Liquids

Based on data from broadband dielectric spectroscopy (BDS) and a molecular model based on the Landau–de Gennes concept, the effect of confinement on the structural, dielectric, and dynamic properties of 4-n-pentyl-4′-cyanobiphenyl (5CB) in the nematic phase is studied. The dielectric permittivity and relaxation times were previously obtained by the BDS technique in a wide frequency range ($1\mathrm{MHz}\le \mathrm{f}\le 1\mathrm{GHz}$) in the nematic phase composed of 5CB molecules confined to Anopore membranes with pore sizes of 0.2 $\mathsf{\mu }$m. The distance-dependent values of the order parameter $P_2\left(r\right)$, the relaxation time $\tau \left(r\right)\equiv {\tau }_{00}^1\left(r\right)$, the rotational diffusion coefficient $D_{\perp }\left(r\right)$, and both rotational viscosity coefficients ${\gamma }_i\left(r\right)$ ($i=1,2$) as functions of the distance r away from the bounding surface are calculated by a combination of existing statistical-mechanical approaches and data obtained by the BDS technique. Reasonable agreement between the calculated and experimental values of ${\gamma }_i(i=1,2)$ for bulk 5CB is obtained. Full article

Dimer and trimer acids are interesting viscous liquids produced from fatty acids derived from renewable sources. The chemical structures of dimer and trimer acids are known and quite complex and are presented here, discussed and further elucidated through electronic absorption spectroscopy, FT-IR and Raman spectroscopy. Dimer and trimer acids have a number of applications in their original form or in the form of derivatives. In the present study, a series of esters of dimer and trimer acids with alcohols from renewable sources were synthesized for use as plasticizers for rubber and plastics. The polarity of the dimer and trimer acids as well as their esters with alcohols from renewable sources (dimerates and trimerates) were systematically studied using a Nile red solvatochromic probe. The resulting E(NR) values were compared with the E(NR) values of the most common types of rubber and plastics. Compatibility and other physical properties expected from the E(NR) scale were studied and successfully confirmed in tire tread rubber compound formulations and in nitrile rubber and PVC matrices, confirming once again the sensitivity and the validity of the Nile red solvatochromic polarity scale for the development of new plasticizers. The validity of the liquids polarity measured with the Nile Red dye is supported by the correlation found between the E(NR) scale and the dielectric constants (ε) of carboxylic acids (including dimer and trimer acids, hydrogenated dimer acids and isostearic acid) and alcohols. A correlation was even found linking the E(NR) values the with the ε values of thin solid films of rubbers and plastics. In the case of the esters the correlation of their E(NR) values was found with the length of the aliphatic chains of the alcohols used in the esterification. Full article

Utilizing the shake-flask technique under atmospheric pressure (101 kPa) within the temperature range of 293.2 to 313.2 K, the experimental solubility and density values of deferiprone were determined in binary mixtures of polyethylene glycol 400 and 1-propanol. The mole fraction solubility of deferiprone exhibited an augmentation with elevated temperature and increased polyethylene glycol 400 mass ratio in polyethylene glycol 400 + 1-propanol compositions. A subsequent regression analysis of the solubility data was conducted employing the van’t Hoff, λh, Yalkowsky, modified Wilson, Jouyban–Acree and Jouyban–Acree–van’t Hoff models upon the comprehensive evaluation of the entire dataset; the van’t Hoff equation demonstrated the most favorable regression. Furthermore, the findings of this study hold significance for advancing the understanding of the basic thermodynamic data pertinent to the crystallization and industrial separation processes of deferiprone. Full article

When examined at the nanometer length scale, metallic liquids exhibit extensive ordering. Bonding enthalpies are balanced against entropic tendencies resulting in a rich complicated behavior that leads to clustering that depends on temperature but evolves on picosecond time scales. The structural organization of metallic liquids affects their thermophysical properties, such as viscosity and density, thus influencing the ability of a metallic liquid to form useful technological phases, such as metallic glasses. The time-dependent pair correlation function (the Van Hove function) was determined for metallic-glass forming Cu₄₉Zr₄₅Al₆ at 1060 °C from time-of-flight inelastic neutron scattering measurements made using the Neutron Electrostatic Levitation facility at the Spallation Neutron Source. The time for changes in local atomic connectivity, which is the timescale of atomic ordering, was determined by examining the decay of the nearest neighbor peak. The results of rigorous statistical analyses were used to distinguish between competing models of ordering, suggesting that a stretched exponential model of coordination number change is valid for this system. Full article

The behavior of the energy of the peaks of the first UV/Vis absorption band and the presence or absence of isosbestic points in this band with changing temperature for all-trans-DPH and all-trans-β-carotene, dissolved in 1-chlorobutane or hydrocarbon solvents, allows us to show conclusively whether these compounds transform their all-trans-molecular structures into a structure of their conformers. From these analyses, it is concluded that in these solvents, all-trans-DPH is not thermally transformed to its conformer s-cis-DPH in a temperature range from 133 K to 350 K. On the other hand, all-trans-β-carotene, as a model-compound, does show changes in its molecular structure in these solvents with changing temperature. We also show that a portion of all-trans-DPH dissolved in cis-Decalin, at room temperature, slowly transforms into its conformer s-cis-DPH. Full article

The relation between the pressure and molar concentration (in mol/L) of real gases in a low- to medium-pressure range is precisely described by a logarithmic two-parameter equation. Increasing the concentration caused an increase in pressure and also the weakening of the effect due to intermolecular interactions, forming the basis for an equation with an adjusted parameter. Exceeding a critical concentration by a further increase caused a switch to another set of parameters in the same equation. At high pressure, a second switch to an exponential term was observed. This equation of state, defined segment by segment, was attributed to three different structures of the medium. The validity of the equations found was verified with experimental data reported in the literature for helium, neon, argon, krypton, and xenon and is discussed in more detail for argon. The temperature dependence of the parameters of the equations is reported and the formation of a liquid phase is discussed. Full article

Raman scattering measurements were performed on 1 mol dm⁻³ aqueous calcium nitrate (Ca(NO₃)₂) and sodium nitrate (NaNO₃) solutions containing 4% (w/w) D₂O in a temperature range from 25 to 350 °C and pressure of 40 MPa. As the temperature increased, the N–O symmetric stretching vibrational band (ν₁) of NO₃⁻ at 1045–1047 cm⁻¹ shifted to a lower wavenumber by 5~6 cm⁻¹. The band analysis using one Lorentzian component showed that the full-width at half maximum (FWHM) did not change significantly below 175 °C but increased rapidly above 200 °C for both solutions. The peak area for an aqueous Ca(NO₃)₂ solution showed a breakpoint between 225 and 250 °C, suggesting a change in the coordination shell of NO₃⁻ at 175~250 °C. The OD symmetric stretching vibrational band of HDO water was deconvoluted into two Gaussian components at 2530 and 2645 cm⁻¹; the former component has high temperature dependence that is ascribed to the hydrogen bonds, whereas the latter one shows less temperature dependence due to the non-hydrogen bonds of water. X-ray scattering measurements were performed on a 1 mol dm⁻³ aqueous Ca(NO₃)₂ solution at 25 to 210 °C and 40 MPa. Empirical potential structure refinement (EPSR) modeling was used to analyze the X-ray scattering data. Ca²⁺ forms a rigid coordination shell consisting of about seven water molecules at 2.48 Å and one NO₃⁻ at 25~170 °C, with further water molecules substituted by NO₃⁻ at 210 °C. NO₃⁻ is surrounded by 13~14 water molecules at an N–Ow distance of 3.6~3.7 Å. The tetrahedral network structure of solvent water pertains from 25 to 170 °C but is transformed to a dense packing arrangement at 210 °C. Full article

Recently, two new polymorphs have been added to the nematic class: the polar-twisted nematic (N_PT) in 2016 and the ferroelectric nematic (N_F) in 2020. Comprised of achiral molecules, both exhibit local polar ordering and adopt modulated structures, right- and left-handed helical organizations—form chirality—albeit on vastly different dimensional scales; modulations have a ~10 nanometer pitch in the N_PT and ~500 nm in the N_F. Here, we focus on the structure and symmetries of the N_PT phase and the ensuing physical properties. Based on an array of order parameters that fully describe the molecular ordering and the nano-modulations thereof, we present a consistent formulation of the dielectric, optical, surface anchoring, and elasticity properties of the N_PT materials. We show that these properties are distinctly different from those associated with an elastically modulated, locally uniaxial, nematic. Full article

With the continuous growth of global energy demand, greenhouse gas emissions are also rising, leading to serious challenges posed by climate change. Carbon Capture, Utilization, and Storage (CCUS) technology is considered one of the key pathways to mitigate climate change. Among the CCUS technologies, CO₂ storage in offshore saline aquifers has gained significant attention in recent years. This paper conducts an in-depth analysis of the Sleipner and Snøhvit projects in Norway and the Tomakomai project in Japan, exploring key issues related to the application, geological characteristics, injection strategies, monitoring systems, and simulation methods of CO₂ storage in offshore saline aquifers. This study finds that CO₂ storage in offshore saline aquifers has high safety and storage potential but faces several challenges in practical applications, such as geological reservoir characteristics, technological innovation, operational costs, and social acceptance. Therefore, it is necessary to further strengthen technological innovation and policy support to promote the development and application of CO₂ storage in offshore saline aquifers. This study provides valuable experiences and insights for similar projects worldwide, contributing to the sustainable development of CO₂ storage in offshore saline aquifers and making a greater contribution to achieving global net-zero emission targets. Full article

This study investigates the dynamics of thermal plumes interacting with the liquid–air interface in straight-chain alcohols and their mixtures using a photothermal imaging technique based on thermal lensing. This method enables the indirect measurement of temperature gradients via changes in refractive index caused by localized laser heating. Employing a collimated laser beam, the results show the formation and evolution of cylindrical heated zones and their interactions with the liquid–air interface. The study reveals that, while some alcohols exhibit stable surface behaviors, others demonstrate complex dynamical behaviors, including strong stable steady-state oscillations. The findings contribute to understanding fluid dynamics in molecular liquids near their liquid–air interfaces. Full article

Understanding the interactions between solutes and solvents is vital in many areas of the chemical sciences. Solvation free energy (SFE) is an important thermodynamic property in characterising molecular solvation and so accurate prediction of this property is sought after. The One-Dimensional Reference Interaction Site Model (RISM) is a well-established method for modelling solvation, but it is known to yield large errors in the calculation of SFE. In this work, we show that a single machine learning free energy functional for RISM can accurately model solvation thermodynamics in multiple solvents. A convolutional neural network is trained on solvation free energy density functions calculated by RISM for small organic molecules in approximately 100 different solvent systems. We achieve an average RMSE of 1.41 kcal/mol and an ${\mathrm{R}}^2$ of 0.89 across all solvent systems. We also compare the performance for the most and least commonly represented solvents and show that higher accuracy is generally seen with higher volumes of data, with RMSE values of 0.69–1.29 kcal/mol and ${\mathrm{R}}^2$ values of 0.78–0.97 for solvents with more than 50 data points. We have shown that machine learning can greatly improve solvation free energy predictions in RISM, while demonstrating that the methodology is generalisable across solvent systems. This represents a significant step towards a universal machine learning SFE functional for RISM. Full article

In this work, we propose a comprehensive experimental study of the diffusion of isoniazid, one of the first-line anti-tuberculosis drugs, in combination with another drug (ethambutol dihydrochloride) and with different cyclodextrins as carrier molecules, for facilitated transport and enhanced solubility. For that, ternary mutual diffusion coefficients measured by the Taylor dispersion method (D₁₁, D₂₂, D₁₂, and D₂₁) are determined for aqueous solutions containing isoniazid and different cyclodextrins (that is, α–CD, β–CD, and γ–CD) at 298.15 K. From the significant effect of the presence of these carbohydrates on the diffusion of this drug, interactions between these components are suggested. Support for this arose from models, which shows that these effects may be due to the formation of 1:1 (CDs:isoniazid) complexes. Full article

The standard molar enthalpies of formation in the liquid phase for ethyl (E)-cinnamate and ethyl hydrocinnamate, two cinnamate derivatives with notable flavor and fragrance characteristics, were determined experimentally using combustion calorimetry in an oxygen atmosphere. To derive the gas-phase enthalpies of formation for these derivatives, their enthalpies of vaporization were measured using a high-temperature Calvet microcalorimeter and the vacuum drop microcalorimetric technique. Additionally, a computational analysis employing the G3(MP2)//B3LYP composite method was conducted to calculate the gas-phase standard enthalpies of formation at T = 298.15 K for both compounds. These findings enabled a detailed assessment and analysis of the structural and energetic effects of the vinyl and ethane moieties between the phenyl and carboxylic groups in the studied compounds. Considering the structural features of ethyl (E)-cinnamate and ethyl hydrocinnamate, a gas-phase enthalpy of hydrogenation analysis was conducted to explore their energetic profiles more thoroughly. Full article

A new method, based on quantum chemical calculations, is proposed for the thermodynamically consistent reformulation of QSPR-type Linear Free-Energy Relationship (LFER) models. This reformulation permits the extraction of valuable information on intermolecular interactions and its transfer in other LFER-type models, in acidity/basicity scales, or even in equation-of-state models. New molecular descriptors of electrostatic interactions are derived from the distribution of molecular surface charges obtained from COSMO-type quantum chemical calculations. The widely used and very successful Abraham’s Linear Solvation Energy Relationship (LSER) model is selected as the reference LSER model for the calculations in solute–solvent systems as well as in solute self-solvation. Hydrogen-bonding free energies, enthalpies, and entropies are now derived for a variety of common solutes. The capacity of the method to address the role of conformational changes in solvation quantities is discussed. The perspectives of the LSER model with the implementation of the new descriptors are also discussed. Full article

Solute descriptors derived from experimental solubility data for oxybenzone dissolved in 21 different organic solvents indicate that the hydrogen atom on the hydroxyl functional group forms an intramolecular hydrogen bond with the lone electron pair on the oxygen atom of the neighboring >C=O functional group. Group contribution methods developed for estimating the Abraham model solute descriptors from the molecule’s Canonical SMILES code significantly over-estimate the Abraham model’s hydrogen bond acidity solute descriptor of oxybenzone. An informed user-modified Canonical SMILES code is proposed to identify which hydrogen atoms are involved in intramolecular H-bond formation. The identified hydrogen atom(s) can be used to define a new functional/fragment group and numerical group contribution value. Full article

Many ionic liquids, including alkylimidazolium salts, form a nanoheterogeneous structure with polar and apolar domains in their liquid phase. Using molecular dynamics simulations, the influence of the structure of the cations of a series of aprotic ([C_nC₁Im][TFSI], [C_nC_nIm][TFSI]) and protic ([HC_nIm][TFSI]) alkylimidazolium bistrilimides on the domain structure of their liquid phase was studied. The characteristic sizes of domains and the extent of domain segregation in different liquids have been compared. It has been shown that the latter, but not the former, is a key factor determining the magnitude of the Gibbs free energy of cavity formation in nanostructured ionic liquids, which in turn governs their solvation properties. Full article

In this work, an approach to the calculation of hydrogen bonding enthalpies is proposed. It employs the correlation proposed by M.H. Abraham, establishing the connection between the equilibrium constant (K_HB) and acidity (${\alpha }_2^{\mathrm{H}}$) and basicity (${\beta }_2^{\mathrm{H}}$) parameters: log K_HB = 7.354 · ${\alpha }_2^H$ · ${\beta }_2^H$ − 1.099. Hydrogen bonding enthalpy (Δ_HBH) is found using the compensation relationship with Gibbs energy (Δ_HBG): Δ_HBG = 0.66 · Δ_HBH + 2.5 kJ·mol⁻¹. This relationship enables the calculation of the enthalpy, Gibbs energy and entropy of hydrogen bonding. The validity of this approach was tested against 122 experimental hydrogen bonding enthalpies values available from the literature. The root mean square deviation and average deviation equaled 1.6 kJ·mol⁻¹ and 0.5 kJ·mol⁻¹, respectively. Full article

We review the statistical mechanic foundations of the fundamental structure-making/breaking functions, leading to the rigorous description of the solute-induced perturbation of the solvent environment for the understanding of the solvation process of any species regardless of the type and nature of the solute–solvent interactions. Then, we highlight how these functions are linked to unambiguous thermodynamic responses resulting from changes in state conditions, composition, and solute–solvent intermolecular interaction asymmetries. Finally, we identify and illustrate the pitfalls behind the use of surrogate approaches to structure-making/breaking markers, including those based on Jones–Dole’s B-coefficient and Hepler’s isobaric-thermal expansivity, while highlighting their ambiguities and lack of consistency and the sources of misinterpretations. Full article

New experimental vapour pressures and vaporisation enthalpies of the ionic liquids [2,4-dimethyl-1,2,4-triazolium][NTf₂], [2-methyl-4-ethyl-1,2,4-triazolium][NTf₂], and [2-ethyl-4-methyl-1,2,4-triazolium][NTf₂] were measured using the Langmuir method in combination with the quartz crystal microbalance. New experimental vapour pressures and vaporisation enthalpies of the molecular liquids 1H-1,2,4-triazole, 1-methyl-1,2,4-triazole, 1-ethyl-1,2,4-triazole, and 1H-1,2,3-triazole were measured using the transpiration method. Structure–property relationships between molecular and ionic liquids were studied. These results will facilitate chemical engineering calculations of processes involving ILs. Full article