygen. [Copyright &y& Elsevier]

The nature of solvation of Reichardt's dye in ionic liquids is investigated through semiempirical calculations. We build on the basis of electrostatic considerations a cluster of three ionic pairs that represent the first solvation shell of the dye. The spatial organization of this shell is a balance between sterical, electrostatic and, in the case of functionalized ionic liquids, specific interactions. This model is not sufficient to obtain values of ET(30) quantitatively comparable to the experimental ones, but some qualitative features can be rationalized. The resulting scenario of solute-solvent interactions is different with respect to molecular solvents. Thus, we suggest caution in comparing ionic and molecular solvents through solvatochromic scales. [ABSTRACT FROM AUTHOR]

Glycerol carbonate is a key multifunctional compound used as solvent, additive, and building block in alternative chlorine-free processes. Here, we report the synthesis of glycerol carbonate from renewable materials (glycerol and dimethyl carbonate, DMC) using basic ionic liquids (ILs) as catalysts. After process optimization, it has been possible to isolate pure glycerol carbonate in quantitative yield using a three-fold excess of DMC and ca. 15 % of IL. The IL could be reused at least four times without any significant reduction in the conversion yield. [ABSTRACT FROM AUTHOR]

A series of new ionic liquids (ILs) based on trialkylglycerylphosphonium cations have been prepared starting from 3-chloropropane-1,2-diol or (2,2-dimethyl-1,3-dioxolan-4-yl)methanol, two compounds readily obtainable from glycerol (a widely available and cheap waste product). All the new phosphonium salts were characterized by NMR, IR and DSC, and their efficacy as polar additives in a typical base-promoted Baylis–Hillman reaction was also evaluated. [ABSTRACT FROM AUTHOR]

Tribromide-based ionic liquids have been synthesized and investigated as efficient bromination agents. The different physicochemical properties of the reaction media, which depend on the cation structure, have been used to improve the efficiency of the bromination process. [ABSTRACT FROM AUTHOR]

A series of hydrophilic N,N-dimethylpyrrolidinium- and N,N-dimethylpiperidinium-based ionic liquids (ILs) have been prepared and applied as reaction media in the Wacker oxidation of styrene by hydrogen peroxide using PdCl2as the catalyst. The efficiency of these ILs was compared with hydrophilic and hydrophobic imidazolium systems (including those with nitrile functionalities). The nature of the ionic liquid strongly influences the product distribution. In particular, in hydrophobic ILs, relevant amounts of 1,3-diphenyl-1-butene arising from styrene dimerization were detected, in addition to the expected phenylmethylketone. The formation of 1,3-diphenyl-1-butene may be attributed to the formation of Pd(0) species from “ClPdOH” (probably formed during the Wacker process) in a side-reaction. Consequently, the ability of the IL to favor or disfavor the reoxidation of “ClPdOH” to “ClPdOOH” by hydrogen peroxide, giving an homogeneous phase or a biphasic system, appears to be the main factor affecting selectivity. [ABSTRACT FROM AUTHOR]

A series of hydrophilic N,N-dimethylpyrrolidinium- and N,N-dimethylpiperidinium-based ionic liquids (ILs) have been prepared and applied as reaction media in the Wacker oxidation of styrene by hydrogen peroxide using PdCl2 as the catalyst. The efficiency of these ILs was compared with hydrophilic and hydrophobic imidazolium systems (including those with nitrile functionalities). The nature of the ionic liquid strongly influences the product distribution. In particular, in hydrophobic ILs, relevant amounts of 1,3-diphenyl-1-butene arising from styrene dimerization were detected, in addition to the expected phenylmethylketone. The formation of 1,3-diphenyl-1-butene may be attributed to the formation of Pd(0) species from “ClPdOH” (probably formed during the Wacker process) in a side-reaction. Consequently, the ability of the IL to favor or disfavor the reoxidation of “ClPdOH” to “ClPdOOH” by hydrogen peroxide, giving an homogeneous phase or a biphasic system, appears to be the main factor affecting selectivity. [ABSTRACT FROM AUTHOR]

This review illustrates how ionic liquid properties can affect Diels–Alder reactions. The mechanisms by which ionic solvents enhance the rate and selectivity of the reaction are discussed on the basis of correlation studies using empirical parameters and theoretical calculations. [ABSTRACT FROM AUTHOR]

As the interest for environmental increases and environmental laws become more stringent, the need to replace existing processes with new more sustainable technologies becomes a primary objective. The use of ionic liquids to replace organic solvents in metal catalyzed reactions has recently gained much attention and great progress has been accomplished in this area in the last years. This paper reviews the recent developments in the application of ionic liquids and related systems (supported ionic liquids, ionic polymers, and so on) in the Heck reaction. Merits and achievements of ionic liquids were analyzed and discussed considering the possibility of increasing the effectiveness of industrial processes. [ABSTRACT FROM AUTHOR]

High-yield reactions of the pentafluoride complexes MF5 (M=Nb, Ta) with a variety of diethers, ROCH2CH(R')OR", afford the ionic derivatives [MF4(K2-ROCH2CH(R')OR")2][MF6] (2a-2e) or [MF4(ROCH2CH(R')OR" )2][M2F11] (3a-3f) according to the metal/diether ratio employed. The structures of [MF4(K2-dme)2][MF6] [M=Nb (2a), Ta (2b); dme=MeOCH2CH2OMe] have been determined by X-ray diffraction. Moreover, the structure of the cationic part of 2a in the gas phase has been optimized by density functional theory calculations (the B3LYP/LANL2DZ method). An analogous computational study has allowed one to predict the existence of a heptacoordinated niobium cation within the species [NbCI4(dme)2][NbCl6]. This prediction has been confirmed by NMR identification at -60°C of the complexes [MCI4(K2-dme)(K1-dme)][MCI6] [M=Nb (4a), Ta (4b)], obtained by the addition of dme to MCI5 in CDCI3. Activation of the coordinated diether in 2 and 3 takes place in solution at high temperature and generally proceeds via cleavage of C-C bonds and coupling of the fragments produced. Thus, OR2 (R=Me, Et) and 1,4-dioxane have been obtained selectively upon thermal reaction of MF5 with rime, diglyme, or 1,2-diethoxyethane, followed by treatment with water. In analogous conditions, 1,2-dimethoxypropane converts mainly into acetone and dimethyl ether. The formation of dioxane from dme occurs in high yield also by using a catalytic amount of NbF5. The activation of dme by NbF5 follows a pathway different from that previously reported for NbCI5, and an explanation based on the thermodynamic parameters calculated at the B3LYP/LANL2DZ level is given: the formation of Me2O and dioxane is the most favored reaction between NbF5 and dme (ΔGr°= -15.16 kcal ∙ molNb-1), while the formation of MeCl and dioxane is the most favored reaction in the case of NbCl5/dme (ΔGr°=-53.13 kcal ∙ molNb-1). [ABSTRACT FROM AUTHOR]

The effect of ionic liquids (ILs) on the Menschutkin reaction between N-methylimidazole and benzyl halides has been investigated. Hammett correlations have been used to obtain information on the reaction mechanism of benzyl chlorides in ionic and molecular solvents. The solvent effects on this reaction have been examined using both multiparameter linear solvation energy relationships and theoretical calculations. These latter have been performed using a supermolecular approach, i.e., the IL is represented by an explicit ionic pair, IP. Two possible different reaction pathways have been obtained changing the position of the IL-IP with respect to the reagents. It is hypothesized that inside the IL the Menschutkin reaction of benzyl chloride with N-methylimidazole can follow different reaction pathways by considering the influence of dynamic heterogeneity in ionic media on the time scale of the lifetime of a transition state. [ABSTRACT FROM AUTHOR]

In this paper, we report on the synthesis and application of monosubstituted diazabicyclo[2.2.2]octane (dabco) cations associated with a basic anion, dicyanamide. Key properties of these salts—phase transitions, density, and conductivity—were measured and compared to those of other common ionic liquids (ILs). Moreover, solvatochromic dyes were used to assess their solvation properties. The Heck cross-coupling reaction was evaluated in dabco-based ILs and compared with the behavior in common unfunctionalized ILs, evidencing good catalyst stability and a high recyclability in these basic ILs. [ABSTRACT FROM AUTHOR]

The Diels-Alder reaction between cyclopentadiene and three dienophiles (acrolein, methyl acrylate and acrylonitrile) in different room temperature ionic liquids containing imidazolium-based cations ([HBIM]+, [BMIM]+ and [BM2IM]+) has been studied at the DFT level using a supermolecular approach. An analysis of the theoretical results shows that the ionic liquid cation coordination affects the equilibrium geometries and electronic structures of the reacting species throughout the reaction pathway leading to changes in reactivity and selectivity. They also indicate that the strong asynchronicity of the Diels-Alder reactions in ionic liquids is due to the polarisation effect of the cation. [ABSTRACT FROM AUTHOR]

Abstract: The effect of hydrophilic ionic liquids (ILs) on the activity of chloroperoxidase (CPO) was checked through kinetic and stereochemical studies. The possibility to employ this enzyme in synthesis has been demonstrated investigating the chemo- and stereoselectivity of oxidation of phenyl methylsulfide in several citrate buffer–IL mixtures. [Copyright &y& Elsevier]

Solute solvent interactions on the keto-enol tautomerism of 2-nitrocyclohexanone in several organic solvents and room-temperature ionic liquids (RTILs) have been analyzed in terms of multiparameter equations. Permittivity and cohesive pressure values of the RTILs, unavailable by direct measurements, have been derived. [ABSTRACT FROM AUTHOR]

Abstract: The ionization of chlorobis(4-methoxyphenyl)methane ( 1-Cl ) was performed in 1:1 mixtures of TFE/ILs (ILs=[emim][Tf2N], [bmim][Tf2N], [bpy][Tf2N]), and TFE/CH3CN. The decay of the immediately formed carbenium ion 1 + was followed by stopped flow, showing that the lifetime of this intermediate significantly decreases on going from CH3CN to [emim][Tf2N]. Ab initio calculations suggest an increase in the electrophilicity of the carbenium ion in ILs. [Copyright &y& Elsevier]

The kinetic constants and activation parameters for the reactions of Br3- and ICl2- with some alkenes and alkynes have been determined in the ionic liquids [bmim][PF6], [emim][Tf2N], [bmim] [Tf2N], [hmim] [TF2N], [bm2im][Tf2N], and [bpy] [TF2N] (where emim = 1-ethyl-3-methylimidazolium, bmim = 1-butyl-3-methylimidazolium, hmim = 1-hexyl-3-methylimidazolium, bm2im = 1-butyl-2,3-dimethylimidazolium, bpy = butylpyridinium, PF6 = hexafluorophosphate, and Tf2N = bis(trifluoromethylsulfonyl)imide) and in 1,2-dichloroethane. The rates of both reactions increase on going from 1,2-dichloroethane to ILs. Evidence suggests that, while the hydrogen bonding ability of the imidazolium cation is probably the main factor able to increase the rate of the addition of ICl2- to double and triple bonds, this property has no effect on the electrophilic addition of Br3- to alkenes and alkynes. Furthermore, in the case of the ICl2- reaction, the hydrogen bonding ability of ILs can be exploited to suppress the unwanted nucleophilic substitution reaction on the products by the Cl- anion. [ABSTRACT FROM AUTHOR]

Soluble epoxide hydrolase (sEH) was shown to catalyze hydrolysis of epoxides using the ionic liquids (ILs) [bmim][PF6], [bmim][N(Tf)2], and [bmim][BF4] (where bmim=1-butyl-3-methylimidazolium, PF6=hexafluorophosphate, N(Tf)2=bis(trifluoromethylsulfonyl)imide, and BF4=tetrafluoroborate) as reaction medium. Reaction rates were generally comparable with those observed in buffer solution, and when the cress enzyme was used the hydrolysis of trans-β-methylstyrene oxide gave, through a stereoconvergent process, the corresponding optically active (1S,2R)-erythro-1-phenylpropane-1,2-diol. [Copyright &y& Elsevier]

Room-temperature ionic liquids have been used as environmentally benign solvents for the preparation of primary and secondary alkyl azides and nitriles under solid-RTIL phase-transfer conditions. The reaction of primary, secondary, and tertiary halides or tosylates with KCN and NaN[sub 3] has been investigated in three ionic liquids ([bmim] [PF[sub 6]], [bmim] [N(Tf)[sub 2]], and [hpyr] [N(Tf)[sub 2]]). The observed nucleofugacity scales for the reaction of NaN[sub 3] are similar to those reported for the same process in cyclohexane, indicating that in these solvents it is possible to evidence the intrinsic ability to depart of leaving groups. Changes in the nature of the IL cation or anion determine significant modifications in reactivity of the investigated substrates. Reactivity has been interpreted considering a gradual shift of the mechanism from concerted S[sub N]2 (primary substrates) to stepwise S[sub N]1 (tertiary substrate, 3), through the nucleophilically assisted formation of an ion pair intermediate, in the case of 2d. [ABSTRACT FROM AUTHOR]

Examines the reactivity of homoallylic substituted adamantylideneadamantanes with bromine. Stability of ionic and nonionic intermediates; Importance of the halogenation of organic compounds; Factors influencing the formation of bromium.

Compares the stereochemical course of the electrophilic additions of halogens, and in particular of bromine, to tri-O-benzyl-D-glucal with that of the dihydropyrans. Factors that contribute to the stereochemical selectivity in the electrophilic addition to cyclic enol ethers.

Investigates the trans-(1-methyl-2-adamantylidene)-1-methyladamantane-bromine system in 1,2-dichloroethane to obtain further information about the correlation between structure and reactivity. Comparison of the results with those found for the parent olefin, adamantylideneadamantane; Indication that steric strain markedly affects the reactivity of the double bond.

Examines an evidence for the formation of bromocarbenium bromide ion pairs in the electrophilic bromination of reactive olefins in chlorinated aprotic solvents. Measurement of the kinetic constants and activation parameters; Examination of the stability of the dibromides; Observation of the lack of anti stereospecificity in the tribromide addition.

Reports on the facial stereoselectivity of methylenecyclohexane derivatives for use as substrates for the stereochemical study of hydrolysis by epoxide hydrolases. Investigation of the stereo- and regiochemistry of additions initiated by electrophilic halogen to methylene cyclohexanes for comparison with the stereochemistry of peroxyacid epoxidation.

Discusses kinetic evidence for rate determination during the nucleophilic step of olefin bromination with 5 H-dibenz[b,f]azepine-5-carbonyl chloride. Measurement of kinetics of bromination at variable temperature and reagent concentrations; Finding of significant conductivity during the course of the reactions.

Enantiodifferentiating photocyclodimerization of 2-anthracenecarboxylic acid and its alkali metal salts performed in a chiral ionic liquid gave chiral cyclodimers in good enantiomeric excesses of up to 41%, which is the highest ever reported for a photochirogenic reaction in chiral media. [ABSTRACT FROM AUTHOR]

Abstract: Dimesityldiclorosilane undergoes reductive coupling with potassium–graphite to afford a mixture of cyclic polysilanes in a high yield and purity; this mixture is quantitatively converted to the title compound by photochemical irradiation. [Copyright &y& Elsevier]

Some clusters of Reichardt’s dye with two ion pairs have been studied at the TD-DFT level in order to understand the effect of the ionic liquid anion on solvatochromism. Coherently with the experimental data, the anion effect results substantially related to the anion size, although generally less important than the cation effect. Only small anions, such as halogenides, show a significant effect. [ABSTRACT FROM AUTHOR]

In this work, we study the solvation thermodynamics and other solvation properties of small ions in two room-temperature ionic liquids, dimethyl imidazolium hexafluorophosphate [mmim] [pf6] and dimethyl imidazolium chloride [mmim][cl] with the reference interaction site model (RISM). The nature of the charge affects several aspects of solvation, from electrostriction to the mutual disposition of cations around the solute; nevertheless, the long-range screening behavior of the liquid appears to be insensitive to both charge and dimensions of the solute. The ion solvation is energy driven, as expected for the nature of the solvent, and displays a marked asymmetry between cation and anion solvation chemical potential. Such asymmetry is dependent, even qualitatively, on the ionic liquid chosen as solvent. Partial molar volumes of ions in solution are found to follow the nature of ion-solvent interaction. [ABSTRACT FROM AUTHOR]

Two new levulinate-based protic ionic liquids (Lev PILs) have been synthesized through an easy, scalable neutralization reaction between levulinic acid (LA), which is one of the most promising renewable building blocks obtainable from cellulose, and amidine superbases (either DBU or DBN). The prepared PILs have been characterized (by means of NMR, FT-IR, TGA and viscosity measurements) and studied as potential cellulose dissolution media. These species display a dissolving ability (weightcellulose/weightPIL) comparable with the popular, and to date best performing, acetate-based PILs. In contrast with these systems, Lev PILs are composed of a larger renewable anion (levulinate vs. acetate): this allows for a reduced amount of the expensive non-renewable superbase cation component while only slightly affecting the cellulose dissolution performance. An application of the proposed Lev PILs, namely the levulination of cellulose, has also been studied. The impact of various reaction parameters (i.e. temperature, amount of anhydride, amount of co-solvent) on the reaction outcome and on the functionalization degree (up to 1.87) has been studied. γ-Valerolactone, a renewable green solvent which is in turn prepared from LA, has been found as an effective DMSO replacement when used as co-solvent for the reaction, allowing for satisfactory functionalization degrees. [ABSTRACT FROM AUTHOR]

Examines the polarizability effects and dispersion interactions in alkene-Br[sub 2] pi-complexes. Electrophilic halogen addition to alkenes; Evidence of a direct relationship between association constants of the pi-complexes and polarization of the olefins; Parameters related to several alkenes and bromine pi-complexes.

Review: [158 refs. [ABSTRACT FROM AUTHOR]

Review: [91 refs. [ABSTRACT FROM AUTHOR]

Unreported ureido cross-linked chitosans were obtained employing the CO2–chitosan–ionic liquid three component system. Under the conditions used, the greenhouse gas functions as a safe cross-linking agent of the biopolymer thanks to the solvent-catalytic effect of [bmim][OAc]. [ABSTRACT FROM AUTHOR]

The vacuum/liquid interface of different ionic liquids obtained by dissolving bistriflimide salts of Ag, Al, Cu, Ni, and Zn in 1-butyl-3-methylimidazolium bistriflimide ([bmim][Tf 2 N]) was investigated under vacuum using AR-XPS and NEXAFS. The XPS spectra show chemical shifts of the nitrogen of the bistriflimide anion as a function of the metal type, indicating different strength of the coordination bonds. In silver bearing ILs, silver ions were found to be only weakly coordinated. On the contrary, Ni, Cu, Zn, and especially Al exhibit large chemical shifts attributable to strong interaction with the bistriflimide ions. The outermost surface was enriched with or depleted of metal ions as a function of the nature of the metals. Nickel and zinc tend to slightly concentrate at the surface while copper, silver, and especially aluminum are depleted at the surface. We also observed that the aliphatic alkyl chains of the cations tend to protrude outside the surface in all systems studied. However, the presence of metals generally increases the amount of bistriflimide at the vacuum/liquid interface. [ABSTRACT FROM AUTHOR]

Vegetable oils and fatty acid esters are suitable precursor molecules for the production of a variety of bio-based products and materials, such as paints and coatings, plastics, soaps, lubricants, cosmetics, pharmaceuticals, printing inks, surfactants, and biofuels. Here, we report the possibility of using Lewis acidic ionic liquids (ILs) to obtain polyunsaturated ester dimerization-oligomerization and/or, in the presence of another terminal alkene (propene), co-polymerization. In particular, we have tested the Lewis acidic mixtures arising from the addition of a proper amount of GaCl3 (X > 0.5) to two chloride-based (1-butyl-3-methylimidazolium chloride, [bmim]Cl, and 1-butylisoquinolium chloride, [BuIsoq]Cl) or by dissolution of a smaller amount of Al(Tf2N)3 (X = 0.1) in 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [bmim][Tf2N]. On the basis of product distribution studies, [bmim][Tf2N]/Al(Tf2N)3 appears the most suitable medium in which methyl linoleate alkylation with propene can compete with methyl linoleate or propene oligomerization. [ABSTRACT FROM AUTHOR]

Five different ionic liquids (ILs), obtained by dissolving bistriflimide salts of Ag, Cu, Co, Ni and zinc in 1-butyl-3-methylimidazolium bistriflimide ([bmim][Tf 2 N]) were synthesized and electrochemically characterized by means of cyclic voltammetry and chronoamperometry. Silver-bearing IL represents the simplest electrochemical system since silver is present as uncoordinated or weakly coordinated Ag + ions. Homogeneous and crack-free silver coatings were potentiostatically obtained from this ionic liquid and the nucleation and growth mechanism were determined. In contrast, copper–cobalt- and zinc-bearing systems were highly moisture sensitive. The presence of large amounts of water changes the nature of the coordination species present in the solution, facilitating the electroreduction of the metal complexes. However, in hydrated solutions we observe simultaneous hydrogen evolution, which impairs the electrochemical investigation of the metal nucleation and growth mechanism. Nevertheless, metallic deposits were obtained and their morphologies investigated as a function of the deposition potential and water content. Conversely, within the investigated electrochemical window, the Ni-bearing IL does not form electroactive species. [ABSTRACT FROM AUTHOR]

Abstract: The aim of this work was to investigate innovative reaction media such as ionic liquids for enzymatic phospholipids transformations in order to get a higher selectivity in the enzymatic transphosphatidylation reactions of natural phosphatidylcholine catalyzed by phospholipase D (PLD) from Streptomyces PMF. The stability and the activity of the PLD in the ionic liquid [BMIM][PF6] were tested. This ionic liquid used as a cosolvent in the synthesis of phosphatidylserine lead surprisingly to the almost quantitative suppression of unwanted hydrolytic side reaction, thus providing a great improvement in the final product purification. [Copyright &y& Elsevier]

The equilibrium constants for ion pair formation of some pyridines have been evaluated by spectrophotometric titration with trifluoroacetic acid in different ionic liquids. The basicity order is the same in ionic liquids and in water. The substituent effect on the equilibrium constant has been discussed in terms of the Hammett equation. Pyridine basicity appears to be less sensitive to the substituent effect in ionic liquids than in water. [ABSTRACT FROM AUTHOR]

While the solvent effect on the rate of tautomerization of 2-nitrocyclohexanone in several organic solvents appears to depend essentially on the permittivity of the solvent, a different behavior is observed in some ionic liquids. In particular the rate of the reaction in ionic liquids (ILs) is much faster than expected solely on the basis of the permittivity of the studied ILs. However, if more solvent parameters are taken into consideration (namely the polarizability, H-bond acidity, and cohesive pressure of the solvent) one comprehensive linear solvation energy relationship (LSER) for both organic and IL media can be obtained and no special "ionic liquid effect" can be highlighted. The kinetic results have also been discussed in terms of the Brønsted equation. It turns out that on passing from molecular solvents to IL5 the transition state structure of the enolization reaction becomes markedly enolate-like (Brønsted β value close to 1). [ABSTRACT FROM AUTHOR]