Thermodynamic Analysis of Homologous α-Amino Acids in Aqueous Potassium Fluoride Solutions at Different Temperatures

Partial molal volumes ( $V_{\phi} ^{0}$ ) and partial molal compressibilities ( $K_{\phi} ^{0}$ ) for glycine, L-alanine, L-valine and L-leucine in aqueous potassium fluoride solutions (0.1 to 0.5?mol?kg^?1) have been measured at T=(303.15,308.15,313.15 and 318.15) K from precise density and ultrasonic speed measurements. Using these data, Hepler coefficients ( $\partial^{2}V_{\phi} ^{0}/\partial T^{2}$ ), transfer volumes ( $\Delta V_{\phi} ^{0}$ ), transfer compressibilities ( $\Delta K_{\phi} ^{0}$ ) and hydration number (n _H) have been calculated. Pair and triplet interaction coefficients have been obtained from the transfer parameters. The values of $V_{\phi} ^{0}$ and $K_{\phi} ^{0}$ vary linearly with increasing number of carbon atoms in the alkyl chain of the amino acids. The contributions of charged end groups ( $\mathrm{NH}_{3}^{+}$ , COO^?), CH₂ group and other alkyl chains of the amino acids have also been estimated. The results are discussed in terms of the solute?Ccosolute interactions and the dehydration effect of potassium fluoride on the amino acids.     

Volumetric and Viscometric Studies in Binary Liquid Mixtures of 2-Methyl-2-propanol with Some Ketones at Different Temperatures

Densities, ??, and viscosities, ??, of binary mixtures of 2-methyl-2-propanol with acetone (AC), ethyl methyl ketone (EMK) and acetophenone (AP), including those of the pure liquids, were measured over the entire composition range at 298.15, 303.15 and 308.15?K. From these experimental data, the excess molar volume $V_{\mathrm{m}}^{\mathrm{E}}$ , deviation in viscosity ????, partial and apparent molar volumes ( $\overline{V}_{\mathrm{m},1}^{\,\circ }$ , $\overline{V}_{\mathrm{m},2}^{\,\circ }$ , $\overline{V}_{\phi ,1}^{\,\circ}$ and $\overline{V}_{\phi,2}^{\,\circ} $ ), and their excess values ( $\overline{V}_{\mathrm{m},1}^{\,\circ \mathrm{E}}$ , $\overline{V}_{\mathrm{m,2}}^{\,\circ \mathrm{ E}}$ , $\overline {V}_{\phi \mathrm{,1}}^{\,\circ \mathrm{ E}}$ and $\overline{V}_{\phi \mathrm{,2}}^{\,\circ \mathrm{ E}}$ ) of the components at infinite dilution were calculated. The interaction between the component molecules follows the order of AP > AC > EMK.     

Excess Acoustical and Volumetric Properties and Theoretical Estimation of Ultrasonic Velocities in Binary Liquid Mixtures of 2-Chloroaniline with Acrylic Esters at 308.15 K

The ultrasonic velocities (u) and densities (??) for three binary mixture systems of 2-chloroaniline (CA) with ethyl acrylate (EA), butyl acrylate (BA), and 2-ethylhexyl acrylate (EHA) were measured over the entire mole fraction range at the temperature 308.15?K, including those of pure liquids. From these data, the deviations in ultrasonic velocity (??u), the excess molar volumes ( $V_{\mathrm{m}}^{\mathrm{E}}$ ), deviations in excess molar volume ( $\delta V_{\mathrm{m}}^{\mathrm{E}}$ ), deviations in isentropic compressibility (??k _S), excess intermolecular free lengths ( $L_{\mathrm{f}}^{\mathrm{E}}$ ), and excess acoustic impedances (Z ^E) have been calculated. The variations of these properties with solution composition are discussed in terms of molecular interactions among unlike molecules of the mixtures. The excess and deviation functions have been fitted to Redlich-Kister type polynomials and the corresponding standard deviations ??(Y ^E) have been calculated. The deviations and excess values were plotted against the mole fraction of CA over the whole composition range. The $V_{\mathrm{m}}^{\mathrm{E}}$ and ??k _S values are negative in the EA + CA and BA + CA systems but are positive in the EHA + CA system, which indicates the presence of specific interactions between unlike molecules. Further, theoretical values of the sound velocity in these mixtures have been evaluated using various theories and have been compared with experimental sound velocities to verify the applicability of such theories to the investigated systems. Two types of polynomial equations, f(x) and g(x), have been fitted to experimental values of ultrasonic velocities. The sound velocities obtained by these polynomials have extremely small deviations from the experimental values.     

Volumetric and Viscosity Properties for the Binary Mixtures of 1-Octyl-3-methylimidazolium Tetrafluoroborate with Butanone or Alkyl Acetates

In this work, densities and viscosities for the binary mixtures of 1-octyl-3-methylimidazolium tetrafluoroborate, [C₈mim][BF₄], with butanone, methyl acetate, ethyl acetate, propyl acetate and butyl acetate have been determined at 298.15?K. These data were used to calculate the excess molar volumes $ V_{m}^{\text{E}} $ and the viscosity deviations (ln??)^E for the mixtures. It is shown that values of $ V_{m}^{\text{E}} $ are negative, while those of (ln??)^E are positive in the whole concentration range. The $ V_{m}^{\text{E}} $ values show their minimum at the composition of x _IL ????0.3, and the (ln??)^E values exhibit a maximum at the same mole fraction. For the binary systems, the absolute values of $ V_{m}^{\text{E}} $ decrease in the order: butanone?>?methyl acetate?>?ethyl acetate?>?propyl acetate?>?butyl acetate, whereas those of (ln??)^E decrease in the order: methyl acetate?>?ethyl acetate?>?propyl acetate?>?butyl acetate?>?butanone. The results are discussed in terms of the ion?Cdipole interactions between cations of the ionic liquid and the organic molecules and hydrogen bonding interactions between anions of the ionic liquid and the organic compounds.     

Density and Viscosity of Binary Mixtures of Thiocyanate Ionic Liquids + Water as a Function of Temperature

Densities and viscosities have been determined for binary mixtures of the ionic liquids (ILs) 1-butyl-3-methylimidazolium thiocyanate [BMIM][SCN], or 1-butyl-4-methylpyridinium thiocyanate [BMPy][SCN], or 1-butyl-1-methylpyrrolidinium thiocyanate [BMPYR][SCN], or 1-butyl-1-methylpiperidinium thiocyanate [BMPIP][SCN] with water over wide range of temperatures (298.15?C348.15) K and ambient pressure. The thermal properties of [BMPy][SCN], i.e. glass transition temperature and the heat capacity at glass transition, have been measured using a differential scanning microcalorimetry, DSC. The decomposition of [BMPy][SCN] was detected. The density and viscosity correlations for these systems have been made using an empirical second-order polynomial and by the Vogel?CFulcher?CTammann equation, respectively. The concentration dependences have been described by polynomials. The excess molar volumes and deviations in viscosity have been calculated from the experimental values and were correlated by Redlich?CKister polynomial expansions. The variations of these parameters, with compositions of the mixtures and temperature, have been discussed in terms of molecular interactions. A qualitative analysis of the trend of properties with composition and temperature was performed. Further, the excess partial molar volumes, $V_{1}^{\mathrm{E}}$ and $V_{2}^{\mathrm{E}}$ , were calculated and discussed. The isobaric expansivities (coefficient of thermal expansion), ??, and the excess isobaric expansivities, ?? ^E, were determined for four ILs and their mixtures with water. The results indicate that the interactions of thiocyanate ILs with water is not as strong as with alcohols, which is shown by the positive/slightly negative excess molar volumes in these binary systems.     

Interaction of Poly(vinyl alcohol) with Poly(acrylic acid) and with Sodium Polyacrylate in Aqueous Solutions: A Volumetric Study at 25 °C

The infinite dilution partial molar volumes $\bar{V}^{\infty}$ of poly(acrylic acid), at different degrees of neutralization α _N with sodium hydroxide, have been experimentally determined in aqueous solutions. Analysis of the data indicates that, to a good approximation, the observed decrease of $\bar{V}^{\infty}$ with α _N can be interpreted in terms of the electrostriction of the water molecules involved in the hydration cospheres of the –RCOO^? groups. The presence of PVA does not significantly affect the value of $\bar{V}^{\infty}$ for the undissociated acid, but causes a large decrease for the sodium salt. This aspect has been discussed in terms of direct interaction between the two polymers.     

Solubility of Thiophene-, Furan- and Pyrrole-2-Carboxaldehyde Phenylhydrazone Derivatives in 2.82 mol⋅L−1 Aqueous DMSO at 298.15 K, Inhibition of Lymphoproliferation and Tubulin Polymerization: A Study Based on the Scaled Particle Theory

In this work, the solubilities of nine phenylhydrazone derivatives in water and in 2.82 mol?L^?1 aqueous DMSO at 298.15 K, expressed on the molar fraction scale, are reported. The estimated value of the standard Gibbs energy for transferring the solute from water to 2.82 mol?L^?1 DMSO, $\Delta G^{0}_{\mathrm{W}\rightarrow \mathrm{mix}}$ , for each system, indicates that it is a spontaneous process. Some of the phenylhydrazone derivatives inhibited the induction of T lymphocyte proliferation by phytohaemagglutinin (PHA) but only DPCT and NPCF efficiently inhibited Guinea pig brain tubulin polymerization. Scaled Particle Theory (SPT) was used to interpretate solubility and biological activity results. Based on the results we suggested that the difference in the work of cavity creation ΔΔG _c, associated with the transfer of the phenylhydrazone derivatives from water to 2.82 mol?L^?1 aqueous DMSO, is the dominant factor in the magnitude of $\Delta G^{0}_{\mathrm{W}\rightarrow \mathrm{mix}}$ . The later quantity was considered to be an indirect measurement of the hydrophobic character of these derivatives, and it can be used to interpret the biological results.     

Effect of CO2 activation of carbon xerogels on the adsorption of methylene blue

The effect of physical activation with CO₂ of carbon xerogels, synthesized by pyrolysis of a resorcinol-formaldehyde aqueous gel, on the adsorption capacities of Methylene Blue (MB) was studied. The activation with CO₂ lead?to carbon materials with micropore volumes ranging from $0.28\ \mathrm{to}\ 0.98~\mathrm{cm}^{3}\,\mathrm{g}_{\mathrm{C}}^{-1}$ . MB-adsorption isotherm studies showed that the increase of micropore volume and corresponding surface area led to: (i) a significant improvement in the capacity of MB-adsorption at monolayer coverage, from $212\ \mathrm{to}\ 714~\mathrm{mg}\,\mathrm{g}_{\mathrm{C}}^{-1}$ , and (ii) an increase of the binding energy related to Langmuir isotherm constant up to 45 times greater than those of commercial microporous activated carbons used as reference (NORIT R2030, CALGON BPL and CALGON NC35). It is proposed that the increase of the binding energy results from chemical cleaning of the O-groups onto carbon surface as a consequence of CO₂-activation, increasing the π–π interaction between MB and graphene layers of the carbon xerogels. Finally, a series of batch kinetics were performed to investigate the effect of CO₂-activation conditions on the mechanism of MB-adsorption. Experimental data were fitted using pseudo-first-order, pseudo-second-order and intraparticle diffusion kinetic models. From pseudo-second-order kinetic model, one observes an increase in the initial rate of MB-adsorption from 0.019 to 0.0565 min^?1, by increasing the specific surface area from $630\ \mathrm{to}\ 2180~\mathrm{m}^{2}\,\mathrm{g}_{\mathrm{C}}^{-1}$ via CO₂-activation. Depending on the activation degree of the carbons, two different mechanisms control the MB-adsorption rate: (i) at low activation degree, the intraparticle diffusion is the rate-limiting phenomenon, whereas (ii) at high activation degree, the reactions occurring at the solid/liquid interface are the rate-limiting steps.     

Thermophysical and Spectroscopic Studies of Pure 1-Butyl-3-methylimidazolium Tetrafluoroborate and Its Aqueous Mixtures

Intermolecular interactions in the aqueous mixtures of the room temperature ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF₄]), have been studied. The thermophysical properties: density ρ, speed of sound u, specific conductivity κ and refractive index n _D have been measured over the whole composition range at different temperatures (293.15–323.15 K) and are discussed. The results from thermophysical measurements are explained with the help of spectroscopy. In order to interpret the nature of molecular interactions occurring between [BMIM][BF₄] and water molecules, as well as to identify the moieties in which interactions are taking place, ¹H, ¹³C NMR and FT-IR spectra of the solutions have been studied. Excess molar volume V ^E, excess molar isentropic compressibility $ K_{S}^{\text{E}} $ , partial molar excess volume $ V_{i}^{\text{E}} $ , partial molar excess isentropic compressibility $ K_{S,i}^{\text{E}} $ , deviation in specific conductivity ?κ, and deviation in refractive index ?R have also been determined and analyzed to have a better understanding of the interactions taking place between the different components. Additionally, the excess ultrasonic speed u ^E and excess isentropic compressibility $ k_{S}^{\text{E}} $ , in terms of volume fractions, have been calculated and analyzed. It has been observed that temperature has a significant effect on the thermophysical properties of the studied system. Spectroscopic measurements confirm the disruption of ion-pair interactions of [BMIM][BF₄] and hydrogen-bonded network of water in the aqueous mixture of [BMIM][BF₄].     

Volumetric Properties of l-Alanine and l-Serine in Aqueous N,N-Dimethylformamide Solutions at 298.15 K

The densities of l-alanine and l-serine in aqueous solutions of N,N-dimethylformamide (DMF) have been measured at 298.15 K with an Anton Paar Model 55 densimeter. Apparent molar volumes $ (V_{\phi } ) $ ( V ? ) , standard partial molar volumes $ (V_{\phi }^{0} ) $ ( V ? 0 ) , standard partial molar volumes of transfer $ (\Updelta_{\text{tr}} V_{\phi }^{0} ) $ ( Δ tr V ? 0 ) and hydration numbers have been determined for the amino acids. The $ \Updelta_{\text{tr}} V_{\phi }^{0} $ Δ tr V ? 0 values of l-serine are positive which suggest that hydrophilic–hydrophilic interactions between l-serine and DMF are predominant. The –CH₃ group of l-alanine has much more influence on the volumetric properties and the $ \Updelta_{\text{tr}} V_{\phi }^{0} $ Δ tr V ? 0 have smaller negative values. The results have been interpreted in terms of the cosphere overlap model.     

Electrogenerated chemiluminescence sensor for glutathione with Ru\left( {bpy} \right)_3^{2+ } -doped silica nanoparticles

An electrogenerated chemiluminescence (ECL) sensor for reduced glutathione was developed based on $ \mathrm{Ru}\left( {\mathrm{bpy}} \right)_3^{2+ } $ -doped silica nanoparticles-modified gold electrode (Ru-DSNPs/Au). These uniform Ru-DSNPs (about 58?+?4 nm) were prepared by a water-in-oil microemulsion method and characterized by transmission electron microscope and scanning electron microscope. With such a unique immobilization method, a considerable $ \mathrm{Ru}\left( {\mathrm{bpy}} \right)_3^{2+ } $ was immobilized three dimensionally on the electrode, which could greatly enhance the ECL response and thus result in an increased sensitivity. The ECL analytical performances of this sensor for reduced glutathione based on the quenched ECL emission of $ \mathrm{Ru}\left( {\mathrm{bpy}} \right)_3^{2+ } $ have been investigated in detail. Under the optimum condition, the ECL intensity was linear with the reduced glutathione concentration in the range of 1.0?×?10^?9 to 1.0?×?10^?4?mol?L^?1 (R?=?0.9971). This method has been successfully applied for the determination of reduced glutathione in serum samples with satisfactory results. The as-prepared ECL sensor for the determination of reduced glutathione displayed good sensitivity and stability.     

Ion-molecular interactions in solutions of potassium and cadmium thiocyanates in N-methylpyrrolidone at 298.15 k, according to calorimetry and densitometry data

The heat capacity and density of KNCS-N-methylpyrrolidone (MP), Cd(NCS)₂-MP, and KNCS-Cd(NCS)₂-MP solutions at 298.15 K are studied by means of calorimetry and densitometry. Standard partial molar heat capacities and volumes ( $\bar C^\circ _{p,2} $ and $\bar V^\circ _2 $ ) of the studied electrolytes in MP are calculated. Standard values of heat capacity $\bar C^\circ _{p,i} $ and volume $\bar V^\circ _i $ of NCS^? ions in MP at 298.15 K are determined. Values of the heat capacity and volume changes upon the formation of the three-component system KNCS-Cd(NCS)₂-MP from binary solutions are obtained and discussed.     

The Oxidation of Iron(II) with Oxygen in NaCl Brines

The oxidation of nanomolar levels of iron(II) with oxygen has been studied in NaCl solutions as a function of temperature (0 to 50?°C), ionic strength (0.7 to 5.6 mol?kg^?1), pH (6 to 8) and concentration of added NaHCO₃ (0 to 10 mmol?kg^?1). The results have been fitted to the overall rate equation: $$\mathrm{d}\mbox{[Fe(II)]}/\mathrm{d}t=-k_{\mathrm{app}}\mbox{[Fe(II)]}[\mbox{O}_{2}]$$ The values of k _app have been examined in terms of the Fe(II) complexes with OH^? and CO ₃ ^2? . The overall rate constants are given by: $$k_{\mathrm{app}}=\alpha_{\mathrm{Fe}2+}k_{\mathrm{Fe}}+\alpha_{\mathrm{Fe(OH)}+}k_{\mathrm{Fe(OH)}+}+\alpha_{\mathrm{Fe(OH)}2}k_{\mathrm{Fe(OH)}2}+\alpha_{\mathrm{Fe(CO3)}2}k_{\mathrm{Fe(CO3)}2}$$ where α _i is the molar fraction and k _i is the rate constant of species i. The individual rate constants for the species of Fe(II) interacting with OH^? and CO ₃ ^2? have been fitted by equations of the form: $$\begin{array}{l}\ln k_{\mathrm{Fe}2+}=21.0+0.4I^{0.5}-5562/T\\[6pt]\ln k_{\mathrm{FeOH}}=17.1+1.5I^{0.5}-2608/T\\[6pt]\ln k_{\mathrm{Fe(OH)}2}=-6.3-0.6I^{0.5}+6211/T\\[6pt]\ln k_{\mathrm{Fe(CO3)}2}=31.4+5.6I^{0.5}-6698/T\end{array}$$ These individual rate constants can be used to estimate the rates of oxidation of Fe(II) over a large range of temperatures (0 to 50?°C) in NaCl brines (I=0 to 6 mol?kg^?1) with different levels of OH^? and CO ₃ ^2? .     

A mathematical approach to chemical equilibrium theory for gaseous systems—III: \hbox {Q}_\mathrm{p}, \hbox {Q}_\mathrm{c}, and \hbox {Q}_{\mathrm{x}}

The reaction quotient Q can be expressed in partial pressures as $\hbox {Q}_\mathrm{P}$ or in mole fractions as $\hbox {Q}_{\mathrm{x}}$ . $\hbox {Q}_\mathrm{P}$ is ostensibly more useful than $\hbox {Q}_{\mathrm{x}}$ because the related $\hbox {K}_{\mathrm{x}}$ is a constant for a chemical equilibrium in which T and P are kept constant while $\hbox {K}_{\mathrm{P}}$ is an equilibrium constant under more general conditions in which only T is constant. However, as demonstrated in this work, $\hbox {Q}_{\mathrm{x}}$ is in fact more important both theoretically and technically. The relationships between $\hbox {Q}_{\mathrm{x}}$ , $\hbox {Q}_\mathrm{P}$ , and $\hbox {Q}_{\mathrm{C}}$ are discussed. Four examples of applications are given in detail.     

Thermodynamic study on the interaction of imidazolium salts and POE-type nonionic surfactant in the adsorbed film

The composition of the adsorbed film and the excess Gibbs energy of adsorption $ {\widehat{g}}^{\mathrm{H},\mathrm{E}} $ were evaluated from thermodynamic analysis of surface tensions for the 1-decyl-3-methylimidazoulium bromide (C₁₀mimBr)–tetraethylene glycol monooctyl ether (C₈E₄) and 1-decyl-3-methyl-imidazolium tetrafluorobrorate (C₁₀mimBF₄)–C₈E₄ systems, where the counter anion of imidazolium salts is different from each other. The higher miscibility of two components compared to an ideal mixing and thus negative $ {\widehat{g}}^{\mathrm{H},\mathrm{E}} $ were observed in the former, which comes from the ion–dipole interaction between imidazolium cation and the oxyethylene group of C₈E₄. On the other hand, the lower miscibility and thus positive $ {\widehat{g}}^{\mathrm{H},\mathrm{E}} $ were observed for the latter. Such differences were attributed to that BF₄ ^? forms two hydrogen bonds and has stronger affinity with the cationic head group of C₁₀mim⁺ than Br^?. This results in that the ion–dipole interaction between C₈E₄ and C₁₀mim⁺ cation is diminished in the C₁₀mimBF₄–C₈E₄ system.     

Thermodynamics of Solution, Interaction with Calf Thymus DNA and Anticancer Activity of?Phenylhydrazone Derivatives

The solubilities in water (W) and in 3 mol?L^?1 aqueous acetonitrile at 298.15 K of thiophene-2-, furan-2- and pyrrole-2-carboxaldehyde phenylhydrazone along with their nitro and 2,4-dinitro derivatives, referred to as PCT, PCF, PCP, NPCT, NPCF, NPCP, DPCT, DPCF and DPCP, respectively, are reported. The standard Gibbs energy of transfer from W to solvent mixtures ( $\Delta G^{\mathrm{transf}}_{\mathrm{W-mix}}$ ) was estimated for each solute. The results indicate that the transfer process for all systems is a spontaneous process. Calculations under the scaled-particle theory suggest that the work of cavity creation (????G _c), which is associated with the transfer of the phenylhydrazone from W to mix, dominates the magnitude of $\mathrm {\Delta} G^{\mathrm{transf}}_{\mathrm{W-mix}}$ . UV spectroscopic measurements suggest that these compounds bind calf thymus(CT)-DNA via intercalation mode in a buffer?C3 mol?L^?1 acetonitrile solution. The binding constant (K _b) depends on the nitro-substitution on the phenyl moiety and the electronegativity of the heteroatom in the heterocyclic ring. The corresponding Gibbs energy of binding ( $\Delta G_{\mathrm{DNA-B}}^{0}$ ) of phenylhydrazone derivatives to CT-DNA shows a marked dependence with ????G _c. The anticancer activity on human breast cancer cell lines MDA-231, MDA-435 and HT-29 human colon adenocarcinoma cell line was evaluated for the compounds NPCT, NPCF, DPCT and PCT.     

Investigation on the Complexation of Dioxovanadium (V) with D-(-)-Quinic Acid in Water + 1-Butyl-3-Methylimidazolium Tetrafluoroborate and Water + Methanol Mixed Solvents Using the KAT Model

The complex formation reaction of the $ {\text{VO}}_{2}^{ + } $ VO 2 + cation with D-(-)-quinic acid {(1R,3R,4S,5R)-(-)-1,3,4,5-tetrahydroxycyclohexane-1-carboxylic acid} at T = 298 K, I = 0.1 mol·dm^?3 of sodium chloride in various aqueous solutions of 1-butyl-3-methylimidazolium tetrafluoroborate, [bmim]BF₄, and methanol were studied by using potentiometric and UV spectrophotometric techniques. As far as we know, the calculated stability constants data presented in the current work are the first reported values for [bmim]BF₄ and methanol mixed solvents. The Kamlet–Abboud–Taft solvatochromic equation enabled us to interpret the UV data and the stability constants values. The Redlich–Kister equation was applied for the calculation of solvatochromic parameters in the binary water + [bmim]BF₄ mixtures. Hydrogen bonding is important for the dissociation constant in both media. In these systems the solvent polarizability and hydrogen-bond donor ability are the main interactions for the stability constants in the aqueous ionic liquid and methanol solutions, respectively.     

Densities and Volumetric Properties of Butyl Acrylate + 1-Butanol, or +2-Butanol, or +2-Methyl-1-propanol, or +2-Methyl-2-propanol Binary Mixtures at Temperatures from 288.15 to 318.15 K

The densities, ρ, of binary mixtures of butyl acrylate with 1-butanol, 2-butanol, 2-methyl-1-propanol, and 2-methyl-2-propanol, including those of the pure liquids, were measured over the entire composition range at temperatures of (288.15, 293.15, 298.15, 303.15, 308.15, 313.15, and 318.15) K and atmospheric pressure. From the experimental data, the excess molar volume $ V_{\text{m}}^{\text{E}} $ V m E , partial molar volumes $ \overline{V}_{\text{m,1}} $ V ¯ m,1 and $ \overline{V}_{\text{m,2}} $ V ¯ m,2 , and excess partial molar volumes $ \overline{V}_{\text{m,1}}^{\text{E}} $ V ¯ m,1 E and $ \overline{V}_{\text{m,2}}^{\text{E}} $ V ¯ m,2 E , were calculated over the whole composition range as were the partial molar volumes $ \overline{V}_{\text{m,1}}^{^\circ } $ V ¯ m,1 ° and $ \overline{V}_{\text{m,2}}^{^\circ } $ V ¯ m,2 ° , and excess partial molar volumes $ \overline{V}_{\text{m,1}}^{{^\circ {\text{E}}}} $ V ¯ m,1 ° E and $ \overline{V}_{\text{m,2}}^{{^\circ {\text{E}}}} $ V ¯ m,2 ° E , at infinite dilution,. The $ V_{\text{m}}^{\text{E}} $ V m E values were found to be positive over the whole composition range for all the mixtures and at each temperature studied, indicating the presence of weak (non-specific) interactions between butyl acrylate and alkanol molecules. The deviations in $ V_{\text{m}}^{\text{E}} $ V m E values follow the order: 1-butanol < 2-butanol < 2-methyl-1-propanol < 2-methyl-2-propanol. It is observed that the $ V_{\text{m}}^{\text{E}} $ V m E values depend upon the position of alkyl groups in alkanol molecules and the interactions between butyl acrylate and isomeric butanols decrease with increase in the number of alkyl groups at α-carbon atom in the alkanol molecules.     

Small-Angle Neutron Scattering Study on Aggregation of 1-Alkyl-3-methylimidazolium Based Ionic Liquids in Aqueous Solution

Aggregation structures of 1-alkyl-3-methylimidazolium based ionic liquids (ILs) in aqueous solution were investigated by small-angle neutron scattering (SANS) from the viewpoint of alkyl chain length, n, and anions (Cl^?, Br^? and trifluoromethanesulfonate, $ {\text{CF}}_{3} {\text{SO}}_{3}^{ - } $ ). In [C₄mIm⁺]-based IL systems, no noticeable SANS intensity was observed for all of the systems examined here, although aqueous [C₄mIm⁺][ $ {\text{BF}}_{4}^{ - } $ ] solutions show a significant SANS profile originating from concentration fluctuations in the solution (Almasy et al. J Phys Chem B 112:2382–2387, 2008). This suggests that [C₄mIm⁺][Cl^?], [C₄mIm⁺][Br^?] and [C₄mIm⁺][ $ {\text{CF}}_{3} {\text{SO}}_{3}^{ - } $ ] homogeneously mix with water, unlike the [C₄mIm⁺][ $ {\text{BF}}_{4}^{ - } $ ] system, due to preferential hydration of the ions. In the case of the C _n mIm cations with longer alkyl chain lengths (n = 8 and 12), SANS profiles were clearly observed in the aqueous solutions at IL concentrations of C _IL > 230 and 20.0 mmol·dm^?3, respectively. For aqueous [C₈mIm⁺][Br^?] solutions, the asymptotic behavior of the scattering function varied largely from I(q) ~ q ^?2 to ~q ^?4 with increasing C _IL, indicating that the solution changes from an inhomogeneous mixing state to a nano-scale micelle state. Aqueous [C₁₂mIm⁺][Br^?] solutions show a typical SANS profile for micelle formation in solution. It was found from a model-fitting analysis that the structure of the [C₁₂mIm⁺][Br^?] micelle is ellipsoidal, not spherical, in solutions over the C _IL range examined here.