Nonaqueous Solvent Mixtures Research Articles

Variation of thermodynamic parameters of crown ether-metal complex formation and reactant solvation in binary nonaqueous solvent mixtures

General trends in the variation of thermodynamic parameters of complex formation of crown ethers with d-metal ions in binary nonaqueous solvent mixtures were determined. An equation was proposed for predicting variation of the stability of coordination compounds upon replacement of one nonaqueous solvent by another on the basis of the change in the Gibbs energy of solvation of the central ion. Calculation of the Gibbs energies for the formation of the [Ag18C6]+ ion in acetonitrile and a number of nonaqueous solvents confirmed the predictive ability of the proposed equation.

Mechanistic Insights into Amplification of Specific Ion Effect in Water–Nonaqueous Solvent Mixtures

Ethylene glycol (EG) and hydrogen peroxide (H2O2) can act as both hydrogen-bond donors and acceptors in the formation of solvent complexes with water molecules. In the present work, we have systematically investigated the ion-specific lower critical solution temperature (LCST) behavior of poly(N-isopropylacrylamide) (PNIPAM) in H2O–EG and H2O–H2O2 mixtures. The results obtained from turbidity measurements show that the specific anion effect is amplified with the increasing molar fraction of EG (x(EG)) but is independent of the molar fraction of H2O2 (x(H2O2)). The studies of Raman spectra and differential scanning calorimetry indicate that the discrepancy in amplification of specific anion effect between H2O–EG and H2O–H2O2 mixtures is due to the difference in the anion–solvent complex interactions rather than the anion–polymer or solvent–polymer interactions. On the other hand, the specific cation effect can also be amplified with the increasing x(EG) but changes only slightly with the x(H2O2). The discrepancy in amplification of specific cation effect between the two types of solvent mixtures is attributed to the difference in the solvent–polymer interactions.

Viscometric investigations and molecular interactions of some derivatives of 5-substituted indole dihydropyrimidines in mixed organic solvents

Colloid chemical behavior of indole dihydropyrimidines in non-aqueous solvent mixture benzene-methanol of varying composition has been investigated by viscometric measurements at 303K± 0.1. The viscosity of the system increases with the increase in concentration. The Trend Change Point (TCP) values have been determined by intersection of two straight lines, which are found to be dependent on the composition of solvent mixtures. The study confirms that the nature of synthesized compounds agglomerate formed below and above 50% benzene concentration is quite different. The viscometric data have been analyzed in terms of Einstein, Vand, Moulik and Jones-Dole equations. These well known equations have been successfully applied to explain the results of viscosity measurements and the viscometric parameters show that the behavior of compound changes in the proximity of 50% benzene concentration.

Viscometric investigations and molecular interactions of some derivatives of 5-substituted indole dihydropyrimidines in mixed organic solvents

Colloid chemical behavior of indole dihydropyrimidines in non-aqueous solvent mixture benzene-methanol of varying composition has been investigated by viscometric measurements at 303K± 0.1. The viscosity of the system increases with the increase in concentration. The Trend Change Point (TCP) values have been determined by intersection of two straight lines, which are found to be dependent on the composition of solvent mixtures. The study confirms that the nature of synthesized compounds agglomerate formed below and above 50% benzene concentration is quite different. The viscometric data have been analyzed in terms of Einstein, Vand, Moulik and Jones-Dole equations. These well known equations have been successfully applied to explain the results of viscosity measurements and the viscometric parameters show that the behavior of compound changes in the proximity of 50% benzene concentration.

The role of solvent in the stepwise electrochemical oxidation of nickelocene to the nickelocenium dication

The anodic electrochemistry of nickelocene, 1, first probed in ethanolic media by Cotton et al. in 1954, has been examined in 12 different nonaqueous solvents or solvent mixtures using [NBu 4][TFAB] (TFAB = [B(C 6F 5) 4] −) as the supporting electrolyte. Two quasi-Nernstian couples were observed for 1/ 1 + and 1 +/ 1 2+ with a potential separation (Δ E 1/2) that is consistent with a modified Born model for low-donor solvents varying in dielectric constant ( ε) from 5.6 (chlorobenzene) to 37.3 (nitromethane). In stronger–donor solvents such as acetonitrile, benzonitrile, and THF, the oxidation of nickelocenium ion to the dication 1 2+ is coupled to chemical follow-up reactions, reversible in the cases of the nitriles, which are likely to involve solvent coordination to the nickel center. The observed complexity of the anodic behavior shows that much of the previous literature on the second oxidation of nickelocene has given oversimplified conclusions. Variations of up to 600 mV in Δ E 1/2 for nickelocene can be achieved by solvent variations when using the weakly-coordinating electrolyte anion [B(C 6F 5) 4] −.

Viscometric investigations and molecular interactions of triphenodioxazine dyes in mixed organic solvents

Colloid chemical behaviour of 6,13-dichloro-3,10-dimethyl triphenodioxazine (TPDO-I) and 6,13-dibromo-3,10-dimethyl triphenodioxazine (TPDO-II) in non-aqueous solvent mixture benzene-methanol of varying composition has been investigated by viscometric measurements at 303 ± 0.1 K. The viscosity of the system increases with the increase in triphenodioxazine concentration. The Trend Change Point (TCP) values have been determined by intersection of two straight lines which are found to be dependent on the composition of solvent mixtures. The study confirms that the nature of triphenodioxazine agglomerate formed below and above 50% benzene concentration is quite different. The viscometric data have been analysed in terms of Einstein, Vand, Moulik and Jones-Dole equations. These well known equations have been successfully applied to explain the results of viscosity measurements and the viscometric parameters show that the behaviour of triphenodioxazine dyes changes in the proximity of 50% benzene concentration.

Solubility prediction of solutes in non-aqueous binary solvent mixtures

Foi investigada a possibilidade de substituir os parâmetros de Abraham calculados teoricamente pelos parâmetros experimentais, na previsao da solubilidade de solutos nao-aquoso em misturas de solventes binarios, utilizando-se o modelo de Jouyban-Acree. As solubilidades de 90 conjuntos de dados, coletados a partir da literatura, foram preditas utilizando-se estes parâmetros, os coeficientes de solventes e tambem as solubilidades de sistemas mono-solventes. A precisao das solubilidades previstas foi avaliada calculando-se a media percentual do desvio (MPD) e tambem dos desvios percentuais (IPDs) individuais. O MPD global para a analise utilizando os parâmetros de Abraham, experimentais e teoricos, foram os mesmos e <14%. Uma boa distribuicao (IPD) foi obtida por estas analises numericas. Os conjuntos de dados investigados neste trabalho foram coletados a varias temperaturas e os resultados confirmaram a possibilidade de previsao da solubilidade em solventes binarios a diferentes temperaturas. Explorou-se a possibilidade de calculos ab initio nesta previsao utilizando as solubilidades calculadas em sistemas mono-solventes. No entanto, a diferenca entre os valores previstos e observados, para os coeficientes dos solventes, aumentou para aproximadamente 60% e 200% quando usou-se gas e agua, respectivamente. Estes, sao valores muito grandes para varias aplicacoes de previsao. The possibility of replacing theoretically computed Abraham parameters with the experimental Abraham parameters in solubility prediction of solutes in non-aqueous binary solvent mixtures using the Jouyban-Acree model was investigated. The solubilities of 90 data sets collected from the literature were predicted using their Abraham parameters, the solvent coefficients and also the solubilities in mono-solvent systems. The accuracy of the predicted solubilities was evaluated by calculating the mean percentage deviation (MPD) and also individual percentage deviations (IPDs). The overall MPD for the analysis using experimental and computed Abraham parameters were the same and was < 14%. A favoured IPD distribution was obtained for these numerical analyses. The data sets investigated in this work were collected at various temperatures and the results confirmed the possibility of solubility prediction in binary solvents at various temperatures. We did explore the possibility of ab initio solubility prediction of solutes in binary mixtures using the calculated solubilities in mono-solvent systems, however, the difference between the predicted and observed values increased to ca. 60% for gas-to-solvent coefficients and ca. 200% for waterto-solvent coefficients, which is too large for many predictive applications.

Solubility prediction of anthracene in nonaqueous solvent mixtures using a combination of Jouyban-Acree and Abraham models

The applicability of previously developed quantitative structure-property relationships was extended to predict the solubility of anthracene in nonaqueous binary and ternary solvent mixtures. The accuracy of the proposed methods was evaluated using 81 solubility data sets collected from the literature. The individual and mean percentage deviation (IPD and MPD) of experimental and computed solubilities were calculated as accuracy criteria. The computations were carried out using experimental and predicted mole fraction solubility of anthracene in monosolvent systems for binary and ternary solvent systems. The overall MPD of solubility prediction using experimental values in monosolvents varied from 5.2% to 4.2% and from 16.5% to 10.7% for binary and ternary solvents, using water to solvent and gas to solvent solvational parameters, respectively. The IPD distribution was better for the gas to solvent model. The corresponding ranges for the predicted solubility of anthracene in monosolvents were 47.9% to 28.1% and 23.9% to 22.5% for binary and ternary solvents, respectively, and IPD distribution was more favourable for the gas to solvent model. In general, the models derived from gas to solvent coefficients provided more accurate predictions and are recommended for practical applications.Key words: solubility, prediction, cosolvency, anthracene, Abraham model, Jouyban-Acree model.

Predicting Solubility of Anthracene in Non-aqueous Solvent Mixtures Using a Combination of Jouyban-Acree and Abraham Models

Quantitative structure property relationships were proposed to calculate the binary interaction terms of the Jouyban-Acree model using coefficients of Abraham solvational models. The applicability of the proposed methods for reproducing solubility data of anthracene in binary solvents has been evaluated using 56 solubility data sets collected from the literature. The mean percentage deviation (MPD) of experimental and calculated solubilities, using predicted mole fraction solubility of anthracene in solvents 1 and 2, has been computed as a measure of accuracy and the MPD of the proposed methods were 5.5 and 4.2%. The accuracy of the method was compared with that of a previously reported method where the MPD was 14.4% and the mean differences between proposed and previous methods was statistically significant. To provide a predictive model, solubility of anthracene was computed using Abraham solvational models and employed to predict the solubility in binary solvents using derived model constants of Jouyban-Acree model and the obtained MPDs were 37.9 and 22.2%, respectively.

Polymetacrylate and hybrid interparticle monolithic columns for fast separations of proteins by capillary liquid chromatography

Preparation of organic polymer monolithic columns in fused silica capillaries was aimed at fast gradient separation of proteins. For this purpose, polymerization in situ procedure was optimized, using ethylene dimetacrylate and butyl metacrylate monomers with azobisisobutyronitrile as initiator of the polymerization reaction in presence of non-aqueous porogen solvent mixtures composed of 1-propanol and 1,4-butanediol. The separation of proteins in totally monolithic capillary columns was compared with the chromatography on a new type of “hybrid interparticle monolithic” capillary columns, prepared by in situ polymerization in capillary packed with superficially porous spherical beds, 37–50 μm. The “hybrid” columns showed excellent stability and improved hydrodynamic flow properties with respect to the “totally” monolithic capillary columns. The separation selectivity is similar in the two types of columns. The nature of the superficially porous layer (bare silica or bonded C18 ligands) affects the separation selectivity less significantly than the porosity (density) of the monolithic moiety in the interparticle space, controlled by the composition of the polymerization mixture. The retention behaviour of proteins on all prepared columns is consistent with the reversed-phase gradient elution theory.

Metallo-tetraazaporphyrin based anion sensors: regulation of sensor characteristics through central metal ion coordination

The iron(III) and cobalt(III) complexes of 2,3,7,8,12,13,17,18-octakis(benzylthio)-5,10,15,20-tetraazaporphyrin, (OBTAP) were synthesized and incorporated into PVC matrix as ionophores to fabricate anion selective membrane electrodes that exhibit selective potentiometric response to azide and nitrite ions, respectively. The membrane of [Fe(OBTAP)] + ( III) with a composition of 6:190:200 ( III:DBP:PVC) (w/w), and of [Co(OBTAP)] + ( IV) with a composition of 10:148:200 ( IV:DOP:PVC) (w/w), i.e. 1a and 2b, respectively (where DBP:dibutylphthalate and DOP=dioctylphthalate) gave the best performance. The membrane 1a showed a slope of 29.2±0.2 mV per decade of activity for N 3 − in the working concentration range of 8.9×10 −6 to 1.0×10 −1 M. The membrane 2b showed a slope of 30.0±0.2 mV per decade of activity for NO 2 − in the working concentration range of 1.1×10 −5 to 1.0×10 −1 M. The membranes worked satisfactorily in the pH range of 4.3–10.5 ( 1a) and 2.8–6.4 ( 2b) and had fast response time of 12±2 and 13±2 s, respectively. Electrodes exhibited a high degree of selectivity for N 3 − and NO 2 −, respectively, over several other monovalent and bivalent anions. Only SCN − and S 2− (at >1.0×10 −4 M) cause moderate interference for electrode 1a and Cl − and S 2− (at >1.0×10 −5 M) for electrode 2b. They gave reproducible results with the relative standard deviation in the observed values of potentials ( σ) of 1.96 and 1.80 mV for electrodes 1a and 2b, respectively, from the least-squares fit line. The 90% confidence limit lies within ±0.2 mV per decade of activity. Reproducible results were obtained over a period of 5 months. Their performance in non-aqueous solvent mixtures having up to 50% (v/v) methanol, ethanol and acetone were evaluated and were found satisfactory. The proposed sensors are superior in terms of detection limit and response time in comparison to the reported ones.

A simple relationship between dielectric constant of mixed solvents with solvent composition and temperature

A simple computational method for calculating dielectric constants of solvent mixtures based on Redlich-Kister extension was proposed. The model was applied to the experimental dielectric constant of binary and ternary solvent mixtures at fixed and/or various temperatures and showed accurate results. Overall average percentage deviation (OAPD) between calculated and experimental dielectric constants was calculated as an accuracy criterion. The OAPDs for correlative and predictive analyses of dielectric constants in binary solvents at a fixed temperature were 0.56 and 1.42%, respectively. The corresponding values for binary solvents at different temperatures were 1.29 and 1.92%, respectively. The OAPDs for correlative and predictive analyses of dielectric constants of a nonaqueous ternary solvent mixture at various temperatures were 1.61 and 3.05%. The accuracy of the proposed models has also been compared with those of previously published models and results showed that the proposed models were superior and capable of providing more accurate results.

Lithium ion transport through nonaqueous perfluoroionomeric membranes

AbstractThe transport properties of lithiated perfluorinated ionomers imbibed with nonaqueous solvents and solvent mixtures were studied. Polymeric ion‐exchange membranes have potential use in the next generation single‐ion secondary lithium polymer batteries, where the lithiated form of the membrane is used as a polymer electrolyte. The novelty of the approach for lithium battery applications lies in the advantage offered by a transference number of unity, no additional salt (e.g., LiPF6) is needed, and the excellent physical and chemical stability of the fluoropolymers. Ion‐exchange membranes were converted to the Li+ salt form and analyzed for total conversion using FT‐IR. Nonaqueous solvents and solvent mixtures were imbibed into the membranes in a glove box, and the uptake was measured over time. A four‐point probe was used to determine the ionic conductivity based on impedance measurements performed over a frequency range of 10 to 35,000 Hz. Conductivities exceeding 10−4 S/cm with transference numbers of unity were achieved making these ionomeric membranes potentially useful in rechargeable lithium polymer batteries.

Relationship between ionic conductivity of perfluorinated ionomeric membranes and nonaqueous solvent properties

Ionic conductivity and swelling data are measured for Nafion ® perfluorinated ionomeric membranes in nonaqueous solvents and solvent mixtures and correlated with solvent physical properties. The dependence of ionic conductivity on solvent uptake and cation type is examined for Nafion ® 117 membranes with a nominal equivalent weight of 1100 g/eq. The most important factors determining ionic conductivity in membranes swollen with polar nonaqueous solvents are the solvent viscosity, molar volume, donor properties, and the solvent uptake by the membrane. Ionic conductivity is generally limited by dissociation of the cation from the fixed anion site indicating that the ionomer fixed anion site basicity is the critical membrane property. Means for increasing membrane ionic conductivity are discussed.

Preferential solvation studies using the solvatochromic dicyanobis(1,10-phenanthroline)iron(II) complex

Solvent effects on the electronic spectra of dicyanobis(1,10-phenanthroline)iron(II) have been investigated in thirteen pure solvents and twenty binary solvent mixtures. In pure solvents, the shifts of the νmax values are found to depend on more than one of the known solvent parameters (AN, α, β, DN and π*). AN, α and π* are found to be the most important solvent parameters, exerting a considerable effect on the solvatochromic shifts of the title complex. The preferential solvation of dicyanobis(1,10-phenanthroline)iron(II) in binary solvent mixtures has been investigated by monitoring the metal–ligand charge transfer band of the indicator complex. Organic solvents are preferred near the indicator complex in aqueous binary solvent mixtures (negative deviation), except in regions rich in MeCN, Me2CO and 1,4-dioxane, where water molecules are preferred over the organic component (dual behavior). However, the indicator complex is preferentially solvated by the component which has the higher acceptor number in non-aqueous binary solvent mixtures. Negative deviation was observed in binary mixtures of CHCl3 and Me2CO with alcohols and positive deviation in mixtures of CHCl3 with THF, DMSO and Me2CO. Different criteria were considered to evaluate the extent of preferential solvation in different solvent mixtures, iz., the local molar fraction (XAL), the excess function (ΔX), the iso-solvation point (XBiso) and the preferential solvation constant (KA/B). The preferential solvation data have been linearly correlated with the different solvent parameters.

Models to predict solubility in ternary solvents based on sub-binary experimental data.

The capability of the extended forms, of two well established cosolvency models, i.e. the combined nearly ideal binary solvent/Redlich-Kister equation and the modified Wilson model, used to predict the solute solubility in non-aqueous ternary solvent mixtures is presented. These predictions are based on the measured solubilities of anthracene in binary solvent mixtures. As a result the values of average percent deviations were less than 2% for the anthracene solubility in ternary mixtures. This work was also extended to other cosolvency models, ie. the extended Hildebrand solubility approach and the mixture response surface method, which are also commonly used for correlating solubility data in ternary solvents. The accuracy of the models is compared with each other and also with a published solubility model for ternary mixtures. The results illustrate that all models produced comparable accuracy.

Solvent effects on the heterogeneous kinetics of N, N, N′, N′-tetramethyl p-phenylendiamine (TMPD) in nonaqueous binary solvent mixtures. The role of the preferential solvation phenomenon

Heterogeneous kinetics for the electrooxidation of N, N, N′, N′-tetramethyl p-phenylendiamine (TMPD) to its corresponding radical monocation (TMPD +) on Pt disk ultramicroelectrodes was studied in binary mixtures of acetonitrile (ACN) with dimethylsulfoxide (DMSO), dimethylformamide (DMF), methanol (MeOH), ethanol (EtOH) and propan-2-ol (Pr-2-OH). Values of the formal rate constant ( k° f ) at different mixture compositions were calculated through cyclic voltammetry at high-scan rates by applying the well known Nicholson method. It was found that changes in the formal rate constant with solvent composition may be explained through differences in the solvation of the activated complex and can be reasonably described by a two-step solvent exchange mechanism. On the other hand, experimental results were also analyzed by performing multiparametric as well as simple linear regressions between ln k° f and different solvent-dependent parameters, which affect both the exponential and the pre-exponential terms in the general expression for k° f . The dependence of k° f on the solvent longitudinal relaxation time was verified through the viscosity values measured at different mixture compositions by considering that values of the longitudinal relaxation times for these mixtures are not available in the literature. Moreover, the dependence of k° f on the Pekar factor and solvation parameters was also verified.

Electrochemical and spectroscopic studies of the TMPD/ TMPD .+ redox couple in non-aqueous binary solvent mixtures by using ultramicroelectrodes. Role of the preferential solvation phenomenon

Thermodynamic and diffusion parameters for the electro-oxidation of the TMPD/ TMPD .+ redox couple (TMPD: N, N, N′, N′-tetramethyl p-phenylenediamine) on Pt disk ultramicroelectrodes were determined in mixtures of acetonitrile with different aprotic and protic solvents: dimethylsulfoxide, dimethylformamide, toluene, methanol, ethanol, propan-2-ol and n-butanol. The dependence of half-wave potentials and diffusion coefficients of the electroactive species on the mixture composition was analyzed. A preferential solvation degree was detected and quantified from the variation of the frequency of the maximum of the uv-visible absorption bands of TMPD and TMPD .+ as well as from the solvodynamic radius of TMPD with the composition of the solvent mixture. Viscosities of the mixtures were measured and half-wave potentials and maximum uv-band frequencies in pure solvents were also analyzed for comparison. The behaviour of the different systems has been explained in terms of both non-specific dipolar and specific interactions, as the most important ones to be considered among the components of the redox couple and the solvents of the mixtures.

Solvent effects on aromatic nucleophilic substitutions. Part 6. Kinetics of the reaction of 1‐chloro‐2, 4‐dinitrobenzene with piperidine in binary solvent mixtures

The kinetics of the reaction between 1-chloro-2,4-dinitrobenzene and piperidine was studied in several completely non-aqueous binary solvent mixtures where the preferential solvation is the rule at 15, 25 and 40°C. The reaction was chosen as the simplest example of aromatic nucleophilic substitutions (ANS). For (aprotic solvent + aprotic co-solvent) binary systems the co-solvent was toluene, and the rest of the solvents used were selected with different structural characteristics and an extensive range of polarity. In this kind of mixture a property of mixed binary solvents would be defined by means of ET(30) values and the solvent effects on this simple model of ANS reactions are similar to those of aprotic pure solvents, especially if hydrogen-bond donor solvent mixtures are excluded from the analysis. For (aprotic solvent + protic co-solvent) binary systems the co-solvent used was methanol. The presence of a protic solvent in the mixture strongly determines the solvent effects on the reaction. In this type of binary mixture, the chemical probe under consideration may not be generally valid to interpret solvation effects. Additionally, empirical solvent polarity parameters ET(30) were determined UV-VIS spectrophotometrically for some pure aprotic solvents and, as a function of the composition, for (dimethylformamide + toluene), (toluene + methanol) and (1,1,1-trichloroethane + methanol) at 15 and 40°C, with the purpose of extending the studies on the empirical polarity indices in binary solvent mixtures to the thermo-solvatochromic area.

Ion solvation in lithium battery electrolyte solutions. 1. Apparent molar volumes

Apparent molar volumes, Vφ{symbol}(MX), of seven electrolytes (NaClO4, NaCF3SO3, NaBPh4, LiClO4, LiAsF6, Ph4AsCF3SO3 and KCF3SO3) have been determined by vibrating-tube densimetry in nonaqueous solvent mixtures of propylene carbonate (PC) with acetonitrile (AN), dimethoxyethane (DME) and tetrahydrofuran (THF). Vφ{symbol}(MX) was measured at an electrolyte concentration of 0.05M over the entire solvent composition range wherever possible. Ionic apparent molar volumes of transfer, ΔtV φ(ion), were obtained via the tetraphenylarsonium tetraphenylborate (TATB) assumption. ΔtV φ(ion) from PC to the mixed solvents are generally strongly negative for both cations and anions consistent with the greater compressibilities and lower dielectric constants of the cosolvents. In PC/AN mixtures cations and anions have similar values of ΔtV φ(ion) but in PC/DME and PC/THF mixtures they differ considerably. Cationic volumes show the expected dependence on ion-size but the differences among the anion volumes are much greater than expected at high cosolvent compositions. These effects are discussed in terms of preferential solvation and other solvent interactions. The implications of these findings for lithium batteries are briefly discussed.