Organic Solvent Molecules Research Articles

Comparison of Implicit and Explicit Solvent Models for the Calculation of Solvation Free Energy in Organic Solvents.

2015, 55, 1192-1201) and experimental data. The comparison indicates that both PB and GB give poor agreement with explicit solvent calculations and even worse agreement with experiments (root-mean-square deviation ≈ 15 kJ/mol). The main problem seems to be the prediction of the apolar contribution, which should include the solvent entropy. The quantum mechanical-based SMD model gives significantly better agreement with experimental data than do PB or GB, but it is not as good as explicit solvent calculation results. The dielectric constant ε of the solvent is found to be a powerful predictor for the polar contribution to the free energy in implicit models; however, the Onsager relation may not hold for realistic solvent, as suggested by explicit solvent and SMD calculations. From the comparison, we also find that with an optimization of the apolar contribution, the PB model gives slightly better agreement with experiments than the SMD model, whereas the correlation between the optimized GB models and experiments remains poor. Further optimization of the apolar contribution is needed for GB models to be able to treat solvents other than water.

The Influence of Processing Conditions on the 3-D Interconnected Structure of Nanosilver Paste

Nanosilver paste is a promising material for power device interconnects. Interconnects are fabricated from nanosilver paste through a sintering process that drives off solvents and dispersants and fuses the silver particles. The integrity of the resulting interconnect is affected by the silver microstructure. This paper explored how sintering temperature, atmosphere, and time influenced microstructure as revealed by transmission electron microscopy and 3-D imaging via dual-beam serial sectioning. Nanosilver paste was sintered in combinations of the following parameters: a sintering atmosphere of air or nitrogen; temperatures of 120 °C or 255 °C; and sintering times of 5, 10, or 30 min. For the 255 °C temperature, oxygen in air facilitated removal of organic solvent and dispersant molecules and led to a microstructure with a coarser ligament network than samples sintered at the same temperature and times in nitrogen. The coarser ligament network was characterized by thick connected ligaments, large connected pores, and few isolated pores; this microstructure has been correlatedwith improved mechanical strength. Details of both 2-D and 3-D ligament network morphology, grain morphology, grain size, and the associated grain boundaries are discussed.

Studies of solvation behaviour of LiI prevailing in diverse solvent systems conductometrically and spectrometrically supported by ab initio technique

Solvation nature of Lithium iodide (LiI) for both polar and nonpolar organic solvents viz., acetonitrile and benzonitrile have been explored by effect of geometry, spectroscopic, conductometric, ab initio methods . Results of vibrational spectroscopic data were compared with experimental values. Centre of attraction is iodide anion on significant vibrational bands of benzonitrile. Fluorescence spectra provide a supporting to the mentioned facts. Ab initio calculations used for shaping the optimum location of Li+ and I− ions in ion-solvent interactions containing varying nitriles as solvent sphere. Emission band positions, intensity, shape of solvent-sensitive molecules in organic solvents of varying polarities are studied.

Enthalpy characteristics of L-proline dissolution in certain water–organic mixtures at 298.15 K

A thermochemical study of the processes of L-proline dissolution in aqueous solutions of acetonitrile, 1,4-dioxane, acetone, dimethyl sulfoxide, nitromethane and tetrahydrofuran at Т = 298.15 K in the range of organic solvent concentrations x2 = 0–0.25 mole fractions is performed. Standard values of the enthalpies of solution and transfer of L-proline from water to mixed solvent, and the enthalpy coefficients of pairwise interactions between L-proline and molecules of organic solvents, are calculated. The effect the composition of a water–organic mixture and the structure of organic solvents have on the enthalpy characteristics of L-proline dissolution and transfer is examined. The effect the energy properties of intermolecular interactions between components of a mixed solvent has on the intermolecular interactions between L-proline and molecules of cosolvent is estimated. The correlation between the enthalpy characteristics of L-proline dissolution and electron-donor properties of organic cosolvent in aqueous solutions is determined.

Lead, zinc and copper fine powder with controlled size and shape

This study describes the preparation of lead, zinc and copper powders by hydrometallurgy from secondary resources. Chloride, sulphate and acetate salts of zinc, copper and lead were prepared. The powders were prepared by reducing the ionic species of these metals by hydrazine hydrate or ascorbic acid. The effect of addition of some water soluble polar organic solvents to the aqueous salt solutions on the morphology and particle size of the prepared powder was studied. Findings were explained on the basis of the transition state theory and according to the Hughes and Ingold’s rule. Aqueous solutions alone produce metal powder having different size and irregular shape. The presence of polar organic solvents with high molecular weight and polarity produce powders having controlled size and regular morphology. The reason was because solvent polarity enhances the rate of red-ox reactions between metal ions and the reducing agent. The mean particle size of the powder was 60 um with zinc, 80 um with copper, and 90 um with lead. The extent of productivity was ≥98%. Results highlighted that the chemical reduction of the ionic species took place in a sequence steps. The first is a diffusion of the reactants across a boundary layer established at the polar site of the organic solvent molecules. The next step is the direct contact of the reactants. The third step involved reduction to yield powder. The last is the backward diffusion of the powder outside the boundary layer. Results showed that addition of water-miscible solvents having high dielectric constant increased the polarity of the medium. This energizes and enhances the one or more t step of the model to be more rapid to yield particles with small size and symmetrical shape.

Denaturation of DNA in Ternary Mixed Solution of Water/Hydrophilic/Hydrophobic Organic Solvent

Denaturation was examined for the first time in a ternary mixed solution of water/hydrophilic/ hydrophobic organic solvent using λ-DNA and a plasmid as models. The absorbance of λ-DNA and the plasmid at 260 nm gradually increased for several days up to 1.68 and 1.38 times the initial values, respectively, in a water/acetonitrile/ethyl acetate (15:3:2, volume ratio) mixed solution, whereas there was little change in a water/acetonitrile (15:3, volume ratio) mixed solution. The plasmid treated with the ternary mixed solution was also examined with agarose gel electrophoresis. These experimental data indicated that λ-DNA changed from a double helix structure to a single helix structure and that the plasmid partially transformed to generate a denaturation bubble in the structure. The new idea of using the ternary mixed solution first enabled the interaction of the hydrophobic organic solvent (e.g., ethyl acetate) molecule with the double helical structure of DNA, leading to specific slow-proceeding denaturation.

Novel fluorescent cyanide-selective chemosensor based on a functionalised pillar[5]arene copper(II) complex

As a novel macrocyclic host, pillar[5]arene can selectively recognise guest molecules in organic solvents. In this study, a fluorescent chemosensor composed of a functionalised-pillar[5]arene and Cu2+ metal complex (PN–Cu), which shows good selectivity for CN− anions, has been designed and synthesised. Complexation between PN–Cu and anions has been probed by means of various fluorescence-based methods. PN–Cu, as a turn-on fluorescence chemosensor showed high selectivity towards CN− ions in comparison to other anions, and its detection limit for CN− was calculated as 9.03 × 10−7 M. The PN–Cu sensor can serve as a recyclable component in sensing materials. Moreover, the interaction between the singly functionalised pillar[5]arene and Cu2+ has been probed through various tests. Based on the remarkable selectivity of the chemosensor PN–Cu, we propose that it might be used as a potential material for CN− recognition.

Improving Estimates of the Crystallization Driving Force: Investigation into the Dependence on Temperature and Composition of Activity Coefficients in Solution

In this work the influence of temperature and composition on the activity coefficient in solution has been investigated, based on isothermal and isobaric vapor–liquid equilibrium data for 30 binary systems classified into four groups: water–organic, polar–polar, polar–nonpolar, and nonpolar–nonpolar systems. It is shown that under most conditions the temperature dependence of the activity coefficient is clearly weaker than the composition dependence. The analysis is extended to include solid–liquid solubility data of 15 binary systems of relatively large and complex organic molecules in organic solvents. Based on this, a novel approach to estimate the thermodynamic driving force of crystallization from solution is proposed. Rather than assuming that the activity coefficient ratio equals unity, it is shown that in most cases a more accurate assumption is to neglect only the temperature dependence of the activity coefficient. This allows the activity coefficient ratio to be estimated from solid–liquid equil...

Enthalpy characteristics of the dissolution of L-valine in water/formamide mixtures at 298.15 K

The thermochemical dissolution of L-valine in solvent mixtures H2O + (formamide, N-methylformamide, and N,N-dimethylformamide) is studied at an organic component concentration of x2 = 0–0.35 molar fractions and a temperature of 298.15 K. The experimental data are used to calculate standard enthalpies of dissolution, the transferring of L-valine from water to a mixed solvent, and the enthalpy coefficients of pairwise interactions (hxy) with organic solvent molecules. The correlation between the enthalpy characteristics of the dissolution of L-valine with the composition of aqueous organic mixtures and the nature of the organic solvent (its physicochemical properties) is determined. A comparative analysis of the values of hxy of a number of aliphatic L-amino acids in similar solvent mixtures with the hydrophobicity parameters of their side chains is performed.

A shrinkable dendritic glutamic acid based supromolecular gel: From microscopic volume phase transition to functional applications

Supramolecular gel is an important class of soft materials formed through the self-assembly of low molecular weight molecules in water or organic solvents via various non-covalent interactions to immobilize the solvents. Supramolecular gels have attracted widespread attentions due to their structural and functional diversity. One of the important features of the gel materials is their responsiveness, which include the reversible gel-to-sol transition, macroscopic volume phase transition (shrinkage-swelling) and so on depending upon the external stimulus such as temperature, light, metal ions, electrical or magnetic field. Among these, volume phse transition is important since it can be used to develop various functions in drug release, biosensing, controlled microvalves, self-healing and so on. Although there are large amount of reports on the volume phase transition in polymer gels, there is fewer reproted on the supramolecualr gels due to the the inherent weak character of non-covalent interactions. Supramolecular hydrogels suffer the reality that the brittle 3D structures have difficulty in maintaining physical change such as folding and curling of the supramolecular chains as in polymer hydrogels to accordingly exhibit phase transition in volume (shrinkage-swelling) and shape (deformation- recovery). Among several shrinkable supramolecular gels, the dendritic glutamic acid amphiphile OGAc containing multi-carboxylic acid as the head group and a long alkyl chain appeared to be one of the good examples of such gels. This minireview focuses on the formation of the supramolecular hydrogel OGAc, the shrinkage-swelling transition, the stimuli-responsive together with such volume phase transition and the potential applications by utilizing the shrinkage/ swelling properties. The paper firstly introduces the unique reversible shrinking and swelling supramolecular gel triggered by divalent metal ions. Then the function of the various metal ions as the inducer for the gel shrinkage was discussed and a mechanism was proposed. Based on these discussions, the design concept for the shrinkable supramolecular gels was suggested. Secondly, the pH responsiveness of the OGAc-Mg2+ is discussed. Thirdly, in order to functionalize the supramolecular gels, charged organic compounds were introduced into the shrinkable gels. It was found that OGAc-AZOC2Py complex system also exhibited reversible shrinkage/swelling transition. Simultaneously, the gel showed a change in supramolecular chirality. Fourthly, the potential applications of the supramolecular assemblies by using the shrinkable gel are discussed, which mainly highlights the application in the efficient separation of the mixtures composed of positively and negatively charged dyes, visualized recognition of chiral amines based on OGAc- Mg2+-PIC system, the construction of dual reversible thermal and light-responsive chiroptical switches for OGAc-AZOC2Py hydrogel and controlled step-wise release of drug or biological substances in OGAc-Mg2+ gels. Finally, the future development and application of supramolecular shrinkable gel is outlooked. It is anticipated to design more sophisticated multi-functional materials based on reversible macroscopic volume phase transition and also to combine the advantage of the shrinkable polymer gels to develop new soft materials. It is expected that the shrinkable gels will find more applications in biological system and biotechnology.

Direct Observation of Electrophoretic Flow of Solvent Molecules with Lithium Ions By NMR Imaging

Lithium ion transport in the organic liquid electrolyte is a key process in conventional lithium ion batteries, where the lithium ion shuttles between the positive and negative electrodes while the charging and discharging process. The translational motion of the lithium ion in the liquid electrolyte is accompanied by the coordinating organic solvent molecules such as EC, DMC etc., which must be detached from the lithium ion at the electrodes by the desolvation process. On the other hand, the counter anions such as PF6 - is thought to move opposite direction, although the local concentration is the same to that of lithium cation in order to keep the electroneutrality condition. Although this picture is based on many evidences by electrochemical measurements, the direct observation of the correlated motion of the lithium ions and solvated molecules has not been reported. In this paper, we first demonstrate the direct observation of the translational motion of solvent molecules (EC,DEC) with the lithium ions by using NMR micro-imaging technique. NMR microimaging is observed by Avance 400 spectrometer equipped with mini-Imaging probe by Bruker Co. The 1H and 19F NMR imaging are observed in this measurement. Model cell is constructed in NMR spectrometer, which is composed by LiMn2O4 cathode, lithium metal anode and liquid electrolyte of EC/DMC+LiPF6. The cell is connected to an electrochemical charge-discharge set-up to operate the cell. Small desolution of Mn2+ from the cathode acts as a contrast agent to enhance the flow image of the cell. Some vertical images of the cell in a charge-discharge process are shown in Fig. 1, where the LiMn2O3 positive electrode is located at the bottom and the lithium metal anode is on the top. Constant current mode of 25 mA is used. While the charging current is set upward from LiMn2O3 cathode to the lithium anode, namely the Li+ cations move upward, then the proton NMR imaging observing the motion of the EC and DMC molecules is confirmed to upward, which is the same direction as that of the Li+ ions. Moreover, the flowing current of the solvent moves toward left and right directions near the lithium anode, where the EC and DMC should release the Li+ to the anode and move aside. This continuous flow generates an electroconvection which can be seen in Fig. 1 as a vortex curling from center to the side wall. On the other hand, when the current is reversed to discharge, the flow of the solvent changes its direction from the top (anode) to the bottom (cathode), which generate the reverse vortex as shown in Fig. 1. Figure 1

A Correlation between the Activity of Candida antarctica Lipase B and Differences in Binding Free Energies of Organic Solvent and Substrate

The ability of enzymes to operate in organic solvent is now widely accepted and is the basis for extensive research in enzymology. The challenge is to select the solvent media that allows the modulation of enzyme activity. For a rational selection of a solvent, it is necessary to understand the effect of organic solvent molecules on enzyme structure and the enzymatic reaction on a molecular level. To gain such insight, we combined experimental kinetics studies with full atomic molecular dynamics simulations and found a correlation between the activity of Candida antarctica lipase B (CALB) [for the esterification reaction between butyric acid and ethanol at a fixed water activity] and the binding of the solvent/substrate molecules in the active site region of CALB. We have investigated the influence of four organic solvents—hexane (HEX), methyl tertiary butyl ether (MTBE), acetonitrile (ACN), and tertiary butanol (TBU)—on the catalytic activity of CALB for the esterification reaction. The solvents have bee...

Separating hydrocarbons using reverse osmosis

A membrane that separates organic solvent molecules based on their shape and size could dramatically cut costs associated with preparing valuable polymer feedstocks, such as p-xylene. It works as part of a reverse-osmosis process, a common method for water desalination that hasn’t been applied to organic solvents until now. Both the membrane and the organic solvent reverse-osmosis process were developed by Ryan P. Lively and Dong-Yeun Koh of Georgia Tech, along with Benjamin A. McCool and Harry W. Deckman of ExxonMobil Research & Engineering. The researchers started with a commercially available hollow fiber made of poly(vinylidene fluoride). The fiber consists of a tube of support material full of microscale pores surrounded by a membrane riddled with molecule-sized pores. This porous material is incompatible with organic solvents, so the researchers converted it to an all-carbon substance, called a carbon molecular sieve, by heating it to 550 °C. But before they did

Acoustical Investigation of N–(2-hydroxybenzylidene)-3-Substituted Pyridine -2- Amine Schiff bases by Ultrasonic Velocity Measurements in Dioxane at Different Temperatures

<div><p><em>The present work deals with the study of acoustic parameters like ultrasonic velocity (V), </em><em>adiabatic compressibility (β<sub>s</sub>), apparent molar volume (</em><em>f</em><em><sub>v</sub></em><em>) and intermolecular free length (L<sub>f</sub>) by ultrasonic </em><em>interferometric measurements</em><em> which reflects structural interaction of water molecules and organic solvent molecules with substituted Schiff bases. The study of N–(2-hydroxybenzylidene)-3-substituted pyridine -2- amine Schiff bases were carried in different percentage of 1,4-dioxane-water medium, at 293, 297 and 300 K. The densities and velocities thus obtained were used to evaluate acoustic parameters for all the ligands.</em></p></div>

Crystal structure of l-leucyl-l-isoleucine 2,2,2-tri-fluoro-ethanol monosolvate.

Hydro-phobic dipeptides with either l-Leu or l-Phe constitute a rather heterogeneous group of crystal structures. Some form materials with large water-filled channels, but there is also a pronounced tendency to incorporate organic solvent mol-ecules, which then act as acceptors for one of the three H atoms of the charged N-terminal amino group. l-Leu-l-Ile has uniquely been obtained as two distinct hydrates, but has so far failed to co-crystallize with a simple alcohol. The present structure of C12H24N2O3·CF3CH2OH, which crystallizes with two dipeptide and two solvent mol-ecules in the asymmetric unit, demonstrates that when 2,2,2-tri-fluoro-ethanol is used as a solvent, its high capacity as a hydrogen-bond donor leads to formation of an alcohol solvate.

Mono/bimetallic water-stable lanthanide coordination polymers as luminescent probes for detecting cations, anions and organic solvent molecules.

Eleven water-stable isostructural mono/bimetallic lanthanide coordination polymers (Ln-CPs) {[EuxTb1-x (HL)(H2O)3]·H2O}n (x = 1.0 (1), 0.9 (3), 0.8 (4), 0.7 (5), 0.6 (6), 0.4 (7), 0.3 (8), 0.2 (9), 0.1 (10), 0.05 (11), 0 (2), H4L = 5,5'-(1H-2,3,5-triazole-1,4-diyl)diisophthalic acid) with uncoordinated Lewis basic triazole sites within the pores were prepared. The Ln-CPs represented by 1 showed a rapid and drastic emission quenching induced by external Fe(3+) and Cr(3+) cations and CrO4(2-) and CO3(2-) anions in aqueous solution. In addition, because of the comparable emission intensities of Eu(3+) and Tb(3+) ions, bimetallic CP 8 can be used as a ratiometric luminescent sensor for organic solvent molecules. Moreover, the luminescent color of the 8 sensor in pyridine and in other guest solvents undergoes obvious changes that can be clearly distinguished by the naked eye.

Reactive oxygen species formed in organic lithium-oxygen batteries.

Li-oxygen batteries with organic electrolytes are of general interest because of their theoretically high gravimetric energy density. Among the great challenges for this storage technology is the generation of reactive oxygen species such as superoxides and peroxides that may react with the organic solvent molecules and other cell components. The generation of such species has been assumed to occur during the charging reaction. Here we show that superoxide is formed also during the discharge reaction in lithium ion-containing dimethyl sulfoxide electrolytes and is released into the solution. This is shown independently by fluorescence microscopy after reaction with the selective reagent 4-chloro-7-nitrobenzo-2-oxa-1,3-diazole and by local detection using a microelectrode of a scanning electrochemcial microscope positioned in a defined distance of 10 to 90 μm above the gas diffusion electrode.

Shape-controlled cobalt phosphide nanoparticles as volatile organic solvent sensor

Shape-controlled cobalt phosphide nanostructures have been synthesized using a one-pot reaction strategy for sensing volatile organic solvent molecules.

Investigation of diffusion mechanisms during pervaporation of molecules of organic solvents in polymer membranes

With the help of the original experimental setup using a pervaporation process, parameters which allow to indirectly determine the mechanisms and models of diffusion of solvent molecules in the polymer membrane body were investigated. The time dependencies of these parameters during pervaporation were obtained for both unsaturated and saturated membranes. It was shown that the mechanism of diffusion of the solvent molecules in the polymer membrane for the unsaturated membranes consists of two components: diffusion through thermal activation of the system and diffusion occurring through the free volume. Moreover, the rate of thermally activated diffusion is much higher and is observed in the beginning of the pervaporation process, whereas the diffusion using the free-volume model begins to emerge in the middle of the process and runs more slowly, but it is a source of transfer of the majority of solvent molecules. For saturated membranes, the main transfer mechanism is diffusion through the structural voids of the polymer. These results allow to interpret diffusion models in polymer membranes.

Dynamic entangled framework based on an iridium-organic unit showing reversible luminescence turn-on sensing.

A new entangled metal-organic framework shows reversible structural dynamics and luminescence changing in response to the loss of guest H2O molecules. Furthermore, an intense and sensitive luminescence turn-on sensing was observed by the naked eye for 1 upon detection of the volatile organic solvent molecule CH3CN, accompanied by reversible structural transformation.