Showing papers on "Solvent published in 2001"

Organic Nanoparticles in the Aqueous Phase-Theory, Experiment, and Use.

Abstract: Many active organic compounds and organic effect materials are poorly soluble in water, or even insoluble. Aqueous forms of application thus require special formulation techniques to utilize or optimize the physiological (pharmaceuticals, cosmetics, plant protection, nutrition) or technical (varnishes, printing inks, toners) action. The most interesting properties of nanodispersions of active organic compounds and effect materials include the impressive increase in solubility, the improvement in biological resorption, and the modification of optical, electrooptical, and other physical properties which are achievable only with particle sizes in the middle or lower nanometer range (50-500 nm). Hence in addition to economic and ecological constraints there are also technical demands which appear to urgently require the development of new processes for the production of organic nanoparticles as alternatives to the established mechanical milling processes. In this context attention is drawn to the recent increase in research activities which have as their objective the continuous, automatic preparation of nanodispersed systems by precipitation from molecular solution. In this review the current state of knowledge of the fundamentals of particle formation from homogeneous solution and the effect of solvent and polymer additives on the morphology and supramolecular structure of the nanoparticle will be discussed. The practical implementation of this new formulation technology will be explored in detail for the carotenoids, a class of compounds of both physiological and technical interest.

Improved Preparation and Use of Room-Temperature Ionic Liquids in Lipase-Catalyzed Enantio- and Regioselective Acylations

Abstract: Polar organic solvents such as methanol or N-methylformamide inactivate lipases. Although ionic liquids such as 3-alkyl-1-methylimidazolium tetrafluoroborates have polarities similar to these polar organic solvents, they do not inactivate lipases. To get reliable lipase-catalyzed reactions in ionic liquids, we modified their preparation by adding a wash with aqueous sodium carbonate. Lipase-catalyzed reactions that previously did not occur in untreated ionic liquids now occur at rates comparable to those in nonpolar organic solvents such as toluene. Acetylation of 1-phenylethanol catalyzed by lipase from Pseudomonas cepacia (PCL) was as fast and as enantioselective in ionic liquids as in toluene. Ionic liquids permit reactions in a more polar solvent than previously possible. Acetylation of glucose catalyzed by lipase B from Candida antarctica (CAL-B) was more regioselective in ionic liquids because glucose is up to one hundred times more soluble in ionic liquids. Acetylation of insoluble glucose in organ...

Recovery of Organic Products from Ionic Liquids Using Supercritical Carbon Dioxide

Abstract: Ionic liquids (ILs) hold great potential as replacements for traditional volatile organic solvents and have been shown to be a viable medium for numerous types of reactions. This work investigates the feasibility of using supercritical carbon dioxide, another environmentally benign solvent, for the separation of organic solutes from an ionic liquid. Recovery rates of aromatic and aliphatic solutes from 1-n-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]) are given. Supercritical fluid extraction is shown to be a viable separation technique with the additional benefits of environmental sustainability and pure product recovery.

Sulfonation of poly(ether ether ketone)(PEEK): Kinetic study and characterization

Abstract: Hydrophobic poly(ether ether ketone) (PEEK) were modified by sulfonation at different temperatures (22, 36, 45, and 55°C) and varying period of time with concentrated sulfuric acid used as solvent A kinetic study was carried out based on the assumption that sulfonation reaction is a second-order reaction, which takes place preferentially in the aromatic ring between the two ether (O) links (the first type substitution), and there is only one substituent attached to each repeat unit of the PEEK before the complete substitution of this preferred aromatic ring More than 100% substitution was observed in experiment All the data with substitution degree less than 95% agree fairly well with the kinetic behavior of the second-order reaction The reaction rate coefficient and activation energy for first type substitution were obtained The sulfonated PEEK samples were characterized in terms of ion-exchange capacity (IEC), 1H-NMR, contact angle, and solubility © 2001 John Wiley & Sons, Inc J Appl Polym Sci 82: 2651–2660, 2001

The universal solvent extraction (unex) process. i. development of the unex process solvent for the separation of cesium, strontium, and the actinides from acidic radioactive waste

Abstract: A synergistic extraction mixture containing chlorinated cobalt dicarbollide (CCD), carbamoylmethyl phosphine oxide (CMPO), and polyethylene glycol (PEG) has been investigated for the simultaneous recovery of cesium, strontium, lanthanides, and actinides from highly acidic media. The extraction properties of this mixture depend on the concentration ratio of the components. For recovery of all major radionuclides, the optimal ratio of [CCD]:[PEG]: [CMPO] = 5:1:1 should be used. The use of diphenyl-N,N-dibutylcarbamoylmethyl phosphine oxide and PEG-400 provides the most efficient recovery of cesium, strontium, lanthanides, and actinides. The possibility of using polyfluorinated ethers, esters, ketones, and sulfones as diluents was examined. Phenyltrifluoromethyl sulfone was the most suitable diluent tested. The use of this diluent allows good extraction properties, chemical and radiation stability, excellent explosion/fire-safety properties, and favorable hydrodynamic characteristics. The extraction of radio...

Nonflammable Trimethyl Phosphate Solvent-Containing Electrolytes for Lithium-Ion Batteries: I. Fundamental Properties

Abstract: To develop nonflammable electrolytes for lithium-ion batteries, the fundamental properties of trimethyl phosphate (TMP)-based electrolytes with LiPF 6 as solute were investigated for natural graphite anode and LiCoO 2 cathodes, It was found that the TMP solvent had good oxidation stability and poor reduction stability, which led to TMP reduction decomposition on the natural graphite electrode at the negative potential of 1.2 V. To solve this problem, ethylene carbonate (EC). propylene carbonate (PC), and diethyl carbonate (DEC) cosolvents were mixed with TMP solvent. As a result, the reduction decomposition of the TMP solvent was considerably suppressed in < 10% TMP containing EC + PC + TMP and <25% TMP containing EC + DEC + TMP electrolytes due to the formation of good solid electrolyte interphase film on natural graphite electrode in these two mixed electrolytes. The nonflammability of the TMP electrolyte declined with mixing flammable cosolvents, which was explained by a flame retarding mechanism involving a hydrogen radical trap in the gas phase. According to this mechanisms it was deduced that the cosolvents with high boiling point and fewer hydrogen atoms were promising for nonflammability of mixed electrolytes Furthermore, a thermal test disclosed that the thermal stability of lithium-ion cells may be improved by using TMP-containing electrolytes.

Self-Assembly and Bonding of Alkanephosphonic Acids on the Native Oxide Surface of Titanium

Abstract: Alkanephosphonic acids assemble from solution on the native oxide surface of titanium to form alkane chain ordered films which, however, are easily removed by solvent rinse. In contrast, assembling the alkanephosphonic acid from solution on the native oxide surface of titanium followed by gentle heating gives an alkane chain ordered film of the acid which is strongly surface-bound; this film resists removal by solvent washing or simple mechanical peel testing. Surface imaging by atomic force microscopy shows comprehensive surface coverage by aggregated islands, with elevations of each consistent with monolayer formation. ω-Carboxyalkanephosphonic acids are also easily bound to the native oxide surface of Ti through self-assembly/heating. Infrared analysis is consistent with surface attachment through the phosphonate headgroup.

Photoinduced Electron and Proton Transfer in Phenol and Its Clusters with Water and Ammonia

Abstract: Ab initio (RHF, MP2, CASSCF, and CASPT2) calculations have been performed for the electronic ground and lowest excited singlet states of phenol, the complexes of phenol with water and ammonia, and the corresponding cations. In agreement with recent experiments it is found that proton transfer is a barrierless process in the phenol−(H2O)3 and phenol−NH3 cations, whereas no proton transfer occurs in the phenol−H2O cation. Novel aspects of the reaction dynamics in the excited-state manifold of the neutral clusters are revealed by the calculations. Predissociation of the S1(ππ*) state by a low-lying 1πσ* state leads to a concerted electron and proton-transfer reaction from the chromophore to the solvent. The excited-state reaction is endothermic in phenol−H2O and phenol−(H2O)3 clusters but exothermic (though activated) in the phenol−NH3 complex. These results substantiate recent reinterpretations of spectroscopic and kinetic data on hydrogen-transfer reactions in phenol−ammonia clusters. The close relationshi...

The Reaction of Charged Cathodes with Nonaqueous Solvents and Electrolytes: I. Li0.5CoO2

Abstract: The thermal decomposition of Li 0 5CoO2 was studied by accelerating rate calorimetry and X-ray diffraction. Oxygen loss from the material according to the reaction Li 0.5 CoO 2 → 0.5 LiCoO 2 + 1/6Co 3 O 4 + 1/6O 2 occurs at temperatures above 200°C. By contrast, the reaction of Li 0.5 CoO 2 with ethylene carbonate:diethyl carbonate (EC:DEC) solvent initiates at temperatures as low as 130°C, which is much lower than the decomposition temperature of Li 0.5 CoO 2 itself, and reduction to CoO occurs. We believe that this is caused by the reducing power of the solvent. The heat generated by this reaction is consistent with that expected from the combustion of the solvent hy the oxygen liberated during the decomposition of the solid. The reaction of Li 0.5 CoO 2 with xM LiPF 6 /EC:DEC (0 < x < 1.5) electrolyte was also studied. As the salt concentration is increased, the solvent combustion reaction is suppressed, suggesting that increased LiPF 6 concentration can slow the cathode/electrolyte reaction in practical Li-ion cells under conditions of electrical or mechanical abuse.

Stable Colloidal Dispersions of Fullerenes in Polar Organic Solvents

Abstract: Colloidal dispersions of C60 and C70 were prepared by simply mixing a fullerene solution in a good solvent with a poor polar organic solvent for fullerenes. The process was very easy and fast and the formation of particles with average diameter in the colloidal range was detected immediately after the components were mixed. The formation and the properties of the fullerene particles were studied mainly with dynamic light scattering and high-resolution transmission electron microscopy. The most interesting findings are the long-term colloid stability of the samples in the absence of any stabilizers, the relatively narrow size distribution, and the different average sizes of the particles formed by C60, C70, and their mixtures. The influence of various factors such as fullerene concentration, mixing procedure, solvent properties, and C60/C70 ratio was investigated. It is shown that the smaller particles are formed when the total fullerene concentration in the good solvent is decreased and that the fullerene...

Compositions and methods for administration of pharmacologically active compounds

Abstract: In accordance with the present invention, there are provided compositions and methods useful for the in vivo delivery of substantially water insoluble pharmacologically active agents (such as the anticancer drug paclitaxel) in which the pharmacologically active agent is delivered in the form of suspended particles coated with protein (which acts as a stabilizing agent). In particular, protein and pharmacologically active agent in a biocompatible dispersing medium are subjected to high shear, in the absence of any conventional surfactants, and also in the absence of any polymeric core material for the particles. The procedure yields particles with a diameter of less than about 1 micron. The use of specific composition and preparation conditions (e.g., addition of a polar solvent to the organic phase), and careful election of the proper organic phase and phase fraction, enables the reproducible production of unusually small nanoparticles of less than 200 nm diameter, which can be sterile-filtered. The particulate system produced according to the invention can be converted into a redispersible dry powder comprising nanoparticles of water-insoluble drug coated with a protein, and free protein to which molecules of the pharmacological agent are bound. This results in a unique delivery system, in which part of the pharmacologically active agent is readily bioavailable (in the form of molecules bound to the protein), and part of the agent is present within.

Microprecipitation method for preparing submicron suspensions

Abstract: The present invention provides a method for preparing submicron sized particles of an organic compound, the solubility of which is greater in a water-miscible first solvent than in a second solvent which is aqueous, the process including the steps of: (i) dissolving the organic compound in the water-miscible first solvent to form a solution, (ii) mixing the solution with the second solvent to define a pre-suspension; and (iii) adding energy to the pre-suspension to form particles having an average effective particle size of 400 nm to 2 microns.

Change of Conductivity with Salt Content, Solvent Composition, and Temperature for Electrolytes of LiPF6 in Ethylene Carbonate-Ethyl Methyl Carbonate

Abstract: We measured the electrolytic conductivities of the electrolytes of LiPF 6 in ethylene carbonate-ethyl methyl carbonate at different salt contents, solvent compositions, and temperatures in the ranges of their practical values. To these data, we fitted a fourth degree trivariate polynomial and obtained a close fit. We then plotted this function as surface and contour plots in the coordinates of salt content and solvent composition for a series of temperatures. These plots showed the change of conductivity with the simultaneous changes of salt content and solvent composition and the influence of temperature on this change, thus mapping the locations for the optimal combinations of salt content and solvent composition for maximum conductivity of the electrolytes at desired temperatures. Here we also discuss and interpret qualitatively the trends found in the change of conductivity with salt content, solvent composition, and temperature, based on the dependency on the same variables of these three factors: the number of dissociated ions in the electrolyte, the dielectric constant of the solvent, and the viscosity of the electrolyte.

Bis(Amino Acid) Oxalyl Amides as Ambidextrous Gelators of Water and Organic Solvents. Supramolecular Gels With Temperature Dependent Assembly-Dissolution Equilibrium

Abstract: Bis(LeuOH) (1a), bis-(ValOH) (2a) and bis(PhgOH) (5a) (Phg denotes (R)-phenylglycine) oxalyl amides are efficient low molecular weight organic gelators of various organic solvents and their mixtures as well as water, water/DMSO, and water/DMF mixtures. The organisational motifs in aqueous gels are dominated primarily by lipophilic interactions while those in organic solvents are formed by intermolecular hydrogen bonding. Most of the gels are thermoreversible and stable for many months. However, 2a forms unstable gels with organic solvents which upon ageing transform into variety of crystalline shapes. For some 1a/alcohol gels, a linear correlation between alcohol dielectric constants (epsilon) and gel melting temperatures (Tg) was found. The 1H NMR and FTIR spectroscopic investigations of selected gels reveal the existence of temperature dependent network assembly/dissolution equilibrium. In the 1H NMR spectra of gels only the molecules dissolved in entrapped solvent could be observed. By using an internal standard, the concentration of dissolved gelator molecules could be determined. In FTIR spectra, the bands corresponding to network assembled and dissolved gelator molecules are simultaneously present. This enabled determination of the Kgel values by using both methods. From the plots of InKgel versus 1/T, the deltaHgel values of selected gels have been determined (-deltaHgel in 10-36 kJ mol(-1) range) and found to be strongly solvent dependent. The deltaHgel values determined by 1H NMR and FTIR spectroscopy are in excellent agreement. Crystal structures of 2a and rac-5a show the presence of organisational motifs and intermolecular interactions in agreement with those in gel fibres elucidated by spectroscopic methods.

Lipase-Catalyzed Enantioselective Acylation in the Ionic Liquid Solvent System: Reaction of Enzyme Anchored to the Solvent

Abstract: The lipase-catalyzed enantioselective acylation of allylic alcohols in an ionic liquid solvent was demonstrated; the reaction was significantly dependent on the counter anion of the imidazolium salt and good results were obtained when the reaction was carried out in [bmim]PF6 or [bmim]BF4 as solvent. We also first demonstrated that it was possible to repeatedly use the enzyme in the ionic liquid solvent system.

Electrophilic nitration of aromatics in ionic liquid solvents.

Abstract: Potential utility of a series of 1-ethyl-3-methylimidazolium salts [emim][X] with X = OTf-, CF3COO-, and NO3- as well as [HNEtPri2][CF3COO] (protonated Hunig's base) ionic liquids were explored as solvent for electrophilic nitration of aromatics using a variety of nitrating systems, namely NH4NO3/TFAA, isoamyl nitrate/BF3.Et2O, isoamyl nitrate/TfOH, Cu(NO3)/TFAA, and AgNO3/Tf2O. Among these, NH4NO3/TFAA (with [emim][CF3COO], [emim][NO3]) and isoamyl nitrate/BF3.Et2O, isoamyl nitrate/TfOH (with [emim][OTf]) provided the best overall systems both in terms of nitration efficiency and recycling/reuse of the ionic liquids. For [NO2][BF4] nitration, the commonly used ionic liquids [emim][AlCl4] and [emim][Al2Cl7] are unsuitable, as counterion exchange and arene nitration compete. [Emim][BF4] is ring nitrated with [NO2][BF4] producing [NO2-emim][BF4] salt, which is of limited utility due to its increased viscosity. Nitration in ionic liquids is surveyed using a host of aromatic substrates with varied reactivities. The preparative scope of the ionic liquids was also extended. Counterion dependency of the NMR spectra of the [emim][X] liquids can be used to gauge counterion exchange (metathesis) during nitration. Ionic liquid nitration is a useful alternative to classical nitration routes due to easier product isolation and recovery of the ionic liquid solvent, and because it avoids problems associated with neutralization of large quantities of strong acid.

Photoalkylation of 10-Alkylacridinium Ion via a Charge-Shift Type of Photoinduced Electron Transfer Controlled by Solvent Polarity

Abstract: A charge-shift type of photoinduced electron-transfer reactions from various electron donors to the singlet excited state of 10-decylacridinium cation (DeAcrH+) in a nonpolar solvent (benzene) is found to be as efficient as those of 10-methylacridinium cation (MeAcrH+) and DeAcrH+ in a polar solvent (acetonitrile). Irradiation of the absorption bands of MeAcrH+ in acetonitrile solution containing tetraalkyltin compounds (R4Sn) results in the efficient and selective reduction of MeAcrH+ to yield the 10-methyl-9-alkyl-9,10-dihydroacridine (AcrHR). The same type of reaction proceeds in benzene when MeAcrH+ is replaced by DeAcrH+ which is soluble in benzene. The photoalkylation of R‘AcrH+ (R‘ = Me and De) also proceeds in acetonitrile and benzene using 4-tert-butyl-1-benzyl-1,4-dihydronicotinamide (ButBNAH) instead of R4Sn, yielding MeAcrHBut. The quantum yield determinations, the fluorescence quenching of R‘AcrH+ by electron donors, and direct detection of the reaction intermediates by means of laser flash p...

Electrochemical Generation of Superoxide in Room-Temperature Ionic Liquids

Abstract: We have demonstrated that superoxide ion can be generated electrochemically in room-temperature ionic-liquid solvents. In the absence of impurities, cyclic voltammetry showed that the super oxide ion is stable in these solvents. Similar superoxide ion chemistry has previously been demonstrated in volatile and environmentally suspect aprotic solvents such as dimethyl formamide and acetonitrile. However, ionic liquids are nonvolatile and should minimize the problems of secondary solvent waste. It is proposed that the resultant superoxide ion can be used to perform low-temperature oxidation of wastes. Low-temperature oxidation of waste solvents can provide a much needed alternative to high-temperature waste incinerators, whose use is greatly complicated by regulatory requirements and locating suitable sites. © 2001 The Electrochemical Society. @DOI: 10.1149/1.1406997# All rights reserved.