Ultrasonic study of binary aqueous mixtures of three common eutectic solvents

Ultrasonic velocities have been measured for different binary mixtures of common choline chloride-based deep eutectic solvents (DESs), namely, reline, glyceline and ethaline with water, in the range of temperature: 303.15–353.15 K. The experimental data measurements with different mole fractions of DES–water solutions were utilised in fitting four different models for speed of sound. These models correlate the speed of sound with some physical properties such as molar volumes, molar components sound velocity, densities, molecular weights, collision factors etc. A close match was obtained with these models with an average relative error of less than 4% for all data points used. It was observed that the ultrasonic velocity increases with the concentration of DES solvent and decreases with temperature. Moreover, this study roughly indicated that the intermolecular interactions in reline and ethaline aqueous mixtures exist in the form of disruption of dipole–dipole interactions (that varies considerably as a function of DES mixture composition and solution temperature). On the other hand, the interactions on the molecular level in glyceline aqueous solution are mainly due to dipole–dipole intermolecular forces.     

Liquid–Liquid Equilibria of Oxygenate Fuel Additives with Water at 25°C: Ternary and Quaternary Aqueous Systems of Methyl tert-Butyl Ether and tert-Amyl Methyl Ether with Methanol or Ethanol

Experimental tie-line data have been determined for the ternary system water + methyl tert-butyl ether + tert-amyl methyl ether and the quaternary systems water + methanol + methyl tert-butyl ether + tert-amyl methyl ether, and water + ethanol + methyl tert-butyl ether + tert-amyl methyl ether at 25°C and ambient pressure. The experimental results have been satisfactorily correlated using the modified UNIQUAC and extended UNIQUAC models with ternary and quaternary, in addition to binary parameters.     

Analysis of ultrasonic velocity in refrigerants using artificial neural network

Several researchers have reported numerous measurements on ultrasonic velocity as a function of temperature and pressure using various experimental techniques. A large amount of experimental data is required in order to obtain accurate results for the chemical substances used. The present article explores the evaluation of ultrasonic velocity as a function of molecular weight, temperature and pressure using an artificial neural network (ANN) in six refrigerants. The network so developed predicts the ultrasonic velocity successfully. Statistical analysis of the results was performed using standard deviation (%) and relative average deviation. The correlation coefficient in our analysis was found to be 0.9999. The trained weights, obtained from ANN, are further employed to form equations to predict ultrasonic velocity at other temperatures and pressures.     

Molecular interaction study through experimental and theoretical volumetric,transport and refractive properties of N-ethylaniline with aryl and alkyl ethers at several temperatures

To investigate the molecular interaction study between secondary amine with aryl and alkyl ether, we report densities, speeds of sound, viscosities and refractive indices of N-ethylaniline (NEA) with aryl (anisole, phenetole) and alkyl (tert-butyl methyl ether) ether over the entire composition regime and in the temperature range of 293.15–323.15 K at 5 K intervals. Various excess and transport properties were derived from the experimental data and the excess parameters were fitted to the Redlich–Kister polynomial equation using multiparametric non-linear regression analysis to derive the binary coefficients and to estimate the standard deviation. Molecular interactions between the unlike molecules were analysed through dipole–dipole interactions, cross-association between the components of the mixtures and H-bond formation. Viscosity and refractive index of the mixtures were predicted through several empirical equations and compared with the experimental results. Prigogine–Flory–Patterson statistical theory was used to predict the excess molar volume results.     

Photochemistry of aryl tert-butyl ethers in methanol: the effect of substituents on an excited state cleavage reaction

The photolysis of a set of 10 substituted aryl tert-butyl ethers, 8a-j, in methanol gave, as the major product, the corresponding phenol along with tert-butyl-substituted phenols resulting from photo-Fries reaction. The corresponding 4-cyanophenyl 1-adamantyl ether, 9, also gave 1-methoxyadamantane 16 (16%), indicating that, at least for this ether, some of the products were ion-derived. Quenching studies with 2,3-dimethylbutadiene for the tert-butyl ethers indicated that these reactions were occurring from the singlet excited state. Rate constants for the reaction, obtained from quantum yields and singlet lifetimes, were found to correlate reasonably well with sigma(h)()(nu) values, rho = -0.77 (r = 0.975), a result that is unexpected for a reaction where the polarity of the bond breaking in the transition state is expected to be -O(delta-). C(delta+).     

Influence of temperature on thermodynamics of ethers + xylenes

The densities and ultrasonic velocity of the binary mixtures methyl tert-butyl ether (MTBE) or ethyl tert-butyl ether (ETBE) + (o-xylene, m-xylene and p-xylene) at the range 288.15–323.15 K and atmospheric pressure, have been measured over the whole concentration range. The experimental excess volumes and deviation of isentropic compressibilities data have been analyzed. The experimental values have been studied in terms of different theoretical models. The gathered data improve open literature related to gasoline additives, as the comparison has proved, and help to understand the ether effect into aromatic environment in terms of steric hindrance and oxygen group polar potency.     

Pervaporation separation of ethyl tert-butyl ether and ethanol mixtures with a blended membrane

A new kind of membrane was prepared by blending cellulose acetate butyrate with cellulose acetate propionate. The properties of this membrane were evaluated by the pervaporation separation of ethyl tert-butyl ether and ethanol mixtures. The experimental results showed that the selectivity and the fluxes of this membrane depend on the blend and on that of processed feed mixtures. With respect to temperature, the overall and the ethanol fluxes obey the Arrhenius equation. The total and the ethanol fluxes increase with the increase of the cellulose acetate butyrate content in the blended membrane, the ethanol concentration in the feed and the experimental temperature. But the selectivity decreases as the cellulose acetate butyrate content in the membrane and the experimental temperature are raised. When the feed composition is varied, the lowest selectivity is observed in the vicinity of the azeotropic composition. The swelling and the sorption experiments also gave the same results.     

Optimizing ultrasonic ellagic acid extraction conditions from infructescence of Platycarya strobilacea using response surface methodology

The infructescence of Platycarya strobilacea is a rich source of ellagic acid (EA) which has shown antioxidant, anticancer and antimutagen properties. Response surface methodology (RSM) was used to optimize the conditions for ultrasonic extraction of EA from infructescence of P. strobilacea. A central composite design (CCD) was used for experimental design and analysis of the results to obtain the optimal processing parameters. The content of EA in the extracts was determined by HPLC with UV detection. Three independent variables such as ultrasonic extraction temperature (°C), liquid:solid ratio (mL/g), and ultrasonic extraction time (min) were investigated. The experimental data obtained were fitted to a quadratic equation using multiple regression analysis and also analyzed by appropriate statistical methods. The 3-D response surface and the contour plots derived from the mathematical models were applied to determine the optimal conditions. The optimum ultrasonic extraction conditions were as follows: ultrasonic extraction temperature 70 °C, liquid:solid ratio 22.5, and ultrasonic extraction time 40 min. Under these conditions, the experimental percentage value was 1.961%, which is in close agreement with the value predicted by the model.     

Study of the Surface Tensions of Binary Mixtures of Isomeric Chlorobutanes with Methyl tert-Butyl Ether

In the present work we report experimental surface tensions for binary mixtures of isomeric chlorobutanes with methyl tert-butyl ether from 283.15 to 303.15 K, measured with a drop volume tensiometer. From these experimental data the corresponding surface tension deviations were calculated and correlated using a Redlich-Kister type polynomial. Finally, we include the calculation of excess surface compositions for all of the mixtures from 288.15 K to 308.15 K.     

Excess functions of binary liquid mixtures at varying pressures

The present investigation comprises of theoretical evaluation of the thermodynamic excess functions, viz. excess energy and excess entropy for five binary liquid mixtures at varying pressures. A statistical mechanical theory, along with the Schaaff’s equation for sound velocity was used in order to calculate the above-mentioned excess properties directly through the use of the experimental data of ultrasonic velocity and density only.     

Thermodynamics of mixed micellar systems of sodium octanoate and ethoxylated alcohols in water at 25°C

Thermodynamic volume and compressibility properties of binary aqueous systems of sodium octanoate (C₈Na) and polyoxyethylene butyl ether compounds (ethoxylated alcohols), with one to three oxyethylene groups (C₄EO_X), and ternary systems of these compounds, have been determined as a function of surfactant and alcohol concentrations at 25°C from density and ultrasonic velocity measurements. Values of standard state apparent molar volume and apparent molar adiabatic compressibility properties of transfer of ethoxylated alcohols from water to aqueous C₈Na solutions were obtained. The observed trends in the properties of the aqueous binary C₈Na systems and of the transfer functions for C₄EO_x, at a given low concentration of 0.05m, were analyzed using theoretical models. Good agreement between the simulated results and the experimental data was achieved. The results obtained for the distribution coefficients of the alcohols and the thermodynamic properties of both components of the mixed micelle show that the hydrophobicity of the ethoxylated alcohols is enhanced by introducing more oxyethylene groups into the alcohol. The distribution behavior of these compounds between the C₈Na micelles and the aqueous phase also depends on the difference between the hydrophobicity of the surfactant and the alcohols.     

Temperature influence on mixing properties of {ethyl tert-butyl ether (ETBE) + gasoline additives}

The densities and ultrasonic velocity of {ethyl tert-butyl ether (ETBE) + (benzene, toluene, ethylbenzene, isooctane, tert-butyl alcohol, and ethanol)} over the temperature range (288.15 to 323.15) K and atmospheric pressure, have been measured over the whole concentration range. The experimental excess volumes and deviation of isentropic compressibilities data have been analysed in terms of different theoretical models. The gathered data improve open literature related to gasoline additives, and help to understand the ETBE volumetric and acoustic trend into different chemical environment.     

Quantum theory of atoms in molecules analysis on the conformational preferences of vinyl alcohol and related ethers

Vinyl alcohol, methyl vinyl ether, and tert-butyl vinyl ether were studied within the framework of the quantum theory of atoms in molecules at the B3LYP/6-311++G(2d,2p) level. Local and integrated properties of the charge density indicate that the anti conformational preference of the tert-butyl derivative is not due to a differing resonance contribution with regard to the less bulky vinyl ethers but to steric effects. There is a small delocalization of charge density, either total or pi, between oxygen and the terminal vinyl carbon, which does not support the resonance picture of vinyl compounds.     

Influence of temperature on ultrasonic velocity measurements of ethanol+water+1-propanol mixtures

The ultrasonic velocity of the ternary mixtures ethanol+water+1-propanol at the range 288.15–323.15 K and atmospheric pressure, has been measured over the whole concentration range. The corresponding change of isentropic compressibility was computed from the experimental data. The results were fitted by means of a temperature dependent equation, such parameters being gathered. The obtained experimental values indicate varying extent of interstitial accommodation among unlike molecules as a function of steric hindrance attending to 1-propanol composition as key component and as a function of hydrogen bond and temperature attending to ethanol composition as key component.     

Densities, viscosities, and ultrasonic velocity studies of binary mixtures of trichloromethane with methanol, ethanol, propan-1-ol, and butan-1-ol at T = (298.15 and 308.15) K

Densities, viscosities, and ultrasonic velocities of binary mixtures of trichloromethane with methanol, ethanol, propan-1-ol, and butan-1-ol have been measured over the entire range of composition, at (298.15 and 308.15) K and at atmospheric pressure. From the experimental values of density, viscosity, and ultrasonic velocity, the excess molar volumes (V^E), deviations in viscosity (Δη), and deviations in isentropic compressibility (Δκ_s) have been calculated. The excess molar volumes, deviations in viscosity and deviations in isentropic compressibility have been fitted to the Redlich-Kister polynomial equation. The Jouyban-Acree model is used to correlate the experimental values of density, viscosity, and ultrasonic velocity.     

Acoustic,excess thermodynamical,molecular interaction and anti-microbial activity studies on binary liquid mixtures of geranyl acetate and benzyl benzoate in the temperature range of 303.15K–318.15K

The binary organic liquid mixture of geranyl acetate + benzyl benzoate was taken at different mole fractions and various temperatures 303.15K, 308.15K, 313.15K and 318.15K and measured their density, ultrasonic sound velocity and viscosity. Data from experiments were used to calculate variations in binary systems at different temperatures regarding excess acoustic parameters. Variations in ultrasonic velocity, intermolecular free length, and adiabatic compressibility were among these. To estimate the coefficients and standard errors for the excess/deviation functions, multi-parametric non-linear regression analysis was used to fit a Redlich-Kister polynomial with the calculated excess/deviation functions. Changes in these properties with temperature and composition have been investigated in the molecular interactions between the molecules of the binary mixtures. FTIR spectra also support the results. Furthermore, liquid mixtures and individual compounds were studied for their antibacterial activity.     

Hydroboration. 97. Synthesis of new exceptional chloroborane--Lewis base adducts for hydroboration. Dioxane--monochloroborane as a superior reagent for the selective hydroboration of terminal alkenes

Several less volatile oxygen-containing Lewis bases, such as tert-butyl methyl ether, dioxane, anisole, ethyl acetate, beta-chloroethyl ether, and monoglyme, were examined as prospective mono- and dichloroborane carriers. Dioxane, ethyl acetate, and beta-chloroethyl ether form relatively stable boron trichloride adducts, but the boron trichloride adduct of monoglyme is not very stable and must be used immediately. On the other hand, tert-butyl methyl ether and anisole fail to form stable boron trichloride adducts and the corresponding ether-cleaved products are obtained. Among the selected oxygen-containing Lewis bases, only dioxane forms stable and reactive mono- and dichloroborane adducts. Monoglyme and beta-chloroethyl ether give stable dichloroborane adducts requiring excess of diborane. Convenient methods for the preparation of mono- and dichloroborane adducts of dioxane from dioxane-BCl(3) and NaBH(4) in the presence of catalytic amounts of tri- or tetraglyme were developed. The dioxane--monochloroborane adduct hydroborates representative olefins cleanly and rapidly. The corresponding alcohols were obtained in quantitative yields after oxidation. Also, the hydroboration of several terminal olefins with dioxane--monochloroborane were highly regioselective and the primary alcohols were obtained almost exclusively (>99.5%), after oxidation. Accordingly, dioxane-monochloroborane should serve as a reagent of choice for such hydroborations. The dioxane--dichloroborane adduct showed remarkable selectivity toward 2-substituted terminal olefins, such as 2-methyl-1-butene and beta-pinene, when compared to simple terminal and hindered olefins, giving a unique tool for selective hydroborations. Dichloroborane adducts of monoglyme and beta-chloroethyl ether also showed high reactivity, even at room temperature, toward simple unhindered olefins. However, hydroboration of hindered olefins is slow and requires either higher temperatures or the addition of 1 equiv of boron trichloride to liberate free dichloroborane, as in the case of the previously known dichloroborane adducts of methyl sulfide and diethyl ether.     

Solubility and solution thermodynamics of sorbic acid in eight pure organic solvents

By the gravimetric method, the solubility of sorbic acid in eight solvents including ethanol, 2-propanol, methanol, 1-butanol, ethyl acetate, methyl tert-butyl ether, acetone and acetonitrile was determined over a temperature range from 285.15 to K at atmospheric pressure. For the temperature range investigated, the solubility of sorbic acid in the solvents increased with increasing temperature. The experimental values were correlated with the linear solvation energy relationship, modified Apelblat equation, λh equation, non-random two-liquid (NRTL) model, and Wilson model. On the other hand, the enthalpy, entropy and Gibbs free energy of dissolution were obtained from these solubility values by using the van’t Hoff and Gibbs equations. The excess enthalpy of solution was estimated on the basis of λh equation. Furthermore, the a priori predictive model COSMO-RS was employed to predict the solubility of sorbic acid in selected solvents and reasonable agreement with experimental values is achieved.     

Simultaneous determination of methyl tert-butyl ether, its degradation products and other gasoline additives in soil samples by closed-system purge-and-trap gas chromatography-mass spectrometry

A new protocol for the simultaneous determination of methyl tert-butyl ether (MTBE); its main degradation products: tert-butyl alcohol (TBA) and tert-butyl formate (TBF); other gasoline additives, oxygenate dialkyl ethers: ethyl tert-butyl ether (ETBE), tert-amyl methyl ether (TAME) and diisopropyl ether (DIPE); aromatics: benzene, toluene, ethylbenzene and xylenes (BTEX) and other compounds causing odour events such as dicyclopentadiene (DCPD) and trichloroethylene (TCE) in soils has been developed. On the basis of US Environmental Protection Agency (EPA) method 5035A, a fully automated closed-system purge-and-trap coupled to gas chromatography/mass spectrometry (P&T-GC/MS) was optimised and permitted to detect microg/kg concentrations in solid matrices avoiding losses of volatile compounds during operation processes. Parameters optimised were the sampling procedure, sample preservation and storage, purging temperature, matrix effects and quantification mode. Using 5 g of sample, detection limits were between 0.02 and 1.63 microg/kg and acceptable method precision and accuracy was obtained provided quantification was performed using adequate internal standards. Soil samples should be analysed as soon as possible after collection, stored under -15 degrees C for not longer than 7 days if degradation products have to be analysed. The non-preservative alternative (empty vial) provided good recoveries of the most analytes when freezing the samples up to 7 day holding time, however, if biologically active soil are analysed the preservation with trisodium phosphate dodecahydrate (Na(3)PO(4).12H(2)O or TSP) is strongly recommended more than sodium bisulphate (NaHSO(4)). The method was finally applied to provide threshold and background levels of several gasoline additives in a point source and in sites not influenced by gasoline spills. The proposed method provides the directions for the future application on real samples in current monitoring programs at gasoline pollution risk sites where till now little monitoring data for MTBE in soils are available.     

Heat capacities and excess enthalpies of the (N-hexylisoquinolinium thiocyanate ionic liquid + water) binary systems

In the present work the binary mixtures containing the ionic liquid N-hexylisoquinolinium thiocyanate, [HiQuin][SCN] and water was considered as a new working pair for absorption refrigeration.Experimental heat capacities and excess enthalpies of the binary mixtures were determined at different ionic liquid mole fractions over a wide range of temperature at ambient pressure. The influence of temperature and composition on measured properties was assessed and suitable equations were used to correlate the experimental data.