The effect of pressure and temperature on the second-order derivatives of the free energy functions for lower alkanediols

The second-order derivatives of the free energy functions, i.e., isochoric molar heat capacities, isentropic and isothermal molar compressibility, and isobaric and isentropic molar thermal expansion, were calculated in the temperature range from (293.15 to 318.15) K and at pressures up to 100 MPa for 1,2- and 1,3-propanediol; 1,2-, 1,3, and 1,4-butanediol; and 2-methyl-2,4-pentanediol. The data for calculations were obtained by means of the acoustic method. The pressure and temperature dependencies for the above mentioned properties are analyzed and discussed together with the literature data on isobaric molar heat capacities. The observed marked difference between isobaric and isentropic thermal expansion is analyzed as well. The differences in behavior of linear 1,2-diols and α,ω-diols as well as a diol with a branched carbon chain are emphasized. The isentropic and isothermal molar compressibilities are used to evaluate the dimensionality and relative rigidity of H-associates

High-pressure speed of sound and related thermodynamic properties of N-alkylpyridinium bis(trifluoromethylsulfonyl)imides

The speed of sound was measured in three N-alkylpyridinium bis(trifluoro-methylsulfonyl)imides containing cations with ethyl, butyl and hexyl chains at pressures up to 101 MPa over a temperature range from 293.15 to 323.15 K. This paper is the first reported direct measurement of the speed of sound in N-hexylpyridinium bis (trifluoro-methylsulfonyl)imide as a function of pressure and temperature at two frequencies (1.95 and 6.25 MHz), demonstrating the absence of ultrasonic velocity dispersion under experimental conditions. An acoustic method was used to determine the high-pressure density, isentropic compressibility, isothermal compressibility, isobaric thermal expansion, isobaric and isochoric heat capacities, and internal pressure. For the studied homologous series, the dependence of the speed of sound on the alkyl chain length of the pyridinium cation exhibits a minimum at both atmospheric and high pressures. With increasing pressure, the minimum becomes shallower and is shifted towards homologues with shorter carbon chains in the cation

Acoustic nonlinearity parameter B/A, internal pressure, and acoustic impedance determined at pressures up to 100 MPa for 1-Ethyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide

The nonlinearity parameter B/A, internal pressure, and acoustic impedance are calculated for a room temperature ionic liquid, i.e. for 1-ethyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl] imide for tem- peratures from (288.15 to 318.15) K and pressures up to 100 MPa. The B/A calculations are made by means of a thermodynamic method. The decrease of B/A values with the increasing pressure is observed. At the same time B/A is temperature independent in the range studied. The results are compared with corresponding data for organic molecular liquids. The isotherms of internal pressure cross at pressure in the vicinity of 70 MPa, i.e. in this range the internal pressure is temperature independent

Isobaric and Isochoric Heat Capacities of Imidazolium-Based and Pyrrolidinium-Based Ionic Liquids as Function of Temperature: Modeling of Isobaric Heat Capacity

International audienceThe isobaric and isochoric heat capacities of seven 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imides, two 1-alkyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imides, and two bis(1-alkyl-3-methylimidazolium) tetrathiocyanatocobaltates were determined at atmospheric pressure in the temperature range from 293.15 to 323.15 K. The isobaric heat capacities were determined by means of differential scanning calorimetry, whereas isochoric heat capacities were determined along with isothermal compressibilities indirectly by means of the acoustic method from the speed of sound and density measurements. Based on the experimental data, as expected, the isobaric heat capacity increases linearly with increasing alkyl chain length in the cation of 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imides and no odd and even carbon number effect is observed. After critical comparison of the obtained data with the available literature data, the most reliable values are recommended. It has been also shown that, although the COSMOthermX calculations underestimated the isobaric heat capacity values whatever the temperature and the ionic liquid structure, the approach used during this work may be applied to estimate physical properties of non-single-charged ions as well. Additionally, based on the speeds of sound the thermal conductivities were calculated using a modified Bridgman relation

Speed of Ultrasound and Internal Pressure of Propanediol and Butanediol Isomers under Elevated Pressures

Speed of ultrasound and internal pressure of 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, and 1,3-butanediol at the temperatures ranging from 293.15 to 318.15 K and pressures up to 101 MPa are analyzed and discussed in terms of molecular structure and ability to form inter- and intramolecular hydrogen bonds

Thermodynamic and acoustic properties of mixtures of dibromomethane + heptane

Densities and speeds of ultrasound in binarymixtures of dibromomethane with heptane have been measured within the temperature range from 288.15K to 318.15 K. From the experimental data, the thermodynamic excess volume, molar isobaric expansion, molar isentropic compression, and ultrasonic speed were calculated. The excess volume and excess isentropic compression have opposite signs, whereas the excess isobaric expansion is an S-shaped function of the mole fraction. An explanation was suggested to account for the excesses in terms of intermolecular interactions. It involved energetic and steric factors. Moreover, itwas shown that the positive excess sound speed results almost entirely from the negative excess compression

Speed of Sound and Ultrasound Absorption in Ionic Liquids

International audienceA complete review of the literature data on the speed of sound and ultrasound absorption in pure ionic liquids (ILs) is presented. Apart of the analysis of data published to date, the significance of the speed of sound in ILs is regarded. An analysis of experimental methods described in the literature to determine the speed of sound in ILs as a function of temperature and pressure is reported, and the relevance of ultrasound absorption in acoustic investigations is discussed. Careful attention was paid to highlight possible artifacts, and side phenomena related to the absorption and relaxation present in such measurements. Then, an overview of existing data is depicted to describe the temperature and pressure dependences on the speed of sound in ILs, as well as the impact of impurities in ILs on this property. A relation between ions structure and speeds of sound is presented by highlighting existing correlation and evaluative methods described in the literature. Importantly, a critical analysis of speeds of sound in ILs vs those in classical molecular solvents is presented to compare these two classes of compounds. The last part presents the importance of acoustic investigations for chemical engineering design and possible industrial applications of ILs

Influence of experimental conditions on the electrochemical window. Case study on bis(trifluoromethylsulfonyl)imide-based ionic liquids

Ionic liquids (ILs) are often selected as electrolytes in various devices, such as batteries, capacitors and sensors, because of their chemical stability, non-flammability, low volatility, high electrical conductivity, low melting point, high thermal stability, and wide electrochemical window (EW). The width of the EW of an IL depends on the cation type, the water content, the electrode material, and the chosen specific current density used to measure it. In this work, the EWs of four ILs containing the common and stable bis(trifluoromethylsulfonyl)imide anion and triethylsulfonium, 1-(2-hydroxyethyl)-3-methylimidazolium, 1-methyl-1-propylpiperidinium and 1-butyl-1-methylpiperidinium cations were investigated by linear sweep voltammetry in order to analyze their electrochemical stability toward reduction and oxidation at polycrystalline platinum, gold and glassy carbon disc electrodes under anhydrous conditions. Specific current densities of 0.1 mA-cm 2 or 1 mA-cm 2 or the linear fitting method were used for the systematic comparison of the EWs obtained from each dataset. The results indicate the dependence of the EW width of each IL on the electrode material and, more importantly, on the chosen specific current density. In this paper, we present new insight into some of the difficulties encountered during determination of the EW for ILs

In Vitro Anticancer and Antivirus Activities of Cyano- And Bis (Trifluoromethylsulfonyl) imide-Based Ionic Liquids

In the current work, we present a broad analysis of cytotoxicity toward normal (kidney and lung) and cancer (lung, liver, and cervix) cells of ionic liquids (ILs) with imidazolium cations and cyano-based or bis(trifluoromethylsulfonyl)imide anions. Additionally, we verify if ILs might be candidates for new potential virucidal agents. We observed the highest biological activity for 1-methyl-3- octylimidazolium bis(trifluoromethylsulfonyl)imide, whereas the least toxic was 1-ethyl-3-methylimidazolium thiocyanate. We found that all investigated ILs revealed a lack of antiviral activity against viruses: human parainfluenza virus type 3 (HPIV-3), human adenovirus 5 (AdV5), human herpesvirus 1 (HSV-1), and human herpesvirus 5 (HCMV) in nontoxic concentrations

Cytotoxicity of ionic liquids on normal human dermal fibroblasts in the context of their present and future applications

The skin is the part of the body that is the most exposed to toxic substances; therefore, the impact of chemicals on the skin should be thoroughly studied prior to their implementation in any industrial-scale application. Herein, we examined and analyzed the influence of the structure of both the cation and anion of 31 different ionic liquids (ILs) on their cytotoxicity against normal human dermal fibroblasts in the context of their present and future potential applications. We found that imidazolium-based ILs combined with dialkyl phosphate anions or with the ethyl sulfate anion are the least cytotoxic. Notably, 1,3-diethylimidazolium ethyl sulfate can be potentially used as a hydraulic fluid similar to the commercially available hydraulic medium based on 1-ethyl-3-methylimidazolium ethyl sulfate. Moreover, the dialkyl phosphate-based ILs are considered as an efficient solvent for the utilization of lignocellulose-based biomass and as an extractant in eco-friendly and cost-effective processes for the extraction of bioplastic. Pyrrolidinium-based and cyano-based ILs, often used as heat transfer media and base fluids for ionanofluids, were also identified herein as good candidates based on their relatively low toxicity compared to other ILs